Thermal Failure Analysis of IGBT Based on the DeLaminations in the Backside Metal Films

A thermal failure analysis of insulated-gate bipolar transistor (IGBT) in engineering applications was introduced. In this paper, the failure mode of IGBT was determined and the failure position was ultimately located in the backside metal films of IGBT chips by a series of failure analysis procedures. The highly accelerated stress test(HAST) and ultrasonic scanning detection have been performed to analyze and verify its root failure causes. It indicated that the delaminations have already formed in the backside metal films of IGBT chips due to the excessive consumption of Ni under high temperature conditions. These defects caused a sustained increase in local junction temperature of IGBT chips during high-load operation, and ultimately leaded to the thermal breakdown of IGBT. Finally, the solutions were proposed from three aspects: structure of backside metal films, welding process, and testing methods.