Note: Descriptions are shown in the official language in which they were submitted.
8~
HEAT PIPE COOLING MODULE FOR
HIGH POWER CIRCUIT BOARDS
1 BACKGROUND OF THE INVEI~TION
1. Field of the In~ention
The present in~ention relates to cooling of elec-
tronic corDponents and~ in particular, to cooling of
high power density electronic components by heat pipe
principles in a sel~-supporting structure
20 Description o~ the Prior Art
'.~rith e~er-increasing density and higher power of
electronic com.ponents~ e.g., in memories and logic
arrays in high speed computersg waste `neat rejection
becomes a limiting factor in such imploved computers
in the absence of improved heat re~ection techniques.
In the pastS cooling was erfected by conduction of
~eat throu~h a solid conductor, of flowing coolant
such as air or ~reon dlrectly over logic boards or
through special paths adjacent thereto, examples being
given in U.S. Patents 3g411,041, 3,3y5,318, 3,648,113
~nd 4,006,3~8. Heat pipe thermal control has also
been used as exempliried by ~.S. Patell~s 3,651,865 and
4,118,756. While adequate for thermal con trol re~uire-
ments of the past, increased heat loads in ne~ high
speed equipment are exceeding the capabilities Or the
prior art. For example, cooling is needed at least
ror high power density 1,000 to 2,000 watts lo~ic
2~ boards~
~q
In addition, the need both to cool the components
and to provide a support therefor did not necessaril~ result
in efficient utilization and comhination of the cooling and
support structure.
S SUM~ARY OF THE INVENTION
The present invention is designed to meet and
exceed such requirements and to integrate the cooling and
suppo~ting struc-ture. It uses heat pipe cooling in a module
which is designed to support electronic components. ~ach
module utilizes condenser and evaporator sections in which
the evaporator section is con~igured as a flat plate to which
electronic components are directly attached. The condenser
sections of a plurality of modules are coupled together and
to a heat sink for drawing the heat away from the condenser
1~ sections.
Several advantages are derived rrom this configura-
tion. It enables heat to be withdrawn directly, quickly and
efficiently from the components. Individual electronic
components or circuit boards of components defining a parti-
cular electronic function grouping a plurality of componentsmay be attached directly and on both sides of the evaporator
plate section for rapid movement of large quantities of heat
therefrom. The evaporation plate section itself resists
deforming pressures in order to maintain proper heat flow and
~5 evaporation.
An aspect of the invention is as follows :
A heat pipe cooling module assembly for cooling
electronic components including a plurality of modules
each comprising a heat pipe having condenser sections
and flat evaporator sections, means for securing said
condenser sections of said modules together -to form
said modules into an assembled structure and to
position said evaporator sections in spaced, parallel
alignment, and electronic components thermally coupled
to said flat evaporator sections.
O-ther aims and advantages as well as a more
complete understanding of the present invention will appear
2a
from the following explanation of exemplary embodiments
and the accompanying drawings thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an end view in elevation of a plurality
of modules coupled together for cooling of electronic
components secured to individual module evaporation fins;
38~
1FIG. 2 is a perspective view o~ a module shown in
FIG. l;
FIG. 3 is a cross-sectional view Or a rrlodule of
FIG. 2 showing its condenser section and a portion Or
its evaporator fin section;
FIG. 4 is a cross-sectional viel,l taken along
lines 4-4 of FIGS. 2 and 3 illustrating ~he construction
of the evaporator section;
FIG. 5 is a front elevational view of a separator
plate placed primarily in the evaporator section;
FIG. 6 is a top view of an open condenser section;
FIG. 7 is a partial view in perspective of a
portion of the condenser section;
FIG. 8 is a view of the condenser section tar~en
along lines 8-8 of FIG. 6;
~ IG. 9 is an edge elevational view of a
secorld eirbodiinent of the present invention illustrating
a plurality of cooling modules coupled to cooling
plenums; and
20FIG. 10 is a side view of the vapor rlow se~arator
pl te used in the module illustrated in FIGS. 9 and 10.
~`ETAILED DESCRIPTION OF THE I~VE~TION
As sho~.~n in FIG. 1, a heat pipe cooling module
~5 asseinbly 20 comprises a plurality of modules 22, each
having a condenser section 24 and an evaporator section
26. Each e~aporator section has the appearance of a fin
or flat plate. Electronic components 28 are coupled
to both sides of evaporator plates Or each ~odule and
rr,ay comprise separate electronlc components, or c~rcuit
or printed wiring boards or the like which incorporate
a plurality o~ individual corr,ponents. The condenser
.
1 sections Or the several modules are secured together
in any convenient manner to form an ~ssem~led structure
and to position tne evaporator sections in spaced,
parallel alignment. A working fluid is sealed within
each of the modules so that heat from the electronic
components will evaporate the working fluid into a
vapor which then moves to the several condenser sec-
tions 24. There, the vapor is condensed into a liquid
which then llows through wick material back into the
evaporator sections. To remove the heat from the
working fluid vapor, any convenient cooling plenum or
other cooling means are coupled to condenser section
24. For example, enclosures 30 are placed between
condenser sections 24 and coolant fluid is fed bet~!een
the enclosures by conduit 32. If desired, a plurality
of parallel tubes may be sealed to and extend through
the condensers. Alternatively, the condenser sections
may be abut~ed together at their sides, and a heat
sink be thermally coupled to their top and/or e~ge
surfacesO
Each ~odule-may be fabricated from any suitable
material, such as copper, stainless steel, aluminum,
aluminum oxide and beryllium oxide. Suitcble wor~ing
fluids include ~iater, ammonia~ meth~-nol and freon. lhe
particular ~.~aterials of the module and working fluid
are chosen in accordance with the operating t~mperature
requiremenks in which tne module assembly is to be used.
An individual module and its consti~uent parts
are depicted in FIC-S. 2~7, with components of the
- 30 evaporator section being shown in FIGS. 4 and 5 and the
condenser section in FIGS. 6-8. Each evaporator section
26 comprises a pair Or flat outer plates 34 to which
electronic components 28 are secured. A pair of pads
36 comprising wick material, for example, of crushed
copper felt, is secured to outer plakes 34, and a
l central separator plate 38 is secured to the wick
pads. Thus, outer plates 36, wick pads 38 and separator
plate 38 ~orm a sandwich construction which ls bonded
together in any convenient manner such as by brazing.
To provide for flow of working fluid vapor,
separator plate 38 is rormed into a channel structure
comprising a plurality o~ parallel bars 40 which form
spaces therebetween comprisin~ parallel slots 42. The
bars are held in position by a peripheral enclosure 44
shown in FIG. 5 as a rectangular constructlon of segments
46, 48~ 50 and 52, in which the parallel bars and slots
extend between opposed segments 48 and 52. In addition,
bars 40 provide a solid connection between outer plates
36. This sandwich construction of bars, plates and wick
lS pads therefore provides a high resistance to crushing
and deformation forces exerted on the evaporator section.
~s a result, the evaporation function is not disturbed
even though such forces are present. Separator plate
38 is intended to extend from evaporator section 26 and
entirely throu~h condenser sectlon 24, with projection
-- 54 of the separator plate de~ined by ~idth reductions
56 in opposed se~ments 46 and 50.
As best shown in FIG. 3, outer plates 34 and wick
pads 36 extend only slightly into condenser section 24.
2S As depicted in FIG. 6-8, condenser section 24
comprises a casing 57 into which a plurality of spaces
58 and 60 are provided, including a central rectangulâr
soace 58 and lobe-shaped spaces 60. CeJitral spaces 58
span the distance between casin~ end se~,ents 59O The
lobe-shaped spaces are divided by rails 61 and extend
from both sides of central space 58. As a result, the
central space is bounded by end se~ments 59 and a
plurality of elongated flat surfaces 62 on rails 61
~hich race one anotherO It is to be understood, of
course, that surfâces 62 need not be perfectly aligned
but could be sta~gered 1~ so desired. For.,ed on the
2~
1 interlor of lobe spaces 60 is trough-shaped wick rnaterial
64. As shown in FIGS. 3 and 7, wick material 64 is
bonded within lobe spaces 60 but terrninate at races 66
short of surfaces 62.
The thickness of separator plate 38 at its pro-
jection 54 approximately equals the distance between
facing surfaces 62 so that the outer surfaces 68 of
separator pro~ection 54 are in contact with and bonded
to surfacos 62~ but are not in contact with terminal
faces 66 of trough shaped wicks 64.
At its top 70 and bottom 72, condenser casing 57
is provided with respective openings 74 and 76.
~ Separator projection 54 extends entirely through
opening 72 but Just short Or the upper surfaces Or top
70 so that an end cap 78 may be brazed to the opening
to seal ofr the top. A ledge 80 extends around the
~eriphery of opening 74 onto which end cap 78 rests.
At bottom 72 of condensor casing 57, opening 76
permits insertio~n of' evaporater outer plates 34 and
wick 36 so that they abut against lower sur~aces 82
formed by the bottom surfaces of rails 61 and end
segrnents 59.
The entire assembly may be brazed tcget}ler to
Join end cap 78 to condenser casing 57, evaporator
section 26 to condenser section 24, and the side and end
surfaces of ev~.porator section 26 denoted by indicium
84 in FIG. 2 between wick pad 36 and respective outer
plates 34 and separator plate 38,
The embodiment depicted in FIGS. 1-8 is primarily
used when condenser sections 24 are higher than evapor-
ator sections 22 o~ the respective modules so that
vapor of the working fluid will flow upwardly through
channel slots 42 from the electronic components and
into condenser sections 24 for condensatlon thereinO
The condensed working fluid then drips dowrlwardly
, ~, . . .
. . .
1 through wick material 64 and exposed portions Or
separator projection 54 by a comblnation o~ capillary
pumping and gravity back to the evaporator where
evaporation can again take place.
For such uses where the modules may not be sta-
tionary with respect to gravity, such as in alrborne
installations, the embodiment depicted in FIGS. 9 and 10
may be used. hs shown in FIG. 9, a plurality of modules
90 are coupled at both ends to a pair of plenums 92
through which a coolant flows. Each module 90 is a
sealed unit including a central evaporator section 94
and a pair of condenser sections 96 at opposed ends.
Condenser sections 96 fit within slots 98 ~ormed within
plenums 92 so that there is a thermal coupling between
the modules and the plenum, as well as a means ~or
supportlng the modules~ and the plenumsO Such a con-
struction also permits the rnodules to be slipped in
and out of slots 98 for insertlon and removal from the
plenums. A plurality of electronic components 100 are
thermally coupled to the evaporator sections of the
respective modules.
Each module 90 comprises a central separator
plate 102 ~see FIG. 10) with wlck pads on its side
sur~aces and evaporator plates on the outside of the
wick pads to ~orm a sandwich construction ~hereof in the
same manner as depicted in FIG. 4 and similar to that
shown for e~aporator section 26 of FIG. 3. The entire
assembly may be brazed together at its outer surraces
to seal a working fluid within the module.
Separator plate 102 comprises a peripheral enclosure
108 comprising seglnents 110, 112, 114 and 116. Within
the interior o~ enclosure 158 is a serpentine construction
118 wlth portions thereor comprising parallel bars 120 and
alternating slots 122 and 124 extending between opposed
segments 110 and 114. Parallel bars 120 terminate at ends
~.3. ~8~8
1 126 which are spaced ~rom peripheral enclosure 108 to
provide opposed openings 128 and 130. Thus, parallel
slots 122 r~rrn vapor ~low passages to space 12~ within
a condenser section 96. Likewise, parallel slots 124
rorm vapor flow passa~es to opposed condenser space
130 and the condenser section at the opposite end of
the module. Connecting pieces 132 connect outer bars
120 of serpentine construction 118 to opposed enclosure
segments 112 and 116. In a manner similar to that of
1~ rIGS. 1-8~ bars 120 resist crushing forces on the
evaporator section to prevent the heat pipe rrom being
deformed.
In the operation of the embodiment depicted in
FIGS. 9 and 10, it therefore does not r,~atter whether one
or the other of the condenser sections Or modules 90
are above or below the central evaporator sections 94,
since there will always be an upper condenser section
with respect to its evaporator section.
Although the invention has been described with
reference to particular embodiments thereof, it should
be realized that various chan~es and modi~ications may
be made therein without departing rrom the spirit and
scope of the invention.
LBS:rp
[25-4]
