Simulation and experiment study of dispensing patterns influence on underfill filling process

Dispensing pattern is important for flip-chips underfill filling quality. This paper uses three-dimensional flow model to simulate underfill capillary flow and filling process for L and I dispensing patterns. The model reckons in influences of surface tension, contact angle and radius of curvature, especially contact angle and radius of curvature at wall of gap between chip and substrate, side wall of chip and surface of sold bump joints. In order to track the moving interface, the VOF model is applied. On the other hand, an experimental device has been constructed to research underfill filling process of the two dispensing patterns. Both simulation results and experiment results show that dispensing patterns have great influences on underfill filling velocity and flow front profile. In L filling pattern, underfill flow velocity is faster in diagonal direction. Comparing with experimental results and simulation results, it can be concluded the 3-D simulation model established can simulate underfill filling process well for the both L type and I type dispensing pattern.