Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Utility Patent
2000-02-04
2001-01-02
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S702000, C361S707000, C361S709000, C361S710000, C257S719000, C257S726000, C165S080300, C165S185000, C174S050510
Utility Patent
active
06169659
ABSTRACT:
FIELD OF INVENTION
The present invention pertains to heat sink for an integrated circuit (IC) package. More specifically, the present invention is related to a system and methodology for coupling a heat sink onto an IC package.
BACKGROUND OF THE INVENTION
As electronic circuits get increasingly more powerful and ever smaller in size, the problem of removing heat from the chips is more critical. In particular, a typical operating IC package heats up to a very high temperature that can actually melt and damage the inner parts of the IC package. Thus, heat sink becomes necessary for preventing dangerous heat build-up within the IC package.
The heat sink dissipates heat away from the IC package before heat is accumulated up to a dangerous scenario wherein the IC package is damaged by high temperature. Specifically, the heat is removed by an external metal heat sink which must be closely coupled to the top surface of the IC package. The more closely the heat sink can be coupled to the IC package, the more efficient the transfer of heat away from the IC package. At the same time, the fragility of the IC package need to be taken into consideration such that the coupling does not exert too much force to damage the IC package.
In view of the heating problem associated with an IC package, various methods and mechanical systems were introduced to couple a heat sink onto the IC package. Prior art approaches includes gluing a heat sink onto the IC package, screwing a heat sink onto the IC package, and applying spring force to press a heat sink onto the IC package. Each approach can be evaluated in terms of ease of installation, ease of removal, reliability and efficiency of heat transfer.
The prior art approach of gluing a heat sink onto the IC package enables a straightforward installation. However, once the heat sink is installed by gluing, the heat sink can hardly be removed without damaging the IC package. Also, for large heat sinks, the weight of the heat sink is supported solely by the case of the IC package and the solder connections. Possibility of damages to the IC package is greatly increased. Moreover, installation by gluing introduces at least one extra layer between the heat sink and the top surface of the IC package. Efficiency of heat transfer is thus reduced.
The prior art approach of screwing a heat sink onto the IC package allows for a straightforward installation. Moreover, the removal of the heat sink can be accomplished simply by unscrewing. However, the tolerances involved in both the assembly of the IC package to the board and the manufacture of the heat sink introduce further problems. Specifically, the tolerances involved require several layers of compressible thermal gasket to be used in order to account for the tolerance. Each layer of gasket reduces the amount of heat that can be removed from the IC package. Thus, this approach is not efficient in transferring heat away from the IC package.
The prior art approach of applying spring force to keep a heat sink in place overcomes many of the problems discussed above. To account for the tolerances mentioned above, multiple springs are implemented to simultaneously apply force to the heat sink such that the heat sink is secured in contact with the top surface of the IC package. However, the compression of these springs must satisfy stringent requirements. That is, the spring must be compressed with sufficient force to seat a thermal gasket while not so much force to cause damage to the IC package. Typically, what is allowed in practice is a very narrow range of force for compressing the springs.
Furthermore, the spring force is usually applied at the corners of he IC package with four separate compression springs. As such, heat sink installation becomes a delicate process because these springs must be compressed in a balanced fashion so as to avoid asymmetrical loading on the case of the IC package. Specifically, damages on the IC package can result from asymmetrical loading on the case of the IC package.
Because of the need to avoid asymmetrical loading on the IC package, heat sink installation according to this prior art approach is difficult to implement. To ascertain that all four springs are collectively pressing in continual balance with each other necessitates extreme care. Moreover, shall the need arises to remove the heat sink from the IC package, this intricate spring system makes removal of heat sink a difficult task as well.
Finally, another disadvantage associated with this prior art approach is that a different IC package/heat sink combination necessitates extensive adjustments. In other words, this prior art approach is not well suited to accommodate different requirements of different heat sink/IC package combinations.
All in all, a need exists for improving and simplifying installation and removal of a heat sink to and from an IC package. Thus, a need exists for a system and method to couple a heat sink onto an IC package without being difficult to install the heat sink. A need also exists for a system and method to couple a heat sink onto an IC package without being difficult to remove the heat sink shall the need to do so arises. A further need exists for a system and method to couple a heat sink onto an IC package without reducing the heat transfer efficiency of the heat sink. Still another need exists for a system and method to couple a heat sink onto an IC package while remaining adaptable to the different force requirements of various IC package/heat sink combinations. Moreover, a need exists for system and method to couple a heat sink while not introducing unbalanced loading on the IC package.
Fortunately, as will be explained in the coming sections, the present invention answers all of the needs discussed above. In addition, the present invention offers new advantages not found in these prior art approaches.
SUMMARY
The present invention is drawn to a system and method for securing a heat sink onto a IC package disposed on a PCB. The present invention differs from the prior art approaches by adapting a stepped procedure that clearly separates the installation process into two finer steps of a attaching step and a tightening step. Also, the present invention differs from one prior art approach by implementing just one single spring. The heat sink and its mechanical support constitute a heat sink assembly that is first attached in a first configuration onto the IC package. Then, this heat sink assembly is modified into a modified configuration adapted to tighten the heat sink onto the IC package without risking damages to the IC package.
The first configuration of the heat sink assembly simplifies the process of attaching the heat sink onto the IC package; the modified configuration of the heat sink assembly enables a load-balanced and efficient thermal contact to be achieved between the heat sink support portion of the mechanism and the IC package. With the delicate contact being formed safely between the heat sink and the IC package, the present invention overcomes all of the disadvantages associated with the prior art approaches. In addition, the present invention introduces additional advantages not available before.
At least three advantageous innovations are implemented by the present invention. The first innovation is the implementation of one single spring. The second innovation is the refinement of heat sink installation by clearly separating attaching heat sink from tightening into a multi-step process. The third innovation is the placement of a spring within a module manufactured independently from the rest of the heat sink assembly.
Specifically, by using just a single spring instead of multiple springs to tighten the heat sink onto the IC package, asymmetrical loading caused by multiple springs is avoided. By removing the need to prevent asymmetrical loading, the present invention simplifies installation of a heat sink onto an IC package. Also, by removing the need to prevent asymmetrical loading, the present invention simplifies removal of a heat sink to an IC package shall such n
Datskovsky Michael
Silicon Graphics Inc.
Tolin Gerald
Wagner , Murabito & Hao LLP
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