Preparation And Performance Optimization Of Low Cost Nano-Silver Conductive Ink Based On Direct Writing

With the development of electronic industry and the increasing problem of environmental protection,the traditional electronic printing technology can’t meet the needs of production,so it is urgent to find a new electronic printing technology.Direct writing technology has been widely concerned because of its simple process,low cost,diversified function,wide applicability of substrate and environmental protection advantages.However,at present,the advanced research of this technology and its materials is mainly concentrated abroad,and the domestic research in this field is relatively backward,also,the import price of machinery and materials needed for this technology is very expensive.Therefore,independent research and development is necessary for our country.In this paper,the silver nanoparticles were prepared by chemical reduction method,and the effects of different parameters on the size and dispersion of silver particles were studied.Finally,the best parameters for the preparation of silver nanoparticles were found.The high performance conductive ink which can be used in flexible electronic products is studied and optimized to make it more suitable for industrial application.Finally,printing patterns on flexible substrates with direct writing technology.The specific contents of this study and the conclusions reached are as follows:(1)The traditional ethylene glycol method has been simplified.Silver nitrate precursor was reduced to silver nanoparticles with ethylene glycol as solvent and acetaldehyde as reducing agent,which was produced by ethylene glycol under high temperature.Effects of reaction time,centrifugal speed,temperature,molar ratio of PVP to silver nitrate and reaction speed on the size and dispersion of silver particles were discussed.An average particle size of 69.9 nm was obtained.A vacuum freeze-drying method was explored to solve the problem of easy agglomeration of silver nanoparticles in vacuum drying box.(2)SEM,XRD,UV characterization of the prepared silver powder was carried out,then it was dispersed in the mixed solution of ethanol,acetone and turpentine.A kind of silver conductive ink based on hand-writing was prepared by adding ethyl cellulose and other additives with the mixture of ethanol.The stability of the ink was good and could be stored at room temperature for about 20 days without obvious precipitation.Compared with the traditional printing technology,pen handwriting technology is portable and can meet the needs of more extensive application.The mechanical properties and water resistance of the handwritten pattern were tested.,and the ink layer showed good bending resistance and water resistance.Finally,after sintering at 250℃ for 30 min,the low resistivity of 4.7×10-7 Ω·m was obtained.(3)A uniform dispersion of silver nanoparticles with a particle size of 81.3±34.1 nm was prepared by chemical reduction with hydrazine hydrate as reducing agent without inert gas protection.The cost of preparing silver nanoparticles was reduced effectively,and the prepared silver nanoparticles were characterized by SEM,TEM,XRD,UV-vis and FTIR.The ink formulation was further optimized,and the micro pen direct writing process was explored,the effect of different sintering time and sintering temperature on the conductivity of silver line was studied.The RFID pattern was printed on polyimide substrate by micro-pen direct writing technology.Finally,the low resistivity of 3.9×10-7Ω·m was obtained after sintering at the best sintering parameter-250℃ for 30 min.Further bending tests confirm that it can be used as a potential circuit substitute for flexible electronic devices.