Note: Descriptions are shown in the official language in which they were submitted.
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` : : ~ LAMINATION OF INTEGRATED CIRC~IT PACXAGES
BACKGRO~ND OF T~E INVENTION
Thia lnventlon relatcs to the preparatlon of
lamlnated lnte6rnted clrcult pacXsgec, and, more
particularly, to the formatlon of ~uch pac~ages from
- a stack of sheet~.
Integrsted clrcult~ are electronlc devlces
that are eYtremely ~lnlaturlzed, ao that hundreds or
even thousands of lndlvldual clrcults and actlve
elements are formed on a chlp that may be only 1/2
lnch on a slde. The reductlon ln slze of such
clrcults reduces their welght ~nd volume, an~ also
lncreases thelr operatlng speeds because the
dlstances that electrons must travel are r-~duced.
The ~ldespread adoptlon of lntegrated clrcultry hss
revolutlonlzed many areas of electronlc~.
The lntegrated clrc~lts themselves are
~- extremely small and fraglle. They must therefore be
packaged and protected ln a manner that permlts
eYternal electrlcal connectlons to be made, and
permlts the lntegrated clrcults to be handled ln a
normal manner durlng the assembly and repalr of
electronic devlces that may utlllze one or many ~uch
packaged lntegrated clrcults.
One common approach to the packaglng of
- lntegrated clrcuits 18 to mount the clrcuits on a
- - ceramic substrate, whlch 18 commonly termed a
npackage~ ln the lndustrg. In the earllest
packages, there was a slngle layer of ceramlc. More
:- 30 recently, as the lntegrated clrcults have become
more compleY, the pacXsges have also become more
comple~. Now, some packages are formed of two or
more la~ers of ceramlc lamlnate, with varlous layers
havlng openings therethrough to permlt lnterlamlnate
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connec~lons and 8 ~ariety of comple~ functions of
the packsge ltself that augment the functlon of the
lntegrated clrcult and permlt th~ varlou~ required
esternal and lnternal lnterconnectlon~ and clrcult
paths.
In one procedure for the preparatlon of
. multllayer ceramlc pac~ages, sheet~ of unflred
. ceramlc materlsl ln a plastlc blnder (termed "Breen"
ceramlc) havlng a relatl~ely lo~ denslty ~uch a~
50-~0 percent of the theoretlcal fully compacted
I denslty are processed to have metalllc trace~ and
i contacts thereon, cut snd ~rimmed to have the
necesssry shapes, lncludlnB the openings
¦ therethrough, and then ~tacked on top of each other
l 15 ln the proper sequence snd allgnment. ~ heated tool
.- I havlng the proper shape of the upper surface of the
¦ flnal ceramlc package ls pressed downwardly agalnst
II the surface of the st~cX, causlng the lamln~tes to
consolldate to about ~0-65 percent of theoretlcal
¦ 20 density and also cau~lng the lamlnate~ to ~tlck
! I together. The compacted package is then flred at
¦ elevated temperature to lncrease the package derslty
¦ ~ to about 9~ percent of the theoretlcal densltg,
whlch 1~ sufflclently strong to carry the lntegrated
. 25 clrcult. The integrated clrcult 18 fa~tened to the
¦ surface of the package, electrlcal connections are
made, and a protectlve cover la sealed lnto place,
, , ¦ thereby complet~ng the fabrlcation of the pac~aged
lntegrated clrcult.
Whlle operable, thls procedure ls subJect to
process variatlons that can affect the qualltg of
the flnal packaged product. It ls dlfflcult to
control the dlstrlbution of pressure ln the metalllc
I presslng tool, wlth the result that dlfferent
ti 35 portlons of the package are compressed by dlfferent
amounts. The more hlghly compressed portlons shrlnk
¦ ¦ ==9 co=pre~aed portlon~, ~ith the
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result that the package tend~ to warp.' Also, there
msy be small item-to-ltem ~arlatlons ln the
¦ thlcknesses of the lamlnates, snd the rlgid tool ls
¦ not well sulted to adapt to such ~arlatlons.
There ha~e' been varlatlons proposed to
lmprove the unlformlty of the pacXsge~ and the
ablllty of the proce~alng to tolerate normal
manufacturlng varlablllty. In one approacn,
dlsclosed ln US Patent 4,~3~,275, the rlgld tool 18
10 replaced by a pressurized fluid. The fluld i8
enclosed ln a rubber or other elasto~er bladder that
contacts the upper 6urface of the ~tack of
' lamlnates. AB the'fluid 1B pressurlzed, the bladder
18 deformed agalnst the upper surface of the ~tac~
to compress`lt.
. I ' The approach of the '27S patent solves some
',' I of the problems lnherent wlth the use of rlgld
I ¦ toollng, but suffers from problem~ of lts own. The
¦ presence of a fluid requlres seals and pr'ecautlon~
¦ 20 to prevent lsa~age that would damage the lamlnates.
I If the bladder 18 too thln, plnholes appearlng
durlng repeated fleslng ln use ~111 allow the fluid
to leak. The leakage of flulds i~ a partlcularly
l~sldlous problem, because very small plnhole leaks
that cannot be readlly detected ma~ contamlnate man~
pac~ages with mlcrogr~m quantltlea of the
pressurlzatlon fluld before the leak 18 detected.
The manufacturer ls then faced wlth the problem of
¦ identlfylng the contamlnated pleces or throwing away
¦ 30 enough of the pleces to be sure that no cont~mlnated
¦ pleces remaln ln the productlon lot. If the bladder
, : 18 made thlck to minlmlze the chances of leakage, lt
may rot conform to small openlngs ln the stack or
i ma~ cause unacceptable rou~dlng of the ed8es of
! ¦ 35 openlngs. E~perlence wlth rubber bladders used ln
' other conte~ts suggests that a bladder suf~lclently
thlc~ to rel~zbly contAln the presDurlzlng fluld
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wlll not reach lnto ~mall vla openlng~ about -
.010-0.050 lncb ln dlameter and ~111 also round the
corner~ of larger openlng~. Moreover, the blsdder
may capture pockets of alr around the lamlnate that
prevent complete con~olldatlon. Another problem
wlth bladders ls that 'he m~terlals whlch can
contaln flulds are often somewhat tacky to tbe touch
snd may stlc~ to the unflred lamlnates. The re~ult
18 that the p~cXage may be pulled apsrt when the
10 bladder i8 remoYed Bfter pre~slng.
In yet another approach, some manufacturers
u~ing elther the rlgld tooling or fluld approsche~
have ln6erted sep~rate toollng pieces into the stack
of lsmlnates. It has been found that multlple set~
of lnserts are requlr~d because of the normal
m~nufacturlng varlabillty of the lamlnates,
dlscus~ed prevlousl~. The lnsertlon and po~ltlonlng
I of toolln~ pleces 18 a slow process that
I signlflcantly lncreases the cost of the flnal
20 package by ~lowlng the throughput of the lamlnation
process.
Thu~, at the present tl3e there 1B a need for
an lmproved approach to the preaslng of lamlnates
used ln mlcroclrcult packsges. The approach should
25 attain the advantages posslble wlth the varlous
prevlously developed lamlnatlon procedures, and not
, lncorporate thelr ~hortcomlng~. The present
; lnventlon fulfllls thls need, and further provldes
related advantages.
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¦ ~ ¦ 30~ -'~MMARY OF T~E ~ ENTION
The present lnventlon provldes ~ process and
spparatu~ for laminatlng mlcroclrcult packages from
stsc~s of lamlnate sheets tbat have been prevlously
~' ~ patterned ~and cut t~ shape. The approach pro~lde~ a
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¦qussl-hydrostatlc laminatlon pressure that hss been
found operable to consolidate ~tacks of lamlnates
havlng openlngs through laminate lsyer~ a3 small s3
0.020 lnche~, wlthout roundlng of the edges. The
5 approach acco~modate~ normal varlatlons ln lamlnate
thlckne~s and quallty, 80 that only a slngle
apparatus i8 required. No flulds are used, and
there 18 no danger of leakage and contamlnatlon of
the packages. The approach 18 operable ln a
10 productlon -context to proce~s lamlnated psckages
rapldly and at low c03t.
IIn accordance wlth the lnventlon, appar~tus
_ Ifor fabricatlng an lntegrated clrcuit package from a
plurallty of layers of lamlnates comprlses a bace
15 upon whlch the lamlnates are stacked to form a stack
havlng an upper surface; a solld pressurlzlng medlum
dlsposed in a faclng relatlonshlp to the stacked
lamlnates, the pressurlzlng medlum belng made of a
materlal that deform3 to conform to the upper
surface of the 8tack of lamlnates under pres3ure but
whlch returns to sub~tantially lts undeformed ~tate
ln the absence.of pressure; and a pressure transfer
membrane between the pre~surlzlng medlum and the
upper 3urface of the stack of lamlnates that 1~
sufflclently flexlble to conform to the upper
surface of the stack of lamlnates, the pres~ure
transfer membrane havln~ a flrst layer adJacent the
lamlnates that does not adhere to the lamlnates and
a second layer adJacent the pressurizlng medlum that
30 prevents contact between the pres~urlzlng medlum and
the lamlrates.
The solid pressurlzlng medlum ls preferably a
polyurethane rubber block made of SorbothaneTM
brand materlal. Such a materlal can conform to the
35 upper surface of the stack of lamlnates.
Preferably, the pressurlzlng medlum is retained by a
lates dlaphragm ln a cavlty of a pres~urlzing tool
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faclng the upper surface of the stack, ~o that the
pressurizlng ~edlum 18 controllably moved lnto
contact wlth the stack of lamlnates and then
removed.
S So~e ~terlal~ that are preaently known for
u~e as the pressurlzlne medlum have a de~ree of
stlcklness or ~tack~, 80 ' thst they would stlck to
the surface of the stack of lamlnates ln the absence
of the pressure trAnsfer membrane. The preferred
pressure transfer membrane hAs two layers, the flrst
la~er adJacent the stack formed of & materlal ~uch
as slllcone rubber than has no tac~ and serves as a
release sgent, and ~ second layer between the flr~t
layer and the pressurlzlne~medlum such a~ a la~er of
urethane rubber that separates the pressurlzing
medlum from the lamlnate~. Each of the layers 18
about 0.015 lnches thlck ln the preferred approach,
whlch 18 sufflclentl~ thln to permlt the presslng of
small dlameter openlngs such as ~ias and also does
not cause roundlng of the edges of lsrge or ~mall
openlngs. Since the pressurlzlng medlum 18 a solld,
there 18 no possiblllty of fluld leakage fro~ the
apparatus onto the laminates.
It has been found that alr;bubbles tr~spped
between the pressure transfer membrane and the stsck
of lamlnates can prevent bondlng locally. The base
of the preferred apparatus i8 therefore
lntentlonally made porous, as by fsbrlcating lt from
slntered stalnles~ steel. A ~acuum ls applled ~o
the underslde of the base to draw 8a8 from the
reglon between the lamlnates and between the
lamlnates and the membrane, thereby avoldlng such
local gas-lnduced delamlnatlons.
The present approach can, of course; be
applled to instances whereln the solld pressurlzlng
medlum 18 not tacky. In accordance wlth thi~ aspect
of the lnventlon, apparatus for fabricatlng an
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lntegrated clrcult package from ~ plurallty of
¦ la~ers of lamlnates comprlses a base upon whlch the
¦ lamlnates sre stacked; and a ~olld pressurlzlng
medlum dlsposed ln a faclng relatlonshlp to the
¦ 5 stacked lamlnates, the pressurlzlng medlum belng
j made of a materlal that deforms to conform to the
upper surface of the stack of lamlnates under
¦ pressure but whlch returns to substantl~lly lts
undeformed state ln the absence of pressure.
I lOThe pressure tranafer membrane Or the present
lnvention has wlde applicablllty. In accordance
wlth this a~pect of the lnventlon, apparatus for
_ fabrlcatlng an lntegrated clrcult package from a
plurallty of la~ers of laml~ates comprlses a base
upon whlch the lamlnates are stacked; a pressurlzlng
medlum dlsposed ln a faclng relatlonshlp to the
stacked lamlnates; and a pressure transfer membrane
between the pressurlzlng medlum and the stack of
lamlnates that 18 sufflclently flexlble to conform
, 20 to the upper surface of the stack of lamlnates, the
I pressure transfer membrane havlng a flrst layer
¦ adJacent the laminates that does not adhere to the
~ lamlnates and a second layer ad~acent the
¦ - pressurlzlng medlum that prevents contact between.
l 2S the pressurlzlng medlum and the lRmlnates.
¦ The present lnventlon also e~tends to the
¦ process for using the approach of the lnventlon to
. ¦ prepare lntegrated clrcult packages from lamlnates.
, ~ In accordance wlth thls aspect of the lnventlon, a
process for pressing lntegrated clrcult packages
comprlses the steps of provldlng a stack of
lamlnates to be pressed; prov~dlng a pressurlzlne
medlum adapted to press agalnst the stack of
lamlnates; placlng a la~ered pressure transfer
j 1 35 membrane to overlle at least a portlon of ~he stack
¦ of lamlnates, the pressure transfer membrane havlng
a flrst la~er adJacent the lamlna~e~ that does not
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adhere to the lamlnate~ and a ~econd layer adJacent
the pres~urlzl~8 medlum that prevent~ contact
between the pressurlzlng medium and the lamlnates,
the pres~ure tran~fer membrane belng sufflclently
fle~lble to conform to the upper surface of the
stack of laminates under pressure; and applylng a
pressure to the pressurlzlng medlum whlch ls thence
transferred to the ~tack of laminates through the
pressure ~ransfer membrane. In the preferred use of
lv the process, the pres6url~1ng medlum 18 a ~olld
ma~erlal that deforms to conform to the upper -
j surface of the ~tsck of lamlnates under pressure but
whlch returns to substantlally lts undeformed state
ln the absence of pressure, such as Sorbothane.
The present lnventlon thus provldes an
. lmportant advance ln the fabrlcatlon of multllayered
packages used to support lntegrated circults.
Packages are pressed and consolldated ln a
. quasl-hydrostatlc manner that achleves unlform
.. 20 presslng that leads to unlform denslty dlstrlbution,
wlthout roundlng of corners and closure of small
openlngs. No potentlally leaky fl~lds are used ln
the presslng operatlon. The approach 18 operable ln
large-scale commerclal manufacturlng operatlons.
Other features and advantaees of the lnventlon wlll
be àpparent from the followlng more detalle~
descrlptlon of the preferred embodlment, ta~en in
.~ con~nctlon wlth the accompanylng drawlngs, whlch
lllustrate, by way of example, the prlnclples of the
lnventlon.
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BRIEF DÉSCRIPTION OF T~E DRAWINGS
Flgure 1 is a slde ~ectlonal vlew of a
ceramlc package;
Flgure 2 18 a slde ~ectlonal vlew of a
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presslng apparatu~: and
Flgure ~ 18 a detail of Flgure 2, ~howlng the
¦ arrangement and conHtructlon of the pre~ure
transfer membrane.
DETAILED DESCRIPTION OF T~E PREFERRED EMBODIMENT
Flgure 1 illustrate~ a ceramlc package 10 o~
the type that can be pressed uslng the approach of
the lnYentlon. The package 10 1~ formed from a
plurallty, ln thls case three, lamlnstes 12 of
unconsolldated ceramlc materlal. The lamirates are
formed by prepsrlng sheets of ceramlc o~ides ~uch as
alumlnum o~lde and small amounts of glasa-forming
I o~ldes, ml~ed wlth an or~anic blndlng materlal such
¦ as poly~lnyl butyral. A typlcal mlsture lnclude~
1 15 about 90 percent by welght of the ceramlc oYide
¦ powders and 10 percent by weight of blnder, although
¦ these relstlYe amounts may vary. The sheets ha~e a
denslty of about 2.1 grams per cublc centlme-ter, as
compared with a density of about 4.0 grams per cublc
centlmeter for fully dense alumlnum o~lde. Thus,
the sheets, termed "green~ materlal, have a denslty
of Just o~er 50 percent of the theoretlcal full
density of the alumlnum o~lde.
As shown in Flgure 1, the lamlnates 12 are
stacked on top of esch other to form a stack 14 of
lamlnates. The bottom lamlnate 18 a full sheet, to
support an lntegrated clrcult 16 thereupon. The
other lamlnates have openings 18 and 20
therethrough, some of whlch remaln open (such as
openlng 18) whlle~ others are fllled with metal in
the flnal processlng (such as the openlng 20). The
lndlYldual laminates may have conductl~e paths 22
thereupon, whlch are connected to the lntegrated
i clrcult 1~ w~th flne wlres 24. (The lamlnate
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structure of Figure 1 18 meBnt to be esemplary, and
the present lnventlon 18 not llmlted to the
preparstlon of lamlnates of thls or any other
particular form.)
Before the lntegrated clrcult 1~ snd the
wlres 24 are attached to the pacXaga 10, the
lamlnatea 12 are consolldated by presslng the green
sheets to lncrease thelr densltles to about ~0~65
percent of theoretlcal denslty, and then slntered to
lncrease thelr densltles to about 9~ percent of
theoretlcal denslty. The pres~lng to achie~e 60-65
percent of theoretlcal den~lty has prevlously been
accompllshed wlth a rlgld tool whose ~urfsce 18 a
. mlrror image of an upper surface 26 of the package
10, or wlth a fluld-fllled bladder as dl~cus~ed ln
~S Patent 4,636,275, who~e di~clo~ure 18
lncorporated by reference. The present approach
al80 deals wlth the presslng operatlon, but provlde~
an alternatlve approach.
In accordance wlth thi~ aspect of the
lnventlon, apparatus for fabrlcatlng an lntegrated
clrcult package from a plurallty of layers of
lamlnates comprlses a porous base upon whlch the
l~minates are stacked to form a stack haYlng an
upper surface; a pressurlzlng tool havlng a ca~lty
thereln dlsposed ln a faclng relatlonshlp to the
upper surface of the stack of lamlnates; a solld
pressurlzlng medlum lncludlng a bodg made of
Sorbothane whlch ls retained ln the cavlty of the
pre~surlzlng tool by a lateY dlaphragm; a pre6sure
transfer membrane overlylng the ~tacked lamlnates,
the pressure transfer membrane havlng a flrst layer
¦adJacent the lamlnates made oY slllcone rubber and a
¦second layer adJacent the pressurlzlng medlum made
¦35 of urethane rubber; and a pump communlcatlng wlth
lthe porous base to remo~e alr from the space between
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Referrlng to Flgure 2, sn appsratus 30 for
fabrlcatlng an lntegrated clrcult packsge ha~ ~ ba~e
32 upon whlch rest~ th~ stsck 1~ of lsmlnate~ 12,
prlor to consolldstlon by pres~lng. The basa ~2 1
msde of a porous materisl ~uch ~ alntered ~tslDle~
steel hs~lng contlnuous por(Jslty. The base 32 rests
upon a support 34 hsYlng an e~scuatlon llne 3~
thereln lesdlng to a ~acuu~ p~mp 38. ~he edges of
the porous base 32 are ~esled agalnst alr los~ and
I ` 10 the gsp between the bsse 32 and the ~upport 34 is
¦ slmllarly sealed wlth a ~eslsnt 40 such as gl~s~,
eposg, or metsl. Operatlon of the pump 38 therefore
I removes gas from the reglon of the stac~ 14, lr. the
¦ manner to be discussed ~ubsequentl~.
A pressurlzing tool 42 flt~ over the base 32,
and ls sealed thereto b~ ~ slldln~ O-ring 44. The
tool 42 i8 generally ln the for~ o~ B bloc~ of metsl
1 4~ ha~lng a caYlty 48 thereln. The csvlt~ 48 ls
I lsterally dlmensloned to be sufflclently larger than
. 20 the lsteral dlmenslons of the base 32 80 that the
tool 42 can fit over the base 32. A remoYable
clamping fltting 50 18 attached to the underslde f
the block of metal ~ wlth any conYenlent fastener,
such as B serles of bolts 52.
A block o. a solid pressurlzlng medlum 54 ls
contained wlthln the cavlty 48. ~he solld
pressurlzln8 medlum 54 la preferably made of
SorbothaneTM elastomerlc msterlal, whlch ls
msnufactured by Sorbothane, Inc., 2144 State Route
59. Kent, Ohlo. SorbothaneTM msterlal ls
patented, and its composltlon snd structure are
dlsclosed ln US Patent 4,34~,205, whose dlsclosure
18 hereby lncorporated by reference. Brlefly,
accordlng to the '205 patent the elastomerlc
materlal ls a fle~lble polyurethane of essentially
llnear structure contalnlng unsatlsfled hydro~yl
groups, and havlng a compression set less than 15
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percent, an elongatlon at break of ~t leH~t 600
percent, and a reco~ery ~hlch ls delayed after
compres~lon by ~t least 0.7 ~econds. The els~tomer
1~ produced by reactlng cub~tantlally llnear pol~ols
based on polyal~ylene glycol ~lth an aYerage
molecular welght ln the range of 600 to 1200, and an
aro~atlc dllsocyanate. SorbothaneTM ha~ been u~ed
a~ an energg sbsorblng materlal prevlou~ly a~
descrlbed ln the '20~ patent, but no prlor use llke
. 10 that of the present lnventlon 18 ~nown.
SorbothaneTM elastomerlc materlal 1~ a
solld, but can be defor~ed around ~he stack 1~ to
apply a quasl-hydrostatic pres~ure ~hen conflned ln
a volu~e ~uch as deflned by the walls of the ca~ity
. 15 ~8, the upper surface 26 of the ~tack 14, and the
base 32. A typlcal presAure level 18 about G00
pounds per ~quare inch, although ~he pressure can be
~arled wldely as necessary. Although the
SorbothaneTM materlal compre~es somewhat at such
a pressure level, the ~olume change ls relatlvely
small and acceptable. Such pressure ls created by
forclng the pressure tool 42 downwardly 1D the vlew
of Flgure 2. When the pressure 1~ removed, the
SorbothsneTM materlal returns to substantlally the
same shape a8 lt had prior to deform~tlon. Durlng
the presslng operatlon, the ~ntlre apparatus 30 ls
heated to a temperature of about 70C b~ a
reslstance heater 56 that ls placed around the
apparatus. The SorbothaneTM materlal retalns the
prevlously descrlbed propertle~ at thls fillghtly
elevated temperature.
Although the SorbothaneTM material can
deform and then return to lt3 orlglnal shape, lt
remalns a solld throughout the entlre operatlon.
3S The solid SorbothaneTM materlal ls to be
dlstlngulshed from a fluld, whether a llquld or a
gas, whlch changes shape to flll a contalner (or a
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portlon of a contalner ln the cs~e of a llquld) even
ln the sb~ence of sn applled force. ~h0
SorbothaneTM materlal cannot lea~ eYen ~hen holes
are present in a coverlng la~er, ~ lt remsln~ a
solld st all tlmes. Thl~ dl~tlnctlon b~t~een the
solld SorbothaneTM msterlsl and a fluld ls
lmportant, because the sorbothaneTM materlal 1
not subJect 'o the leakage proble~s lnheren~ ln the
use of fluids ln pres~lng appllcatlons.
Other solid materlsl~ ~lth ~lmllar propertle~ !
¦ can be used. For e~ample, urethane block~ can be
used as the pressurlzlng medium ~4. Hlghly
¦ compresslble foams ~ould normally not b~ acceptable,
as the volume change durlng pressurlzlne ~ould not
permlt the toollng to functlon properly.
Tbe SorbothaneT~ materlal solid
I pres~urlzlng medlum 54 18 held ln place ~lthln the
I cavity 48 by a fle~lble, deformable dlaphrsgm 58,
¦ whose edge~ are captured between the bloc~ of
msterlal 4~ snd the flttlng 50. The dlaphragm 58 i8
¦ preferably formed of a sheet of natural or
artlflclsl lates rubber. A sheet about 0.015 lnches
thlc~ hss been found satlsfsctory. Late~ rubber ls
preferred for the dlaphragm 58 because lt deforms
around the stac~ 14 and can be ~tretched e~tenslvel~
wlthout fallure durlng presslng. When the pre~sure
ls remo~ed, lt returns to lts orlglnal flat
dlaphragm shape a~ the SorbothaneTM materlal of
the pressurlzlng medlum 54 returns to lts orlglnal
shape, and contlnues to retaln the presfiurlzlng
medlum 54 ln the cavlty 48. Tbe latex dlaphragm 58
may be locally plerced~ as by plnholes or tears,
durlng its use over a perlod of tlme. Such damage
ls fully acceptable as long as the solld
;35 pressurlzlng medlum 54 contlnues to be held in
I,place. Because the pressurlzlng medlum 18 a solld,
I L ~ ~ ~ ag= ~ ~
. li
, ._... _._.
-
2036169
I`' ' . ~
Il~ requlred.
A pre~sura tran~er ~e~bran~ ~0 ls placed
over the ~tack 14, betweeD the upper ~urface 2~ of
the ~tack 1~ ~nd the pre~nurlzing medluM 5~.
Prefersbly, the ~embrane ~0 ln dr~ped over the 0tac~
14 ln the manner lllustrated ln Flgure 3. The
membrane 60 18 not captured between the block 4~ snd
the flttlng 50 as 1~ the ca~e for the dlsphragm 58.
The drsplng of th~ me~brane ~0 permlts lt to move
10 laterally to rendJust lts po~ltlon ss the pres~ure
ls spplled to the upper ~urface 2~ of the stack 14
through the pres~urlzlng ~edlum 54.
Also a~ lllustrated ln Flgure 3, the pres~ure
transfer membrane ~0 18 preferably formed of two
lsyers of deformsble materlal, a ~lrst l~er ~2 thst
contacts the upper ~urface 26 of the stack 14 of
lamlnates 12, and a second layer ~4 thst lc between
the first layer S2, and the dlaphrag~ 58 and
pressurlzlng medlum 54. The flrst layer 62 i~
20 preferably made of slllcone rubber, and most
preferably has a thlckness of about 0.015 lnches.
The second layer 64 ls preferably msde of urethsne
rubber, and most preferably has a thlckness of sbout
0.015 lnches.
25The flrst layer ~2 acts as a reles~e layer,
to- prevent adherence between the preasure tran~fer
membrane ~0 and the upper ~urface 26 of the ,f
lamlnates 12. Slllcone rùbber i8 well known ln the
lndustry, and 18 avallable commercially in ~heets of
30 various thicknesses. It 18 eenerally formed by
cross llnklng of silicones wltn groups such as
organic peroxides. The slllcones are llnear
polymerlc structures derlved from silo2anes by
substltution of an organlc group such as the ~ethyl
35 group for the o~ygen atom~ of the slloxane abo~e and
below the slllcon atom. Chlorlne or other halogens
are ofter. commonly lncluded. For the present
. L
~. .
i , .
~ 2,~g~69
appllcatlon, ~lllcone rubber ha~ the important
property that lt has llttle ~tlc~lnes~ or tack
agalnst laminate msterlals ~uch as aluminum o~lde
lsmlnate~. Thu~, with a flr~t layer 62 of ~llicone
rubber pre~ent, th0re 1~ no ~tlcklng of any of the
o~erlylng layer~ or structure to the upper ~urface
26 of the lamlnates 12. Slllcone rubbers do not
deform e~tenslvely wlthout formatlon of plnholes,
but pinholes are acceptable ln the pre~ent u~e a~
long as the essentlal separatlon functlon ls
retalned.
The ~econd layer 64 act~ as a barrler between
the diaphrag~ 68 and the pres~urlzlng medlum ~4, on
the one hand, and the upper surface 26 of the
- 15 l~mlnates 12 on the other. Urethane rubber, the
preferred materlal, 18 well known ln the lndustrg.
The urethane rubber is formed from polyurethane, the
llnear condensatlon polymer that can be made by the
reactlon of a dllsocyanate and a dlhydrlc alcohol.
The polyurethanes are characterlzed by the presence
of the urethane group (-N~COO-~ ln the polymer. The
ureth~ne rubbers are ver~ elastlc and fleYlble, and
can deform to a Breat e~tent and over many cycles
wlthout formatlon of holes or tears. ~rethane
rubbers al80 have the property that they are
typlcally sllehtly tacky agalnst ceramlc ma-~erlals
such as the alumlnum o~lde lamlnates. The flrst
layer 62 separates the urethane rubber from the
upper surface 26 of the lamlnstes 12 80 tha~ ~he
urethane rubber does not adhere to the ceramlc
materlal and damage lt when the pres~ure ls
released. Late~ rubbers are not preferred for the
second layer 62 because the~ tend to fatlgue and
form holes durln~ rspeated cycles of operation.
Slllcone rubbers are not preferred for the second
layer 62 because they are not sufflclently ela~tlc.
The pressure transfer membran0 bO as
~1~'
f . ~36~69
..
~'__I
,". .
.
- -lb-
descrlbed hereln ha~ been found to be partlcularly
advantsgeou~l~ employed ln the preaent apparatu~
Q0. It can deform lnto openlng~ 20 as 8m811 as
about 0.020 lnchea or smaller to preYent closure of
the openlng~ durlng presslng. The comblnatlon of
the pres~ure trsn~fer membrsne 60 and the
pressurlzlng medlum 64 has been found not to round
the edges of openlng~ such as the openlng~ 18 and 20
durlne the pre~ln8 operatlon, an lmportsnt
advantage that s~d~ ln malntalnlng preclse
geometrles durlng the pressin~ and sub~equent
~lnterlng operations.
To prepBre B package u~lng the appro~ch of
the lnven~lon, the stack 14 of unconsolldated
lamlnates 18 flr~t prepared usln~ ~nown technlquea.
(The preparatlon of th0 lamlnates themselves does
not form part of the present lnventlon.) ~he stack
14 18 then placed lnto the spparatus 30 of the
lnveltlon wlth the membra~e ~0 ln place draped over
the ~tack 14, ard the apparatus 18 closed by placlng
! the pressurl~ing tool 42 over the base ~2. The
lnterlor of the apparatus 18 prefersbly evacuated
i wlth the vacuum pump ~8 ln the manner prevlously
descrlbed, so that the interlor has a ~llghi
vacuum. A hlgh vacuum ls not requlred, as the
purpose of the vacuum 18 slmply to ensure that
bubbles of gas do not remsln between the lamlnates
or between the pressure transfer membrane 60 and the
lamlnates. Such bubbles could prevent consolldatlon
or bondlng. The pumplng operatlon could be omltted
; ln some clrcumstances, although it ls preferred.
The block 4~ 1~ pressed downwardly wlth a
sufflclent force to create the deslred pressure ln
l the lnterlor of the apparatus and simultaneously
il 35 heated. A preferred comblnatlon of temperature and
I pressure for the consolldatlon of alumlnum o~lde
¦ la=instes are 70C and 500 pounds per square
i
..
1 / 2~
,. .
-17-
lnch. After about lO-l~ seconds, the pres~ure is
released and the partially consolldated stack 14
removed. The elevated temperature pressurlzing
treatment lncrea~es the denslty of the lamlnates
S from about 60-5~ percent of theoretical denslty to
about ~0-~5 percent of theoretlcal densltg. The
pressurizlng treatment also causes the lsmlnate~ 12
to stlck together ~ufflclently 80 that the stsck can
be handled durlng the ne~t production step.
The stack 14 ic sintered according to
establlshed procedure~ to lncrease the den~lty to
about 9~ percent of theoretlcsl den~lty. (The
slnterlng treatment doeq not form part of the
present lnvention.) A t~plcal sinterlng treatment
15 i8 a temperature of lhOOC for 90 mlnutes, wl-th no
applled pressure. The package i8 read~ for further
processing such as adding e~ternally accesslble
contacts, attachment of the lntegrated clrcult, and
. ~ final processlng such a8 attachment of lead wires.
The present approach can be readlly applled
in a production settlng. A plurallty of bases and
stacks can be prepared for prQcesslng at one time,
or the stacks can be pressed one at a time. The
procedure ls essentiallg a3 fast as pressing wlth B
rlgld dle, but i8 tolerant of manufacturing
variatlons ln the configuration and thickness of
lndividual stacks of laminates. The apparatus 30,
lncludlng both the solid pressurlzlng medlum and the
pressure transfer membrane, can be reused for mang
cycles of operatlon.
~Although a particular embodiment of the
¦lnvention has been descrlbed-in detail for purposes
Iof illustratlon, various modlflcstions mag be made
Iwlthout departlng form the splrit and ~cope of the
135 lnventlon. Accordlngly, the lnvention i5 not to be
¦llmlted escept as by the appended claims.
,. I
