Interfacial IMC Layer and Tensile Properties of Ni-Reinforced Cu/Sn–0.7Cu–0.05Ni/Cu Solder Joint: Effect of Aging Temperature

Abstract

Thermal aging behavior on the intermetallic compounds (IMCs) layer and mechanical properties of Cu/Sn–0.7Cu/Cu and Cu/Sn–0.7Cu–0.05Ni/Cu joints has been investigated from aging temperature of 60–180 °C for 100 h. Layer thickness increases as aging temperature rose for both the joints. Mechanical properties deteriorates with increase in aging temperature. After aging at 180 °C, any signs of ductile fracture surface with a large amount of dimples are absent. Instead, an intergranular fracture surface is obtained for both the joints, indicating that the process transformes from ductile to brittle behavior. However, brittle Cu3Sn layer is observed between Cu6Sn5 layer and Cu substrate for Cu/Sn–0.7Cu/Cu joint after aging at 60 °C, while (Cu, Ni)3Sn IMC layer is detected until aged at 140 °C for Cu/Sn–0.7Cu–0.05Ni/Cu. Compared with Cu/Sn–0.7Cu/Cu joint, the interfacial morphology directly changes from scallop-shaped into layer-shaped structure with lower Gibbs free energy, and the layer thickness is obviously suppressed after addition of Ni particle. Excellent mechanical properties, including UTS, elongation, and hardness, are obtained for Cu/Sn–0.7Cu–0.05Ni/Cu because of the slight increase in layer thickness and dense layer-shaped interfacial morphology. Thermal aging reliability is enhanced for the Cu/Sn–0.7Cu–0.05Ni/Cu solder joint after doping with 0.05 wt% Ni particle.