Effect of Ni on interfacial IMC and mechanical properties of Sn2.5Ag0.7Cu0.1RE/Cu solder joints

The effects of Ni on the microstructure and mechanical properties of Sn2.5Ag0.7Cu0.1RE solder and solder joints were studied by using the scanning electronic microscope and X-ray diffraction.The results show that adding proper amount of Ni in Sn2.5Ag0.7Cu0.1RE solder alloys can refine the initial β-Sn phase and eutectic structure, suppress the growth of the(Cu, Ni)₆Sn₅ intermetallic compound(IMC) at the interface of solder joints, and reduce the roughness of interfacial IMC, improve the shear strength of the SnAgCuRE/Cu solder joints.The solder alloy structure was fine and homogenous, eutectic structure proportion was large, interfacial IMC was thin and flat and the grain size of(Cu, Ni)₆Sn₅ was small.The shear strength got the maximum value(45.6 MPa) when the Ni content was 0.1 wt%, which was 15.2% higher than the solder joints without Ni.