Synthesis of nano-copper particles for conductive ink in gravure printing

Controllable and mono-disperse copper nanoparticles were synthesized via a simple chemical method which copper nitrate trihydrate, hydrazine hydrate and poly (vinylpyrrolidone) were used as copper source, reducing agent and capping agent, respectively. Copper nanoparticles so-prepared were characterized by UV-Visible spectroscopy, X-ray diffraction measurements (XRD), scanning electron microscopy (SEM). The colloid of the copper nanoparticles was obtained after washing and centrifuging by deionized water and acetone three times by which impurity ions can be removed. Suspension of nano-copper conductive ink for gravure printing was obtained by adding some solvent and additives. Then, samples were obtained by proofing and sintered under the nitrogen ambience. The resistance and thickness were measured. The result illustrated that the copper particles prepared have size about 80 nm and majority particles are spheroidal. The suspension of nano-copper conductive ink has 35.15% copper content according to thermal gravimetric analysis (TGA) and 1.29 % PVP. Surface resistance of samples proofing on polyimide film after sintering can reach 6.16 Ω/sq and the resistivity is 1.09×10^-4 Ω·cm.