Microstructure evolution and mechanical properties of Cu interconnects bonded with Ni-foam reinforced pure Sn solder

Ni-foam reinforced pure Sn composite solder was used to solder copper at low temperature in this study. The microstructure and mechanical properties of Cu/Ni-Sn/Cu joints were investigated in terms of the bonding time. Results showed that the intermetallic compounds formed in the Cu/Sn/Ni system were sensitive to the bonding time, and the existence of Ni-foam refined the grain size of (Cu,Ni)6Sn5 phase and improved the strength of joints. The joints bonded for 60 min exhibited the highest shear strength of 52.7 MPa, and the shearing failure mainly occurred in the (Cu,Ni)6Sn5 phase. The (Cu,Ni)6Sn5 grain refinement and Ni skeletons reinforcement enhanced the shear strength, but the excessive growth of Cu3Sn layer caused elastic modulus mismatch and strength decrease of joint.