bluuebunny/crossref_metadata_2025 huggingface dataset:
Z-, Y- and M-type Hexagonal Ferrites for High-Frequency Inductive Multilayer Devices
Authors: Töpfer J. , Bierlich S. , Barth S. , Pawlowski B. , Bechtold F. , M¨ller J.
Published: October 2015

Hexagonal ferrites can be used as soft magnetic materials for multilayer inductors for high frequency applications up to 3 GHz. We report on the preparation, thermal stability and magnetic properties of Z-, Y- and M-type hexagonal ferrites.

Co2Z-type ferrite Ba3Co2Fe24O41 and iron excess Ba3Co2−yFe24+yO41 (0 ≤ y ≤ 0.8) were prepared by the mixed oxide route. Single phase Z-type ferrites were obtained after sintering at 1300°C. The permeability of a sample with y = 0.6 sintered at 1300°C is μ = 30 with a resonance frequency of 1 GHz. The addition of Bi2O3 as sintering aid shifts the maximum shrinkage down to 950°C and dense samples were sintered at 950°C; however, their permeability is only μ = 3…5. It is shown that Co2Z ferrites are not stable under LTCC conditions. Cu-substituted Z-type ferrites Ba3Co2-xCuxFe24O41 exhibit enhanced sintering ability, but sintering at 950°C also results in low permeability.

Y-type hexagonal ferrites Ba2Co2−x−yZnxCuyFe12O22 were prepared at 1100°C and a permeability of μ = 20 was found for x = 1.2 and y = 0.8. Samples with Bi2O3 addition were sintered at 950 and 900°C exhibiting a permeability of μ = 10. Similar values were measured for M-type ferrites BaFe12-2yCoyTiyO19 with y = 1.2 which were sintered at 900°C using additives. Co/Ti co-substitution is an essential prerequisite for tailoring the magneto-crystalline anisotropy. Co/Ti- substituted M-type materials are stable under LTCC conditions.

Ferrite multilayer devices were fabricated by screen printing coils onto ferrite tapes, stacking and lamination. Firing was performed between 1300°C and 900°C, i.e. at HTCC and LTCC conditions, respectively. The inductance behavior of the devices was evaluated and modeled. It is shown that hexagonal ferrites are suitable materials for the high-frequency multilayer inductors; however, Y- and M-type ferrites are preferred for LTCC-type inductors cofired at 900°C with Ag metallization.
Wide Frequency Characterization of Magnetic Properties of Commercial LTCC Ferrite Material
Authors: Blaž Nelu , Marić Andrea , Radosavljević Goran , Mitrović Nebojša , Atassi Ibrahim , Smetana Walter , Živanov Ljiljana
Published: October 2015

Complex magnetic permeability and hysteresis characteristic are key parameters that determine properties of ferrite components. This paper offers effective, accurate and simple method for complex permeability determination of LTCC (Low Temperature Co-fired Ceramic) ferrite sample at wide frequency range (up to 1 GHz). Presented research can be found to be of importance in fields of ferrite components design and application, as well as RF and microwave engineering.

The characterization sample is a stack of LTCC tapes forming a toroidal shape structure. Commercially available ferrite tape ESL 40012 was used and standard LTCC processing applied for the sample fabrication. Permeability is determined in the frequency range from 10 kHz to 1 GHz and characterization procedure is divided in two segments - for low and high frequencies. Low frequency measurements (from 10 kHz to 1000 kHz) are performed using LCZ meter and discrete turns of wire, while a short coaxial sample holder and Vector Network Analyzer were used for the higher frequency range (from 1000 kHz to 1 GHz).

Hysteresis properties of this material are also determined. B-H hysteresis loops were measured with BROCKHAUS Tester MPG 100D system using the maximum excitation of 2 kA/m and frequencies of 50 Hz, 500 Hz and 1000 Hz. In addition, we presented another important factor in the practical design, the temperature variation of the permeability dispersion parameters.

Obtained results show good agreement with datasheet values given by the manufacturer at lower frequencies and are in good correlation with results extracted from developed dispersion model at higher frequencies.
A Novel Approach to the Measurement and Characterization of Losses due to Surface Roughness in High Speed Transmission Lines
Authors: Akinwale Femi , Engin A. Ege
Published: October 2015

An accurate measurement technique is required to fully characterize the losses observed at high frequencies in transmission lines. Evaluation of losses seen at high frequencies is necessary to meet the high-speed data transfer rates that future applications will demand. Conductor properties and losses are two critical issues in signal path characterization. The nature of conductor losses is not well understood at high speeds. Classical models used for predicting the effects of surface roughness on signal propagation are known to breakdown around 5 GHz. Novel methods are sought to quantify the effects beyond 5 GHz. In this paper, a simple methodology to extract conductor loss is derived and validated based on a stripline configuration of two different widths. The proposed methodology is applicable to surface roughness loss characterization of both organic and ceramic packaging materials.
High current conductors in LTCC
Authors: Ziesche Steffen , Ihle Martin
Published: October 2015

The publication discusses the possibilities of integrating high cross section - metallization structures within fired LTCC substrates. After comparison of different methods for building such metallization structures it focuses on laser ablation to form channel structures, which will be further filled by stencil printing. Furthermore the variants of firing LTCC substrates with high amounts of metallization are discussed and our chosen solution is presented. Finally the processed LTCC substrates are characterized and their ampacities discussed.
Inkjet Printing Technology: A Novel Bottom-up Approach For Multilayer Ceramic Components and High Definition Printed Electronic Devices
Authors: DOSSOU-YOVO C. , MOUGENOT M. , BEAUDROUET E. , BESSAUDOU M. , BERNARDIN N. , CHARIFI F. , COQUET C. , BORELLA M. , NOGUERA R. , MODES C. , LEJEUNE M. , LAURIER P. , DETEMMERMAN D. , ESCURE P. , LAVILLE H. , DELHOTES N. , VERDEYMES S.
Published: October 2015

This paper describes the methodology of thick film and Multilayer Ceramic Capacitor (MLCC) components manufacturing by inkjet printing. The printing unit is a CERADROP 3D multimaterial inkjet printer. Aqueous conductive and dielectric inks were formulated according to the printheads specifications in terms of viscosity, surface tension, particles size and sedimentation. Jetting behavior was controlled and optimized to reach the best droplets characteristics with regard to the design. Numerical processing simulation tool helps to control the printing job and to identify beneficial potential issues during the processing. Therefore printing parameters (droplet spreading, layer thickness, filling strategy, layer drying, etc.) were optimized according to material and component design characteristics. By this way, high definition and thin conductive tracks were achieved on alumina substrate with good electrical properties. Moreover, two printheads were used to build successively 3D multimaterial MLCC components with thin dielectric and conductive layers (i) with a good margins precision compared to traditional processes and (ii) with very high complex configurations thanks to the flexibility of the inkjet printing process. For both applications, large area components were accessible in a single batch.
LTCC system for light absorbance measurement
Authors: Czok Mateusz , Bembnowicz Pawel , Golonka Leszek
Published: October 2015

The paper describes technology of the LTCC structure which enables light absorbance measurements of liquid sample. The manufactured ceramic structure contains buried microfluidic channels. The structure consists of two co-fired glass windows which 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 LEDs (Light Emitting Diode) – red, green and blue – can be used in the absorbance measurements. The light intensity is measured by the TCS3414CS (TAOS) 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 bacteria growth.
PRELIMINARY MODEL AND TECHNOLOGY OF PIEZOELECTRIC LOW TEMPERATURE CO-FIRED CERAMIC (LTCC) UNIAXIAL ACCELEROMETER
Authors: Jurków Dominik , Dąbrowski Arkadiusz , Zawada Tomasz , Golonka Leszek
Published: October 2015

Design procedure, technology and basic properties of a piezoelectric Low Temperature Co-fired Ceramics (LTCC) accelerometer are presented in this paper. The sensor consists of a LTCC membrane with a seismic mass. Meggitt InSensor® PZT thick film has been applied as the sensing material. Finite element method (FEM) has been used to analyze the impact of the sensor geometry (membrane thickness, membrane and seismic mass radii) and PZT thick film placement on basic properties (sensitivity and bandwidth) of the device. The LTCC process was optimized in order to create thin and planar ceramic membrane with relatively huge seismic mass. Selected properties of the sensor have been measured and compared with the simulated ones.
Fine-Line Structuring of Microwave Components on LTCC Substrates
Authors: Stöpel D. , Drüe K.-H. , Humbla S. , Mache T. , Rebs A. , Reppe G. , Schulz A. , Vogt G. , Hein M. , Müller J.
Published: October 2015

Low temperature co-fired ceramics (LTCC) are used in a wide range of RF and microwave applications. The ceramic multilayer technology provides a truly three-dimensional circuit technology, hermetical sealing, hybrid integration, and favorable microwave properties at moderate costs. In order to take full advantage of millimeter wave frequencies, resolutions of lines and spaces below the typical, screen printable 50 μm are desired.

This paper describes the technological development of a fine-line structuring process based on resinate thin films and electroplating on LTCC. A combination of thin-film technology and thick-film technology leads to a novel resinate technology. This new process replaces the commonly used expensive sputtered layers, usually required for thin-film structuring combined with standard LTCC technology.

The initial layer is replaced by a screen-printed metallo-organic paste (resinate paste). Resinate pastes consist of metallo-organic noble metal compounds (e.g. gold and silver), which are dissolved in organic suspensions. The film thickness after firing is typically below 1 μm. This layer can be used to define structures with high precision using photolithography and electroplating followed by an etching process. The etching processes investigated here showed promising resolutions of 25 μm for lines and spaces. But wet-chemical processes can be applied to sintered LTCC surfaces only. Buried fine structures may be achieved with tape-on-substrate (ToS) technology which allows for laminating and subsequent sintering of structured greensheets onto sintered ceramics.

The benefits of this technology for microwave applications are obvious, given an improved resolution and parameter spread, and an accordingly reduced variation of the resulting structures.
Automated Complex Permittivity Characterization of Ceramic Substrates Considering Surface-Roughness Loss
Authors: Engin A. Ege , Pasunoori Pavithra
Published: October 2015

This paper presents a new method to extract the frequency-dependent dielectric constant and loss tangent of ceramic substrates from high frequency measurements of cavity resonators. A cavity resonator can simply be realized using two ground planes connected with vias to form the side walls. Recently, a rapid plane solver has been developed to efficiently and accurately simulate cavity resonators and extract materials properties by manually fitting simulations to measurements. In this paper, we will demonstrate how the fitting process can be automated. In order to extract the dielectric constant and loss tangent, many simulations need to be run to find the parameters that provide the best match with the measurements. This is a computationally expensive approach. We will present a new method based on tracking sensitivity, which provides a parameterized macromodel for the resonators. Using this approach, the simulation data can be expressed as a low-order rational function of the complex permittivity. Hence, varying the complex permittivity to find the best fit can be done in negligible time after the macromodel has been generated. This new method will be applied to extract the dielectric constant and loss tangent of a ceramic substrate.
Support Vector Regression Modeling for LTCC Interconnection Based on Prior Knowledge
Authors: Xia Lei , Xu Ruimin , Yan Bo
Published: October 2015

This paper presents a prior knowledge based support vector regression modeling method to characterize the RF performance of the low temperature co-fired ceramic (LTCC) structure. A coarse surrogate is formed by multidimensional Cauchy approximation as the prior knowledge to improve the accuracy of modeling. 3D LTCC based vertical interconnection model is developed as an example using the proposed method. Experimental results show that the developed SVR model perform a better predictive ability.
The Rapid Discovery of Novel Dielectric and Magnetic Ceramics, and Structure-Property Relationships, through Combinatorial High Throughput Methods
Authors: Pullar Robert C.
Published: October 2015

Combinatorial Materials Science is the rapid synthesis and analysis of large numbers of compositions in parallel, created through many combinations of a small number of starting materials. The various samples are synthesised in a single piece, or on a single substrate, called a “library”. To date, most Materials Science combinatorial high throughput methods use deposited thin films.

However, for many ceramic interconnect applications, bulk or thick film ceramics are required. It could also be argued that bulk properties are much more relevant than those of thin films when constructing large structure-property data bases, for data mining and prediction of novel compositions. Strain and skin effects in thin films often cause major discrepancies, e.g. ferroelectric measurements, changes in lattice parameters. Also, many thin films are epitaxial or single crystal, and hence have no grain boundaries, which can have a large effect on properties.

At Aveiro we are developing novel methods of processing and analysing multiple combinatorial high throughput thick film or bulk ceramic libraries, as a series of compositional and functional steps. These can be produced with or without a supporting substrate. As well as composition, effects of variation in processing parameters such as firing temperature, time, atmosphere, substrate / electrode reactions, etc. can also be investigated.

The structure-property relationships of dielectric, magnetic, and particularly magnetoelectric / multiferroic ceramics, are highly complex and difficult to predict, and therefore combinatorial searching could be an essential tool. As well as accelerating discovery, the amount of quantitative data produced will enable accurate predictions for multifunctional materials.
ADVANCED HIGH FREQUENCY LTCC MATERIALS FOR APPLICATIONS BEYOND 60 GHZ
Authors: Brunner Sebastian , Stadler Manfred , Wang Xin , Bauer Frank , Aichholzer Klaus
Published: October 2015

In this paper we will present an application of advanced Low Temperature Cofired Ceramic (LTCC) technology beyond 60 GHz. Therefore a RF frontend for 76–81 GHz radar frequency was built. LTCC is a well established technology for applications for consumer handheld units <5 GHz but will provide solutions for applications for high frequencies in the range of 60 GHz and beyond. Radar sensors operating in the 76-81 GHz range are considered key for Advanced Driver Assistance Systems (ADAS) like Adaptive Cruise Control (ACC), Collision Mitigation and Avoidance Systems (CMS) or Lane Change Assist (LCA). These applications are the next wave in automotive safety systems and have thus generated increased interest in lower-cost solutions especially for the mm-wave frontend section.
All-Dielectric Metamaterials for New Areas of Applications
Authors: Semouchkina Elena , Semouchkin George , Lanagan Michael
Published: October 2015

The properties and applications of different types of ceramic all-dielectric metamaterials are presented. Metamaterials composed of arrays of identical ceramic resonators are shown to provide for negative refraction, enhanced transmission, and backward wave propagation. It is also demonstrated that arrays of dielectric elements can be used as non-resonant metamaterials to form a gradient index medium. Employment of such media in antenna substrates is shown perspective for antenna miniaturization without deteriorating antenna parameters. The development of a microwave transmission cloak composed of identical low-loss ceramic resonators to conceal object with the dimensions far exceeding the wavelength of incident radiation is also described.
Recent Advances in Practical Metamaterial Engineering
Authors: Rajab Khalid Z. , Munoz Max , Fan Yifeng , Bao Di , Hao Yang
Published: October 2015

Metamaterials have received significant interest over the last decade, with the promise of a host of novel devices ranging from the perfect lens to the invisibility cloak. However, many implementations of these metamaterials were shown to be overly lossy and/or narrowbanded, and with unacceptably poor performance. The primary reason for this was that component materials were highly dispersive, for example with negative permittivity or permeability that required resonant properties. We will demonstrate that many metamaterial structures can in fact be practically engineered to exhibit good performance over large frequency bands. First, we will examine the paradigm of transformation optics (TO), which has allowed a rethink of the engineering design procedure. Using this technique, a mathematical transformation of the geometrical space can be represented by a transformation in material properties. This means that the engineering problem is reduced to one of matching a range of material properties. Furthermore, in many cases the resulting materials are primarily isotropic dielectrics. We will demonstrate a number of devices that we have fabricated using various ceramics and ceramic composites, including a sub-wavelength transmission device and a broadband invisibility cloak. Finally, we will discuss what is likely to be the next stage in the evolution of metamaterials: the incorporation of active components. These active components can be used to overcome many of the limitations of passive structures, such as high loss and narrow bandwidth. However, they introduce a new set of difficulties, such as noise and most importantly potential instability. Our approach has been to introduce negative impedance components to modulate the properties of the effective medium. We will discuss these implementations, with the current state of research and where the future may lie.
Design, Fabrication, and Operation of a Nitrogen Measurement Device Based on LTCC
Authors: Geiling Thomas , Welker Tilo , Müller Jens
Published: October 2015

We present a so called micro total analytical system (μTAS) for the measurement of low nitrogen monoxide (NO) concentrations in gas flows. The measurement principle is based on the chemiluminescent reaction of NO with ozone (O3). The presented system scales down this measurement principle into the realm of micro fluidics and micro sensors. Low temperature co-fired ceramics (LTCC) have proven to be the ideal technology for the realization of a μTAS, as they offer high chemical and thermal stability as well as high degree of freedom of design.

The system consists of 4 components: an ozone generator, an ozone concentration measurement via UV transmission, a chemiluminescent detection (CLD) chamber, and an exhaust gas treatment.

The ozone generator is a micro plasma device in which ozone is produced by a dielectric barrier discharge (DBD) mechanism. From the generator the ozone is fed into a chamber with an optical port, where the concentration is determined by UV transmission measurements. Then it is brought into contact with the NO-containing analyte gas inside the reaction chamber, where the chemiluminescent reaction occurs. The reaction chamber is outfitted with an optical port as well, so that the emitted radiation can be detected and analyzed with a photo diode. The gas mixture leaving the reaction chamber is fed through a platinum catalyst, in order to decompose leftover ozone and prevent buildup of hazardous concentrations in the surroundings of the device.

The contribution presents the design of each component as wells as the integrated system and gives detailed measurements of its operation.
Room-Temperature Fabrication for Functional Oxide Nanofilms Using Oxide Nanosheets
Authors: Osada Minoru , Sasaki Takayoshi
Published: October 2015

Oxide nanosheets, which possess atomic or molecular thickness and infinite planar lengths, have increasingly attracted fundamental research interest because of their potential to be used as conductors, semiconductors, insulators, and even ferromagnets, depending on their chemical composition and how their atoms are arranged. An attractive aspect of oxide nanosheets is that nanosheets can be organized into various nanoarchitectures by applying solution-based synthetic techniques. It is even possible to tailor superlattice assemblies by tuning the number of nanosheets and their stacking sequences. Sophisticated functionalities or nanodevices can be designed through the selection of nanosheets and combining materials, and precise control over their arrangement at the molecular scale. We utilized oxide nanosheets as a building block in the bottom-up assembly, and successfully developed various functional nanofilms.
Characterization of the Fabrication Process of Rolled LTCC Structures
Authors: Parrish Kelci , Taff Jesse , Yates Mallory , Reis Derek , Plumlee Donald
Published: October 2015

This work focuses on the fabrication and assembly of cylindrical plasma containment tubes using DuPont's 951 Low Temperature Co-fired Ceramics (LTCC) for use in miniature electrostatic thrusters. The use of LTCC allows for robustness post-firing yet flexibility in the “green” un-fired state. Some of the main advantages of this flexibility include the ability to stack or roll the LTCC sheets into various shapes as well as incorporating embedded electrical interconnections using silver paste on the rolled layers. The tube is used to contain argon plasma, which is generated by a spiral Inductively Coupled Plasma antenna and is also fabricated in LTCC. The tube also interfaces with two electrically biased grids on the opposite end, which accelerate the plasma out of the tube. These interfaces are highly dependent on the dimensions and tolerances of the containment tube. The development of the fabrication process will be presented for the incorporation of the tubes onto the base as a single structure. This includes constructing the antenna base, shaping the “rolled” LTCC containment tube using a jig and isostatic press, and integrating the tube and antenna base during the firing. Following the fabrication, measurements will be taken to determine the tube circularity and the hermeticity of the seal at the interface between the tube and the antenna base. The results will be presented and characterized to evaluate the effectiveness of the structure as well as the documentation of the development of a rolled LTCC tube structure integrated with a planar LTCC antenna base.
Development of Thin-Film Manufacturing Technologies for Solid Oxide Fuel Cells and Gas Separation Membranes
Authors: Menzler N.H. , Han F. , van Gestel T. , Schafbauer W. , Schulze-Küppers F. , Uhlenbruck S. , Meulenberg W.A. , Buchkremer H.P.
Published: October 2015

The development of solid oxide fuel cells (SOFCs) and gas separation membranes for fossil (fuel?) power plants has previously suffered from cost issues like the manufacturing of the core components including i) the ceramic fuel cell and ii) the ceramic membrane, and from insufficient power density (current density or flow rate) on the stack, module or system level. Forschungszentrum Jülich has been working on SOFC development for 20 years, and on membrane development for 6 years. Both energy-related applications are based on similar materials systems, similar micro-structural features (porous-dense, coarse-fine), comparable application parameters (e.g. high temperature) and are manufactured with similar technologies. In the past the focus laid mostly on basic materials research and proving the functionality of the membranes or fuel cells. Meanwhile, one key topic has been the application of low-cost thin-film high-throughput manufacturing technologies. This includes the fabrication of the supports (mostly tape-casting), the coating with functional layers by ceramics technologies (screen printing, roll coating) and the reduction of sintering steps and temperatures. Additionally special thin-film technologies like sol-gel technique and electron beam evaporation / sputtering have also been applied for functional layers, depending on the functional necessities. The presentation gives an overview regarding the state-of-the-art in SOFC and gas separation membrane development at Forschungszentrum Jülich with an emphasis on the manufacturing technologies, resulting in optimized layer micro-structures and thickness. Additionally it summarizes the electrochemical and permeation data obtained so far.
PROPERTIES OF GLASS-LESS PHOTOIMAGEABLE PASTE FOR MULTILAYER LTCC STRUCTURES FABRICATION
Authors: Markowski Piotr , Zwierkowska Elżbieta , Jakubowska Malgorzata , Kiełbasiński Konrad , Muckett Steve
Published: October 2015

Properties of Ag-based glass-less photoimageable paste designed for unfired LTCC were investigated. The paste isn't designed for patterns performing on the external surface of the substrate. Because it doesn't contains glass layer to substrate adhesion after the firing process is very weak. Also between individual grains of the silver there is no glass what could resulting in increased contact area of adjacent grains. It may improve the paste sintering. As a result lower electrical resistivity of the layer can be achieved. But also mechanical strength of the layer is reduced. In practice, the paste is not suitable for patterns fabrication on the external surface of the substrate - it detaches from it. The ink is designed for performing the buried layers inside LTCC ceramics. Investigations showed good compatibility of the paste and the DP951 and DP9K7 green tapes (DuPont). The tests showed designed pattern was precisely imaged on the substrate. Details had sharp, perpendicular edges what is characteristic for the photoimageable inks technique.
Assembly of a Microoptical Glucose Sensor with Nanoporous Separation Membrane
Authors: Hintz M. , Fischer G. , Freitag J. , Mitrenga D. , Schmidt A.
Published: October 2015

Blood sugar measurement is an important topic for an increasing number of people suffering from diabetes mellitus. The paper shows the physical principle as well as technologies for assembly of an insertable glucose sensor.

Base of the device is an insertable ceramic measuring chamber with nanoporous membrane. It separates glucose from the complex composition of the tissue fluid. This allows continuous blood sugar measurement by detection of polarization rotation of linear polarized light in the liquid.

However, the measurement of minimal polarization rotation requires highest geometrical accuracy and stability of all components, especially optical transmitter and receiver. Other demands are low cost, miniaturization and reliability requirements of medical devices.

New approaches are necessary to fulfil all requirements. Innovative assembly techniques such as active adjustment, high precision stacking and flip-chip soldering are used. First measurement results of the complete sensor system give a promising outlook.
Bonding of 2 mm thick silicon wafers using LTCC as an intermediate layer
Authors: Günschmann S. , Fischer M. , Bley T. , Käpplinger I. , Brode W. , Mannebach H. , Müller J.
Published: October 2015

For the fabrication of a micro fluidic high pressure oil sensor (400 bar) based on an infrared transmission measuring principle the bonding of 2 mm silicon wafers is necessary. Conventional bonding techniques such as silicon fusion bonding or anodic bonding are not suitable for bonding thick and inflexible silicon wafers, because these techniques can not compensate for the wafer bow. We present a new bonding procedure for silicon substrates thicker than 1 mm using a silicon adapted LTCC tape as an intermediate leveling layer. The wafers are preprocessed by etching a nano structured silicon surface on the internal side. The silicon wafers are aligned and stacked with pre-structured green LTCC tapes by an optical stacking unit. During the hot isostatic lamination at 55 bar the structured LTCC tape is adjusted to the silicon. A subsequent pressure assisted sintering leads to a wafer bonding strength up to 5000 N/cm2. With the bonding technique it is possible to create cavities and channels between the thick wafers by the use of punched and laser cut LTCC. The fabrication steps of the sandwich build-up especially the sequential lamination and the optical adjusting procedure of the flexible (LTCC) and inflexible (2 mm Wafer) substrates will be explained in detail. A method to reduce the shrinkage and distortion of the green LTCC during handling is demonstrated. The distribution of the bonding and bursting strength of the single fluidic systems on a complete sandwich substrate is analyzed.
Improvement of ampacity of LTCC conductors
Authors: Shorina O. , Müller J.
Published: October 2015

Improvement of the current load-carrying capacity can be achieved by combining different technologies in Low Temperature Cofired Ceramics (LTCC). Screen and stencil printing, full tape thickness features (FTTF) and embossing in LTCC were investigated. Silver paste conductors with 80 – 200 μm line width are included in the study.

The structures on the test substrates are fed with an increasing current until the surface reaches an equilibrium temperature of 100°C measured by an infrared camera. 200 μm lines created by screen printing and stencil printing are able to bear 4.3 A and 14 A, respectively. For the FTTF conductor with a thickness of 190 μm the estimated maximum current is about 30 A and for the embossed conductor (thickness approx. 125μm) about 20 A.

FTTF allowed the highest current without strong LTCC heating. However, such conductors are relatively difficult to process by laser and to fill with paste. Therefore the line resolution cannot be much smaller than 200 μm. Furthermore, spiral structures are not compatible to this technology. Hot embossing supports both structural resolution and a high current load-carrying capacity but requires additional tooling. Embossing can be used for the production of curved conductors and coils. With the laser cut stencil, structures with small line width and considerable line thickness can be achieved. Screen printing gives a good possibility to produce small conductors, complex structures and coils.
Tunability, Frequency and Temperature Behavior of Cofired LTCC-Integrated Barium-Strontium-Titanate up to 8 GHz
Authors: Rentsch Sven , Müller Jens , Hein Matthias
Published: October 2015

A new approach towards embedding barium-strontium-titanate (BST) patches into a commercial low temperature co-fired ceramic (LTCC) is described, using a tape transfer technique. Pressure-assisted sintering is successfully employed to achieve flat multi-layer multi-material modules without internal cracks or delaminations. Beside the description of the processing technology, the paper presents also a specific procedure of determining the microwave properties of embedded thick BST films, which is based on using the experimental evaluation of a shunt capacitor.

The permittivity of the embedded BST determined at room temperature is about 214 and remains constant at least from 100 MHz up to 8 GHz. In addition, the effects of temperature and bias voltages on the microwave properties of LTCC BST were studied systematically from 1 MHz up to 8 GHz. We observed a tuning of the permittivity by about −49 %, either by raising the temperature from 21°C to 125°C, or by applying a bias electrical field of up to 10 V/μm. Additionally, breakdown voltages were investigated. The embedded BST withstands field strengths of more than 20 V/μm under laboratory conditions.
Thermal Characterization of an LTCC Module for Miniature Atomic Clock Packaging
Authors: Vecchio Fabrizio , Slater Conor , Maeder Thomas , Ryser Peter
Published: October 2015

This paper presents the design and thermal characterization of a 15 × 22 mm2 LTCC module dedicated to the packaging of the elements of a miniature atomic clock. This module acts as a carrier for the components of the clock as well as temperature controller; this is particularly attractive since each component of the atomic clock requires precise and well defined working temperatures. For the thermal characterization of the designed module, various thermal simulations have been performed, by finite-element modelling using the software ANSYS; in each simulation a different experimental heating configuration was hypothesized, in order to determine the power required for achieving the desired temperature in the ideal case (module in perfect vacuum with no losses rather than conduction towards the external “cold” zone, through two small bridges) , and also for estimating the thermal losses that convection introduces into the system. The simulations were then experimentally validated by realizing and characterizing the different configurations, yielding results that were consistent with the simulations. The best experimental configuration was found, in which the heating performance was fairly close to the ideal one. The results show that LTCC is a very attractive technology for atomic clock packaging also in terms of dissipated power, provided the system is efficiently insulated.
Gas Sensors Based on Ceramic MEMS Structures Made of Anodic Alumina and Yttria Stabilized Zirconia Films
Authors: Vasiliev A.A. , Lipilin A.S. , Mozalev A.M. , Lagutin A.S. , Pisliakov A.V. , Zaretskiy N.P. , Samotaev N.N. , Sokolov A.V. , Soloviev S.A.
Published: October 2015

The application of thin ceramic films for the fabrication of MEMS devices enables the extension of their working temperature range up to 600°C, a decrease in heating power consumption, and a very considerable decrease in production cost of sensors and actuators based on this technology. These advantages are very important for the application of gas sensors under harsh environmental conditions, in autonomous and wireless sensor networks.

The methods of the fabrication of MEMS platforms for metal oxide semiconductor and thermocatalytic gas sensors, fast thermometers, and flowmeters based on yttria stabilized zirconia (YSZ) and alumina membranes for gas sensors are described. Alumina membranes stable up to 800°C have thickness of about 12 microns and are produced by anodic oxidation of aluminum foil in diluted oxalic acid followed by high-temperature annealing. YSZ membrane with the same thickness is made by slip casting with consequent annealing under mechanic load.

Platinum heaters are deposited onto the surface of the membrane by magnetron sputtering through metallic shadow mask. Perfect adhesion of platinum to ceramic material permits us to avoid the application of adhesive sub-layers, and, therefore, improves long-term stability of the heater at high temperature.

The sensor chip has a shape of triangle cut by laser beam; the heater meander is located in the vertex of triangle. This approach simplifies the technology of the fabrication of the platform and decreases power necessary for the heating of the sensing layer up to working temperature of 400 – 600°C.

It is shown that the application of such triangle shaped membranes permits a decrease in power consumption of the MEMS working at 450°C down to ~ 40 mW at continuous and down to < 1 mW at pulse heating of gas sensor with duty cycle of 1 %. Thermal response time of the microheater is of about 80 ms.
In-Situ Blending of Inkjet-Printed Thick-Film Resistors
Authors: Jeschke Dietrich , Niemann Mathias , Krüger Klaus
Published: October 2015

Thick-film resistors are widely used passive components. Considering circuit design and layout, decoupling the resistance from geometry is desirable. Inkjet printing offers an approach to reach this aim by allowing for in-process blending of resistor inks.

To model the electric behavior of printed resistors, a conductance based linear model is derived, that is both, physically plausible and mathematically convenient. Generally the model is based on resistor layers connected in parallel. To allow for fine graduation the parallel layers are not just realized with different decadic inks but with a discrete number of ink mixtures (“virtual inks”) which are generated in-situ during printing.

Both, the conductance model and the in-process ink blending are proven by real inkjet-printed resistors. For manufacturing these resistors, the used inkjet printing system was improved.
Inkjet Printing of Piezoelectric Lead Magnesium Niobate-Lead Titanate Thick Films
Authors: Rathjen Andreas , Junker Clemens , Uršič Hana , Kosec Marija , Krüger Klaus
Published: October 2015

This study shows the fabrication of lead magnesium niobate-lead titanate (PMN–PT) thick-films by inkjet printing on ceramic substrates for the first time. PMN–PT powder, prepared by mechanochemical synthesis, is dispersed in an organic solvent using a three roll mill to form a high-viscosity paste. For printing, the paste is thinned to a low-viscosity ink. Small amounts of ethyl cellulose in the ink prevent sedimentation. Glass particles are added to the paste to improve adhesion on the substrate surface. A two step inkjet-printing process forming homogeneous layers is introduced. After sintering at 950 °C for 2 h, piezoresponse force microscopy (PFM) is used to investigate the piezoelectric response of the printed films.
Dielectrics for Power Capacitors
Authors: Karmazin R. , Koch A. , Matz R. , Männer R. , Metzger W. , Wolff A.
Published: October 2015

High voltage capacitors are key components for transient storage and release of electrical energy in mobile electric devices, electric vehicles, stationary power systems and power transmission. Due to their high electric breakdown voltage, self-healing capability and affordability, polymer-based film capacitors are widely used, particularly those made from biaxially oriented polypropylene (BOPP). Their maximum operating temperature near 100°C, however, requires careful thermal management and oversize design.

In high temperature applications well above 200°C, the preference shifts from organic to ceramic dielectric materials. Multilayer ceramic capacitors (MLCCs) are known for their excellent mechanical and thermal robustness, have a mature fabrication technology and have found a wide spectrum of applications in power electronic systems. Their higher cost level is frequently over-compensated by their robustness, a unique selling point particularly in high temperature applications.

The present investigation deals with the suitability of various ceramic materials like mica, several high and low temperature sinterable tapes (HTCC, LTCC) as well as atmospheric plasma-sprayed (APS) alumina under such conditions. Aspects of manufacturability and component design are taken into account as well. Dielectric materials performance is particularly addressed by high temperature impedance spectroscopy up to several hundred °C to minimize further self heating of the components above the operating temperature. Although these materials, commercial as well as non-commercial ones, were originally developed for either electric or high temperature applications, the analysis suggests promising materials choices also in cases, when both requirements come together. Although dissipation factors obtained from capacitive test structures cover a wide range, capacitors made from pure alumina (HTCC) generally have lower dielectric loss at all temperatures than those made from glass-ceramic composites (LTCC). Quite diverse properties are obtained with APS alumina, which would represent a promising fabrication alternative due to the possible solid deposition on metal surfaces.
Material Requirements for Power and High Temperature Multilayer Ceramic Capacitors (MLCC)
Authors: Engel Guenter F.
Published: October 2015

Recent trends and progresses in power electronics rely on fast, miniaturized, high current and high temperature switching semiconductors. However, in electronics system design, passive components technologies, in particular capacitors, limit their full exploitation. The goal of the present paper is, firstly, to analyse the capacitor technologies, in particular ceramic technologies for the limits set by high current, high voltages, high temperatures, high frequencies, and by cost items. Secondly, for each of the identified limits, to define the tools and technologies that are capable to overcome it. The new technologies include a new PLZT based antiferroelectric ceramic material with high switching field, copper inner electrode for the multilayer construction, firing in reducing atmosphere, applying a sputter method for the outer connecting electrode combined with silver sintering of a flexible termination or of a pressfit connector. The third goal is to show how the new technologies are applied such that the cost forecast in production scale is giving a good economic perspective for future use in power electronic systems. Finally, specific applications in power electronics are selected and described, where the benefits resulting from the new technologies are made evident.
High modulus oxide glasses
Authors: Philipps K. , Stoffel R. P. , Dronskowski R. , Conradt R.
Published: October 2015

Elastic properties of glassy materials were studied in comparison to the isochemical crystalline phases. Structural changes were studied by density-functional theory with respect to electronic, vibrational, mechanical and thermodynamic properties. It turned out that topology is essential for elastic moduli. For both, glasses and crystals, elastic moduli are a function of atomic packing density, short range order, and especially the nature of the connection of adjacent polyhedra. Both, glassy and crystalline phases, behave in a commensurable way so that the glassy phase can be handled as a member of a series of polymorphs with the same stoichiometry.
Heat development at the microscale in ceramic components - thermography and complementary tools
Authors: Röhrig Sören , Petschenig Isabella , Bermejo Raul , Hofstätter Michael , Aldrian Franz , Danzer Robert , Supancic Peter
Published: October 2015

In many ceramic components for electric applications, small defects in the microstructure may cause an anomalous current flow. Especially in components exhibiting nonlinear electro-thermal properties, such as varistors, PTC or NTC resistors, inhomogeneities lead to high concentrations of current and localized heat generation due to positive feedback effects. While the integral behavior of those components is often nearly not affected by these defects, the local load at these hot spot regions is considerably high and can even lead to the complete failure of the device.

In this work micro-analytical tools are combined to identify the location and type of defects which may cause leakage currents, overheat or other reasons for inhomogeneous current distributions in functional ceramic components. Lock-in thermography is used to localize dominating current paths. This is even possible if the heat sources are in the micrometer range or less. Additionally, micro-sectioning techniques (e.g. Focus Ion Beam) are utilized to expose such regions to investigate features of the microstructure and causes for the enhanced current flows. Examples are shown in PTC resistor components as well as in LTCC based modules.
Micro-Dispense Direct Printing for Thermal Management Structure Using LTCC
Authors: Chen Xudong , Church Kenneth , Karbasi Ali , Jones W. Kinzy
Published: October 2015

The microelectronic manufacturing industry has been seeking improved efficiencies and faster fabrication turn-around for decades. The demand for better thermal management has been increasing in recent years and better materials and new processing techniques have been emphasized. LTCC technology has demonstrated great potential for satisfying most performance, cost and processing requirements. A novel approach for LTCC is micro-dispense direct printing which can print a wide range of materials to include a variety of screen printable thick film conductors, thick film resistors, dielectric materials and solder. Those with experience in micro-dispensing recognize the size limitation using a dispensing approach and understand that the hope of achieving smaller line widths, smaller pad sizes, and precise placement of the material is challenging. nScrypt has demonstrated the ability to build a complete branching micro-channel structure using a micro-dispensing LTCC approach. nScrypt has also demonstrated how the 3D capability and ability to handle materials compatible with LTCC will rival traditional screen printing and other maskless technologies, thus making this a viable manufacturing tool for many applications in microsystems and packaging.
Aerosol jet printing of two component thick film resistors on LTCC
Authors: Swiecinski K. , Ihle M. , Jurk R. , Dietzen E. , Partsch U. , Eberstein M.
Published: October 2015

Aerosol jet printing is a rather new technology for the deposition of thick film structures offering high line and space resolution. This offers a high potential for miniaturization for thick film structures. The advantages of this technology could be shown with inks carrying single solid powder (e.g. silver, platinum, ceramic or glass powder). Challenging is printing of solid powder mixtures due to the differences in the aerodynamic properties of different powders. Those differences result in changes of the mixing ratio within the aerosol jet and therefore poor reproducibility in the final film properties is obtained.

In this work, thick film resistors consisting of RuO2 with particle size < 1 μm as the conducting phase and different glass powders with particle size around 1 μm as the isolating phase were investigated. One glass had a density rather close to RuO2, the other glass significantly lower. Inks were made from RuO2/glass powder mixtures, a solvent and organic additives. After manufacturing the inks are printed on LTCC and the microstructures of the dried and the fired films were visualized by FIB preparation and SEM. The resistances as well as the temperature coefficients of the resistors were measured and compared to resistor films with an identical solid composition manufactured by conventional screen printing. The results of the obtained resistors are presented and discussed in terms of powder properties, ink dispersion and printing parameters.