JP4874039B2 - Aluminum alloy foil for electrolytic capacitor cathode and alloy foil used therefor - Google Patents

Description

  The present invention relates to an aluminum alloy foil for an electrolytic capacitor cathode and an alloy foil used in the production thereof for obtaining an electrolytic capacitor electrode with little ineffective dissolution during etching and high capacitance and strength.

  The aluminum foil can be increased in surface area by etching and forming etching pits. And the surface is anodized to form an oxide film, which functions as a dielectric. For this reason, aluminum foil electrode foils for various types of electrolytic capacitors suitable for various applications are manufactured by etching an aluminum foil and forming an anodized film on the surface with various voltages according to the operating voltage. be able to.

  The etching pit formed by the etching process is processed into a shape corresponding to the anodic oxidation voltage.

  Specifically, it is necessary to form a thick oxide film for a medium-high voltage capacitor application. For this reason, in order to prevent the etching pits from being filled with such a thick oxide film, in the aluminum foil for medium and high pressure anodes, the etching pit shape is made tunnel type by mainly performing DC etching, and the thickness according to the voltage. To be processed. In low voltage capacitor applications, fine etching pits are required, and spongy etching pits are formed mainly by AC etching.

  On the other hand, the surface area of the cathode foil is similarly increased by etching. The capacity of the electrolytic capacitor is a combined capacity of the anode part and the cathode part. Particularly, a cathode foil for a low voltage capacitor having a large electrostatic capacity is required to have a high electrostatic capacity. In order to achieve a high capacity, the etching pits formed by the etching process must be fine and travel uniformly in the depth direction of the foil. If the aluminum foil is excessively dissolved during etching, the formed fine etching pits are destroyed, and effective surface area enlargement cannot be achieved, resulting in a non-uniform shape in the depth direction. On the other hand, the strength after etching is also important, and the central portion of the foil that has not been etched maintains its strength, but it is necessary to increase the strength of the central portion.

  By the way, various compositions have been proposed as aluminum alloy foils for electrolytic capacitor cathodes.

  For example, Patent Document 1 discloses an aluminum alloy foil for an electrolytic capacitor cathode containing 0.01 to 0.1% by mass of manganese and having a titanium content of 0.001% by mass or less.

  In Patent Document 2, Si: 0.15 to 0.25 mass%, Fe: 0.35 to 0.70 mass%, Cu: 0.10 to 0.50 mass%, Mn 0.2 to 2.0 mass% An aluminum alloy foil for an electrolytic capacitor cathode is disclosed, which is composed of a remaining Al and inevitable impurities, and is Fe / Si: 1.5 to 3.0.

  In Patent Document 3, Si: 0.05 to 0.30 mass%, Fe: 0.22 to 0.60 mass%, Cu: 0.01 to 0.19 mass%, Mn 0.21 to 2.0 mass% An aluminum alloy foil for an electrolytic capacitor cathode is disclosed, which is characterized by comprising a remaining percentage of Al and inevitable impurities.

However, these aluminum alloy foils need to be further improved in order to obtain an electrolytic capacitor electrode with little ineffective dissolution during etching and high capacitance and strength.
JP-A-63-250110 JP 2004-76059 A JP 2006-104542 A

  Accordingly, the main object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor cathode for obtaining an electrolytic capacitor electrode having a low capacitance during etching and a high capacitance and strength, and an alloy foil used for the production thereof. There is.

  As a result of intensive studies in view of the current state of the prior art, the inventor of the present invention contains a specific amount of Mn and Ga in aluminum, and when impurities such as Si, Fe, and Cu are set to a certain value or less, It has been found that the above object can be achieved.

That is, the present invention relates to the following aluminum alloy foil for an electrolytic capacitor cathode and an alloy foil used therefor.
1. An aluminum alloy foil,
Al: 96 mass% or more,
Mn: 0.1 mass% or more and 3.5 mass% or less,
Ga: 0.003 mass% or more,
Si: 0.07 mass% or less,
Fe: 0.07 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001 mass% or less,
An aluminum alloy foil for an electrolytic capacitor cathode, characterized in that
2. An aluminum alloy foil,
Al: 96 mass% or more,
Mn: 0.12% by mass or more and 1.0% by mass or less,
Ga: 0.003 mass% or more and 0.05 mass% or less,
Si: 0.025 mass% or less,
Fe: 0.05 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001% by mass or less of an aluminum alloy foil for an electrolytic capacitor cathode.
3. An aluminum alloy foil for an electrolytic capacitor cathode, comprising the composition according to item 1 above.
4). 3. An aluminum alloy foil for an electrolytic capacitor cathode, comprising the composition according to item 2.

  According to the aluminum alloy foil for an electrolytic capacitor cathode of the present invention, when an electrolytic capacitor electrode is formed by etching the foil, it is possible to etch more deeply and uniformly while suppressing destruction of etching pits due to ineffective dissolution. Therefore, a higher capacitance can be obtained.

  In addition, since the nonuniformity of the etching depth due to ineffective dissolution can be reduced or eliminated, the thickness of the central portion of the foil that has not been etched can be made uniform, and in addition to the effect of Mn addition, the strength can be further increased Obtainable.

1. Aluminum alloy foil for electrolytic capacitor cathode and foil Aluminum alloy foil for electrolytic capacitor cathode of the present invention and alloy foil used therefor are:
Al: 96 mass% or more,
Mn: 0.1 mass% or more and 3.5 mass% or less,
Ga: 0.003 mass% or more (0.05 mass% or less),
Si: 0.07 mass% or less,
Fe: 0.07 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001 mass% or less,
Is the basic composition.

  The aluminum alloy foil for an electrolytic capacitor cathode of the present invention and the alloy foil used therein are those in which significant elements are specified and added, and the impurity content is controlled. The reason for the addition of each component and the reason for the limitation will be described below.

  In the present invention, Mn is 0.1% by mass or more and 3.5% by mass or less, preferably 0.12% by mass or more and 1.0% by mass or less.

When Mn is added to aluminum, Mn is dissolved and precipitated as an Al—Mn compound such as Al ₆ Mn. The potential of the Al—Mn compound does not promote ineffective dissolution because the difference in corrosion potential with the aluminum matrix is small. On the other hand, Mn can improve the strength of the aluminum alloy foil. When the Mn content is less than 0.1% by mass, the effect of improving the strength is hardly recognized. On the other hand, if the Mn content exceeds 3.5% by mass, the rollability of the aluminum alloy foil may be deteriorated, or pinholes may be generated.

  Ga is 0.003% by mass or more, preferably 0.006% by mass or more.

  Ga has the effect of promoting uniform growth of etching pits and suppressing ineffective dissolution. For this reason, it is preferable to set content of Ga in the said range. The upper limit value of the Ga content is not particularly limited, but if the content is excessive, the etching pit diameter tends to increase and the capacity tends to decrease, so the upper limit value should be about 0.05% by mass. preferable.

  The aluminum alloy foil for an electrolytic capacitor cathode of the present invention and the alloy foil used therefor can contain Mn and Ga within the above range, and can be etched more deeply and uniformly while suppressing the destruction of etching pits due to ineffective dissolution. High capacitance and strength can be obtained.

  The amounts of Si, Fe, Cu, Ni, and Ti contained as impurities are controlled so as to be within the following ranges, respectively.

  Si is 0.07 mass% or less, preferably 0.025 mass% or less. The reason for controlling the amount of Si is as follows.

  When Si is contained in aluminum, it precipitates as an Al—Fe—Si compound when Fe is present. These Al—Fe—Si based compounds are likely to precipitate particularly during the hot rolling and annealing processes, and promote the ineffective dissolution because of the large difference in corrosion potential with the aluminum matrix. For this reason, when Fe exists, it is necessary to set Si amount to the said range. The lower limit of the amount of Si is not particularly limited, but is preferably 0.005% by mass or more in terms of obtaining higher strength.

  Fe is 0.07 mass% or less, preferably 0.05 mass% or less. The reason for controlling the amount of Fe is as follows.

When Fe is contained in aluminum, Fe precipitates as an Al—Fe compound such as Al ₃ Fe. These Al—Fe compounds are likely to precipitate particularly during the hot rolling and annealing processes, and promote the ineffective dissolution because of the large difference in corrosion potential with the aluminum matrix. For this reason, it is necessary to set the amount of Fe within the above range. The lower limit of the amount of Fe is not particularly limited, but is preferably 0.005% by mass or more from the viewpoint that etching pits are easily formed.

  Cu is 0.008 mass% or less, preferably 0.002 mass% or less. The reason for controlling the amount of Cu is as follows.

  Cu has a high solid solubility in aluminum and is difficult to precipitate. However, if Cu ions eluted in the etching solution by etching are deposited on the surface of the aluminum alloy foil, the etching rate increases, thereby promoting ineffective dissolution. For this reason, the amount of Cu needs to be set in the above range. The lower limit of the amount of Cu is not particularly limited, but is preferably 0.0005% by mass or more from the viewpoint that etching pits are easily formed.

  Ni is 0.008 mass% or less, preferably 0.001 mass% or less. The reason for controlling the amount of Ni is as follows.

When Ni is contained in aluminum, precipitation of Al—Fe compounds such as Al ₃ Fe is promoted when Fe is present. These Al—Fe compounds are likely to precipitate particularly during the hot rolling and annealing processes, and promote the ineffective dissolution because of the large difference in corrosion potential with the aluminum matrix. Further, since the etching rate is increased, ineffective dissolution may be promoted. For this reason, the amount of Ni is preferably set in the above range. The lower limit of the amount of Ni is not particularly limited, but is preferably 0.0001% by mass or more from the viewpoint that etching pits are easily formed.

  Ti is 0.001 mass% or less, preferably 0.0005 mass% or less. The reason for controlling the Ti amount is as follows.

Ti inhibits the uniform growth of the etching pits and dissolves the aluminum alloy foil nonuniformly, thus promoting ineffective dissolution. For this reason, it is preferable to set the amount of Ti within the above range. The lower limit of the Ti amount is not particularly limited, but is preferably 0.0001% by mass or more from the viewpoint that etching pits are easily formed. The amount of Ti can be easily controlled, for example, by adding B (boron) to the molten aluminum and separating and removing TiB ₂ to be generated.

  As other impurities, for example, one or two elements such as magnesium (Mg), zinc (Zn), vanadium (V), chromium (Cr), zirconium (Zr), boron (B), and bismuth (Bi) are used. It may contain more than seeds. These contents should just be in the range which does not have a bad influence on the characteristics etc. of this invention alloy foil etc., and generally it is preferred to make it 0.005 mass% or less, respectively.

  The aluminum content (Al purity) of the aluminum alloy foil of the present invention is usually 96% by mass or more, preferably 96 to 98% by mass.

  Although the thickness of the aluminum alloy foil of the present invention is not limited, it is usually preferably 20 to 100 μm, particularly preferably 30 to 70 μm.

  The aluminum alloy foil of the present invention can be suitably used for an electrolytic capacitor cathode. That is, the aluminum alloy foil of the present invention can be used as a cathode of an electrolytic capacitor by performing an AC etching process and performing an etched foil or anodizing the etched foil.

2. Aluminum alloy foil for electrolytic capacitor cathode and method for producing foil The aluminum alloy foil of the present invention is produced by carrying out casting, rolling, etc. according to a normal method, except that the composition is set in the above range, Furthermore, it can be rolled to a predetermined thickness to produce a foil. Moreover, you may heat-process suitably for aluminum alloy foil fabric and aluminum alloy foil.

  As a manufacturing method, for example, an ingot is manufactured by preparing a molten raw material having the above composition and solidifying the molten metal. In this case, you may perform the homogenization process for about 1 to 20 hours at about 400-630 degreeC to the obtained ingot. Thereafter, the ingot is subjected to hot rolling and cold rolling to form a foil, and further rolled into a foil having a desired thickness. When a thin aluminum alloy is produced by continuous casting, a foil having a desired thickness can be obtained by direct cold rolling after continuous casting. When producing a soft aluminum alloy foil, the aluminum alloy foil may be heat-treated at about 250 to 450 ° C. for about 1 to 30 hours.

3. Electrolytic Capacitor Cathode The method for etching the aluminum alloy foil of the present invention to form the electrolytic capacitor cathode is not particularly limited, and may be performed according to a known method. Each processing condition may be as follows, for example, but is not limited thereto.

  The etching solution used in the etching treatment is not limited, and a known etching solution such as a mixed aqueous solution containing any one of sulfuric acid, phosphoric acid, nitric acid and the like in hydrochloric acid can be used. The concentration of the etching solution is not particularly limited, but is usually set to 1 to 10 mol / L, preferably 3 to 8 mol / L. The temperature of the etching solution is not particularly limited, but a preferable solution temperature is 30 to 70 ° C. If the liquid temperature is high, the reaction is promoted, which is preferable. However, if the temperature is too high, the reaction is too fast, and the foil surface is so melted that it becomes difficult to form uniform initial pits.

The etching process can generally be performed by alternating current (AC). In that case, the current density is generally preferably about 0.1 to 1 A / cm ² . The treatment time is usually about 1 to 10 minutes.

  Examples, conventional examples and comparative examples are shown below to further clarify the features of the present invention. In addition, this invention is not limited to an Example.

Examples 1 to 6, conventional examples and comparative examples 1 to 5
First, an aluminum alloy ingot having a composition shown in Table 1 was manufactured using an aluminum ingot having a purity of 99.9% by mass. The obtained ingot was homogenized at 550 ° C. for 10 hours, and then rolled to a thickness of 6 mm by hot rolling. Thereafter, cold rolling is performed to obtain a foil of 0.35 mm, intermediate annealing is performed as necessary, cold rolling is further performed to 50 μm, and annealing is performed at 350 ° C. in an inert gas for 5 hours to obtain an aluminum alloy foil. Obtained.

Test example 1
The aluminum alloy foils obtained in Examples 1 to 6, Conventional Examples and Comparative Examples 1 to 5 were mixed at a current density of 0.3 A / cm in a 60 ° C. mixed aqueous solution of hydrochloric acid 3 mol / L and sulfuric acid 0.5 mol / L. Each of the characteristics was evaluated after AC etching for 90 seconds at ² . The results are shown in Table 1.

  In addition, each physical property in Table 1 was measured as follows.

<Capacitance>
After the etching, 3V conversion was performed in an aqueous solution of ammonium adipate (150 g / L). The electrostatic capacity was measured with an aqueous solution of ammonium adipate (150 g / L) using an LCR meter. The relative value is shown with the value of the conventional example (Table 1) or Comparative Example 1 (Table 2) as 100%. The measurement area was 10 cm ² each.

<Tensile strength>
It measured with the tension tester according to JISB7721.

<Bending strength>
According to JIS P 8115, it was measured with an MIT type automatic bending tester. The number of times until cutting was performed with a 90 ° bend as one time was measured under the conditions of a radius of curvature of 0.5 mm, a load of 250 g, and a bending angle of 90 ° to the left and right.

  As shown in Table 1, the aluminum alloy foil of the comparative example is inferior in capacitance, tensile strength or bending strength, whereas the aluminum alloy foil of the example maintains a high capacitance. On the other hand, it can be seen that excellent effects of a tensile strength of 20 N / cm or more (particularly 30 N / cm or more) and a bending strength of 120 or more (particularly 130 or more) can be achieved.

Test example 2
5 parts of the aluminum alloy foil obtained in Example 5 was prepared, and AC etching was performed for 90 seconds (Example 5) and 100 seconds in a 60 ° C. mixed aqueous solution of hydrochloric acid 3 mol / L and sulfuric acid 0.5 mol / L. (Example 6) After 120 seconds (Example 7), 135 seconds (Example 8), and 150 seconds (Example 10), each characteristic was evaluated in the same manner as in Test Example 1. In all the examples, the current density was 0.3 A / cm ² . The results are shown in Table 2. Table 2 also shows the results of Comparative Example 1 for comparison.

  As is clear from the results in Table 2, it can be seen that the aluminum alloy foil of the present invention can obtain a higher capacitance while maintaining a tensile strength equal to or higher than that of Comparative Example 1.

Claims (6)

An aluminum alloy foil,
Al: 96 mass% or more,
Mn: 0.1 mass% or more and 3.5 mass% or less,
Ga: 0.003 mass% or more,
Si: 0.07 mass% or less,
Fe: 0.07 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001 mass% or less,
An aluminum alloy foil for an electrolytic capacitor cathode, characterized in that An aluminum alloy foil,
Al: 96 mass% or more,
Mn: 0.12% by mass or more and 1.0% by mass or less,
Ga: 0.003 mass% or more and 0.05 mass% or less,
Si: 0.025 mass% or less,
Fe: 0.05 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001% by mass or less of an aluminum alloy foil for an electrolytic capacitor cathode. An aluminum alloy foil for an electrolytic capacitor cathode, comprising the composition according to claim 1. An aluminum alloy foil for an electrolytic capacitor cathode, comprising the composition according to claim 2. The following characteristics:
Al: 96 mass% or more,
Mn: 0.1 mass% or more and 3.5 mass% or less,
Ga: 0.003 mass% or more,
Si: 0.07 mass% or less,
Fe: 0.07 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001 mass% or less,
A method for producing an aluminum alloy foil for an electrolytic capacitor cathode, comprising:
(1) A process for producing an aluminum alloy ingot using an aluminum ingot; and
(2) a step of subjecting the ingot to hot rolling and cold rolling;
The manufacturing method characterized by including. The following characteristics:
Al: 96 mass% or more,
Mn: 0.12% by mass or more and 1.0% by mass or less,
Ga: 0.003 mass% or more and 0.05 mass% or less,
Si: 0.025 mass% or less,
Fe: 0.05 mass% or less,
Cu: 0.008 mass% or less,
Ni: 0.008 mass% or less,
Ti: 0.001 mass% or less
A method for producing an aluminum alloy foil for an electrolytic capacitor cathode, comprising:
(1) A process for producing an aluminum alloy ingot using an aluminum ingot; and
(2) a step of subjecting the ingot to hot rolling and cold rolling;
The manufacturing method characterized by including.