Preparation And Application Of Microwave Low Dielectric Materials With High Quality

Low temperature co-fired ceramics?LTCC? has become the main technology of manufacture, integration and packaging for various electronic components. Microwave low dielectric ceramics are drawing considerable attention because of its low permittivity, high quality factor and temperature coefficient close to zero.In this thesis, microwave low dielectric ceramics, composed of Ca O-Si O₂-B₂O₃?CBS?system, were prepared by the multi-step solid phase reaction method. The influences of Ca to Si molar ratios and B₂O₃ contents on the crystal textures of as-powders and the morphology and dielectric properties of ceramic samples were studied, respectively. On the foundation of the appropriate Ca to Si molar ratio and B₂O₃ content, the ceramic powder applied for LTCC was obtained under the low sintering temperature through adding the moderate cosolvent BBAS powder. The crystal structure and Zeta potential of the as-powders were identified by an X-ray diffractometer?XRD? and Zeta potentiometer,respectively. The morphologies of the ceramic samples were observed by scanning electron microscopy?SEM?, and densities of the ceramic samples were tested by Archimedes principle. The LTCC green tapes were prepared by flow casting method through changing the slurry ratio with the CBS ceramic powders as filler and the process parameters. The LC resonant antenna was obtained with the LTCC green tape and the resonant frequency of the LC antenna was tested.The results show that the powder sample C prepared at 900?, and Ca O:Si O₂:B₂O₃=21:13:16 is consisted of a small number of Si O₂ phase in addition to the primary Ca Si O3 and Ca2B₂O₄. The ceramic sample C is mainly composed of the compact lath-like particles and possesses higher density. Moreover, the C sample displays the best dielectric performance with ?r=6.3, Q·f = 2.4×104 GHz at 11.7 GHz, ?f =-67 ppm/?, and thermal conductivity 3.6w/m×k.To reduce sintering temperature, the moderate cosolvent BBAS powder was added into the powder sample C. It is found that the crystal structure of the sample is not obviously changed and the morphologies of the particles still keep the lath-like after adding the BBAS powder. The ceramic sample C₆ was obtained at low sintering temperature 920 ?. The particle sizes are about 1.0-2.0 mm. However, the particles exhibit negative electricity and instability. The C₆ ceramic displays excellent dielectric performance with ?r=6.3, Q·f=1.1×104 GHz at 12.7 GHz, and ?f =-84 ppm/?.The slurry, the ceramic powder C₆ as filler and the mixture of ethyl acetate and alcohol as solvent, were prepared through changing the contents of the binder PVB and plasticize.The LTCC green tape was prepared by the flow casting method. Furthermore, the LC resonant antenna used to test strain was designed through computer aided drafting?CAD?method via the processed of screen print, punching, lamination, heated isotactic pressing,super glue and co-fire. The resonant frequency of the LC antenna was tested by contact and non-contact methods. The results show that the resonant frequency of the as-antenna is about f=155 MHz, which close to the design goal f=120MHz.