Metal-metal bonding process using metallic copper nanoparticles prepared in aqueous solution

摘要

A method for preparing metallic Cu nanoparticles in aqueous solution is proposed, and metal-metal bonding with the use of the nanoparticles is demonstrated. The metallic Cu nanoparticle colloid solution was prepared by mixing a 0.01 M aqueous solution of copper salt (copper chloride (CuCl2), copper nitrate (Cu(NO3)2), or copper acetate ((CH3COO)2Cu) (copper source) and a 0.2-1.0 M hydrazine aqueous solution (reducing reagent) in the presence of 0.0005 M citric acid and 0.005 M cetyltrimethy-lammonium bromide (stabilizers). The metallic Cu nanoparticles with average sizes in the range of 54-64 nm were prepared for all the copper salts and the hydrazine concentrations examined. A stage and a plate of metallic Cu were successfully bonded under annealing at 400 ℃ and pressurizing at 1.2 MPa for 5 min in H2 gas with the help of the metallic Cu particles. The shear strength with the use of (CH3COO)2Cu was large compared to CuCl2 and Cu(NO3)2. A shear strength required for separating the bonded Cu substrates reached the maximum value at a hydrazine concentration of 0.6 M, and it decreased beyond the concentration. Consequently, the largest shear strength of 37.7 MPa was achieved using (CH3COO)2Cu at the 0.6 M hydrazine concentration.