Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-12-14
2003-09-16
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C361S676000, C427S209000, C428S448000, C428S450000, C524S404000, C524S428000, C524S430000, C524S433000, C524S434000, C524S588000, C528S025000, C528S031000
Reexamination Certificate
active
06620515
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a thermally conductive phase change composition (PCC) and methods for preparation and use of the PCC. More particularly, this invention relates to a PCC comprising an organofunctional silicone wax and a thermally conductive filler. The PCC can be used as a thermal interface material (TIM).
BACKGROUND
Electronic components such as semiconductors, transistors, integrated circuits (ICs), discrete devices, and others known in the art are designed to operate at a normal operating temperature or within a normal operating temperature range. However, the operation of an electronic component generates heat. If sufficient heat is not removed, the electronic component will operate at a temperature significantly above its normal operating temperature. Excessive temperatures can adversely affect performance of the electronic component and operation of the device associated therewith and negatively impact mean time between failures.
To avoid these problems, heat can be removed by thermal conduction from the electronic component to a heat sink. The heat sink can then be cooled by any convenient means such as convection or radiation techniques. During thermal conduction, heat can be transferred from the electronic component to the heat sink by surface contact between the electronic component and the heat sink or by contact of the electronic component and heat sink with a TIM. The lower the thermal impedance of the medium, the greater the flow of heat from the electronic component to the heat sink.
Surfaces of the electronic component and the heat sink are typically not completely smooth, therefore, it is difficult to achieve full contact between the surfaces. Air spaces, which are poor thermal conductors, appear between the surfaces and increase impedance. These spaces can be filled by inserting a TIM between the surfaces.
Some commercially available TIMs are organic polymers or elastomers filled with thermally conductive fillers. However, elastomers suffer from the drawbacks that they may be difficult to apply in an uncured state, and they may not fully adhere or mesh with the surfaces if cured before application. Polymers suffer from the drawback that they can flow out of the spaces after application. Some polymers may also suffer from the drawback that they lack sufficient thermal conductivity.
Silicone greases with conductive fillers have also been proposed as TIMs. However, greases suffer from the drawbacks that they can be messy to apply and can flow out of the spaces after application.
PCCs have been proposed for use as TIMs. PCCs are advantageous in solving the above problems because they can be formulated to be a solid at low temperatures and deformable at a phase change temperature. The phase change temperature can be equal to or above the normal operating temperature of the electronic component.
PCCs can comprise organic materials such as waxes, and conductive fillers. However, organic waxes suffer from the drawback that they can flow out of the spaces after application, during operation of the electronic component. Organic waxes may also be brittle at room temperature.
SUMMARY OF THE INVENTION
This invention relates to a phase change composition (PCC) and methods for its preparation and use. The PCC comprises a matrix and a thermally conductive filler. The matrix comprises an organofunctional silicone wax.
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“Handbook of Fillers, second edition”, George Wypych, 2000, Chem Tec Publishing, Yoronto, Ontario, Chapter 6, pp. 312, 318 320.*
Thermal Trends, “Parameter Optimization for Measuring Thermal Properties of Electronic Materials Using the Transient Plane Source Technique”, Craig A. Dixon, Michael R. Strong, and S. Mark Zhang, vol. 7, No. 5, p. 1, 2000.
American Chemical Society, “Effect of Stabilization of Polypropylene During Processing and Its Influence on Long-Term Behavior Under Thermal Stress”, Han Sweifel, p. 376-396, 1996.
ITherm abstract submission,“Silicone Organic Phase Change Materials for TIM”. Mark Zhang, Diane Swarthout, Jane Feng.
ITherm abstract submission, “Novel Silicone Based Phase Change Thermal Interface Materials”. Dorab E. Bhagwagar, Kimmai T. Nguyen and Andrew A. Mojica.
Feng Qian Jane
Petroff Lenin James
Swarthout Diane Elizabeth
Zhang Shizhong
Brown Catherine U.
Dawson Robert
Dow Corning Corporation
Zimmer Mark S
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