Low-temperature Co-fired Ceramic Technology Research Articles

LTCC Filtering Rat-Race Coupler Based on Eight-Line Spatially-Symmetrical Coupled Structure

In this paper, a compact filtering rat-race coupler implemented in low-temperature co-fired ceramic (LTCC) technology is presented. In order to reduce the dimensions, the schematic and the coupling topology of a planar filtering rat-race coupler are first studied and then simplified to fit the 3-D multilayer LTCC structure. An eight-line spatially symmetrical coupled structure is, therefore, proposed to obtain the required coupling topology between resonators. Thus, the filtering rat-race coupler can be constructed only by using four resonators, which is only half that of the planar one. Consequently, the size could be reduced substantially. For validation, a design example centered at 3.5 GHz is simulated, fabricated, and measured. All the measured results are in good agreement with the full-wave simulation results. Besides, the size of the circuit is only $3.8 \times 4 \times 2.1$ mm3, which demonstrates that by employing the eight-line spatiallysymmetrical coupled structure, the proposed rat-race coupler obtains good performance and compact size.

Characterization of LC sensor structures realized by PCB and LTCC technology for determining moisture in building materials

This paper compares performances of two wireless sensors for measuring water concentration in building materials, one manufactured by the printed circuit board (PCB) technology and another one using the low temperature co-fired ceramics (LTCC) process. The fabricated sensors consist of inductive part (L) and interdigitated capacitive part (C) in one metal layer, connected in parallel. Inductance of inductive part was kept constant, whereas capacitance of capacitive part was changed by exposing the sensor to different moisture concentration, changing its resonant frequency. The variation of resonant frequency as a function of different water concentration was measured, using antenna coil and impedance analyser, in two widely used construction materials: clay brick and autoclaved aerated concrete block. Surface analysis for two sensors was performed by means of 3D profilometer. Mechanical properties of the sensors were measured for both conductive segments (copper and silver) and substrates materials (PCB and ceramics substrates) using nanoindenter. Comparative characteristics of the sensors are presented from their application point of view.

Size-Reduced Planar and Nonplanar SIW Gysel Power Divider Based on Low Temperature Co-fired Ceramic Technology

Aiming at reducing the size of substrate integrated waveguide (SIW) Gysel power divider (PD), a SIW-based planar Gysel PD is redesigned based on low temperature co-fired ceramic (LTCC). In addition, another novel SIW-based nonplanar Gysel PD is first presented and implemented on multilayer LTCC, which can further reduce size over 83% when compared with planar Gysel PD. Both of the two SIW Gysel PDs are fabricated and measured, and the measured results show that within frequency range from 17 to 19 GHz, the planar Gysel PD has the performances of return losses 20 dB, and phase ripple about ±7.5°; while the nonplanar Gysel PD has the performances of return losses 10 dB, and phase ripple about ±7°.

Review of State-of-the-Art Integration Technologies in Power Electronic Systems

As an important development direction of power electronic systems, the integration technologies can bring many benefits, such as size reduction, reliability improvement, cost saving and so on. With the continuous development of power semiconductor devices, especially the emergence of wide band-gap devices, more advanced integration technologies are needed. This paper reviews the state-of-art integration technologies, including active and passive integration technologies. Active integration technology is reviewed in terms of the interconnect, packaging material, packaging structure, and module integration. Passive integration technology is reviewed from the aspects of magnetic integration technology, electromagnetic integration technology, and low-temperature cofired ceramic (LTCC) technology. Higher-level integration technologies, namely power supply on chip (PwrSoC) and power supply in package (PwrSiP), are also investigated, which are mainly used in low power applications.

90 GHz CMOS Phased-Array Transmitter Integrated on LTCC

This paper presents the design of a 90 GHz phased-array transmitter front end on low-temperature co-fired ceramic (LTCC) technology. The monolithic microwave integrated circuit components have been fabricated by the CMOS technology and flip chipped on the LTCC to realize the transmitter front end. The dc and differential hybrid IF signals are provided to the flip-chipped components through the bias and IF lines designed on the LTCC. An $1 \times 4$ patch antenna array has been designed for the transmitter and fabricated on the LTCC. The dc and IF signal pads on the LTCC were soldered to the designed printed circuit board pads for measurements. The measurement results show that by using a receiver horn antenna, the maximum received power at 92 GHz is −37.3 dBm at a communication distance of 1 m. The transmitter is capable of providing ±25° beam steering with respect to boresight and 20° half-power beamwidth at 90 GHz. The total power consumption of the transmitter front end is 656 mW.

A Microwave Microfluidic Sensor Based on a Dual-Mode Resonator for Dual-Sensing Applications.

In this paper, we propose a novel microwave microfluidic sensor with dual-sensing capability. The sensor is based on a dual-mode resonator that consists of a folded microstrip line loaded with interdigital lines and a stub at the plane of symmetry. Due to the specific configuration, the resonator exhibits two entirely independent resonant modes, which allows simultaneous sensing of two fluids using a resonance shift method. The sensor is designed in a multilayer configuration with the proposed resonator and two separated microfluidic channels—one intertwined with the interdigital lines and the other positioned below the stub. The circuit has been fabricated using low-temperature co-fired ceramics technology and its performance was verified through the measurement of its responses for different fluids in the microfluidic channels. The results confirm the dual-sensing capability with zero mutual influence as well as good overall performance. Besides an excellent potential for dual-sensing applications, the proposed sensor is a good candidate for application in mixing fluids and cell counting.

Microwave dielectric properties of Bi(Sc1/3Mo2/3)O4 ceramics for LTCC applications

A novel microwave dielectric ceramics Bi(Sc1/3Mo2/3)O4 with low firing temperature were prepared via the solid reaction method. The specimens have been characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and DC conductivity. The Bi(Sc1/3Mo2/3)O4 ceramics showed B-site ordered Scheelite-type structure with space group C2/c. Raman analysis indicated that prominent bands were attributed to the normal modes of vibration of MoO4 2− tetrahedra. The dielectric loss of Bi(Sc1/3Mo2/3)O4 ceramics can be depended strongly the bulk conductivity by DC measurement. The superior microwave dielectric properties are achieved in the Bi(Sc1/3Mo2/3)O4 ceramic sintered at 875 °C/4 h, with dielectric constant ~ 25, Q × f ~ 51,716 GHz at 6.4522 GHz and temperature coefficient of resonance frequency ~ − 70.4 ppm/°C. It is a promising microwave dielectric material for low-temperature co-fired ceramics technology.

LTCC magnetic components for high density power converter

This paper deals with multilayer magnetic components for power electronics application and specifically for high frequency switching. New formulations based on nickel-zinc-copper spinel ferrites were developed for high power and high frequency applications. These ferrites can be sintered at low temperature (around 900°C) which makes them compatible with the LTCC (Low Temperature Co-fired Ceramics) technology. Metallic parts of silver or gold can be fully integrated inside the ferrite while guaranteeing the integrity of both the ferrite and the metal. To make inductors or transformers with the required properties, it is mandatory to have nonmagnetic parts between the turns of the winding. Then it is essential to find a dielectric material, which can be co-sintered both with the ferrite and the metal. We will present the solution we found to this problem and we will describe the results we obtained for a multilayer co-sintered transformer. We will see that these new components have good performance compared with the state of the art and are very promising for developing high density switching mode power supplies.

Analytical Microsystem for the Monitoring and Analysis of Cobalt in Aqueous Solutions Using LTCC Technology

<p>This work is focused on the design and implementation of a microsystem for continuous colorimetric determination of cobalt in aqueous solutions in real time. The main goal is the colorimetric determination of cobalt by adapting colorimetric methodologies used in discontinuous analysis systems to a continuous flow system and its subsequent miniaturization using the LTCC (Low Temperature Co-fired Ceramics) technology. The measure absorbance was recorded using an optical detection system based on a LED (Light Emitting Diode) with a wavelength of 540 nm. </p>

The influence of BBZ glass on phase evolution, sintering behavior and dielectric properties of BaTi4O9 ceramics

A low temperature co-fired ceramic (LTCC) material has been fabricated by mixing BaTi4O9 ceramic powder with a BaO–B2O3–ZnO (BBZ) glass and sintering the mixture at 925 °C/2 h. The influence of the BBZ glass on sintering behavior, phase evolution, microstructure and microwave dielectric properties of the BaTi4O9-based LTCC material has been investigated. The results show that the BBZ glass can significantly lower the sintering temperature of the BaTi4O9 ceramics from 1350 °C to below 950 °C. The XRD patterns exhibit that remarkable chemical reactions happen between BaTi4O9 and the BBZ glass during sintering, forming two new phases BaTi(BO3)2 and Ba4Ti13O30 in the material. As BBZ glass is increased from 5 to 30 wt%, BaTi(BO3)2 phase gradually dominates the material and BaTi4O9 decreases and almost disappears at the end. At the same time, the dielectric constant decreases from 33 to 25, the temperature coefficient of resonant frequency decreases from +25.44 to −3.19 ppm/°C, and the quality factor firstly increases and then decreases with the peak value of 29500 GHz. The changes of the dielectric properties with the BBZ glass content are correlated with the phase evolution of the material during sintering. Typically, the BaTi4O9-based ceramics with 25 wt% BBZ glass sintered at 925 °C for 2 h displays excellent comprehensive properties with a maximum density of 4.33 g/cm3, the dielectric constant of 27.08, quality factor of 29,500 GHz and temperature coefficient of resonant frequency of +3.5 ppm/°C. In addition, the good chemical compatibility of this material with Ag electrode makes it a potential candidate for LTCC technology.

A Multilayer Power Inductor Fabricated by Cofirable Ceramic/Ferrite Materials With LTCC Technology

A cofired hetero-laminated low-temperature cofired ceramics (LTCC) power inductor device comprising cofirable NiCuZn ferrite body and Zn2SiO4 ceramic layers was designed, manufactured, and characterized. These produced LTCC power inductors were revealed to possess excellent characteristics including high inductance of $2.0~\mu \text{H}$ , small volume of 2 $\times1.2\times0.9$ mm3 (0805 packaging standard), low resistance of $0.20~\Omega $ , large current handling capability of 430 mA, low cost, and wide operating temperature range via a combination of characterization tools. Unlike the previously reported ceramic/ferrite hetero-laminates fabrication method, the process introduced in this paper involves no extra buffer layer or mechanical pressing sinter. Instead, a conventionally standard LTCC process was used for manufacturing these power inductors. To select the NiCuZn ferrite body with simultaneous high inductance and current handling capability for targeted power inductor design, the saturation magnetization and intrinsic coercivity of a variety of NiCuZn ferrite body prepared under different compositions, additives, and sintering conditions were carefully measured via vibrating sample magnetometer and under swept superpositioned dc magnetic field. Then, the power inductors with uniform sizes were mass produced using the selected NiCuZn body and Zn2SiO4 ceramic layers. The microstructure, magnetic element interdiffusion, interior circuit position, and inductance were detailed examined utilizing scanning electron microscopy, energy-dispersive X-ray spectroscopy, industrial computerized tomography scan, and RF impedance/material analyzer.

Multilayer LTCC structures based on glass-cordierite layers with different porosity

PurposeThe paper aims to report on fabrication procedure and present microstructure and dielectric behavior of multilayer porous low-temperature cofired ceramic (LTCC) structures based on glass-cordierite and glass-alumina.Design/methodology/approachThe LTCC structures were created as multi-layered composites with dense external layers and inner layers with intentionally introduced porosity. Two preparation methods were applied – subsequent casting of both kinds of slurries and conventional isostatic lamination of dried green tapes arranged in the designed order. Optical microscope observations were carried out to analyze the microstructure of green and fired multilayer structures and pore concentration. To evaluate the adhesion strength of the composite layers, pull test was performed. Dielectric behavior of the composites was studied in the frequency range 50 kHz-2 MHz.FindingsThe fabricated porous LTCC structures showed dielectric constant of 3-5.6. The lowest dielectric constant was attained for glass-cordierite composite made by the conventional tape casting/lamination/firing method from slurry with 50 per cent graphite content. The samples prepared using multiple casting were of worse quality than those fabricated in conventional process, contained irregular porosity, showed tendency for deformation and delamination and exhibited a higher dielectric constant.Originality/valueSearch for new low dielectric constant materials applicable in LTCC technology and new methods of their fabrication is an important task for development of modern microwave circuits.

K-Band Planar Magic-T Using LTCC Technology

This letter presents the design of magic-T using low-temperature co-fired ceramic (LTCC) technology by microstrip-slotline transitions and aperture-coupled structures. The magic-T is designed to work at the center frequency of 21 GHz with the bandwidth of 8 GHz. The size of the circuit is only 6 mm × 6 mm due to LTCC multilayer structures. Measured data and numerical simulations show good amplitude and phase characteristics, and high isolation is also achieved.

94-GHz Compact 2-D Multibeam LTCC Antenna Based on Multifolded SIW Beam-Forming Network

This communication presents a compact 94-GHz 2-D multibeam antenna using the low-temperature co-fired ceramic (LTCC) technology. A good 2-D substrate integrated waveguide (SIW) beam-forming network (BFN) for eight beams is proposed, where four-phase shifters are properly introduced to increase the flexibility of the beams. Benefiting from multilayer LTCC, the BFN is compactly implemented in a completely symmetrical structure by using two multifolded SIW Butler matrixes with 50% reduction of the longitudinal size, and four couplers placed on different layers with interlaced signal routes to avoid overlaps or crossovers. Combined with a $2 \times 4$ SIW slot antenna array, the multibeam antenna can realize eight symmetric scanning beams on 2-D with stable gains for a wide coverage. For demonstration, the two single-port antennas with different pitch-angle beams are fabricated and measured, and good agreements with the expectations are observed. The differences of the beam orientations are less than 5°, while the measured peak gains of the beams are about 8.5 dBi.

Sintering mechanism and microwave dielectric properties of BaTi4O9-BBZ composite for LTCC technology

Abstract A low temperature co-fired ceramic (LTCC) material was fabricated by mixing BaTi 4 O 9 ceramic with BaO-B 2 O 3 -ZnO (BBZ) glass. The sintering mechanism was further analyzed through the wetting behavior, activation energy, phase evolution, microstructure and microwave dielectric properties of the BaTi 4 O 9 -BBZ composite. The results show that the sintering temperature of the BaTi 4 O 9 ceramics can be significantly lowered from 1300 to 925 °C by the BBZ glass. This is due to the three-stage partially reactive liquid assisted sintering process which consists of glass redistribution and local grains rearrangement, solution-reprecipitaion including glass crystallization and reactions between the glass and ceramic, and global grain rearrangement, closure of pores and viscous flow. XRD patterns exhibit that BaTi 4 O 9 reacts with the crystallization phase of BBZ glass obviously during sintering to form two new phases BaTi(BO 3 ) 2 and Ba 4 Ti 13 O 30 . The activation energy of BaTi 4 O 9 ceramic is calculated to be 520.9 ± 40.46 kJ/mol, while that of BaTi 4 O 9 -BBZ composite is reduced to 330.98 ± 47.34 kJ/mol. With increasing sintering temperature, the dielectric constant (e r ) and the quality factor (Q×f) value increases firstly and then decreases, and the temperature coefficient of resonant frequency (τ f ) value slightly decreases. Typically, the BaTi 4 O 9 -BBZ composite sintered at 925 °C for 2 h displays excellent microwave dielectric properties of e r = 26.4, Q×f = 27300 GHz and τ f = + 0.3 ppm/°C. In addition, the good chemical compatibility of this material with Ag electrode makes it as a potential candidate for LTCC technology.

Microwave Dielectric Properties of BiCu2PO6 Ceramics with Low Sintering Temperature

A BiCu2PO6 microwave dielectric ceramic was prepared using a solid-state reaction method. As the sintering temperature increased from 800°C to 880°C, the bulk density of BiCu2PO6 ceramic increased from 6.299 g/cm3 to 6.366 g/cm3; the optimal temperature was 860°C. The best microwave dielectric properties [permittivity (ɛ r ) = ∼16, a quality factor (Q × f) = ∼39,110 GHz and a temperature coefficient of resonant frequency (τ f ) = ∼−59 ppm/°C] were obtained in the ceramic sintered at 860°C for 2 h. Then, TiO2 with a positive τ f (∼+400 ppm/°C) was added to compensate the τ f value. The composite material was found to have a near-zero τ f (+2.7 ppm/°C) and desirable microwave properties (ɛ r = 19.9, Q × f = 24,885 GHz) when synthesized at a sintering temperature of 880°C. This system could potentially be used for low-temperature co-fired ceramics technology applications.

Dopamine sensing with fluorescence strategy based on low temperature co-fired ceramic technology modified with conducting polymers

A convenient fluorescence sensing strategy for dopamine (DA) detection was developed based on polydopamine (poly(DA)) formed on the surface of graphene quantum dots (GQDs). The prepared GQDs were highly luminescent due to the planar structure in aromatic molecules. The ceramic-based miniature biosensor was designed and constructed through the immobilization of laccase in an electrochemically synthesized polymer − poly[dithienotetraphenylsilane] based on low temperature co-fired ceramics technology (LTCC). This sensing system utilized the catalytic oxidation of DA to dopamine-o-quinone (DOQ), and then to poly(DA) (in alkaline conditions), which can selectively quench the strong luminescence of GQDs owing to Förster resonance energy transfer (FRET). The detection process was based on substarte oxidation in the presence of the enzyme − laccase. In optimized conditions, the analytical performance illustrated high sensitivity, selectivity in a broad linear range with detection limit of 80nM. Moreover, the method was successfully applied to test labeled pharmacological samples for DA.

Wideband low‐profile low‐temperature co‐fired ceramic patch antenna with a differential‐fed structure

A novel wideband patch antenna with a differential-fed structure is proposed in this study. For this antenna, an H-shaped patch is first adopted to build a compact design. Then, by introducing a via-wall-plate pair as the differential feeding scheme, favourable radiation patterns and enhanced operating bandwidth can be achieved in a low profile. Furthermore, a Marchand balun is incorporated into the overall design to facilitate the test and direct integration with existing single-end radio-frequency circuits. The proposed antenna, which is designed and fabricated, using low-temperature co-fired ceramic technology, could be used to develop a highly integrated system-in-package. The measured results demonstrate that the proposed antenna with a low profile of 0.06λ 0 obtains an impedance bandwidth of 11.2%, a peak gain of 7.1 dBi, and a low cross-polarisation of better than −20 dB.

35-GHz Wideband Circularly Polarized Patch Array on LTCC

A 35-GHz wideband circularly polarized (CP) patch array of $2\times 2$ elements using low-temperature cofired ceramic technology is presented. The widened 3-dB axial ratio (AR) bandwidth is achieved by constructing a $1 \times 2$ sequentially rotated CP patch array with small inner-element spacing in the antenna element. The antenna element consists of two close circular patches with diagonal perturbations, and the patches are rotated with respect to each other. The two patches are fed with equal amplitude and orthogonal phase difference using one probe, which has one vertical part and two different horizontal parts. The fabricated array with a dimension of $15.3 \times 28.3\times 1.3$ mm3 shows wide −10-dB $\mid S_{11} \mid $ and 3-dB AR bandwidths of over 29.6% and 26%, respectively. The measured maximum gain of the four-element array is 9.3 dBi with slight fluctuations over 31–39 GHz frequency range.

LTCC Out-of-Phase Filtering Power Divider Based on Multiple Broadside Coupled Lines

This paper presents a compact microwave out-of-phase filtering power divider in low-temperature co-fired ceramic (LTCC) technology. The proposed device is composed of three resonators and an isolation resistor. One resonator is symmetrically coupled with the other two by employing multiple broadside coupled lines. Utilizing the transmission line theory, the magnitude and phase characteristics are addressed. Theoretical analysis indicates the proposed circuit provides two signal paths with bandpass responses and 180° phase difference. Also, the realization of the isolation between two output ports is analyzed. For validation, a filtering power divider with out-of-phase outputs is designed, fabricated, and measured. It occupies a compact area of $3.1 \times 3.2 \times 1.6$ mm3. Comparisons of the measured and simulated results are presented to verify the theoretical method.