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At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Review of the NASA Voyager spacecraft polycarbonate capacitor failure incident

The premission failure of a Voyager spacecraft capacitor has prompted an investigation into the use of polycarbonate capacitors in high impedance circuits, during which capacitor failures were induced by thermal cycling together with extended periods at high temperature. Measurement of leakage path temperature coefficients indicates that there are two distinct leakage types whose mechanisms are complicated by movement within the capacitor during temperature changes. A novel system for pulse detection during capacitor burn-in and ramp testing has proven to be beneficial.

Ott, F. M.↗

NASA NTRS1990

Charging/Safety-Interlock Connection For Capacitor Bank

Electrically controlled mechanical interlock apparatus prevents connection of bank of capacitors to battery or other dc power supply until capacitors precharged to nearly full supply voltage. Precharge eliminates excessive inrush current, which damages capacitors, wires, or connectors. Circuit in apparatus also discharges capacitors after power turned off or capacitors disconnected from power supply.

Rippel, Wally E.↗

NASA NTRS1995

Hermetically sealed aluminum electrolytic capacitor

Aluminum electrolytic capacitors are presently not allowed on NASA missions because they outgas water and organic vapors, as well as H2. As a consequence, much larger and heavier packages of tantalum capacitors are used. A hermetically sealed aluminum capacitor has been developed under NASA-MSFC SBIR contracts. This capacitor contains a nongassing electrolyte that was developed for this application so internal pressure would remain low. Capacitors rated at 250 to 540 V have been operated under full load for thousands of hours at 85 and 105 C with good electrical performance and low internal pressure. Electrolyte chemistry and seal engineering concepts will be discussed.

Alwitt, Robert S.↗

NASA NTRS1999

Investigation Into The Effects of Microsecond Power Line Transients On Line-Connected Capacitors

An investigation was conducted into the effect of power-line transients on capacitors used by NASA and installed on platform primary power inputs to avionics. The purpose was to investigate whether capacitor voltage rating needs to be derated for expected spike potentials. Concerns had been voiced in the past by NASA suppliers that MIL-STD-461 CS06-like requirements were overly harsh and led to physically large capacitors. The author had previously predicted that electrical-switching spike requirements representative of actual power-line transient potentials, durations and source impedance would require no derating. This investigation bore out that prediction. It was further determined that traditional low source impedance CS06-like transients also will not damage a capacitor, although the spikes themselves are not nearly as well filtered. This report should be used to allay fears that CS06-like requirements drive capacitor voltage derating. Only that derating required by the relatively long duration transients in power quality specification need concern the equipment designer.

Javor, Ken↗

NASA NTRS2000

Investigation into the Effects of Microsecond Power Line Transients on Line-Connected Capacitors

An investigation was conducted into the effect of power-line transients on capacitors used by NASA and installed on platform primary power inputs to avionics. The purpose was to investigate whether capacitor voltage ratings needs to be derated for expected spike potentials. Concerns had been voiced in the past by NASA suppliers that MIL-STD-461 CS06-like requirements were overly harsh and led to physically large capacitors. The author had previously predicted that electrical-switching spike requirements representative of actual power-line transient potentials, durations. and source impedance would require no derating. This investigation bore out that prediction. It was further determined that traditional low source impedance CS06-like transients also will not damage a capacitor, although the spikes themselves are not nearly as well filtered. This report should be used to allay fears that CS06-like requirements drive capacitor voltage derating. Only that derating required by the relatively long duration transients in power quality specification need concern the equipment designer.

Javor, K.↗

NASA NTRS2004

The ISR Asymmetrical Capacitor Thruster: Experimental Results and Improved Designs

A variety of Asymmetrical Capacitor Thrusters has been built and tested at the Institute for Scientific Research (ISR). The thrust produced for various voltages has been measured, along with the current flowing, both between the plates and to ground through the air (or other gas). VHF radiation due to Trichel pulses has been measured and correlated over short time scales to the current flowing through the capacitor. A series of designs were tested, which were increasingly efficient. Sharp features on the leading capacitor surface (e.g., a disk) were found to increase the thrust. Surprisingly, combining that with sharp wires on the trailing edge of the device produced the largest thrust. Tests were performed for both polarizations of the applied voltage, and for grounding one or the other capacitor plate. In general (but not always) it was found that the direction of the thrust depended on the asymmetry of the capacitor rather than on the polarization of the voltage. While no force was measured in a vacuum, some suggested design changes are given for operation in reduced pressures.

Canning, Francis X.↗

NASA NTRS2006

Performance and Reliability of Solid Tantalum Capacitors at Cryogenic Conditions

Performance of different types of solid tantalum capacitors was evaluated at room and low temperatures, down to 15 K. The effect of temperature on frequency dependencies of capacitance, effective series resistances (ESR), leakage currents, and breakdown voltages has been investigated and analyzed. To assess thermo-mechanical robustness of the parts, several groups of loose capacitors and those soldered on FR4 boards were subjected to multiple (up to 500) temperature cycles between room temperature and 77 K. Experiments and mathematical modeling have shown that degradation in tantalum capacitors at low temperatures is mostly due to increasing resistance of the manganese cathode layer, resulting in substantial decrease of the roll-off frequency. Absorption currents follow a power law, I approximately t(sup -m), with the exponent m varying from 0.8 to 1.1. These currents do not change significantly at cryogenic conditions and the value of the exponent remains the same down to 15 K. Variations of leakage currents with voltage can be described by Pool-Frenkel and Schottky mechanisms of conductivity, with the Schottky mechanism prevailing at cryogenic conditions. Breakdown voltages of tantalum capacitors increase and the probability of scintillations decreases at cryogenic temperatures. However, breakdown voltages measured during surge current testing decrease at liquid nitrogen (LN) compared to room-temperature conditions. Results of temperature cycling suggest that tantalum capacitors are capable of withstanding multiple exposures to cryogenic conditions, but the probability of failures varies for different part types.

Teverovsky, Alexander↗

NASA NTRS2010

Physical and Electrical Characterization of Aluminum Polymer Capacitors

Polymer aluminum capacitors from several manufacturers with various combinations of capacitance, rated voltage, and ESR values were physically examined and electrically characterized. The physical construction analysis of the capacitors revealed three different capacitor structures, i.e., traditional wound, stacked, and laminated. Electrical characterization results of polymer aluminum capacitors are reported for frequency-domain dielectric response at various temperatures, surge breakdown voltage, and other dielectric properties. The structure-property relations in polymer aluminum capacitors are discussed.

Liu, David↗

NASA NTRS2010

Physical and Electrical Characterization of Polymer Aluminum Capacitors

Liu, David↗

NASA NTRS2011

Towards Prognostics of Electrolytic Capacitors

A remaining useful life prediction algorithm and degradation model for electrolytic capacitors is presented. Electrolytic capacitors are used in several applications ranging from power supplies on critical avionics equipment to power drivers for electro-mechanical actuators. These devices are known for their low reliability and given their criticality in electronics subsystems they are a good candidate for component level prognostics and health management research. Prognostics provides a way to assess remaining useful life of a capacitor based on its current state of health and its anticipated future usage and operational conditions. In particular, experimental results of an accelerated aging test under electrical stresses are presented. The capacitors used in this test form the basis for a remaining life prediction algorithm where a model of the degradation process is suggested. This preliminary remaining life prediction algorithm serves as a demonstration of how prognostics methodologies could be used for electrolytic capacitors.

Celaya, Jose R.↗

NASA NTRS2014

Evaluation of Commercial Automotive-Grade BME Capacitors

Three Ni-BaTiO3 ceramic capacitor lots with the same specification (chip size, capacitance, and rated voltage) and the same reliability level, made by three different manufacturers, were degraded using highly accelerated life stress testing (HALST) with the same temperature and applied voltage conditions. The reliability, as characterized by mean time to failure (MTTF), differed by more than one order of magnitude among the capacitor lots. A theoretical model based on the existence of depletion layers at grain boundaries and the entrapment of oxygen vacancies has been proposed to explain the MTTF difference among these BME capacitors. It is the conclusion of this model that reliability will not be improved simply by increasing the insulation resistance of a BME capacitor. Indeed, Ni-BaTiO3 ceramic capacitors with a smaller degradation rate constant K will always give rise to a longer reliability life.

reliability↗

NASA NTRS2021

Acceleration Factors for Reliability Assessment of Polymer Tantalum Capacitors

Using polymer tantalum capacitors in Hi-Rel systems requires an assessment of the reliability characteristics of the parts. For this assessment, tantalum capacitors are typically subjected to reliability testing at temperatures and voltages exceeding their specified values, and the failure rate (FR) — or the probability of failure during use conditions — is calculated based on voltage and temperature acceleration factors. In this work, various types and lots of polymer tantalum capacitors have been tested at highly accelerated life test (HALT) conditions and the acceleration factors have been determined using different techniques. It has been shown that the behavior of capacitors under HALT conditions can be described based on the time-dependent dielectric breakdown (TDDB) model, which explains the presence of infant mortality (IM) and wear-out failures using the same failure mechanisms and allows for an assessment of the acceleration factors. The difference in acceleration factors obtained using exponential and power models is discussed. Analysis shows that with proper derating, screening, and qualification testing, the reliability of frameless Hi-Rel COTS polymer tantalum capacitors is adequate for space missions.

Alex Eidelman↗

NASA NTRS2021

A Paradigm Shift in Quality Assurance of COTS Capacitors for Space Applications

Limitations of a traditional approach to screening and qualification of COTS capacitors for space applications that is based on burn-in and life test requirements described in the relevant military specifications are analyzed. An alternative approach that is originated from analysis of highly accelerated life testing (HALT) of capacitors susceptible to wear-out failures and allows for assessments of the risks of failure during the mission is suggested. Examples include results of reliability testing of advanced BME ceramic capacitors, polymer tantalum capacitors and multianode manganese oxide tantalum capacitors.

Alexander A Teverovsky↗

NASA NTRS2021

Acceleration Factors for Reliability Assessment of Polymer Tantalum Capacitors

Alex Eidelman↗

NASA NTRS2020

An Embedded Planar-Foil Capacitor Material, FPGA Based Interposer, Aimed at Improving System Performance and Reduced Board Size for Space Based Electronics

This paper presents our work to date in developing, and testing an embedded planar-foil capacitor based interposer intended to be integrated together with high-density components such as Field Programmable Gate Arrays (FPGAs), and Application Specific Integrated Circuit (ASIC) applications. FPGA devices typically have a large number of I/O and power pins. The high speed enabled by these devices requires a large number of discrete bypass capacitors as close as possible to the power pins. These capacitors take up a considerable amount of the board area on the application circuit board. Our interposer replaces these components freeing up space of traditional bypass capacitors for other circuitry. Our Interposer focuses on the needs of Micro Semi’s RTG4 FPGA. We developed the interposer using COTS embedded foil capacitors. The Interposer is customized to the capacitance requirements for each of the FPGA banks. We evaluated three foil manufactures Oak Mitsui, 3M and TDK. The three different designs were evaluated, but we will focus on the Oak-Mitsui based Interposer that we constructed and tested. Through simulations, we validate the horizontal and vertical interconnect inductances, that FPGA decoupling requirements are met. The use of the interposer results in an overall reduction in our Printed Wiring Board (PWB) area.

Hunter, Don J↗

NASA NTRSDate not supplied

An Electron Backscatter Diffraction (EBSD)-Based Automated Tool for Ceramic Capacitor Grain Size Analysis

Ceramic capacitors continue to be recurring problem parts for NASA, despite best efforts to screen out potential defects and failures through environmental and electrical testing and nondestructive inspection techniques such as acoustic microscopy. The physical properties of ceramic capacitors necessitates thin dielectric layers capable of withstanding significant electric fields. Any defects in those ceramic layers can result in reduced insulation resistance failure modes including short circuit failures, so the quality and consistency of the dielectric material is critical. The size of the individual ceramic grains in the dielectric material is a critical parameter. However, judging “grain size” is not so simple—in a single capacitor there can be wide variation in grain sizes observed. It is theorized that by studying the grain size distributions of “known good” and “known bad” lots of capacitors, some conclusions could be drawn that would allow us to better predict to the reliability of future lots based on grain size distributions. The initial goal of this effort was to find or develop an automated tool that could inspect a capacitor and return grain size distribution results.

Robert Hodson↗

DOE OSTI2016

Switched-capacitor isolated LED driver

A switched-capacitor voltage converter which is particularly well-suited for receiving a line voltage from which to drive current through a series of light emitting diodes (LEDs). Input voltage is rectified in a multi-level rectifier network having switched capacitors in an ascending-bank configuration for passing voltages in uniform steps between zero volts up to full received voltage V.sub.DC. A regulator section, operating on V.sub.DC, comprises switched-capacitor stages of H-bridge switching and flying capacitors. A current controlled oscillator drives the states of the switched-capacitor stages and changes its frequency to maintain a constant current to the load. Embodiments are described for isolating the load from the mains, utilizing an LC tank circuit or a multi-primary-winding transformer.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2018

Film capacitor and the method of forming the same

A film capacitor is presented. The film capacitor includes a thermally conductive support. The thermally conductive support includes a core including a first end and a second end. The thermally conductive support further includes a protrusion extending from at least one of the first end and the second end of the core, where at least one of the core and the protrusion includes a phase change material. Further, the film capacitor also includes a plurality of films disposed on at least a portion of the thermally conductive support, where the plurality of films includes a plurality of electrode films and a dielectric film. Further, the thermally conductive support for the film capacitor and a method of forming the film capacitor are also presented.

36 MATERIALS SCIENCE↗