Showing papers on "Tantalum capacitor published in 2017"

Potentials and Barriers for Tantalum Recovery from Waste Electric and Electronic Equipment

Abstract: Summary Circular economy approaches aim to close material cycles along the value chain. As such, the circular economy can be a long-term strategy to mitigate the risks of critical raw material (CRM) supply. Tantalum, with a current end-of-life recycling rate of less than 1%, has been intermittently discussed as critical. Even though the specificity of tantalum applications and high-mass fractions of tantalum in relevant components provide good boundary conditions, recycling barriers hinder the successful implementation of recycling technologies. With this case study, we identify potentials and barriers for implementing the recovery of CRM, using the example of tantalum. To this end, information about visually identifiable tantalum capacitors (VICs) and printed circuit boards (PCBs) in various equipment types was obtained by disassembly campaigns for mobile phones, smartphones, tablets, notebooks, desktop personal computers, flat screen monitors, servers, etc., and the chemical analyses of resulting fractions. Results show great differences in the application of tantalum in various equipment types. Because of this, the tantalum potential of put-on-market (POM) or of waste electric and electronic equipment (WEEE) devices differs between products and regions. Worldwide, the highest POM tantalum flows originate from desktop computers, but in Germany they originate from notebooks. A focus on particular products leads to higher yields in recycling and supports circular economy approaches. Recycling of tantalum from WEEE is generally possible. But an accurate separation of tantalum from PCBs is not feasible solely by separation of VICs. This process also leads to the loss of silver. Further, this study reveals potential miniaturization trends, decreasing the use of VICs, with an anticipated substitution of tantalum with niobium. These barriers impede long-term recycling strategies for tantalum aimed at establishing a circular economy.

Method for Recycling Tantalum from Waste Tantalum Capacitors by Chloride Metallurgy

Abstract: The demand for tantalum (Ta) is rapidly increasing due to the manufacture of Ta capacitors (TCs) for electronic devices. With the increasing awareness of environmental protection and conservation of rare metal Ta, recycling of Ta from waste TCs (WTCs) is becoming a hot topic in current society. In this study, an efficient and environmentally friendly process for recycling Ta from WTCs by chloride metallurgy (CM) is proposed. In the CM process, the nontoxic FeCl2 is chosen as the chlorination agent. Thermodynamic analysis demonstrates that Ta can selectively react with FeCl2, and the generated TaCl5 can be easily separated and then condensed in the condensation zone. The recovery of Ta can reach 93.56% under the optimal chlorination parameters as follows: heating temperature of 500 °C, FeCl2 addition amount of 50%, holding time for 2 h, and particle size of Ta-rich powder less than 0.24 mm. Moreover, the kinetic mechanism is discussed, and the rate-controlling step in the chlorination reaction of Ta is det...

Rough Electrode Creates Excess Capacitance in Thin-Film Capacitors

Abstract: The parallel-plate capacitor equation is widely used in contemporary material research for nanoscale applications and nanoelectronics. To apply this equation, flat and smooth electrodes are assumed for a capacitor. This essential assumption is often violated for thin-film capacitors because the formation of nanoscale roughness at the electrode interface is very probable for thin films grown via common deposition methods. In this work, we experimentally and theoretically show that the electrical capacitance of thin-film capacitors with realistic interface roughness is significantly larger than the value predicted by the parallel-plate capacitor equation. The degree of the deviation depends on the strength of the roughness, which is described by three roughness parameters for a self-affine fractal surface. By applying an extended parallel-plate capacitor equation that includes the roughness parameters of the electrode, we are able to calculate the excess capacitance of the electrode with weak roughness. Mor...

Recovery of Valuable Materials from Waste Tantalum Capacitors by Vacuum Pyrolysis Combined with Mechanical–Physical Separation

Abstract: Waste tantalum capacitors (WTCs), dismantled from waste printed circuit boards, are considered a high quality tantalum (Ta) resource. Ta is a rare and strategic material. Nearly half of the Ta consumption is used for manufacturing tantalum capacitors. Furthermore, large amounts of energy and chemicals are consumed during the Ta purification process. Therefore, recovering Ta from WTCs can sustainably utilize the Ta resource and reduce pollution. However, the recycling technology has been poorly developed. This study proposed vacuum pyrolysis (VP) and mechanical–physical separation (MPS) to recover Ta and other materials from WTCs. First, the WTCs were treated by VP to decompose the organics. The suitable VP parameters were considered as 400 °C, 50 Pa, and 60 min. Then, the residues were performed by MPS. Consequently, nickel–iron terminals were recovered by magnetic separation. Ta and silica were separated by corona electrostatic separation. The recovery rate and purity of Ta could reach 97.02 ± 0.85% and ...

Atomic Layer Deposition Alumina-Passivated Silicon Nanowires: Probing the Transition from Electrochemical Double-Layer Capacitor to Electrolytic Capacitor

Abstract: Silicon nanowires were coated by a 1–5 nm thin alumina layer by atomic layer deposition (ALD) in order to replace poorly reproducible and unstable native silicon oxide by a highly conformal passivating alumina layer. The surface coating enabled probing the behavior of symmetric devices using such electrodes in the EMI-TFSI electrolyte, allowing us to attain a large cell voltage up to 6 V in ionic liquid, together with very high cyclability with less than 4% capacitance fade after 106 charge/discharge cycles. These results yielded fruitful insights into the transition between an electrochemical double-layer capacitor behavior and an electrolytic capacitor behavior. Ultimately, thin ALD dielectric coatings can be used to obtain hybrid devices exhibiting large cell voltage and excellent cycle life of dielectric capacitors, while retaining energy and power densities close to the ones displayed by supercapacitors.

A Solid State Variable Capacitor With Minimum Capacitor

Abstract: A solid state variable capacitor (SSVC) with minimum capacitor is proposed. A variable ac capacitor (with capacitance varied from 0 to $C_{{{\rm ac}}}$ ) is traditionally implemented by an H-bridge inverter and a large electrolytic dc capacitor, whose capacitance is 20 times of the ac capacitor's value, in order to absorb the ripple power pulsating at twice the line frequency (2 ω ripple power). The proposed SSVC system consists of an H-bridge and an additional phase leg connected to an ac capacitor with fixed capacitance $C_{{{\rm ac}}}$ and can reduce the dc capacitance to minimum value for absorbing switching ripples. The ac capacitor absorbs the 2 ω component and theoretically can eliminate 2 ω ripples to the dc capacitor completely. The total capacitor size is reduced by 13 times if same type capacitors (film) are used. Moreover, the proposed SSVC shows special advantages in terms of the switches’ current and voltage stress compared to other applications and the total device power rating is only 1.125 times of H-bridge. Since the proposed SSVC only has a small dc capacitor, a novel control system directly based on ripple power is also proposed to achieve stable dc voltage and fast dynamic response. Simulation and experimental results are shown to prove the effectiveness of the proposed SSVC with minimum capacitor.

Failure of Polymer Aluminum Electrolytic Capacitors Under Elevated Temperature Humidity Environments

Abstract: Polymer aluminum (PA) electrolytic capacitors have solid conductive polymers as electrolyte. Reliability of polymer capacitors at elevated temperature humidity is not well understood. Elevated temperature–humidity testing was performed on PEDOT PA electrolytic capacitors by two manufacturers, Nichicon and Nippon Chemi-Con. Both the companies are among the top suppliers of aluminum electrolytic capacitors worldwide. Two different dominant failure modes of increase in equivalent series resistance and increase in leakage current (LC) were found in the PA capacitors from the two different capacitor manufacturers. The capacitance value of the polymer capacitors remained stable during the test. In the subsequent analysis, a new failure mechanism that has not been previously reported in the literature was found that leads to the high LC failure of PA electrolytic capacitors. The criteria for evaluation for this new failure mechanism should be included during the part and manufacturer selection process.

Experimental Investigation of Laser Spot Welding of Ni and Au-Sn-Ni Alloy

Abstract: Many microelectronic devices are miniaturizing the capacitance density and the size of the capacitor. Along with this miniaturization of electronic circuits, tantalum (Ta) capacitors have been on the market due to its large demands worldwide and advantages such as high volumetric efficiency, low temperature coefficient of capacitance, high stability and reliability. During a tantalum capacitor manufacturing process, arc welding has been used to weld base frame and sub frame. This arc welding may have limitations since the downsizing of the weldment depends on the size of welding electrode and the contact time may prevent from improving productivity. Therefore, to solve these problems, this study applies laser spot welding to weld nickel (Ni) and Au-Sn-Ni alloy using CW IR fiber laser with lap joint geometry. All laser parameters are fixed and the only control variable is laser irradiance time. Four different shapes, such as no melting upper workpiece, asymmetric spherical-shaped weldment, symmetric weldment, and, excessive weldment, are observed. This shape may be due to different temperature distribution and flow pattern during the laser spot cutting.

Degradation effect on reliability evaluation of aluminum electrolytic capacitor in backup power converter

Abstract: DC capacitors in power electronic converters are a major constraint on improvement of power density as well as reliability. In this paper, according to the degradation data of electrolytic capacitors through the accelerated test, the time-to-failure of the capacitor cell is acquired and it can be further extended to lower stress levels. Then, in a case study of a fuel cell backup power application, the mission profile based lifetime expectancy of the individual capacitor and the capacitor bank is estimated in terms of the standby mode and operation mode. The lifetime prediction of the capacitor banks can be obtained and compared with and without the degradation effect.

High-temperature dielectric responses in all-nanosheet capacitors

Abstract: We have investigated high-temperature dielectric responses of layer-by-layer assembled nanosheet capacitors All-nanosheet capacitors are fabricated by stacking metallic Ru095O2 as electrodes and dielectric Ca2Nb3O10 nanosheets as insulators Through in situ characterizations, we find that all-nanosheet capacitors exhibit a size-free high-k dielectric response (~155) and a moderate insulation resistance (~1 × 10−5 A/cm2) at high temperatures up to 200 °C The concomitant presence of high er, low leakage profile, and thermal stability in high-k nanocapacitors is critically important for application in high-temperature electronics

Capacitive voltage sensor for medium voltage metering

Abstract: Two cylindrical capacitors of different values are created in series within a single dielectric resin body to form a capacitive voltage divider for a Medium Voltage sensor. By eliminating temperature variance both capacitors' permittivity is the same, and consistent measurements may be achieved. A first capacitor in the picofarad capacitance range is formed by a rod-shaped central primary conductor, one layer of a wrapped foil capacitor as a second conductor, and the resin body as a dielectric. The wrapped foil capacitor provides a second capacitor in the nanofarad capacitance range and is also embedded within the resin body. The resin body provides a dielectric material almost impervious to ambient changes in operating range and allows for a compact design. A precision resistor can be added in parallel to the first and second capacitors to damp transients and increase the transformation ratio.

Tantalum Capacitor Technology : Options for high-temperature and harsh-environment applications

Abstract: Traditionally, hermetically sealed, wet axial tantalum capacitors, which incorporate a nonsolid electrolyte that promotes self-healing and long lifetimes, have been used for both high-bulk capacitance (up to 5,600 nF) and high-voltage applications (up to 125 Vdc) suited to industrial applications. In recent years, this technology has been developed even further to meet the 200°C operational requirements of harsher environment industrial applications.

A method for hotspot temperature estimation of aluminum electrolytic capacitors

Abstract: Lifetime of aluminum electrolytic capacitors is of paramount importance, since in many power electronic voltage source converter systems this capacitor type is used in the DC-link. Thermal stress is one of the most critical stressors for electrolytic capacitors leading to wear-out and failures. Therefore, methods to perform online monitoring of the hotspot temperature of capacitors would lead to beneficial information, which could be used for protection or lifetime prediction purposes. This paper proposes a hotspot temperature estimation method based on the linear dependence between capacitance and temperature of electrolytic capacitors. For this, a set of nine samples of the same aluminum capacitor type is characterized by means of capacitance measurements at different hotspot temperatures. The obtained linear correlation is used to calibrate hotspot temperature estimation for the investigated electrolytic capacitor type. It is verified experimentally that the temperature estimation error of the proposed method is well below 5 K. Thus, the proposed procedure can be used as a basis for future research on improving condition monitoring of electrolytic capacitors.

Impedance characteristics modeling of a two-terminal active capacitor

Abstract: Conventional capacitors contribute to a considerable scale of system level size, cost and failure, and suffer from one or more issues on energy density, cost, and reliability. A two-terminal active capacitor, which has the same level of convenience as passive capacitors, is proposed recently to overcome the above issues. In this paper, the modeling of the active capacitor is investigated and a voltage feed-forward compensation scheme is proposed for overshoot reduction. Therefore, the impedance, equivalent capacitance, ESR, and ESL, of the active capacitor can be specified. A case study based on a single-phase full-bridge rectifier with an active capacitor demonstrates the theoretical analyses.

Tunable MEMS capacitor: influence of fluids

Abstract: The effect of a dielectric liquid on the tunability of capacitor operating in RF domains is evaluated. The RF measurement shows a high variation of the resonant frequency accompanied with a low insertion loss. Moreover, the fluid positions between electrodes modify the capacitance value up to Tr = 6660% at 600 MHz. The quality factor decreases in response of water filling from Q max = 51.9 when it is empty to Q min = 1.49 when it is fully filled. According to the finite-element method analysis, the change of the dielectric permittivity influences the capacitor performances. Essentially, the tuning range of the capacitance and the quality factor could reach, respectively: Tr = 7660% and Q min = 35.

A novel flicker-free AC-DC LED driver without electrolytic capacitor

Abstract: In this paper, a novel flicker-free ac/dc LED driver without electrolytic capacitor is presented. The driver comprises a single-stage boost-forward converter and a bidirectional buck-boost converter, which serves to bypass the low frequency ripple. Therefore, electrolytic capacitor is no longer needed. Compared with other electrolytic capacitor-less topologies, the proposed driver has the advantages of almost unity input power factor, less energy storage, less capacitance needed, and constant output current. The operation principle, design process, and control strategy are presented. And the feasibility of the proposed converter is verified by a prototype with 30-V, 1.0-A output.

Wide Band Frequency Characterization of Al-Doped and Undoped Rutile TiO 2 Thin Films for MIM Capacitors

Abstract: In this letter, the dielectric properties of rutile TiO2 thin films are studied for metal–insulator–metal capacitor applications. The dielectric constant, the ac conductivity, and the loss tangent are measured in a wide band frequency range, from 1 Hz to 2 GHz. The effect of aluminum doping, as well as the influence of film thickness, on the dielectric properties is presented.

Solid electrolytic capacitor with enhanced humidity resistance and method for producing the same

Abstract: An improved capacitor is provided. The capacitor comprises an anode and a functional dielectric on said anode and a conductive layer on the functional dielectric. An anode wire extends from said anode wherein the anode wire has a thickened dielectric layer thereon.

Special forming mold for circular tantalum core of tantalum capacitor and using method thereof

Abstract: The invention discloses a special forming mold for the circular tantalum core of a tantalum capacitor and a using method thereof in order to solve the technical problem that most of the tantalum cores formed by the existing forming mold are of a long and thin cylindrical structure and a circular tantalum core cannot be formed using the existing forming mold is solved. The forming mold comprises an upper convex mold, a concave mold, a lower convex mold, an adjusting cushion block, a tantalum wire limiting block, and adjusting gaskets. The adjusting cushion block matches the lower convex mold. The concave mold matches the lower convex mold. The concave mold and the lower convex mold constitute a semi-closed circular forming cavity. Tantalum powder is poured into the semi-closed circular forming cavity, and a tantalum wire is placed on the tantalum powder. The tantalum wire limiting block is used for limiting the tantalum wire. After the tantalum wire is limited, tantalum powder is poured into the cavity. The upper convex mold matches the concave mold. The upper convex mold, the concave mold and the lower convex mold constitute a closed circular forming cavity to form a circular tantalum core through pressing. Adjusting gaskets of appropriate size can be selected according to the size of a tantalum core to realize layered pressing. The special forming mold for the circular tantalum core of a tantalum capacitor has the advantages of simple structure, good pressing quality, good batch consistency, convenient de-molding, and the like, and has a wide application prospect in the technical field of electronic component production and manufacture.

Degradation and ESR Failures in MnO2 Chip Tantalum Capacitors

Abstract: Equivalent series resistance (ESR) of chip tantalum capacitors determines the rate of energy delivery and power dissipation thus affecting temperature and reliability of the parts. Employment of advanced capacitors with reduced ESR decreases power losses and improves efficiency in power systems. Stability of ESR is essential for correct operations of power units and might cause malfunctioning and failures when ESR becomes too high or too low. Several cases with ESR values in CWR29 capacitors exceeding the specified limit that were observed recently raised concerns regarding environmental factors affecting ESR and the adequacy of the existing screening and qualification testing. In this work, results of stress testing of various types of military and commercial capacitors obtained over years by GSFC test lab and NEPP projects that involved ESR measurements are described. Environmental stress tests include testing in humidity and vacuum chambers, temperature cycling, long-term storage at high temperatures, and various soldering simulation tests. Note that in many cases parts failed due to excessive leakage currents or reduced breakdown voltages. However, only ESR-related degradation and failures are discussed. Mechanisms of moisture effect are discussed and recommendations to improve screening and qualification system are suggested.

Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors

Abstract: High temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL) variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5. Here, the equilibrium between the ion drift and diffusion is achieved. The process of leakage current degradation is therefore partially reversible. When the external electric field is lowered, or the samples are shortened, the leakage current for a given voltage decreases with time and the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5, thus the ion redistribution by diffusion becomes dominant.

Method for preparing oxygen tantalum nitride photocatalytic material by means of waste tantalum capacitors

Abstract: Provided is a method for preparing an oxygen tantalum nitride photocatalytic material by means of waste tantalum capacitors The method comprises the following steps that various waste tantalum capacitors are subjected to mechanical crushing and decladding; metal and nonmetal are separated; metal materials are subjected to magnetic separation, and ferro-nickel magnetic materials are separated; screening is conducted, and tantalum-containing powder is obtained; the tantalum-containing powder is subjected to chlorination treatment, and tantalum chloride is obtained; tantalum chloride is dissolved into an alcoholic solution, ammonia gas is introduced to separate ammonium chloride out, filtration is conducted, and an alcoholic solution of tantalum is obtained; the alcoholic solution of tantalum is hydrolyzed, tantalum oxide sol is obtained, drying is conducted, and tantalum oxide gel is obtained; the tantalum oxide gel is subjected to high-temperature calcination in ammonia gas atmosphere, and the oxygen tantalum nitride photocatalytic material is obtained The method for preparing the oxygen tantalum nitride photocatalytic material by means of the waste tantalum capacitors has the advantages that the waste tantalum capacitors in the market are utilized, requirements of photocatalytic tantalum material preparation on tantalite ore are reduced, and nickel and iron electrodes in the waste tantalum capacitors are recycled

Cooling of electrolytic capacitors in electrical climate compressors

Abstract: A system for mounting at least one cylindrical electrolytic capacitor on a heat sink, the heat sink having at least one bore for at least partially receiving a cylindrical electrolytic capacitor, and the bore partially or fully encompassing the cylindrical electrolytic capacitor once it has been received, wherein lateral surfaces of the cylindrical electrolytic capacitor are mechanically and thermally connected to surfaces forming the bore. The system providing thermal cooling of the electrolytic capacitor and enabling substantially uniform thermal cooling of the capacitor. A method for producing a connection between the at least one cylindrical electrolytic capacitor and the heat sink, and to a connection, obtainable by the method, between the at least one electrolytic capacitor and the heat sink.

Solid electrolyte tantalum capacitor

Abstract: The utility model discloses a solid electrolyte tantalum capacitor, include: negative pole lead wire, shell, solid electrolyte layer, membrane layer, tantalum agglomerate, positive wire, the one end of positive wire is fixed in the tantalum agglomerate, the outside of tantalum agglomerate is equipped with membrane layer in proper order, solid electrolyte layer, the tantalum agglomerate, membrane layer, solid electrolyte layer's tip passes through the encapsulation of resin package layer, solid electrolyte layer's the outside is equipped with the graphite layer in proper order, the core shell, the inboard in shell one end is fixed through the soldering layer to the tip of core shell, the outside of shell one end is connected with the negative pole lead wire, the inboard of the shell other end is fixed with packaging cover plate, the other end of positive wire is worn out from packaging cover plate, the utility model has the advantages of small, electric capacity gauge height, security are good.

SMD tantalum electrolytic capacitor supersound antifriction mould of piezoelectric patches

Abstract: The utility model discloses a SMD tantalum electrolytic capacitor supersound antifriction mould of piezoelectric patches to it has had uneven, the numerous and diverse scheduling problem of assembly step of structure complicacy, suppression density distribution that exists to solve in the powder suppression technique, and had that the inefficiency, the structure that exist in the powder supersound shaping suppression technique are complicated, low scheduling problem is rateed to energy utilization, the utility model discloses a SMD vibration female die assembly, go up the ejector die, down ejector die, demould cushion, heighten fork piece, electrode briquetting, the utility model discloses the structure that can be effectual exists in the solution powder suppression technique is complicated, suppression density distribution is uneven and had that the inefficiency, the structure that exist are complicated, low scheduling problem is rateed to energy utilization in the powder supersound shaping suppression technique.

MnO2 coating liquid of tantalum capacitor and preparation method of MnO2 coating liquid

Abstract: The invention discloses a MnO2 coating liquid of a tantalum capacitor and a preparation method of the MnO2 coating liquid. The preparation method comprises the steps of preparing 50-56wt% of manganese nitrate aqueous solution; adding 0.01-0.2wt% of non-ionic surfactant into the manganese nitrate aqueous solution, and uniformly stirring the non-ionic surfactant until the non-ionic surfactant is dissolved; adding 0.01-0.1wt% of water-soluble viscosity reducer into the manganese nitrate solution, and uniformly stirring the water-soluble viscosity reducer until the water-soluble viscosity reducer is dissolved; and continuously adding 1-2.5wt% of water-soluble alcohol into the manganese nitrate solution, and uniformly stirring the water-soluble alcohol until the water-soluble alcohol is dissolved. In the MnO2 coating liquid of the tantalum capacitor, prepared by the method, the surface tension can be reduced to 1.2*10 -1.5*10 N/m (25 DEG C), the viscosity can be reduced to (0.6-1.2)cp (25 DEG C), the micropore immersion capability is greatly improved, the manganese nitrate solution can be coated on a MnO2 negative electrode with enough area only by impregnation/thermal decomposition for one time, so that the capacity leading-out ratio reaches over 90%, the electrical performance of the tantalum capacitor is ensured, meanwhile, the production process can be remarkably simplified, and the production efficiency is improved.