Recent advances in the synthesis of copper-based nanoparticles for metal–metal bonding processes

Abstract

This review introduces our study on the development of Cu-based nanoparticles suitable as fillers in the metal–metal bonding process. Colloid solutions of various nanoparticles such as cuprous iodide, cupric oxide (CuO), CuO mixed with silver oxide (Ag2O/CuO), cuprous-oxide (Cu2O), metallic Cu, plolypyrrole-coated metallic Cu, and metallic Cu containing metallic Ag (Ag/Cu) were prepared by liquid phase processes such as reduction and a salt–base reaction. Metal–metal bonding properties of their powders were evaluated by sandwiching the particle powder between metallic discs, annealing them at a pressure of 1.2 MPa, and measuring the shear strength required for separating the bonded discs. Various particles (above-mentioned), various metallic discs (Cu, Ag, and Ni), various bonding temperatures (250–400 °C), and different atmospheres in bonding (H2 and N2) were examined to find nanoparticle filler suitable for metal–metal bonding. As a result, it was confirmed that the metallic Cu, the CuO, the Ag2O/CuO, and the Ag/Cu particles were suitable for CuCu bonding in H2, low-temperature CuCu bonding in H2, AgAg bonding in H2, and CuCu bonding in N2, respectively. The metallic Cu particles also had functions of AgAg and NiNi bondings in H2. These results were explained with the particle size, the amount of impurity, and the d-value.

Keywords

• Cupper
• Nanoparticle
• Colloid
• Filler
• Metal–metal bonding