3D Simulation of fine pitch underfill encapsulation

The flip chip molding is much smaller than a traditional carrier-based system; the chip sits directly on the circuit board, and is much smaller than the carrier both in area and height. The short wires greatly reduce inductance, allowing higher-speed signals, and also carry heat better. However, fine pitch flip chip molding has difficulty meeting mechanical shock and prevention voids for underfill in on-site process. Applying the conventional trial-and-error method to resolve these problems is difficult and costly because of the complex interactions among fluid flow, heat transfer, structural deformation and polymerization of the underfill. In this study, a general-purpose, 3D simulation tool is proposed to accurately track the propagation of the underfill in microchips. The capillary flow, which is influenced by the surface tension of underfill and the contact angle between bumps and substrate, of dispensing process for flip chip underfill is discussed by numerical analysis. The proposed methodology developed in this work accounts for most of the physical phenomena believed to play an important role in underfill flows. The results demonstrate not only show how an encapsulant fills an underfill gap, flowing around the bumps, but also simulate the different moving speeds of the injection The simulation tool provides a promising simulation solution for the microchip encapsulation process.