Study on the shear strength evolution of the Au studs bonding under different thermal aging and temperature cycling times

In this work, the reliability of Au stud bumps soldering on the dummy chip is studied. The shear strength of the Au stud bumps is measured before and after the environment experiments based on temperature cycling and thermal aging experiments. It is found the initial average shear strength of the Au stud is 980g through the chip shear test, while the shear strength will be changed after the experiments. The average shear strength decreases to 870g after the thermal aging test with the condition of 200°C for 100 hours, and raises to 1375g after 300 hours. On the other hand, the shear strength shows the same regular pattern after the temperature cycling test. The average shear strength decreases to 637g after 50 temperture cyclesand it raises to 1382g after 200 temperture cycles. At last, Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS) analysis are further conducted to clarify the mechanism of the shear strength variation. It is found the atomic percent of Si has the same trend with the average shear strength while the atomic percent of Cu has the reverse trend. Al and Au were appeared on fracture surface with different ratio after different aging time.