Controllable Preparation Of Silver Micro/nano-particles And Its Application In Printed Electronics

Silver micro/nano-particles are one of the most important conductive materials in the electronic information manufacturing industry.In recent years,with the development of large-area and flexibility of electronic products,the market demands for high-quality silver powders have increased constantly.The conductivity of silver powders mainly depended on the morphology and size of Ag,while the controllable preparation of silver micro/nano-particles started late in our country,compared with the developed countries,the technology and industry of China have lagged far behind,so it is of realistic significance to develop and prepare high-performance silver micro/nano-particles.In this paper,the preparation of high-quality silver micro/nano-particles were explored systematically throuth three different liquid reducion systems which have different reduction capabilities,the effects of the amount of dispersant,the molecular weight of the dispersant,the initial pH value,the reaction temperature and the feeding method were studied deeply.At the same time,the the silk-screen printing conductive silver paste and the ink-jet printing conductive silver ink were successful prepared,the electrical conductivity and sintering process were studied.The main contents are as follows:Micron spherical silver powder with particle size around 1?m and submicron with particle size around 200 nm were successfully prepared by a chemical route,in which ascorbic acid?V_c?was used as reducing agent,poly?vinylpyrrolidone??PVP?was used as capping agent under 30^oC.The effects of PVP dosage and the initial pH value on the particle size of silver powders were studied.The study found that with the increase of PVP dosage,the particle size of silver powders increased first and then decreased.With the increase of initial pH value,the particle size of silver powders decreased first and then increased.Silver micro/nano-particles with different shapes were successfully prepared via a polymermediated polyol process under 160 ^oC.Ethylene glycol?EG?was used as solvent,PVP was used as capping agent.It was found that the amount of PVP and the molecular weight of PVP could affect the selective adsorption of PVP on the surface of silver crystals and then affected the shape and the size of silver particles;The feeding ways effected the particle size of the silver powders;By fastly pouring,the silver nanoparticles with average particle size of 90 nm can be quickly prepared after 15 min.Monodispersed silver nanoparticles can be quickly prepared using EG and PEG mixed as reducing agents,PVP as capping agent under 140 ^oC,the particles were around 40 nm in size and spherical in shape.The effects of reaction temperature,reaction time,and the ratio of PEG and EG were studied.It was found that 140^oC was a critical temperature which experimental reacted completely;The nano-silver powders with different particle size range could be prepared by adjusting the ratio of PEG and EG,when PEG:EG was 1:2 and the reaction time was 20 min,the size was the smallest,the size distribution was the narrowest and the yield was the highest;Because PEG has higher reducibility and viscosity than EG,the addition of PEG can effectively control the size of silver nanoparticles.The conductive silver paste was formulated with as-synthesized silver nanoparticles as conductive phase,with the mixture of thyl cellulose,the Span-80,terpineol and other substances as organic vehicle.The formula of conductive silver paste and the related process of screen printing were explored.The resistivity of the printed pattern was 1.03×10^-4?·cm after heating300°C for 30 min.The conductive silver ink was formulated with OP-10 as disperse agent,with ethylene glycol,isopropanol and ethanol as additives.The influence of parameters such as paper substrates,sintering temperature,sintering time on the conductivity of the printed pattern were studied.It was found that Lucky porous high glossy photo paper was a good candidate to the substrates,and the the resistivity of the printed pattern after heating at 100 ^oC for 2 h could reach5.1×10^-3?·cm.The LED lighted after connectting to the conductive circuit,the phenomenon indicated that the conductivity of the printed pattern was good.Self-made conductive silver ink can be applied to the flexible substrate,it presented a high application value.