Low-temperature Co-fired Ceramic Technology Research Articles

Preparation and characterization of doped LiZn0.92Cu0.08PO4 ceramic for microwave and millimeter-wave substrates

PurposeThis paper aims to report on fabrication procedure and presents microstructure and dielectric behaviour of LiZn0.92Cu0.08PO4 ceramic material with Li2CO3 as a sintering aid.Design/methodology/approachSubstrates based on LiZn0.92Cu0.08PO4 with Li2CO3 addition were prepared via solid-state synthesis, doping, milling, pressing and sintering. Characterization of the composition, microstructure and dielectric properties was performed using X-ray diffractometry, energy dispersive spectroscopy, scanning electron microscopy, impedance spectroscopy in the 100 Hz to 2 MHz range and time-domain spectroscopy in the 0.1–3 THz range.FindingsDoped LiZnPO4 ceramic, which exhibits a low dielectric constant of 5.9 at 1 THz and low sintering temperature of 800 °C, suitable for low temperature co-fired ceramics (LTCC) technology, was successfully prepared. However, further studies are needed to lower dielectric losses by optimising the doping level, synthesis and sintering conditions.Originality/valueSearch for new low dielectric constant materials applicable in LTCC technology and optimization of processing are essential tasks for developing modern microwave circuits. The dielectric characterization of doped LiZnPO4 ceramic in the terahertz range, which was performed for the first time, is crucial for potential millimetre-wave applications of this substrate material.

The Modeling of Magnetic Fields in Electromagnetic Microgenerators Using the Finite Element Method

The purpose of this paper is to analyze the magnetic field distribution over a disc with magnets. This disk is part of an electromagnetic microgenerator that allows the generation of electricity as a result of changes in the magnetic field. The other part of the microgenerator is the structure of the coils. In the previous work of the authors, a complete microgenerator system was presented where the coils were made using thick-film and low-temperature co-fired ceramic (LTCC) technology. Several studies related to the influence of the shape and number of coils on the generated power were carried out, as well as the realization of complete electromagnetic microgenerators with voltage rectifying circuits. Until now, a disc with 28 neodymium magnets of size 10 × 3 × 1.5 mm3 was used for testing. In order to optimize the structure of the microgenerator with respect to the disc with magnets and thus increase the generated power, it was decided to perform appropriate tests to analyze the magnetic field distribution for several configurations of the disc varying in the shape and the dimensions of the magnets. Simulations were performed in COMSOL Multiphysics using the finite element method.

LTCC Strip Electrode Arrays for Gas Electron Multiplier Detectors.

The Low Temperature Cofired Ceramic (LTCC) technology has proven to be highly suitable for 3D microstructures manufacturing in electronic devices due to its excellent electrical and mechanical properties. In this paper, a novel idea of implementing the LTCC structures into high-energy particle detectors technology is proposed. It can be applied in High Energy Physics (HEP) laboratories, where such sophisticated sensors are constantly exposed to particles of the TeV energy range for many years. The most advanced applications of the concept are based on dedicated gas amplifier systems coupled with readout microstructures. Typically, the readout microstructures are made in the Printed Circuit Boards (PCB) technology and processed in a sophisticated and patent-protected way. This article presents the manufacturing process and parameters of the novel microstructures made in the LTCC technology. The structures were implemented into the high-energy particle detector, and the first results are presented.

(Cu1/3Nb2/3)4+ ionic substituting effects, low-temperature sintering behaviors, and improved temperature stability of Ba3Nb4Ti4O21 microwave dielectric ceramics

In this study, (Cu1/3Nb2/3)4+ complex cation and BaO–ZnO–B2O3 glass frit were adopted to solve the high sintering temperature and poor temperature stability of Ba3Nb4Ti4O21 ceramics. It is shown that pure Ba3Nb4Ti4O21 phase was formed when Ti site was partially replaced by (Cu1/3Nb2/3)4+ cation. The increasing number of dopants decreases the dielectric polarizability, correspondingly, the dielectric constant and temperature coefficient of the resonance frequency values are reduced consistently. The variation of the Q × f value is determined by internal ionic packing fraction and external sintering densification. The (Cu1/3Nb2/3)4+ cation effectively decreases the suitable sintering temperature from 1200 to 1050 °C while greatly improving the temperature stability. BaO–ZnO–B2O3 glass was used to further improve the low-temperature sintering characteristics of Ba3Nb4Ti4O21 ceramics. It is proven that the addition of glass frits effectively decreases the temperature to 925 °C with combinational excellent microwave dielectric properties: εr ∼55.6, Q × f ∼5700 GHz, τf ∼3 ppm/°C, making the Ba3Nb4Ti4O21 ceramics promising in the applications of low-temperature cofired ceramic technology.

Meshed Stacked LTCC Antenna for Space Application

Meshed conductors have been used to realize antenna systems. Previous studies have concentrated on single layer patch designs. In this paper, different mesh configurations of stacked meshed patch antennas are studied; when both patches are meshed, when only the top patch is meshed, when only the bottom patch is meshed and when both patches are continuous solid metal. In addition, the effect of conventional slot loading on stacked meshed patches is also investigated through parametric studies. The designs are fed by coaxial feed probe in the lower patch. The results showed that the stacked mesh performance in terms of the resonant frequency, return loss, gain and radiation efficiency can be comparable to that of a typical, continuous metal stacked design. Both patches are 20.86 mm <inline-formula> <tex-math notation="LaTeX">$\times21.46$ </tex-math></inline-formula> mm. The maximum absolute gain and radiation efficiency of the solid stacked patch were 5.05 dBi and 91.6&#x0025; while those of the meshed stacked patch were 5.22 dBi and 91.8&#x0025; respectively. The measurements of stacked meshed design showed that the antenna was resonant at 2.52 GHz with a reflection coefficient in dB of &#x2212;23.69 dB. It has a 40 MHz &#x2212;10 dB impedance bandwidth (1.5&#x0025;) from 2.50 GHz to 2.54 GHz. The antenna exhibited a maximum measured gain of &#x2212;0.12 dBi and cross polarization of 10 dB at boresight. An equivalent circuit model for the design was also proposed. The antenna was intended for space application, and therefore it was implemented using Low Temperature Co-fired Ceramic (LTCC) technology as the LTCC properties can withstand the harsh environment of space. Although the meshed lines increase the line impedance and therefore can result in increased losses, this can be mitigated by careful mesh selection. Lastly, the meshed design allows for better bonding between the LTCC tape layers.

A review on wireless sensors fabricated using the low temperature co-fired ceramic (LTCC) technology

ABSTRACT In recent years, with the development of wireless communication systems and intelligent auxiliary equipment, the development of various wireless sensors has attracted more and more scientific and commercial attention. A new type of LC (Lenz (inductor) – Capacitor) wireless sensor was designed and fabricated using Low Temperature Co-fired Ceramics (LTCC) technology, including the advantages of low-cost wireless sensing of radio frequency (RF) communications and high operating temperature, miniaturisation, low weight, excellent thermal management, and multilayer printed circuit board of LTCC technology. LTCC technology offers functionalities such as high/low permittivity, low dielectric loss in a single multilayer package and multi-functional features by integration and interconnections. It also offers the highest interconnect density for the fabrication of 3D structures with multilayer additive fabrication of ceramic 2D sheets. In this article, an introduction to the LTCC technology and the mechanism of LC resonance wireless interrogation are overviewed. Then, we summarise the latest developments in wirelessgas, pressure, proximity and microfluidic sensors based on LTCC technology.

60 GHz dual‐polarized magneto‐electric dipole antenna array with hybrid gap waveguide feeding network in low temperature co‐fired ceramic technology

AbstractA 60 GHz 8 × 8 dual‐polarized aperture‐coupled magneto‐electric (ME) dipole antenna array in low temperature co‐fired ceramic (LTCC) technology is proposed. Taking advantage of the LTCC technology of high integration, the antenna array is composed of three parts, including the wideband ME dipole elements, dual‐polarized strip‐line series feeding network and low‐loss gap waveguide (GWG) feeding network. The ME dipole antenna element is fed by aperture coupling with 45° rotation. Two separate orthogonal strip lines are located right below the aperture to realize dual polarization performance. The simulated −10 dB impedance bandwidth of the dual‐polarized antenna element is 50–66.5 GHz with an isolation lower than −20 dB for two input ports. By employing the proposed radiating element, a 4 × 4 wide‐band dual‐polarized antenna subarray is realized by using strip‐line series‐feed technology. A compact hybrid low‐loss feeding network is realized by combing the GWG technology with the strip‐line series feed technology. For demonstration, one prototype was fabricated. The measured impedance bandwidth is 14.2% and 16.7% respectively for dual polarizations with |S11| &lt; −8 dB, and the port isolation is lower than −20 dB over the entire frequency band of interest.

Synthesis of a new sodium strontium borate composite ceramic and its microwave dielectric properties

A novel microwave dielectric material, the NaSrB5O9 based composite ceramics with low synthetic temperatures of 750–825 °C were prepared via the solid-phase sintering route. All the fabricated ceramics were composed of NaSrB5O9 and SrB2O4. At higher temperatures, some of NaSrB5O9 decomposed to SrB2O4. Dense composite ceramics were obtained under a sintering temperature of 800 °C for 4 h, which exhibited an optimal microwave dielectric performance (εr = 5.67, Q × f = 49,824 GHz, τf = −18.28 °C/ppm). The results suggest that NaSrB5O9 based composite ceramics can be promising materials applied in low-temperature co-fired ceramics (LTCC) technology.

Effects of LBSCA glass addition on sintering behavior, Raman spectroscopy, and microwave dielectric properties of LiNb0.6Ti0.5O3 ceramics

In this study, LiNb0.6Ti0.5O3 (LNT) ceramics with x wt.% (0 ≤ x ≤ 2.0) of added Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass were prepared by conventional solid-state reaction method. Effects of LBSCA glass on phase composition, microstructure, lattice vibration, and microwave dielectric properties of the LNT-x wt.% LBSCA ceramics were investigated. X-ray diffraction analysis confirmed the formation of single-phase Li1.075Nb0.625Ti0.45O3 in all samples. Combined with Raman spectroscopy, it was suggested that the microwave dielectric properties were highly associated with the bulk density, the vibration damping behavior, the Nb–O bond strength, and the degree of order in crystal structure. Introduction of LBSCA glass resulted in effective decrease in the sintering temperature to 925 °C and contributed to the improvement of quality factor (Q × f) value. The LNT-0.4 wt% LBSCA sample sintered at 925 °C exhibited excellent microwave dielectric properties with ϵr = 62.9, Q × f = 7561 GHz, and τf = 12.56 ppm/°C coupled with good chemical compatibility with silver), which offers good application prospects in the field of low-temperature co-fired ceramic technology.

Temperature Difference Sensor to Monitor the Temperature Difference in Processor Active Heat Sink Based on Thermopile

The monitoring of processor temperature is crucial to increase its efficiency. One of the novel approaches is use the information not only about the CPU (Central Processing Unit) thermal state, but also about changing environmental conditions. The additional temperature difference sensor to monitor thermal changes in the processor environment is necessary. The sensor dedicated for active heat sink, often used inside laptops, was designed, fabricated and investigated. To fulfill the requirements and to match to the specific shape of the active heat sink, the hybrid sensor was proposed. It was composed of six thermocouples and fabricated using thick-film and LTCC (Low Temperature Cofired Ceramic) technology combined with wire thermocouples. Thick-film/LTCC flat substrates with thermoelectric paths ensured good thermal contact between the sensor and the monitored surface. The thermoelectric wires allowed adjusting the sensor to the complicated shape of the active heatsink. Three different versions of the sensor were realized and compared. All of them seem to be suitable for measuring the temperature difference in the given application and they can be used in further works.

LTCC-Integrated Dielectric Resonant Antenna Array for 5G Applications.

A millimeter-wave dielectric resonator antenna array with an integrated feeding network and a novel alignment superstrate in Low Temperature Cofired Ceramics (LTCC) technology is presented. The antenna array consists of 16 cylindrical DR antenna (CDRA) elements operating at 28 GHz for mm-Wave 5G applications. The array is fed by an inverted microstrip corporate feeding network designed and built in the same LTCC stack as the resonators. A grooved and grounded superstrate is introduced to facilitate the alignment of the individual array elements while enhancing the overall performance of the antenna array. The performance of the proposed stack is evaluated numerically and compared with measured data. Measured results show an impedance bandwidth of 9.81% at 28.72 GHz with a maximum realized gain of 15.68 dBi and an efficiency of 88%, and are in excellent agreement with simulations.

Microwave dielectric high-entropy ceramic Li(Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)GeO4 with stable temperature coefficient for low-temperature cofired ceramic technologies

High-entropy ceramics are new single-phase materials with at least four cation or anion types. Their large configurational entropy is believed to enhance the simultaneous solubility of many components, which can be used to optimize certain properties. In this work, a high-entropy oxide, Li(Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2 Lu 0.2 )GeO 4 (LRG) was explored as a microwave dielectric ceramic for low-temperature cofired ceramic technologies. The LRG high-entropy ceramic with an olivine structure formed in the sintering temperature range of 1020–1100 °C. The minimal distortion (5 × 10 -4 ) of the [RO 6 ] octahedron led to a stable temperature coefficient of resonant frequency ( τ f ) of –5.3 to –2.9 ppm/°C. Optimal microwave dielectric properties were achieved in the high-entropy ceramics at 1080 °C for 4 h with a relative density of 94.9%, a relative permittivity ( ε r ) of 7.2, and a quality factor ( Q × f ) of 29000 GHz (at 15.3 GHz). For low-temperature cofired ceramic technology applications, the sintering temperature of the LRG high-entropy ceramic was reduced to 900 °C by the addition of 3 wt% H 3 BO 3 , which exhibited outstanding microwave dielectric properties ( ε r = 7.6, Q × f = 11700 GHz, and τ f = –7.4 ppm/°C) and a good chemical compatibility with silver. • The high-entropy strategy is applied to the field of microwave dielectric ceramics to study the effect of crystal structure on microwave dielectric properties. • A high-entropy oxide Li(Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2 Lu 0.2 )GeO 4 (LRG) with olivine structure is prepared as a microwave dielectric ceramic at the sintering temperature range of 1020 – 1100 °C. • LRG high-entropy ceramic exhibits a near-zero τ f value of -2.9 ppm/°C, which is due to the distortion of oxygen octahedron caused by the five cations of Gd 3+ , Ho 3+ , Er 3+ , Yb 3+ , and Lu 3+ simultaneously occupy the position of the [RO 6 ] octahedron. • The LRG high-entropy ceramic doped with 3 wt% H 3 BO 3 provides low sintering temperature (900 °C), good chemical compatibility with silver, and microwave dielectric properties ( ε r = 7.6, Q × f = 11700 GHz, and τ f = -7.4 ppm/°C), which are suitable for LTCC technologies.

Intelligent mine vehicle terminal antenna based on LTCC technology

A new type of laminate antenna for smart mining vehicle terminal based on low temperature co-fired ceramic (LTCC) technology is proposed. This antenna adopts a simple structure on an LTCC substrate which consists of two layers of rectangular radiating patches with cut corners and a gap inserted in the middle. A laminate structure is designed to cause dual-frequency resonance in order to expand working bandwidth further. A good circular polarization performance can be obtained by adjusting the gap and cut corner size of the upper and lower radiation patches. The software HFSS is used for simulation design. It can be seen form simulation results that the impedance bandwidth(IBW)of the antenna with return loss less than-10dB is 102MHz, ranging from 2.507 to 2.609GHz, and the size of the antenna is 25 × 28×4.6 mm3.

Wireless Microfluidic Sensor for Metal Ion Detection in Water

In the present work, a wireless microfluidic sensor based on low-temperature cofired ceramic (LTCC) technology for real-time detection of metal ions in water is proposed. The wireless sensor is composed of a planar spiral inductor and parallel plate capacitor (LC) resonant antenna, which integrates with the microchannel in the LTCC substrate between the capacitor plates. Aqueous solutions of Pb(NO3)2, Cd(NO3)2, Mg(NO3)2, Ca(NO3)2, NaNO3, and KNO3 with concentrations of 0–100 mM were tested with the sensors. The metal ion and its concentration in water can be tested by the amplitude of the reflection coefficient (S11) and the resonance frequency (fr) of the wireless microfluidic sensor. The metal ion species can be distinguished from the wireless response behavior of the sensor. The detection limit of the sensor for the selected metal ionic solutions could reach as low as 5 μM. The normalized sensitivity of the sensor is 0.47%, which is higher than that of the reported liquid microfluidic sensors based on microwave resonators. The wireless microfluidic sensor of this study is promising for rapid and convenient detection of heavy metal ion pollutants in the industrial wastewater.

Continuous-Mode Inverse Class-GF Power Amplifier With Second-Harmonic Impedance Optimization at Device Input

In this article, a continuous-mode inverse class GF (CCGF <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) power amplifier is introduced based on a new closed-form expression for the drain current. This analytical expression is utilized to exploit second source harmonic impedance manipulation in order to expand the design space of the output matching circuit resistively. This approach allows to diminish the complexity of the design of the load matching network at the fundamental and harmonic frequencies and to achieve wider bandwidth while simultaneously improving drain efficiency across the new optimum admittance points. Using the nonlinear model of a commercially available 10-W gallium nitride (GaN) device, load-pull and source-pull techniques are used to design a wideband CCGF <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The designed amplifier is fabricated using the selected transistor in low-temperature co-fired ceramic (LTCC) technology. Measurement results show that, over the frequency band between 3.05 and 3.85 GHz, a drain efficiency of more than 70%, 11-12.4-dB gain, and 39.9-41.4-dBm output power at 3-dB gain compression have been achieved. Although not designed for linearity, the fabricated amplifier shows an adjacent channel power ratio better than 26 dBc under a 20-MHz long-term evolution (LTE) signal having a 10.45-dB peak-to-average power ratio.

60 GHz Broadband LTCC Antenna for 5G Mobile Communication Systems

This paper provides a numerical investigation in designing wideband circularly polarized 60 GHz antenna using Low-Temperature Co-fired Ceramic technology (LTCC). The LTCC provides high-density multilayer integration, low dielectric loss, and low costs. The use of LTCC technology is advantageous for easy and flexible 3D integration and freer vias distribution in the substrate. The designed antenna focuses on obtaining a better trade-off in terms of size, gain, circular polarization (CP), and large bandwidth. The circular polarization was chosen in order to minimize the transmission errors caused by polarization inconsistency between the transmitter and the receiver. The antenna geometry is developed taking into consideration the design rules of the LTCC with a layer thickness of 100 µm after firing and a metal layer thickness of 9 µm. A bandwidth of more than 33% centered at 60 GHz was obtained for this designed multilayer antenna. The results are obtained by using the High-Frequency Structure Simulator (HFSS). The proposed integrated antenna can be used in future 5G wireless communication systems and other 60 GHz spectrum applications.

Effect of graphene addition on a borosilicate glass/alumina composite for LTCC technology

The effect of graphene nanoplatelets (GNPs) on the thermal conductivity of low temperature co-fired ceramic (LTCC) materials based on ZnO–B2O3–Na2CO3–Al2O3–SiO2 (ZBNAS) glass/Al2O3 composites sintered at 850 °C for 2 h were systematically investigated. The sintered sheets were prepared by standard tape casting process and solid phase sintering. The microstructure and phase composition of the sintered sheets were characterized by SEM and XRD, respectively. With the addition of 0.75 wt% GNPs, the thermal conductivity of the sintered sheet was increased from 3.91 to 7.85 W/(m·K). Meanwhile, the 0.75 wt% GNPs-Al2O3-ZBNAS glass (GNPs(0.75)/Al2O3/ZBNAS) composite achieved low dielectric constant of 5.16 and dielectric loss of 0.13 at 18 GHz. The coefficients of thermal expansion (CTE) of the sintered sheets decrease first and then increase. The CTE of GNPs(0.75)/Al2O3/ZBNAS composite is −7.13 × 10−6 °C−1 and 3.20 × 10−6 °C−1 at low temperature (25–80 °C) and high temperature (80–200 °C), respectively. The obtained graphene-based LTCC materials are promising candidates in terms of the potential application of electronic devices with high thermal conductivity requirement.

Small ozone generator fabricated from low-temperature co-fired ceramics

PurposeThe purpose of this study is the design, fabrication and evaluation of a miniature ozone generator using the principle of electric discharge are presented.Design/methodology/approachThe device was fabricated using a low-temperature co-fired ceramics (LTCC) technology, by which a multilayered ceramic structure with integrated electrodes, buried channels and cavities in micro and millimeter scales was realized.FindingsThe developed ozone generator with the dimensions of 63.6 × 41.8 × 1.3 mm produces approximately 1 vol. % of ozone in oxygen flow of 15 ml/min, at an applied voltage of 7 kV.Originality/valueA miniature ozone generator, manufactured in LTCC technology, produces high amount of ozone and more than it is described in the available references or in datasheets of commercial devices of similar size.

Sintering behavior and properties of Li2O–MgO–ZnO–B2O3–SiO2 ceramic composites for applications in low temperature co-fired ceramic (LTCC) technologies

Herein, the Li2O–MgO–ZnO–B2O3–SiO2 (LMZBS) ceramic with low sintering temperatures were prepared via the traditional solid-state method, and the Mg2SiO4/LMZBS ceramic composite was prepared by adding Mg2SiO4 ceramic, and the results showed that the properties of LMZBS ceramic was improved upon addition of Mg2SiO4 ceramic. The sinterability, microstructure, dielectric properties, mechanical properties and coefficient of thermal expansion (CTE) of composite were determined. The crystal structure was determined using X-ray diffraction, and Mg2SiO4, Mg3B2O6, Mg2B2O5 were the main phase. The 20 wt% Mg2SiO4 ceramic sintered at 900 °C exhibited superior performance: $${\varepsilon }_{\rm{r}}$$ of 6.97, Q value of 1732 at 10 GHz and flexural strength of 206 MPa, and CTE value of 10.06 ppm/°C. The composite was also found to match well with the Ag electrode in an investigational study. These properties have made the Mg2SiO4/LMZBS ceramic composite great candidates in low-temperature co-fired ceramics technology.

The synthesis of Li2ZnTi3O8 and Li2Zn3Ti4O12 powders for Low Temperature Cofired Ceramic (LTCC) production

The powders of different phase compositions in the Li2O-ZnO-TiO2 system were prepared. These powders can be used as major components in microelectronic devices production using Low Temperature Cofired Ceramic (LTCC) technology. The influence of factors such as the synthesis temperature and holding time on phase transformations processes and composition of synthesized powders were studied. It was determined that the synthesis of Li2ZnTi3O8 and Li2Zn3Ti4O12 compounds can be carried out at 850-900 °C. At the same time, the synthesized phases are extremely sensitive to the ratio of the initial components.