U.S. patent application number 11/404388 was filed with the patent office on 2007-02-15 for high performance cooling assembly for electronics.
Invention is credited to Jack Phillip Hall.
Application Number | 20070034360 11/404388 |
Document ID | / |
Family ID | 37499161 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070034360 |
Kind Code |
A1 |
Hall; Jack Phillip |
February 15, 2007 |
High performance cooling assembly for electronics
Abstract
An assembly for high performance cooling of electronics is
described that includes a container for heat transfer liquid in
which complex electronic assemblies are immersed. The electronics
are sealed inside the liquid container such that an electrical
connector protrudes to the exterior of the container. A thermally
conductive plate is made part of the liquid filled container
assembly such that a portion of the plate is in contact with the
liquid and a portion of the plate protrudes from or forms part of
the exterior of the container.
Inventors: |
Hall; Jack Phillip; (Del
Mar, CA) |
Correspondence
Address: |
WESLEY B. AMES
7031 LOS VIENTOS SERENOS
ESCONDIDO
CA
92029
US
|
Family ID: |
37499161 |
Appl. No.: |
11/404388 |
Filed: |
April 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60688641 |
Jun 8, 2005 |
|
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|
Current U.S.
Class: |
165/104.33 ;
165/104.19 |
Current CPC
Class: |
G06F 2200/201 20130101;
H05K 7/20418 20130101; H05K 7/20763 20130101; G06F 1/183 20130101;
G06F 1/20 20130101 |
Class at
Publication: |
165/104.33 ;
165/104.19 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Claims
1. A liquid cooled electronics circuit board, comprising a circuit
board comprising a plurality of heat generating components; a
sealed container surrounding said circuit board and containing a
heat transfer, dielectric liquid such that said circuit board is
substantially submerged in said liquid, wherein said container
comprises a fill port, at least one heat conductive plate that is
in contact with said liquid and protrudes to the exterior of said
container, and a thermal expansion compensating surface; and an
electrical connector connecting to said circuit board and extending
to the exterior of said container.
2. The liquid cooled electronics circuit board of claim 1, wherein
said circuit board is installed in a computer system.
3. The liquid cooled electronics circuit board of claim 1, wherein
the volume of said liquid is at least 50 ml.
4. The liquid cooled electronics circuit board of claim 1, wherein
said heat generating components together generate 20-150 watts.
5. The liquid cooled electronics circuit board of claim 1, wherein
said heat generating components together generate 50-100 watts.
6. The liquid cooled electronics circuit board of claim 1, wherein
thermal expansion volume of said liquid within said container is
accommodated by a flexible diaphragm that is in contact with the
liquid on one side and ambient atmosphere on the other side.
7. The liquid cooled electronics circuit board of claim 6, wherein
said flexible diaphragm is a low curvature, concave wall of said
container.
8. The liquid cooled electronics circuit board of claim 6, wherein
said flexible diaphragm is a circular disk diaphragm.
9. The liquid cooled electronics circuit board of claim 1, wherein
said heat conductive plate is adjacent said connector.
10. The liquid cooled electronics circuit board of claim 1, wherein
said heat conductive plate is distal from said connector.
11. The liquid cooled electronics circuit board of claim 1, wherein
said liquid is a fluorocarbon or an oil.
12. The liquid cooled electronics circuit board of claim 1, wherein
said container can be opened or removed allowing access to
components on said circuit board, and sealably replaced.
13. The liquid cooled electronics circuit board of claim 1, wherein
said fill port is configured to allow extraction and replacement of
said liquid.
14. The liquid cooled electronics circuit board of claim 1, wherein
said heat conductive plate is thermally coupled with a heat
sink.
15. The liquid cooled electronics circuit board of claim 14,
wherein the thermal coupling is accomplished through a heat
conductive elastomeric material.
16. An electronics cooling assembly, comprising a sealed container
substantially filled with a heat transfer, non-electrically
conducting liquid and comprising a fill port allowing filling of
said container with said liquid after sealing, at least one
conductive plate that is in contact with the liquid inside the
container, and protrudes to the exterior of the container, and a
thermal expansion compensating surface; at least one circuit board
mounted within said container substantially submerged in said
liquid; and an electrical connector connecting to said circuit
board and extending to the exterior of the container.
17. The electronics cooling assembly of claim 16, wherein the walls
of said container consist essentially of a material selected from
the group consisting of polycarbonate, acrylic, and ABS
plastic.
18. The electronics cooling assembly of claim 16, wherein said fill
port comprises an orifice that can be breached by a nozzle and is
self-sealing when the nozzle is retracted.
19. The electronics cooling assembly of claim 16, wherein said heat
conductive plate comprises at least 80% copper, aluminum, or heat
conductive ceramic.
20. The electronics cooling assembly of claim 16, wherein thermal
expansion volume of said liquid within said container is
accommodated by a flexible diaphragm that is in contact with the
liquid on one side and ambient atmosphere on the other side.
21. The electronics cooling assembly of claim 20, wherein said
flexible diaphragm is a low curvature, concave wall of said
container.
22. The electronics cooling assembly of claim 20, wherein said
flexible diaphragm is a circular disk diaphragm.
23. The electronics cooling assembly of claim 16, wherein said
liquid is a fluorocarbon or an oil.
24. A computer system comprising a plurality of electronics cooling
assemblies, wherein each said cooling assembly comprises a sealed
container substantially filled with a heat transfer,
non-electrically conducting liquid and comprising a fill port
allowing filling of said container with said liquid after sealing,
at least one conductive plate that is in contact with the liquid
inside the container, and protrudes to the exterior of the
container, and a thermal expansion compensating surface; a circuit
board mounted within said container substantially submerged in said
liquid; and an electrical connector connecting to said circuit
board that protrudes to the exterior of said container.
25. A method for cooling a complex electronics assembly, comprising
enclosing said complex electronic assembly in a sealed container
substantially filled with a heat transfer, non-electrically
conducting liquid and comprising a fill port allowing filling of
said container with said liquid after sealing, at least one
conductive plate that is in contact with the liquid inside the
container, and protrudes to the exterior of the container, a
thermal expansion compensating surface, and an electrical connector
connecting to said circuit board and extending to the exterior of
said container.
26. The method of claim 25, further comprising thermally coupling
said conductive plate with a heat transfer device.
27. A method for thermally coupling a thermally conductive plate
that conducts heat from an electronic assembly, with a thermally
conductive device, comprising mechanically compressing a thermally
conductive compliant material between said thermally conductive
plate and said thermally conductive device, wherein an electronic
connector connected with said electronic assembly is mounted
adjacent to or penetrates said thermally conductive plate.
28. The method of claim 27, wherein said mechanical compression is
performed using at least one over-center clamp.
29. A cooling assembly for heat generating electronics, comprising
a first thermally conductive plate which conducts heat from said
heat generating electronics; a second thermally conductive element
attached to a surface of said thermally conductive plate using a
means for providing a low thermal resistance connection between the
conductive plate and second heat transfer element, and a first
electronics connector adjacent to or penetrating said first
thermally conductive plate which connects said heat generating
electronics with separate electronic components.
30. The cooling assembly of claim 29, wherein said means for
providing a low thermal resistance connection comprises a high
thermal conductance elastomer and an over-center clamping
mechanism.
31. The cooling assembly of claim 29, further comprising a second
electronic connector mounted on said second thermally conductive
element which connects with said first electronic connector.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/688,641 filed on Jun. 9, 2005, which is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of cooling
systems for electronic circuit boards.
BACKGROUND OF THE INVENTION
[0003] The following discussion is provided solely to assist the
understanding of the reader, and does not constitute an admission
that any of the information discussed or references cited
constitute prior art to the present invention.
[0004] Heat dissipation is an important operational aspect of
electronic assemblies. As performance and density of electronics
increases, the devices typically produce more heat. Fans are widely
used to provide cooling in electronics enclosures, but certain
configurations of electronic circuits are difficult to cool
sufficiently solely with forced air. Air has low density and poor
thermal conductivity compared to other materials. To cool dense,
high heat generating electronic assemblies, a high volume of air
must be moved past the electronics to maintain optimal or even
acceptable operating temperatures. Moving high volumes of air
typically generates high levels of noise and turbulence.
[0005] Electronic assemblies are cooled more efficiently when the
electronics are in direct contact with a substance having good
thermal conductance properties, such as a dielectric liquid. Being
denser than air, a dielectric fluid is a superior conducting medium
and is conformal, able to be in contact with all surfaces of an
electronic assembly. On the other hand, use of liquid with
electronic assemblies is problematic because of the potential for
spillage and leakage.
[0006] Liquids have been employed in electronics cooling for some
time. Liquid cooling of electronics has generally been done in one
of three ways. (1) Liquid is contained in tubes and substrates that
are proximal or in contact with electronic devices. (2) Liquid is
sprayed, or misted onto electronics and collected in a drip tray
for reuse. This technique may be combined with air cooling. (3)
Electronics are submerged in liquid and the liquid is circulated
via tubing to a heat exchanger and back again. The first technique
may use a variety of heat transfer liquids, while the later two
techniques require use of a dielectric, inert liquid.
[0007] Several patents describe the use of cooling liquids
indirectly by isolating a heat transfer liquid within tubes and
substrates in order to prevent wetting of the electronics. In U.S.
Pat. No. 5,343,358 by Hilbrink, electronic components and heat
pipes are assembled on a circuit board. The circuit boards are
attached to a backplane via electronic connectors and the heat
pipes are connected via collets. The collets are used to connect
the board mounted heat pipes to a fluid circulating system. In this
invention heat transfer is limited to individual electronic
component surfaces that are in contact with the heat pipes. While
this solution may work for microprocessors and other flat
components; it is impractical where heat generating components of
odd shapes and/or a large number of components are present. In this
invention the electronic devices to be cooled are not engulfed by
the cooling fluid and therefore the heat flow path is limited.
Further, the system is prone to leaks due to the numerous fluid
connections.
[0008] Similarly, U.S. Pat. No. 5,177,666 by Bland provides a
cooling rack that circulates cooling fluid to conductive pads that
are fitted closely to heat generating components on a circuit
board. The pads are connected to the rack by use of fluid
connectors. The heat flow path is limited to the specific
components that are in contact with the pads, and the system is
prone to leaks due to the numerous fluid fittings.
[0009] In U.S. Pat. No. 5,057,968 by Morrison, a configuration is
described as a cooling system for printed circuit boards that has
guide rails with serpentine cooling passages inside. The serpentine
passages contain a liquid that is regulated to produce phase
change, or boiling of the liquid. There are circuit board mounted
heat pipes that are clamped to the guide rails, and heat migrates
from the hot components, through the heat pipes, to the metal guide
rail. The fluid in this configuration does not engulf the
electronic components and so the thermal pathway is limited to the
surfaces in contact. The fluid is contained within channels and is
circulated from the rack to an external heat exchanger. Because of
the numerous fluid couplings, this design is prone to leakage.
[0010] U.S. Pat. No. 4,962,444 by Niggemann describes a cold
chassis with impingement attached circuit boards. The circuit
boards are constructed with electronic components mounted to an
aluminum plate. A clamping mechanism is used to attach the aluminum
plates to the cold chassis. The cold chassis utilizes internal
cooling fluid as a means of dissipating the heat from the chassis.
As described this invention relies on an aluminum plate to conduct
the heat away. The plate is not conformal; it does not engulf each
electronic device as a fluid does, and so heat transfer is
limited.
[0011] In U.S. Pat. No. 6,616,469 by Goodwin, an electronic
component is cooled by means of a substrate containing a channel
for liquid to flow through. The substrate is pressed against the
electronic component to be cooled and heat is conducted through the
substrate and into the fluid. The cooling channel is connected to a
fluid valve that controls fluid flow in and out of the substrate.
The design provides connectors for electrical and fluid coupling.
In this invention electronic components of different sizes and
shapes are difficult to accommodate. Only the component surface in
contact with the substrate is cooled and therefore heat transfer is
limited. The tubes, valves and fluid connections described in this
invention are prone to leakage.
[0012] U.S. Pat. No. 5,323,292 by Brzezinski describes a container
made with a heat sink on the outside. A metallic membrane sealed to
the inside of the heat sink is pressed against the components
inside the container. Between the membrane and the heat sink, a
pressurized dielectric fluid forces the membrane against the
electronic devices. Dielectric fluid is therefore not in direct
contact with the electronic devices. This invention can accommodate
slight variations in device planarity but is impractical for
electronic assemblies containing a wide range of component shapes
and circuit board configurations. Further, the components are not
engulfed in a heat transfer medium and the invention provides a
heat flow path from only one surface of each component. The
invention is therefore only partially efficient as a cooling
technique.
[0013] In U.S. Pat. No. 6,744,136 by Dubhashi, a heat generating
electronic device such as a semiconductor die, a diode, transistor
or thyristor is suspended inside an enclosure filled with heat
transfer liquid. The enclosure that houses the fluid has a wall
that is thermally conductive and is sealed to the remainder of the
enclosure. The patent describes electrodes that protrude through
the enclosure and are sealed to prevent fluid leakage. The
invention is an improvement over the epoxy encapsulation method
typically used to package semiconductor devices, however, it is not
suitable for larger assemblies of components such as a circuit
board. There is no accommodation for expansion and contraction of
the fluid that occurs with larger volumes of fluid.
[0014] U.S. Pat. No. 4,312,012 by Frieser and U.S. Pat. No.
3,741,292 by Aakalu, et al, describe an enclosure containing a heat
generating electronic device partially filled with inert liquid.
The invention relies on nucleate boiling of the liquid to transfer
heat to the enclosure walls and the walls are configured to promote
condensation of the liquid. In this configuration the fluid is not
circulated and ultimately relies on air flow to remove heat from
the ambient exterior of the package.
[0015] In U.S. Pat. No. 4,590,538 by Cray, heat generating circuit
boards are immersed in a coolant liquid. The liquid is pumped to a
heat exchanger, cooled and pumped back to the vessel containing the
circuit boards. This technique is similar to U.S. Pat. No.
4,302,793 by Rohner. In the Rohner patent a circuit board is
suspended inside a fluid filled tank and a circulating pump is used
to move the liquid into heat exchanger and back again. Systems that
use a pumping device to circulate cooling liquid are difficult to
seal because of the numerous connections between hoses, fittings,
gaskets and pumps.
SUMMARY OF THE INVENTION
[0016] The present invention provides a high performance method for
the cooling of complex, heat generating circuit boards and other
complex electronic assemblies, using a dielectric liquid as a heat
conducting medium, without necessitating the use of complex
apparatus for circulating cooling liquid. This is accomplished
using a container enclosing the entire electronic assembly such
that the assembly is submerged in the dielectric liquid. A
thermally conductive plate is in contact with the fluid and the
plate extends beyond the exterior wall of the container. The plate
can be attached to a thermal pathway such as a heat pipe that is
connected to a heat exchanger. By cooling the heat pipe and
consequently cooling the conductive plate, the fluid inside the
container becomes cooler through diffusion, and consequently the
electronic components are cooled. Electrical connection between the
electronic assembly within the container and other external
electronic devices is made through a sealed electrical connector.
The protruding connector may be attached to a mating connector on
either a printed wiring board or electrical wiring cable.
[0017] The invention provides a number of distinct advantages,
including for example, the following: [0018] a) Electronic
assemblies are contained within an enclosure sealed in a manner
that provides a deterrent to anyone attempting to tamper with these
devices. [0019] b) The sealed liquid filled containers are easy to
remove and replace, without risk of spillage. [0020] c) The sealed
container can be assembled and serviced in a factory environment
where proper tools, equipment and trained personnel are present.
[0021] d) Electronic assemblies of varying sizes and shapes can be
accommodated. [0022] e) Expansion and contraction of the fluid is
accommodated by means of a flexible surface such as diaphragm or an
expandable surface of the enclosure, permitting a large volume of
fluid to be used. [0023] f) The dielectric fluid used as a thermal
transfer medium is sealed within the enclosure and does not
circulate outside of the enclosure. The absence of fluid couplings,
tubing, valves and pumps makes this invention more reliable,
mitigating the issues of spillage and leakage. [0024] g) The
absence of fluid couplings, tubing, valves and pumps makes this
invention more economical than fluid circulating inventions due to
the reduced number of parts. [0025] h) A wide range of cooling
devices may be used in this invention including refrigerators, heat
exchangers, evaporators, and heat sinks. [0026] i) When compared to
conventional fan cooling, this invention has a lower noise
potential.
[0027] Thus, in a first aspect the invention provides a liquid
cooled electronics circuit board that includes a circuit board
containing a plurality of heat generating components, a sealed
enclosure or container surrounding the circuit board and containing
a heat transfer, dielectric liquid such that the circuit board is
at least partially (and preferably fully) submerged in that liquid.
The enclosure also has a fill port, at least one heat conductive
plate that is in contact with the liquid and protrudes to the
exterior of the enclosure, and a thermal expansion compensating
surface. An electrical connector extends from the circuit board to
the exterior of the enclosure.
[0028] In particular embodiments the circuit board is installed in
a computer system; the heat generating components on the circuit
board together generate 20-200 watts, or 50-150, 50-100, 20-40,
40-60, 60-80, 80-100, 150-200 wafts; the circuit board includes at
least 10, 20, 30, 40, 50, or even more heat generating components;
the container contains at least 10, 20, 30, 40, 50, 75, 100, 200,
or 500 ml or is in a volume range defined by taking any two
different values from those listed as the endpoints; thermal
expansion of the liquid volume inside the enclosure is accommodated
by a flexible diaphragm (a thermal expansion compensating surface)
that is in contact with the liquid on one side and ambient
atmosphere on the other side, such as a low curvature, concave or
essentially flat wall of the container or a flexible diaphragm; the
thermal expansion compensating surface expands at least 1, 2, 3, 4,
or 5 ml upon heating of thermally conductive liquid within the
container with a heat rise of 20 degrees C.; the thermal expansion
compensating surface expands at least 1, 2, 3, 4, or 5 ml with a
pressure differential across the surface of no more than 70
g/cm.sup.2; the thermally conductive liquid expands approximately
1% of the volume of the liquid for every 10.degree. C. rise in
temperature.
[0029] In certain embodiments, the heat conductive plate is
adjacent to the connector; the connector penetrates through the
heat conductive plate: the heat conductive plate is distal from the
connector (e.g., in or on a surface of the container opposite from
the surface in which the connector is located); the liquid is a
fluorocarbon, an oil, or distilled water; the enclosure can be
opened or removed allowing access to components on the circuit
board, and sealably replaced; the fill port is configured to allow
extraction and replacement of the liquid; the fill port comprises
an orifice that can be breached by a nozzle and is self-sealing
when the nozzle is retracted; the fill port includes an elastomeric
material with a re-sealable aperture through which a liquid fill
and/or removal nozzle is inserted; the heat conductive plate is
thermally coupled with a heat transfer component such as a heat
sink, heat pipe, or heat exchanger; the heat transfer component is
held against the heat conductive plate with a clamp such as an
over-center clamp; the thermal coupling is accomplished through a
thermal interface material such as a heat conductive elastomeric
material, a phase change material, an aligned fiber material, a
thermal gel, or a thermal grease.
[0030] In particular embodiments, the walls of the container are
formed of a thermoplastic or a thermoset plastic; the walls of the
container comprise, consist essentially of, or consist of a
material selected from the group consisting of polycarbonate,
acrylic, and ABS plastic; the walls of the container comprise,
consist essentially of, or consist of a metal, e.g., steel,
aluminum (which can be an alloy), or copper (which can be an
alloy); the thermally conductive plate includes at least 80%
copper, aluminum, or heat conductive ceramic; the thermally
conductive plate averages at least 1, 2, 3, 4, or 5 mm thick; the
contact portion of the thermally conductive plate averages at least
1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mm thick.
[0031] A related aspect concerns an electronics cooling assembly
that includes a sealed or sealable container that has a fill port
allowing filling of the container with a heat transfer,
non-electrically conducting liquid after the container is sealed,
at least one thermally conductive plate that is (or will be) in
contact with the liquid inside the container and protrudes to the
exterior of the container, and a thermal expansion compensating
surface. At least one circuit board is or can be mounted within the
container such that it is (or will be) substantially submerged in
the liquid. In many cases, the assembly includes an electrical
connector that has or is designed to have interior connections with
the circuit board, and extends to the exterior of the container. As
indicated, the sealed container is substantially filled with the
heat transfer, non-electrically conducting liquid.
[0032] In particular embodiments, the container is as described for
the preceding aspect.
[0033] In certain embodiments, the assembly includes a plurality of
circuit boards, e.g., 2, 3, 4 or more circuit boards; the container
encloses a power supply, e.g., on a circuit board; the walls of the
container are formed of a thermoplastic or a thermoset plastic; the
walls of the container comprise, consist essentially of, or consist
of a material selected from the group consisting of polycarbonate,
acrylic, and ABS plastic; the walls of the container comprise,
consist essentially of, or consist of a metal, e.g., steel,
aluminum (which can be an alloy), or copper (which can be an
alloy); the fill port comprises an orifice that can be breached by
a nozzle and is self-sealing when the nozzle is retracted; the
thermally conductive plate comprises at least 80% copper, aluminum,
or heat conductive ceramic.
[0034] The circuit boards or electronics cooling assemblies are
particularly applicable to computers. Thus, another related aspect
concerns a computer system that includes at least one (commonly a
plurality, e.g., at least 2, 3, 4, 5, 10, or more) of such liquid
cooled circuit boards or cooling assembles as described in the
aspects above. In some case, the computer system includes a
circulating coolant system for removing and/or dissipating heat
from the exterior of the heat conductive plate in the
container.
[0035] Likewise, in another aspect the invention provides a method
for cooling a complex electronics assembly (e.g., a circuit board
or boards) by enclosing the complex electronic assembly in a liquid
submersion cooling assembly (e.g., using a liquid cooled circuit
board as described herein) as described above. The method can also
include thermally coupling the thermally conductive plate of the
cooling assembly with another heat transfer device, e.g., a heat
pipe, heat sink, pumped liquid cooling system, and the like.
[0036] In certain embodiments, the other heat transfer device is
mechanically attached against the thermally conducting plate, e.g.,
using one or more over-center clamps, screws, or clips; the thermal
coupling involves a thermally conductive compliant material, such
as an elastomeric material, compressed between the plate and the
other heat transfer device.
[0037] Thus, in another aspect, the invention concerns an
electronic assembly heat transfer device that includes a thermally
conductive plate that conducts heat from an electronic assembly
(e.g., as described in an aspect above), and a thermally conductive
device thermally coupled with the thermally conductive plate
through a compliant, thermally conductive material between the
plate and the thermally conductive device. The compliant material
may, for example, be an elastomeric material. The device can
include a connector located adjacent to or penetrating through the
thermally conductive plate, e.g., such that the thermal pathway
from the plate to the thermally conductive device is established
concurrently with mating of the connector with a corresponding
external connector.
[0038] In particular embodiments, the plate and/or thermally
conductive device and/or compliant material are as described herein
and/or the mechanism for attaching the plate and thermally
conductive device together are as described herein.
[0039] Similarly, in a related aspect the invention concerns a
cooling assembly for heat generating electronics that includes a
thermally conductive plate which conducts heat from the heat
generating electronics (e.g., in a cooling device or liquid cooled
circuit board as described above), a second thermally conductive
element attached to a surface of the thermally conductive plate
using a means for providing a low thermal resistance connection
between the conductive plate and second heat transfer element. For
example, the means for providing a low thermal resistance
connection may involve a high thermal conductance elastomer and an
over-center clamping mechanism. The assembly can include a first
electrical connector mounted adjacent to or penetrating the
thermally conductive plate. This first electrical connector may be
engaged with a matching external connector by the same action by
which the low thermal resistance connection between the conductive
plate and the second heat transfer element is established (e.g.,
attaching the plate also engages the electrical connectors).
[0040] In certain embodiments, the cooling assembly also includes
an electronic connector mounted on the second thermally conductive
element.
[0041] In a further related aspect, the invention concerns a method
for thermally coupling a thermally conductive plate that conducts
heat from an electronic assembly with a thermally conductive
device, by mechanically compressing a thermally conductive
compliant material between the thermally conductive plate and the
thermally conductive device. As indicated above, the mechanical
compression can utilize an elastomeric material and/or one or more
over-center clamps. In certain advantageous applications, a
connector is located adjacent to or penetrating the thermally
conductive plate. In particular cases, the connector location is
such that creation of the thermal pathway by attaching the
thermally conductive plate to the thermally conductive device
concurrently establishes electrical conduction pathway through the
connector with a second connector (which may be mounted in or on
the thermally conductive device).
[0042] The term "circuit board" is used to refer to a board used in
electronic devices that are made from an insulating material and
contain electronic components that are interconnected to form a
circuit or group of circuits that perform a specific function.
Typically the board includes a printed metal pattern which serves
as interconnections in the electrical circuit. Other circuit
components are typically soldered to the board.
[0043] As used herein, the term "dielectric" means that the
referenced material has zero or near zero electrical conductivity.
In particular the term "dielectric liquid" refers to a material
which is liquid over the intended operating range of a particular
electronic system (e.g., over the range of 20-150 degrees C.).
[0044] The term "electrical connector" or "electronics connector"
is used to refer to a substantially rigid device in which
electrical conductors (e.g., wires and/or printed circuit
conductors) are terminated and which is constructed for replaceable
connection with a mating connector such that an electrical pathway
is established across the pair of connectors. In most cases, for
use in the present invention such a connector will connect with at
least 5 conductors and commonly more, e.g., at least 10, 15, 20,
40, or more conductors. Such connectors may be in various formats,
e.g., rectangular, circular, edgeboard, and strip connectors.
[0045] In the present context, the term "fill port" refers to a
structure that includes a penetration channel from the exterior to
the interior of a container through which liquid can be introduced
and which is sealable after such liquid introduction, e.g.,
includes a valve or elastomeric seal. For example, a hollow needle
or nozzle can be used to pass through a sealable channel in an
elastomeric material, liquid is introduced through the hollow
needle, and the channel is sealed upon removal of the needle (e.g.,
automatically or by mechanical compression.
[0046] As used herein, the term "heat transfer liquid" means a
liquid that has a thermal conductivity of at least 0.05
Wm.sup.-1K.sup.-1, or in some cases at least 0.06, 0.07, 0.10,
0.15, 0.2, 0.3, or 0.4 Wm.sup.-1K.sup.-1.
[0047] The terms "heat conductive" and "thermally conductive" as
used in connection with the heat conductive plate means that the
plate material has a thermal conductivity of at least 1.0
Wm.sup.-1K.sup.-1, more typically at least 10 Wm.sup.-1K.sup.-1,
and in many cases at least 20, 30, or 40 Wm.sup.-1K.sup.-1 (e.g.,
bronze, heat conductive plastics), and often at least 100 or even
200 Wm.sup.-1K.sup.-1, for example, copper, brass, or aluminum.
[0048] The term "heat generating devices" is used in the present
context to refer to electronic devices that produce substantial
heat under normal operation, such that the device or a portion
thereof will experience a temperature rise in still air at 1 atm of
at least 10 degrees C. under normal operating conditions from an
unpowered temperature of 21 degrees C.
[0049] In connection with the present invention, the term "liquid
cooled" means that the temperature of particular heat producing
devices is reduced or controlled by contact with a liquid that
functions as part of a heat conducting pathway in which heat from
the devices is dissipated distal from the source.
[0050] In the context of the present invention, the term "sealed
container" refers to a device having a hollow interior such that a
chemically compatible liquid in that hollow interior will not leak
or otherwise escape during normal operation with the container in
any orientation.
[0051] The term "substantially submerged" as used in connection
with electronic assemblies enclosed in the present devices means
that the components in the assembly that generate at least 80% of
the heat are within the liquid in the container. In many cases, at
least 90% or even 100% of the heat generating components are within
the liquid.
[0052] As used in reference to the present liquid-filled containers
and assemblies, the phrase "thermal expansion compensating surface"
refers to a section of the container or attached structure that
accommodates thermal expansion of the enclosed liquid by flexing
and/or stretching, thereby creating increased internal volume. Such
surface may, for example, be wall of the container or portion
thereof that can expand outward, e.g., a wall or wall section
having low curvature (i.e., flat or nearly flat, advantageously
with a slight inward curvature or concavity). An alternative
involves an expansion diaphragm sealed to the container that is
exposed to liquid pressure on one face and ambient exterior
pressure on the other face. Other structures that accommodate
thermal expansion of the liquid can also be used.
[0053] Additional embodiments will be apparent from the Detailed
Description and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] The drawings provided are for purpose of illustration and
description and not limit the scope of the invention.
[0055] FIG. 1 is a perspective right-side view of a liquid filled
container with a circuit board assembly inside. The circuit board
assembly includes multiple electronic components, and the container
is filled with an electrically non-conductive fluid.
[0056] FIG. 2 is a lateral cross section showing the upper and
lower housings of the container ultrasonically welded together and
a fill port fused to one of the container walls.
[0057] FIG. 3 is a section drawing showing a hook, a snap, and a
screw, as examples of attachment features that can be used to
suspend a circuit board assembly in position within the
container.
[0058] FIG. 4 is a cross section through a container showing the
thermally conductive plate of a container and a diaphragm exposed
to ambient air on one side and to the dielectric liquid in the
interior of the container on the other.
[0059] FIG. 5 is a cross section drawing showing a board mounted
connector that is sealed with a compliant gasket.
[0060] FIG. 6 is a cross section drawing showing a circuit board
edge connector protruding beyond the container envelope and sealed
with a compliant gasket.
[0061] FIG. 7 is a cross section drawing showing a thermally
conductive plate that protrudes through the container envelope, and
is sealed with a compliant gasket.
[0062] FIG. 8 is a cross section drawing showing a thermally
conductive plate fused into the wall of the container.
[0063] FIG. 9 is a perspective view of the liquid filled container
showing a simplified thermally conductive plate with lateral
mounting flanges.
[0064] FIG. 10 is a perspective view of the liquid filled container
showing a thermally conductive plate with lateral mounting flanges
and cooling fins.
[0065] FIG. 11 is a perspective view showing a liquid filled
container with a thermally conductive plate attached to a heat pipe
having a clamping mechanism holding the plate against the surface
of the heat pipe.
[0066] FIG. 12 is a side view of a clamping mechanism which has an
over-center mechanism mated to a heat pipe.
[0067] FIG. 13 is a perspective view of the back of the heat pipe,
an attached heat exchanger, and a printed wiring board
backplane.
[0068] FIG. 14 is a cross sectional view of a container showing the
liquid-filled enclosure, a circuit board, a thermally conductive
plate, a heat pipe, and a printed wiring board.
[0069] FIG. 15 is a perspective drawing of the cooling assembly
showing the general direction of heat flow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0070] The present invention provides advantageous devices and
methods for cooling complex and often rather large, electronics
assemblies. In many cases, the electronic assemblies are or include
circuit boards. As explained herein, the devices utilize thermally
conductive, dielectric liquid-filled containers in which circuit
boards or other complex electronic devices are mounted. The heat
generated by components on the circuit board or other complex
device is conducted through the liquid and through a thermally
conductive plate that extends from the interior of the container in
contact with the liquid to the exterior of the container, thereby
providing an efficient heat conduction pathway. From the exterior
surface of the plate, the heat can be conducted or dissipated away
from the container.
[0071] Additional advantageous features of such devices relate to
compensating for thermal expansion of the large volume of liquid in
the container, the mechanisms used to thermally couple the
thermally conductive plate with further thermal conductors, and the
connectors used to electrically connect the complex electronic
device inside the container with other electronic components or
devices.
Heat Conduction Components
[0072] As pointed out above, the present devices are directed to
providing a quiet and simple but effective method for cooling
complex electronic devices. In many cases, the complex device is a
complete circuit board, or a set of mounted circuit boards, that
includes a number of heat generating components. In many cases the
circuit boards include a large number of such heat generating
components.
[0073] In the absence of an effective cooling mechanism, heat
build-up is often a problem, contributing to shortened operating
lifetimes and reduced performance. Forced air cooling (e.g., fans)
has frequently been used, but has limitations due to the relatively
low heat capacity and thermal conductivity of air. The result is
that boards generating large amounts of heat are not effectively
cooled, thereby adversely affecting component lifetimes and
limiting performance. To address such limitations, and as discussed
in the Background, a number of techniques have been used for
cooling using liquids, but generally those techniques have
limitations of complexity, leak potential, and/or uneven cooling,
or are directed to cooling of individual devices (e.g.,
[0074] The present invention addresses all of those limitations or
concerns. In particular, effective and even cooling is provided by
using a thermally conductive, but electrically non-conductive
liquid in direct contact with the circuit board or other complex
electronic device. This liquid provides an efficient pathway
conducting heat away from the vulnerable electronics. The direct
contact between the thermally conductive liquid and the circuit
board or other complex device is achieved by using a container that
encloses the circuit board and is filled with the liquid.
[0075] Any of a number of heat conducting dielectric liquids can be
used, such as halogenated hydrocarbon compounds, especially
fluorinated compounds (e.g., GALDEN.RTM. PFPE from Solvay Solexis
S.A. and FLUORINER.TM. liquids from 3M Corporation). Other
compounds can also be used, such as oils, and distilled water. In
most cases, the oils or halogenated compounds will be
preferred.
[0076] To maintain the temperature gradient so that heat is
efficiently conducted away from the circuit board, the container
includes a thermally conductive plate that is in contact with the
liquid on the interior of the container and extends to the exterior
of the container. Such thermally conductive plate can be configured
in many different ways, so long as it provides an efficient heat
flow pathway from the interior of the container to the exterior.
While the term "plate" is used to refer to this component, it will
not necessarily have parallel planar surfaces. Thus, in many cases,
the plate will have a planar exterior surface, but can also have
other shapes. In come cases, the interior surface of the plate will
be planar, e.g., to allow maximum clearance for the electronic
components, but can have other shapes, e.g., to increase surface
area allowing greater heat conduction into the plate and thus to
the exterior. For example, the interior surface of the plate can be
ribbed or can include other shape projections.
[0077] Likewise, in many cases the plate is a thermally conductive
element mounted in a container wall such that a unitary material
extends from the interior to the exterior across one wall of the
container. However, other constructions can be used. In some cases,
the plate will include a thermally conducting portion of the wall
in thermal contact (e.g., bonded to such as using solder or heat
conductive glue) with an externally attached thermally conducting
material that provides a conduction path away from the container
wall and may also provide stiffness and/or mounting for further
heat conduction components. In such cases, the "plate" includes
both the first heat conductive element and the portion of container
wall to which it is attached.
[0078] The plate can also extend into more than one wall of the
container. For example, a plate may be formed in a U-shape such
that it covers at least part of three contiguous walls, an L-shape
that covers at least part of two contiguous walls, cup-shaped such
that it covers at least part of five contiguous walls, and the
like.
[0079] The plate may be present in any desired surface of the
container. However, in certain advantageous configurations, the
container has an electrical connector that penetrates one surface
(can also be referred to as a face or wall) of the container (or
has electrical conductors that penetrate one surface and terminate
in the connector) and the plate is located such that the contact
surface of the plate (i.e., the plate surface that contacts the
further heat conducting device) is on the same face of the
container. In these configurations, the assembly can be designed
such that electrical connection and the thermal pathway are created
at essentially the same time, that is, as the electrical connector
is mated with its corresponding connector, the exterior contact
surface of the plate is brought into contact with the further heat
conducting device. Such contact and/or the electrical connection
can be positively created and/or stabilized by fastening the
assembly into place with mechanical fasteners such as screws,
clamps, clips, slide latches, and the like.
[0080] The exterior surface of the conductive plate of the
container assembly is usually attached to (or formed with) another
heat transfer device (secondary heat transfer device) such as a
heat pipe, heat sink, or other such devices. The secondary heat
transfer device can be attached using a mechanical fastener(s),
e.g., a clamping mechanism, a screw device, or a slide latch. The
thermal pathway across the interface between the exterior plate
surface and the secondary heat transfer device can be facilitated
by using a conforming material between the two surfaces (or on at
least one of the surfaces). Use of such conforming material allows
a more uniform connection to be made across the areas of the
surfaces, thus allowing more uniform and/or efficient heat
transfer. Such conforming materials can be soft metals, but can
also advantageously be heat conductive elastomeric materials and
other such termally conductive materials. Such elastomeric
materials are beneficial because their inherent resiliency assists
in creating and maintaining thermal contact, e.g., throughout
multiple cycles of heating and cooling, as well as with mechanical
disturbances such as accidental bumping.
[0081] The secondary heat transfer device provides a thermal
pathway to a heat dissipation medium, e.g., to a heat exchanger.
The heat exchanger or other thermal dissipation medium cools the
thermal pathway, the attached thermally conductive plate, the
liquid inside the container, and the heat generating electronics
within.
[0082] In this high performance cooling system, the enclosed heat
generating devices will be cooled by conduction and/or convection
of heat through the various materials and sections of the heat
transfer path. When the heat generating devices have reached their
steady operating state, and the heat exchanger has reached its
steady operating state, the transfer of heat will be almost
constant and can be expressed mathematically. Heat transfer through
the heat flow path is limited by the sum of the boundary contact
resistance between sections of the path, plus the thermal
resistance of each section. The sum of thermal resistance (R) of
the system can be approximated by using the formula:
R=K1+K2+K3+K4+K5+K6+K7 Where each K= [0083] the resistance across
boundary conditions between respective sections (K1,K3,K5,K7), and
[0084] the thermal resistance across each material section
(K2,K4,K6). With the sum of the thermal resistances (R) derived,
the total heat loss (or heat transfer) of the system can be
approximated as: Q=-(T.sub.1-T.sub.2)/R [0085] Where [0086]
Q=approximate heat dissipated, (W/h) [0087] T.sub.1=Temperature at
the heat source, (.degree. C.) [0088] T.sub.2=Temperature at the
heat exchanger, (.degree. C.) [0089] R=sum of the thermal
resistance, (m.sup.2K/W)
[0090] The present invention contrasts with certain techniques in
which cooling devices are constructed around simple electronic
components such as transistors and the like. In such constructs,
the liquid volumes are so small that thermal expansion is minimal.
Further, the amount of heat generated by the enclosed transistors
and the like are relatively small, so that simple air flow over a
thermally conductive surface of the enclosure is generally
sufficient. Still further, the constructs are configured with leads
or conductors from the devices passing directly to the exterior of
the enclosure.
Operation and Exemplary Devices
[0091] In typical configurations of the present devices, the
complex electronic assemblies to be cooled (e.g., circuit boards),
the heat transfer plate(s) and thermal expansion diaphragm (when
present) are attached to the inside of the container parts. The
container parts are joined, sealed and filled with dielectric
liquid (e.g., through a fill port).
[0092] One or more such liquid filled containers are fastened to a
heat transfer element such as a heat pipe, using a suitable
fastening mechanism. In certain embodiments, as the container is
fastened to the heat pipe, the internal electrical connector is
simultaneously mated to an external electrical connector. The
external electrical connector may be a wired connector or a circuit
board mounted connector.
[0093] The electrical system including circuit boards, heat
exchanger (when present), and power supply, are connected to an
external power source that will supply necessary operating power.
When power is turned on to the system, heat generating components
begin to generate heat. If a heat exchanger is part of the system,
it begins cooling the heat transfer system. The heat exchanger is
connected to the thermally conductive plate, creating an efficient
heat flow path from inside the liquid filled container through the
thermally conductive plate to an external heat transfer element(s),
which can be further coupled to a heat exchanger or other heat
dissipation device. The effect is that heat is conducted from the
heat generating components to be dissipated in the surroundings,
resulting in cooling of the electronic components suspended within
the liquid.
[0094] In some cases, for the purpose of providing the end-user
with a finished product, the fluid filled container, electrical
backplane, electrical wiring, heat pipe, heat exchanger power
supply, and associated electronics, may be enclosed within a
cabinet or other outer housing or structure. The present invention
includes such products, e.g., computers or computer systems, which
include the present cooling devices.
[0095] As pointed out in the Summary above, the present invention
provides a number of advantages over conventional electronics
systems cooling devices. These include: [0096] a) Liquid is
contained within a sealed enclosure and is not pumped out of the
container and back again. This eliminates hoses, fittings, seals
and pumps, thus reducing cost and complexity. The invention is
therefore a more reliable system. [0097] b) The sealed enclosure
acts as a deterrent to unauthorized persons attempting to tamper
with the electronics contained within, while still being easy to
remove and replace. Usually defective modules will be serviced in a
factory environment. [0098] c) Due to the reduced number of parts,
the system is also more economical to build than circulated coolant
systems. [0099] d) Electronic assemblies of varying sizes, shapes,
and heat generating levels can be placed inside the enclosure.
[0100] e) Expansion and contraction of the fluid is accommodated by
means of a flexible diaphragm or surface, permitting a large volume
of fluid to be used [0101] f) When compared to conventional fan
cooling, this invention has a lower noise potential. As a result,
systems incorporating the present devices are more acceptable in
general office and home environments.
[0102] The present invention is further illustrated by the
drawings, which are not intended to limit the scope of the
invention.
[0103] As shown in perspective view in FIG. 1, a circuit board
assembly 2 is positioned inside a container 1. Discrete electronic
components 3 are hard wired (soldered) to the circuit board. The
container is sealed and filled with a dielectric liquid in internal
volume 4. Thermal expansion of the liquid is compensated by
flexible diaphragm 10, i.e., a thermal expansion compensating
surface. The assembly includes a heat transfer plate 15 covering
one end and extended partially up two opposing walls of the
container.
[0104] It is preferred that factory servicing of the container is
necessary instead of allowing user access. Tampering with the
electronics inside the container and accidental spillage of
dielectric fluid by an unauthorized person is thereby deterred. In
preferred embodiments, the container is sealed ultrasonically along
a seam 5 as illustrated in FIG. 2, without common fasteners that
would allow an unauthorized person to open the container. The
container is designed such that it can easily be opened at the
factory by personnel using custom built fixtures to drain and open
the container.
[0105] A number of electrically inert liquids will work in this
invention including fluorocarbons, oil, and distilled water.
Individual formulations of these insulating liquids have different
physical properties. If the heat transfer liquid has a high
dielectric constant, then device connector sockets may be used
reliably. If the heat transfer liquid has a relatively low
dielectric constant then solder connections are recommended.
[0106] The size of the container will generally depend upon the
size of the electronic assembly to be contained. The recommended
operating temperature of the electronic devices in the assembly
determines the amount of heat the system will be designed to
dissipate. The specific dimensions and configuration of the high
performance cooling assembly described herein are, therefore,
determined by the specific electronic components to be cooled.
[0107] FIG. 2 shows a self-sealing fill port 6 fused into one wall
of a container housing. After the housing is sealed, a fill nozzle
is inserted into the fill port and dielectric liquid is pumped into
the container. When the nozzle is withdrawn the fill port closes.
As pointed out above, the housing is constructed using overlapping
seam sections 5 which are ultrasonically welded along the
overlapping seam. During such a filling operation, air or other gas
displaced from the container can be vented, e.g., through a
separate passage in the nozzle.
[0108] The incorporation of exemplary holders for holding the
circuit board inside a container is shown in FIG. 3. The supporting
features extend from opposing wall of the container (the top and
bottom in FIG. 3). Illustrated examples of supporting features that
can reliably hold a circuit board assembly in position with a
container include hooks 7, snaps 8, and screws 9.
[0109] The container is made of a relatively rigid material
suitable to contain the liquid (although the container material can
deform to some extent). The container material may be thermally
and/or electrically conductive or non-conductive. On average,
typical dielectric liquids increase in volume approximately 1% for
every 10.degree. C. rise in temperature due to thermal expansion of
the liquid. To accommodate increases in volume, the container is
fitted with a thermal expansion compensating surface. As shown in
cross-section in FIG. 4, such compensating surface can be provided
by a diaphragm 10. In this configuration, the diaphragm is made of
a compliant material and is in contact with the heat transfer
liquid on the interior side 4 and surrounding atmosphere on the
exterior 11. As the fluid expands the diaphragm stretches to
accommodate the increased volume, and upon cooling the liquid
volume decreases and the diaphragm returns to its original
position. Also illustrated is an exemplary positioning of a U-shape
thermally conductive member 15 encasing or forming one end of the
container, with the plate fused or bonded with container wall 1. In
such configurations, the plate may be edge-bonded, e.g., welded,
with the container wall, such that the plate forms both the wall
and the thermally conductive plate in that area, or the member may
be bonded to a face or the container wall such that the wall in
that area together with the U-shaped member form a thermally
conductive plate which conducts heat from the liquid inside the
container to the exterior.
[0110] In order to connect the circuit board or boards within a
container assembly with external electronic components and devices,
a connector extending from the interior to the exterior of the
container is used. One exemplary configuration is shown in FIG. 5,
where a connector 12 is provided so that electric current can flow
between the internal electronic assembly 2 and electronic devices
that are external to the container. The connector is sealed against
the container, preventing liquid from leaking out of the container
using gasket 13 made of compressible material which creates a seal
between the connector and the container wall 1.
[0111] An alternative is shown in FIG. 6, where the edge of circuit
board 2 (i.e., an edge connector) is shown protruding through the
container wall 1. A gasket 14 made of compressible material is used
to form a seal between the connector and the container wall 1.
[0112] An alternative configuration of thermally conductive plate
as compared to that shown in FIGS. 1 and 4 is illustrated in FIG.
7, where thermally conductive plate 15 protrudes into the liquid
filled space inside the container 2 proximal to circuit board 1 and
extends to the exterior of the container. The conductive plate 15
can, for example, be sealed with a compressible material 16 or
fused or otherwise bonded directly to the container such that no
liquid will leak out.
[0113] Such a alternative configuration is illustrated in FIG. 8,
where thermally conductive plate 17 (having a generally T-shaped
cross-section) penetrates through the wall of container I such that
the "head" of the T is on the exterior of the container, and the
"leg" of the T is in contact with the liquid in the interior of the
container and in proximity to the circuit board 2. The plate is
fused or otherwise bonded with the container wall to prevent
leaks.
[0114] The thermally conductive plate can be configured according
to the application. FIG. 9 shows a simple U-shaped plate 15 which
wraps around the connector end of the container 2 and that has
flanges 18 at each side that are designed to allow the plate to be
clamped to another heat transfer element such as a heat pipe. The
edge connector portion of circuit board 2 extends through the
container wall and through the plate. In most cases, clamping of
the plate to another heat transfer element also positively engages
the edge connector into a matching external connector.
[0115] Where low to moderate heat loads are to be dissipated, a
heat sink may be sufficient for heat dissipation (with or without
forced air flow) depending on heat load and installation
environment. For example, as shown in FIG. 10, a thermally
conductive plate 15 that extends into the heat transfer liquid and
also extends beyond the exterior of the container walls 1 may be
fashioned in the shape of a heat sink, with additional fins 19
added to its configuration to make a heat sink. This configuration
allows the thermally conductive plate to be cooled by free or
forced convection. The fins may be formed as part of the plate, or
may be formed separately and attached to the plate (e.g., glued,
soldered, clamped, screwed, and the like).
[0116] Where higher heat loads are to be dissipated, the thermally
conductive plate can, for example, be attached to another heat
transfer element such as a heat pipe or a heat sink, typically by
means of a mechanical fastening system. In the exemplary
configuration shown in the top perspective view of FIG. 11, the
container 1 with thermally conductive plate 15 is fastened to a
heat pipe 20 utilizing a clamping mechanism 21. The heat pipe
conducts heat to heat exchanger 24 for dissipation.
[0117] An over-center type of clamping mechanism as shown in FIG.
12 can be used as the clamping mechanism (as shown in FIG. 11) and
provides ease of operation. The clamping mechanism has a lever 22
that moves an opposable jaw 23. As used in the manner shown in FIG.
11, the clamp forces the thermally conductive plate firmly against
the other heat transfer element 20 (for example a heat pipe),
providing efficient heat transfer between the plate 15 and the heat
pipe 20. Parts comprising the clamping mechanism can advantageously
be made of thermally conductive material and mounted on the heat
pipe 20 providing additional heat flow through the clamping
mechanism 21 into the heat pipe.
[0118] FIG. 13 shows a bottom perspective view of an assembly as in
FIG. 11, and shows the opposite side of the heat pipe 20. As
indicated for FIG. 11, located on the heat pipe is a heat exchanger
24 that acts to cool the heat pipe 20.
[0119] An assembly as shown in FIG. 13 is shown in cross-section in
FIG. 14, where the heat pipe 20 acts as a thermal transfer pathway
for heat between the liquid-filled container 1 via thermally
conductive plate 15, and the heat exchanger apparatus 24. Several
types of heat exchanger apparatus may be employed to cool the heat
pipe, including, for example, heat sinks, refrigerant coils and
evaporative liquid systems. The heat exchanger choice is usually
based upon the level of cooling required and the space available
per a given electronics assembly. Circuit board assembly 2
contained inside each fluid filled container 1 connects
electrically to other, external electrical devices through one or
more electrical connectors (e.g., circuit board edge connectors)
that protrude through the container. More than one electrical
connector may be required depending on the requirements of the
circuits being enclosed. The connector may be mated directly into a
circuit board back plane 25 as shown in FIG. 14 or may be mated to
a wire terminated, cable connector. In the illustrated
configuration, heat flows from the components on the internal
circuit board, into the surrounding liquid in the interior 4, into
the thermally conductive plate 15, and into the heat pipe 20 for
dissipation externally. Heat flow at the interface between
thermally conductive plate and the heat pipe can be enhanced by
providing a compliant (e.g., soft), thermally conductive layer of
material 26 which increases the contact area between the plate
surface and the heat pipe surface (or other thermal conductor
surface). Such a material can be a compliant material, e.g., a soft
gasket, elastomer, or grease with low thermal resistance (i.e.,
thermal grease). Use of such materials can substantially reduce
thermal resistivity at the interface.
[0120] When power is turned on, the enclosed electronic devices
generate heat and after a short period of time the heat is
transferred to adjacent materials through conduction (and internal
fluid convection). The electronic devices and adjacent materials
reach thermal equilibrium and the maximum amount of heat transfer
is achieved. Heat will travel through each section of the thermally
conductive system as shown generally by the arrows in FIG. 15
[0121] All patents and other references cited in the specification
are indicative of the level of skill of those skilled in the art to
which the invention pertains, and are incorporated by reference in
their entireties, including any tables and figures, to the same
extent as if each reference had been incorporated by reference in
its entirety individually.
[0122] One skilled in the art would readily appreciate that the
present invention is well adapted to obtain the ends and advantages
mentioned, as well as those inherent therein. The methods,
variances, and compositions described herein as presently
representative of preferred embodiments are exemplary and are not
intended as limitations on the scope of the invention. Changes
therein and other uses will occur to those skilled in the art,
which are encompassed within the spirit of the invention, are
defined by the scope of the claims.
[0123] It will be readily apparent to one skilled in the art that
varying substitutions and modifications may be made to the
invention disclosed herein without departing from the scope and
spirit of the invention. For example, variations can be made to the
shape of the fluid filled container can have other shapes than
those illustrated (such as spherical, pyramidal, asymmetric, etc.);
the method of leak proofing the enclosure may use gaskets, sealing
compounds, etc.; the conductive plate may attached to the heat pipe
with screw fasteners, slide latches, and other clamping mechanisms;
etc. Thus, such additional embodiments are within the scope of the
present invention and the following claims.
[0124] The invention illustratively described herein suitably may
be practiced in the absence of any element or elements, limitation
or limitations which is not specifically disclosed herein. Thus,
for example, in each instance herein any of the terms "comprising",
"consisting essentially of" and "consisting of" may be replaced
with either of the other two terms. The terms and expressions which
have been employed are used as terms of description and not of
limitation, and there is no intention that in the use of such terms
and expressions of excluding any equivalents of the features shown
and described or portions thereof, but it is recognized that
various modifications are possible within the scope of the
invention claimed. Thus, it should be understood that although the
present invention has been specifically disclosed by preferred
embodiments and optional features, modification and variation of
the concepts herein disclosed may be resorted to by those skilled
in the art, and that such modifications and variations are
considered to be within the scope of this invention as defined by
the appended claims.
[0125] In addition, where features or aspects of the invention are
described in terms of Markush groups or other grouping of
alternatives, those skilled in the art will recognize that the
invention is also thereby described in terms of any individual
member or subgroup of members of the Markush group or other
group.
[0126] Also, unless indicated to the contrary, where various
numerical values or value range endpoints are provided for
embodiments, additional embodiments are described by taking any 2
different values as the endpoints of a range or by taking two
different range endpoints from specified ranges as the endpoints of
an additional range. Such ranges are also within the scope of the
described invention.
[0127] Thus, additional embodiments are within the scope of the
invention and within the following claims.
* * * * *