JPH10106896A - Manufacturing method for electrode foil of aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high electrostatic capacity by provisional processing before real forming which forms a forming film on an aluminum foil being made etching by anode oxidation, by thermal processing after forming by each specific range of a voltage and a current density and after that by the real forming. SOLUTION: As provisional processing for real forming in which a forming film is formed by anode oxidation on an aluminum foil having been made etching, forming by voltage in a range of 1-5V and electric current density of 0.01-0.08 A/cm2 is performed, and after that thermal processing is performed, the real forming is performed. Thermal processing temperature is set in a range of 300-570 deg.C and processing duration is set in a range of 2-5 minutes. By the means the forming film with a proper thickness is formed before the real forming, ineffective solution of thin holes during a first period of the real forming is suppressed and a high electrostatic capacity is obtained because crystallization of the forming film is promoted by increasing crystal nucleus in the forming film by thermal processing afterwards.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode foil for an aluminum electrolytic capacitor used for a low-voltage aluminum electrolytic capacitor.

[0002]

2. Description of the Related Art Generally, an electrode foil for an aluminum electrolytic capacitor of this type is formed by immersing an etched aluminum foil in an aqueous solution of phosphoric acid, ammonium adipate, or the like, applying a constant voltage to the anodic oxide film having a desired thickness. (Hereinafter, referred to as a chemical conversion film), and a heat treatment step of leaving the film in a high-temperature atmosphere of several hundred degrees for several minutes is repeated several times.

[0003] In order to obtain a high-capacity electrode foil, it is necessary to prevent the pores formed by the etching process from being collapsed by ineffective dissolution, and to form a chemical conversion film uniformly and to have no defective portions. It is. For this purpose, as disclosed in JP-A-2-216810, as a post-etching treatment, an aluminum foil is immersed in high-temperature pure water to which an amine is added to form a hydrated film. To improve the film quality of
As shown in Japanese Patent No. 283085, the chemical conversion step is divided into two steps, and in the first step, a voltage of 15 V or less is applied at a low current density of 0.05 A / cm ² or less to form a chemical conversion film, Various proposals have also been made as a chemical conversion method, such as a method of forming a dense chemical conversion film with few defects by applying a constant voltage in the second step to form a chemical conversion film having a desired withstand voltage thickness. .

[0004]

However, in the above-mentioned chemical conversion method, satisfactory results have not always been obtained with respect to further increase in capacitance.

The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing an electrode foil for an aluminum electrolytic capacitor capable of obtaining a high capacitance.

[0006]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
Method for producing electrode foil for aluminum electrolytic capacitor of the present invention
By anodizing the etched aluminum foil
As a pretreatment of the chemical conversion to form a chemical conversion film, the voltage is 1 to
Current density 0.01 to 0.08 A / cm in the range of 5V ^TwoBy
After performing chemical conversion, heat treatment is performed, and then
According to this manufacturing method, a high capacitance can be obtained.
What you can get.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention provides a pretreatment for forming a chemical conversion film by anodic oxidation on an etched aluminum foil, in which a voltage of 1 to 1 is used.
In the range of 5 V, heat treatment is performed after current formation at a current density of 0.01 to 0.08 A / cm ² , and then main formation is performed. An appropriate thickness of the chemical conversion film is formed, thereby suppressing the ineffective dissolution of the pores at the initial stage of the chemical conversion, and increasing the crystal nuclei in the chemical conversion film by the subsequent heat treatment. Since the crystallization of is accelerated, a high capacitance can be obtained.

[0008] The reason why the voltage is in the range of 1 to 5 V is that if the voltage is 1 V or less, there is no thickness of the chemical conversion film enough to suppress the ineffective dissolution of pores in the present chemical conversion. It is not possible to further increase the capacity as compared with that performed at a voltage in the range of 1 to 5 V.
In order to form a chemical conversion film having an optimum thickness for suppressing ineffective dissolution in the present chemical conversion, the voltage is optimally in the range of 1 to 5V.

Further, the current density is 0.01 to 0.08 A /
Why is cm ² is, 0.01 A / cm ² or less in poor productivity because the time to reach a longer to a predetermined voltage, whereas,
At 0.08 A / cm ² or more, the amount of ineffective dissolution increases and the capacitance decreases. Therefore, the optimum current density is 0.01 to 0.08 A / cm ² .

[0010] According to a second aspect of the present invention, the heat treatment temperature is set at 3
Set in the range of 00 to 570 degrees and the processing time is 2 to 5
Minutes, the heat treatment temperature is 300-57.
The reason for the range of 0 degrees is that when the temperature is 300 degrees or less, crystal nuclei are hardly generated in the chemical conversion film, and when the temperature is 570 degrees or more, the aluminum foil is dissolved.

When the treatment time is less than 2 minutes, the number of crystal nuclei is not generated sufficiently. On the other hand, when the treatment time is more than 5 minutes, the number of crystal nuclei is saturated, so that the increase in the capacitance reaches a peak and the productivity increases. Therefore, the optimal heat treatment temperature is 300 to 570 degrees, while the optimal treatment time is 2 to 5 minutes.

Hereinafter, specific embodiments of the present invention and comparative examples will be described. As an etching process, purity 9
A sample (effective area: 2 × 5 cm) of a high-purity aluminum foil having a thickness of 9.98% and a thickness of 100 μm was prepared by using a solution having a liquid temperature of 25 ° C.
The resultant was immersed in an electrolytic solution obtained by adding 1 wt% of sulfuric acid to a wt% hydrochloric acid solution, and subjected to AC etching at a current density of 0.5 A / cm ² and a frequency of 35 Hz for 3 minutes. Thereafter, the etched aluminum foil is placed in a 12 wt.
The sample was immersed in a 2% sulfuric acid solution for 2 minutes to perform a dechlorination treatment.
Thereafter, the aluminum foil was immersed in pure water at 95 ° C. for 2 minutes to perform a hydration treatment to form a hydrated film on the surface of the aluminum foil, followed by a heat treatment at 300 ° C. for 1 minute.

Then, after that, the liquid temperature is 3 wt% at 60 ° C.
Was performed in an aqueous solution of ammonium adipate, followed by applying a formation voltage of 22 V to carry out constant current main formation.

As shown in Table 1, the conditions for the pretreatment for chemical conversion were such that the heat treatment temperature was 500 ° C., the treatment time was 2 minutes, and the voltage and current density were changed. That is, in the first embodiment of the present invention, the current density was 0.01 A / cm ² and the voltage was 2 V.

In the second embodiment, the current density is 0.025 A
/ Cm ² and a voltage of 2 V. In the third embodiment, the current density was 0.08 A / cm ² and the voltage was 2 V.

In the fourth embodiment, the current density is 0.1 A / cm
² and a voltage of 2V. In the fifth embodiment, the current density was 0.025 A / cm ² and the voltage was 0.9 V.

In the sixth embodiment, the current density is 0.025 A
/ Cm ² and a voltage of 1 V. In the seventh embodiment, the current density is 0.025 A / cm ² and the voltage is 5 V.

In the eighth embodiment, the current density is 0.025 A
/ Cm ² and a voltage of 6 V. In the comparative example, only the heat treatment was performed, and then the chemical conversion was performed.

The results of measuring the capacitances of the treated foils shown in the first to eighth embodiments of the present invention and the comparative examples are shown in Table 1.
Shown in

[0020]

[Table 1]

As is clear from Table 1, when the capacitance of the comparative example is set to 100, a high capacitance is obtained at a voltage of 1 to 5 V and a current density of 0.01 to 0.08 A / cm ^2. Is obtained. Although the current density in the present formation is not particularly limited, it is 0.1 A / cm ²
It is desirable to perform the following.

Table 2 shows the results of changing the temperature and time of the heat treatment in the pretreatment for chemical conversion. This chemical conversion pretreatment is performed in a 3 wt% aqueous solution of ammonium adipate having a liquid temperature of 60 ° C. at a current density of 0.01 A / cm ² and a voltage of 2 V. After that, the heat treatment time and temperature are changed. The formation was performed at a constant current by applying a formation voltage of 22V. That is, in Embodiment 9 of the present invention, the heat treatment temperature is 250 ° C.
The processing time was 2 minutes.

In the tenth embodiment, a heat treatment temperature of 300
C. and a processing time of 1 minute. In the eleventh embodiment, the heat treatment was performed at a heat treatment temperature of 300 ° C. and a treatment time of 2 minutes.

In the twelfth embodiment, the heat treatment temperature is 500
C. and a processing time of 1 minute. In the thirteenth embodiment, the heat treatment is performed at a heat treatment temperature of 500 ° C. for a treatment time of 5 minutes.

In the fourteenth embodiment, the heat treatment temperature is 500
C. and a treatment time of 10 minutes. In the fifteenth embodiment, the heat treatment was performed at 570 ° C. for 1 minute.

In the sixteenth embodiment, the heat treatment temperature is 570
C. and a processing time of 5 minutes. In the seventeenth embodiment, the heat treatment was performed at 570 ° C. for 10 minutes.

In the comparative example, after forming at a current density of 0.01 A / cm ² and a voltage of 2 V, no heat treatment was performed, and a forming voltage of 22
V was applied to perform constant current main formation.

The results of measuring the capacitance of the treated foils shown in the ninth to seventeenth embodiments of the present invention and the comparative examples are shown in Table 2 below.

[0029]

[Table 2]

As is clear from Table 2, when the capacitance of the comparative example is set to 100, the heat treatment temperature is 300 to 570.
A high capacitance can be obtained in a temperature range of 2 to 10 minutes. Although the current density in the present chemical formation is not particularly limited, it is preferable that the current density be 0.1 A / cm ² or less.

[0031]

As described above, the method for producing an electrode foil for an aluminum electrolytic capacitor according to the present invention comprises a pretreatment for forming a chemical conversion film by anodic oxidation on an etched aluminum foil. Range, current density 0.0
After performing chemical conversion at ¹ to 0.08 A / cm ^2, heat treatment is performed, and then main chemical conversion is performed. According to this manufacturing method, a chemical conversion film having an appropriate thickness is formed before performing main chemical conversion. In this way, the ineffective dissolution of the pores in the initial stage of the chemical conversion is suppressed, and the subsequent heat treatment increases the crystal nuclei in the chemical conversion film to promote the crystallization of the chemical conversion film. A high capacitance can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koji Kamimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A pre-treatment for forming a chemical conversion film on an etched aluminum foil by anodic oxidation,
When the voltage is in the range of 1 to 5 V, the current density is 0.01 to 0.08
A method for producing an electrode foil for an aluminum electrolytic capacitor in which a chemical treatment is performed at A / cm ^2, a heat treatment is performed, and then the chemical formation is performed. 2. The method for producing an electrode foil for an aluminum electrolytic capacitor according to claim 1, wherein the heat treatment temperature is set in a range of 300 to 570 degrees and the processing time is set in a range of 2 to 5 minutes.