Experimental study of filling behaviors in the underfill encapsulation of a flip-chip

An underfill encapsulant was used to fill the gap between the chip and the substrate around the solder joints to improve the long-term reliability of the flip-chip interconnecting system. The underfill encapsulant was filled by the capillary effect. In this study, experiments were designed to investigate the effects of bump pitch and the edge detour flow on the underfill encapsulation. The bump array was patterned on a glass plate using the lithography technology. This patterned glass plate was used to simulate a flip-chip with solder bumps. The patterned glass was bounded to a substrate to form a simulated flip-chip system. With the lithography technology, it is easy to construct the test samples for underfill flow experiments with different configuration of solder bumps. It was observed that the filling flow was affected by the bump pitch. The edge detour flow depends mainly on the arrangement of the underfill dispensing process.