Microstructure and mechanical properties of Cu/Sn-In/Cu joints obtained by ultrasonic-assisted transient liquid phase bonding in air

Abstract

Ultrasonic-assisted transient liquid phase bonding of pure Cu with Sn-In solder was realized at 140°C in air. Shear test was carried out on the weldment. The effect of ultrasonic vibration on microstructure and mechanical properties of the weld seam was studied. The relationship between the formation of intermetallic compounds and their mechanical properties was analyzed by means of electronic scanning and element analysis. (Sn) solid solution, ε(Cu 3 Sn), η(Cu 6 Sn 5 ), Cu 10 Sn 3 , Cu 11 In 9 , Cu 9 In 4 , γ, β phase were detected in the weld seam. When the ultrasonic vibration time is 30 s, the shear strength reached a maximum of 22.76 MPa. The fracture occurred on the surface of the fine-grained η(Cu 6 Sn 5 ) phase. The fracture surface was partially covered with coarse-grained Cu 11 In 9 phase, which belonged to a brittle fracture.