Research On Stereolithography 3D Printing Of MgTiO₃-based Microwave Dielectric Ceramic RF Passive Device

Microwave dielectric ceramics,as key electronic materials,are widely used in wireless communications,such as microwave circuits,dielectric substrates and RF passive devices.However,with the development of ceramic-based RF devices to high performance and miniaturization,the structure becomes more complex,and the accuracy becomes higher,and then the traditional manufacturing technology has been challenged.3D printing has the advantages of preparing complex structures without molds,low labor costs,short development cycle and high precision.Especially,stereolithography apparatus(SLA)-3D printing is widely used for ceramic 3D printing due to high surface finish and good applicability.However,due to the particularity of RF devices,related research of SLA-3D printed ceramic RF devices is seldom.In this thesis,MgTiO₃-based microwave dielectric ceramic slurry for SLA-3D printing is proposed and its molding properties are studied.This research has broad application prospects and practical significance,which can be extended to other electronic ceramic devices.The configuration research results of MgTiO₃-based microwave dielectric ceramic SLA-3D printing and its RF passive device preparation are shown as follows:1.Due to high viscosity of bisphenol A epoxy acrylate,UV-resin for ceramic 3D printing is configured by introducing acrylate monomers with different functional group contents,and the regulation of UV-resin for ceramic 3D printing is studied in this thesis first.The effects of reactive diluents and photoinitiators on the curing characteristics,rheological characteristics and thermal decomposition characteristics of UV-resins are discussed using single-layer curing measurement,rheological analysis,thermogravimetric analysis and Fourier infrared.It is found that the curing depth and refractive index will be improved with the increase of the acrylate group content in the UV-resins,but are bad for reducing the viscosity and the decomposition.Finally,Irgacure 2022 is selected as the photoinitiator,and the regulation method and the proportion of UV-resins for ceramic 3D printing are determined.2.The dispersion and UV-curing characteristics of the ceramic slurry are adjusted to realize high solid content(1-x)MgTiO₃–xCaTiO₃ microwave dielectric ceramics slurry.The dispersant and its content suitable for ceramic 3D printing are optimized,and the uniform dispersion of ceramic particles in the slurry is realized.The relationship between the curing depth of the MgTiO₃-based ceramic slurry with composition and process parameters is explored.Increasing the laser power,reducing the scanning speed,reducing the scanning distance,reducing the solid content of the slurry and preferably the content of the photoinitiator can effectively increase the exposure per unit area,thereby indirectly increase the absorbance of the resin component in the slurry.Finally,acrylate-based photosensitive resin is used as the ceramic slurry solvent,1.7 wt%–2.8 wt%BYK110 is used as the dispersant,and 1 wt%–2 wt%Irgacure 2022 is used as the photoinitiator to configure 60 vol%MgTiO₃-based UV-curable ceramic slurry.3.The forming,debinding and sintering process of MgTiO₃-based ceramic slurry are designed,and its microwave dielectric properties are also studied.Experiments have shown that ceramic warpage and delamination are related to the effective exposure of the ceramic slurry.Hence,the relationship between deformation and process parameters are discussed,and the problem of body warping and delamination are solved by preferably layer thickness,increasing the laser scanning rate and increasing the laser scanning distance.The debinding process is designed by analyzing the thermal decomposition characteristics,a sintering rate of 1?/min is selected,and it is kept at 220?,400?and 600?to reduce the cracking and deformation of the green body.Following,the ceramic 3D printed samples are prepared.The microwave dielectric properties of 3D printed samples are analyzed and studied from the perspectives of phase composition,microscopic morphology and electrical properties.It is found that 3D printed samples have a little crystal voids,a few oxygen vacancies and high density.Finally,the 3D printed MgTiO₃ ceramics can achieve a Q×f value up to104000 GHz,which is improved by 30%compared to the dry pressing method.4.Based on the filter network matching principle,using MgTiO₃ ceramic 3D printing technology,combined with metallization and laser etching,an X-band ceramic filter is designed and prepared,and the ability of ceramic 3D printing to prepare miniaturized high-precision RF passive devices in one-step molding is explored.The prepared miniaturized ceramic filter has a center frequency of 8.235 GHz,a bandwidth of 480 MHz,an insertion loss of 1.2 d B,and an out-of-band suppression of 28 d B at 500 MHz from the center frequency.This preparation method is suitable for rapid manufacturing and small lot production,which provides a new technology roadmap for the preparation of miniaturized passive microwave ceramic devices.5.Based on metamaterial structures and transformation optics theory,using MgTiO₃ceramic SLA-3D printing,a flat Luneburg lens antenna for Ku-band applications is designed and prepared,which realize the gradient dielectric constant,compress the height and reduce the weight of proposed Luneburg lens,and the feasibility of ceramic 3D printing to prepare RF devices with complex structures is explored.The measurement results show that the loading of the lens increases the gain of the horn antenna by an average of 7 d B in the operating frequency range.The proposed flat Luneburg lens is expected to realize the miniaturization of the low-cost beam scanning antenna.The research provides a new way to prepare ceramic-based lenses with complex structures by 3D printing,and this exploration of ceramic 3D printing can serve as reference for the development of ceramic components with complex structures.