Effect of Silver Content on the Shear Fatigue Properties of Sn-Ag-Cu Flip-Chip Interconnects

The mechanical shear fatigue test has been performed to study the effect of silver content on the fatigue properties of Sn-xAg-0.5Cu (x = 1, 2, 3, and 4) for flip-chip interconnections. The strength of the solder alloy increases with increasing silver content, preventing shear plastic deformation of the solder bump. The flip-chip joints made using higher silver content solder, such as 3%Ag and 4%Ag, exhibit longer fatigue life for all conditions. The fatigue ductility of the solder decreases with an increase in the silver content. The fatigue endurance of 1%Ag solder is superior to other solders over the plastic strain range of 3%, even though the strength of the solder is the lowest in the solders tested. Based on this study, the 3Ag solder may exhibit good fatigue performance for all conditions, and the 1Ag solder is optimum for severe strain conditions.