Influence of Ultrasonic Vibration Power on the Wettability and Interfacial Microstructure of Sn2.5Ag0.7Cu0.1RE0.05Ni Solder Alloy on Cu Substrate

Abstract

The effect of ultrasonic vibration (USV) power on the wettability and interfacial microstructure of Sn2.5Ag0.7Cu0.1RE0.05Ni solder alloy on Cu substrate were investigated during the fluxless wetting process. Results showed that the wettability of Sn2.5Ag0.7Cu0.1RE0.05Ni solder alloy improved with USV assisted. With the increasing of USV power, the wetting angle decreased and corresponding the spreading area and spreading ratio increased. A wetting angle minimum of 24.5°, the spreading area and spreading ratio maximum of 51.3 mm2, 62.1%, respectively, were obtained from the solder sample treated with 100 W. The wettability of Sn2.5Ag0.7Cu0.1RE0.05Ni solder alloy on Cu substrate was better with the USV assisted compared to the commercial Sn3.0Ag0.5Cu solder alloy (SAC305). Additionally, with the increasing of USV power, the microstructure of wetting interfacial intermetallic compounds (IMCs) was refined, and the average thickness, roughness and grain size of the interfacial IMC decreased. When the USV power increased to 130 W, the thickness, roughness and (Cu,Ni)6Sn5 grain size of the wetting interfacial IMC decreased by 58.7%, 51.6%, and 35.1%, respectively.