The mechanical shear fatigue test has been performed to look for the effect of silver content on the fatigue properties of Sn-xAg-0.5Cu (x=1, 2, 3 and 4) flip chip interconnections. As the strength of the solder alloy increases with increasing silver content, the increase in silver content results in preventing a shear plastic deformation of solder bump. Therefore, the flip chip joints made using higher silver content solder such as 3 and 4Ag exhibit longer fatigue life, if the same levels of displacement is applied. The fatigue ductility of the solder decreases with increasing the silver content. Therefore, the fatigue endurance of the 1Ag solder itself is superior to other solders in high plastic strain regime, even though the strength of the solder is the lowest in the solders tested. Based on this study, the 3Ag solder might exhibit good fatigue performance for all condition, and the 1Ag solder is optimum for severe strain condition.