A Novel Conductive Particle Dispersing Method via EHDA for POB-COG Packaging

摘要

With the continuous evolving of Liquid Crystal Display (LCD) panels and Integrate Circuits, conventional Anisotropic Conductive Film (ACF) has confronted with two paradoxical requirements: higher conductive particle density, while avoid serious aggregation. To solve this problem, a wafer level pretreatment technique, Particle on Bumps (POB), was proposed to renovate the usual Chip on Glass (COG) technology. Although we have demonstrated its feasibility and reliability, a fundamental route towards fully accomplishing the POB technique still needs to be paved out, that is the dispersing of conductive particles. Herein we introduced the method of Electrohydrodynamic Atomization (EHDA). EHDA is a technique which ultra-fine droplets can be induced due to electrical force. We build up a prototype apparatus for particle dispersing. With the help of high speed camera, we are able to verify certain behaviors and characteristics of different modes during the EHDA process. The deposition patterns generated under different spraying modes are observed and compared; the stable cone jet mode is therefore chosen as the operational state during our following deposition process. We investigate the connections between onset voltage and relevant spray parameters to optimize our EHDA configurations. By implementing the particle dispersing experiment via stable cone jet EHDA, we successfully obtained a pattern with high densely and uniformly distributed particles.