Size Effect on the Electromigration Characteristics of Flip Chip Pb-free Solder Bumps

To understand the size effect on electromigration (EM) behavior in flip chip Pb-free Sn-3.5Ag solder bumps, EM tests were performed with changes in the pad opening size and solder bump height at 140 °C and 4.6 × 10 4 A/cm 2 . Additionally, to exclude extrinsic factors such as Joule heating, EM behavior was observed using a multi Sn96.5Ag3.0Cu0.5 solder line sample at 150 °C and 6–7.5 × 10 4 A/cm 2 . The EM lifetime increased with decreasing pad opening size and bump height, and the EM critical current density (J th ) increased with decreasing line length. This result indicates that the EM resistance increases as the dimensions of the solder bump decreases, which can be understood by the EM jL product. Graphical Abstract