A comparison study of TIM degradation of phase change material and thermal grease

Abstract

All electronic packages will induce excess heat during usage and heat dissipation methods were developed to remove spare heat from the die in order to improve reliability. Thermal interface materials (TIMs) are one of the key solutions to decrease the thermal resistance between the power device and heat sink. There are a wide variety of TIM material types in electronic packages. Thermal grease is a thermally conductive chemical with high thermal conductivity and commonly used for high-power packages. Phase change materials (PCMs) which are epoxy-based polymer with some thermally conductive fillers will soften with heat and change state from solid to semi-solid and semi-liquid. Compare to thermal grease, PCMs are easy to assemble and no need to dry-out and reduced the voids, pump-out, or delamination. In this study, PCMs and thermal grease during thermal cycling and power cycling were studied. For power cycling, heaters were built inside the die and corresponding thermal sensors were designed to spread all over the die to monitor the thermal resistance changes which reflect temperature changes through the cycling. Wind speed and loading pressure were set as working conditions. According to the resistance of each heater, adjust current to keep total power a constant. After cycling, TIM material behaviors were analyzed. The performance of PCMs and thermal grease under thermal cycling and power cycling and the effect of the degradation of these TIMs are studied and discussed. Based on experiment results, PCMs has better performance in thermal cycle test but thermal grease is more stable than PCMs in power cycle test.