Low Temperature Co-fired Ceramics System Research Articles

Characteristics Improvement of Low-temperature Sintered SrFe 12 O 19 Ferrites in LTCC System Applications

In order to improve the sintering characteristics of the low-temperature sintered M-type hexagonal strontium ferrites (SrFe 12 O 19 ) prepared by a solid phase method, the Bi 2 O 3 additive was used as a sintering aid. The crystal structure, electrical properties, and magnetic properties of the ferrites were investigated. The results show that the single phase structural SrFe 12 O 19 ferrites can be obtained even with a low sintering temperature of 900 °C. The Bi 2 O 3 additive is found to possess a significant effect on the electrical properties and magnetic properties for the ferrites sintered at low temperatures enhancing resistivity ρ , saturation magnetization M s , intrinsic coercivity H ci , and magnetic anisotropy field H a . It is suggested that the low-temperature sintered SrFe 12 O 19 ferrites with ρ of 0.42×10 8 Ω·cm, M s of 285.6 kA·m −1 , H ci of 347.3 kA·m −1 , and H a of 1546.6 kA·m −1 provide an important potential application in nonreciprocal LTCC (low temperature co-fired ceramics) ferrite devices

Design of Small-size and Low-loss LTCC Filters on Capacitively Loaded Cavities

Design of microwave filters for portable electronics is complicated by conflicting requirements to be met simultaneously such as high selectivity, low insertion loss and compact size. Substrate integrated waveguide (SIW) technology allows designing low-profile high-Q resonators and low-loss bandpass filters based thereof. However, SIW filters are not well-suited for telecommunication applications because of remarkably large size in plane. The size of a SIW cavity can be dramatically reduced by a capacitive loading. Capacitively loaded cavities (CLCs) operating in the TM110 mode can be as small as 1/8 of the guided wavelength and even smaller, i.e. comparable in size with lumped-element resonators. Although the unloaded Q-factor decreases proportionally to cavity size, miniaturized CLCs can exhibit much higher Q-factor than that of lumped-element resonators. This paves the way for designing small-size and low-loss filters for wireless communications and different applications. Miniaturized capacitively loaded SIW cavities are favorably implemented by means of the low temperature co-fired ceramics (LTCC) technology. The goal of the paper is to demonstrate manifold possibilities and flexibility offered by the LTCC technology to the design of advanced microwave filters on CLCs. Different design and manufacturing aspects are considered. Various design examples of high-performance LTCC resonators and filters for single- and dual-band wireless applications are presented. The designed resonators and filters were manufactured using the commercial DuPont Green Tape 951 LTCC system. The LTCC filters on miniaturized CLCs are shown advantageous with regard to small size, low loss, and absence of spurious response over a wide frequency range.

Preparation of LTCC materials with adjustable permittivity based on BaO–B2O3–SiO2/BaTiO3 system

This paper studied the preparation and characterization of LTCC (low temperature co-fired ceramics) materials based on BaO–B2O3–SiO2/BaTiO3 glass–ceramics, where the sintering temperature was about 900°C and dielectric constant was effectively adjustable from 5 to 30 by changing the BaTiO3 fraction from 60wt% to 90wt%. X-ray diffractometer (XRD), scanning electron microscopy (SEM) were used to examine the effect of different amounts additive on the dielectric properties of this LTCC system and the crystal structure change. The results indicated that BaTiO3 can be used as a dielectric additive aim to adjust the permittivity of BaO–B2O3–SiO2 glass, which the main influence factors on dielectric are the contents of the secondary phase, the BaTiO3 phase fraction and the porous structure of the sintered body. Therefore, the microstructure and dielectric property of BaO–B2O3–SiO2/BaTiO3 glass–ceramics composites could be controlled by adjusting the content of BaTiO3 additive.

Low‐Temperature Co‐Fired Ceramics System for Light Absorbance Measurement

The article describes technology of the low‐temperature co‐fired ceramics (LTCC) structure that enables light absorbance measurements of liquid sample. The manufactured ceramic structure contains buried microfluidic channels. The structure consists of two co‐fired glass windows that separate the light source and detector from the test solution. A construction of an electronic measurement system is described as well. The signal from three light‐emitting diodes (LED)s — red, green, and blue — can be used in the absorbance measurements. The light intensity is measured by the TCS 3414CS (TAOS, Plano, TX) color detector. Optical properties of the fabricated microfluidic LTCC system is investigated with several concentrations of potassium permanganate (KMnO4) in water solution. The system can be applied in microbiology for constant monitoring of bacterial growth.

LTCC based chip for monitoring in biological applications

The presented paper describes the technology of an low temperature co-fired ceramics (LTCC) structure that enables monitoring in biological applications. The results are achieved by light absorbance measurements of liquid samples. The described ceramic structure contains buried microfluidic channels and two co-fired glass windows as well. The signal from three light emitting diodes (LEDs) – red, green and blue – can be used in the absorbance measurements. These three components are connected to the LTCC device through a light guide switch and a polymer optical fibre. Thanks to that it is possible to switch the stimulation wavelength in wide range of visible spectrum. The optical properties of the fabricated microfluidic LTCC system are investigated with several solutions of different concentrations of Rhodamine 6G in ethanol. The test results indicate very good stability during measurements. The measured light intensity was proportional to the concentrations of the test solutions.

Micro Fluidic Mass Flow Sensor Concept for Functional Ceramic Circuits

Low temperature co-fired ceramics (LTCC) is established as a widespread platform for advanced functional ceramic circuits in many different applications, such as space, aviation, medical and sensor technology. MLC (Multi Layer Ceramics) based systems allows integrating passive components which leads to a high integration level. For micro fluidic devices the integration of 3D structures like channels and chambers are necessary. Using LTCC is predestined to integrate sensor elements due to the high reliability qualities, the good characteristics of the ceramic as well as the excellent physical properties. To realize 3D micro channels not only in lab status adequate manufacturing processes are mandatory. This study proposes the realization of micro fluidic channels and show in which ways these can be realized by a range of new developed manufacturing methods during the LTCC process. A benchmark of 3D laser structuring and two cold embossing technologies were investigated to show the benefits and also the limits of each technology. The sensor elements, which were directly integrated into the LTCC body, are based on PTC and resistor materials realized in thick film technology. The excellent performance of a micro fluidic LTCC system will be shown based on a manufactured demonstrator. The final conclusion is, that these established manufacturing and integration methods offer a remarkable potential to meet the requirements for future circuit designs, where actual design concepts cannot solve all issues satisfying, in particular where harsh environmental conditions occur or a high integration concept is mandatory.

LTCC Based Microfluidic Mass Flow Sensor Concept†

Low temperature cofired ceramics (LTCC) is established as a widespread platform for advanced functional ceramic circuits in many different applications, such as space, aviation, medical, and sensor technology. MLC (multi layer ceramics) based systems allow the integration of passive components, which leads to a high integration level. For microfluidic devices, the integration of 3D structures such as channels and chambers is necessary. Using LTCC will lead to integrating sensor elements due to high reliability, the good ceramic characteristics, and excellent physical properties. To realize 3D micro-channels beyond the laboratory, adequate manufacturing processes are essential. This study proposes the realization of microfluidic channels and shows in which ways these can be realized by a range of newly developed manufacturing methods during the LTCC process. A benchmark of 3D laser structuring and two cold embossing technologies were investigated to show the benefits and also the limits of each technology. The sensor elements, which were directly integrated into the LTCC body, are based on PTC and resistor materials realized in thick film technology. The excellent performance of a microfluidic LTCC system will be shown based on a manufactured demonstrator. The final conclusion is that these established manufacturing and integration methods offer remarkable potential to meet the requirements for future circuit designs, where actual design concepts cannot solve all issues, in particular where harsh environmental conditions occur or a high integration concept is mandatory.

LTCC based Chip for Monitoring in Biological Applications

Abstract The paper describes technology of the LTCC (Low Temperature Co-fired Ceramics) structure which enables monitoring in biological applications. The results are achieved by light absorbance measurements of liquid sample. Described ceramic structure contains buried microfluidic channels and two co-fired glass windows as well. The signal from three LEDs (Light Emitting Diode) – red, green and blue – can be used in the absorbance measurements. These three elements are connected through the light guide switch and a polymer optical fiber. Thanks to that it is possible to switch stimulation wavelength in wide range of visible spectrum. Optical properties of the fabricated microfluidic LTCC system is investigated mostly with several concentrations of potassium permanganate in water solution.

Low-temperature sintering and microwave dielectric properties of 3Z2B glass–Al 2O 3 composites

A potential low temperature co-fired ceramics system based on zinc borate 3ZnO–2B 2O 3 (3Z2B) glass matrix and Al 2O 3 filler was investigated with regard to phase development and microwave dielectric properties as functions of the glass content and sintering temperature. The densification mechanism for 3Z2B–Al 2O 3 composites was reported. The linear shrinkage of 3Z2B glass–Al 2O 3 composites exhibited a typical one-stage densification behavior. XRD patterns showed that a new crystalline phase, ZnAl 2O 4 spinel, formed during densification, indicating that certain chemical reaction took place between the 3Z2B glass matrix and the alumina filler. Meanwhile, several zinc borate phases, including 4ZnO·3B 2O 3, crystallized from the glass matrix. Both of the reaction product phase and crystallization phases played an important role in improving the microwave dielectric properties of composites. The optimal composition sintered at 850–950 °C showed excellent microwave dielectric properties: ɛ r = ∼5.0, Q· f 0 = ∼8000 GHz, and τ f = ∼−32 ppm/°C at ∼7.0 GHz.

Effect of Particle Shape on Anisotropic Packing and Shrinkage Behavior of Tape‐Cast Glass–Ceramic Composites

In this study, the influence of particle shape anisometry and particle alignment in tape‐cast green sheets on the shrinkage behavior of low‐temperature co‐fired ceramics (LTCCs) was investigated quantitatively. A new method for the characterization of particle shape with the use of a particle image analyzer is presented, and its application to real material systems demonstrated. A commercial LTCC system and three developed composite powders with different average particle sizes were analyzed. After tape casting, particle alignment in the green sheets was analyzed using image analysis of SEM micrographs of cross sections. The investigations showed that the degree of particle alignment correlates significantly with the particle shape and size of the materials. A further increase in particle orientation was seen after the lamination process. Additionally, the powder packing of both single layers and laminates was analyzed by mercury porosity. The anisotropic shrinkage behavior during the sintering process was determined by means of optical dilatometry. The data obtained on the particle morphology, particle orientation in the tapes, and their effects on the shrinkage anisotropy will be discussed.

Influences of alkali oxides on crystallization and dielectric properties of anorthite-based low temperature dielectrics

The influences of alkali oxides as glass constituents for producing LTCC (Low Temperature Co-fired Ceramics) materials were investigated in terms of variations in physical and dielectric parameters. The LTCC materials were based on typical calcium zinc aluminoborosilicate glasses containing 1-3.5 mol% alkali oxides such as K2O, Na2O and Li2O. All samples were prepared in the same experimental condition, i.e., the ratio of glass/filler and the final firing temperature of 850°C. Densification and crystallization behavior strongly depended on the type and amount of alkali oxides used. For example, crystallization peaks in the DTA curves tended to shift towards the lower temperature region by increasing the content of Na2O and K2O. Specifically, the effect of Li2O was distinct in determining the crystallization behavior and subsequent dielectric properties of the LTCC system. Dielectric constant was measured as values of 7.18-7.78 but dielectric loss was significantly degraded specifically with the addition of 3 mol% Li2O.

Influence of Low‐Temperature Co‐Fired Ceramics Green Tape Characteristics on Shrinkage Behavior

To establish a better understanding of the complex densification and shrinkage processes of low‐temperature co‐fired ceramics (LTCC) and to improve the dimensional control in the manufacture of LTCC multilayer devices, the influence of glass, composite, and microstructural green tape characteristics on the densification and shrinkage behavior of LTCC materials, with special focus on the development of anisotropy, was investigated. To study the influence of these factors, a commercial LTCC system was analyzed regarding chemical and microstructural composition as well as sintering behavior. The results of the analysis showed that the commercial LTCC system is composed of alumina as a ceramic filler and a CaO–SiO2–B2O3–Al2O3 glass. Based on these results, a similar glass was produced. To understand the mechanisms of densification, its wetting behavior and viscosity as a function of temperature were investigated. As developed glass was mixed with an alumina powder and milled down to average grain sizes of 1, 2, and 3 μm, respectively. From these composite powders, slurries were prepared and tape cast. The sintering kinetics including onset temperature, development of viscous flow as well as phase development of both commercial and internally developed LTCC tapes LTCC tapes in relation to their modified composition and green tape structures were analyzed in situ by means of optical dilatometry, thermo‐mechanical analysis (TMA), and high‐temperature‐X‐ray diffraction. The viscous behavior of the glass‐filler composites was determined by means of cyclic dilatometry in a TMA device.

Development of a Novel Low Temperature Co-Fired Ceramics System Composed of Two Different Co-Firable Low Temperature Co-Fired Ceramics Materials

Two co-firable low temperature co-fired ceramics (LTCC) materials with different permittivities were investigated. The first material has low-K and high stiffness, and the second material has high-K, high-Q, and near zero temperature coefficient of capacitance (TCC). A resistor material, which is mainly composed of RuO2 and glass, is able to be buried into the LTCC substrate. To adjust the properties to the electric circuits, laser trimming of the embedded capacitors and resistors was performed. The constrained sintering method was applied to the substrate, and the dimension accuracy of the substrate is excellent.

LTCC meso-analytical system for chloride ion determination in drinking waters

The low temperature co-fired ceramics (LTCC) technology is introduced as an excellent alternative to silicon, glass or plastic materials for the fabrication of miniaturized analytical devices. This fabrication technology enables the generation of complex three-dimensional geometries, as well as the integration of sample pretreatment steps and even the detection system. The evaluation of an LTCC-made device which integrates a three-dimensional serpentine mixer and an ion selective electrode for the detection of Cl − ion was performed. Analytical features derived from calibration experiments were: slope = 59(±2) mV/dec, LLLR = 0.56 mM (20 ppm), r 2 > 0.99; LOD = 0.16(±0.03) mM (6(±3) ppm), the R.S.D. (for n = 7 and 95% confidence) at 1.41 mM (50 ppm) Cl −, was 1.44%. Drinking water samples were analyzed by the LTCC system and results were compared with those obtained by capillary electrophoresis, showing no significant differences between both methods.

Phase Evolution and Microwave Dielectric Properties of Lanthanum Borate‐Based Low‐Temperature Co‐Fired Ceramics Materials

A new potential low‐temperature co‐fired ceramics (LTCC) system based on a simple lanthanum borate (La2O3–B2O3) glass was investigated with regard to phase development and microwave dielectric properties as functions of alumina filler content less than 50 wt% and firing temperature up to 1050°C. Unexpected crystalline phases, such as La(BO2)3, LaAl2.03(B4O10)O0.54, LaBO3, and Al20B4O36, developed during the firing process are likely responsible for substantial resultant changes in physical and microwave dielectric properties. As a specific example, a high‐quality factor of 785 at 15.8 GHz obtained for a composition containing 30 wt% alumina supports the hypothesis that the phase‐dielectric property relation exists in this LTCC system. On a practical basis, two phases of LaAl2.03(B4O10)O0.54 and LaBO3 must be important in determining the final dielectric performance by manipulating the ratios of glass and filler and by selecting a desirable temperature.