Hierarchical Modeling of Creep Behavior of SnAg Solder Alloys

In this paper, a microstructure-dependent creep model is developed that accounts for the hierarchal micro structure 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 phase; at a much smaller length scale the eutectic phase consists of sub-micron size Ag₃Sn particles embedded in a homogeneous Sn matrix. The model predictions agree well with creep test data of RE doped SnAg solders.