U.S. patent application number 12/032459 was filed with the patent office on 2008-08-28 for liquid cooling system.
This patent application is currently assigned to ALPS ELECTRIC CO., LTD.. Invention is credited to Jiro Nakajima, Hitoshi ONISHI.
Application Number | 20080202730 12/032459 |
Document ID | / |
Family ID | 39714565 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080202730 |
Kind Code |
A1 |
ONISHI; Hitoshi ; et
al. |
August 28, 2008 |
LIQUID COOLING SYSTEM
Abstract
Embodiments of the present disclosure may include a liquid
cooling system in which an inlet hole and an outlet hole that are
located at both ends of a circulating flow passage opened onto a
heat-radiating sheet having the circulating flow passage between a
pair of heat-conductive metal plates that are superimposed on each
other, a pump having a discharge port and a suction port that
communicate with the inlet hole and the outlet hole installed on
the heat-radiating sheet, a heat-generating element set on the
heat-radiating sheet via a heat spreader, and used as a
heat-receiving area, and the circulating flow passage having a
heat-absorbing flow passage located in a lower face of the heat
spreader and a heat-radiating flow passage located in the
heat-radiating area other than the heat spreader and having a
sufficiently larger length than the flow passage length of the
heat-absorbing flow passage.
Inventors: |
ONISHI; Hitoshi;
(Niigata-ken, JP) ; Nakajima; Jiro; (Niigata-ken,
JP) |
Correspondence
Address: |
HUNTON & WILLIAMS LLP;INTELLECTUAL PROPERTY DEPARTMENT
1900 K STREET, N.W., SUITE 1200
WASHINGTON
DC
20006-1109
US
|
Assignee: |
ALPS ELECTRIC CO., LTD.
Tokyo
JP
|
Family ID: |
39714565 |
Appl. No.: |
12/032459 |
Filed: |
February 15, 2008 |
Current U.S.
Class: |
165/104.28 ;
165/104.33; 257/E23.098 |
Current CPC
Class: |
G06F 2200/201 20130101;
F28D 15/00 20130101; H01L 2924/0002 20130101; F28F 2250/08
20130101; H01L 2924/0002 20130101; H01L 2924/00 20130101; H01L
23/473 20130101; G06F 1/203 20130101 |
Class at
Publication: |
165/104.28 ;
165/104.33 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2007 |
JP |
2007-043879 |
Claims
1. A liquid cooling system comprising: a heat-radiating sheet
having a pair of heat-conductive metal plates that are superimposed
on each other, and having a circulating flow passage between the
pair of heat-conductive metal plates; an inlet hole and an outlet
hole opened to the surface of the heat-radiating sheet and located
at both ends of the circulating flow passage; a pump having a
discharge port and a suction port that communicate with the inlet
hole and the outlet hole, and installed on the heat-radiating
sheet; a heat-receiving area and a heat-radiating area set on the
heat-radiating sheet; and a heat-generating element installed on
the heat-receiving area via a heat spreader made of a
heat-conductive material, wherein the circulating flow passage has
a heat-absorbing flow passage located in a lower face of the heat
spreader of the heat-receiving area, and a heat-radiating flow
passage located in the heat-radiating area and having a
sufficiently larger length than the flow passage length of the
heat-absorbing flow passage.
2. The liquid cooling system of claim 1, wherein the flow passage
length of the heat-radiating flow passage is 10 or more times the
flow passage length of the heat-absorbing flow passage.
3. The liquid cooling system of claim 1, wherein the heat-absorbing
flow passage has a main heat-absorbing flow passage located
directly below the heat-generating element, and at least one
heat-absorbing U-shaped flow passage adjacent to the main
heat-absorbing flow passage.
4. The liquid cooling system of claim 3, wherein the heat-radiating
flow passage from the heat-absorbing U-shaped flow passage to the
heat-radiating area has a heat-radiating reciprocating flow passage
that reciprocates multiple-times in the heat-radiating area before
returning again to the heat-absorbing area.
5. The liquid cooling system of claim 3, wherein the main
heat-absorbing flow passage is one in an inlet and an outlet, and
is branched into a plurality of flow passages directly below a
heat-generating source.
6. The liquid cooling system of claim 3, wherein the main
heat-absorbing flow passage is connected to an outermost peripheral
heat-radiating flow passage that returns to the outlet hole through
the outermost periphery of the heat-radiating sheet after passing
through the main heat-absorbing flow passage.
7. The liquid cooling system of claim 1, wherein the area of the
heat-radiating sheet is 10 or more times the area of the heat
spreader.
8. The liquid cooling system of claim 1, wherein the inlet hole and
outlet hole of the circulating flow passage are formed as tubular
projections in the heat-radiating sheet, and the discharge port and
suction port of the pump are formed as a discharge port that
communicates with the tubular projection serving as the inlet hole,
and a suction port that communicates with the tubular projection
serving as the outlet hole.
9. The liquid cooling system of claim 1, wherein the pump is a
piezoelectric pump.
10. The liquid cooling system of claim 1, wherein a spacer block is
interposed between the pump and the heat-radiating sheet, and the
spacer block is formed with a liquid injection hole extending to
the circulating flow passage.
11. The liquid cooling system of claim 1, wherein the
heat-generating source is a CPU of a notebook computer, and the
whole liquid cooling system is received inside a main body having a
keyboard.
12. The liquid cooling system of claim 11, wherein the
heat-radiating sheet of the liquid cooling system is provided along
the surface of the keyboard.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of Japanese Patent
Application No. 2007-043879 filed on Feb. 23, 2007, which is hereby
incorporated by reference.
BACKGROUND
[0002] 1. Field of the Disclosure
[0003] The present disclosure relates to a thin liquid cooling
(water cooling) system, and particularly, to a liquid cooling
system that is suitable to be used for a notebook computer.
[0004] 2. Description of the Related Art
[0005] The present applicant is developing a liquid cooling system
that cools a heat-generating source (CPU) of a notebook computer.
In a notebook computer in which the storage space for components is
limited, as can also be seen in Japanese Unexamined Patent
Application Publication Nos. 2000-323880, 2004-6563, 2004-95891,
and the like, a liquid cooling system that is thin as a whole and
has a high unit property is needed.
[0006] However, a conventional liquid cooling system needs tubes in
order to connect elements to one another because a pump, a
heat-absorbing unit, a heat-radiating unit, and the like are
provided independently. Therefore, it lacks in integrity (unit
property), and has a problem in assembling performance. Further,
there is a room for improvement in that the heat-generating source
(CPU) is cooled effectively and heat is distributed (a locally hot
portion is eliminated).
SUMMARY
[0007] Embodiments of the present disclosure may provide a liquid
cooling system that does not need tubes throughout the system, and
may have excellent unit property that all elements are provided on
a heat-radiating sheet. Further, embodiments of the present
disclosure may provide a liquid cooling system capable of
efficiently distributing heat in the heat-radiating sheet, and
making it hard for a local hot portion to be created.
[0008] A liquid cooling system according to the present disclosure
may include: a heat-radiating sheet having a pair of
heat-conductive metal plates that are superimposed on each other,
and having a circulating flow passage between the pair of
heat-conductive metal plates; an inlet hole and an outlet hole
opened to the surface of the heat-radiating sheet and located at
both ends of the circulating flow passage; a pump having a
discharge port and a suction port that communicate with the inlet
hole and the outlet hole, and installed on the heat-radiating
sheet; a heat-receiving area and a heat-radiating area set on the
heat-radiating sheet; and a heat-generating element installed on
the heat-receiving area via a heat spreader made of a
heat-conductive material. The circulating flow passage may have a
heat-absorbing flow passage located in a lower face of the heat
spreader of the heat-receiving area, and a heat-radiating flow
passage located in the heat-radiating area and having a
sufficiently larger length than the flow passage length of the
heat-absorbing flow passage.
[0009] Specifically, the flow passage length of the heat-radiating
flow passage may be 10 or more times the flow passage length of the
heat-absorbing flow passage.
[0010] Preferably, the heat-absorbing flow passage may be provided
with a main heat-absorbing flow passage located directly below the
heat-generating element, and at least one heat-absorbing U-shaped
flow passage adjacent to the main heat-absorbing flow passage. In
one embodiment, the heat-radiating flow passage from the
heat-absorbing U-shaped flow passage to the heat-radiating area may
have a heat-radiating reciprocating flow passage that reciprocates
multiple-times in the heat-radiating area before returning again to
the heat-absorbing area.
[0011] The main heat-absorbing flow passage may be one in an inlet
and an outlet, and may be branched into a plurality of flow
passages directly below a heat-generating source.
[0012] In one embodiment of the main heat-absorbing flow passage,
the main heat-absorbing flow passage may be connected to an
outermost peripheral heat-radiating flow passage that returns to
the outlet hole through the outermost periphery of the
heat-radiating sheet after passing through the main heat-absorbing
flow passage.
[0013] The area of a heat-radiating sheet may specifically be 10 or
more times the area of the heat spreader.
[0014] The inlet hole and outlet hole of the circulating flow
passage may be formed as tubular projections in the heat-radiating
sheet, and the discharge port and suction port of the pump may be
formed as a discharge port that communicates with the tubular
projection serving as the inlet hole, and a suction port that
communicates with the tubular projection serving as the outlet
hole.
[0015] If a piezoelectric pump is used as the pump, the liquid
cooling system may be made small and thin.
[0016] A spacer block may also be interposed between the pump and
the heat-radiating sheet, and the spacer block may be formed with a
liquid injection hole extending to the circulating flow
passage.
[0017] The liquid cooling system of the present disclosure may be
used to cool a CPU of a notebook computer. In this embodiment, the
whole liquid cooling system may be received inside a main body
having a keyboard. It may be advantageous in heat-radiating
performance that the heat-radiating sheet of the liquid cooling
system is provided along the surface of the keyboard.
[0018] The liquid cooling system of the present disclosure may have
a high unit property because the pump, the heat spreader, and the
heat-generating source are all mounted on the heat-radiating sheet.
Further, since the circulating flow passage in the heat-radiating
sheet includes the heat-absorbing flow passage located below the
heat spreader (heat-absorbing area), and the heat-radiating flow
passage located in the heat-radiating area, and the flow passage
length of the heat-radiating flow passage is sufficiently larger
than the flow passage length of the heat-absorbing flow passage,
effective heat radiation and comparatively equal heat distribution
may be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 depicts a plan view showing a liquid cooling system
according to an embodiment of the present disclosure as applied to
a cooling system of a notebook computer;
[0020] FIG. 2 depicts a partially enlarged plan view of the
embodiment shown in FIG. 1;
[0021] FIG. 3 depicts a right side view of the embodiment shown in
FIG. 2;
[0022] FIG. 4 depicts a sectional view taken along the line IV-IV
of the embodiment shown in FIG. 3;
[0023] FIG. 5 depicts an expanded perspective view of a portion of
the embodiment shown in FIG. 2;
[0024] FIG. 6 depicts a plan view of a piezoelectric pump in the
liquid cooling system of the embodiment shown in FIG. 1;
[0025] FIG. 7 depicts a sectional view taken along the line VII-VII
line of the embodiment shown in FIG. 6.
[0026] FIG. 8 depicts a sectional view showing a state in which the
liquid cooling system of the embodiment shown in FIG. 1 is
assembled into a notebook computer;
[0027] FIG. 9 depicts a sectional view corresponding the embodiment
shown in FIG. 4, illustrating an additional configuration of the
flow passage of the heat-radiating sheet, according to another
embodiment of the present disclosure;
[0028] FIG. 10 depicts a sectional view showing the additional
configuration of the flow passage, according to another embodiment
of the present disclosure.
DESCRIPTION OF THE EMBODIMENTS
[0029] FIG. 1 depicts a liquid cooling system 100 according to the
present disclosure. As shown in FIG. 8, the liquid cooling system
100 may be received in a main body 103 having a keyboard 102 of a
notebook computer 101, and may be used to cool a CPU 104 as a
heat-generating source. The liquid cooling system 100 of this
embodiment may be provided completely independently of an LCD
(display) 105 that may be opened and closed with respect to the
main body 103.
[0030] As also shown in FIGS. 2 to 4, the liquid cooling system 100
may have a heat-radiating sheet 10, a piezoelectric pump 20 placed
on the heat-radiating sheet 10, and a heat spreader 40 made of a
heat-conductive metallic material, and the CPU 104 may be placed on
the heat spreader 40. A cover 41 may be located on the CPU 104 (the
CPU 104 may be sandwiched between the heat spreader 40 and the
cover 41), and a spacer 42 may be located between the
heat-radiating sheet 10 and the piezoelectric pump 20. In addition,
although the piezoelectric pump 20, the heat spreader 40, and the
CPU 104 are provided at the back (back of the keyboard 102) of the
heat-radiating sheet 10, FIGS. 1, 2, and 5 depict a liquid cooling
system 100 as seen from the back for convenience of
illustration.
[0031] The heat-radiating sheet 10 may be composed of a pair of
heat-conductive metal plates (brazing sheet) 10U and 10L that are
superimposed on each other, and the one brazing sheet 10L may be
formed with a flow-passage recess 11a that constitutes a
circulating flow passage 11. The depth of the flow-passage recess
11a may be, for example, around 0.2 mm. A brazing sheet may be
formed by bonding brazing materials to the surface and back of a
sheet core made of a metallic material (generally aluminum alloy).
The flow-passage recess 11a may be formed by press working. By
making a pair of brazing sheets abut on each other and heating them
under pressure, brazing materials may be melted and bonded to each
other. Generally, although the brazing plate 10U (10L) may have a
thickness of about 0.4 mm, the material, thickness, and others of
the heat-radiating sheet 10 (brazing sheet) may not matter.
[0032] The whole shape of the circulating flow passage 11 of the
heat-radiating sheet 10 is depicted in FIG. 1. The circulating flow
passage 11 may circulate between an inlet 11b and an outlet 11c
(refer to FIGS. 2 and 5), and an inlet projection (inlet hole) 12
and an outlet projection (outlet hole) 13 that communicate with the
inlet 11b and the outlet 11c that are both ends of the flow-passage
recess 11a may be formed so as to project from the brazing sheet
10U. The inlet projection 12 and the outlet projection 13 may
communicate with (e.g., fit into) a discharge port (hole) 34 and a
suction port (hole) 35 of the piezoelectric pump 20, respectively,
via the spacer 42. More specifically, as shown in FIG. 7, the
spacer 42 may be formed with relay holes 42a and 42b, the inlet
projection 12 and the outlet projection 13 of the heat-radiating
sheet 10 (brazing sheet 10U) may fit into the relay holes 42a and
42b, respectively, and annular projections 42a' and 42b' that are
made to project coaxially with the relay holes 42a and 42b may fit
into the discharge port 34 and suction port 35 of the piezoelectric
pump 20.
[0033] Further, the spacer 42 may be formed with a liquid injection
plug 42c that communicates with a liquid injection hole 14 formed
in the brazing sheet 10U. The spacer 42 may be omitted by providing
the liquid injection plug 42c in other portions. In other words,
the inlet projection 12 and the outlet projection 13 of the
heat-radiating sheet 10 may directly fit on the discharge port 34
and the suction port 35 of the piezoelectric pump 20. The
liquid-tight structure of these fitting portions is not shown. The
fitting portions between the annular projections 42a' and 42b' and
the discharge port 34 and suction port 35 of the piezoelectric pump
20 may be connected via O rings. In this case, more reliable
sealing performance may be obtained.
[0034] Although the configuration of the pump (piezoelectric pump)
20 does not matter in the present disclosure, the piezoelectric
pump 20 of the embodiment will be described with reference to FIGS.
6 and 7. The piezoelectric pump 20 may have a lower housing 21 and
an upper housing 22 sequentially from below.
[0035] The discharge port 34 and the suction port 35 may be bored
in the lower housing 21 so as to be orthogonal to a plate thickness
plane of the housing and parallel to each other. A piezoelectric
vibrator (diaphragm) 28 may be liquid-tightly sandwiched and
supported between the upper housing 21 and the lower housing 22 via
the O ring 29, and a pump chamber P may be formed between the
piezoelectric vibrator 28 and the lower housing 21. An atmospheric
chamber A may be formed between the piezoelectric vibrator 28 and
the upper housing 22.
[0036] The piezoelectric vibrator 28 may be a unimorph vibrator
having a central shim 28a, and a piezoelectric body 28b may be
stacked on one (upper face of FIG. 7) of the surface and back of
the shim 28a. The shim 28a may face the pump chamber P and contacts
liquid. The shim 28a may be made of a conductive metallic thin
plate material, for example, a metallic thin plate having a
thickness of about 50 to 300 .mu.m and formed of stainless steel, a
42 alloy, etc. The piezoelectric body 28b may be made of, for
example, PZT (Pb(Zr, Ti)O.sub.3) having a thickness of about 300
.mu.m, and may be subjected to polarizing treatment in the
direction of the surface and back thereof.
[0037] The discharge port 34 and suction port 35 of the lower
housing 21 may be respectively provided with check valves
(umbrella) 32 and 33. The check valve 32 may be a suction-side
check valve that allows flow of fluid from the inlet port 35 to the
pump chamber P, and may not allow flow of the fluid in a direction
reverse thereto, and the check valve 33 may be a discharge-side
check valve that allows flow of the fluid from the pump chamber P
to the outlet port 34, and may not allow flow of the fluid in a
direction reverse thereto.
[0038] The check valves 32 and 33 may have the same form, and may
be constructed by mounting umbrellas 32b and 33b made of an elastic
material on perforated substrates 32a and 33a bonded and fixed to
flow passages.
[0039] In the piezoelectric pump 20, if the piezoelectric vibrator
28 elastically deforms (e.g., vibrates) normally and/or reversely,
the suction-side check valve 32 may be opened and the
discharge-side check valve 33 may be closed, in a stroke where the
volume of the pump chamber P increases. Therefore, liquid may flow
into the pump chamber P from the suction port 35 (outlet projection
13 of the heat-radiating sheet 10). On the other hand, in a stroke
where the volume of the pump chamber P reduces, the discharge-side
check valve 33 may be opened and the suction-side check valve 32
may be closed. Therefore, the liquid may flow out of the pump
chamber P into the discharge port 34 (inlet projection 12 of the
heat-radiating sheet 10). Accordingly, a pumping action may be
obtained by making the piezoelectric vibrator 28 continuously
elastically deform (e.g., vibrate) normally and/or reversely, and
liquid may flow into the outlet 11c from the inlet 11b of the
circulating flow passage 11 of the heat-radiating sheet 10. In
addition, in one embodiment, FIG. 7 shows that the piezoelectric
pump 20 may be disposed on the heat-radiating sheet 10 for the
purpose description. However, in another embodiment, with the
heat-radiating sheet 10 facing upward, the piezoelectric pump 20
may be installed at the back of the heat-radiating sheet, e.g., at
the face of the heat-radiating sheet 10 opposite to the keyboard
102 of the personal computer 101.
[0040] In the surface of the heat-radiating sheet 10, a portion
where the heat spreader 40 (cover 41) may be installed is a
heat-receiving area, and an area excluding the heat spreader 40
(cover 41) and the spacer 42 (piezoelectric pump 20) may be a
heat-radiating area. The whole area of the heat-radiating sheet 10
may be set to 10 or more times (about 17 times in this embodiment)
the area of the heat spreader 40. Further, the total flow passage
length of the circulating flow passage 11 in a heat-absorbing flow
passage located in the lower face of the heat spreader 40 may be
set to be sufficiently larger (10 or more times (about 20 times in
this embodiment)) than the total flow passage length of the
circulating flow passage 11 in a heat-radiating flow passage
located in the heat-radiating area.
[0041] In the liquid cooling system 100 having the above-mentioned
configuration, the heat spreader 40 (CPU 104) and the pump 20 may
be mounted on the heat-radiating sheet 10. Thus, all circulating
flow passages may be formed without using a flexible tube.
[0042] The flow in the circulating flow passage 11 of this
embodiment that returns to the suction port 35 (the outlet
projection 13 or outlet 11c) out of the discharge port 34 (the
inlet projection 12, the inlet 11b) of the piezoelectric pump 20
may be as follows when being sequentially traced by reference
numerals 1f to 38f given to the inside of the circulating flow
passage 11 as depicted in FIG. 1. After the circulating flow
passage 11 that goes straight along heat-radiating straight flow
passages 1f and 2f from the inlet 11b is folded back in a U-shape
in a heat-radiating U-shaped flow passage 3f, and goes straight
along a heat-radiating straight flow passage 4f, the circulating
flow passage may go into the lower face of the heat spreader 40
(heat-absorbing area), and may be folded back in a heat-absorbing
U-shaped flow passage 5f. When passing through the heat-absorbing
U-shaped flow passage 5f, the heat of the heat spreader 40 (CPU
104) may be primarily absorbed by the liquid passing through the
flow passage.
[0043] After the circulating flow passage 11 comes out of the lower
face of the heat spreader 40, the circulating flow passage may go
straight along the heat-radiating straight flow passage 6f, may
then be folded back in a heat-radiating U-shaped flow passage 7f,
and may then be folded back in a heat-radiating U-shaped flow
passage 9f without going into the flow passage directly below the
heat spreader 40. Next, after the circulating flow passage goes
straight along a heat-radiating straight flow passage 10f, the
circulating flow passage may go round largely outward in
heat-radiating right-angled flow passages 11f and 12f, may then be
folded back in a heat-radiating straight flow passage 13f, and may
then be folded back in a heat-radiating U-shaped flow passage 14f.
In this example, the circulating flow passage may still reciprocate
in the heat-radiating area without going into the flow passage
directly below the heat spreader 40. Moreover, after the
circulating flow passage goes straight along a heat-radiating
straight flow passage 15f, is folded back in a heat-radiating
U-shaped flow passage 16f, and goes straight along a heat-radiating
straight flow passage 17f, the circulating flow passage may lead to
the heat-absorbing area directly below the heat spreader 40. As
described above, the heat-radiating flow passage that has led to
the heat-radiating area from the heat-absorbing U-shaped flow
passage 5f may reciprocate multiple times in the heat-radiating
area before it returns again to the heat spreader 40
(heat-absorbing area), and during this time, the liquid that has
absorbed heat and risen in temperature by the heat spreader 40 (CPU
104) may be sufficiently cooled.
[0044] The circulating flow passage 11 that has led to the
heat-absorbing area may go out to the heat-radiating area after it
is folded back in the heat-absorbing U-shaped flow passage 18f and
absorbs heat. After the circulating flow passage goes out to the
heat-radiating area, the circulating flow passage may go straight
along the heat-radiating straight flow passage 19f, may be folded
back in a heat-radiating U-shaped flow passage 20f, may go straight
along a heat-radiating straight flow passage 21f, may be folded
back in a heat-radiating U-shaped flow passage 22f, may go straight
along a heat-radiating straight flow passage 23f, and may be folded
back in a heat-radiating U-shaped flow passage 24f, and may go
straight along a heat-radiating straight flow passage 25f. During
this time, the circulating flow passage rarely goes into the
heat-absorbing area directly below the heat spreader 40. That is,
the heat-radiating flow passage that has led to the heat-radiating
area from the heat-absorbing U-shaped flow passage 18f may
reciprocate multiple times in the heat-radiating area before it
returns again to the heat spreader 40 (heat-absorbing area).
Similarly, the liquid that has absorbed head and has risen in
temperature by the heat spreader 40 (CPU 104) may be sufficiently
cooled by a plurality of times of reciprocation in the
heat-radiating area.
[0045] The circulating flow passage 11 that goes straight along a
heat-radiating straight flow passage 25f may go again into the flow
passage under the heat spreader 40 in a heat-absorbing inlet 26f.
The flow passage that leads to a heat-absorbing outlet 28f via a
branching flow passage 27f from the heat-absorbing inlet 26f may be
a main heat-absorbing flow passage located directly below the CPU
104 on the heat spreader 40. This main heat-absorbing flow passage
may be located between the heat-absorbing U-shaped flow passages 5f
and 18f. The branching flow passage 27f may be a flow passage that
branches (e.g., widens the total flow passage area) one flow
passage in the heat-absorbing inlet 26f and the heat-absorbing
outlet 28f into a plurality of flow passages directly below the CPU
104, may reduce liquid velocity below the CPU 104, and may
effectively absorb the generated heat of the CPU 104.
[0046] The circulating flow passage 11 that comes out of the flow
passage directly below the heat spreader 40 (CPU 104) may lead to
an outer peripheral flow passage 34f from an outer peripheral flow
passage 29f passing through the outermost periphery of the
heat-radiating sheet 10. Effective cooling may be attained as the
liquid that has passed through the flow passage directly below the
CPU 104 and has risen to a highest temperature passes through the
outermost periphery of the heat-radiating sheet 10, e.g., a portion
having a larger temperature difference with respect to the outside
air. After the circulating flow passage is folded back inward in a
heat-radiating U-shaped flow passage 34f, the circulating flow
passage may go straight along a heat-radiating straight flow
passage 35f, may be folded back in a heat-radiating U-shaped flow
passage 36f, may go straight along heat-radiating straight flow
passages 37f and 38f, and may return to the suction port 35 (outlet
projection 13 or outlet 11c).
[0047] FIGS. 9 and 10 depict other examples in which the
circulating flow passage 11 of the heat-radiating sheet 10 may be
formed. FIG. 9 depicts an embodiment where flow-passage recesses
11a may be respectively formed in facing surfaces between the
brazing sheets 10U and 10L by stamping, and FIG. 10 depicts an
embodiment where a flow-passage recess 11a may be similarly formed
only in one brazing sheet 10L.
[0048] The aspect of the circulating flow passage 11 shown in the
above-mentioned embodiment is exemplary, and may therefore be
changed, altered, or varied. The positions of the heat spreader 40
and pump 20 on the heat-radiating sheet 10 may also be changed,
altered, or varied.
* * * * *