Preparation And Sintering Properties Of Cu@Ag Core-shell Nanoparticles

With the development of electronic components miniaturization,lightweight and flexibility,higher requirements about cost and performance were required.Electronic interconnection materials are an important part of electronic components.In addition,silver nanoparticles and copper nanoparticles are common electronic functional materials,which have characteristics of flexible connectivity,good conductivity and low sintering temperature.And the two kinds of materials have become a hotspot in the field of flexible displays and sensors.However,silver nanoparticles are expensive,and have a problem of electromigration.Due to the existence of these problems,the silver nanoparticles cannot use massively.The cost of copper nanoparticles is low.However,copper nanoparticles are poor in antioxidant activity and easily generate oxide impurities,which greatly limits their application and performance.Therefore,this paper systematically develops a new type of interconnection material.It can improve the antioxidant activity of copper nanoparticles,and have good electrical conductivity.The printing process and the sintering performance were characterized,and the reliability of the sintering pattern of the best scheme was explored.Cu@Ag core-shell nanoparticles with different silver contents were prepared by displacement method and chemical reduction method.The preparation process was carried out in two steps.In the first step,the optimal conditions of Cu nanoparticles were analyzed by controlling the concentration of dispersant of PVP,reducing agent of Na H2PO2·H2O,reaction temperature and time.In the second step,Cu@Ag core-shell nanoparticles with different silver contents were prepared.The nanoparticles were achieved by varying the concentration of sodium citrate,silver sulfate,and Cu nanoparticles produced in the first step.The average size of the core-shell Cu@Ag nanoparticles was about 30 nm.When the molar ratio of sodium citrate to silver ion was 0.50,and the molar ratio of silver ion to copper was 0.15 and 0.30,two kinds of core-shell Cu@Ag nanoparticles with low silver content were prepared.The core-shell structure and antioxidant activity of the nanoparticles were characterized by HR-TEM,SEM,EDS,XRD and UV-visible absorption spectroscopy.The optimum Cu@Ag ink preparation and printing process were selected for different flexible substrates.Four kinds of conductive ink with solid content of 30%,40%,50% and 60% were prepared by mixing proper solvent with Cu@Ag powder.The Cu@Ag inks were printed on two types of flexible substrates,respectively.By comparing the printed flexible circuit,the optimum solid content ratio was found.The results showed that Cu@Ag ink with a solid content of 50% had the best printing effect on photographic paper.Based on the results,the Cu@Ag ink with a solid content of 60% was the best plan for the PI film.The sintering process of Cu@Ag nanoparticles with different Ag contents was analyzed by characterizing the microstructural changes of the Cu@Ag patterns at five different sintering temperatures.The SEM and corresponding resistivity of sintered microstructure were analyzed,and the optimu m sintering temperature was 240 °C.Based on the porosity and conductivity of the four kinds of solid content patterns sintered at 240 °C,the resistivity of the PI film pattern with the best conductivity was obtained.When the molar ratio of silver ions to copper was 0.30,and the Cu @ Ag solid content was 60%,the lowest resistivity of 36 ??·cm was obtained when sintered at 240 °C for 30 min.The results of the reliability test of the PI film showed that the film has certain bending resistance and chemical corrosion resistance.