Hierarchal modeling of creep behavior of SnAg solder alloys

In this paper, a microstructure-dependent creep model is developed that accounts for the hierarchal microstructure at multiple length scales. The model considers three distinguishable phases in the solder alloy at two different length scales: at the larger scale Sn dendrites of micrometer size are embedded in a homogeneous eutectic region; at a much smaller length scale the eutectic region consists of submicron size Ag3Sn particles embedded in a homogeneous Sn matrix. The model predictions agree well with creep test data of lanthanum doped SnAg solders.