Abstract
The demand for electronic packages with lower profiles, lighter weights, and higher I/O densities are leading to a rapid expansion of the electronics industry, especially in portable electronic products. As a result, flip chip technology has become very popular in the electronic packaging industry. To enhance the long-term reliability of flip chip technology, the space between the chip and substrate must be filled. This underfill improves reliability, which is influenced by coefficient of thermal expansion (CTE) mismatch between the chip and the substrate. However, it is difficult to fill the underfill space perfectly between the chip and the substrate because of the presence of impurities, voids and other defects in solder joining and underfilling during manufacturing. In addition, it is nearly impossible to achieve a perfect contact between the solder joints and the underfill. The purpose of this research is to investigate the impact of imperfect contact behavior and contact performance involving the solder joints and underfill on flip chip solder interconnects. Because of the above reliability issues, this study adopted the contact theory of the finite element and element death/birth methods to analyze the physical behavior of packaging structures under thermal cycling conditions. Simulation results indicated that the fatigue life of the flip chip packages would decrease due to two phenomena: One is imperfect bonding between solder ball and underfill, and the other is void size exceeding 334 μm 2 . Subsequently, this study effectively utilized a novel finite element method to simulate the real manufacturing processes of flip chip packaging. © 2004, Taylor & Francis Group, LLC.