Interfacial Reaction of the Ultrasonic-assisted Soldering Copper and Sn-3.0Ag-0.5Cu Solder Alloys

摘要

In this paper, ultrasonic-assisted soldering method was used in the joining of pure copper (Cu) using Sn-3.0Ag-0.5Cu (SAC305) solder alloy. The effect of vibration time on the formation of intermetallic compounds (IMCs) in the solder joints was investigated. The samples were heated to 250°C and hold for 5 minutes, followed by air-cooled in normal atmosphere. The top substrate was exposed to high-amplitude-low-frequency ultrasonic vibration for vibration time of 1s to 4s during the peak temperature holding time. The soldered samples were cross-sectioned and the joint microstructures were examined by SEM and EDS. Both Cu_6Sn_5 and Cu_3Sn IMC layers were observed at the joint interface. However, the formed IMC layers were found to be thinner in ultrasonic soldered samples. The thinnest IMC layers were found in the sample soldered with vibration time of 3s, where the Cu_6Sn_5 IMC layer decreased by 55.97% and the Cu_3Sn IMC layer decreased by 43.45%. At the same, these joints obtained the highest shear strength which is 38.14 MPa. The present work revealed that the growth of IMC was suppressed due to the acoustic cavitation effect of ultrasonic vibration. However, prolonged vibration time can cause excessive dissolution of Cu elements from the substrates which in turn, promoting the growth of both IMC layers and reducing the joint strength.