Preparation of copper nanoparticles and metal-metal bonding process using them

This work describes a metal-metal bonding process by the use of Cu nanoparticles as a filler material. The Cu particles used were prepared by reduction of Cu2+ with hydrazine in the presence of cetyltrimethylammonium bromide as a dispersing agent (uncoated Cu particles). Polypyrrole (PPy)-coated Cu nanoparticles were also used as the filler. Strong bonding for Cu discs was not obtained by using the PPy-coated particles. For the uncoated Cu particles, a shear strength required for separating the discs bonded by annealing at 400°C in H2 gas was as large as 18.1 MPa.