U.S. patent application number 11/994501 was filed with the patent office on 2009-05-07 for heat sink.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Seiji Haga, Shigetoshi Ippoushi, Toru Kimura, Akihiro Murahashi, Tetsuro Ogushi, Hideo Okayama, Nobuaki Uehara, Hiroshi Yamabuchi, Akira Yamada.
Application Number | 20090114372 11/994501 |
Document ID | / |
Family ID | 37864662 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090114372 |
Kind Code |
A1 |
Ippoushi; Shigetoshi ; et
al. |
May 7, 2009 |
HEAT SINK
Abstract
A heat sink includes a heat-transfer container incorporating a
flow path through which a cooling fluid flows, for cooling a
heating element in contact with the heat-transfer container The
flow path includes a first cross-sectional portion that becomes
narrower as the distance between a given point in the flow path and
a side of the heat-transfer container which makes contact with the
heating element becomes longer in a direction perpendicular to the
direction in which the cooling fluid flows, and a second
cross-sectional portion that is approximately constant in the
direction perpendicular to the direction in which the cooling fluid
flows. The first cross-sectional portion and the second
cross-sectional portion alternately continue in the direction in
which the cooling fluid flows causing a three-dimensional flow so
the heat-transfer properties are enhanced with a simplified
structure.
Inventors: |
Ippoushi; Shigetoshi;
(Tokyo, JP) ; Ogushi; Tetsuro; (Tokyo, JP)
; Haga; Seiji; (Tokyo, JP) ; Kimura; Toru;
(Tokyo, JP) ; Yamada; Akira; (Tokyo, JP) ;
Yamabuchi; Hiroshi; (Tokyo, JP) ; Murahashi;
Akihiro; (Tokyo, JP) ; Okayama; Hideo; (Tokyo,
JP) ; Uehara; Nobuaki; (Tokyo, JP) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW, SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
37864662 |
Appl. No.: |
11/994501 |
Filed: |
September 13, 2005 |
PCT Filed: |
September 13, 2005 |
PCT NO: |
PCT/JP2005/016796 |
371 Date: |
January 3, 2008 |
Current U.S.
Class: |
165/104.14 ;
165/104.19 |
Current CPC
Class: |
F28F 3/12 20130101; F28F
3/022 20130101; H01L 23/473 20130101; H01L 23/467 20130101; F28F
13/12 20130101; H01L 2924/0002 20130101; H01L 2924/0002 20130101;
H01L 2924/00 20130101 |
Class at
Publication: |
165/104.14 ;
165/104.19 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Claims
1. A heat sink comprising: a heat-transfer container incorporating
a flow path through which a cooling fluid flows; and a heating
element in contact with the heat-transfer container and in the flow
path, wherein the flow path includes a first cross-sectional
portion that becomes narrower as the distance between a given point
in the flow path and a side of the heat-transfer container which
makes contact with the heating element becomes longer in a
direction perpendicular to the direction in which the cooling fluid
flows, and a second cross-sectional portion that is approximately
constant in the direction perpendicular to the direction in which
the cooling fluid flows, and the first cross-sectional portion and
the second cross-sectional portion alternately continue in the
direction in which the cooling fluid flows.
2. The heat sink according to claim 1, wherein the first
cross-sectional portion has a shape including one or more
protrusions located inside the heat-transfer container.
3. The heat sink according to claim 2, wherein the protrusion has a
shape selected from the group consisting of an approximate cone, an
approximate multi-sided pyramid, an approximate sphere, and a
hemisphere.
4. The heat sink according to claim 1, including a fin extending in
the direction in which the cooling fluid flows and located on an
inner surface of the heat-transfer container.
5. The heat sink according to claim 2, including a plurality of the
protrusions on a substrate located in the heat-transfer
container.
6. The heat sink according to claim 5, wherein the substrate is
disposed inside the heat-transfer container divides the flow path
into first and second flow paths, the protrusions are arranged on
both sides of the substrate, and the heat-transfer container has a
first side in contact with the first flow path and a second side in
contact with the second flow path, and the first and second sides
contact respective heating elements.
7. A heat sink comprising: a heat-transfer container having a flow
path through which a cooling fluid flows; and a heating element in
contact with the heat-transfer container and in the flow path,
wherein the heat-transfer container has an opening for bringing the
cooling fluid into direct contact with the heating element, the
flow path includes a first cross-sectional portion that becomes
narrower as distance between a given point in the flow path and a
side of the heat-transfer container which makes contact with the
heating element, becomes longer in a direction perpendicular to the
direction in which the cooling fluid flows, and a second
cross-sectional portion that is approximately constant in the
direction perpendicular to the direction in which the cooling fluid
flows, and the first cross-sectional portion and the second
cross-sectional portion alternately continue in the direction in
which the cooling fluid flows.
8. The heat sink according to claim 7, including a fin extending in
the direction in which the cooling fluid flows and located on a
side of the heating element which makes contact with the cooling
fluid.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat sink having a
heat-radiation structure for cooling a heating element formed with
electronic components or the like, and more particularly to a heat
sink having a heat-radiation structure for carrying out cooling by
use of forced convection.
BACKGROUND ART
[0002] A conventional heat sink is configured in such a way that
the flow of a cooling fluid is stirred by pin-shaped fins so that
the heat-transfer performance (heat radiation) is enhanced in
comparison with a heat-radiation member provided with a continuous
fin (e.g., refer to Patent Document 1).
[0003] [Patent Document 1]
[0004] Japanese Patent Application Laid-Open No. 2004-63898 (Page 6
and FIG. 8)
DISCLOSURE OF THE INVENTION
Problems that the Invention is to Solve
[0005] A conventional heat sink is configured in such a way that
pin-shaped fins are provided in a two-dimensional flow to utilize
the turbulence effect so that the heat-transfer performance is
enhanced; however, in recent years, it has been a problem that the
heat-transfer performance such that an increasing amount of heat
generated in an electronic apparatus is sufficiently radiated
cannot be obtained.
[0006] The present invention has been implemented in order to solve
the foregoing problem of the conventional technique; the objective
of the present invention is to provide a heat sink in which a
three-dimensional flow of a cooling fluid is caused so that the
heat-transfer efficiency is enhanced with a simpler structure.
Means for Solving the Problems
[0007] A heat sink according to the present invention is provided
with a heat-transfer container incorporating a flow path through
which a cooling fluid flows; the heat sink cools a heating element
in contact with the heat-transfer container, by means of the
cooling fluid that flows through the flow path. The flow path
includes a first cross-sectional portion that becomes narrower as
the distance between a given point therein and a side, of the
heat-transfer container, which makes contact with the heating
element becomes longer in a direction perpendicular to the
direction in which the cooling fluid flows and a second
cross-sectional portion that is approximately constant in the
direction perpendicular to the direction in which the cooling fluid
flows; the first cross-sectional portion and the second
cross-sectional portion alternately continue in the direction in
which the cooling fluid 1 flows.
[0008] Moreover, in a heat sink according to the present invention,
the shape of the first cross-sectional portion of the flow path is
formed based on one or more protrusions provided inside the
heat-transfer container.
[0009] Still moreover, in a heat sink according to the present
invention, the protrusion has at least one of the shapes of an
approximate cone, an approximate multi-sided pyramid, an
approximate sphere, and a hemisphere.
[0010] Still moreover, in a heat sink according to the present
invention, a fin extending in the direction in which the cooling
fluid flows is provided on the inner surface of the heat-transfer
container.
[0011] Furthermore, in a heat sink according to the present
invention, the protrusions are arranged in plurality on a substrate
provided in the heat-transfer container.
[0012] Still furthermore, in a heat sink according to the present
invention, the substrate is disposed inside the heat-transfer
container in such a way as to divide the flow path into two flow
paths, the protrusions are arranged on both sides of the substrate,
and the heat-transfer container is configured in such a way that a
side thereof in contact with one of the divided flow paths and a
side thereof in contact with the other of the divided flow paths
make contact with respective heating elements.
[0013] Moreover, a heat sink according to the present invention is
provided with a heat-transfer container having a flow path through
which a cooling fluid flows; the heat sink cools a heating element
in contact with the heat-transfer container, by means of the
cooling fluid that flows through the flow path. The heat-transfer
container has an opening for bringing the cooling fluid into direct
contact with the heating element; the flow path includes a first
cross-sectional portion that becomes narrower as the distance
between a given point therein and a side, of the heat-transfer
container, which makes contact with the heating element becomes
longer in a direction perpendicular to the direction in which the
cooling fluid flows and a second cross-sectional portion that is
approximately constant in the direction perpendicular to the
direction in which the cooling fluid flows; the first
cross-sectional portion and the second cross-sectional portion
alternately continue in the direction in which the cooling fluid 1
flows.
[0014] Still moreover, in a heat sink according to the present
invention, a fin extending in the direction in which the cooling
fluid flows is provided on a side, of the heating element, which
makes contact with the cooling fluid.
Advantage of the Invention
[0015] A heat sink according to the present invention is configured
in such a way that the flow path thereof includes a first
cross-sectional portion that becomes narrower as the distance
between a given point therein and a side, of the heat-transfer
container, which makes contact with the heating element becomes
longer in a direction perpendicular to the direction in which the
cooling fluid flows and a second cross-sectional portion that is
approximately constant in the direction perpendicular to the
direction in which the cooling fluid flows, and the first
cross-sectional portion and the second cross-sectional portion
alternately continue in the direction in which the cooling fluid 1
flows; therefore, a three-dimensional flow of the cooling fluid is
caused, whereby the heat-transfer properties can be enhanced with a
simplified structure.
[0016] Moreover, in a heat sink according to the present invention,
the shape of the first cross-sectional portion of the flow path is
formed based on one or more protrusions provided inside the
heat-transfer container; therefore, the three-dimensional flow of
the cooling fluid is caused with a simplified structure, whereby
the heat-transfer properties can be enhanced.
[0017] Still moreover, in a heat sink according to the present
invention, a fin extending in the direction in which the cooling
fluid flows is provided on the inner surface of the heat-transfer
container; therefore, heat can more effectively be radiated.
[0018] Furthermore, in a heat sink according to the present
invention, the protrusions are arranged in plurality on the
substrate provided in the heat-transfer container; therefore, by
inserting the substrate into the heat-transfer container, the
protrusions can simply be arranged inside the heat-transfer
container.
[0019] Still furthermore, in a heat sink according to the present
invention, the substrate is disposed inside the heat-transfer
container in such a way as to divide the flow path into two flow
paths, the protrusions are arranged on both sides of the substrate,
and the heat-transfer container is configured in such a way that a
side thereof in contact with one of the divided flow paths and a
side thereof in contact with the other of the divided flow paths
make contact with respective heating elements; therefore, a
plurality of heating elements can concurrently and efficiently be
cooled.
[0020] Moreover, a heat sink according to the present invention is
provided with a heat-transfer container having a flow path through
which a cooling fluid flows; the heat sink cools a heating element
in contact with the heat-transfer container, by means of the
cooling fluid that flows through the flow path. The heat sink is
configured in such a way that the heat-transfer container has an
opening for bringing the cooling fluid into direct contact with the
heating element; the flow path includes a first cross-sectional
portion that becomes narrower as the distance between a given point
therein and a side, of the heat-transfer container, which makes
contact with the heating element becomes longer in a direction
perpendicular to the direction in which the cooling fluid flows and
a second cross-sectional portion that is approximately constant in
the direction perpendicular to the direction in which the cooling
fluid flows; and the first cross-sectional portion and the second
cross-sectional portion alternately continue in the direction in
which the cooling fluid 1 flows. As a result, because the heating
element is brought into direct contact with the cooling fluid so as
to be cooled, cooling can more efficiently be carried out.
[0021] Still moreover, in a heat sink according to the present
invention, a fin extending in the direction in which the cooling
fluid flows is provided on a side, of the heating element, which
makes contact with the cooling fluid; cooling can further
efficiently be carried out.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is an exploded perspective view symbolically
illustrating a heat sink according to Embodiment 1;
[0023] FIG. 2 is a cross-sectional view symbolically illustrating a
heat sink according to Embodiment 1;
[0024] FIG. 3 is an exploded perspective view symbolically
illustrating a heat sink that is a variant example of Embodiment
1;
[0025] FIG. 4 is an exploded perspective view symbolically
illustrating a heat sink that is another variant example of
Embodiment 1;
[0026] FIG. 5 is a perspective view symbolically illustrating
protrusions for a heat sink that is another variant example of
Embodiment 1;
[0027] FIG. 6 is a cross-sectional view symbolically illustrating a
heat sink that is another variant example of Embodiment 1;
[0028] FIG. 7 is a cross-sectional view symbolically illustrating a
heat sink that is another variant example of Embodiment 1;
[0029] FIG. 8 is an exploded perspective view symbolically
illustrating a heat sink that is another variant example of
Embodiment 1;
[0030] FIG. 9 is an exploded perspective view symbolically
illustrating a heat sink according to Embodiment 2;
[0031] FIG. 10 is a cross-sectional view symbolically illustrating
a heat sink that is a variant example of Embodiment 2;
[0032] FIG. 11 is a perspective view symbolically illustrating a
heat sink according to Embodiment 3; and
[0033] FIG. 12 is a flow path cross-sectional view symbolically
illustrating a heat sink that is a variant example of Embodiment
3.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
[0034] FIG. 1 is an exploded perspective view for explaining a heat
sink according to Embodiment 1 of the present invention.
[0035] FIG. 2 is a cross-sectional view of the heat sink in FIG. 1;
FIGS. 1(a) and 1(b) are a transverse cross-sectional view and a
longitudinal cross-sectional view, respectively. FIG. 3 is an
exploded perspective view for explaining a variant example of
Embodiment 1; FIG. 4 is a perspective view for explaining another
variant example of Embodiment 1. In addition, in the figures
including those for other embodiments, the same reference
characters denote the same or equivalent portions.
[0036] In FIGS. 1 and 2, a heating element 6, such as an electronic
component, which is the cooling subject of a heat sink is disposed
thermally coupled with a base 8 of a heat-transfer container 3. The
base 8 is molded integrally with four sidewalls 9. In the
heat-transfer container 3, a cooling-fluid inlet 1 and a
cooling-fluid outlet 4 are provided; a flow path 2 is formed inside
the heat-transfer container 3. The cooling-fluid inlet 1 and the
cooling-fluid outlet 4 are connected to a fluid-flow pipe 15. A lid
10 is fixed to one side, of the heat-transfer container 3, which
faces the base 8 thereof; on the lid 10, conical (approximately
cone-shaped) protrusions 7 exposed toward the inside of the
heat-transfer container 3 are provided in a predetermined
arrangement. The protrusions 7 play a role of facilitating
turbulence in a cooling fluid 11 that flows inside the
heat-transfer container 3. The cooling-fluid inlet 1, the
cooling-fluid outlet 4, and the heat-transfer container 3 form a
continuous fluid-flow path 5.
[0037] The cross sections, of the flow paths 2, in a direction
perpendicular to the direction in which the cooling fluid 11 as a
refrigerant flows are arranged in such a way that first
cross-sectional portions each of which, due to the existence of the
protrusion 7, becomes narrower as a given viewing point in the
first cross-sectional portion moves away from the base 8, on which
the heating element 6 is mounted, toward the lid 10 and second
cross-sectional portions each of which, i.e., the width of the flow
path 2, due to no existence of the protrusion 7, is constant even
though a given viewing point in the second cross-sectional portion
moves away from the base 8, on which the heating element 6 is
mounted, toward the lid 10 alternately continue in the direction in
which the cooling fluid 11 flows. As a result, the flow path 2 is
configured in such a way that approximately trapezoidal flow paths
the width of each of which gradually decreases, in the height
direction (thickness direction) of the heat-transfer container 3,
from the vicinity of the base 8 on which the heating element 6 is
mounted and flow paths the width of each of which is approximately
constant in the height direction of the heat-transfer container 3
are sequentially coupled in the direction in which the cooling
fluid 11 flows. The heat-transfer container serves as a main body
of the heat sink.
[0038] The heat sink is a heat-radiation structure configured in
such a way that the cooling-fluid inlet 1 for inputting the
low-temperature cooling fluid 11, the heat-transfer container 3
with which the heating element 6 is thermally coupled and inside of
which the flow path 2 is formed, and the cooling-fluid outlet 4 for
outputting the cooling fluid 11 that has absorbed heat from the
heating element 6 and has become high-temperature form the
continuous fluid-flow path 5. The foregoing heat sink is coupled
with an unillustrated pump or fan, by the intermediary of a
fluid-flow pipe, and the cooling fluid 11 is made to flow in the
heat sink, so that heat generated by the heating element 6 is
radiated toward surroundings. Moreover, by coupling the heat sink
with a heat-radiation device by means of an unillustrated
fluid-flow pipe, a circulating fluid-flow loop may be formed; still
moreover, a reservoir and a filter may be provided in midstream of
the fluid-flow loop. In this case, the cooling fluid 11 circulates
within the fluid-flow loop, the cooling fluid 11 transports heat
generated by the heating element 6 to the heat-radiation device,
and then the heat is radiated from the heat-radiation device toward
the surroundings. In addition, a distribution header or a merging
header may be provided in the heat-transfer container 3 so that the
cooling fluid 11 flows more evenly within the flow path.
[0039] In Embodiment 1, the base 8 thermally coupled with the
heating element 6 and the sidewall 9 are integrally molded; by
combining the lid 10 with the integrated base 8 and the side wall
9, the heat-transfer container 3 is formed. However, the present
invention is not necessarily limited thereto; the base 8, the
sidewall 9, and the lid 10 may be separately produced and then
combined, or the sidewall 9 and the lid 10 may be integrally molded
and then combined with the base 8. Moreover, the base 8, part of
the sidewall 9, and the lid 10 may be integrally molded, and then
combined with the residual sidewall 9.
[0040] Next, the operation of the heat sink according to Embodiment
1 of the present invention will be explained. In FIGS. 1 and 2, the
cooling fluid 11 inputted through the cooling-fluid inlet 1 to the
heat-transfer container 3 travels to the cooling-fluid outlet 4,
while avoiding the protrusions provided on the lid 10 when passing
through the flow path 2 formed of the base 8, the sidewall 9, and
the lid 10. The protrusion 7 is pointed; therefore, in the passage
section (A-A) section in FIG. 2) where the protrusions 7 are
arranged transversely, because the closer to the base 8 a given
position is, the larger the passage-section area is and the more
excellent the fluid-flow properties are, the cooling fluid 11 in
the vicinity of the lid 10 moves toward the base 8, whereby the
flow rate in the vicinity of the base 8 is increased. In contrast,
in the passage section (B-B section in FIG. 2) which lies between
the two lines of the protrusions 7 and in which no protrusion 7 is
situated, because no obstacle exists, the fluid-flow properties are
homogeneous in the passage section, whereby the speed distribution
in the passage section tends to be homogenized.
[0041] Accordingly, when the passage section for the cooling fluid
11 changes from a passage section corresponding to the A-A section
to a passage section corresponding to the B-B section, the cooling
fluid 11 moves from the vicinity of the base 8, where the flow rate
is high, toward the lid 10. Because the longitudinal travel (in the
thickness direction of the heat sink) of the cooling fluid 11 and
the transverse travel (in the width direction of the heat sink) due
to the cooling fluid 11 traveling while avoiding the protrusions 7
are concurrently caused, three-dimensional travels of the cooling
fluid 11 occur, thereby stirring the cooling fluid 11.
[0042] In other words, as indicated by the arrows in the transverse
section in FIG. 2(b), the cooling fluid 11 that travels in the
depth direction with respect to the paper plane collides with the
roots of the protrusions 7 and then travels toward the base 8 along
the slopes of the protrusions 7. After that, the cooling fluid 11
collides with the inner surface of the base 8 and travels in the
middle portions between the protrusions 7; then, swirling flows
that travels toward the lid 10 are caused. In the case where the
protrusions 7 illustrated are in a staggering arrangement, which is
a predetermined arrangement, the swirling flow causes a flow that
alternates its swirling direction with respect to the main flow
direction. In addition, although being unillustrated, in the case
where the protrusions 7 are in a grid arrangement, which is a
predetermined arrangement, a continuous swirling flow having the
same flow direction is caused. As described above, the
three-dimensional flow of the cooling fluid 11 is caused; the
swirling flow and a stirring effect due to the collision of the
cooling fluid 11 with the inner surface (the surface that makes
contact with the flow path 2) of the base 8 enhance the
heat-transfer properties on the inner surface of the base 8.
[0043] The base 8 that makes direct contact with the heating
element 6 receives heat and becomes high-temperature, whereby the
temperature difference between the cooling fluid 11 in the flow
path 2 and the base 8 is produced; thus, the heat is transferred
from the base 8 to the cooling fluid 11. The cooling fluid 11
becomes high-temperature and then outputted from the cooling-fluid
outlet 4. Accordingly, while passing through the cooling-fluid
inlet 1, the flow path 2 inside the heat-transfer container 3, the
cooling-fluid outlet 4, and further the flow path 5, the cooling
fluid 11 becomes high-temperature, and then the high-temperature
cooling fluid 11 is outputted from the cooling-fluid outlet 4.
[0044] As described above, in the heat sink according to Embodiment
1 of the present invention, the cone-shaped protrusions 7 cause the
three-dimensional flow of the cooling fluid 11; thus, the
forced-convection heat transfer due to the flow of the cooling
fluid 11 inside the heat sink, the sensible heat change in the
cooling fluid 11, the swirling flow, in the flow path 2, which
causes a three-dimensional flow, and the stirring effect due to the
collision enable heat to be efficiently radiated from the heating
element 6 to the outside of the heat sink.
[0045] In the case of a conventional finless heat sink in which no
fin is provided in the flow path of the heat-transfer container, a
cooling fluid linearly (in a one-dimensional manner) travels from
the cooling-fluid inlet to the cooling-fluid outlet; therefore, a
relatively thick temperature boundary layer is formed in the
vicinity of the inner surface of the base, whereby the heat
characteristics are deteriorated. In addition, in the case of a
conventional straight-fin heat sink in which a plurality of tabular
fins are provided in the flow path of the heat-transfer container,
the heat-transfer area in which the base and the cooling fluid make
contact with each other increases, whereby the heat-transfer
properties are enhanced; even in this case, however, a relatively
thick temperature boundary layer is formed in the vicinity of the
heat-transfer surface, whereby the effect that enhances the heat
characteristics becomes relatively small. In addition, the fin here
denotes a fin that has a function of radiating heat from the
heating element 6 to the cooling fluid 11.
[0046] Moreover, in the case of a conventional pin-fin heat sink in
which a plurality of pins are provided in the flow path of the
heat-transfer container, the heat-transfer area in which the base
and the cooling fluid make contact with each other increases and a
two-dimensional flow is produced because the cooling fluid avoids
the pins, whereby the heat-transfer properties are enhanced to some
extent; however, the production thereof is difficult and the
production costs become high. Additionally, in general, pin-fin
heat sinks are produced through die-casting; however, because, in
the case where a pin-fin heat sink is produced through die-casting,
the heat conductivity of the heat-sink material is low, the
thermal-diffusion properties of the base unit and the fin
efficiency of the fin unit are lowered, whereby the heat
characteristics of the heat sink are deteriorated. Moreover, in
producing the pin-fin heat sink, it is required to provide a draft
angle to some extent (1.5.degree. to 2.degree.); because this draft
angle makes the passage-section area in the vicinity of the base
small, the cooling fluid inside the flow path is likely to pass in
the vicinity of the lid, whereby the heat-transfer properties are
deteriorated. In addition, it is normally considered that the
larger the draft angle is, the more the heat-transfer properties of
the heat sink are deteriorated.
[0047] In contrast, in the case of the heat sink according to
Embodiment 1 of the present invention, the protrusions 7 provided
on the inner surface of the lid 10 are facilitators of turbulence
in three-dimensional directions, especially in three-dimensional
directions including the thickness direction of the heat sink;
therefore, it is not required to produce the heat sink with a
material of high heat conductivity. Moreover, in Embodiment 1 of
the present invention, the larger is the draft angle of the
protrusion 7, i.e., the conical angle, the more is the cooling
fluid 11 likely to pass in the vicinity of the base 8, whereby the
longitudinal travels (the collision and the swirling flow) are
further facilitated; the heat-transfer properties are enhanced. In
other words, in Embodiment 1 of the present invention, instead of
obtaining an effect of enhancing the heat transfer through increase
in the heat-transfer area in which the base 8 and the cooling fluid
11 make contact with each other, the stirring effect is improved by
use of a material that is low-cost and high-workability.
Furthermore, by enlarging the draft angle of the protrusion 7 up to
the range that is normally not utilized, the passage-section area
in the vicinity of the base 8 is increased while improving the
workability of the protrusion 7, and the cooling fluid 11 is
situated to be close to the base 8, so that the heat-transfer
efficiency can be enhanced. Still moreover, because the finer
protrusions 7 can be provided on the inner surface of the lid 10,
the heat-transfer properties are enhanced in comparison with heat
sinks having a conventional structure.
[0048] Because the increase in fluid-stirring power enhances the
heat-transfer properties of the heat sink, it is not required that
the material of the protrusion 7 is of high heat conductivity;
therefore, the flexibility in selecting of the material of the
protrusion 7 is raised, and, for example, in the case where the
heat sink is produced through die-casting, the draft angle can be
enlarged so as to improve the workability, whereby the production
is readily carried out and the production costs can be lowered.
[0049] In the figures, the heating element 6 is symbolically
illustrated. The heating element 6 includes heat sources such as a
heater, an electronic apparatus, and an electronic component, or
the heat-radiation units and the heat exchangers of the apparatuses
that transport heat from the foregoing heat sources (a heat sink
similar to that of the present invention is included). The
structure and the size of the heating element 6 are not limited, as
long as the heating element 6 applies heat to a heat sink. In
addition, the heating element 6 may be directly mounted to the base
8 through soldering or brazing, pressure welding, and the like; it
may thermally be connected to the base 8 by the intermediary of a
contact-thermal-resistance reduction structure such as thermal
grease.
[0050] The heat-transfer container 3 serves as a container for the
cooling fluid 11 and as a path through which the cooling fluid 11
travels; the heat-transfer container 3 can play roles of connecting
the heating element 6 with the cooling fluid 11 and of diffusing
and equalizing heat from the heating element 6. Moreover, the
heat-transfer container 3 can be utilized for fixing the heating
element 6 and the accompanying components. Still moreover, the
heat-transfer container 3 plays, at the downstream side of the
cooling-fluid inlet 1, a role of distributing the cooling fluid 11
into the flow paths 2 and equalizing the flows, and plays, at the
upstream side of the cooling-fluid outlet 4, a role of merging the
cooling fluids 11.
[0051] As a variant example, illustrated in FIG. 3, of Embodiment 1
of the present invention, in order to facilitate the distribution
of the cooling fluid 11 and the merge of the cooling fluids 11, the
configuration may be in such a way that, at the downstream side,
inside the heat-transfer container 3, of the cooling-fluid inlet 1,
a distribution header 12 for distributing the cooling fluid 11 is
provided and, at the upstream side, inside the heat-transfer
container 3, of the cooling-fluid outlet 4, a merging header 13 for
merging the cooling fluids 11 is provided. Additionally, only one
of the distribution header 12 and the merging header 13 may be
provided.
[0052] In addition, in the variant example, illustrated in FIG. 3,
of Embodiment 1, the cooling-fluid inlet 1 and the cooling-fluid
outlet 4 are provided at the same side (bottom left in the plane of
the paper) of the heat-transfer container 3; however, they may be
provided at opposite positions, for example, in such a way that one
of them is situated at the bottom left of the plane of the paper
and the other one is situated at the top right of the plane of the
paper. In order to facilitate the flow equalization of the cooling
fluid, a wire mesh, a rectification plate having slits or pores, or
the like may be provided at the coupling position between the
distribution header 12 or the merging header 13 and the flow path 2
so as to adjust the flow rate. Additionally, the rectification
plate may be molded integrally with the lid 10. Additionally, a
plurality of heating elements 6 may be provided on the external
surface of the heat-transfer container 3; accordingly, a plurality
of flow paths 2 that are parallel to one another may be provided
inside the heat-transfer container 3. By providing the distribution
header 12 as a distributor for the cooling fluid and the merging
header 13 as a merger, further intensive cooling of a specific
position of the heat-transfer container 3 or equalized cooling can
efficiently be carried out.
[0053] The protrusion 7 has a role of stirring the cooling fluid 11
and, in some cases, has a role as a pillar or a reinforcement
member for holding the space between the base 8 and the lid 10. In
Embodiment 1, the structure of the heat sink has been explained by
utilizing an example in which the protrusions 7 are provided on the
inner surface of the lid 10; however, as a variant example,
illustrated in FIG. 4, of Embodiment 1, the structure of the heat
sink may be in such a way that the protrusions 7 are provided on
the substrate 18 that is inserted into the heat-transfer container
3. Alternatively, the structure of the heat sink may be in such a
way that the substrate 18 provided with the protrusions 7 is
provided fixed inside the heat-transfer container 3.
[0054] As a result, for example, in the case where the heat sink is
considerably large, mold processing such as die-casting or forging
cannot be carried out in some cases, depending on pressurization
performance of the processing machine; however, by dividing and
diminishing the substrate 18 provided with the protrusions 7, the
production of the substrate 18 can readily be performed. Moreover,
by exchanging the substrate 18, the heat characteristics of the
heat sink can readily be changed. Still moreover, by combining a
plurality of the substrates 18 each provided with the different
types of the protrusions 7, a heat sink can readily be produced in
which the heat-transfer properties differ depending on positions in
the flow path 2. In addition, the substrate 18 may be fixed to the
heat-transfer container 3 by providing protrusions as guides in the
flow path within the heat-transfer container 3; alternatively, the
substrate 18 may be adhered by means of an adhesive or welded by
means of a solvent to the inner surface of the heat-transfer
container 3.
[0055] Although, in Embodiment 1 illustrated in FIGS. 1 to 4, an
example has been explained in which the protrusion 7 is formed of a
conical body illustrated in FIG. 5(a), the protrusion 7 may be a
conical body illustrated in FIG. 5(e) or FIG. 5(i); moreover, even
in the case where the protrusion 7 is an approximately conical body
such as an approximate multi-sided pyramid, for example,
illustrated in FIG. 5(b), FIG. 5(c), or FIG. 5(d), the same effect
can be demonstrated. Moreover, even in the case where the
protrusion 7 is an approximate hemisphere, illustrated in FIG.
5(f), which is generally not included in the category of a conical
body, the same effect as that of a hemi-conical body can be
demonstrated in the present invention. Still moreover, the
protrusion 7 may be an approximately hemi-conical body, illustrated
in FIG. 5(g), FIG. 5(h), or FIG. 5(j), or the like; when the
cooling fluid 11 collides with the foregoing protrusions 7 in the
direction from the left to the right of FIG. 5, the same effect as
obtained with an approximate conical body can be demonstrated.
Furthermore, the front end of the protrusion 7 may either have a
sharp vertex angle illustrated in FIG. 5(a), 5(b), 5(c), 5(g),
5(h), 5(i), or 5(j) or may have a flat face illustrated in FIG.
5(d).
[0056] Moreover, the front end of the protrusion 7 may be of a
spherical surface illustrated in FIG. 5(e) or 5(f); alternatively,
although not illustrated, the root portion of the protrusion 7 may
be formed in such a way as to have a spherical surface. Still
moreover, as illustrated in FIGS. 5(h) and 5(i), the protrusion 7
may be formed in such a way as to have a hollow. Furthermore,
although not illustrated, the portion, of the protrusion 7, which
corresponds to the generator may be either swollen outward as a
bamboo shoot or recessed. Still furthermore, as illustrated in FIG.
5(j), the protrusion 7 may not be axisymmetric.
[0057] In addition, in the case where the front end of the
protrusion 7 is flat and makes contact with the inner surface of
the base 8, the heat-transfer area where the inner surface of the
base 8 and the cooling fluid 11 make contact with each other
decreases, whereby the heat-transfer properties are deteriorated.
Therefore, it is desirable that the structure of the heat sink is
in such a way that the front end of the protrusion 7 is formed in
such a way as to have a sharp vertex angle or a spherical surface
so that the front end of the protrusion 7 makes point contact with
the inner surface of the base 8. Additionally, the smaller the
space between the protrusion 7 and the inner surface of the base 8
is, the more excellent the heat-transfer properties are; it is more
preferable that the inner surface of the base 8 and the protrusion
7 make contact with each other.
[0058] Meanwhile, the inner surface of the base 8 and the front end
of the protrusion 7 may thermally be coupled, e.g., through
soldering or brazing. In that case, the front end of the protrusion
7 may not have a sharp vertex angle. In the case where the front
end of the protrusion 7 and the inner surface of the base 8 are
thermally coupled, the protrusion 7 demonstrates an effect as a
fin; heat is transferred from the inner surface of the base 8 to
the protrusion 7 and further to the lid 10, and then the heat is
radiated from the outer surface of the protrusion 7 and the lid 10
to the cooling fluid 11, whereby the heat can efficiently be
radiated.
[0059] Additionally, for the purpose of actively creating the
three-dimensional flow of the cooling fluid 11, it is desirable
that the root portion of the protrusion 7, i.e., the portion, of
the protrusion 7, which makes contact with the lid 10 (in FIG. 1)
or the substrate 18 (in FIG. 4) is of a spherical surface. Thus,
the cooling fluid 11 gradually rises from the root of the
protrusion 7, and the cooling fluid 11 collides with the inner
surface of the base 8, so that the stirring of the cooling fluid 11
in the vicinity of the base 8 is facilitated.
[0060] In addition, the draft angle for the protrusion 7, i.e., the
conical angle may be 1.5.degree.; however, the conical angle of the
same as or larger than 5.degree. is preferable. The conical angle
is preferably 20.degree. or larger. That is because, in the case
where the protrusion 7 is produced through die-casting and removed
from the mold, the draft angle of 5.degree. or larger enables the
protrusion 7 to be extremely readily removed. Additionally, in the
case where the draft angle is 20.degree. or larger, the
passage-section area in the vicinity of the base 8 is increased and
the cooling fluid 11 is situated to be close to the base 8, so that
the heat-transfer effect can be enhanced.
[0061] The cooling-fluid inlet 1 has a role of inputting the
low-temperature cooling fluid 11; in contrast, the cooling-fluid
outlet 4 has a role of outputting the high-temperature cooling
fluid 11. The respective fluid-flow pipes 15 to be connected to the
cooling-fluid inlet 1 and the cooling-fluid outlet 4 are formed of
a circular tube, a rectangular tube, a flexible tube, a rubber-made
hose, or the like. In the case where the cross section of the flow
path 2 in the heat-transfer container 3 is flat, it is desirable to
flatten the respective cross sections of the cooling-fluid inlet 1
and the cooling-fluid outlet 4; accordingly, it is desirable to
flatten the cross section of the portion, of the fluid-flow pipe
15, which is in the vicinity of the coupling position between the
fluid-flow pipe 15 and the foregoing inlet and outlet. In addition,
in Embodiment 1 illustrated in FIG. 1, the cooling-fluid inlet 1
and the cooling-fluid outlet 4 are provided symmetrically with each
other in the sidewall of the heat sink; however, they may be
provided in either the base 8 or the lid 10, or they may be
provided at positions that are asymmetric with each other.
[0062] With regard to the materials that form the heat sink, it is
desirable that the base 8 is made of a material having high heat
conductivity; accordingly, the base 8 is formed of a metal
material, having high heat conductivity, such as aluminum, copper,
or an Al--Co composite material. In contrast, the sidewall 9, the
lid 10, the protrusion 7, the substrate 18, and the fluid-flow pipe
15, which are the portions other than the base 8, may also be
formed of a similar metal material; however, in terms of ease of
molding and cost reduction, the protrusion 7 may be produced by
molding a resin material. The lid 10 and the substrate 18 may also
be formed through sheet-metal machining so as to reduce the costs.
In this case, a recess is formed in the rear side, whereby the
protrusion 7 becomes hollow; however, because the protrusion 7 is a
turbulence facilitator, no problem such as deterioration in the
heat characteristics exists. In addition, in consequence, weight
saving can be achieved.
[0063] The cooling fluid 11 is a liquid such as distilled water,
antifreeze solutions alcohol, ammonia, or ammonia water;
alternatively, the cooling fluid 11 is a gas such as air, or
nitrogen gas. In addition, in the present invention, when the
cooling fluid is a liquid, the effect thereof is enlarged.
[0064] FIG. 6 illustrates another variant example of Embodiment 1
for a heat sink according to the present invention; The
heat-transfer container 3 is provided with the respective bases 8
on the top and bottom sides thereof; on each of the bases 8, the
heating element 6 is disposed. A substrate 14 is provided inside
the heat-transfer container 3; on each of the top and bottom sides
of the substrate 14, the protrusions 7 having an approximately
conical shape are provided in a predetermined arrangement. The heat
sink of the variant example is configured in such a way that a pair
of the heat sinks, illustrated in FIGS. 1 to 4, in each of which
the heating element 6 is disposed only on one side of the
heat-transfer container 3 are piled plane-symmetrically with each
other by the intermediaries of the lids 10 and the two lids 10 are
replaced by the substrate 14. Unlike a heat sink having a
configuration in which a pair of the heat sinks illustrated in
FIGS. 1 to 4 are simply piled plane-symmetrically with each other,
the heat sink in the variant example illustrated in FIG. 6 enables
one of the cooling-fluid inlet 1 and the cooling-fluid outlet 4 to
be utilized for the purpose of the other, whereby the configuration
is further simplified. In the foregoing configuration, by causing a
three-dimensional flow, the heat-transfer properties can be
enhanced with a simplified structure; therefore, even only one heat
sink enables the upper and lower (two set of) heating elements 6 to
be concurrently cooled.
[0065] In addition, by providing the protrusions 7 in a
predetermined arrangement on at least one side of the substrate 14,
instead of providing the protrusions 7 on the both sides of the
substrate 14, the cooling effect of the portion, of the heat sink,
in which the protrusions 7 are provided can be enhanced. In
addition, a plurality of the substrates 14 on one side of which the
protrusions 7 each having an approximately conical shape are
provided in a predetermined arrangement may be mounted inside the
heat-transfer container in such a way that the respective surfaces,
of the substrates 14, on which the protrusions 7 are not provided
are brought into contact with each other.
[0066] FIG. 7 illustrates a further variant example of the heat
sink according to Embodiment 1 of the present invention; FIG. 7(a)
is a transverse cross-sectional view; FIG. 7(b) is a longitudinal
cross-sectional view taken along the line A-A; FIG. 7(c) is a side
cross-sectional view taken along the line B-B. In FIG. 7, on the
inner surface of the lid 10, a plurality of separating plates 20
extending in the direction in which the cooling fluid 11 flows is
provided; the separating plates 20 separates the flow path 2 into a
plurality of paths. Hemi-conical protrusions 7 as illustrated in
FIG. 5(g) are provided on both sides of each of the separating
plates 20. With this configuration, the flow path 2 is configured
in such a way that, only in the direction in which the cooling
fluid 11 flows from the cooling-fluid inlet 1 to the cooling-fluid
outlet 4, a flow path 2a (including an approximately triangular
flow path) whose width is diminished and a flow path 2b whose width
is approximately constant are coupled in turn.
[0067] In Embodiment 1 illustrated in FIGS. 1 to 4, an example in
which the protrusions 7 each having an approximately conical shape
are provided in a predetermined arrangement on the inner surface of
one wall, of the heat-transfer container 3, facing the wall, of the
heat-transfer container 3, on which the heating element 6 is
mounted, an example in which the protrusions 7 each having an
approximately conical shape are provided in a predetermined
arrangement on one side of the substrate 18 provided inside the
heat-transfer container 3, and an example in which the substrate 14
is provided and the protrusions 7 each having an approximately
conical shape are provided in a predetermined arrangement on at
least one side of the substrate 14 have been explained; however, in
the present invention, it is only necessary that, in the heat sink
provided with the cooling-fluid inlet 1, the heat-transfer
container 3 inside which the flow path 2 is formed, and the
cooling-fluid outlet 4, the flow path 2 is configured in such a way
that the approximately trapezoidal flow path 2a (including an
approximately triangular flow path) whose width decreases, in the
longitudinal direction of the heat-transfer container 3, from the
vicinity of the place where the heating element 6 is mounted and a
flow path 2b whose width is approximately constant are coupled in
turn; thus, the variant example illustrated in FIG. 7 can also
demonstrate the same effect.
[0068] FIG. 8 is a further variant example of the heat sink
according to Embodiment 1 of the present invention. In FIG. 8, a
plurality of turbulence facilitators 19 each having an
approximately spherical shape is mounted on the inner surface of
the lid 10 of the heat-transfer container 3. This variant example
is configured in such a way that a flow path whose width changes,
in the longitudinal direction of the heat-transfer container 3,
from the vicinity of the place where the heating element 6 is
mounted and a flow path whose width is approximately constant are
coupled in turn; thus, the same effect as that of each of other
examples can be demonstrated.
[0069] In addition, a recess may be provided in the inner surface
of at least one side of the flow path 2 in order to facilitate the
positioning of the turbulence facilitator 19. Additionally, the
turbulence facilitator 19 may thermally be coupled with at least
one surface of the flow path 2, e.g., through soldering or brazing.
When being thermally coupled with the surface of the wall, of the
heat-transfer container 3, on which the heating element 6 is
provided, the turbulence facilitator 19 demonstrates an effect of a
fin; heat is transferred through heat conduction from the inner
surface to the turbulence facilitator 19 and the heat is radiated
from the outer surface of the turbulence facilitator 19 to the
cooling fluid 11, whereby the heat can efficiently be radiated.
[0070] When the turbulence facilitator 19 is thermally coupled with
the inner surfaces of both sides, in the flow path, of the
heat-transfer container 3, heat is transferred through heat
conduction from the inner surface of the heat-transfer container 3
to the turbulence facilitator 19 and further to the lid 10; thus,
the heat is radiated from the outer surface of the turbulence
facilitator 19 and the lid 10 to the cooling fluid 11, whereby the
heat can further efficiently be radiated. The turbulence
facilitators 19 may be spaced apart from one another or may make
contact with one another. Moreover, the turbulence facilitator 19
may be a hollow sphere; the material of the turbulence facilitator
19 may be of high heat conductivity, as is the case with the
protrusion 7, or a material, such as a resin, of low heat
conductivity.
[0071] In the foregoing cases, in the cross section, of the flow
path 2, perpendicular to the flow direction, a portion that narrows
in proportion to the distance from the side on which the heating
element 6 is mounted and a portion in which the width of the flow
path 2 is constant are also formed alternately. In addition, the
flow path 2 is configured in such a way that approximately
trapezoidal flow paths the width of each of which gradually
decreases, in the height direction (thickness direction) of the
heat-transfer container 3, from the side on which the heating
element 6 is mounted and flow paths the width of each of which is
approximately constant are sequentially coupled.
Embodiment 2
[0072] FIG. 9 is an exploded perspective view symbolically
illustrating a heat sink according to Embodiment 2 of the present
invention. As illustrated in FIG. 9, as the heat-transfer container
3, a heat-transfer container is utilized which has an opening 16 in
its side on which the heating element 6 is mounted. Other
configurations are the same as those of Embodiment 1; therefore,
explanations therefor will be omitted.
[0073] According to Embodiment 2, unlike Embodiment 1, the
heat-transfer container 3, as illustrated in FIG. 9, has an opening
in its side on which the heating element 6 is mounted; by mounting
the heating element 6, the opening is covered and a flow path is
formed. In other words, by providing the heating element 6 so as to
cover the opening 16, the flow path 2 is formed; the heat sink is
configured in such a way that the mounting side for the heating
element 6 directly makes contact with the cooling fluid 11 and heat
is directly transferred to the cooling fluid 11. Accordingly, in
this case, the fluid-flow path 5 and the flow path 2 are formed
with the cooling-fluid inlet 1, the heat-transfer container 3, the
cooling-fluid outlet 4, and the heating element 6. In consequence,
the contact thermal resistance between the heating element 6 and
the base 8 and the thermal resistance of the base 8 can be
eliminated, whereby the heat characteristics of the heat sink can
be enhanced.
[0074] In Embodiment 2, without providing any fin in the heating
element 6, the heat transfer between the heating element 6 and the
cooling fluid 11 is enhanced through turbulence facilitation
effects of the protrusions 7 provided on the lid 10, whereby the
radiation characteristics are enhanced. As described above, because
no fin is directly provided in the heating element 6, the heating
element 6 of an electronic apparatus, a power module, or the like
is readily produced, whereby the costs can be lowered. Moreover,
even in the case where the amount of heat generated by the heating
element 6 changes depending on usage conditions, the radiation
characteristics can be changed by changing the shapes, the sizes,
the arrangement pitch, or the like of the protrusions 7 provided on
the lid 10. Still moreover, because it is not required to change
the structure of the heating element 6 itself, the heating element
6 can be produced so as to be universal, whereby the convenience is
enhanced and the costs of the overall system can be reduced.
[0075] In addition, the coupling between the heating element 6 and
the heat-transfer container 3 can be carried out through
pressure-bonding utilizing an O-ring or a gasket or through
adhesion utilizing an adhesive.
[0076] Moreover, as illustrated in FIG. 10, the structure of the
heat sink may be in such a way that the opening 16 is provided in
each of both sides of the heat-transfer container 3 and the
substrate 14 on both sides of which the protrusions 7 are provided
is inserted into the flow path 2 in the heat-transfer container 3.
The substrate 14 is provided in the heat-transfer container 3, and
the protrusions 7 each having an approximately conical shape are
provided in a predetermined arrangement on both sides of the
substrate 14, so that two heating elements can be cooled with a
single heat sink. In addition, by providing the protrusions 7 in a
predetermined arrangement on at least one side of the substrate 14,
instead of providing the protrusions 7 on the both sides of the
substrate 14, the cooling effect of the portion, of the heat sink,
in which the protrusions 7 are provided can be enhanced.
Embodiment 3
[0077] FIG. 11 is an exploded perspective view symbolically
illustrating a heat sink according to Embodiment 3 of the present
invention. In FIG. 11, conical pin fins 17 are arranged on the
inner surface of the base 8 that makes contact with the heating
element 6. Additionally, the protrusions 7 each having a conical
shape similar to that of the pin fin 17 are provided on the inner
surface of the lid 10. As illustrated in FIG. 11, the pin fins 17
are arranged on a grid, the protrusions 7 arranged on a grid in
such a way as to avoid the pin fins 17 are provided on the lid 10,
and the base 8 and the lid 10 are combined, so that a structure is
formed in which the pin fins 17 and the protrusions 7 form a
staggering arrangement. Accordingly, pins in a staggering
arrangement, which are generally difficult to machine can readily
be produced. In addition, the heat-transfer area decreases in
comparison with a heat sink in which pin fins are provided in a
staggering arrangement on the heat transfer surface; however, even
in the case of Embodiment 3, a three-dimensional flow is produced
in the cooling fluid 11, whereby the heat transfer on the
heat-transfer surface is enhanced; therefore, the heat
characteristics becomes relatively high. On the contrary, because
the number of the pin fins 17 to be mounted is halved, pin fins 17
and protrusions 7 can be arranged further in a sparse manner; by
combining the pin fins 17 and the protrusions 7, densification is
enabled, whereby the heat-transfer properties can be enhanced.
[0078] FIG. 12 is a flow path cross-sectional view symbolically
illustrating a heat sink that is a variant example of Embodiment 3;
FIGS. 12(a), 12(b), 12(c), and 12(d) illustrate respective variant
examples. In each of FIGS. 12(a), 12(b), 12(c), and 12(d), the
upper figure illustrates a longitudinal cross section, and the
lower figure illustrates the transverse cross section taken along
the line C-C. With regard to the variant examples in FIG. 12, FIGS.
12(a), 12(b), 12(c), and 12(d) illustrate a case where a plurality
of tabular straight fins is provided on the inner surface of the
base 8, along the flow of the cooling fluid 11; a case where a
plurality of pin fins 17 is provided on the inner surface of the
base 8; a case where a plurality of wavy fins, heliborne fins, or
serrated fins 17 is provided on the inner surface of the base 8,
along the flow of the cooling fluid 11; and a case where a
plurality of offset fins or porous plate fins 17 is provided on the
inner surface of the base 8, along the flow of the cooling fluid
11, respectively.
[0079] In addition, with the heating element 6 disposed in an
opening provided in the heat-transfer container 3, the foregoing
fins 17 may be provided on the heat-transfer surface, of the
heating element 6, which makes contact with the cooling fluid
11.
[0080] In the heat sink according to Embodiment 3, the fins 17 are
provided in Embodiment 1 or in Embodiment 2 so as to enlarge the
heat-transfer area; thus, the heat-transfer properties can be
enhanced.
INDUSTRIAL APPLICABILITY
[0081] A heat sink according to the present invention can be
utilized as a cooling device for cooling a heating element such as
an electronic component in an electronic apparatus.
* * * * *