Preliminary study on the effect of Ni addition on tin (Sn) whisker growth from lead-free solder coating

Abstract

It has been widely confirmed that alloying significantly can mitigate the formation of tin (Sn) whiskers and consequently became a possible candidate as a lead-free alloys coating material in the microelectronics industry. In this study, the effect of 0.05 wt.% Ni addition on the formation and growth of Sn whisker in Sn-0.7Cu solder coatings have been investigated under continuous mechanically stress induced at room temperature. It is clearly found that Ni addition have significantly enhanced stress relaxation by reducing the growth rate of formation Sn whiskers in Sn-0.7Cu solder coatings. The morphology of (Cu,Ni)6Sn5 interfacial IMC was more refine and thinner with a fine scallop-shaped interfacial intermetallic layer purposely to lower the compressive stress of Sn coating and extend the nucleation period, thus mitigating the formation and growth of Sn whiskers.