Study on the Method to Measure the Junction-to-Case Thermal Resistance of Press-Pack IGBTs

Accurate measurement of the junction-to-case thermal resistance of press-pack insulated gate bipolar transistors (PP IGBTs) is a great challenge due to their special packaging style and working conditions. The traditional thermocouple and transient dual interface methods have been successfully applied to measure the junction-to-case thermal resistance of wire-bonded IGBT modules. In this paper, a single fast-recovery diode (FRD) chip submodule is fabricated to determine the best method to measure the junction-to-case thermal resistance of PP IGBTs. Therefore, both the traditional thermocouple method and the transient dual interface method were used to measure the junction-to-case thermal resistance of the collector-side cooling with the emitter-side adiabatic. The transient dual interface method, which does not require locating a thermocouple to measure the case temperature, is ideal for the PP IGBTs measurement based on the experimental results and theoretical verification. Most importantly, both bulk thermal resistance of specific layers and thermal contact resistance between multilayers in PP IGBTs can be obtained by transforming the transient thermal-impedance curve.