Study on the Method to Measure Thermal Contact Resistance Within Press Pack IGBTs

The accurate measurement of the thermal contact resistance between multilayers within press pack insulated gate bipolar transistors (PP IGBTs) is significant for optimizing their thermal resistance to improve reliability, as thermal contact resistance accounts for about 50% of their total thermal resistance under the rated clamping force. The components within PP IGBTs are very small, and an external clamping force is needed to ensure they work normally. Thus, the methods of thermal contact resistance measurement of steady-state and transient methods are no longer suitable. In this paper, the method of thermal structure function is proposed to measure the thermal contact resistance between multilayers within PP IGBTs. The accurate measurement of the transient thermal impedance curve of PP IGBTs is the key to this method, and it can then be transformed to a cumulative and differential structure function to determine the thermal contact resistance accurately. A single fast recovery diode chip submodule is fabricated to predict the thermal contact resistance behavior within PP IGBTs in this experiment, and the experimental results agree well with theoretical values. Furthermore, the influence of both the high temperature and the clamping force on the thermal contact resistance can also be obtained from this method accurately.