Evaluation of tin whisker growth

Evaluation of tin whisker growth during thermal aging combined with mechanical stress and roughing of the surface is being observed. We are using 2 types of test conditions: temperature 50°C plus humidity 93% and dry hot 75°C. Under those conditions the samples are exposed 1000 hours. We are testing electroplated copper sheet, hot dipped copper sheet with pure tin and solder SnAg. After coating samples were mechanically modified. One group of samples was bent and another one was scratched with emery paper with granularity P60 and P100 to birth stress in the structure. It is supposed that mechanism of the formation of tin whiskers is accelerated with stress in material. Such modified samples underwent conditions mentioned above. We identified tin whisker on samples with surface covered with tin, both electroplated and hot dipped. The whiskers were identified only under dry hot 75°C conditions.