Sn whiskers are a serious reliability problem in Pb-free electronics manufacturing. Whiskers (as in fig. 1) grow out of pure Sn coatings and have been responsible for numerous system failures, such as the Galaxy IV satellite. To increase our understanding of whisker growth, we have performed systematic measurements to quantify the whisker growth kinetics and the correlation between the formation of a Sn-Cu intermetallic compound (IMC), stress in the Sn and whisker nucleation.