Evaluation of thermophysical properties and structure of heat dissipation sheets as thermal interface materials

Abstract

Thermal interface materials (TIMs) are used in the mounting of semiconductor devices for rapid heat transfer from heat source to heat sink. The advantages of using TIMs include a lower total cost, elimination of liquid cooling, lower system cooling, lower power consumption, longer operating life and safety, and improved performance. However, there exist various interfaces called “air gaps” between the heat source and heat sink, resulting in reduced heat transfer at the interface depending on the thermal conductivity of the air layer. In this study, the structure of a typical heat dissipation sheet was examined, and the results were correlated with the distribution characteristics of the thermophysical properties. The distribution of the thermal diffusivity depended on the dispersion and orientation of graphite in the resin, making it difficult to obtain uniform thermal properties. These results suggest the need to develop new TIMs that can adequately fill the voids at the device interface, especially in a heat-dissipating adhesive that is in the liquid form at the time of use.