Thermal characterization system for transient thermal impedance measurement and power cycling of IGBT modules

This paper presents a custom-designed thermal characterization system for insulated-gate bipolar transistor (IGBT) modules. The main purpose of this system is to provide experimental capability for transient thermal impedance (Zth) measurement and power cycling reliability test on IGBT modules. LabVIEW programming was applied for circuit control and data acquisition. Gate-emitter voltage (Vge) of IGBT was used as the temperature-sensitive parameter for junction temperature (Tj) measurement. The linear relationship between Vge and Tj for IGBT can be measured by the system. Variation coefficient of lower than 0.5% was achieved for Zth measurement. IGBT modules with the same sample geometry but different die-attach processes were used for system verification: IGBT modules with nanosilver-sintered die-attach have on the average a 12% lower Zth than SAC305 soldered modules. The power cycling capability of the system was demonstrated by cycling a nanosilver-sintered IGBT module with Tj cycled between 45 °C and 175 °C. The cycling lifetime of the IGBT module was recorded as 48,000 cycles with the failure criteria of 20% increase on Zth. Such lifetime is 50% longer than the predicted value from lifetime prediction model.