A model of Sn whisker growth by coupled plastic flow and grain boundary diffusion

摘要

Finite element simulations are used to calculate the rate of whisker growth due to intermetallic formation in a Sn film with columnar grain structure on a Cu substrate. The simulations account for plastic flow by dislocation motion within the grains, as well as diffusion along grain boundaries. Grains with a slightly lower yield stress than their neighbors are shown to act as sinks for material and are progressively extruded from the film. A simple analytical model is developed to estimate the resulting whisker growth rate, and is shown to be in good agreement with experimental measurements.