Soldering Performance And Interfacial Reliability Between Lead-free Solder And Ni-based Composite Coating On Cu Substrate

In recent years, with the replacement of the tradutional Sn-Pb solder by Sn-Ag-Culead-free solder, the interfacial reaction between Sn and Cu and related reliability issueshave caused high attention. The high proportion of Sn in lead-free solder will lead to a fastreaction between Cu and Sn. A large number of Intermetallic compounds(IMC) formationwill damage the reliability of components. Plating a diffusion barrier layer on Cu substractwill let the reaction slow down and also help to decrease the IMC thickness, which is aefficient way to improve lead-free solder joints.In this research, Ni coating, SiO2-added Ni composite coating and SiC-added Nicomposite coating have been prepared on Cu substrate. Studies focused on the wettingperformance, the IMC formation and the shear strength of Sn-3.0Ag-0.5Cu(SAC305) andSAC305-0.05SiO2composite solder on Cu substrate, Ni coating and Ni composite coating.The results of experiments showed:(1) As Ni/Sn reaction is slower than that of Cu/Sn, the wetting performance ofSAC305on Cu substrate decreases. Howerver, Ni coationg on Cu substrate can inhibit theIMC formation between solder and substrate, and improve the shear strengh of joints.(2) Adding SiO2or SiC can help to inhibit the IMC formation between solder andsubstrate. Compared with SiC-added Ni composite coating, SiO2-added Ni compositecoating showed a better performance. Adding SiO2in Ni coating can also increases thewetting performance and the shear strength of joints as well. The best addition is6g/L.(3) Compared with SAC305solder, by adding0.05wt.%of SiO2in SAC305solder, thewetting performance with Cu substrate and that with Ni-plated Cu sutstrate has beenincreased significantly. What’s more, the IMC growth rate ε is smaller and the shearstrength is better as well. Howerver, adding SiO2in SAC305solder can reduce the wettingperformance on Ni-SiO2composite coating, weaken the inhibition effect on IMC growthand decrease the shear strength of joints.