Synthesis of nanoparticles composed of silver and copper for metal–metal bonding

Abstract

A metal–metal bonding technique is described that uses nanoparticles composed of silver and copper. Colloid solutions of nanoparticles with an Ag content of 0–100 mol% were prepared by simultaneous reduction of Ag⁺ and Cu²⁺ using hydrazine with polyvinylpyrrolidone and citric acid as stabilisers. The nanoparticles ranged in size from 34 to 149 nm depending on the Ag content. Copper discs were strongly bonded at 400°C for 5 min under 1.2 MPa pressure in hydrogen gas; the maximum shear strength was as high as 23.9 MPa. The dependence of shear strength on the Ag content was explained by a mismatch between the d-spacings of Cu metal and Ag metal.