Wear-Out Mechanism of Press-Pack IGBTs Under Accelerated Aging Test

Abstract

The study of wear-out mechanism of press-pack insulated-gate bipolar transistors (IGBTs) (PPIs) is conducted insufficiently now. In this article, both the numerical and experimental methods are utilized to investigate the wear-out mechanism of PPIs. After conducting an accelerated aging test, three wear-out modes are observed: fretting scratches, cracks next to the additional metallization area, and oxidation of the additional metallization area. The oxidation of the additional metallization area is the newly found wear-out mode. In order to explain the deterioration mechanism of the modes, the fully coupled multiphysical model considering the aging state inside PPIs is utilized to analyze the temperature, pressure, and voltage distribution. The results show that fretting wear is the main reason for the three wear-out modes. First, the fretting scratches caused by fretting wear lead to the increment of surface roughness. The junction temperature and thermal resistance of the PPI both show approximately linear increment with surface roughness, while the saturation voltage remains unchanged. Second, high mechanical pressure during fretting wear results in the fatigue cracks next to the additional metallization area. Finally, it is found that the fretting wear also leads to the oxidation of the additional metallization area.