The synergistic effect of micron spherical and flaky silver-coated copper for conductive adhesives to achieve high electrical conductivity with low percolation threshold

Abstract In the application of electronic products, it is critical for conductive adhesives to ensure high electrical conductivity and good adhesion reliability. In this study, isotropic conductive adhesives (ICAs) with high conductivity and low percolation threshold can be achieved by making full use of the synergistic effect of micron spherical and flaky silver-coated copper (Cu@Ag) conductive fillers. The flaky Cu@Ag powder prepared by electroless plating was chosen as the main conductive filler, and the spherical core-shell structure Cu@Ag powder was used as an auxiliary conductive filler to be dispersed in the flaky Cu@Ag particles, providing more possibilities for building a large number of conductive bridges. In this study, the Cu@Ag powder was synthesized to eliminate the disadvantages of Cu oxidation and Ag electrochemical migration, while making the ICAs low cost and favourable conductivity. Furthermore, the curing parameters were optimized for the matrix resin in corresponding experiments. The results showed that a combination of spherical and flaky Cu@Ag powders in ICAs could not only significantly reduce the percolation threshold and the bulk resistivity but also increase the shear strength compared with the single component. In particular, the bulk resistivity of the optimum sample was 1.95×10-3 Ω·cm, and the shear strength was 22.69 MPa when the filler content was only 60 wt%. Hence, the ICAs filled with spherical and flaky Cu@Ag will pave the way for high-performance and low-cost ICAs in the electronics packaging industry.