TIM selection criteria for silicon validation environment

Thermal interface materials (TIMs) are widely used as heat conductive medium between a heat source and a heat dissipating device. A high thermal performance TIM can provide a low thermal resistance path and thus improve the thermal management of the heat source. This paper presents various criteria for TIMs used in silicon validation environment in addition to the well-known criteria for high performance TIMs. Seven commercially available greases and eight different thermal pads were evaluated based on the requirements for use in the silicon validation environment. These criteria include thermal performance before and after subjected to elevated temperature, adhesiveness of the grease before and after subjected to elevated temperature, adhesiveness of the grease over multiple usages, compliance of the thermal pad, reusability of the thermal pad for multiple loading and unloading cycles, and severity of silicone bleed from the thermal pad under elevated temperature and pressure. In addition to these validation requirements of TIMs, there is an additional requirement of high cycle of reusability in the robotic testing environment to minimize human interface. Indium TIM, a metallic TIM, provides well over 500 reusability cycles. Adhesion issue with high Indium content becomes dominant at high temperature and needs to be well addressed to take advantage of the reusability characteristics of Indium TIM.