Bending Properties of Fine Pitch Flexible CIF (Chip-in-Flex) Packages Using APL (Anchoring Polymer Later) ACFs (Anisotropic Conductive Films)

In this paper, the bending reliability of the CIF package using new APL ACFs was investigated, and compared with that of conventional ACFs. APL ACFs are new ACFs structure including conductive particles incorporated polymer film which suppresses the flow of the conductive particles during ACFs bonding process. By using APL ACFs, it is possible to completely solve the short-circuit problem at fine pitch interconnection by suppressing the movement of the conductive particles, and stable electrical resistance can be obtained. APL ACFs can be an excellent packaging solution for future flexible displays requiring very high resolution such as 8K UHD Virtual Reality (VR) and bendable and rollable displays. Our research group has investigated the Chip-In-Flex (CIF) assembly using ACFs for flexible packaging applications and reported their bending properties before. APL ACFs was fabricated using PAN (Polyacrylonitrile) polymer APL film and Non-conductive Films (NCFs) as adhesive films. And dynamic bending tests of CIF packages using two types of ACFs were also performed up to 150,000 dynamic bending cycles at the bending radius of 6 mm. As a result, it was confirmed that APL ACFs show excellent bending reliability than conventional ACFs, and can be successfully applied for ultra-fine pitch applications such as 8K UHD and VR displays. This is because the PAN APL has very high modulus, which increase the overall modulus of PAN APL ACFs system.