Room temperature sintering of Cu-Ag core-shell nanoparticles conductive inks for printed electronics

The monodisperse Cu-Ag core-shell nanoparticles (Cu@Ag NPs) for electric conductive inks were successfully prepared by a simple two-step process consisting of thermal decomposition and galvanic displacement. It was found that 20 mol.% coverage of Ag enabled Cu@Ag NPs oxidation resisting with air. A new approach to achieve coalescence and sintering of Cu@Ag NPs at room temperature was proposed. 1-amino-2-propanol (MIPA), hydrophilic amine with a short C-chain, was first applied to replace the strong stabilizer, the strong stabilizer oleylamine (OAM) adsorbed on particles, thereby obtained preliminary agglomeration and hydrophobic -to- hydrophilic transition to improve the wetting capability of electrolyte solution on the surface of metal film. Then, the reducing electrolyte NaBH₄ solution was used as the destabilizing agent to deeply coalesce particles, and also inhibit the electrochemical corrosion. It takes only a few minutes to achieve sintering in air at room temperature. Due to the effective sintering at room temperature, the conductive patterns could be formed on thermo-sensitive substrates. The eventual resistivity was found to be as low as 36.3 μΩ·cm.