The effect of coating thickness and external force on the growth of tin whisker

In this paper, tin whisker behaviour of electroplating tin coating was studied in different environments. Different thickness of electroplating tin coating on copper substrate had been tested. Two different environmental conditions had been applied :one temperature tests (70 °C)and one external force tests(70 °C /17.5N). The growth of tin whisker was studied by using scanning electron microscopy (SEM). It is observed that the electroplating tin coating was capable of growing tin whiskers. Most of the detected whiskers are so called “nodule” type whiskers, approximately 10-15μm length with 3.28μm thickness. It was found that the thickness of coating has a major effect on causing tin whiskers of the electroplating tin coating. Another reason is large residual stress in the thin coating. In addition, it is found that pressure can induce the growth of tin whisker more easily than tension.