Advanced Bump Structure for Improving the Board Level Characteristics of WLCSP

Abstract

In this study, to increase solder joint reliability, we developed the epoxy reinforced bump structure surrounding the solder bump joint. The thermal-mechanical reliability of the epoxy reinforced solder bumped wafer level package was carried out during the thermal cycle and drop shock test of the package. The reliability of solder bump joint was evaluated by means of the thermal cycle in the range -40° to 125°. The experimental results revealed that the thermo-mechanical fatigue properties of the epoxy reinforced bump structure was better than that of the conventional solder bump structure. Epoxy reinforced bump structures improved the WLP characteristic life by at least 2 times. Also, the drop shock reliability of epoxy reinforced bump structure was enhanced 3 times better drop characteristic life than that of conventional single bump structure. The life time of epoxy reinforced solder bump joint was longer than that of the conventional WLCSP solder joint.