34 GHz Bandpass Filter for Low-temperature Co-fired Ceramic System-in-Package Application

Modern electronic circuit requires compact,multifunctional technology in communication systems.However,it is very difficult due to the limitations in passive component miniaturization and the complication of fabrication process.The bandpass filter is one of the most important passive components in millimeter（mm）-wave communication system,attracting significant interest in three-dimension（3D） miniaturized design,which is few reported.In this paper,a bandpass filter structure using low-temperature co-fired ceramic（LTCC） technology,which is fully integrated in a system-in package（SIP） communication module,is presented for miniaturized and high reliable mm-wave application.The bandpass filter with 3D end-coupled microstrip resonators is implemented in order to achieve a high performance bandwidth characteristic.Specifically,all of the resonators are embedded into different ceramic layers to decrease the insertion loss and enhance the out-of-band rejection performance by optimizing the coupling coefficient and the coupling strength.A fence structure,which is formed by metal-filled via array with the gap less than quarter wavelength,is placed around the embedded bandpass filter to avoid electromagnetic（EM） interference problem in multilayer structure.This structural model is validated through actual LTCC process.The bandpass filter is successfully manufactured by modifying the co-fireablity characteristics,adjusting the sintering profile,releasing the interfacial stress,and reducing the shrinkage mismatch with different materials.Measured results show good performance and agree well with the high frequency EM full wave simulation.The influence of layer thickness and dielectric constant on the frequency response in fabricated process is analyzed,where thicker ceramic sheets let the filter response shift to higher frequency.Moreover,measured S-parameters denote the center frequency is also strongly influenced by the variation of ceramic material＇s dielectric constants.By analyzing the relationship between the characteristics of the ceramic tape and the center frequency of the filter,both theoretical and experimental data are accumulated for broadening application filed.With the coupling resonators embedded into the ceramic layers,the bandpass filter exhibits advantages of small size and high reliability compared to conventional planar filter structure,which makes the bandpass filter suitable for SIP communicational application.

Microwave dielectric properties of Ca0.7Nd0.2TiO3 ceramic-filled CaO–B2O3–SiO2 glass for LTCC applications

The effects of the Ca0.7Nd0.2Ti O3 ceramic addition on the crystallization,densification,and dielectric properties of CaO–B2O3–SiO2–(Al2O3)glass(C1:CaO–B2O3–SiO2 glass and C1A03:CaO–B2O3–SiO2–Al2O3 glass)for low-temperature co-fired ceramic(LTCC)applications are investigated.The cristobalite phase crystallized from C1 glass was inhibited by adding Al2O3.During sintering,Ca0.7Nd0.2TiO3 ceramic reacted with CaO–B2O3–SiO2–(Al2O3)glass to form the sphene(CaTiSiO5)phase.The amount of sphene phase increases with increasing sintering temperature.By adding 50–60 wt%C1 or C1A03 glass,Ca0.7Nd0.2TiO3 can be densified at 850–900℃.The relative dielectric constants for Ca0.7Nd0.2TiO3 added with C1 and C1A03 glasses were all 20–23.Ca0.7Nd0.2TiO3 added with C1 glass exhibited a lower dielectric constant than C1A03 glass due to cristobalite phase formation.For Ca0.7Nd0.2TiO3 ceramics added with 50 wt%glass,the variation in Q×f value presented the same trend as the sphene formation amount variation.The best Q×f value of 2380 GHz was achieved for Ca0.7Nd0.2TiO3 ceramics added with 50 wt%C1A03 glass sintered at 900℃due to the dense structure and greater amount of sphene.Ca0.7Nd0.2TiO3 ceramics added with50 wt%C1A03 glass sintered at 900℃exhibited a dielectric constant of 22.8 and Q×f value of2380 GHz,which are suitable for microwave LTCC applications.

Sintering behaviour and microwave dielectric properties of MgO-2B_(2)O_(3)--xwt%BaCu(B_(2)O_(5))-ywt%H_(3)BO_(3) ceramics

This study investigates the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) series ceramics synthesised by solid-state reaction.According to the X-ray diffraction and microstructural analyses,the as-prepared MgO-2B_(2)O_(3) ceramics possess a single-phase structure with a rod-like morphology.The effects of different quantities of H_(3)BO_(3) and BaCu(B_(2)O5)(BCB)on the bulk density,sintering behaviour,and microwave dielectric properties of the MgO-2B_(2)O_(3) ceramics were investigated.Accordingly,the optimal sintering temperature was obtained by adding 30 wt%H_(3)BO_(3) and 8 wt%BCB.We also reduced the sintering temperature to 825°C.Furthermore,the addition of 40 wt%H_(3)BO_(3) and 4 wt%BCB increased the quality factor,permittivity,and temperature coefficient of resonance frequency of MgO-2B_(2)O_(3) to 44,306 GHz(at 15 GHz),5.1,and-32 ppm/℃,respectively.These properties make MgO-2B_(2)O_(3) a viable low-temperature co-fired ceramic with broad applications in microwave dielectrics.

SINTERING BEHAVIOR AND MICROWAVE DIELECTRIC PROPERTIES OF NOVEL LOW TEMPERATURE FIRING Bi_(3)FeMo_(2)O_(12)CERAMIC

In the present work,a novel low temperature-ring Bi_(3)FeMo_(2)O_(12) ceramic was synthesized via the solid-state reaction method.The monoclinic Bi_(3)FeMo_(2)O_(12) phase can be formed at a low temperature 670℃.A relative density above 96%can be obtained when sintering temperature is above 800℃.The Bi_(3)FeMo_(2)O_(12) ceramic sintered at 845℃ for 2 h shows high microwave dielectric performance with a permittivity-27.2,a Qf value of 14,500GHz and a temperature coefficient of-80 ppm/℃.It might be a candidate for low temperature co-fired ceramics technology.