High conductivity Cu@Ag core-shell heterostructure assembled by an intelligent method

The Cu@Ag core-shell particles can be employed as conductive phase in conductor paste. Ag shell is designed to protect Cu core from oxidation. To obtain thin, dense and uniform Ag shell on Cu core, a novel electroless Ag plating process for Ag coating is developed. In the process, acacia gum (AG) acts as surfactant and dispersant, manipulating Ag deposition on Cu slowly and accurately. Benefit from the reduction potential difference between Ag and Cu, a thin reduced Ag shell is plated on Cu core with layer growth mode firstly. Then, inhomogeneous surface energy of Ag shell commands its following growth with an island mode. Finally, these Ag islands grow to contact and bond together, resulting in an uniform and dense Ag shell for Cu@Ag. After optimization, the Cu@Ag particle shows excellent oxidation resistant. A mass increase of only 0.5% is observed in it at 300°C. Meanwhile, the Cu@Ag with regular structure also presents remarkable volume conductivity. Over all, the spectacular performance of prepared Cu@Ag powder indicates its promising application in conductive paste.