U.S. patent application number 09/752780 was filed with the patent office on 2001-08-30 for cooling unit for cooling heat generating component and electronic apparatus having the cooling unit.
Invention is credited to Aoki, Hiroshi, Hisano, Katsumi, Nakamura, Hiroshi, Tomioka, Kentaro, Yamamoto, Katsuhiko.
Application Number | 20010017764 09/752780 |
Document ID | / |
Family ID | 18531017 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017764 |
Kind Code |
A1 |
Nakamura, Hiroshi ; et
al. |
August 30, 2001 |
Cooling unit for cooling heat generating component and electronic
apparatus having the cooling unit
Abstract
A cooling unit for cooling a semiconductor package has a heat
sink and an electric fan device. The heat sink includes a heat
receiving portion for heat generated by the semiconductor package,
and a heat exchange portion thermally connected to the heat
receiving portion. The heat exchange portion is located adjacent to
the heat receiving portion and separate from the semiconductor
package. The heat sink is movable toward and away from the
semiconductor package, and always urged by a plate spring toward
the semiconductor package. The electric fan device sends cooling
air at least to the heat exchange portion of the heat sink.
Inventors: |
Nakamura, Hiroshi; (Tokyo,
JP) ; Hisano, Katsumi; (Kashiwa-shi, JP) ;
Tomioka, Kentaro; (Sayama-shi, JP) ; Aoki,
Hiroshi; (Nagaoka-shi, JP) ; Yamamoto, Katsuhiko;
(Nagaoka-shi, JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Family ID: |
18531017 |
Appl. No.: |
09/752780 |
Filed: |
January 3, 2001 |
Current U.S.
Class: |
361/697 ;
361/679.48; 361/679.54; 361/709 |
Current CPC
Class: |
G06F 1/203 20130101 |
Class at
Publication: |
361/697 ;
361/709; 361/687 |
International
Class: |
H05K 007/20; G06F
001/20; H05K 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2000 |
JP |
2000-001832 |
Claims
What is claimed is:
1. A cooling unit for cooling a heat generating component,
comprising: a heat sink including a heat receiving portion for
receiving heat generated by the heat generating component, and a
heat exchange portion thermally connected to the heat receiving
portion, the heat exchange portion being located adjacent to the
heat receiving portion and separate from the heat generating
component, the heat sink being movable toward and away from the
heat generating component, the heat sink being urged by an elastic
member toward the heat generating component; and ventilation means
for sending cooling air at least to the heat exchange portion of
the heat sink.
2. The cooling unit according to claim 1, further comprising heat
transfer means for transferring, to the heat exchange portion, the
heat generated by the heat generating component and transmitted to
the heat receiving portion.
3. The cooling unit according to claim 1, further comprising a
thermal conductive sheet interposed between the heat receiving
portion and the heat generating component for thermally connecting
the heat receiving portion to the heat generating component.
4. The cooling unit according to claim 1, wherein the heat exchange
portion of the heat sink has at least one cooling air passage into
which the cooling air is introduced, and a plurality of cooling
fins provided in the cooling air passage.
5. The cooling unit according to claim 1, wherein the ventilation
means includes a fan for sending the cooling air, a fan casing
supporting the fan, and a heat sink support connected to the fan
casing, the fan casing and the heat sink support being arranged
adjacent to each other, and the heat sink being movably supported
by the heat sink support via the elastic member.
6. The cooling unit according to claim 5, wherein the elastic
member touches a center of gravity of the heat sink or a portion of
the heat sink located near the center of gravity.
7. The cooling unit according to claim 5, wherein the heat sink
support has a first fitting portion, and the heat sink has a second
fitting portion fitted in the first fitting portion, a direction in
which the heat sink can move being determined and the heat sink
being thermally connected to the heat sink support, when the first
fitting portion is fitted in the second fitting portion.
8. The cooling unit according to claim 7, wherein a thermal
conductive material having a higher thermal conductivity than air
is interposed between the first and second fitting portions.
9. A cooling unit for cooling a heat generating component,
comprising: a heat sink including a heat receiving portion for
receiving heat generated by the heat generating component, and a
heat exchange portion thermally connected to the heat receiving
portion, the heat exchange portion being located adjacent to the
heat receiving portion and separate from the heat generating
component; and an electric fan device for sending cooling air at
least to the heat exchange portion of the heat sink, the electric
fan device including a fan, a fan casing supporting the fan, and a
heat sink support arranged adjacent to the fan casing, wherein the
heat sink is pivotably supported by the heat sink support such that
the heat receiving portion can move toward and away from the heat
generating component, and the heat receiving portion is always
urged by an elastic member toward the heat generating
component.
10. The cooling unit according to claim 9, further comprising a
thermal conductive sheet interposed between the heat receiving
portion and the heat generating component for thermally connecting
the heat receiving portion to the heat generating component.
11. The cooling unit according to claim 9, wherein the heat sink
has a fulcrum on which it can pivot, the fulcrum being located on
that side portion of the heat exchange portion, which is remote
from the heat receiving portion.
12. The cooling unit according to claim 9, wherein the heat sink
support and the heat sink are thermally connected to each
other.
13. The cooling unit according to claim 11, wherein the heat sink
support has a first section that surrounds the heat receiving
portion of the heat sink, and a second section that has a support
wall against which the fulcrum of the heat sink abuts, the first
and second sections being adjacent to each other.
14. An electronic apparatus comprising: a housing; a heat
generating component housed in the housing; a heat sink housed in
the housing, and including a heat receiving portion for receiving
heat generated by the heat generating component, and a heat
exchange portion thermally connected to the heat receiving portion,
the heat exchange portion being located adjacent to the heat
receiving portion and separate from the heat generating component,
the heat sink being movable toward and away from the heat
generating component, the heat sink being urged by an elastic
member toward the heat generating component; and ventilation means
housed in the housing for sending cooling air at least to the heat
exchange portion of the heat sink.
15. The electronic apparatus according to claim 14, further
comprising a circuit board housed in the housing, the circuit board
having an area on which the heat generating component is mounted,
the area being opposed to the heat receiving portion of the heat
sink.
16. The electronic apparatus according to claim 14, wherein the
ventilation means includes a fan for sending the cooling air, a fan
casing supporting the fan, and a heat sink support connected to the
fan casing, the fan casing and the heat sink support being arranged
adjacent to each other, and the heat sink being movably supported
by the heat sink support via the elastic member.
17. The electronic apparatus according to claim 16, wherein the
heat exchange portion of the heat sink has at least one cooling air
passage into which the cooling air is introduced, and a cooling air
outlet located at a downstream end of the cooling air passage.
18. The electronic apparatus according to claim 17, wherein the
housing has a bottom wall and a side wall standing from an edge of
the bottom wall, the heat sink and the ventilation means being
arranged adjacent along the bottom wall, the heat exchange portion
of the heat sink being located along the side wall of the housing,
the side wall having a discharge port at a location corresponding
to the cooling air outlet.
19. The electronic apparatus according to claim 18, wherein the
cooling air passage has a plurality of cooling fins arranged in a
matrix at a location corresponding to the cooling air outlet.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2000-001832, filed Jan. 7, 2000, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a cooling unit for
facilitating the radiation of heat from a heat generating component
such as a semiconductor package, and also an electronic apparatus,
such as a portable computer, which incorporates the cooling
unit.
[0003] In recent years, various types of portable electronic
apparatuses, as typified by notebook-sized portable computers or
mobile information apparatuses, have been developed. Electronic
apparatuses of this type each incorporate a semiconductor package
for processing multimedia information such as characters, voices
and/or images. The power consumption of semiconductor packages
increases more and more in accordance with increases in processing
speed and/or increasing number of functions incorporated therein.
Accordingly, the amount of heat generated during the operation of
the packages is rapidly increasing. Therefore, in order to secure
reliable operation of the semiconductor packages, it is necessary
to facilitate their heat radiation. To this end, various types of
radiation/cooling means such as a heat sink, an electromotive fan
for supplying cooling air, etc. are indispensable.
[0004] The conventional heat sink has a heat receiving portion for
receiving heat generated from a semiconductor package, and a heat
exchange portion thermally connected to the heat receiving portion.
This heat sink is fixed on a circuit board with the semiconductor
package mounted thereon.
[0005] If a gap exists between the heat receiving portion of the
heat sink and the semiconductor package, it serves as a heat
insulating layer and interrupts transmission of heat from the
semiconductor package to the heat sink. To avoid this, in the prior
art, a thermal conductive grease or a flexible thermal conductive
sheet is interposed between the heat receiving portion of the heat
sink and the semiconductor package to enhance the adhesion
therebetween.
[0006] As a surface-mount type semiconductor package for use in a
portable computer, a BGA-type semiconductor package is generally
used. Where the BGA-type semiconductor package is mounted on a
circuit board, it is possible that the thickness of the package on
the circuit board will vary within a range of .+-.0.25 mm. Further,
since an injection molded product of an aluminum alloy is used as
the heat sink, a dimensional tolerance will inevitably occur.
Accordingly, where the heat sink is secured to the circuit board,
the thickness from the heat receiving portion to the circuit board
may vary between different heat sink products.
[0007] In light of this, in the prior art, when a semiconductor
package is thermally connected to the heat receiving portion of a
heat sink by a thermal conductive sheet, the thickness of the sheet
is set at a value that exceeds a maximum gap due to, for example,
the dimensional tolerance of the heat sink. This enables the thick
thermal conductive sheet held between the semiconductor package and
the heat receiving portion to be forcibly elastically deformed so
as to absorb variations in thickness between mounted semiconductor
packages or the dimensional tolerance of the heat sink.
[0008] However, the thermal conductive sheet is generally formed of
a rubber elastic member of a low density, and hence has a lower
thermal conductance than a metal material. Therefore, in the
conventional structure that requires the use of a thick thermal
conductive sheet, a thermally-connected portion of the
semiconductor package and the heat receiving portion will have a
high thermal resistance. As a result, the heat of the semiconductor
package cannot effectively be transmitted to the heat sink. In
other words, there is room for improvement in enhancing the
radiation of the semiconductor package.
BRIEF SUMMARY OF THE INVENTION
[0009] It is the object of the invention to provide a cooling unit
and an electronic apparatus, in which the adhesion of a heat
generating component and a heat sink is kept high to enable
effective transmission of heat from the heat generating component
to the heat sink, and a thermal conduction path from the heat
generating component to a heat exchange portion is formed thin and
compact.
[0010] According to a first aspect of the invention, there is
provided a cooling unit for cooling a heat generating component,
comprising: a heat sink including a heat receiving portion for
receiving heat generated by the heat generating component, and a
heat exchange portion thermally connected to the heat receiving
portion, the heat exchange portion being located adjacent to the
heat receiving portion and separate from the heat generating
component, the heat sink being movable toward and away from the
heat generating component, the heat sink being urged by an elastic
member toward the heat generating component; and ventilation means
for sending cooling air at least to the heat exchange portion of
the heat sink.
[0011] According to a second aspect of the invention, there is
provided an electronic apparatus comprising: a housing; a heat
generating component housed in the housing; a heat sink housed in
the housing, and including a heat receiving portion for receiving
heat generated by the heat generating component, and a heat
exchange portion thermally connected to the heat receiving portion,
the heat exchange portion being located adjacent to the heat
receiving portion and separate from the heat generating component,
the heat sink being movable toward and away from the heat
generating component, the heat sink being urged by an elastic
member toward the heat generating component; and ventilation means
housed in the housing for sending cooling air at least to the heat
exchange portion of the heat sink.
[0012] In the above-described structure, the heat of the heat
generating component is transmitted to the heat receiving portion
of the heat sink and then to the heat exchange portion of the same.
Accordingly, the heat of the heat generating component is diffused
over the entire heat sink and radiated to the outside of the heat
sink. Heat diffusion and subsequent heat radiation is a natural
cooling process. Since the ventilation means sends cooling air to
the heat exchange portion, the heat exchange portion is forcibly
cooled. Thus, the heat of the heat generating component is
efficiently radiated from the heat exchange portion.
[0013] The heat receiving portion of the heat sink is movable
toward and away from the heat generating component. If there is a
variation in the thickness of the heat generating component or in
the size of the heat sink, the movement of the heat sink can absorb
the variation.
[0014] Moreover, since the heat receiving portion is always urged
toward the heat generating component, the adhesion between the heat
receiving portion and the heat generating component is kept high.
Therefore, when providing a thermal conductive sheet between the
heat receiving portion and the heat generating component, it is
sufficient if the thermal conductive sheet has a thickness that
enables the heat receiving portion and the heat generating
component to be prevented from partially touching.
[0015] As a result, the thermal conductive sheet can be thinned to
a required minimum limit.
[0016] Accordingly, the thermal resistance between the heat
receiving portion and the heat generating component can be
suppressed. This means that the heat of the heat generating
component can be efficiently transmitted to the heat sink.
[0017] In addition, since, in the above-described structure, the
heat receiving portion is not vertically parallel to the heat
exchange portion, and the heat exchange portion is horizontally
separate from the heat generating component, the thermal conduction
path from the heat generating component to the heat exchange
portion is formed horizontal. This enables the heat sink to be
formed thin and hence to be easily incorporated in the housing.
[0018] According to a third aspect of the invention, there is
provided a cooling unit for cooling a heat generating component,
comprising: a heat sink including a heat receiving portion for
receiving heat generated by the heat generating component, and a
heat exchange portion thermally connected to the heat receiving
portion, the heat exchange portion being located adjacent to the
heat receiving portion and separate from the heat generating
component; and an electric fan device for sending cooling air at
least to the heat exchange portion of the heat sink, the electric
fan device including a fan, a fan casing supporting the fan, and a
heat sink support arranged adjacent to the fan casing.
[0019] The heat sink is pivotably supported by the heat sink
support such that the heat receiving portion can move toward and
away from the heat generating component, and the heat receiving
portion is always urged by an elastic member toward the heat
generating component.
[0020] In the above structure, if there is a variation in the
thickness of the heat generating component or in the size of the
heat sink, the variation can be absorbed by pivoting the heat sink.
Further, since the heat receiving portion is always urged toward
the heat generating component, the adhesion between the heat
receiving portion and the heat generating component is kept high.
Therefore, when providing a thermal conductive sheet between the
heat receiving portion and the heat generating component, the
thermal conductive sheet can be thinned to a required minimum
limit. Accordingly, the thermal resistance between the heat
receiving portion and the heat generating component can be
suppressed, and hence the heat of the heat generating component can
be efficiently transmitted to the heat sink.
[0021] In addition, in the above-described structure, the heat
receiving portion is not vertically parallel to the heat exchange
portion, the heat exchange portion is horizontally separate from
the heat generating component, and the heat sink is not vertically
parallel to the fan casing. Accordingly, the thermal conduction
path from the heat generating component to the heat exchange
portion is formed horizontal. This enables the cooling unit to be
formed thin and compact.
[0022] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0023] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0024] FIG. 1 is a perspective view illustrating a portable
computer according to a first embodiment of the invention;
[0025] FIG. 2 is a sectional view of the portable computer,
illustrating a state in which a cooling unit is housed in the
housing of the computer;
[0026] FIG. 3 is a sectional view of the portable computer,
illustrating the positional relationship between a heat sink and a
semiconductor package;
[0027] FIG. 4 is a sectional view of the portable computer,
illustrating the positional relationship between a cooling air
passage of a heat exchange portion and a heat receiving
portion;
[0028] FIG. 5 is a sectional view illustrating thermal connection
between a BGA-type semiconductor package and a heat receiving
portion;
[0029] FIG. 6 is a plan view of the portable computer, illustrating
the positional relationship between second suction ports formed in
the bottom wall of the housing and the cooling unit;
[0030] FIG. 7 is a perspective view illustrating the positional
relationship between the second suction ports of the housing, the
cooling unit and the BGA-type semiconductor package;
[0031] FIG. 8 is a perspective view illustrating a state in which
the cooling unit is fixed on a circuit board;
[0032] FIG. 9 is a perspective view showing the cooling unit;
[0033] FIG. 10 is a perspective view of the cooling unit, showing
the positional relationship between an electric fan device and the
heat sink;
[0034] FIG. 11 is a sectional view of the portable computer,
illustrating a state in which the cooling unit is housed in the
housing;
[0035] FIG. 12 is a perspective view illustrating a cooling unit
according to a second embodiment of the invention;
[0036] FIG. 13 is a perspective view of the cooling unit of FIG.
12, showing the positional relationship between an electric fan
device and a heat sink;
[0037] FIG. 14 is a plan view showing the cooling unit of FIG.
12;
[0038] FIG. 15 is a sectional view of the portable computer of the
second embodiment, showing the positional relationship between the
heat sink and a semiconductor package; and
[0039] FIG. 16 is an enlarged sectional view of a section indicated
by reference letter A in FIG. 15.
DETAILED DESCRIPTION OF THE INVENTION
[0040] A portable computer according to a first embodiment of the
invention will be described with reference to FIGS. 1-10.
[0041] FIG. 1 shows a notebook-sized portable computer 1 as an
electronic apparatus. The portable computer 1 includes a computer
main body 2 and a display unit 3 supported by the computer main
body 2.
[0042] The computer main body 2 has a box-shaped housing 4. The
housing 4 is made of a metal that is light and has a high thermal
conductivity, such as a magnesium alloy. The housing 4 has a bottom
wall 4a, a top wall 4b, a front wall 4c, left and right side walls
4d and a rear wall 4e. The side walls 4d stand from the respective
side edges of the bottom wall 4a. As shown in FIG. 1, the right
side wall 4d of the housing 4 has a first suction port 5a and a
discharge port 6. The first suction port 5a is located at a middle
portion of the housing 4 in its depth direction. The discharge port
6 is located at a rear portion of the housing 4.
[0043] The bottom wall 4a of the housing 4 has multiple second
suction ports 5b as shown in FIG. 6 or 7. The second suction ports
5b are located at a right end portion of the bottom wall 4a,
adjacent to the first suction port 5a.
[0044] The top wall 4b of the housing 4 has a palm rest 7, a
keyboard attachment recess 8 and a pair of display supports 11a and
11b. The palm rest 7 constitutes a front half portion of the
housing 4 in its width direction. The keyboard attachment recess 8
receives a keyboard 9. The display supports 11a and 11b are located
behind the keyboard 9, separated from each other in the width
direction.
[0045] The display unit 3 includes a flat-box-shaped display
housing 12 and a liquid crystal display device 13. The display
housing 12 has a front surface provided with a rectangular opening
14. The liquid crystal display device 13 is housed in the display
housing 12, and has a display screen 13a for displaying information
such as characters, images, etc. The display screen 13a is exposed
to the outside through the opening 14 of the housing 12.
[0046] The display housing 12 has a pair of legs 15a and 15b
projecting from the lower edge of the housing 12 to the supports
11a and 11b, respectively. The legs 15a and 15b are attached to the
housing 4 by respective hinges (not shown).
[0047] Accordingly, the display unit 3 is coupled to the housing 4
such that it can pivot between a closed position in which the unit
3 is folded onto the palm rest 7 and the keyboard 9, and an open
position in which the palm rest 7, the keyboard 9 and the display
screen 13a are exposed.
[0048] As shown in FIGS. 3 and 4, a circuit board 17 is housed in
the housing 4. The circuit board 17 is located below the keyboard 9
and extends parallel to the bottom wall 4a of the housing 4. The
circuit board 17 has a reverse surface 17a that is opposed to the
bottom wall 4a and has a BGA-type semiconductor package 19 mounted
thereon as a heat generating component. The semiconductor package
19 constitutes an MPU (Micro Processing Unit) as the nerve center
of the portable computer 1, and is mounted on a mount area 17b that
is situated at a right end portion of the reverse surface 17a of
the circuit board 17.
[0049] As shown in FIG. 5 or 7, the semiconductor package 19 has a
rectangular base plate 20 and an IC chip 21. The base plate 20 is
soldered to the reverse surface 17a of the circuit board 17 with
multiple solder balls 22 interposed therebetween. The IC chip 21 is
flip-chip bonded to a central portion of the base plate 20 with
multiple solder balls 23 interposed therebetween. The IC chip 21
consumes a lot of power during operation since it processes, at
high speed, multimedia information such as characters, voices and
images. Accordingly, the IC chip 21 generates a lot of heat during
operation, and hence must be cooled to maintain its stable
operation.
[0050] As shown in FIGS. 2, 3 and 11, the housing 4 houses a
cooling unit 25 for cooling the semiconductor package 19. The
cooling unit 25 extends from below a right end portion of the
circuit board 17 to the right side wall 4d of the housing 4.
[0051] As most clearly illustrated in FIGS. 7-10, the cooling unit
25 has an electric fan device 26 as ventilation means and a heat
sink 27. The electric fan device 26 includes a flat fan casing 29,
a centrifugal fan 30 supported by the fan casing 29 and a flat
motor (not shown) for driving the centrifugal fan 30.
[0052] The fan casing 29 has a base panel 31 and an upper panel 32
connected to the base panel 31. The base panel 31 is formed of a
metal that is light and has an excellent thermal conductivity, such
as an aluminum alloy or a magnesium alloy. As shown in FIG. 7, the
base panel 31 is opposed to the bottom wall 4a of the housing 4.
The base panel 31 has a first circular suction port 33 formed
therein at a location slightly separate from a central portion
thereof.
[0053] The base panel 31 has a motor support section 34 projecting
to the inside of the first suction port 33. The centrifugal fan 30
is supported by the upper surface of the motor support section 34
with the aforementioned flat motor interposed therebetween.
Accordingly, the centrifugal fan 30 is incorporated in the base
panel 31 with its axis-of-rotation O1 directed vertically (i.e. the
fan 30 rotates horizontally), and driven by the flat motor when the
temperature of the IC chip 21 reaches a predetermined value.
[0054] The base panel 31 has a circumferential wall 35 that
upwardly extends from its circumferential edge. The circumferential
wall 35 surrounds the centrifugal fan 30, and has support chips 36
horizontally extending from two portions thereof.
[0055] The upper panel 32 is formed of a metal such as a stainless
steel. The upper panel 32 is fixed on the upper end of the
circumferential wall 35 and extends parallel to the base panel 31.
The upper panel 32 has a second suction port 38. The second suction
port 38 is opposed to the first suction port 33, and the
centrifugal fan 30 is located between the first and second suction
ports 33 and 38. An air passage 39 as shown in FIG. 11 is formed
between the upper panel 32 and the base panel 31. The first and
second suction ports 33 and 38 are located at the upstream end of
the air passage 39.
[0056] As illustrated in FIG. 10 or 11, the fan casing 29 has an
discharge port 40, which is in the form of a slit extending in the
width direction of the fan casing 29. The discharge port 40 is
located at the downstream end of the air passage 39.
[0057] In the electric fan device 26 constructed as above, when the
centrifugal fan 30 is driven, air is guided to the centrifugal fan
30 through the first and second suction ports 33 and 38. This air
is radially outwardly discharged from a circumferential portion of
the centrifugal fan 30 and introduced into the discharge port 40
through the air passage 39. Through the discharge port 40, the air
is blown to the outside of the fan casing 29.
[0058] As shown in FIG. 10, the base panel 31 of the fan casing 29
has a heat sink support 42 integrated therewith as one body. The
heat sink support 42 and the base panel 31 are adjacent to each
other, and the discharge port 40 of the fan casing 29 is located at
a junction of the heat sink support 42 and the base panel 31.
[0059] The heat sink support 42 has first and second sections 43
and 44 arranged adjacent to each other along the length of the
discharge port 40. The first section 43 is in the form of a
rectangular frame. The second section 44 is formed rectangular, has
long sides longer than each side of the first section 43, and
horizontally extends from the discharge port 40 to the outside.
[0060] The second section 44 has a plurality of seat sections 45.
The seat sections 45 and the support chips 36 of the fan casing 29
are screwed, by respective screws 48, to a plurality of boss
sections 46 (see FIG. 2) upwardly projecting from the bottom wall
4a of the housing 4. Thus, the heat sink support 42 and the fan
casing 29 are arranged adjacent in the depth direction of the
housing 4 and thermally connected to the bottom wall 4a of the
housing 4.
[0061] As shown in FIG. 11, when the fan casing 29 is secured to
the bottom wall 4a, the second section 44 of the heat sink support
42 extends along the right side wall 4d of the housing 4. Further,
the second section 44 is located adjacent to the discharge port 6
formed in the right side wall 4d. In addition, as shown in FIG. 6,
the first suction port 33 of the base panel 31 is opposed to the
second suction ports 5b formed in the bottom wall 4a, while the
second suction port 38 of the upper panel 32 is located near the
first suction port 5a of the right side wall 4d. The upper panel 32
faces the lower surface of the keyboard 9.
[0062] The first section 43 of the heat sink support 42 is located
between a right end portion of the circuit board 17 and the bottom
wall 4a of the housing 4, facing the mount area 17b of the circuit
board 17 on which the semiconductor package 19 is mounted. The
first section 43 has four upwardly extending reception seats 47.
The reception seats 47 touch the reverse surface 17a of the circuit
board 17 outside the edges of the semiconductor package 19. The
reception seats 47 are screwed to the circuit board 17 by
respective screws 48. Where the reception seats 47 are secured to
the circuit board 17, the semiconductor package 19 and the heat
sink support 42 are positioned such that the semiconductor package
19 faces a part of the discharge port 40 of the fan casing 29.
[0063] The heat sink 27 is formed of a metal that is light and has
an excellent thermal conductivity, such as an aluminum alloy or a
magnesium alloy. The heat sink 27 comprises a heat receiving
portion 50 and a heat exchange portion 51. The heat receiving
portion 50 is formed of a rectangular plate member, and has a size
that enables it to cover the semiconductor package 19 from below
and to be fitted in the first section 43 of the heat sink support
42. Accordingly, the heat receiving portion 50 is surrounded by the
sides of the first section 43.
[0064] The heat receiving portion 50 has an upper surface 52
opposed to the reverse surface 17a of the circuit board 17. A
projection 53 slightly upwardly projects from a substantially
central portion of the upper surface 52. The projection 53 has a
flat upper surface that serves as a flat heat-receiving surface 54.
The heat receiving surface 54 is opposed to the IC chip 21 of the
semiconductor package 19.
[0065] As shown in FIG. 10, the heat exchange portion 51 is
integrated as one body with the heat receiving portion 50 and
thermally connected thereto. The heat exchange portion 51 extends
from the heat receiving portion 50 such that the length of the
portion 51 is perpendicular to that of the portion 50. The heat
exchange portion 51 is received by the second section 44 of the
heat sink support 42.
[0066] The heat exchange portion 51 has a rectangular bottom wall
56 extending from and at the same level as the heat receiving
portion 50. A pair of side walls 57a and 57b upwardly extend from
the long sides of the bottom wall 56. A rectangular metal cover
plate 58 is secured to the upper ends of the side walls 57a and
57b.
[0067] As shown in FIG. 3 or 4, the cover plate 58 is located
slightly above the circuit board 17 between the right end of the
circuit board 17 and the right side wall 4d of the housing 4. The
cover plate 58, the bottom wall 56 and the side walls 57a and 57b
constitute a cooling air passage 59 incorporated in the heat
exchange portion 51.
[0068] As illustrated in FIG. 11, the cooing air passage 59
linearly extends along the second section 44 of the heat sink
support 42 in the depth direction of the housing 4. The cooling air
passage 59 has a cooling air inlet 61 and a cooling air outlet 62.
The cooling air inlet 61 is located at the upstream end of the
cooling air passage 59 and opposed to the discharge port 40 of the
fan casing 29. The cooling air outlet 62 is located at the
downstream end of the cooling air passage 59, and opens at the side
and at the rear of the heat exchange portion 51.
[0069] That part of the cooling air outlet 62, which opens at the
side of the heat exchange portion 51, faces the discharge port 6 of
the housing 4. On the other hand, that part of the cooling air
outlet 62, which opens at the rear of the heat exchange portion 51,
faces a right end portion of the rear wall 4e of the housing 4. A
plurality of auxiliary discharge ports 60 are formed in a corner
defined by the rear wall 4e and the bottom wall 4a.
[0070] As most clearly shown in FIGS. 3, 4 and 11, the heat
exchange portion 51 has a plurality of first cooling fins 63 and a
plurality of second cooling fins 64 provided on the upper surface
of the bottom wall 56. The first and second cooling fins 63 and 64
are exposed to the cooling air passage 59. The first cooling fins
63 linearly extend along the length of the cooling air passage 59,
parallel to each other with respective spaces interposed
therebetween. The first cooling fins 63 are located upstream of the
cooling air outlet 62 with respect to the flow of cooling air. The
second cooling fins 64 are in the form of pins, arranged in a
matrix and located downstream of the first cooling fins 63 with
respect to the flow of cooling air.
[0071] As shown in FIGS. 4 and 7, a recess 66 is formed in the
lower surface of the heat sink 27 such that it extends from the
heat receiving portion 50 to the heat exchange portion 51. A flat
heat pipe 67 as heat transfer means is buried in the recess 66. The
heat pipe 67 includes a first end portion 67a and a second end
portion 67b. The first and second end portion 67a and 67b are
thermally connected to the heat receiving portion 50 and the heat
exchange portion 51, respectively.
[0072] As shown in FIGS. 2 and 10, the bottom wall 56 of the heat
exchange portion 51 has first and second fulcrums 70a and 70b
upwardly projecting therefrom. The first fulcrum 70a is located at
the cooling air inlet 61, while the second fulcrum 70b is located
at the cooling air outlet 62. Thus, the first and second fulcrums
70a and 70b are separated from each other in the longitudinal
direction of the cooling air passage 59.
[0073] When the heat exchange portion 51 of the heat sink 27 is
mounted on the second section 44 of the heat sink support 42, the
first and second fulcrums 70a and 70b are respectively positioned
below support walls 71a and 71b that are respectively provided on
the fan casing 29 and the second section 44. The ends of the first
and second fulcrums 70a and 70b are opposed to the support walls
71a and 71b, respectively. The first and second fulcrums 70a and
70b are located on the heat exchange portion 51 remote from the
heat receiving surface 54 of the heat receiving portion 50, with
the cooling air passage 59 interposed therebetween.
[0074] As illustrated in FIG. 5 or 10, the heat receiving portion
50 of the heat sink 27 has a through hole 72 formed in an end
portion thereof remote from the heat exchange portion 51. The heat
receiving surface 54 is situated between the through hole 72 and
the fulcrums 70a and 70b.
[0075] The first section 43 of the heat sink support 42 has a wall
portion 73 extending below the through hole 72. A cylindrical boss
74 upwardly projects from the upper surface of the wall portion 73.
The boss 74 has a height greater than the thickness of the heat
receiving portion 50. The boss 74 is inserted in the through hole
72. A space S1 exists between the entire outer peripheral surface
of the boss 74 and the entire inner surface of the through hole
72.
[0076] A screw 76 is screwed in the upper end of the boss 74. A
washer 75 having a larger diameter than the through hole is
provided on the upper surface 52 of the heat receiving portion 50
and aligned with the upper surface of the boss 74. Thus, the heat
sink 27 is secured to the heat sink support 42 at the positions of
the fulcrums 70a, 70b and the through hole 72.
[0077] Since the height of the boss 74 is greater than the
thickness of the heat receiving portion 50 as shown in FIG. 5, a
space S2 is defined between the upper surface of the wall portion
73 and the lower surface of the heat receiving portion 50.
Accordingly, the heat sink 27 is supported by the heat sink support
42 so that it can vertically move in the thickness direction of the
housing 4 by an amount corresponding to the space S2.
[0078] As shown in FIGS. 7 and 10, the first section 43 of the heat
sink support 42 has a plate spring 80 as an elastic member. The
plate spring 80 extends between two opposite sides of the first
section 43 below the heat receiving portion 50 in the depth
direction of the housing 4. When the cooling unit 25 is viewed from
above, the plate spring 80 is situated between the heat receiving
surface 54 of the heat receiving portion 50 and the heat exchange
portion 51.
[0079] The plate spring 80 has a pressing section 81 upwardly and
arcuately curved at a central portion thereof. The pressing section
81 elastically touches the lower surface of the heat receiving
portion 50 at or in the vicinity of the center-of-gravity G of the
heat sink 27, thereby raising the heat receiving portion 50. As a
result, the fulcrums 70a and 70b of the heat sink 27 abut against
the support walls 71a and 71b, respectively, and the upper surface
of the heat receiving portion 50 abuts against the washer 75.
[0080] Accordingly, the heat sink 27 is movably supported by the
heat sink support 42 so that the heat receiving surface 54 of the
heat receiving portion 50 can pivot on the contact portions of the
fulcrums 70a, 70b and the support walls 71a, 71b toward and away
from the semiconductor package 19. At the same time, the heat sink
27 is always elastically urged by the plate spring 80 toward the
semiconductor package 19.
[0081] As most clearly shown in FIG. 11, when the cooling unit 25
is viewed from above, the contact portions of the fulcrums 70a and
70b on which the heat sink 27 pivots, the washer 75 and the heat
receiving portion 50 have a triangular positional relationship.
Accordingly, the position of the heat sink 27 with respect to the
heat sink support 42 is stabilized, thereby suppressing shaking of
the heat sink 27.
[0082] As shown in FIGS. 3 to 5, a thermal conductive sheet 82 is
interposed between the heat receiving surface 54 of the heat
receiving portion 50 and the IC chip 21 of the semiconductor
package 19. The thermal conductive sheet 82 is an elastic rubber
member that is formed by, for example, adding alumina to silicone
resin, and has a high thermal conductivity. The thermal conductive
sheet 82 is thermally connected to the heat receiving surface 54
and the IC chip 21.
[0083] In the portable computer 1 constructed as above, when the IC
chip 21 of the semiconductor package 19 generates heat, the heat is
transmitted to the heat receiving portion 50 of the heat sink 27
via the thermal conductive sheet 82. Since the heat receiving
portion 50 is thermally connected to the heat exchange portion 51
via the heat pipe 67, part of the heat transmitted to the heat
receiving portion 50 is further transmitted to the first end
portion 67a of the heat pipe 67. As a result, an operation liquid
sealed in the heat pipe 67 is heated and evaporated, and vapor of
the operation liquid flows from the first end portion 67a to the
second end portion 67b of the heat pipe 67.
[0084] The vapor guided to the second end portion 67b of the heat
pipe 67 radiates heat and condenses. The condensed operation liquid
returns from the second end portion 67b to the first end portion
67a by a capillary force, and is again heated by the heat of the IC
chip 21. The heat of the heat receiving portion 50 is actively
transmitted to the heat exchange portion 51 by the repetition of
the evaporation and condensation of the operation liquid.
[0085] Accordingly, the heat of the IC chip 21 transmitted to the
heat receiving portion 50 is diffused to the entire heat sink 27,
and radiated to the outside of the heat sink. Heat diffusion and
subsequent heat radiation is a natural cooling process.
[0086] When the temperature of the IC chip 21 has reached a
predetermined value, the centrifugal fan 30 of the electric fan
device 26 is driven. In accordance with the rotation of the
centrifugal fan 30, air outside the housing 4 is introduced therein
through the first and second suction ports 5a and 5b. The
introduced air is guided to the centrifugal fan 30 through the
first and second suction ports 33 and 38 of the fan casing 29, and
then discharged to the cooling air passage 39 from a
circumferential portion of the centrifugal fan 30. Thus, the air
introduced into the housing 4 is discharged as cooling air from the
discharge port 40 of the fan casing 29.
[0087] Part of the discharge port 40 opens to the interior of the
housing 4 and faces the semiconductor package 19, while the other
part of the port 40 communicates with the cooling air inlet 61 of
the cooling air passage 59. Accordingly, cooling air discharged
from the discharge port 40 is guided to both the semiconductor
package 19 and the cooling air passage 59.
[0088] Since a plurality of first cooling fins 63 extends in the
cooling air passage 59 along its length, cooling air reaches the
downstream end of the cooling air passage 59 after flowing along
the first cooling fins 63. Further, since a plurality of second
cooling fins 64 are arranged in a matrix at the downstream end of
the cooling air passage 59, the cooling air guided by the first
cooling fins 63 to the downstream end of the passage 59 weaves
between the second cooling fins 64.
[0089] Accordingly, the contact area of the heat exchange portion
51 and the cooling air increases, and hence the exchange portion 51
is forcibly cooled by the cooling air. As a result, the degree of
radiation of the heat exchange portion 51 increases, whereby the
heat of the IC chip 21 transmitted to the heat exchange portion 51
is efficiently discharged.
[0090] As indicated by the arrows in FIG. 11, the cooling air flows
at the downstream end of the cooling air passage 59 such that it
weaves between the pin-shaped second cooling fins 64. Accordingly,
the flow of the cooling air becomes a turbulent flow, which enables
the cooling air to be diverted at the downstream end of the cooling
air passage 59 toward the discharge port 6. The major part of the
cooling air having forcibly cooled the heat exchange portion 51 is
discharged from the discharge port 6 formed in the right side wall
4d of the housing 4. The remaining part of the cooling air is
discharged to the interior of the housing 4 through the cooling air
outlet 62 of the cooling air passage 59, and then discharged to the
outside through the auxiliary discharge ports 60 formed in the rear
wall 4e of the housing 4.
[0091] Since the cooling air has a turbulent flow at the downstream
end of the cooling air passage 59, it is diffused to all the second
cooling fins 64. In other words, all the second cooling fins 64 are
brought into contact with the cooling air, and hence a sufficient
contact area is secured between the heat exchange portion 51 and
the cooling air. As a result, the heat exchange portion 51 can
perform excellent heat radiation.
[0092] In addition, if the discharge port 6 of the housing 4 is
partially blocked for some reason, the cooling air directed to the
blocked portion is guided to another portion of the downstream end
of the cooling air passage 59 through adjacent ones of the second
cooling fins 64. Thus, the flow of the cooling air is not
interrupted, and therefore a sufficient amount of cooling air
flowing through the cooling air passage 59 can be secured, thereby
preventing degradation of the radiation performance of the heat
exchange portion 51.
[0093] Part of the cooling air discharged from the discharge port
40 of the fan casing 29 is directly guided to the semiconductor
package 19. Accordingly, a flow of cooling air occurs around the
semiconductor package 19, thereby cooling the semiconductor package
19 and/or the heat receiving portion 50. At the same time, since
cooling air flows within the housing 4, the housing 4 has a high
air permeability, which makes it difficult to accumulate heat
around the semiconductor package 19. This further enhances the
radiation performance of the semiconductor package 19.
[0094] As shown in FIG. 11, part of the cooling air outlet 62 opens
to the side wall 57a of the heat exchange portion 51. Therefore,
the distance from the part of the cooling air outlet 62 to the
cooling air inlet 61 is shortened. This means that the length of a
longitudinally central portion of the cooling air passage 59 is
longer than that of a side portion of the passage 59 along the side
wall 57a. Accordingly, the flow resistance of the cooling air is
greater at the longitudinally central portion of the passage 59
than at the side portion of the passage 59 along the side wall 57a,
and hence the amount of cooling air flowing through the central
portion of the passage 59 is reduced. This being so, it is possible
that the second cooling fins 64 located at the central portion of
the cooling air passage 59 cannot effectively be used for
radiation.
[0095] If in this case, the pitch of the second cooling fins 64
located near the side wall 57a is narrowed to increase the flow
resistance of the cooling air flowing along the side wall 57a, a
uniform flow distribution of the cooling air can be realized in the
cooling air passage 59. As a result, the cooling air can be
uniformly guided to all the second cooling fins 64, thereby
enhancing the radiation performance of the heat exchange portion
51.
[0096] In the above-described cooling unit 25, the heat sink 27 for
receiving heat generated from the semiconductor package 19 is
movably supported by the heat sink support 42 of the fan casing 29,
and always elastically urged by the plate spring 80 toward the IC
chip 21 of the semiconductor package 19.
[0097] Therefore, even if the thickness of the semiconductor
package 19 mounted on the circuit board 17 or the thickness of the
heat receiving portion 50 of the heat sink 27 varies between
different products, the heat sink 27 vertically pivots on contact
portions of the fulcrums 70a and 70b and the support walls 71a and
71b, thereby absorbing variations in the thickness of the
semiconductor package 19 or the heat receiving portion 50.
[0098] Moreover, since the heat receiving portion 50 of the heat
sink 27 is urged against the IC chip 21, the heat receiving surface
54 of the heat receiving portion 50 is kept in tight contact with
the IC chip 21. Therefore, when interposing the thermal conductive
sheet 82 between the heat receiving surface 54 and the IC chip 21,
it is sufficient if the thermal conductive sheet 82 has a thickness
that enables the heat receiving surface 54 and the IC chip 21 to be
prevented from partially touching, i.e. enables the heat of the IC
chip 21 to be diffused on the entire heat receiving surface 54.
[0099] As a result, the thermal conductive sheet 82 can be thinned
to a required minimum limit, and hence the thermal resistance that
occurs at the thermal connection of the heat sink 27 and the IC
chip 21 can be reduced. This means that the heat of the IC chip 21
can be efficiently radiated to the outside of the apparatus through
the heat sink 27.
[0100] Furthermore, since in the above-described structure, the
fulcrums 70a and 70b on which the heat sink 27 pivots are located
remote from the heat receiving surface 54 of the heat receiving
portion 50, with the heat exchange portion 51 interposed
therebetween, there is a long distance between the fulcrums 70a,
70b and the heat receiving surface 54. Accordingly, when the heat
sink 27 is rocked vertically, the heat receiving surface 54 of the
heat sink 27 vertically moves while it is kept substantially
parallel to the IC chip 21. As a result, partial contact between
the IC chip 21 and the heat receiving surface 54 can be avoided,
which means that the IC chip 21 and the heat receiving surface 54
can be kept in appropriate contact with each other.
[0101] Also, since the heat receiving portion 50 and the heat
exchange portion 51 of the heat sink 27 are arranged adjacent to
each other at the same level, the thermal conduction path from the
IC chip 21 to the heat exchange portion 51 via the heat receiving
portion 50 is flat. This enables the heat sink 27 to be formed thin
and compact and hence to be easily incorporated in the housing 4
that is demanded to be made thin.
[0102] In addition, as shown in FIG. 3 or 8, the heat exchange
portion 51 having the cooling air passage 59 is horizontally
separate from the circuit board 17, the position of the upper panel
32 as the ceiling of the cooling air passage 59 is not limited by
the circuit board 17. Therefore, the upper panel 32 can be
positioned at substantially the same level as the circuit board 17,
thereby securing the height of the cooling air passage 59. This
imparts a sufficiently large cross section to the cooling air
passage 59, and hence a sufficient amount of cooling air can pass
through the passage. At the same time, the first and second cooling
fins 63 and 64 can have a sufficient height, and therefore have a
sufficient area in contact with the cooling air. As a result, the
radiation performance of the heat exchange portion 51 can be
further enhanced.
[0103] Further, the pressing section 81 of the plate spring 80 is
in contact with the lower surface of the heat receiving portion 50
at or in the vicinity of the center-of-gravity G of the heat sink
27. Accordingly, even when, for example, the portable computer 1
shakes, the pivotable heat sink 27 does not easily shake
independently. This being so, the IC chip 21 is prevented from
colliding with the heat receiving surface 54 or from being
excessively pressed by it. This means that the semiconductor
package 19 can have a high impact resistance.
[0104] Yet further, since, in the cooling unit 25, the heat sink
support 42 is connected to the fan casing 29 of the electric fan
device 26, it can be made of a simple shape that is suitable for
surrounding the heat sink 27. Accordingly, the heat sink support 42
can be made light, which contributes to reducting the weight of the
entire cooling unit 25. Therefore, even when, for example, the
portable computer 1 shakes, a load applied to a connection section
of the housing 4 and the cooling unit 25 can be reduced, and hence
the attachment structure of the cooling unit 25 can be
simplified.
[0105] Although, in the above-described first embodiment, a single
cooling air passage is formed in the heat exchange portion of the
heat sink, a plurality of cooling air passages may be formed
therein.
[0106] Moreover, in the first embodiment, it is not always
necessary to make the plate spring urging the heat receiving
portion be in contact with the lower surface of the heat receiving
portion at or in the vicinity of the center of gravity of the heat
sink. Instead, the spring plate may be made to come into contact
with those two portions of the lower surface of the heat receiving
portion, between which the center of gravity of the heat sink is
situated.
[0107] It is not necessary to make the first section of the heat
sink support continuously surround the heat receiving portion of
the heat sink. The first section may contain a space.
[0108] The invention is not limited to the above-described first
embodiment. Referring now to FIGS. 12-16, a second embodiment of
the invention will be described.
[0109] A cooling unit 90 according to the second embodiment is
similar to the cooling unit employed in the first embodiment,
except for the structure of a heat sink 91 for mainly receiving
heat generated from an IC chip 21, and a structure for movably
supporting the heat sink 91. Therefore, in the second embodiment,
structural elements similar to those in the first embodiment are
denoted by corresponding reference numerals, and no detailed
description is given thereof.
[0110] AS shown in FIG. 12 or 13, the second section 44 of the heat
sink support 42 has a first side wall 92 upwardly projecting from
an edge section thereof that is located remotely from the first
section 43. The first side wall 92 has a first cooling air outlet
93. The first cooling air outlet 93 is remote from the fan casing
29 and opposed to the discharge port 6 of the housing 4.
[0111] The second section 44 of the heat sink support 42 has a
second side wall 94 projecting upwardly. The second side wall 94 is
opposed to the first cooling air outlet 93. A second cooling air
outlet 95 is defined between the second side wall 94 and the first
side wall 92, and opposed to the rear wall 4e of the housing 4.
[0112] The first section 43 of the heat sink support 42 has a pair
of projections 97a and 97b as first fitting sections. The
projections 97a and 97b are located on respective opposed sides of
the first section 43. The projections 97a and 97b upwardly project
from the upper surface of the first section 43, and extend parallel
to each other in the depth direction of the housing 4.
[0113] As shown in FIGS. 12, 13 and 15, the heat sink 91 has a heat
receiving portion 100 and a heat exchange portion 101. The heat
receiving portion 100 is arranged to cover the semiconductor
package 19 from below, and formed rectangular so that it is fitted
in the first section 43. The heat receiving portion 100 has an
upper surface 102 opposed to the reverse surface 17a of the circuit
board 17. A projection 103 slightly upwardly projects on a
substantially central portion of the upper surface 102. The upper
end of the projection 103 forms a flat heat receiving surface 104.
The heat receiving surface 104 is arranged to face the IC chip 21
of the semiconductor package 19.
[0114] The heat receiving portion 100 has a flat lower surface 106.
A pair of recesses 107a and 107b as second fitting sections are
formed in the lower surface 106. The recesses 107a and 107b are in
the form of slits and extend in the depth direction of the housing
4. The projection 103 is situated between the recesses 107a and
107b.
[0115] The projections 97a and 97b of the first section 43 are
fitted in the recesses 107a and 107b, whereby the heat sink 91 is
vertically movably supported by the heat sink support 42. As a
result, the heat sink 91 can move toward and away from the
semiconductor package 19.
[0116] As shown in FIG. 16, a clearance 108 is defined between the
projection 97a (97b) and the recess 107a (107b) for allowing their
relative movement. The clearance 108 is filled with flexible grease
109 as a heat conductive material. The grease 109 has a higher
thermal conductivity than air, and thermally connects the heat sink
91 to the heat sink support 42.
[0117] The heat exchange portion 101 of the heat sink 91 is formed
rectangular and opposed to the second section 44 of the heat sink
support 42. The heat exchange portion 101 is connected to an end of
the heat receiving portion 100 via a connection wall 110, whereby
the heat exchange portion 101 and the heat receiving portion 100
are integrated as one body. The connection wall 110 upwardly
extends from the end of the heat receiving portion 100.
Accordingly, the heat exchange portion 101 is situated at a higher
level than the heat receiving portion 100 and at the same level as
the circuit board 17.
[0118] As shown in FIG. 15, the heat exchange portion 101, the
second section 44 and the first and second side walls 92 and 94 of
the heat sink support 42, and the connection wall 110 are joined to
form a cooling air passage 111. The upstream end of the cooling air
passage 111 communicates with the discharge port 40 of the fan
casing 29. The downstream end of the cooling air passage 111
communicates with the first and second cooling air outlets 93 and
95.
[0119] The lower surface of the heat exchange portion 101 faces the
cooling air passage 111. Multiple pin-shaped radiation fins 112 are
arranged on the lower surface of the heat exchange portion 101. The
radiation fins 112 are arranged in a matrix in the cooling air
passage 111.
[0120] As is shown in FIGS. 13-15, a spring member 115 as an
elastic member is attached to the first section 43 of the heat sink
support 42. The spring member 115 includes a semispherical pressing
section 116, and four arm sections 117 radially extending from the
pressing section 116. The arm sections 117 are screwed to the
respective lower ends of the reception seats 47 by respective
screws 118 such that the pressing section 116 of the spring member
115 is situated at a substantially central portion of the first
section 43 of the heat sink support 42. The pressing section 116 of
the spring member 115 is in elastic contact with the lower surface
106 of the heat receiving portion 100 of the heat sink 91, thereby
raising the heat receiving portion 100. This being so, the heat
receiving surface 104 of the heat sink 91 is always elastically
urged toward the semiconductor package 19.
[0121] In the above-described structure, the heat sink 91 for
receiving heat generated from the semiconductor package 19 is
vertically movably supported by the heat sink support 42, and is
elastically urged by the spring member 115 toward the IC chip 21 of
the semiconductor package 19.
[0122] Accordingly, even if there is a variation in the thickness
of the semiconductor package 19 mounted on the circuit board 17
and/or in the thickness of the heat receiving portion 100 of the
heat sink 91, the heat sink 91 vertically moves along those
projections 97a and 97b of the first section 43 of the heat sink
support 42, which are fitted in the recesses 107a and 107b of the
heat receiving portion 100, thereby absorbing the variation in the
thickness.
[0123] Moreover, since a force urging the heat receiving portion
100 of the heat sink 91 toward the IC chip 21 is always applied to
the heat receiving portion 100, the adhesion between the heat
receiving portion 100 and the IC chip 21 is kept high. Therefore,
when interposing the thermal conductive sheet 82 between the heat
receiving surface 104 and the IC chip 21, it is sufficient if the
thermal conductive sheet 82 has a thickness that enables the heat
receiving surface 104 and the IC chip 21 to be prevented from
partially touching, i.e. enables the heat of the IC chip 21 to be
diffused on the entire heat receiving surface 104.
[0124] As a result, the thermal conductive sheet 82 can be thinned
to a required minimum limit, and hence the thermal resistance that
occurs at the thermal connection of the heat sink 91 and the IC
chip 21 can be reduced. This means that the heat of the IC chip 21
can be efficiently radiated to the outside of the apparatus through
the heat sink 91.
[0125] Also, since the heat receiving portion 100 and the heat
exchange portion 101 are arranged adjacent to each other, the
thermal conduction path from the IC chip 21 to the heat exchange
portion 101 via the heat receiving portion 100 is flat. This
enables the heat sink 91 to be formed thin and compact and hence to
be easily incorporated in the housing 4 that is demanded to be made
thin.
[0126] Furthermore, in the above structure, the heat receiving
portion 100 of the heat sink 91 is thermally connected to the first
section 43 of the heat sink support 42 via the projections 97a and
97b fitted in the recesses 107a and 107b, respectively.
Accordingly, the heat of the IC chip 21 transmitted to the heat
receiving portion 100 can be quickly transmitted to the fan casing
29 via the heat sink support 42. This means that the heat sink
support 42 and the fan casing 29 connected thereto can be used as
radiator components, thereby enhancing the radiation performance of
the heat sink 91.
[0127] In addition, since the clearance 108 between the projection
97a (97b) and the recess 107a (107b) is filled with grease 109, the
thermal resistance of the thermally-connected portion of the heat
receiving portion 100 and the heat sink support 42 can be
minimized. At the same time, when vibration occurs from the outside
to the cooling unit 90, vibration transmitted from the heat sink
support 42 to the heat sink 91 can be attenuated by the grease
109.
[0128] This being so, the IC chip 21 is prevented from colliding
with the heat receiving surface 104, or from being excessively
pressed by it, with the result that 41 the semiconductor package 19
can have a high impact resistance.
[0129] The present invention is not limited to the above-described
embodiments, but may be modified in various ways without departing
from its scope.
[0130] For example, although, in the above-described embodiments, a
thermal conductive sheet is provided between the IC chip of the
semiconductor package and the heat receiving portion of the heat
sink, thermal conductive grease may be provided therebetween,
instead of the thermal conductive sheet. Depending upon the
situation, the heat receiving portion may be in direct contact with
the IC chip, without any thermal conductive sheet or grease.
[0131] Yet further, it is not always necessary to integrate the
heat receiving portion and the heat exchange portion of the heat
sink with each other. These elements may be formed as separate
bodies and connected to each other by, for example, a screw.
[0132] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *