Green Electroless Plating Method Using Gold Nanoparticles for Conducting Microbeads: Application to Anisotropic Conductive Films

Abstract

We have developed a green electroless plating method, i.e., a method that ensures the saving of resources and reduction of emissions to the environment, for the formation of a conductive coating on micrometer-sized core beads. This method has great advantages in practical applications because it uses a self-assembling reaction between gold nanoparticles (AuNPs) that are synthesized by combining a nonhazardous reducing agent with a nontoxic thiol binder. Moreover, the method does not require sophisticated instruments. In our study, beads with uniform surfaces were obtained by the adsorption of AuNPs; furthermore, AuNP-growth processes were employed subsequently to increase the electrical resistance of the AuNP-fixed single microbead to a value suitable for practical applications . Various plastic cores, viz., monodisperse microbeads of acrylic resin, nylon 6, nylon 12, polylactic acid, and polystyrene, were used in this study. The prepared beads were well dispersed in an epoxy resin film. To demonstrate practical applications, they were then successfully applied to an anisotropic conductive film.