JPH02189912A - Manufacture of aluminum foil for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To make etching magnification higher by carrying out etching at lower values of at least two conditions among three conditions consisting of etching frequency, current density, and liquid temperature, as compared to those of immediately preceding etching process. CONSTITUTION:Etching process is divided into a plurality of alternating current etching process, and in the latter etching process, etching is carried out at lower values of at least two conditions among three conditions consisting of etching frequency, current density, and liquid temperature, as compared to those of the preceding etching processes. When three or more etching processes are performed, in the succeeding processes, etching is carried out at lower values of etching frequency, current density, and liquid temperature, as compared to those of the immediately preceding etching process. Thus, etching magnification can be made larger.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing aluminum foil used in electrolytic capacitors, and in particular to an etching method.

[Prior Art] It is well known that aluminum foil used in electrolytic capacitors is electrochemically etched, and the etching methods include a direct current etching method using direct current and an alternating current etching method using alternating current. There is.

For anode foils used in low-voltage electrolytic capacitors, alternating current etching is believed to be effective because it can produce uniformly fine irregularities in the etched shape of the foil, and various types of etching have been developed. In other words, there are various etching methods that skillfully combine additives such as inorganic or organic acids such as sulfuric acid, phosphoric acid, and nitric acid to an etching solution made of hydrochloric acid or sodium chloride, the temperature of the etching solution, and the alternating current density. It has been implemented.

[Problems to be Solved by the Invention] As mentioned above, as an etching foil for low-voltage electrolytic capacitors, the structure with very fine irregularities has a unique power (required, but constant liquid temperature and current are required). When etching is performed at high density and AC frequency, as etching progresses, the fine irregularities formed at the beginning of etching begin to dissolve into the etching solution, reducing the etching magnification of the foil and decreasing its mechanical strength. The problem was that it became weak.

In order to solve these problems, a method is proposed in which the etching process is divided into multiple steps and a foil etching suppression process is provided between the etching processes.
JP-A-52-64659, JP-A-52-1116
56) or a method in which etching is performed by increasing the current density sequentially (Japanese Patent Laid-Open No. 63-268239). The former method has the problem that the mass production process of the foil becomes very complicated because it is necessary to provide an etching suppression process between the etching processes.

On the other hand, the latter method simply changes only the current density, and the effect is not so great.

[Means for Solving the Problem] However, the present invention provides a method for manufacturing aluminum foil for electrolytic capacitors that can obtain an even higher etching ratio. In the etching step, at least two of the three conditions consisting of etching frequency, etching current density, and etching solution temperature are set to lower values than those in the previous etching step.

In the present invention, the etching process may be performed in two, three or more stages. In the case of three or more etching steps, the etching frequency, etching current density, and etching liquid temperature are set to lower values as the etching steps proceed to the later steps than those of the immediately preceding etching step.

The etching frequency may be a commercial frequency of 50 or 60 Hz, or a lower or higher frequency.

[Examples] Examples of the etching method of the present invention will be described below along with comparative examples.

Example 1 First, an aluminum foil (ordinary softened cylinder) having a thickness of 90 μm and a purity of 99.993% was prepared. Also,
The etching solution was 10 wt% IIcI and H3P.
2.0 wt% O4, 1.0 wt% HNO3 and H
, S04 was prepared as an aqueous solution containing 0.05 wt%.

This aluminum foil was subjected to two-stage etching under the conditions shown in Table 1. In this case, the liquid temperature, current density, and frequency in the second stage are all lower than those in the first stage.

Table 1 Etching Conditions Example 2 Using the aluminum foil and etching solution of Example 1, two-stage etching was carried out under the conditions shown in Table 2. In this case, the liquid temperature and current density were varied.

Example 3 Using the aluminum foil and etching solution of Example 1, two-step etching was performed under the conditions shown in Table 3. In this case, the liquid temperature and frequency were varied.

Example 4 Using the aluminum foil and etching solution of Example 1, two-step etching was performed under the conditions shown in Table 4. In this case, the current density and frequency were varied.

Table 4 Comparative Example 1 of Etching Conditions Using the aluminum foil and etching solution of Example 1, two-stage etching was performed under the conditions shown in Table 5. In this case, only the liquid temperature was changed.

Table 5 Comparative Example 2 of Etching Conditions Using the aluminum foil and etching solution of Example 1, two-stage etching was performed under the conditions shown in Table 6. In this case, only the current density was changed.

Comparative Example 3 Using the aluminum foil and etching solution of Example 1, two-stage etching was performed under the conditions shown in Table 7. In this case, only the frequency was changed.

Table 7 Etching Conditions Example 5 Using the aluminum foil and etching solution of Example 1, three stages of etching were performed under the conditions shown in Table 8. In this case, the liquid temperature, current density, and frequency in the second stage are all lower than those in the first stage, and those in the third stage are even lower than those in the second stage.

Table 8 Etching conditions Next, aluminum foils etched according to Examples 1 to 54-3 and Comparative Examples 1 to 3 were etched at 70°C with 10wt%
Formation was carried out at 50 V in an ammonium adipate aqueous solution, and the foil capacity and bending strength were measured. The result is the 9th
Shown in the table.

Table 9 Foil Capacity and Bending Strength [Effects] According to the present invention, an aluminum foil for electrolytic capacitors having a high etching ratio can be obtained.

Moreover, the bending strength of the foil is not impaired.

Patent applicant: Elna Co., Ltd.

Claims (1)

[Claims] (1) In the process of manufacturing aluminum foil for electrolytic capacitors by multi-stage AC etching, at least two of the three conditions consisting of etching frequency, etching current density, and etching solution temperature are lower than those of the immediately preceding etching process. A method for producing aluminum foil for electrolytic capacitors, characterized by etching.