| This thesis presents numerical modeling and experimental results for the procedure of underfill flow in a large cross-section die with a non-uniform bump pattern in a flip-chip packaging configuration. Two different two-dimensional (2-D) flow models that account for the gapwise resistance are investigated and coupled with the volume-of-fluid (VOF) method to track the underfill flow front during simulations. The first model employs the modified Washburn model and uses a time-dependent inlet velocity to account for the gapwise resistance in the presence of bump interconnects. The second model introduces a momentum source term in the Stokes equation to represent the gapwise resistance. Rheological properties, surface tension, and dynamic contact angles for an underfill material are experimentally determined. Simulation results based on the two models are compared with in-situ flow visualization conducted using bumped quartz dies. The comparison demonstrates the applicability of each model for simulating the underfill encapsulation process. |
