bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of thick-film resistors for manufacturing piezoresistive sensors
Authors: Maeder Thomas , Jacq Caroline , Ryser Peter
Published: October 2015

A complete line of resistors materials are tested for the manufacture of thick-film piezoresistive sensors and associated simple adjustment / amplification circuits: 10 kΩ compositions for the gauge resistors, together with 100 Ω and 100 kΩ ones for electronics and trimming, as well as PTC compositions for temperature compensation. Several aspects are considered, such as process sensitivity, overglazing and trimming.
Multi-layer Tunable Capacitors Fabricated by Thick Film Processes
Authors: KAGEYAMA Keisuke
Published: October 2015

Multi-layer cofired tunable capacitors (MLCTC) were fabricated with MLCC thick film technology. (Ba,Sr)TiO3 (BST) has been utilized as a tunable material. We compared the tunability of BST plate sample with that of MLCTC. Though the tunability of BST plate sample was about 80% at 5V/μm, that of MLCTC suddenly decreased at 3V/μm. This might be caused by stray capacitance of MLCTC because of high dielectric constant of via layers. In this paper, basic concepts of MLCTC and properties of tunable capacitors which have been fabricated with thick film processes are described, and further discussion to decrease stray capacitance will be discussed.
Effect of platinum metallization in cofired platinum / alumina microsystems for implantable medical applications
Authors: Karbasi Ali , Hadjikhani Ali , Jones W. Kinzy
Published: October 2015

Typically, hermetic feedthroughs for implantable devices, such as pacemakers, use an alumina ceramic insulator brazed to a platinum wire pin. This material combination has a long history in implantable devices and is the desired structure due to the acceptance by the FDA for implantable hermetic feedthroughs. The growing demand for increased input/output (I/O) hermetic feedthroughs for implantable neural stimulator applications can be addresses by developing a new, co-fired platinum/alumina multilayer ceramic technology in a configuration that supports 300 plus I/Os, which is not commercially available. Different densification rate of platinum and alumina is the major issue in developing a high-density feedthrough. This difference in densification rate could create delamination and crack in feedthrough structure and decrease the reliability and degree of the hermeticty of the final assembly. In this paper different metallization were evaluated to minimize this difference. Additionaly the firing atmosphere and the firing profiles were evaluated to minimize this difference. FIB nano-machining and SEM with EDS were used for the analysis of these conditions.
All-Crystal-State Lithium-Ion Batteries: Innovation Inspired by Novel Flux Coating Method.
Authors: Teshima Katsuya , Wagata Hajime , Oishi Shuji
Published: October 2015

All-solid-state lithium-ion rechargeable batteries (LIBs) consisting of solid electrolyte materials have attracted a number of research interests because no use of organic liquid electrolyte increases packaging density and intrinsic safety of LIB, which contribute the development on environmentally-friendly automobiles such as electric vehicle (EV), hybrid vehicle (HV), and plug-in hybrid vehicle (HEV), in addition to efficient utilization of electric energy in smart grid. Among various solid electrolytes, inorganic electrolyte materials have achieved relatively high lithium-ion conductivity and better stability at an ambient atmosphere. Nevertheless, there is a drawback that is relatively high internal resistance owing to relatively slow Li ion movement caused by low crystallinity of materials, scattering at interfaces such as current collector/electrode active materials and electrode active materials/electrolyte materials. In this context, we have proposed a concept, all-crystal-state LIB, in which all the component materials have high crystallinity and those interfaces are effective for Li ion diffusion. Here, we present the fabrication of oxide crystals and crystal layers via flux method and flux coating. Flux method is one of the solution processes in which idiomorphic highly crystalline materials can be obtained under the melting point of the target ones. In addition, it provides simple, low-cost and environmentally-benign pathway compared to conventional solid-state-reaction method. Flux coating method is developed to fabricate high-quality crystal layers (films) on various substrates. High-quality crystals and crystal layers of cathode, anode and electrolyte materials were successfully fabricated.
Electrostatic Dry Coating of Cathode Materials for Li ion battery
Authors: Abe Hiroya , Kondo Akira , Naito Makio , Wakimoto Takashi , Yamaguchi Masayuki
Published: October 2015

Organic solvents are widely used in wet coating for manufacturing Li ion batteries. This study focused on switching to environmentally benign solvent-free process, and examined a possibility of electrostatic dry coating (EDC) of cathode materials which are generally composed of active oxides, conductive and binder additives. Firstly, the composite particles containing the three components were prepared by dry mechanical treatment, and then EDC experiment was performed for the composite particles. Interestingly, the composite particles could be tribo-charged enough for electrostatic deposition on an earthed Al foil in air, with relatively high deposition rate. The as-deposited film was further dry-pressed to increase the film density (3 × 103kg/m3). A half cell was assembled using the pressed film as cathode electrode, and it was demonstrated that the initial charge-discharge characteristics were comparable to those obtained for wet-coated films. The results obtained indicate that there are some opportunities for the practical implementation of the EDC method for manufacturing functional composite films.
High-Temperature, Bulk-CMOS Integrated Circuits for a Distributed Control System-Performance Results
Authors: Howe Dan , Majerus Steve , Garverick Steve , Merrill Walter , Semega Ken
Published: October 2015

Four integrated circuits (ICs) have been developed to provide sensing, actuation, and power conversion capabilities in a high-temperature (200 °C) distributed control 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. A high-temperature development system has been created using the four ICs and a DSP for actuator controller prototypes. A reference application was implemented using this system to drive a torque motor using LVDT position feedback.
A Design Paradigm to Facilitate Multiple Parts from a Single Silicon Design
Authors: Rea Richard N.
Published: October 2015

To reduce overall design complexity and cost for RAM, a design paradigm is discussed that is based on a single silicon device containing multiple, configurable interfaces with a common RAM core. This will help bring to market more devices that operate in extreme environments. The cost per die is higher due to the addition of the configurable interface, but yields a net reduction in overall engineering development time for a given product family by a factor of four to five. To demonstrate this design paradigm a family of five RAM chips built on a single silicon design is developed. They are designed for low-power consumption and highly reliable, fault-tolerant operation, while operating over a temperature range of −55 to +300 degrees C.
A Drop-in Die-Attach Solution for the High Temperature Lead-Free BiAgX Solder Paste System
Authors: Zhang HongWen , Lee Ning-Cheng
Published: October 2015

In the current work, a mixed powder BiAgX solder paste system with the melting temperature above 260°C and comparable, or better, reliability to the high lead-containing solders has been studied. The mixed powder solder paste system is composed of a high-melting first alloy solder powder as a majority and the additive solder powder as a minority. The additive solder is designed to react aggressively with various surface finish materials before, or together with, the melting of the majority solder to form a controllable IMC layer. The IMC layer of the mixed powder system is controllable by the species and quantity of the additive solder, and it is observed to be insensitive to thermal aging and thermal cycling in current tests, while the high lead-containing solders show a considerable increase in IMC layer thickness. Microstructure investigation shows that the fishbone shaped IMC layer interlocks with the bonding interface between solder and components. Both micron-sized and nano-sized Ag-rich precipitations in the joints have been observed to be well distributed in the joint. The exposed Ag-rich particles and the surrounding stepwise pattern in the Bi matrix on the fracture surface indicate that these Ag-rich particles constrain the dislocation movement in Bi matrix, enhancing the strength and the ductility of the joint. Under thermal aging and thermal cycling, both the micron-sized and nano-sized Ag-rich precipitations exhibit only discernible and localized coarsening. The stable interfacial IMC together with the existence of the well-dispersed Ag-rich particles are attributed to the promising reliability in the BiAgX solder paste system.
Thermal Stress Reliability Study on Substrates for High Temperature, Silicon Carbide Power Electronic Modules
Authors: Shaw R. , Doyle P. , Hornberger J. , Lostetter A. , McPherson B. , Procell H. , Schupbach R.
Published: October 2015

The goal of this study is to investigate packaging techniques for extreme environment (i.e., −50 °C to 250 °C) power electronics. Areas of interest include substrate materials and baseplate/heat spreader materials. Multiple substrate technologies are evaluated, including direct bond copper (DBC), direct bond aluminum (DBA), and active metal braze (AMB) substrates. When possible, varying thicknesses of ceramic and metal layers are included to determine if that parameter affects reliability. Within each material and thickness sample lot, different layout geometries and overall sizes are tested, again to determine if that specific parameter has an impact on reliability. In a power electronics application, these substrates are required to be attached to a baseplate/heat spreader for mechanical support and to improve thermal performance. Therefore, a smaller sample size of substrate materials was also tested for reliability when soldered to a metal matrix composite (MMC) baseplate. To evaluate the reliability of said materials, several inspection methods are utilized, comprising of scanning acoustic microscopy (SAM), optical microscopy, florescent penetrant inspection, cross section analysis, and optical profilometery.

This paper will present the results of thermal stress studies on each of the materials under varying conditions. The conditions include: thermal dwell conditions of 250 °C in excess of 1000 hours and thermal cycling from −50 °C to 250 °C in excess of 1000 cycles. Current results will be presented and discussed.
Characterization and Reliability Testing on an LTCC Transformer Operable to 250 °C
Authors: Galipeau James , Slama George
Published: October 2015

Environments prone to vibration and shocks can cause premature failure in small wire-wound transformers due to cracked cores and broken wires. These problems are only exacerbated by temperatures exceeding 200 °C where the heat causes organic compounds to age rapidly. As more electronics are used in harsh, high temperature environments, high reliability, compact transformers for use in power, filtering, and isolation applications are needed. To address this need monolithic low-temperature co-fired ceramic transformers were developed. In this work transformers were made from a low-temperature, co-fire compatible, ferrite with a Curie temperature of 350 °C. The transformers were first subjected to a 2,000 hour life test at 250 °C in which the transformer was used to charge a load capacitor once every two seconds. The inductance, resistance, core loss, and saturation flux density of the transformers were measured at various temperatures. Additional testing focused on the effect of temperature on the device's frequency profile and performance changes under thermal cycling.
A High Temp standalone 4MByte Flash memory with SPI Interface for 210C applications
Authors: VonBergen Wade , Basude Madhu
Published: October 2015

This paper covers the internal architecture, testability & performance characterization of Texas Instruments ™ High-Temp 210C 4MByte standalone Flash storage device. It will be available in a 14-pin ceramic dual Flat pack package as well as a Known Good Die (KGD) option. The device is manufactured in TI's 180nm 1.8V flash process with 3.3V IOs. The design implements 8 banks of flash organized into 2M × 16 bits surrounded by a SPI controller. The SPI controller interfaces asynchronously with an internal flash controller. The flash controller is clocked by FCLK, and controls the flash charge pump to access & operate the flash to program, read, erase, validate etc. The SPI controller is responsible for translating and executing the high level SPI protocol commands to the internal flash controller & its registers. A simple and flexible protocol was developed to access the flash array via the SPI supporting various commands and configuration capabilities. Testability of critical parameters for reliable 210C flash operation is ensured with the implementation of an internal test port accessible through a parallel interface (for TI Internal use only). The test port, and a SPI initiated BIST controller are used to provide full & comprehensive characterization of the flash bit cell array, as well as the flash-pump across temperature & frequencies. The form factor, size, and pin out of this flash device is primarily focused on data logging for narrow & space limited extreme harsh environments such as the down-hole drilling industry.
High temperature anti short circuit function for normally-on SiC JFET in an inverter leg configuration
Authors: Falahi Khalil El , Phung Luong Viêt , Allard Bruno , Bergogne Dominique , Dubois Fabien
Published: October 2015

The SiC JFET is commercially available as a normally-on device. In an inverter leg configuration, many temperature effects must be compensated. Moreover, specific safety functions have to be implemented and the JFET drivers are generally the best locations to implement latter requirements. The paper describes experimental results about a SOI CMOS core driver operated up to 250°C. Particularly, an option is presented to compensate for the decrease in the driver output current with temperature. It is also demonstrated primary results of the integration of an anti short-circuit solution previously verified as a hybrid vehicle. It is shown that the reactivity of the safety function is reduced to less than 5μs at 250°C compared to 100μs in earlier vehicle at 200°C.
SLID Bonding for Energy Dense Applications – Thermo-Mechanics
Authors: Larsson Andreas , Tollefsen Torleif André
Published: October 2015

Solid-Liquid Inter-Diffusion (SLID) bonding is traditionally a technology used for high performance and high reliable die attach/interconnect applications. The generic properties of SLID allows the bonding to occur at a relatively low process temperature. However, when the bond is completed, the final joint has a melting point well above the process temperature. This makes it well suited as for high performance electronic assemblies. The typical bonding temperature of Cu-Sn SLID and Au-Sn SLID are 250–300 °C and 320–350 °C respectively. These temperatures compare to that of other high temperature (HT) electronic adhesives e.g. Staystik® 101G. The thermal performance of the SLID bond is superior to other electronic interface materials. This is due to the thin joint (∼ 10 μm) and the high thermal conductivity (∼ 60 W/m·K for Au-Sn). Thus, the thermal resistance of a SLID joint, about 2×10−3 cm2·K/W, is significantly lower than most other thermo-mechanical joints suitable for use in electronic assemblies. SLID joints have also proven to be mechanically robust for harsh environment applications.

In this study the thermo-mechanical properties of large Cu-Sn SLID bond are investigated. Simulations are performed to explore the stationary thermo-mechanical performance of the joint. Finite element analysis (FEA) is used to perform the simulations. The study is based on a case study involving a HT (> 200 °C) power controller device for a brushless DC motor for downhole applications. The effective strain was found to be high in the bond adjacent Cu layers but reasonably small, < 1%, within the joint itself.
Large-area Nanosilver Die-attach by Hot-pressing Below 200°C and 5 MPa
Authors: Xiao Kewei , Calata Jesus N. , Zheng Hanguang , Ngo Khai D.T. , Lu Guo-Quan
Published: October 2015

Sintered nanoscale silver joint is an emerging lead-free die-attach solution for high-temperature packaging because of silver's high melting temperature. For bonding small chips, the nanosilver solution can be achieved with a simple heating profile under atmospheric pressure. However, for bonding large-area chips, e.g. > 1 cm2 IGBT chips, uniaxial pressure of a few MPa has been found necessary during the sintering stage of the bonding process, which is carried out at temperatures below 275°C. Hot-pressing at high temperatures can cause significant wear and tear on the processing equipment, resulting in high maintenance cost. In this study, we ran a series of experiments aimed at lowering the hot-pressing temperature. Specifically, we examined a process involving hot-press drying, followed by sintering without any applied pressure. A fractional factorial design of experiments was used to identify the importance and interaction of various processing parameters, such as hot-pressing pressure/temperature/time and sintering temperature/time, on the final bond quality of sintered nanosilver joints. Based on the results, a simpler process, consisting of hot-press drying at 180°C under 3 MPa, followed by sintering at 275°C under atmospheric pressure was found to produce attachments with die-shear strength in excess of 30 MPa.
High-temperature Characterization of a 1200 V Power Module with 36 mm2 of SiC VJFET Area
Authors: Speer Kevin M. , Schrader Robin , Sheridan David C. , Lemmon Andrew , Gafford Jim , Parker Chris , Mazzola Michael S. , Casady Jeffrey B.
Published: October 2015

This is the first high-temperature static and dynamic characterization of a half-bridge power module using 1200 V, 45 mΩ depletion-mode vertical JFETs. With only 36 mm2 of JFET area, the peak pulsed current is measured to be nearly 500 A at room temperature (transistors not saturated), decreasing to 230 A at 250 °C (transistors saturated). Total switching losses are less than 3.2 mJ from 25 °C to 250 °C and show negligible dependence on junction temperature. The achievement of this level of performance with such a small SiC transistor area is important, since die area directly impacts achievable module footprint (system-level power density and cost), device capacitance (switching losses), and semiconductor cost.
Development of Low RON,Diff, 12 kV, 4H-SiC GTOs For High-Power and High-Temperature Applications
Authors: Cheng Lin , Agarwal Anant K. , Oloughlin Michael , Burk Al , Capell Craig , Lam Khiem , Zhang Jon , Richmond Jim , Palmour John , Temple Victor , Ogunniyi Aderinto A. , O'Brien Heather K. , Scozzie Charles J.
Published: October 2015

In this paper, we report our recently developed 1 × 1 cm2, 12 kV SiC GTOs with a very low differential on-resistance (RON,Diff) of 4 mΩ·cm2 with respect to the device active area at high injection level current of 100 A/cm2 or higher, which is more than a 40% reduction from our previously reported work. This significant reduction in the on-resistance was attributed to an improvement of carrier lifetime in the SiC bulk region. The SiC GTO was wire-bonded and attached to a high-voltage package before the high-temperature measurement. Forward characteristics of the device were then measured using a Tektronics 371 curve tracer from room temperature up to 400°C. Over the temperature range, the RON,Diff of the 4H-SiC GTO increased modestly from 4 mΩ·cm2 at 20°C to 4.7 mΩ·cm2 at 400°C, while the forward voltage drop at 100 A decreased slightly from 3.97 V at 20°C to 3.6 V at 400°C. The gate to cathode blocking voltage (VGK) was measured using a customized high-voltage test set-up. The leakage current was measured 0.66 μA at a VGK of 12 kV at 20°C.
Analog Component Development for 300°C Sensor Interface Applications
Authors: Ohme Bruce W. , Larson Mark R.
Published: October 2015

The development of Enhanced Geothermal Systems (EGS) for base-load electrical power generation will require electronics for sensing and control during exploration and drilling and also during production. The operating temperature environments for these applications will generally be more extreme than those encountered by electronics currently deployed for oil and gas development and production monitoring. To address this requirement, electronic components have been designed and fabricated for operation at temperatures of 300°C. These integrated circuits use silicon-on-insulator (SOI) fabrication processes to achieve high temperature operation. High-fidelity simulation models have been developed by characterization of SOI devices at 300°C. These device models were employed to design components required for the development of a down-hole orientation module. A wide-bandwidth, low-noise operational amplifier has been developed for use with MEMS accelerometer sensors. A multi-channel synchronous voltage-to-frequency converter with built-in reference and oscillators has also been developed for use with 3-axis flux-gate magnetometers. The components themselves are general purpose and could easily be used for other high-temperature sensor-interface applications. .
High-Temperature Versatile Voltage-Mode PWM Controller
Authors: Laplace Fabien , Montmayeur Xavier , Thomas Jérôme , Picun Gonzalo
Published: October 2015

In this paper we present the operation of the XTR30011 device, a high-temperature, versatile, PWM controller with in-specification performance achieved from −60°C to 230°C using a CMOS SOI process. The circuit features a voltage-mode PWM controller that can be used in Buck-mode converters as well as in Boost, Buck-boost, Push-pull and Flyback. Several functional features are implemented including duty-cycle limitation allowing cycle-by-cycle current limitation, hiccup short-circuit protection and complex functionalities for improved efficiency at low load currents.

These advanced features for improved efficiency include automatic synchronous-asynchronous mode transition in Buck-mode, pulse skipping logic with adjustable threshold, low-power mode with capability to receiving the 5V converter output voltage.

Efficiency in DC-DC converters operated at low load currents is dominated by switching as well as intrinsic consumption losses. The XTR3011, in addition to having a low intrinsic current consumption, allows reaching very good efficiencies at low load currents thanks to its functional features.

We present here the operation of several functional features and experimental results across temperature of the efficiency in several configuration modes, and in particular for low load currents.
High Temperature Characterization up to 450 °C of MOSFETs and basic circuits realized in a Silicon-on-Insulator (SOI) CMOS-Technology
Authors: Grella K. , Dreiner S. , Schmidt A. , Heiermann W. , Kappert H. , Vogt H. , Paschen U.
Published: October 2015

Standard Bulk-CMOS-technology targets use-temperatures of not more than 175 °C. Silicon-on-Insulator-technologies are commonly used up to 250 °C. In this work we evaluate the limit for electronic circuit function realized in thin film SOI-technologies for even higher temperatures. At Fraunhofer IMS a versatile 1.0 μm SOI-CMOS process based on 200 mm wafers is available. It features three layers of tungsten metalization with excellent reliability concerning electromigration, voltage independent capacitors, various resistors, and single-poly-EEPROMs. We present a study of the temperature dependence of MOSFETs and basic circuits produced in this process. The electrical characteristics of NMOSFET- and PMOSFET-transistors were studied up to 450 °C. In a second step we investigated the functionality of ring oscillators, representing digital circuits, and bandgap references as examples of simple analog components. The frequency and the current consumption of ring oscillators and the output voltage of bandgap references were also characterized up to 450 °C. We found that the ring oscillator still functions at this high temperature with a frequency of about one third of the value at room temperature. The output voltage of the bandgap reference is in the specified range up to 250 °C. The deviations above this temperature are analyzed and measures to improve the circuit are discussed. The acquired data provide an important foundation to extend the application of CMOS-technology to its real maximum temperature limits.
High Power Lithium Primary Cells for High Temperature Downhole Applications
Authors: Johnson Arden P. , Miller John S. , Wang Yufei
Published: October 2015

The power demands of downhole tools used in petroleum exploration continue to increase as new instrumentation is added for measurement and for communicating data to the surface. At the same time there is increasing demand for higher temperature capabilities that will allow exploration in hotter formations. As the use of high temperature electronic devices expands, new types of batteries are needed that can provide the necessary power at the higher temperatures.

Here we describe a new lithium alloy primary battery technology that can power downhole tools and other high temperature devices up to 200°C under significantly higher loads than has been possible previously. The higher rate capability of the cell also enables sufficient operation at surface ambient temperatures to allow the functioning of the tool to be assessed at the surface before it is deployed downhole. Cell discharge results over a broad range of temperatures and rates are presented.
High Temperature Lithium Alloy Cells With Improved Low Temperature Performance
Authors: Johnson Arden P. , Wang Cuiyang , Miller John S.
Published: October 2015

Lithium-thionyl chloride cells are widely used in downhole applications where the temperatures exceed 100°C. These cells cannot be used above the melting point of lithium, 180°C, but modified oxyhalide cells are available that use higher-melting lithium alloy anodes that allow safe operation at temperatures as high as 200°C. However, the higher temperature capability comes at the cost of low temperature performance; the alloy cells typically show very poor rate capability below 50°C. The low temperature rate limitations can be particularly disadvantageous in cases where a tool is started up at the surface, where the ambient temperatures are cooler, before it is placed into operation downhole.

Here we present test results defining and characterizing the capabilities and limitations of various types of lithium alloy cells at lower temperatures, as well as discharge results at higher temperatures for new cell types that have been designed for improved rate capability at both lower and higher temperatures.
The Development and Qualification of a DC-DC Converter for 225°C (437°F) Operating Temperature
Authors: Hunt Bob
Published: October 2015

This paper presents the development and qualification of high temperature electronic module packaging technology to service the requirements for extended and reliable operation at 225°C (437°F) for applications in the Oil & Gas, Automotive and Aerospace markets. It also covers the application of this technology to the first in a range of DC-DC converter modules and is based on Cissoid's ‘ETNA’ semiconductor components.
Reliability Assessment of Passives for 300C using HALT
Authors: Shaddock David , Tilak Vinayak , Zhang Tan , Zhang Rui , Johnson R. Wayne
Published: October 2015

Highly accelerated life testing (HALT) is used to quickly assess the reliability of passive components for geothermal applications operating at 300°C ambient temperature. The HALT methodology uses combined stresses to accelerate the failure of capacitors and resistors. This paper describes the test methodology, special fixture designed, and results on capacitors and resistors. Life models for the components are presented. A process to modify component terminations is presented to make them appropriate for 300°C.
“Migration of Sintered Nanosilver Die-attach Material on Alumina Substrate at High Temperatures”
Authors: Mei Yunhui , Ibitayo Dimeji , Chen Xu , Luo Susan , Lu Guo-Quan
Published: October 2015

A nanoscale silver paste that can be sintered at temperatures below 300°C without external pressure is emerging as a promising die-attach material for implementing the low-temperature joining technology in high-temperature packaging. In this paper, we report our findings on silver migration in sintered nanosilver electrode-pair patterns on alumina substrate. The electrode pairs were biased at electric field ranging from 10 to 100 V/mm and at temperature between 250 °C and 400°C in dry air. Leakage currents across the electrodes were measured as the silver patterns were tested in an oven. Silver dendrites formed across the electrode gap were observed under an optical microscope and analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Silver migration was found in samples tested at 400°C, 350°C, and 300°C, and 250°C. The measurements on leakage current vs. time were characterized by an initial incubation period, called “lifetime”, followed by a sharp rise as silver dendrites were shorting the electrodes. A rapid rise in the “lifetime” with decreasing oxygen partial pressure was also found. A simple phenomenological model was derived to account for the observed dependence of “lifetime” on electric field, temperature, and oxygen partial pressure. The reliability of sintered nanosilver die-attachment over silver migration in high temperature applications can be significantly improved through packaging or encapsulation to reduce oxygen exposure.
High Temperature Performance of Normally-off SiC JFET's Compared to Competing Approaches
Authors: Casady J.B. , Sheridan D.C. , Ritenour A. , Bondarenko V. , Kelley R.
Published: October 2015

Normally-off Silicon Carbide (SiC) power Junction Field Effect Transistors (JFETs) were compared with competing power transistor technology at temperatures from 25 °C to 150 °C as limited by the packaging. Switching energies were measured from 1200 V, 125 mΩ and 50 mΩ (room temperature) rated SiC power JFETs and compared with 900 V silicon (Si) super-junction Metal Oxide Semiconductors (MOSFETs) and 1200 V Si Insulated Gate Bipolar Transistors (IGBTs). For both comparisons, measured performance for the SiC power JFET was advantageous at all temperatures when switching at 50 kHz, including a total switching energy (ESW) of 97 μJ for the SiC JFET, compared with 158 μJ for the Si super-junction MOSFET, and 550 μJ for the Si IGBT at 25 °C. At 150°C, the ESW was 138 μJ for the SiC power JFET, 413 μJ for the Si super-junction MOSFET, and 1020 μJ for the Si IGBT. Increasing the die size of the 1200 V, normally-off SiC JFET by 2.25 resulted in an measured increase in switching energy of 2.7 and 2.37 at 25 °C and 150 °C, respectively, a quasi-linear relationship. Higher power preview products of the SiC normally-off JFET technology were also examined including a 1200 V, 25 mΩ (room-temperature rating) power JFET characterized up to 250 °C, and a module capable of 1200 V, 120 A DC performance at 25 °C.
Rugged ICs against Corrosion, Shock plus Hotter Temperatures
Authors: Wang James J.
Published: October 2015

More applications need microcontrollers to operate at higher temperatures. ICs must survive faster corrosion rate and higher stresses. Improving wire bonding, mold compound or package design requires engineering effort, long evaluation and cost. Because packages are already optimized, further optimization often does not yield the needed improvements. Without changing either chip design or the packaging, one can achieve high temperature reliability by protecting ICs with a gold, over passivation metal (OPM).

Low cost CMOS liquid crystal display driver ICs are plated with gold bumps at high volume. Similar gold plating process can be quickly and cheaply implemented over all microcontrollers. Between ICs to the electroplated gold OPM is a barrier metal that slows gold diffusion into aluminum and thereby increases operating life before Au-Al intermetallic wire bond failure. Reliability is improved 6x to 94x under different test conditions.

Ball bonding to gold pads are 10% to 40% stronger than onto aluminum pads. Furthermore, gold-gold mono-metallic bonds are ductile and can withstand stresses of extreme package reliability tests consisting of: AATC, MSL1 preconditioning, autoclave and then 190C HTB for 1000 hours. Ductile bonds can strain under mechanical stress and shock. Gold is resistant against corrosion such that packaged ICs survive reliability tests causing mold compound delamination and then moisture ingress from autoclave.
Thermomechanical Stresses in Copper Films at Elevated Temperature
Authors: Lederer Martin , Zarbakhsh Javad , Huang Rui , Detzel Thomas , Weiss Brigitte
Published: October 2015

Thermomechanical stresses in metallic films are a root cause for material fatigue which limits the lifetime of electronic devices. Since the yield stress of metals is temperature dependent, plastic deformations during thermal cycling are increased at elevated temperature. This effect reduces the reliability of electronic parts. In order to investigate this problem, a 20μm thick copper film was deposited on a silicon wafer. After annealing at 400°C, the sample was exposed to thermal cycles in the temperature range between room temperature and 600°C. The different values for the CTE of copper and silicon lead to a curvature of the sample. The wafer curvature was measured by a multi-laser beam method. On the basis of the experimental results, a new theoretical model was developed, which describes the stress evolution in the film during thermal cycling. In this investigation, the relation between wafer curvature and film stress is calculated by analogy to a model by Freund [1] which is an improvement to the well known Stoney formula. In addition to the elastic response, the new model considers plasticity of the copper film as well as temperature dependence of creep. It is demonstrated that the model can well describe the experiment and thus thermomechanical stress in copper films.
Performance of commercial SOI driver in harsh conditions (up to 200°C)
Authors: El Falahi K. , Allard B. , Tournier D. , Bergogne D.
Published: October 2015

Power electronics based on wide band gap materials, such as silicon carbide (SiC) or gallium nitride (GaN), are nowadays capable of operation at increased ambient temperatures. High Temperature Intelligent Power Modules are unfortunately not available due to a lack of integrated driver able to withstand either harsh environment or enhanced junction temperature due to reduction in the cooling system. The most appropriated technology for such a driver seems to be Silicon on Insulator (SOI). The maximum operating temperature of commercial SOI devices with conventional packaging is usually 150°C up to 175°C as specified by manufacturers. In this paper, we actually try to observe the performance and de-ratings of these SOI circuits at temperatures above 175°C.

Experimental characterization of commercial SOI MOSFET drivers from room temperature to 200°C and beyond is presented. Parameters such as output current amplitude, delay time, rise time and fall time of the output waveforms of the drivers are monitored. The test results will be discussed, and will help produce the specifications of an integrated SOI-based core-driver with the necessary functionalities to drive an inverter up to 220°C ambient temperature.
Packaging Technology for High Temperature Capacitive Pressure Sensors
Authors: Chen Liang-Yu , Beheim Glenn M. , Meredith Roger D.
Published: October 2015

High temperature pressure sensors are critical sensing elements for the next generation of intelligent aerospace engine technology, as well as long-term exploration missions to Venus, where the surface temperature is 485°C. Various high temperature pressure sensors based on different sensing mechanisms are under development at the NASA Glenn Research Center. In order to test long-term performance and reliability of these sensors in a high temperature environment, and eventually commercialize these sensors, high temperature durable and long-term reliable packaging is essential. A prototype packaging technology for micro-sensors designated for applications in high temperature and high differential pressure environments has been developed and reported previously. Packaged high temperature silicon carbide pressure sensors have been successfully tested between room temperature and 500°C. This paper reports an improved version of this packaging technology and testing results of a packaged commercial Si capacitive pressure sensor at elevated temperatures. The parasitic parameters of the packaging are electrically characterized from room temperature to 500°C at 120Hz, 1kHz, 10kHz, and 100kHz. This packaging is primarily designed for high temperature capacitive pressure sensors, but it also applies to other high temperature sensors, especially those for high differential pressure environments.
High Temperature Capacitors Based on [0001] and [1120] Sapphire Dielectrics
Authors: Chen Liang-Yu
Published: October 2015

The test results of the dielectric properties of [0001] (C-plane) and [1120] (A-plane) sapphire (single crystalline Al2O3) at high temperatures indicate that these materials have very stable dielectric constants and low dielectric losses (compared with polycrystalline alumina) at low frequencies in the temperature range from room temperature to 550°C. Therefore, sapphire materials have become likely candidate dielectric materials for high temperature capacitors. This paper reports prototype low-volume (∼100pF) capacitors based on sapphire dielectrics for high temperature and low frequency applications.

Low-volume parallel-plate capacitors using C-plane and A-plane sapphire as dielectric material were fabricated by stacking metallized sapphire substrates. These prototype capacitors were characterized in the temperature range from room temperature to 550°C by measuring the capacitance and parallel resistance of these devices at 120Hz, 1kHz, 10kHz, 100kHz, and 1MHz. The capacitance and equivalent parallel resistance of these capacitors were all directly measured by an AC LCZ impedance meter in controlled temperature environments.

These prototype devices demonstrate stable capacitances over a wide temperature range, and therefore, have the potential to be integrated with silicon carbide (SiC) devices to enable high temperature electronics. The needs of thin-film metallization and encapsulation for these sapphire substrates are also discussed.
Assessing the Reliability of Die Attach Materials in Electronic Packages for High Temperature Applications
Authors: Sousa M.F. , Riches S. , Johnston C. , Grant P.S.
Published: October 2015

The operation of electronic packages under exceptionally harsh environments presents a significant challenge for the microelectronics industry. The traditional temperature limit for high temperature exposure of electronics system (for example, in down-hole, well-logging and aero-engine applications) has now to be extended from 125 to 250°C. The present work aims at developing understanding of how and why attach materials for Si dies degrade/fail under harsh environments. Two types of die attach materials have been studied: electrically conductive adhesives (ECAs) that offer low temperature assembly, low cost, and relatively low stresses imparted on the die and substrate but are generally considered unsuitable for harsh environments; and Au-2wt.%Si eutectic that offers elevated temperature stability and stiffness but requires high temperature processing and more complex manufacturing steps. Die attach assembly has been investigated using scanning electron microscopy and scanning acoustic microscopy (SAM) after ageing, thermal shock and thermal cycling treatments. The failure behaviour of the die attach materials included phenomena such as cracking of die and/or attach material; outgassing and voiding; and delamination. SAM images were particularly helpful in studying non-destructively die/die attach and die/substrate interfaces.
Demonstrated Performance Characteristics For Improved High Temperature Ceramic Capacitors Intended For Use In Extreme, Harsh Environments
Authors: Syammach Mustafa A. , Roach Michael J. , Syammach Fauzi A. , Habibi Mustapha
Published: October 2015

Availability of a reliable and consistent source for high temperature ceramic capacitors has been an ongoing issue for design engineers looking at developing product for applications up to and including +300°C. The general practice has been to derate standard X7R ceramic capacitors for high temperature applications and settle for a device characterized by a significant reduction in those critical performance features related to capacitance value, operating voltage, insulation resistance and breakdown voltage, not to mention a substantial roll off in temperature coefficient above +150°C. In addition, the need to provide coated and / or leaded options also presents additional concerns related to operational integrity.

This paper presents packaging options, life test reliability data and compares performance characteristics for a unique high K, high temperature ceramic capacitor, to the more traditional options. This approach utilizes leading edge, Class II dielectric and packaging materials that have been specifically developed for use at +300°C and then benefit from enhanced reliability when operated at lower temperatures. As shown in this paper, capacitors manufactured with this dielectric material exhibit much higher capacitance per unit volume and significant improvements in insulation resistance, without having to sacrifice mechanical strength, voltage rating or long term reliability.
New High Temperature Electronic Components for Power Management and Motor Control Applications
Authors: Delatte Pierre , Dessard V. , Saib A. , Pequignot N. , Picún G. , Demeûs L. , Martinez L. , Krebs T. , Doucet J.-C.
Published: October 2015

This paper presenst CISSOID's new high temperature chips for Power Management and Motor Control in automotive, oil & gas, aerospace and industrial applications.

High temperature DC-DC reference designs, called respectively ETNA, VESUVIO™ and EREBUS™, have been announced recently. These Buck (step-down) DC-DC converters are built with proven CISSOID products as active components rated from −55°C up to 225°C. These DC-DC converters can have input voltages from 6V up to 50V. The output voltage can be adjusted from 10% up to 90% of the input voltage. Power efficiencies in excess of 90% above 200°C have been demonstrated. VESUVIO™ and EREBUS™ are based on MAGMA PWM controller, HYPERION half-bridge driver and two power transistors to implement a synchronous Buck converter.

For high voltage and power levels, new Silicon-Carbide devices allow operating at high junction temperatures. They enable high power modules with higher densities in terms of size and weight. Having power drivers able to operate very close to these devices allow further integration of power modules while increasing the performances thanks to lower parasitic capacitances and inductances. This will also ease to increase switching frequencies, another key advantage of these new devices. For these applications, CISSOID has released PROMETHEUS I Power Driver reference design that can sink and source currents up to 2Amps at a supply voltage from 11V up to 30V. Recently announced PROMETHEUS II design, based on HYPERION driver, enables rise and fall times of 25ns on a 1nF load.
Performance and Reliability of MEMS Gyroscopes and Packaging at High Temperatures
Authors: McCluskey Patrick , Patel Chandradip , Lemus David
Published: October 2015

Elevated temperatures can significantly affect the performance and reliability of MEMS gyroscope sensors. A MEMS vibrating resonant gyroscope measures angular velocity via a displacement measurement which can be on the order on nanometers. High sensitivity to small changes in displacement causes the MEMS Gyroscope sensor to be strongly affected by changes in temperature which can affect the displacement of the sensor due to thermal expansion and thermomechanical stresses. Analyzing the effect of temperature on MEMS gyroscope sensor measurements is essential in mission critical high temperature applications, such as inertial tracking of the movement of a fire fighter in a smoke filled indoor environment where GPS tracking is not possible. In this paper, we will discuss the development of the high temperature package for the tracking application, including the characterization of the temperature effects on the performance of a MEMS gyroscope. Both stationary and rotary tests were performed at room and at elevated temperatures on 10 individual single axis MEMS gyroscope sensors.
High Temperature SiC Power Module Electrical Evaluation Procedure
Authors: Ning Puqi , Wang Fred , Ngo Khai D. T.
Published: October 2015

In order to take full advantage of SiC semiconductor devices, high temperature device packaging needs to be developed. The potential defects in design and fabrication procedure are detailed and their detection steps in the electrical evaluation are presented. The established systematic testing procedure can rapidly detect defects and reduce the risk in high temperature packaging testing. The multi-chip module development procedure is also presented and demonstrated with an example.
Practical Oil Field Requirements for New High-Temperature Batteries
Authors: Normann Randy
Published: October 2015

There is a growing need for batteries to power electronic systems deep within wells. These systems do everything from powering sensor systems with wireless communication to driving motor-controlled valves. This paper presents the practical oil field industry requirements that battery engineers need to know in order to develop new high-temperature batteries subterranean wells, both for the oil industry and for geothermal energy generation.