Quantitative Characterization of a Flip-Chip Solder Joint

Based on an energy minimization principle, a mathematical/numerical model has been developed to study the impact of design and process variations associated with flip-chip solder joint on its ability to align in lateral and axial direction. The minimum-energy shape needed for joint evaluation is computed by a novel numerical method based on motion by mean curvature. The analysis shows that (1) the magnitude of the reaction force in lateral and axial direction reduces with increase in solder volume, (2) the normal reaction is an order of magnitude higher compared to the lateral reaction (restoring force) thus making the joint more susceptible to lateral misalignment compared to the axial misalignment, and (3) the axial misalignment is primarily dictated by the accuracy of the solder deposition height.