Low-temperature Co-fired Ceramic Technology Research Articles

Design, Simulation, and Experiment of an LTCC-Based Xenon Micro Flow Control Device for an Electric Propulsion System

A xenon micro flow control device (XMFCD) is the key component of a xenon feeding system, which controls the required micro flow xenon (µg/s–mg/s) to electric thrusters. Traditional XMFCDs usually have large volume and weight in order to achieve ultra-high fluid resistance and have a long producing cycle and high processing cost. This paper proposes a miniaturized, easy-processing, and inexpensive XMFCD, which is fabricated by low-temperature co-fired ceramic (LTCC) technology. The design of the proposed XMFCD based on complex three-dimensional (3D) microfluidic channels is described, and its fabrication process based on LTCC is illustrated. The microfluidic channels of the fabricated single (9 mm diameter and 1.4 mm thickness) and dual (9 mm diameter and 2.4 mm thickness) XMFCDs were both checked by X-ray, which proved the LTCC method’s feasibility. A mathematical model of flow characteristics is established with the help of finite element analysis, and the model is validated by the experimental results of the single and dual XMFCDs. Based on the mathematical model, the influence of the structure parameters (diameter of orifice and width of the groove) on flow characteristics is investigated, which can guide the optimized design of the proposed XMFCD.

W-Band LTCC Circularly Polarized Antenna Array With Mixed U-Type Substrate Integrated Waveguide and Ridge Gap Waveguide Feeding Networks

In this letter, a low-temperature co-fired ceramic (LTCC) substrate integrated 8 × 8 circularly polarized (CP) antenna array is proposed for the wideband and high-gain W-band antenna-in-package application. By introducing the planar L-probe together with the original coupling probe, the E-fields in the substrate-integrated-waveguide (SIW) cavity are changed, and additional E-field components with a 90° phase difference are produced. Then, a CP antenna array is obtained. To reduce the losses in the feeding network, the gap waveguide technology is utilized with the SIW technology, as a mixed feeding network. To validate the proposed CP antenna array design, an 8 × 8 CP antenna array is fabricated by the LTCC technology and measured. Measured results show that the LTCC CP antenna array obtains a gain of 22.3 dBi, and its axial-ratio (AR) bandwidth is from 89 to 98.5 GHz for AR <; 3 dB. Besides, good agreements of the radiation patterns between the simulations and measurements are achieved within the operational frequency range.

$W$ -Band High-Gain Substrate Integrated Cavity Antenna Array on LTCC

A $4\times4$ high-gain substrate integrated cavity (SIC) antenna array using multilayered low-temperature cofired ceramic (LTCC) technology is proposed and designed for $W$ -band applications. The TM211 mode of the SIC is utilized. Two parasitic patches are introduced on the top surface of the SIC to adjust the aperture electromagnetic field distribution of the TM211 mode in the cavity for obtaining a high-gain broadside radiation pattern. A bow tie shape is adopted for the parasitic patches to improve the matching characteristic of the SIC. The SIC is modified to a stepped flared shape to improve the gain characteristic of the antenna element. Subsequently, a two-layer low-loss substrate integrated waveguide (SIW) feeding network is designed for the $4\times4$ antenna array on the basis of the proposed high-gain SIC radiating element. The proposed antenna array shows a wide measured bandwidth of 17.48% from 81.45 to 97.05 GHz at $\vert \textrm {S}_{11} \vert dB and a measured gain of up to 20.3 dBi.

Modelling of microwave filters based on LTCC

Microwave filters made according to the technology of low-temperature co-fired ceramics (LTCC) are considered. The main features of LTCC technology are described. The parameters of the domestic glass-ceramic material are given. The stages of designing an integrated microwave filter, all elements of which are in the volume of ceramics, are considered. In the course of this work, a model of a LTCC microwave filter with a nominal frequency of 300 MHz was developed taking into account the parameters of domestic materials. According to the modeling outcomes, conclusions were made.

Li5Ti2O6F: a new low-loss oxyfluoride microwave dielectric ceramic for LTCC applications

Use of microwave dielectric ceramics can significantly promote the development of communication devices. The primary criteria for determining their applications are excellent microwave dielectric properties and suitability for co-firing with cheap metals (e.g., Ag, Al). This study first reports the low-temperature synthesis of Li5Ti2O6F with a cubic rock salt structure. Li5Ti2O6F was prepared at 880 °C and had er of 19.6, Q × f of 79500 GHz, and τf of − 29.6 ppm/ °C. The infrared reflectivity spectrum revealed that the dielectric contribution of Li5Ti2O6F in the microwave range was mainly affected by phonon absorption. Experimental study indicated that Li5Ti2O6F had good chemical compatibility versus Ag electrode at 880 °C for 2 h. Given these characteristics, Li5Ti2O6F ceramics exhibited potential for low-temperature co-fired ceramic technology.

Synthesis and Design of LTCC Filtering Balun With Wide Stopband

This brief presents a synthesis method to design compact low temperature co-fired ceramic (LTCC) filtering balun with harmonic suppression. To achieve wide upper stopband, the design equations are driven based on the schematic. Benefiting from the three-port synthesis method and the flexible 3-D layout on LTCC technology, the coupling matrices at the second and third harmonics are manipulated to achieve the harmonics suppression without extra circuits. Meanwhile, the coupling elements of the passband can keep their desired values. A LTCC filtering balun is designed and implemented for demonstration. A 20 dB stopband rejection from $1.2{f} _{0}$ to $4.1{f} _{0}$ is observed. Good agreement between simulated and measured results verifies that the proposed method is suitable and the LTCC technology is reliable for wide stopband filtering balun designs.

A Broadband Planar Balun Using Aperture-Coupled Microstrip-to-SIW Transition

Based on low-temperature cofired ceramic (LTCC) technology, a broadband 60-GHz planar balun using longitudinal aperture-coupled microstrip-to-substrate-integrated-waveguide (SIW) transition is proposed. The proposed balun consists of a 3-dB SIW power divider and three longitudinal aperture-coupled microstrip-to-SIW transitions. To broaden the bandwidth of the microstrip-to-SIW transition, a matching post and a fork-type structure is employed in this work. With the proposed microstrip-to-SIW transition, it is very convenient to achieve a frequency-independent out-of-phase or in-phase property, and it does not require a tight coupling factor like the marchand balun. A prototype balun operating at 60 GHz is designed, fabricated and measured. The results show that the proposed balun provides a simulated and measured 10-dB return loss fractional bandwidth of 42.3% and >31.8% (limited by the measurement equipment), respectively. Across the operating frequencies, the measured amplitude imbalance and phase imbalance are within ±0.4 dB and ±5°, respectively.

PEDOT coating applied on thick film gold electrodes for increased miniaturization capability

Cost-effective thick film manufacturing offers a wide material portfolio for sensor solutions. Low Temperature Cofired Ceramic (LTCC) technology as thick film based multilayer manufacturing process enables the design of complex fluid reactors used in versatile application scenarios. The technology meets the requirements for the design of 3-dimensional electrode arrays, which are essential for impedance monitoring in 3D cell cultures. Since the miniaturization of gold electrodes is limited, electrode functionalization is necessary for achieving high spatial resolution in sensor arrays. Coating of thick film gold electrodes with electropolymerized poly-3,4-ethylenedioxythiophene can significantly decrease the impedance. This work optimizes the coating process applying design of experiments. Electrode topography, chemical composition and electrochemical properties of coated and uncoated electrodes are compared and scaling effects are discussed based on fit parameters obtained from impedance spectroscopy. In addition to a reduction of impedance by two orders of magnitude, poly-3,4-ethylenedioxythiophene coating induces a reduction of size effects and a significant decrease of the variation. The scaling-down capability of electrodes achieves herewith dimensions of several tens of μm. The results evince an approach for sensor array integration with high spatial resolution providing increased measurement certainty for impedance monitoring in ceramic fluid systems and 3-dimensional bioreactors.

A Capacitive Pressure Sensor Based on Cofirable Ceramic/Glass Materials with LTCC Technology

Abstract Because of good thermal, electrical, and mechanical properties, low-temperature cofired ceramic (LTCC) has shown great potential in microelectronic applications. One of the most promising directions of LTCC technology development are integrating and packing sensors. In this article, a wireless passive capacitive pressure sensor operating in the MHz range based on cofiring of heterogeneous materials with LTCC technology is proposed, and the design, simulation, and fabrication of the sensor are demonstrated and discussed. It consists of a circular spiral inductor and a capacitor of two electrodes separated by a glass medium. Furthermore, a unique process of cofiring of heterogeneous materials was introduced to avoid deformation of the capacitive embedded cavity during lamination or sintering. The results show that the inductance of the inductor and the capacitance of the capacitor embedded in the sensor are .28 μH and 16.80 pF, respectively. The novel sensor has a sensitivity of approximately 847 Hz/MPa within the pressure range from atmospheric pressure to 100 MPa.

Novel Ultrawideband and Multimode LTCC Common-Mode Filter Based on the Dual Vertical Coupling Paths

A novel ultrawideband and miniaturized common-mode filter (CMF) is proposed for suppressing the CM noise based on the dual vertical coupling paths. In the proposed CMF, a modified quarter-wavelength transmission line resonator and a modified half-wavelength transmission line resonator are utilized to introduce three CM transmission zeros. Moreover, another CM transmission zero is produced by the dual vertical path coupling. An ultrawide CM stopband is achieved by the four CM transmission zeros. Subsequently, equivalent circuit models have been established to give physical insight into the CMF operating mechanism, and the design procedures are also provided. By using the low-temperature cofired ceramic technology, a surface-mounted device prototype is fabricated and measured. The measured results show that the CM noise can be suppressed over 10 dB from 2.45 to 9.85 GHz with 120.3% fractional bandwidth. Meanwhile, the low insertion loss and the relatively constant group delay for differential mode ensure that the proposed CMF can maintain the signal integrity of differential signals below 10 GHz.

Impact of process parameters on printing resolution and dielectric properties of LTCC substrate

Purpose The low-temperature co-fired ceramics (LTCC) microfluidic-microwave devices fabrication requires careful consideration of two main factors: the accuracy of deposition of conductive paths and the modification needed to the standard process of the LTCC technology. Neither of them are well-described in the literature. Design/methodology/approach The first part of this paper deals with the individual impact of screen parameters such as aperture, photosensitive emulsion thickness and mounting angle on the precision of the screen-printed conductive paths fabrication. For the quantitative analysis purposes, the design of experiment method with Taguchi orthogonal array and analysis of variance was used. The second part contains the characterization of the complex permittivity measured for different values of LTCC substrates lamination pressure. Findings It can be concluded, that the combination of aperture, equal to 24 µm, emulsion thickness 20 µm and mounting angle 22.5° ensures the highest quality of printed conductive metallization. Furthermore, the obtained results indicate, that the modification of the lamination pressure does not affect significantly the dielectric parameters of the LTCC substrates. Originality/value This paper shows two aspects of the fabrication of the microfluidic-microwave LTCC devices. First, the resolution of the applied metallization is critical in manufacturing high-frequency structures. The obtained experimental results have shown that optimal screen parameters, in terms of conductive pattern quality, can be found. Second, the received outcomes indicate that the changes in the lamination pressure do not affect significantly the electrical parameters of the substrate. Hence, this effect does not need to be taken into account.

Synthesis of lithium zinc ceramics with a high saturation magnetization and a low ferromagnetic resonance line-width via two-step sintering strategy using low temperature co-fired ceramic technology

Abstract Lithium zinc ferrite (Li0·435Zn0·26Mn0·06Ti0.1BiyFe2.155-yO4) with a high saturation magnetization (Ms) and a low ferromagnetic resonance line-width ( Δ H ) was successfully synthesized by Low Temperature Co-Fired Ceramic (LTCC) technology using a two-step sintering strategy. In the pre-sintering stage, the optimal amount of active agent (Bi2O3) was added to LiZnMnTi ferrite to reduce reaction activation energy and promote grain growth at low temperature. SEM revealed that active agent effectively reduced critical sintering temperature to 920 °C and promoted grain growth at low temperature. During the final sintering process, various amount of V2O5 additive was added to make up the defect of asymmetrical grain growth caused by imbalances between grain growth and boundary diffusion from the influence of Bi2O3. It not only further promoted grain growth, but also greatly improved grain uniformity, reduced defects and increased material density. Finally, LiZnMnTi ferrite with a high Ms (353 kA/m), a low Δ H (182Oe), and a large average grain size (∼8 μm) was successfully synthesized by adding an optimal amount of V2O5 (0.6 wt%).

Packaging Solution Based on Low-Temperature Cofired Ceramic Technology for Frequencies Beyond 100 GHz

In this paper, a package concept based on low-temperature cofired ceramic (LTCC) technology is illustrated. The concept is specifically designed for frequencies beyond 100 GHz, taking into consideration the inherent LTCC manufacturing defects, e.g., shrinkage, layer misalignment, and warping. Simple techniques are used for package assembly which can be automated using standard industrial processes. The proposed concept is implemented by integrating a 122-GHz silicon-germanium (SiGe) radar transceiver chip in an LTCC-based package. The off-chip components of the package, operating at 122 GHz, include a transmit (Tx) and a receive (Rx) aperture-coupled patch antenna array, a stripline to grounded coplanar waveguide signal transition feeding each of the antenna arrays, and three parallel, self-matched ground-signal-ground wirebonds connecting the SiGe radar transceiver chip and the LTCC package on Tx and Rx side. The simulation and measurement results of the Tx and Rx antenna arrays along with the signal transitions in the frequency range of 110–140 GHz are shown. The radar front end (RFE) is encapsulated using an epoxy molding compound, Polytec TC 430-T with suitable dielectric characteristics in the desired frequency range. The encapsulated RFE is surface mounted on a baseband printed circuit board, thereby realizing a fully functional 122-GHz frequency modulated continuous wave (FMCW) radar. The FMCW radar is used to measure the distance of a target, and the measurement results are compared with those of a commercial 122-GHz RFE.

Design of Compact Dual-Band LTCC Second-Order Chebyshev Bandpass Filters Using a Direct Synthesis Approach

A new lumped-element circuit model suitable for dual-band bandpass filter (D-BPF) response is proposed. Using even-/odd-mode analysis, analytical equations are developed and used for the development of a direct synthesis design procedure. The proposed procedure is applied to the design and realization of a D-BPF prototype in low-temperature cofired ceramic technology covering two industrial–scientific–medical (ISM) bands of 0.9 and 2.45 GHz. This filter has been successfully measured with an insertion loss of less than 2 dB, return loss better than 18 dB for both bands and out-of-band attenuation higher than 20 dB.

An LC Wireless Microfluidic Sensor Based on Low Temperature Co-Fired Ceramic (LTCC) Technology.

This work reports a novel wireless microfluidic biosensor based on low temperature co-fired ceramic (LTCC) technology. The wireless biosensor consists of a planar spiral inductor and parallel plate capacitor (LC) resonant antenna, which integrates with microchannel bends in the LTCC substrate. The wireless response of the biosensor was associated to the changes of its resonant frequency due to the alteration in the permittivity of the liquid flow in the microchannel. The wireless sensing performance to different organic liquids with permittivity from 3 to 78.5 was presented. The measured results are in good agreement with the theoretical calculation. The wireless detection for the concentration of glucose in water solution was investigated, and an excellent linear response and repeatability were obtained. This kind of LC wireless microfluidic sensor is very promising in establishing wireless lab-on-a-chip for biomedical and chemical applications.

Passive Wireless LC Proximity Sensor Based on LTCC Technology.

In this work, we report a passive wireless eddy current proximity sensor based on inductive-capacitive (LC) resonance using a low temperature co-fired ceramic (LTCC) technology. The operation principle of the LC proximity sensor to the metal targets was comprehensively discussed through electromagnetic simulation and circuit model. Copper and aluminum were selected as the metal target materials for the measurements. Circular copper plates with different diameters and thickness were used to investigate the influence of the surface area and thickness of the target on the sensitivity. The decreases of the sensitivity with the decrease of the surface area and thickness were observed. The LC proximity sensor showed a high sensitivity of 11.2 MHz/mm for the proximity distance of 1–3 mm, and large detection range up to 10 mm. The developed LC proximity sensor is promising for passive wireless metal detections and proximity measurements under harsh environments.

Monolithic Microwave-Microfluidic Sensors Made with Low Temperature Co-Fired Ceramic (LTCC) Technology.

This paper compares two types of microfluidic sensors that are designed for operation in ISM (Industrial, Scientific, Medical) bands at microwave frequencies of 2.45 GHz and 5.8 GHz. In the case of the first sensor, the principle of operation is based on the resonance phenomenon in a microwave circuit filled with a test sample. The second sensor is based on the interferometric principle and makes use of the superposition of two coherent microwave signals, where only one goes through a test sample. Both sensors are monolithic structures fabricated using low temperature co-fired ceramics (LTCCs). The LTCC-based microwave-microfluidic sensor properties are examined and compared by measuring their responses for various concentrations of two types of test fluids: one is a mixture of water/ethanol, and the other is dopamine dissolved in a buffer solution. The experiments show a linear response for the LTCC-based microwave-microfluidic sensors as a function of the concentration of the components in both test fluids.

Low-Temperature Sintering and Microwave Dielectric Properties of CaMoO4 Ceramics

Low-loss CaMoO4 dielectric ceramics with scheelite structure have been synthesized by a solid-state route. The effects of BaCu(B2O5) (BCB) dopant on the micromorphology, density, and microwave dielectric properties of CaMoO4 ceramic were studied. BCB dopant could effectively reduce the sintering temperature of the ceramic to 875°C, while the dielectric properties decreased only slightly. In particular, 0.75 wt.% BCB-doped CaMoO4 ceramic sintered at 875°C presented good microwave dielectric properties of er = 10.67, Q × f = 84,775 GHz, and τf = − 46.48 ppm/°C. Besides, energy-dispersive x-ray spectroscopy (EDX) line scanning analysis confirmed that the CaMoO4 ceramics exhibited good chemical compatibility with silver electrodes and could thus be applied in low-temperature cofired ceramic (LTCC) technology.

Enhanced grain-boundary diffusion on power loss of low-temperature-fired NiCuZn ferrites for high-frequency power supplies

NiCuZn ferrite ceramics with high permeability, low power loss and excellent thermal stability are vital materials for high-frequency power devices. This paper analyzed grains growth and grain-boundary diffusion of Ni0.2Cu0.2Zn0.6Fe2O4 ferrite ceramics at lower temperatures by adding optimized additives. X-ray diffraction reveals that the samples are pure spinel ferrite phase sintered at low temperatures. SEM images indicate that uniform and compact NiCuZn ferrite ceramics were obtained at 920 °C for 4 h, which is very advantageous for low-temperature co-fired ceramic (LTCC) technology. In addition, the ferrite ceramics with higher permeability (~ 411 @ 1 MHz), lower power loss in high frequency (~ 442 kW/m3 @ 7 MHz) and good thermal stability were synthesized by controlling grains growth and grain-boundary diffusion. The results indicate that this ferrite ceramic material is a good candidate for the application of miniaturized power electronics in high frequency.

60 GHz wideband LTCC microstrip patch antenna array with parasitic surrounding stacked patches

This work presents a wideband 60 GHz microstrip patch antenna (MPA) array based on low-temperature co-fired ceramic (LTCC) multilayer technology. Four parasitic patches are stacked above the driven MPA. An additional resonant mode is excited by the proposed parasitic surrounding stacked patches (PSSPs) to enhance the bandwidth of the MPA. The structure of the PSSPs increases the gain of the MPA due to its array configuration. The proposed PSSP structure can find many applications in designs for large-scale antenna arrays because the PSSPs and the driven microstrip patch are distributed at different layers. This arrangement allows a direct feed network to the MPA without the blockage caused by the PSSPs. A 2 × 2 antenna array was designed and fabricated with the PSSPs to further increase its gain. The proposed array can achieve a gain of 10.5 dBi and a wide bandwidth of 27.3% at 60 GHz.