Previous theories of the tin whisker growth proposing various dislocation mechanisms have been largely disproved. This paper presents a new and different theory for the mechanism of tin whisker growth. The theory addresses the fundamental requirements for Sn to diffuse to the base of the whisker grain and proposes a mechanism for whisker initiation and growth. Part of this is a theoretical proposal as to what makes the whisker grain different. The role of oxidation in whisker growth is also briefly addressed. Using this theory, attempts are made to illustrate how different whisker shapes are created. Finally, a proposed potential solution to tin whisker growth is presented, assuming that this theory is correct.

The electrodeposition conditions that contribute to microvoid formation during isothermal aging of Pb-free solder-electrodeposited copper were evaluated in a systematic series of processing experiments. The results of 2 K full-factorial design of experiment are presented to show the effect of prescreened electroplating parameters such as brighteners, wetting agent, bath age, and current density on the propensity for microvoiding at solder-copper interfaces after annealing at 125°C for 40 days. It was found that the amount of microvoiding is greatly affected by bath age, wetting agent, brightener, and their interactions. Time-of-flight secondary-ion mass spectroscopy and glow discharge spectroscopy allowed us to establish a correlation between impurities incorporated in copper during electroplating and microvoiding at the solder-copper interface.