Simulation and experimental study of Cu wedge bond reliability

Copper (Cu) wire has many advantages and is replacing Aluminum (Al) wire in high performance power electronics. A power cycling test system was developed and cycling tests were performed to compare reliability of Al wire and Cu wire and to investigate how a wire surface defect and the bond process affect the reliability. A finite element analysis (FEA) model was created and simulations were run to analyze failure mechanisms of test samples. The results show Cu wire can carry more current, works at higher temperature, and has much better reliability. For both Al and Cu wires, stronger bonds have higher reliability and are less sensitive to wire surface defects. The defects affect bond reliability especially for lightly bonded wires. A wedge imprint at a bond from special wedge design does not affect the bond reliability even it appears similar to a surface defect.