U.S. patent application number 12/218434 was filed with the patent office on 2009-01-22 for heat diffusing device and method of producing the same.
This patent application is currently assigned to Sony Corporation. Invention is credited to Yasuo Kawabata.
Application Number | 20090020274 12/218434 |
Document ID | / |
Family ID | 40263890 |
Filed Date | 2009-01-22 |
United States Patent
Application |
20090020274 |
Kind Code |
A1 |
Kawabata; Yasuo |
January 22, 2009 |
Heat diffusing device and method of producing the same
Abstract
A heat diffusing device includes first and second metallic thin
plates that are alternately laminated to each other, and that are
joined along with an upper sealing metallic thin plate and a lower
sealing metallic thin plate by diffusion joining so as to form a
sealed space in an interior defined by the first and second thin
plates and the upper and lower sealing metallic thin plates. A
C-shaped groove defined by a steep wall face is formed at a wall
face defining the sealed space due to a difference (.DELTA.w)
between the dimensions of the first metallic thin plates and the
dimensions of the second metallic thin plates.
Inventors: |
Kawabata; Yasuo; (Kanagawa,
JP) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, P.C.
600 ATLANTIC AVENUE
BOSTON
MA
02210-2206
US
|
Assignee: |
Sony Corporation
Tokyo
JP
|
Family ID: |
40263890 |
Appl. No.: |
12/218434 |
Filed: |
July 15, 2008 |
Current U.S.
Class: |
165/168 ;
29/890.03 |
Current CPC
Class: |
F28D 15/0233 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; F28D 15/0266
20130101; F28F 3/12 20130101; H01L 2924/00 20130101; Y10T 29/4935
20150115; H01L 23/427 20130101 |
Class at
Publication: |
165/168 ;
29/890.03 |
International
Class: |
F28F 3/12 20060101
F28F003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2007 |
JP |
JP2007-188373 |
Claims
1. A heat diffusing device comprising: first metallic thin plates
and second metallic thin plates, dimensions of the first metallic
thin plates being different from dimensions of the second metallic
thin plates; an upper sealing metallic thin plate; and a lower
sealing metallic thin plate, wherein the first and second metallic
thin plates are alternately laminated to each other, and are joined
along with the upper and lower sealing metallic plates by diffusion
joining so that a sealed space is formed in an interior defined by
the first and second metallic thin plates and the upper and lower
sealing metallic plates, wherein a groove defined by a steep wall
face is formed at a wall face defining the sealed space due to the
difference between the dimensions of the first and second metallic
thin plates, and wherein a liquid is sealed in the groove under
reduced pressure in an initial state.
2. The heat diffusing device according to claim 1, wherein the
sealed space is rectangular, wherein the groove communicates with
an entire periphery of the sealed space, and wherein one end
portion side of the sealed space in a longitudinal direction is an
evaporation portion, and the other end portion side of the sealed
space in the longitudinal direction is a heat-exhausting
portion.
3. The heat diffusing device according to claim 2, wherein a
plurality of the rectangular sealed spaces are disposed in
parallel.
4. The heat diffusing device according to claim 1, wherein the
first and second metallic thin plates each have a plurality of
radiating portions communicating with respective peripheral
portions from respective central portions of the first and second
metallic thin plates, wherein a radiating-portion pattern of each
first metallic thin plate differs from a radiating-portion pattern
of each second metallic thin plate, wherein a flow path for a
return liquid is disposed between the radiating portions of the
metallic thin plates of one type that are laminated to each other
so that the metallic thin plates of the one type are disposed on
both sides of the metallic thin plates of the other type, and
wherein each central portion is the evaporation portion, and each
peripheral portion is the heat-exhausting portion.
5. The heat diffusing device according to claim 1, wherein the
first and second metallic thin plates and the sealing metallic thin
plates are formed of a same material.
6. A method of producing a heat diffusing device comprising the
steps of: alternately laminating first and second metallic thin
plates to each other, and disposing sealing metallic thin plates at
a top side and a bottom side of the laminated first and second
metallic thin plates, dimensions of the first metallic thin plates
being different from dimensions of the second metallic thin plates;
forming an integrated laminated body by subjecting the first and
second metallic thin plates and the sealing metallic thin plates to
diffusion bonding, forming a sealed space in an interior of the
laminated body, and forming a groove at a wall face of the sealed
space due to the difference between the dimensions of the first and
second metallic thin plates, the groove being defined by a steep
wall face; and sealing a liquid in the groove in an initial state
in which pressure in the sealed space is reduced.
7. The method of producing the heat diffusing device according to
claim 6, wherein thin plates each having a rectangular opening and
a peripheral portion at the opening are used as the first and
second metallic thin plates, the peripheral portions having
different widths, wherein thin plates having areas allowing the
openings to be closed are used as the upper and lower sealing
metallic thin plates, and wherein the groove communicating with an
entire periphery of the sealed space, formed by the openings, is
formed.
8. The method of producing the heat diffusing device according to
claim 7, wherein thin plates each having a plurality rectangular
openings disposed in parallel are used as the first and second
metallic thin plates.
9. The method of producing the heat diffusing device according to
claim 6, wherein thin plates each having a plurality of radiating
portions communicating with a peripheral portion from a central
portion, and each having an opening between the radiating portions,
are used as the first and second metallic thin plates, patterns of
the radiating portions of the thin plates differing from each
other, wherein the sealed space is formed by the openings, and
wherein the groove is formed at the central portion and the
peripheral portion of each thin plate.
10. The heat diffusing device according to claim 6, wherein the
first and second metallic thin plates and the sealing metallic thin
plates are formed of thin plates of a same material.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present invention contains subject matter related to
Japanese Patent Application JP 2007-188373 filed in the Japanese
Patent Office on Jul. 19, 2007, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a heat diffusing device
that restricts the temperature of a heat source to a temperature
less than or equal to a predetermined temperature by diffusing heat
of the heat source in, for example, an electronic apparatus or
other apparatuses.
[0004] 2. Description of the Related Art
[0005] Hitherto, in, for example, an electronic apparatus, such as
a personal computer or a projector (display apparatus), a heat
diffusing device for dissipating heat of a heat source is required.
What is called a heat pipe is known as an example of the heat
diffusing device. The heat pipe has, for example, the following
structure. That is, for example, as shown in FIG. 23, in a heat
pipe 1, a plurality of grooves 3, disposed in parallel along a
longitudinal direction, are formed at the inner side of a metallic
pipe 2 so that their cross sections in a circumferential direction
are uneven. In addition, a wick 4, formed of wires, is disposed at
the inner sides of the grooves 3, and water 4 is sealed in the
grooves 3. When one end of the heat pipe 1 contacts a heat source,
the water in the grooves 3 evaporates at this one end, and the
steam instantaneously spreads to the other end side. The other end
side is in contact with outside air. Therefore, heat exchange
occurs, thereby cooling and condensing the steam back into water.
This water flows through the wick 4, and returns to the one end. By
repeatedly evaporating, condensing, and returning the water, the
temperature rise of the heat source is restricted.
[0006] Japanese Unexamined Patent Application No. 2004-198098
discloses an example of a heat pipe.
SUMMARY OF THE INVENTION
[0007] In the above-described heat pipe 1, as shown in FIG. 22, if
the grooves 3 are defined by steep wall faces, that is,
right-angled wall faces, a contact angle .theta. of water 10, in
each grooves 3, with respect to a wall face 3a becomes small, so
that a thin portion 9 of the water 10 tends to evaporate.
Therefore, the temperature of the wall face at this portion 9 can
be made very low. At the same time, capillary action makes it
possible to pass the condensed water 10 through the grooves 3, and
to return it to an evaporation portion side. However, actually,
since the pipe 2 having the plurality of grooves 3 is formed by a
drawing process, the grooves 3 defined by steep wall faces cannot
be formed. Therefore, the wick 4, formed of wires, is required.
[0008] As shown in FIG. 21A, a planar heat diffusing device 11 may
be formed. In the heat diffusing device 11, a plurality of grooves
3 are formed by etching a surface of a first metallic thin plate
12. A second metallic thin plate 14, serving as a cover, is joined
to the first metallic thin plate 12, to form sealed spaces defined
by the grooves 13. The grooves 13 are filled with water 15 under
reduced pressure in an initial state. However, as shown in FIG.
21B, when the grooves 13 are formed by etching, the cross sections
of the grooves become curved. As a result, grooves defined by steep
wall faces cannot be formed.
[0009] In view of the aforementioned points, it is desirable to
provide a heat diffusing device which makes it possible to
precisely form grooves defined by steep wall faces and to provide
good heat diffusion, and a method of producing the same.
[0010] According to an embodiment of the present invention, there
is provided a heat diffusing device including first metallic thin
plates and second metallic thin plates, an upper sealing metallic
thin plate, and a lower sealing metallic thin plate. The dimensions
of the first metallic thin plates are different from dimensions of
the second metallic thin plates. The first and second metallic thin
plates are alternately laminated to each other, and are joined
along with the upper and lower sealing metallic plates by diffusion
joining so that a sealed space is formed in an interior defined by
the first and second metallic thin plates and the upper and lower
sealing metallic plates. A groove defined by a steep wall face is
formed at the wall face defining the sealed space due to the
difference between the dimensions of the first and second metallic
thin plates. A liquid is sealed in the groove under reduced
pressure in an initial state.
[0011] In the embodiment of the present invention, since the first
and second metallic thin plates whose dimensions differ are
alternately laminated, a groove defined by a steep wall face is
formed with good precision at the wall face defining the sealed
space. Since a contact angle .theta. of the liquid with respect to
the wall face defining the groove can be made small, water is
efficiently evaporated.
[0012] According to another embodiment of the present invention,
there is provided a method of producing a heat diffusing device
including the following steps. That is, the method includes
alternately laminating first and second metallic thin plates to
each other, and disposing sealing metallic thin plates at a top
side and a bottom side of the laminated first and second metallic
thin plates, dimensions of the first metallic thin plates being
different from dimensions of the second metallic thin plates. In
addition, the method includes forming an integrated laminated body
by subjecting the first and second metallic thin plates and the
sealing metallic thin plates to diffusion bonding, forming a sealed
space in an interior of the laminated body, and forming a groove at
a wall face of the sealed space due to the difference between the
dimensions of the first and second metallic thin plates, the groove
being defined by the steep wall face. Further, the method includes
sealing a liquid in the groove in an initial state in which
pressure in the sealed space is reduced.
[0013] In the method of producing a heat diffusing device according
to another embodiment of the present invention, the first and
second metallic thin plates whose dimensions differ are alternately
laminated, so that a groove defined by a steep wall face can be
formed with good precision at the wall face defining the sealed
space. When the groove is filled with the liquid, the groove can be
filled with the liquid while a contact angle .theta. of the liquid
with respect to the wall face defining the groove is small.
[0014] According to the heat diffusing device according to one
embodiment of the present invention, a groove defined by steep wall
face is formed, and the liquid in the groove can be evaporated with
good efficiency. Therefore, a heat diffusing device providing good
heat diffusion can be provided.
[0015] According to the method of producing a heat diffusing device
according to another embodiment of the present invention, a groove
defined by a steep wall face can be formed with good precision.
Therefore, a heat diffusing device providing good heat diffusion
can be produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIGS. 1A and 1B are, respectively, a partly cutaway plan
view and side view of a heat diffusing device according to a first
embodiment of the present invention;
[0017] FIGS. 2A and 2B are, respectively, a plan view of an upper
sealing metallic thin plate according to the first embodiment, and
a sectional view taken along line IIB-IIB thereof;
[0018] FIGS. 3A and 3B are, respectively, a plan view of a first
metallic thin plate according to the first embodiment, and a
sectional view taken along line IIIB-IIIB thereof;
[0019] FIGS. 4A and 4B are, respectively, a plan view of a second
metallic thin plate according to the first embodiment, and a
sectional view taken along line IVB-IVB thereof;
[0020] FIGS. 5A and 5B are, respectively, a plan view of a lower
sealing metallic thin plate according to the first embodiment, and
a sectional view taken along line VB-VB thereof;
[0021] FIG. 6 is an enlarged sectional view of a peripheral portion
in the heat diffusing device according to the first embodiment;
[0022] FIGS. 7A and 7B are, respectively, an enlarged sectional
view and an enlarged plan view of a central portion in the heat
diffusing device according to the first embodiment;
[0023] FIG. 8 is a perspective view of radiating portions in the
heat diffusing device according to the first embodiment;
[0024] FIG. 9 is a partly cutaway plan view of a liquid supplying
portion and a liquid/gas discharging portion of the heat diffusing
device according to the first embodiment;
[0025] FIGS. 10A and 10B are, respectively, an exploded perspective
view of an exemplary liquid supplying portion and an exemplary
liquid/gas discharging portion, and a sectional view taken along
line XB-XB thereof;
[0026] FIG. 11 is a sectional view of a main portion showing the
relationship between a groove defined by a steep wall face and a
sealed liquid according to the embodiment of the present
invention;
[0027] FIG. 12 is a partly cutaway plan view of a heat diffusing
device according to a second embodiment of the present
invention;
[0028] FIGS. 13A and 13B are respectively, a sectional view taken
along line XIIIA-XIIIA of FIG. 12, and a sectional view taken along
line XIIIB-XIIIB of FIG. 12;
[0029] FIGS. 14A, 14B, and 14C are, respectively, a perspective
view of a first metallic thin plate according to the second
embodiment, a sectional view taken along line XIVB-XIVB thereof,
and a sectional view taken along line XIVC-XIVC thereof;
[0030] FIGS. 15A, 15B, and 15C are, respectively, a perspective
view of a second metallic thin plate according to the second
embodiment, a sectional view taken along line XVB-XVB thereof, and
a sectional view taken along line XVC-XVC thereof;
[0031] FIG. 16 is a perspective view of an upper sealing metallic
thin plate according to the second embodiment;
[0032] FIGS. 17A and 17B are, respectively, a perspective view of a
lower sealing metallic thin plate according to the second
embodiment, and a sectional view taken along line XVIIB-XVIIB
thereof;
[0033] FIG. 18 is an exploded perspective view of a main portion
showing an exemplary liquid supplying portion and an exemplary
liquid/gas discharging portion in the heat diffusing device
according to the second embodiment;
[0034] FIG. 19 is a sectional view of the main portion of the
liquid supplying portion and the liquid/gas discharging portion in
the heat diffusing device according to the second embodiment;
[0035] FIG. 20 is a perspective view of the main portion after
sealing the liquid supplying portion and the liquid/gas discharging
portion in the heat diffusing device according to the second
embodiment;
[0036] FIGS. 21A and 21B are, respectively, a partly cutaway
perspective view of a comparative-example heat diffusing device,
and a sectional view taken along line XXIB-XXIB thereof;
[0037] FIG. 22 is a sectional view of an ideal groove shape;
and
[0038] FIG. 23 is a partly sectional perspective view of a related
heat pipe.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] Embodiments of the present invention will hereunder be
described with reference to the drawings.
[0040] FIGS. 1 to 5 illustrate a heat diffusing device and a method
of producing the same according to a first embodiment of the
present invention. As shown in FIGS. 1A and 1B, a heat diffusing
device 21 according to the embodiment includes a laminated body 24
and sealing metallic plates 25 and 26. The laminated body 24
includes first metallic thin plates 22 and second metallic thin
plates 23, which are alternately laminated, and which have
rectangular contour shapes, that is, rectangular contour shapes of
the same size in the embodiment, as viewed from above. The
dimensions of the second metallic thin plates 23 differ from those
of the first metallic thin plates 22. The sealing metallic thin
plates 25 and 26 seal the top and bottom of the laminated body 24,
respectively. The first and second metallic thin plates 22 and 23
have the same film thickness. The upper and lower sealing metallic
thin plates 25 and 26 also have the same film thickness.
[0041] As shown in FIGS. 3A and 3B, each first metallic thin plate
22 has a pattern including a central portion 31, a rectangular
frame peripheral portion 32, and a plurality of radiating portions
communicating with the peripheral portion 32 from the central
portion 31. In the embodiment, there are four radiating portions 33
(331, 332, 333, and 334) that radiate in the form of a cross so as
to divide each of the four sides into two equal parts. The
peripheral portion 32 has the same width over the entire periphery,
and a predetermined width w1 is selected as its width. The
radiating portions 331 to 334 have a same width d1 up to respective
certain points from the peripheral portion 32, and taper so that
their widths are gradually decreased towards the central portion 31
from their respective certain points. In the embodiment, the
radiating portions 33 (331 to 334) are formed linearly
symmetrically. Four through holes 35, which receive support columns
formed integrally with the lower sealing metallic thin plate 26
(described later), are formed in the four radiating portions 331 to
334, respectively. The first metallic thin plates 22 can be formed
by pressing one metallic thin plate.
[0042] As shown in FIGS. 4A and 4B, each second metallic thin plate
23 has a pattern including a central portion 36, a rectangular
frame peripheral portion 37, and a plurality of radiating portions
communicating with the peripheral portion 37 from the central
portion 36. In the embodiment, there are four radiating portions 38
(381, 382, 383, and 384) that radiate in the form of a cross in
which two diagonals intersect each other. That is, the pattern of
each second metallic thin plate 23 differs from the pattern of each
first metallic thin plate 22 in its radiating portions. The
peripheral portion 37 has the same width over the entire periphery,
and a predetermined width w2, which is smaller than the width w1 in
each metallic thin plate 22 (w1>w2), is selected as its width.
The radiating portions 381 to 384 have a same width d2 up to
respective certain points from the peripheral portion 37, and taper
so that their widths are gradually decreased towards the central
portion 36 from their respective certain points. In the embodiment,
the radiating portions 38 (381 to 384) are formed linearly
symmetrically. Four through holes 39, which receive support columns
formed integrally with the lower sealing metallic thin plate 26
(described later), are formed in the four radiating portions 381 to
384, respectively. The first metallic thin plates 23 can be formed
by pressing one metallic thin plate.
[0043] The width d1 of each radiating portion 33 of each first
metallic thin plate 22 and the width d2 of each radiating portion
38 of each second metallic thin plate 23 may be the same (d1=d2),
or may be different from each other (d1.noteq.d2). It is desirable
that the diameters of the through holes 35 and 39 of the radiating
portions 33 and 38 of the respective first and second metallic thin
plates 22 and 23 be the same.
[0044] Since the width w1 of the peripheral portion 32 of each
first metallic thin plate 22 and the width w2 of the peripheral
portion 37 of each second metallic thin plate 23 differ from each
other, a dimension difference .DELTA.w=w1-w2 occurs at the
peripheral portions 32 and 37 at the inner side when they are
laminated.
[0045] As shown in FIG. 2, the upper sealing metallic thin plate 25
has a rectangular shape, and has through holes 41, which receive
ends of the support columns, at locations corresponding to the
radiating portions 33 and 38 of the respective first and second
metallic thin plates 22 and 23, that is, at locations corresponding
to the support columns formed integrally with the lower sealing
metallic thin plate 26. In the embodiment, eight through holes 41
are formed.
[0046] As shown in FIG. 5, the lower sealing metallic thin plate 26
has a rectangular shape, and has support columns 42 integrally
provided upright at locations corresponding to the through holes 41
of the upper sealing metallic thin plate 25 and the through holes
35 and 39 of the radiating portions 33 and 38 of the respective
first and second metallic thin plates 22 and 23. In the embodiment,
eight support columns 42 are formed. The support columns 42 have
large-diameter portions 42a, which are inserted into the through
holes 35 and 39 of the radiating portions 33 and 38 of the
respective first and second metallic thin plates 22 and 23, and
small-diameter portions 42b, which are inserted into the through
holes 41 of the upper sealing metallic thin plate 25, at ends of
the large-diameter portions 42a. The support columns 42 withstand
internal pressure to maintain the interval between the lower
sealing metallic thin plate 26 and the upper sealing metallic thin
plate 25. The support columns 42 may not be joined to the radiating
portions 33 and 38. Instead, they may pass through the radiating
portions 33 and 38. The support columns 42 may be omitted. The
eight support columns are subjected to diffusion bonding
simultaneously with the laminated structure, thereby connecting the
upper and lower planar surfaces. FIG. 5 shows that, for ensuring
strength, a caulking mechanism may also be used.
[0047] The first and second metallic thin plates 22 and 23, the
upper sealing metallic thin plate 25, and the lower sealing
metallic thin plate 26 are formed of a metal allowing diffusion
bonding, such as copper or beryllium copper. In the embodiment,
they are formed of copper.
[0048] In the embodiment, the laminated body 24 is formed by
alternately laminating a plurality of the first and second metallic
thin plates 22 and 23 (for example, 21 thin plates) so that the
first metallic thin plates 22 are disposed at the uppermost layer
and the lowermost layer. The laminated body 24 is disposed on the
lower sealing metallic thin plate 26. That is, the laminated body
24 is disposed on the lower sealing metallic thin plate 26 so that
the large-diameter portions 42a of the support columns 42 of the
lower sealing metallic thin plate 26 are inserted into the through
holes 35 and 39 of the respective radiating portions 33 and 38 of
the laminated body 24. The upper sealing metallic thin plate 25 is
disposed on the laminated body 24. The upper sealing metallic thin
plate 25 is disposed on the laminated body 24 so that the
small-diameter portions 42b at the ends of the support columns 42,
integrally formed with the lower sealing metallic thin plate 26,
are inserted into the through holes 41.
[0049] In addition, in the embodiment, the laminated body 24,
having the sealing metallic thin plates 25 and 26 disposed at the
top and bottom sides thereof, is, in this state, pressed and heated
in a vacuum. This causes the laminated body 24 to be formed into an
integrated structure by diffusion bonding, so that the laminated
structure 24 is air-tightly and liquid-tightly sealed. The support
columns 42 are bonded to the upper sealing metallic thin plate 25
by diffusion bonding while stepped surfaces at the ends of the
support columns 42 are in contact with the back surface of the
upper sealing metallic thin plate 25. At the same time, grooves
(described later), which are formed at side wall faces at sealed
spaces in the laminated body 24, are filled with a liquid, which
becomes a refrigerant under reduced pressure in an initial state.
Accordingly, the heat diffusing device 21 is formed.
[0050] In the heat diffusing device 21 according to the first
embodiment, as shown in FIG. 6, grooves 44 defined by steep wall
faces are formed at side walls of peripheral portions 28 in sealed
spaces 45 in FIG. 1 due to the difference .DELTA.w between the
dimensions of the first and second metallic thin plates 22 and 23.
That is, the C-shaped grooves 44 defined by upper and lower wall
faces that are at right angles with respect to respective back wall
faces as viewed in cross section of the grooves are formed. In
addition, as shown in FIGS. 7A and 7B, grooves 44 defined by steep
wall faces are formed at side wall faces of respective central
portions 27 in the sealed spaces 45 due to the difference .DELTA.w
between the dimensions of the first and second metallic thin plates
22 and 23. That is, the C-shaped grooves 44 defined by upper and
lower wall faces that are at right angles with respect to
respective back wall faces as viewed in cross section of the
grooves are formed. The grooves 44 are formed at the central
portions 27 in accordance with the star-shapes of the central
portions 27 as indicated by an alternate long and short dash line
29 as viewed from the top.
[0051] In the first metallic thin plates 22 disposed at the upper
and lower sides of their corresponding second metallic thin plates
23, flow paths 51 are formed between the upper and lower radiating
portions 33 (331 to 334). The flow paths 51 are provided for a
return liquid (described later), and have small intervals providing
capillary action. Similarly, in the second metallic thin plates 23
disposed at the upper and lower sides of their corresponding first
metallic thin plates 22, flow paths 52 are similarly formed between
the upper and lower radiating portions 38 (381 to 384). The flow
paths 52 are provided for a return liquid, and have small intervals
providing capillary action. (Refer to FIG. 8.)
[0052] It is desirable that the liquid, which becomes a
refrigerant, be, for example, water (pure water). As shown in FIG.
11, a width t1 (corresponding to the thickness of each second
metallic thin plate 23) of each groove 44, and a depth .DELTA.w
thereof can be freely set in accordance with the refrigerant. For
example, when water is used as the refrigerant, the groove width t1
is optimally from 20 .mu.m to 100 .mu.m. However, depending upon
the surface tension of the refrigerant, the groove width t1 is not
limited to this value.
[0053] Next, the operation of filling the interior of the heat
diffusing device 21 with the liquid will be described in detail
with reference to FIGS. 9 and 10. As shown in FIG. 9, a liquid
supplying portion 54 and a liquid/gas discharging portion 55 are
previously provided at, for example, respective corners that oppose
each other on a diagonal of the heat diffusing device that is
integrally formed by diffusion bonding. As shown in FIGS. 10A and
10B, the liquid supplying portion 54 and the liquid/gas discharging
portion 55 have the same grooved structure. Each of the liquid
supplying portion 54 and the liquid/gas discharging portion 55 is
formed as follows. For example, two notches 56a and 56b
communicating with the sealed space 45 are formed at respective
locations of the uppermost first metallic thin plate 22, and a
groove 57 whose ends communicate with the notches 56a and 56b at
the lower side of the upper sealing metallic thin plate 25 are
formed in the upper sealing metallic thin plate 25. In addition, a
through hole 58 communicating with the outside from the groove 57
is formed in the upper sealing metallic thin plate 25.
[0054] The upper sealing metallic thin plate 25, the laminated body
24, and the lower sealing metallic thin plate 26 are disposed in
layers and subjected to diffusion bonding, and formed in a sealed
state as mentioned above. Then, liquid, such as water, is supplied
from the through hole 58 of the liquid supplying portion 54 to the
interior of the sealed space 45 through the groove 57 and the
notches 56a and 56b. The liquid can be supplied so as to fill up
the interior of the sealed space 45. In this state, both sides of
the groove 57 on respective sides of the through hole 58 in the
liquid supplying portion 54 are temporarily pressed inwards by, for
example, stupid caulking, to seal the liquid supplying portion 54.
Then, the liquid in the sealed space 45 is sucked out and
discharged from the through hole 58 of the liquid/gas discharging
portion 55, and is exhausted. This causes a portion of the liquid
to remain in the groove 44 at the wall face defining the sealed
space while the pressure in the interior of the sealed space 45 is
in a reduced state. In this state, both sides of the groove 57 on
the respective sides of the through hole 58 in the liquid/gas
discharging portion 55 are pressed inwards by, for example, stupid
caulking, to seal the liquid/gas discharging portion 55. Reference
numerals 59 in FIG. 10A denote caulking positions. At the end of
this process, the heat diffusing device 21 according to the first
embodiment is completed.
[0055] Next, the operation of the heat diffusing device 21
according to the first embodiment will be described. First, as
shown in FIG. 11, in the heat diffusing device 21, the groove 44,
formed at the wall face defining the sealed space, has a
cross-section rectangular shape defined by a vertical wall face,
which is an ideal groove shape. When this groove 44 is filled with
water 100 (which is a refrigerant), a contact angle .theta. of the
water 100 with respect to a wall face 44a is less than 40.degree.
(.theta.<40.degree.). Since the contact angle .theta. of the
water 100 is reduced, the water 100 is in a state in which a thin
portion 101 adhered to an open side tends to evaporate.
[0056] In the heat diffusing device 21, a heat source is disposed
at the central portions 27. What is called a point heat source is
disposed. The peripheral portions 28 of the heat diffusing device
21 operate as heat-exhausting portions, that is, cooling portions.
When the central portions 27 of the heat diffusing device 21
generate heat using the heat source, the water 100 in the grooves
44 at portions corresponding to the central portions 27 evaporates,
and is turned into steam. Steam radiation is performed with respect
to the wide sealed spaces 45 (see FIG. 1), so that the steam
instantaneously flies towards the peripheral portions 28. The steam
is cooled by the peripheral portions 28 (that is, the steam heat is
exhausted at the heat-exhausting portions at the other end), and is
condensed back to water. The resulting water enters the grooves 44
at the peripheral portions 28. When the width t1 of the
cross-section rectangular groove 44 shown in FIG. 11 is on the
order of from 20 .mu.m to 100 .mu.m, the water that has entered the
linear groove 44 spreads in the groove 44 due to capillary action.
Therefore, the water that has entered the grooves 44 at the
peripheral portions 28 and become a return liquid flows through the
grooves 44. Then, it flows between the radiating portions 33 and 33
and between the radiating portions 38 and 38 by capillary action,
and returns to the grooves 44 at the central portions 27. The
spaces between the radiating portions 33 and 33 and between the
radiating portions 38 and 38 are formed as return flow paths. The
narrow spaces between the radiating portions 33 and 33 and between
the radiating portions 38 and 38 operate as wicks that widely
diffuse the water.
[0057] According to the heat diffusing device 21, repeatedly
evaporating, condensing, and returning the water diffuses the heat,
generated at the point of the central portions, to an entire area
extending to the peripheries, so that the heat diffusing device 21
is not heated to a temperature greater than or equal to a
predetermined temperature. Therefore, it is possible to restrict a
temperature rise at the heat source.
[0058] FIGS. 12 to 17 show a heat diffusing device and a method of
producing the same according to a second embodiment of the present
invention. As shown in FIGS. 12 and 13, a heat diffusing device 61
according to the embodiment includes a laminated body 64 and
sealing metallic thin plates 65 and 66 that seal the upper and
lower sides of the laminated body 64. In the laminated body 64,
first metallic thin plates 62 and second metallic thin plates 63
are alternately laminated, and have rectangular shapes in which a
long side of a contour shape is sufficiently longer than a short
side of the contour shape as viewed from above. The dimensions of
each second metallic thin plate 63 differ from those of each first
metallic thin plate 62. The first and second metallic thin plates
62 and 63 have the same thickness. The upper sealing metallic thin
plate 65 and the lower sealing metallic thin plate 66 also have the
same thickness.
[0059] As shown in FIGS. 14A to 14C, each first metallic thin plate
62 is formed into a pattern in which a plurality of elongated
openings 68, extending in a long-side direction, are formed in
parallel in a short-side direction. A long-side width of a
peripheral portion 67 is selected so that it is a predetermined
width w3, and a short-side width of the peripheral portion 67 is
selected so that it is a predetermined width w4. In this case, when
the entire periphery of the peripheral portion 67 has the same
width, the width w3=the width w4. The width of partitions 69
partitioning the respective openings 68 are selected so that it is
a predetermined width w5. The widths of the two short sides of the
peripheral portion 67 and the widths of the two long sides of the
peripheral portion 67 can be selected so that they are suitable
widths as required. Each first metallic thin plate 62 can be formed
by pressing one metallic thin plate.
[0060] As shown in FIGS. 15A to 15C, each second metallic thin
plate 63 is similarly formed into a pattern in which a plurality of
elongated openings 71, extending in a long-side direction, are
formed in parallel in a short-side direction so as to be positioned
in correspondence with the elongated openings 68 of each first
metallic thin plate 62. The overall pattern of each second metallic
thin plate 63 is similar to that of each first metallic thin plate
62. However, since the overall dimensions of its pattern differs
from those of the pattern of each first metallic thin plate 62, its
pattern is, properly speaking, different from that of each first
metallic thin plate 62.
[0061] That is, in each second metallic thin plate 63, the width of
a peripheral portion 72 and the width of partitions 73 are smaller
than the width of the peripheral portion 67 and the width of the
partitions 69 of each first metallic thin plate 62, so that the
dimensions of each second metallic thin plate 63 differs from those
of each first metallic thin plate 62.
[0062] As shown in FIGS. 15A to 15C, in each second metallic thin
plate 63, the long-side width of the peripheral portion 72 is
selected so that it is a predetermined width w6 that is smaller
than the width w3 in each first metallic thin plate 62 (w3>w6).
In addition, the short-side width of the peripheral portion 72 is
selected so that it is a predetermined width w7 that is smaller
than the width w4 in each first metallic thin plate 62 (w4>w7).
In this case, when the entire periphery of the peripheral portion
72 has the same width, the width w6=the width w7. The width of
partitions 73 partitioning the respective openings 71 are selected
so that it is a predetermined width w8 that is smaller than the
width w5 in each first thin metallic plate 62. The widths of the
two short sides of the peripheral portion 72 and the widths of the
two long sides of the peripheral portion 72 can be selected so that
they are suitable widths as required. Each second metallic thin
plate 63 can be formed by pressing one metallic thin plate.
[0063] The long-side width w3 of the peripheral portion 67 of each
first metallic thin plate 62 and the long-side width w6 of the
peripheral portion 72 of each second metallic thin plate 63 differ
from each other. In addition, the short-side width w4 of the
peripheral portion of each first metallic thin plate 62 and the
short-side width w7 of the peripheral portion 72 of each second
metallic thin plate 63 differ from each other. Further, the width
w5 of the partitions 69 and the width w8 of the partitions 73
differ from each other. Therefore, at the inner side when they are
laminated, dimensional differences .DELTA.w=w3-w6, .DELTA.w=w4-w7,
and .DELTA.w=w5-w8 occur in the side wall faces at the elongated
openings 68 and 71. That is, the same dimension differences
.DELTA.w occur over the entire periphery of the wall faces at the
elongated openings.
[0064] As shown in FIG. 16, the upper sealing metallic thin plate
65 is formed using a rectangular thin plate having a contour shape
of a size that is the same as that of the first and second metallic
thin plates 62 and 63. The upper sealing metallic thin plate 65 can
be formed by pressing one metallic thin plate.
[0065] As shown in FIGS. 17A and 17B, the lower sealing metallic
thin plate 66 is formed using a rectangular thin plate having a
contour shape of a size that is the same as that of the first and
second metallic thin plates 62 and 63. The lower sealing metallic
thin plate 66 is formed so as to have a plurality of horizontal
grooves 75 on both ends of the rectangular shape at the top surface
of the lower sealing metallic thin plate 66. The horizontal grooves
75 communicate with the openings 68 of the first metallic thin
plate 62 and the openings 71 of the second metallic thin plate 63.
The lower sealing metallic thin plate 66 can be formed by pressing
one metallic thin plate.
[0066] The first and second metallic thin plates 62 and 63, the
upper sealing metallic thin plate 65, and the lower sealing
metallic thin plate 66 are formed of a metal allowing diffusion
bonding, such as copper or beryllium copper. In the embodiment,
they are formed of copper.
[0067] In the embodiment, the laminated body 64 is formed by
alternately laminating a plurality of the first and second metallic
thin plates 62 and 63 (for example, 21 thin plates) so that the
first metallic thin plates 62 are disposed at the uppermost layer
and the lowermost layer. The upper sealing metallic thin plate 65
and the lower sealing metallic thin plate 66 are disposed at the
top and the bottom of the laminated body 64. The upper sealing
metallic thin plate 65, the laminated body 24, and the lower
sealing metallic thin plate 66 are integrated to each other by
diffusion bonding as a result of being pressed and heated in a
vacuum. Therefore, they are air-tightly and liquid-tightly sealed.
At the same time, grooves (described later), which are formed at
side wall faces, defining sealed spaces 77 formed by the openings
68 and 71 in the laminated body 64, are filled with a liquid (which
becomes a refrigerant under reduced pressure in an initial state).
Accordingly, the heat diffusing device 61 is formed.
[0068] In the heat diffusing device 61 according to the second
embodiment, grooves 78 (see FIGS. 13A and 13B), defined by steep
wall faces, are formed over the side wall faces, defining the
respective sealed spaces 77 formed by the elongated openings in
FIG. 12, due to the dimension difference .DELTA.w between the
dimensions of the first and second metallic thin plates 62 and 63.
The grooves 78 are formed into annular shapes continuously formed
with the entire peripheries of the respective sealed spaces 77.
Similarly to the first embodiment, as viewed from the cross section
of the grooves, the grooves 78 have C shapes having upper and lower
wall faces that are at right angles to respective back wall
faces.
[0069] As mentioned above, it is desirable to use, for example,
water (pure water) as the liquid that becomes a refrigerant.
[0070] Next, the operation of filling the interior of the heat
diffusing device 61 with the liquid will be described in detail
with reference to FIGS. 18 to 20. In the embodiment, a liquid
supplying portion 81 is previously provided at one end portion side
in a longitudinal direction and a liquid/gas discharging portion 82
is previously provided at the other end portion side in the
longitudinal direction with respect to the heat diffusing device 61
that is integrally formed by the diffusion bonding. The liquid
supplying portion 81 and the liquid/gas discharging portion 82 have
the same structure. As shown in FIG. 18, each of the liquid
supplying portion 81 and the liquid/gas discharging portion 82 is
formed as follows. For example, two notches 83a and 83b
communicating with the sealed space 77 are formed at, for example,
respective locations of the uppermost first metallic thin plate 62
of the laminated body 64. A groove 84 whose ends communicate with
the notches 83a and 83b at the lower side of the upper sealing
metallic thin plate 65 is formed in the upper sealing metallic thin
plate 65. In addition, a through hole 85 communicating with the
outside from the groove 84 is formed in the upper sealing metallic
thin plate 65.
[0071] The upper sealing metallic thin plate 65, the laminated body
64, and the lower sealing metallic thin plate 66 are disposed in
layers and subjected to diffusion bonding, and formed in a sealed
state as mentioned above. Then, liquid, such as water, is supplied
from the through hole 85 of the liquid supplying portion 81 to the
interior of the sealed space 77 through the groove 84 and the
notches 83a and 83b. The water is supplied to all of the interiors
of the sealed spaces 77 (see FIG. 12) partitioned by the partitions
68 and 73 through the horizontal grooves 75, formed in the inside
surface of the lower sealing metallic thin plate. The water can be
supplied so that it fills completely the interiors of all of the
sealed spaces 77. In this state, both sides of the groove 84 on
respective sides of the through hole 85 in the liquid supplying
portion 81 are temporarily pressed inwards by, for example, stupid
caulking, to seal the liquid supplying portion 81. Then, the liquid
in the sealed space 77 is sucked out and discharged from the
through hole 85 of the liquid/gas discharging portion 82, and is
exhausted. This causes a portion of the liquid to remain in the
groove 78 at the wall face defining the sealed space 77 while the
pressure in the interior of the sealed space 77 is in a reduced
state. In this state, both sides of the groove 84 on the respective
sides of the through hole 85 in the liquid/gas discharging portion
82 are pressed inwards by, for example, stupid caulking, to seal
the liquid/gas discharging portion 82. Reference numerals 89 in
FIG. 10A denote caulking positions. At the end of this process, the
heat diffusing device 61 according to the second embodiment is
completed.
[0072] Next, the operation of the heat diffusing device 61
according to the second embodiment will be described. As discussed
with reference to FIG. 11, in the heat diffusing device 61, the
grooves 78, formed along the entire peripheries of the side wall
faces defining the sealed spaces 77 formed in parallel, have a
cross-section rectangular shape having vertical wall faces, which
is an ideal groove shape. When the grooves 78 are filled with, for
example, water 100 (which is a refrigerant), a contact angle
.theta. of the water 100 with respect to a groove wall face is less
than 40.degree. (.theta.<40.degree.) (see FIG. 11). Since the
contact angle .theta. of the water 100 is reduced as mentioned
above, the water 100 is in a state in which a thin portion adhered
to an open side tends to evaporate.
[0073] In the heat diffusing device 61 according to the second
embodiment, a heat source is disposed at one end side thereof. The
other end side of the heat diffusing device 61 operates as a
heat-exhausting portion, that is, a cooling portion. The linear
sealed spaces 77 become gas flow paths, and the grooves 78 at the
side wall faces become liquid return flow paths. When the one end
portion of the heat diffusing device 61 generates heat using the
heat source, the water in the grooves 78 at the one end portion
side evaporates, and is turned into steam. Steam radiation is
performed with respect to the wide sealed spaces 77, so that the
steam instantaneously flies to the other end side. The steam is
cooled by the cooling portion at the other end (that is, the steam
heat is exhausted at the heat-exhausting portion at the other end),
and is condensed back to water. The returned water enters the
grooves 78 at the other end portion. When the width of each
cross-section rectangular groove 78 is on the order of from 20
.mu.m to 100 .mu.m, the water that has entered the grooves 78
spreads into the long-side grooves 78 from the short side due to
capillary action. Therefore, the water returns to the grooves 78 at
the one end portion through return flow paths formed by the
long-side grooves 78.
[0074] According to the heat diffusing device 61, repeatedly
evaporating, condensing, and returning the water diffuses the heat,
generated at the one end portion, to an entire area extending to
the other end portion, so that the heat diffusing device 61 is not
heated to a temperature greater than or equal to a predetermined
temperature. Therefore, it is possible to restrict a temperature
rise at the heat source.
[0075] According to the diffusing device 61, the laminated
structure, in which the first and second metallic thin plates are
alternately laminated to each other, makes it possible to form the
grooves 78 defined by steep wall faces. The grooves 78 operate as
wicks that widely diffuse water. In the wick structure formed by
the grooves 78, the wall faces rise steeply compared to those
formed by etching or mechanical processing. Therefore, a heat
transport capacity is large as a result of making the contact angle
.theta. of the liquid small.
[0076] The heat diffusing device according to the above-described
embodiments of the present invention is applicable to, for example,
restricting heat generation in an electronic apparatus. For
example, the heat diffusing device according to the embodiments is
suitable for use in restricting heat generation of a light-emitting
diode of a projector or heat generation in a central processing
unit (CPU) in a personal computer.
[0077] It should be understood by those skilled in the art that
various modifications, combinations, sub-combinations and
alterations may occur depending on design requirements and other
factors insofar as they are within the scope of the appended claims
or the equivalents thereof.
* * * * *