Reliability investigation of SiC MOSFETs under switching operation in various packages

Abstract:
Wide bandgap devices like Silicon Carbide (SiC) offer the possibility for higher efficiency compared to Silicon (Si) devices. Nevertheless, several authors state lower power cycling reliability compared to Si devices for similar interconnection technology. In this work, different transistor outline (TO-247) and a baseplate free (easy-pack) package equipped with SiC MOSFETs are investigated. To test more application close, special power cycling equipment is used, which actively switches the devices under test and therefore provides conduction and switching losses. The experimental lifetime results show no major difference between standard test method and advanced power cycling for all investigated packages. The failure location is package dependent. The TO-247 devices failed with bond wire lift-off, while the easy-pack devices showed chip solder fatigue. Supporting 3D-simulations could confirm experimental findings in the TO devices, indicating that a higher number of small and short bond wires is superior to less but thicker bond wires.