Research On Synthesis,Sintering And Application Of Copper Nanoparticles Used For Printed Electronics

With the rapid development of internet and information technology,many countries put forward the latest concept “internet of things”.To achieve this aspiration,in addition to the support of information technology,the development of electronic components is also very important.As the traditional manufacturing process is complex and expensive,printed electronics has become a new and promising method to fabricate electronic components,which leads people to focus on conductive ink.With good conductivity,low sintering temperature and excellent flexibility,metal nanoparticles has become a promising ink material.Compared with gold and silver nanoparticles,anti-migration ability and low cost make more researchers pay attention to copper nanoparticles,whose poor inoxidizability makes the research about synthesizing antioxidative copper nanoparticles become meaningful.In this paper,we varied the precursor,reaction time,reactant concentration,reaction temperature and adding order of reactant in sequence to obtain the best copper nanoparticles reduced by hydrazine hydrate,sodium borohydride,sodium hypophosphite and L-ascorbic acid respectively.The results showed that the majority of copper nanoparticles reduced by L-ascorbic acid are between 120-160 nm and had good dispersibility and large output,which was suitable for metal conductive ink.The size and morphology of copper nanoparticles prepared with L-ascorbic acid as reducing agent were analyzed and characterized by SEM and TEM,and an amorphous layer was observed on the surface,which was PVP and L-ascorbic acid according to the results of XPS,TG and EDS.Moreover,XRD analysis showed that the prepared nanoparticles could be stored for at least three months in dry air.Therefore,PVP and ascorbic acid not only inhibited the growth of nanoparticles during the preparation of copper nanoparticles,but also made the nanoparticles have good oxidation resistance in the synthesis and storage process.The change of the resistivity of copper nanoparticles with the sintering temperature and sintering time was studied by scraping the nanoparticles on polyimide substrate.The resistivity of copper nanoparticles could be as low as 17.0??·cm sintering 120 min at 250°C and only 5.7??·cm sintering 30 min at 400°C,which was three times that of bulk copper.The change of the resistivity colud be explained by the behavior of the surface melting of nanocopper particles.The SEM results shows that copper particles had obvious sintering neck at 250°C,and when the temperature reaches 300°C or above,the copper nanoparticles were obviously sintered together,and even could form a copper film.The self-made copper nanoparticles conductive paste was printed on polyimide forming the pattern of interdigital electrode by screen printing,which exhibited good flexibility and electrical conductivity after sintering.Copper nanoparticles conductive inks with different solvents were printed on the silicon substrate by ink-jet printing.The conductive ink using ethanol as solvent could form a continuous line,whose minimum line width could reach 60?m.However,the conductive ink line width of ethylene glycol could reach 30?m theoretically.