The role of surface oxides and stabilising carboxylic acids of copper nanoparticles during low-temperature sintering

This article provides a detailed discussion of 1-hexanoic-acid-stabilised copper nanoparticles with an average diameter of similar to 80 nm prepared from cupric oxide micro-powders for low-temperature sintering applications. The obtained fine particles were dispersed in dipropylene glycol using a bead mill to obtain a stable paste containing 50 wt% copper. Sintering experiments at temperatures in the range of 120-250 degrees C were performed under a nitrogen or 3%H-2-N-2 gas flow. The lowest resistivity, approximately three times that of bulk copper, was obtained at 250 degrees C. These particles exhibited good conductivity upon sintering under nitrogen only. 1-Hexanoic acid contributed to the acceleration of sintering by removing the Cu64O oxide layer of the particles and activating the surface. The dispersed copper paste and the copper layer after sintering were observed using SEM