FEM Study of Fatigue Crack Growth in a Power Semiconductor Chip Subjected to Transient Thermal Loading

A detailed finite element analysis of fatigue crack growth between metallisation layers of a power semiconductor device subjected to active cycling conditions is carried out. The active cycling and the resulting transient thermal loading is the source of the thermally-induced cyclic stresses in the microelectronic device, which may cause the fatigue failure. To model the fatigue crack formation and propagation under the transient thermal loading conditions, a coupled thermomechanical cyclic cohesive zone model based on an irreversible damage evolution equation is utilised. The contact formulation of the implemented cohesive zone model allows to consider evolving tractions and heat flux across the cohesive zone both in open and closed crack states. To accelerate simulations, a cycle jump technique without the need of damage extrapolation is utilised.