The Research And Application Of Low-temperature Coefficient LTCC Ceramic Based On Tungstate

In recent years,Mobile communications get rapid development in many aspects such as: miniaturization,integration,and high reliability.This will be a big challenge for microwave dielectric ceramics.Therefore,the low temperature co-fired ceramics?LTCC?with low loss and low temperature coefficient will be a hot research topic.Tungstate ceramics is a popular research direction in low dielectric microwave ceramics field.CaWO₄ as an example,The ceramics dielectric properties sintered at 1150? is ?r?10,Q×f ?75,000 GHz,?f =-25ppm/?.In this paper,CaWO₄ has used as the main component of tungstate ceramics.The temperature coefficient of tungstate is adjusted by adding Li₂TiO₃ and Ba₅Nb₄O₁₅ material with positive temperature coefficient.By doping low melting point oxide Li₂WO₄ or low melting point glass BBSZ,LBSCA to reduce the sintering temperature of the material.Firstly,we study on the three element LTCC material system?1-x?[0.9CaWO₄-0.1Li₂WO₄] +xLi₂TiO₃.When x=0.49 the materials sintered at 950?,the ceramics Q×f value is 23,600 GHz,the temperature coefficient ?f =+1.2 ppm/?.Due to the excessive doping of Li₂TiO₃,it will lead to the low temperature sintering performance of tungstate ceramics decline.Then,we doping low melting point glass?BBSZ,LBSCA?to promote the performance of low temperature sintering materials.Through the contrast experiment we can get the results.0.86CaWO₄-0.14Li₂TiO₃+x%LBSCA?x=0.25²?,When x=0.5,the ceramic is sintered at 900? for 3 hours shows the best performance: ?r =12.43,Q×f =76,000 GHz,?f =-2.9?ppm/ ??.When tungstate ceramics were doped with BBSZ glass,the microstructure and microwave dielectric properties were studied by the same method.The results are shown as follows,When x=0.5 the ceramic sintered at 900?,the Q×f value is 23,600 GHz.The temperature coefficient of CaWO₄ was adjusted by introducing Ba₅Nb₄O₁₅ which has positive temperature coefficient.Firstly,fixed the doping ratio of glass,through the microscopic phase analysis of?1-x?CaWO₄-xBa₅Nb₄O₁₅+0.5wt%LBBS.We found the crystal phase of BaWO₄.The results shown that two kinds of materials can not coexist in one solid solution during high temperature.Because Ba₅Nb₄O₁₅ sintering temperature is very high,so we carried out low temperature sintering experiments of doping glass.We analyzed the dielectric properties of 0.79CaWO₄-0.21Ba₅Nb₄O₁₅+x% LBBS?x=0.5wt%²wt%?.When the doping amount x=1wt%,the Q×f value of the ceramic material reaching the peak value is 18,300 GHz.Based on the tungstate ceramics 0.86CaWO₄-0.14Li₂TiO₃+0.5wt%LBSCA,we designed and simulated a miniaturized Microstrip dual band antenna.Through HFSS we carried out the structure simulation and electromagnetic simulation,The simulation results are as follows: f0=2.8GHz;5.4GHz;BW>10MHz;S11>15dB;G0=4.8dB.