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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Evaluation of Aluminum Polymer Capacitors for Space Applications

Layered aluminum polymer capacitors (APC) may be viable replacements to currently used chip tantalum capacitors due to their lower ESR, weight, and smaller size. So far, there is a lack of information regarding the reliability of these parts. Available technical literature is mostly related to the effect of humidity. Although APCs have a limited moisture resistance, it may be contained to the level sufficient for space applications. This work analyzes construction and characteristics of seven types of commercial APCs manufactured by four vendors and rated to voltages from 6.3 to 35 V were analyzed. Their reliability under environmental stresses and highly accelerated life tests was assessed in the range of temperatures and voltages to determine reliability acceleration factors. For this purpose, characteristics of the parts, including breakdown voltages, the level of anomalous charging currents (ACC), capacitance, DF, ESR and leakage currents were measured in the process of storage at high-temperatures (from 100 to 150 °C) and high humidity at 85 °C. Monitored highly accelerated life tests have been carried out at temperatures of 85 °C and 125 °C and voltages varying from 1.2 to 1.9 times the rated voltage. Degradation processes and reliability of APCs have been compared to polymer tantalum capacitors.

Alexander A Teverovsky↗
NASA NTRS2014

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

dielectric polarization↗
NASA NTRS2016

Degradation of Leakage Currents and Reliability Prediction for Tantalum Capacitors

Two types of failures in solid tantalum capacitors, catastrophic and parametric, and their mechanisms are described. Analysis of voltage and temperature reliability acceleration factors reported in literature shows a wide spread of results and requires more investigation. In this work, leakage currents in two types of chip tantalum capacitors were monitored during highly accelerated life testing (HALT) at different temperatures and voltages. Distributions of degradation rates were approximated using a general log-linear Weibull model and yielded voltage acceleration constants B = 9.8 +/- 0.5 and 5.5. The activation energies were Ea = 1.65 eV and 1.42 eV. The model allows for conservative estimations of times to failure and was validated by long-term life test data. Parametric degradation and failures are reversible and can be annealed at high temperatures. The process is attributed to migration of charged oxygen vacancies that reduce the barrier height at the MnO2/Ta2O5 interface and increase injection of electrons from the MnO2 cathode. Analysis showed that the activation energy of the vacancies' migration is ~ 1.1 eV.

acceleration factors↗
NASA NTRS2016

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

testing↗
NASA NTRS2017

Ceramic Capacitor Delamination Problem

Update on ceramic capacitors issues since last years meeting. To including the story behind the issues behind the TIRS and SDO leaky capacitors.

Ceramic Capacitor↗
NASA NTRSDate not supplied

Infant Mortality and Wear-Out Failures in Polymer and MnO2 Tantalum Capacitors

Reliability testing of modern tantalum capacitors shows the presence of both types, infant mortality (IM) and wearout (WO) failures. To assure reliable operation, the probability of IM failures should be reduced to below the specified level, and the time of WO inception should be greater than the required useful life of the parts at operation conditions. In this work, several types of MnO2 and polymer cathode tantalum capacitors have been tested at highly accelerated conditions to assess voltage acceleration factors, determine adequate burn-in conditions, and assess the useful life. A modified time dependent dielectric breakdown (TDDB) model has been suggested to explain both types of failure, and a physical mechanism of degradation that is based on migration and reactions of oxygen vacancies explains increase of the defect related, IM failures with the level of stress.

tantalum capacitors↗
NASA NTRS2023

Metrics for Anomalous Charging currents in Polymer Tantalum Capacitors

Anomalous charging currents (ACC) in polymer tantalum capacitors may appear as a temporary short circuit that can last for dozens of milliseconds, cause failures to the parts, or cause malfunctions to fast operating electronic systems. Currently, there is no standard technique or set of metrics to evaluate the level of ACC which compares results obtained by different users and manufacturers. In this work, ACC in different types of capacitors were characterized by analysis of current transients during the constant voltage ramp or power surge testing (PST) techniques. It is shown that although the shape of transients may vary at different test conditions, the transfer charge and energy remain practically the same. The level of ACC is characterized by the energy dissipated in the part during PST. Variations of the dissipated energy with moisture content, test temperature, and voltage are evaluated. Effects of different reflow soldering conditions and long-term (up to 3000 hours) storage at 125 °C are discussed.

polymer tantalum capacitor↗
NASA NTRS1965

Three-dimensional wire-mesh capacitor system measures fluid density

Gaging system automatically measures the bulk density of a stored, electrically nonconductive fluid containing varying portions of liquid and vapor. The system employs a three-dimensional wire-mesh capacitor whose capacitance varies with the bulk density of the fluid dielectric medium between the capacitor plates.

Source record↗
NASA NTRS1966

Large capacitor performs as a distributed parameter pulse line

Capacitor of extended foil construction performs as a distributed parameter pulse line in which current, amplitude, and period are readily controlled. The capacitor is used as the energy storage element in a pulsed plasma accelerator.

Gooding, T. J.↗
NASA NTRS1966

Nonelectrolytic tantalum capacitors developed

Large area, nonelectrolytic tantalum foil capacitor has capacitance of approximately 1 microfarad and is capable of operating at 125 deg C at 150 volts with an insulation resistance of at least 1 megohm. In tests at a potential of 100 volts, capacitors remained stable through a temperature range from 25 deg to 125 deg C.

Source record↗
NASA NTRS1967

Miniature capacitor functions as pressure sensor

Miniature capacitor operates as a differential pressure telemetry sensor during free flight of test model in a hypersonic wind tunnel. The capacitor incorporates a beryllium copper diaphragm. It is also used as an absolute pressure sensor.

Harrison, R. G.↗
NASA NTRS1967

Precision capacitor has improved temperature and operational stability

Vacuum dielectric capacitor is fabricated from materials with very low temperature coefficients of expansion. This precision capacitor in the 1000-2000 picofarad range has a near-zero temperature coefficient of capacitance, eliminates ion chamber action caused by air ionization in the dielectric, and minimizes electromagnetic field charging effects.

Brookshier, W. K.↗
NASA NTRS1967

High-temperature /1100 degrees F/ capacitors operate without supplement cooling

Multilayered capacitor with one-mil thick pyrolytic boron nitride and wrap around sputtered electrodes achieves parallel electrical interconnections in a stacked configuration of 3 to 9 wafers. These capacitors are compact, lightweight, and suitable for operation in high temperatures without supplemental cooling.

Stapleton, R. E.↗
NASA NTRS1973

Research into the feasibility of metal- and oxide-film capacitors

Thin film capacitors with up to twenty-two active layers have been deposited by RF sputtering. The materials were aluminum electrodes of 1200 to 1500 angstrom thickness and silica dielectric layers of 3000 to 6000 angstrom thickness. The best electrical characteristics were capacitances of nearly 0.1 microfarad for an active area of 1.25 square centimeters, dissipation factor of less than 0.01 over a frequency range of 0.5 to 100 kilohertz and energy density of approximately 70 millijoules per cubic centimeter of active deposited material at a working voltage of 40 volts. These aluminum-silica capacitors exhibit excellent electrical stability over a temperature range from -55 C to +300 C.

Jorgenson, G. V.↗
NASA NTRS1973

Characteristics of capacitor-type micrometeoroid flux detectors when impacted with simulated micrometeoroids

A series of impact tests are described and data presented which characterize the operation of the capacitor-type micrometeoroid flux detectors used on the Meteoroid Technology Satellite (MTS). Capacitor-type detectors with silicon dioxide dielectric thickness of 0.4 and 1.0 microns were tested in the micrometeoroid impact simulator at the Langley Research Center, a 4-MV Van de Graaff electrostatic accelerator. The carbonyl iron projectiles were from 0.5 to 5.0 microns in diameter with velocities from 4 to 10.0 km/sec. The detector bias voltage was varied from -20 to -60 V; some tests were at detector temperatures of 90 C to -100 C; and the angle of impact varied from 0 deg to 75 deg from the normal to the detector. These tests showed that: (1) the detector operation is reliable when the bias voltage is greater than 30 V; (2) after an impact the detector returns to its original condition with an insignificant loss of active area; and (3) the sensitivity of the detector is inversely proportional to the detector thickness. The test results suggest a theoretical model in which the signal is an arc triggered by the impacting projectile, and the detector bias voltage must be high enough to insure that an arc will form.

Kassel, P. C., Jr.↗