U.S. patent application number 12/939309 was filed with the patent office on 2011-05-12 for heat sink.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Hisao ANZAI.
Application Number | 20110108244 12/939309 |
Document ID | / |
Family ID | 43973274 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110108244 |
Kind Code |
A1 |
ANZAI; Hisao |
May 12, 2011 |
HEAT SINK
Abstract
A heat sink includes a base board, a fin group, heat pipes, and
a radiation plate. The fin group includes a plurality of fins
arranged on the base board at right angles to the base board. Each
of the heat pipes has the shape of the letter "U," is arranged, on
the whole, in parallel with each fin, and conducts heat from the
base board to the radiation plate placed on the fin group. The base
board and the radiation plate are thermally connected to each
fin.
Inventors: |
ANZAI; Hisao; (Kawasaki,
JP) |
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
43973274 |
Appl. No.: |
12/939309 |
Filed: |
November 4, 2010 |
Current U.S.
Class: |
165/104.26 |
Current CPC
Class: |
F28D 15/0275 20130101;
F28D 15/0266 20130101; F28F 3/02 20130101; H01L 23/427 20130101;
H01L 2924/0002 20130101; H01L 23/467 20130101; H01L 2924/0002
20130101; F28F 1/32 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/104.26 |
International
Class: |
F28D 15/04 20060101
F28D015/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2009 |
JP |
2009-257925 |
Claims
1. A heat sink comprising: a base; a fin group including a
plurality of fins arranged on the base at right angles to the base:
at least one U-shaped heat pipe both straight portions of which are
arranged in parallel with the plurality of fins and which conducts
heat from the base to the plurality of fins; and a radiation plate
which is placed on the fin group and which is thermally connected
to the plurality of fins.
2. The heat sink according to claim 1, wherein: notches the shape
of which corresponds to a curve in the heat pipe are cut in part of
the plurality of fins; and the curve in the heat pipe is placed in
the notches.
3. The heat sink according to claim 1, wherein the straight
portions of the heat pipe are arranged at a determined angle with a
longitudinal direction of each fin.
4. The heat sink according to claim 1, wherein: the radiation plate
has a groove corresponding to a straight portion of the heat pipe;
and the straight portion of the heat pipe is fitted into the
groove.
5. The heat sink according to claim 1, wherein: the base has a
groove corresponding to a straight portion of the heat pipe; and
the straight portion of the heat pipe is fitted into the groove.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority of the prior Japanese Patent Application No. 2009-257925,
filed on Nov. 11, 2009, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] The embodiment discussed herein is related to a heat
sink.
BACKGROUND
[0003] Heat sinks for dissipating heat which radiates from heat
generation sources (such as CPUs (Central Processing Units) or
switching elements) of products are known.
[0004] With many products equipped with heat sinks, space for a
heat sink is limited. In addition, for example, there has been an
increase in CPU speed or the switching speed of switching elements,
so the amount of heat which radiates from the heat generation
sources is increasing.
[0005] Accordingly, various attempts to improve heat radiation
efficiency in a limited space are being made.
[0006] A heat pipe for efficiently conducting heat to fins is
included in a heat sink as one of such attempts.
[0007] FIG. 5 illustrates a heat sink including heat pipes.
[0008] A heat sink 90 includes two base plates 91 opposite to each
other and many plate-like fins 92 arranged between the base plates
91 at right angles with surfaces of the base plates 91 opposite to
each other.
[0009] Parallel portions 94 of each U-shaped heat pipe 93
illustrated in FIG. 5 are fitted into penetration holes 95.
Parallel portions 94 of two heat pipes 93 are fitted into one
penetration hole 95 from both sides and the tips of the parallel
portions 94 are touching each other in the middle of the
penetration hole 95.
[0010] Japanese Laid-open Patent Publication No. 11-145354
[0011] With the structure illustrated in FIG. 5, connecting
portions 96 between the two base plates 91 are sticking out of the
main body. However, fins are not arranged around the connecting
portions 96, so heat radiation space around these portions is
useless.
SUMMARY
[0012] According to an aspect of the present invention, there is
provided a heat sink including a base, a fin group having a
plurality of fins arranged on the base at right angles to the base,
at least one U-shaped heat pipe both straight portions of which are
arranged in parallel with the plurality of fins and which conducts
heat from the base to the plurality of fins, and a radiation plate
which is placed on the fin group and which is thermally connected
to the plurality of fins.
[0013] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims.
[0014] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a perspective view of a heat sink according to an
embodiment;
[0016] FIG. 2 is an exploded perspective view of the heat sink;
[0017] FIG. 3 illustrates a modification of the heat sink;
[0018] FIG. 4 illustrates an application of the heat sink; and
[0019] FIG. 5 illustrates a heat sink including heat pipes.
DESCRIPTION OF EMBODIMENT(S)
[0020] An embodiment will now be described in detail with reference
to the accompanying drawings.
[0021] FIG. 1 is a perspective view of a heat sink according to an
embodiment.
[0022] A heat sink (radiator) 1 according to an embodiment includes
a base board (heating plate) 2, a fin group 3, heat pipes 4a and
4b, and a radiation plate 5.
[0023] The base board 2 is rectangular.
[0024] Two grooves 21 and 22 parallel with a side 2a of the base
board 2 are cut in the base board 2 at determined distance from
each other. Part of the heat pipe 4a is touching the groove 21 with
solder therebetween. Part of the heat pipe 4b is touching the
groove 22 with solder therebetween.
[0025] In addition, a surface of the base board 2 opposite to a
surface over which the fin group 3 is arranged is touching a heat
generation source (not illustrated) with a heat conduction member,
such as grease or a thermal sheet, therebetween.
[0026] For example, a semiconductor chip such as a CPU, a switching
element, a resistance element, or a semiconductor package including
them is a heat generation source.
[0027] In addition, the base board 2 is made of copper, aluminum,
or the like.
[0028] If the base board 2 is made of aluminum, a heat pipe (other
than the heat pipes 4a and 4b) may be embedded in the base board 2
for diffusing heat.
[0029] The fin group 3 is arranged over the base board 2 with
solder therebetween.
[0030] The fin group 3 includes a plurality of fins 3a. Each fin 3a
has a platelike shape. The plurality of fins 3a are arranged at
right angles to the base board 2. There is a determined distance
between two adjacent fins 3a and each fin 3a is arranged regularly
so that it will be parallel to the other fins 3a.
[0031] In addition, each fin 3a is arranged so that its
longitudinal direction will be equal to that of the base board
2.
[0032] The length of the fin group 3 (length in the longitudinal
direction of each fin 3a) is longer than its width.
[0033] Each fin 3a is made of aluminum, copper, or the like.
[0034] For example, each fin 3a may have a connecting portion (not
illustrated) for connection to another fin 3a. The fins 3a may be
connected to one another by these connecting portions.
[0035] The heat pipes 4a and 4b are arranged within the fin group
3.
[0036] The radiation plate 5 is placed opposite the base board 2 so
that it will cover most of the top of the fin group 3. That is to
say, the heat sink 1 has a structure (what is called a sandwich
structure) in which the fin group 3 is put between the base board 2
and the radiation plate 5.
[0037] In FIG. 1, the length in the longitudinal direction of the
radiation plate 5 is slightly shorter than the length in the
longitudinal direction of the top of the fin group 3.
[0038] The radiation plate 5, the fin group 3, and the heat pipes
4a and 4b are thermally connected to one another.
[0039] The function of the radiation plate 5 is not only to conduct
heat conducted from the heat pipes 4a and 4b to each fin 3a of the
fin group 3 but also to directly radiate heat conducted from the
heat pipes 4a and 4b into the air.
[0040] The radiation plate 5 is made of copper, aluminum, or the
like.
[0041] If the radiation plate 5 is made of aluminum, a heat pipe
(other than the heat pipes 4a and 4b) may be embedded in the
radiation plate 5 for diffusing heat.
[0042] FIG. 2 is an exploded perspective view of the heat sink.
[0043] Each of the heat pipes 4a and 4b has a main body which has
the shape of the letter "U" and which is made of metal such as
copper. The main body is tubular. The tips of the main body having
the shape of the letter "U" are closed and the main body is
airtight. Wicks each having porous substances or narrow grooves are
arranged on an internal wall of the main body.
[0044] A small amount of liquid (working liquid) is sealed within
the main body. Pure water, ammonia, a chlorofluorocarbon-replacing
material, or the like is used as a working liquid.
[0045] There is no special limitation to the shape of a cross
section of each of the heat pipes 4a and 4b. The shape of a cross
section of each of the heat pipes 4a and 4b may be round, oval, or
flat. If the shape of a cross section of each of the heat pipes 4a
and 4b is flat, it is easy to work them. In addition, if the shape
of a cross section of each of the heat pipes 4a and 4b is flat, the
base board 2 and the radiation plate 5 can be made thinner. As a
result, the heat sink 1 can be miniaturized.
[0046] By the way, notches 31 are cut in part of the plurality of
fins 3a included in the fin group 3 according to the shape of a
curve 41 in the heat pipe 4a and a curve 42 in the heat pipe 4b. In
other words, the length in the longitudinal direction of the fins
3a in which the notches 31 are cut is shorter than the length in
the longitudinal direction of the other fins 3a.
[0047] As illustrated in FIG. 1, the heat pipes 4a and 4b are
arranged so that the curves 41 and 42 will be at right angles to
the base board 2 as viewed from the side of the initial point of an
arrow A drawn along the side 2a (as viewed from the front). That is
to say, the curve 41 in the heat pipe 4a and the curve 42 in the
heat pipe 4b are arranged in parallel with each fin 3a.
[0048] In addition, the curve 41 in the heat pipe 4a and the curve
42 in the heat pipe 4b are arranged between fins 3a. There is a
space of about 2 millimeters between the curve 41 in the heat pipe
4a and the fin 3a adjacent thereto and between the curve 42 in the
heat pipe 4b and the fin 3a adjacent thereto so that air will
flow.
[0049] Straight portions 43 and 45 of the heat pipe 4a and straight
portions 44 and 46 of the heat pipe 4b are arranged in the
longitudinal direction of each fin 3a.
[0050] When the above heat sink 1 is assembled, the tips of the
straight portions 43 and 45 of the heat pipe 4a are placed at end
portions 32 in the longitudinal direction of the fins 3a in which
the notches 31 are cut.
[0051] Furthermore, the tips of the straight portions 44 and 46 of
the heat pipe 4b are placed at end portions 32 in the longitudinal
direction of the fins 3a in which the notches 31 are cut.
[0052] A substantial reduction in the number of fins 3a which
results from cutting the notches 31 will now be described.
[0053] For example, it is assumed that the thickness of each fin 3a
is 0.5 mm, that the fins 3a are arranged at intervals of 2 mm, that
the diameter of the heat pipes 4a and 4b is 6 mm, that the radius
of the curvature of the curves 41 and 42 is 15 mm, and that the
length of the straight portions 43, 44, 45, and 46 is 60 mm.
[0054] As stated above, the internal wall of each heat pipe has a
minute structure, so there is a limit to the radius of the
curvature. If the diameter of the heat pipes 4a and 4b is 6 mm,
then the limit of the radius of the curvature is about 15 mm. The
radius of the curvature is measured with the center line of each
heat pipe as reference.
[0055] The number of the fins 3a in which the notches 31 are cut
depends on the diameter of the heat pipes 4a and 4b.
[0056] If the heat pipes 4a and 4b are arranged within the fin
group 3, the number of the fins 3a in which the notches 31 are cut
is 5 (=10 mm (=6 mm+2 mm (space).times.2)/2 mm) for each of the
heat pipes 4a and 4b. Therefore, the total number of the fins 3a in
which the notches 31 are cut is 10.
[0057] In addition, the area of the notches 31 depends on the
radius of the curvature of the curves 41 and 42.
[0058] In this example, a notch 31 accounts for about 25 percent of
the area of an entire fin 3a.
[0059] Accordingly, a reduction in the number of fins 3a in the
entire fin group 3 which results from cutting the notches 31 in the
part of the plurality of fins 3a is 2.5 (=10.times.25(%)).
[0060] In FIG. 5, on the other hand, the width of the curve 96 is
18 mm (=15 mm (radius of curvature)+6 mm/2). Accordingly, about 7
fins (=18 mm/(2 mm (interval)+0.5 mm (thickness))) cannot be
mounted on one side.
[0061] That is to say, with the conventional heat sink 7 fins
cannot be mounted. With the heat sink according to the present
embodiment, however, a reduction in the number of fins is only
2.5.
[0062] If the number of heat pipes increases, this difference
becomes smaller. However, usually the number of heat pipes used in
a heat sink is two.
[0063] The mechanism of heat radiation by the heat sink 1 will now
be described.
[0064] When the heat sink 1 is used, the heat sink 1 is placed so
that a heat generation source will be touching a nearly central
portion of the base board 2.
[0065] First heat is conducted from the heat generation source to
the base board 2.
[0066] Part of the heat conducted to the base board 2 is conducted
from the groove 21 to the straight portion 45 of the heat pipe 4a.
In addition, another part of the heat conducted to the base board 2
is conducted from the groove 22 to the straight portion 46 of the
heat pipe 4b. Still another part of the heat conducted to the base
board 2 is conducted directly to the fins 3a.
[0067] When heat is conducted to the working liquid in the heat
pipes 4a and 4b, the temperature of the working liquid rises and
the working liquid vaporizes into vapor. The vapor flows through
the curves 41 and 42 and to the straight portion 43 of the heat
pipe 4a and the straight portion 44 of the heat pipe 4b.
[0068] The vapor which flows to the straight portion 43 of the heat
pipe 4a and the straight portion 44 of the heat pipe 4b is then
cooled by the fin group (low temperature member) 3 and is
liquefied. To be concrete, heat is conducted from the vapor which
flows to the straight portion 43 of the heat pipe 4a and the
straight portion 44 of the heat pipe 4b to the radiation plate 5
connected to the straight portions 43 and 44 with solder
therebetween and the fins 3a. As a result, the vapor condenses into
the working liquid.
[0069] The working liquid flows along the internal walls and
returns to the straight portions 45 and 46 by capillary action.
[0070] An example of a method for fabricating the heat sink 1 will
now be described.
[0071] First the base board 2 in which the grooves 21 and 22 are
cut is prepared.
[0072] In addition, the fins 3a are connected to one another by,
for example, the above connecting portions to form the fin group
3.
[0073] Cream solder is then applied to the base board 2 and the
radiation plate 5 and the base board 2 and the radiation plate 5
are bonded to the fin group 3. At this time cream solder is also
applied to the grooves 21 and 22 in the base board 2 and grooves 51
and 52 in the radiation plate 5.
[0074] The straight portion 45 of the heat pipe 4a is then fitted
into the groove 21 in the base board 2 so that the end of the
straight portion 45 will reach the far side of the groove 21. The
straight portion 43 of the heat pipe 4a is fitted into the groove
51 in the radiation plate 5 so that the end of the straight portion
43 will reach the far side of the groove 51. In addition, the
straight portion 46 of the heat pipe 4b is fitted into the groove
in the base board 2 so that the end of the straight portion 46 will
reach the far side of the groove 22. The straight portion 44 of the
heat pipe 4b is fitted into the groove 52 in the radiation plate 5
so that the end of the straight portion 44 will reach the far side
of the groove 52.
[0075] In this state, the base board 2 and the radiation plate 5
are fixed by jigs (not illustrated) so that their positions will
not shift.
[0076] After that, these members are put into a furnace to melt
cream solder. Solder hardens, so the base board 2, the fin group 3,
the heat pipes 4a and 4b, and the radiation plate 5 adhere to one
another.
[0077] By doing so, the heat sink 1 can be fabricated.
[0078] With the heat sink 1, as has been described, the heat pipes
4a and 4b are arranged, on the whole, in parallel with the fins 3a.
As a result, the fin mount efficiency of the heat sink 1 rises and
heat radiation efficiency can be improved.
[0079] In addition, the notches 31 are cut in the fins 3a and the
curve 41 in the heat pipe 4a and the curve 42 in the heat pipe 4b
are arranged within the fin group 3.
[0080] As a result, the heat pipes 4a and 4b can be embedded in the
fin group 3 by an easy working. Accordingly, the heat sink 1 can be
fabricated easily.
[0081] To be concrete, for example, heat pipes are inserted at
right angles to fins. In order to arrange fins around curves in the
heat pipes, it is necessary to make holes in fins according to the
shape of the curves in the heat pipes. In this case, however, it is
necessary to make the holes different in shape in the fins.
[0082] With the heat sink 1, on the other hand, two kinds of fins
3a different in length are prepared. In addition, each fin 3a is
rectangular, so it is worked easily.
[0083] Furthermore, the curve 41 in the heat pipe 4a and the curve
42 in the heat pipe 4b are embedded in the fin group 3, so the heat
sink 1 can be miniaturized. For example, if the heat sink 1 is
placed in a unit, space can be saved.
[0084] Moreover, by arranging the heat pipes 4a and 4b, on the
whole, in parallel with the fins 3a, the number of the fins 3a in
which the notches 31 are cut and the area of the notches 31 can be
reduced. As a result, heat radiation efficiency can be
improved.
[0085] In addition, the grooves 21 and 22 are cut in the base board
2. The straight portion 45 of the heat pipe 4a is fitted into the
groove 21 and the straight portion 46 of the heat pipe 4b is fitted
into the groove 22. The grooves 51 and 52 are cut in the radiation
plate 5. The straight portion 43 of the heat pipe 4a is fitted into
the groove 51 and the straight portion 44 of the heat pipe 4b is
fitted into the groove 52.
[0086] As a result, there is no need to work the straight portions
43 and 45 of the heat pipe 4a and the straight portions 44 and 46
of the heat pipe 4b. The heat sink 1 can be fabricated easily.
Furthermore, when the heat sink 1 is fabricated, the grooves 21 and
22 in the base board 2 and the grooves 51 and 52 in the radiation
plate 5 also function as guides for inserting the heat pipes 4a and
4b.
[0087] In this embodiment each fin 3a is arranged in the
longitudinal direction of the base board 2. However, each fin 3a
may be arranged in the lateral direction of the base board 2. In
this case, the heat pipes 4a and 4b are also arranged in parallel
with each fin 3a, that is to say, in the lateral direction of the
base board 2.
[0088] In this embodiment the number of heat pipes is two. However,
the number of heat pipes is not limited to two. The number of heat
pipes may be one or three or more.
[0089] Furthermore, in this embodiment the heat pipes 4a and 4b are
arranged so that the curves 41 and 42 will be at right angles to
the base board 2 as viewed from the front. However, the heat pipes
4a and 4b may be arranged so that the curves 41 and 42 will form a
determined angle other than 90.degree. with the base board 2 as
viewed from the front.
[0090] Moreover, in this embodiment the straight portions 43 and 45
of the heat pipe 4a and the straight portions 44 and 46 of the heat
pipe 4b are arranged in parallel with each fin 3a. From the
viewpoint of heat diffusion, however, they may be arranged at an
angle with each fin 3a.
(Modification)
[0091] FIG. 3 illustrates a modification of the heat sink.
[0092] With a heat sink la a straight portion 43 of a heat pipe 4a
and a straight portion 44 of a heat pipe 4b extend outwardly. As a
result, heat diffusion efficiency improves. Each of the straight
portions 43 and 44 is arranged at a determined angle with the
longitudinal direction of each fin 3a. As illustrated in FIG. 3, a
groove is not cut in a radiation plate 5a. The straight portions 43
and 44 are touching the top of the radiation plate 5a. The straight
portions 43 and 44 may be soldered further to the radiation plate
5a.
[0093] In this embodiment, the grooves 21 and 22 are cut in the
base board 2 and the grooves 51 and 52 are cut in the radiation
plate 5. The straight portions 43 and 45 of the heat pipe 4a are
fitted into the grooves 51 and 21, respectively, and the straight
portions 44 and 46 of the heat pipe 4b are fitted into the grooves
52 and 22 respectively. For example, however, the heat pipes 4a and
4b may be embedded in penetration holes made in the base board 2
and the radiation plate 5. In this case, the heat pipes 4a and 4b
may be soldered to the penetration holes.
[0094] In addition, it is not necessary to cut a groove or a
penetration hole especially in the radiation plate 5. An effect can
be obtained only by soldering the straight portions 43 and 44 to
the radiation plate 5.
[0095] Furthermore, in this embodiment the whole of the curve 41 in
the heat pipe 4a and the curve 42 in the heat pipe 4b is arranged
within the fin group 3. However, part or the whole of the curves 41
and 42 may be arranged outside the fin group 3. By doing so, the
area of the notches 31 cut in the fins 3a decreases.
(Application)
[0096] An example in which a fan is used for radiating heat will
now be described.
[0097] FIG. 4 illustrates an application of the heat sink.
[0098] In the application illustrated in FIG. 4, a printed board or
a heat generation element is not illustrated.
[0099] A cooling system 10 illustrated in FIG. 4 includes a heat
sink 1, an enclosure base 11, and a fan 12.
[0100] The enclosure base 11 includes a rectangular platelike flat
portion 111 and a side portion 112 which bends at right angles from
one end of the flat portion 111.
[0101] The fan 12 is installed on the side portion 112. In order to
send a uniform amount of air, there is a certain space between the
heat sink 1 and the fan 12.
[0102] The fan 12 takes in air from air intakes (openings) 113
formed in the side portion 112, and sends it in the direction of
fins 3a of the heat sink 1. A space between adjacent fins 3a forms
a ventilation flue. Air sent from the fan 12 flows along the
ventilation flue and flows out from a side of a fin group 3
opposite the fan 12.
[0103] Even if part or the whole of curves 41 and 42 is arranged
outside the fin group 3 by the use of the space between the fan 12
and the heat sink 1 of the cooling system 10, the part or the whole
of the curves 41 and 42 is housed in the space between the heat
sink 1 and the fan 12. Therefore, it is possible to cut no notches
31 or reduce the area of notches 31.
[0104] According to the heat sink disclosed, heat radiation
efficiency can be improved in a limited space.
[0105] All examples and conditional language recited herein are
intended for pedagogical purposes to aid the reader in
understanding the invention and the concepts contributed by the
inventor to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions, nor does the organization of such examples in the
specification relate to a showing of the superiority and
inferiority of the invention. Although the embodiment(s) of the
present invention has(have) been described in detail, it should be
understood that various changes, substitutions, and alterations
could be made hereto without departing from the spirit and scope of
the invention.
* * * * *