U.S. patent application number 11/410772 was filed with the patent office on 2007-10-18 for support structure for a planar cooling device.
This patent application is currently assigned to CELSIA TECHNOLOGIES KOREA, INC.. Invention is credited to Jae Joon Choi, Sung Sik Kwack, George A. IV Meyer, Ki-Bu Nam.
Application Number | 20070240860 11/410772 |
Document ID | / |
Family ID | 38603735 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070240860 |
Kind Code |
A1 |
Meyer; George A. IV ; et
al. |
October 18, 2007 |
Support structure for a planar cooling device
Abstract
A support structure for a compact planar cooling device is
presented. The support structure allows the cooling device to be
made with a simpler structure than most conventional cooling
devices. The cooling device includes a planar casing, a wick layer,
and the support structure. The support structure includes a flat
plate with a portion cut out to form an opening and a spacer on the
flat plate. The spacer is made by bending or folding the cut-out
portion of the plate. The spacer enhances coolant circulation
inside the cooling device by pushing the wick layer against the
inner surface of the casing and maintaining a set distance between
the support structure and the casing to allow unimpeded coolant
movement. The cooling device can be made cost-effectively without
compromising heat transfer efficiency.
Inventors: |
Meyer; George A. IV; (San
Jose, CA) ; Nam; Ki-Bu; (Seoul, KR) ; Kwack;
Sung Sik; (Seoul, KR) ; Choi; Jae Joon;
(Sungnam-City, KR) |
Correspondence
Address: |
DLA PIPER US LLP
2000 UNIVERSITY AVENUE
E. PALO ALTO
CA
94303-2248
US
|
Assignee: |
CELSIA TECHNOLOGIES KOREA,
INC.
|
Family ID: |
38603735 |
Appl. No.: |
11/410772 |
Filed: |
April 24, 2006 |
Current U.S.
Class: |
165/104.26 ;
257/E23.088; 29/890.032 |
Current CPC
Class: |
Y10T 29/49353 20150115;
F28D 15/0233 20130101; G06F 1/20 20130101; H01L 2924/0002 20130101;
H01L 23/427 20130101; F28D 15/046 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/104.26 ;
029/890.032 |
International
Class: |
F28D 15/04 20060101
F28D015/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2006 |
KR |
10-2006-0034917 |
Claims
1. A support structure for a cooling device, the support structure
comprising: a flat plate with a portion cut out to form an opening;
and a spacer on the flat plate, wherein the spacer is made by
bending the cut-out portion of the flat plate.
2. The support structure of claim 1, wherein the cut-out portion is
bent while partially attached to the flat plate so that the spacer
is attached to the flat plate.
3. The support structure of claim 1, wherein two cut-out portions
are formed in forming the opening, and wherein the two-cutout
portions are made into two spacers.
4. The support structure of claim 3, wherein the flat plate is cut
out in the shape of an H so that the opening is a rectangular
opening and the two spacers are formed along parallel sides of the
rectangular opening.
5. The support structure of claim 3, wherein the two cut-out
portions are bent in different directions so that the two spacers
are formed on different surfaces of the flat plate.
6. The support structure of claim 3, wherein the two cut-out
portions are bent in the same direction so that the two spacers are
formed on the same surface of the flat plate.
7. The support structure of claim 1, wherein bending the cut-out
portion of the flat plate comprises folding the cut-out portion
onto a surface of the flat plate.
8. The support structure of claim 1, wherein bending the cut-out
portion of the flat plate comprises bending the cut-out portion so
that it forms a substantially 90.degree.-angle with respect to the
flat plate.
9. The support structure of claim 1 further comprising a plurality
of cut-out portions that form a plurality of openings and a
plurality of spacers.
10. The support structure of claim 1, wherein the flat plate is
made of one of aluminum, titanium, plastic, metallized plastic,
graphite, and copper.
11. A cooling device comprising: a planar casing; a wick layer
positioned inside the casing; and a support structure positioned
inside the casing, wherein the support structure has: a flat plate
with a portion cut out to form an opening; and a spacer on the flat
plate, wherein the spacer is made by bending the cut-out portion of
the flat plate.
12. The device of claim 11, wherein the planar casing comprises a
first plate and a second plate attached together to form a space
between them.
13. The device of claim 11, wherein the planar casing comprises a
flattened tube.
14. The device of claim 11, wherein the planar casing has fins.
15. The device of claim 4, wherein the fins have a hollow space so
that fluid in the planar casing travels in the hollow space.
16. The device of claim 11, wherein the wick layer is positioned
between an inner surface of the planar casing and the support
structure.
17. The device of claim 11, wherein the wick layer is attached to
an inner surface of the planar casing.
18. The device of claim 11, wherein the wick layer is a first wick
layer, further comprising a second wick layer positioned on the
other side of the support structure from the first wick layer.
19. The device of claim 11, wherein the wick layer is a copper felt
layer.
20. The device of claim 11, wherein the wick layer is a hydrophilic
wick capable of absorbing fluid by capillary force.
21. The device of claim 111, wherein the cut-out portion of the
support structure is bent while partially attached to the flat
plate so that the spacer is attached to the flat plate.
22. The device of claim 11, wherein there are two cut-out portions
formed in forming the opening and the two cut-out portions are made
into two spacers.
23. The device of claim 22, wherein the opening is a rectangular
opening and the two spacers are formed along parallel sides of the
rectangular opening.
24. The device of claim 22, wherein the two cut-out portions are
bent in different directions so that the two spacers are formed on
different surfaces of the flat plate.
25. The device of claim 22, wherein the two cut-out portions are
bent in the same direction so that the two spacers are formed on
the same surface of the flat plate.
26. The device of claim 11, wherein bending the cut-out portion of
the flat plate comprises folding the cut-out portion onto a surface
of the flat plate.
27. The device of claim 11, wherein bending the cut-out portion of
the flat plate comprises bending the cut-out portion so that it
forms a substantially 90.degree.-angle with respect to the flat
plate.
28. The device of claim 11, wherein the support structure has a
plurality of cut-out portions that form a plurality of openings and
a plurality of spacers.
29. A method of making a cooling device, the method comprising
forming a support structure by: providing a flat plate; cutting a
portion of the flat plate to create an opening; and forming a
spacer on the flat plate by bending the cut portion of the flat
plate.
30. The method of claim 29 further comprising placing the support
structure in a planar casing.
31. The method of claim 30 further comprising attaching the support
structure to the planar casing by welding or soldering.
32. The method of claim 30 further comprising placing a wick layer
inside the planar casing.
33. The method of claim 32, wherein the wick layer is a first wick
layer, further comprising placing a second wick layer inside the
planar casing such that the first and the second wick layers are on
different sides of the support structure.
34. The method of claim 30 further comprising forming the planar
casing by attaching a first plate and a second plate with a
seal.
35. The method of claim 30 further comprising forming the planar
casing by flattening a cylindrical tube.
36. The method of claim 30 further comprising forming fins on the
planar casing.
37. The method of claim 30 further comprising forming hollow spaces
inside the fins so that fluid in the planar casing can travel
inside the fins.
38. The method of claim 29, wherein the forming of the spacer on
the flat plate comprises bending the cut portion of the flat plate
while a part of the cut portion is attached to the flat plate.
39. The method of claim 29, wherein forming of the spacer on the
flat plate comprises forming a plurality of spacers for the
opening.
40. The method of claim 39, wherein the plurality of spacers are
formed on different sides of the support structure.
41. The method of claim 39, wherein the plurality of spacers are
formed on the same side of the support structure.
42. The method of claim 29, wherein bending the cut portion
comprises folding the cut portion against the flat plate.
43. The method of claim 29, wherein bending the cut portion
comprise forming a substantially 90.degree.-angle between the cut
portion and the flat plate.
44. The method of claim 29 wherein the cutting of the portion of
the flat plate comprises cutting an "H" pattern on the flat plate
to form two flaps that are capable of being bent to form the
opening.
45. The method of claim 29 wherein the cutting of the portion of
the flat plate comprises cutting a "C" or a "U" pattern on the flat
plate to produce a flap capable of being bent to form the opening.
Description
CROSS REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority from Korean Patent
Application No. 10-2006-0034917 filed on Apr. 18, 2006, the content
of which is incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to heat transfer devices and
more specifically to cooling devices capable of being placed in
small spaces.
[0004] 2. Background Information
[0005] Today, memory chips, central processing units, and embedded
chips are used in numerous types of electronic devices. To ensure
reliable operation of these devices, the devices have to be
prevented from overheating. Keeping various electronic devices cool
enough for optimal performance has become more challenging as the
circuit density increases and many of these devices are made
smaller and lighter. Furthermore, many consumer electronic devices
today include additional heat sources such as optical display
components. For example, laptops, personal digital assistants
(PDA), and mobile phones may include liquid crystal display (LCD)
panels using lamps or light emitting diodes (LEDs) as light
sources. With electronic devices getting more compact yet including
more heat sources, the traditional methods of dealing with heat
dissipation, such as open packaging or cooling fans, do not provide
an adequate solution to heat generation in these devices.
[0006] Recently, cooling devices that use evaporation and
condensation, generally called "heat pipes," have become popular
for dissipating heat in electronic devices. An advantage of heat
pipes over cooling fans is that they can be made smaller, in line
with the general size trend of consumer electronics.
[0007] FIGS. 1A and 1B are exploded perspective view and a
cross-sectional view, respectively, of a conventional planar heat
pipe 1. As shown, the heat pipe 1 has an open box 5 and a lid 2
that are designed to be combined. The open box 5 includes a base 6
and sidewalls 7. The lid 2 is a plate having a thick portion 3 near
its center. As shown, the thick portion 3 is located such that it
is placed inside the cooling device 1 when the open box 5 is
combined with the lid 2.
[0008] A plurality of support structures 8, 10 are formed inside
the heat pipe 1. The support structure 8 is of such height that it
extends between the base 6 and the part of the lid 2 that is not
the thick portion 3. The support structure 10 extends between the
base 6 and the thick portion 3. The outer layers of the support
structures 8, 10 are made with capillary wicks, thus enhancing the
circulation of fluid (e.g., coolant) through capillary force.
[0009] If a heat source (e.g., CPU) is attached to the lid 2 of the
heat pipe 1, the fluid that was absorbed in the capillary wick
layer of the support structures 8, 10 evaporate by absorbing the
heat. The gas-phase fluid moves toward the base 6 and condenses as
heat is dissipated through the sidewalls 5. The condensed fluid is
absorbed back by the capillary wick layer of the support structures
8, 10, and the evaporation-condensation cycle repeats.
[0010] The heat pipe I shown in FIGS. 1A and 1B has numerous
disadvantages. First, the design of the support structures 8, 10
cause the cooling device 1 to be thicker than what is acceptable
for many applications. The overall thickness cannot be decreased
without compromising the cooling efficiency. Second, the heights of
the support structures 8, 10, which span the distance between the
base 6 and the lid 2, have to be exact for the cooling device to
function properly. A small manufacturing error that changes the
height of one of the support structures 8, 10 could prevent the
cooling device 10 from being properly assembled, possibly adversely
affecting its performance.
[0011] FIG. 2 is an exploded perspective view of another
conventional heat pipe 10. The heat pipe of FIG. 2 includes an
upper member 20 and a lower member 30 that can be combined to form
a coolant space. Similarly to the heat pipe 1 of FIGS. 1A and 1B,
the lower member 30 has a base 40 and sidewalls 50. However, unlike
the cooling device 1, the cooling device 10 has a capillary sheet
60 that fits in the space defined by the sidewalls 50. The support
structure 70 are also different from the support structures 8, 10
of the heat pipe 1 because it is designed to fit with holes 80 on
the capillary sheet 60.
[0012] The heat pipe 10 is not without shortcomings. For example,
each support structure 70 is manufactured separately and placed in
the holes 80 before it is placed in the heat pipe 10. These steps
complicate the fabrication process. Furthermore, because the
capillary sheet 60 and the support structures 70 contain ceramic or
metal, the cost of fabrication becomes higher. Therefore, the heat
pipe 10 does not lend itself to cost-effective fabrication of thin,
light-weight apparatuses.
[0013] A need exists for a small, planar heat pipe having a
relatively simple structure that can be made cost-effectively.
SUMMARY OF THE INVENTION
[0014] In one aspect, the invention is a support structure for a
cooling device. The support structure includes a flat plate with a
portion cut out to form an opening and a spacer on the flat plate.
The spacer is made by bending the cut-out portion of the flat
plate. The support structure may be useful for a planar, thin
cooling device.
[0015] In another aspect, the invention is a cooling device
including a planar casing. A wick layer and the above support
structure are positioned inside the casing.
[0016] In yet another aspect, the invention is a method of making a
cooling device. The method entails forming a support structure by
providing a flat plate, cutting a portion of the flat plate to
create an opening, and forming a spacer on the flat plate. The
spacer is formed by bending the cut portion of the flat plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A and 1B show a conventional planar heat pipe.
[0018] FIG. 2 shows another conventional planar heat pipe.
[0019] FIG. 3 is an exploded perspective view of the cooling device
in accordance with a first embodiment of the invention.
[0020] FIG. 4 is a cross-sectional view of the cooling device of
FIG. 3.
[0021] FIG. 5 is a close-up view of a portion of the support
structure in the cooling device of FIG. 3.
[0022] FIG. 6 is a close-up view of a portion of an embodiment of
the support structure usable with the cooling device of the
invention.
[0023] FIG. 7 is a close-up view of a portion of another embodiment
of the support structure usable with the cooling device of the
invention.
[0024] FIG. 8 is an exploded perspective view of a second
embodiment of the cooling device in accordance with the
invention.
[0025] FIG. 9 is a third embodiment of the cooling device in
accordance with the invention.
[0026] FIG. 10 is an open perspective view of a fourth embodiment
of the cooling device in accordance with the invention.
[0027] FIG. 11 is an exploded perspective view of the cooling
device attached to a heat source.
[0028] FIG. 12 is a cross-sectional view of the cooling device of
FIG. 11 illustrating its operation.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The present invention provides a planar cooling device that
is structurally simpler than the above-described conventional heat
pipes. In the planar cooling device of the invention, a bent
portion is incorporated into the support structure to maintain the
coolant travel path at a desired size. The design allows for
increased coolant travel space, allowing efficient coolant
circulation and improved cooling. The cooling device of the
invention may be made as thin as 0.5-5 mm.
[0030] An additional benefit of the structure of the invention is
that the support structure imparts rigidity to the device, making
the cooling device more reliable.
[0031] Due to its simplified structure, the invention can be
produced more cost-effectively than the conventional heat pipes
without compromising the cooling power.
[0032] As used herein, "planar" structure is a structure having a
flat portion.
[0033] FIG. 3 is an exploded perspective view of the cooling device
in accordance with a first embodiment of the invention, FIG. 4 is a
cross-sectional view of the cooling device of FIG. 3, and FIG. 5 is
a close-up view of a portion of the support structure in the
cooling device of FIG. 3.
[0034] As shown in FIG. 3, the cooling device of the invention
includes a casing made of a first plate 200 and a second plate 210.
The first plate 200 and the second plate 210 may be combined to
form an enclosed space between the two plates 200, 210. The two
plates 200, 210 may be sealed together to form the enclosed space
so that a coolant fluid (e.g., water, methanol, ethanol) is
contained in the enclosed space. The seal may be formed around the
edges so as to not intrude upon the enclosed space. Either or both
of the first and second plates 200, 210 is designed so that it can
be attached to a printed circuit board (PCB) or a chip. For
example, the first plate 200 may have a flat surface that can
easily be attached to a PCB or a chip, and an adhesive layer may be
placed on the flat surface.
[0035] The first plate 200 and the second plate 210 are made of a
material that has sufficient rigidity to protect the structures in
the space between the two plates. The material may be, for example,
aluminum, titanium, plastic, metallized plastic, graphite, copper,
or any plastic combination capable of transferring heat
effectively. Preferably, the first plate 200 and the second plate
210 are prepared from one large sheet of material. The first plate
200 and the second plate 210 may be laminated to facilitate their
attachment to a heat source.
[0036] Between the first plate 200 and the second plate 210 is a
capillary wick 220. The capillary wick 220, which is attached to
the first plate 200, is capable of absorbing the coolant fluid by
capillary action. The capillary wick 220 is preferably made of a
hydrophilic wick. A hydrophilic wick, which is well-known, contains
a plurality of micro-fibers and each micro-fiber is capable of
absorbing and retaining the coolant fluid. In some embodiments, the
capillary wick 220 may be attached to the second plate 210.
[0037] A support structure 230 is also located between the first
plate 200 and the second plate 210. In the particular embodiment of
FIG. 3, the support structure 230 is located between the wick layer
220 and the second plate 210. The support structure 230 supports
the capillary wick 220 and forms the coolant fluid travel path by
maintaining a certain distance between itself and the second plate
210. The support structure 230 has openings 231 through which the
gaseous coolant can travel from one side of the support structure
230 to the other side (e.g., from the side closer to the first
plate 200 to the side closer to the second plate 210).
[0038] To form the openings 231, the support structure 230, which
initially starts out as a solid plate, is cut to form one or more
"flaps" that are partially attached to the main body of the solid
plate. For example, an "H" may be cut into the solid plate so that
two flaps are formed for each opening 231. The flaps are then bent
or folded to open up the openings 231, and the bent/folded portion
of the flap forms spacers 235 located near the openings 231. The
folded portion is bent by more than a 90.degree.-angle such that
the flap touches the flat plate.
[0039] The side of the cooling device that has the capillary wick
220 is the side that is closer to the heat source. The coolant
fluid is absorbed by the capillary wick 220. When the cooling
device receives heat from the heat source, the coolant fluid in the
capillary wick 220 evaporates by absorbing the latent heat. The gas
passes through the openings 231 to the other side of the support
structure 230, where it cools down and condenses.
[0040] The spacers 235, 236 may be formed so that some of them
(spacers 235) are bent toward the first plate 200 and others
(spacers 236) are bent toward the second plate 210. As illustrated
in FIG. 4, the spacers 235 "push" the capillary wick 220 toward the
first plate 200, eliminating any unevenness in the contact area
between the capillary wick 220 and the first plate 200 and
enhancing the efficiency of heat absorption and the effect of
capillary force. The spacers 236 push against the second plate 210
to maintain a substantially uniform gap between the support
structure 230 and the second plate 210, thereby maintaining an
unimpeded travel path for the coolant fluid. The support structure
230 is made of a material that is rigid enough that the spacers 236
prevent the coolant travel path from being deformed by pressure
applied to the cooling device from the outside.
[0041] The support structure 230 may be made from a similar list of
materials as the first and the second plates 200, 210, such as
aluminum, titanium, plastic, metalized plastic, graphite, copper,
any plastic combination.
[0042] FIG. 6 is a close-up view of a portion of a support
structure 330 usable with the cooling device of the invention.
Unlike in the embodiment of FIGS. 3, 4, and 5, all the spacers 335
are bent in the same direction in this embodiment. The support
structure 330 is particularly suited for use with a multi-wick
embodiment of the cooling device such as the one illustrated below
in FIG. 8.
[0043] FIG. 7 is a close-up view of a portion of a support
structure 430 usable with the cooling device of the invention. As
shown, the spacers 435, 436 are bent to form a substantially
90.degree. angle in this embodiment, unlike in the embodiment of
FIGS. 3, 4, and 5 where the cut-out flaps were "folded."
[0044] In yet another embodiment, it is possible to form one spacer
per opening instead of two spacers per opening as in the above
embodiments. In this case, the support structure 230 would be
formed by cutting lines through a solid plate such that the lines
form three sides of a rectangle, a "C" shape, or a "U" shape
(instead of an "H" shape as in the above embodiments). The flap
would then be bent/folded to create the opening and a spacer.
[0045] The spacers and the openings do not always have to be formed
together. For example, the solid plate of the support structure may
be cut with lines that form multiple rectangles so that the piece
that is cut out is completely detached from the solid plate. The
cut-out piece can then be formed into a desired shape and attached
to a desired spot on the solid plate so that it can maintain a
separation distance between the support structure and an adjacent
layer.
[0046] The support structure 230/330/430 may be attached to one of
the first and second plates 200, 210 by any well-known attachment
method, such as welding (tig welding, plasma welding, seam welding,
high frequency welding, etc.) or soldering a surface of the support
structure 230/330/430 to the plate. Attaching the support structure
to one of the plates 200, 210 improves heat exchange and enhances
general reliability of the cooling device.
[0047] FIG. 8 is an exploded perspective view of a second
embodiment of the cooling device in accordance with the invention.
As shown, the cooling device of the multi-wick embodiment includes
the first plate 200, the second plate 210, and the support
structure 330. In addition, the cooling device includes a first
wick layer 220a and a second wick layer 220b positioned between the
support structure 330 and one of the plates 200, 210, respectively.
The support structure 330 is, therefore, located between the two
wick layers 220a, 220b. Details of the support structure 330 were
provided above in reference to FIG. 6. The cooling device of FIG. 8
may be made with the support structure 230 or 430 as well. The
multi-wick embodiment of the cooling device works particularly well
when there are two heat sources, one near each of the two plates
200, 210. In the case where there are two heat sources, the parts
of the cooling device that are closest to the two heat sources act
as evaporation areas, and condensation occurs in the other parts of
the cooling device.
[0048] FIG. 9 is a third embodiment of the cooling device in
accordance with the invention. The finned-embodiment that is shown
is substantially similar to the embodiment of FIG. 3 except that it
has fins 213 on the lower plate 211 to increase the heat exchange
surface. In this embodiment, the first plate 210 is designed so it
can be positioned adjacent to a heat source. The coolant fluid
evaporates on the side of the support structure 230 that is closer
to the first plate 200, then expands into the side that is closer
to the second plate 210 through the openings 231. Optionally, each
of the fins 213 is designed with a hollow space 215 so that the
coolant fluid can travel inside the fins 213 for a more effective
heat dissipation. However, the fins 213 being designed to hold
coolant fluid is not a requirement of the invention. The presence
of the fins 213, even without the hollow spaces 215, aids heat
dissipation by increasing the heat exchange surface.
[0049] FIG. 10 is an open perspective view of a fourth embodiment
of the cooling device in accordance with the invention. Unlike the
embodiment shown in FIG. 3, the casing for this embodiment does not
use a first plate and a second plate. Instead, the casing is formed
with a planar tube 600. The planar tube 600 may be prepared by
obtaining a cylindrical pipe and pressing it down to a planar
shape. Methods that may be used to press the pipe to form a planar
tube are well known, and depends on the material from which the
cylindrical pipe is made. The capillary wick 220 is attached to an
inner surface of the planar tube 600, and the support structure 230
is positioned inside the planar tube. Once the capillary wick 220
and the support structure 230 are placed in the tube 600, the open
ends of the tube 600 are sealed. Although FIG. 10 shows the support
structure 230 as being used, support structures of other designs
(e.g., support structures 330, 430) may be used with the tube
embodiment. The tube embodiment is cost-effective because it is
simple to manufacture.
[0050] The tube 600 may be made of the same material as the first
and the second plates 200, 210, such as aluminum, titanium,
plastic, copper, metalized plastic, graphite, plastic combinations,
and other suitable metals with good heat conduction properties.
[0051] FIG. 11 is an exploded perspective view and FIG. 12 is a
cross-sectional view illustrating the operation of the cooling
device of the invention. In the example that is illustrated, a PCB
550 with a chip 500 (a heat source) is attached to the cooling
device. The first plate 200 of the cooling device is adjacent to
the PCB 550, so that the heat that is generated from the chip 500
reaches the first plate 200 through the PCB 550. The heat that
reaches the first plate 200 evaporates at least some of the coolant
fluid that was absorbed in the wick layer 220. As some of the
coolant fluid in the wick layer 220 evaporates, more liquid-phase
coolant is pulled to fill the space by capillary force (see dark
arrows). Due to the thinness of the cooling device, the weight of
the water vapor is low enough that gravitational effects do not
interfere with the liquid absorption by capillary force.
[0052] In the hot part of the cooling device, the coolant fluid
absorbs latent heat to change its phase from liquid to gas, making
the heat absorption that occurs at the interface between the
cooling device and the PCB 550 highly efficient.
[0053] Some of the evaporated gas-phase coolant fluid expands in
the space between the first plate 200 and the wick layer 220. Some
gas-phase coolant fluid crosses over to a cooler portion of the
cooling device through the openings 231 in the support structure
230, as shown by the light arrows. The coolant fluid that passes
through the openings 231 expands in all directions to fill the
space between the support structure 230 and the second plate 210.
As the coolant fluid expands in the cool portion of the cooling
device and dissipates heat through the second plate 210,
condensation occurs. The condensed liquid is absorbed back by the
wick layer 220 through capillary force and repeatedly goes through
the evaporation-condensation cycle. The spacers 235 maintain the
distance between the support structure 230 and the first plate 200,
while the spacers 236 maintain the distance between the support
structure 230 and the second plate 210. Thus, with the wick layer
220 and the space created by the support structure 230, there is an
open path through which the coolant fluid can circulate unimpeded
between the hot and cool portions of the cooling device.
[0054] The cooling device of the invention simplifies manufacturing
and therefore allows cooling devices to be made cost-effectively.
The support structure 230 "pushes" the wick layer 220 close to the
surface of the cooling device that is closest to the heat source,
improving heat transfer. At the same time, the support structure
230 maintains a circulation space for the coolant fluid to aid heat
dissipation. Furthermore, the support structure 230 makes the
cooling device rigid, and therefore more reliable. Without the
support structure, the cooling space could be deformed (e.g., the
two plates collapse toward each other) easily upon impact, impeding
the coolant circulation path and disturbing the flow of the coolant
fluid. The simple design of the spacers 235, 236 and the openings
231 allow the support structure to perform all these functions
without raising the manufacturing cost.
[0055] Although the invention has been described with reference to
the above example, it will be understood that modifications and
variations are encompassed within the spirit and scope of the
invention. For example, the shape and number of the spacers are not
limited to the particular embodiments shown here. Any structure
that may be formed from a solid plate to maintain a certain
distance between the support structure and an adjacent plate would
be within the spirit and scope of the invention. Accordingly, the
invention is limited only by the following claims.
* * * * *