Uncertainty Analysis of the Interface Thermal Resistance Between Power Module and Heatsink

Thermal resistance of the Thermal Interface Materials (TIMs) between power module and heatsink plays a significant role in thermal stress. This paper investigates the variances in thermal resistances of TIMs during thermal cycling test and among different chips of a six-switch power module. An experimental setup to facilitate the emulation of practical power state operation is built for the test. The dual interface method with structure function analysis is applied to characterize the TIMs thermal resistances. The results reveal considerable changes and variances in the thermal resistances during the test and among the six switches of the power module, implying high-level of uncertainty caused application-level thermal modeling. A case study of PV inverter application is presented to demonstrate the impact on thermal stress and reliability modeling.