Effect of Ag-4Pd alloy bonding wire properties and structure on bond strengths and reliability

The different of Ag-4Pd and Ag-4Pd-0.3Ru alloy bonding wire properties and structure were analyzed by scanning electron microscope, strength tester and thermal conductivity tester, the effects of Ru on Ag-4Pd alloy bonding wire ball size, bonded micro phonology and bonded strength were investigated. The results show that the thermal conductivity of Ag-4Pd alloy bonding wire decreases from 403 W/m·k to 365 W/m·k because of doping Ru, and the free air ball shape of Ag-4Pd-0.3Ru alloy bonding is more uniform than Ag-4Pd alloy bonding wire, the Ag-4Pd-0.3Ru alloy bonding wire bonded strength is higher than AgA1 alloy bonding wire. The heat affect zone length decreases from 50µm to 35µm because of doping Ru, and the ball neck crack defect cause of excessive long heat affect zone length will decrease. For Ag-4Pd alloy bonding wire, Ru can refine the grain, then the grain size decreases, and the grain quantity increases, then the inhomogeneous deformation of different grain decrease, and the ball bonded shape is uniform. After HTS test, cracks phenomenon happens at the bonding interface because of Ag atoms rapidly migrate, Zn can decrease the Ag migrate rate and avoid the crack in bonded interface.