Optimization of anodizing process of tantalum for Ta2O5-based capacitors

Zaffora, Andrea; Franco, Francesco Di; Quarto, F. Di; Santamaria, Monica

doi:10.1007/s10008-020-04704-0

Cited by 15 publications

(13 citation statements)

References 47 publications

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“…In the Mott–Davis model of an amorphous semiconductor (SC), the Δ E am term is essentially positive or zero, but we are aware that this term can turn to a negative value if, apart from the absence of long-range crystalline order, intense optical transitions originated by a distribution of vacant/filled electronic states (DOS distribution) within the mobility gap are occurring. In this case, the presence of other possible crystallographic defects as well as of impurities and/or nonstoichiometry has been suggested in the literature. − ,,,− …”

Section: Modeling the Optical Band Gap Of Ternary Oxide Systemsmentioning

confidence: 96%

“…This aspect is particularly intriguing in the case of thin films of oxides obtained by using different growth techniques or grown in different conditions but with the same technique. In the case of anodic oxide films grown by anodizing in different solutions, two common sources of variability can be attributed to the differences in the crystallinity degree of the anodic films as well as to the possible incorporation, into the oxide film, of chemical species derived from reacting species lying in solution. − …”

Section: Introductionmentioning

confidence: 99%

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A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymorphs

et al. 2021

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A generalization of the modeling equation of optical band gap values for ternary oxides, as a function of cationic ratio composition, is carried out based on the semiempirical correlation between the differences in the electronegativity of oxygen and the average cationic electronegativity proposed some years ago. In this work, a novel approach is suggested to account for the differences in the band gap values of the different polymorphs of binary oxides as well as for ternary oxides existing in different crystalline structures. A preliminary test on the validity of the proposed modeling equations has been carried out by using the numerous experimental data pertaining to alumina and gallia polymorphs as well as the crystalline ternary Ga(1–x)Al x O3 polymorphs (α-Ga(1–x)Al x O3 and β-Ga(1–x)Al x O3) covering a large range of optical band gap values (4.50–8.50 eV). To make a more rigorous test of the modeling equation, we extended our investigation to amorphous ternary oxides anodically formed on Al-d-metal alloys (Al-Nb, Al-Ta, and Al-W) covering a large range of d-metal composition (x d‑metal ≥ 0.2). In the last case, the novel approach allows one to overcome some difficulties experienced in fitting the optical band gap dependence from the Al-d-metal mixed anodic oxide composition as well as to provide a rationale for the departure, at the lowest d-metal content (x d‑metal < 0.2), from the behavior observed for anodic films containing higher d-metal content.

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Section: Modeling the Optical Band Gap Of Ternary Oxide Systemsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymorphs

et al. 2021

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“…Many methods of anodizing tantalum and other valve metals to form a dielectric oxide have been reported in the literature. [8][9][10][11] Here we chose to use combination galvanostatic/potentiostatic method widely used in the tantalum capacitor industry. Namely, the anodization of the sintered tantalum anodes was performed in 0.1 wt.…”

Section: Methodsmentioning

confidence: 99%

Reliability and Failure Mode in Solid Tantalum Capacitors

Freeman

Lessner

Luzinov

2021

ECS J. Solid State Sci. Technol.

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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.

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“…Due to the large capacitance density, wide operating temperature range and excellent frequency characteristics, tantalum electrolytic capacitors are an essential passive component in filtering, bypassing, rectification, coupling and energy conversion. [1][2][3][4][5][6][7] With the rapid development of the electronics industry and the demand for comfort of terminal products, electronic devices are gradually developing in the direction of thinness, flexibility and wearability. 8,9 Tantalum electrolytic capacitors are therefore in high demand to become thinner and easier to integrate with silicon wafer, glass and Polyimide (PI).…”

Section: Supplementary Materials For This Article Is Available Onlinementioning

confidence: 99%

Morphological Evolution of Corrosion Pits on the (200) and (211) Surfaces of Tantalum Foil

Zhao¹,

Xu²,

Sun³

et al. 2023

J. Electrochem. Soc.

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As an extremely passive metal, tantalum is often used as an additive element in corrosion-resistant alloys. Although the electrochemical corrosion mechanisms of these tantalum-based alloys have been extensively studied, the corrosion properties of the tantalum metal itself have received little attention. In this study, we developed a numerical simulation model to qualitatively describe the propagation of corrosion pits on different crystal surfaces of tantalum. The morphological characteristics of the corrosion pits predicted by the model are in high agreement with those observed by scanning electron microscopy, indicating the validity of the model. Due to the difference in crystallographic orientation, the corrosion pits on the surface of (200) have a square shape while those on the surface of (211) have an inverted triangle shape. Although the dimensions of the two types of pits are close, the square pit is more likely to develop deeper and thus the (200) surface exhibits a higher specific surface area. Therefore, the present work provides a reference for the fabrication of etched foils for tantalum electrolytic capacitors.

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Optimization of anodizing process of tantalum for Ta2O5-based capacitors

Cited by 15 publications

References 47 publications

A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymorphs

A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymorphs

Reliability and Failure Mode in Solid Tantalum Capacitors

Morphological Evolution of Corrosion Pits on the (200) and (211) Surfaces of Tantalum Foil

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