Co-electrodeposition of tin with 0.2-20% indium: Implications on tin whisker growth

The growth of whiskers on tin-plated interconnects causes acute short circuit problems and system failures in electronic components. In the past, this problem was suppressed by the addition of a few percent Pb in the electroplated tin, but following the introduction of international laws restricting the use of lead in electronics, alternative strategies are necessary. Recently it has been shown that 5-10% indium can eliminate whisker growth in electroplated tin on copper substrates under ambient temperature aging. However, there is no currently known method for co-electrodepositing Sn with a small amount of In using an acidic electrolyte that is similar to that currently used in the industry. This paper reports on a method to co-electroplate tin with 0.2 to 20 atomic percent indium from a methanesulfonic acid (MSA) electrolyte, which is the most widely used bath for electroplating of Sn, with only a small amount of other additives. The impact of co-deposited Sn-In platings on the susceptibility to whisker growth has been demonstrated.