Effects of Sn grain orientation on substrate dissolution and intermetallic precipitation in solder joints under electron current stressing

Electron current stressing of Ni/Sn3Ag/Ni solder joints was conducted in a straight-line configuration to avoid the complication of current crowding. It was confirmed that Sn grain orientation dominated the dissolution of the Ni substrate and the precipitation of intermetallic inside Sn3Ag. Current crowding played no role here. Additionally, it was found that the direction of serrated cathode dissolution exhibited a strong correlation with Sn grain orientation. These effects were explained in terms of the extreme anisotropy of Ni diffusion in Sn.