Online Calculation of the Increase in Thermal Resistance Caused by Solder Fatigue for IGBT Modules

This paper addresses the catastrophic failure of power converter systems caused by the aging of the insulated-gate bipolar transistor (IGBT) module. Monitoring the aging state of IGBT in real time enables the defective module to be found and be replaced timely. Solder fatigue increasing the internal thermal resistance of the module has been identified as one of the main root causes of IGBT module aging. In this paper, a novel event-driven solder fatigue monitoring mechanism is proposed. The proposed method consists of two models which are a dynamic solder aging monitoring model and an event-driven online calculation model of the increase in thermal resistance. The dynamic solder aging monitoring model detects solder fatigue in real time by the variations of case temperatures with thermal sensors on the bottom surface of the baseplate. The event-driven online calculation model estimates the increase in thermal resistance at the occurrence of the solder aging event by the junction temperature from thermosensitive electrical parameters, which are not affected by the solder fatigue. With the cooperation of two models, the aging level of the IGBT module caused by solder fatigue is evaluated. Simulation and experimental results are provided to verify the effectiveness of the proposed method.