Preparation And Properties Of Nano-silver Conductive Ink For Ink-jetting

With the rapid development of electronic industry, electronic products based onglass substrates have been unable to meet the demand of convenience gradually becauseof their weight, fragilibility and high cost. Miniaturization and flexibility of electroniccomponents are becoming competitive and prospective.Compared with conventional etching and photolithography, ink-jet printing is aparticularly attractive alternative. As a convenient and rapid processing technique，ink-jet printing is becoming a promising technology in the filed of electronic products.Through ink-jetting, functional materials can be deposited directly on flexiblesubstrates to form circuit, electrode and thin film etc. To meet the requirements oflow-temperature sintering and smaller feature size of electronic products, thedevelopment of nano-silver conductive ink has a crucial importance to the electroniccomponents with ink-jet printing.Firstly, the chemical reduction method was employed to prepare nano-silverparticles. Sodium borohydride and polycarboxylate （PCE） were used as reducing agentand dispersant, respectively. Influences of different dosage of oxidant and dispersant onparticle size and dispersibility were discussed. Appearance of silver nanoparticles wascharacterized by TEM and SEM. Monodisperse nano-silver particles with high puritywere prepared through simple process. When [AgNO₃]=0.10mol/L，w（PCE）/w（Ag）=0.20were employed, the average size of synthesized silver particles was16nm.Secondly, aqueous conductive nano-silver ink was prepared usingabove-mentioned nanoparticles. Viscosity and surface tension of ink should be adjustedto be applied in a piezoelectric printer. The ink exhibited remarkable dispersion stabilityfor inkjet printing. Content of Ag in the conductive ink was20wt.%. Patterns withdifferent line width were printed. Influences of viscosity and surface tension on printingproperty were discussed. When viscosity and surface tension of formulated ink was2.5mPa s and32.3mN/m, the ink showed excellent printability and printed patterns hadhigh resolution.Thirdly, effects of different sintering temperature and time on conductivity of silverfilm were discussed. The printed patterns containing nano-silver particles could formconductive films when the patterns were sintered at lower temperature. The patterns hadshown excellent conductivity. The surface microstructures of the deposited nano-silverfilm on PI substrate were characterized by TEM and AFM. After heat-treatment at200 oC for10minutes, the resistivity of the printed Ag patterns was6.8μ cm. Theresistivity variation and microstructure evolution of the Ag films were discussed as afunction of temperature.