JP2007123552A - Manufacturing method for etching foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To equalize the generation of a pit in the case of etching, to expand the effective surface area of an electrode foil, and to improve an electrostatic capacity. <P>SOLUTION: In a manufacturing method for an etching foil for an electrolytic capacitor, an aluminum foil is passed between a pair of electrodes in an aqueous solution mixing at least one kind in phosphoric acid, nitric acid, sulfuric acid, and oxalic acid in a hydrochloric-acid aqueous solution; and an AC current is applied. In the manufacturing method for the etching foil for the electrolytic capacitor, a waveform for the positive half period of the AC current contains a section largely lowering from the case of a peak and the section rising or lowering constantly or slowly, from a time immediately after the completion of the lowering to the time of the completion of the half period. In the manufacturing method for the etching foil for the electrolytic capacitor, the ratio of a current value is 0.2 to 0.7 in the case of the completion of the lowering to the current value in the case of the peak, the ratio of the current value is 0.7 to 1.2 in the case of the completion of the subsequent half period to the current value immediately after the completion of the lowering, the ratio of the time is 0.1 to 0.7 from the case of the start of the half period to the case of the peak to a half-period time, and the ratio of the time is ≤0.4 from the time of the peak to the time of the completion of the lowering to the half-period time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an etching foil for an aluminum electrode foil for electrolytic capacitors.

The aluminum foil for electrolytic capacitors is generally used by roughening the surface in an etching process for both the anode and cathode and expanding the surface area.
As an etchant, a solution in which phosphoric acid, nitric acid, sulfuric acid, oxalic acid, or the like is mixed with an aqueous hydrochloric acid solution is used to dissolve aluminum.

As the electrolytic capacitor etching foil, a method is used in which an alternating current is applied by passing an aluminum foil between a pair of electrodes in an aqueous solution containing hydrochloric acid or the like.
As a waveform of the alternating current to be applied (hereinafter, referred to as a waveform), a standard waveform such as a sine waveform, a triangular waveform, or a rectangular waveform, or a waveform obtained by modifying these waveforms is used (for example, Patent Documents 1 and 2, (See Patent Document 1).
JP 2003-86468 A Japanese Patent Laid-Open No. 06-272097 Aluminum, Vol. 2, No. 4 (1995), P136

  In recent years, the demand for miniaturization of electrolytic capacitors has been increasing, and accordingly, electrode foils used in electrolytic capacitors are required to have higher capacitance than before, and the development of etching foils with a larger surface area is required. It has been.

  However, in the alternating current waveform used in the etching process so far, the generated etching pits are combined and become non-uniform, which is inefficient in terms of surface area expansion. Therefore, there has been a demand for an etching method that has a low capacity per etching loss and can increase the surface area.

The present invention solves the above-mentioned problem, and in an aqueous solution in which at least one of phosphoric acid, nitric acid, sulfuric acid, and oxalic acid is mixed with an aqueous hydrochloric acid solution, an aluminum foil is passed between a pair of electrodes to generate an alternating current. In the manufacturing method of the etching foil for electrolytic capacitors to apply
The electrolytic capacitor characterized in that the waveform in the positive half cycle of the alternating current includes a portion that greatly decreases from the peak time, and a portion that rises or falls gradually or immediately after the end of the decrease until the end of the half cycle. It is a manufacturing method of the etching foil for water.

  In the above waveform, the ratio of the current value at the end of the decrease to the current value at the peak is 0.2 to 0.7.

  Furthermore, in the above waveform, the ratio of the current value at the end of the subsequent half cycle to the current value immediately after the end of the decrease is 0.7 to 1.2. .

  And in the said waveform, the ratio of the time from the half-cycle start time to the peak time with respect to half-cycle time is 0.1-0.7, It is a manufacturing method of the etching foil for electrolytic capacitors characterized by the above-mentioned.

  Further, in the above waveform, the ratio of the time from the peak time to the end of the reduction with respect to the half cycle time is 0.4 or less.

  As described above, by providing a portion in which the waveform of the alternating current greatly decreases from the peak in the positive half cycle and a portion in which the waveform of the alternating current rises or falls slowly from immediately after the end of the decrease until the end of the half cycle The problem that the etching pits generated in this waveform are combined is improved. As a result, the pits become uniform, the aluminum loss during etching can be suppressed, and the capacitance can be improved. That is, the surface area can be further increased, and the capacitance per etching loss can be improved.

Examples of the present invention will be described below.
In the following description, the ratio of the current value b at the end of the decrease to the current value a at the peak is the waveform parameter A, and the ratio of the current value c at the end of the subsequent half cycle to the current value b immediately after the end of the decrease. The waveform parameter B, the ratio of the time T2 from the start of the half cycle to the peak time with respect to the half cycle time T1, the waveform parameter C, the ratio of the time T3 from the peak time to the end of decrease with respect to the half cycle time T1, the waveform parameter Denoted by D.
Here, the waveform parameters A, B, C, and D are illustrated as shown in FIG. 1, and A = b / a, B = c / b, C = T2 / T1, and D = T3 / T1. It is expressed in

[Examples 1-4] Comparison of Waveform Parameter A The composition of the etching solution was 15.0 wt% hydrochloric acid, 2.0 wt% phosphoric acid, 2.0 wt% nitric acid, and 1.0 wt% sulfuric acid, and the aluminum foil had a purity of 99. 9% was used.
First, the waveform parameter A was compared in the range of 0.2 to 0.7. B was fixed at 1.0, C at 0.4, and D at 0.
After applying a predetermined amount of etching electricity to the aluminum foil, chemical cleaning was performed by a known method to prepare an electrode foil.

(Comparative Examples 1 and 2)
An electrode foil was produced in the same manner as in Example 3 except that the waveform parameter A was set to 0.1 or 0.8.

[Examples 5, 10, (3)] Comparison of waveform parameter B An electrode foil was prepared in the same manner as in Example 3 except that the waveform parameter B was in the range of 0.7 to 1.2.

(Comparative Examples 3 and 7)
An electrode foil was produced in the same manner as in Example 3 except that the waveform parameter B was set to 1.3 or 0.6.

[Examples 6, 7, and (3)] Comparison of waveform parameter C An electrode foil was prepared in the same manner as in Example 3 except that the waveform parameter C was set in the range of 0.1 to 0.7.

(Comparative Examples 4 and 5)
An electrode foil was produced in the same manner as in Example 3 except that the waveform parameter C was set to 0.8 or 0.05.

[Examples 8, 9, and (3)] Comparison of Waveform Parameter D An electrode foil was manufactured in the same manner as in Example 3 except that the waveform parameter D was set in the range of 0 to 0.4.

(Comparative Example 6)
An electrode foil was produced in the same manner as in Example 3 except that the waveform parameter D was set to 0.5.

(Conventional examples 1 and 2)
A triangular waveform was applied as Conventional Example 1, a rectangular waveform was applied as Conventional Example 2, and the rest was the same as Example 3 to produce an electrode foil.

For the electrode foils of Examples 1 to 10, Comparative Examples 1 to 7, and Conventional Examples 1 and 2, the weight loss [g / cm ² ] by etching and the capacitance [μF / cm ² ] when formed 20V were measured. Then, the capacitance per μL of etching [μF / g] was calculated.
Moreover, each etching waveform by said Examples 1-10, Comparative Examples 1-7, and a prior art example is shown to FIGS.
The results are shown in Table 1.

[Comparison by waveform shape]
As is apparent from Table 1, an embodiment including a portion where the waveform greatly decreases from the peak time during the positive half cycle and a portion where the waveform increases or decreases gradually from immediately after the end of the decrease until the end of the half cycle is It can be seen that, compared with the conventional examples 1 and 2 that do not include such a portion, the etching weight loss is small, the 20V conversion capacity is large, and the electrostatic capacity per etching weight loss is also large.

[Comparison of waveform parameter A]
Here, the ratio of the current value at the end of the decrease (waveform parameter A) to the current value at the peak of the waveform is suitably in the range of 0.2 to 0.7 (Examples 1 to 4). At 0.1, the pit coupling is suppressed, but the pit growth does not proceed (Comparative Example 1), and at 0.7, the pit coupling proceeds too much (Comparative Example 2). .

[Comparison of waveform parameter B]
Further, the ratio of the current value at the end of the subsequent half cycle (waveform parameter B) to the current value immediately after the end of the decrease is suitably in the range of 0.7 to 1.2 (Examples 3, 5, and 10). In 1.3, the pit coupling is too advanced (Comparative Example 3), and in 0.6, the pit growth is insufficient (Comparative Example 7). In either case, the effect of improving the capacitance is small.

[Comparison of waveform parameter C]
The ratio of the time from the start of the half cycle to the peak time (waveform parameter C) with respect to the half cycle time is suitably in the range of 0.1 to 0.7 (Examples 6, 3, and 7). When 0.05, pit generation is insufficient (Comparative Example 5), and when 0.8, pit coupling is too advanced (Comparative Example 4), and the effect of improving the capacitance is small.

[Comparison of waveform parameter D]
The ratio of the time from the peak time to the end of decrease (waveform parameter D) with respect to the half cycle time is suitably 0.4 or less (Examples 8, 9, and 3). At 0.5, the pit coupling is too advanced (Comparative Example 6), and the effect of improving the capacitance is small.

In the above embodiment, the etching solution is composed of 15.0 wt% hydrochloric acid, 2.0 wt% phosphoric acid, 2.0 wt% nitric acid, and 1.0 wt% nitric acid. However, the present invention is not limited to this. .
The etching waveform described above can be used for some of the etching steps.

It is a figure which shows the parameter which prescribes | regulates the waveform and the waveform by the Example of this invention. 6 is a diagram showing an etching waveform according to Comparative Example 1. FIG. It is a figure which shows the etching waveform by Example 1 of this invention. It is a figure which shows the etching waveform by Example 2 of this invention. It is a figure which shows the etching waveform by Example 3 of this invention. It is a figure which shows the etching waveform by Example 4 of this invention. 6 is a diagram showing an etching waveform according to Comparative Example 2. FIG. 10 is a diagram showing an etching waveform according to Comparative Example 3. FIG. It is a figure which shows the etching waveform by Example 5 of this invention. It is a figure which shows the etching waveform by the comparative example 4. It is a figure which shows the etching waveform by Example 6 of this invention. It is a figure which shows the etching waveform by Example 7 of this invention. 10 is a diagram showing an etching waveform according to Comparative Example 5. FIG. It is a figure which shows the etching waveform by the comparative example 6. It is a figure which shows the etching waveform by Example 8 of this invention. It is a figure which shows the etching waveform by Example 9 of this invention. It is a figure which shows the etching waveform by Example 10 of this invention. 10 is a diagram showing an etching waveform according to Comparative Example 7. FIG. It is a figure which shows the triangular waveform by a prior art example. It is a figure which shows the rectangular waveform by another prior art example.

Explanation of symbols

1 Current value at peak (a)
2 Current value at the end of decline (b)
3 Current value at end of half cycle (c)
4 At the start of decline 5 At the end of decline 6 Half cycle T1 Half cycle time T2 Time from half cycle start to peak time T3 Time from drop start to end time

Claims (5)

A method for producing an etching foil for electrolytic capacitors, wherein an alternating current is applied by passing an aluminum foil between a pair of electrodes in an aqueous solution in which at least one of phosphoric acid, nitric acid, sulfuric acid, and oxalic acid is mixed with an aqueous hydrochloric acid solution In
The electrolytic capacitor characterized in that the waveform in the positive half cycle of the alternating current includes a portion that greatly decreases from the peak time, and a portion that rises or falls gradually or immediately after the end of the decrease until the end of the half cycle. Method for producing etching foils.   2. The method of manufacturing an etching foil for an electrolytic capacitor according to claim 1, wherein the ratio of the current value at the end of the reduction to the current value at the peak is 0.2 to 0.7.   2. The manufacturing method of an etching foil for an electrolytic capacitor according to claim 1, wherein the ratio of the current value at the end of the subsequent half cycle to the current value immediately after the end of the decrease is 0.7 to 1.2. Method.   2. The method of manufacturing an etching foil for an electrolytic capacitor according to claim 1, wherein the ratio of the time from the start of the half cycle to the peak time with respect to the half cycle time is 0.1 to 0.7. 2. The method of manufacturing an etching foil for an electrolytic capacitor according to claim 1, wherein the ratio of the time from the peak time to the end of the decrease with respect to the half cycle time is 0.4 or less.

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