U.S. patent application number 09/732915 was filed with the patent office on 2001-06-21 for cooling unit for cooling circuit component generating heat and electronic apparatus comprising the cooling unit.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Yamaoka, Yoji.
Application Number | 20010004313 09/732915 |
Document ID | / |
Family ID | 18429066 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004313 |
Kind Code |
A1 |
Yamaoka, Yoji |
June 21, 2001 |
Cooling unit for cooling circuit component generating heat and
electronic apparatus comprising the cooling unit
Abstract
A cooling unit comprises a heat sink overlapped on a
semiconductor package. The semiconductor package has an IC chip
mounted on a circuit board. The heat sink has a heat receiving
portion for receiving heat of the IC chip. A flexible heat-transfer
member such as grease and a heat-transfer sheet is provided between
the heat receiving portion and the IC chip. The heat sink is pushed
toward the IC chip via a fixing spring and thereby the heat
receiving portion and the IC chip are thermally connected while
sandwiching the heat-transfer member therebetween. A spacer is
provided between the circuit board and the heat sink. The spacer
supports the heat sink, at a position remote from the IC chip.
Inventors: |
Yamaoka, Yoji; (Hino-shi,
JP) |
Correspondence
Address: |
Finnegan, Henderson, Farabow
Garrett & Dunner, L.L.P.
1300 I Street, N.W.
Washington
DC
20005-3315
US
|
Assignee: |
Kabushiki Kaisha Toshiba
|
Family ID: |
18429066 |
Appl. No.: |
09/732915 |
Filed: |
December 11, 2000 |
Current U.S.
Class: |
361/704 ;
257/E23.086; 257/E23.102; 257/E23.104; 361/679.48; 361/679.54 |
Current CPC
Class: |
H01L 2224/16225
20130101; H01L 2224/32245 20130101; H01L 2924/19106 20130101; H01L
2023/4062 20130101; H01L 2224/73253 20130101; H01L 2924/15311
20130101; H01L 23/4093 20130101; H01L 2023/4043 20130101; H01L
23/3675 20130101; H01L 2924/15311 20130101; H01L 23/367 20130101;
G06F 1/20 20130101; H01L 2224/73204 20130101; H01L 2224/73204
20130101; H01L 2224/32225 20130101; H01L 2924/16251 20130101; H01L
2924/00 20130101; H01L 2224/73204 20130101; H01L 2224/32225
20130101; H01L 2224/32225 20130101; H01L 2224/16225 20130101; H01L
2924/00 20130101; H01L 2224/16225 20130101 |
Class at
Publication: |
361/704 ;
361/687 |
International
Class: |
H05K 007/20; G06F
001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 1999 |
JP |
11-353174 |
Claims
What is claimed is:
1. A cooling unit for cooling a circuit component including a base
of synthetic resin having a mounting surface and a heat generating
unit mounted on the mounting surface of said base, said cooling
unit comprising: a heat sink overlapped on said circuit component,
said heat sink having a heat receiving portion for receiving heat
of said heat generating unit; a flexible heat-transfer member
provided between said heat generating unit and said heat receiving
portion, for thermally connecting said heat generating unit and
said heat receiving portion to one another; pushing means for
pushing said heat sink toward said heat generating unit to sandwich
said heat-transfer member between said heat generating unit and
said heat receiving portion; and a spacer provided between said
base of said circuit component and said heat sink, for supporting
said heat sink, at a position remote from said heat generating
unit.
2. A cooling unit according to claim 1, wherein said heat
generating unit has a plurality of connection terminals, which are
electrically connected to said base.
3. A cooling unit according to claim 1, wherein said spacer is
integral with said heat sink.
4. A cooling unit according to claim 2, wherein said spacer has
heat conductivity.
5. A cooling unit according to claim 1, wherein said base of said
circuit component has a plurality of current-carrying terminals,
which are arranged on an opposite side to said heat generating
unit.
6. A cooling unit according to claim 5, further comprising a wiring
board having a surface equipped with said circuit component, said
wiring board electrically connected to said current-carrying
terminals of said base.
7. A cooling unit according to claim 6, further comprising a socket
provided on the equipped surface of said wiring board and
electrically connected to said current-carrying terminals of said
base.
8. A cooling unit according to claim 6, wherein said
current-carrying terminals are constituted by solder balls, which
are soldered on the equipped surface of said wiring board.
9. A cooling unit according to claim 7, wherein said spacer faces
said socket through said base disposed therebetween.
10. A cooling unit according to claim 7, wherein said heat
generating unit is positioned at a central part of said base, said
current-carrying terminals are arranged in an area avoiding said
heat generating unit, on an opposite side to said heat generating
unit, and said socket has a hollow portion at a position
corresponding to the central part of said base.
11. A cooling unit according to claim 10, wherein said base has
another mounting surface on an opposite side to said mounting
surface, said another mounting surface has a first arrangement
region in which said current-carrying terminals are arranged and a
second arrangement region surrounded by said first arrangement
region, and said second arrangement region faces the hollow portion
of said socket.
12. A cooling unit according to claim 11, further comprising at
least one, other circuit component mounted in said second
arrangement region, said other circuit component being contained in
the hollow portion of said socket.
13. A cooling unit for cooling a circuit component including a base
of synthetic resin having a mounting surface and a heat generating
unit mounted on the mounting surface of said base, said cooling
unit comprising: a heat sink overlapped on said circuit component,
said heat sink having a heat receiving portion for receiving heat
of said heat generating unit; a spacer provided between said base
and said heat sink, said spacer constituting a grease-filled
chamber surrounding said heat generating unit in cooperation with
said base and said heat sink; fixing means for fixing said heat
sink on said base to allow said spacer to be sandwiched between
said heat sink on said base; and heat-transfer grease packed in
said grease-filled chamber to thermally connect said heat
generating unit and said heat sink to one another.
14. A cooling unit according to claim 13, wherein said spacer has
heat conductivity.
15. A cooling unit according to claim 13, wherein said spacer is
integral with said heat sink.
16. A circuit module comprising: a wiring board; a semiconductor
package containing a circuit board of synthetic resin, which has a
mounting surface and a plurality of current-carrying terminals on a
opposite side to said mounting surface, and an IC chip, which is
mounted on the mounting surface of said circuit board and generates
heat, said current-carrying terminals being electrically connected
to said wiring board; a heat sink overlapped on said semiconductor
package, said heat sink having a heat receiving portion for
receiving heat of said IC chip; a flexible heat-transfer member
provided between said IC chip and said heat receiving portion, for
thermally connecting said IC chip and said heat receiving portion
to one another; pushing means for pushing said heat sink toward
said IC chip to sandwich said heat-transfer member between said IC
chip and said heat receiving portion; and a spacer provided between
said circuit board of said semiconductor package and said heat
sink, for supporting said heat sink, at a position remote from said
IC chip.
17. A circuit module according to claim 16, wherein said wiring
board comprises a reinforcing plate for receiving a pushing force
applied via said pushing means.
18. An electronic apparatus comprising: a housing; a circuit
component contained inside said housing, said circuit component
comprising a base of synthetic resin having a mounting surface and
a heat generating unit mounted on said mounting surface of said
base; a heat sink overlapped on said circuit component, said heat
sink having a heat receiving portion for receiving heat of said
heat generating unit; a flexible heat-transfer member provided
between said heat generating unit and said heat receiving portion,
for thermally connecting said heat generating unit and said heat
receiving portion to one another; pushing means for pushing said
heat sink toward said heat generating unit to sandwich said
heat-transfer member between said heat generating unit and said
heat receiving portion; and a spacer provided between said base of
said circuit component and said heat sink, for supporting said heat
sink, at a position remote from said heat generating unit.
19. An electronic apparatus according to claim 18, further
comprising a wiring board contained inside said housing, said
wiring board being electrically connected to said circuit
component.
20. An electronic apparatus according to claim 19, wherein said
base of said circuit component has a plurality of current-carrying
terminals on an opposite side to said mounting surface and said
current-carrying terminals are electrically connected to said
wiring board.
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. 11-353174,
filed Dec. 13, 1999, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a cooling unit for
promoting heat radiation of circuit components that generate heat,
such as a semiconductor package, and an electronic apparatus such
as a personal computer comprising the cooling unit.
[0003] An electronic apparatus such as a desktop personal computer
and a workstation comprises a semiconductor package for
multi-purpose multimedia information such as characters, speech and
images. In the semiconductor package of this kind, the power
consumption is increased in accordance with the acceleration of the
processing speed and the versatility, and in proportion to this the
amount of heat in the operation is also inclined to rapidly
increase.
[0004] For this reason, heat radiation of the semiconductor package
needs to be enhanced to maintain the stable operation thereof.
Therefore, various heat radiating/cooling means such as a heat sink
or a heat pipe are indispensable.
[0005] A conventional heat sink has a heat receiving portion
thermally connected to the semiconductor package. If there is a
poor contact between the heat receiving portion and the
semiconductor package, a gap occurs therebetween and thereby
prevents transfer of the heat from the semiconductor package to the
heat receiving portion. Thus, in the prior art, heat conductive
grease or a rubber heat transfer sheet is provided between the heat
receiving portion and the semiconductor package and the heat sink
is pressed against the semiconductor package through a spring to
enhance the close contact between the heat receiving portion and
the semiconductor package.
[0006] Incidentally, if the heat receiving portion of the heat sink
is forcibly pressed against the semiconductor package, load is
applied to the semiconductor package through the heat receiving
portion and may be the stress to the semiconductor package. In this
case, there is no problem if the semiconductor package has strength
enough to overcome the stress. Recently, however, the semiconductor
package has been structurally simplified due to various requests
such as reduction of the manufacturing costs, saving of the weight,
miniaturization and the like. For this reason, some kinds of the
semiconductor packages do not have the structural strength enough
to bear the stress.
[0007] Specifically, in the ceramic package, which is a typical
airtight sealing package, an IC chip generating heat is covered
with a ceramic board or a ceramic lid having high rigidity. The
load of the heat sink can be therefore received by the ceramic
board or the ceramic lid.
[0008] On the other hand, in the BGA (Ball Grid Array) package and
PGA (Pin Grid Array) package in which the IC chip is subjected to
flip chip bonding on a synthetic resin circuit board, or the TCP
(Tape Carrier Package) in which the IC chip is bonded to polyimide
tape, the IC chip is exposed to the outside and the circuit board
or tape supporting the IC chip is formed of synthetic resin. For
this reason, it cannot be said that the package of this kind has
the strength enough to bear the load from the heat sink.
[0009] Therefore, for example, if the heat receiving portion of the
heat sink is pressed against the IC chip of the BGA package, the
stress concentrates on the IC chip and the IC chip may be broken.
In addition, as the IC chip receives the load caused by pressing
the IC chip against the circuit board, the load acts as a bending
force to the circuit board and the circuit board may be curved or
bent backward. As a result, the stress is continuously applied to
the connection portions of the IC chip and the circuit board, which
may cause the faulty bonding.
[0010] Therefore, the heat sink cannot be pressed against the IC
chip with a large force in the semiconductor package such as the
BGA, PGA and the like. For this reason, it is difficult to
sufficiently maintain the close contact between the heat sink and
the semiconductor package, and efficient transfer of heat from the
semiconductor package to the heat sink is prevented.
BRIEF SUMMARY OF THE INVENTION
[0011] The object of the present invention is to provide a cooling
unit and circuit module capable of efficiently radiating the heat
of the circuit component to the heat sink while reducing the stress
applied to the circuit components, and also provide an electronic
apparatus comprising the cooling unit.
[0012] To achieve the object, there is provided a cooling unit
according to the present invention, for cooling a circuit component
including a base of synthetic resin having a mounting surface and a
heat generating unit mounted on the mounting surface of the base.
The cooling unit comprises a heat sink, which is overlapped on the
circuit component and which has a heat receiving portion for
receiving heat of the heat generating unit, a flexible
heat-transfer member provided between the heat generating unit and
the heat receiving portion, for thermally connecting the heat
generating unit and the heat receiving portion to one another,
pushing means for pushing the heat sink toward the heat generating
unit to sandwich the heat-transfer member between the heat
generating unit and the heat receiving portion, and a spacer
provided between the base of the circuit component and the heat
sink, for supporting the heat sink, at a position remote from the
heat generating unit.
[0013] In addition, to achieve the above-described object, there is
also provided an electronic apparatus comprising a housing, a
circuit component, which is contained inside the housing, and which
comprises a base of synthetic resin having a mounting surface and a
heat generating unit mounted on the mounting surface of the base, a
heat sink overlapped on the circuit component, the heat sink having
a heat receiving portion for receiving heat of the heat generating
unit, a flexible heat-transfer member provided between the heat
generating unit and the heat receiving portion, for thermally
connecting the heat generating unit and the heat receiving portion
to one another, pushing means for pushing the heat sink toward the
heat generating unit to sandwich the heat-transfer member between
the heat generating unit and the heat receiving portion, and a
spacer provided between the base of the circuit component and the
heat sink, for supporting the heat sink, at a position remote from
the heat generating unit.
[0014] In this structure, when the heat sink is thermally connected
to the heat generating unit, the heat sink is pushed on the heat
generating unit by the pushing means. At this time, as the spacer
is provided between the heat sink and the base of the circuit
component, most of the load of heat sink applied to the heat
generating unit is received by the spacer. Thus, excessive stress
is not concentrated on the heat generating unit and thereby bending
or warping of the base supporting the heat generating unit can be
prevented. For this reason, it is possible to prevent floating of
the heat generating unit or damage of the mounting part of the heat
generating unit.
[0015] In addition, the close contact between the heat generating
unit and the heat receiving portion can be maintained by
appropriately pushing down the flexible heat-transfer member
between the heat receiving portion and the heat generating unit.
Therefore, the thermal connection between the heat generating unit
and the heat receiving portion can be stably maintained and the
heat of the heat generating unit can be efficiently transferred to
the heat sink.
[0016] To achieve the above-described object, there is also
provided a cooling unit according to the present invention, for
cooling a circuit component including a base of synthetic resin
having a mounting surface and a heat generating unit mounted on the
mounting surface of the base. The cooling unit comprises a heat
sink, which is overlapped on the circuit component and which has a
heat receiving portion for receiving heat of the heat generating
unit, a spacer, which is provided between the base and the heat
sink and which constitutes a grease-filled chamber surrounding the
heat generating unit in cooperation with the base and the heat
sink, fixing means for fixing the heat sink on the base to allow
the spacer to be sandwiched between the heat sink on the base, and
heat-transfer grease packed in the grease-filled chamber to
thermally connect the heat generating unit and the heat sink to one
another.
[0017] In this structure, as the heat generating unit is embedded
in the grease, the contact area of the heat generating unit and the
grease and the contact area of the heat sink and the grease can be
adequately maintained. Therefore, the heat of the heat generating
unit can be efficiently transferred to the heat sink through the
grease.
[0018] Moreover, if the heat sink is fixed on the base, the spacer
is sandwiched between the heat sink and the base. Thus, the heat
generating unit is not directly pushed down by the heat sink or no
stress is not applied to the heat generating unit. In addition, the
load of the heat sink applied to the base when the heat sink is
fixed is dispersed in a wide range around the heat generating unit
via the spacer, and the excessive stress cannot be concentrated on
a specific part of the base. Therefore, it is possible to prevent
the bending or warping of the base supporting the heat generating
unit, and also possible to prevent the floating of the heat
generating unit or damage of the mounting part of the heat
generating unit.
[0019] To achieve the above-described object, there is also
provided a circuit module according to the present invention,
comprising a wiring board, a semiconductor package containing a
circuit board of synthetic resin, which has a mounting surface and
a plurality of current-carrying terminals on a opposite side to the
mounting surface, and an IC chip, which is mounted on the mounting
surface of the circuit board and generates heat, the
current-carrying terminals being electrically connected to the
wiring board, a heat sink, which is overlapped on the semiconductor
package and which has a heat receiving portion for receiving heat
of the IC chip, a flexible heat-transfer member provided between
the IC chip and the heat receiving portion, for thermally
connecting the IC chip and the heat receiving portion to one
another, pushing means for pushing the heat sink toward the IC chip
to sandwich the heat-transfer member between the IC chip and the
heat receiving portion, and a spacer provided between the circuit
board of the semiconductor package and the heat sink, for
supporting the heat sink, at a position remote from the IC
chip.
[0020] In this structure, when the heat sink is thermally connected
to the IC chip of the semiconductor package, the heat sink is
pushed on the IC chip by the pushing means. At this time, as the
spacer is provided between the heat sink and the circuit board of
the semiconductor package, most of the load of heat sink applied to
the IC chip is received by the spacer. Thus, excessive stress is
not concentrated on the IC chip and thereby the bending or warping
of the circuit board supporting the IC chip can be prevented. For
this reason, it is possible to prevent the floating of the IC chip
or the damage of the mounting part of the IC chip.
[0021] Further, the load applied to the circuit board through the
spacer is transferred to the wiring board via a plurality of
current-carrying terminals. Therefore, the load on each of the
current-carrying terminals can be reduced, deformation or breakage
of the current-carrying terminals can be prevented, and the damage
of the connecting part between the current-carrying terminals and
the wiring board can also be prevented.
[0022] In addition, the close contact between the IC chip and the
heat receiving portion can be maintained by appropriately pushing
down the flexible heat-transfer member between the IC chip and the
heat receiving portion. Therefore, the thermal connection between
the IC chip and the heat receiving portion can be stably maintained
and the heat of the IC chip can be efficiently transferred to the
heat sink.
[0023] 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
[0024] 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.
[0025] FIG. 1 is a perspective view showing a desktop personal
computer according to a first embodiment of the present
invention;
[0026] FIG. 2 is a perspective view showing a desktop personal
computer according to the first embodiment of the present invention
as seen from the back of the main body;
[0027] FIG. 3 is a side view showing a desktop personal computer
according to the first embodiment of the present invention,
illustrating a partial section of a housing of the main body;
[0028] FIG. 4 is a sectional view showing a state of attaching a
heat sink to a PGA semiconductor package mounted on a printed
wiring board, in the first embodiment of the present invention;
[0029] FIG. 5 is a sectional view as seen along a line F5-F5 of
FIG. 4;
[0030] FIG. 6 is a sectional view showing a state of attaching a
heat sink to a PGA semiconductor package mounted on a printed
wiring board, in a second embodiment of the present invention;
[0031] FIG. 7 is a sectional view showing a state of attaching a
heat sink to a PGA semiconductor package mounted on a printed
wiring board, in a third embodiment of the present invention;
[0032] FIG. 8 is a sectional view showing a state of attaching a
heat sink to a PGA semiconductor package mounted on a printed
wiring board, in a fourth embodiment of the present invention;
[0033] FIG. 9 is a sectional view showing a state of attaching a
heat sink to a PGA semiconductor package mounted on a printed
wiring board, in a fifth embodiment of the present invention;
[0034] FIG. 10 is a sectional view showing a state of attaching a
heat sink to a PGA semiconductor package mounted on a printed
wiring board, in a sixth embodiment of the present invention;
and
[0035] FIG. 11 is a plan view showing a reinforcement plate for
reinforcing the printed wiring board, in the sixth embodiment of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The desktop personal computer according to the first
embodiment of the present invention will be explained below with
reference to FIGS. 1 to 5.
[0037] FIG. 1 shows a desktop personal computer 1 as an electronic
apparatus. The computer 1 comprises a main body 2, and a keyboard 3
connected to the main body 2.
[0038] The main body 2 has a housing 5 formed of synthetic resin.
The housing 5 is composed of a base portion 6 and a stand portion
7. The base portion 6 is shaped in a flat square casing and
contains a CD-ROM drive 8 or a floppy disk drive (not shown) so
that it can be removed from the base portion 6.
[0039] The stand portion 7 extends upwardly from a rear end of the
base portion 6. The stand portion 7 is shaped in a hollow casing
having a front wall 9a, a rear wall 9b, right and left side walls
9c and 9d, and a top wall 9e. A plurality of air vents 10 are
formed on the rear wall 9b.
[0040] A flat liquid-crystal display unit 12 is supported at a top
end of the stand portion 7. The display unit 12 comprises a display
housing 13 and a liquid-crystal display panel 14 contained in the
display housing 13. The display housing 13 has a front face on
which an opening portion 15 is formed. A display screen 14a of the
display panel 14 is exposed to the outside through the opening
portion 15.
[0041] A circuit module 18 is contained in the stand portion 7 as
shown in FIG. 3. The circuit module 18 comprises a printed wiring
board 20 and also a PGA semiconductor package 26, which is a
circuit component. The printed wiring board 20 is arranged along
the front wall 9a of the stand portion 7. The printed wiring board
20 has a component-mounted surface 21. The component-mounted
surface 21 faces the rear wall 9b. A CPU socket 22 is mounted on
the component-mounted surface 21.
[0042] The CPU socket 22 is a square frame having a hollow portion
23 at the center as shown in FIG. 4. The CPU socket 22 has a CPU
support surface 24 on the opposite side to the printed wiring board
20. A plurality of terminal holes (not shown) are arranged in a
matrix on the CPU support surface 24. The terminal holes are
electrically connected to pads (not shown) on the component-mounted
surface 21.
[0043] The PGA semiconductor package 26 is supported on the printed
wiring board 20 via the CPU socket 22. The semiconductor package 26
comprises a circuit board 27 of synthetic resin, which serves as a
base, and an IC chip 28, which is a heat generating unit.
[0044] The circuit board 27 has a first mounting surface 29a and a
second mounting surface 29b. The second mounting surface 29b is on
the opposite side to the first mounting surface 29a. The first
mounting surface 29a of the circuit board 27 includes a
pin-arranged area 30a and a component-arranged area 30b. The
pin-arranged area 30a corresponds to the CPU support surface 24 of
the CPU socket 22 and is positioned on an outer peripheral portion
of the first mounting surface 29a. The component-arranged area 30b
corresponds to the hollow portion 23 of the CPU socket 22 and is
positioned at the center of the first mounting surface 29a. For
this reason, the component-arranged area 30b is surrounded with the
pin-arranged area 30a.
[0045] A plurality of pin-like current-carrying terminals 31 are
arranged in the pin-arranged area 30a of the circuit board 27 as
shown in FIG. 4. The current-carrying terminals 31 are arranged in
a matrix to correspond to the terminal holes of the CPU socket 22
and are formed to protrude downwardly from the pin-arranged area
30a of the circuit board 27. A plurality of other circuit
components 32, for example, capacitors are mounted in the
component-arranged area 30b of the circuit board 27.
[0046] The IC chip 28 of the semiconductor package 26 consumes
large power during the operation since it processes the
multi-purpose multimedia information such as characters, speech and
images at a high speed. In accordance with this, the amount of heat
from the IC chip 28 becomes large such that the IC chip 28 needs to
be cooled. The IC chip 28 is subjected to flip-chip bonding on the
second mounting surface 29b of the circuit board 27 via a plurality
of solder balls 34. The IC chip 28 is arranged at the center of the
second mounting surface 29b and positioned on the opposite side to
the component-arranged area 30b. For this reason, the
current-carrying terminals 31 are arranged in an area except the
position corresponding to the IC chip 28, on the first mounting
surface 29a.
[0047] In the semiconductor package 26, when a lock lever (not
shown) of the CPU socket 22 is operated after inserting the
current-carrying terminals 31 into the terminal holes of the CPU
socket 22, the current-carrying terminals 31 are locked such that
they cannot be detached from the CPU socket 22. Thus, the fitting
of the current-carrying terminals 31 to the terminal holes is
maintained and the semiconductor package 26 is electrically
connected to the printed wiring board 20. When the semiconductor
package 26 is mounted on the CPU socket 22, heating IC chip 28 is
positioned just above the hollow portion 23 of the CPU socket 22
and the circuit components 32 are contained in the hollow portion
23.
[0048] A heat sink 36 overlaps the semiconductor package 26 as
shown in FIG. 4. The heat sink 36 is formed of a metal material
excellent in heat conductivity, for example, an aluminum alloy. The
heat sink 36 is shaped in a flat plate that is slightly larger than
the plane shape of the semiconductor package 26.
[0049] The heat sink 36 has a first surface 37a and a second
surface 37b positioned on the opposite side to the first surface
37a. The first surface 37a faces the semiconductor package 26. A
heat receiving portion 38 for receiving the heat from the IC chip
28 is formed integrally with a central part of the first surface
37a. The heat receiving portion 38 protrudes from the central part
of the first surface 37a. The protruding end of the heat receiving
portion 38 is a flat heat receiving surface 39. The heat receiving
surface 39 has substantially the same size as that of the upper
surface of the IC chip 28 and faces the IC chip 28. A flexible
heat-transfer member 41 is provided between the heat receiving
surface 39 and the IC chip 28. The heat-transfer member 41 is
formed of heat-transfer grease or a heat-transfer sheet of a
rubber-like elastic material.
[0050] A plurality of pin-shaped radiator fins 42 are formed
integrally with the second surface 37b of the heat sink 36. The
radiator fins 42 are arranged in a matrix on the second surface
37b.
[0051] The heat sink 36 is fixed on the CPU socket 22 via a fixing
spring 44 serving as pressurizing means so as to be detached
therefrom. The fixing spring 44 has a strip-shaped pressurizing
portion 45 and a pair of arm portions 46a and 46b connected to both
ends of the pressurizing portion 45. The pressurizing portion 45
extends across the central part of the second surface 37b of the
heat sink 36 and is curved in a shape of an arc so as to warp to
the second surface 37b. For this reason, the central part in the
longitudinal direction of the pressurizing portion 45 elastically
touches the second surface 37b. The arm portions 46a and 46b are
formed by turning up both ends of the pressurizing portion 45 at
substantially right angles in the same direction. Engaging portions
47a and 47b are formed respectively at the top ends of the arm
portions 46a and 46b. The engaging portions 47a and 47b are hooked
in the engagement holes 48a and 48b of the CPU socket 22 so as to
be detached therefrom.
[0052] For this reason, when the engaging portions 47a and 47b of
the fixing spring 44 are hooked in the engagement holes 48a and 48b
of the CPU socket 22, the pressurizing portion 45 of the fixing
spring 44 elastically abuts on the second surface 37b of the heat
sink 36 and thereby the heat sink 36 is pushed toward the
semiconductor package 26. Thus, the heat-transfer member 41 is
sandwiched between the IC chip 28 and the heat receiving surface 39
of the heat sink 36, so that the IC chip 28 and the heat receiving
surface 39 are thermally connected via the heat-transfer member
41.
[0053] A spacer 50 is provided between the circuit board 27 of the
semiconductor package 26 and the heat sink 36 as shown in FIGS. 4
and 5. The spacer 50 formed of a rigid material such as synthetic
resin, metal or ceramic. The spacer 50 is shaped in a square frame
to surround the IC chip 28 and the heat receiving portion 38 of the
heat sink 36, and a through hole 51 is formed at the central part
of the spacer 50 while avoiding the IC chip 28 and the heat
receiving portion 38.
[0054] The spacer 50 has a thickness extremely greater than the
height of the IC chip 28. When the heat sink 36 is fixed at the CPU
socket 22 by the fixing spring 44, the spacer 50 is sandwiched
between the outer peripheral part of the first surface 37a of the
heat sink 36 and the second mounting surface 29b of the circuit
board 27 and is positioned just above the CPU socket 22 and the
current-carrying terminals 31.
[0055] Thus, the spacer 50 supports the heat sink 36 at the
position remote from the IC chip 28 and receives most of the load
of the heat sink 36 applied to the IC chip 28. Therefore, the
heat-transfer member 41 is pushed down between the IC chip 28 and
the heat receiving surface 39 to an appropriate degree by
appropriately setting the thickness of the spacer 50 in accordance
with the height of the IC chip 28, the degree of the protrusion of
the heat receiving portion 38 and the like. As a result, the
heat-transfer member 41 is packed at high density without gap
between the IC chip 28 and the heat receiving surface 39.
[0056] In this structure, when the IC chip 28 of the semiconductor
package 26 generates heat, the heat of the IC chip 28 is
transferred to the heat receiving portion 38 of the heat sink 36
through the heat-transfer member 41. Then, the heat of the IC chip
28 is diffused to the heat sink 36 by the transfer of heat from the
heat receiving portion 38 to the heat sink 36 and radiated into the
stand portion 7 via the radiator fins 42.
[0057] The heat sink 36 is forcibly pushed down on the
semiconductor package 26 via the fixing spring 44, in the state of
thermally connecting the heat sink 36 to IC chip 28, as shown in
greatest detail in FIG. 4. At this time, as the spacer 50
surrounding the IC chip 28 is provided between the semiconductor
package 26 and heat sink 36 and the heat sink 36 is supported by
the spacer 50, most of the load of the heat receiving portion 38 of
the heat sink 36 applied to the IC chip 28 is received by the
spacer 50.
[0058] For this reason, the excessive load of the heat receiving
portion 38 of the heat sink 36 is not concentrated on the IC chip
28 and therefore it is possible to prevent the IC chip 28 from
being damaged. In addition, it is possible to prevent the central
part of the circuit board 27 supporting the IC chip 28 from bending
or warping, the soldering part between the circuit board 27 and the
solder balls 34 is not peeled, or no cracks occur at the solder
part. Electric connection between the circuit board 27 and the IC
chip 28 can be therefore maintained preferably.
[0059] In addition, as the central part of the circuit board 27
corresponds to the component-arranged area 30b on the circuit board
27, bending or warping of the component-arranged area 30b can be
prevented. For this reason, it is possible to prevent the connected
part between the component-arranged area 30b and the circuit
components 32 from being peeled off or damaged, and it is also
possible to remarkably maintain the reliability on the electric
connection between the circuit board 27 and the circuit components
32.
[0060] Further, as the spacer 50 abuts on the second mounting
surface 29b of the circuit board 27, at the position corresponding
to the CPU socket 22, the load of the spacer 50 applied to the
circuit board 27 can be received by taking advantage of the CPU
socket 22. For this reason, the circuit board 27 is deformed more
hardly and, therefore, it is possible to certainly prevent the
soldering part between the circuit board 27 and the IC chip 28 from
being peeled off or damaged.
[0061] Moreover, the close contact between the IC chip 28 and the
heat receiving portion 38 of the heat sink 36 can be maintained by
appropriately pushing down the flexible heat-transfer member 41 and
packing it between the IC chip 28 and the heat receiving portion 38
at high density. Therefore, it is possible to increase the
reliability on the electric connection between the IC chip 28 and
the circuit board 27 while maintaining the stable heat connection
state between the IC chip 28 and the heat sink 36.
[0062] The present invention is not limited to the above-described
first embodiment. FIG. 6 shows a second embodiment of the present
invention.
[0063] In the second embodiment, the structure of the heat sink 36
is different from that in the first embodiment, but the structures
of the CPU socket 22 and the semiconductor package 26 are the same
as those in the first embodiment. For this reason, the same
constituent elements as those in the first embodiment are denoted
by the same reference numerals in the second embodiment, and their
explanations will be omitted.
[0064] The heat sink 36 has a protruding portion 61 formed
integrally with the heat sink 36 as shown in FIG. 6. The protruding
portion 61 protrudes from the outer peripheral part of the first
surface 37a toward the second mounting surface 29b of the circuit
board 27 and is shaped in a frame surrounding the heat receiving
surface 39 of the heat sink 36. The height of protrusion of the
protruding portion 61 is set to be larger than the height of the IC
chip 28.
[0065] The protruding portion 61 has a flat contact surface 62 at
its protruding end. The contact surface 62 is in contact with the
second mounting surface 29b of the circuit board 27 in the outer
periphery of the IC chip 28 when the heat sink 36 is fixed at the
CPU socket 22. Thus, the protruding portion 61 functions as a
spacer in the second embodiment.
[0066] In this structure, the heat sink 36 overlaps the
semiconductor package 26 and the protruding portion 61 of the heat
sink 36 contacts the second mounting surface 29b of the circuit
board 27. For this reason, when the heat sink 36 is fixed at the
CPU socket 22 via the fixing spring 44, most of the load of the
heat receiving portion 38 of the heat sink 36 applied to the IC
chip 28 can be received by the protruding portion 61 and,
therefore, excessive stress is not concentrated on the IC chip
28.
[0067] Further, as the work for providing a spacer between the heat
sink 36 and the circuit board 27 is unnecessary, the steps of the
working process can be reduced and the fixation of the heat sink 36
can be easily executed. In addition, as the protruding portion 61
of the heat sink 36 also serves as a spacer, the number of
components can be decreased and the manufacturing costs can be
reduced as compared with a case where the spacer is separated from
the heat sink 36.
[0068] Moreover, as the protruding portion 61 is a part of the heat
sink 36 in the above structure, the protruding portion 61 itself
has heat conductivity. Thus, the heat radiated from the IC chip 28
to the circuit board 27 can be transferred to the heat sink 36
through the protruding portion 61. Therefore, the heat radiation
path from the IC chip 28 to the heat sink 36 is constituted by a
route passing through the heat receiving portion 38 and a route
passing from the circuit board 27 through the protruding portion
61, and the heat radiating ability of the IC chip 28 can be
enhanced.
[0069] FIG. 7 shows a third embodiment of the present invention. In
the third embodiment, the structure of the heat radiation path from
the IC chip 28 to the heat sink 36 is different from that in the
first embodiment, and other constituent elements are the same as
those of the first embodiment.
[0070] As shown in FIG. 7, the spacer 50 sandwiched between the
heat sink 36 and the second mounting surface 29b of the circuit
board 27 constitutes a grease-filled chamber 71 in cooperation with
the heat receiving surface 39 of the heat sink 36 and the second
mounting surface 29b of the circuit board 27. The IC chip 28 of the
semiconductor package 26 is contained in the grease-filled chamber
71. Grease 72 having heat conductivity is packed at high density in
the grease-filled chamber 71. The grease 72 is in contact with the
IC chip 28, the heat receiving surface 39 of the heat sink 36, the
inner surface of the through hole 51 of the spacer 50, and the
second mounting surface 29b of the circuit board 27. Therefore, the
IC chip 28 is embedded in the grease 72 so that the contact area of
the IC chip 28 and the grease 72 and the contact area of the grease
72 and the heat sink 36 are adequately maintained.
[0071] In this structure, the heat of the IC chip 28 can be
efficiently transferred to the heat sink 36 through the grease 72
and heat radiating ability of the IC chip 28 can be enhanced.
Moreover, as the grease 72 is also in contact with the inner
surface of the through hole 51 of the spacer 50, the heat of the IC
chip 28 can be transferred to the heat sink 36 through the spacer
50. For this reason, particularly, if the spacer 50 is formed of a
material excellent in the heat conductivity, the spacer 50 can be
positively employed as a part of the heat radiation path and
thereby the heat radiating ability of the IC chip 28 can be
enhanced.
[0072] FIG. 8 shows a fourth embodiment of the present invention.
The fourth embodiment is similar to the second embodiment shown in
FIG. 6, but is different therefrom with respect to the structure of
the heat transfer path from the IC chip 28 to the heat sink 36.
[0073] As shown in FIG. 8, the height of the protruding portion 61
of the heat sink 36 is set to be remarkably larger than the height
of the IC chip 28. The protruding portion 61 constitutes a
grease-filled chamber 81 in cooperation with the heat receiving
surface 39 of the heat sink 36 and the second mounting surface 29b
of the circuit board 27. The IC chip 28 of the semiconductor
package 26 is contained in the grease-filled chamber 81. Grease 82
having heat conductivity is packed at high density in the
grease-filled chamber 81. The grease 82 is in contact with the IC
chip 28, the heat receiving surface 39 of the heat sink 36, the
inner surface of the protruding portion 61, and the second mounting
surface 29b of the circuit board 27. Therefore, the IC chip 28 is
embedded in the grease 82 so that the contact area of the IC chip
28 and the grease 82 and the contact area of the grease 82 and the
heat sink 36 are adequately maintained.
[0074] In this structure, the grease 82 is packed not only between
the upper face of the IC chip 28 and the heat receiving surface 39,
but also between the side face of the IC chip 28 and the inner
surface of the protruding portion 61. For this reason, the heat of
the IC chip 28 can be efficiently transferred to the heat sink 36
through the grease 82 and heat radiating ability of the IC chip 28
can be enhanced.
[0075] FIG. 9 shows a fifth embodiment of the present
invention.
[0076] The fifth embodiment is different from the first embodiment
with respect to the structure of the heat radiation path to
transfer the heat of the IC chip 28 to the heat sink 36.
[0077] As shown in FIG. 9, a first heat-transfer sheet 91 serving
as a heat-transfer member is provided between the heat receiving
surface 39 of the heat sink 36 and the upper face of the IC chip
28. The first heat-transfer sheet 91 is formed of a rubber-like
elastic material having the heat conductivity.
[0078] The heat sink 36 has a protruding portion 92 formed
integrally with the heat sink 36. The protruding portion 92
protrudes from the outer peripheral part of the first surface 37a
toward the second mounting surface 29b of the circuit board 27 and
is shaped in a frame surrounding the heat receiving surface 39. The
protruding portion 92 has a flat contact surface 93 on its
protruding end. When the heat sink 36 is fixed at the CPU socket
22, the contact surface 93 faces the second mounting surface 29b of
the circuit board 27 in the outer periphery of the IC chip 28.
[0079] A second heat-transfer sheet 94 is provided between the
contact surface 93 of the protruding portion 92 and the second
mounting surface 29b of the circuit board 27. The second
heat-transfer sheet 94 is formed of a rubber-like elastic material
having the heat conductivity. The second heat-transfer sheet 94 has
a through hole 95 that avoids the IC chip 28 at its central part.
When the heat sink 36 is fixed at the CPU socket 22, the second
heat-transfer sheet 94 is sandwiched between the contact surface 93
of the protruding portion 92 and the second mounting surface 29b of
the circuit board 27.
[0080] Thus, the protruding portion 92 and the second heat-transfer
sheet 94 function as a spacer 96 for supporting the heat sink 36 in
this embodiment. The load of the heat sink 36 applied to the IC
chip 28 is received by the spacer 96.
[0081] In this structure, as the spacer 96 supporting the heat sink
36 has the heat conductivity, the heat radiated from the IC chip 28
to the circuit board 27 can be transferred to the heat sink 36
through the spacer 96. Thus, the heat radiation path of the IC chip
28 is constituted by a route passing from the first heat-transfer
sheet 91 through the heat receiving portion 38 and a route passing
from the circuit board 27 through the spacer 96. Therefore, the
routes for heat radiation from the IC chip 28 to the heat sink 36
can be increased and the heat radiating ability of the IC chip 28
can be enhanced.
[0082] FIGS. 10 and 11 show a sixth embodiment of the present
invention.
[0083] A BGA semiconductor package 100 is employed as a circuit
component in the sixth embodiment.
[0084] As shown in FIG. 10, the semiconductor package 100 comprises
a circuit board 101 of synthetic resin, which serves as a base, and
the IC chip 28, which radiates heat. The circuit board 101 has a
first mounting surface 102a and a second mounting surface 102b
positioned on the opposite side to the first mounting surface 102a.
The IC chip 28 is subjected to the flip-flop bonding at the central
part of the first mounting surface 102a of the circuit board 101
via a plurality of solder balls 34. The second mounting surface
102b of the circuit board 101 has a ball arrangement region 103.
The ball arrangement region 103 is positioned at the outer
peripheral part of the second mounting surface 102b remote from the
central part thereof. A plurality of solder balls 104, which serve
as current-carrying terminals, are arranged in a matrix and
soldered in the ball arrangement region 103. Thus, the solder balls
104 are arranged in an area except that just below the IC chip
28.
[0085] The semiconductor package 100 is mounted on the printed
wiring board 20 by soldering the solder balls 104 on pads (not
shown) on the component-mounted surface 21 of the printed wiring
board 20.
[0086] A heat sink 106 for promoting the heat radiation of the
semiconductor package 100 is provided on the component-mounted
surface 21 of the printed wiring board 20. The heat sink 106 is
formed of, for example, a metal material such as an aluminum alloy
having excellent heat conductivity. The heat sink 106 is shaped in
a flat plate slightly larger than the plane of the semiconductor
package 100.
[0087] The heat sink 106 has a first surface 107a and a second
surface 107b positioned on the opposite side to the first surface
107a. The first surface 107a faces the semiconductor package 100.
The central part of the first surface 107a functions as a heat
receiving portion 108 for receiving the heat of the IC chip 28. The
heat receiving portion 108 has a heat receiving surface 109
positioned in the same plane as the first surface 107a. A
heat-transfer sheet 110 serving as a heat-transfer member is
provided between the heat receiving surface 109 and the upper face
of the IC chip 28. The heat-transfer sheet 110 is formed of a
rubber-like elastic material having the heat conductivity.
[0088] The heat sink 106 integrally has a protruding portion 112.
The protruding portion 112 protrudes from the outer peripheral part
of the first surface 107a except the heat receiving surface 109
toward the second mounting surface 102b of the circuit board 101
and is shaped in a frame surrounding the heat receiving surface
109. The height of protrusion of the protruding portion 112 is set
to be greater than the height of the IC chip 28.
[0089] The protruding portion 112 has a flat contact surface 113 at
its protruding end. The contact surface 113 is in contact with the
first mounting surface 102a of the circuit board 101 in the outer
periphery of the IC chip 28. The contact part between the contact
surface 113 and the first mounting surface 102a is positioned just
above the solder balls 104. Thus, the protruding portion 112
functions as a spacer in the sixth embodiment.
[0090] A plurality of radiator fins 114 are integrally formed on
second surface 107b of the heat sink 106.
[0091] The heat sink 106 has a plurality of support legs 115. The
support legs 115 are positioned at corner parts of the heat sink
106 so as to protrude from the corner parts toward the printed
wiring board 20. Distal ends of the support legs 115 are fixed on
the component-mounted surface 21 of the printed wiring board 20 by
screws 116.
[0092] For this reason, if the support legs 115 are fixed on the
printed wiring board 20, the heat sink 106 is pushed toward the
semiconductor package 100. Thus, the heat-transfer sheet 110 is
sandwiched between the heat receiving surface 109 of the heat sink
106 and the upper face of the IC chip 28, so that the heat
receiving surface 109 and the IC chip 28 are thermally connected
through the heat-transfer sheet 110. At the same time, the contact
surface 113 at the protruding end of the protruding portion 112
abuts on the first mounting surface 102a of the circuit board 101,
so that the protruding portion 112 receives most of the load of the
heat sink 106 applied to the IC chip 28.
[0093] Therefore, the screws 116 function as pressurizing means for
pushing down the heat sink 106 on the semiconductor package 100, in
the present embodiment.
[0094] A metal reinforcement plate 121 as shown in FIG. 11 is
attached to a back surface 120 on the opposite side to the
component-mounted surface 21 of the printed wiring board 20. The
reinforcement plate 121 is shaped in a square frame extending along
the outer peripheral part of the heat sink 106. Tongues 122 are
integrally formed at four corners of the reinforcement plate 121,
respectively. The tongues 122 are fixed on the printed wiring board
20 via the screws 116.
[0095] For this reason, the reinforcement plate 121 is positioned
opposite to the semiconductor package 100 and the heat sink 106
about the printed wiring board 20, so as to prevent the bending or
warping of the printed wiring board 20 caused by pushing down the
heat sink 106 toward the semiconductor package 100.
[0096] In this structure, the heat sink 106 receives the load of
being pushed down on the semiconductor package 100 in accordance
with the fastening of the screws 116, in the state that the heat
sink 106 is thermally connected to the IC chip 28 of the
semiconductor package 100. At this time, the heat sink 106 has the
protruding portion 112 that functions as a spacer and the contact
surface 113 at the protruding end of the protruding portion 112 is
in contact with the first mounting surface 102a of the circuit
board 101. Therefore, the heat sink 106 can be supported by the
protruding portion 112 and most of the load of the heat sink 106
applied to the IC chip 28 can be received by the protruding portion
112.
[0097] As a result, excessive stress is not concentrated on the IC
chip 28, and it is possible to prevent the bending or warping of
the central part of the circuit board 101. Thus, the soldering part
between the circuit board 101 and the solder balls 34 is not peeled
off, crack does not occur at the soldering part, or the electric
connection between the IC chip 28 and the circuit board 101 can be
preferably maintained.
[0098] As the protruding portion 112 is in contact with the first
mounting surface 102a of the circuit board 101, at the position
corresponding to the solder balls 104, the load of the protruding
portion 112 applied to the circuit board 101 can be received by a
plurality of solder balls 104. Thus, the circuit board 101 is
hardly deformed and, of course, the load on each of the solder
balls 104 can be reduced. Therefore, it is possible to prevent the
solder balls 104 from being deformed or damaged, and also possible
to the soldering part between the solder balls 104 and the printed
wiring board 20 from being peeled off or damaged.
[0099] Moreover, in the above-described structure, the close
contact between the IC chip 28 and the heat receiving portion 108
of the heat sink 106 can be maintained as the elastic heat-transfer
sheet 110 is pushed down to some extent and is packed between the
IC chip 28 and the heat receiving portion 108 at high density. It
is therefore possible to increase the reliability on the electric
connection between the IC chip 28 and the circuit board 101 and
between the semiconductor package 100 and the printed wiring board
20, while maintaining the stable heat connection state between IC
chip 28 and the heat sink 106.
[0100] In the sixth embodiment, the solder balls are arranged in
the area avoiding the IC chip. However, the solder balls may be
arranged over the entire first mounting surface of the circuit
board and may also be provided just beyond the IC chip.
[0101] In this structure, as the central part of the circuit board
is supported by the solder balls, deformation at the central part
of the circuit board can be certainly prevented. In addition, the
load on each of the solder balls can be reduced to be smaller and
thereby the reliability on the electric connection between the
solder balls and the circuit board or the printed wiring board can
be more increased.
[0102] Moreover, the present invention is not limited to the
cooling of the PGA or BGA semiconductor package, but can be applied
to a TCP (Tape Carrier Package) type semiconductor package obtained
by bonding the IC chip on, for example, a polyimide tape used as a
base.
[0103] Further, the electronic apparatus according to the present
invention is not limited to a desktop personal computer, but can
also be applied to a notebook-size portable computer.
[0104] 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.
* * * * *