Failure Analysis of Anisotropic Conductive Adhesive Packages in Narrow-Pitch Flip Chip Packaging

With the development of microelectronics packaging technology, the interconnection size of chip packaging has gradually decreased to 10μm.ACA (anisotropic conductive adhesive) packaging technology has become one of the key technologies to realize this trend. In this paper, we analyze how to minimize the failure probability of ACA in the case of narrow-pitch chip packaging. The failure mode of ACA can be divided into two kinds: opening failure in the conductivity direction and bridging failure in the insulation direction. Before the bond, it is assumed that the conductive particles obey the Poisson distribution. After the bond, considering the volume curing rate of ACA, the failure probability was calculated by using the probability theory and the improved box model. The prediction model of overall failure for the ACA interconnection of narrow-spacing chips was established. When the pitch is constant, the overall failure probability of pad is evaluated as a function of the optimal diameter and volume fraction of the particles, as well as how the distance between pad and the length of pad should be distributed. This will be useful to optimize the size of the bumps and to choose more suitable ACA material.