Correlation between Ag content and Cu pad consumption in lead-free solder joints under electron current stressing

White tin (or β-Sn) has a body-center tetragonal (BCT) crystal structure with lattice parameters of a = b = 5.83 Å and c = 3.18 Å. We found that the orientation of the β-Sn phase strongly correlated with the Ag content in the Sn-Ag-Cu solder joints. When the Ag content is equal to or greater than 3 wt.%, the Sn grains display a strong preferred orientation of the c-axes in the direction parallel with the interface (or perpendicular to the electron flow upon current stressing) that substantially reduces the pad consumption induced by electromigration A more detailed analysis through electron backscatter diffraction (EBSD) on the β-Sn grain orientation with respect to the pad consumption is established in this study.