Takafumi Maeda

Metal–metal bonding process using copper oxide nanoparticles

Abstract This work performs metal–metal bonding using CuO nanoparticles prepared with salt base reaction in aqueous solution. A colloid solution of CuO nanoparticles was prepared by mixing Cu(NO3)2 aqueous solution and NaOH aqueous solution. Submicrometre sized leaf-like aggregates composed of CuO nanoparticles were produced at a Na/Cu ratio of 1·7 and at 20°C, though Cu2(OH)3NO3 was also obtained. An aging process, which is a process composed of preparation of the particles at 20°C and then aging them at 80°C, provided transformation from Cu2(OH)3NO3 to CuO with no damage of the leaf structure. The shear strength, which was required for separating discs bonded using the particles as a filler at 400°C in H2 gas, was 32·5 MPa at the maximum for the particles prepared at the Na/Cu ratio of 1·7 with the aging process. These results indicated that the formation of leaf-like aggregates of CuO particles with high purity led to efficient metal–metal bonding.

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.

Metal-Metal Bonding Process Using Ag2O/CuO Mixed Particles

The present study describes metal-metal bonding process using mixture of CuO nanoparticles and Ag2O nanoparticles (Ag2O/CuO mixed particles). The leaf-like aggregates with a longitudinal size of 1116 nm and a lateral size of 460 nm composed of CuO nanoparticles with a size of ca. 10 nm and the Ag2O nanoparticles with a size of 20.6 nm were fabricated with a salt-base reaction. Metal-metal bonding could be successfully performed by using the mixed particles as a filler sandwiched between metallic discs and pressurizing the discs at 1.2 MPa for 5 min under annealing in H2 gas at 400oC. The mixed particles bonded not only metallic Cu discs but also metallic Ag discs strongly; The shear strengths were as large as 17.3 and 22.4 MPa for the Cu discs and the Ag discs, respectively.

Fabrication of ITO particles using a combination of a homogeneous precipitation method and a seeding technique and their electrical conductivity

Abstract The present work proposes a method to fabricate indium tin oxide (ITO) particles using precursor particles synthesized with a combination of a homogeneous precipitation method and a seeding technique, and it also describes their electronic conductivity properties. Seed nanoparticles were produced using a co-precipitation method with aqueous solutions of indium (III) chloride, tin (IV) chloride aqueous solution and sodium hydroxide. Three types of ITO nanoparticles were fabricated. The first type was fabricated using the co-precipitation method (c-ITO). The second and third types were fabricated using a homogeneous precipitation method with the seed nanoparticles (s-ITO) and without seeds (n-ITO). The as-prepared precursor particles were annealed in air at 500 °C, and their crystal structures were cubic ITO. The c-ITO nanoparticles formed irregular-shaped agglomerates of nanoparticles. The n-ITO nanoparticles had a rectangular-parallelepiped or quasi-cubic structure. Most s-ITO nanoparticles had a quasi-cubic structure, and their size was larger than the n-ITO particles. The volume resistivities of the c-ITO, n-ITO and s-ITO powders decreased in that order because the regular-shaped particles were made to strongly contact with each other.