Preparation of silver-coated polystyrene microspheres intermediated with polyaniline and their application in array-patterned anisotropic conductive films

Array-patterned anisotropic conductive films (A-ACFs) possessing periodically arranged conductive particles distributed in curable resins can have high circuit-bonding precision; however, the preparation of A-ACFs is a challenging work. On the other hand, the traditional electrolysis coating of metal on polymer cores as the conductive particles needs long preparation steps. Herein, a new simplified approach uses polyaniline (PANI) as an intermediate layer to wrap the polystyrene (PS) microspheres and also chelate silver to prepare silver-coated PS microspheres (PS@PANI@Ag). Through a series of experimental regulation, neat PS@PANI@Ag microspheres with an average diameter of 4.73 ± 0.13 μm possessing a silver layer of about 65 nm and weight percentage of 23.6% were prepared. For developing A-ACFs, an approach is loading the prepared particles into the microcavities with a diameter of 6 μm and depth of 4 μm in silicon template through rubbing assembly process, transferring these particles onto the surface of a kind of chosen polymerizable acrylate resin to keep their periodicity, and embedding these particles in the polymeric resin films. These A-ACFs were used to bond indium-tin-oxide (ITO) and flexible-printed circuits (FPC) with 200-μm spacing to achieve low connection resistance of 1.78 ± 0.03 Ω/0.4 mm² and high insulation resistance over 200 MΩ. After aging at 85 °C and 85% relative humidity condition for 120 h, the connection resistance change is less 9.8%, showing the bonded device’s good environmental stability. The anisotropic property was also demonstrated using a homemade device through turning LEDs on or off. Therefore, the conductive particles’ and A-ACFs’ preparation methods may provide new insights for ACFs’ designing strategy and application in industry.