Effect of Nd on tin whisker growth in Sn-Zn soldered joint

摘要

In this paper the behavior and mechanism of tin whisker growth in Nd-doped Sn-Zn soldered joint were investigated, and the effect of Nd on the growth of tin whisker at 150 ℃ thermal condition was studied in detail. It was found that spontaneous growth of tin whisker occurred on the surface of soldered joint with excessive Nd addition, and the maximum length of tin whisker exceeded the safety range after aging treatment. With the oxidation of NdSn_3 phase, the compressive stress continuously drives the fresh tin atoms out from the fractures around NdSn_3 phase until the NdSn_3 phase was totally oxidized. The tin whisker growth from IMC in soldered joint was due to the diffusion-induced stress in the IMC layer between the Cu pad and the solder. As a result of stress release, voids and cracks formed in IMC layer and tin whisker sprout out from these fractures after aging treatment, which further decreased the mechanical property of soldered joint.