Low-temperature Co-fired Ceramic Technology Research Articles

Dielectric relaxation and microwave dielectric properties of low temperature sintering LiMnPO4 ceramics

LiMnPO4 with olivine structure is usually widely studied as a promising cathode material for lithium batteries. In present work, LiMnPO4 ceramic has been found to have potential application on low-temperature co-fired ceramic technology. Single phase of LiMnPO4 was synthesized by one-step solid state reaction using ammonium polyphosphate (APP) as PO4 precursor. Compatibility test shows the coexistence of LiMnPO4 and silver at 750 °C. Dense LiMnPO4 ceramic with more than 95% theory density can be obtained at 750 °C. The dielectric measurement shows the dielectric relaxation which obeys the universal law with fractional exponent. The dielectric spectra are well fitted with the equivalent circuit capacitance parallel with constant phase degree. The optimized microwave dielectric properties show low dielectric constant (8.1), and high quality factor (44,224 GHz).

Technology and application of the LTCC-based microfluidic module for urea determination

Purpose – The purpose of this paper is to focus on the technology and performance of the miniature microfluidic module for urea determination. The presented module was made using low-temperature co-fired ceramics (LTCC). It shows the possibility for the integration of the bioreceptor layers with structures that have been fabricated using modern microelectronic technology. Design/methodology/approach – The presented microfluidic module was fabricated using LTCC technology. The possibility for the fabrication of an enzymatic microreactor in a multilayer ceramic substrate, made of CeramTec glass ceramic (GC) material systems with an integrated thick-film heater, is studied. Different configurations of the LTCC/heater materials (gold, silvers and palladium-silver) are taken into account. The performance of the LTCC-based microfluidic module with the integrated heater and immobilized enzyme was examined experimentally. Findings – A compatible material for the heater embedded in the CeramTec GC-based structures was found. The preliminary measurements made for the test solution containing various concentrations of urea have shown stability (for seven days of operation) and a relatively high signal-to-noise ratio (above 3 pH units) for the microreactor’s output signal. Research limitations/implications – The presented research is a preliminary work which is focused on the fabrication of the LTCC-based microfluidic module, with an integrated heater and immobilized enzyme for urea determination. The device was positively tested using a model reaction of the hydrolysis of urea. However, urea concentration in real (biological) fluid should also be measured. Practical implications – The development of the LTCC-based microfluidic module for urea determination provides opportunity for the construction of a lab-on-chip, or μTAS-type system, for fast medical diagnoses and the continuous monitoring of various biochemical parameters, e.g. for estimating the effectiveness of hemodialysis. Originality/value – This paper shows the design, fabrication and performance of the novel microfluidic module for urea determination, made with LTCC technology.

3D LTCC structure for a large-volume cavity-type chemical microreactor

Purpose – The purpose of this paper is to present the research activity and results to research and development society on the field of ceramic microsystems. Design/methodology/approach – The chemical reactor was developed as a non-conventional application of low temperature co-fired ceramic (LTCC) and thick-film technologies. In the ceramic reactor with a large-volume, buried cavity, filled with a catalyst, the reaction between water and methanol produces hydrogen and carbon dioxide (together with traces of carbon monoxide). The LTCC ceramic three-dimensional (3D) structure consists of a reaction chamber, two inlet channels, an inlet mixing channel, an inlet distributor, an outlet collector and an outlet channel. The inlet and outlet fluidic barriers for the catalyst of the reaction chamber are made with two “grid lines”. Findings – A 3D ceramic structure made by LTCC technology was successfully designed and developed for chemical reactor – methanol decomposition. Research limitations/implications – Research activity includes the design and the capability of materials and technology (LTCC) to fabricate chemical reactor with large cavity. But further dimensions-scale-up is limited. Practical implications – The technology for the fabrication of LTCC-based chemical reactor was developed and implemented in system for methanol decomposition. Originality/value – The approach (large-volume cavity in ceramic structure), which has been developed, can be used for other type of reactors also.

LTCC Multilayered Helical Filters With a Mixed Electric and Magnetic Coupling Structure

In this paper, compact multilayered helical resonators and various coupled resonator pairs with a mixed electric and magnetic coupling structure were developed. A multilayer structure is suitable for miniaturization and enhances mutual coupling. A pair of transmission zeros (TZs) can be created using mixed coupling between two coupled helical resonators, achieving superior frequency selectivity. An equivalent circuit model was proposed to analyze the creation of TZs. The planar helical structure provides design flexibility in control of TZs. Eight coupled resonator pairs were proposed for synthesizing various filter responses. An experimental second-order helical filter was fabricated using low-temperature cofired ceramic technology. The measurement results of this second-order filter showed the center frequency to be 0.976 GHz, with two TZs located at 0.8 and 1.4 GHz. The insertion loss was lower than 1.96 dB, and the return loss was 25 dB at $f_{0}$ . The size of this filter was only $5.7~\textrm {mm} \times 3.4$ mm ( $0.051~\lambda _{g}\times 0.031~\lambda _{g}$ ), which is highly compact compared with filters from other published studies. In addition, the proposed coupled pairs have potential in the construction of high-order filters with superior frequency selectivity by cascading multiple coupled helical pairs.

Efficient Wi-Fi Power Amplifier LTCC Module Using a Buck Converter With a Power Inductor Implemented in Ferrite-Filled PCB Technology

This paper presents a power amplifier module (PAM) that operates efficiently in low-power mode for IEEE 802.11g Wi-Fi applications. The PAM consists of a power amplifier (PA), a buck converter, and a power detector. Two packaging technologies were used to integrate the compact module: a low-temperature co-fired ceramic (LTCC) technology and a ferrite-filled printed circuit board (PCB) technology. The LTCC portion includes radio-frequency inductors, capacitors, transmission lines, and interconnection lines to minimize the overall size, while a power inductor for the buck converter is implemented in ferrite-filled PCB. The PA and the buck converter are designed in 2-μm InGaP/GaAs heterojunction bipolar transistor technology and 0.35-μm CMOS technology, respectively. The output power level is converted into a voltage by the power detector, and the voltage controls the buck converter, thereby optimizing the supply voltage of the PA. This adaptive supply voltage helps to improve the power-added efficiency (PAE) in the low-power regime while maintaining linearity. The PAM showed an error vector magnitude of less than 4% up to an output power of 22 dBm. The PAE is 8% and 11% at output powers of 11 and 16 dBm, respectively, representing respective improvements of 60% and 43%. The overall size of the PAM is 5×7.5×1.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

A Two-Stage Process for Laser Prototyping of Microwave Circuits in LTCC Technology

An improved technique for laser prototyping of microwave circuits in low-temperature cofired ceramic (LTCC) technology is presented. This builds on the method of laser machining of conductor layers in unfired LTCC tapes. The proposed process presents the hybrid approach of circuit fabrication by employing both unfired and post fired laser machining of LTCC substrate, hence giving more flexibility of realizing multilayer components. This allows the low-tolerance microwave structures like couplers and filters to be fabricated on the outer layers because shrinkage uncertainty is no longer a problem. Track widths and gaps of 30 μm are demonstrated with an edge definition of ±2 μm. A stripline coupler and a four-layer spiral inductor is successfully fabricated using this technique to demonstrate the process. The improved process can produce high-precision microwave and millimeter-wave components on the outer layers and provides rapid system-in-package prototyping for research and development.

Fabrication of Microstructures in LTCC Technology Using Selective Laser Ablation

This paper presents a technique and initial conditions for the laser ablation of microstructures in a low temperature co-fired ceramic (LTCC) technology. It is demonstrated that 2.5-D microstructures can be realized cost effectively and precisely by deploying the proposed technique in which an infrared laser is used to carefully ablate portions of unfired LTCC green tape. A demonstration prototype consisting of three gears and their mounting platform is realized along with a detailed description of the attendant micromachining process. The ablated surface is examined using a scanning electron microscope and a surface profiler. The optimization of the laser parameters required to equalize the surface roughness of the ablated material to that of an unmachined LTCC substrate is also described.

Implementation of a Compact EMI Filter Array for 4G-LTE Applications on LTCC

In this paper, a mixed type material is described for the first time whereby a fully integrated electromagnetic interference (EMI) filter array in low-temperature co-fired ceramic technology is implemented. To miniaturize the size of the component and have high rejection and low insertion loss, a mixed powder material with a higher permittivity and a lower loss tangent is employed to design and fabricate the filter. The material system used in this paper is BaNd2Ti4O12 + Ni–Cu–Zn ferrite. The addition of Bi2O3 reduces the sintering temperature to below 900 °C. A compact EMI filter array architecture that has a wide rejection band and sufficient isolation is also introduced. For the development of wireless communications, the spectrum for global 4G-Long Term Evolution (LTE) covers different frequencies within 700–2600 MHz. In this paper, an EMI filter array that rejects unwanted frequencies from 700 to 2700 MHz, which covers all 4G-LTE bands, is presented. The EMI filter array is $1.6~\textrm {mm}~(L) \times 0.8~\textrm {mm}~(W) \times 0.5$ mm ( $H$ ), the smallest reported so far. The measured results of the developed filter are in good agreement with the simulated results by a full-wave electromagnetic simulator.

The Implementation of Fluorescence‐Based Detection in LTCC (Low‐Temperature‐Co‐Fired‐Ceramics) Microfluidic Modules

The possibility of the application of fluorescence‐based detection method in a microfluidic system is discussed. It consists of a microfluidic module and complementary housing. Both parts are made from LTCC technology. Three microfluidic module designs are analysed. They vary by way of their constructions of a transparent window, which is used for the transmission of a fluorescence signal from the module to the photodetector integrated onto the housing. The influence of the type of materials used for optical windows on performance of the system is discussed. According to the performed measurements, a concentration as low as 0.03 ng/mL was detected.

A Wireless LC Sensor Coated with Ba0.9Bi0.066TiO3 for Measuring Temperature.

This paper presents a passive LC wireless sensor for measuring temperature. The sensor is designed as a parallel connection of a spiral inductor and an interdigitated capacitor and it was fabricated in a conductive layer using LTCC (Low Temperature Co-fired Ceramic) technology. The inderdigitated capacitor electrodes were coated with a thin film of bismuth doped barium titanate (Ba0.9Bi0.066TiO3), whose permittivity changes with temperature, which directly induces changes in the capacitance of the interdigitated capacitor and consequently changes the resonant frequency of the sensor. The measurements of S-parameter of the sensor were performed using a Vector Network Analyzer (E5071B, Agilent Technologies, Santa Clara, CA, USA), whose port was connected to the antenna coil that was placed around the sensor in order to be able to wirelessly detect temperature, in the temperature range from 25 °C to 165 °C.

Effect of La–Co substitution on the crystal structure and magnetic properties of hot press sintered Sr1−xLaxFe12−xCoxO19 (x=0−0.5) ferrites for use in LTCC technology

The La3+ and Co2+ substituted Sr1−xLaxFe12−xCoxO19 (x=0−0.5) ferrites with Bi2O3 additive were prepared by hot press sintering method at a low sintering temperature of 870°C compatible with LTCC (low temperature co-fired ceramics) systems, and their crystal structure and magnetic properties were mainly investigated. The results show that the pure M-type crystal phase is successfully obtained for the ferrites with La–Co substitution amount x not higher than 0.3. When the substitution amount further increases to 0.4 and 0.5, the α-Fe2O3 phase and La2O3 phase are found to coexist with the M-type phase, thus the multiphase structure is formed. Besides, the saturation magnetization Ms, intrinsic coercivity Hci, and Curie temperature TC of the ferrites are strongly correlated with the La–Co substitution amount. Enhanced Ms and Hci are obtained when the substitution amount varies from 0.2 to 0.4, which can exceed 3600Gs and 4000Oe, respectively. However, the TC decreases rapidly when the substitution amount exceeds 0.3, and a value under 410°C is observed. It is suggested that the La3+–Co2+ ions can partially substitute the Sr2+–Fe3+ ions for the hot press sintered ferrites at low sintering temperatures, leading to improved Ms and Hci for use in microwave LTCC ferrite devices.

Antenna in LTCC Technologies: A Review and the Current State of the Art

This paper presents a chronological review of the research carried out on antennas in low-temperature cofired ceramics (LTCC) technology over the last ten years or so. Major breakthroughs in LTCC technologies and its shortcomings are highlighted. The current state of the art of LTCC-technology-based antennas is then evaluated. All realizable features of the LTCC-based antennas, which are compact and of light weight and offer high-speed functionality for portable electronic devices, are illustrated. Different techniques used by researchers for broadbanding, multiband designs, and fabrication of LTCC-based antennas are also presented. This paper ends with some recommendations and concluding remarks.

Compact T-septum substrate integrated waveguide (TSSIW) filter with wide stopband

Proposed is a compact fourth-order band-pass filter based on T-septum substrate integrated waveguide (TSSIW) resonators. By introducing a T-septum in the conventional SIW cavity, the TSSIW resonator has lower resonant frequency and wider monomode bandwidth. In order to verify our theory, a TSSIW filter sample is fabricated in low-temperature co-fired ceramic technology, and good agreements are obtained between simulated and measured S-parameters. In comparison with planar SIW cavity filters, the proposed filter has compact size, better frequency selectivity, and wider stopband.

Compact 60 GHz LTCC balun bandpass filter with two transmission zeroes

A new balun–bandpass filter with a quasi-elliptic response for 60 GHz wireless communication systems is proposed. It is designed in the form of a substrate integrated waveguide (SIW) and fabricated with the standard low-temperature co-fired ceramic (LTCC) technology. Both simulated and experimental results are provided, which have good agreement. The results indicate that the proposed balun filter has a good balance performance with <1.1 dB amplitude imbalance and better than 3.4° phase imbalance, compact size, as well as high selectivity.

Wideband 60 GHz circularly polarised stacked patch antenna array in low‐temperature co‐fired ceramic technology

A wideband circularly polarised (CP) cross-aperture-coupled stacked feed antenna array with the top-metal strip via fence based on multilayer low-temperature co-fired ceramic technology is designed and measured for 60 GHz wireless communication applications. The influence of the large substrate and ground size on the radiation patterns of the proposed CP antenna array is investigated. Considering the 10 dB impedance bandwidth, 3 dB axial ratio bandwidth and 3 dB gain bandwidth, the measured results reveal that a wide operating bandwidth more than 17% at the centre frequency of 61.75 GHz from 56.5 to 67 GHz of the presented CP antenna array is achieved.

Laccase biosensor based on low temperature co-fired ceramics for the permanent monitoring of water solutions

A ceramic-based miniature biosensor was designed and constructed through the immobilization of laccase in an electrochemically synthesized copolymer N-hexylacridone derivative, based on low temperature co-fired ceramics technology (LTCC). This sensing system can be suitable for the permanent monitoring of water solutions (i.e. presence of phenolics). The laccase, from Cerrena unicolor, was successfully immobilized (by adsorption) on the surface of the thin polymer film built from 2,7-bis(thiophene)-N-hexylacridone, covering the microreaction chamber. The detection process was based on the oxidation of substrate in the presence of the enzyme–laccase. The response of the biosensing system was evaluated in the presence of ABTS (ammonium salt of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid)), used as an enzymatic assay substrate. The system exhibited clear catalytic activity, and the substrate could be optically determined.Considering the fact that the immobilization strategy showed high efficiency, the obtained results suggest that this method for phenoloxidase immobilization has great potential to enable the high throughput fabrication of bioelectronic devices.

Novel LTCC Distributed-Element Wideband Bandpass Filter Based on the Dual-Mode Stepped-Impedance Resonator

In this paper, a novel compact 3-D dual-mode stepped-impedance resonator (SIR) with centrally loaded stub is constructed for designing a wideband low-temperature cofired ceramic (LTCC) bandpass filter (BPF). By fully taking advantage of the LTCC technology, the dual-mode SIR, as a cell unit of the proposed filter, is reasonably folded in 3-D environment, and its properties are investigated using the transmission line theory. Accordingly, benefiting from the 3-D circuit layout, the proposed BPF designed by combining the SIR and dual-mode techniques can effectively overcome a vital and common drawback of large circuit size of the LTCC distributed-element filters. For demonstration, a fourth-order wideband BPF centered at 5 GHz is designed, fabricated, and measured. The circuit size of the designed BPF has a compact size of 3.875 × 4.8 × 1.4 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The impact of the package on the coupling and routing scheme and frequency response/transmission zero has been analyzed and demonstrated. The simulated and measured results are presented and compared, showing a good agreement.

Low temperature co-fired ceramics plasma generator for atmospheric pressure gas spectroscopy

Accurate and reliable measurements of gas composition are very important in science and industry applications. One way to accomplish this task is to measure spectrum of plasma gas discharge. In our work, we propose integrated microcell for optical measurements of gas discharge at atmospheric pressure. This device is fabricated using Low Temperature Co-fired Ceramics (LTCC) technology. Investigated gas is excited in buried air-cavity, placed between two electrodes. Discharge is created using high alternating voltage (30kV). Optical signal is then transmitted through an integrated optical fibre to the miniature spectrometer. Because different gases have different emission lines, plot of light intensity vs. wavelength provides information about molecular composition of the investigated gas sample. In this work, design, fabrication and performance of the LTCC-based gas discharge chamber is presented. Spectral measurements are performed for air, argon and nitrogen. Moreover, influence of gas flow rate on obtained emission spectrum is discussed.

Microwave dielectric properties of low firing (Na0.5Ln0.5)MoO4 (Ln=Nd and Ce) ceramics

A new series of sheelite structured (Na0.5Ln0.5)MoO4 (Ln=Nd and Ce) ceramics was prepared by using the traditional solid state reaction method. The (Na0.5Nd0.5)MoO4 ceramic could be well densified at 760°C with excellent microwave dielectric properties (a permittivity of ~10.5, a quality factor Q×f of ~19,605GHz (f=9.15GHz) and a temperature coefficient of frequency of (TCF or τf)~ −49ppm/oC). Meanwhile, the (Na0.5Ce0.5)MoO4 ceramic sintered at 780°C possessed the best microwave dielectric properties with a permittivity of ~11.2, a Q×f value of 19,365GHz (f=8.98GHz) and TCF of approximately −44ppm/°C. The (Na0.5Nd0.5)MoO4 ceramic was found to be chemically compatible with Ag electrode at its sintering temperature. It is a promising microwave dielectric material for low-temperature co-fired ceramic technology (LTCC). However, the (Na0.5Ce0.5)MoO4 ceramic was found to react with Ag after co-firing at 780°C for 2h and this limited its application in LTCC technology.

U-Shape Slots Structure on Substrate Integrated Waveguide for 40-GHz Bandpass Filter Using LTCC Technology

Millimeter-wave (mmW) bandpass filter using substrate integrated waveguide (SIW) is proposed in this paper. The propagation constants of three different types of electromagnetic bandgap (EBG) units are discussed and compared with their passbands and stopbands performance. The slotted-SIW unit shows a very good lower stopband and upper stopband performance. The mmW bandpass filter with three cascaded uniform slotted-SIW-based EBG units is constructed and designed at 40 GHz. The extracted coupling coefficient ( ${K}$ ) and quality factor ( ${Q}$ ) are used to determine the filter circuit dimensions. To prove the validity, the previous proposed structure is fabricated in a single circuit layer using low-temperature co-fired ceramic technology and measured at 40 GHz, respectively. The measured results are in good agreement with simulated results in such frequency and the measured insertion losses at 40 GHz is 1.42 dB, respectively.