U.S. patent number 4,489,363 [Application Number 06/462,275] was granted by the patent office on 1984-12-18 for apparatus for cooling integrated circuit chips.
This patent grant is currently assigned to Sperry Corporation. Invention is credited to Norman Goldberg.
United States Patent |
4,489,363 |
Goldberg |
December 18, 1984 |
Apparatus for cooling integrated circuit chips
Abstract
Apparatus is provided for cooling a closely grouped plurality of
integrated circuit chips by forced air convection. A heat sink,
having a plurality of fins and a narrow channel between each fin,
is connected to a first side of a substrate and has one end
protruding into an aperture in the substrate. A chip is connected
directly to the one end of the sink and is electrically connected
to a second side of the substrate.
Inventors: |
Goldberg; Norman (Dresher,
PA) |
Assignee: |
Sperry Corporation (New York,
NY)
|
Family
ID: |
23835849 |
Appl.
No.: |
06/462,275 |
Filed: |
January 31, 1983 |
Current U.S.
Class: |
361/693;
174/16.1; 361/690 |
Current CPC
Class: |
H01L
23/467 (20130101); H01L 2924/0002 (20130101); H01L
2924/0002 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
H05K
7/20 (20060101); H05K 007/20 () |
Field of
Search: |
;361/380,381,382,383,384,385,386,387,395,399,413,415
;174/15R,16HS,16R ;165/122,124,126 ;357/81 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Tuckerman et al., "High-Performance Heat Sinking for VLSI", IEEE
Electron Device Letters, vol. 2 EDL-2, No. 5, 5/81. .
Dumaine et al., "IBM Technical Disclosure Bulletin", vol. 20, No.
4, 9/77, p. 1472. .
Archey, "IBM Technical Disclosure Bulletin", vol. 19, No. 2, 7/76,
p. 412. .
Tiffany, "IBM Technical Disclosure Bulletin", vol. 13, No. 1, 6/70,
p. 58..
|
Primary Examiner: Pellinen; A. D.
Assistant Examiner: Thompson; Gregory D.
Attorney, Agent or Firm: Bell; James R. Scott; Thomas J.
Truex; Marshall M.
Claims
Having thus described the invention, what is claimed is:
1. An apparatus for cooling integrated circuit chips
comprising:
a housing including a substrate, said substrate having apertures
formed therethrough, said housing also including a partition
mounted therein defining an inlet chamber and an outlet chamber,
said partition having a plurality of openings formed
therethrough;
a plurality of heat sinks mounted on said substrate, each heat sink
having a first end extending into a respective one of said
apertures;
each of said sinks having a second end extending into a respective
one of said openings in said partition and having an inlet side of
each sink exposed to said inlet chamber and having an outlet side
of each sink exposed to said outlet chamber;
a fluid inlet and a fluid outlet in said housing, each inlet side
being connected for conducting fluid from said inlet chamber and
each outlet side being connected for conducting fluid to said
outlet chamber;
each heat sink further having a plurality of elongated spaces
formed therethrough for defining a plurality of spaced apart fins
for permitting fluid to flow through said heat sink from said inlet
side to said outlet side; and
means covering each inlet side for resisting fluid flow between the
fins.
2. The apparatus of claim 1 including:
a chip connected directly to said first end of said heat sink.
3. The apparatus of claim 1 including:
a flange interconnecting each heat sink and said substrate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to heat exchange of an electrical
article and more particularly to cooling an integrated circuit
chip.
2. Description of the Prior Art
The temperature of integrated circuit chips must be kept below
specified limits to ensure proper function, reliability and useful
life. The trend in integrated circuit technology is toward large
scale integration which results in increased functions per chip.
Also, system designers are mounting chips closer together to
minimize propagation delays in the circuit interconnections. As a
result of the foregoing, heat is not only increased for each chip
but is also concentrated due to the closely mounted chips. Cooling
of these chips is a problem.
A limitation of chip cooling is that compact areas are often too
confining to provide adequate cooling. The prior art discloses that
liquid cooling promises to be more compact than forced air
convection. However, limitations to liquid cooling include
increased cost due to complexity of cooling circuits, i.e. pumping
and guiding liquid to and from the vicinity of the chips and
cooling the fluid so that it can be recirculated in a closed loop
system. Also, there is an inherent aversion to using a liquid
within an electrical system due to the obvious problems created if
leakage of the liquid should occur.
A heat sink having narrow air channels formed between adjacent fins
has been mounted on one side of a board or substrate adjacent a
respective chip which is mounted on an opposite side of the board.
Heat from the chip is conducted through the substrate to the sink.
Air moved through the channels and across the fins carries heat
from the sink by convection. Heat conducted through substrate
encounters the thermal resistance of the board.
The foregoing illustrates limitations of the known prior 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.
SUMMARY OF THE INVENTION
In one aspect of the present invention, this is accomplished by
providing an apparatus for cooling integrated circuit chips
including a substrate having an aperture formed therein. A heat
sink has an integrated circuit chip connected to one end. The sink
is then mounted on a first side of the substrate. The one end of
the heat sink having the chip, extends into the aperture adjacent a
second side of the substrate. The chip is electrically connected to
the second side of the substrate.
The foregoing and other aspects will become apparent from the
following detailed description of the invention when considered in
conjunction with the accompanying drawings. It is to be expressly
understood, however, that the drawings are not intended as a
definition of the invention but are for the purpose of illustration
only.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is an isometric view illustrating an embodiment of the
apparatus of this invention;
FIG. 2 is a plan view of the underside of substrate 14;
FIG. 3 is an exploded elevational view graphically illustrating an
embodiment of the outlet side of the heat sink of this invention
taken along line 3--3 of FIG. 1; and
FIG. 4 is a view taken along line 4--4 of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIGS. 1-4, a modular apparatus for cooling integrated circuit
chips is generally designated 10 and comprises a housing 12
including a well-known ceramic substrate 14, typically alumina,
having a plurality of apertures 15 formed therein. A plurality of
heat sinks 20 are each mounted in a respective aperture of
substrate 14 by means of a flange 17 connected to a surface 22 of
substrate 14 and also connected to sink 20. Flange 17 is provided
so as to position a gold-plated end 21 of sink 20 adjacent a
surface 18 of substrate 14. In this manner an integrated circuit
chip 16, bonded directly to end 21 of sink 20, preferably by a
Silicon-Gold eutectic bond, is positioned adjacent surface 18 of
substrate 14. Another end 23 of each sink 20 protrudes
substantially from substrate 14 and includes fins forming narrow
channels therebetween sufficient for permitting fluid to flow
through sink 20.
Housing, or plenum 12 is of aluminum or plastic and includes a
plurality of sides 12a, 12b, 12c and 12d, and a top 12e. Housing 12
and substrate 14 are connected so that substrate 14 forms a bottom
of housing 12. Also included in housing 12 are a plurality of
partitions 12f, 12g, 12i and 12h defining a plurality of separated
inlet chambers 24, 26 and a plurality of separated outlet chambers
28, 30 and 32. An exemplary fluid conduit 34 is connected to side
12a and a similar fluid conduit 36 is connected to side 12c.
Conduit 34 is provided for conducting a fluid, preferably air under
pressure, to inlet chambers 24, 26 via a plurality of inlet ports
38, 40, whereas conduit 36 is provided for conducting the fluid
from outlet chambers 28, 30, 32 via a plurality of outlet ports 42,
44 and 46. Partitions 12f, 12g, 12i and 12h include openings 25
sufficient to receive end 23 of each sink 20.
Each heat sink 20 is formed of flat pieces of Copper and preferably
of Copper Alloy No. 110 distributed by North America Brass and
Aluminum, Inc. The nearest applicable ASTM specifications for flat
No. 110 Copper alloy are B11, B48, B101, B124, B133, B152, B187,
B272 and B370. Flat pieces of Copper alloy No. 110 having
thicknesses of 0.025", 0.010" and 0.005" were used to form
fabricated sinks 20.
Each sink 20 includes a base 48 and a top 50 and has a plurality of
substantially parallel, elongated fins 52 extending from base 48 to
top 50 and also extending from an inlet side 54 to an outlet side
56. Each sink 20 is mounted in one of the partitions 12f, 12g, 12i
and 12h exposing inlet side 54 to one of the inlet chambers 24, 26
and exposing outlet side 56 to one of the outlet chambers 28, 30
and 32.
Fabricating sinks 20 can be accomplished by selecting flat pieces
of copper alloy No. 110 and welding together a plurality of fins 52
at base 48 and top 50 by the well known tig welding method. Fins 52
are each separated at base 48 by a piece of flat Copper alloy No.
110 having the same thickness as each fin 52. Similarly, fins 52
are each separated at top 50 by a piece of flat Copper alloy 110
having the same thickness as each fin 52. In this manner, for
example, a sink 20 having fins 52 of a 0.025" thickness define a
narrow gap or channel 58 between each adjacent fin 52 also having a
thickness of 0.025". Similarly, a sink having fins 0.010" thick has
gaps of 0.010" thick, and a sink having fins 0.005" thick has gaps
of 0.005" thick, and so on.
Flange 17 is formed of a suitable material and is connected to sink
20 and to surface 22 of substrate 14 by a suitable epoxy 19. Chip
16 is electrically connected by means 27, such as wire bonding or
tape automated bonding, to surface 18 of substrate 14.
Means, such as a mesh covering 60, can be provided to cover inlet
side 54 of each sink 20. In this manner, sufficient resistance is
provided to permit a substantially equal rate of fluid to flow
though each sink 20 from inlet chambers 24, 26 through channels 58
between fins 52 and into outlet chambers 28, 30, 32. Thus, mesh
cover 60 causes fluid pressure to be increased in inlet chambers
24, 26 during operation. A typical mesh cover 60 is a screen formed
of 316 stainless steel having an 80.times.80 mesh of 0.007" wire
distributed by Newark Wire Cloth Company.
In accordance with this invention, heat sinks having fins of a
0.010" thickness and gaps therebetween also of a 0.010" thickness
were tested on a substrate with 16 chips on 1/2" centers. This
arrangement provided adequate cooling for chips running at 10 watts
each with an air flow of 20 liters per minute, per sink. An air
pressure of 10.5 inches of water was required. The thermal
resistance of this arrangement was 5.degree. C./watt from junction
to ambient air. This corresponds to a power density of 40 watts per
square inch. Prior to this invention, it was felt that such high
power densities required liquid cooling.
The performance of a heat sink is usually described by its thermal
resistance; the increase in temperature per unit of dissipated
power. One of the most significant contributions to this resistance
is at the surface of the sink where heat is transferred to the
coolant fluid. Previous heat sink designers recognized that this
resistance can be reduced by increasing the area of the sink and
therefore the use of fins is common in heat sinks. However,
previous forced air heat sink designers did not recognize, the
possibility of increasing the heat transfer coefficient between the
sink and the fluid. This can be done by using very narrow channels
or gaps between the fins. With a short distance between the fin and
the center of the gap, the temperature gradient is larger, and
therefore the heat transfer coefficient is larger.
During manufacture, each integrated circuit chip 16 is first
attached to one end 21 of each sink 20 by a eutectic bond which
requires high heat. It is important to accomplish this bond prior
to mounting the sink 20 on the substrate 14 as this advantageously
avoids exposing the substrate 14 to high heat. Also, each sink/chip
combination can be tested prior to mounting on the substrate.
After bonding and/or testing the sink 20 is then mounted on one
side 22 of the substrate 14 so that the chip 20 extends into the
aperture 15 formed in the substrate 14, and a surface 29 of chip 20
is substantially flush with surface 18 of substrate 14. Chip 20 is
then electrically connected to surface 18 of substrate 14 by means
of well-known wires or tape 27. It is advantageous to have chip
surface 29 and substrate surface 18 substantially flush as this
avoids under flexing of wire or tape 27.
The foregoing has described a narrow channeled forced air heat sink
capable of providing adequate cooling of a compact concentration of
integrated circuit chips. Each chip 16 is connected directly to
each respective sink 20 thereby avoiding the thermal resistance of
substrate 14.
It is anticipated that aspects of the present invention, other than
those specifically defined in the appended claims, can be obtained
from the foregoing description and the drawings.
* * * * *