Analysis of flip-chip ball grid array underfill flow process

This study provides an in-depth simulation of the capillary underfill (CUF) process for flip-chip packages using Moldex3D, offering a comprehensive analysis that integrates material properties, process parameters, and structural factors within a unified framework. The material properties explored include viscosity and reaction kinetics, while the process parameters focus on controllable factors such as resin temperature, mold temperature, dispensing start time, dispensing weight, and dispensing end time. Structural parameters like bump pitch and gap height are also studied. The study further validates its findings with experiments conducted on a high bump count of 1530, showing that the experiment and simulation results are consistent. Key findings reveal that a larger die pitch accelerates the filling process, the incorporation of edge channels enhances filling efficiency, and optimizing the dispensing path improves flow uniformity. Adjusting the dispensing weight and intervals can mitigate edge effects and tongue spreading. Regarding material properties, higher surface tension and lower contact angle significantly increase filling speed, though they have a minimal impact on the overall flow pattern during the underfill filling process. These insights are crucial for optimizing the CUF process, ultimately improving the reliability and performance of flip-chip packages.