bluuebunny/crossref_metadata_2025 huggingface dataset:
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 (>95%) and high conductivity (<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.
Improved Trans-endothelial Electrical Resistance Sensing using Microfluidic Low-Temperature Co-fired Ceramics
Authors: Mercke William L. , Dziubla Thomas , Eitel Richard E. , Anderson Kimberly
Published: October 2015

Trans-endothelial Electrical Resistance (TEER) and cellular impedance measurements are widely used to evaluate the barrier properties and functional change of endothelial cell monolayers. In the current work, low temperature cofired ceramics (LTCC) are applied enabling the incorporation of TEER and impediametric measurements in an integrated microfluidic chip. LTCC materials are an ideal substrate for biomedical and cell-based microfluidics due to their biocompatibility and ability to combine complex three dimensional structures with optical, fluidic, and electrical functionality. Multilayer microfluidic ceramic devices incorporating gold measurement electrodes where prepared using standard LTCC manufacturing procedures. The sensitivity of the resulting LTCC devices were compared to systems currently on the market for TEER measurements. These results indicate the LTCC device is able to effectively detect the growth of an endothelial cell monolayer. Results further evaluate endothelial cell viability using electrical resistance and Live/Dead assay. Finally, the results from this study also display improved sensitivity through the optimization of the electrode geometry and use of a lock-in amplifier. These results provide a solid basis for using low temperature co-fired ceramic materials for microfluidic TEER devices.
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.
Multiple System Configurations in a 32-bit Extreme Environment
Authors: Brown Michael C.
Published: October 2015

Full computational systems are needed at extreme environments (to 300°C) to increase functionality and reduce cost in the ever advancing oil/gas, geothermal, aeronautic, and automotive industries. Commercially available electronic components are not available to build a reliable system. A single microcontroller device can be used in systems of varying complexity, from small, mid, large, and multiprocessor scale. The 32-bit microcontroller will use a low power silicon-on-insulator CMOS process to increase long term reliability. Communication ports are provided to allow for simple systems with a single processor to complex multiprocessor systems with multiple controlled devices and external memory. As no adequate non-volatile solution is available for extreme conditions, multiple boot options are available to load instructions from external sources. Fault tolerance should be provided by system error detection. Battery backup must be provided for program and data retention. The resulting microcontroller will allow a wide variety of extreme environment systems, from simple to complex.
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 >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.
An Ultra-Low Noise Instrumentation Amplifer Designed for High Temperature Applications
Authors: Watson Jeff , Castro Gustavo
Published: October 2015

This paper discusses a very low noise instrumentation amplifier designed specifically for high temperature applications. The device uses a proprietary silicon-on-insulator process that minimizes parasitic leakage currents at elevated temperature. Variance in device parameters are managed to maintain high performance over a wide temperature range. Layout and packaging considerations that would affect long term reliability are addressed. The amplifier is well characterized above 200°C and attains much higher performance than amplifiers not optimized for high temperature operation. Comprehensive reliability testing over temperature has been completed.
Modeling of the Punch-Through Effect in Normally-On SiC JFET used in High Temperature Inverter for Aerospace Application
Authors: Dubois Fabien , Morel Hervé , Bergogne Dominique , Meuret Régis
Published: October 2015

This paper presents a qualitative description of the punch-through mechanism in Silicon Carbide (SiC) JFET from Infineon/SiCED. A detailed one-dimensional analytical expression is derived for the current-voltage characteristic of the punch-through effect in the SiC JFET. The proposed model based on physical parameters is validated with experimental results for low current level.
Electrical Performance of Co-Fired Alumina Substrates at High Temperatures
Authors: Chen Liang-Yu
Published: October 2015

A 96% polycrystalline alumina (Al2O3) based prototype packaging system with Au thick-film metallization successfully facilitated long term testing of high temperature SiC electronic devices for over 10,000 hours at 500°C previously. However, the 96% Al2O3 chip-level packages of this prototype system were not fabricated via a commercial co-fire process which is more suitable for large scale commercial production. The co-fired alumina materials adopted by the packaging industry today usually contain several percent of glass constituents to provide better adhesion and sealing at interfaces formed during a co-firing process at temperatures usually lower than the regular sintering temperature for alumina. In order to answer the question if co-fired alumina substrates can provide reasonable high temperature electrical performance comparable to those of regular 96% alumina sintered at 1700°C, this paper reports on the dielectric performance of a selected high temperature co-fired ceramic (HTCC) alumina substrate and a low temperature co-fired ceramic (LTCC) alumina (polycrystalline aluminum oxides with glass constituents) substrate from room temperature to 550°C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. Parallel-plate capacitive devices with dielectrics of these co-fired alumina and precious metal electrodes were used for measurement of the dielectric properties of the co-fired alumina materials in the temperature and frequency ranges. The capacitance and AC parallel conductance of these capacitive devices were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of selected LTCC and HTCC co-fired alumina substrates are presented and compared to those of 96% alumina. Metallization schemes for co-fired alumina for high temperature applications are discussed to address packaging needs for low power 500°C SiC electronics.
A Cyclic RSD Analog-Digital-Converter for Application Specific High Temperature Integrated Circuits up to 250°C
Authors: Schmidt Alexander , Kappert Holger , Heiermann Wolfgang , Kokozinski Rainer
Published: October 2015

Silicon-on-Insulator (SOI) CMOS is the most commonly used technology for integrated circuits suitable for high temperatures and harsh environmental conditions. Data acquisition circuitry operating at these conditions has to consider the impact of wide temperature range operation. Therefore, the accurate operation of elementary building blocks is essential for proper system performance. To overcome the accuracy limitations set by channel leakage and performance degradation of NMOS and PMOS transistors, advanced circuit design methods are necessary. By introducing advanced leakage compensation, the overall performance of analog circuits at elevated temperatures is significantly improved. In this paper we present a cyclic analog-to-digital converter with a resolution of 12 bit, fabricated in a 1.0 μm SOI CMOS process. It utilizes the redundant signed digit (RSD) principle in a switched capacitor circuit and is thus insensitive to amplifier or comparator offset. In order to reduce the conversion error, leakage current compensated switches have been used. The ADC features two high gain operational amplifiers. Thereby a gain of more than 110 dB over the whole temperature range has been realized. The ADC's performance has been verified up to 250°C with an input voltage range from 0 V to 5 V. Preliminary results report an accuracy of more than 10 bits with a conversion rate of 1.25 kS/s. The supply voltage is 5 V with a maximum power consumption of 3.4 mW for the analog part of the circuit. The ADC is intended as an IP module to be used in customer specific mixed signal integrated circuits.
High Temperature Ageing of Fe-based Nanocrystalline Ribbons
Authors: Martin Christian , Robutel Rémi , Buttay Cyril , Sixdenier Fabien , Bevilacqua Pascal , Morel Hervé , Meuret Régis
Published: October 2015

The impact of long-term high-temperature stress on nanocrystalline Finemet materials is measured by keeping samples at 200 °C for 1300 hours. The standard industrialized, high permeability Finemet materials as well as the recently available low permeability Finemet materials are investigated. Characterizations are performed at different frequencies, temperatures and magnetic field excitations on both aged and non-aged samples. Their complex permeability is also measured during the ageing test. Irreversible changes are pointed out on permeability, coercive field and magnetic flux density at saturation. Regarding the design considerations for high temperature power electronics, the suitability of these materials is demonstrated but an ageing effect has to be considered nonetheless. The presented data can be extrapolated to several thousand hours at 200 °C using the presented empiric ageing law.
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, < 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.
Robust Class-I BME Ceramic Capacitors for High Temperature Applications
Authors: Gurav Abhijit , Xu Xilin , Magee Jim , Franklin Jeff , Ashburn Travis
Published: October 2015

In capacitors for applications at temperatures of 150°C or above, such as automotive under-the-hood electronics and power electronics, a robust dielectric material is necessary. In traditional X8R ceramic capacitors (EIA specification, ΔC/C within ±15% between −55°C and +150°C compared that at 25°C), the dielectric material is designed for applications up to 150°C. However, at temperatures above 150°C, the X8R capacitors typically suffer from degradation of reliability performance and severe reduction in capacitance, especially under DC bias conditions. Recently, a Class-I C0G dielectric has been developed using Nickel electrodes for high temperature application up to 200°C. Due to its linear dielectric nature, this material exhibits highly stable capacitance as a function of temperature and voltage. Multi-layer ceramic capacitors (MLCC) made from this material can be qualified as X9G with robust reliability. This paper will report electrical properties and reliability test data on these Class-I C0G ceramic capacitors at temperatures ≥150°C. In addition, test data from D-E curves and energy density measurements will be reported along with a discussion of possible mechanisms behind the robust reliability of this material.
1200 V 6 A High Temperature SiC BJTs
Authors: Lindgren Anders , Domeij Martin
Published: October 2015

Silicon carbide (SiC) bipolar junction transistors (BJTs) are normally-off devices which can block high voltages at high temperature operation. The SiC BJTs can be switched very fast with low losses [2] compared to BJT's made in silicon (Si), and can be operated at temperatures up to and above 250 °C. Vertical 1200V 6A rated NPN SiC BJTs were fabricated and packaged in a high-temperature capable metal package of the type TO-258. The transistors were characterized both statically and in terms of switching. A SPICE model was developed for the transistors, including the parasitic capacitances of the internal pn-junctions, as well as temperature dependence of the current gain and the collector series resistance. Switching measurements were performed showing VCE voltage rise- and fall-times in the range of 20 ns. The switching behavior is in qualitative agreement with SPICE simulations.
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 (>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.
High-Temperature, Bulk-CMOS Integrated Circuits for a Distributed FADEC System
Authors: Majerus Steve , Howe Daniel , Garverick Steven , Hiscock David , Merrill Walter
Published: October 2015

The greatest roadblock to distributed engine control development is the lack of high-temperature, high-reliability electronic components. Four integrated circuits (ICs) have been developed to provide sensing, actuation, and power conversion capabilities in a high-temperature (over 150°C) environment. Patented high-temperature techniques facilitate designs in a conventional, low-cost, 0.5-micron bulk CMOS foundry process. The HHT104 eight-channel instrumentation IC measures LVDTs, RTDs, thermocouples, and other sensors with up to 12-bit resolution. Dual sigma-delta converters and independent, programmable gain allow simultaneous conversion of two differential-output sensors. A stimulus driver may be used to drive bridge sensors with AC excitation and a temperature-stabilized oscillator provides 1.5- and 24-MHz system clocks for microprocessor use. The HHT212 current driver IC may be used to control two motors in full-bridge configuration or four independent half-bridge loads. Each channel is capable of driving up to 300 mA with 12-bit resolution. An internally-generated, temperature-stabilized current reference minimizes external components. The output current is programmed using a SPI serial interface, and the chip has built-in over-current and over-temperature protection. The HHT250 is a quad load driver featuring an integrated PWM controller, push-pull outputs and flexible drive capability. The HHT300 quad-output switched-mode power supply IC implements a compact power solution for multi-voltage microprocessors, sensors, and actuators. The external part count is minimized using integrated output FETs and a novel voltage feedback topology. Synchronous rectification reduces power dissipation and improves current capacity. Each channel has a pin-programmable output voltage and may be independently enabled for power supply sequencing.
Piezoelectric Structural Sensor Technology for Extreme Environments
Authors: Lapsley Michael Ian , Alberta Edward F. , Sahul Raffi , Hackenberger Wesley , Jiang Xiaoning , Zhang Shujun , Shrout Thomas
Published: October 2015

High temperature sensors are desired for down-hole well monitoring, future propulsion components, as well as improving performance and maintainability of power production facilities and other rotary combustion engines. Recently discovered high temperature oxyborate crystals showed stable piezoelectric properties and high resistivity at temperatures close to its melting point (∼ 1500°C, or 2730°F ), which is very promising for high temperature sensor applications. In this paper the feasibility of using oxyborate based high temperature piezoelectric crystal (HTPC) for high temperature piezoelectric sensor applications is demonstrated. Oxyborate HTPC with various crystal cuts and vibration modes were investigated to obtain high temperature resistivity, dielectric, piezoelectric and thermal expansion properties. YCa4O(BO3)3 crystals (YCOB) showed excellent piezoelectricity, low dielectric loss and high resistivity at temperatures up to 1000°C (> 1800°F). The measured thermal expansion coefficients of YCOB are about ∼3–8 ppm/K, depending on different orientations. High temperature accelerometers were demonstrated using YCOB HTPC at temperatures up to 1000°C with sensitivity remaining steady (∼ 2.4 pC/g) across the temperature range of 20°C-1000°C.
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.
Comparison of High Temperature Operation of Silicon Carbide MOSFETs and Bipolar Junction Transistors
Authors: Richmond Jim , Ryu Sei-Hyung , Zhang Qingchun (Jon) , Hull Brett , Das Mrinal , Burk Albert , Agarwal Anant , Palmour John
Published: October 2015

Power devices based on Silicon Carbide (SiC) have unmatched potential for extending the operational temperature range of power electronics well past what is possible with silicon devices. SiC JBS diodes are already demonstrating part of that potential but the full benefit will not be realized until a SiC power switch is available. Recently, normally off SiC unipolar and bipolar switching devices have become available with the manufacture of 1200V, 20A MOSFETs and 1200V, 20A bipolar junction transistors (BJT). While both of these device types have undergone considerable study, most of this characterization has been conducted in the normal commercial temperature range which has an upper limit of 150 – 175°C. The SiC BJT is considered to be a superior device for high temperature operation due to its lower on-state voltage and increased reliability due to it not having a gate oxide. As presented, the advantages of the SiC BJT over the SiC MOSFET are not as great as expected and may not warrant the increased complexity of dealing with the current driven base that the BJT requires. Otherwise, both devices offer exceptional performance at high temperature.
Capacitor Characterization Study for a High Power, High Frequency Converter Application
Authors: Lanter William C. , Kosai Hiroyuki , Bixel Tyler , Tolson B. Allen , Stricker Jeffery , Scofield James , Brar Navjot , Ray Biswajit
Published: October 2015

Recent advances in SiC power devices and high temperature magnetic and insulation materials has led to an increase in activity to develop compact, high switch rate power system components that can operate at temperatures in excess of 200°C. These efforts have highlighted the need to develop capacitor technology for high power, high frequency power filter applications, which can experience cycling over a wide range of temperature (−55 °C to 250 °C). A modeling and simulation capability was used to investigate device architecture and electrical performance relationships for a select group of wound and stacked devices, which were then evaluated for use in a power conditioning application. A finite element analysis of the device architectures was used to develop a better understanding of how magnetic fields and thermal profiles affect the performance of the capacitors in maintaining a low ripple voltage at high switch rates (>20 kHz). Both predicted electrical properties and empirical data were utilized as SPICE simulation input parameters to evaluate the performance of the different capacitors in an interleaved DC-DC boost converter model. Of interest is developing a better understanding of how the device architecture and its electrical properties affect its performance as a filtering device in a high power, high frequency application.
Swelling Phenomena in Sintered Silver Die Attach Structures at High Temperatures: Reliability Problems and Solutions for an Operation above 350°C
Authors: Heuck N. , Müller S. , Palm G. , Bakin A. , Waag A.
Published: October 2015

A very effective method to bond an electronic device to a substrate is the pressure assisted sintering of a sub-micron silver paste at temperatures between 150°C and 300°C. This technique-sometimes called “Silver-Sintering” or “Low Temperature Joining Technique (LTJT)” is already used in many power electronics industry applications. It provides die attach layers with excellent pull-strength of more than 100 MPa at room temperature and 30 MPa at 300°C. Additionally the electrical and thermal conductivity is nearly as good as it is in pure silver. Such sintered die attach layers are said to be stable up to temperatures above 500°C, but no detailed investigations in this temperature range are available up to now. Our recent investigations by shear- tests on monometallic chip/substrate-samples and dilatometer measurements showed a non-linear thermal expansion of the sintered structures above 350°C including a strong irreversible expansion of the whole sintered structure after long term heat treatments. Beyond the investigations on the swelling effect itself we present studies on the relationship between the expansion of the sintered layer and the resulting layer properties. Finally we discuss possibilities to take advantage out of this effect and additionally analyze options to reduce the swelling by adding SiC-particles to the silver paste. As a result, we demonstrate that swelling of the silver paste has to be taken into consideration when silver sintering is to be used for device operation temperatures above 350°C.
High Temperature (250 °C) Silicon Carbide Power Modules With Integrated Gate Drive Boards
Authors: Reese B. , McPherson B. , Shaw R. , Hornberger J. , Schupbach R. , Lostetter A. , Rowden B. , Mantooth A. , Ang S. , Balda J. , Okumura K. , Otsuka T.
Published: October 2015

Arkansas Power Electronics International, Inc., in collaboration with the University of Arkansas and Rohm, Ltd., have developed a high-temperature, high-performance Silicon-Carbide (SiC) based power module with integrated gate driver. This paper presents a description of the single phase half-bridge module containing eight Rohm 30 A SiC DMOSFETs in parallel per switch position. The electrical and thermal performance of the system under power is also presented.
Using Parallel High Voltage Multipliers for 100kV Downhole Neutron Generator Power Supplies
Authors: Hanington Gary
Published: October 2015

Operating 100kV downhole neutron tube power supplies at temperatures above 175 °C yield low operating efficiency due to excessive diode leakage in the series Cockroft - Walton multipliers typically used. Such circuits are usually limited to less than twelve stages due to N3 voltage regulation effects resulting in immoderate potentials across the switching rectifiers. This paper discusses the merits of using parallel multipliers with 30 stages or more to achieve higher conversion efficiencies at elevated temperatures in tools with 1.3 inch (32mm) diameters. By minimizing the per-stage voltage, definite improvements are realized due to reductions in reverse current leakage per device. Efficiencies of up to 32% may be achieved at 200 °C operating temperature by this technique. In addition, ripple voltages present on the output are not a function of the number of multiplying stages in parallel designs.
Demonstration of SiC Pressure Sensors at 750 °C
Authors: Okojie Robert S. , Lukco Dorothy , Nguyen Vu , Savrun Ender
Published: October 2015

We report the first demonstration of MEMS-based 4H-SiC piezoresistive pressure sensors tested at 750 °C and in the process confirmed the existence of strain sensitivity recovery with increasing temperature above 400 °C, eventually achieving near or up to 100 % of the room temperature values at 750 °C. This strain sensitivity recovery phenomenon in 4H-SiC is uncharacteristic of the well-known monotonic decrease in strain sensitivity with increasing temperature in silicon piezoresistors. For the three sensors tested, the room temperature full-scale output (FSO) at 200 psig ranged between 29 and 36 mV. Although the FSO at 400 °C dropped by about 60 %, full recovery was achieved at 750 °C. This result will allow the operation of SiC pressure sensors at higher temperatures, thereby permitting deeper insertion into the engine combustion chamber to improve the accurate quantification of combustor dynamics.
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.
A Low Power, Precision SAR Analog to Digital Converter for High Temperature Applications
Authors: Watson Jeff , Pachchigar Maithil
Published: October 2015

A growing number of industries are calling for low power electronics that operate reliably at temperatures of 175°C and higher. Many of these applications require a precision data acquisition signal chain in order to digitize analog data so that it can be collected and processed. Designing circuits that meet these needs can be very challenging, requiring a data converter that can deliver high performance and reliability in these harsh environments. There are currently a very limited number of integrated circuits commercially available that are specified for operation at these temperatures, and no low power precision data converters with sample rates greater than 100kSPS. This paper presents a new 210°C rated precision analog to digital converter capable of sample rates up to 600 kSPS with 16 bit resolution while maintaining low power consumption and packaged in a small form factor. We will explore the converter architecture of this ADC, present initial test results, and show how high reliability is achieved through qualification and advanced packaging techniques.
Design and Assembly of High Temperature Distributed Aero-engine Control System Demonstrator
Authors: Riches S T , Warn C , Cannon K , Rickard G , Stoica L , Johnston C
Published: October 2015

This paper covers the development of a distributed high temperature electronics demonstrator for integration with sensor elements to provide digital outputs that can be used by the FADEC (Full Authority Digital Electronic Control) system or the EHMS (Engine Health Monitoring System) on an aircraft engine. This distributed electronics demonstrator eliminates the need for the FADEC or EHMS to process the sensor signal, which will assist in making the overall system more accurate and efficient in processing only digital signals. This will offer weight savings in cables, harnesses and connector pin reduction.

The design concept was to take the output from several on-engine sensors, carry out the signal conditioning, multiplexing, analogue to digital conversion and data transmission through a serial data bus. The unit has to meet the environmental requirements of DO-160 with the need to operate at 200°C, with short term operation at temperatures up to 250°C.

The work undertaken has been to design an ASIC based on 1.0μm Silicon on Insulator (SOI) device technology incorporating sensor signal conditioning electronics for sensors including resistance temperature probes, strain gauges, thermocouples, torque and frequency inputs. The ASIC contains analogue multiplexers, temperature stable voltage band-gap reference and bias circuits, ADC, BIST, core logic, DIN inputs and two parallel ARINC 429 serial databuses. The ASIC was tested and showed to be functional up to a maximum temperature of 275°C.

The ASIC has been integrated with other high temperature components including voltage regulators, a crystal oscillator, precision resistors, silicon capacitors within a hermetic hybrid package. The hybrid circuit has been assembled within a stainless steel enclosure with high temperature connectors. The high temperature electronics demonstrator has been shown to operate from −40°C to +250°C.

This work has been carried out under the EU Clean Sky HIGHTECS project with the Project being led by Turbomeca (Fr) and carried out by GE Aviation Systems (UK), GE Research – Munich (D) and Oxford University (UK).
230°C Accelerometer with Digitized Output for Directional Drilling
Authors: MacGugan Douglas C. , Abbott Eric C. , Milne J. Chris
Published: October 2015

Measurement-While-Drilling (MWD) technology for oil and gas, and geothermal directional drilling exploration is pushing into ever higher temperature environments - beyond 200°C. Orientation sensors supporting these high temperature environments need to provide highly accurate elevation and tool face measurements on the order of 0.1°. Honeywell has developed a new digital high temperature down-hole accelerometer, DHTA230, capable of providing the required accuracy at the elevated temperatures of 230°C, in the rugged MWD shock and vibration environment, with expected excellent reliability and life.

The DHTA230 is designed for use in the downhole environment, but is based upon a mature Honeywell accelerometer using dual vibrating beam sensing elements. These sensing elements are configured as double-ended-tuning-forks in a push-pull orientation attached onto a pendulous proof mass. This push-pull configuration provides an acceleration signal proportional to the frequency difference of the vibrating beams, an easily captured digital signal through measurement of the two vibrating beam phases. The digitized accelerometer eliminates the need for A/D electronics in the high temperature drilling environment. The DHTA230 is 0.79” in diameter with a depth of .393” at the mount flange. The ruggedized configuration of the DHTA230 is expected to provide reliable orientation measurement in high temperature direction drilling applications up to 1000h.

The DHTA230 electronics incorporate ceramic hybrids with chip and wire construction. Active die are based upon proven 300°C chips developed previously for the Enhanced Geothermal Systems OM300, fabricated using Honeywell HTSOI4 process. The electronics include power conditioning providing reliable operation using a single power supply between 7V and 15V. Dual oscillator electronic circuits provide the necessary function to drive and sense the dual vibrating beams, while providing a CMOS logic level signal of the frequency pulse train. The accelerometer provides precision output up to 15g acceleration inputs, and allows sensing of higher-g vibration levels.

This paper contains information on the target application, electrical and mechanical component requirements, design, fabrication approach, and initial prototype testing. The DHTA230 is expected to enter production transition in 2015.
HPHT cased-hole CCL tool enhancement via DSP techniques for accurate depth control in wire-line well interventions
Authors: Mijarez Rito , Pascacio David , Guevara Ricardo , Tello Carlos , Pacheco Olimpia , Rodríguez Joaquín
Published: October 2015

Down-hole oil and gas operators require a precise depth control method during well interventions. Wire-line technologies using conventional cased-hole casing collar locator (CCL) tools have been proven effective. However, extremely high pressure and high temperature (HPHT) environments make this a challenging task. This work describes a HPHT down-hole tool that use a conventional inductive CCL enhanced by a DSP based electronic module that performs in real-time DSP techniques such as digital filtering and cross-correlation, which permit to store and transmit analog or digital information to a data acquisition system located in the surface. The obtained laboratory tests results of the enhanced CCL down-hole tool, using changes in temperature from 75 °C – 185 °C, provide a firm basis for testing and evaluating the system in the field.
Characterization of AgBiX™ Solder Paste on Thick Film for 200°C Applications
Authors: Shen Zhenzhen , Johnson Wayne , Hamilton Michael C.
Published: October 2015

AgBiX™ (Indium Corporation) solder paste has a solidus temperature of ∼262°C after reflow, which is suitable for passive component, semiconductor and power die attach for 200°C applications. In this work, the paste has been used to assemble SiC die with Ti/Ni/Ag thin film metallization to Ag and PdAg thick film substrates. High temperature storage testing (200°C) was preformed to characterize the reliability of the assemblies. Surface mount chip resistors attached to thick film substrates were also subject to high temperature storage. Comparisons of the performance of die attach and resistor attach on Ag substrates and PdAg substrates are made. EDX and failure analysis was used to understand the role of Pd on the failure mode and lower aged shear strengths with the thick film PdAg conductors.
Reliability and Corrosion Resistance of High Temperature Lead-Free BiAgX™ Paste
Authors: Zhang HongWen , Mao RunSheng , Lee Ning-Cheng , Tanimoto Satoshi
Published: October 2015

The BiAgX™ paste, designed for die attach application, composed of the majority of BiAg powders (melting point >260°C) and the minority of additive powders. The additive powders are dominating the interfacial reaction to improve the wetting of the paste on various commonly-used surface finish materials. After reflow, the joint shows the above 260°C remelting temperature. The average bond shear strength of BiAgX joint between SiC die and AMBC-SiN substrate (Package A) decreases from 54MPa to 16MPa with increasing temperature from RT to 250°C. Upon thermal storage at 200°C or 230°C for 3000hrs, the bond shear strength decreases from 54MPa to 38MPa and 21MPa, respectively. Upon thermal cycling from −55°C to 125°C for 2000cycles and thermal shock from −55°C to 150°C for 2000cycles, BiAgX outperforms Pb5Sn2.5Sn (Package B). BiAgX also show the better corrosion resistance than SAC305 and Pb5Sn2.5Ag under 96hrs salt water spray (SWS) tests.
A High Current (>1500A) Power Module for High Temperature, High Performance Applications Using SiC TMOS Power Switches
Authors: Passmore B. , Hornberger J. , McPherson B. , Bourne J. , Shaw R. , Cilio E. , Cilio W. , Reese B. , McNutt T. , Schupbach M. , Lostetter A.B.
Published: October 2015

A high temperature, high performance power module was developed for extreme environment systems and applications to exploit the advantages of wide bandgap semiconductors. These power modules are rated > 1200V, > 100A, > 250 °C, and are designed to house any SiC or GaN device. Characterization data of this power module housing trench MOSFETs is presented which demonstrates an on-state current of 1500 A for a full-bridge switch position. In addition, switching waveforms are presented that exhibit fast transition times.
High Temperature capable SiC Schottky diodes, based on buried grid design.
Authors: Hjort Tomas , Schöner Adolf , Zhang Andy , Bakowski Mietek , Lim Jang-Kwon , Kaplan Wlodek
Published: October 2015

Electrical characteristics of 4H-SiC Schottky barrier diodes, based on buried grid design are presented. The diodes, rated to 1200V/10A and assembled into high temperature capable TO254 packages, have been tested and studied up to 250°C. Compared to conventional SiC Schottky diodes, Ascatron's buried grid SiC Schottky diode demonstrates several orders of magnitude reduced leakage current at high temperature operation.