Preparation of Au-Ni bimetallic-coated monodisperse PS@Ni/Au microspheres with excellent conductivity and their application in acrylate-based anisotropic conductive adhesives

Anisotropic conductive adhesives (ACAs) provide an efficient and easy method of interconnecting small electronic devices compared to traditional solder joint connections. In this paper, PS@Ni/Au metal composite microspheres with excellent electrical conductivity in the size of 2.76 μm were prepared by chemical plating technique and in situ redox method. The effects of PS@Ni metal composite microspheres with different shell thicknesses and compactness on the preparation of Ni-Au bimetallic shell layers were investigated, and the effects of different Au:PS@Ni mass ratios on the volumetric conductivity of PS@Ni/Au metal composite microspheres were discussed. The composite microspheres were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy spectrometry (EDS), and X-ray diffraction (XRD). Thick and compact Ni metal shells are the key to preparing PS@Ni/Au metal composite microspheres with the complete degree of encapsulation. When the mass ratio of Au:PS@Ni was 0.15:1, the conductivity was as high as 1.3 × 105 S·cm−1. The acrylate pressure-sensitive containing 3.1∼8.3 vol% conductive particles presented an obvious anisotropy. When the mass ratio of the conductive particles was higher than 8.3 vol%, the conductive particles appear to be significantly aggregated. The research ideas and methods have great application potential for replacing the traditional solder joint connections.