In-Situ Transient Testing of Run-in and Degradation Effects of Thermal Interface Sheets in Power Switch Assemblies

Abstract:
A major factor influencing the performance of a power appliance is the quality of the thermal interface materials (TIM) in the assembly. Although some information on the expected behavior of a TIM layer can be obtained by testing in dedicated thermal conductivity testers, the in-situ behavior of a TIM in actual position can significantly differ. The paper demonstrates the change of the heat conducting path at the priming (first powering event), run-in (early powering cycles) and curing at high temperature. The TIM properties are monitored by thermal transient testing, where structure function analysis helps differentiating between internal device details, thermal interface and cooling mount. The selection of TIM materials is supported by a preliminary test in standard conductivity tester.