Power Cycling Reliability of SiC MOSFETs in Discrete and Module Packages

This paper presents an analysis of power cycling (PC) capabilities of two industry-standard packages with silicon carbide power MOSFET dies: the discrete TO-247 package and a base-plate-less power module with silicone gel encapsulation. PC experiments show a more than an order of magnitude higher number of cycles to failure for the TO-247. The significant spread in the PC lifetime of TO-packaged SiC power MOSFETs by different manufacturers is correlated with die thickness, bond wire diameter, and number of bond wires. A failure analysis and electro-thermo-mechanical simulations point out that shorter PC lifetime in the case of power modules is due to a high stress in solder, while in the case of TO-packages it is ascribed to wire lift-off. The simulations indicate that rather than die thickness, the wire diameter is a critical parameter influencing wire lift-off.