bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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 &lt; 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.
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.
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.
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 &lt; 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.
Advanced Surface Finishes for Ceramic Electronics for Soldering, Conductive Adhesive, Aluminum- , Gold-, and Copper Wire Bonding.
Authors: Bruder Maren , Heinz Guenter , Oezkoek Mustafa 
Published: October 2015

Surface finishes for ceramic electronics are an important feature. . The suitable surface finish allows the appropriate assembly technology to be performed on the ceramic substrate. The paper will present the possible surface finish options for ceramic substrates and include the advantages and challenges of each surface finish. Furthermore it will show the potential of a new surface finish called “Direct EPAG”. The demand for these new finishes is based on needs for new assembly technologies like copper wire bonding and for high frequency applications. Furthermore Nickel which the main layer of many surface finishes like ENIG or ENEPIG, is more and more regarded as an unpleasant element due to several disadvantages.
All these concerns are supporting the introduction of a new surface finish called “direct EPAG” (Electroless Palladium, Autocatalytic Gold) finish. In particular, its suitability for copper wire bonding and its fine line capability makes it very attractive from a cost standpoint. In addition, the mentioned technological drawbacks of nickel based finishes could be solved by applying a revolutionary surface finish: “direct palladium with an optional direct gold layer on copper”. The direct deposition of palladium on copper with an optional gold layer does have a number of technological, environmental and economic benefits. The suggested paper will describe and discuss the advantages and challenges using this new surface finish. It will also exhibit the results of various soldering and wire bond tests on the EPAG finish.
Application of Cylindrical Pipe-Type LTCC Substrates as a Platform for Multi-Array Gas Sensors
Authors: Kita Jaroslaw , Brandenburg Annica , Moos Ralf 
Published: October 2015

Thick-film technology-based gas sensors have been known for many years. On a ceramic substrate, a thick-film heater, electrodes, and a gas sensitive layer are deposited. Due to the ease of layer deposition, such structures are usually manufactured as planar ones. However, recently-suggested cylindrical pipe-type substrates made in LTCC technology offer unique inherent advantages for gas sensor technology, like a uniform temperature profile along the gas sensitive layer or a reduction of the distortion of the gas flow in the pipe.
As shown in our previous study, cylindrical LTCC substrates with inner electrodes and integrated heaters may be very promising in the field of high-temperature gas sensors. In this paper, we continue our work on cylindrically shaped LTCC sensor substrates, with special focus on the construction of a platform with multiple heater/electrodes couples for multi-array gas sensors. For such multi-sensor structures, decoupling of the heat sources is the most important platform feature. Therefore, a cylindrical substrate with integrated heaters was FEM-modeled and optimized in the first stage. Subsequently, tubes with three integrated heaters were prepared. In this paper, it is discussed how reduced thermal masses can be obtained by thinner tube walls or by the integration of laser-patterned cavities and how different integrated heat sources can be decoupled.
Electrical characterization of thick film materials
Authors: Rebenklau L. , Gierth P. , Grießmann H. 
Published: October 2015

The thick-film technology is one of the fundamental technologies for the production of circuit carriers for electronic modules. It is mainly used in areas with harsh environmental conditions, such as sensor or automotive applications. Basis of the thick film technology are glass-based pastes, which are screen printed on ceramic substrates and fired in a high temperature process at (500…1000) ° C. Such thick film pastes are commercially available from various suppliers as elements of paste systems, which mainly include compatible isolation, resistance and conductive pastes.
There are a number of requirements according the fired thick film characteristics, such as high breakdown voltage of isolation thick films or low noise performances of resistance thick films. However, the most requirements are concentrating on conductor thick films. They should guarantee excellent properties in terms of assembling (soldering, bonding) which are focused in a many publications. Simultaneously, they should also offer very good electrical characteristics that have not been completely investigated until today.
At Fraunhofer IKTS different measurement methods are developed and adapted to characterize the electrical performance of thick film structures. Already well known is the short term overload (STOL) measurement of thick film resistances, which determining the maximum power dissipation of the thick film structure. The basic concept of this measurement is adapted on conductive thick film structures like conductive tracks or vias. The investigations show correlations between geometrical thick film properties and the resulting thermal characteristics of the thick film structure. Results can be used to improve screen-printing layouts in terms of cost reduction (paste consumption) and thermal management (track width, via diameter), but can also help to improve paste compositions itself. The paper will give an overview of the used electrical measurement methods and present exemplary results.
Mechanical characterization of miniaturized functional substrates and components in different environments
Authors: Bermejo Raul , Krautgasser Clemens , Deluca Marco , Pletz Martin , Supancic Peter , Aldrian Franz , Danzer Robert 
Published: October 2015

Functional components such as multilayer low temperature co-fired ceramics are examples of the combination of a ceramic-based substrate with internal electrodes as well as surface features (e.g. metallization, contacting pads, cylindrical vias, etc) employed to provide the component with a given functionality. Another example is that of functionalized silicon chips to be embedded into polymer circuit boards in order to enhance integration and save costs. The functionality of the system can be influenced by the mechanical reliability of the different components. Due to miniaturization and design complexity, no standard methods for mechanical testing can be applied for the characterization of these brittle components.
In this work, an experimental approach is presented, which enables determining the strength distribution in functional components (e.g. rectangular plates as small as 2 × 2 × 0.1 mm3) in different environments at different temperatures. The method is based on localized biaxial testing using a ball-on-three-balls fixture. The high accuracy of the test allows quantifying the effect of surface quality, surface features and/or metallization (e.g. contact pads or cylindrical vias) on the component strength distribution.
Experimental findings show that the strength distribution of ceramic components can be affected by environmental degradation, whereby subcritical crack growth phenomena can be enhanced in environments with high relative humidity. In addition, metallization at the surface subjected to tensile stresses can even raise the strength of the component, acting as a protective layer against environmental degradation, whereas cylindrical vias can become weak points in the design. It is shown that functionalized layers such as those used in silicon chips can have a significant effect on the strength parameters, thus influencing the lifetime of the device.