Multi-layered Structure Cyanate Ester Composites With High Dielectric Permittivity And High Energy Density

Printed circuit boards(PCBs)are regarded as the mother of electronics industry,their performances determine the quality of electric products.Embedded capacitors have become the foundation of manufacturing new generation PCBs.Polymer composites with high dielectric permittivity,acting as core dielectrics of embedded capacitors,have attracted great attentions of industry and academy worldwide.High dielectric polymer composites should have outstanding overall performances including high permittivity.low loss tangent and high energy density for embedded capacitors.Ceramic/polymer and conductor/polymer composites are commonly used as dielectric materials for embedded capacitors,however,each of them has bottleneck problems,those are high filler content and low permittivity for ceramic/polymer composites while high dielectric loss and reduction in breakdown strength for conductor/polymer composites.Therefore,it is meaningful to develop multi-layered structure composites with high dielectric permittivity and high energy density.The main contents of this thesis include following two partsFirstly,starting from a conductive layer(C-layer)with negative dielectric permittivity,a dielectric layer(D-layer)with positive dielectric permittivity and insulating layer(1-layer).Six multi-layered structure composites,coded as DCI,CDI,IDCI,DCICD,DCIDC and CDIDC according to their spatial stacking order,were prepared.Among them,C-layer is graphite/polyvinylidene fluoride,D-layer is reduced graphene oxide-(K0.5Na0.5)NbO3/cyanate ester resin,and I-layer is boron nitride/cyanate ester resin.The effects of relative position and spatial stacking order of three-,four-and five-layer structures on performances of multi-layered composites were intensively discussed for the first time.Results show that CDIDC has outstanding performances reflected by the highest dielectric permittivity(347,100Hz),low loss tangent(0.009,100Hz)and biggest dielectric ratio(38556)of dielectric permittivity to loss tangent over multi-layered composites based on conductor/polymer reported so far.In addition,compared to conventional conductor/polymer composite,CDIDC has about 105%and 356%increased breakdown strength and energy density,respectively.The discussion reveals that breakdown strength is determined by the position of I-layer,while dielectric permittivity is mainly controlled by the order of C-layer and D-layer when the position of I-layer is fixed.Secondly,based on three five-layer composites of DCICD,DCIDC and CDIDC,the composition,thickness and position of I-layer are fixed,and the thickness ratio of C-layer to D-layer(coded as h)is adjusted to be 1:9,3:7,5:5,7:3 and 9:1,respectively.The effects of the thickness ratio of C-layer to D-layer on performances of five-layered composites were intensively discussed.Specifically,higher h brings higher dielectric permittivity and lower breakdown strength for five-layered composites with the same stacking order.When h is 9:1,CDIDC composite has the highest dielectric permittivity of 886(100Hz)and biggest dielectric ratio of 42442,moreover,about 1.72 times and 8.2 times higher breakdown strength and energy density compared with D-layer,respectively.Results show that by adjusting the thickness of C-layer and D-layer,high-energy-density dielectric materials with higher dielectric permittivity and breakdown strength can be obtained.