Underfill of flip chip on laminates: simulation and validation

The flow characteristics of a number of underfills were evaluated with quartz dies of different patterns and pitches bonded on different substrate surfaces. Perimeter, mixed array, and full array patterns were tested. Observations on the flow front uniformity, streaking, voiding, and filler segregation were collected, The information was compared with the results predicted by a new simulation code, plastic integrated circuit encapsulation-computer aided design (PLICE-CAD) under DARPA-funded development. The two-phase model of the combined resin and air takes into account geometrical factors such as bumps and die edges, together with boundary conditions in order to track accurately the propagation of the flow fronts, The two-phase flow field is based on the volume-of-fluid (VOF) methodology embedded in a general-purpose three-dimensional (3-D) flow solver.