Preparation of micron-scale Cu@Ag conductive particles by displacement coating to reinforce epoxy conductive adhesives

Abstract

Epoxy resin conductive adhesives with high electrical conductivity have been prepared by adding micron-scale silver-coated copper (Cu@Ag) particles. The silver-coated copper particles have been prepared with 1 μm Cu particles as the substrates, which utilizes Cu autocatalytic properties and does not require any reducing agent. The reaction time and temperature on the properties of Cu@Ag particles have been studied. The sample has a high loading of 32.5% at 60 °C, and the activation energy of the displacement reaction is 3.2 × 10³ J mol⁻¹. The Cu@Ag particles have been immersed in a 20% HNO₃ solution. We found that the conductive particles prepared under high-temperature conditions (≥50 °C) had high corrosion resistance. Through thermogravimetric analysis, it could be seen that the silver could improve the oxidation resistance of the material, and the oxidation resistance also increased with the increase of the temperature of preparing conductive particles. The Cu@Ag particles prepared under the conditions of 10, 30, 40, 60 °C and epoxy resin were prepared into conductive adhesives containing 75% conductive particles. The stability of the samples has been tested, and the results have shown that the resistivity of the conductive adhesives prepared under the condition of 60 °C and 80 hours baking was stable within 2.0 × 10⁻⁴ Ω m, and then the resistivity fluctuates in a small range, but it is consistent with the pure silver conductive adhesives.