Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Insulating material
Reexamination Certificate
1998-03-24
2001-04-03
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Insulating material
C257S713000, C257S718000, C361S704000
Reexamination Certificate
active
06211566
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
Generally, this invention relates to the removal of heat from the surface of a semiconductor. More particularly, this invention relates to a method and apparatus to improve the thermal interface between a heat sink and a semiconductor.
BACKGROUND OF THE INVENTION
As semiconductors continue to decrease in size while power densities increase, heat dissipation problems must continue to be resolved. Typically, heat sinks are used to cool semiconductors. Semiconductors can use ceramic or plastic packages. Heat sinks are very difficult to attach to plastic packages. Adhesives do not stick very well, and mechanical attachment is expensive. Some mechanical attachment methods can damage the semiconductor package.
One prior art method uses double sided thermal adhesive tape to attach heat sinks to the plastic packages. An external device provides additional support and protection to the heat sinks. This device is a piece of molded plastic that fits over the top of the heat sinks and is attached to the circuit board with screws. A piece of thin foam rubber is attached to the device over the location of the heat sinks. The foam rubber applies even pressure to the top of the heat sinks and compensates for height tolerance problems.
However, this approach is time consuming and expensive. Labor is needed to attach the foam rubber to the device and the foam rubber adds to the cost.
Therefore, it would be highly desirable to reduce the cost and labor associated with installing heat dissipation devices for semiconductor devices.
In addition, the double sided tape may weaken with age. If the heat sinks are not handled properly, then the loss of the mechanical strength of the tape will increase the thermal impedance at the thermal interface between the heat sink and the semiconductor package.
Therefore, it would be highly desirable to improve the thermal interface of the heat sink and semiconductor package by improving the mechanical strength at the thermal interface.
SUMMARY OF THE INVENTION
An apparatus to improve the thermal interface between a heat sink and a semiconductor comprises a support member attached to a bias plate. The support member facilitates a fixed connection with a surface. The bias plate has a beam for alignment with a heat sink that is attached to the semiconductor. The bias plate is attached to the support member such that the support member forces the beam against the heat sink to improve the thermal interface between the heat sink and the semiconductor.
The bias plate of the present invention is used in a computer. The computer has a semiconductor attached to a circuit board. A heat sink is attached to the semiconductor. The bias plate includes a beam for alignment with the heat sink. The bias plate is positioned such that the beam is forced against the heat sink to improve the thermal interface between the heat sink and the semiconductor.
A method improves the thermal performance of a semiconductor by attaching a heat sink to a semiconductor, and biasing a pivoting beam against the heat sink such that the heat sink achieves an improved thermal interface with the semiconductor.
This invention is more cost effective because it eliminates the foam rubber and the labor of attaching the foam. The function of the foam rubber is now supplied by a beam that is molded into the bias plate to apply the appropriate pressure to the heat sinks. The bias plate can be manufactured at a very low cost, for example, by injection molding.
REFERENCES:
patent: 4254431 (1981-03-01), Babuka et al.
patent: 5247426 (1993-09-01), Hamburgen et al.
patent: 5288203 (1994-02-01), Thomas
patent: 5466970 (1995-11-01), Smithers
patent: 5654876 (1997-08-01), Sathe et al.
patent: 5841633 (1998-11-01), Haung
patent: 5978223 (1999-11-01), Hamilton et al.
Chambliss Alonzo
Chaudhuri Olik
Galliani William S.
Pennie & Edmonds LLP
Sun Microsystems Inc.
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