Note: Descriptions are shown in the official language in which they were submitted.
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PLASTIC PLATELET FUEL CELLS EMPLOYIN6 INTEGRATED FLUID MANAGEMENT
Sr~ClrlCATlON Dt~ r 1 1l~1J
CROSS-httt~tr~lCE TO RELATED APPLICATION: This ~ ;on is a continuation-in-part of US
~FP ~ .SN 08f322.823filedOctoberl2. l994byspearetal.~entitledFuelcellsEmployingllll~ldl~d
FluidMa,layt:,llentplateletT~llnùloy!f~thebenefitofthefilingdateofthecollllllonsubiectmatterofwhich
is claimed under 35 U.S.C. 120 and the subject matter of which is hereby i--co.~o.dl~d by lef~ ce
herein.
TECHNICAL FIELD:
This invention relates to plastic platelet fuel cells. and more particularly to fuel cells constructed
of stacked platelets having i..leyldled fluid ~--~,ag~l-ent (IFM) features, and to methods of manufacture
and op~dliùn of the IFM cells. A particular ~--bodi,--ent employing the ~ci-i..L,i~,les of this invention is a
hydrogen-airiO2fuelcellemployingmultiplecc....pGaitesepd,dlu-afOrmedOfbondedplateletsofplast
fomling a fluid ...~,dy~--enl core. with metallic or other el~hi~.al conduction type surPdce pl t ~
f~)~;~io~ ~9 as current ~~ 'c a. The platelets have individually configured ~ ,.uul.a....el reactant gas.
coolant and hu-- ' - ~ zones therein. Typical IFM plastic platelet cells of this invention operate in the
range of about 50 to 150 C, with an output on the order of .25-1.0 kW per Kg t.5-1.0 kW/L) for use in both
sldliùlh~y and mobile power ye~dtiùl~ ~F-F' ~a in open or closed loop configurations. The IFM
platelet and s~ dtOI design can be ~r~jllct~ throughout the fuel cell stack to acco~ dte var~fin9
thermal l--a..ag~.-w.l and hu-l ~l ~ re~l~ ~--e lta within each cell as a function of its position in the
StdCk.
BACKGROUND OF THE ART:
Fuel cells for direct conversion of hydrogen or Cdl bonaceous fuels to LIQ,I- i~.ity have shown great
Il ~e~ li"al promise. but have not become widely used in co-, -. . .~;e t~ec~ ~ce of ~h- ~ ~- ubl~ - -s and
econo...ic reasons. In the field of hydrogen-air/02 fuel cells. power density, that iâ h'~w~ila of power
gen~ dlion per ! ' _ dl l l, has been I l ldl ~ Idl, and the lifetime has been u~ - ,Iy short. Prior art cells
have ~eli~lced drop-off in power with age due in part to po;soi ~9 of catahysts or r;l~l-ulyte
111~11 It~l dl ~es. and the poor distribution of fuel gases i- ,le- . 'Iy has led to thermal hot spots leading to cell
failure and the like.
A particularly illlpulldlll class of fuel cells with promise for ~laliùnaly and mobile ele~ .ily
gw ~t:- cLiol) is the low temperature H2/~2 fuel cell employing solid polymwric proton excha.-ge membrane
having a noble metal catalyst coated on at both sides thereof, which mem~rane is located between the
fuel cell elec,l.udes. These fuel cells employ H2 as fuel, whether directly sl~FFI ~i as such or gen~dled
in a~<o~ .n with the cell by Cl)w"il,al reaction, such as electrolysis, from metal hydrides or from reformed
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hydloLdlL~ùns. The oxidant is ~2 or air where suitable. Water is required both for cooling and for
hul~ r~ n of the m~ dlle, to keep it from drying out and becoming il,t Iri-,;~"L or stnucturally
v.,~ ~ ,~ through sl,c~ h ,9 and cracking. Typieally, the anode side dries out first for a variety of
reasons, including: electro-osmotic pumping from anode to cathode; supply of gases in excess of the
el~L.uclle,.l.cal reaction rate; and the air or oxygen flow on the cathode side purges both the product
water and the water vapor passing through the membrane from the hydrogen anode side. Acc-ul .J;~ ~y~,
the fuel gases need to be humidified In the fuel cell stack to reduce the dehydration effect. The cooling
water removes excess heat generated in the slow combustion of the catalyst-mediated ele ll ocl ,el l ,ical
reaction in the cells. and is conducted extemal of the stack for heat ~:~cl.dnye. In some designs the
cooling water is used to humidify the reactant gases.
- There are several suitable ele~ude me.,-~.dne dSSt~ (EMAs) available for such low
le.,.p~dlure fuel cells. One is from l l Pc N~D' Corp of P~" :;cJ~, New Jersey which employs a Pt catalyst
coated on a polymer film, such as DuPont NAFION~ brand perflourosulru.,dlad hyd.ucd,L,o,, as the
, - l~l l Ibl ane. Altematively, Dow Chemical provides a perflourosulfonated poiymer which has been, ~pGI led
in US Patent 5,316.869 as perrnitting current dt n~itias on the order of 4000 ampsls.f. with cell voltages
in excess of .5V/cell, for a cell stack power density in excess of 2 kW/s.f.
A typical design of a currently available fuel cell stack is the Ballard Fuel Cell Stack of 35 active
el~l, ocl ,~,lical cells, 19 thermal md,)cy~ l-~ ll cells. and 14 reactant hull ~id~ I ;on cells el I l, ' ,1;. l9 a Pt
on NAFION-117 EMA in stacks of 1/4~ thick graphite plates. The staek is r~po,lad to have an overall
volume of 0.5 cu. ft. with a weight of 94 Ibs and a 3 kW output from H2 and ~2-
However, the graphite plates must be relatively thick to provide structural integrity and to preventreactant crossover. That is, since the graphite is porous to H2 and ~2. it must be
at least .060~ thick to
reduce the permeation crossover to an r~ ' ' level. Further, graphite plates are brittle. Thus, they
are prone to crack as the cell sbcks must be placed under co,llp,~sion to effect intra and inter-eell
sealing to prevent reactantgas leakage. Graphite plates have low thermal and elecl- ical conductivitywhich
gives rise to hot spots and dead spots. They are also difficult to manufacture. es~.e ~ "y the gas
distribution cl~anr,~ . The stack output is relatively low, on the order of .03 kW/lb. In the example cited
above, the number of inactive cooling and hurr.~ ;ol) cells almost equals the number of active
el~LIucl,~,ical cells. This effectively doubles the number of g~cl~lecl seals required in a stack thereby
d~l~asil Ig stack reliability and pel ~ul-llance.
The aforementioned US Patent ri,316,869 does not offer a solution to graphite plate cell stack
design as it is con~;ell,ad with ",hilu,ulucessor control of a closed loop system extemal to the stack.
Accol ~lil ,gly, there is a need for an improved fuel cell design, and I II~U lods of producing the fuel
cells and ope, c,~ion thereof which overcome limiting pl u~ '~ lls of the prior art.
Dl~ OslJRE OF INVENTION:
sllr~1ARy: The invention is directed to improved fuel cell stacks constnucted from a plurality of cells,
each co.,.,u,isi..9 a series of i.lLt~ laled, plastic, ceramic and metal platelets having illl~yldL~I fluid
I l la. ,agel I lent (IFM) features. The invention also includes methods for design, construction, platelet feature
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forming~assemblyandbondin9oftheplateletsintomodularpolarselJdldlola(~llhst~kcellassemblies)~
and ..,~II,ocis of op~dLion of fuel cell stacks employing the Illl~ldldd Fluid Ma"ag~",ent TechnGlo
(IMFT) metal and plastic platelets of this invention.
While particularly ~iic~oS~ as ~PF'-- '~ to proton excl,~ge membrane (PEM) fuel cells
employing H2 and Air/02 as fuel (whichever is most app,up,idld), the l~ch-l, ~os of this invention are
equally applicable to alkaline, molten l.;dl i~ordle and solid oxide type fuel cells, and to reformers used in
conjunction with fuel cells. A wide variety of other fueVoxidizer comb ndlions may be employed, such as
NH3/02; H2/C12 H2/Br2 CH30H/02. and the like, it being IJ"de alood that .~e,~ce to ~2 includes Air.
In referring to ~fuel cells~ herein. it should be u, .d~. alOOd that temm includes one or more unit cells, each
of which cu,..p.iaes a bipolar sep~dlù, plate (BSP) in contact with an app-upridld cle_t.ude mernbrane
(EMA) as an assembly and includes stacks of unit cells lt~---;, aled by current ce" ' plates.
The fuel cells of this invention are constructed of one or more cells, each cell of which in tum
c-olllpliaes a pair of bi-polar sdpdldlul plates (BSP) sandwiching an elecl.ude membrane assembly (EMA)
11 ~~l~b~we~. The sep~dlu- a may be either unipolar (for the terminal end plates) or bipolar, with one side
being the anode (H2) side and the other the cathode (~2) side. In tum, each unipolar or bipolar sepa. alul
assembly of this invention comprises a fluid ,..d..ag~---enl core assembly (FMCA) sandwiched between a
pair of mic. uacl ~n plates (MSP). Each of the core asst~ ~-bly and the ~--;~- USLI ~dn plate may be made of
a plurality of pl-lF~ in contact with each other, and pr_.t~,.dbly bonded as a unitary whole. The
~.,ic.usc,~en plate (MSP) functions as a current cc"~ to pass eleu~-uns to edge conductors (bridges,
tabs, spring clips, edge jumpers, pleated conductive current bridges, edge bus bars, and the like) and/or
to intemal bus bars, and is constructed of current conductive material, such as metal or conductive plastic.
The ~--ic-osc.~" plate may be of window frame design, with a ,ecessed or inset central section
surrounded by a posilior .9 frame. In bus barembodiments, the window frame may be of non-conductive
material, such as plastic or ceramic. while the screen is conductive. e.g., conductive plastic, metal,
graphite, metal i...prt yndled graphitepaper. orthelike. Bytheterm l,.ic.uac.~n, wemeananysheet-like
construction which permits distributed flow ll ,e~ ~tl " uugh of a gas, such as a pe, ~u, dled, drilled, woven or
non-woven sheet material having very small holes or p~CC~g,oc 1 hdl~lhl uugh.
The fluid ",a-.dge..-ent core assembly (FMCA) colllplia~:, a plurality of thin plates, p-~i~ ~dLly of
non-conductiveplastic,ceramicorothersuitablematerialintowhichnumerousintriCatelnicluyluuvefluid
distribution cl ,a. Incla have been fommed, preferably by compression molding but also by injection molding,
laser ablation or cutting, embossing, solvent etching. pressing, sld. ,.F ,g or other pressure p, oceases that
create through-and-partial-depth features. Adjacent plates, each having coo- ,Ji- ~ale partial depth features
(e.g., half-cl .a. .nel~i), upon bonding provide gas, coolant and vapor distribution channels, typically round
or oval in cross section which, by virtue of their continuous, sinusoidal and b- dnLI 1' Iy configurations are
~ ollldl~ .c illlpc~- ' ' to constnuct. Platelet fluid ",anage",ent circuits are constructed from depth and
through features. Combi"alions of these features are used to create flow fields, close-outs. man ' ~ '~
vias, via bases, clldllllcl~, filter elements. metering orifices, mixers, splitters. diverters, lands, islands,
NACA ports and Coanda-effect fluid control circuits. The p, _~ d material of the FMCA is plastic, hence
the ~ nce herein to plastic platelet fuel cells. These plastic FMCA and MSP window frame pl~t~letc or
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assemblies also may be constructed by laser photolithography, in which a laser beam impinges on a
monomer or prepolymerto photopoiymerize the monomer to a hard stnucture. Iayer-by-layet i"~ " ,entally.
This teL;I " ~ ,~e can be used for individual p'~t~l~ts or to build the entire FMCA so that individual platelet
bonding is not required, but the mi-.,uyluu~es and cl,annel~ are constructeci internal to the FMCA in the
process.
When two uni-polar sepa dlu,a are assembled with an EMA II,~bel~Neen it co",p,iaes an
01~l.ucl.emical cell. An array of aligned cells. when secured together by bonding or clamping, and
oplion 'ly including sealing gaskets between cells. cc"-,p~isea a fuel cell stack, a finished fuel cell.
In typical examples, the number of platelets to fomm an individual Cell Polar sep~ dLùr s~ ss~ bly
of the overall fuel cell stack may range from 3-10 plates, and pl~dbl;~ 4 7. EMAs are ~ uos~ b~
aLijdcent polar sepa dlu~:" and p-~f~.dl ly are inserted in anode and cathode ,ecesses therein. rhe
presently prdre,, ~d EMA comprises a 2-17 mil thick perflournsl 'fondled membrane coated on both sides
with a mixture of microfine Pt-black and carbon black in a solvent, and overlain on each side with a 10 mil
thick 65% open graphite paper having a Teflon hyd- ophobic binder therein.
The IFMT fuel cell p,;" ~ 13~ of this invention will be des-,,iLed herein, by way of ~,~d-"ple only, in
r~rdl~ce to a bipolar hydrogen/air or oxygen fuel cell employing a Pt-black/NAFlON EMA, ope, dLil ,9 in
the l~"pe,dt-Jre range of from 70-115C.
An important feature of the plastic platelet design of this invention is that 5iyl ,if,c~ IL improvements
are made in thermal "-a..ay~"~l and in hul~l- ~- ~ " ~ of the gases and electrolyte ",~--,b,dnes to very
siyl .ifi~;d"lly improve the power output of the platelet fommed fuel cell of this invention as co" ".~ ~ to the
prior art. In a p, ~,f~., ~ ~, Ibod~. "enl, the surface conduction tcurrent .. - " ~ ' ) platelets are constructed
of metal, typically aluminum, copper, ! ' ' I' 9 steel. niobium or titanium, and the fluid " ,~ ,ayt:",ent core
platelets are constructed of plastic, typically filled or unfilled plastic such as: polyc~ Londle, polyamide,
polystyrene, polyplefin, PVC, nylon, or copolymers, terpolymers, or the like, thereof. The metal r' ~-
provide surface conductivity leading to edge conducting current bridges or through-conducting bus bars.
The metal surface platelets surround or sandwich the plastic core fluid m dl ,as~" ,ent ~' ~ " The metal
current ~c~'~ 'c - platelets can be evated or treated, e.g., by nitriding, for co"uaiun ,eaisld"ue, after, but
pl~:~d,~y before assembly into the BSPs.
After the platelets are formed, they are then IdlllilldLiùn bonded tc,rJr,ll,e~ by any suitable
combinationofadl,es;Jc,heatand/orpressuretofomlapolarsepd dLors~ cc~,-bly. TheEMAsarethen
insetintooptionalspecialmembrane~ c~windowframed~p~essiu"s~inthese~3d~dlu~ plates,forming
individual ele~.~, uel ,~, . ,icc,l cells, and a plurality of the cells are stacked to form fuel cell stacks. The entire
stack assembly is then bound under compression to promote sealing. e.g., by through tie rods, nuts and
cor,sLd--L culllplt:àsion devices, to form a unitary monolithic fuel cell sl.ack, with gaskets as required.
A wide variety of solid but porous polymeric proton excbd, lcJe membranes may be employed,
typically s~ lf~ naLed fluorocarbon membranes from Dow Chemical, Asahi Chemical, Gore or DuPont, with
duPont's NAFION being presently p-t~ --e~. The membrane is coated on both sides with a noble metal
catalyst such as Pd, Pt, Rh, Ru, noble metal oxides or mixtures thereof. A ,u- .,~Ç~. I ~ membrane of this type
is available from H Power Corp of '' ~ ;. t" New Jersey. Other types of EMAs that can be used include
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porous thin sheets of carbon or graphite, or catalyst-coated polyimidazole membranes.
While a specific membrane type and manufacturer may provide some improvement in
p~ ru, 1, Idl ,ce, the invention is not dependent on any one type of membrane or EMA. The i, lleyl dled fluid
management leclmoloyy (IFMT), plastic platelet approach of this invention is ~rt~hle to a wide variety
of fuel cell types, and improved pe, ~UI l l ldl ,ce will result therefrom .
The plastic platelet technique pemmits fomming a wide variety of ",i~-ucl,a..nel designs for any
exterior configuration of the fuel cell. yet with ~,~ " IL themmal eAC hdl ~ye and humidity control for more
efficient distribution of the gases with no fuel or oxygen starvation and better steady-state r;lecl, ical output.
An important advantage in the IFM plastic platelet lech,)ology of this invention is that the
manufacture of the fuel cells can be aulull-dl~d. and emptoys high rate ph_'L' loy,duh;c, etchlng,
p,~si"g, elllbossi~g or sld,, ,9 lecl-nuloyy to ~dLIlicale platelets from thin metal and plastic sheets,
typically4to40milsthick. C.,,bossi,.g,comp-t~siùnmolding.injectionmolding,ornumericallycùnl..''
milling is plt r~ IdLJly used to rdLIicdle the plastic (FMCA) core p~t~9t~
A siynir,c~" industrial apF'- " ty and lech" - ' advantage arises from the fact that the IFM
platelet lechncjloyy pemmits rapid changes to be made in the sepdldLor ~ s~ bly design using
phol 'i ,og,d~b lecl", ~PS bothwithrespecttoPlasticandmetalp~-te'~ Asinglefactorycansupport
a wide range of fuel cell designs without the need for high output c", ~dlily recJuired for production
econo",y. That is, fewer fuel cells of widely different design can be produced and still be econG" - '~
feasible. In addition, the capital invesl",~nl is sub~la, ' lly and s;y" ~lly reduced as the production
eql i",e"l is close to off-the-shelf ph3~c' ,oy,dphic, masking, and etching or sldl"p;.,g ec~uipment.
By way of exam ple of the ph ~c ' ' hoy, d~hlc u printingU process, the multiple sheets of a se~.d, ~
can be accurately yl dp~ 'y desiy"ed in large fommat, pholoyl d,ul~ ~ 'Iy reduced, and the plates ~ "ped,
embossed or co",p,t:ssion molded out of continuous rolls of metal, plastic or conductive plastic sheet
material. Altematively, and in the present best mode, the current c ~ "r. metal sheets are
ph-- "'hoy,d~ 'lymasked with resist. etched to fomm the fluid Illa lag~l,entmicro-grooves~ the photo-
resist mask layer cl ~", i~ - ~'y or physically removed, and the platelets cleaned. Plastic core (FMC) p~:~t~let~
are formed from sheets of plastic stock by compression molding. Alternatively plastic core pl~3t~4t~ can
beformedusingrollerembossing,injectionmoldingor~ldlllr ,9. Preferablythetoolingfortheembossing
or comp,~asiun molding can be ph ~ loyldpl 'Iy etched in metal as described above with negative
instead of positive masks, or vice versa.
The finished platelets are then assembled to fomm the sepdldlul-~i, placed in a lamination bonding
oven having a pressure ram and ld~ dled together under a specific schedule of heat and pressure to form
a monolithic composite sepdldlul plate s~h~sPmbly having conductive surface features and intricate
intemal plastic FMC mic, ucl)annela~ including channel~ at different levels o, ll ,ogonal to each other, through
which the various gases and water or other coolant flow. Lamination bond aids such as adhesives,
solvents or glues may be applied to the surfaces of the plastic and metal platelets to facilitate bonding and
sealing. The specific choice of metal and core plastic dictates the particular choice of bond aids used, if
any.
The metallic surface.platelets may be treated with specific chemicals to fomm a passivating or
--5-
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anLiccl I usiveand conductive layer. In the preferred embodiment, titanium micl osw ~, platelets are placed
in a nitrogen atmosphereat elevated temperature which resuits in the reaction of nitrogen with the titanium
to fomm a passivating or an anti-corrosive and conductive titanium nitride layer on all ~Yposed surfaces,
including the interior gas and water cl~annels.
Platelet polar sepd,dlo, design and production can be done on a continuous production line,
~, 'c ,- ,c to a PC-boara manufacturing iine. The EMAs are then inserted between individual BSPs, the
cells then stacked, and exterior end plates added to form the completed fuel cell stack which is held
together under pressure by tie rods, and nuts, or other co, Isldl IL compression devices, to effect reactant-
tight sealing. Electrical leads, reactant gases and coolant water are hooked-up, gas and/or fluid fuels
introduced, and the cells brought on line.
In a typical 4-platelet IFMT bipolar sep~alo- c~ Ib~ hly of this invention, there are 4 different
plates, with plates 1 and 4 being joined by a current bridge, and each of plates 2-3 being different. The
platelets in sequence are:
1. Anode metal . . .ic. us~,- ~n platelet (to provide current conduction from the EMA);
2. Anode plastic flow field platelet (to provide anode flow field distribution, anocle
reactant humi~liri~ inn and cathode water circulation);
3 . Cathode plastic flow field platelet (to provide sepa ~lo. /cell thermal ~ - ~anage. . ,e, .l,
cathode flow field distribution, cathode reactant hu,..;d r~ n,- and anode watercirculation; and
4. Cathode metal ...ic.osc.~en platelet (to provide current conduction to the EMA);
Intheedgeconductionembo~;,..entthetwo,--ic,uac-~en -"~ plateletsarejoinedbyatleastoneedge
current bridge to effect electron flow from anode to cathode.
The current carrying capacity of the current bridge may be augmented by one or more current tabs
that are folded over and ela ;l- lly bonded to effect elect, ical conduction thorough the sep~ alor.
In the bus bar embodiment, the two ...icrc,s...~en ~ ,t~ platelets are joined by at least one bus
bar, preferabiy two, passing transversely t~rough the FMC separator to effect electron flow from anode
to cathode. There is at least one, p- ~le, dLly two, bus bars that are elecl, 'ly bonded to the anode and
cathode ll~iCIu5CIwn platelets and occupy positions with in the plastic core platelets to effect ele~l.icdl
conduction thorough the separator.
The details of platelet fommation, described herein by way of example, are shown to evidence that
there is no Illil..lUI~:IIdllllt:l collapse or in-fill during the cell Id..-inalion bonding process.
In the two bipolar St:~dldlul examples above, plates 1 and 4 are each about 12 mils thick and
plates 2 and 3 are each about 35 and 45 mils thick respectively. Upon lamination bonding the plates
compress somewhat, and the total ll lichl ,ess of the resulting monolithic: bipolar sepd, dtur laminate is about
1 00 mils.
For embodiments incorporating a wrndow frame de~ sion to receive the EMA, the anode and
cathode recess depths are on the order 11 mils deeP to accommodate 11 mil thick EMA graphite paper
el~l,udes. The total EMA tl k..ess is on the order of 26 - 30 mils thick depending upon the choice of
graphite paper elecL-udes, catalyst ink and membrane II.;~.h.less and is somewhat compliant. The
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p~ d DuPont NAFION mem~rane coated on ~oth sides with the microdispersed Pt-black catalyst in
carbon bic-Ck~ is on the order of 4-5 mils thick and each of the outer graphite/teflon paper layers is about
11 mils thick. The graphite paper is on the order of 65% open to provide good and uniform reactant gas
distribution. On the anode side the graphite paper conducts el~-l~ un5 away from the catalytic reaction
sites on the electrolyte membrane to the lands of the separator plate for draw-off as fuel cell el~il,ical
output. Electrons return from the extemal circuit via the cathode. On the cathode side graphite paper
conducts elecl,uns from the lands of the sepdldlor plate to the catalytic reaction sites on the el~l,ulyte
mem~rane.
The fuel cell multiple bipolar sepdl dtOr stack must be temminated at each end with an anode and
a cathode unipolar sepd-dlo~ terrninal end plate which also serves as the terminal current cc"e ~ " ~. For
the unipolar anode sepdldlol we use: an anode ,.,iL;,usc,~n (platelet 1); an anode flow field plate~et
(platelet 2); and a one-sided cathode platelet. i.e. the cooling circuits of the cathode flow field platelet
(platelet 3) with the cathode flow field circuits closed out. For the unipolar cathode s~pa,dlu- we use: a
one sided platelet i.e.. the anode flow field platelet (platelet 2) with the anode flow field closed out; a
cathode flow field platelet (platelet 3); and a cathode ..,i~;.us.i.~ an platelet (platelet 4). In both the edge
conduction and bus ~ar through-conduction embodi,--anl~ the temminal end plates conduct ele_l.i,;al
power to the extemal load. Both embodi(,-arls may use terminal end plates of similar design and
construction.
As an altemative example where no reactant gas hurr~;di~c~ n is required a 4-platelet bipolar
sepd,dlu, assembly may be employed and the sequence of platelets is as follows:
Anode metal mic-,u:,c,~n platelet (to provide current conduction from the EMA);
2 Anode plastic flow field platelet (to provide anode flow field distribution and
cathode water circulation);
3 Cathodeplasticflowfieldplatelet(toProvideSePd,dlu,/cellthemmal,,,d,,ag~,,,anL
cathode flow field distribution and anode water circulation; and
4 Cathode metal mic,osc,~" platelet (to provide current conduction to the EMA);
As with the two previous 4-platelet ,. ,s current conduction is accomplished using the edge
conduction or bus bar conduction me~;hanh",s previously desc, il.ed.
The assembled sep~ alOI (multi-platelet sub-assembly) is on the order of 100 mils l h hl ,ess and
weighs around 3-6 oz (85-170 grams) depending on the number and thickness of plates and materials.
Ap,~lu~illla~!y 10 sepdldlul~kw are used in a cell stack. Completed bipolar sefidldlul plates are
assem bled with alle" Idlil ,9 EMAs on tie rods to effect alignment and com pression. After assembly on the
tie rods, comp,~ssiun endyldleS on the order of 1.5 inches thick are applied and the entire fuel cell stack
assembly is placed under compression of 50-200 psi by threaded tie rods to fomm the monolithic fuel cell
stack. The cell operating pressure of 1-65 psi is easily achievable with output at around 70-150 amps at
a voltage detemmined by the number of cells. To seal adjdce"l sepa dur sub-assemblies an inl~l lockil lg
sealing ridge (which is generally triangular in cross section) on the order of 1-2 mils in height is etched
pressed or molded onto the sealing surface (outside surface) surrounding IlldnifGl.ls and flow so that the
ridge will fully interlock with the mating seal ridge of the adjac~,L se~d~dlu, sub-assembly or with the
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app.uprid1e temminal endplate. as the case may ,~e.
The fuel cells of the IFMT platelet design of this invention can include a refomler section to provide
H2 e.g., via the steam-shift process employing an unde, w~idi~ d bumer plus steam to produce H2. ~2
and C02. Any other hypocarbon refommer may be employed in combination with the IF,MT platelet cells
of this invention.
A key feature of the platelets of this invention is the use in CUII t ~ ~dliUn of gas and water
distribution cl~dl)l.el~ fommed in co"~ o"di"g aligned half chdlll.cl~ in each of a pair of coo,di Id1e
opposec~ mating plate faces (i.e. mating faces of acljace, 11 plates that face each other and contact each
other in the stack) and similarly formed delivery 1"~ - Optional but ,sl~r~ d are formed sealing
rir ges on the periphery of the plates to assist in sealing adjacent ceil ass-"
Critical to efficient high-output operation of PEM cells is proper thermal balance arld hydration, and
controlthereofbyunifommgasflow. CurrentPEMfuelcellsexhibitp,l ,sofpoorthemmal",~.age,..e.~l
and water balance low graphite conductivity and ductility limited - : y and excessive reactant
Proper themmal ",~,ag~",e,l1 in PEM cells is critical. The p-~-~l membranes have a
maximum op~ dling lt:" ".~ dlure in the range of 9~98 C. since temperatures above that permanently ruin
the membrane by dd ll _ ,9 the ionophoric pore stnucture. Since the IFMT plastic platelet fuel cells of this
invention have heat ~ ,~,;h~ ,ge,- sections i, ll~ yl dl~ d in each bipolar sepd, ~llor as co,~ Ipdl ~I to one bet~veen
every 4-5 se~pd~ dlOI a in graphite PEM cells our stacks can be scaled easily to larger sizes since both the
heat g~ ,e,dliun and control (heat t:AC hcu)ge) scalewith area. Since we can easily tailor heat control to each
type of m~:- "~, dl ,e and fuel, and the intra-cell location within the stack we can ernploy higher p~ ~u, " ,ance
EMAs resulting in higher power de"siti~s.
In regard to water balance the il lley- dl~d hul l ~ ;on in eacll sep~ dLu, maintains better water
balance as each is individually varied to acco" " "o~l~le the different req- i ~" ,e"Ls of the anode and cathode
sides of the fuel cell. Water is removed from the anode side by electro-osmotic pumping through the
membrane and reactant gas flow drying. Water builds up on the cathode side from the throughput of the
electro-osmotic pumping and production o~ reaction water which are both removed by airt ~2 gas flow
drying.
In contrast to graphite PEM cells the composite metaVplastic IFMT sepdldlùl~ of this invention
are some 3~ times more conductive thus reducing the 12R losses in the stack under high current de"sities.
These losses reduce voltage and power o~: ,dL,le from the stack. The lower intemal ~is1d"ce of the
composite sepdJ dlUI a provides a more even distribution of current thus reducing the build-up of hot spots
and dead spots in the cells. Graphite sepdld1ula are placed under compression to effect sealing, but
pressure affects the . ~:~i;,1ance of graphite in a non-linear fashion. This cl ,~ d~ l islic makes it very difficult
to produce graphite cells with unifomn output. In contrast composite separators have excelle. ,L themlal
and clc~1, ical conductivity which reduces hot and dead spots.
Graphite is porous to H2. ~2 and a~ which reduces the ch~.llicdl efficiency of graphite stacks
because some H2 is consumed in non-productive. sometimes destructive direct oxidation. To overcome
the porosity of yl dpl, ~ . nonconl uctive plastic binders are used which further dec, ~ases the conductivity
of the sep~1ù, plates. t~nother commonly used a,up~uach to reducing graphite plate permeation is to
W~;nTUI~ SHEr ~E 2~)
CA 02220901 1997-11-12
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make the plates thicker but this adversely affects electrical and the. .,îal conductivity.
Graphite se~dldlula also crack when the cell is subjected to comp,~asion to effect the sealing
necessary to prevent gases leakage. as the cells operate at 1-60 psig. The tende",.-y to crack severely
limits the number and size of the cells in the stack. Where one or more sepd,dlo.s on the interior of the
~ stack develops leaks the t:le~ al output is co,.,~,u",ised or siu,l;"ca"lly reduced. Composite
metaVplastic p'~t~le~c being ductile do not present these problems.
Further it is an important advantage of the invention that the IFM technoloyy of the invention
permits variation of intra-stack platelet design to effect better themmal management. That is the cells in
the middle of an uncooled stack do not have the same themmal env;- u~ ~n ~dnl, and aCc~- di~ Iyly not the same
hurn;cl;r~ n rec;uirements of cells at or nearer the ends of the stack. The platelet design, in temms of
relativeanode~cathode~coolantandhlJlllid;ricA~ lllicluLllanneldesigncanbeeasilych~lgedandintra-
stack position defined to accG----.-odate the various yl_ ~la within the stack. i ~k ..;~c stacks can be
desiyned to suit a wide variety of extemal conditiùns an arctic design differing from a troplcal and a
subsea differing from a space design.
This advantage of flexibility of design--the c~p ' y to tailor the configuration and path lengths
and channel widths of mic-, u. l Idl 11 ICI:~ in each zone of the Sepdl dlUr (anode cathode heat e.~cl ,al ,ge and
hu..,i~l;fin~lio,,)andfromsep~dlù~ tosepdldlol (celltocell)p,uyressivelyand individuallywithinthestack
to acco,-,..,odate the intra stack env;-u-"--elll and y,dd;cnla--results in ease of scaling to higher power
outputs e.g., on the order of greater than 50-1 OOkw.
The series/parallel serpentine channel design provides more unifomm distribution of the reactant
gases. Thisisparticularlyi".po.ld,.linprovidings;y.,;'i--dnllybettercathodepe,ru,---~,-cewhenoperating
with Air due to ~e~ ~f ~2 as the air travels through the clldllll_ls. In current channel design, air
enters ~2 rich and leaves ~2 cl~ . since the ~2 is consumed in the cl~cl-uche--,ical reaction. The
same f~Apletion effect is true of H2 resulting in i"..,t:asi"g conce"l,dlions of impurities relative to H2. In
our invention the shorter series of cl Idl InC13 11 ,an;rc Ided in parallel and the ability to design and r~des;y"
Ch~)~ ,el ~ of varying configurations or graduated width improves cathode kinetics a currently dc,l l ,i. ,~ ll
limitation of current fuel cells. In our invention the flow is divided into a series of parallel circuits in which
the precise pressure drops can be obla;. ,ed. By i". ~t:as;"g the number of parallel circuits the pressure
drop can be lowered as the flow rate is reduced and the channel side wall r, i~lional effects are reduced
due to shorter path length.
While the currently p,t:rt~ d best mode of the invention employs window frame pl~teletc with
EMAs of carbon paper over the catalyst/carbon-black coated membrane to provide a highly porous sheet
having random gas distribution cl-ann l, there throughl an important altemative embodiment of the
invention employs a carbon-paper-less membrane wherein microfine holes are etched through the
~window pane area of the window frame to effect the same gas distribution function. In producing the
window frame plateletl the window pane area is defined in the apprup, iale medial areas of the plate that
is located interiorly of the outer plate edges. (Lines defining the pane area may be through-fomled except
for a few thin bridges holding the window pane section in place during platelet rdL,ricalion. The bridges
are later cut and the pane removed or let fall out to complete the window frame platelet.) The open areas
CA 02220901 1997-11-12
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receive the carbon fiber paper upon compression of the full sheet membrane between adjacent rll~tF~l~tC.
In the altemate embodiment, instead of removing the window pane area material, a "window screen" area
is created in the window pane area by micro-fine through fomming, the holes being on the order of 5000-
1 0,000/sq. inch. Then carbon paperless membrane is co" ,p, essed between the adjacent sepd, alOt plates.
Objects and A~l.d,.la~a. It is among the objects and advantages of this invention to provide an
improved fuel cell design and methods of constnuction and operation, particularly plastic platelet fuel cells
of the hydrogen an~ oxygen or air tyPe designed with IFM features which show 3X or better improvement
in cost and pe, ru",.a"ce over currently available graphite cells.
The improved fuel cell stacks of the invention have the advantage of employing plastic platelet
s~paldlula, which platelets have specially configured gas and water distribution mic.u(.hdnncls created
by COlllpl ~aaion molding, injection molding, t:lllbossil ,g, etching, laser ablation or cutting, or aldl llp 19.
It is another object to provide improved cc""posiLe bipolar and unipolar sepdla~ul plates and
methods of constnuction having the advantage of construction from plastic fluid l.,dn~r",ent platelets
which are e,)closed by conductive rlli-,luScl~ll current sol'-~ tL - platelets of metal or conductive plastic.
Another advantage of the IFM plastic platelets of this invention is that bipolar and unipolar
sepd dLo, plates constructed therefrom exhibit improved current c~ by use of one or more edge-
conductive current bridges and/or through-conductive metal bus bars.
It is another object to provide an i, lleyl aLed process for manufacture of fuel cells via a plurality of
stackedse~c,a,dLu, plateassemblies,co",p-iai-,y. ph:' ' ,oy,a~.hyofaseriesofindividualmetalliccurrent
, p'-te~ets followed by feature fomming thereof by etching ~cl-e",ical milling), pounding or
s~ r ,9. and oplior 'Iy coating the metal current ~-"'L platelets with an ~ILiUAid~lL, fcllc~ by
co,-,,u,~ :s ion molding, etching, stamping, or injection molding of core plastic fluid ",andy~".ent r~ -~PIetC
and Ll ,e, edtLer assembly of the metal and plastic platelets into sepa, dLor stacks; and then low temperature
la",i"aLio,) bonding of the co",posiLt:unipolar or bipolar sepa,dlol platelet stacks under heat and pressure
schedules with the advantages of low cost, ease of manufacture, and rapid design change to suit power
demand needs.
It is another advantage of the invention to apply i"Ley,al~d fluid management (IFM) to fuel cell
stack design, particularly to the design of plastic, conductive plastic, plastic and metal and cu",posite
platelets assembled into unipolar or bipolar sepdldlul~ (individual cells), and plural cells into stacks, to
improve fuel and oxidant gas hu" ,i. l~r,~ " and distribution for contact with the membranes, and for heat
and humidity control to prevent hot spots and membrane deg,adalion due to dehydration.
It is another object and advantage to provide !~hC ' ,oy, ~pl~;c~lly and Lh~:l 1 l ' 'Iy milled tooling
for comp, ~sion or iniection molding of plastic platelets employing IFM pri"c;~.les. It is another advantage
that the IFM designs of plastic platelets of the invention can be rapidly produced by any suitable sheet
plastic p,ucessi"9 technique, including injection molding, stamping, solvent or plasma etching, and laser
pl- _: ' ,ography in a suitable monomer or prepo~ymer bath. It is another object to provide com p, essiu, -
or injection molded plastic platelets for fuel cell separator assemblies having special sealing ridges which
have the advantage of pe- " lillil ,9 good sealing of EMAs between polar sep~ alul ~ to fomm cells which are
then secured under co",p.~:,SiO,l to fomm fuel cell stacks.
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It is another advantage of the invention that IFM clesign principles permit rapid design redesign
or ,-,oA-~c~l;on of platelet polar sepdldlula which include i"ley,dled reactant humid;ri~ n thermal
,and~e",ent, and reactant flow and distribution control within a polar sepa,dlu, formed of a plurality of
plastic composite or conductive plastic platelets bonded into a monolithic unitary stnucture. It is another
object of the invention to provide variable IFM platelet polar se~d, dlor design within a fuel cell stack with
the advantage that use of a plurality of different platelet and polar 5~dlul designs within a stack can
acco",l~mûdate the differing thermal envi,o""~enl and humi~lir~ n recluirements that are intra-stack
position dependent. Still other objects and advantages will be evident from the desc, i~tion drawings and
claims of the invention.
BRIEF DESC~lr I l~t~ OF DRAWINGS:
The invention will be des-;,iL,ed in more detail by r~fe.~"ce to the drawings grouped by
suL,~ ~ ,gs i.l~:nliried below.
General Fuel Cell, Sepd-alu-;- and Plat~let~.
Fig. 1 is a sche~"alic section view through a fuel cell stack employing plastic/conductive IFM
plateletbipolarsepa,dlu,aembodyingtheprinciplesofthisinventionparticularlyadaptedforoperationwith
H2 and Air/02;
Figs. 2A and 2B are schematic section views through a cooled, non-humidified (Fig. 2A) and a
humidified (Fig. 2B) and cooled fuel cell IFMT platelet sepdldh)l of this invention showing the wide variation
pss- '~ in number of platelets used;
Fig. 3 is a sch~",dlic cross section detailing elecl.ude membrane dss~",bl;~ constnuction with a
part r~;r 'c de 5 away;
Fig. 4A is a schematic of the fluid circuits for an illl~yldl~d humidity and thermal ",d"age",ent
bipolar St:~dldlOI of this invention;
Flg. 4B is a schematic of the fluid circuits for an i"t~, dled thermai " ,~u ,age, ~ ,ent bipolar se~ dlO
of this invention;
Fig. 5 is a s.~ " ,alic drawing of the ele~ll uLl~emBll y of a PEM i~ lleyl dled humidity and thermal
."d"agt:",ent fuel cell of this invention;
Figs. 6A and 6B are diagrams cullLld~til,g single level depth and through features formed by
chemical etching of metal (Fig. 6A) with multilevel depth and through features fommed by CGIllplt:55h~n or
injection molding of plastic (Fig. 6B);
Fig. 7 shows a plan view of a metal conductive plastic or m ~ - ~ plastic current ~ having
first (upper) cathode section joined by an edge conductive current bridge (lower section) in which the
screen apertures are slots;
- Figs. 8A-D depict typical but not exhaustive hole patterns for metal current . ~ ~ 1 l liC-I uSCi ~n
Fig. 8A being hexagons Fig. 8B et~i, sqids Fig. 8C dlltllldlillg inverted Ts and Fig. 8D
~ alt~., Idlil ,g inverted interleaved chevrons;
Edge Conductlon Blpolar Sepd~alor Plate:
Fig. 9 is an ~Yp'oded iso",el, ic view of 2-cell sub-assembly for a fuel cell stack made from edge
1 1
SUIlSrl~UlE S~ ~LE26)
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conduction bipolar se~a, dLul ~, with window frame and with i~ gl dlecl humidity, therrnal and reactant flow
field ll,a.lage---ent of the invention in Figs. 10 and Figs. 11A-G;
Fig. 10 is an ~ lo~l~d isu,~ . view of one t:---bodL..ent of a 4-platelet CGIllpOSile edge
conduction bipolar sep~ dlor with window frame and il It~gl dl~d humidity, thermal and reactant flow field
management for an IFMT fuel cell sep~dl~" of this invention;
Figs. 11 A-G are a series of detailed plan views of the em bodiment of a 4-platelet edge conduction
sepdldLur of Fig. 10 in which: Figs. 11A-C depict a double ~"i-,,usc,~" platelet with the front side of the
anode mi~;-ua-,reen at bottom and back side of the cathode ll,i.;loscl~en platelet at top (,~ t~ ,ta 1 and
4), cu, ,n~led by a single bridge.
Fig. 11 A is a front view of a single current bridge double mic- usc- ~n platelet with window frame
an inset detail depicts one e-..bodi,..~-~ of a typical ,-.ic-u~c;-~- hole pattern;
Fig. 11B shows the double mic.u~c-~n platelet of Fig. 1lA and coll~spondi.l~J section views;
Fig. 11 C shows a double mic. usc- ~:, . platelet without window frame and corresponding section
views;
Figs. 11 D and 11 E are front and back sides, respectively, of the plastic anode flow field platelet
(platelet 2);
Figs. 11 F and 11 G are front and back sides, respectively, of the plastic cathode flow field platelet
(platelet 3);
Fig. 12 is an t., 1~ iaOI I leLI ic view of 2-cell sub-assembly for a fuel cell stack made from edge
conduction bipolar sepdldlola, with window frame and with illl~ldl~ themmal and reactant flow field
,ana~,l,ent of the invention in Figs. 14A-G;
Fig. 13 is an exploded isometric view of one embodiment of a 4-platelet composite edge
conduction bipolar sep~dlc~l with window frame and illleyldl~d thermal management and reactant flow
field l"anage",ent for an IFMT fuel cell sepdldlol of this invention;
Figs. 1 4A-G are a series of detailed plan views of the embodiment of a 4-platelet edge conduction
sepdldlul of Fig. 13 in which:
Figs. 14A-C depict a double miclusc;l~en platelet with the front side of the anode Illicr~.acr~en at
bottom and back side of the cathode mic. ua-,-~n platelets at bottom (platelets 1 and 4) COI Inecl~ by a
single current bridge; an inset detail depicts one embodiment of a typical mi-;lusc-lt en hole pattern;
Fig. 1 4A is a front view of a single current bridge double ~ - -i~,- us.il ~, . platelet with window frame;
Fig. 14B shows the double ~ ;lua~;l~l I platelet of Fig. 14A and corresponding section views:
Fig. 1 4C shows a double ,. Ii~;r~scl e~n platelet without window frame and co" t:sponclil 19 section
views;
Figs. 14D and 14E are front and back sides, respectively, of the plastic anode flow field platelet
(platelet 2):
Figs. 1 4F and 1 4G are front and back sides, respectively. of the plastic cathode flow field platelet
(platelet 3);
Fig. 15 is a detailed plan view of a micloscl~en platelet having multiple current bridges and/or
tabs;
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Fig. 16 is an ~Y~ de~ i~o"~ ic view of one em~odiment of a 4-platelet composite edge
conduction bipolar sepd,dlu, with window frame having four edge conduction current bridges and
featuring h lleg- dled humidity themmal " lal ~age~ ~ent and reactant flow field management for an IFMT fuel
cell septD alur of this invention;
Bus Bar Through-Conduction Bipolar Sepd, dlo- Plate:
F~g. 17 is an PYrlocled isometric view of a 2-cell sub-assembly for a fuel cell stack made from bus
bar through-conduction bipolar sepd, dlol ~ with window frame and with i"ley, aled thermal and reactant
flow field ",d"agt:",ent of the invention in Figs. 19A-G;
Fig. 18 is an ~Yr'~ded isometric view of one embodiment of a 4-platelet composite bus bar
through-conduction bipolar sepd,du, with illleyldled humidity thermal and reactant flow field
.na. !ag~..,e, ll for an IFMT fuel cell of this invention;
Figs. 1 9A-G are a series of detailed plan views of the embodiment of a 4-platelet bus bar through-
conduction sepdldlu, of Fig. 18 in which:
Fig. 1 9A depicts the anode (left side) and cathode (right) current ~ c mk ~ o~c, ~en platelets
(plat~ lel i 1 and 4) in the lower right;
Fig. 19B is a plan view of the anode flow field platelet (platelet 2) and fragmentary portion of the
anode current ~ n ~-,ic-u:.c.~n (platelet 1) oriented thereon;
Figs. 19C and 19D are front and back sides of the plastic anode flow field platelet (platelet 2);
Figs. 19E and 19F are front and back sides of the plastic cathode flow field platelet (platelet 3);
Fig. 19G is a plan view of the cathode flow field platelet (platelet 3) and a fragmentary portion of
the cathode current ~ ~--ic.osc~een (platelet 4);
Fig. 20 is a e-~,'oded isometric view of a 2-cell sub-assembly for a fuel cell stack made from bus
bar through-conduction bipolar sepd, dlUI ::., with i, ll~yl dLt d thermal and reactant flow field, nd, lagel 1 ,ent
of the invention in Figs. 22A-22G;
Fig. 21 is an ~Yp~ ed isometric view of one embodiment of a 4-platelet composite bus bar
through-conduction bipolar sepdld~cl with i, lleyl dlacl thermal and reactant flow field ",dndye",ent for an
IFMT fuel cell of this invention;
Figs.22A-Garedetailed planviewsoftheembodimentofa4-plateletbusbarthrough-conduction
sepa dlU~ of Fig. 21. in which:
Flg. 22A depicts both the identical anode and cathode current 2C"~ mic,us~-~n F
e~ 1 and 4);
Fig. 22B is a plan view of the anode flow field platelet (platelet 2) and a fragmentary portion of the
anocie current 2-'1~ 1 ,,,ic.usc.~n (platelet 1);
Figs. ~c and 22D are front (22C) and back (22D) sides of the plastic anode flow field platelet
- (platelet 2);
Figs. 22E and 22F are front and bacic sides of the plastic cathode flow field platelet (platelet 3);
~ Fig. 22G is a plan view of the cathode flow field platelet (platelet 3) and a fragmentary portion of
the cathode current ''C'~L ' ~ mic,us~,~n (platelet 4);
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SUBSTI~UIE S~EJ ~RULE ~6)
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Edge and Through-Conductlon Section Views:
Figs. 23A-23D show various altemative constructions of the metal mic,usc,~ ~"e ~ ~ plates
al 1 dl ,ged for edge conduction with respect to the core plastic platelets in the sepa, aLol plates of the type
of Fig. 16 taken along line 23-23 therein;
Figs. 24A and 248 show t~,vo altemative constnuctions of the through-conduction bus bars for the
sep~aIu, p~ate assembly of the type of Fig. 18 taken along the line 24-24 therein;
Platelet, BSP and Cell Fab,icaIlon P~ ~cess~s
Fi~. 25 is a flow sheet of a continuous metal platelet manufacturing process in which features are
formed by depth and through etching;
Fig. 26 is a flow sheet of a continuous plastic piatelet manufacturing process in which features are
formed by co---p-~ss;un molding and cc,-..pc site bipolar sepm~lor plates are ~aiJIicaLed by lamination
bu- '' )g
F~g. 27 is a flow sheet of the process for adaptively rapid ~n~,aIion of the pi ' '--'
al l~hork:, for individual platelet designs in accord with the IFMT principles of this invention.
BEST MODE OF CA~P.~ OUT THE INYENTION:
The ~ ,;..g detailed descli~ tion illustrates the invention by way of example not by way of
I lilalion of the ,u- i, ~ ~ of the invention. This desc, iplic.n will clearly enable one skilled in the art to make
and use the invention, and describes several embodi., lenl~;, a, ~r~ ol l~ a, ialions. altematives and uses
of the invention including what we presently believe is the best mode of carrying out the invention.
Fig. 1 shows in simplified (scl~e,--alic) cross section a fuel cell stack 1 of this invention ~-,~' ,ri--g
a plurality of multi-platelet bipolar s~pa,alo,:j 2A B C and a pair of cathode and anode unipolar end
sepaldlul:,3 4respectively. Protonec~l~angeElectrodeMe"~b,a"eAsSemblieS(EMAs)5A B C andD
are ~ poc~ between the sepa,aIo,a as shown. Air and/or o2 is inlet via ~a~-irold system 6; H2 and/or
other fuel is inlet via r~lal ,iroW 7; and cooling/hum~ fi~tion water is inlet at 8 and outlet at 9.
Figs. 2A and 2B show in schematic section view the construction of one embodiment of
composite bipolar sep~ aIol :, 2 formed from bonded metal and plastic or ceramic platelets 12 for the non-
humidified version of Fig. 2A and platelets 13 for the humidified version 15 of Flg. 2B. This figure also
illustrates the wide variation in the number and types of plates that may be employed to constnuct a
sepalalur by various COlllt' ~alions of depth etching (or feature forming) and through-etching (through
feature fomming) of metal pl~tPlPt~ Plastic platelet features are fo~med by compression or injection
molding. For example Fig. 2A shows a 4-platelet configuration as follows: 12-1 is the anode mi.., ~s~
current ~ ~ " - ~ 12-2 is an anode flow field platelet; 12-3 is the cathode flow field platelet; and 12-4 it the
cathode",i~;,us"~current~ . Themetalanode",i-,usc,~enplatelet12-1 iseleul,i.allycol")e~;l~l
to the conductive current bridge 14 which is ele( l,: 11y co~"1ecled to the cathode mic~u~c~wn current
cc'l~ ' -12-4. The anode flow field platelet is constructed from plastic or ceramic and contains the
features that implement the se"~enIi"e cl~a"nel~ of the anode active area flow field. The cathode flow field
platelet is constnucted from plastic or ceramic and contains the features that illlpl~llelll the se,~e"li"e
~;l ,a, Inels of the cooling water heat ~ g~, and the cathode active area flow field.
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CA 02220901 1997-11-12
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Similarly Fig. 2B shows a 4-platelet configuration as follows: 13-1 is the anode mic,usc,~,l
current cc '~ . 13-2 is an anode flow field platelet; 13-3 is the cathode flow field platelet; and 13-4 the
cathode miL, O5L- ~en current s ~ . ~( . The metal anode mic~ usc, ~n platelet l 3-1 is elr~l, ically co,)nected
to the conductive current bridge 14 which is cle_ll 'Iy co~,ecltd to the cathode ~"ic,usc,~n current
- - - 13-4. The anode flow field platelet is constnucted from plastic or ceramic and co" ,s the
features that implement the serpentine channels of the hydrogen hUl~ r~ on flow field. cathode
~ hurr~ ;ri.-~llion water flow field and anode active area flow field. The cathode fiow field platelet is
constnucted from plastic or ceramic and contains the features that implement the serpentine chdl l, ~ Is of
the cooling water heat e,-~.l ,ar,ge" anode water flow field. air hurr~id;f~ inn flow field. and the cathode
active area flow field.
Fig. 3 is a partially a., - ~ - ~ view of the constnuction of an cl~l- ude membrane assembly ~EMA)
H1 of the type used with this invention. EMA H1 coi,~,onds to the EMA 5 (5A-D) of Fig. 1. An EMA is
constructed from a laminate of a graphite anode eleol,ode H3, anode catalyst layer H4 el~l,l,lytic
membrane H2 cathode catalyst layer H6 and a graphite cathode electrode H~. In typical EMA
constnuction the elecil,udes, catalyst layers and electrolytic membrane are lamination bonded to fomm an
ionically conductive composite structure.
EleCtrOdeSare~d~ljCaledfrOm 9raPhjtePaPer,TOraYTGP-HQ9OtYPjCallYbejn9USed. CGIIIPOS;~
platinum catalysts are dApO i~~~ on the cl~l,ude prior to Idlllilldlion bonding with the ele~llulytic
membrane. Typical catalysts are mixtures of platinum black, carbon black and h~.lluphobh agents.
Car~on black Vulcan XC-72R is typically used to suspend the platinum black. Teflon is used to give the
Gle_tl ude hy~, ophobic p, up~ lies. DuPont Teflon PTFE suspension TFE027 is a typical h~dl upho~h; agent
used to treat el~l,udes. DuPont Nafion~ is the sldnddld electrolytic membrane used in PEM fuel cells.
Lamination bonding of the anode and cathode el~l, ode assemblies H8 and H7 (I ~n~oded away from H2)
pe ;li~ely is '. ~ ~ by treating the Lle~l.udes with a 5% solution of Nafion~ polymer. Lamination
bonding follows a p,~ele""ined schedule of temperature and pressure to effect a polymeric bond
between the electrode assemblies H8 and H7 and the membrane H2.
Bipolar Sepd,alur Scllt:llldliw,.
Fig. 4A is a single cell fluid flow circuit schematic for il lleyl dled humidity and themmal l lla~ ~agt:",e"l
IFM sepdldlola. The sL~ ",dlic is drawn down the center line D32 of the el~l,ucl,t:,.,ical cell. The
ce, llel ,e passes down the center of the electrolytic membrane D2. The anode side of a sepd, dlul is on
the left side la~eled Anode, and depicts the features found on the anode flow field platelet. The cathode
side of a sepd-dlù, is l~ ~ on the right side. Iabeled Cathode, and depicts the features found on the
cathodeflowfieldplatelet. Thescll~:lllali~clearlyshowstheillLeyldlionofsevenfluidmanagementdevices
into a single bonded composite s~:pdldlur. The seven functions are the cathode hU"~ r~ on water
serpentinechannelDlûflowfield~hydrogenhumkJi~ ollserpentinechannelDl8flowfield~anodeactive
area serpentine channel D21 flow field, anode humidir;~ ;on water serpentine channel D14, cooling water
s~",enli,le channel D6 heat ~,~cha,)ge" cathode humid~r~ o-1 serpentine channel D26 flow field and
cathode active area se"Je, llil ,e channel D29 flow field. These functions are co, Inecled using a series of
intemal manifolds. This mecl-d, ~I fluid and thermal i,,l~y,dliùn is a key element of this invention.
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Counter-flow humidific~tinn flow D1 through the electrolytic memorane D2 which is a key element
of this invention is clearly derirtecl by the di~ ~iliundl arrows, t:pn:à~"li"g molecular water flow. Counter-
flow humiri;r~ n is implemented using water on the anode side (referred to as cathode water) to
humidify cathode air (oxygen). By analogy, water on the cathode side (re~erred to as anode water) is used
to humidify anode hydrogen. In IFM fuel cells the electrolytic membrane performs a dual rolls as a
hulllifl;f..~ n membrane and a solid electrolyte.
Theelectrolytic membrane D2 is ionically conductiveto hydrated protons. During nommal operation
protons D3 fommed on the anode are electro-osmotically pumped across the membrane to the cathode.
Protons being pumped across the membrane carry one or more ~coci~t~ water m~-'e ' - causing
anode dry-out during high power operation. Hul~ r~ ~linn of anode hydrogen ",;ligall:s this problem.
Hu".iJ:r~ n of cathode air is also required becauseair is only 20% oxygen and is 78% nitrogen.
Toco,,,~,~nsc.lefortheloweroxygencu,.,posilionofair,cathodeclldlll~ havelargercrosssectionsthan
co, . espond;. ,9 pure oxygen designs. Larger cross sections are required to support higher flow rates while
", , , ~9 . ~afJ. ' ' pressure drops. High air flow rates tend to dry out the cathode which is I l l iliycll
by cathode air h~ r~
Control of the amount of hum ' " - - n is achieved by varying the area ratio of anode active area
to hydrogen humi~l;r;~ n area, and by COIIIl " 19 the ratio of cathode active area to air (oxygen)
hull ''1L ~ area. Typical anode and cathode area ratios are 15% to 24% hur~ r~ n to active area.
Dry hydrogen gas enters the hydrogen inlet D16. flows through intemal Illdl ,ifold~ and feed circuits
to the ano~de hull~;~lir~ lion s~ "li"e channel inlet D17, flows through the anode hUllli~J;rili~lio~l
serpentine channel D18 picking up water vapor (beco",i"g hydrated). flows out the anode h~ ;cJir~ n
se~ ~.enli"e channel exit D19, through intemal _ - " , and distribution " ,~ifol~s to the anode active area
s~".e,-li"e channel inlets D20, passes through the anode active area serpentine cl ,am~el3 D21 where the
hydrogen is oxidized to produce protons and r,l~;l,o,)s, leaves the active area through the anode active
area serpentine channel exits D22, flowing through intemal ~ - 'le ' ~n manifold finally exiting as d ?F '~
hydrogen through the hydrogen exit D23.
Dry air (oxygen) gas enters the air (oxygen) inlet D24, flows through internal Illdllirulels and feed
circuits to the cathode hulllirJ;f~ n s~ er,li"e channel inlet D25, flows through the cathode
hurrli~lifi~liu,)serpentinechannelD26pickingupwatervapor(becominghydrated)~flowsoutthecathode
humid;f..-..l;u ~ serpentine channel exit D27. through internal cc"e ' ~ and distribution manifolds to the
cathode active area serpentine channel inlets D28, passes through the cathode active area serpentine
~hdl " ~ a D29 where the air (oxygen) is reduced by elecll ~ns and protons to produce product water, leaves
the active area through the cathode active area serpentine channel exits D30, flowing through intemal
cc"e ~ manifold and finally exiting as deple~ air (oxygen) and product water through the air (oxygen)
exit D31.
Coolin~}andhurni~l;r~ onwaterentersthecoolingwaterinletD4.flowsthroughintemal,,,~)ifulds
to the cooling water serpentine channel inlet D5, flows through the cooRng water serpentine channel
picking up heat produced as by product of the elacl,ut;ll~lllical lua~iliùns, flows out the cooling water
serpentine channel exit D7, into intemal ",a, lirùlcls, to the hur~ ;r~ n water inlet manifold junction D8,
SUBS~I~TE S~tRULE~)
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feeding the two hurrliclir~ on water circuits. Hot water from the humidification water inlet manifold
junction D8 flows through intemal manifolds to the cathode hurr~ ;ri, ~l ion water 5el ~,e, ~Li- ,e channel inlet
Dg flows into the cathode hurr~id ~ n water Se"~enline channel D10 with a small potion osmotically
pumped across the electrolytic membrane D2 to humidify cathode air (oxygen) flows out the cathode
hurriiclir;c~l;.Jn water serpentine channel exit D11 through internal ",al.ifoW,~ finally exiting through the
cooling water outlet D12.
By analogy hot water from the humifl;r~ n water inlet Illdnifold junction D8 flows through
internal manifolds to the anode hum;~l;ri. ~i;on water se,~,e"li"e channel inlet D13 flows into the anode
hL",~ - ~ water serpentine channel D14 with a small portion osmotically pumped across the
electrolyticmembraneD2tohumidifyanodehydrogen~flowsouttheanodehum~ e~lionwaters~ lille
channel exit D15 through intemal ",an finally exiting through the cooling water outlet D12.
Fi~3. 4B is a fluid circuit s~ ",dlic for inley,dlec themmal (only) ",anay~l"ent IFM sepdldlul~. The
s..l lel l lalic is drawn down the center line E18 of the u le~ l, uu h ~" ,ical cell. The cenle, ~e passes down the
center of the electrolytic membrane E1. The anode side of a sepdidlol is on the left side labeled An,ode
and depicts the features found on the anode flow field platelet. The cathode side of a sep~,dlu- is
depictr~ on the right side labeled Cathode and depicts the features found on the cathode flow field
platelet. The s~ llldlic clearly shows the illleyldliol) of three fluid ",d"ag~,nent devices into a single
bonded composite sepd,dlur. The three functions are: an anode active area serpentine channel E10 flow
field; cooling water se,~e"li"e channel E5 heat e~clldnyel, and a cathode and cathode active area
se",e"li"e channel E15 flow field. These functions are conne~led using a series of internal distribution and
~~ ~ Illdl,ifoliis. This mec~l,d" ~ I fluid and therrr,al i"ley,dlion is a key element of this invention.
The electrolytic me" ~L" di ,e E1 is ionically conductive to hydrated protons. During normal ope. dlion
protons E2 fomned on the anode are electro-o:"".: ~Iy pumped across the membrane to the cathode.
Protons being pumped across the membrane carry one or more ~c50r;~ watem~ causing
anode dry-out during high power operation. At low powers this is ",iliydled by back diffusion of water
moleculesfromcathodetoanode. Athighpowersthisismitigatedbyextemalhu",iclir~Calionofhydrogen.
Cathode dry-out occurs when operating on air at high power. This is also mitigated by extemal
hulllirJ;HI~ c n of cathode air.
Hydrogen gas enters the hydrogen inlet E8 Hows through intemal distribution manifolds and feed
circuits to the anode active area se,~,~"li"e channel inlets E9 passes through the anode active area
serpentine clldl)l)el~ E10 where the hydrogen is oxidized to produce protons and el~llulls leaves the
active area through the anode active area se, ~ , llil ,e channel exits E11, flowing through intema H ~ t ~ -,
C ~L' finally exiting as ~Pp'et~d hydrogen through the hydrogen exit E12.
Air (oxygen) gas enters the air (oxygen) inlet E13, flows through intemal distribution manifolds and
feed circuits to the cathode active area s~ l ILiue channel inlets El 4, passes through the cathode active
area se,l-e"li"e Cl~dlll-~.lS Ela where the air ~oxygen) is reduced by ele~ t,uns and protons to produce
product water leaves the active area through the cathode active area serpentine channel exits E16 flowing
throughintemal A~ ' )1l ,a"U,ld finallyexitingas~ler~c'--1air(oxygen)andproductwaterthroughthe
air (oxygen) exit El 7.
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Cooiingandhum~ rlc~lllnnwaterentersthecoolin9waterinletE3~flowsthroughintemalmanifolas
to the cooling water serpentine channel inlet E4. flows through the cooling water serpentine channel
picking up heat produced as by product of the ele. I-ucht:",ical ,~aclions flows out the cooling watff
se",a. .li. .e channel exit E5 into internal manifolds to the humil l;t~ " water inlet manifold junction E6
flowing into internal manifolds finally exiting through the cooling water outlet E7.
Flg. 5 depicts the overall el~l- ucl ~em ical fuel cell operation for an i- Il~yl dLed humidity and the rrnal
Ill~D~dyelll~t fuel cell. The center section of Flg. 5 depicts the overall fuel cell e;~ ,ucl)el,,istry and is
cross-,ef~ ced to Fig. 3, H 1 H 2 on the anode side is catalytically oxidized to yield two el~l,uns
(indi.-. Ied by 2e- at the end of a di~ ~lional arrow) and two hydrated protons (i".li- . led by H+/H20 in the
membrane). The el~l.u,-s are conducted away from the anodic catalytic site by the graphite G~ lu~leS
WtliCh are in contact with the metal mic,os~;,~n platelet. The hydrated protons are electro-osmotically
pumped through the wet electrolytic membrane (illdicdl~cl by H+/H20 in the ",e",b, D~e) to the cathocfe
catalytic site where they combine with ~2 and two r;le_l,u.)s (i---licated by 2e-) to form product water
(H2O). The upper and lower sections of Fig. 5 depict the counter-flow hu. . .i~l ric~ n mecl ..D ,;~", which
is a central element of this invention. The electrolytic membrane serves a dual roll as a solid electrolyte
and hum i~l;r~ n membrane. The upper section Shows oxygen gas on the cathocfe side being humidified
by water on the anode sfde. Conversely hydrogen on the anode side is humidified by water on the
cathode side.
Platelet Drawing Desc..i~ n.
Flg. 6 A is a diagram conl-dali- ~9 single level depth 17 and through-features 18 formed by etching
metal platelets 16, e.g. by cl 'e, . IiCdl, plasma. or erosion by ele~l- ical arc w high pressure fluid, or the like
techniques. Fig. 6 B shows multilevel depths 20 21 and through-features 22 formed by embossing,
compr~asion or injection molding plastic platelets 19. Chemical (solvent) etching, or the aforeme, ~lioned
erosion or plasma techniques may also be used on plastic. Platelets are typically designed with depth
features that are 6û% of the II.;ch.,ess of the platelet stock. Through features 18 are formed by
simultaneously etching depth features 17 from both sides. Etching yields round bottom features with the
result that etched through features have a residual cusp 23. This cusp aiyl ~ii-.c~ ILly changes the fluid flow
cl .a, dclt:l ialiCS of through features and must be taken into account when desiy- ~ ~9 etched platelet devices.
Fig. 6 B sho w s features fommed cc,- ~ ~p- e:aaiun molding yields more rectangular features with slight
mold draft. These features may be of varying and ~ P~ d depths 20 21. The multiplicity of depths
available in cû~p~a:,ion molded plastic platelets siy"iri- ~Inlly reduces manufacturing costs and design
CGIllr . ~y by reducing the number of platelets required to achieve a given depth proflle. Analytical fluid
models are simpler due to the lack of residual cusps.
Fig. 7 is a plan view of a llliCI US~ el l current c ~ having a slotted flow field patterns Z1 and
Z2 as shown. The slots are posilioned to be COOI di- ldl~ with grooves and ~ h~ -nels in the plastic fluid
"~ ,age, . ~ent core pl -t~lPtC For many stack designs slotted flow field patterns Z1 and Z2 are the preferred
embodiment.
Figs. 8 A-D depicttypicalbut not exhaustive hole patterns for m etalcurrent col'e ~ mic,u~c,t~en
pl~tel~, 8A being heAagons 8B being ~ ;ds. 8C being Tees and 8D being dll~lllal~: inverte~
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interleaved chevrais. These patterns are fahricated by cnemical miliing, punching, or piercing thin metal
plates. Microscreens are typically 65% open with uniform spacing of holes. The hole features are typicaliy
8 - 20 mils with the web being 4 - 10 mils. Oriented he~a~ons Fig. 8A with major and minor axis aligned
to the underlying serpentine ~ihdllllels are the p-~r~-,ed embodiment for mi.,lus.;le~lls. 1 I~,~agc".s yield
the best design control over hole to web dimensions. In another embodiment, x-met (sheet that is slit in
pattems, opened and nallt ,-ed) is also useful.
Detailed Platelet Sepd,dL~r Drawing Des-,.l~.li.~...
There are two major embodiments of composite metaUplastic se~udlu, ~;, edge conduction with
one or more current bridges and through-conduction with one or more bus bars. These embodiments will
be ~is~ ~s~e~ sequentially starting with the edge conduction realizations.
Edge Conduction 1~ llèy~ dldd Humldlty and Them-al ' ' ~age~
Fiç1. 9 is an ~ isometric view of a single cell F1 internal of the stack co. ~ ~p~isi- ~g sepd- alul :,
F2A and F2B Sdn~ ~9 on two EMAs F3A and adjact:, ~l EMA F3B of the next cell in the series. In this
view, only the H2 (anode) side of the bipolar sepd dlu.~ are visible, but as shown below, there are
COGI dind~e air (oxygen) zones on the hidden (call ,ode) side. The large rectangular areas on the bipolar
sep~du, plates are conductive screens that cover the ele~l-ocl-t:l..ical active area on the EMA, F4A
- ~li- ~9 the anode side and F4C (hidden) the cathode side. The small rectangular areas above and
belowtheactiveareaarethecathodewaterhumi~l r~c~tionareaF6andanodehydrogenhu--~ 'ri~lionflow
field F5 respectively, and will be desc, iL,ed in more detail below.
The EMAs F3A and F3B include catalyst coated areas F7A and F7C that are COGI dil ~ate with the
C-OI I t:apOUdil 19 active areas F4A, F4C. Reactant and cooling water I l ldl _ ' are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet Il ldl l-' 'd F9, flows through the hydrogen hu-- ~;~ I r~ l ;on flow
field F~, through the anode active area F4A and leaves via the hydrogen outlet ~ - Idl ~ f~ 'd F8. Air (oxygen)
enters via the air (oxygen) inlet manifold, flows field through the air (oxygen) hu- "irl~;c~ ;on flow field F14,
through the cathode active area F4C and leaves through the air (oxygen) outlet l--dl-ifold F12. Water for
hu-, ~ ;ri~ on and thermal management enters through water inlet - - ,~ -i~uld F1 1. flows through an intemal
heatLAcl,d..ge"dividesandflowsthroughthecathodewaterh-l,--id;r;~ ;onareaF6andtheanodewater
humi~lir~ n area F6. Water leaves through the water outlet Ill~llifold F10. M~l;f.'d~ pass through
bipolar sepdldlu~:i F2 and EMAs F3. Culllp,~sion tie rod holes F16 are evident on the margins of the
bipolar sepdldlùl:j and EMAs.
Fig. 10 is an ~Yp'oded isometric view of a composite 4-platelet humidified bipolar IFMT sépa- dlUr
F2 of this invention comprising plates of three different types, plates F17-1 and F17-4 being identical
configuration conductive current - r,'l~ n ,..i.i- usc, ~, p' ' '~ - While the configuration is p.t i~dLly
identical, although it could be different, the conductive material may be metal, conductive plastic,
- conductive ceramic, or ceramic or plastic having its surface metalized by plating or vacuum dPpo~ition).
Current is conducted around the two plastic core platelets F17-2 and F17-3 by one or more edge current
~ bridges F18, shown partly broken away. Sealing is effected around the margin of the miw us~;. ~n platelet
by the anode mic. u:,cr~n sealing surface F23, which may include sealing ridges (not shown) around the
reactant and water ~a~liful~s F93. Optional sealing ridges (not shown) may be used to effect sealing
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around the active and hurr~ c~'ion areas F19 as well.
Platelet F17-1 is the anode current ~c 1. - ~ miclusc,~n consialillg of a repeating pattem of
through etched, punched or otherwise forrned holes, ,lldl)ll~ or slots. Platelet F17-2 is the plastic or
ceramic anode flow field platelet co"sialil ,9 of molded depth and through features. Platelet F17-2 contains
the features that define the hydrogen humirl;r;o~ on flow field F5, anode active area flow field F21, and the
cathode water hurr~;~li'ic~'ion area F6. The obverse side of platelet F17-2 forms the close out for the
themnal ",ai,agt:",ent circuit F20 of platelet F17-3. Platelet F17-3 is the plastic or ceramic cathode flow
field platelet consialillg of molded depth and through features. Platelet F17-3 contains the features that
define the thermal ".anage",~l-l heat L,cch~-ger F20, air (oxygen) humid;ri ~'ion flow field F14, cathode
activeareaflowfieldF22andtheanodewatffhull~ ;c~ nareaF15. Theair(oxygen)hu".;.i;ri.~ .)flow
field F14, cathode active area flow field F22 and the anode watff hull~ ;c~ l area F15 are on the
obverse side of platelet F17-3.
In all plates Ft7-2 to F17-3, the through transverse border p~s~es or Illdr, f~ l~ F93 and
comp.~asion tie rod holes F16 are coo-~.-ale with those of EMA F3 in Fig. 9.
Fi~s. 11A-G are a series showing in plan view from the facing side of each platelet and the details
of one ~ bod;~ of the through and depth features of the 4 platelet bipolar se~ dldot plate of Fig. 10
in accord with the IFM pri" , le~ of the invention. The plOyl~:,aiOII of plates is as shown in Flg. 10, with
the figure desig"dlion ~Front~ being the front of the plate as seen from the anode (foreground) side of Flg.
10, while the Back side is the non-visible side of the respective platelets of Fig. 10 when tumed over.
That is, the views are all ~artwork or plate facing (face-up) views. Platelets 1 and 4 are e55~n' lly the
same with the ~ pl n of when sealing ridges are employed. Figs. 11 A-11 C are plan views showing the
front of platelet 1 and the back of platelet 4 joined by the current bridge Ft 8. The anode platelet current
~c ~ ~u~ ~"i ;,usc,~n F17-1 is ~1, on the bottom with the cathode platelet current -C"t;
~ic-~us~ten F17-4 on the top joined by the current bridge F18 in the middle. The anode and cathode
current .,- ~ t~ ~"i~,us ;,~n platelets are constnucted with through features that define the ,,,ic,uscrt:an
(shown cr~,sal)al.;l ,~). These features may be of diverse shapes and sizes as de~ ed in Figs. 7 and 8.
As seen in Fig. 11A the anode current rc - mic,usc,~, platelet F17-1 features define the
cathode water hun~id;riG<.IiPn area F6, anode active area F4A, and hydrogen hurr~; ';t~ on flow field F5.
A sealing surface F23 with optional sealing ridges surrounds the active and humi~l r;~ on areas F19.
Manifold close-outs for distribution and ~- ~ ~ ) Ill~liFulls of the anode flow field platelet F17-2 are
formed by the anode mil.,usc,t:e" Illdl~ifUId close-outs F25. The cathode current col ~l ",i.,.~,sc,~,
platelet F17-4 features define the air (oxygen) humi~J;';c~liul) flow field F14, cathode active area F4C, and
theanodewaterhumi~lirir~lionareaF15. AsealingsurfaceF24withoptionalsealingridgessurroundsthe
active and hullli~lit~ lion areas F19. Manifold close outs for distribution and co"~ li~ n Ill~lirulds of the
anode flow field platelet F17-3 are formed by the cathode ~ usu~n manifold close outs F26.
Flg. 11B is a plan and section views of typical metal mi,,os,,~n current col;_cLu, platelets with
window screen dt:,c,e:ssions. The anode current co le ,~ " i1 US .,~en dep,~ssion F31, cathode current
us~ de~ ssionF9O,transverseborderp~s~ orlllarliful~JaF93~anodemic~ùscl~:l)
sealingsurfaceF23,cathode~ic~uac~l)sealingâurfaceF24~anodemicluscl~lllllani~oldclose-outF25
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and cathode microscreen manifold close-out F16 are derict~d in plan and section view. The depth of the
windows screen dep, ~ssions F3 1 and F90 are desiy"ed match the depth of the dep, ~::,sions on the anode
and cathode flow field platelets F17-2 and F17-3.
Fi~. 11C is a plan and section views of metal mic,osc-,~n current co" ' platelets without
w;.ldo.vs screen de~ ssions. The transverse border p~ es or manifolds F93 anode mic,u:,c.~,
sealingsurfaceF23.cathodemic,us~ ensealingsurfaceF24,anodemiclus~;l~nmanifoldclose-outF25
and cathode mic,uscl~n manifold close-out F16 are ~r~ d in plan and section view.
Fig. 11 D depicts the front side of the plastic anode flow field platelet F17-2 -Front. This platelet
has both through and depth features. The major through features are the comp~t:ssion tie rod holes F16,
transverse Illall'' ' ' hydrogen outlet ",anirold F8 hydrogen inlet Illanifold F9 water inlet ",an;~W F10
water outlet ",an,f~,ld F11, air (oxygen) outlet Illdn '~ 'd F12 and air (oxygen) inlet Illdn ' ~' F13. Other
through features are the hydrogen inlet via F32 hydrogen outlet via F35 cathode hu",i- ~-r;u.~ n water inlet
via F44 and cathode humicl:~ic ~ n water outlet via F41. The major depth features on the front of the
anode flow field platelet are the hydrogen hu".;~ ;on serpentine cl-~-,-eL F36 anode active area
S~ ~ llil ,e chdl " lelj F39 and the cathode hul- I jr l;r;~ n water se, ~ l llil ,e channel F43. These features
are designed to opli",i~e the flow rates and pressure drops of the device.
Hydrogen fuel for the anode enters the hu"~ ;f~ n area through the hydrogen inlet via F32
enters the hydrogen distribution " Idl lifuld F27 through the hydrogen distribution " Idl '' ' inlet F33 and is
distributed to the two hydrogen serpentine chdl 0~r l ~ F36 through the hydrogen se, u~ ,li"e channel inlets
F34. HydrogengasishumidifiedthroughthewaterpemmeableeleCtrOIyticmelllb,d,,ewhichisincontact
withthehydrogenhn",i.i;fi. ~ nse"J~,Ii"echannelF36. Humidifiedhydrogenleavesthehu"-;-~;rc~l;o.,
area through the hydrogen serpentine channel exits F37, enters the hydrogen ~ ~ "~ ",anirGI.I F28 and
passes into the anode active area distribution " ,a"irùld F29. flows into the anode active area serpentine
c~a, Inel3 F39 though the anode active area st:"~ il ,e channel inlets F38. Within the active area hydrogen
is catalytically oxidized on the anode side of an EMA to produce el~ll o"s and protons. Protons pass from
the anode catalytic site through the electrolytic membrane to the cathode. Electrons are drawn off from
the anode catalytic site through the graphite electrode. Electrons from the graphite electrode are c ~
by the anode current c - '~ ' - mi~, usc, ~" F17-1 and conducted through the composite bipolar Sepdl dlOI
by edge conductors F18.
l~ep~et~d hydrogen leaves the active area via the anode active area serpentine ul ,annels exits F40
and flows into the hydrogen c - 'It " ~ manifold F31 finally exiting through the hydrogen exit via F35.
Hotwaterforcathode(air,oxygen)hu,,,i~lir;c-~ionentersthroughthecathodehtJ,,,i~ ic~lionwater
inlet via F44. passes into the cathode hulll~ fi~-~liot- water st:"ue,)li"e channel F43 through the cathode
hull.i~l~fi~ n water serpentine channel inlet F4~ exits through the cathode hurrlid;ri-~al;on water
~ se, ye"li"e channel exit F42, and leaves through cathode hull-;cl r~ - water outlet via F41. Part of the
hot water flowing through the serpentine channel is osmoticaliy pumped across the electrolytic membrane
- to humidify cathode air ~oxygen).
me anode current -"- ' mic,u~c,~n platelet F17~1 is bonded to the anode flow field platelet
F17-2 and forms Illdll;f~ld close-outs for the hydrogen distribution Illdl '~ ~d F27 hydrogen c-~ : n
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The optional anocle microscreen d~p-t:ssion F31 receives the corresponding anode current
collector mi~ ,osc,~en platelet F17-1 with anode mic-,us,_,~an dep,~ssion F31ci-~pict~ci in Fi~. 11B. The
depth of the anode current c ~ " ~ mi~;, usc, ~n dep, ~ssion F31 is set to place the surface of the anode
current cel'- -~ - mil,,usc.een platelet F17-1 flush with the surface of the anode flow field platelet F17-2,
or it may be set to forrri a recess which receives graphite paper elecl,.,des of the el~l,ucie membrane
assemblies.
Fig. 11E depicts the back side of the plastic anode flow field platelet F17-2 -Back. This platelet
has both through and depth features. The major through features are the compression tie rod holes F16,
transverse manifolds; hydrogen outlet ~ if old F8, hydrogen inlet manifold F9, water inlet manifold F10,
water outlet manifold F11. air (oxygen) outlet " ,ar, ' 'd F12, and air (oxygen) inlet " ,a"iruld F13. Other
through features are the hydrogen inlet via F32. hydrogen outlet via F35, cathode humid;fi~ oll water inlet
via F44, and cathode hurr~ ri~ inn water outlet via F41. The major depth features are the hydrogen ~nlet
channel F47, hydrogen outlet channel F~0. air (oxygen) outlet channel F63, and the air (oxygen) outlet via
base FJ5. Most of the surface of the anode flow field platelet F17-2 is used as a close out for the cooling
water ~,I Idl 11)_~5 on the cathode flow field platelet F17-3.
Hydrogen flows from the hydrogen inlet manifold F9, through the hydrogen inlet channel inlet F48,
into the hydrogen inlet channel F47, through the hydrogen inlet channel exit F46, and finally into the
hydrogen inlet via F32. Hydrogen passes from back to front of the anode flow field platelet Fig. 1tD,
through the hydrogen inlet via F32. Dep'~t~ hydrogen from the active areas flows back through anoc-le
flow field platelet through the hydrogen outlet via F35, into the hydrogen outlet channel inlet F49, through
the hydrogen outlet channel F~0 and the hydrogen outlet channel exit F51, finally exiting into the hydrogen
outlet ",aniflJI d F8.
Derleteci air (oxygen) is removed from the cathode humi~l;r..~ n and active areas through the air
(oxygen) outlet via F55, air (oxygen) outlet channel inlet F64. air (oxygen) outlet channel F53, air (oxygen)
outlet channel exit Fs2, finally flowing into the air (oxygen) outlet manifold.
Fig.11 F depicts the front side of fhe plastic cathode flow field platelet F17-3 -Front. This platelet
has both through and depth features. The major through features are the compression tie rod holes F16,
transverse manifolds; hydrogen outlet manifold F8, hydrogen inlet manifold F9, water inlet manifold F10,
water outlet manifold F11, air (oxygen) outlet manifold F12, and air (oxygen) inlet Illdl C~d F13. Other
through features are the air (oxygen) inlet via F60, air (oxygen) outlet via F61, anode hurr~ ~if ~ ' ~n water
inlet via Fs8, and anode hur~ on water outlet via F57. The major depth features are the cooling
water serpentine cl ~ l3 F62~ humi~ n water inlet manifold F64 and the humidiri~ n water outlet
~.,ani[old F63.
Cooling water enters through the water iniet manifold F10, cooling water channel inlet F66, cooling
water channel F66 finally entering the cooling water serpentine channel F62 through the cooling water
serpentine channel inlet F67. Flowing throu9n the cooling water serpenl ine channel the cooling water picks
up heat which is a by product of the elecl, ucht:- l licdl r~acLions~ Hot water leaves through the cooling water
s~iJ~"li"e channel exit F68 and flows into the hUll~idiri~ ion water inlet manifold junction F69, into the
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W 096/37005 = ~ PCT~US96/06877
humi. I;r;~ n water inlet manifold F64, and finally exits through the humi ';'i~ n water cathode exitFr~
and cathode water hurl~idir~ n inlet via F56 or the hurlliciir~ water anode exit F71 and anode water
humi~Jiri~ ion inlet via F58. Hot water is used for humi~l;rc-.lion because of it high diffusion activity.
Air (oxygen) enters the cathode from the air (oxygen) inlet manifold F13, flows into the air (oxygen)
inlet channel inlet F72. passes through the air (oxygen) inlet channel i-73, into the air (oxygen) inlet channel
exit F74, and flows to the cathode humidi i~lil n and active area clldnnelj through the air (oxygen) inlet
via F60. Air (oxygen) is humidified as it passes through the air (oxygen) humidirlc~'io,l ch~llll~ls and is
consumed in the cathode active area d~ t~ in Fig.11 G. ~'er le~c air (oxygen) and product water leave
via the air (oxygen) outlet via F61 which conll~la to the air (oxygen) outlet manifold F12 through the air
(oxygen) outlet channel on the anode flow field platelet F17-2.
Fig.11 G depicts the back side of the pl~tic cathode flow field plate'et F17-3 -Back. This plate~et
has both through and depth features. The major through features are the co, ~ ssi ,n tie rod holes F16,
transverse ., Idl ~' ~ . hydrogen outlet ., Idn-' ~(- F8, hydrogen inlet ~ ~ Idl lifol J F9, water inlet ~ ~ ~~": c F10,
water outlet Illdl l'' ' ' F11, air (oxygen) outlet md~iruld F12, and air (oxygen) inlet l.lanifuld F13. Other
through features are the air (oxygen) inlet via F60. air (oxygen) outlet via F61, anode humid;r~AIil n water
inlet via F58, and cathode humi~'~r~ n water outlet via F59. The major depth features on the cathode
flow field platelet are the air (oxygen) hurr~ lio~l s~,lJe"li"e chdrlnels F80, cathode active area
serpentine cl ,~n~ls FB6, and the anode hull,L; r c~ n water serpentine channel F77.
Air (oxygen) for the cathode enters the hul, ~ area through the air (oxygen) inlet via F60,
enters the air (oxygen) distribution ",a"irol i F79 through the air (oxygen) distribution Ill~,iful i inlet F78
and is distributed to the two air (oxygen) s~,~,li"e ch~",.~ F81 through the air (oxygen) se,,uel)lille
channei inlets F80. Air (oxygen) gas is humidified through the water permeable electrolytic membrane
which is in contact with the air (oxygen) hu"-idir~ lil n serpentine channel F81. Humidifieci air (oxygen)
leaves the hum i~ l ri~ ion area through the air (oxygen) serPentine channel exits F82. enters the air (oxygen)
hum i l;ri. ~l il n cc ~ " ,anircJI i F83, and passes into the cathode actiYe area distribution l "~ L' F84,
flows into the cathode active area serpentine chan,.~ F86 though the cathode active area se",enline
channel inlets F85. Within the active area oxygen is catalytically reduced receiving protons and el~l,ùns
from the anode to produce water. Electrons flow from anode to cathode via current bridge F18, into the
cathode current - - en or mi~. usc, ~" 17-4, through the cathode graphite el~l, ude on the EMA and finally
docking with a cathode catalytic site where the el~ll u,-s react with anode ~ene~ dl~d protons and oxygen
to produce surplus heat and product water. ~ air (oxygen) and product water leaves the active
area via the cathode active area se".e"li,)e channels exits F87 and flows into the air (oxygen) ~r"~ 'i I
".ar.iruld F88, through the air (oxygen) ., - ~c ~n l~ Idl 1' _ ~(' exit F89 finally exiting through the air (oxygen)
exit via F61.
~ Hotwaterforanode(hydrogen)humi~;f~ nentersthroughtheanodehumid~riC~l~ionwaterinlet
via F58, passes into the anode hurni~'ir~ n water s~, ,u~, ,li, ,e channel F77 through the anode
humi~l;ril,,lil~nwaterserpentinechannelinletF76~exitsthroughtheanodehun~ r~ lionwaterserpentine
channel exit F75, and leaves through anode hu",i~' ril~lion water outlet via F59. Part of the hot water
flowing through the se".;--Li,.e channel is os.,-uli~.llly pumped across the electrolytic membrane to
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SUB~ ESHE~t~26)
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W 096/37005 PCTrUS96/06877
humidify anode hydrogen~
Platelet F17-3 is bonded to platelet F17-4 which may have an ol~tional cathocde current ~ c
,l ua-,l e~- clep, ~aSiOn Fso and forms manifold close outs for the air (oxygen) hul, ~ un distribution
manifold F79, air(oxygen) humid;t~ n ~ )n '''an ~ 'c F83~ cathodeactiyeareadistribution nlanil~Jh
F84 and cathode active area ~ n manifold F88.
The depth of the cathode current ~ mi,;, osc, ~- de~l ~asion F90 is set to place the surface
ofthecathodecurrentcr' mi.;,~sc,~nplateletF17-4flushwiththesurfaceofthecathodeflowfield
platelet F17-3 or it may be set to form a recess which receives graphite paper elecl, odes of the electrode
membrane assemblies F~ in Fig. 9.
EdRe Conduction l~ cy.dl~d Thermal ~- .ag~-..e..l.
Fig.12isan~ lc~o~iaG",e~ ;viewofasinglecellG1 internalofthestackco".~,iai"gsep~dlo~
G2A and G2B sandwiching EMA G3A and conlacli"g the next EMA G3B of the next adjac~ IL cell in the
stack. In this view, only the H2 (anode) side of the bipolar se~,d, dlul :- are visible but as shown below,
there are COGI~ ' Idlt3 ~2 zones on the hidden (cdlhodd) side. The lar~e rectangular areas G4A are the
active areas of the cell G4A I ~ ael llil 19 the anode side and G4C the cathode side.
The EMAs G3A and G3B include catalyst coated areas G7A ancl G7C that are COGI di, Idl~3 with the
corresponding active areas G4A. G4C. Reactant and cooling water Illdl ~ituW~ are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet mdl);fokl G7 flows through the anode active area G4A and
leaves via the hydrogen outlet manifold G6. Air (oxygen) enters via the air (oxygen) inlet Illdnif~ld G10
flows through the cathode active area F4C and leaves through the air (oxygen) outlet manifold G11.
Cooling water for thermal " lanas~en ,~ ,l enters through water inlet manifold G9 flows through an internal
heat e,~cl Idl ,gef and leaves through the water outlet Illdl ,itolcl G8. Transverse reactant and cooling water
inlet and outlet n ,a, lifulJs G6, G7 G9. G11 G10 and G12 pass through bipolar sepa, dlU~ G2 and EMAs
G3. Compression tie rod holes G12 are evident on the margins of the bipolar sepa, dl.n a and EMAs.
Fig. 13 is an ~Yp'oded isometric view of a 4-platelet bipolar IFMT sep~dlur G2 of this invention
comprising plates of three different types plates G13-1 and G13-4 being identical current CC"~L 3--
~I~ic~usc~ee~l platelets con"ecled by current bridge G14 shown partly in dashed lines. Platelet G13-1 is
the anode current ~ mic, OaCI ~" consisling of a, t:pedlin9 pattern of through etched or punched
holes. Platelet G13-2 is the plastic or ceramic anode flow field platelet conaialillg of molded depth and
through features. Platelet G13-2 contains the features that define anode active area flow field G16. The
obversesideofplateletG13-2formsthecloseoutforthethermal"-anage"-entcircuitG170fplateletG13-
3. Platelet G13-3 is the plastic or ceramic cathode flow field platelet collsialil,g of molded depth and
through features. Platelet G13-3 contains the features that define the therrnal management heat ~,~ch~ ,gel
G17 and cathode active area flow field G18. The cathode active area flow field G18 is on the obverse side
of platelet G13-3. Sealing is effected around the margin of the mi~ ,s.;,~n platelet G13-1 and G13-2.
Optional sealing ridges (not shown) may be used to effect sealing around the active areas G4A and G4C.
In all plates G13-2 to G13-3 the through transverse border p~ g~s or manifolds G15 and
cu"",,t::,sion tie rod holes G12 are coo,di. ,ale with those of EMA G3 in Fig. 12.
Figs. 14A-G and G are a series showing in plan view from the facing side of each platelet and the
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CA 02220901 1997-11-12
W O 96/37005 PCT~US96/06877
details of one em~odiment of the ttlroush and depth features of the 4 platelet bipolar separator plate of
Fig.13 in accord with the IFM p, in '~~ of the invention. The p. oy, t:asion of platelets and fronVback sides
are the same as the Figs. 11 A-G series.
Fig. 14A is a plan view of the anode and cathode current ~2 'e '- - microscreen pl~t,~letC G13-1
and G13-4 anode screen on the bottom cathode screen on top. The through features of the
~iC~uSC~ S may be of diverse shapes and sizes as dep - ~ ?d in Fig. 8. The anode current ~-
mi~i,uac,~,l platelet has features that define the anode active area G4A. A sealing surface G19 wlth
optional sealing ridges G60 (shown in phdlllolll) surrounds the active G4A. Manifold close outs for
distribution and c~ lifolds of the anode flow field platelet G13-2 are formed by the anode
",i~;,usc,~n Illal,iru,W close outs G21.
The cathode current cc - - mic-,usL,een platelet G13-4 features define the cathode active area
G4C. A sealing surface G22 with optional sealing ridges surrounds the cathode active area G4C. Manifold
close outs for distribution and c~ Illdn ~d of the anode flow field platelet G13-3 are formed by
the cathode .,.ic,usc-w,, manifold close outs G22.
Fig. 14B is a plan view of metal ",ic,usc,~n current ~ platelets with window screen
dep, t:ssions shown in sections to the right. The two platelets G13-1 and G13-4 are joined by the current
bridge G14. The anode current ~c ~ ~ ~ ".i.,os-r~n dep,~ssion G25 cathode current c-l -
.us~n de~,~asion G59 trarlsverse border p~c~g~c or Ill~irolda G15 anode ",ic,us.;,~:" sealingsurface G19 cathode mi~.,usc,~n sealing surface G20, anode ",i~,usc,~n ",a-, close-out
G21 and
cathode IlliClu5~ "an close-out G22 are d?,' ' in plan and section view. The depth of the
window screen dep, ~SaiunS G25 and G59 are desiy"ed match the depth of the de~ asionâ on the anode
and cathode flow field platelets G13-2 and G13-3.
Fig. 14C is a plan view of metal Illi..lusc,~" current ~. 'e platelets without window screen
depl~as.ons with coll~aponlJ;.,g plan as section views shown to the right. The two platelets G13-1 and
G13-4 are joined by the current bridge G14. The transverse border p~Csa9~c omlldllirulds G15 anode
",i~;,usL.~-,sealingsurfaceGl9 cathodemic,usc,~nsealingsurfaceG20.anodemic,usc,~n,,,~,i
close-out G21 and cathode microscreen ",anirul-J close-out G22 are d~ tt.~ in plan and section view.
Fig. 14D depicts the front side of the plastic anode flow field platelet G13-2 -Front. This platelet
has both through and depth features. The majorthrough features are the co",p,~ssiùn tie rod holes G12,
transverse ",~ ,irol~s hydrogen outlet manifold G6 hydrogen inlet manifold G7 water inlet manifold G8
water outlet Ill~irGld G9 air (oxygen) outlet manifold G11, and air (oxygen) inlet ",an 'c't G1û. Other
through features are the hydrogen inlet via G2~ and the hydrogen outlet via G28. The major depth features
on the front of the anode flow field platelet are anode active area seu~enli"e cl)~ll ln IS G31 anode active
area distribution I,,an 't G23 and the anode active area cc ~n manifold G24. These features are
~ desiyned to optimize the flow rates and pressure drops of the device.
Hydrogen fuel for the anode area enters through the hydrogen inlet via G26 passes through the
- anode active area distribution manifold inlet G27 into the anode active area distribution manifold G23
flows into the anode active area serpentine channels G31 though the anode active area s~".,~"line channel
inlets G30. Within the active area hydrogen is catalytically oxidized on the anode side of the EMA to
SU~I~rES~tE~T (R~F2~
CA 02220901 1997-11-12
W 096/37005 PCTrUS96/06877
produce e~ectrons and protons. Protons pass from the anode catalytic site through the electrolytic
membrane to the cathode. Electrons are drawn off from the anode cal:alytic site through the graphite
electrode. Electrons from thegraphiteelecl.udeare~ ' bytheanodecurrent c-"~ liclusL.
G13-1 and conducted by tab or bridge G14 to the cathode mic,os~,~en G13-4.
Depleted hydrogen leaves the active area via the anode active area serpentine Lh~ Incl3 exits G32
and flows into the anocie active area cc" ' ~ manifold G24, through the active area ~ -''e ' ~ manifotd
exit G29 and finally exits through the hydrogen exit via G28.
Platelet G13-1 is bonded into an anode current _-"~ ' - miLi.us~ e,- deu.ussiù.) G25 and forms
manifold close outs for the anode active area distribution manifold G23 and anode active area ~c" ''
manifold G24.
Thedepthoftheanodecurrentcc"~tc mic-us~,~,areaG25maybeselectedflushtoplacethe
surface of the anode mic,usc,~, platelet G13-1 flush with the surface of the anode flow field platelet
G13-2, or it may be dep, ~sed to fomm a recess which receives graphite paper el~_l- ucles of the elc ~.t~ u~le
..~..,tj.dne assell -''
Fi~. 14E depicts the back side of the plastic anode flow field platelet G13-2 -aack. This platelet
has both through and depth features. The maior through features are the compression tie rod holes G12,
transverse ,..~ '~ hydrogen outlet ",dnirold G6, hydrogen inlet ~- ~a. ~irul~i G7, water inlet Il lalli~old G9,
water outlet ",an '~ ' ~' G8. air (oxygen) outlet Illdl l''.i~d G11, and air (oxygen) inlet I lldn''~ G10. Other
through features are the hydrogen inlet via G28 and the hydrogen outlet via G26. The major ciepth features
are the hydrogen inlet channel G34, and the hydrogen outlet channel G37. Most of the surface of the
anode flow field platelet G13-2 is useci as a close out for the cooling water cl Idl In'c31~; on the cathode flow
field platelet G13-3.
Hydrogen flows from the hydrogen inlet ~ - Id n,fold G7, through the hydrogen inlet channel inlet G35,
into the hydrogen inlet channel G34, through the hydrogen inlet channel exit G33, and finally into the
hydrogen inlet via G26. Hydrogen passes from back to front of the anode flow field platelet Fig. 14D,
through the hydrogen inlet via G26. n p~e~i hydrogen from the active areas flows back through anode
flow field platelet through the hydrogen outlet via G2a, into the hydrogen outlet channel inlet G36. through
the hydrogen outlet channel G37 and the hydrogen outlet channel exit G38. finally exiting into the hydrogen
outlet ",ar ~c' -' G6.
Fig.14F depicts the front side of the plastic cathode flow field platelet G13-3 -Front. This platelet
has both through and depth features. The major through features are the comp~b~sio~ l tie rod holes G12.
transverse ",ani~l~s, hydrogen outlet Illal);fullJ G6. hydrogen inlet manifold G7, water inlet manifold G9,
water outlet ,,,a-,iruW G8, air (oxygen) outlet Illall '~'d G11, and air (oxygen) inlet Illalliruld G10. Other
through features are the air (oxygen) inlet via G44 and the air (oxygen) outlet via G45. The major depth
features are the cooling water s~- ~e"Li- ,e ch~ "~els G46, air ~oxygen) inlet and outlet cl ,a"n~ G50 and
G40.
Cold cooling waterenters through the cooling water inlet ,,,anirulcl G9. flows into the cooling water
serpentine channel inlet G47, and passes into the cooling water s~:u,e, ILi"e channel G46. Flowing through
the cooling water serpentine channel G46 the cooling water picks up heat which is a by product of the
CA 02220901 1997-11-12
W 096/37005 PCT~US96/06877
electrochemicai reactions. Hot water exits through the cooling water serpentine channel exit G48. finally
leaving through the cooling water outlet manifold Ga.
Air (oxygen) flows from the air (oxygen) inlet manifold G10, through the air (oxygen) inlet channel
inlet G49, into the air (oxygen) inlet channel G50, through the air (oxygen) inlet channel exit G51, and finally
into the air (oxygen) inlet via base G42 which communicates with the air (oxygen) inlet via G44 on the
cathode flow field platelet G13-3 in Fig. 14D. The air (oxygen) inlet via G44 brings air (oxygen) to the
cathode active area flow field.
rler' - air (oxygen) is removed from the cathode active area through the air (oxygen) outlet via
G45 (Fig. 14G) into the air (oxygen) outlet via base G28, into air (oxygen) outlet channel inlet G36, through
the air (oxygen) outlet channel G37. past the air (oxygen) outlet channel exit G38, finely exiting through the
air (oxygen) outlet ..,ar ' 'd G6.
Fig. 14G depicts the back side of the plastic cathode flow field platelet G13-3 Back. This platelet
has both through and depth features. The major through features are the co, . . pfession tie rod holes G12,
transverse ..-;~irul~s, hydrogen outlet ..,an ' ' ' G6, hydrogen inlet ,--ar ' ~I G7, water inlet ~lanirold G9,
water outlet ."~,irol~ G8. air (oxygen) outlet manifold G11, and air (oxygen) inlet ...~.ifol~ G10. Other
through features are the air (oxygen) inlet via G44 and the air (oxygen) outlet via G45. The major depth
features on the cathode flow field platelet are the cathode active area distribution ~- -ar if uld G53, cathode
active area c-"- ~ ~ Illdnifùl~ G57, and the cathode active area s~ ~,e"li"e chdnnels G55.
Air (oxygen) for the cathode enters the hulll ' ~ ~ area through the air (oxygen) inlet via G44,
passes the cathode distribution manifold inlet G52, flows into the cathode distribution manifold G53 and
is distributed to the cathode active area s~ t:,-li--e .,hdn-)~,ls G55 though the cathode active area
serpentine channel inlets G54. Within the active area oxygen is catalytically reduced - ~ce;~;ng protons and
el~l. uns from the anode to produce water. El~ll uns flow from anode to cathode via current bridge G14,
into the cathode current ~ mi-" u:,~.,~,, 13-4, through the cathode graphite r le_l, ude on the EMA
and finally docking with a cathode catalytic site where the el~llu"s react with anode gene,.lled protons
and oxygen to produce surplus heat and product water. rey~' ' ' air (oxygen) and product water leaves
the active area via the cathode active area s~ ~,e, llil ,e channcla exits G56 and flows into the cathode active
area c~ G57, through the air (oxygen) c:" ' , manifold exit G58 finally exiting through
the air (oxygen) exit via G45 which communicates with the air (oxygen) outlet channel G40 and the air
(oxygen) outlet ",anifol~ G11 on the cathode flow field platelet 13-3 -Front Fig. 14F.
Fig. 15 is a plan view of an anode (bottûm) and cathode (top) current c~" micros~,een
p~ ~t~ F17-1 and F17-4, respectively, with a current bridge F18 and multiple current tabs. The anode
current cc"~~ ~"ic.osc.~e,l platelet features define the cathode water humi~l;r~ orl area F6, anode
active area F4A, and hydrogen humirJir~ lion flow field F5. Three current conducting tabs F94 protrude
from the edges of platelet F17-1. These current tabs mate with the three corresponding current tabs on
platelet F17-4 and are joined by spot welding, micro brazing, SGIdt:lill9 or gluing with conductive
adhesives. The number of current bridges is p~ clec as a function of the required current-carrying
requirements of a given sealing ridges F95 are optional.
The cathode current c "~ mic,us.;,~en platelet F17-4 features define the air (oxygen)
S~Bs~~sHEET~
CA 0222090l l997-ll-l2
W 096/3700S PCTrUS96/06877
hu, . ~ r~ Al flow field F1 4l cathode active area F4c~ and the anode water hLll l ~ n area F15 Three
current condJcting tabs F94 protnude from the edges of platelet F17-4. These current tabs mate with the
three corresponding current tabs on platelet F17-1 and are joined by spot welding, micro brazing,
sol:le. i. .g or gluing with conductive adhesives.
Through reactant and cooling water Illdllirolds F93 and tie rod holes F16 are located in the same
peripheral positions as for the single current bridge 1 ' n d~rictecl in Fi~. 14A.
Fig. 16 is an ~ ~ isG..-el,ic view of a 4-platelet humidified bipolar IFMT sepdldlur F2 of this
invention comprising plates of three different types, plates F17-1 and F17-4 being identical current
cc " ~ - -iL. usc. c en platelets as above. Current is conducted around the two plastic core platelets F17-
2 and F17-3 by an edge current bridge F18 and three joined current tab-~ F94.
Platelet Ft7-1 is the anode current ~ lua~.l~ll cOll~ialill9 of a l~pedlillg pattem of
through-etched or punched holes. Platelet F17-2 is the plastic or cerdmic anode flow field platelet
consiali"g of molded depth and through features. Platelet F17-3 is the plastic or ceramic cathode flow
field platelet cons;sli--g of molded depth and through features. Platelet F17-4 is the cathode current
e~le ~ mic-ua-,.~" cùnsisli"9 of a rt:pedlillg pattem of through-etche!d or punched holes.
Bus Bar Conduction Integrated Humidity and Therrnal IU .agc~....~lo
Fig. 17 is an , ' ' o ~ iaul~~el ic view of asinglecell A1 internal of the stack co...~ i- ~g sepd..~t~a
A2A and A2B s~ .~w;~;l ~ .9 an EMAs A3A in contact with EMA A3B of the next adjdc~l cell. The plate
sequence and views are as above. The ~ "ic-. uaL- ~-) A4A, ~ ael lla the anode side and A4C the cathode
side which are conne~l~d by intemal bus bars desc, iL,ed in detail below. Anode hydrogen hul, ~ ;l riri,~ Jn
flow field A5 and cathode water hul..i l;f~ o n area A6 are present in the sepdldlùla, and described in
more detail below.
The EMAs A3A and A3B include catalyst coated areas A7A and A7C that are coo, di~ with the
c~ spord;, .g active areas A4A, A4C. Reactant and cooling water ,~Idl '( ' ' are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet manifold A9, flows through the hydrogen hurr~irl;~ic~ ,) flow
field A5, through the anode active area A4A~nd leaves via the hydrogen outlet manifold A8. Air ~oxygen)
enters via the air (oxygen) inlet Illdl .;fuhl, flows field through the air (oxygen) hull~ r;c,.lion flow field A14,
through the cathode active area A4C and leaves through the air ~oxygen) outlet manifold A12. Water for
hurn irl r,c~ and thermal management enters through water inlet manifold A11, flows through an intemal
heat e,~l ,d, ,g~, divides and flows through the cathode water h~ u~liol l area A6 and the anode water
hurnirl;~ area A~. Water leaves through the water outlet manifold AlQ. Mall ~ulds pass through
bipolar sepd,dlola A2 and EMAs A3. Compression tie rod holes A16 are evident on the margins of the
bipolar sepd dlu,a and EMAs.
Fig. 18 is an ~-, ' ied isometric view of a 4-platelet humidified bipolar IFMT sepdldll~l A2 of this
invention comprising plates of three different types. plates A17-1 and A17-4 being identical current
c~ n mic.o:,c.een p.~ c Current is conducted through the two plastic core platelets A17-2 and
A17-3 by one or more intemal bus bars A18. While two rectangular cross section bus bars are depiAt~ri
any number, geometrical cross-se.,tion and o, ie"ldlion may be employed, both within the screen field or
extemal of it. Sealing is effected around the margin of the .- ,ic. osc. ~n platelet by the plastic core pl~t~l.-t~::
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S~ ESHEEl lRU~
CA 02220901 1997-11-12
W 096/37005 PCTrUS96/06877
A17-2 and A17-3. which may inciude sealma riclges (not shown) around the reactant and water manifolds,
and around tne active areas A21, A22, and the hurr irlifiuc~ion areas A5, A6, A14, A15 and A19.
The two metallic current ~ n mic,u~;-~n platelets At7-1 (anod* and A17-4 (cathode) are
identical. Platelet A17-2 is the plastic or ceramic anode flow field platelet consisli"g of molded depth and
through features. Platelet A17-2 contains the features that define the hydrogen humi~l r;~ n flow field
A5, anode active area flow field A21, and the cathode water humid;ric~ion area A6. The obverse side of
platelet A17-2 fomms the close out for the thermal management circuit A20 of platelet A17-3. Platelet A17-
3 is the plastic or ceramic cathode flow field platelet cu-,sisli--g of molded depth and through features.
Platelet A17-3 contains the features that define the thermal ~, Idl ,aye, ~ ,enl heat e~chan9ef A20. air toxY9en)
hu..,i~ n flow field A14, cathode active area flow field A22 and the anode water hurr~ ;on area
A15. Theair (oxygen) hurr~;rl~fi-~ "~ flow field A14, cathode active areaflow field A22 and the anodewater
hul~ area A15 are on the obverse side of platelet A17-3.
In all plates A17-2 to A17-3 the through transverse border p~ ec or Illd -;fuld~ A93 and
comp. ~sion tie rod holes A16 are coo. ii. Idl~ with those of EMA A3 in Fig. 1~.Figs. 1 9A-G are a series showing in plan view from the facing side of each platelet and the details
of one embodiment of the through and depth features of the 4 platelet bipolar sep~dlor plate of Fig. 18
in accord with the IFM p, i, , ' s of the invention. It should be noted that the ri, uyl ~:asion of plates is as
shown in Flg. 18 with the same conventions as used above in the edge conduction embodiments.
PI~Ll-,b 1 and 4 are ess~ 'Iy the same with the ~ - ~ epl;on of when sealing ridges are employed,
Fig. 19A shows as A17-1 the front of platelet 1 on the left and as A17-4 the back of platelet 4 on the right.
The anode current c - " ~ ~ - ,ic-. usc. ~n platelet features define the Cathode water hum i~ ~:r~ n area A6~
anode active area A4A, and hydrogen hu---i-J;r~ on flow field A5. A sealing surface A23 with optional
sealing ridges surrounds the active and hul ~ ~;d;fi~ ;~1 ion areas A19. Manifold close outs for distribution and
...d..iruldsoftheanodeflowfieldplateletA17-2arefOrmedbytheanode~ic~us~ dnir~ld
close outs A25.
The cathode current c-"~ - ..,i..rosc.~e" platelet A17-4 features define the air (oxygen)
humir~ i(Jn flow field A14, cathode active area A4C, and the anode water hu..licl;ri~ n area A15. A
sealing surface A24 with optional sealing ridges surrounds the active and hul-.;~l;r~ l;on areas A19.
Manifold close-outs for distribution and ~ lion ",a"itulds of the anode flow field platelet A17-3 are
formed by the cathode mi~,.us~.~n l~dnifùld close-outs A26.
Fig. 19E~ is a plan view of the plastic anode flow field platelet A17-2 -Front with a fragmentary
portionoftheanodecurrentc-"- ",i..,osc-,tenplateletA17-1 overlainonthelowerrightcomertoslow
the posilio, ,9 and Oli~ldliOn. Platelet A17-1 is bonded into an anode current c~ ",ic-,u:,c,~
de,u.~asion A31 and forms "~d~.ir.~ld close outs for the hydrogen distribution manifold A27, hydrogen
--"~'-- ~ Illdlli~OICl A28, anode active area distribution manifold A29 and anode active area cc"e
Illdl '' ' ' A30. Two bus bars A18 are el~l" "y bonded to the anode current cO"?C~ mic,us~ en
platelet.
The anode current c c "~ ~ mic, USL, ~en area A3 1 may be COpldl Idl with the rest of the platelet to
place the surface of the anode current --"~ ~c microscreen platelet A17-1 flush with the surface of the
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anode flow field platelet A17-2 or it may be inset to form a recess which receives graphite paper
r le_l, udes of the EMAs.
Fig. 19C depicts the front side of the plastic anode flow field platelet A17-2 -Front. This platelet
has both through and depth features. The major through features are the comp, ~sion tie rod holes A16
transverse manifolds; hydrogen outlet manifold A8, hydrogen inlet manifold A9 water inlet manifold A10,
water outlet ,,,a,,ifulu A11 air (oxygen) outlet manifold A12 and air (oxygen) inlet manifold A13. Other
through features are the hydrogen inlet via A32 hydrogen outlet via A35 cathode hul, ~ ; r;C ~ n water inlet
via A44 and cathode humicl;r;~ ;on water outlet via A41. The major depth features on the front of the
anode flow field platelet are the hydrogen hull~ rc~liol) s~l-er,li"e c~neL, A36 anode active area
se".t:"li"e cl~annr ls A39 and the cathode humi~ lir~ - l water serpentine channel A43. These features
are desi~"ed to optimize the flow rates and pressure drops of the device.
Hydrogen fuel for the anode enters the h~"--;d;r~ n area through the hydrogen inlet via A32
enters the hydrogen distribution ,--ar ~ A27 through the hydrogen distribution ...anif~ld inlet A33 and
is distributed to the two hydrogen st:, ~.e"li"e .J ~dnnr lj A36 through the hydrogen se~ ~e,)li, ,e channel inlets
A34. Hydrogen gas is humidified through the water p~""-~ ~ electroiytic membrane which is in contact
with the hydrogen hu",i~/ ~;. .liorl se, I,~"li"e channel A36. Humidified hydrogen leaves the hurni~iiri, ~ n
area through the hydrogen se".~ ~li- .e channel exits A37 enters the hydrogen 'e ~ ,- Idl A28, and
passes into the anode active area distribution manifold A29, flows into the anode active area st:. ~er,li- Ie
il ,annel~ A39 though the anode active area ~ ,e, llil ,e channel inlets A38. With in the active area hydrogen
is cataiytically nY~ Pd on the anodesideof an EMAto produceel~l-u, s and protons. Protons pass from
the anode catalytic site through the electrolytic m~" ~b~ dl ,e to the cathocie. El~l, u, la are drawn off from
the anode catalytic site through the graphite el~il, ude. Electrons from the graphite elect, ude are c
bytheanodecurrents- 'e ~c Illiclu:,- l~nA17-1 andconductedthroughthecompositebipolarsepcudto,
by bus bars A18.
n~p'etcd hydrogen leaves the active area via the anode active area se".~"li"e il Idl .nr l ~ exits A40
and flows into the hydrogen Ic~ man~old A31 finely exiting through the hydrogen exit via A35.
Hot water for cathode (air, oxygen) hu.,,~ r~ n enters throu9h the cathode hum;~ ion water
inlet via A44, passes into the cathode hu~ l riu~lio~ l water se",~:"li"e channel A43 through the cathode
hu,,~;cl;r~ lion water se"~,li"e channel inlet A45 exits through the cathoc~e humi.lir;~ n water
sel ~J~I lline channel exit A42 and leaves through cathode hu-, id;ri~ .1 ;on water outlet via A41. Part of the
hot water flowing through the serpentine channel is osmotically pumped across the electrolytic membrane
to humidify cathode air ~oxygen).
Fig. 19D depicts the back side of the plastic anode flow field platelet A17-2 -Back. This platelet
has both through and depth features. The major through features are the comp,~sion tie rod holes A16
transverse m~ ,ifol~l:" hydrogen outlet manifold A8 hydrogen inlet manifold A9 water inlet manifold A10
water outlet Illdl.;fol~ A11 air (oxygen) outle~manifold A12 and air (oxygen) inlet IlldnifOld A13. Other
through features are the hydrogen inlet via A32 hydrogen outlet via A35 cathode hurT~ ;ri.i tl i.~n water inlet
via A44 and cathode hull .~ r;~ ~lion water outlet via A41. The maior depth features are the hydrogen inlet
channel A47, hydrogen outlet channel A50, air (oxygen) outlet channel A.~3, and the air (oxygen) outlet via
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base A55. Most of the surface of the anode flow field platelet A17-2 is used as a ciose out for the cooling
water channels on the cathode flow field platelet A17-3.
Hydrogen flows from the hydrogen inlet " lal lifuld A9, through the hydrogen inlet channel inlet A48,
into the hydrogen inlet channel A47, through the hydrogen inlet channel exit A46, and finally into the
hydrogen inlet via A32. Hydrogen passes from back to front of the anode flow field platelet (Flg. 19C),
through the hydrogen inlet via A32. Depleted hydrogen from the active areas flows back through anode
flow field platelet through the hydrogen outlet via A35, into the hydrogen outlet channel inlet A49, through
the hydrogen outlet channel A50 and the hydrogen outlet channel exit A51, finely exitlng into the hydrogen
outlet ,,,~irul~ A8.
DPr' ~.~ ' air (oxygen) is removed from the cathode hUll~ ;u~liorl and active areas (Fig. 19F),
through the air (oxygen) outlet via base A55, air (oxygen) outlet channel inlet A54, air (oxygen) outlet
channel As3, air (oxygen) outlet channel exit A52, finally flowing into the air (oxygen) outlet " ,~ 'c ' '
Current is conducted through the anode flow field platelet via the two bus bars A18.
Fig.1 gE depicts the front side of the plastic cathode flow field platelet A17-3 -Front. This platelet
has both through and depth features. The major through features are the C GI I Ipl ~:~iùn tie rod holes A16,
transverse I l lal~ 'c ~c~ hydrogen outlet " ,~ ' 'c' A8, hydrogen inlet I l IdnitGId A9, water inlet manifold A10,
water outlet Illdl 'L ~C' A11, air (oxygen) outlet ",~ ' ' A12, and air (oxygen) inlet ,,,cu, ' 'c' A13. Other
through features are the air (oxygen) inlet via A60, air (oxygen) outlet via A61. anode hu", ' q~ ~n water
Inlet via As8~ and anode hull ~ ~ ~ water outlet via A57. The major depth features are the cooling
waterse,i,enli"ecl,~"~ A62,h~""iJ';~ nwaterinlet",ar,'':''A64andthehL""i~lric~lionwateroutlet
IIIcD '' ' ' A63.
Cooling water enters through the water inlet I l lcl lifulcl A10, cooling water channel inlet A65, cooling
water channel A66 finally entering the cooling water sc u,e"li"e channel A62 through the cooling water
sc_, ~ li"e channel inlet A67. Flowing through the cooling water serpentine channel the cooling water
picks up heat which is a by product of the 01~ ~ill ucl)e,, ,ical, ~aclions. Hot water leaves through the cooling
waterserpentinechannelexitA68andflowsmtotheh~ ;r~ nwaterinletlllallifuld junctionA69,into
the humi~l r~ on water inlet manifold A64, and finely exits through the hlJ" ~ riC~ ,n water cathode exit
A70 and cathode water humicl~ n inlet via A56 or the hum~ ic~ n water anode exit A71 and anode
waterh~""i~l r.. ,~lioninletviaA58. Hotwaterisusedforhu"~ c~lionbeCauseofithighdiffusionactivity.
Air (oxygen) enters the cathode from the air (oxygen) inlet " ,ar 'd A13, flows into the air (oxygen)
inlet channel inlet A72, passes through the air (oxygen) inlet channel A73, into the air (oxygen) inlet channel
exit A74, and flows to the cathode humi~ n and active area .,I ,annels through the air (oxygen) inlet
via A60. Air (oxygen) is humidified as it passes through the air (oxygen) hu"~ lion channels and is
consumed in the cathode active area d ~ r ;c ~ in Fig.19F. Depleteci air (oxygen) and product water leave
via the air (oxygen) outlet via A61 which conne~b to the air (oxygen) outlet Illaniruld A12 through the air
(oxygen) outlet channel on the anode flow fierd platelet A17-2.
Current is conducted through the cathode flow field platelet via the two bus bars A18.
Fig.19F depicts the back side of the plastic cathode flow field platelet A17-3 -Back. This platelet
has both through and depth features. The major through features are the co" ,p, ~aSiOn tie rod holes A16,
SUllSrnU~E SHEE~ (RULE 2B~
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transverse manifolds; hydrogen outlet manifold A8 hydrogen inlet manifold A9 water inlet manifold A10
water outlet manifold A11 air (oxygen) outlet Illal)ifuldi A12 and air (oxygen) inlet ~ irul~ A13. Other
through features are the air (oxygen) inlet via A60 air (oxygen) outlet via A61, anode humi- l;r(j .lion water
inlet via A58. and cathode hum i- l;r c~l ;on water outlet via A59. The major depth features on the cathode
flow field platelet are the air (oxygen) humi-l;r~ on serpentine l.;hdllll_i A80, cathode active area
se. ye, .Lil ,e cl Idl ll'.CIS A86 and the anode hurr~;Uir.~ " water serpentine channel A77.
Air (oxygen) for the cathode enters the hulllid~r~ area through the air (oxygen) inlet via A60
enters the air (oxygen) distribution manifold A79 through the air (oxygen) distribution manifold inlet A78
and is distributed to the two air (oxygen) st:.~.~,li"e ch~ " ,cls A81 through the air (oxygen) serpentine
channel inlets A80. Air (oxygen) gas is humidified through the water permeable electrolytic membrane
which is in contact with the air (oxygen) hu-. ' ' ~ ' ) se~- ~.~ ~li- ~e channel A81. Humidified air (oxygen)
leaves the hu- - "~ ~ ~ area through the air (oxygen) se. ~ t:r li- -e channel exits A82, enters the air (oxygen)
hu~ c-~e.t ~.. Idllirl.~ i A83 andpassesintothecathodeactiveareadistribution,- IdnirUIli A84
flows into the cathode active area serpentine cl ,dnnels A86 though the cathode active area se".er,li"e
channel inlets A85. With in the active area oxygen is catalytically reduced receiving protons and el~l- un~
from the anode to produce water. Electrons flow from anode to cathode via bus bars A18, into the
cathode current c ~ "e ' - " ,ic, osc, ~n 17-4 through the cathode graphite el~ll uoe on the EMA and finely
docking with a cathode catalytic site where the electrons react with anode ge"t:,dl~d protons and oxygen
to produce surplus heat and product water. r~, ~ air (oxygen) and product water leaves the active
area via the cathode active area se- ~ t:"lil ,e ~ l ldl ll l. ls exits A87 and flows into the air (oxygen) c ~
~"~ ' 'd A88 through the air (oxygen) c c " ~ manifold exit A89 finely exiting through the air (oxygen)
exit via A61.
Hot water for anode (hydrogen) hu. "id~ ;on enters through the anode h~ d;~ n water inlet
via A58 passes into the anode hu, ~ ca~ n water serpentine channel A77 through the anocle
hU."iri:~;c~l;. nwaterserpentinechannel inletA76, exitsthroughtheanodehum~ waterst:" enli"e
channel exit A75 and leaves through anode humi~ ;on water outlet via A59. Part of the hot water
flowing through the se-~,enline channel is os".oi --'ly pumped across the electrolytic membrane to
humidify anode hydrogen.
The bus bars A18 (top and bottom) project through the plate to contact the ~ - ,ic-, ~,sc, ~n - ~ "~ 'o~-
plate A17-4 as seen in Fig.19a which shows a plan view of the plastic cathode flow field platelet A17-3 -
Back with a fragment of the cathode current c ~ mi~.l USLI ~n platelet A17-4 in the lower right comer.
Platelet A17-4 is bonded into a cathode current c "~ t~ micl u~ en deprt:~siùn A90 and forms manifold
close outs for the air (oxygen) hull,i~ n distribution manifold A79, air (oxygen) hull~ ion
~ ~ "~ " l manifold A83 cathode active area distribution manifold A84 and cathode active area " - r ~
I-l~l'~'-A88. TwobusbarsA18arebondedtothecathodecurrent~ c-llli~,uS-,tenplateletA17-4
to provide a good el~l. icdl connection.
The cathode current c-"- ~ - microscreen area A90 is selected to either place the surface of the
cathode current - 'l~ h ll licl us~ en platelet A17-4 flush with the surface of the cathode flow field platelet
A17-3 or it may be inset to form a recess which receives graphite paper elec~,ùdes of the elecl,ude
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membrane assemblies A3 in Fi~. 17.
Bus Bar Conduction l~.lag,aled Therrnal l~i .age~-~Q~
Thefollowingdetaileddesc~ tionillustratesbusbarthrough-conductionlH~ noftheinvention
by way of example, not by way of limitation of the p- i- , 'e~ of the invention. This desLi- i,uLion will cleariy
enable one skilled in the art to make and use the invention, and describes several emboLli...e~
adapldliUns, \~dl idlions, altematives and uses of the invention, including what I presently believe is the best
mode of cartying out the invention.
Fig. 20 is an ~ isometric view of a single cell B 1 intemal of the stack CCJI 11 pl isil 19 sepd. dlul :,
B2A and B2B sar,~vricl . ~9 EMA B3A and cu, lld~lil ,9 EMA B3B of the next adja.;~ ~t cell. In this view, only
the H2 (anode) side of the bipolar sepdldlul:, are visible, but as shown below, there are cool~L~iirldle ~2
zones on the hidden ~cdtl .ode) side. The large rectangular areas B4A are the active areas of the cell, B4A
r~pl~s~,li"g the anode side and B4C the cathode side.
The EMAs B3A and B3B include cataiyst coated areas B7A and A7C that are coo- Liil ldle with the
CGI I ~ponciil~9 active areas B4A, B4C. Reactant and cooling water ~ - .~u ~irOIds are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet ...ar f~ B7 flows through the anode active area B4A and
leavesviathehydrogenoutlet...ar.'~'dB6. Air(oxygen)entersviatheair(oxygen)inlet---a ~'c'B10flows
through the cathode active area A4C and leaves through the air (oxygen) outlet Illdlli~oWi B11. Cooling
water for thermal ...anag~ ent enters through water inlet ~--d -iful~ B9, flows through an intemal heat
L~ I ~ge and leaves through the water outlet .. Id n;fold B8. Transverse reactant and cooling water inlet
and outlet Illal~iful~s B6, B7, B9, B11, B10 and B12 pass through bipolar sepdldlol:~ B2 and EMAs B3.
Compression tie rod holes A16 are evident on the margins of the bipolar sepdldlul:~ and EMAs.
Fig. 21 is an e ,'~i~ isometric view of a 4-platelet humidified bipolar IFMT sepd dlur B2 of this
invention comprising plates of three different types, plates B13-1 and B13-4 being identical current
~ "~ ;' ' ~ I. .ic. uaL. t en pl ~ Current is conducted through the two plastic core platelets B13-2 and
B13-3 by one or more intemal bus bars B14. While two rectangularcross section bus bars are depicted,
any number, geometrical cross section, and o- il :r,ldlion may be employed, both within the screen field or
extemaltoit. Sealingiseffectedaroundthemarginofthe---i-.,us~ enplateletbytheplasticcorer'=t~ole~c
B13-2 and B13-3, which may include sealing ridges (not shown) around the reactant and water " ,dn ~ 'cl~,
and around the active areas B4A and B4C.
The two metallic current c ~ .-,iu-c,~.;-~,- platelets B13-1 and B13-4 are identical. Platelet
B13-1 is the anode current - - "~ ~ ~ ~- -ic- usc~ con~ialing of a rt:pedlil lg pattem of through etched or
punched holes. Platelet B13-2 is the plastic or ceramic anode flow field platelet consiili"g of molded
depth and through features. Platelet B13-2 contains the features that define anode active area flow field
B16. TheobversesideofplateletB13-2fommstheCloseoutforthethemmalllldllag-:l,,~,tcircuitB17Of
platelet B13-3. Platelet B13-3 is the plastic or ceramic cathode flow field platelet cu~ lil ,9 of molded
depthandthroughfeatures. PlateletB13-3containsthefeaturesthatdefinethethemmalllldnage,,,entheat
cAchanger B17 and cathode active area flow field B18. The cathode active area flow field B18 is on the
obverse side of platelet B13-3.
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In all plates B13-2 to B13-3 the through transverse border p~s~ges or manifolds B15 ana
Cull Ipl ~ ion tie rod hoies B12 are coo- dil IdLt~ with those o~ EMA B3 in F~g. 20.
Figs. 22A-G are a series showing in plan view from the facing side of each platelet the details of
one embodiment of the through and depth features of the 4 platelet bipolar st:pdl~lol plate of Fig. 21 in
accord with the IFM pri"c;~.lrs of the invention. The p,ug,~:ssiùn of plates is as above. with Fig. 22A
showing front (anode B13-1 ) of platelet 1 on the left and the back ~cathode B13-4) of platelet 4 on the right.
The anode current c ~ m ic, u5L;I t en platelet B13-1 has features that define the anode active area B4A.
A sealing surface B19 with optional sealing ridges surrounds the active B4~. Manifold close outs for
distribution and ~ manifolds of the anode flow field platelet B13-2 are forrned by the anode
...ic,usc.~,,...dn'c,c''closeoutsB21. Thecathodecurrent~~" ' ~--ic.us~,.~nplateletB13-4features
define the cathode active area B4C. A sealing surface B22 wUh optional sealing ridges surrounds the
active area B4C. Manifold close outs for distribution and ~~" '' )n ~ irulda of the anode flow field
platelet B13-3 are fomled by the cathode ~ u~) ~--arifoW close outs B22.
Fig. "~B is a plan view of the plastic anode flow field B13-2 -Front with a section of the anode
current ~ "~c' mic.u:,L.een platelet B13-1 in the lower right comer. Platelet B13-1 is bonded into an
anode current -~ ~ mic.usc-~-, c~e,c,~;un B25 and forms IlldllirUId close outs for the anode active
area d~stribution ~ ifol~l B23 and anode active area ~ d~iruld B24. Two bus bars B14 are
bonded to the anode current ~c'~- ~c mic.os.,.~n platelet to foml a good el~l-i..al cc--ne~;lion.
The anode current ~ ;-os..-~n de~-~as;on B25 is selected to place the surface of the
anode ~ Iu~Ll~ll platelet B13-1 flush with the surface of the anode flow field platelet B13-2, or it may
be inset to forrn a recess which receives graphite paper u'~_L- udes of the el~l- ude me- ~ .b. dl ~e asse. ~ ~I'
Fig. ~'7C depicts the front side of the plastic anode flow field platelet B13-2 -Front. This platelet
has both through and depth features. The major through features are the com~ sion tie rod holes B12,
transverse Illdl lirUI~.Js, hydrogen outlet manifold B6, hydrogen inlet Illdl lirc~ld B7, water inlet manifold B8.
water outlet Illdll'' '' B9, air (oxygen) outlet manifold B11, and air (oxygen) inlet manifold B10. Other
through features are the hydrogen inlet via B26 and the hydrogen outlet via B28. The major depth features
on the front of the anode flow field platelet are anode active area serpentine Clldlll)el~ B31, anode active
area distribution ~--d--ifold B23 and the anode active area "~~' n manifold B24. These features are
de~;y"ed to opli",i~: the flow rates and pressure drops of the device.
Hydrogen fuel for the anode area enters through the hydrogen inlet via B26, passes through the
anode active area distribution Illar,iruld inlet B27, into the anode active area distribution manifold B23,
flows into the anode active area serpentine cl~annels B31 though the anode active area St~ , llil ,e channel
inlets B30. Within the active area hydrogen is catalytically oxidized on the anode side of an EMA to
produce ele~L,uns and protons. Protons pass from the anode catalytic site through the elc~ll.,lytic
ll,t:---b-~,e to the cathode. Electrons are drawn off from the anode catalytic site through the graphite
electrode. Elecl. uns from the graphite electrocie are cc " ' i by the anode current ., ~ "~ ' m iCI usc, ~"
B13-1 and conducted through the composite bipolar se~dldLùl by bus bars B14.
Depleted hydrogen leaves the active area via the anode active area serpentine ch~ -- .e:s exits B32
and flows into the anode active area ~ manifold B24, through the active area ~ ..a, ~irold
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SUBST TU~ES~U~2B,)
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exit B29 and finally exits through the hvdroaen exit via B28.
Fig.22D depicts the back side of the plastic Anode Flow Field Platelet B 13-2 -Back. This platetet
has both through and depth features. The major through features are the CGIllpl~:ss;on tie rod holes B12,
transverse Illallir~Jlda, hydrogen outlet manifold B6, hydrogen inlet ",a"if~,lcl B7, water inlet manifold E~9,
water outlet ")ar,iruld B8, air (oxygen) outlet ll)dllifuld B11, and air (oxygen) inlet ..,dnifulcl B10. Other
through features are the hydrogen inlet via B28 and the hydrogen outlet via B26. The major depth features
are the hydrogen inlet channel B34, hydrogen outlet channel B37, air (oxygen) outlet channel B40, air
(oxygen) outlet via base B43, air (oxygen) inlet channel BCi0, and the air (oxygen) inlet via base B42. Most
of the surface of the anode flow field platelet B13-21s used as a close-out for the cooling water ~;l Idnl ~el
on the cathode flow field platelet B13-3.
Hydrogen flows from the hydrogen inlet Illdn-' ~d B7, through the hydrogen inlet channel inlet B35,
into the hydrogen inlet channel B34, through the hydrogen inlet channel exit B33. and finely into the
hydrogen inlet via B26. Hydrogen passes from back to front of the anode flow field platelet Flg. ggD,
through the hydrogen inlet via B26. re r ~ hydrogen from the active areas flows back through anode
flow field platelet through the hydrogen outlet via B28, into the hydrogen outlet channel inlet B36, through
the hydrogen outlet channel B37 and the hydrogen outlet channel exit B38, finaliy exiting into the hydrogen
outlet Illdllirold B6.
Air (oxygen) flows from the air (oxygen) inlet ",~ ~irold B10, through the air (oxygen) inlet channel
inlet B49, into the air (oxygen) inlet channel BJ0, through the air (oxygen) inlet channel exit BCil, and finsly
into the air (oxygen) inlet via base B42 which communicates with the air (oxygen) inlet via B44 on the
cathode flow field platelet B13-3 in Fig. ggE. The air (oxygen) inlet via B44 brings air (oxygen) to the
cathode active area flow field.
air (oxygen) is removed from the cathode active area through the air (oxygen) outlet via
B4s (Fig. 22E) into the air (oxygen) outlet via base B43, into air (oxygen) outlet channel inlet B41, through
the air (oxygen) outlet channel B4û, past the air (oxygen) outlet channel exit B39, finally exiting through the
air ~oxygen) outlet Illdl lirGld B11.
Current is conducted through the anode flow field platelet via the two bus bars B14.
Fig. 22F depicts the front side of the plastic cathode flow field platelet B13-3 -Front. This platelet
has both through and depth features. The majorthrough features are the com",~ssion tie rod holes B12,
transverse Ill~D ,ir. ' ~ hydrogen outlet Illdnifold B6, hydrogen inlet ~"anirold B7, water inlet Illdl lirUId B9,
water outlet manifold B8, air (oxygen) outlet Illdl ''_' ' B11, and air (oxygen) inlet manifold B10. Other
through features are the air (oxygen) inlet via B44 and the air (oxygen) outlet via B45. The major depth
feature is the cooling water sel~ e ,li"e cl Idl ll i. ls B46.
Cold cooling water enters through the cooling water inlet " ,anifold B9, flows into the cooling water
s~, ,ut:nline channel inlet B47, and passes into the cooling water serpentine channel B46. Flowing through
the cooling water serpentine channel B46 the cooling water picks up heat which is a by product of the
cl~l.u.,lle,,,ical l~:aclions. Hot water exits through the cooling water serpentine channel exit B48, finally
leaving through the cooling water outlet IllalliruW B8.
Air (oxygen) passes through to the cathode flow field platelet B13-3 -Back through the air (oxygen)
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inlet via B44 which communicates with the air (oxygen) inlet via base B42 and the air (oxygen) inlet
manifold B, O on the anode flow field platelet B13-2 -Back in Fig. ""D. Depleted air (oxygen) and product
water leaves the cathode flow field active area through the air (oxygen) outlet via B45 which communicates
with the air (oxygen) outlet via base B43 and the air (oxygen) outlet manifold B11 on the anode flow field
platelet B13-2 -Back in Fig. 22D.
Current is conducted through the cathode flow field platelet via the two bus bars B14.
Fig. G depicts the back side of the plastic cathode flow field p~atelet B13-3 Back with a portion
of the cathode current r ~ .l uaCl ~n platelet B13-4 shown in position (fragmentary portion shown
in the lower right comer). This platelet has both through and depth features. The major through features
are the compr~:asion tie rod holes B12, transverse ",~ '( 'd~ hydrogen outlet manifold B6, hydrogen inlet
Illar ' 'd B7, water inlet I lld~ old B9, water outlet Illal ' 'd B8, air (oxygen) outlet ~"ar iruld B11, and air
(oxygen) inlet manifold B10. Other through features are the air (oxygen) inlet via B44 and the air (oxygen)
outlet via B45. The major depth features on the cathode flow field platelet are the cathode active area
distribution ,,,ar,irul~ B53, cathode active area --"- ~ ",~,' ' ' B57, and the cathode active area
s~ ~-e, llil ,e cl ,d- Inels B55.
Air (oxygen) for the cathode enters the hull~ f~ or. area through the air (oxygen) inlet via B44,
passes the cathode distribution Illdr ' ' ' inlet B52, flows into the cathode distribution manifold B53 and
is distributed to the cathode active area s~ ,e cl-~,ncla B55 though the cathode active area
serpentine channel inlets B54. Within the active area oxygen is catalytically reduced receiving protons and
ele_LI uns from the anode to produce water. Electrons flow from anode to cathode via bus bars B14. into
the cathode current & - " - ...;~,. OSL;I ~,- 17-4, through the cathode graphite el~l-ude on the EMA and
finely docking with a cathode catalytic site where the ele_L. u-)s react with anode 9~ ~~- cled protons and
oxygen to produce surplus heat and product water. Depleted air (oxygen) and product water leaves the
active area via the cathode active area s~" e- lli"e channels exits B56 and flows into the cathode active
area c-"~ ifoW B57, through the air (oxygen) c~ manifold exit B58 finely exiting through
the air (oxygen) exit via B4~ which COIlllllull;~ dL~s with the air (oxygen) outlet via base B43 and the air
(oxygen) outlet Ill~)iful~ B11 on the anode flow field platelet 13-2 -Back Fig. 22D.
Platelet B13-4 is bonded into a cathode current ~ ",ic, us~,, ~n dep- ~asiun B59 and forms
, ..a. .i~uld close outs for the air (oxygen) active area distribution manifold B53, and the air (oxygen) active
area ~ irul~ B57. Two bus bars B14 are bonded to the anode current ~ ~ " - ~ . ,i~i, ua~,-l ~,-
platelet in a manner to provide good el~ .al conduction. The cathode current c - " miL. usc, ~n area
B59 is selected either to place the surface of the anode mi.;, usc, ee,- platelet B13-4 flush with the surface
of the cathode flow field platelet B13-3~ or it may be inset to fomm a recess which receives graphite paper
electrodes of the electrode me".br~e assemblies B3 in Fig. 20.
Edge and Through-Conduction Section Views:
Fiç1s. 23A-D show several altemative constructions for edge conduction, taken along the section
line 23-23 of Fig. 16. Fig. 23A shows the embodiment of Fig.16 in which the anode mic, us,i,~" F17-1
and cathode mic.usc-.~ en F~7-4 are connecL~d by current bridge F18, and folded togell.e. and bonded
to the platelets F17-2 and F17-3 therebetween to form the BSP. Various depth, through and close-out
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features are descri~ed a~ove with respect to Fig- 16 (and related platelet drawings) so they will not be
repeated here or in Fiç~s. 23B-D.
Flg. 23B shows the tabs F94 on both the anode mic,usc,~n F17-1 and cathode mi..-,usc,et,l
platelet F17-4 bent together and bonded at the bottom, by methods such as brazing, SGldt:,ill9, spot
welding, conductive cement. roll crimping, and the like. Fig. 23C shows an overlap of tabs F94 and
bonded at F96. This type of contact could also be a press fit of tab F94 of platelet F1701 into the gap
between the tab F94 of platelet F17-4 and the bottom of the two core pl~t~4t~ Fig. 23D shows an
example of two edge bus bars or strips F97 top and bottom spot welded or bonded at F98.
Figs. 24A and B show section views of various emb- ll~ ll~ of the bus-bar conduction taken
along line 24-24 of Fig. 18. FTg. 24A shows an e" lbodi. "enl wherein the " ,ic, us ;1 ~ ,s A17-1 and A17-4
are inset in a ,~cesses A94 in the respective core platelets A17-2 and A17-3. The bus bars A18 are
inserted through the bus bar .~t~nliol) slots A95. The various depth, through and close-out features are
des.,-. iL,ed above in cGl)l)eclion with Fi~. 18 and related platelet d~ yS. Fi~. 24B shows I I ,ic, usc, ~ ,:,
with pe, i~,l)e, al edges COGI Ui. Idl~ with the edges of the core pl~t~letc
Co.,.~.o~ B~polar Sep.-.dl~r FaL,icd~ P ~"ess~
Fig. 25 is a flow sheet depi ,lil lg the pl il l ,i~Jal steps in the platelet manufacturing process involving
feature ru,ll,dlion by cl)~.,ical milling (etching). While this applies plill ~ Iy to a metal ",ic,us",~.,
platelet as desc, iL,ed in the example below, the metal dies for the plastic core ~ ~ ~ ~ are produced by
thisprocess. Further~thisprocessisusedtoproducetheplasticplateletslll~lllselvesby~;llelllicalmilling~
typically by solvents. The steps are as follows:
A. PLATELETSTOCKlNSr~~ ; I,,cu,,,i.,gmetalplateletorsld,, ,gdiestockC1 is
s~,s t~ ~ to il lip~liun C2 to verifymaterial type, rolled hdl-ll le~s, rolled l h 'c n:Ss, surface unifommity, and
relevant supplier il lru~ dLiol).
B. PLATELET STOCK CLEANING AND DRYING: Platelet stock is cleaned and dried C3
forpholo,~sis~F~'ic ~ ~byscrubbing,deyltd~illg.andCll~llliCalCleaningUSinganaUtomatiCmaChine.
This process removes residual sheet stock roiling grease and oils in the case of metals and dirt and static
cling COIIIdlllilldlll:, in the case of plastics. After dey,~dsi.lg the platelet is sll~, t~ ~ to a mild chemical
cleaning at room temperature by a dilute etching solution to remove oxides and surface impurities. For
titanium the cleaning solution is 3%-9~/O HF and 10%~18% HNO3. For other metals such as, I e s steel
or aluminum, ferric chloride of 30-45 degree Baume at room temperature is used as the cleaning solution.
For plastics, the apprup, idle plastic solvent may be employed. Platelets are dried in a forced convection
dryer as the final step prior to ~r~r~ n of pholo, ~si;il.
Depe~- Ig on whether the resist is wet or dry, the resist ~pp ~ ;on pl uceeds by either Steps C-1
and C-2, or by C-3, below.
~C-1. WET PROCESS PHOTORESIST APPLICATION: Wet process pholùl ~;sl allows the
finest ~I s - - Ition of details due to the thinness of the pholol esisl layer. Wet pholul e:,isl is typically applied,
-C4, using a dip tank. Small platelets may be spin coated using spin coating machines developed for the
se,l l ,ico" luctor industry.
C-2. RESIST OVEN: Wet resist is baked (cured) in oven C5 to from a hard resilient layer.
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C-3. DRY PROCESS PHOTO-RESIST APPLICATION: Dry film photo-resist is used where
tolerances can be relaxed. For fuel cell sep~ ~llul i dry film resist is typically used. Dry film resist is peeled
off a backing sheet and bonded, C6, using a heated roller press. The roller press is similar to those used
in the printed circuit industry. The rolling process automatically peels off the backing material from the
phOIolt:ai,l. Typical dry film photo-resist material is 2 mil "Riston 462~" manufactured by the duPont
Company.
D. PHOTO-RESIST MASK UV EXPOSURE: Platelets are ~o~posed C7 using a UV contact
exposure machine. Careful dLL~)Iion is paid to precise alignment of both sides of the artwork. Rey;~LI dLion
targets on the mask are used to aid this process.
E IMAGE DEVELOPING: Tho ~ - ~ .oced platelet is passed, C8, through adeveloping solution
and oven. Wet process resist is developed in a hylJI u~.-dl bon dcvelo,u~l . which removes uncured resist.
Typical dcv_lupe( is ~S~odd~J-s Solution", part number GW 325, manufactured by Great Western
Ch~ and Butyl Acetate, part number CAS 104-46-4, available from \lan Waters and Rogers. Wet
process dcvelopl"ent uses these solutions full strength at room temperature. After exposure to the
dûv~ i.lg agents the ,~"~..., ~,9 wet resist is rebaked to form a resilient layer. Dry process dcv~ ,g
uses duPont "Liquid Dcvelupel Conc~,LIdL~, part number D-4000, in a 1.5% solution at 80'F.
F. SPRAY ETCH TANK Cl -'1!C.'~I MACHINING: Developed platelets are etched C9 in
a spray etch tank. Spray tanks are pl _~. l t d to dip tank etchers due to the higher etch rates which result
in highe m "acl, ,e throughput rates. In some cases finer r- ~ 'ution can be _ t. ,~l with dip tank etchers
than can be obtained from spray etchers. The etching process is ver~ sensitive to the strength of the
etchant solution, speed of the conveyer belt, spray pressure and process l~:l l l ,ut:l dlure. Process f~ ~ k
C11 on these parameters is " , ~ Ied during a production run by continuous in-process inspection C10.
Line speed is typically varied to obtain the desired etch results. Either ferric chloride or HF/nitric acid
solution is used as the etchant. Ferric chloride is used for copper. aluminum, and r~ steel. HF/nitric
acid is used for titanium. For titanium typical etchant conct:"l,dLions nun from 3%-10% HF and 1 û%-18%
HNO3. The range of etching temperatures for titanium are 80-130 F. For other metals typical ferric
chloride concer,L,dLiuns are 30-45' Baume' with the etching temperature " ~ ,ed in the range of 80-
130'F. The specific concel ILI dLiun and lel l ,pe, dlure condiLions can be cul lll~ for each different metal
employed. Line speed is a function of the number of active etching tanks. Typical etchers are built up
from individual etching tanks joined by a co"""on conveyer. Typical etchers are available from Schmid
Systems, Inc. of Maumee, OH and Atotech Chemcut of State College, PA. Platelets are washed in a
cascade washer after the last etch tank. The cascade washer removes excess etchant prior to il Ispe~liun.
G. IN-PROCESS INSI~ lOiN; Platelets are inspected at C10 to feed back etch rate and
line speed il ,lu" "dliun to the etching process. In-process inspection is typicaliy performed visually.
H. STRIP RESIST: Wet process photo resist is stripped C'12 using a hydrocarbon stripper
at 200'F. A suitable one being "Chem Strip", part number PC 1822, rnanufactured by Alpha Metals of
Carson, C~ llia. Dry process photo resist is stripped using a ccmmercial strip solution such as
~Ardrox~, part number PC 40~i5, manufactured by Ardrox of La Mirada, (: ' , lia. Ardrox is diluted to 1 -
3% and used at 130 F. After Ll i~pi. .g the platelets are cleaned using a cascade washer.
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1. FINAL INS~ ON: Visuai final inspection is performed C13 by measuring and
cc""pd,i.,gwiththecriticaldimensions.plateletinspectioninformationC30selectedduringtheCADdesign
process. This i"~, llldlion is fed back to control the etching and design process. After finai inspection the
completed metal platelets are p,ucessed by either process J-1 or J-2.
J~ vl.Jr~ FD. .NACF- Completed titanium platelets are subjected to nitriding C14 in a
vacuum fumace. Sepa,dlu,a are loaded into a vacuum fumace which is evacuated to 10-6 torr. Dry
nitrogen is introduced into the fumace to a pressure of 1 psig. This cycle is ,~r~ Once the final
pressure of 1 psig is attained the fumace is heated to between 1200 F and 1625 F for a period of from
about 20 to about 90 minutes. The specific times and temperatures depend upon the thickness of the
titanium nitride coating desired. The furnace is cooled, repressured and the finished product nitrided
(passivated) platelet is ready for ass~"bl~ with plastic core fluid l,l~,ag~,lenl platelets to make a
cu",posi~e sepdl
J_2 NITRIDING FU..IJA~F BYPASS: Metals other than titanium are not nitrided.
K. METAL MIO~OS~I ~LLN MOTHER SHEETWORK IN l'I ~0; t~S BUFFER INVENTORY:
Completedmetallll;~lùscl~nmothersheetsarequeuedinabufferinventorybeingkeptlùy~:lll~ bytype
or in groups. Note the roll stock is typically titanium of ll ~ 'c. ,ess 4-25 mils (dep~ ~ ,9 on platelet design
req~ r ~, It:nla) 36 ' wide and the platelet blanks are 6-x8~, so that in the continuous feed process des., iL,ed
above the pl-tF~letc are ~u I dl l~ed 6-up that is, 6 across the width of the sheet.
It is i",po,l~,l to note that this process can be used for forming the plastic core platelet
CGIllpf255iOl I or embossing dies.
Flg. 26 is a process flow sheet depicli"g the presently p, ~ d method of r~bl icali~ ~9 plastic fluid
anagel"ent platelets and Idlllilldlillg with metal Illiclus~l~n platelets to form Illon- h;~ composite
bipolar sepdldlula.
A. COhll~t~SlON MOLDlNG PROCESS: Inco" ,i"g plastic platelet stock Cl 7 is s~ Ibjected
to illspeclion to verify material type rolled hdl-~lless. rolled ll ;(hless. surface unifommity and relevant
supplier i"lu" "alion. After i, lape~lion plastic sheet stock is Col llp- t:ssion molded C18 to fomm depth and
through features. Co,,,~ asion molding is capable of fomming depth features with infinitelY variable depths
as well as widths.
B. PLASTIC PLATELET SINGULATOR: Plastic platelet mother sheets are singulated by the
plastic platelet singulator C19. Shears saws knives and punches are typical methods of singulating
plastic pl~tPIetC
C. ADHESIVE 80ND AID APPLICATION PROCF~:S- Adhesive bond aid C20 is applied to
the plastic core platelets to facilitate leak free bonding. The specific nature of the bond aid depends on
the type of plastic being bonded. Bond aid varies from solvents epoxy glues and contact adhesives.
Bond aid is applied using spray or screen printing processes depending upon the plastic platelet being
~dbl iCdl~.
Bond aid is applied to the mating lands of platelets and must be prevented from flowing into depth
features which can cause partial or total b'ock~ge of fluid p~Cs~es This requires precise control of bond
aid viscosity and ~ppl;c~tion th P~.,ess. The viscosity and Ihiclh)ess parameters vary for each plastic /
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CA 02220901 1997-11-12
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bond aid combination and are well known in the art.
D. METAL PLATELET SINGULATOR: Metal mit,,usc,~,) platelets mother sheets C16 aresingulated by the metal platelet singulator C21. Shears, or saws are typical methods of singulating metal
r'
E. STACKING PROCESS: Metal and plastic platelets are oriented hu,i ul ly ordered(placed in proper sequence~. and verticaliy stacked in sequence C22 on hot platens. The platelet alignment
holes (compression tie rod holes of the various figures) are placed over pins to precisely align the platel~
so that mating platelet features coll~ldle to foml thevias, lands, Illdllilulds and cl1dlll)els. in this manner
up to 100 composite bipolar Sepdl dlUI ::i may be stacked for lamination at a time in a single bonding stack
between a top and a bottom platen.
F. LAMINATION BONDING: The asselllbled platelet stacks are loaded into a heated
Id"-i--dliun press for bonding C23. Different metals, plastic and bond aid comb;.,aliu.ls require different
bonding schedules. Bonding cor - 1S are d~,---i--ed by a specific schedule of applied pressure and
t~"p~dl,Jre. Typicat bond t~..pe,d-lresrange 15û deg. C to 30û deg. C. Bond pressureand temperature
must be precisely co- .I-, ~ t to prevent excessive de~o",~dlion of internal p~csageC while achieving leak
proof bonds.
G. PROOF AND/OR LEAK CHECK Bonded platelet sepdldlo.a are ledk checked, C24,
using a test fixture to apply interrlal pressure to the ~;l Idl In~,lS, Illdl ~ifulds and vias to verify bond integri~y,
i.e., that there are no edge ieaks or internal channel short circuits.
H. FINALTRIM: P, uces:,iny aids. such as handling frames and platelet se~uencing numbers
(formed on the edges of the pl ~t~ ) are removed (cut offl in the final lrim op~dlion C25 to produce the
composite bonded platelet sepdldlùt having the intricate, intemal Illil.;lUCIldllll~al fields des.;-iL,ed above.
Fig. 27 depicts the process of p. ~ldl il l9 the platelet design artwork for the ph - ~s ,og. dpl Iy wet
or dry process etching of platelets des-" ibed above in Figs. 25 and 26. The steps are as follows:
A. PLATELET DRAWINGS: Platelet assembly drawings are developed on computer
auLo,..dled drawing CAD systems C27. The II~Juiny~ are dimensioned in net dimensions. Both sides of
each platelet are finalized as plan views riepi~li"g the front and back. These ~J, c.~;. ~yS are ele ,l, u- ily
transmitted to the platelet mask artwork generation CAD system C29. From the CAD drawings a platelet
i"spe~;lion ~ ce C30 is gene, dled. This inspection ~ e consists of critical dimensions that need
to be verified during the artwork creation and manufacturing plucl~55es Both artwork and pl~t~'etC are
inspecte~ during the manufacturing process.
B. MASK ARTWORK GENERATION: Platelet CAD dICL~ I9S are converted in the mask
artwork CAD system C29 to photo tooling masks for each platelet. Etch factors are applied to each feature
in each drawing. Etch factors adiust the width of the phot~ u )g mask to the width of the features to
compensate for undercutting that occurs during the Ll,~:",ical etching p,ucesses used to mill individual
~ ~t~lefc This entails reducing channel d~mensions in the photo tooling mask to compensate for
undercutting. EtchfactorsdependuponthetypeOfmetal.typeof ;h~lllicdlmi~ingequipment,etchspeed~
type and strength of the etchant used. FabriCdliOn aids are added during the mask 9 ~ 1dlion process.
Fab,icalion aids include .~;~,dlion targets, platelet numbers and handling frames to aid in the stacking
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and bonding process.
C. bRTWORK PHOTOPLOTTING: Platelet art work is plotted at a 1 times magnification on
a film using an automatic photopl~tt~r C31.
D. POSITIVE INSI~tL~ I ION: Video inspection of the finished artwork is performed, C32.
using the i.,~pe~;lion ~ ce C30 ~el-elnL~d during the Platelet CAD drawing process. After i--speclion
the top (front) and bottom (back) platelet artworks are joined in precise l ~.~1l dlion to fom platelet artwork
C33.
Platelet artwork is used in the chemical milling p-ucesses that make metal ~ usCI~ r 't'
It is also used to develop co...p.~:,sion molding tooling.
It should be Ul .~ ;.luod that various mo~ 'ic~ , ~s within the scope of this invention can be made
by one of ordinary skill in the art without depd- li. ~9 from the spirit thereof. We ll ~~ ~u. ~ wish our invention
to be defined by the scope of the appended claims as broadly as the prior art will pem~it, and in view of
the sre~ :r~ n if neeci be.
