Tantalum Capacitors Research Articles

Failure behavior of tantalum electrolytic capacitors under extreme dynamic impact: Mechanical–electrical model and microscale characterization

Tantalum electrolytic capacitors have performance advantages of long life, high temperature stability, and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatronic equipment, including penetration weapons. The latter are high-value ammunition used to strike strategic targets, and precision in their blast point is ensured through the use of penetration fuzes as control systems. However, the extreme dynamic impact that occurs during penetration causes a surge in the leakage current of tantalum capacitors, resulting in a loss of ignition energy, which can lead to ammunition half-burst or even sometimes misfire. To address the urgent need for a reliable design of tantalum capacitor for penetration fuzes, in this study, the maximum acceptable leakage current of a tantalum capacitor during impact is calculated, and two different types of tantalum capacitors are tested using a machete hammer. It is found that the leakage current of tantalum capacitors increases sharply under extreme impact, causing functional failure. Considering the piezoresistive effect of the tantalum capacitor dielectric and the changes in the contact area between the dielectric and the negative electrode under pressure, a force–electric simulation model at the microscale is established in COMSOL software. The simulation results align favorably with the experimental results, and it is anticipated that the leakage current of a tantalum capacitor will experience exponential growth with increasing pressure, ultimately culminating in complete failure according to this model. Finally, the morphological changes in tantalum capacitor sintered cells both without pressure and under pressure are characterized by electron microscopy. Broken particles of Ta–Ta2O5 sintered molecular clusters are observed under pressure, together with cracks in the MnO2 negative base, proving that large stresses and strains are generated at the micrometer scale.

X-ray Induced Electric Currents in Anodized Ta2O5: Towards a Large-Area Thin-Film Sensor.

We investigated the characteristics of radiation-induced current in nano-porous pellet and thin-film anodized tantalum exposed to kVp X-ray beams. We aim at developing a large area (≫cm2) thin-film radiation sensor for medical, national security and space applications. Large area (few cm2) micro-thin Ta foils were anodized and coated with a counter electrode made of conductive polymer. In addition, several types of commercial electrolytic porous tantalum capacitors were assembled and prepared for irradiation with kVp X-rays. We measured dark current (leakage) as well as transient radiation-induced currents as a function of external voltage bias. Large transient currents (up to 50 nA) under X-ray irradiation (dose rate of about 3 cGy/s) were measured in Ta2O5 capacitors. Small nano-porous Ta and large-area flat Ta foil capacitors show similar current-voltage characteristic curve after accounting for different X-ray attenuation in capacitor geometry. The signal is larger for thicker capacitor oxide. A non-negligible signal for null external voltage bias is observed, which is explained by fast electron production in Ta foils. Anodized tantalum is a promising material for use in large-area, self-powered radiation sensors for X-ray detection and for energy harvesting.

Electrochemical impedance of porous tantalum solids: modeling of frequency response

The paper proposes a new approach to the analysis of electrochemical impedance spectra of porous tantalum bodies, which involves modeling the frequency response via an equivalent circuit that takes into account the pore hierarchy. It was shown that the proposed circuit describes well the experimental data and allows characterization of the porous structure, including the contribution of different types of pores to the total capacitance of the porous body, characteristic relaxation times, and activation frequencies for different type pores. Two types of samples were analyzed: a porous tantalum body obtained by sintering Ta powder and a porous tantalum body covered with a Ta2O5 dielectric layer. Modeling showed a significant redistribution of contributions from pores of different types into the total capacitance after the formation of Ta2O5 due tothe preferential isolation of the smallest pores and/or those difficult to access. The results of modeling of the frequency response of the analyzed samples agree well with the scanning electron microscopy data. The proposed approach has the potential to be advantageous for the technology of tantalum capacitors

Synergetic treatment of waste tantalum capacitors and polyvinyl chloride by subcritical water: Tantalum recovery, benzoic acid production and dechlorination

The rapid upgrading of electronic products led to the generation of a great deal of waste tantalum capacitors (WTCs). The recovery of WTCs is of great interest due to the high-value metal tantalum and resin materials. However, it is difficult to separate/recover the materials from WTCs because of the special structure and composition. Polyvinyl chloride (PVC) waste with high level of chlorine could result in severe corrosion and emission of chlorinated pollutants in the conventional disposal process. In this study, a synergetic and high-efficiency treatment of WTCs and PVC by subcritical water (SubCW) process was developed based on the interaction of the two kinds of wastes. The interaction between WTCs and PVC in SubCW could significantly reduce the treatment temperature and shorten the reaction time for recovering high-purity metal tantalum from WTCs, and it could also markedly improve the dechlorination efficiency (DE) of PVC. The optimized conditions for the synergetic treatment of WTCs and PVC were 325 ℃, 30 min, solid-to-liquid ratio of 1:5 g/mL, and PVC-to-WTCs ratio of 6:1 g/g. The resin conversion efficiency (RCE) of WTCs and the DE of PVC could reach 100% and 97.39% under the optimized conditions. The HCl released from PVC in SubCW could significantly promote the acid-catalytic hydrolysis of resin materials in WTCs and resulted in the production of abundant phenol/phenol derivates. In turn, hydroxyl functional group of phenol/phenol derivates could enhance the dechlorination of PVC by promoting the hydroxyl substitution reaction pathway. High level of benzoic acid (72.52%) could be obtained from the interaction between the decomposition products of WTCs and PVC by radical and oxidation reactions. The SubCW synergetic process developed in this study provided a high-efficiency and low-energy strategy for metal tantalum recovery, benzoic acid production, and dechlorination from WTCs and PVC wastes.

Responsibility boundaries and the governance of global value chains: The interplay of efficiency, ethical, and institutional pressures in global strategy

AbstractResearch SummaryI explore the relationship of firm global strategy and global value chain (GVC) governance, within a context of expanding responsibility boundaries for unethical practices in the value chain. Specifically, focusing on the tantalum supply chain within the digital electronics GVC, I conduct a case‐based process study that contextualizes the different strategic responses of three manufacturers of tantalum capacitors when faced with similar efficiency, ethical, and institutional pressures. Integrating the GVC and global strategy literatures, I find that structural inertia in GVCs limits the efficacy of strategies that preserve, rather than alter, the governance structure, instead requiring a strategic restructuring carried out by individual firms, whose internalization of responsibility boundaries is encouraged by the institutionalization of these boundaries through public policy.Managerial SummaryUnethical practices within global value chains are increasingly becoming the responsibility of firms with no direct control over such practices, leading to growing pressures for firms to alter their global strategies to meet social and institutional demands. Research has focused on strategies that preserve the structure of the value chain, despite questions about the efficacy of these approaches. By looking at the case of “conflict minerals” within the digital electronics value chain, this study finds that inherent flaws in value chain structures, which managers can identify, require individual firms to implement strategies that change the structure of the value chain, specifically by increasing ownership and control over the linkages where unethical practices occur and encouraging public policies that add value to these strategies.

An update on high temperature tantalum capacitor technology

Developments and improvements in the materials, design and manufacturing of tantalum bulk capacitors have resulted in new case sizes, improved ESR, higher operating voltages and temperatures. This work discusses the basic design and manufacture of hermetic tantalum and wet tantalum capacitors and the resulting high temperature performance offered by each technology. Specifically, hermetic sealed tantalum capacitors offer a novel set of design options for the high temperature designer. This technology, exhibits superior stability when exposed to high temperatures, high humidity, and ambient atmosphere. The device is impervious to the typical capacitance drop common to high temperature capacitor operation. Thus they enable potentially significant size reductions, lower component counts, and reliability improvements in extremely high temperature applications, such as downhole oil drilling. Both electrical and physical comparisons are made between the characteristics of bulk stacked ceramic capacitors, hermetic tantalum and wet tantalum devices across an operating range of -55°C to +230°C. Lifespan and recommended de-ratings are presented.

Numerical Simulation of Tantalum Capacitor Reflow Soldering in Temperature Field

This article aims to simulate and design the thermal stress during the welding process of tantalum capacitors, which is prone to failure. In this paper, the subsection function is defined, the boundary conditions of thermal stress are set, and the mesh is divided through the temperature diagram of high temperature reflow welding process; Analyze the temperature changes in the welding machine based on time changes, and conduct simulation analysis of thermal stress and cross-sectional analysis of thermal stress. Through simulation results, improve the design structure to minimize the impact of welding process on capacitor failure.

Sustainable recycling process for tantalum recovery from printed circuit boards

In IRETA2 project a process to recycle tantalum capacitors from end-of-life printed circuit boards was developed. The process starts with an optical detection of the capacitors followed by capacitors disassembly from both sides of the PCBs within 90 ms using lasers. Both detection and disassembly were integrated into an automated system which takes an average of 2.9 s per capacitor. Furthermore, a refining process was developed to separate the tantalum from the capacitor which includes mechanical treatment, magnetic and density separation, refining electrolysis and thermal oxidation to produce tantalum pentoxide. With the process developed, an overall efficiency for tantalum of at least 73% was achieved. The economic assessment shows that the process is cost-efficient if the market price of tantalum increases by 23 EUR/kg or the process time of optical detection and the laser-based removal reduced by 0.2 s. An environmental LCA demonstrates the ecological benefits of this recycling process compared to primary production.

Techno-economic analysis of the sequential recovery of valuable metals from waste tantalum capacitors in Indian context

The necessity for urban mining of metals has arisen due to the growing demand for metals brought about by technological innovation, the depletion of natural resources, and the exponential growth in e-waste generation. However, to be industrially adaptable, any recycling process must be economically profitable. Therefore, in this article, an economic feasibility study was conducted to determine the profitability of the proposed recycling process for recovering valuable metals from waste tantalum capacitors. Firstly, an integrated process was developed for the recovery of almost all economically and strategically significant metals. A detailed elemental and metallurgical balance followed this to determine the mass flow of metals during various stages of treatment. Lastly, the economic feasibility analysis has been done by estimating various cost components from capital and operating costs (utilizing Indian cost as foundation for calculation) to evaluate the profit that might be made by operating the suggested recycling facility for a month. Sensitivity and scenario analysis further investigated the impact of the most significant cost component on the percentage profit. The findings of this study support the notion that the suggested recycling method has a great deal of potential value and is commercially feasible with an ample profit margin.

Separation of manganese and nickel from tantalum capacitor leach liquor- A comparative study of D2EHPA and CYANEX272 as extractant

Tantalum capacitor is widely distributed in almost every electronic equipment due to its superior volumetric efficiency, which allows miniaturization of size of the gadgets- a prime demand of today’s technological driven society. These capacitors, after reaching the end-of-life stage, should be considered as a rich secondary resources for recovery of different valuable metals. In these work, we have developed a hydrometallurgical method for recovery of manganese and nickel from tantalum capacitors leach liquor. Firstly, the capacitors were subjected to preprocessing treatment for removal of outer mold housing containing epoxy resin with silica. After this, the metal-rich fraction was subjected to leaching using hydrochloric acid to selectively dissolve all the manganese and nickel into the solution. This leach liquor was then subjected to solvent extraction using D2EHPA and CYANEX272 to study the effectiveness of these carrier in separation of manganese from nickel and other minute metals. Both the carrier shows excellent selectivity for separation of manganese from other metallic elements. Extraction efficiency of manganese was 97% and 99% for D2EHPA and CYANEX272, respectively.

Surface enlargement of tantalum capacitor foils by pulsed direct current etching and laser cladding

Electrochemical etching for the surface enlargement of tantalum capacitor foils has always been a challenge, due to the ultra-high chemical stability of tantalum foils. Herein, pulsed direct current etching of tantalum capacitor foils assisted by laser cladding was investigated and high surface area enlargement was achieved. The effects of electrolyte composition, power supply parameters and external environment on the etching process of tantalum foil were systematically studied, to screen out the best experimental conditions. Furthermore, iron particles with diameters of 3–5 μm were successfully laser cladded on the surface of tantalum foils. These particles will be easily etched in the electrochemical process to form more previous pores, which can serve as etching sites for further tantalum foil etching. Under the best conditions, high-specific capacitance tantalum foils with a capacitance of 155.1 nF/mm2 were obtained at a high forming voltage of 100 V, which were 8 times larger than the unetched light foils. The surface enlargement of tantalum capacitor foils is expected to realize the development of novel tantalum capacitors with both high operating voltage and high capacitance.

РАЗРАБОТКИ ИНСТИТУТА ХИМИИ И ТЕХНОЛОГИИ РЕДКИХ ЭЛЕМЕНТОВ И МИНЕРАЛЬНОГО СЫРЬЯ В ОБЛАСТИ ТЕХНОЛОГИИ ТАНТАЛОВЫХ КОНДЕНСАТОРНЫХ ПОРОШКОВ С УДЕЛЬНЫМ ЗАРЯДОМ ОТ 3 000 ДО 120 000 мкКл/Г

The results of research in the field of obtaining tantalum capacitor powders in ICT KSC RAS are presented. The basic technological schemes and original solutions of individual operations included in them for obtaining agglomerated electron-beam (EB) powders with a specific charge 3 000–6 500 C/g, sodium-thermal powders with a specific charge 8 000–70 000 C/g, and magnesium-thermal tantalum powders (specific charge 80 000–120 000 C/g) are considered.

Hybrid leaching of tantalum and other valuable metals from tantalum capacitor waste

We propose a novel integrated model for the recovery of tantalum from tantalum-rich waste using a combination of hydrometallurgical and bio-metallurgical processes. To this end, leaching experiments with heterotrophs (Pseudomonas putida, Bacillus subtilis and Penicillium simplicissimum) were carried out. The heterotrophic fungal strain leached manganese with an efficiency of 98%; however, no tantalum was detected in the leachate. An unidentified species did mobilise 16% tantalum in 28days in an experiment with non-sterile tantalum capacitor scrap. Attempts to cultivate isolate and identify these species failed. The results of a range of leaching trials resulted in an effective strategy for Ta recovery. A bulk sample of homogenised Ta capacitor scrap was first subjected to microbial leaching using Penicillium simplicissimum, which solubilised manganese and base metals. The residue was subjected to the second leach using 4M HNO3. This effectively solubilised silver and other impurities. The residue collected after the second leach was pure tantalum in concentrated form. The hybrid model produced derives from observations from previous independent studies and shows that we can effectively recover tantalum along with silver and manganese in an efficient and environmentally friendly manner from tantalum capacitor scrap.

An Ultra‐Thin, Ultra‐High Capacitance Density Tantalum Capacitor for 3D Packaging

AbstractAlthough embedded capacitors have been applied and researched for many years, their large‐scale application still faces challenges such as low capacitance density, high thickness, high cost, and incompatibility with integrated processes. In this work, a breakthrough has been made in the fabrication of ultra‐thin tantalum (Ta) capacitors with ultra‐high capacitance density that can be used for 3D packaging. The key to these excellent performances is the application of Ta foil with nano‐porous structure to the anode of the capacitor. The Ta foil with high specific surface area (SSA) is successfully prepared by direct current pulse etching. At a current density of 15 mA cm−2, a pulse frequency of 50 Hz, and a duty cycle of 30%, the SSA of Ta foil is increased by 76 times after etching in an electrolyte with 0.01 v% TOA for 30 min. Based on this, Ta capacitors with a form factor of less than 40 µm, showing a capacitance density of 750 nF mm−2 and a leakage current of less than 2.1 × 10−7 A at 8 V is successfully fabricated. To the best of the authors’ knowledge, this is the highest capacitance density reported to date for the mentioned form factors.

Recycling of metallic values from discarded tantalum capacitors

ABSTRACT The generation of electronic waste generation has led to significant attention towards metal recovery from urban sources. Due to scarcity, finite resources, and geopolitical constraints, tantalum recycling from capacitors is essential. In this study, sequential separation involving the removal of tightly bound epoxy resin and metallic impurities is carried out. Pyrolysis as a pre-treatment and its response on phase transformation, resin decomposition and metal enrichment are investigated. Pyrolysis effectively liberates the tantalum–rich sintered core from outer resin which is followed by mild organic acid leaching. The manganese impurity was removed from the core to obtain Ta recovery of ∼94.8% with ∼96% purity in the leach residue. The separated resin component was subjected to conventional sink-float separation for the recovery of metallic values (silver, tantalum). It is found that 100 g (666 units) of Ta capacitors can yield 34 g of Ta, equivalent to 0.28 tons of primary ore.

Relationship of the Mechanical Properties of Porous Anode Bodies with the Electrical and Reliability Characteristics of Tantalum Capacitors

Relationship of the Mechanical Properties of Porous Anode Bodies with the Electrical and Reliability Characteristics of Tantalum Capacitors

Separation of waste tantalum capacitors by supercritical methanol: Recovery of high-purity metal tantalum and producing of bisphenol/diphenyl chemicals

With the rapid upgrading of electronic products, a large amount of waste tantalum capacitors (WTC) were generated. The recovery and purification of the WTC attracted widespread interest due to the high-value rare metal tantalum and resin materials. However, the recovery and purification of the WTC was difficult due to the heterogeneous complex composition including metal tantalum, nickel–iron, silver, and organic resins. High-temperature and the potential formation of the hazardous compounds such as dioxins are the main bottleneck of the traditional thermochemical treatment methods for the WTC. In this study, a novel and high-efficiency supercritical methanol (SCM) process was developed for the recovery and purification of tantalum and resins from the WTC based on the low hydrogen bonding numbers and dielectric constant of methanol. The tantalum could be recovered as pure metal tantalum, and the resins were converted into oil by the SCM process. The temperature, time, and solid-to-liquid ratio have significant effect on the conversion ratio of resins. Under the optimal SCM conditions (350 °C, 90 min, and 1:20 g/mL), 97.1% of the external resins of capacitor were converted into oil (99.5%) and gas (0.5%), and the high-purity metal tantalum could be fully recovered. GC–MS and FT-IR analysis showed that the products converted from the resins in the WTC mainly included high level of aromatic derivatives of bisphenol and diphenyl (88.02%), which could be used as fuel or chemical feedstock after proper upgrade. The SCM method is an environmentally friendly process for the recovery and purification of the WTC without any discharge of waste water and off-gas due to that the treatment medium methanol could be recycled. The conversion mechanism of resins in the WTC by the SCM process was proposed.

MicroCrack-Net: A Deep Neural Network With Outline Profile-Guided Feature Augmentation and Attention-Based Multiscale Fusion for MicroCrack Detection of Tantalum Capacitors

The microcrack defect in the terminal electrode of the tantalum capacitor seriously affects the service life of the capacitor. However, the microcrack displays low contrast and large noises in the image. Meanwhile, the width of the microcrack is small, and the area in the image is tiny, which brings additional challenges to the detection of microcracks on the terminal electrodes. To improve the performance of detecting microcracks, this article proposes a detection model with outline profile-guided feature augmentation and attention-based multiscale fusion, titled with MicroCrack-Net. In this method, the microcrack outline is utilized to guide the lossless feature extraction to strengthen unobvious microcrack features without pooling operation to avoid information loss of tiny defects during the layer-by-layer processing in the convolutional neural network. A gradual attention mechanism is proposed to attract the attention of the detection model to local defect areas in the image with noises. Multiscale feature extraction and fusion are designed to process the data in tensors of the same size. The experimental results demonstrated that the proposed model is effective and has superior performance over VGG16, resNet50, resNext50, DenseNet, Racki-Net, and SegDecNet in detecting microcracks.

Fault Analysis and Treatment of GE Brivo MR355 1.5 T Magnetic Resonance Gradient System and Cooling System

The GE Brivo MR355 1.5 T magnetic resonance system is difficult to maintain due to its complex structure and principle. Clinical engineers should be familiar with the basic structure and operation principle of the equipment. After the failure of the equipment occurs, they should first check the error information, combine the fault phenomenon and maintenance manual, clear their thoughts and carefully analyze the possible causes of the failure, and adopt the method of step-by-step elimination, principle analysis and exchange of the same principle. After replacing the chip tantalum capacitor and sumitomo cold head of the same model, the equipment resumed normal operation. As a clinical engineer, regular equipment inspection and preventive maintenance should be done for large equipment, which is conducive to reducing the equipment failure rate.

Hydrometallurgical recovery of manganese and nickel and isolation of tantalum from obsolete tantalum capacitor

Tantalum capacitor demand is rapidly growing, primarily from the electronic and superalloy industries. Indeed, the global tantalum market is anticipated to boost at a compound annual growth rate of around 6% over the next decade. With increasing technological advancements, electronics' obsolescence rate has also increased. The obsolete capacitors from these electronics are a rich secondary resource for recycling strategically and economically significant metals. In this article, we have developed an environment-friendly hydrometallurgical route for recovery of manganese and nickel from the tantalum capacitors. Firstly, silica-free tantalum capacitor procured after pre-processing was leached using hydrochloric acid (1–3 M) for preferred dissolution of manganese and nickel, to facilitate a tantalum-rich residue. Manganese was then selectively separated from leach liquor using solvent extraction with D2EHPA and CYANEX272, with the extraction efficiency of each reagent compared. Quantitative dissolution of both manganese (99.9%) and nickel (98.9%), with no tantalum dissolution, was witnessed under the optimized leaching condition of 3 M HCl, 50 g/l pulp density, 60 °C, and 120 min. Kinetic data for manganese and nickel in the temperature range of 30–60 °C demonstrated the leaching reaction at the surface to be the rate controlling step. D2EHPA and CYANEX272 each showed excellent selectivity for manganese under the optimized conditions. However, CYANEX272 proved to be a better extractant in light of higher extraction efficiency in single-stage extraction (∼75%), than D2EHPA (∼40%), with less organic consumption. Above 99% manganese was selectively extracted with predicted 2-stages extraction by McCabe-Thiele plot using CYANEX272 under the optimized condition.