ANNEALING EFFECT AND TENSILE INTERFACE FRACTURE MECHANISM OF PURE SILVER BONDING WIRES

Since Ag wires have similar hardness and bonding properties to Au wires, they can be applied in some pads. In the present study, the annealing effect (at 225 degrees C similar to 275 degrees C for 30min) on the tensile mechanical properties of silver wires with phi=23 mu m was investigated. In addition, the microstructural characteristics and the mechanical properties before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that with annealing temperatures of more than 250 degrees C, the silver wires possessed a fully annealed structure, the tensile strength and the hardness decreased, and the elongation was raised significantly. Under the thermal effect of EFO, the necks of the Ag balls underwent recrystallization and grain growth was induced, and the annealed Ag wires had a shorter zone of HAZ (220 mu m). The bonding strength and the neek-strength of the Ag wires were more than 7gf and possessed excellent bonding properties.