Study On The Synthesis Of Silver-coated Copper Powder And Silver Nanoparticle Conductive Fillers

With the developing of modern science and technology, conductive paste has a wide range of application in various kinds of electronic devices. So far, two kinds of conductive filler are mainly applied to conductive paste, one is silver series and the other is copper series. However, the copper series are usually oxidized easily, which will lower their stability of electrical properties. And the silver series are costly. In this paper, silver nanoparticles, micron copper particles and silver-coated copper particles were prepared in liquid phase environment based on the concept of ?green?. These three kinds of conductive filler are low cost and have the possibility of mass production and all of them are expected to have practical applications, so that a new-type conductive paste with low cost, low sintering temperature and stable performance can be prepared successfully. The main research contents and results in this paper are as follows:1. During liquid reduction method, silver nitrate(Ag NO3) and trisodium citrate(Na3C6H5O7) were used as precursor and reductant, respectively. The influence of reaction time, reaction temperature and additives on experimental results was discussed. The results showed that reaction rate increased with rising the temperature and aging caused the subsequent growth and morphological differentiation of the synthesized nanoparticles. When reaction time was 60 min, reaction temperature was 80 ? and no additive introduced, well-dispersion quasi-sphere silver nanoparticles with a mean size of 59.33 nm were produced.2. Under the optimal procedure, micron copper particles with a mean size of 1.1 ?m were also produced in large-scale by a two-step liquid phase reduction method. PVP, Cu SO4, Na OH, C6H12O6 and C6H8O6 were served as dispersant, source, complexing agent and reductant, respectively. It was found that copper powder, produced by two-step method, had lower impurity content than one-step method. The ways of adding sodium hydroxide solution would indirectly influence on the size, form and dispersity of copper particles via directly impact on the size and morphology of cuprous oxide which was an intermediate product. The dispersion and particle size of copper powder would also been influenced by PVP.3. Finally, silver-coated copper particles with smooth surface and clear interface were synthesized from homemade micron copper powder. The way of adding Tollens' reagent had important influence on the surface morphology of silver-coated copper particles. In addition, the silver atomic mass fraction on the surface of silver-coated copper particles would increase from 56.59% to 73.96% when PVP was added.