A Study on the Flexible Chip-on-Fabric (COF) Assembly using Anisotropic Conductive Films (ACFs) Materials

In this study, flexible Chip-on-Fabric (COF) assemblies using anisotropic conductive films (ACFs) and cover layer structure were demonstrated. Fabric substrates were fabricated by Cu pattern lamination method with additional electroless nickel immersion gold (ENIG) metal finish before laminating onto the fabrics. Thermo-compression (T/C) bonding method was used to bond the 50μm-thick Si chip on the fabric substrates. After T/C bonding, stable ACFs joint interconnection was formed between chips and substrates. Polymer cover layer structure was applied on the flip-chip surface of the COF packages. After polymer cover layer structure was applied, minimum bending radius before chip crack drastically decreased down to 10 mm radius. In addition, a dynamic bending test was performed to evaluate the dynamic bending reliability of the COF assemblies with polymer cover layer structure, and cross-section SEM analysis and digital image correlation (DIC) method were used to analyze the bending test results.