Insights into the dual-roles of alloying elements in the growth of Sn whiskers

Abstract

• This work revealed the alloying elements (Bi, Pb, Ga) could effectively postpone the formation of Sn whiskers by introducing an apparent incubation period. • Combined with the experiments and DFT simulation, the correlation between the mobility of Sn atoms and growth rate of whiskers has established, which will shed light on the search of effective mitigation strategies in general materials. • The enthalpy calculation implies that Sn atoms prefer growing whiskers to staying in body as defects in the energy aspect. The growth of Sn whiskers from Ti 2 SnC/Sn- X ( X = Sn, Bi, Pb, Ga) samples was studied in this work to understand the effect of alloying elements on whiskering behaviors. The mobility of source Sn atoms relating with the formation and migration of defects was found to be the critical factor dominating the growth rate, with the gathering of which to grow whiskers on the surface acts as an effective means to lower the enthalpy. As a result, the source Sn atoms would migrate to whisker root spontaneously, making the growth of whiskers the nature of materials, and external factors like compressive stress or oxidation are no more necessary but facilitate the whiskering process by promoting the mobility of source Sn atoms.