The crack propagation analysis in an IGBT package under in-service conditions by VCCT

Insulated Gate Bipolar Transistors (IGBTs) are critical power components used in electric vehicles, new energy systems, and industrial automation applications. As the performance requirements for power devices continues to grow, ensuring IGBT reliability has become a significant challenge due to the high currents and severe temperature variations during operation, especially during the long period of working conditions. One of the common failures, i.e., the propagation of cracks in the package, can seriously affect the electrical and thermal performance of IGBTs, such as the reduced efficiency, increased power dissipation, and ultimately device damage. Previous studies have focused on reliability testing with little consideration of the actual operating conditions. Therefore, a deeper understanding of crack propagation under in-service conditions is essential to help improve the reliability of power devices. This study focuses on the crack propagation in a typical IGBT with a transistor outline (TO) package under its in-service conditions. Three-dimensional (3D) structures of the IGBT package were built in Abaqus according to the designed dimensions. A user subroutine was developed to involve the power dissipation on the chip as a function of case temperature to simulate the operating conditions. The crack propagation was predicted along vulnerable interfaces using the 3D virtual crack closure technique (VCCT) which assumes that the energy required to close a crack is the same as that required to create it. The energy release rate calculated along straight crack and quarter circular crack fronts showed that shear modes primarily drive crack propagation and the most vulnerable interface is at between the epoxy molding compound (EMC) and exposed pad.