JP2811648B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer film as a solid electrolyte.

[0002]

2. Description of the Related Art In recent years, as a solid electrolytic capacitor which has responded to the demand for miniaturization and high performance, there is one disclosed in JP-A-60-244017 or JP-A-63-181308.

[0003] The technology disclosed in these publications is based on a method in which an anode body obtained by forming a valve action metal having a roughened surface and forming an oxide film is immersed in an electrolytic solution as an anode and energized to form a film on the oxide film. Although the electropolymerized film formed as above is used as a solid electrolyte, since the oxide film is an insulator, effective energization with the cathode is not performed, and current is applied to a defective portion of the oxide film or a place where the distance between the cathode and the cathode is short. And it was extremely difficult to obtain a uniform electrolytic polymerized film as a solid electrolyte.

[0004] Therefore, the anode body is immersed in, for example, a pyrrole solution, and thereafter, a chemical oxidation polymerization means by immersing the anode body in an oxidizing agent solution is taken. Electrolytic oxidative polymerization is performed in an electrolytic solution using the film as an anode to effectively form an electrolytic polymerized film on the chemically polymerized film.

However, if the oxide film has a defect, the conductive chemically polymerized film comes into direct contact with the defective portion during chemical oxidative polymerization, which causes a short circuit. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2-260516, there is a method of performing a chemical conversion treatment after forming a chemically polymerized film.

However, as described above, since the conductive chemically polymerized film is in direct contact with the defective portion, the chemical conversion is very poor.
Conversely, the concentration of current may cause deterioration of the oxide film or the chemically polymerized film, and even if the re-chemical treatment generally performed after the formation of the chemical polymerized film is performed, the breakdown voltage, short circuit, LC
It could not be a drastic measure for failure.

[0007]

The solid electrolytic capacitor obtained by the above-mentioned means is worthy of attention as meeting the demand for small size and high performance. However, when the oxide film has a defective portion, it is short-circuited. Failure and LC failure
There is a problem that the yield is very low in the manufacturing process.

The present invention has been made in view of the above points, and a method of manufacturing a solid electrolytic capacitor using a conductive polymer film as a solid electrolyte, which can prevent short defects, LC defects and the like of a solid electrolytic capacitor. The purpose is to provide.

[0009]

According to a method of manufacturing a solid electrolytic capacitor of the present invention, a chemically polymerized film is formed on an oxide film formed on a valve metal by chemical oxidation polymerization, and then the electrolytically oxidized film is formed on the chemically polymerized film. In the method for manufacturing a solid electrolytic capacitor in which an electrolytic polymerized film is formed by polymerization, after forming a chemically polymerized film on the oxide film, a current density and an applied voltage are respectively set to 0.05 to 0.5 A / dm ^{2 in} a chemical conversion solution. The voltage is controlled by controlling the voltage to 1/2 to 1 times the foil formation voltage.

[0010]

According to the above construction, the chemical polymerization film is re-formed at an appropriate voltage and current density, so that the oxide film defective portion can be repaired very smoothly, resulting in short-circuit failure and short-circuiting.
LC defects and the like can be completely prevented, and the withstand voltage can be significantly improved.

When re-formation is performed after chemical oxidation polymerization at a current density of 0.5 A / dm ² or more and / or a voltage of foil formation voltage or more, current concentrates on the oxide film defect, The foil surface is destroyed and corroded, and the chemically polymerized film on the foil surface is destroyed.
Each of the characteristics such as the ESR and the capacity achievement rate is significantly deteriorated.

Conversely, when the current density is 0.05 A / dm ²
When the chemical conversion is performed after the chemical oxidation polymerization in the range of less than or equal to 1/2 of the foil formation voltage, the film defective portion is hardly repaired. Not be.

[0013]

An embodiment of the present invention will be described below. That is, an anode lead wire is attached to an anode foil made of, for example, high-purity aluminum at an applied voltage of 50 V on which an oxide film has been formed by performing a chemical conversion step by enlarging the surface area by etching. Is immersed in an aqueous solution of pyrrole, thiophene, or furan / ethanol, and then further immersed in an aqueous solution of ammonium persulfate containing tetraethylammonium paratoluenesulfonate as a supporting electrolyte to perform chemical oxidative polymerization, thereby forming a conductive film on the oxide film. A chemically polymerized film made of a conductive polymer is formed.

Next, this device was immersed in a chemical conversion solution containing ammonium adipate or the like as a solute,
~0.5A / dm ^2, efficiently performing reformation of the film defective part by applying the 1/2 to 1 times the voltage of the forming voltage. Then, it is immersed in an electrolytic oxidation polymerization solution containing a supporting electrolyte and a monomer such as pyrrole, thiophene, and furan, and subjected to electrolytic oxidation polymerization to form an electrolytic polymerization film made of a conductive polymer on the chemical polymerization film. Thereafter, a cathode layer is provided by immersion-silver paste coating on a colloidal carbon, a cathode lead is attached to the portion of the cathode layer, and finally an exterior is applied.

According to the method for manufacturing a solid electrolytic capacitor having the above-described structure, the chemical conversion treatment after the formation of the chemically polymerized film is performed at an appropriate voltage and current density.
In addition to short-circuiting, LC failure, and the like, it is possible to completely prevent short-circuiting, LC-defectiveness, and the like. The use voltage can be remarkably increased.

When re-formation is performed after the chemical oxidation polymerization at a current density of 0.5 A / dm ² or more and / or a voltage of the foil formation voltage or more, the current concentrates on the film defect portion,
Corrosion occurs on the foil surface, and the chemically polymerized film on the foil surface is destroyed, and all properties such as pressure resistance, LC, tan δ, ESR, and capacity achievement rate are significantly deteriorated. Conversely, when chemical conversion is carried out after the chemical oxidation polymerization at a current density of 0.05 A / dm ² or less and / or a voltage of 1/2 or less of the foil formation voltage, almost the coating defect is repaired. Is not performed, so that it is not a countermeasure for short failure and LC failure.

Next, a comparison of various characteristics between the solid electrolytic capacitor obtained by the present invention using the anode foil made of aluminum formed with an oxide film by forming at an applied voltage of 50 V and the solid electrolytic capacitor obtained by the conventional example. Is described.

Table 1 shows Example A and Conventional Example B described below.
9 shows various characteristics of a solid electrolytic capacitor rated at 10 V-3 μF according to Conventional Example C.

In addition, short defects were excluded from the numerical values in the table.
The values are the average values of 100 samples.
Is shown.Example A  (1) Chemical oxidative polymerization conditions Aluminum oxide chemically converted to a pyrrole ethanol solution
After the electrode foil is immersed for 5 minutes, toluene sulfo is used as a supporting electrolyte.
Containing 0.05 mol / l of tetraethylammonium phosphate
5 minutes in 0.1 mol / l ammonium persulfate aqueous solution
Immersion. (2) Conditions for electrolytic oxidation polymerization Pyrrole monomer-1 mol / l and
A containing 1 mol / l sodium toluenesulfonate
Immerse in an electrolyte consisting of cetonitrile,
(1mA / cm^Two, 30 minutes). (3) Re-formation conditions after chemical oxidative polymerization Re-formation in 0.15 M ammonium adipate aqueous solution
(0.1 A / dm^Two, 30V, 10 minutes).Conventional example B  (1) Chemical oxidation polymerization conditions Same as Example A (2) Electrolytic oxidation polymerization conditions Same as Example A (3) Rechemical formation conditions after chemical oxidation polymerization Rechemical formation in 0.15 M aqueous ammonium adipate solution
(1A / dm^Two, 50V, 10 minutes).Conventional example C  (1) Chemical oxidation polymerization conditions Same as Example A (2) Electrolytic oxidation polymerization conditions Same as Example A (3) Rechemical formation conditions after chemical oxidation polymerization Rechemical formation in 0.15 M aqueous ammonium adipate solution
(0.01 A / dm^Two, 30V, 10 minutes).

[0020]

[Table 1]

As is clear from the above table, the device according to the embodiment A has a lower L value than the devices according to the conventional examples B and C.
The C characteristic is remarkably improved, and a remarkable improvement effect of short-circuit failure is observed. In addition, it can be seen that it does not cause any other characteristic deterioration such as tan δ in the conventional example.

In the above embodiment, an anode foil using an aluminum foil has been described as an example. However, the invention can be applied to a foil using a valve metal foil such as a tantalum foil or a niobium foil.

In the above embodiment, the formation voltage is 5
Although an example of 0V has been described, the present invention is not limited to this.

[0024]

According to the present invention, since the re-chemical conversion treatment after the chemical oxidative polymerization is performed at an appropriate voltage and current density, the film can be repaired smoothly, and short shots and LC defects can be prevented. This can be completely prevented, and the operating voltage can be significantly increased as compared with the case where re-formation is performed outside the scope of the present invention or the case where re-formation is not performed.

Claims (1)

(57) [Claims] 1. A method for manufacturing a solid electrolytic capacitor, comprising: forming a chemically polymerized film by chemical oxidation polymerization on an oxide film formed on a valve metal, and then forming an electrolytic polymerized film on the chemically polymerized film by electrolytic oxidation polymerization. After forming a chemically polymerized film on the oxide film, a current density of 0.05 to 0.5 A / dm ² and an applied voltage of 1/2 to 1 times the formation voltage are applied to the capacitor element in the chemical conversion solution. A method for manufacturing a solid electrolytic capacitor.