Abstract
SynopsisFlip chip assembly has widely been adopted in the electronics industry for realizing smaller and thinner semiconductor packages. In encapsulating flip chip packages, it is important, not only to maintain the interconnect reliability of bumps, but also to control the warpage of the package. In this paper, the effects of several assembly methods on the performance of flip chip package, i.e the warpage of package and interconnect reliability, were investigated. Additionally, three types of underfill material with different mechanical and thermal properties were prepared to understand the factors, which lead to improved protection of the bumps and control of warpage of package. Underfill material with higher Young’smodulus showed a longer interconnect life. From the results of failure analysis after thermal cycling, bump cracking at the corner of chip was observed. It was found from finite element analysis that underfill material with higher Young’s modulus can effectively reduce the strain accumulating inside the bump. Note that the properties of the underfill material affect the relationship between the interconnect reliability and the prestrain caused during encapsulation process, the selection of the optimal underfill material and the appropriate encapsulation process is essential in order to satisfy the high performance requirements of flip chip packaging.
