Effect of displacement rate on bump shear properties of electroplated solder bumps in flip-chip packages

The effect of displacement rate and intermetallic compound growth on the shear properties of the electroplated Sn-37Pb (wt.%) flip-chip solder bumps with Cu under-bump metallization (UBM) were investigated after multiple reflows. The compounds Cu₆Sn₅ and Cu₃Sn were formed at the interface after one reflow, and their thicknesses increased with increasing reflow number up to 10. The shear properties peaked after four reflows, and then decreased with increasing reflow number. Increasing displacement rate increased the shear force, but decreased the displacement until fracture. The tendency toward the brittle fracture characteristics was intensified with increasing displacement rate and reflow number.