Enhancement of electrical stability of anisotropic conductive film (ACF) interconnections with viscosity-controlled and high T-g ACFs in fine-pitch chip-on-glass applications

Abstract

This paper describes how anisotropic conductive film (ACF) properties including viscosity affect the electrical stability of ACF interconnections for fine pitch chip-on-glass (COG) applications. In this study, new ACFs for COG applications were designed by combining a high viscosity ACF layer and a low viscosity NCF layer to prevent the electrical shortage between bumps. As expected, the viscosity-controlled ACF showed better electrical insulation stability than a conventional ACF in fine pitch COG assemblies. According to the results of thermo-mechanical analysis (TMA) and dynamic-mechanical analysis (DMA), the viscosity-controlled ACF showed the improved thermo-mechanical properties such as lower coefficient of thermal expansion (CTE), higher storage modulus (E') at higher temperature region, and higher glass transition temperature (T-g) than the conventional ACF. Furthermore, hot air reliability test and pressure cooker test (PCT) results showed that the viscosity-controlled ACF with higher T-g had better hot air test and PCT reliabilities than the conventional ACF. (C) 2011 Elsevier Ltd. All rights reserved.