bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Permeation Measurements on Low Temperature Cofired Ceramics
Authors: Goeke R.S. , Grubbs R.K. , Yazzie D. , Casias A.L. , Peterson K.A. 
Published: October 2015

Commercial low temperature cofired ceramic (LTCC) technology is established in microelectronics and microsystems packaging, multichip and radio frequency (RF) modules, and sensors. The ability to combine structural considerations with embedded traces and components using laminated glass-ceramic tapes has created solutions to unconventional packaging requirements of micro-electro-mechanical systems (MEMS) devices. Many MEMS devices such as resonators are very sensitive to pressure and require packaging in a vacuum environment. Attaining and maintaining desirable pressure levels in sealed vacuum packages requires knowledge of the permeation characteristics of the vacuum envelope and the sealing materials.
An experimental system to measure the time dependent gas permeation through LTCC at temperatures from room temperature to 500°C has been developed. This system utilizes a membrane technique in which a gas is allowed to permeate through a test sample, held at a constant temperature, into a high vacuum chamber where it is detected using mass spectrometry. The gas permeation value is determined from the steady state gas flux through the sample. The gas diffusivity and solubility in the material were calculated using data from the time dependent approach to the steady state condition. The gas-solid permeation data for helium through DuPont 951 LTCC is presented and compared to the permeation through other common vacuum envelope materials such as glasses and high-purity alumina ceramics. Application of the permeation data to the prediction of vacuum levels inside typical LTCC packaging is discussed. This data can further be utilized in designs to create LTCC packages that meet specific pressure/time operating requirements.
Lamination of LTCC at low pressure and moderate temperature using screen-printed adhesives
Authors: Maeder Thomas , Jiang Bo , Vecchio Fabrizio , Jacq Caroline , Ryser Peter , Muralt Paul 
Published: October 2015

In this work, we investigate a new method of low-pressure lamination of low-temperature cofired ceramic (LTCC) tapes, by pre-coating with specially-formulated adhesive layers. This allows fabrication of intricate structures that would be destroyed by high lamination pressures, yet preserves compatibility with standard processing operations, such as blanking, laser cutting, punching, via filling and screen printing.
Techniques proposed previously are application of adhesive tapes, solvents or glues. These methods are applied after the tape processing steps and therefore require an extra operation in the processing chain, which may be unpractical, especially if the tape is very thin has been extensively cut.
In our procedure, the adhesives are printed and dried on the blanked tape before any other operation, with the drying step also useful for pre-conditioning the tapes, which may then be stored as "standard" blanks. The adhesives are formulated to have low tack at room temperature, making them compatible with standard processing, but to become very soft at 50–60°C, allowing lamination at low pressures. Compatibility with different tape materials is investigated, and the requirements for adequate adhesive formulation are discussed.
Improving Performance of Laser-Printed Conductive Silver Lines
Authors: Büttner Dustin , Krüger Klaus 
Published: October 2015

Within the last decade, large efforts were made to implement digital printing as a production method for printed electronics. Especially in production of thick-film electronics, innovation is pushed forward to overcome the lacks of established screen-printing regarding flexibility and tooling. Besides the numerous approaches in using ink-jet printing for printed electronics, researchers at Helmut Schmidt University already showed huge progress in applying electrophotography (“laser printing”) as a method to print conductive silver lines in order to form a conductive layout for thick-film circuits.
Electrophotography is a solvent-free method, able to directly print silver toner onto ceramic substrates, forming a conductive line after firing. Benefits are high speeds and flexibility and a huge potential regarding precision. Now, after the feasibility of the method was proven and even functional conductive layouts like RFID coils were printed, the next steps have to be taken towards developing electrophotography to an applicable method in a thick-film production process.
Thus, this paper describes the efforts in improving the method's performance. Different kinds of silver particles are tested towards their possibility of forming a silver toner. The resulting silver lines are examined regarding conductivity and printing precision. Also, surface treatment of substrates is considered as a method to reduce the number of required print cycles. Corresponding tests are performed. Furthermore, different firing profiles are tested towards their influence onto the resulting silver lines. Combining the results of these examinations, the performance of conductive silver lines could be improved significantly.
3D FOCALIZATION MICROFLUIDIC DEVICE BUILT WITH LTCC TECHNOLOGY FOR NANOPARTICLE GENERATION USING NANOPRECIPITATION ROUTE
Authors: Gomez Houari Cobas , Gongora-Rubio Mario Ricardo , Agio Bianca Oliveira , Kimura Vanessa Tiemi , de Oliveira Adriano Marim , da Silva de Luca Ramos Luciana Wasnievski , Seabra Antonio Carlos 
Published: October 2015

Nanoprecipitation is a nanonization technique used for nanoparticle generation. Several fields, like pharmacology and fine chemistry, make use of such technique. Typically are used a bulky batch mechanical processes rendering high polydispersity index of generated nanoparticles, poorly particle size reproducibility and energy wasting.
LTCC-based microsystem technologies allow the implementation of different unitary operations for chemical process, making it an enabling technology for the miniaturization of chemical processes. In fact, recently LTCC microfluidic reactors have been used to produce micro and nanoparticles with excellent control of size distribution and morphology.
The present work provides a report on the performance of a 3D LTCC flow focusing Microfluidic device designed to fabricate polymeric nanocapsules for Hydrocortisone drug encapsulation, using nanoprecipitation route. Monodisperse Hydrocortisone nanocapsules were obtained with sizes (Tp) from 188.9 nm to 459.1 nm with polydispersity index (PDI) from 0.102 to 0.235.
Aligned Co2Z Hexagonal Ferrite Fibers
Authors: Pullar Robert C. 
Published: October 2015

The hexagonal ferrites, also know as hexaferrites, have become massively important materials commercially and technologically, accounting for the bulk of the total magnetic materials manufactured globally, and they have a multitude of uses and applications. They all have a magnetocrystalline anisotropy; that is the induced magnetization has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetization, the uniaxial hexaferrites, and those with an easy plane (or cone) of magnetization, known as the ferroxplana or hexaplana ferrites.
There is currently increasing interest in composite materials containing hexaferrite fibers. It had been predicted that properties such as thermal and electrical conductivity, and magnetic, electrical and optical behavior will be enhanced in material in fibrous form. This is because a continuous fine fiber can be considered as effectively one-dimensional, and it does not behave as a homogeneously distributed solid. Although the intrinsic magnetization of the material is unaffected, the effective magnetization of an aligned fiber sample should be greater when a field is applied parallel with fiber alignment compared to when applied perpendicularly to fiber alignment. This feature was first demonstrated by the author for aligned hexaferrite fibers in 2006, who was also the first to synthesize fibers of BaM, SrM, Co2Y, Co2Z, Co2W, Co2X and Co2U hexaferrites, as micron-scale (3–10 μm) continuous fibers in both random and aligned blankets. The magnetic properties of aligned Co2Z (Ba3Co2Fe24O41) hexaferrite microfibers are presented in this paper.
It is shown that unlike with the uniaxial M ferrite fibers, the ferroxplana Co2Z ferrite fibers do not shown any significant alignment affects with direction of applied field. They have high Ms values in all orientations. This is attributed to the microstructure of these fibers, in which the hexagonal plates are stacked and oriented parallel to the fiber axis. This appears to counteract the expected effects of fiber alignment on measured Ms values.
Thick film pastes for silicon nitride ceramics
Authors: Wenzel Marco , Schmidt Richard , Partsch Uwe , Eberstein Markus 
Published: October 2015

Silicon nitride ceramic is a potential new substrate material for thick film- / hybrid applications in the field of power electronics or microwave technology. The main advantages are the excellent thermal shock resistance, high fracture toughness, a thermal expansion coefficient close to silicon, high thermal conductivity and good dielectric properties. Nevertheless, the use of Si3N4 as chip carries or power electronic package is no achieved due to the lack of suitable connection technology such as thick film pastes. The main challenge for the respective pastes is the adhesion on the substrate. The low thermal expansion of about 2.8 ppm/K of Si3N4 and material interactions with the thick film components need to be considered in the paste development. Therefore, new glasses and glass-ceramic composites are required.
Reason developments were performed towards thick film pastes for Si3N4, consisting of AgPd conductor, resistor and encapsulating paste. Good solder wetting (&gt;95%) and high conductivity (&lt;25 mΩ/sq) of the AgPd conductor film is achieved in presence of 2 percent glass with matching composition and 2 percent of an inorganic additive. A high adhesion of up to 23 N/4mm2 (wire pull test) of the fired film was obtained.
For resistors, RuO2 was used as conductive material. The influence of the conductive material content on the sheet resistivity and of the TCR modifier was studied. The developed resistor paste has a sheet resistivity of 10 Ω/sq with a temperature coefficient of the resistance (TCR) between -100 and 100 ppm/K. The film structures were analyzed in FESEM studies of cross sections.
Key Technology and Materials for the Development of DC-DC Converter Module
Authors: Hsiang Hsing-I , Chueh Jui-Fu , Fan Liang-Fang 
Published: October 2015

Portable devices are often powered by batteries and DC-DC converters are used to convert battery energy to supply power for microprocessors and integrated circuits. Portable electronic devices are required to be compact and, hence, space for converters is very limited. Therefore, the demand for integrating individual components into modules to reduce the size and increase the power density of DC-DC converters is increasing. It is important to develop a low temperature sintering NiCuZn ferrites with a superior DC-bias-superposition characteristic; the nonmagnetic materials co-fired with the magnetic NiCuZn ferrites, and the low-pressure assisted constrained sintering process for the large area NiCuZn ferrites substrates for the DC-DC converter modules.
This study successfully developed the key technologies and materials for the development of DC-DC converter module. It integrated the magnetic NiCuZn ferrites with superior DC-bias superposition characteristic and nonmagnetic ferrite materials using multilayer ceramic processing and low-pressure assisted constrained sintering technologies to prepare a large area NiCuZn ferrite substrate for DC-DC converter module.
Preparation of inorganic-organic hybrid membrane for peripheral nerve reconstruction
Authors: Shirosaki Yuki , Hayakawa Satoshi , Osaka Akiyoshi , Lopes Maria A. , Santos José D. , Maurício Ana C. , Geuna Stefano 
Published: October 2015

The treatment of peripheral nerve injuries is still one of the most challenging tasks in neurosurgery, as functional recovery is rarely satisfactory in these patients. The concept behind the use of biodegradable nerve guides is that no foreign material should be left in place after the device has fulfilled its task, so as to spare a second surgical intervention. In a previous study, flexible and biodegradable chitosan-3-glycidoxypropyltrimethoxysilane (GPTMS) hybrid membranes exhibited better cytocompatibility in terms of osteoblastic cells than chitosan membrane. Porous chitosan hybrid membranes, derived by freeze-drying the hybrid gels, showed that the cells were attached and proliferated both on the surface and into pores.
In this study, the porous chitosan-silicate hybrid membranes with non-differentiated human mesenchymal stem cells isolated from Wharton's jelly of umbilical cord were used to reconstruct the crushed peripheral nerve. Axonotmesis lesion of 3 mm was enwrapped with the hybrid membranes with or without a monolayer of non-differentiated human mesenchymal stem cells. Motor and sensory functional recovery was evaluated throughout a healing period of 12 weeks. The combination of hybrid membranes and human MSCs infiltration showed a slightly better recovery than the untreated control (the just crushed nerve). On the other hand, the hybrid membrane alone promoted the crushed peripheral nerve reconstruction. It is expected that the porous chitosan hybrid membranes is candidate for the clinical tool in peripheral nerve reconstructive surgery.
Extreme Thermal Transient Stress Analysis with Pre-Stress in a Metal Matrix Composite Power Package
Authors: Hopkins Douglas C. , Baltis Theodore , Pitaress James M , Hazelmyer Donald R. 
Published: October 2015

This paper culminates several years of development of a SiC MOSFET-based solid-state circuit breaker power module designed and fabricated for aluminum-based composite metal-ceramic packaging. The aluminum composite structure was used for high temperature thermal management &gt;350°C and high reliability. Testing of the final module surpassed 750 total cycles.
The module was optimized for four dies, 4.1mm × 4.1 mm each for SiC or GaN. The electrically loading per die was 48 A for 5 ms with a di/dt of 2.1 kA/us (23 ns opening time). An internal snubber increased the response to 390 ns. The die absorbed ∼4.6 J causing a transient junction temperature increase of ∼245 °C. Two ambient temperatures were used in testing and set at 25 °C and 105 °C. The maximum junction temperature was conservatively projected to reach 350 °C during the 5 ms pulse. Electrical, thermal and mechanical design and testing results are presented.
Nanocomposite Film Dielectrics for High Temperature Power Conditioning Capacitors
Authors: Slenes Kirk , Bragg Lew 
Published: October 2015

Emerging power electronics in a broad range of military, aerospace, hybrid vehicle, renewable energy and drilling applications rely on advances in dielectric materials for capacitors. Compact capacitors possessing low dielectric loss and high operating temperature capability are needed for power conditioning in advanced converter and inverter designs for these applications. Wound film capacitors represent the preferred capacitor technology but are limited by low operating temperature capabilities, &lt; 150°C, and low volumetric efficiency, capacitance per unit volume less than 1.0 μF/cc.
TPL is developing processes and manufacturing techniques for fabrication of advanced capacitor films comprised of high temperature polymers modified with ceramic nanoparticles. The selected polymers enable high temperature operation and the ceramic nanoparticles enhance volumetric efficiency by increasing the dielectric constant. The fabricated films are directly adaptable to conventional wound film capacitor construction methodologies.
This paper provides an overview of TPL's experience to-date with a film dielectric material system comprised of fluorenone polyester polymer and titanate nanoparticle filler. The fluorenone polyester polymer was selected to provide a stable operating temperature of at least 300°C, while the addition of the titanate powder increases the dielectric constant and, in turn, the volumetric efficiency of wound film capacitors constructed with this film system. The targeted device for the film is a 500 to 800 V filter capacitor for high temperature power conditioning applications.
Edge-Controlled Mechanical Failure of Si and SiC Semiconductor Chips†
Authors: Wereszczak A. A. , Jadaan O. M. , Kirkland T. P. 
Published: October 2015

Silicon (Si) and silicon carbide (SiC) semiconductor chips are subjected to thermal gradients during service, have coefficient of thermal expansion mismatches with the constituents they are attached to, and are therefore subjected to thermomechanical tensile stresses that can initiate their fracture. Because of inherent brittleness, their probabilistic (Weibull) tensile failure strength was examined to understand sustainable tensile stresses and any exhibition of strength-size-scaling. Failure stress testing of entire (10-mm-square) chips was conducted using uniaxial flexure (3-point-bending) and biaxial flexure (anticlastic bending). The advantage of the anticlastic bend test is all eight primary edges are subjected to identical sinusoidal stress distribution so tensile failure stress is concurrently sensitive to edge-state quality, surface-state quality, crystallographic orientation, and any strength anisotropies of any of those.
Tensile stress tolerance of both Si and SiC chips was limited by extrinsic strength-limiting flaws located at their edges and on lapped surfaces too in the case of the Si. Both materials exhibited strength-size scaling; namely, a larger chip is likely to fail at a lower tensile stress. The anticlastic bend test method was effective for evaluating edge failure stress provided surface-type strength-limiting flaws were not dominant. Edge-strength anisotropy (i.e., crystallographic orientation dependence) was observed with both the Si and SiC chips. Surface-strength anisotropy also occurred with Si chips because one side was lapped and the other polished. Lastly, the SiC chips failed at much higher tensile stresses than Si chips; however, that strength difference could be a ramification of differences in edge-slicing quality and not necessarily from intrinsic material differences.
A Comparison of Multilayer Ceramic Capacitor Technologies for High Temperature Applications
Authors: Nies Craig , Harris Scott , Cygan Stanley 
Published: October 2015

Multilayer ceramic capacitors remain an important component in high temperature circuitry due to the general robustness of ceramics at application temperatures greater than 200°C. However, standard MLCC dielectric compositions either exhibit very low dielectric constants at high temperatures or show excessive capacitance loss with increasing temperature in this regime. Many also see a significant degradation in insulation resistance, leading to very low RC products for the materials. Stability of properties with dielectric field is also a critical factor in many applications, both for improved energy storage and capacitance per unit volume.
In recent years, a new class of weakly-coupled relaxor ceramic compositions has emerged which offer significant benefits in dielectric constant and capacitance stability at high temperatures. Tailoring of these compositions can offer increased capacitance stability over wide temperature regimes, or maximized capacitance in the high temperature (&gt;200°C) realm.
In this discussion, a comparison is made between MLCCs constructed of a standard commercial dielectric material and one of these new compositions. Emphasis on performance at high temperature and the outlook for expansion of this class is given.
Compact modeling of the high temperature effect on the single event transient current generated by heavy ions in SOI 6T-SRAM
Authors: Boufouss E. , Alvarado J. , Flandre D. 
Published: October 2015

A temperature dependence analysis of the single event transient current induced by heavy ions irradiation is performed in the range of 300K to 500K on a 1μm SOI CMOS MOSFET standard 6T-SRAM cell. The Sentaurus TCAD mixed-mode numerical simulation showed a significant impact of the temperature on the current induced by the radiation and as a result, an increase of the 6T-SRAM sensitivity upon radiation.
A SOI MOSFET compact model introduced in SPICE as a Verilog-A module reproducing the single event effects was developed. This model shows a very good agreement with the TCAD simulations results but with a drastic reduction of the simulation time. Furthermore this model could be extended to other circuits simulations. This result is of importance to allow for extensive circuit design studies which cannot be carried out with TCAD physical simulations.
HIGH TEMPERATURE HYBRID NANODIAMOND SENSOR SYSTEMS
Authors: Fraley John R. , Kegley Lauren , Minden Stephen , Davidson Jimmy L. , Kerns David 
Published: October 2015

In recent years, high temperature semiconductors have been utilized in wireless telemetry systems for use in military and commercial applications, wherein a high temperature environment combined with other factors such as rotating machinery or weight-constraints preclude the use of conventional silicon based wireless telemetry or wired sensor solutions. Present systems include those which can measure temperatures, pressures, vibrations, and strains. By combining the advanced electronics developed for these systems with novel sensor elements created using chemical vapor deposition (CVD) nanodiamond technology, a wide range of other high temperature sensing systems can be enabled.
The unique properties of the diamond sensors have proven in principle the capability to sense, with quantifiable signal, a wide variety of parameters under extreme conditions including very high temperatures and pressures. It has been clear for some time that diamond would be the ideal material of choice for solid-state sensors, but only in recent years has the advent of CVD diamond (as opposed to natural or HPHT [high pressure, high temperature] formation) opened the door for its practical development into harsh environment sensor systems. By combining these diamond sensor elements with high temperature electronics and high temperature packaging approaches, smart sensors can be developed to measure parameters ranging from gas chemical species on the surface of Venus, to neutron flux rates outside of a nuclear reactor core. The research presented here is centered around the use of hybrid diamond sensors for neutron detection applications in Nuclear Thermal Propulsion systems. The current technology state and development needs for these hybrid high temperature diamond smart sensors will be highlighted to potentially encourage future R&D from the high-temperature electronics community.