FEM-based combined degradation model of wire bond and die-attach for lifetime estimation of power electronics

A combined damage model has been built by the use of degradation models and finite element simulations as physics-of-failure method to determine degradation rates. This approach has some advantages over the more common Coffin-Manson approach like the ability to explicitly consider interactions of failure modes and a better transferability to new geometries. Experimental data from literature, with the example of wire bond and soldered die-attach degradation of a power module under power cycling conditions, has been used to calibrate the degradation models. Degradation rates, failure modes and numbers of cycles to failure could be predicted with a manageable amount of FE simulations and good accuracy; typical observations from power cycling experiments could be reproduced with the combined damage approach. The proposed methodology could be expanded to other degradation effects, e.g. deterioration of the thermal interface to the heatsink, to determine their interaction with other failure modes and effect on lifetime.