The influences of electrical overstress (EOS) on the reliability of power insulated gate bipolar transistor (IGBT) modules were investigated by switching, frequency, and blocking tests. This paper reports the test results and the failure analysis results. Some conclusions, from the point of IGBT application reliability view, are also provided in this paper. ' This work was partly supported by National Natural Science Foundation of China (69696035). 0-7803-4306-9/98/510.00 1998 IEEE