Degradation Analysis of TO-247 Package SiC-MOSFETs Subjected to High Temperature Storage and Heavy Thermal Cycle Test

Abstract

Abstract Three types of TO-247 package SiC-MOSFETs, denoted as A, B and C and fabricated by different manufacturers, were subjected to thermal cycle tests (TCT) ranging from −40°C to 200°C and a high temperature storage test (HTST) at 200°C in air. Their reliability was continuously investigated based on electrical characterizations, X-ray inspection and scanning acoustic tomography (SAT). Intermittent SAT observation revealed that, regardless of the device type, the epoxy resin (encapsulant) first peeled on the Cu die pad around the outer edge of the SiC power die and then peeling rapidly spread outward as the number of thermal cycles or storage time increased. The number of cycles or storage time differed depending on the device type (manufacturer). Subsequently, further peeling occurred on the SiC die and the devices failed or showed instability. The deterioration pattern tended to differ somewhat between the TCT and HTST. Uplift of the die attachment was observed for device A after thermal storage for 1000 hours.