Preparation And Properties Of Nano Silver Conductive Ink

With the rapid development of the electronics industry,inkjet printing technology has been widely concerned due to its low cost,high precision,fast speed,environmental protection and various applicable materials.Metal conductive ink is an indispensable part of inkjet printing technology which has important research significance.Metal conductive ink mainly uses gold,silver and copper as the conductive materials.Among them,gold is expensive and copper is easy to oxidize.In contrast,silver has the advantages of high conductivity,oxidation resistance and relatively reasonable cost.At present,the development of high-performance and environmental friendly silver conductive ink is one of the main bottlenecks of inkjet printing technology,which should meet the requirements of environmental protection,low temperature sintering,high stability and high conductivity.Focusing on how to improve ink conductivity,stability,environmental protection and reduce the sintering temperature and cost.This paper mainly works on the following aspects:Firstly,a kind of water-based silver conductive ink was prepared to improve the environmental protection and reduce the costs of conductive ink,and proper ink components was selected to improve the conductivity and reduce the sintering temperature.Specifically,taking the silver acetate as the precursor,the deionized water functions as the solvent and the organic amine as the complexing agent to prepare the silver acetate conductive inks.The results of the experiment showed that the six organic amines can form complexes with silver acetate respectively,which can reduce the thermal decomposition temperature of silver acetate to varying degrees.Among them,isopropanolamine had the strongest complexing ability as the complexing agent and the thermal decomposition temperature of the formed complex was only162 ? which was 133 ? lower than that of silver acetate,therefore,isopropanolamine was determined as the best complexing agent.Although adjusting the silver amine ratios or silver contents cannot further reduce the thermal decomposition temperature of the conductive ink,the sintered silver film of the ink prepared with the silver amine ratio of 1:3 had the lowest resistivity which was 397.2 ??·cm.In addition,with the increase of silver content(10-18%),the resistivity of the conductive silver film decreased from 397.2 ??·cm to 81.9 ??·cm.The sintering temperature and holding time had a great influence on the resistivity of the silver film.When the holding time was extended to 50 min and the sintering temperature increased from130 ? to 250 ?,the resistivity of the conductive silver film dropped from 7980.8 ??·cm to76.5 ??·cm.Due to silver acetate conductive inks had high sintering temperature and poor conductivity,a solution was designed to reduce the sintering temperature and increase conductivity by adding reducing agents.Specifically,formic acid and polyethyleneimine(PEI)was selected as two reducing agents for conductive ink and two silver conductive inks were prepared separately,taking the silver acetate as the precursor,deionized water as the solvent,isopropanolamine as complexing agent at the same time.Through experiments,it was found that adding 1% to 5%PEI not only increased the ink viscosity from 18 cp to 37 cp,but also improved the adhesion of the sintered silver film on the PI substrate from level 3 to the highest level.In addition,the addition of 3% PEI can reduce the resistivity of the sintered silver film to a certain extent.The resistivity of the silver film sintered at 250 ? for 50 minutes reached 20.1 ??·cm and it was worth noting that PEI makes the size of the silver particles generated more uniform.Adding 1%? 5% formic acid can greatly reduce the resistivity of the sintered silver film.When the formic acid content was 4%,the resistivity of the sintered silver film at 130 ? for 50 min reached 14.4??·cm and the resistivity of the silver film sintered at 250 ? for 50 min was only 4.5 ??·cm.In order to explore the stability of silver acetate conductive inks,two different storage environments were designed,one was stored in the refrigerator(5 ?),the other was stored at room temperature(25 ?).Through experiments,it was found that the ink prepared with formic acid as the reducing agent had the best stability.Not only can it be stored stably for more than6 months at low temperature(5 ?)and 2 months at room temperature(25 ?),but also the resistivity of the sintered silver film was basically unchanged.The stability of the ink prepared with polyethyleneimine as the reducing agent was worse and it can be stored stably for 2 months at a low temperature(5 ?).In addition,through comparison of UV data,it was found that formic acid,silver acetate and isopropanolamine can form a ternary complex and the complex had better solubility in solvent water.