Interfacial Microstructure and Mechanical Properties of Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu Solder Joint under Thermal Shock

To study the effect of solder process parameters and thermal shock on Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu of soldered joints, the interface intermetallic compounds and strength of the joints were analyzed by SEM, EDS and XRD. The results show that 0.05 wt% Ni addition can refine the primary beta-Sn phase and eutectic of the Sn2.5Ag0.7Cu0.1RE solder alloy. The maximum shear strength is 26.9 MPa from the joint at the soldering temperature of 270 degrees C for soldering time 240 s, which increases by 8.9% compared with Sn2.5Ag0.7Cu0.1RE/Cu joint. The average thickness of the Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu joint rises with the increasing of temperature and time. The interface roughness of the joint increases and then decreases. The interface IMC of the solder joints grows irregularly with the rising of thermal shock cycle. At the same time, the strength of the joint decreases. The 0.05 wt% Ni addition can inhibit the decrease of the reliability of soldered joint in the process of the thermal shock.