Lifetime of thermosonic copper ball bonds on aluminum metallization pads

A novel accelerated mechanical fatigue testing system in combination with a special set-up was used to evaluate the reliability of Cu- ball bonds. Tailor made test structures were designed and prepared out of commercial wire bonded devices to assess bonding strength of the interconnects under various modes of cyclic loading. Fracture surface analysis of the interconnects showed wire bond lift-off as the dominant failure mode. Based on experimental results and FEM simulations, lifetime prediction curves for two different types of ball bonded devices could be established.