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Replacement of MnO2 with conductive polymers as cathode materials in chip tantalum capacitors allows for a substantial reduction of the equivalent series resistance (ESR), improvement of frequency characteristics, and elimination of the possibility of ignition during failures. One of the drawbacks of chip polymer tantalum capacitors (CPTCs) is a relatively poor long-term stability at high temperatures. In this work, variations of capacitance, dissipation factor, and ESR in different types of capacitors including automotive grade parts from three manufacturers have been monitored during storage at temperatures from 100 °C to 175 °C for up to 18,000 hours. Results show that ESR is the most and capacitance the least sensitive to degradation parameter. Times to parametric failures have been simulated using a Weibull-Arrhenius model that allowed for assessments of activation energies of the degradation and prediction of times to failure at the use temperature. Degradation of CPTCs was explained by thermo-oxidative processes in conductive polymers that result in exponential increasing of the resistivity with time of ageing. This process starts after a certain incubation period that depends on packaging materials and design and corresponds to the time that is necessary to form delamination between the encapsulating molding compound and lead frame. The effectiveness of the existing qualification procedures to assure stable operation of CPTCs is discussed.

In this work, different types of polymer and MnO 2 cathode capacitors are tested for scintillation breakdown using a constant current stress (CCS) technique modified to allow detection of amplitudes and duration of current spikes. Monitoring of leakage currents with time under bias is used to assess the effect of scintillations. The appearance and composition of damaged sites are examined after deprocessing and cross-sectioning. Thermal processes during scintillations are analyzed, a mechanism of breakdown based on growth of conductive filaments in the dielectric is suggested, and self-healing processes in polymer and MnO 2 cathode capacitors is discussed.

Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs in chip tantalum capacitors. The sensitivity of components to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors. The effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have not been studied properly yet, and there is no sufficient information regarding the difference in the sensitivity to soldering between polymer and MnO2 capacitors. In this work, 16 types of polymer and 9 types of MnO2 tantalum capacitors with different moisture content have been tested before and after reflow soldering. The level of moisture release during soldering has been estimated and thermo-mechanical analysis used to assess deformation of capacitors during soldering simulations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more likely to fail catastrophically with a short circuit and possible ignition during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption that corresponds to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage.

The basic bilayer of all types of tantalum capacitors, tantalum anode, and anodic oxide film of tantalum as a dielectric is not a thermodynamically stable system. This is demonstrated by the tantalum-oxygen equilibrium diagram that does not contain two-phase equilibrium areas for pure tantalum and tantalum pentoxide]. Relaxation of the Ta-Ta2O5 system into the thermodynamically stable state occurs through oxygen migration from Ta2O5 to Ta, resulting in oxygen vacancies in the tantalum oxide dielectric. Conductivity of the dielectric and, thereby, DCL of tantalum capacitor increase exponentially with the concentration x of oxygen vacancies in the depleted with oxygen Ta2O5–x. Another reason for the thermodynamic instability of tantalum capacitors is the amorphous structure of the anodic oxide film of tantalum formed on crystalline tantalum. Amorphous dielectrics trend to ordering and crystallization spontaneously to reduce their internal energy. Growth of crystalline inclusions in amorphous matrix of the anodic oxide film induces mechanical stress in the film, which results in a disruption of the dielectric and, thereby, in the failure of the capacitor.

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.

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.

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.

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.

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.

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.

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.

The major advantage of Polymer Tantalum capacitors over other types of tantalum capacitors is their low equivalent series resistance (ESR), providing a higher capacitance stability with frequency and ripple current capability. When Polymer Tantalum capacitors were introduced to the market in mid 1990s, they were low voltage, leaky, and unreliable, which limited their applications to commercial electronics. Today, some types of polymer tantalum capacitors demonstrate the highest working voltage, lowest DC leakage, and highest reliability ever achieved in tantalum capacitors. These Polymer Tantalum capacitors combine outstanding performance and reliability with superior volumetric charge efficiency, which makes them cost effective and attractive for numerous applications, including mission critical ones. This paper is dedicated to the major technological breakthroughs and scientific discoveries that enabled the radical evolution of Polymer Tantalum capacitors.

LTCC multilayer substrate (LTCC, Low Temperature Co-fired Ceramic) is one of the most widely used substrate in the high performance MCM (MCM, multi-chip module). Many kinds of passive elements and active devices can be integrated on the surface of the substrate. As one kind of the passive element, solid tantalum electrolytic capacitor has many advantages such as the bigger capacity per unit volume and the lower resistivity impedance, which are benefit for the emission performance of the MCM modules. In this paper, two kinds of process are used for the assembly of large-scale solid tantalum electrolytic capacitor surface mounted on the LTCC multilayer substrate. Verified experiments are carried out on the basis of soldering and experimental process analysis. A new soldering method is creatively proposed to solve the reliable problem of the soldering of solid tantalum electrolytic capacitors on the LTCC substrate. After environment tests, the resistance between tantalum capacitor lead and soldering pad is less than 100 milliohm, the shear strength of tantalum capacitor joint is larger than 50N. And this method is successfully applied in the existing products.

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.

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.

High-density passive components are needed for continued miniaturization of complex high-performance electronic systems. Tantalum (Ta) capacitors provide some of the highest volumetric densities achieved due to their combination of high-surface area and relatively high dielectric constant, but suffer from low frequency stability and large form-factors due to the electrode design. In this paper, a printed thin-film tantalum capacitor design is presented. Tantalum capacitor arrays of 1 μF/mm2 up to and beyond 1 MHz. The improved frequency stability comes from the ultra-thin structure of the capacitors, which reduces the path length of the charging and discharging current. The capacitors showed low equivalent series resistance and consistent electrical performance before and after thermal moisture testing at 65°C and 95% relative humidity for 500 h and 1000 h. Due to the ultra-low form-factor, the thin-film Ta capacitor technology can be extended to highly-miniaturized power converters with efficient substrate- or wafer-scale integration.

Recycling rare metal tantalum from waste tantalum capacitors (WTCs) is significant to alleviate the shortage of tantalum resource. However, environmental problems will be caused if the organic materials from WTCs are improperly disposed. This study presented a promising vacuum pyrolysis technology to recycle the organic materials from WTCs. The organics removal rate could reach 94.32 wt% according to TG results. The optimal parameters were determined as 425 °C, 50 Pa and 30 min on the basis of response surface methodology (RSM). The oil yield and residual rate was 18.09 wt% and 74.94 wt%, respectively. All pyrolysis products can be recycled through a reasonable route. Besides, to deeply understand the pyrolysis process, the pyrolysis mechanism was also proposed based on the product and free radical theory. This paper provides an efficient process for recycling the organic material from WTCs, which can facilitate the following tantalum recovery.

Waste printed circuit boards (WPCBs) are valuable urban ore for recycling. Many efforts have been done to recover resources from basal boards of WPCB. In addition to basal boards, WPCBs contain many electronic components. However, the recycling technology for electronic components has been poorly developed. This study proposed an integrated and environment-friendly technology for recycling waste tantalum capacitors (WTCs) of WPCBs. Firstly, the WTCs were treated by argon pyrolysis to decompose mold resin. The pyrolysis temperature of 550 °C and holding time for 30 min were considered as the optimal parameters. Then, the pyrolysis residues were performed by crush and magnetic separation to recover nickel-iron terminals. Finally, chloride metallurgy (CM) was used to recover rare metal tantalum (Ta). The Ta recovery rate could reach 92.87 ± 0.36%. The optimal parameters were determined as temperature of 493 °C, adding FeCl 2 ·4H 2 O of 53 wt% and holding time for 150 min based on the response surface methodology (RSM). This study exploits an efficient approach for recycling WTCs and provides a reference for future industrial application.

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. Moreover, we introduce the roughness parameter limits for which the simple parallel-plate capacitor equation is sufficiently accurate for capacitors with one rough electrode. Our results imply that the interface roughness beyond the proposed limits cannot be dismissed unless the independence of the capacitance from the interface roughness is experimentally demonstrated. The practical protocols suggested in our work for the reliable use of the parallel-plate capacitor equation can be applied as general guidelines in various fields of interest.

Tantalum capacitors (TCs) are widely used in electronic appliances. The rapid replacement of electronic products results in generating large amounts of waste TCs (WTCs). WTCs, rich in valuable tantalum, are considered as high quality tantalum resources for recycling. However, environmental pollution will be caused if the organics of WTCs were not properly disposed. Therefore, effectively recycling the organics of WTCs is significant for recovering the valuable parts. This study proposed an argon (Ar) pyrolysis process to recycle the organics from WTCs. The organic decomposition kinetic was first analyzed by thermogravimetry. The results showed that the organics were decomposed in two major steps and the average activation energy was calculated to 234kJ/mol. Then, the suitable pyrolysis parameters were determined as 550°C, 30min and 100ml/min. The organics were effectively decomposed and converted to oils (mainly contained phenol homologs and benzene homologs) and gases (some hydrocarbon). These pyrolysis products could be reutilized as energy sources. Moreover, based on the products and bond energy theory, the pyrolysis mechanisms of the organics were also discussed. Finally, a reasonable technological process for products utilization was presented. This study contributes to the efficient recycling the organics before valuable material recovery from WTCs.

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.

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.

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.

Recycling e-waste has been a significant topic for environmental protection and also for resource recovery. Waste tantalum capacitors (WTCs), widely existing in discarded small appliances, are rich in high quality tantalum (Ta) resources. However, recovering Ta from WTCs is difficult due to the tightly covered mold resin. This study proposes an efficient and environmentally friendly process using supercritical water (SCW) to decompose the organics and recover Ta from WTCs. Two methods of SCW were studied: SCW depolymerization (SCWD) and SCW oxidation (SCWO). The results indicated that the mold resin (packing) of WTCs were effectively decomposed by SCW treatments. The organic decomposition efficiency in SCWD was lower than that in SCWO. The optimal parameters for SCWD and SCWO were, respectively, considered to be 425 °C, 25 MPa, and 120 min and 400 °C, 25 MPa, and 90 min, adding a 10% volume ratio of H2O2. After SCWO treatment, Ta electrodes were directly recovered, and the purity of Ta could reach 93.18%....

The capacitor is a passive electrical device, used to collect electrical energy by generating a potential difference. It is generally consisting of combination of two conductors placed next to each other separated by dielectric medium. The performance of a capacitor expressed in terms of the capacitance (C) depends on the dimension/geometry of the plate/electrode and the dielectric constant of the material, where the dielectric can be defined by insulating medium having permittivity, with no AC power losses or DC leakage. The capacitor shows different response to AC and DC sources. These are mainly used to supply power in several electronic and electrical systems. Therefore, this chapter provides the fundamental aspects of the capacitors and their basic properties. It emphasizes on the parallel plate model, the basic terminologies associated with the capacitors along with the equivalent circuits of the capacitor and its response to the externally applied AC and DC sources. It also describes about different types of capacitors that are being fabricated using different materials and different construction techniques. These different types of capacitors provide some unique properties.

Increasingly dense microprocessors will require high-density passive components that can enable integrated power delivery with larger conversion ratios and higher output currents. Of these, nanoparticle-based tantalum capacitors can provide some of the highest volumetric densities compared to other capacitor technologies, due to the high surface area-to-volume ratio. Additionally, their temperature-stable dielectric can handle higher current ratings. However, the complex nanoparticle-based electrode structure results in long conduction paths, resulting in higher ESR and reduced frequency stability. A model is needed that can accurately predict the relationship between capacitor nanostructure and electrical performance so that the nanostructure can be optimized to meet the theoretical limits of device performance. This paper develops such a model, and demonstrates its accuracy by characterizing a real tantalum capacitor device. The model is then used to study the effect of capacitor materials and device geometry on the device performance, including capacitance density, frequency stability, and ESR.

The reliability and failure modes in surface mount Solid Electrolytic and Polymer Tantalum capacitors were investigated using the parts manufactured with conventional technology and flawless technology (F-Tech) that suppresses typical defects such as crystalline inclusions in the amorphous matrix of the tantalum oxide dielectric. The accelerated tests were performed; failure rates were calculated based on the cumulative percent of failed parts vs time and acceleration factor. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and thermo-gravimetric/deferential scanning calorimetry analysis (TGA/DSC) were included in the investigation to analyze chemical and structural transformations in the capacitors failed in the accelerated tests. Results show strong impact of technology on reliability and failure mode including the lowest failure rate and no wear-out failure mode in Polymer Tantalum capacitors manufactured with F-Tech. No ignition and burning tantalum were found in the Solid Electrolytic Tantalum capacitors that failed short. Limiting temperatures and protecting the encapsulating epoxy compound from ignition and burning at normal conditions of the accelerated testing take place via ablation process—heat consuming irreversible structural and chemical transformations in the material such as carbonization process.

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 ...

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...

Aluminum electrolytic capacitors with polymer electrolytes were developed to obtain lower equivalent series resistance (ESR) than that is achievable with liquid electrolytes. Replacement of the liquid electrolyte with a solid conductive polymer also overcomes the propensity of the liquid to evaporate over time, which leads to a reduction in capacitance and an increase in ESR values. However, capacitor manufacturers acknowledge that humidity can degrade the polymer, thereby having an adverse effect on the reliability of polymer aluminum (PA) capacitors. In the current study, surface mount and thru-hole PA capacitors from two different manufacturers were subjected to highly accelerated stress testing (110 °C, 85% RH) and elevated temperature–humidity (85 °C, 85% RH) conditions for rapid assessment. The polymer electrolyte in the capacitors was poly(3,4-ethylenedioxythiophene). Failure analysis was performed to determine the observed failure modes and the underlying failure mechanisms. The dominant failure modes observed were an increase in leakage current and an increase in ESR.

This work focuses on a polymer based capacitive harvester which can be fabricated with help of roll-to-roll and low cost printing methods. In contrast to electrostatic MEMS based parallel plate transducers or dielectric elastomer systems here, the capacitance is varied as function of the mechanical load by changing of the top electrode area with help of an electrically conducting composite elastomer. In case of a composite elastomer electrode the maximum capacitance in compressed state does not only depend on the thickness and permitivity of the dielectric but first of all on the quality of the interface and the micro structure of the conducting phase in the composite electrode at the interface which was investigated by FEM Maxwell simulation. An equivalent circuit model is used to study the influence of the leakage current inside the dielectric and the bulk resistivity of the elastomer electrode. First experiments with state of the art polymer, thin film and novel printed dielectrics in contact with elastomer electrodes have been performed to prove the harvesting principle at low frequencies. Charges between 25 and 70 nAs per cm2 have been transferred per cycle at 100 V/200 V while the maximum capacity was between 0.4 and 0.8 nF/cm2.

When the valve metal is used as anode material, the dielectric properties of sol–gel-derived thin film are greatly enhanced. That is because anodized self-healing occurs at the interface of the anode and the thin film. An oxide insulating layer with a good dielectric property is generated. Anodization heals the defects and the breakdown spots of thin film. Other than anodized self-healing, electrode contact is also an important factor, affecting the dielectric characteristics of the thin film capacitor, which cannot be ignored, especially when both factors exist in one film device. In this study, the sol–gel-derived strontium titanate thin film is used as dielectric material in the film capacitor, and platinum and aluminum as electrode materials. We find that the Schottky barrier at the interface of platinum and strontium titanate greatly reduces the leakage current. However the interface barrier restricts the anodizing of aluminum electrode and the further enhancement of the dielectric strength of the thin film capacitor.

This paper describes active shunt LC decoupling circuit with ceramic capacitors, allowing volume reduction and lifetime improvement of the high-voltage dc filters. Active filtering is based on the energy exchange between high-voltage coupling and low-voltage auxiliary capacitors. The coupling capacitor enables use of the low-voltage switched-mode power stage and low-voltage auxiliary decoupling capacitor. Advantageously, this allows to reduce power dissipation, switching frequency ripple current, and to reduce volume of the circuit. Additionally, power efficiency and capacitor lifetime are improved by using recent high-voltage coupling multilayer ceramic capacitors, reaching very low ESR . This paper provides description of the active decoupling capacitor, and shows an example of the feedback control. Obtained performances are demonstrated on the prototype of 1300-μF/450-V capacitor, allowing to reduce volume by three, when compared to ordinary 450-V electrolytic capacitor.

Among all the raw materials for aluminum electrolytic capacitors, there is no doubt that the anode foil is one of the most important raw materials influencing the performance of capacitors. The voltage, capacitance, thickness and impurity content of the anode foil have a direct effect on the performance of capacitor. The cost of anodes also contributes to the total cost of capacitors by a high percentage. Thus, for the manufacturers of capacitors, minimizing the anode foil costs needs also to be taken into account besides its performance. Against such a background, this article evaluates the anode foil of a new supplier to be used in a 400 V medium and in a high voltage aluminum electrolytic capacitor with the purpose of minimizing the product costs while achieving the same performance. The capacitors with new supplier's anode foil are compared with that using the current anode foil by evaluating the performance by the change of the various electrical properties.

Because of the fabricability of polymer and excellent dielectric properties of ceramics, ceramic-polymer composites have been investigated widely for embedded capacitors which can improve electric performance greatly. In order to obtain further application of composite, the embedded capacitors with three-layer sandwich structure containing the BaTiO3/epoxy composites as dielectric layer and copper foil as electrodes were fabricated. The dielectric properties are improved by preventing the defect in dielectric layer through lamination process. Our results show that the capacitors exhibit high dielectric permittivity (e = 20), low dielectric loss (0.01) at 103 Hz from 40 to 100 °C and high breakdown strength (24 kV/mm), which indicate that the lamination is a promising process for embedded capacitor fabrication and BaTiO3/epoxy composites have potential for high-performance embedded capacitors application in field of microelectronics.

The highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films were prepared on porous tantalum pentoxide surface as cathode for polymer tantalum capacitors (PTC). The electrical performances of PTC with PEDOT:PSS films as cathode were optimized by dimethyl sulfoxide (DMSO) bath treatment. With the DMSO-bath treatment of PTC, the equivalent series resistance (ESR) of PTC decreased from 25 mΩ to 9 mΩ. The ultralow ESR led to better capacitance-frequency performance. The device reliability investigation revealed the enhanced environmental stability of PTC. The enhanced performances were attributed to the conductivity improvement of PEDOT:PSS cathode films and the removal of excess PSS from PEDOT:PSS films.

In this study, the dielectric properties of metal-oxide-metal capacitors based on Tantalum Titanium Oxide (TiTaO) thin films deposited by reactive magnetron sputtering on aluminum bottom electrode are investigated. The structure of the films was characterized by Atomic Force Microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric properties of TiTaO thin films were studied by complex impedance spectroscopy over a wide frequency range (10 -2 - to 10 5 Hz) and temperatures in -50 °C to 325 °C range. The contributions of different phases, phases’ boundaries and conductivity effect were highlighted by Cole – Cole diagram (ɛ” versus ɛ’). Two relaxation processes have been identified in the electric modulus plot. A first relaxation process appears at low temperature with activation energy of 0.37 eV and it is related to the motion of Ti 4 + (Skanavi’s model). A second relaxation process at high temperature is related to Maxwell-Wagner-Sillars relaxation with activation energy of 0.41 eV.

We report that efficient high dielectric polymer/ceramic composite materials can be optically printed into three-dimensional (3D) capacitor by the projection based stereolithography (SLA) method. Surface decoration of Ag on Pb(Zr,Ti)O 3 (PZT@Ag) particles were used as filler to enhance the dielectric permittivity. Polymer nanocomposites were fabricated by incorporating PZT@Ag particles into the photocurable polymer solutions, followed by exposure to the digitally controlled optical masks to generate 3D structures. The dielectric permittivity of Flex/PZT@Ag composite reaches as high as 120 at 100 Hz with 18 vol% filler, which is about 30 times higher than that of pure Flex. Furthermore, the dielectric loss is as low as 0.028 at 100 Hz. The results are in good agreement with the effective medium theory (EMT) model. The calculated specific capacitance of our 3D printed capacitor is about 63 F g −1 at the current density of 0.5 A g −1 . Cyclic voltammetry (CV) curves indicate 3D printed capacitors possess low resistance and ideal capacitive properties. These results not only provide a tool to fabricate capacitor with complex shapes but lay the groundwork for creating highly efficient polymer-based composites via 3D printing method for electronic applications.

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.

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.

Tantalum (Ta) is the one of the most critical elements according to the European Commission. Research on tantalum recovery from secondary sources such as waste electrical and electronic equipment (WEEE), bottom ash and by products of the industrial activities, however, is limited. In this study, the recovery potential of tantalum from spent tantalum capacitors was tested using bioleaching. Three different kinds of microorganisms were tested for tantalum recovery, which were Pseudomonas putida (DSM No. 6125), Bacillus subtilis (DSM No. 1088532), and Penicillium simplicissimum (DSM No. 1078). It turned out that P. simplicissimum has the ability to leach tantalum from wasted tantalum capacitors with a maximium leaching rate of 1.25 g Ta per kg sample. An unknown species achieved the highest leaching rate (9.88 g Ta / kg sample) but isolation and identification failed. The potential of tantalum recovery by bioleaching is demonstrated, however, further research needs to be carried out.

Gamma radiation induces surface defects in PEDOT which could recover under electric field, where gamma ray restricts the polarization of dipole. Parameters of PEDOT tantalum capacitor in space could be stable when resting and vary less when working. Gamma ray favors the use of PEDOT cathode tantalum capacitor in space.

The first article in this series [1] covered the early history of electrolytic capacitors, from their invention around 1880 to the invention of the modern Al electrolytic capacitor structure in 1925. The second article [2] takes us from Samuel Ruben’s 1925 invention to the wide range of Al electrolytic capacitors presently on the market. The present article discusses electrolytic capacitors based on metals other than Al.

Electrochemical capacitors are becoming promising energy conversion/storage and power output devices. However, high cost and low energy density are two serious disadvantages. By integrating the advantages of Li-/Na-ion batteries and electrochemical capacitors, Li-/Na-ion capacitors have been explored recently. Al is very cheap and is the most abundant metal element on the earth. There are few reports on Al-ion capacitors due to the challenges in finding a suitable anode with large capacitance and good rate performance. Here, the feasibility of assembling an Al-ion capacitor with good electrochemical performance is demonstrated. The Al-ion capacitor is assembled by using a composite of MoO3 nanotubes coated by a conductive polypyrrole (PPy@MoO3) as an anode, which functions via a redox intercalation/deintercalation of Al3+ ions in aqueous solution. It delivers a capacitance of 693 F g−1, about 3 times higher than that of electrode materials for sodium-ion capacitors in aqueous solution. Combined with an activated carbon (AC) cathode, the Al-ion capacitor presents an energy density of 30 W h kg−1 and an excellent cycling life with 93% capacitance retention after 1800 cycles. This finding provides another energy storage device with low cost and promotes the application of capacitors.