Analysis on the Bonding-wire Failure Mechanisms of Si/SiC Hybrid Switch under UIS Test

In this paper, the failure mechanisms of bonding wires inside the 1200V Si/SiC hybrid switch under unclamped inductive switching (UIS) has been investigated using experiment testing combinated with finite element method (FEM). The finite element simulation quantitatively takes coupling effect among electrical, thermal and mechanical stresses experienced by the real hybrid switch into consideration. It is found that since the power loss of the internal SI IGBT is higher, its temperature rising is rapid to reacch the critical level, which is the root reason for the typical thermal-runaway fault of the hybrid switch in the UIS case. The electro-thermal-mechanical multiphysics cosimulation results indicate that non-uniform temperature distribution within the Si IGBT chip induced localized mechanical stress concentration at the edges of bonding wires, rendering these regions susceptible to delamination or detachment.