Electron microscpy study of deformation and recrystallization behavior of pure tin for mitigation of whiskers

Abstract

The clarification of whisker growth mechanism is a key to the mitigation of tin-whiskers. In order to confirm the growth model the present authors had proposed, the process of recrystallization of tin was investigated. A single crystal of tin was prepared by using a slow-cooling method and plate samples were prepared by using a spark-cutter and electro-polishing. Deformation was applied to the plate samples by scratching. The microstructural changes with time at room temperature after scratching were observed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The experimental results showed clearly that recrystallization can proceed even at room temperature. A tensile test was also performed in order to investigate its ordinary deformation behavior. The present results have supported the model for tin whisker growth mechanism, suggesting that if the recrystallization phenomenon can be controlled to proceed homogenously in tin solder and plating, the whisker growth will be mitigated.