Numerical Prediction of Failure in SnAgCu solder under shear and tensile-dominant cyclic loading

In the first part of this paper difference between simulated SN-Curves under shearing and tensile cyclic load are presented and compared with measurement performed by A. Desphante and A. Dasgupta [1-2]. The two load modes are simulated until a specified force reduction. The material model used in this work is based on visco-plasticity extended with a damage formulation, enabling cyclic softening of the structure. Additionally, multiaxiality of governing stress state is intrinsically included, with aim to account for different damage evolutions under shear and tensile load cases. The calculated damage paths are investigated and compared with cross-sections. Finally, numerically determined lifetimes under different shear and tensile load levels are represented by means of SN-Woehler curves, showing a satisfying agreement with experimental findings. Second part of the paper extends the investigation scope to lifetime prediction of a chip resistor soldered on PCB under temperature cycling. The component is simulated under different temperature profiles, until a specific lifetime reduction is observed. Also in this case, lifetime is compared with measured data.