Suppression of Ag dewetting and sinterability improvement of submicron Ag-coated Cu particles as fillers in sintering paste by surface modification with stearic acid

Four types of submicron Ag-coated Cu particles with different Ag contents were prepared as sintering paste fillers, and the Ag contents of the particles were measured to be 10, 20, 30, and 40 wt.%. Four types of particles (in order of increasing Ag content: A10, A20, A30, and A40) were surface-modified with stearic acid, to suppress the Ag shell dewetting and improve sinterability. The surface-modified particles were mixed with a polyol-based solvent to fabricate a resin-free paste. Subsequently, the pastes were screen-printed onto a slide glass and sintered at 250 °C in a nitrogen atmosphere for 1-10 min to form an electrode. The electrical resistivity of the sintered film as a function of sintering time was measured using a four-point probe. All the four surface-modified Cu@Ag particles with different Ag contents exhibited decreased electrical resistivity. Particularly, the largest difference in values after and before the surface modification was observed for A40 with the highest Ag content; the electrical resistivities of the initial and surface-modified particles were 1.51×10⁻⁴ and 6.67×10⁻⁵ Ω·cm, respectively, after sintering for 10 min. The findings of this study confirmed that the surface modification using stearic acid effectively suppressed the dewetting of the Ag shell and improved the sinterability of the submicron Cu@Ag particles.