The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Alexander Teverovsky - One of the best experts on this subject based on the ideXlab platform.
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Degradation of leakage currents and reliability prediction for Tantalum capacitors
2016 Annual Reliability and Maintainability Symposium (RAMS), 2016Co-Authors: Alexander TeverovskyAbstract: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.
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Reliability of High-Voltage Tantalum Capacitors. Parts 3 and 4)
2010Co-Authors: Alexander TeverovskyAbstract:Weibull grading test is a powerful technique that allows selection and reliability rating of Solid Tantalum capacitors for military and space applications. However, inaccuracies in the existing method and non-adequate acceleration factors can result in significant, up to three orders of magnitude, errors in the calculated failure rate of capacitors. This paper analyzes deficiencies of the existing technique and recommends more accurate method of calculations. A physical model presenting failures of Tantalum capacitors as time-dependent-dielectric-breakdown is used to determine voltage and temperature acceleration factors and select adequate Weibull grading test conditions. This model is verified by highly accelerated life testing (HALT) at different temperature and voltage conditions for three types of Solid chip Tantalum capacitors. It is shown that parameters of the model and acceleration factors can be calculated using a general log-linear relationship for the characteristic life with two stress levels.
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Effect of Post-HALT Annealing on Leakage Currents in Solid Tantalum Capacitors
2010Co-Authors: Alexander TeverovskyAbstract:Degradation of leakage currents is often observed during life testing of Tantalum capacitors and is sometimes attributed to the field-induced crystallization in amorphous anodic Tantalum pentoxide dielectrics. However, degradation of leakage currents and the possibility of annealing of degraded capacitors have not been investigated yet. In this work the effect of annealing after highly accelerated life testing (HALT) on leakage currents in various types of Solid Tantalum capacitors was analyzed. Variations of leakage currents with time during annealing at temperatures from 125 oC to 180 oC, thermally stimulated depolarization (TSD) currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. Annealing resulted in a gradual decrease of leakage currents and restored their initial values. Repeat HALT after annealing resulted in reproducible degradation of leakage currents. The observed results are explained based on ionic charge instability (drift/diffusion of oxygen vacancies) in the Tantalum pentoxide dielectrics using a modified Schottky conduction mechanism.
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Degradation of leakage currents in Solid Tantalum capacitors under steady-state bias conditions
2010 Proceedings 60th Electronic Components and Technology Conference (ECTC), 2010Co-Authors: Alexander TeverovskyAbstract:Degradation of leakage currents in various types of Solid Tantalum capacitors under steady-state bias conditions was investigated at temperatures from 105 °C to 170 °C and voltages up to two times the rated voltage. Variations of leakage currents with time under highly accelerated life testing (HALT) and annealing, thermally stimulated depolarization currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. During HALT the currents increase gradually up to three orders of magnitude in some cases, and then stabilize with time. This degradation is reversible and annealing can restore the initial levels of leakage currents. The results are attributed to migration of positively charged oxygen vacancies in Tantalum pentoxide films that diminish the Schottky barrier at the MnO2/Ta2O5 interface and increase electron injection. A simple model allows for estimation of concentration and mobility of oxygen vacancies based on the level of current degradation.
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Scintillation and surge current breakdown voltages in Solid Tantalum capacitors
IEEE Transactions on Dielectrics and Electrical Insulation, 2009Co-Authors: Alexander TeverovskyAbstract:Scintillation and surge current breakdown voltages were measured using constant-current-stress and step-stress-surge-current techniques. Distributions of breakdown voltages were analyzed for 30 different lots of commercial and military-grade capacitors. Results of measurements of temperature dependencies of breakdown voltages were analyzed and the physical nature of surge current and scintillation breakdowns in Tantalum capacitors is discussed. The suggested model explains both the scintillation and surge current breakdowns as a result of electron impact ionization and avalanche breakdowns. Charges trapped in the dielectric during a slow voltage increase result in raising of the barrier at the cathode/dielectric interface and enhancing scintillation breakdown voltages compared to surge current breakdown voltages. An anomalous characteristic of the time-dependent breakdown in Tantalum capacitors, for which the higher the rate of the voltage increase, the lower the breakdown voltage, is due to the presence of electron traps in anodic Ta2O5 dielectrics. A high concentration of fast electron states is a characteristic feature of anodic Ta2O5 dielectrics and is the major reason for scintillation breakdown voltages being significantly greater than the surge current breakdown voltages.
Katsumi Yoshino - One of the best experts on this subject based on the ideXlab platform.
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highly conducting polypyrrole prepared from homogeneous mixtures of pyrrole oxidizing agent and its applications to Solid Tantalum capacitors
Synthetic Metals, 1994Co-Authors: Masaharu Satoh, Hitoshi Ishikawa, Kosuke Amano, Etsuo Hasegawa, Katsumi YoshinoAbstract:Abstract Reaction parameters for the cationic oxidative polymerization of pyrrole are investigated for the preparation of a highly conductive material for electronic devices. The homogeneous reaction mixture is prepared by dissolving pyrrole and iron(III) dodecylbenzenesulfonate at a very low temperature of −70 °C, which gives polypyrrole with high conductivity. The conductivity increases with increasing concentrations of monomer and oxidizing agent. The maximum conductivity reaches 80 S/cm, which is comparable to that of electrochemically prepared film. The method is successfully used for the formation of the counter electrode of a Tantalum Solid capacitor. The capacitor demonstrates the proportional decrease of impedance up to the resonance frequency with capacitance above 90% of the design value.
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Highly conducting polypyrrole prepared from homogeneous mixtures of pyrrole/oxidizing agent and its applications to Solid Tantalum capacitors
Synthetic Metals, 1994Co-Authors: Masaharu Satoh, Hitoshi Ishikawa, Kosuke Amano, Etsuo Hasegawa, Katsumi YoshinoAbstract:Abstract Reaction parameters for the cationic oxidative polymerization of pyrrole are investigated for the preparation of a highly conductive material for electronic devices. The homogeneous reaction mixture is prepared by dissolving pyrrole and iron(III) dodecylbenzenesulfonate at a very low temperature of −70 °C, which gives polypyrrole with high conductivity. The conductivity increases with increasing concentrations of monomer and oxidizing agent. The maximum conductivity reaches 80 S/cm, which is comparable to that of electrochemically prepared film. The method is successfully used for the formation of the counter electrode of a Tantalum Solid capacitor. The capacitor demonstrates the proportional decrease of impedance up to the resonance frequency with capacitance above 90% of the design value.
A. Teverovsky - One of the best experts on this subject based on the ideXlab platform.
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Scintillation Breakdowns and Reliability of Solid Tantalum Capacitors
IEEE Transactions on Device and Materials Reliability, 2009Co-Authors: A. TeverovskyAbstract:Scintillations are momentarily local breakdowns in Tantalum capacitors, which are often considered as nuisances rather than failures. However, this paper shows that scintillations are damaging for more than 30% of part types and up to 100% for some lots. Scintillations can be observed after many hours of operation, and the probability of repeat scintillations is higher than of the initial event. In this paper, a time-dependent scintillation breakdown is considered as one of the major reasons of failures during steady-state operation of the capacitors. Using a modified thermochemical model, the distribution of times to failure can be simulated based on the distribution of breakdown voltages. The analysis of distributions of scintillation breakdown voltages and the assessment of the safety margins are critical to assure high quality and reliability of Tantalum capacitors.
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Effect of Mechanical Stresses on Characteristics of Chip Tantalum Capacitors
IEEE Transactions on Device and Materials Reliability, 2007Co-Authors: A. TeverovskyAbstract:The effect of compressive mechanical stresses on chip Solid Tantalum capacitors is investigated by monitoring the characteristics of different part types under axial and hydrostatic stresses. An exponential increase of leakage currents was observed when stresses exceeded a critical value, which varied on average from 10 to 40 MPa depending on the part type. For the first time, reversible variations of leakage currents (up to two orders of magnitude) with stress have been demonstrated. Mechanical stresses did not cause significant changes of ac characteristics of the capacitors, whereas breakdown voltages measured during the surge-current testing decreased substantially, indicating an increased probability of failures of stressed capacitors in low-impedance applications. Variations of leakage currents are explained by a combination of two mechanisms: stress-induced scintillations and stress-induced generation of electron traps in the Tantalum pentoxide dielectric.
Yadong Jiang - One of the best experts on this subject based on the ideXlab platform.
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Vapor phase polymerization deposition of conducting polymer/graphene nanocomposites as high performance electrode materials.
ACS applied materials & interfaces, 2013Co-Authors: Yajie Yang, Zhang Luning, Wenyao Yang, Yadong JiangAbstract:In this paper, we report chemical vapor phase polymerization (VPP) deposition of novel poly(3,4-ethylenedioxythiophene) (PEDOT)/graphene nanocomposites as Solid Tantalum electrolyte capacitor cathode films. The PEDOT/graphene films were successfully prepared on porous Tantalum pentoxide surface as cathode films through the VPP procedure. The results indicated that the high conductivity nature of PEDOT/graphene leads to the decrease of cathode films resistance and contact resistance between PEDOT/graphene and carbon paste. This nanocomposite cathode film based capacitor showed ultralow equivalent series resistance (ESR) ca. 12 mΩ and exhibited better capacitance-frequency performance than the PEDOT based capacitor. The leakage current investigation revealed that the device encapsulation process does not influence capacitor leakage current, indicating the excellent mechanical strength of PEDOT-graphene films. The graphene showed a distinct protection effect on the dielectric layer from possible mechanical damage. This high conductivity and mechanical strength graphene based conducting polymer nanocomposites indicated a promising application future for organic electrode materials.
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Vapor Phase Polymerization Deposition Conducting Polymer Nanocomposites on Porous Dielectric Surface as High Performance Electrode Materials
Nano-Micro Letters, 2013Co-Authors: Yajie Yang, Zhang Luning, Zhiming Wang, Wenyao Yang, Yadong JiangAbstract:We report chemical vapor phase polymerization (VPP) deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) and PEDOT/graphene on porous dielectric Tantalum pentoxide (Ta2O5) surface as cathode films for Solid Tantalum electrolyte capacitors. The modified oxidant/oxidant-graphene films were first deposited on Ta2O5 by dip-coating, and VPP process was subsequently utilized to transfer oxidant/oxidant-graphene into PEDOT/PEDOT-graphene films. The SEM images showed PEDOT/PEDOT-graphene films was successfully constructed on porous Ta2O5 surface through VPP deposition, and a Solid Tantalum electrolyte capacitor with conducting polymer-graphene nano-composites as cathode films was constructed. The high conductivity nature of PEDOT-graphene leads to resistance decrease of cathode films and lower contact resistance between PEDOT/graphene and carbon paste. This nano-composite cathode films based capacitor showed ultralow equivalent series resistance (ESR) ca. 12Ω and exhibited excellent capacitance-frequency performance, which can keep 82% of initial capacitance at 500 KHz. The investigation on leakage current revealed that the device encapsulation process has no influence on capacitor leakage current, indicating the excellent mechanical strength of PEDOT/PEDOT-gaphene films. This high conductivity and mechanical strength of graphene-based polymer films shows promising future for electrode materials such as capacitors, organic solar cells and electrochemical energy storage devices.
Masaharu Satoh - One of the best experts on this subject based on the ideXlab platform.
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highly conducting polypyrrole prepared from homogeneous mixtures of pyrrole oxidizing agent and its applications to Solid Tantalum capacitors
Synthetic Metals, 1994Co-Authors: Masaharu Satoh, Hitoshi Ishikawa, Kosuke Amano, Etsuo Hasegawa, Katsumi YoshinoAbstract:Abstract Reaction parameters for the cationic oxidative polymerization of pyrrole are investigated for the preparation of a highly conductive material for electronic devices. The homogeneous reaction mixture is prepared by dissolving pyrrole and iron(III) dodecylbenzenesulfonate at a very low temperature of −70 °C, which gives polypyrrole with high conductivity. The conductivity increases with increasing concentrations of monomer and oxidizing agent. The maximum conductivity reaches 80 S/cm, which is comparable to that of electrochemically prepared film. The method is successfully used for the formation of the counter electrode of a Tantalum Solid capacitor. The capacitor demonstrates the proportional decrease of impedance up to the resonance frequency with capacitance above 90% of the design value.
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Highly conducting polypyrrole prepared from homogeneous mixtures of pyrrole/oxidizing agent and its applications to Solid Tantalum capacitors
Synthetic Metals, 1994Co-Authors: Masaharu Satoh, Hitoshi Ishikawa, Kosuke Amano, Etsuo Hasegawa, Katsumi YoshinoAbstract:Abstract Reaction parameters for the cationic oxidative polymerization of pyrrole are investigated for the preparation of a highly conductive material for electronic devices. The homogeneous reaction mixture is prepared by dissolving pyrrole and iron(III) dodecylbenzenesulfonate at a very low temperature of −70 °C, which gives polypyrrole with high conductivity. The conductivity increases with increasing concentrations of monomer and oxidizing agent. The maximum conductivity reaches 80 S/cm, which is comparable to that of electrochemically prepared film. The method is successfully used for the formation of the counter electrode of a Tantalum Solid capacitor. The capacitor demonstrates the proportional decrease of impedance up to the resonance frequency with capacitance above 90% of the design value.