Microstructure of metallic copper nanoparticles/metallic disc interface in metal-metal bonding using them

This paper describes a metal-metal bonding technique using metallic Cu nanoparticles prepared in aqueous solution. A colloid solution of metallic Cu particles with a size of 54 +/- 15 nm was prepared by reducing Cu2+ (0.01 M (CH3COO) Cu-2) with hydrazine (0.6 M) in the presence of stabilizers (5 x 10(-4) M citric acidand5 x 10(-3) M cetyltrimethylammoniumbromide) in water at room temperature in air. Discs made of metallic materials (Cu, Ni/Cu, or Ag/Ni/Cu) were successfully bonded under annealing at 400 degrees C and pressurizing at 1.2 MPa for 5 min in H-2 gas with help of the metallic Cu particle powder. Shear strength required for separating the bonded discs was 27.9 +/- 3.9 for Cu discs, 28.1 +/- 4.1 for Ni/Cu discs, and 13.8 +/- 2.6 MPa for Ag/Ni/Cu discs. Epitaxial crystal growth promotes on the discs with a good matching for the lattice constants between metallic nanoparticles and metallic disc surfaces, which leads to strong bonding. Copyright (C) 2013 John Wiley & Sons, Ltd.