Influence of bonding temperature on the properties of Cu/(SAC mixed powder)/Al joints under ultrasonic-assisted

Purpose This study aims to research properties of Cu/SAC0307 mixed solder balls/Al joints with different bonding temperature under ultrasonic-assisted. Design/methodology/approach A new method that 1 mm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 mm were mixed to fill the joint and successfully achieved micro-joining of Cu/Al under ultrasonic-assisted. Findings The results indicated that when the bonding temperature was 180°C, there was only one layer of CuZn 5 intermetallic compounds (IMCs) at the Cu interface. However, when the bonding temperature was 190°C, 200°C and 210°C, the Cu interface IMCs had two layers: for one layer, the IMCs near the Cu substrate were Cu 5 Zn 8 and for another layer, the IMCs near the solder were CuZn 5 . In addition, the thickness of the Cu interfacial IMCs increased with the bonding temperature. In particular, the thickness of IMCs at the Cu interface of the Cu/Al joints soldered at 210°C was 4.6 µm, which increased by 139.6% compared with that of the Cu/Al joints soldered at 180°C. However, there was no IMC layer at the Al interface, but there might be a Zn–Al solid solution layer. The shear strength of Cu/Al joints soldered at 180°C was only 15.01 MPa, but as the soldering temperature continued to increase, the shear strength of the Cu/Al joints increased rapidly. When the soldering temperature was 200°C, the shear strength of the Cu/Al joints reached the maximum of 38.07 MPa, which was 153.6% higher than that at 180°C. When the soldering temperature was 180°C, the fracture of Cu/Al joints was mainly on the Al side. However, when soldering temperature was 190°C, 200°C and 210°C, the fracture of Cu/Al joints was mainly broken in the Zn particles layer. Originality/value A new method that 1 mm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 mm were mixed to fill the Cu/Al joint at 210°C.