A key factor in determining the effectiveness of etchants for electrochemical surface enlargement of Ta foil for electrolytic capacitor

Zhao, Jiping; Xu, Youlong; Li, Yizhuo; Wang, Jingping; Ding, Xiangdong

doi:10.1016/j.apsusc.2022.155366

Cited by 5 publications

(6 citation statements)

References 38 publications

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“…Our previous studies have shown that the pit walls are easily protected by adsorbed oxygen in the solution containing Br, while the bottom of the pit is continuously etched due to the high concentration of Br ions. 11 In addition, in this study we do not study the mechanism of pitting, but only the morphological evolution of pitting after its formation. Based on this, we developed two microscopic models of the etch pits as shown in Figs.…”

Section: ) Boundary Conditionsmentioning

confidence: 98%

“…If ultra-thin etched tantalum foil with a high specific surface area (SSA) is used as the anode, none of the above will be a problem. In order to effectively increase the SSA of tantalum foil, our group has carried out a series of works to investigate the passivation mechanism, 10 electrochemical corrosion mechanism 11,12 and anisotropy of electrochemical corrosion of tantalum. 13 We found that oxygen (including dissolved oxygen in liquids) is the main species that causes spontaneous passivation of tantalum.…”

Section: Supplementary Materials For This Article Is Available Onlinementioning

confidence: 99%

“…Only when the wall of the pit is protected by dissolved oxygen and the bottom of the pit is exposed can the tantalum foil be effectively etched by certain aggressive ions. 11 In addition, due to the specific crystallographic orientation, the pits on the (200) surface are square while the etched pits on the (211) surface are inverted triangles. 13 Apparently, the crystallographic anisotropy triggers a very different corrosion morphology.…”

Section: Supplementary Materials For This Article Is Available Onlinementioning

confidence: 99%

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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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Section: ) Boundary Conditionsmentioning

confidence: 98%

Section: Supplementary Materials For This Article Is Available Onlinementioning

confidence: 99%

Section: Supplementary Materials For This Article Is Available Onlinementioning

confidence: 99%

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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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“…We have proven in another work that the re-passivation of Ta in a corrosive agent is a key factor in obtaining high SSA. [13] In addition, the pit walls are always more likely to be re-passivated in a solution containing Br than the pit bottom. Electrochemical machining processes with DC pulses as the power source undergo anodic dissolution only at PWH (high level), but not at the PWL (low level) stage.…”

Section: Sufficient Time To Complete Re-passivationmentioning

confidence: 99%

“…Our research group has been committed to solving this problem and has done a lot of research. In the previous work, the effect of etching agent type [12,13] and crystal surface orientation [14] on tantalum foil SSA has been discussed theoretically. These works have laid a good theoretical foundation for this topic.…”

Section: Introductionmentioning

confidence: 99%

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

Zhao

Hou

et al. 2023

Adv Materials Technologies

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Although 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.

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Electrical Performance Enhancement of 400 V Level Aluminum Solid Electrolytic Capacitors with Interface Modulation through Intervention of PVA

Liu,

An,

et al. 2024

Adv Eng Mater

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Poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a conductive polymer dispersion, is widely used in cathodes of solid electrolytic capacitors. However, it still suffers from performance limitations when used at high frequencies, and its withstand voltage must be improved. Herein, impregnation drying introduces a polyvinyl alcohol (PVA) coating onto alumina, which regulates the interface between the PEDOT:PSS cathode and alumina. The equivalent series resistance (ESR) of the capacitor is significantly reduced, whereas the withstand voltage is slightly improved. This study demonstrates that the presence of PVA enhances the wettability of PEDOT:PSS dispersions on alumina surfaces. Changes in the infrared peak positions of the OH and SO3H groups following the mixing of the PVA and PEDOT:PSS films, along with alterations in the thermal decomposition temperature, indicate the occurrence of crosslinking. Theoretical calculations demonstrate the presence of hydrogen bonds between the OH groups in PVA and the SO3H groups of PEDOT:PSS. Interface modulation effectively improves capacitor performance, as the capacitance ratio of capacitors with 400 V level withstand voltages increases from 97.35% to 98.85%, and the ESR at 100 kHz is significantly reduced by ≈40%. This study provides a valuable reference for the preparation of high‐performance solid electrolytic capacitors.

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A key factor in determining the effectiveness of etchants for electrochemical surface enlargement of Ta foil for electrolytic capacitor

Cited by 5 publications

References 38 publications

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

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

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

Electrical Performance Enhancement of 400 V Level Aluminum Solid Electrolytic Capacitors with Interface Modulation through Intervention of PVA

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