Preparation And Dielectric Properties Of Copper/Insulation Materials Nanocomposites For Embedded Capacitor Applications

In recently years, with the rapid development of technology, people have pay more attention to theelectronic products with the propreties of miniaturization, lightweight, low cost, full-featured and highreliability. Many attentions have been focused on the miniaturized electronic packaging materials,especially. Currently, ceramic/polymer composites have been intensively investigated as embeddeddielectrics, but the low dielectric constants of these composites limit their further applications. Recently,much more attention has been focused on the conductor particles filling polymer composites because oftheir high dielectric constants. Based on the percolation theory, the dielectric constants and dielectric lossesof these composites will increase dramatically when conductor fillers’ content are close to thevicinity of thepercolation threshold. This phenomenon limits composites’ application in the field of electronic products.In order to delay percolation theory, increase the adding amount of the conductive particles, in this paperwe used the copper nanoparticles which have well properties of low prices and excellent conductiveproperties as fillers. What is more, the surfaces of the copper nanoparticles were coated with insulatingshells or shell materials which had lower conductivity to preparad the core-shell nanoparticles. Thesecore-shell nannoparticle would reduce the direct contact in the polymer matrix. Here we provided a feasibleapproach to prepare high dielectric constant of the conductive particles/polymer composites. The maincontents and the research results of this paper are as follows:(1) Preparation of Cu@SiO2nanoparticles and didielecrtric properties coated with silica solCopper nanoparticles were prepared through a facile precipitation method which could be ease ofindustrial production. Then the silica sol and the copper nanoparticles were mixed together in order to makethe silica nanoparticles deposit on the surface of the copper nanoparticles. Finally Cu@SiO2core-shellnanocomposites were formed. Combined with the in-situ surface-modification of nanosilica particles, alayer of hydrophobic groups were modified on the surface of the silica layers to make these core-shellnanoparticles had supersivity and stability in many types of organic solvents. The structures and theantioxidant properties results showed that the particle size of nano-copper cores were between50-300nmand the core-shell Cu@SiO2nanoparticles had good dispersibility in organic solvents. From the dielectric properties of the as-preparaded core-shell nanoparticles, we could know that the core-shell Cu@SiO2nanoparticles could effectively improve the dielectric properties of Cu@SiO2/epoxy composites andCu@SiO2/BaTiO3/epoxy composites. It could be concluded that Cu@SiO2core-shell nanoparticles playedkey roles to improve the dielectric properties of the composite materials.(2) Preparation and dielectric properties of the Cu@SiO2core-shell nanoparticles used TEOS assilica precursorsThe nano-copper cores with good monodispersity, uniform particle size distribution and with particlesize around80nm were preparaded in polyol system, by exploring the appropriate reaction conditions.Referring to the classical st ber method, a layer of silica was successfully coated on the surface of thenona-copper cores. Transmission electron microscopy (TEM) showed that the thickness of silica shell in theCu@SiO2core-shell nanoparticles was about5nm. And the experimental characterization results indicatedthat the Cu@SiO2core-shell nanoparticles had good antioxidant properties. We tested the dielectricproperties of the as-prepared core-shell nanoparticles. Compared with copper nanoparticles, the as-preparedCu@SiO2core-shell nanoparticles could effectively improve the dielectric properties of the polymer matrixand effectively slow the appearance of percolation threshold.(3) Preparation and dielectric properties of carbon-coated copper nanoparticlesThe carbon-coated core-shell structure Cu@C nanoparticles were successfully synthesized with asimple thermal decomposition method. The as-prepared Cu@C core-shell nanoparticles were measured byfield emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-raypowder diffraction (XRD) and thermal gravimetric analysis (TG).The results showed that the size range ofnano-copper cores was20-50nm. Amorphous carbon layers were effectively coated on the surface of thecopper cores with shell thickness about5nm. We tested the dielectric properties of the as-preparedcore-shell nanoparticles by complexing with PVDF. From the test results, we could give the conclusionsthat the Cu@C core-shell nanoparticles effectively improve the dielectric properties of the polymer matrixmaterials.