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

PurposeThis study aims to research properties of Cu/SAC0307 mixed solder balls/Al joints with different bonding temperature under ultrasonic-assisted. Design/methodology/approachA 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. FindingsThe results indicated that when the bonding temperature was 180 degrees C, there was only one layer of CuZn5 intermetallic compounds (IMCs) at the Cu interface. However, when the bonding temperature was 190 degrees C, 200 degrees C and 210 degrees C, the Cu interface IMCs had two layers: for one layer, the IMCs near the Cu substrate were Cu5Zn8 and for another layer, the IMCs near the solder were CuZn5. 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 degrees C was 4.6 mu m, which increased by 139.6% compared with that of the Cu/Al joints soldered at 180 degrees 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 degrees 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 degrees 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 degrees C. When the soldering temperature was 180 degrees C, the fracture of Cu/Al joints was mainly on the Al side. However, when soldering temperature was 190 degrees C, 200 degrees C and 210 degrees C, the fracture of Cu/Al joints was mainly broken in the Zn particles layer. Originality/valueA 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 degrees C.