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.