Fabrication of PS-DVB@Cu core-shell microsphere for anisotropic conductive adhesives by electroless plating with copper nanoparticles as seeds

Polymer@metal core-shell microspheres are widely used in anisotropic conductive adhesives (ACAs). Styrene-divinylbenzene copolymer (PS-DVB) copper core-shell microspheres (PS-DVB@Cu) with high conductivity and anti-oxidation performance were successfully prepared by combining copper nanoparticles (Cu NPs) and electroless plating copper. The Cu NPs served as catalytic seeds, substituting noble metals to promote electroless deposition. Using environmentally benign ammonia borane as the reductant to replace toxic formaldehyde, the dense copper film was deposited on the surface of PS-DVB microspheres. The thickness of the Cu layer and bulk electrical resistivity of PS-DVB@Cu were tuned by controlling the concentration of the reducing agent. The minimum resistivity of PS-DVB@Cu was 3.27×10⁻⁶ Ω·m and merely slightly changed in the air for two months. The prepared PS-DVB@Cu-based ACAs could be effectively applied to anisotropic conductive connections in small-scale circuits with satisfactory anisotropic conductivity.