Molecular dynamics simulations combined with experimental investigations of Cu@Ag core-shell nanoparticles and their applications in electronic pastes

The growing demand for flexible electronics necessitates low-temperature conductive pastes, yet silver-based solutions face limitations from high costs and electromigration risks. Copper@silver nanoparticles (Cu@Ag NPs), combining copper's cost benefits with silver's oxidation resistance, present a viable strategy, though their sintering mechanisms and paste performance optimization still require deeper exploration. This study investigates the sintering behavior of Cu@Ag NPs through integrated molecular dynamics (MD) simulations and experimental synthesis. MD results revealed the sintering temperature of Cu@Ag NPs is lower than those of Ag NPs and Cu NPs, the calculated value of 690 K (416.85 °C) was consistent with experimentally determined 412.8 °C through chemically reduced nanoproducts, both indicated Cu@Ag NPs owned a low-temperature sintering characteristic. The optimization of the Ag/Cu molar ratio determined the ratio of 0.5:1 achieved complete silver shell encapsulation, enhancing oxidation resistance and thermal stability compared to Cu NPs. Incorporating 20 wt% optimized Cu@Ag NPs into silver pastes, the nanoparticles were uniformly distributed on silver flakes, which helped to reduce the cross-sectional porosity to 19.69 % ± 1.12 % while maintaining 5B adhesion. Four probe tests demonstrated that Cu@Ag NPs reduced the resistivity by 33.33 % and 92.59 % compared to Cu NPs-added and pure Ag pastes, respectively, achieving a resistivity of 8.46 × 10⁻⁴ Ω·cm after 200 bending cycles. The low-temperature sintering characteristics of Cu@Ag NPs enable silver pastes to achieve optimal overall performance. These findings, supported by both theoretical simulations and experimental results, confirm the promising potential of Cu@Ag NPs for applications in the flexible electronics industry.