Advantages of the extended finite element method for the analysis of crack propagation in power modules

Abstract

• XFEM and Level set methods with submodelling has been implemented in this study. • Method easily allows inclusion of crack growth in IGBT wire bond reliability analysis • Bond wire diameter and loop height significantly affect IGBT wire bond reliability. • Wire bond degradation parameter values decrease with increasing crack length. • For similar load density, smaller wire diameter produces longer wire bond lifetime. The techniques of extended finite element method, level set method and the submodelling approach are implemented in this study to model crack and crack growth in ultrasonically bonded thick aluminium wire for the IGBT power electronics modules under different loading conditions for the purpose of lifetime prediction and reliability assessment during design and manufacturing stages. The crack growth and lifetime prediction were performed under cyclic fatigue passive thermal cycling and active power cycling for the bond wire lift-off failure mechanism while the J-integral for different heel crack lengths are predicted under mechanical loads. The analyses showed that the techniques implemented in this paper are effective for modelling such complex geometries and loading conditions and can easily be integrated in a virtual design platform for power electronics. The accuracy of the technique is evaluated by comparing with trends in the published experimental tests and simulation results as well as the standard finite element method which are all in a good agreement. The wire bond crack growth rate under cyclic loading is strongly influenced by the bond thickness and loading conditions.