Potential failure modes of cement-based encapsulation concepts for reliable power electronics

Abstract:
The introduction of new encapsulation materials – like cement-based concepts – with enhanced thermal, mechanical and thermomechanical properties is one opportunity to increase the performance and reliability of power electronic devices. Within first studies, an increase of lifetime by a factor 2.3 was observed in power cycling tests for “Econo3” power modules with cement-based encapsulation in comparison to modules encapsulated with standard silicone gel. Finite element analysis has shown variations of the local stress distribution during power-cycling test resulting in potential new or modified failure modes. In order to verify the outcomes of finite element modelling, comprehensive failure analysis was performed. As a result, a failure catalog will be presented including and discussing potential new failure modes. In addition, the impact to well-known failure modes – based on modified material properties of the cement-based encapsulation – is discussed. The analyzed failure modes include crack propagation within the cement-based encapsulant itself, fracture and wear out issues related to chip- or substrate failure as well as bond wire and solder fatigue.