Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
Cooling System Having Independent Fan Location
FIELD OF THE INVENTION
The present invention relates generally to cooling systems and more
particularly to cooling systems for use with integrated circuits (ICs) and
printed
circuit boards.
BACKGROUND OF THE INVENTION
As is known in the art, there is a trend to reduce the size of semiconductor
devices, integrated circuits and microcircuit modules while at the same time
having
the devices, circuits and modules perform more functions. To achieve this size
reduction and increased functionality, it is necessary to include a greater
number of
active circuits, such as transistors for example, in a given unit area. As a
consequence
of this increased functionality and dense packaging of active devices, such
devices,
circuits and modules (hereinafter collectively referred to as "circuits") use
increasingly more power. Such power is typically dissipated as heat generated
by the
circuits.
This increased heat generation coupled with the need for circuits to have
increasingly smaller sizes has led to an increase in the amount of heat
generated in a
given unit area. To further exacerbate the problem, the circuits are often
densely
mounted on printed circuit boards.
This increase in the amount of heat generated in a given unit area has led to
a
demand to increase the rate at which heat is transferred away from the
circuits in
order to prevent the circuits from becoming damaged or destroyed due to
exposure to
excessive heat. To increase the amount of heat that such circuits can
withstand, the
circuits can include internal heat pathways that channel or otherwise direct
heat away
from the most heat-sensitive regions of the circuits.
Although this internal heat pathway technique increases the amount of heat
which the circuits can withstand while still operating, one problem with this
internal
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heat pathway technique is that the amount of heat generated by the circuits
themselves
often can exceed the amount of self generated heat which the circuits can
successfully
expel as they are caused to operate at higher powers. Furthermore, other heat
generating circuit components mounted on printed circuit boards proximate the
circuits of interest further increase the difficulty with which heat can be
removed from
heat sensitive circuits. Thus, to increase the rate at which heat is
transferred away
from the circuits, a heatsink is typically attached to the circuits.
Such heatsinks typically include a base from which project fins or pins. The
l0 fins or pins are typically provided by metal extrusion, stamping or other
mechanical
manufacturing techniques. The heatsinks conduct and radiate heat away from the
heat
generating and thermally vulnerable regions of circuits. To further promote
the heat
removal process, fans are typically disposed adjacent the heatsink to blow or
otherwise force air or gas through the sides of the fins or pins of the
heatsink.
One problem with this approach, however, is that the amount of air or other
gas which a fan or blower can force through the heatsink fms/pins is limited
due to the
significant blockage of gas flow pathways due to the fins/pins themselves.
Furthermore, in a densely populated printed circuit board (PCB) or multi-
circuit
module (MCM), other circuit components and mechanical structures required to
provide or mount the PCB or module present additional blockage to gas pathways
and
also limits the amount of gas flow through the heatsink thus limiting the
effectiveness
of the heatsink. Thus, the ability of such conventional heatsinks and heatsink
fan
assemblies is limited and is not sufficient to remove heat as rapidly as
necessary to
ensure reliable operation of state of the art devices, circuits and modules
having
increased thermal cooling requirements.
Another problem associated with earlier heat removal systems is that the gas
supply source had to be in linear aligrunent with the device being cooled, and
was
typically provided along only a single side of the heat removal device. This
further
limits the ability to provide redundancy if one of the gas supply sources
should
malfunction.
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It would, therefore, be desirable to provide a cooling system that is capable
of
removing an amount of heat that is greater than the amount of heat removed by
conventional cooling systems. Additionally, it would be desirable to provide
the a
cooling system which does not have a linear dependency requirement between the
heatsink and the gas supply source so that the gas supply source could be
positioned
at any direction with respect to the heatsink, and such that redundancy for
the gas
supply source can be easily and effectively incorporated into the heat removal
system.
SUMMARY OF THE INVENTION
In accordance with the present invention, a cooling system comprises a first
heatsink adjacent a first device and wherein a gas supply can be located to
provide gas
in any direction with respect to the heatsink. The gas supply may be realized
as a fan,
a blower, or a compressed gas source. The gas supply may be provided in any
direction or in multiple directions. The heatsink is in thermal communication
with a
first heat-producing device such as a microprocessor. In a preferred
embodiment the
heatsink comprises a radial shaped folded fin heatsink arranged for axial
flow.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing features of this invention, as well as the invention itself, may
be
more fully understood from the following description of the drawings in which:
Figure 1 is an isometric view side view of a first embodiment of a cooling
system having independent fan location;
Figure 2 is an isometric view of the cooling system of Figure 1 including a
pair of blowers;
Figure 3 is an isometric view of the cooling system of Figure 2 including a
housing;
Figure 4 is another embodiment of a cooling system having independent fan
location including four blowers;
Figure S is an isometric view of the cooling system of Figure 4 including a
3o housing;
Figure 6 is another embodiment of a cooling system having independent fan
location including eight fans; and
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Figure 7 is an isometric view of the cooling system of Figure 6 including a
housing.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to Figures 1-7 in which like elements are provided having like
reference designations throughout the several views, a cooling system having
independent fan location is shown in Figure 1. The cooling system 1 includes a
first
axial heatsink 10. While additional heatsinks are shown in this figure, the
first axial
heatsink can function itself as the cooling system having independent fan
location. A
cooling gas supply source, such as a blower, fan, or compressed gas source,
can be
provided to axial heatsink 10 from any direction, as long as he gas exiting
the gas
supply source impinges on the fins of the axial heatsink. In this particular
embodiment, a pair of axial heatsinks 10 and 20 are provided disposed adjacent
one
another. Each of the heatsinks is thermally coupled to respective devices, and
provide
for removal of heat from the devices. A sidewall of the heatsink fin may
further
include at least one aperture extending through the sidewall. The apertures
may be
provided in a predetermined pattern, shape and size to provide the desired
cooling.
The top edges of the fins may be closed, and the bottom edges of the troughs
may also
be closed, thereby allowing the fin/trough combination to act as a plenum.
Each axial heatsink may further include a thermally conductive member 12
and 22. A first surface of the member is adapted to be in contact with an
active
portion of a heat-generating device (e.g. an integrated circuit). Thus the
folded fin
stock is wrapped around the member and is in thermal communication with the
member. Typically, the folded fin stock and member are provided from tinned
copper
or aluminum.
Ideally, the portion of the member in contact with the heat-generating device
is provided having a shape that covers as much as possible the active area of
the heat-
generating device. In one embodiment, the member is machined flat and a
thermal
interface material is disposed on the surface of the member which will be in
contact
with the heat generating device. Thus, for example, in the case where the heat-
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generating device is an IC which itself includes an internal heatsink, the
member
should cover the internal heatsink of the IC.
Also, it may be desirable or necessary to provide folded fin members of the
heatsink as a single unitary piece or as more than one piece. The particular
number of
pieces from which the first heatsink is provided may be selected in accordance
with a
variety of factors including but not limited to the particular application,
the amount of
heat which must be transferred away from heat generating devices, the amount
of
space available for mounting of the heatsink and other components, the
particular
to material from which the heatsink pieces is provided, the particular
manufacturing
techniques used to fabricate heatsink and the cost of manufacturing the
heatsink.
In order to prevent the fins of the heatsinks from interfering with each other
or
otherwise overlap, a section 30 has been removed from each axial heatsink to
allow
the heatsinks to be mounted within frame 40. In the depicted embodiment a same
amount of material (approximately 25 percent maximum for a selected set of
fins) has
been removed from each axial heatsink. In another embodiment the amount
removed
from one heatsink could be more than the amount removed from the other
heatsink,
especially if the heatsink having the most fin material removed was disposed
on a
device providing less heat than the device on which the other axial heatsink
is
disposed. Additionally, after the cut is made into the heatsink to remove some
material, such as by using electric discharge milling (EDM), when the fins
include a
plurality of holes such that the fins act as plenums, it is desirable to seal
the open ends
of the cut fms after they have been machined by the EDM procedure.
The particular embodiment shown in Figure 1 further includes a pair of linear
heatsinks 50 and 60. Linear heatsinks 50 and 60 are coupled to respective
second
devices. While the linear heatsink is shown having a generally rectangular
shape,
other shapes could also be used. These linear heatsinks may be realized as
standard
folded fin heatsinks and in this embodiment are used to cool devices that
provide
power to the devices cooled by axial heatsinks 10 and 20.
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The axial heatsinks 10, 20 and the linear heatsinks 50,60 may be coupled to
any type of integrated circuit package including, but not limited to, dual-in-
line
packages (DIP) leadless chip Garners, leaded chip carriers, flat packs, pin-
grid arrays
as well as other surface mount packages and small outline integrated circuit
packages
for surface-mounting.
The heatsinks as shown and described herein may be disposed over a first
surface of an integrated circuit that is disposed on a printed circuit board.
Disposed
between a first surface of a circuit and a first surface of a heatsink is a
sheet of a
thermally conductive matrix material. The matrix material facilitates an
extraction of
heat from the circuit to the heatsink.
It should also be noted that in some applications it might be desirable to
mount
the circuit on the printed circuit board prior to placing the
heatsink/thermally
conductive matrix material assembly on to the circuit. It should also be noted
that in
some applications it might be desirable to apply the thermally conductive
matrix
material first to the surface of the circuit and then to mount the heatsink to
the
circuit/thermally conductive matrix assembly and then mount the assembly on
the
PCB.
Referring now to Figure 2, the assembly of Figure 1 is shown along with a pair
of blowers 70 and 80. In a preferred embodiment, the blower comprises a
"squirrel
cage" type blower. Blower 70 and blower 80 are similar, however blower 80 has
been
inverted with respect to blower 70. As is known in the art, blowers typically
have a
non-uniform velocity profile at their output. Accordingly, blower 80 has been
inverted in order to provide its maximum gas velocity directly to heatsink 20,
since
both blowers 70 and 80 are single-sided blowers. Alternately a left rotation
blower
and a right rotation blower could have been used. The distance between the
blower
and the axial heatsink is chosen to provide a more uniform flow to the
heatsink.
Blower 70 is arranged to provide cooling gas to heatsink 10 while blower 80 is
disposed to provide cooling gas to heatsink 20. In the event that one of the
blowers
fails, non-uniform cooling would result as gas would leak back through the
failed
blower.
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Refernng now to Figure 3, the assembly of Figure 2 is shown further
comprising a housing 90 disposed over the heatsinks. Housing 90 provides a
cover
extending from blowers 70 and 80, over the axial heatsinks (not shown) and
over the
linear heatsinks (not shown). Additionally, housing 90 may be provided with a
plurality of vanes. The vanes may be located at a first end of the housing,
where the
blowers interface to the housing. Additionally vanes may be provided at an
area of
the housing that corresponds to the space between the axial heatsinks and the
linear
heatsinks. The vanes are designed to reduce the turbulence within the housing,
prevent or reduce air boundary separation within the housing, and to maintain
the
velocity head pressure. The vanes minimize the discontinuities in the airflow
through
the housing. As a result, a high pressure, generally uniform stream of gas is
provided
through the housing. The vanes are preferably solid pieces having a smooth
finish in
order to minimize turbulence. Transition vanes may also be incorporated at the
end of
the housing.
Housing 90 may further include flapper valves at the first end thereof. The
gas stream resulting from an operational blower would keep the flapper valve
in the
open position. The flapper valves would be biased to a closed position when a
blower
fails, thereby preventing back leakage of cooling gas through the failed
blower.
Refernng now to Figure 4, the assembly of Figure 2 is shown with two
additional blowers 75 and 85. Due to the radial design of heatsinks 10 and 20,
cooling
gas can be provided from any direction. Accordingly, there is no linear
relationship
dependency between the blowers) and the remainder of the assembly.
The fact that the blowers can be positioned anywhere around the radial
heatsinks provides great flexibility in the design and layout of devices, as
well as
providing for redundancy. For example, blower 75 can be used as a redundant
blower
3o with respect to blower 70. Thus, if blower 70 malfunctions, blower 75 can
be enabled
and provide the same supply of gas as that provided by blower 70. Blower 85
can be
used in a similar manner to provide redundancy for blower 80. Alternately,
blowers
70 and 80 could be used to provide redundancy for blowers 75 and 85
respectively.
Additionally, all four blowers 70, 75, 80 and 85 can be used at the same time
to
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provide cooling gas to the heatsinks 10 and 20. Since the blowers can be
provided in
any direction adjacent to the heatsinks, multiple blowers can be easily and
effectively
implemented.
Refernng now to Figure 5, the assembly of Figure 4 is shown further
comprising a housing 95 disposed over the heatsinks. Housing 95 provides a
cover
extending from blowers 70, 75, 80 and 85, over axial heatsinks 10 and 20 and
over
linear heatsinks 50 and 60. Additionally, housing 90 may be provided with a
plurality
of vanes. The vanes may be located where the blowers interface to the housing.
l0 Additionally vanes may be provided at an area of the housing, which
corresponds to
the space between the axial heatsinks and the linear heatsinks. Transition
vanes may
also be incorporated at the end of the housing.
Housing 95 may further include flapper valves at the blower interfaces. The
air stream resulting from an operational blower would keep the flapper valve
in the
open position. The flapper valves would be biased to a closed position when a
blower
fails, thereby preventing back leakage of cooling gas through the failed
blower.
Referring now to Figure 6, a heat sink assembly is shown with a plurality of
2o fans. The first plurality of fans 100 provides gas to the assembly. The
second
plurality of fans 110 removes gas from the assembly 1. Multiple fans may be
required
to achieve the desired cooling. Fans could also be disposed about the sides of
axial
heatsinks 10 and 20.
Figure 7 shows the assembly of Figure 6 further comprising a housing 120.
Housing 120 provides a cover extending from the first plurality of fans 100,
over axial
heatsinks 10 and 20 and over linear heatsinks 50 and 60 and extending to the
second
plurality of fans 110. Additionally, housing 90 may be provided with a
plurality of
vanes. Housing 95 may further include flapper valves at the fan interfaces.
The air
3o stream resulting from an operational fan would keep the flapper valve in
the open
position. The flapper valves would be biased to a closed position when a fan
fails,
thereby preventing back leakage through the failed fan. By use a plurality of
fans, in
the event one fan fails the system is not significantly affected since, due to
the
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combination of fan curves, only an approximately four percent reduction is
realized in
the event of a fan failure.
Having described preferred embodiments of the invention it will now become
apparent to those of ordinary skill in the art that other embodiments
incorporating
these concepts may be used. Accordingly, it is submitted that that the
invention
should not be limited to the described embodiments but rather should be
limited only
by the spirit and scope of the appended claims.
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