Solder Volume Effect on Electromigration Failure Mechanism of Cu/Ni/Sn-Ag Microbumps

Effects of solder volume on the electromigration (EM) failure mechanism of Cu/Ni/Sn-2.5Ag microbumps were systematically investigated at 150 °C with a current density of 1.5 × 10
⁵
A/cm
²
. While the electrical resistances of Cu/Ni/SnAg microbump with large solder volume increased quickly, those with small solder volume increased slowly, which depends on the difference in solder volume effect on the intermetallic compound formation mechanisms. For a structure with large solder volume, the Ni barrier layer was extensively consumed due to substantial reaction between Ni barrier and large solder volume. For a structure with small solder volume, the initial Ni barrier structure was preserved due to the limited volume of solder reacting with Ni barrier, which mainly contributes to better EM reliability of Cu/Ni/Sn-Ag microbump.