Study on the interfacial evolution and mechanical properties of Cu/SAC105/Cu solder joint modified by Si3N4 nanowires

In the present study, Si3N4 nanowires (NWs) with a mass fraction of 0.6 wt% were incorporated into Sn1.0Ag0.5Cu (SAC105) solder. Cu/SAC105/Cu and Cu/SAC105-Si3N4/Cu 3D structure joints were constructed by transient liquid-phase (TLP) bonding. To investigate the influence mechanism of Si3N4 NWs, the interfacial IMC evolution and mechanical properties of two solder joints were analyzed. It was found that the interfacial Cu3Sn IMC layer thickness of the joints containing Si3N4 NWs was thinner than that of the undoped ones at any given time. The growth of interfacial Cu6Sn5 IMC was inhibited, resulting in the retarded formation of interfacial IMC bridging and full-IMC joints. In addition, combined with the fracture morphology analysis, the brittle fracture behavior of the solder joints was suppressed, and the shear strength of the joints showed a significant improvement following the introduction of Si3N4 NWs. Moreover, Si3N4 NWs were found exposed on the fracture surface of Cu3Sn IMC layer, demonstrating that the doping of Si3N4 NWs shaped a joint similar to that of reinforced concrete structure, which facilitates the limitation of dislocations and crack expansion.