Thermal-Interface-Material Degradation Detection Method via In-ternal Gate Resistance in an IGBT chip

Abstract:
This paper presents a method to detect the degradation of thermal resistance in a power module by a temperature sensing circuit that uses the temperature dependence of the internal gate resistance of the power devices. A repetitive temperature variation causes an increase in thermal resistance of thermal interface material (TIM), which is inserted between a power module and a heatsink, due to a difference in a coefficient of thermal expansion. An increase in the thermal resistance of TIM results in a higher junction temperature. The authors conducted the experiments to monitor the junction temperature with altering the number of heat dissipation sheets between a power module and a heatsink. A difference in the number of heat dissipation sheets corresponds to degradation of TIM. An increase in thermal resistance is directly associated with an increase in junction temperature. Experimental results show that an increase in the thermal resistance of TIM can be detected by the temperature sensing circuit. The proposed method is easy-to-install and cost effective because it utilizes the internal gate resistor that already present in a power module.