Reliability testing of silicone-based thermal greases

Thermal interface materials (TIMs) play a key role in the thermal management of microelectronics by providing a path of low thermal impedance between the heat generating devices and the heat dissipating components (heat spreader/sink). Thermal greases are TIM solutions that are widely utilized in the industry for the cooling of microelectronics. Thermal greases are expected to provide a very low thermal resistance path due to their ability to penetrate into the surface features of heat spreaders/sinks and silicon die. In addition, thermal greases do not require post-processing. However, some of the disadvantages associated with thermal greases are their tendency to "dry-out" and "pump-out" during prolonged periods of operation. These phenomena can drastically reduce the heat dissipation capability of the thermal grease layer. A "perfect" high thermal conductivity and low contact resistance TIM layer may become a voided and cracked layer on exposure to thermal and mechanical stresses. In this research, various tests are explored to determine the ability of thermal greases to deliver a reliable thermal interface, utilizing various thermal grease formulations, different TIM layer geometries, and testing conditions.