Using Intaglio-Shaped Bumps for Increasing the Conductive Particle Density in Lateral Thermosonic Process With Anisotropic Conductive Film

In this paper, a method to reduce the contact resistance of lateral thermosonic bonding with an anisotropic conductive film (ACF) is proposed. Despite the various advantages of the ACF-based bonding process, it suffers from higher contact resistance between a chip and a substrate, which increases the power consumption and decreases the reliability. The contact resistance largely relies on the conductive particle density. However, in the thermosonic process, a large portion of conductive particles flow out along with the adhesives at the reflow state. To tackle this issue, an intaglio-shaped bump is newly proposed. Thanks to the proposed bump, more conductive particles remain inside the intaglio shape after the reflow state, which results in increment of the conductive particles' density. Through the experiments with a commercialized ACF, it will be shown that the proposed intaglio-shaped bump does increase the conductive particle density of the lateral thermosonic bonding process.