Microstructure and mechanical properties of Co/Sn-10Bi couple and Co/Sn-10Bi/Co joint

Abstract The growth behavior of interfacial intermetallic compounds (IMCs) layer of Co/Sn-10Bi and Co/Sn-10Bi/Co couple has been studied by scanning electron microscope. The critical temperature and shear strength of Co/Sn-10Bi/Co joints were tested by universal testing machine. The results showed that the thickness of CoSn 3 IMCs layer increased as the increase of aging time and temperature. The growth rate of CoSn 3 IMCs layer of Co/Sn-10Bi/Co couple was suppressed and was lower than that of Co/Sn-10Bi couple as the decline in Sn concentration of residual Sn-Bi layer. The critical temperature of Co/Sn-10Bi/Co joint that could hold a load of 1 N changed as the chemical composition of residual Sn-Bi layer changed. The shear strength of Co/Sn-10Bi/Co joints bonded at 240 °C for 20 min, 30 min, 40 min, and 50 min was between 58 MPa and 82 MPa. The shear strength of Co/Sn-10Bi/Co joint bonded at 240 °C for 60 min was only about 17 MPa. The damage in shear strength of Co/Sn-10Bi/Co joint bonded for 60 min was led by the crack in residual Bi layer.