Microanalysis for tin whisker risk assessment

Abstract

We use microanalysis to illustrate several effects of plating microstructure on tin whisker growth, such as grain size, plating composition, and plating thickness. Starting from the diffusion-based theory of tin whisker growth, we explain why large-grained and thin platings grow fewer whiskers, and why Ni diffusion barriers and Sn-3% Pb solder composition may not be protective against tin whisker growth. We also use tin whisker growth rate data to quantify the diffusion model and predict the time evolution of whisker length distributions. The results provide a consistent framework for tin whisker risk assessment from a materials perspective.