Preparation And Properties Of High Performance Dielectric Materials For Embedded Capacitor Application

With the rapid development of science and technology, the electronic products requireminiaturization, light-duty, low cost, multi-function and high reliability. In printed circuit（PCB），the ratio of the passive to active components is over20and the passive componentsoccupied40%of board space. Thus capacitor occupies the important position in the electronicproducts. The polymer matrix composites for embedded capacitor application withhigh-dielectric constant, low-dielectric loss and good compatibility with PCBs wereembedded inside PCBs as capacitor dielectric material. And it can miniature the size ofelectronic products and improve its electrical performance. Therefore，it’s arise more attentionin electrical industry. Based on compound rules, the ceramic-polymer composites with highdielectric constant which consist of ferroelectric ceramic powders as filler and polymer asmatrix were prepared. Based on percolation theory, the conductor-polymer composites withhigh dielectric constant which consist of conductive material as filler and polymer as matrixwere prepared. What’s more, the conductor/ceramic/polymer composites which are higherdielectric constant were prepared.In chapter three of this thesis, firstly, we were synthetized BaTiO₃powders byhydrothermal method and analyzed phase constituent and morphology of BaTiO₃powders byXRD and SEM test. The result showed that the powders is cubic phase barium titanate, after600℃burn-in two hour the powders emerged tetragonal structure and the particle size about130nm. With extending time of burn-in, the powders size grows up, and tetragonal structurecontent increases. Secondly, sedimentation experiment and FT-IR test has been used tocharacterize the KH550modified BaTiO₃.Reseach results showed that hydroxyl generatedthough the hydrolysis of KH550was bond together with Ba-O and Ti-O on the surfaceBaTiO₃and improved its compatibility with Epoxy. Thirdly, the modified BaTiO₃was addedinto Epoxy resin, then the BaTiO₃/Epoxy composites were prepared and its microstructureand dielectric properties were tested. Results show that filled BaTiO₃effectively improved thedielectric properties of composites, and with the BaTiO₃content’s increasing, the composites’ dielectric constant increased. To some extent, it can meet the requirements for embeddedcapacitor.The chapter four studied the method of surface modification of carbon black （CB） andthe preparation and properties of CB/Epoxy composites. The CB surface was oxidized bynitric acid, then on the oxidation CB surface coated a layer of SiO₂though KH550and TEOShydrolysis-polycondensation reaction. Result show that CB surface coated by SiO₂layer, andexistence of chemical bonds of C-Si-O on the surface between CB and SiO₂layer byXRD,FT-IR and SEM test. Then the coated CB was filled in Epoxy resin, studied themicrostructure and dielectric properties. Results show that the percolation threshold ofCB/Epoxy composites is6vol%, while the percolation threshold of CB@SiO₂/Epoxy is17vol%which reduced calculation of pure CB is9vol%. And when the volume content of CBapproach the percolation threshold, the composites’ dielectric constant greatly improve.The chapter five focused on preparation and properties of CB@SiO₂/BaTiO₃/Epoxytri-phase composites, and studied the influence of the volume content of BaTiO₃andCB@SiO₂for composites’ microstructure and dielectric performance. Results show that thepercolation threshold of composites was13vol%at the volume content of BaTiO₃, and thecomposites’ percolation threshold was minished with the increase of the content of BaTiO₃.Compared with the diphase composites, the tri-phase composites’ dielectric property hasincreased greatly. When the volume content of BaTiO₃and CB@SiO₂is35%and11%respectively, the dielectric constant and loss of composites were110.1and0.0368at100KHz.In printed circuit board （PCB）, the passive component were occupied an importantposition, and it’s the main obstacle to limit the electronic products’ miniaturization. It’s aneffective way of miniaturization of electronic products to embed with the components in PCB,and the dielectric materials for embedded capacitor always are polymer matrix composites.