Low Temperature Bonding of Metals by Deposition of Nanoparticles at the Interface

Abstract

Copper nanopartices having some tens nanometer in diameter were prepared by pulsed laser ablation in a helium background gas to form active interface of copper-to-copper bonding. The nanoparticles deposited on Cu plate were annealed in hydrogen gas atmosphere. The sintering starts from below 473 K and boundary of nanoparticles was hardly observed above 673 K. Bonding of copper-to-copper metal pieces has been carried out by deposition of copper nanoparticles on the test piece as active interface followed by annealing at 673 K. The measured shear strength of the copper-to-copper bonding was 106 MPa, which is much higher value than that when solder was used as bonding material. The sintering process of Cu nanoparticles is discussed.

Copper film prepared from copper fine particle paste by laser sintering at room temperature: Influences of sintering atmosphere on the morphology and resistivity

“…28) In the sintering of copper fine particles, the particle size is one of the important factors because the melting point remarkably depends on the size. 29,30) It has been reported that melting points of copper nanoparticles with the sizes of 34,40,50,59, and 63 nm were 168, 202, 427, 500, and 565 °C, respectively. 29) The smaller copper particle has the lower melting point, which is advantageous to the sintering at the lower temperatures.…”