Directional Solidification Structure and Deformation Behavior of Silver Bonding Wire

The silver bonding wire of φ0.018mm was fabricated by directional solidification technique and severe plastic drawing technology. The effect of micro-alloying on directional solidification structure and deformation behavior of silver bonding wire was analyzed. The correlation among micro-alloying, directional solidification structure and deformation behavior was described. The results show that micro-alloying elements influence grain growth direction, restrict the grain growth, and then form ingot with special morphology, such as dendritic crystal, columnar crystal and lamellar structure and so on. Silver bonding wire with grains distributed along the wire radial direction and containing a large number of twins in the crystal grains have good plasticity and toughness in severe plastic drawing process. The yield can reach up to 65%, and the length of a single wire can reach 24000 meters. The silver bonding wire with dendritic morphology has a high breaking rate, and the fracture mechanism is transgranular cleavage fracture.