Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to heat exchange of an electrical
article and more particularly to cooling a module containing a plurality of
integrated circui~ chips.
The temperature o~ integrated circuit chips must be kept below speci-
fied limits to ensure proper function, reliability and useful life. The trend
in integrated circuit technology is to pack more circuits per chip which in-
creases the heat generation per chip. Also, system designers are mounting chips
closer together to minimize propagation delays in the interconnections. These
trends and designs have increased heat flux, i.e. power per unit area, and
caused a need for new cooling tec~miques.
In the conduction cooling of heat producing elements, a conductive
heat transfer medium (a solid) is placed into contact with a heat producing ele-
ment. The medium either has, or contacts another element which has, a greater
surface area relative to the heat producing element so that heat is more easily
dissipated from the greater surface area. To enhance heat dissipation from
surface areas, a fluid is often used as a heat transfer medium by being moved
over the heat dissipating surface area to "carry away" heat by convection.
From the foregoing it becomes quite clear that heat transfer is enhanced when
there is greater surface contact between a heat producing element and a heat
transfer medium.
The development of multichip thermal conduction modules to enhance the
cooling of concentrations of chips resulted in various conduction cooling tech-
niques including a plurality of resiliently urged pistons each contacting a
chip and providing a thermal path to a portion of the module housing which is
convection cooled by a fluid coolant.
This technique was further enhanced by encapsulating the pistons in
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helium gas to promote conduction cooling. Also, coolants such
as air, water or fluorocarbons have been pumped through the hou-
slngs .
Such pistons limit heat transfer regardless of piston
geometry due to the rigidity of the piston. For example, if
the piston has a curved contact surface then limited point contact
with the relatively planar chip sur-face results in reduced heat
transEer. Where the piston also has a relatively planar contact
surface, the piston and chip contact surfaces must be in substan-
]0 tial alignment to avoid point contaet.
The foregoing illustrates limitations of the knownprior art. Thus, it is apparent that it would be advantageous
to provide an alternative directed to overcoming one or more
of the limitations as set forth above~ Accordingly, a suitable
alternative is provided including features more fully disclosed
hereinafter.
In one aspect of the present invention, this is accom-
plished by providing an integrated circuit chips cooling apparatus,
comprising: a housing including a board having integrated circuit
ehips mounted thereon, said chips having a substantially planar
surface; means mounted in the housing for separating first and
second eooling portions, said separating means including a cold
plate and said chips being in said first portion opposite said
plate; means including bunched, heat-conductive strands connected
together at a first end to one side ofsaid cold plate and having
a second end extending into said first cooling portion flexing
and spreading apart in contact with said planar surface of a
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respective chip; a fluid inlet in said housing; a fluid outlet
in said housing; and other bunched, heat conductive strands having
a first end connected to another side of said cold plate oppo-
site said one side, said other strands having a second end spread-
ing and extending freely into said second cooling portion.
The invention will now be described in greater detail
with reference to the accompanying drawings, in which:
Figure 1 diagramma-tically illustrates an embodiment
of the module of this invention; and
Figure 2 diagramrnatically illustrates another embodi-
ment of the
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module of this invention.
An apparatus for cooling integrated circuit chips is illustrated in
Figure 1 as an improved thermal conduction module generally designated 10.
Module 10 includes a housing assembly 12 having a cap 14, a cold plate 16, a
board 18, and flexible means 20.
Generally, modules 10 are known and cap 14 is preferably of aluminum
or copper and includes a fluid inlet 22 and a fluid outlet 24. Cold plate 16
is typically of aluminum or copper and board 18 includes a plurality of in-
tegrated circuit chips 26 mounted thereon having a substantially planar surface
28. A plurality of connector pins 30 are also mounted on board 18. Several of
such boards 18 and their respective modules 10 are mounted on a card (not shown)
via pins 30, as is well known. The above mentioned components of housing 12 are
commonly held together by a plurality of suitable bolts 32.
Cold plate 16 and cap 14 provide a means mounted in housing assembly
12 for forming a first cooling portion 34 and a second cooling portion 36.
Chips 26 extend into first portion 34. The first and second cooling portions
34, 36 are fluid tight and, as it is well known, a more conductive environment
than air, such as an inert fluid, helium, may be provided in irst portion 34.
Also well known, is the practice of moving a fluid coolant such as air, water
or Eluorocarbons througll second portion 36 via inlet 22 and outlet 24.
The rate of heat transfer from chip 26 to cold plate 16 is vastly im-
proved when contact resistance between chip 26 and the heat conductor is reduced.
The present invention reduces contact resistance by providing a flexible conduc-
tor means 20 such as a plurality of bunches of heat conducting flexible strands
38, preferably beryllium copper~ having a first end 40 recessed into a bore 42
formed in co]d plate 16. First end 40 may be secured in bore 42 by brazing,
welding or the like. A second end 44 of strands 38 flex and spread apart
slightly as in a broom or brush so as to conform to planar surface 28 of chip
26 in response to being urged into deflecting contact with chip 26. A deflec-
tion of about 4 or 5 mils is preferred.
A pump 46 and ~LopLiate conduit 48 may be ~plopriately connected
to inlet 22 and outlet 24 for moving a fluid coolant, as above-mentioned,
through second cooling portion 36. A heat exchanger 49, or some suitable
means for re-cooling the fluid, is provided.
In another embodiment, Figure 2, first cooling portion 34 includes
a fluid inlet 50 and a fluid outlet 52 connected to pump 46 via conduit 48
for moving the fluid coolant of second cooling portion 36 also through first
cooling portion 34. Also, another plurality of bunches of strands 38a have
a first end 40a recessed into a bore 42a formed in cold plate 16 and have a
second end 44a extending freely into second cooling portion 36. In addition,
the first named bunches of strands 38 may extend at an angle "V" relative to
cold plate 16 to provide better contact distribution between end 44 and surface
28 of chip 26. It should be noted that, if desired, different coolants may be
used in portions 34, 36. Also, inlets 22, 50 and outlets 24, 52 may be provided
in multiples or have a slotted configuration,depending on factors such as the
desired cooling effect, the type of coolant used, etc.
In operation, heat is conducted~ Figure 1, from chips 26 to cold
plate 16 via strands 38. Thermal conduction in first cooling portion 34 is
enhanced by the presence of helium. Fluid moved through second cooling portion
36 by a pump 46 provides convection cooling to dissipate heat tran~erred ~o
cold plate 16.
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In Figure 2 heat is conducted from chips 26 to cold plate 16 via
strands 38. Thermal convection is provided to first cooling portion 34 by fluid
moved therethrough by pump 46. Additionally, strands 38a conduc~ heat from
cold plate 16 into second cooling portion 36. Thermal convection is provided
to second cooling portion 36 by the fluid moved by pump 46.
As a result of this invention, a conductive heat transfer medium is
provided which is axially and angularly compliant with the chip surface. Thus,
there is a substantial increase in surface area contact between the medium, in
this case a plurality of strands, and a surface of the chip.
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