|
|
Microwave dielectric materials with high quality factor
Anatolii Belous
V.I.Vernadskii Institute of General and Inorganic Chemistry of National Academy of Sciences of Ukraine, Kyiv, Ukraine
Abstract:
In the modern microwave (MW) engineering there is a sustainable demand for the dielectric materials which combine at once high permittivity (e= 10-100), low dielectric loss (tan d) or high quality factor (Q ~1/tand), and near zero temperature coefficient of permittivity (te). These materials are widely used as dielectric resonators, antennas, substrates, etc. Their utilization allows miniaturization of MW circuits, integration of components, and hence improved reliability of MW apparatus combined with a significant reduction of production cost. However, a proper combination of the MW dielectric properties is hardly attended in real materials because of the physical limitations. Therefore, several different approaches in the development of the high-Q MW ceramics will be considered and discussed. The presentation includes the examples of the single-phase MW dielectrics based on the solid solutions, the effect of a partial substitution in the crystal lattices of dielectric compounds on their phonon spectra and MW properties of the materials, and the ways to combine different crystal phases in a single multiphase material with a high microwave Q-factor. As a consequence, the examples of some applications of the high-Q dielectric materials in the MW apparatus will also be presented.
Research activities at the Department of Biomedical Engineering TUG
Antoni Nowakowski
Gdańsk University of Technology, Gdańsk, Poland
Abstract:
This year we are celebrating 20 anniversary of the Department of Biomedical Engineering, Gdansk University of Technology. It was formally established on 1 June 1991 as the Department of Medical and Ecological Electronics, but changed the name into Department of Biomedical Engineering in 2003. The main research focus is on monitoring and diagnostics methods to be applied in medicine and in environmental protection. Education is concentrated recently on Biomedical Engineering courses at the basic (B.Sc.), graduate (M.Sc.) and advanced (PhD) levels.
One of major fields of research is development of sensor technology and applications. We run laboratory allowing use of different thick and thin film technologies devoted for ceramic as well as polymer components but also electrochemical and optoelectronic sensors development. Such applications as gas sensors using electrochemical reactions in bulk and thick film ceramic structures, based on ionic interactions are of our special attention. One of strongly researched fields is development of fuel cells and related components. Our interests are focused not only on specific technology processes but also on new methods of materials, structures and devices characterization. Especially electrical and thermal methods are of our basic interest.
Another area of interest covers broad field of electroimpedance applications, including sensor development but also electrical impedance tomography applications. Here multifrequency probes and some other sensors have been developed. Very important is also our involvement in development of diagnostic methods based on analysis of thermal processes using IR-imaging and active dynamic thermography. Both – electrical and thermal applications have been successfully implemented in medicine, in skin burn diagnostics, in analysis of cardiosurgery procedures and in some other fields.
Also a lot of efforts are directed to development of new electrochemical sensors suitable in environmental monitoring. Here several new concepts are regarded for intellectual protection.
Another new field of interest is development of wearable sensors for telemedicine applications. Especially solutions to be used by elderly and disabled persons are of our main interest.
Typically full cycle of development is performed, starting with problem analysis, modeling and simulation study, development of production technology and ending on specific applications. As a result during the related 20 year period also 20 PhD projects and 3 habilitation procedures have been completed. The number of completed research and development grants is also of the same number. It is worth to underline that every year around 20 M.Sc. projects strongly related to the research are also completed, but this number is recently growing due to opening education on the Biomedical Engineering direction of study.
Optical properties of SrxBa1-xNb2O6 crystals in UV and VUV photon energy range
B. Andriyevsky, A. Patryn, K. Dorywalski, C. Cobet, M. Piasecki, I. Kityk, N. Esser
Koszalin University of Technology, Koszalin, Poland
Abstract:
The crystals of strontium-barium niobate, SrxBa1-xNb2O6 (SBN), is a known ferroelectric material, which is attractive for practical applications: spatial light modulators, 4 wave mixing, phase conjugation, optical memory and computing. However, the electronic band structure and optical properties of this crystal in the photon energy range of fundamental excitations, E > 3.5 eV, are studied not sufficiently. In the present paper the real and imaginary parts of dielectric permittivity of SBN have been measured in the photon energy range of 1.5 – 9.9 eV using the spectral ellipsometry method and synchrotron radiation. Independently, the electronic band structure of SBN has been calculated using the ab-initio package VASP. The experimental and theoretical results are found to be in satisfactorily agreement. Especially, the experimentally observed the bowing effect (nonlinear dependence of the energy gap Eg on the compound index x) has been obtained from our band structure calculations.
Methods of Varistor Quality Monitoring
Janusz Smulko
Gdansk University of Technology, Gdansk, Poland
Abstract:
Varistors are very popular elements that protect power supply networks against lightning or high voltage surges. Therefore, quality of these elements is important to avoid losses when expensive laboratory equipment is not saved from intense and random overvoltages.The paper presents properties of varistors that comprise of different ZnO grains types (having strongly nonlinear, weakly nonlinear or ohmic junctions between the grains) and can have various quality that changes continuously during exploitation (due to exposition to overheating and overvoltage pulses). Therefore, it is important to monitor varistors during their ageing (causing changes within their microstructures). A few methods of varistors properties diagnosis were considered and compared with the methods currently applied in laboratory or industry applications.A new measurement system that monitors varistors during ageing and can be widely used in practise is presented.
Study of IDE as a Sensor Head for Interfacing with Handheld Electrochemical Analyzer System
Vijayalakshmi Velusamy, Khalil Arshak, Olga Korostynska and Catherine Adley
University of Limerick, Limerick, Ireland
Abstract:
Electrochemical sensors for various applications including diagnosis of infectious diseases, detection of chemicals, DNA hybridization and detection of pathogenic micro-organisms have been reported in recent years. Real-time monitoring of food and water is a high priority globally and the presence of pathogenic micro organisms is a particular environmental concern. Although various measures like good agricultural practices, good manufacturing practices, hazard analysis and critical control point (HACCP) and the food code indicating approaches, have been taken to monitor the food quality, there are still reports of outbreaks.
Detailed in this work is the design of a sensor head for use in a handheld electrochemical analyzer system to detect environmental variables including pathogenic micro-organisms in real-time. A thick-film interdigitated gold electrode (IDE) prepared by screen printing technique was employed as a sensor to detect DNA of the foodborne pathogen Bacillus cereus. Polypyrrole (PPy) was used as an immobilization matrix and the combination of PPy modified interdigitated micro-electrode with impedance measurements yielded a sensitive label-free biosensor which was able to detect DNA. The IDE prepared by thick-film technology is sensitive, rapid and cost effective. The electrical detection of 100 pM concentration of DNA immobilized onto the PPy modified gold IDE was achieved, with an IDE width of 400µm.
Bonding Technologies for 3D-Packaging
Klaus-Juergen Wolter
Technical University Dresden, Dresden, Germany
Abstract:
Electronics System Integration by System in Package improves the performance, reduces the size, power and cost of electronic systems. Three dimensional Systems in Package are a new way for integrating functional blocks in vertical structures. This implementation leads to shorter signal and power interconnects and this results into lower propagation delay and power consumption. The paper will present bonding technologies for Package on Package and Die to Wafer 3-D-technologies. Results of our research group on 3D-Integration in the field of reliable solder flip chip interconnections, self-alignment approaches for die stacking, die to wafer bonding by SLID-technology and the application of Ag-nano-wires for anisotropic adhesives will be demonstrated.
Influence of Electrical Stress on Printed Elastic Resistors with CNTs
Marcin Słoma, Małgorzata Jakubowska
Warsaw University of Technology, Warsaw, Poland
Abstract:
Nanostructures such as carbon nanotubes are the most investigated group of materials this days due to their superior properties. These properties were utilized by the authors in fabrication of elastic, printed electronic resistors. In most common applications, such as electrodes or sensors, only basic electrical and mechanical properties are investigated, leaving aside other key parameters related to the stability and reliability. In this paper, we present experiment results on the properties of resistive printed layers. One of the most important issues is their stability under high currents, creating abnormal thermal stresses. In order to investigate that behavior, a pulsed measurement technique was applied along with observation of temperature distribution that allows to gain fundamental insights into the electrical behavior at higher current densities. These experiments allows to observe parametric failure or catastrophic damage that occur under abnormal supply parameters.
Tantalum technologies
Martin Barta, Tomas Zednicek
AVX, Lanskroun, Czech Republic
Abstract:
Recent years have seen the emergence of one or two equivalent technologies offering many of the advantages of tantalum,such as volumetric efficiency and reliability. Two new technologies recently introduced into their commercialization phase are niobium oxide capacitors and tantalum capacitors with conductive polymer cathodes. A circuit designer trying to choose between these solid electrolyte capacitor systems has a number of tradeoffs and subtleties of operation to consider. Presentation reviews the main features of the two technologies, the latest electronic application needs and discusses the feasibility of the latest technology trends in tantalum, niobium oxide and polymer capacitors.
Overview of SiC Die Assembly Technologies for High Temperature Electronics
R. Kisiel, J. Szmidt , M. Sochacki, M. Guziewicz1)
Warsaw University of Technology, Institute of Microelectronics and Optoelectronics, Warszawa, Poland
1) Institute of Electron Technology, Warsaw, Poland
Abstract:
The main technical problems relating to fabrication of SiC power devices are the formation of stable ohmic contacts and engineering a package capable to work at temperatures range up to 400°C. In the paper the survey of materials for ohmic contacts to n-type as well as to p-type SiC will be presented. The results of own experiments connected with influence of metallization type as well as the condition of heat treatment on specific contact resistance and contact morphology for both Ni and Ti metallization to n-type SiC ant Ti/Al metallization to p-type SiC will be given. The influence of high temperature annealing on resistance changes of ohmic contacts will be mentioned.
The overview of methods for mechanical, thermal and electrical connections between SiC die and DBC substrate will be discussed too. The silver glass composition and nano-Ag paste were selected as conductive connection materials between SiC die and DBC substrate. The results of own measurements of mechanical, thermal and electrical properties of such created joints will be presented too.
ACKNOWLEGEMENTS
The work was supported by The National Centre for Research and Development, NCBiR, Poland (Grant no N N515 499240)
Testing of passive elements embedded in PCB using impedance spectroscopy
Tomasz Piasecki, Karol Nitsch, Andrzej Dziedzic, Konrad Chabowski, Wojciech Stęplewski, Grażyna Kozioł
Wrocław University of Technology, Wroclaw, Poland
Abstract:
One of the methods of achieving high packaging density of passive elements on the PCB is using the resistors and capacitors embedded in multilayer PCB. Test structures consisting of embedded resistors and capacitors were fabricated using the Ohmega-Ply Technologies resistive and Farradflex capacitive internal layers. Impedance spectroscopy and equivalent circuit modelling was used to determine their electric properties such as the resistance, capacitance, parasitic inductance, leakage and series parasitic resistance. Use of several stages of accelerated ageing allowed to test the durability of structures. The results showed good quality stability of the embedded elements. The spatial distribution of the capacitance of test structures on the surface of the PCB form was tested. It revealed the influence of the process parameters during lamination on the values of embedded capacitors.
LTCC as Advanced Substrate Material for Miniaturized Devices and Systems
U. Schmid and A. Bittner
Vienna University of Technology, Department for Microsystems Technology, Institute of Sensor and Actuator Systems. Vienna, Austria
Abstract:
In the recent years, LTCC (low temperature co-fired ceramics) has attracted much attention as technology platform for the realization of advanced sensor solutions due to a large variety of outstanding properties. In particular, LTCC offers a high chemical resistance, a high temperature stability, good mechanical properties and an excellent high frequency performance. Due to the multilayer approach the 3rd dimension can be used to enhance the integration level of buried components and to realize micromachined structures within the monolithic glass-ceramic body. These features as well as the flexibility in the design favour the applicability of LTCC-based devices for a large field of application scenarios ranging from automotive to airborne and industrial processes. In this paper we will focus on our developments done in the last years to optimize or to expand the use of micromachined LTCC devices and systems.
In the field of high frequency applications such as radar systems operated up to 79 GHz a wet chemical etching technique is introduced in order to generate regions with different permittivity in one single LTCC layer. The high frequency performance of commercial LTCC materials as DP951 with a dielectric constant of εr= 7.8 is preferred below e.g. the distributing network to minimize radiation losses. However, in the area below the RF
patch antennas a reduced permittivity is desirable to improve the RF performance by a lower capacitive coupling to the substrate. By selectively dissolving crystallographic phases out of the composite glass-ceramic a nano-scaled porous structure can be formed enabling air to penetrate in the LTCC body and hence, to decrease the effective dielectric constant. Using phosphoric acid a maximum porosification depth of dp= 35 μm is feasible reducing the effective permittivity of a 820 μm thick substrate to εr= 5.2. As expected, it could be shown that a further reduction of the permittivity down to εr= 2.9 can be achieved when applying thinner LTCC tapes.
Thin film technology is recommended on LTCC substrates when targeting a proper realization of the patch antenna elements for RF applications as a high lateral resolution in the μm-range is needed or for metallization systems within sensor devices requesting a low film thickness. Therefore, different thin film metallization systems based on silver, molybdenum or titanium/platinum are comparatively evaluated on LTCC as unconventional and silicon as well-established substrate taking into account their specific properties such as the surface roughness which in turn has a direct impact on the microstructure of the thin films.
In this context, LTCC is discussed as an attractive technology platform for the realization of sensors devices operating in harsh environments. Both a high mechanical strength and an enhanced chemical inertness are fundamental requirements for the realization of flow sensors integrated in the injection nozzle of common-rail diesel engines where the injection pressure ranges up to 1350 bar or even higher. Due to the direct implementation of the thermo-resistive sensor element into the automotive hydraulic system important injection parameters such as the begin/end of the injection pulse as well as the fuel volume are determined. The sensor characteristics are evaluated with an injection amount indicator and hydraulic simulations on system level showing a good correspondence.
All in all, it can be stated that LTCC is a promising technology platform offering the high potential for advanced sensor solutions in the near future.
Aerosol Printed Co- and Postfired Functional Films for LTCC-Multilayer Components
Uwe Partsch, Sindy Mosch, Martin Ihle
Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany
Abstract:
LTCC (Low Temperature Co-fired Ceramic) is a well known technology for highly integrated, reliable, high-frequency suited, high-temperature stable 3D electronic packages for mobile communication, automotive, airborne/space or medical applications.
The paper presents a new technology for the deposition of 3D-high resolution functional films for LTCC multilayer systems. The films can be sintered either using the LTCC cofire technology at 850°C or at lower temperature using a post firing process.
The aerosol printing technology uses a pneumatic or an ultrasonic ‘atomizer’ to bring micro droplets into a continuous gas flow. At the printing head a sheet gas focuses the gas flow. The long focus length ensures the 3D printing capability. Ink characteristics as particle size distribution, viscosity, wetting behaviour have to be controlled very carefully as well as the printing parameters (gas flows, ink reservoir temperature, substrate table velocity and temperature). With optimized inks and printing parameters line widths of 10 µm are achievable as well as 70 µm with the same ink.
Actual printable materials are different metallization (silver, gold) and resistor compositions.
Applications for aerosol printed films are LTCC rapid prototyping, repair as well as high resolution structures for high frequency and sensors applications.
Noise, Electro-Ultrasonic Spectroscopy and Resonant Ultrasonic Spectroscopy of Conducting Polymer Thick Films
V. Sedlakova1, J. Majzner1 , P. Sedlak1, M. Kopecky1, J. Sikula1, L. Hasse2, A. Szewczyk2
1Department of Physics, Brno University of Technology, Brno, Czech Republic
2Department of Optoelectronics and Electronic Systems, Gdansk University of Technology, Gdansk, Poland
Abstract:
Thick conducting films based on conducting polymer are characterised by DC conductivity and noise in temperature range 10 to 360 K. Conducting polymers could be used e.g. for the top electrode (cathode) in the solid tantalum or niobium capacitors. On the conducting polymer layer the top layer of carbon/graphite and/or silver polymer based pastes is applied in the capacitor technology. Our samples structure consists of conducting polymer layers with semiconductor conductivity applied on the alumina substrate of the size 40 x 3 mm2. Contact electrodes are prepared either from two layers - carbon/graphite paste (lower one) and silver paste (upper one), or by silver paste layer only. We are measuring DC conductivity of the structures, which is of the order of 1 mS at the room temperature and decreases with decreasing temperature for both types of contact technologies. For the evaluation of the contact technology two testing methods are proposed. The first is the measurement of the potential distribution on the sample surface, which is able to measure interface resistance between two layers. The second is based on the evaluation of the low frequency noise measurements. It is generally accepted that charge transport in conducting polymer structures occurs by disordered controlled thermally activated hopping of charge carriers through a manifold of localized states. Transport sites can be of various types, e.g. additive molecules in highly-doped polymers, pendant side groups or conjugated segments in the main chain of the polymer. Local variation in molecular packing and orientation results in the variation of the electronic polarization energy in the vicinity of transport sites and variation in the intersite distances. This type of transport must generate a noise, which is assumed to be 1/f type.The sources of fluctuations are both in the conducting polymer volume and in contact region between conducting polymer, carbon/graphite and dipping silver electrodes. We suppose that there is a fundamental 1/f noise component as a result of mobility fluctuation and the others components related to intra-molecular and intra-chain electrical conductivity. Additional is excess 1/f noise component generated at structural defects and at the interfaces between conducting polymer and contacts. Additional methods sensitive to the material structure are Electro-Ultrasonic Spectroscopy (EUS) and Resonant Ultrasonic Spectroscopy (RUS). The correlation of the noise spectroscopy and EUS and RUS data will be given.
Piezoelectric integrated devices based on thick film technology
Wanda W. Wolny
Meggitt Sensing Systems, Kvistgaard, Denmark
Abstract:
Thick film printing and related pad -printing are feasible methods of manufacturing commercial low cost piezoelectric devices with excellent performance, both as high frequency transducers, low frequency sensors and as energy harvesting devices. Substantial work has been carried out for the miniaturisation and integration of the piezoelectric films into more complex devices and systems including deposition on light weight substrates, which required modification of existing technologies. The results, in particular for vibration sensor systems based on energy harvesting principle, have demonstrated that the tested devices can generate energy sufficient for independent battery free operation. Examples of working devices will be presented. Another trend observed in the area of piezoelectric thick films is a quest for lowering of the processing temperature enabling deposition of the films on substrates such as polymers, paper and textiles. Successful examples of the in-house development in this field will be given as well.
Ohmic contacts based on Ti/Al matallization to n-type AlGaN/GaN heterostructures
Wojciech Macherzyński, Bogdan Paszkiewicz, Andrej Vincze, Regina Paszkiewicz, Marek Tłaczała
Wroclaw University of Technology, Wroclaw, Poland
Abstract:
The electrical I-V characteristics, van der Pauw Hall mobility measurements and interfacial reactions between Ti/Al/Ni/Au metallization and AlGaN/GaN heterostructures at various annealing temperatures ranging from 745 to 835 °C were performed. The Ti/Al/Ni/Au ohmic metallizations were annealed at various temperatures in rapid thermal annealing system. To study of the influence of annealing process parameters on the properties of the 2 dimensional electron gas (2DEG) the van der Pauw Hall mobility measurement was used. Interfacial reactions between contact metals and heterostructures were analysed through depth profiles of secondary ion mass spectroscopy. It was observed that transition from nonlinear to linear I-V behaviour occurred after the annealing at 790 ºC. For studied samples, the most promising results were obtained for the annealing temperature of 790 ºC and 805 ºC. These temperatures delivered not only low contact resistance but also lead to maintenance of 2DEG.
|
