Preparation Of Aqueous Nano-silver Conductive Ink And Application On Flexible Substrate

Electronic products have grown to "light, flexible and thin" direction and printed electronics have a revolutionary impact on the manufacture of printed circuit board(PCB). Therefore the investigation of nano-s ilver conductive ink’s preparation and conductibility improvement is of great importance. The preparation of nano-s ilver conductive ink should be low-cost, high-yield and available. Nano-s ilver conductive ink not only has excellent conductibility, but also conforms to the trend of green environmental and sustainable development polic ies. The applic ation of conductive ink in fabric and film will be benefic ial to the development of wearable electronic products and exploit road for the smart textile development.Nano-Silver dispers ion system for aqueous conductive ink was prepared by reducing silver nitrate(AgNO3) with Iron(II) sulfate heptahydrate(FeSO4·7H2O) as reduc ing agent in the presence of trisodium citrate dihydrate(Na3C6H5O7·2H2O) as a stabilizer on the basis of Carey-Lea method. The prepared silver nanopartic les were rinsed by sodium nitrate(Na NO3) to obtain a thinner dispersant layer between silver nanopartic les.In this experiment, the size distribution of nanopartic les in different stages of the reaction was analyzed to study the s ize growth of s ilver nanopartic les. In the initial stage of the preparation, silver nanopartic les were formed quickly and large aggregates of loose structure were formed. As the dispersing agent increases, the loose and large aggregates began to disp erse s lowly and ultimately formed uniform partic les with major size distribution within 10 nm. By changing the reaction temperature, silver nanopartic les with small and uniform size can be obtained at room temperature, and low temperature is more favorable. The adding order that mixing a small amount of dispersing agent with s ilver nitrate before the mixture of reduc ing agent and dispersant is added to the silver nitrate was benefic ial to obtain small and uniform s ilver nanopartic les. The silver nanopartic les were washed with sodium nitrate, whic h was favorable for removing Fe3+ and SO42-in the reaction solution, thinning the dispersant layer on s ilver nanopartic les and reducing the res istance during the ink s intering process.Then conductive ink was acquired by adding corresponding additives into aqueous silver nanopartic les. Then the conductive ink was printed on cotton fabric and excellent conductive pattern was obtained after sintering process.In order to improve the conductivity of nano-silver conductive ink, this paper is based on four directions : adding polyaniline; adding s intering initiators such as HCl; changing s intering method; making pretreatment of printed material. The results showed that the four directions can greatly improve the conductivity of conductive ink.Polyaniline was well compatible with silver through the C-N bond and had a soft molecular chains compared with silver, which facilitated the filling of polyaniline into the space between sintered neck and increase the contact area. In addition, polyaniline also had better affinity and coating property to the substrate, contributing to the formation of a more complete conductive pathway and the development of printed circuit’ conductivity.The addition of the initiator HCl can signific antly improve the conductivity, espec ially for the room temperature s intering from 4416Ω/□ to 0.86Ω/□ after adding HCl. Chloride ion has a strong adsorption on the surface of metal silver. With the evaporation of the solvent in the conductive ink, the chloride ion concentration increased to a certain extent, then the sodium c itrate departted from silver nanopartic les. Without the protection of dispersing agent, the sintering neck generated and formed a conductive path.Compared with heat sintering, heat pressing s intering can achieve better results in less sintering time and lower s intering temperature, which can reduce the processing time and energy consumption. In the experiment, the sheet res istance was as low as 0.16Ω/□ by heat pressing sintering. In this paper, various room temperature s intering agents were added for room temperature sintering to greatly improve conductivity avoiding high temperature damage of printed substrate.The pretreatment of the substrate mainly studied the application of the cotton fabric by roughening cotton fabric with different amount of additives, reaction temperature and time in the pretreatment process. The experiment showed that the conductivity was greatly improved us ing cotton fabric pretreated by acid and alkali.