Influence of Ni foam/Sn composite solder foil on IMC growth and mechanical properties of solder joints bonded with solid-liquid electromigration

Abstract The effects of Ni foam addition and solid-liquid electromigration on the bonding of Cu/Sn-3.0Ag-0.5Cu/Cu joints under condition of 320 °C for 2, 4 and 8 h with the electric densities of 0, 3.33 and 6.67 × 102 A/cm2 were investigated. The results indicated that intermetallic compounds (IMCs) performed non-interfacial growth in the Cu/Ni foam/SAC305 system and were distributed in an island-like aggregation, and the asymmetric growth pattern of IMCs in both the cathode and anode sides disappeared after addition of Ni foam. In addition, the grain size of IMCs was significantly reduced and the tensile strength of the joints was enhanced by the addition of Ni foam. However, when the current density reached 6.67 × 102 A/cm2, the tensile strength of the joints containing Ni foam decreased dramatically after bonding for 8 h, this was due to the fact that IMCs grains were excessively coarse and the grain growth direction tended to be parallel to the current direction during bonding.