Effect of Trace Elements on Etching of Aluminum Electrolytic Capacitor Foil

Arai, Kozo; Suzuki, Takao; Atsumi, Taisuke

doi:10.1149/1.2114188

Cited by 57 publications

(25 citation statements)

References 12 publications

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“…[3][4][5][6] Bulk concentrations of certain impurities ͑e.g., Cu and Pb͒ are carefully controlled during foil processing. 5 Apart from the surface concentrations of impurities, the grain size and microstructure of the aluminum foil ͑especially the ''cubicity,'' i.e., the proportion of surface grains having ͑100͒ orientation͒ influence the etch morphology, as does the uniformity of the surface oxide layer.…”

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confidence: 99%

Atomic Force Microscopy Study of Anodic Etching of Aluminum: Etching Morphology Development and Caustic Pretreatment

Martin

Hebert

2001

J. Electrochem. Soc.

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Atomic force microscopy ͑AFM͒ was used to investigate the topographic characteristics of pitting sites during anodic galvanostatic etching of high-purity aluminum foils in hot baths containing HCl and H 2 SO 4 . Pit sites near pre-existing ridges formed by rolling are preferred, and the distribution of sites depends on the foil fabrication process. Etch tunnels are found only within shallow pits formed by surface dissolution, which may be a prerequisite for tunnel formation. Pit sites are more numerous and evenly distributed after pretreatment of foils by immersion in 1 N NaOH. AFM imaging during acid dissolution of NaOH treated foils reveal submicrometer cavities formed as a result of NaOH treatment. Some cavities appear to form near oxide particles or inclusions. It is argued that these cavities are subsurface voids exposed by uniform dissolution in the acid. If the void surface is oxide-free, they may dissolve as pits when exposed by the shallow surface dissolution shown to take place in the etchant bath.

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confidence: 99%

Atomic Force Microscopy Study of Anodic Etching of Aluminum: Etching Morphology Development and Caustic Pretreatment

Martin

Hebert

2001

J. Electrochem. Soc.

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“…Therefore, improvements in pit distribution density and the homogeneity of pit sizes, while avoiding an excessive dissolution of the aluminium surface, are essential for maximising the surface area of etched aluminium. Although the dispersibility of the initiation sites of pits is generally improved by the addition of a small amount of the element into the aluminium substrate, [17,18] problems preventing the perfect control of pit distribution still remain.…”

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confidence: 99%

Control of nano/microstructure and pit initiation sites on aluminium surface by use of self‐assembled spheres

Ono

Uchibori

Asoh

2010

Surface & Interface Analysis

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Nano/microstructure control and electrochemical etching of aluminium substrate using a honeycomb alumina mask fabricated by anodisation with self-assembled spheres aligned on the aluminium surface were studied to directly control the initiation sites of pits. The transfer of the hexagonally ordered pattern of self-assembled spheres to the aluminium substrate could be achieved by substantially suppressed anodic oxide growth under the spheres where selective electrochemical etching proceeded. That is, etch pits are generated only in the thinner areas or holes of the honeycomb alumina mask with a one-to-one correspondence. With this process, improvements in pit distribution density and the homogeneity of pit sizes, while avoiding excessive dissolution of the aluminium surface, could be achieved easily in comparison with the conventional method. The density of pits could also be controlled by changing the diameter of spheres used as an indirect mask.

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“…[1][2][3][4][5][6][7][8][9][10] To maximize the capacitance of the electrolytic capacitors, the size and interval of the tunnel pits must be controlled precisely by considering the operating voltages. 1 In our previous report, we showed the control of the initiation sites of the tunnel pits using a patterned mask composed of a polymer film on Al.…”

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Fabrication of Site-Controlled Tunnel Pits with High Aspect Ratios by Electrochemical Etching of Al Using Masking Film

Nishio

Fukushima

Takeda

et al. 2007

Electrochem. Solid-State Lett.

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The process for the site-controlled formation of tunnel pits with high aspect ratios by anode etching of Al͑100͒ foil is described.Introduction of a small amount of Cu on the Al foil, which has a patterned thin layer of polymers, initiated the uniform development of pits and generated the tunnel pits with sufficiently high aspect ratios. The obtained ordered array of tunnel pits with high aspect ratios will be used for the preparation of several types of functional devices in addition to the improvement of electrolytic capacitors, which use the Al foil with tunnel pits as a surface-enlarged electrode.Formation of tunnel pits on Al by the anisotropic anode etching of Al͑100͒ foils in an electrolyte containing Cl − ions has been widely used for the enlargement of the surface area of electrodes in electrolytic capacitors. 1-10 To maximize the capacitance of the electrolytic capacitors, the size and interval of the tunnel pits must be controlled precisely by considering the operating voltages. 1 In our previous report, we showed the control of the initiation sites of the tunnel pits using a patterned mask composed of a polymer film on Al. 11 In this process, a very thin patterned mask of poly͑chloro-prene͒ rubber ͑CR͒ with the thickness of ϳ200 nm formed on Al can be used to control the initiation of tunnel pits at the initial stage of the anode etching of Al. However, tunnel pits with sufficient depth could not be formed due to the preferential growth of the tunnel pit in the lateral directions. In the present report, we show the process for the formation of tunnel pits with sufficiently high aspect ratios. For the uniform growth of tunnel pits with high aspect ratios, we introduced a small amount of Cu on an Al surface as an initiator for the uniform development of tunnel pits. The uniform development of the pits effectively improved their growth with uniform depth, and yielded the tunnel pits with sufficiently high aspect ratios. The obtained ordered array of tunnel pits on Al prepared by the present process will be used for the fabrication of various types of functional devices in addition to the improvement of the capacitance in electrolytic capacitors. Figure 1 shows the process for the fabrication of highly ordered tunnel pits with high aspect ratios on Al. A patterned mask composed of a polymer film placed on Al with the ͑100͒ plane ͑Ͼ95%͒ was formed using a process reported previously. 11 A thin patterned mask of CR was formed using a poly͑dimethylsiloxane͒ ͑PDMS͒ stamp, which has an ordered hole array. Diameter, depth and interval of holes of the stamp were 1.5, 1.5, and 5.0 m, respectively. Size of the stamp was typically 6 ϫ 6 mm. Before making a patterned mask, an Al foil was electrochemically polished in a mixed solution of perchloric acid and ethanol. Then, a small amount of Cu was formed on the surface of Al by vacuum evaporation or sputtering. The amount of deposited Cu was controlled using a quartz crystal thickness monitor. Electrochemical etching of Al was carried out under a constant-current cond...

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Effect of Trace Elements on Etching of Aluminum Electrolytic Capacitor Foil

Cited by 57 publications

References 12 publications

Atomic Force Microscopy Study of Anodic Etching of Aluminum: Etching Morphology Development and Caustic Pretreatment

Atomic Force Microscopy Study of Anodic Etching of Aluminum: Etching Morphology Development and Caustic Pretreatment

Control of nano/microstructure and pit initiation sites on aluminium surface by use of self‐assembled spheres

Fabrication of Site-Controlled Tunnel Pits with High Aspect Ratios by Electrochemical Etching of Al Using Masking Film

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