Minimization of tin whisker formation for lead-free electronics finishing

Many theories regarding whisker growth exist. It has been demonstrated in a variety of reference sources that tin whiskers can form in both pure tin and tin alloy deposits. Conversely, an equal number of claims exist in the literature demonstrating no whisker growth in the same types of deposits. The lack of an industry standard whisker test is a significant limitation in addressing tin whiskers. Historically in the electronics industry, addition of lead (Pb) was found to be an effective method of minimizing tin whisker formation and so for many years electronic components have been electroplated with tin-lead (Sn-Pb). With the advent of Pb-free electronics finishing, the risk of tin whiskers is again a significant concern. This paper will review the theories behind whisker formation, identify the common characteristics of same, and demonstrate how Pb-free electroplating processes can be formulated to minimize the risk of whisker formation.