bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterisation of test vehicle for in-situ measurement of die attach thermal conductivity
Authors: Slater Conor , Vecchio Fabrizio , Maeder Thomas , Ryser Peter
Published: October 2015

The continuing trend in the automotive and aviation industries to reduce complexity of electronic systems by removing cooling results in a need for high temperature electronics and associated packaging technologies. To ensure reliability over long periods of time the degradation of the packaging materials should be characterised. Epoxies show great promise as a reliable die attach solution for high temperature electronics due to their high bond strength, resistance to fatigue and chemical stability at temperatures up to 250°C. This work presents a method and test vehicle for measuring the thermal conductivity of an epoxy die attach. The test vehicle is constructed by using the epoxy under test to bond a die with an integrated PTC heater to an alumina substrate. To measure the thermal conductivity the heater heats the die for a few seconds after which the die allowed to cool down to the temperature of the substrate. The temperature of the cooling die is monitored and the time constant of the temperature decay is used to calculate the thermal conductivity of the die attach. Previous work demonstrated that this method can provide realistic information on the state of the die attach by relating the measured thermal conductivity to the shear strength of the die. Additionally the method is non destructive and can be used to monitor the degradation of the attach, such as fatigue cracking during thermal cycling. Here the test vehicle is modeled using the finite element method to get a better understanding of what temperatures the die attach is subjected to and to improve the thermal conductivity measurement.
Determination of the Stability of Low Viscous Particle Inks
Authors: Currle Ulrike
Published: October 2015

Inkjet printing is a flexible contactless deposition method for a variety of materials and applications in microelectronics. For a reliable printing process the stability of the ink is essential and verification of the stability of a suspension remains a demanding task. After presenting some fundamentals of ink preparation, several methods of determining the stability of inks considering different particles are discussed. In a stable suspension no sedimentation occurs i.e. the solid content remains constant over a long period. The simplest way of evaluating the stability is supposed to be visual inspection however this method yields no measurable information about the stability. Standard photometric methods deliver a measurement signal but the signal does not contain any information about the sedimentation processes. Scanning photometry compensates this deficit and provides furthermore information about the distribution of the solid content over the sample. Therefore a method of determining the solid content of a sample from transmission and backscattering measurement data is introduced. However, these contactless photometric methods work only with certain particles. If photometric methods fail, the evaluation of samples from the suspension is required. With non-contactless methods sample taking has to be performed very carefully and due to small sample amounts weighting of the samples in order to determine the solid content requires very precise measurement systems. For small sample amounts flame absorption spectrometry has been found to be a good method to receive reliable measurement results. In conclusion the application of rheological methods for the determination of stability is discussed.
Inkjetprinting of Multilayer Capacitors
Authors: Jeschke D. , Ahlfs E. , Krüger K.
Published: October 2015

Capacitors are widely used passive components. Considering microhybrid circuits printed capacitors are desirable, however today's screen printing technology results in very low specific capacitance per area. Thus usually SMD components are preferred. In order to achieve a higher specific capacitance, simple plate capacitors are stacked to form multilayer components. The mask-less inkjet printing allows for realization of such structures. To keep the process simple, no in-between-sintering is applied; the entire component is co-fired in one final step.

For defining the geometry of the component, first general processability of the used material combination is examined. Among others it is determined, to which extend the structures can be decreased in size without affecting their functionality. In further experiments the effects of thermal expansion and sinter shrinkage are analysed.

To create multilayer capacitors, in a second step design is completed. Vias are embedded to bypass the dielectric layer respectively the opposing electrode. When increasing the height of the structure, the aspect ratio achievable by the printing process is considered.
Yttrium-Aluminum-Garnet Laser Assisted Ink-Jet Printing for Fine Ag Wiring
Authors: Endo Akito , Tsuda Hiroki , Akedo Jun
Published: October 2015

High throughput fine electrical wiring on the non flat surface is desired for the integration between LSI chips and micro electric components such as MEMS chips, micro actuator devices and micro optical devise in the wide frequency range. Ink-jet printing method is one of the good candidates as a direct writing method on the non flat substrate. However, by conventional ink-jet printing, it is very difficult to realize the fine wiring pattern less than 30μm in these practical conditions. We develop a newly ink-jet printing system assisted by YAG laser to reduce the pattern width and to increase the large transmittance current at high frequency range. At first, we investigated heating effect of a substrate by normal heater for a patterned dot size at the Ag ink droplet diameter of 45μm. As results, a dot diameter decreased from 178μm to 74μm according to increase the substrate temperature from 22 C° to 100 C° . Next the Si substrate was heated by the YAG laser irradiation with consideration of the above experimental results. The Ag wiring was drawn on the Si substrate using a 35μm diameter droplet by an ink-jet system. Therefore the line width was decreased with about 200μm to about 40μm and at the scanning speed 3 mm/s. The wiring width was determined by the balance between the heat supplements by laser irradiation and the volume of ink droplet. In this presentation, electrical properties of ink-jet patterned Ag line with laser irradiation will be reported.
Biocompatibility Evaluation of Human Umbilical Vein Endothelial Cells Directly onto Low-Temperature Co-fired Ceramic Materials for Microfluidic Applications
Authors: Mercke William L. , Dziubla Thomas , Eitel Richard E. , Anderson Kimberly
Published: October 2015

Expansion of Low-Temperature Co-fired Ceramic materials into microfluidic systems technology has many beneficial applications due to their ability to combine complex three dimensional structures with optical, fluidic, electrical functions. Evaluations of the biocompatibility of these Low-Temperature Co-fired Ceramic materials are vital for expanding into biomedical research. The few biocompatibility studies on Low-Temperature Co-fired Ceramics generally show negative cellular response to thick film pastes used in generating the electronic circuitry patterns. In this study, biocompatibility of Human Umbilical Vein Endothelial Cells was examined on Heraeus's Low-Temperature Co-fired Ceramic tape and two of their conductive pastes. The biocompatibility was assessed by monitoring cellular attachment and viability up to three days. This study examines the idea of leachates being detrimental to cells due to a study that suggests the possibility of harmful leachates. Results indicate difficulty in initial attachment of Human Umbilical Vein Endothelial Cells to sintered Low-Temperature Co-fired Ceramic tapes, but no hindrance of cellular attachment and growth onto the two conductive pastes. Outcomes also demonstrate that possible harmful leachates from Low-Temperature Co-fired Ceramic materials don't thwart cellular attachment and growth for up to three days of cell culturing. These results provide a basis for biological devices using Low-Temperature Co-fired Ceramic materials.
Materials Interaction in Cofired Platinum /Alumina High Density Feedthrough for Implantable Applications
Authors: Karbasi Ali , Jones W. Kinzy
Published: October 2015

Neurostimulator applications will require much higher I/O feedthrough density for hermetic implantable enclosures, often greater than 100 I/O. This work evaluates the development of high-density platinum via structure cofired in alumina. The platinum was observed to melt when cofired at 1550°C, almost 200°C below its melting point, independent of the particle size (nano to micron size particles) or particle morphology. An analysis of the effect of particle size (nano to micron size Pt), firing atmosphere (air, hydrogen, inert), firing temperatures, intermetallic reactions and additives to control thermal expansion and adhesion strength was performed to evaluate and minimize this exothermic reaction. The interaction of platinum and alumina has been evaluated using X-ray diffraction and SEM.
LTCC 3D MICROMIXER OPTIMIZATION FOR PROCESS INTENSIFICATION
Authors: da Cunha Marcio Rodrigues , Seabra Antonio Carlos , Gongora-Rubio Mário R.
Published: October 2015

Mixing of fluids is a very important unit operation for Chemical, Biochemical, & Pharmaceutical processes among others, with a great deal of interest for industrial and research sectors. Micromixers a new implementation in micro scale of mixers are being studied. Active (electrokinetic, pressure disturbances, ultrasonic, magneto-hydrodynamic) and passive (jet breakup, vortex, microchannels ) methods appear in the literature. In particular research of micromixers with microchannels having different kind of elbows are conducted focusing hydrodynamic phenomena in microscale, like caotic advection.

LTCC Microsystem Technology is suitable for the construction of micromixers because their inherent capacity of implementing 2D and 3D structures. The goal of the present work is to report our current study on LTCC micromixers based on microchannels having different kind of elbows for geometry optimization applying finite element Computational Fluid Dynamic numerical methods for process chemical intensification.

The study will contemplate nine different 2D and 3D LTCC micromixer geometries compared with straight channel micromixer and prospect hydrodynamic parameters as: flow rate, pressure difference, friction factor and head loss coefficient. It is also presented a description of flowage as a function of diffusion-convection equation in order to obtain the mixing performance of designed devices.
Large Strain Actuation of 0.65PMN–0.35PT/Pt Thick-Film Bimorphs
Authors: Uršič Hana , Holc Janez , Zarnik Marina Santo , Hrovat Marko , Kosec Marija
Published: October 2015

The effect of clamping a piezoelectric layer to a relatively stiff substrate results in smaller displacements in comparison to substrate-free structures. To ensure a sufficient amount of the bending of actuators, it is important to reduce the thickness of the substrate. For this reason an approach to preparing “substrate-free”, large-displacement actuators using the screen-printing method was developed. The “substrate-free” 0.65PMN–0.35PT/Pt actuators were prepared by screen-printing the 0.65PMN–0.35PT and Pt pastes on alumina substrates. After the screen printing and the subsequent firing the 0.65PMN–0.35PT/Pt composites were peeled off from the substrates. The normalized displacement (the displacement per unit length) of 55 μm/cm at 18 V was achieved, which is approximately five times higher than the displacement of related actuators from the literature.
Effects of Vapor Phase Soldering on the Properties of Piezoceramic Materials
Authors: Bramlage Silke , Wolter Klaus-Jürgen
Published: October 2015

Eight different PZT (lead zirconate titanate) materials (Navy Type I and II) with Curie temperatures between 250 °C and 350 °C were subjected to a standard vapor phase soldering process with a peak temperature of 240 °C for three cycles. As indicators for the depolarization, the piezoelectric charge coefficient (d33) and the coupling coefficient (keff) were measured both before and after each heat treatment. Our studies demonstrate reductions in piezoelectric properties between 5% and 20%, depending on the Curie temperature of the corresponding material. The effects of the second and third cycle were minimal. The drop in performance, especially for materials with higher Curie temperatures, is moderate, and can be accounted for in the design of the device. Thus batch soldering processes become a viable alternative to selective soldering.
Effective Compensation of the Temperature Coefficient of Resonant Frequency in LTCC
Authors: Dai Steve , Hsieh Lung-Hwa
Published: October 2015

The temperature coefficient of resonant frequency (τf) of a stripline (SL) ring resonator in a multilayer low temperature cofireable ceramic (LTCC) package can be adjusted towards zero by integrating a cofirable compensating dielectric with an opposite τf to that of the host dielectric. Studies on resonator panels with a compensating dielectric revealed that the most effective τf compensation is achieved when the compensating dielectric is integrated next to the SL conductor rings. Method of Momentum (MoM) electromagnetic simulations are consistent with the experimental observations. The results are further explained by the calculated effective dielectric constant of a heterogeneous layered dielectric structure using the transverse transmission line method combined with the variational technique.
Steps towards a novel cost efficient low weight LTCC packaging technology for high-end RF applications
Authors: Bechtold Franz
Published: October 2015

The emerging of a new GaN based generation of RF semiconductors provides new challenges to the packaging technology. RF performance, circuit functionality and power dissipation create new challenges to the packaging technology with respect to low losses, electrical stability, SiP integration, thermal management and reliability. Today LTCC provides a proven packaging solution for Standard GaAs devices. Increasing the frequency, power and functionality of the systems is the driving force to investigate novel packaging solutions. This paper describes the different steps how LTCC technology can cope with these requirements.

Based on a comparison between different available LTCC systems and a benchmark between DP 943 and DP 9k7, the packaging performance of the 9k7 system is in detail investigated. Technological features, relevant for RF performance, like cavities, conductor line resolution, via diameter and flatness are considered. Process capability, relevant for thermal management, SiP integration and hermeticity like brazing of heat sinks, integration of heat pipes, integrated capacitors and resistors are analyzed.

The impact of novel materials for heat sink and low cost materials for metallization and brazing will be evaluated with respect to weight and cost. The progress beyond the state of the art will be demonstrated by packaging solutions recently developed for RF applications.
Creation of Titania Artificial Interfaces with Geometric Patterns by Using Micro Stereolithography and Aqueous Solution Techniques
Authors: Kirihara Soshu , Itakura Yousuke , Tasaki Satoko
Published: October 2015

Titania micro patterns with periodic arrangements were formed on glass substrates successfully for electromagnetic wave energy resonations and localizations in terahertz frequency ranges. Geometric arrangements of acryl polygon tablets with titania particles dispersions by using micro patterning stereolithography. Moreover, periodically arranged full titania tablets with anatase phase were created homogeneously though liquid phase crystal depositions of water solvent processes under micro templates fabricated by using the stereolithography system. The terahertz wave properties were measured and simulated by a using time domain spectroscopic system and finite difference time domain method. The terahertz waves having micrometer order wavelengths and belonging in far-infrared frequency ranges are expected to apply for various types of novel sensors which can detect micro cracks on materials surfaces, micro defects in electric devices, bacteria in foods, and cancer cells in human skins.
Template-Based Surface Nano-Patterning and Device Applications
Authors: Wen Liaoyong , Zhao HuaPing , Grote Fabian , Lei Yong
Published: October 2015

Surface nano-patterns on substrates are the fundamental structures of various nano-devices. Template-based surface nano-patterning techniques are highly efficient methods in realizing different surface nano-patterns. The time-saving and low-cost fabrication processes of the UTAM (ultra-thin alumina membranes) template-based surface patterning are highly desirable for industry in fabricating different kinds of nano-devices. This manuscript summarizes the recent advancements in the field of UTAM template based surface nano-patterning, the basic concepts, the general fabrication processes, the structure-related properties, and the device applications of these template-based surface nano-patterning techniques are introduced.
Direct Filament Formation of Biological Carbon Nanotube Suspensions
Authors: Abe Hiroya , Tan Zhenquan , Kondo Akira , Naito Makio
Published: October 2015

In this study, aqueous carbon nanotube (CNT) suspensions were prepared using biological surfactant of sodium deoxycholate (NaDC). The influence of NaDC concentration on the NaDC self-association in water and the rheological responses of the NaDC-CNT-water system were investigated. It has been found that the yield stress of the suspension increased with NaDC concentration, which was strongly related to the NaDC self-association of lyotropic liquid crystals. Due to the enhanced rheological properties at high NaDC concentration (30%), it allowed the shear-induced filament formation in which the CNTs were aligned along to the shear direction. This filament formation may be attractive for transferring aligned CNTs on substrates in a controlled manner.
Depth of Laser Etching in Green State LTCC
Authors: Zaraska Krzysztof , Machnik Monika , Bieńkowski Adam , Synkiewicz Beata
Published: October 2015

Laser etching of green state LTCC is a useful rapid prototyping and precision manufacturing process. Laser etching allows selective removal of screen printed conductor layer, producing patterns with higher precision than conventional screen printing. Its usefulness for rapid prototyping is due to elimination of time consuming screen preparation process. The etching is performed using a near UV (355 nm), pulsed laser. The process is characterized by three parameters: laser power, pulse frequency, and etching speed. From the practical standpoint, we are interested in finding a combination of parameters which allows for achieving required etching depth at the maximum etching speed. We present an empirical mathematical model relating etching depth to process parameters, allowing to theoretically determine optimum processing parameters for a specified etching depth.
Fabrication of Oxide Ceramics Dendrites for Porous Electrodes by Using Stereolithography
Authors: Tasaki Satoko , Komori Naoki , Kirihara Soshu
Published: October 2015

Porous oxide ceramics such as zinc oxide are applied for dye sensitized solar cell. This device requires consideration of high surface area, mechanical strengths and porous networks. Thus, we focused on the dendrite structures constructed from micrometer order rods with coordination numbers of 4, 8, and 12. There perfectly controlled structures were fabricated by stereolithography. Variations of the aspect ratios (lattice length to diameter ratios) were adjusted to control the porosity in the range 50–80 vol. % by using computer graphic software. The dendrite models sliced into a series of cross sectional patterns with uniform thickness by using a stereolithographic file format convertor. These numerical data were transferred into the micro processing equipment. High viscosity slurry material was prepared by mixing oxide ceramic powder and photosensitive acrylic resin. This slurry was spread on a flat stage and smoothed. An ultraviolet laser beam was exposed over the deposited layer to create cross-sectional planes. Through layer-by-layer processes, solid components were fabricated. These precursors were dewaxed at 600°C for 2 h at a heating rate of 1.0°C/min and sintered at 1400°C for 2 h at a heating rate of 5.0°C/min in air. The oxide ceramics microstructure was observed using a scanning electron microscope.
High Frequency Approaches for LTCC Based Sensors
Authors: Zhang Haolun , Neuberger Thomas , Perini Steve , Lanagan Mike , Semouchkina Elena , Semouchkin George
Published: October 2015

Low temperature co-fired ceramics (LTCC) have been developed for RF and microwave circuits for a number of applications (i.e. cell phones and wireless systems). The same attributes that make LTCC an important technology for telecommunications are also important for sensors. Compact three-dimensional architectures with low dielectric loss materials are available with LTCC technology. The underlying electric and magnetic responses of materials in the RF and microwave frequency ranges will be discussed and these unique responses can be exploited in a sensor system. Gases, liquids and solids have unique dipolar responses in the RF and microwave ranges. For example, the dielectric relaxation of water has been investigated in water/starch mixtures. Classic dipolar relaxation of water occurs at 30GHz and additional relaxation mechanisms have been found in the 1–10 GHz range because of the starch gelation process. These relaxations could be the basis for a sensor system to monitor the gelation of food starches. In addition, miniature coil assemblies for magnetic resonance imaging (MRI) systems with operation in the 300 MHz to 850 MHz range will be presented. These types of coils with additional passive components are envisioned in a LTCC-based circuit topology.
New generation of dew point sensors based on LTCC substrate with decoupled contact system
Authors: Bechtold Franz , Heymel Armin , Hummel Wolf , March Barbara , Schneider Mike , Steinke Arndt
Published: October 2015

LTCC is used as a substrate for dew point sensor, e.g. multisensing system consisting of detection system for condensation, temperature sensors, stray field sensor for measurement of condensed water mass. All these components as well as through LTCC vias have been integrated in the LTCC substrate. The mentioned through vias enable the separation of corrosive environment from the electric contact system, the cooling element e.g. peltier element and open new application fields for in line measurement of technical and non-technical processes.
Integrated Microwave Noise Suppressor Fabricated on Magnetic/Dielectric Composite Ceramic Substrate
Authors: Chen Zheng , Li Yanqiu , Li Liangliang
Published: October 2015

We fabricated coplanar waveguide noise suppressors on anodic aluminum oxide ceramic substrates filled with 20 nm Co ferromagnetic nanowires, and measured the microwave properties of the integrated noise suppressors from 10 MHz to 40 GHz. The working frequency of the device is 16–20 GHz and the transmission coefficient S21 of the device is about −5 dB. We analyzed the characteristic impedance matching for the magnetic nanowire-based noise suppressors and provided the theoretical equations to calculate the ferromagnetic resonance frequency of the magnetic nanowires for various cases.
Size Effect Investigation on Nano-Scale Ferroelectric Ceramic Materials
Authors: Li Longtu , Wang Xiaohui , Zhang Hui , Gui Tieyu Sun Zhilun
Published: October 2015

The monodispersed BaTiO3 nanocrystals have been synthesized by one-step solvothermal method. The average particle size of BaTiO3 powders is as small as 5 nm with a narrow size distribution. Using this powder, 5nm bulk dense Nano ceramics have been prepared by pressureless two-step sintering method. The microstructure, properties, phase transition and size effect of BaTiO3 ceramics have been investigated systematically by using TEM, HRTEM, XRD and Raman spectra. The Raman Spectra revealed successive transitions from rhombohedral to orthorhombic, tetragonal and cubic with the temperature increased from −190°C to 500°C. Piezoelectric loop measurement results are also shown that ferroelelctricity could still retained in BaTiO3 ceramics with grain size down to 5 nm.
Low Temperature Growth of Oxide Thin Films by Photo Reaction of Nanoparticles
Authors: Tsuchiya Tetsuo , Nakajima T. , Shinoda K.
Published: October 2015

Printed electronics is creating many new products given the benefits of the technology compared to conventional electronics, such as thinness, flexibility, cost, ease of manufacture, fast production turn around, “green” technology, power efficiency and more. For this purpose, we have developed the photo reaction of nano-particle method (PRNP) for the preparation of the patterned metal oxide thin film on organic and glass substrates. In this paper, we demonstrate the preparation of transparent conducting thin film by the PRNP process, and their properties of the obtained film. By using the combination of the two procedures, the resistivity of the film was 5.94×10−4 Ωcm. The resulting ITO film showed mobility as high as 9.99 cm2 V−1 s−1 at the carrier density of 1.05 ×1021 cm−3.
Ultraviolet LED Multi-Chip Module Based on Ceramic Substrate
Authors: Burkhardt T. , Hornaff M. , Acker A. , Peschel T. , Beckert E. , Suphan K.-H. , Mensel K. , Jirak S. , Eberhardt R. , Tünnermann A.
Published: October 2015

A high power ultraviolet (UV) light emitting diode (LED) multi-chip module package based on aluminum nitride (AlN) and alumina (Al2O3) is presented. The AlN substrate with a high thermal conductivity of up to 180 W/(m· K) and LED chips based on a copper alloy provide superb thermal management and heat extraction. Efficient cooling is an important prerequisite for the increase of extractable optical power and decrease of thermally induced wavelength shift. A design of a stackable module featuring arrays of 7×2 indium-gallium-aluminum- nitride UV LED chips at 395 nm is developed. This configuration of sub-modules allows for the scalable assembly of line sources with different lengths. Applications using UV LEDs cover market segments such as curing of adhesives, inks and coatings, sterilization of medical equipment and treatment of potable water, as well as various uses in chemical detection, biochemical analytics and spectroscopy.

Thermal and thermo-mechanical modelling of the sub-mount is conducted using finite elements analysis. Die attach using eutectic gold-tin solder, lower melting tin-lead solder and silver-filled adhesive are compared with respect to optical output power and wavelength drift. Mechanical strength and structure of the resulting joints are investigated using shear force measurements, cross-sectioning and micro-tomography. An optical output power of 7.7 W is achieved using a cluster of 14 LED chips at 1050 mA resulting in a peak irradiance of 30.8 W/cm2 at the LED surface with respect to the footprint and pitch of the attached chips.
Metal-based Optical MEMS Scanning Devices Using Lead-Free Piezoelectric Sheets Prepared by Aerosol Deposition
Authors: Park Jae-Hyuk , Akedo Jun
Published: October 2015

We demonstrate metal-based lamb-wave resonant optical MEMS scanning devices actuated by aerosol deposition (AD) piezoelectric film and report their temperature properties and durability. Metal-based structure was introduced to reduce the production cost and to improve the optical scanning performance, simultaneously. The optical scanning devices with large mirror size as well as high scanning angle were fabricated. A high optical scanning angle (more than 60 °) and a high resonant frequency (more than 25 kHz) were achieved in ambient air without vacuum packaging. The resonant frequency and the scanning angle do not have any changes during life test of approximately 50,000 hours. In this report, BaTiO3 (BTO) thick film as a lead free piezoelectric material was prepared by AD process for a piezoelectric exaltation source of scanning devices. Piezoelectric d31 of BTO-AD film was approximately −138 pm/V. The performance of optical scanner driven by AD-BTO thick film was comparable with that of BTO bulk material and AD-PZT thick film. From these results, AD-BTO film might be used to practical applications on the MEMS devices.
Optimized cavities for microwave applications using the new low loss LTCC material Du Pont 9k7
Authors: Schulz Alexander , Welker Tilo , Gutzeit Nam , Stoepel Dirk , Wollenschlaeger Frank , Mueller Jens
Published: October 2015

This paper presents two different novel methods to manufacture optimized cavity structures, which are suitable for multilayer System-in-Package (SiP) and Multi-Chip-Module (MCM) applications, in the new low temperature cofired ceramic (LTCC) material Du Pont 9k7. In contrast to standard manufacturing, the improved DP 9k7 cavities show almost perfectly orthogonal cross sections and straight edges, achieved by applying special cavity inlays or cast silicone. Ball-wedge bond wires and wedge-wedge ribbons are implemented directly to the cavity rim successfully.

Therefore, these cavities are suitable for very short bond wires in complex RF systems and the introduced techniques are very promising for future applications using DP 9k7.
An evaluation of thick-film silver die-attachment as micro solid oxide fuel cells (μ-SOFCs) interconnection packaging
Authors: Jiang Bo , Muralt Paul , Maeder Thomas
Published: October 2015

Micro solid oxide fuel cells (μ-SOFCs) based on MEMS fabrication processes have become an increasingly attractive development for portable power generation applications, due to their high power density and their compatibility with hydrocarbon fuels. For system packaging, the silicon-based fuel cell membrane module needs to be integrated together with other functional elements such as the gas processing unit and the post-combustor. Silicon wafer bonding techniques can be utilized to avoid thermo-mechanical stresses, however, the complete integration in silicon technology is very challenging; ceramic carriers combined with thick film technology are much more practical for total integration, but exist other challenges. As ceramics may have a slight thermal mismatch with silicon, hermetic assembly by glass sealing can be problematic due to stress build-up. Moreover, the high necessary sealing temperatures are somewhat beyond the survival conditions of the current fuel cell modules. Therefore, a metallic thick-film silver die-attach approach is proposed as a potential bonding solution, due to its flexible fabrication requirements, the relatively low process temperatures and the high ductility and chemical stability of silver materials. Such a seal could potentially compensate the thermal mismatch between the silicon and the ceramic substrate as well as provide reasonable hermeticity under μ-SOFC operating conditions. In this work, we preliminarily evaluated several commercial thick-film silver products as interconnection materials in terms of mechanical strength, firing process and metallization approach, using shear testing and microstructure characterization. The failure mode of the die-attach was discussed in details and related to their bonding mechanism. The influence of firing temperature and additional prior metallization on those thick-film bonds were also studied.
Stack of Planar Double-Sided Solid Oxide Fuel Cells
Authors: Magonski Zbigniew , Dziurdzia Barbara , Jankowski Henryk , Koprowski Jan , Kenig Teresa , Szwagierczak Dorota , Kulawik Jan
Published: October 2015

A new design of a small power SOFC battery is presented. The battery consists of an array of flat double-sided fuel cells assembled with only two screws. Fuel cells are made with the application of commercially available HTCC green tapes. Eight layers of 180μm thick anode tape (YSZ+NiO) constitute the anode base structure of the double-sided fuel cell. Within the anode base structure, the separate areas serve as: the functional anode, the anode current collector, and the support for the anode functional layer. Also a network of fine micro channels is embedded within the anode base structure. The individual double-sided fuel cell is completed by deposition of the following layers, which constitute the electrolyte, the cathode, and the cathode current collector These layers are deposited on both sides of the anode base structure by means of screen-printing. Each double-sided fuel cell is provided with the own separate fuel distributor and combustion product collector. That beneficial feature enables completing the tests, separately for each cell, prior assembly into battery.
Fab in a Package: LTCC Microfluidic Devices for Micro and Nanoparticle Fabrication
Authors: Gongora-Rubio Mário Ricardo , Freitas Kellen Heloizy Garcia , de Novais Schianti Juliana , de Oliveira Adriano Marim , Cerize Natália Neto Pereira , Zanin Maria Helena Ambrosio
Published: October 2015

The chemical industry is moving toward miniaturization with the help of microreaction technology and automated control systems. Besides the evident advantages of Microtechnology like improved portability, reduced energy use, safety and flexibility, the main advantage associated with the miniaturization of chemical processes is the increased microreactor control due to predictable thermal and mass transportation properties. We understand that LTCC Microsystem technology have a relevant role in this area.

LTCC Microfluidic devices have been applied to carry out several chemical processes operations, including mixing, separation, chemical reactions, heterogeneous catalysis, heat exchange and so on. More recently, LTCC microfluidic systems have also been used to produce micro- and nanoparticles with excellent control of size distribution, morphology and constitution.

The present work give an account of some LTCC Microfluidic devices aimed for Micro and Nanoparticle fabrication. At this time we report devices for: Emulsion generation for obtaining alginate microparticles by ionic gelation; Electrospinning applications, Microreactors for silver nanoparticle production and 3D Flow focusing devices for pharmaceutical active nanocrystallization.
Cold Embossing of Ceramic Green Tapes
Authors: Kucera Anja , Richter Hans-Jürgen , Moritz Tassilo
Published: October 2015

The development of alumina green tapes, made of water based binder systems, allows the structuring by so-called cold embossing. The cold embossing disclaims time expensive heating and cooling phases as needed for hot embossing. That allows a reduction of process time. The structuring by embossing becomes more practicable for high throughput manufacturing. For investigating the influence of powder amount and with or without plasticizer inside ceramic green tapes on deformation behaviour, tensile tests have been carried out. Furthermore, cold embossing tests with uniaxial compression tools were carried out. Channel structures allow investigations concerning stability against elastic recovery. In a first series of tests various green tape compositions have been investigated. As results inferences to the elastic and plastic material behaviour can be obtained. The characterisation of structured tapes in green state has been carried out by using SEM and scanning surface area by confocal white light microscopy.
Fully Integrated Applications of Thin Films on Low Temperature Cofired Ceramic (LTCC)
Authors: Wolf Ambrose , Peterson Ken , O'Keefe Matt , Huebner Wayne , Kuhn Bill
Published: October 2015

Thin film multilayers have previously been introduced on multilayer low temperature cofired ceramic (LTCC), as well as initial thin film capacitors on LTCC. The ruggedness of a multipurpose Ti/Cu/Pt/Au stack for connectivity and RF conductivity has continued to benefit fabrication and reliability in state of-the-art modules, while the capacitors have followed the traditional Metal-Insulator-Metal (MIM) style. The full integration of thin film passives with thin film connectivity traces is presented. Certain passives, such as capacitors, require specifically tailored and separately patterned thin film (multi-)layers, including a dielectric. Different capacitance values are achieved by variation of both the insulator layer thickness and the active area of the capacitor. Other passives, such as filters, require only the conductor – a single thin film multilayer. This can be patterned from the same connectivity thin film material (Ti/Cu/Pt/Au), or a specially tailored thin film material (e.g. Ti/Cu/Au) can be deposited. Both versions are described, including process and integration details. Examples are discussed, ranging from patterning for maximum tolerances, to space and performance-optimized designs. Cross-sectional issues associated with integration are also highlighted in the discussion.
HIGH TEMPERATURE PROPERTIES OF MINIATURIZED THICK-FILM COMPONENTS
Authors: Nowak Damian , Dziedzic Andrzej , Piasecki Tomasz , Baraniecki Tomasz , Reiner Jacek
Published: October 2015

This paper presents systematic studies of thick-film or LTCC microcomponents (capacitors, inductors) made with the aid of laser-shaping and operating at temperature up to 450 °C. The minimum dimensions i.e. conductive path width and spacings were about 30 μm. Such small patterns have been created by laser cutting of fired Au- or Ag-based conductive films. Laser system equipped with Nd:YAG-laser (beam wavelength of 1064 nm) was applied. The inductance, capacitance, as well as parasitic impedances were measured in the frequency range from 10 kHz to 110 MHz and temperature between 25 °C and 450 °C.
Realisation of Hermetically Tight Joints for Microfluidic Applications in LTCC - Technology
Authors: Balluch Bruno , Atassi Ibrahim , Weilguni Michael , Radosavljevic Goran , Myrtezani Arsim
Published: October 2015

Channel clogging by particles inside microfluidic LTCC devices for biochemical analytics may lead to critical system pressures especially affecting joints, seals or areas of material transition. Biological contamination by device leaks could become a crucial factor regarding operational safety. Therefore, this hereby presented work deals with technological aspects concerning cavity sealing of microfluidic LTCC- devices. Aluminum oxide cover elements as well as sapphire glasses acting as optical windows for spectroscopic investigations are bonded to microfluidic test modules by different glass solders. Different material combinations are discussed by means of compressive strength experiments. CeramTec GC test samples consisting of four layers with a fired thickness of 1mm and a test area of 33mm2 withstand pressures up to 90bar.
Microwave Dielectric Characteristics of Butyl Rubber- Barium Titanate Composites
Authors: Chameswary J. , Sebastian M. T.
Published: October 2015

Butyl rubber-micron barium titanate (BR/BT) and butyl rubber-nano barium titanate (BR/nBT) composites were prepared by sigma mixing followed by hot pressing. The tensile tests show that both the composites were mechanically flexible. The microwave dielectric properties of both BR/BT and BR/nBT composites were investigated as a function of ceramic loading and were found to be improved with filler content. The butyl rubber has relative permittivity (εr) of 2.4 and loss tangent (tan δ) of 0.0017 at 5 GHz. At a filler loading of 0.24 volume fraction (vf) of micron sized barium titanate (BaTiO3) powder loading, the composite attained a εr of 7 and tan δ of 0.014 and for the same filler content of nano BaTiO3 the composite have εr of 8.9 and tan δ of 0.019 at 5 GHz. The thermal stability of the relative permittivity of both the composites was investigated. The experimental values of εr of both BR/BT and BR/nBT composites were compared with theoretical models.
Stability of a Piezoresistive Ceramic Pressure Sensor Made With LTCC Technology
Authors: Zarnik Marina Santo , Belavic Darko
Published: October 2015

This paper discusses the stability of a piezoresistive, LTCC-based, pressure sensor that was designed for measurements in a low-pressure range below 100 mbar. The intrinsic stability of the sensor's offset was evaluated at a constant ambient temperature and different conditions regarding the atmospheric humidity. The sensors were also subjected to functional fatigue tests, which included a full-scale and an overload pressure cycling. The results of the fatigue testing revealed the vulnerability of the sensor's structure from the point of view of the long-term stability and the life-cycle. Nevertheless, the stability of the key characteristics of the prototype sensors was found to be satisfactory for accurate measurements in the low-pressure ranges.
Modified Organic low-k Dielectric Layers on Fired LTCC Substrates
Authors: Bittner Achim , Schmid Ulrich
Published: October 2015

In this study, the reduction of permittivity of LTCC substrates by coating with a polyimide compound containing hollow glass microspheres as filler material is described. By incorporating the filler material, the dielectric constant of the substrate material is locally lowered to improve the high-frequency performance of antennas operated in the GHz range. Furthermore, by adding the filler material to the liquid polyimide precursor the layer thickness is heightened from maximum 10 μm to above 80 μm which is enough to fill cavities in LTCC substrates. Two compound materials with filler to polymer ratios 1:7.5 and 1:10 are mixed. Afterwards they are deposited by spin coating onto LTCC substrates. The film thickness depends on the rotating speed and the filler content. With the higher filler concentration and low rotating speed of 500 rpm 82 μm thick polymer films can be achieved. The high surface roughness can be reduced afterwards by adding additional pure polyimide layers on top to Ra= 3 μm. The dielectric constant of the entire substrate consisting of the LTCC and the resulting compound material is measured using a ring resonator in microstrip configuration. From the resonances occurring in the transmission S-parameter |S21| spectrum between 1 to 10 GHz, the relative dielectric constant can be determined. Using 820 μm thick LTCC substrates a relatively low reduction from εr = 7.8 to 6.6 is achieved. However, due to permittivity can be reduced with higher microsphere amounts, the dielectric constant of pure polyimide of εr= 3.3 can also be reduced. Furthermore due to the sufficiently high film thickness of the modified substrates, the compound layer can be used as single dielectric layer.
Tunable Ferroelectric Ceramic Components for Reconfigurable Wireless Communications
Authors: Zheng Y. , Sazegar M. , Maune H. , Binder J. R. , Zhou X. , Kohler C. , Nikfalazar M. , Mehmood A. , Jakoby R.
Published: October 2015

This paper focuses on the technology evolvement and novel concepts of ferroelectric microwave components. They aim to enable reconfigurable wireless frontends for frequency-agile, software-defined and cognitive radios. Such components are an emerging technology based on the nonlinear solid state ferroelectric materials like Barium-Strontium-Titanate namely BST thick-films. They are expected to cope with the demands of multiband and multi-standard operation. Processing and integration technologies are revised to enable multilayer component realization, including selective sol-gel printing and vertical connection through laser drilling. Several novel kernel frontend components based on ferroelectric thick-film ceramic are addressed then. The challenging trend of antennas towards compactness with wider spectrum coverage is coped with several tunable resonant modes in the antennas with integrated BST varactors. The optimized prototype for frequency division duplex services covers 1.47 GHz to 1.76 GHz with a variable distance between up- and down-link channels. The environmental impact on antennas can be compensated by tunable matching networks. In the commercial frequency range from 1.8 GHz to 2.1 GHz, a demonstrative module exhibits an insertion loss less than 0.98 dB, in a compact multilayer package. A compact bandpass filter is enabled by an evanescent mode substrate integrated waveguide cavity in ferroelectric ceramics, integrated with tunable complementary split ring resonator scatterers and tunable matching networks. The compact module covers 2.95 GHz to 3.57 GHz with a comparatively low insertion loss.
Embedded Ceramic Capacitors in LTCC
Authors: Bartsch Heike , Barth Stefan , Müller Jens
Published: October 2015

The integration of passive elements in ceramic interconnect devices promises higher package densities and reliability. LTCC compatible high-k dielectrics are commercially available with k-values up to 250. Barium titanate dielectrics stand out for their high permittivity even at low sintering temperatures. This fact allows the co-firing with common metallization and commercially available tapes. In this study we investigate the co-firing of barium titanate LTCC tapes with commercially available standard tapes. Pressure assisted sintering and constraint sintering is used for the manufacturing of buried capacitors. Crucial process parameters are worked out using a statistical set up according to Taguchi. High k-values up to 2300 are obtained for embedded dielectric tape patches. Beside of the capacitor properties the process constancy is observed.
Pressure-Assisted Sintering of Multilayer Transformer Using LTCC-Compatible NiCuZn-Ferrite and Silver Conductor
Authors: Naghib-zadeh Hamid , Rabe Torsten
Published: October 2015

A low-fired NiCuZn-ferrite and a new LTCC dielectric material with matched sintering shrinkages and coefficients of thermal expansion were used for integration of magnetic function into LTCC. Silver was used as inner conductor material. Silver diffusion during sintering into the surrounding glassy phase modifies the sintering behaviour of LTCC near the silver conductor and generates warping and delamination of the multilayer. Silver diffusion can be prevented by sintering in nitrogen atmosphere. However, sintering in nitrogen atmosphere causes partial decomposition of NiCuZn-ferrite by reduction of divalent copper oxide (CuO) to cuprite (Cu2O). It was found that diffusion of silver and associated deformation can be highly reduced if a higher heating rate during sintering in air is used. A Defect-free multilayer transformer with several silver conductive layers could be manufactured by pressure-assisted sintering only.
The Effect of Phase Composition on the Mechanical and Thermal Properties of LTCC Material
Authors: Makarovič Kostja , Meden Anton , Hrovat Marko , Holc Janez , Benčan Andreja , Dakskobler Aleš , Kosec Marija
Published: October 2015

Low-temperature co-fired ceramic (LTCC) is an important material in the production of ceramic multilayer structures. Large and complex multilayer structures are usually fired at higher temperatures and/or longer firing times compared to the relatively thin LTCC tapes. The firing conditions of LTCC determine the phase composition and the microstructure, which both influence the physical characteristics, such as the mechanical and thermal properties. In this work the effect of the phase composition on the biaxial flexural strength and the temperature coefficient of expansion of the DuPont 951 LTCC is presented. The samples were fired at different temperatures and times to obtain different phase compositions. The phase composition, especially the mass fraction of anorthite, was correlated with the biaxial flexural strength and the thermal coefficient of expansion (TCE). A very long firing time, i.e., 100h at 800 °C, yields, apart from crystalline anorthite, the cristobalite phase. The anorthite that crystalizes from the glass phase in a dense LTCC material changes the crack-propagation mechanism and improves the biaxial flexural strength of the material. The major change in the biaxial flexural strength is observed when the anorthite phase appeared. The increasing mass fraction of anorthite does improve the biaxial flexural strength less drastically. With the increasing mass fraction of the anorthite, decreases of the TCE of the material and a small decrease of the density of the LTCC material occur.