Reinforcement of vanadium on the microstructure and properties of Sn-58Bi lead-free solder joints

The microstructure and the mechanical properties of the Sn-58Bi based composite solder joints reinforced by different content vanadium (V) particles were investigated. The results showed that the Sn-58Bi-0.4 V solder alloy with spreading area 52.51 mm(2) exhibited an appropriate wettability. The microstructure of Sn-58Bi solder alloy consisted of rich Bi phase and rich Sn phase, and the spacing of Sn-rich phase was reduced from 2.13 mu m to 0.98 mu m by adding 0.4 wt% V particles. The intermetallic compounds (IMCs) layer of Cu/Sn-58Bi/Cu solder joint was presented as scallop shape, and the IMCs layers thickness of Cu/Sn-58Bi-xV/Cu (x = 0-1.0) solder joints was firstly increased to the maximum 0.95 mu m and then decreased with increasing V content. The tensile strength and the shear strength of Cu/Sn-58Bi/Cu solder joint were 72.76 MPa and 38.44 MPa, then were reached the maximum 83.81 MPa and 42.81 MPa by Cu/Sn-58Bi-0.4 V/Cu solder joint, respectively. The tensile and the shear fracture morphologies of Cu/Sn-58Bi-xV/Cu (x = 0-1.0) solder joints with the brittle fracture mode were both presented as cleavage fracture, and a couple of dimples occur in the tensile and the shear fracture of Cu/Sn-58Bi-0.4 V/Cu solder joint.