Identification of thermo-mechanical fatigue fracture location by transient thermal analysis for high-temperature operating SiC power module assembled with ZnAl eutectic solder

In this paper, we demonstrate that the structural degradation of a silicon carbide (SiC) power module corresponding to thermal cycles can be detected and tracked non-destructively by transient thermal analysis method. The purpose of this evaluation is to analyze the distribution of the thermal resistance in the power module and to identify the structure deterioration part. The power module with SiC-MOSFET were assembled using ZnAl eutectic solder as device under test. The individual thermal resistance of each part such as the SiC-die, the die-attachment, the AMCs, and the baseplate was successfully evaluated by analyzing the structure function graph. A series of thermal cycle test between −40 and 250°C was conducted, and the power modules were evaluated their thermal resistance taken out from thermal cycle test machine at 100, 200, 500 and 1000 cycles. We confirmed the increase in thermal resistance between AMCs and base plate in each thermal cycle. The portion where the thermal resistance increased is in good agreement with the location of the structural defect observed by scanning acoustic tomography (SAT) observation.