Tantalum Capacitors Research Articles

Environmental Stability of Polymer Tantalum Capacitors

Stability of Polymer Tantalum capacitors with pre-polymerized PEDOT (slurry PEDOT) cathodes were investigated under different environmental conditions. Capacitance dependence on temperature, frequency, and dc bias voltage were investigated in humid and dry capacitors with different dielectric thicknesses. Electrical measurements and scanning electron microscopy (SEM) were used to characterize the capacitors. Humid capacitors were observed to have higher capacitance than dry capacitors for all dielectric thicknesses. The capacitance for all dielectric thicknesses was observed to increase with temperature in both humid and dry capacitors. Humid capacitors showed a strong temperature dependence at lower temperatures while dry capacitors showed a strong temperature dependence at higher temperatures. These temperature effects were more pronounced in thinner dielectric capacitors, and the results were explained by the integrity of the dielectric-polymer interface. The capacitance for all dielectric thicknesses was also observed to decrease with an increase in frequency, both in humid and dry capacitors. The frequency effect was more pronounced in humid capacitors with thinner dielectrics. These results were explained by a distributed capacitance model, secondary transitions of the polar segments of the polymer cathode, and lower reactance and lower self-resonance frequency of the thinner dielectric capacitors. The technological principles of improving environmental stability of Polymer Tantalum capacitors are also discussed.

Exploration of alternative routes for recycling critical metals from waste PCB and tantalum capacitors

Abstract Printed Circuit Boards (PCB), secondary source of critical metals, are usually recycled to recover precious metals. Alternative routes, aiming to pre-concentrate critical metals, were tested at lab scale. An up-scaling process is proposed involving a thermomechanical separation of PCB and surface mounted devices (SMD). PCB without SMD are treated by solvolysis for desilication and debromination. Further calcination provides a presumably leachable metallic mix. Tantalum capacitors, a specific type of SMD, are treated by pyrolysis, to isolate metallic cores, which are further leached to obtain 92% pure tantalum oxide. LCA data show that tantalum recycling process is profitable for the environment.

Исследование электрических свойств танталовый конденсаторов циклическими поляризационными и импедансными измерениями

The automization complex device SOLARTRON-1280C was used for measurement electrical parameters of the industrial tantalum electrolytic capacitors. It was shown that the method for detection of the defective products is applied to constant current mode and impedance measurements. The impedance measurements was used for determination of the electric capacity tantalum capacitors and how it depends on the aperiodic current frequency. In addition impedance method is able to indicates on the secondary processes that occurs in the capacitor when it works in electric circuit. The general parameters of the tantalum capacitors in direct current were determined by polarization methods.

Techno-economic potential of recycling Tantalum containing capacitors by automated selective dismantling

Abstract Because of the low concentrations of Tantalum on printed wiring boards, today it is not economically viable to recycle Tantalum in pyro- and hydrometallurgical processes. However, in case the Tantalum can be up concentrated, the recycling of the Tantalum can become economically viable in the multi-stage process used to refine Tantalum from ores. Therefore, the presented research investigates the techno-economic potential of selectively removing Tantalum capacitors from PWBs prior to treating the complete PWBs in integrated precious metal smelting and refining installations. In the presented research the economic potential is analysed using return on investment analysis for automated selective dismantling and the viability of manual selective dismantling. These analyses are based on the measured metal concentration of Tantalum capacitors, the composition of a typical PWB and the results of lab experiments for the removal and detection of components using deep learning computer vision.

Poole–Frenkel Emission Saturation and Its Effects on Time-to-Failure in Ta-Ta2O5-MnO2 Capacitors

I-V characterization of Ta-Ta2O5-MnO2 capacitors was investigated at different temperatures, and Poole–Frenkel (PF) emission saturation was experimentally observed. Under the saturation voltage, the I-V curves at different temperature converged, and the temperature dependency was vanished. Above the saturation voltage, the leakage current was decreasing as the temperature increased. In order to evaluate the effects of saturation voltages (VS) on time-to-failure (TTF) of the capacitors, VS were first determined at +2°C and +25°C, then voltage accelerating tests were conducted at 85°C under 1.6 times of rated voltage. The distribution of VS and TTF of the samples were plotted and compared. It was shown that samples with lower saturation voltage failed earlier in the distribution of time-dependent dielectric breakdown. Comparing conventional methods for evaluating the quality of tantalum capacitors by measuring the leakage current at elevated temperature, the nondestructive measurement of saturation voltage at +2°C and +25°C may provide a novel and practicing approach tool to screening out capacitors with defected Ta2O5 layers.

Recycling waste tantalum capacitors to synthesize high value-added Ta2O5 and polyaniline-decorated Ta2O5 photocatalyst by an integrated chlorination-sintering-chemisorption process

Abstract Waste tantalum capacitors, containing about 30–40 wt% rare metal tantalum (Ta), are one of the main Ta secondary resources. Not just to achieve the Ta resource recovery but to realize the value-added utilization, we recycled waste tantalum capacitors to prepare Ta2O5 photocatalyst by a chlorination-sintering process. To enhance the photocatalytic performance, Ta2O5 was further decorated by polyaniline (PANI) through a chemisorption approach. The as-prepared Ta2O5 and Ta2O5/PANI photocatalysts exhibited irregular nanoparticles with the particle size of 50–80 nm. After the PANI decoration, the photocatalytic performance of Ta2O5 was significantly enhanced. The optimal simulated sunlight H2 evolution rate and RhB degradation rate constant of Ta2O5/PANI (3 wt%) could reach 200.8 μmolg−1h−1 and 0.1342 min−1, which were about 3.3 and 5.6 times higher than those of Ta2O5. The superior photocatalytic performance of Ta2O5/PANI was ascribed to the intense interfacial interaction, increased visible light absorption and efficient charge carrier separation. In short, this study demonstrates a sustainable approach to convert e-waste to high-value-added and high-efficient photocatalyst, which is significant for waste utilization and environmental protection.

Ordered clustering method and degradation trend analysis for performance degradation of tantalum capacitor

The performance degradation trend of a tantalum capacitor has different characteristics in different degradation regimes with different temperatures and humidity. Clustering method and degradation trend analysis can be useful for early warning of life. In this paper, according to the degradation characteristics of the capacitance and the dissipation factor with different temperature and humidity, the experiment is designed, and the failure mechanisms of different degeneration regimes are analyzed. After the ordered clustering method is introduced, using the natural property and the change rate α(k) of the slope β(k) of the error function δ[p(m,k)], the determination method of the optimization clustering number is put forward. The Davies‐Bouldin Index is proposed as the evaluation method of the ordered clustering result, and the validation of the evaluation method was verified by the degradation data with other stresses. For the stable degradation regime, the degradation trend analysis is completed. The error result shows that the degradation fitting functions can be a good fit for the degradation trend with different stress. According to the degradation fitting analysis, the degradation prediction method is described to find the relationship between prediction life and different temperature and humidity to realize the failure time prediction with different stresses using the early degradation data. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Effect of Moisture on AC Characteristics of Chip Polymer Tantalum Capacitors

Contrary to conventional tantalum capacitors with MnO2 cathodes, chip polymer tantalum capacitors (CPTCs) might degrade in both high humidity and dry environments. A better understanding of the kinetics of moisture content variations in CPTCs is necessary to determine bake-out conditions for the parts before soldering to avoid pop-corning failures and to select adequate preconditioning before reliability and qualification testing. In this paper, ac characteristics in different types of CPTCs have been studied with time during moisture sorption and desorption at temperatures from room to 125 °C. Capacitance increased with moisture content from minimal to maximal values reproducibly. This allowed using tantalum slugs as humidity sensors and measurements of capacitance variations with time to describe processes of moisture diffusion. A model that relates characteristic times of capacitance variations with the size of the case and moisture characteristics of polymer materials has been developed. Temperature dependencies of the characteristic times follow Arrhenius law with activation energy in the range from 0.4 to 0.5 eV. The equivalent series resistance (ESR) remained relatively stable during environmental testing, but dissipation factors (DFs), reached maximum and increased more than 10 times at characteristic times of moisture accumulation or release. The phenomena have been explained by changes in the charge absorption processes caused by variations of the barrier at the conductive polymer/Ta2O5 interface with moisture content.

3-D Packaging and Integration of High-Density Tantalum Capacitors on Silicon

High-density, point-of-load (PoL) power conversion and power delivery are required to continue scaling electronic systems with increased functionality, more bandwidth, and smaller sizes. To meet the demands of these highly complex and miniaturized electronic systems, new 3-D integration schemes of advanced passive and active components are needed to enable the next-generation power distribution networks (PDNs). In addition, shorter interconnect lengths are required to provide low losses and better transient response in switch-based power conversion systems. Tantalum capacitors have the potential to provide some of the highest volumetric densities of any current capacitor technology, but are generally bulky components with low frequency stability, limiting their use in future 3-D power systems. In this paper, a process for the embedding and integration of ultrathin, high-density tantalum capacitors with improved frequency stability is demonstrated. The 5-V capacitors show a density of $1~\mu \text{F}$ /mm2 at 1 MHz with only a 100- $\mu \text{m}$ thickness, and are shown to be capable of direct integration on silicon for short interconnect length of $ . The electrical performance of the capacitors is tested after integration and shows that they retain high capacitance density and low equivalent series resistance (ESR), while also providing low leakage currents. The combination of low loss, high volumetric density, and 3-D integration capability make the capacitors an ideal candidate for next-generation power modules.

Characteristics of energetic semiconductor bridge initiator based on different stoichiometric ratios of Al/MoO3 reactive multilayer films under capacitor discharge conditions

Three types of Al/MoO3 energetic semiconductor bridge (ESCB) initiators were prepared by integrating Al/MoO3 reactive multilayer films (RMFs) of different stoichiometric ratios on semiconductor bridges through magnetron sputtering. The stoichiometric ratios of Al:MoO3 were 4:1, 2:1, and 4:3. An experimental investigation for obtaining the electrical explosive characteristics of the ESCBs with different stoichiometric ratios of Al/MoO3 RMFs was carried out under the stimulation of a 47 μF tantalum capacitor discharge. The results reveal a ‘stagflation’ phenomenon in the voltage–current–resistance curves of the ESCBs, which is obvious at low discharge voltages. The critical burst energy and critical burst time decrease with an increase in the MoO3 ratio in RMFs for initiators discharged with identical voltages. Moreover, among the three ESCBs, the one with a stoichiometric ratio of 4:3 exhibits the highest performance with the shortest critical burst time, lowest critical burst energy, and most violent explosion phenomenon. This suggests that the ignition performance of ESCBs can be enhanced by optimising the stoichiometric ratio of Al/MoO3 RMFs.

Dissolution of manganese (IV) oxide from tantalum capacitor scrap by organic acids

The dissolution of MnO2 from tantalum capacitor scrap using organic acids in various process conditions was studied. The initial materials were of two types: LTC (leaded tantalum capacitors) and SMDTC (surface-mounted device tantalum capacitors). The research materials were prepared by pyrolysis, grinding and sieving and the preparation processes were characterized. Dissolution of MnO2 was carried out with the use of sulfuric acid solutions with the addition of acetic, ascorbic, citric and oxalic organic acids. Results show that the addition of organic acids significantly improves dissolution yields (72-94 vs 90-99 % for H2SO4 and acid mixtures, respectively). In practice, a concentration of organic acid above 1 M results in the complete removal of MnO2.

Electrothermal processing of tantalum capacitor powders

A low-pressure arc discharger with the hollow cathode is a newly developed electrotechnological device for finely dispersed powders of particles having dimensions 50 micron and less. The discharger is useful for putting powder into a high reactive zone of a plasma column and for thermal and mechanical action on particles. In the NSTU, the plain scales of the splinter tantalum powder were gained experimentally. Based on the results of the experiments, several constructive solutions are proposed for the heating of powders with subsequent deformation of tantalum powder particles on the target.

Hydrometallurgical Process for Tantalum Recovery from Epoxy-Coated Solid Electrolyte Tantalum Capacitors.

Tantalum is a critical metal that is widely used in electronic products. The demand for tantalum is increasing, but the supply is limited. As tantalum waste products have increased in Taiwan in recent years, the treatment of spent tantalum capacitors has become necessary and important. The recycling of tantalum from tantalum capacitors will not only decrease pollution from waste, but will also conserve tantalum resources. The tantalum content in epoxy-coated solid electrolyte tantalum capacitors (EcSETCs) is over 40 wt.%. Here, we designed a recycling process that includes pre-treatment, leaching, and solvent extraction to recover tantalum. In the pre-treatment process, epoxy resin and wires were removed. During hydrometallurgical process, pressure leaching by hydrofluoric acid was used to leach tantalum and manganese from solid electrolyte tantalum capacitors (SETCs). During our testing of this proposed process, the acid concentration, reaction time, temperature, and solid–liquid ratio were examined for leaching. After the leaching process, Alamine 336 was used to extract tantalum from the leaching solution. The pH value, extractant concentration, extraction time, and aqueous–organic ratio were investigated. Then, tantalum was stripped using HNO3, and the HNO3 concentration, stripping time, and organic–aqueous ratio were analyzed in detail. Under optimal conditions, the recovery efficiency of tantalum reached over 98%, and a final product of tantalum pentoxide with 99.9% purity was obtained after chemical precipitation and calcination.

Circuit-integratable high-frequency micro supercapacitors with filter/oscillator demonstrations

Micro supercapacitor (MSC) featured by high capacitance density, has great potential for replacing bulky electrolytic capacitors in circuits to make electronics of miniaturization, yet suffers from sharp capacitance drop under alternating current. Here, we report a circuit-integratable high-frequency MSC with hybrid architecture electrode, in which 2D pseudocapacitive MXene served as the active material provides large capacitance and multi-walled carbon nanotube applied as interlayer support offers fast ion transport paths. Such design brings the device an excellent frequency response and a capacitance density much higher than commercial tantalum capacitors at 120 Hz. A novel transfer-free filtration technology greatly eliminates the equivalent series resistance and the consequent thermal loss, and makes the MSC a more circuit-integratable planar geometry. Moreover, such high-frequency MSC is applied in a low-pass filtering circuit and a relaxation oscillator circuit, displaying advantages in function, size and intergratability compared with electrolytic capacitors.

Метод выявления внутренних дефектов танталовых конденсаторов для снижения количества отказов аппаратуры

Метод выявления внутренних дефектов танталовых конденсаторов для снижения количества отказов аппаратуры

Manganese Dioxide Purification Methods for Producing Tantalum Capacitors with Low Equivalent Series Resistance

Manganese Dioxide Purification Methods for Producing Tantalum Capacitors with Low Equivalent Series Resistance

Manganese Dioxide Purification Methods for Producing Tantalum Capacitors with Low Equivalent Series Resistance

Manganese Dioxide Purification Methods for Producing Tantalum Capacitors with Low Equivalent Series Resistance

Abnormal Capacitance Increasing at Elevated Temperature in Tantalum Capacitors with PEDOT:PSS Electrodes

Due to the importance of capacitance temperature stability in precise analog circuit applications, capacitance instability at elevated temperature of 125°C was investigated in tantalum capacitors with PEDOT:PSS counter electrodes. Capacitance-voltage measurement supposed that residual ions in the PEDOT:PSS dispersion caused an accumulation of charges at the dielectric-cathode interface which contributed to an increase in the dielectric constant and resulted in the capacitance increasing at high temperature. Based on the hypothesis, water wash process was applied and capacitance dropped significantly at high temperature. This study shows that an additional water wash process is necessary to improve the capacitance temperature stability after each dispersion dip step.

Development of High Temperature Tantalum Polymer Capacitors

Abstract This paper focuses on the development of new 150°C capable surface mount polymer tantalum capacitors and the enabling technologies. The conductivity stability of the conducting polymers at high temperatures as well as the equivalent series resistance (ESR) stability of the polymer tantalum capacitors at these temperatures were investigated in this study. Analysis of the oxygen permeation paths causing polymer oxidation and materials solutions for preventing oxygen permeation and polymer oxidation are described. The development of new cathode and protective coating material technology is presented. Their effectiveness in providing high temperature ESR stability is demonstrated by high temperature life test at 150°C of polymer capacitors.

Integrative Quality Control of Wet Tantalum Capacitors Terminal Welding

С целью оценки качества крепления монтажных выводов танталовых объемно-пористых конденсаторов и для рассмотрения необходимости и целесообразности проведения своевременных корректирующих и предупреждающих мероприятий проведен комплексный контроль качества приварки выводов танталовых конденсаторов по методике системного межэтапного комплексного анализа качества танталовых конденсаторов на основе анализа претензионных изделий с учетом конструкторско-технологического, производственного и человеческого факторов. По статистическому анализу возращенных изделий выявлена необходимость рассмотрения качества приварки катодного вывода, и с использованием метода полного факторного эксперимента на операции «приварка катодного вывода к корпусу конденсатора» для двух различных типов конструкций вывода исследовано количественное влияние характеристик технологического процесса с целью выявления режимов, наиболее эффективно воздействующих на качество сварочного соединения. Проведен многофакторный эксперимент, в результате которого построена регрессионная модель качества процесса сварки катодного вывода к корпусу танталового конденсатора и выявлена зависимость от энергетических режимов сварки. Обнаружено сильное влияние на качество выполнения операции токового значения сварки и давления на свариваемые поверхности. Область подачи инертного газа также вносит свой вклад в температурное поле зоны сварки, но в меньшей степени по сравнению с параметрами режима сварки. На основании результатов апробации можно заключить, что методика системного межэтапного комплексного анализа качества танталовых конденсаторов может быть применима для оценки качества танталовых конденсаторов как на этапе производства - для совершенствования технологических процессов, на этапе доработки конструкции, так и на этапе эксплуатации - для удовлетворения требований потребителей, и может дать экономический эффект от снижения доли возвращаемых конденсаторов, подлежащих замене. Комплексный контроль по совокупности параметров на стадии производства, испытаний и эксплуатации позволяет исключить попадание потребителю некачественной продукции.