A study on the interfacial adhesion mechanism of thermoplastic anchoring polymer layer(APL) films and epoxy-based nonconductive film(NCF) for APL ACFs

Abstract

Recently, trends in the electronic display filed are towards higher resolution and flexibility, as a result, anchoring polymer layer (APL) anisotropic conductive films (ACFs) structures having ultra-fine pitch capability and high tensile strength have been introduced. However, poor interfacial adhesion of APL ACFs can affect reliability of assembly and cause display problems. To improve the interfacial adhesion, interfacial adhesion mechanisms of APL ACFs need investigation. In this study, chemical factor affecting the interfacial adhesion mechanism was studied in terms of thermoplastic polymer types and the curing agent powder amount in APL films. Furthermore, APL ACFs compositions were optimized by deciding whether the optimized curing agent amount should be added into NCF or APL film. No chemical reaction existed in PVDF APL ACFs. The optimized PVDF APL ACFs was PVDF APL film without curing agent. Chemical reactions were observed in Nylon66 and PAN APL ACFs, respectively. Curing agent added into APL films reduced APLs’ tensile strength. Therefore, the optimized PAN APL ACFs and Nylon66 APL ACFs composition was concluded as PAN APL + 2NCFs with 3×C.A, and Nylon66 APL + 2NCFs with 3.5× C.A, respectively. The adhesion strength of the optimized PAN APL ACFs and Nylon66 APL ACFs was improved by 8.4times, and 15.6times, separately. Electrical properties including contact resistance, and short circuit rate were measured. Pressure cooker test (PCT), thermal cycle (TC) test, and 85℃/85% relative humidity (RH) test were performed to evaluate the reliability of the optimized APL ACFs structures. All three optimized APL ACFs structures showed excellent electrical properties and reliability.