Spontaneous tin whisker growth from rare-earth tin alloys

Tin whisker growth phenomena from rare-earth tin alloys were investigated with both scanning electron microscopy and transmission electron microscopy. Large quantities of tin whiskers with diameters from 20 nm to 10 μm and length from 50 nm to 500 μm were formed on the surface of the alloys at a growth rate of 0.1~1.8 nm·s^-1. The growth directions of tin whiskers were studied among more than 200 whiskers. It was found that this kind of tin whisker is single crystal β-Sn even it has striations, steps, and kinks, but no dislocation and twin or grain boundary was observed within the whisker body. RESn₃ compounds in the alloys endure selective oxidation during whisker growth, which provides continuous tin atoms for tin whisker growth and compressive stress as driving force. The growth models of tin whisker and hillock on rare-earth tin alloys were discussed upon the observations.