Aluminum etched foil for electrolytic capacitors

Abstract

An aluminum etching foil (300) for an electrolytic capacitor disclosed herein includes: a core part having a width in the range of 460-520 mm, and a length of 100 m or greater; and two porous parts continuing from the core part and constituting first and second main surfaces. The porous parts are formed by etching. When defining the smaller etching amount among etching amounts per unit area in two end regions (300b1, 300b2) at a distance in a range of 2-7 mm from both ends in the width direction of any position as E1 (mg / cm2), and the average value of etching amounts per unit area in a center region inward of the two end regions (300b1, 300b2) as E2 (mg / cm2), the ratio E1 / E2 is 0.90 to 1.30.

Description

[Technical Field]

[0001] This disclosure relates to aluminum etched foil for electrolytic capacitors. [Background technology]

[0002] The electrode foils of electrolytic capacitors are typically formed by cutting large pieces of metal foil. Various proposals have been made regarding metal foils for electrolytic capacitors.

[0003] Claim 1 of Patent Document 1 (Japanese Patent Application Publication No. 2008-159922) describes "a method for manufacturing electrode foil for electrolytic capacitors, wherein aluminum foil is etched by passing it between a pair of electrode plates in an electrolyte, and an electrical shielding plate having a plurality of slit-shaped openings is installed between the aluminum foil and the electrode plates facing it, and etching is performed while controlling the current flowing between the electrodes and the aluminum foil, characterized in that the slit-shaped openings of the electrical shielding plate are V-shaped, extending from one point in the width direction of the center of the aluminum foil toward the ends and toward the upward direction of the etching bath." [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-159922 [Overview of the project] [Problems that the invention aims to solve]

[0005] Aluminum etching foils for electrolytic capacitors are traded in the market in a form with a width of about 500 mm and a length of 100 to 2000 m. Since the aluminum etching foil is manufactured by electrolytic etching, there are places where the etching amount is less at both ends in the width direction of the foil compared to the central part in the width direction of the foil. When the etching amount varies in the width direction of the foil, the thickness of the oxide film generated in the subsequent formation treatment is likely to vary in the width direction. As a result, bending and wrinkles are likely to occur at both ends of the foil. These bending and wrinkles cause unwanted foil breakage in processes such as formation treatment, slitting treatment, and winding.

[0006] Also, when the thickness of the etching layer, the etching amount, and the capacitance vary in the width direction, a difference in the elongation of the foil occurs due to the tension during the conveyance of the foil, the stress generated in the conveyance roller, and the pressure when pressing the foil, resulting in wrinkles and cracks in the foil and cracks in the etching layer.

[0007] In response to the recent demand for higher capacitance, the capacitance has been improved by increasing the etching amount (that is, deepening the etching layer). However, as a result, problems regarding wrinkles and strength of the etching foil have become significant. The influence of this problem is particularly large in hybrid capacitors where the width of the foil is narrow and it is often used at high voltages.

[0008] In such a situation, one of the objectives of the present disclosure is to provide an aluminum etching foil capable of stably manufacturing a high-capacitance electrolytic capacitor at a low cost, and a manufacturing method thereof.

Means for Solving the Problems

[0009] One aspect of the present disclosure relates to an aluminum etching foil for an electrolytic capacitor. The etching foil has a width in the range of 460 to 520 mm, a length of 100 m or more, and includes a core portion and two porous portions connected to the core portion, the two porous portions constituting the first and second main surfaces. The porous portions are porous portions formed by etching, and the smaller of the etching amounts per unit area in two end regions where the distances from both ends in the width direction at any position are in the range of 2 to 7 mm is designated as E1 (mg / cm 2 ), and when the average value of the etching amounts per unit area in the central region inside the two end regions is designated as E2 (mg / cm 2 ), the ratio E1 / E2 is 0.90 or more and 1.30 or less.

[0010] Another aspect of the present disclosure relates to another aluminum etching foil for an electrolytic capacitor. The other aluminum etching foil has a width in the range of 460 to 520 mm, a length of 100 m or more, and includes a core portion and two porous portions connected to the core portion, the two porous portions constituting the first and second main surfaces. When the total thickness of the two porous portions at a position where the distance from one end in the width direction at any position is 2 mm is designated as T1 (μm), and the total thickness of the two porous portions at the central position in the width direction at any position is designated as T2 (μm), 0.1 ≦ T1 / T2 is satisfied.

Advantages of the Invention

[0011] According to the present disclosure, an aluminum etching foil capable of stably manufacturing a high-capacity electrolytic capacitor at a low cost can be obtained. The novel features of the present invention are described in the appended claims. However, the present invention relates to both the configuration and the content, and will be better understood from the following detailed description in conjunction with the drawings, together with other objects and features of the present invention.

Brief Description of the Drawings

[0012] [Figure 1]This diagram schematically shows one step of an example of a method for manufacturing aluminum etched foil according to this disclosure. [Figure 2A] Figure 1 is a schematic top view showing the structure of aluminum etched foil manufactured by the process shown. [Figure 2B] This is a schematic top view showing the structure of an example of an aluminum etching foil related to this disclosure. [Figure 3] This is a schematic cross-sectional view showing the structure of an example of an aluminum etching foil related to this disclosure. [Figure 4] This is a schematic diagram illustrating the method for measuring etching amount. [Modes for carrying out the invention]

[0013] The embodiments relating to this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". When multiple materials are given as examples, unless otherwise specified, one of the given materials may be selected and used alone, or two or more may be used in combination.

[0014] (Aluminum etched foil for electrolytic capacitors) The following describes the first and second aluminum etched foils for electrolytic capacitors. The first and second aluminum etched foils may be referred to as "Foil (F1)" and "Foil (F2)" respectively. Furthermore, Foil (F1) and Foil (F2) may be collectively referred to as "Foil (F)". The information provided for Foil (F) applies to both Foil (F1) and Foil (F2).

[0015] The raw aluminum foil (the first sheet described later) used as the material for foil (F) is usually aluminum foil with a purity of 99.5% by mass or higher, and it is preferable to use aluminum foil with a purity of 99.90% by mass or higher (for example, 99.95% by mass or higher). The raw aluminum foil may contain trace amounts of other elements as long as it is possible to manufacture aluminum etched foil for electrolytic capacitors. The other elements are not particularly limited. Examples of other elements include metallic elements such as Cu, Fe, and Si.

[0016] The foil (F) can be used as the electrode foil material for an electrolytic capacitor. The foil (F) may be used as the anode foil material or as the cathode foil material. The foil (F) is cut to the size of the anode foil or cathode foil and used as the electrode foil for an electrolytic capacitor. A predetermined process may be performed before and / or after cutting. For example, when the foil (F) is used as the anode foil, a chemical treatment may be performed before and / or after cutting.

[0017] (First aluminum etched foil) The first aluminum etched foil (foil (F1)) has a width W in the range of 460 to 520 mm and a length L of 100 m or more. Foil (F1) includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces. The porous portions are formed by etching. The etching amount per unit area in two end regions located at arbitrary positions within a distance of 2 to 7 mm from both ends in the width direction is the smaller of the two etching amounts E1 (mg / cm²). 2 ) and the average value of the etching amount per unit area in the central region (inner region) inside the two end regions is E2 (mg / cm²), and the average value of the etching amount per unit area in the central region (inner region) inside the two end regions is E2 (mg / cm²). 2 When this is the case, the ratio E1 / E2 is between 0.90 and 1.30.

[0018] In foil (F1), the difference between the etching amount at the edges and the etching amount in the central region in the width direction is small. Therefore, curvature and wrinkling at both ends of foil (F1) can be suppressed. Furthermore, when processing foil (F1) to manufacture electrode foil for electrolytic capacitors, cracking of the foil and etching layer can be suppressed. Therefore, by using foil (F1), it is possible to manufacture high-capacitance electrolytic capacitors stably and at low cost.

[0019] The etching amount per unit area is the amount of etching per 1 cm of foil (F1) 2 This refers to the amount of etching per unit area. Specifically, 1 cm 2 This is represented by the sum of the etching amounts of the two porous regions on either side of the core of the foil. Details of the etching amount measurement method will be explained in the examples. The two end regions and the central region are selected from the regions that exist in the width direction of any position on the foil (F1).

[0020] The etching rate per unit area in the edge region is measured by the following procedure. First, a 10 cm long sample is cut from one end in the width direction at an arbitrary position, within a range of 2 to 7 mm. In this way, a sample with a width of 0.5 cm (width in the width direction Dw in Figure 2A) and a length of 10 cm (length in the longitudinal direction DL in Figure 2A) is obtained. Next, the etching rate of the obtained sample is measured, and the area of ​​the sample (5 cm²) is measured. 2 Divide by ) to find the etching amount per unit area. The etching amount per unit area of ​​the end region at the other end in the width direction can be found using the same method. Then, the smaller of the two etching amounts per unit area found is taken as etching amount E1.

[0021] The average etching amount E2 per unit area in the central region inside the edge regions is measured by the following procedure. First, in the central region inside the two edge regions mentioned above (a 20cm wide region within 10cm of the center), samples (0.5cm wide, 10cm long) are cut out at multiple points (6 or more points, for example, 6 points) at approximately equal intervals. Then, the etching amount per unit area of ​​each sample is determined using the method described above. Finally, the average value E2 is obtained by taking the arithmetic mean of the obtained etching amounts per unit area.

[0022] Traditionally, aluminum etched foil for electrolytic capacitors has been manufactured using AC etching. In AC etching, an AC voltage is applied between two opposing plates that sandwich an aluminum foil, causing an AC current to flow between the two plates. Electrolytic etching is performed by passing this AC current through the aluminum foil. In principle, current cannot flow through the center of the aluminum foil without going through it, so a current close to the theoretical value passes through the aluminum foil.

[0023] On the other hand, at both ends of the aluminum foil, a portion of the alternating current bypasses the edges of the aluminum foil and flows between the electrodes without passing through the foil. Therefore, at both ends of the aluminum foil, the current for etching is smaller than the current passing through the center of the foil. Consequently, in conventional aluminum etched foils, the etching amount E1 in the edge region could decrease significantly. In conventional aluminum etched foils, the etching layer was thin, so a large decrease in E1 did not always pose a problem. However, as the demand for higher capacitance increases and the etching layer becomes thicker, variations in the etching amount have become a major problem. In the foil (F) (foil (F1) and (foil F2)) according to this embodiment, the variation in the etching amount of the foil is reduced. Therefore, it can be preferably used in electrolytic capacitors even when the etching layer is thickened.

[0024] The etching amount of the aluminum etching foil can be measured by the method described in the examples. The etching amount can be varied depending on the time and conditions of the etching process. The ratio E1 / E2 can be varied by changing the shape of the electrodes during etching, the shape of the current shielding plate, the etching conditions, etc. Conventionally, the both ends of the etching foil have not been focused on, but the inventors of the present application have newly found that by controlling the etching amount at both ends, it is possible to suppress even the curvature and wrinkles in the vicinity of both ends.

[0025] The ratio E1 / E2 is preferably 0.97 or more, 0.98, or 0.99 or more, and may be 1.20 or less, 1.10 or less, or 1.06 or less. The ratio E1 / E2 may be 0.94 or more and 1.10 or less (for example, 0.97 or more and 1.06 or less). By setting the ratio E1 / E2 within this range, a particularly high effect can be obtained.

[0026] In the foil (F1), when the maximum value and the minimum value of the etching amount (per unit area) in the two end regions and the etching amount (per unit area) in the central region are respectively Emax (mg / cm 2 ) and Emin (mg / cm 2 ), (Emax - Emin) ≤ 5.1 may be satisfied. According to this configuration, a particularly high effect can be obtained. The value of (Emax - Emin) is preferably 1.0 or less, and more preferably 0.95 or less. The value of (Emax - Emin) is 0 or more. Although it is preferable that the value of (Emax - Emin) is small, it is difficult to make it exactly zero, and in actual production, it may be 0.1 or more (for example, 0.2 or more).

[0027] (Second aluminum etching foil) The second aluminum etched foil (foil (F2)) has a width W in the range of 460 to 520 mm and a length L of 100 m or more. Foil (F2) includes a core and two porous parts connected to the core, which constitute the first and second main surfaces. When the sum of the thicknesses of the two porous parts at a distance of 2 mm from one end in the width direction at any given position is T1 (μm), and the sum of the thicknesses of the two porous parts at the center of the width direction at any given position is T2 (μm), the condition 0.1 ≤ T1 / T2 is satisfied.

[0028] In foil (F2), the thickness T1 of the porous portion near the edges in the width direction and the thickness T2 of the porous portion at the center satisfy 0.1 ≤ T1 / T2. Therefore, curvature and wrinkling at both ends of foil (F2) can be suppressed. Furthermore, cracking of the foil and etching layer can be suppressed when processing foil (F2) to manufacture electrode foil for electrolytic capacitors. Therefore, by using foil (F2), it is possible to manufacture high-capacitance electrolytic capacitors stably and at low cost.

[0029] Thicknesses T1 and T2 are measured at a position in the width direction of an arbitrary location on the foil (F2). Thicknesses T1 and T2 were measured directly using a scanning electron microscope (SEM) at the cross-section after the cross-section of the aluminum etched foil was exposed. The method of exposing the cross-section may be by polishing after embedding the foil in resin, or by exposing the cross-section by ion milling, etc. The values ​​of T1 / T2 can be changed by changing the shape of the electrode during etching, the shape of the current shielding plate, the arrangement of the foil, electrode and shielding plate, and the etching conditions (temperature, current, etc.).

[0030] The T1 / T2 ratio is preferably 0.70 or higher or 0.85 or higher, and preferably 1.3 or lower or 1.15 or lower. By setting the T1 / T2 ratio to 1.15 or lower, foil breakage, cracking, and bending caused by excessive melting near the edges and a decrease in edge strength can be suppressed.

[0031] When Tz (μm) is the sum of the thicknesses of the two porous sections at a distance Z mm from one end in the width direction, and T2 (μm) is the sum of the thicknesses of the two porous sections at the center of the width direction at any given position, the condition 0.1 ≤ Tz / T2 may be satisfied. The value of Tz / T2 may be within the range exemplified for T1 / T2. Here, Z is preferably 1 (mm) and more preferably 0.5 (mm).

[0032] For foil (F2), the thickness of foil (F2) may be 90 μm or more and 220 μm or less, and the thickness T2 may be 50 μm or more. By setting the thickness of foil (F2) and the value of T2 within the above range, a particularly high effect can be obtained. When the thickness of foil (F2) is 90 μm or more and 220 μm or less, the thickness T2 may be 50 μm or more or 60 μm or more, and may be 190 μm or less or 170 μm or less. In addition, a thickness T1 of 60 μm or more is preferred. When the thickness of foil (F2) exceeds 120 μm, the thickness T1 is preferably 80 μm or more, 115 μm or more or 128 μm or more, and may be 180 μm or less or 170 μm or less.

[0033] (Matters common to foil (F1) and foil (F2)) The following describes foil (F). In other words, the following describes matters common to foil (F1) and foil (F2). Note that an example of foil (F1) may satisfy the requirements for foil (F2), and an example of foil (F2) may satisfy the requirements for foil (F1).

[0034] In foil (F), the two porous portions are arranged so as to sandwich the core. One porous portion is present on one side of the foil, and the other porous portion is present on the other side of the foil.

[0035] The width W of the foil (F) is generally constant throughout the foil. The width W of the foil (F) is 460 mm or more, preferably 480 mm or more, or 490 mm or more. A foil width closer to 500 mm makes it easier to set into the chemical equipment in the subsequent chemical process. Also, if the foil width is narrow, the number of slit foils decreases when slitting is performed during the capacitor manufacturing process, resulting in a lower yield.

[0036] The width W is 520 mm or less, and preferably 515 mm or less (for example, 510 mm or less). If the foil is too wide, it will be difficult to set into existing chemical processing equipment, and even if it can be set, the edges will come into contact with the chemical processing equipment, increasing the probability of foil cracking, scratches, bending, etc.

[0037] The width W is preferably in the range of 480 to 515 mm, or 490 to 510 mm. By setting it within these ranges, it becomes easier to use the same equipment currently used for storing and processing (chemical conversion) commercially available aluminum etching foil.

[0038] The thickness of the foil (F) may be 70 μm or more, or 90 μm or more, and preferably 100 μm or more. The foil (F) is particularly effective when used as foil for high-capacitance electrolytic capacitors (high-capacitance foil). By setting the thickness of the foil (F) to a certain value or more, foil suitable for high-capacitance electrolytic capacitors can be obtained.

[0039] Furthermore, the thickness of the foil (F) may be 250 μm or less, 200 μm or less, or 150 μm or less. By keeping the thickness of the foil (F) below a certain value, the transport of the foil becomes easier.

[0040] The thickness of the foil (F) is preferably in the range of 90 to 200 μm (for example, 100 to 190 μm). This range allows for the production of high-capacity electrode foils using etching technology, and also minimizes equipment-related challenges such as foil transport.

[0041] The length L of the foil (F) is 100m or more, preferably 200m or more, or 300m or more. When producing the same amount, if the length L is shorter, the number of foils will increase, requiring a larger storage area. Also, when producing the same amount of foil, if the length L is shorter, the number of times the foil needs to be set in the chemical processing machine and in the capacitor manufacturing process will increase, resulting in more labor.

[0042] The length L of the foil (F) may be 2000m or less, or 1000m or less. If the foil (F) is too long, it may be difficult to set it in the chemical processing equipment, or it may be too heavy, making it difficult to set it in the equipment, move, transport, and ship the foil. It is preferable that the foil (F) be in a rolled state.

[0043] The foil (F) may be a foil in which a porous portion has been formed by etching, but both ends in the width direction have not been cut. In this case, the end faces in the width direction of the foil are porous due to etching.

[0044] The foil (F) may be a foil in which a porous portion has been formed by etching, and then both ends in the width direction have been cut. This configuration makes it easy to make the porous portion uniform across the width direction.

[0045] In foil (F), the porous portion may include an inner layer region on the core side and a surface layer region on the opposite side of the core. In this case, when the thickness of the porous portion is T (μm), the surface layer region is a region where the distance from the outer surface of the porous portion is T / 4 or less, and the inner layer region is a region where the distance from the boundary between the porous portion and the core is T / 4 or less. Furthermore, the average diameter D1 (nm) of the pores in the surface layer region may be smaller than the average diameter D2 (nm) of the pores in the inner layer region. This configuration makes it possible to produce electrode foils with higher capacitance and higher strength. By making the average diameter D1 (nm) smaller than the average diameter D2 (nm), the tensile strength of foil (F) can be increased. As a result, foil breakage due to bending and foil breakage during the capacitor manufacturing process can be reduced.

[0046] The average diameters D1 and D2 can be determined as follows. (i) Obtain a cross-sectional image of the electrode foil using a scanning electron microscope (SEM). Using this image, measure the thickness of 10 arbitrary points in the porous region, calculate the average value of these measurements, and define the thickness T of one porous region as such. (ii) The region of the porous part that is less than or equal to T / 4 from the outer surface (surface S in Figure 3) is defined as the surface region. (iii) Obtain a cross-sectional image of the surface region, and perform a binarization process on the image to distinguish between the region of the metal skeleton constituting the surface region and the region of pores (pits) other than the region of the metal skeleton. (iv) Select an arbitrary point within the pore region of the surface area, draw a line segment that passes through that point and crosses the pore region, and measure the length of the shortest line segment. Perform this measurement for 20 arbitrary points within the pore region of the surface area, and the average of the obtained measurements is taken as the average diameter D1 of the pores in the surface area. (v) The inner layer region is defined as the region within the porous area where the distance from the boundary between the porous area and the core (boundary B in Figure 3) is T / 4 or less. The average diameter D2 of the pores in the inner layer region is also determined in the same manner as in (iii) and (iv) above.

[0047] From the viewpoint of improving capacitance, the ratio of the average diameter D1 to the average diameter D2, D1 / D2, may be 0.5 or more, 0.55 or more, 0.6 or more, or 0.7 or more. From the viewpoint of suppressing the reduction in surface strength and improving capacity per unit volume, D1 / D2 may be 0.98 or less, 0.95 or less, or 0.9 or less. The range of D1 / D2 may be any combination of the above upper and lower limits, but from the viewpoint of suppressing the reduction in surface strength and improving capacity per unit volume, it is preferably 0.5 or more and 0.98 or less, and more preferably 0.55 or more and 0.95 or less.

[0048] The ratio of D1 to D2, D1 / D2, may be 0.5 or more and 0.98 or less (for example, 0.6 or more and 0.92 or less). This configuration makes it possible to produce electrode foils with higher capacitance and higher strength. By setting the ratio D1 / D2 within the above range, the tensile strength of the foil (F) can be increased. As a result, foil breakage due to bending and foil breakage during the capacitor manufacturing process can be reduced. Furthermore, by suppressing the decrease in pore diameter in the inner layer region, it is possible to increase capacitance, especially on the high-voltage side. In addition, impregnation of electrolyte and polymer into the inner layer region becomes easier, and the effect of reducing the ESR of the capacitor can also be obtained.

[0049] From the viewpoint of suppressing the decrease in strength of the surface layer and improving the retention of electrolytes within the pores, the porosity P1 of the surface region may be smaller than the porosity P2 of the inner layer region. From the viewpoint of improving capacitance, the ratio P1 / P2 of P1 to P2 may be 0.5 or more, 0.55 or more, 0.6 or more, or 0.7 or more. From the viewpoint of suppressing the decrease in strength of the surface layer and improving capacity per unit volume, the ratio P1 / P2 may be 0.95 or less, 0.92 or less, or 0.85 or less. The ratio P1 / P2 may be within a range of any combination of the above upper and lower limits. The ratio P1 / P2 may be 0.5 or more and 0.95 or less, or 0.55 or more and 0.92 The following is also acceptable.

[0050] The porosity P1 of the surface region can be determined using the cross-sectional image of the surface region after the binarization process described in (iii) above, which is obtained in the process of determining D1 above. Specifically, the area S0 of the entire region of the image and the area S1 of the region occupied by pores within the image are measured, and the porosity P1 can be determined by calculating (S1 / S0) × 100. The porosity P2 of the inner region can be determined in the same manner as above.

[0051] The surface roughness Ra of the foil (F) is preferably 2.0 μm or less, more preferably 1.5 μm or less, and even more preferably 0.8 μm or less. Here, the surface roughness Ra is the surface roughness of the outer surface of the porous portion. The surface roughness Ra of the electrode foil refers to the arithmetic mean roughness Ra obtained in accordance with JIS (Japanese Industrial Standards) B 0601:2001. By setting the surface roughness Ra of the electrode foil to 2.0 μm or less (for example, 1.5 μm or less), it is possible to suppress the reduction in strength and capacity caused by surface roughness.

[0052] For foil (F), in the pore distribution of the porous portion measured by the mercury intrusion method, the cumulative pore volume V0 (cm³) in the range of pore diameter between 0.01 μm and 1 μm is measured. 3 ( / g) and the cumulative pore volume V in the range of pore diameter 0.01 μm or more and 0.06 μm or less. S1 (cm 3 / g) means V S1 The relationship / V0 ≤ 0.07 may also be satisfied.

[0053] In foil (F), the pore distribution of the porous portion measured by the mercury intrusion method is V S2 It is preferable that the relationship / V0 ≤ 0.05 (or 0.04) is further satisfied. As described above, V0 is the cumulative pore volume (cm³) in the range of pore diameters from 0.01 μm to 1 μm. 3 V S2 This refers to the cumulative pore volume (cm³) in the range of pore diameters between 0.01 μm and 0.05 μm. 3 The pore size is ( / g). The pore size distribution is measured by mercury intrusion, for example, using the AutoPore V series from Micromertics.

[0054] Small pores with a diameter of 0.01 μm or more and 0.06 μm or less (or 0.05 μm or less) are easily blocked by the dielectric layer, which is disadvantageous in terms of high capacitance, low ESR, and strength. In porous areas, the parts where pores are blocked by the dielectric layer not only do not contribute to improving capacitance, but also become hard and brittle. When the number of small pores increases and the above-mentioned blocked areas increase, the strength of the electrode foil decreases, and cracks or foil breakage may occur in the electrode foil during the manufacturing process of electrolytic capacitors (electrode foil transport, slitting, winding, connection by crimping with lead members, etc.). In contrast to this, V S1 / V0(and V S2 When / V0) is within the above range, there are few small pores and many pores with pore sizes suitable for improving capacitance are distributed, making it possible to increase capacitance. In this case, the above-mentioned blockage area is small, and the reduction in strength can be suppressed. By using such foil, it becomes possible to manufacture high-capacity electrolytic capacitors with excellent reliability.

[0055] In foil (F), the pore distribution of the porous portion measured by the mercury intrusion method is as follows: 3 ( / g) and the cumulative pore volume V in the range of pore diameter from 0.16 μm to 1 μm. L1 (cm 3 / g) means V L1 It is preferable that the relationship / V0 ≤ 0.4 is satisfied. In foil (F), in the pore distribution of the porous portion measured by the mercury intrusion method, V L2 It is preferable that the relationship / V0 ≤ 0.1 (or 0.08) is also satisfied. L2 This refers to the cumulative pore volume (cm³) in the range of pore diameters between 0.5 μm and 1 μm. 3 It is / g).

[0056] Large pores with a diameter of 0.16 μm or more (or 0.5 μm or more) and less than or equal to 1 μm are unlikely to contribute to improved capacitance. Large pores are disadvantageous in terms of increasing the surface area of ​​the electrode foil. For example, in the case of large pores, if two pores are formed close together, they tend to collapse, reducing the perimeter length of the pores (the total length of the contours of the inner walls of the pores per unit area of ​​the cross-section of the porous portion), thus hindering improved capacitance. L1 / V0(and V L2 When / V0) is within the above range, there are few large pores. Therefore, many pores with pore sizes suitable for improving capacitance are distributed, the surface area of ​​the electrode foil tends to increase, and high capacitance can be easily achieved.

[0057] The pore size distribution described above can be changed, for example, by altering the etching conditions. Specifically, the proportion of small pores can be increased by increasing the current density during etching.

[0058] The foil (F) may be cut and used as electrode foil after an oxide film is formed on its surface by chemical conversion treatment. An example of a method for evaluating the formed oxide film includes evaluation by the CV value, which is the product of capacitance C and breakdown voltage V. The smaller the variation in CV values, the more stable the electrolytic capacitor can be manufactured. In foil (F), the variation in the thickness (etching amount) of the porous part is small, so the variation in CV values ​​after oxide film formation can be reduced. When the CV value is measured by the method described in the examples below, it is preferable that the standard deviation σ of the CV value is 0.7 or less.

[0059] (Method of manufacturing aluminum etched foil) An example of a manufacturing method for the aluminum etching foil (foil (F)) described above is explained below. This manufacturing method may be referred to as "manufacturing method (M)" below. According to manufacturing method (M), both foil (F1) and foil (F2) can be manufactured. The matters described for foil (F1) and foil (F2) are applicable to manufacturing method (M) below, so redundant explanations will be omitted. The matters described for manufacturing method (M) may also be applied to foil (F1) and foil (F2). Note that foil (F1) and foil (F2) may be manufactured by methods other than manufacturing method (M).

[0060] (Etching process) The manufacturing method (M) includes an etching step in which an aluminum sheet (hereinafter sometimes referred to as the "first sheet") is etched to form porous portions on both sides of the sheet. The etching step roughens the surface of the sheet, forming a second sheet having the aforementioned core portion and two porous portions.

[0061] The thickness and size of the first sheet are selected according to the required thickness and size of the foil (F) (foil (F1) or foil (F2)). The thickness of the first sheet may be within the range exemplified for the thickness of foil (F). If pressing is performed after the etching process, the thickness of the first sheet is selected taking into account the reduction in thickness due to pressing.

[0062] When the processed sheet of the first sheet is used as foil (F) without being cut, the size (width and length) of the first sheet may be within the range of the sizes (width W and length L) exemplified for the size of foil (F). When a cutting process (described later) is performed on the processed sheet of the first sheet and it is used as cut foil (F), the size (width and length) of the first sheet is larger than the sizes (width W and length L) exemplified for the sizes of foil (F1) and foil (F2). For example, when a cutting process is performed to cut both ends in the width direction, the width of the first sheet is larger than the width W exemplified for foil (F). If the sum of the widths of the cut ends is Wcut (mm), then the width of the first sheet is smaller by Wcut than the width W exemplified for foil (F). The width of the first sheet may be in the range of 490 to 540 mm (for example, in the range of 500 to 530 mm).

[0063] In the manufacturing method (M), electrolytic etching is preferred. Performing electrolytic etching under predetermined conditions facilitates the production of the foil (F) described above.

[0064] From the viewpoint of forming large-diameter pores, electrolytic etching is performed at 2.0 A / cm 2 The following current densities may also be used: 1.5 A / cm² 2 The following current densities may also be used: 1.2 A / cm² 2 The process may be carried out at the following current densities. The current density may also be changed during etching. Larger pore diameters make it easier to form thicker dielectric layers, which is advantageous in terms of increasing voltage.

[0065] Electrolytic etching is preferably performed using AC etching, but DC etching may also be used. AC etching tends to form porous regions containing relatively small-diameter sponge-like pits. DC etching tends to form porous regions containing relatively large-diameter tunnel-like pits.

[0066] T is the etching time for electrolytic etching. E In this case, 0~0.7T EDuring this period, the etching solution temperature should be between 10°C and 60°C, and the temperature should be 0.7T. E ~T E During this period, the etching solution temperature may be set to between 5°C and 40°C. In this case, variations in pit diameter in the thickness direction of the porous portion can be reduced. Etching time T E For example, it could be between 15 minutes and 60 minutes.

[0067] The etching solution used in electrolytic etching is not particularly limited, and known etching solutions may be used. Hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid may be used as the etching solution, or a mixture of these acids may be used. The hydrochloric acid concentration of the etching solution is preferably in the range of 0.2 to 1.5 N.

[0068] An example of an AC etching method is schematically shown in Figure 1. As shown in Figure 1, the first sheet 301 is transported in the direction of arrow A so as to pass through the etching solution 501 placed in the processing tank 500. Inside the processing tank 500, an electrode pair 510 (first electrode 511, second electrode 512) is arranged so as to sandwich the transported first sheet 301. By applying an AC voltage between the first electrode 511 and the second electrode 512, the first sheet 301 is etched. As a result, the second sheet 302, which has the core portion and porous portion described above, is manufactured.

[0069] Figure 1 shows an example using two electrode pairs 510. However, the number of electrode pairs is not particularly limited; there may be one or two or more. The width of the first electrode 511 and the width of the second electrode 512 are each approximately the same as the width of the first sheet 301.

[0070] When etching is performed using a general method, the amount of etching on the first sheet 301 varies greatly depending on its position in the width direction of the sheet. For example, at both ends in the width direction, a portion of the current flowing due to the application of voltage passes outside the sheet, resulting in less etching. As a result, the porous portion becomes thinner at both ends in the width direction. Therefore, when performing electrolytic etching, a shielding plate made of an insulating material is placed near both ends in the width direction of the first sheet 301. By placing the shielding plate, a foil (F) having the above-described configuration can be formed. In other words, in this case, the second sheet 302 obtained by the etching process can be used as foil (F).

[0071] The shielding plate may be flat. Alternatively, the shielding plate may be shaped to surround the edge of the first sheet 301. For example, the cross-sectional shape of the shielding plate may be U-shaped to surround the edge of the first sheet 301.

[0072] Figure 2A schematically shows a top view of an example of the second sheet 302. The example of the second sheet 302 shown in Figure 2A has two strip-shaped regions 302b at both ends in the width direction Dw. Regions 302b extend along the two ends (both ends) 302e in the width direction Dw of the second sheet 302. Figure 2A also shows a line 302c located in the center of the longitudinal direction DL and the width direction Dw of the second sheet 302. Region 302a (central region) exists between the two regions 302b. If the shielding plate or the like described above is not used, region 302b is a region where the average thickness of its porous portion is smaller than the average thickness of the porous portion of region 302a. In other words, if the shielding plate or the like is not used, region 302b is a region where the etching amount is smaller than the etching amount of region 302a. The non-uniformity of the etching amount can be reduced by the shielding plate or the like described above. As mentioned above, the ratio E1 / E2 should be between 0.90 and 1.30. In other words, the etching amount of region 302b may be greater than or equal to the etching amount of region 302a.

[0073] After the etching process, a pressing process and / or a cutting process may be performed. In the pressing process, the second sheet 302 is pressed. In the cutting process, both ends of the second sheet 302 (at least a portion of region 302b) are cut. By cutting at least a portion of region 302b, the non-uniformity of the etching amount (non-uniformity of the thickness of the porous portion) can be reduced.

[0074] The width of the second sheet 302 cut during the cutting process can be selected according to the width of region 302b and the degree of non-uniformity in the thickness of the porous portion. However, if the area to be cut is too large, there will be a lot of loss. Therefore, even when performing a cutting process, it is preferable to reduce the area to be cut by reducing the non-uniformity of the etching amount in the etching process. The width of the second sheet 302 cut during the cutting process may be in the range of 5 to 40 mm (for example, in the range of 5 to 20 mm) at each end.

[0075] As described above, foil (F) (foil (F1) and foil (F2)) are manufactured. The manufactured foil (F) is usually distributed in a rolled state. A schematic top view of an example of the final foil (F) is shown in Figure 2B. The example aluminum etching foil 300 shown in Figure 2B has two end regions 300b that extend along the two ends (both ends) 300e in the width direction Dw, and a central region 300a that is inside these end regions 300b. The central region 300a is the region sandwiched between the two end regions 300b. Figure 2B also shows a line 300c located in the center of the aluminum etching foil 300 in the longitudinal direction DL and the width direction Dw.

[0076] Figure 3 is a schematic cross-sectional view showing an example of an aluminum etching foil (foil (F)) according to this disclosure. Figure 3 shows a cross-section of the aluminum etching foil in the thickness direction.

[0077] The aluminum etched foil 300 includes a core portion 330 and porous portions 310 and 320 connected to the core portion 330. The porous portions 310 and 320 are formed so as to sandwich the core portion 330.

[0078] One porous portion 310 has a thickness T (μm). The porous portion 310 has an inner layer region 312 on the core portion 330 side and a surface layer region 311 on the opposite side of the core portion 330. The surface layer region 311 is a region where the distance from the outer surface S of the porous portion 310 is T / 4 or less. The inner layer region 312 is a region where the distance from the boundary B between the porous portion 310 and the core portion 330 is T / 4 or less. The other porous portion 320 also has a surface layer region 321 and an inner layer region 322, similar to the porous portion 310.

[0079] (Note) The above description discloses the following technologies: (Technology 1) Aluminum etched foil for electrolytic capacitors, The width is in the range of 460-520mm. The length is 100m or more, It includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces, The porous portion is a porous portion formed by etching, E1 (mg / cm²) is the smaller of the two etching amounts per unit area in two end regions located at a distance of 2 to 7 mm from both ends in the width direction at any given position. 2 ) and the average value of the etching amount per unit area in the central region inside the two end regions is E2 (mg / cm²). 2 Aluminum etched foil in which, when set to ), the ratio E1 / E2 is 0.90 or greater and 1.30 or less. (Technology 2) The aluminum etching foil described in Technical 1, wherein the ratio E1 / E2 is 0.94 or greater and 1.10 or less. (Technology 3) The maximum and minimum values ​​of the etching amount per unit area in the two end regions and the etching amount per unit area in the central region are Emax(mg / cm²), respectively. 2 ) and Emin (mg / cm³) 2 ) when Aluminum etching foil as described in Technology 1 or 2, satisfying (Emax-Emin)≦5.1. (Technology 4) Aluminum etched foil for electrolytic capacitors, The width is in the range of 460-520mm. The length is 100m or more, It includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces, Let T1 (μm) be the sum of the thicknesses of the two porous portions at a distance of 2 mm from one end in the width direction at any given position. When the sum of the thicknesses of the two porous portions at the center of the width direction of the arbitrary position is T2 (μm), Aluminum etched foil that satisfies 0.1 ≤ T1 / T2. (Technology 5) The thickness is 90 μm or more and 200 μm or less. The aluminum etching foil according to Technology 4, wherein the T2 is 50 or greater. (Technology 6) An aluminum etched foil according to any one of techniques 1 to 5, wherein the end face in the width direction is porous due to etching. (Technology 7) The porous portion includes an inner layer region on the core side and a surface layer region on the opposite side of the core. When the thickness of the porous portion is T (μm), the surface region is the region at a distance of T / 4 or less from the outer surface of the porous portion, and the inner region is the region at a distance of T / 4 or less from the boundary between the porous portion and the core portion. The aluminum etching foil according to any one of the technologies 1 to 6, wherein the average diameter D1 (nm) of the pores in the surface region is smaller than the average diameter D2 (nm) of the pores in the inner layer region. (Technology 8) The aluminum etching foil according to Technical Reference 7, wherein the ratio of D1 to D2, D1 / D2, is 0.5 or more and 0.98 or less. (Technology 9) The aluminum etching foil according to Art 7 or 8, wherein the porosity P1 of the surface region is smaller than the porosity P2 of the inner region. (Technology 10) The aluminum etching foil according to Technical Reference 9, wherein the ratio of P1 to P2, P1 / P2, is 0.5 or more and 0.95 or less. (Technology 11) An aluminum etching foil described in any one of the technologies 1 to 10, having a surface roughness Ra of 1.5 μm or less. (Technology 12) In the pore distribution of the porous portion measured by the mercury intrusion method, Cumulative pore volume V0 (cm³) in the range of pore diameter from 0.01 μm to 1 μm 3 / g) and Cumulative pore volume V in the range of pore diameter 0.01 μm or more and 0.06 μm or less S1 (cm 3 / g) means V S1 / V0≦0.07 An aluminum etching foil described in any one of the technologies 1 to 11 that satisfies the relationship. (Technology 13) In the pore distribution of the porous portion, The cumulative pore volume V0 (cm³) 3 / g) and Cumulative pore volume V in the range of pore diameter from 0.16 μm to 1 μm L1 (cm 3 / g) means V L1 / V0≦0.4 An aluminum etching foil as described in Technology 12 that satisfies the relationship.

[0080] [Examples] The present disclosure will be described in more detail below based on examples, but this disclosure is not limited to these examples. In the following examples, etching was performed under different etching conditions to produce multiple aluminum etched foils. The produced aluminum etched foils were then evaluated.

[0081] (Etching process) A foil-shaped aluminum sheet (thickness: 115 μm, width W: 500 mm) was subjected to AC etching to form porous areas on both sides of the aluminum sheet. The length of the aluminum sheet was sufficient to reproduce an etched foil of 100 m or more. A mixed acid mainly composed of hydrochloric acid was used as the etching solution. Shielding plates were placed at both ends of the foil. The shielding plates were positioned so that their surface direction was perpendicular to the surface direction of the aluminum sheet. The distance X between the ends of the electrodes (first electrode 511, second electrode 512) and the shielding plates, and the average current density were adjusted to the values ​​shown in Table 1, and etching was performed to produce etched foils (aluminum etched foils) A1-A5 and C1. The etching time was finely adjusted as needed to ensure an appropriate amount of etching. Foils A1-A5 are foils (F1), and etched foil C1 is an etched foil of a comparative example. The etching conditions for etched foil C1 were the same as conventional etching conditions.

[0082] [Table 1]

[0083] (evaluation) The resulting etched foils were evaluated using the following method.

[0084] (1) Etching amount The etching amount of the etching foil was measured using the following method. First, an arbitrary point was selected on the etching foil (aluminum etching foil 300), and samples were taken from that point at eight positions in the width direction Dw. The positions of the cut samples are schematically shown in Figure 4. For sample SP1 from one end region 300b1, the distance G from end 300e1 was 2 mm, the width SW in the width direction Dw was 5 mm, and the length SL in the longitudinal direction DL was 100 mm. Similarly, for sample SP2 from the other end region 300b2, the distance G from the other end 300e2 was 2 mm, the width SW was 5 mm, and the length SL was 100 mm. In other words, samples SP1 and SP2 were cut from distances of 2 to 7 mm from ends 300e1 and 300e2, respectively. Samples SP3 to SP8 (samples SP4 to SP7 are not shown) in the central region between end region 300b1 and end region 300b2 were cut out so that they were approximately equally spaced in the region between end region 300b1 and end region 300b2. Like the samples in the end region, samples SP3 to SP8 had a width SW of 5 mm and a length SL of 100 mm.

[0085] Next, the mass M1 (mg) of each sample was measured. The thickness H1 of one sample was also measured. Then, from the true density of aluminum, the area of ​​5 cm² was calculated. 2 The mass M0 (mg) of aluminum with no voids and a thickness of H1 was determined. Since the thickness of the etching foil was nearly constant and the change in thickness before and after etching was small, the thickness H1 measured for one sample was considered to be the thickness H1 for all samples. Then, using the following formula, the mass M0 (mg) of each sample at 1 cm² was calculated. 2 The amount of etching per unit was calculated. Etching amount E (mg / cm²) 2 ) = (M0 - M1) / 5

[0086] (2) Calculation of CV value The obtained etched foils were subjected to chemical conversion treatment in accordance with the EIAJ standard RC2364A to form an oxide film on the surface of the etched foils. Then, the capacitance C and breakdown voltage V were measured at multiple measurement points for each etched foil. The measurement points were selected in the same manner as the method used to select the sample collection locations for the etching amount measurement described above. Capacitance and breakdown voltage were measured in accordance with the EIAJ standard (RC-2364A). The product of capacitance C and breakdown voltage V (CV value) was then calculated.

[0087] The evaluation results of the etching amount are shown in Tables 2 and 3. In Table 2, etching amount E1 is the smaller of the two etching amounts (per unit area) measured in the edge region. Etching amount E2 is the average of the six etching amounts (per unit area) measured in the central region. The ratio E1 / E2 is the value obtained by dividing E1 by E2. In Table 3, the standard deviation of the etching amount is the standard deviation of all measured etching amounts. Maximum etching amount Emax (mg / cm²) 2 ) is the maximum value among all measured etching amounts. The minimum etching amount is Emin (mg / cm³). 2 ) is the minimum value among all measured etching amounts. Here, all measured etching amounts are the etching amounts at eight locations located in the width direction of a randomly selected point. Two of the eight locations are in two end regions. Six of the eight locations are selected to be approximately equally spaced in the region between the two end regions.

[0088] [Table 2]

[0089] [Table 3]

[0090] Etching foils A1 to A5 are foils (F) according to this disclosure, and etching foil C1 is an etching foil of a comparative example. As shown in Table 2, the ratio E1 / E2 for etching foils A1 to A5 was 0.90 or greater and 1.30 or less. As shown in Table 3, (Emax-Emin)≦5.1 was satisfied for etching foils A1 to A5.

[0091] The evaluation results for the CV values ​​are shown in Table 4. In Table 4, the maximum and minimum CV values ​​are the highest and lowest values ​​among all measured CV values, respectively.

[0092] [Table 4]

[0093] As shown in Table 4, the standard deviation of the CV value could be kept below 0.7 for etching foils A1 to A5. [Industrial applicability]

[0094] This disclosure is used in aluminum etched foil for electrolytic capacitors. Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention. [Explanation of Symbols]

[0095] 300: Aluminum etched foil 300a: Central area 300b: Edge area 300e: End (both ends) 310, 320: Porous part 311, 321: Surface area 312, 322: Inner layer region 330: core 500: Processing tank 501: Etching solution 510: Electrode pair 511: First electrode 512: Second electrode Dw: width direction

Claims

1. Aluminum etched foil for electrolytic capacitors, The width is in the range of 460 to 520 mm. It is more than 100m in length. It includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces, The porous portion is a porous portion formed by etching, E1 (mg / cm²) is the smaller of the two etching amounts per unit area in two end regions located at a distance of 2 to 7 mm from both ends in the width direction at any given position. ２ ) and the average value of the etching amount per unit area in the central region inside the two end regions is E2 (mg / cm²), and the average value of the etching amount per unit area in the central region inside the two end regions is E2 (mg / cm²). ２ When this is the case, the ratio E1 / E2 is 0.90 or greater and 1.30 or less. The porous portion includes an inner layer region on the core side and a surface layer region on the opposite side of the core. When the thickness of the porous portion is T (μm), the surface region is the region at a distance of T / 4 or less from the outer surface of the porous portion, and the inner region is the region at a distance of T / 4 or less from the boundary between the porous portion and the core portion. An aluminum etched foil in which the average diameter D1 (nm) of the pores in the surface region is smaller than the average diameter D2 (nm) of the pores in the inner layer region.

2. The aluminum etching foil according to claim 1, wherein the ratio E1 / E2 is 0.96 or more and 1.10 or less.

3. The maximum and minimum values ​​of the etching amount per unit area in the two end regions and the etching amount per unit area in the central region are given by Emax (mg / cm²). ２ ) and Emin (mg / cm³) ２ ) when The aluminum etching foil according to claim 1, satisfying (Emax - Emin) ≤ 5.

1.

4. Aluminum etched foil for electrolytic capacitors, The width is in the range of 460 to 520 mm. It is more than 100m in length. It includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces, Let T1 (μm) be the sum of the thicknesses of the two porous sections at a distance of 2 mm from one end in the width direction at any given position. When the sum of the thicknesses of the two porous portions at the center of the width direction of the arbitrary position is T2 (μm), 0.1 ≤ T1 / T2 is satisfied, The porous portion includes an inner layer region on the core side and a surface layer region on the opposite side of the core. When the thickness of the porous portion is T (μm), the surface region is the region at a distance of T / 4 or less from the outer surface of the porous portion, and the inner region is the region at a distance of T / 4 or less from the boundary between the porous portion and the core portion. An aluminum etched foil in which the average diameter D1 (nm) of the pores in the surface region is smaller than the average diameter D2 (nm) of the pores in the inner layer region.

5. The thickness is 90 μm or more and 200 μm or less. The aluminum etching foil according to claim 4, wherein T2 is 50 μm or more.

6. The aluminum etched foil according to claim 1 or 4, wherein the end faces in the width direction are porous due to etching.

7. The aforementioned D ２ D １ Ratio D １ / D ２ The aluminum etching foil according to claim 1 or 4, wherein the coefficient is 0.5 or greater and 0.98 or less.

8. The porosity P of the surface layer region １ is smaller than the porosity P ２ of the inner layer region, the aluminum etching foil according to claim 1 or 4.

9. The aforementioned P ２ P １ Ratio P １ / P ２ The aluminum etching foil according to claim 8, wherein the coefficient is 0.5 or greater and 0.95 or less.

10. The aluminum etching foil according to claim 1 or 4, wherein the surface roughness Ra is 1.5 μm or less.

11. Aluminum etched foil for electrolytic capacitors, The width is in the range of 460 to 520 mm. It is more than 100m in length. It includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces, The porous portion is a porous portion formed by etching, E1 (mg / cm²) is the smaller of the two etching amounts per unit area in two end regions located at a distance of 2 to 7 mm from both ends in the width direction at any given position. ２ ) and the average value of the etching amount per unit area in the central region inside the two end regions is E2 (mg / cm²), and the average value of the etching amount per unit area in the central region inside the two end regions is E2 (mg / cm²). ２ When this is the case, the ratio E1 / E2 is 0.90 or greater and 1.30 or less. In the pore distribution of the porous portion measured by the mercury intrusion method, The cumulative pore volume V0 (cm³ / g) in the range of pore diameter from 0.01 μm to 1 μm, The cumulative pore volume V S1 (cm³ / g) in the range of pore diameters from 0.01 μm to 0.06 μm is: V S1 / V 0 ≦0.07 Aluminum etching foil that satisfies the following conditions.

12. Aluminum etched foil for electrolytic capacitors, The width is in the range of 460 to 520 mm. It is more than 100m in length. It includes a core portion and two porous portions connected to the core portion, which constitute the first and second main surfaces, Let T1 (μm) be the sum of the thicknesses of the two porous sections at a distance of 2 mm from one end in the width direction at any given position. When the sum of the thicknesses of the two porous portions at the center of the width direction of the arbitrary position is T2 (μm), 0.1 ≤ T1 / T2 is satisfied, In the pore distribution of the porous portion measured by the mercury intrusion method, The cumulative pore volume V0 (cm³ / g) in the range of pore diameter from 0.01 μm to 1 μm, The cumulative pore volume V S1 (cm³ / g) in the range of pore diameters from 0.01 μm to 0.06 μm is: V S1 / V 0 ≦0.07 Aluminum etching foil that satisfies the following relationship.

13. In the pore distribution of the porous portion, The cumulative pore volume V ０ (cm ３ / g) and, Cumulative pore volume V in the range of pore diameter 0.16 μm or more and 1 μm or less Ｌ１ (cm ３ / g) means, V Ｌ１ / V ０ ≦0.4 The aluminum etching foil according to claim 11 or 12, which satisfies the relationship.

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