Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-12-11
2002-08-27
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C257S719000, C361S710000, C361S719000, C439S487000
Reexamination Certificate
active
06442026
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
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
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
In one embodiment of the invention, there is provided an apparatus comprising a wiring board having a surface; a circuit component containing a base of synthetic resin, said base having a first mounting surface, a second mounting surface positioned on an opposite side to the first mounting surface, a plurality of terminals arranged on said second mounting surface, and a heat generating unit positioned on a central part of the first mounting of said base, said plurality of terminals arranged in an area around said heat generating unit; a socket provided on the surface of said wiring board and electrically connected to said plurality of terminals, said socket having a hollow portion at a position corresponding to the central part of said base, said second mounting surface of said base facing the hollow portion of said socket; a heat sink 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; and a spacer provided between said base of said circuit component and said heat sink, for supporting said heat sink.
In another embodiment of the invention, there is provided an electronic apparatus comprising a housing; a wiring board contained inside said housing, said wiring board having a surface; a circuit component containing a base, said base having a first mounting surface, a second mounting surface positioned on an opposite side to the first mounting surface, a plurality of terminals arranged on said second mounting surface, said plurality of terminals, said socket having a hollow portion at a position corresponding to the central part of said base, said second mounting surface of said base facing the hollow portion of said socket; a heat sink 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; a pushing member 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.
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.
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 b
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Thompson Gregory
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