Electromigration studies of lead-free solder balls used for wafer-level packaging

Electromigration experiments have been conducted on lead-free solder balls in wafer-level packages (WLP). Lifetime distribution, Joule heating, failure mode, and the effect of current-direction are discussed. In addition, these results are compared with similar BGA interconnects in packages surface-mounted to boards as well as lead-free flip-chip bumps. It is concluded that the interconnects of this study are robust for electromigration reliability owing to its under bump metallurgy (UBM) and size.