Synthesis of Conductive Nano Ink Using 1-Octanethiol Coated Copper Nano Powders in 1-Octanol for Low Temperature Sintering Process

A conductive nanoink was prepared using copper nanoparticles (CNPs). In order to prevent the oxidation of CNPs, the particles were coated by 1-octanethiol using Vaporized Self-Assembled Multi-layers (VSAMs) method. The coating of 1-octanethiol onto CNPs was confirmed by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Dispersion stability of CNPs was checked by monitoring its viscosity over 6 weeks. The sheet-type of patterned samples using the fabricated ink was sintered at 350 and 230°C, respectively. Electrical resistivity was measured to be 5.69 × 10−8 Ω·m when sintered at 350°C and 7.67 × 10−8 Ω·m when sintered at 230°C. These results were 3.4 and 4.6 times than the value for bulk copper. During the sintering process, the optimum temperature of removing organic materials was found to be 200°C. This removal temperature dramatically influenced necking and the density of samples. Therefore, 1-octanethiol VSAMs and 1-octanol ink were used successfully for the low-temperature sintering process to fabricate conductive Cu patterns by finding the optimum temperature of 200°C for complete removal of organic materials prior to the sintering process.