JPH118165A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen a solid electrolytic capacitor in fraction defective by a method wherein the effect of an aging treatment on a reduction in a leakage current is improved. SOLUTION: A dielectric oxide film is formed on an anode of valve metal such as Al, Ta, or the like, and a cathode layer of solid-state conductive organic material such as conductive high-molecular material, organic semiconductor, or the like is formed on the dielectric oxide film for the formation of a capacitor element 1, and a casing is provided to the capacitor element 1 through projection molding or the like for the manufacture of a solid electrolytic capacitor. As this point, the casing is provided to the capacitor element 1 after the element 1 is subjected to aging, and then the capacitor 1 with the casing is subjected to aging again.

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 high-performance solid electrolytic capacitor having excellent high-frequency characteristics, and more particularly to an aging step in a manufacturing process.

[0002]

2. Description of the Related Art Generally, an electrolytic capacitor is made of a valve metal such as Al (aluminum) or Ta (tantalum).
l) forming a dielectric oxide film on the surface of the anode body comprising electrolytic solution by electrolytic oxidation treatment;
A cathode layer made of a conductive material such as nO ₂ (manganese dioxide) or a conductive organic material is formed. Here, the valve metal is a metal that forms a very dense and durable dielectric oxide film by the electrolytic oxidation treatment. In addition to Al and Ta, Ti (titanium), Nb (niobium), etc. Is applicable. Since the thickness of the dielectric oxide film is very small, the electrolytic capacitor can produce a small-sized and large-capacity capacitor as compared with other paper capacitors and film capacitors. The electrolytic capacitor, as a cathode layer,
A capacitor using a solid conductive material such as MnO _{2 or} a conductive organic material is called a solid electrolytic capacitor, and a capacitor using a solid conductive organic material is called an organic solid electrolytic capacitor.

With the recent development of electronic equipment, there is a need for a small and large-capacity capacitor having a low internal impedance and excellent high-frequency characteristics in a high-frequency region. The internal impedance of the capacitor
ESR (equivalent serie) mainly caused by the material of the cathode layer
s resistance (equivalent series resistance) and self-inductance mainly caused by the lead wire. Among the conductive materials used for the cathode layer of the electrolytic capacitor, TCNQ
(7,7,8,8-tetracyanoquinodimethane) complex salt,
A conductive organic material such as polypyrrole has a higher electric conductivity than an electrolytic solution or MnO ₂ . Therefore, an organic solid electrolytic capacitor using a conductive organic material is used in various electronic devices as a small and large-capacity capacitor excellent in high-frequency characteristics because of its low ESR. Further, among conductive organic materials, a conductive polymer material such as polypyrrole has higher electric conductivity than an organic semiconductor such as a TCNQ complex salt. Therefore, an organic solid electrolytic capacitor using a conductive polymer material such as polypyrrole has a smaller ESR and is a small and large-capacity capacitor having extremely excellent high frequency characteristics.

[0004] A method of manufacturing a general solid electrolytic capacitor will be described below. First, an anode lead wire is attached to the anode body, a dielectric oxide film is formed on the surface of the anode body by electrolytic oxidation treatment, and a cathode layer made of a solid conductive material is formed on the dielectric oxide film, By forming a carbon and silver paste layer on the cathode layer, a capacitor element is completed. Metal terminal plates are attached to the anode lead wire and the carbon and silver paste layers of the capacitor element, respectively.
By coating the capacitor element and part of the metal terminal plate with resin by injection molding, etc., and forming the outer shell,
The assembly of the solid electrolytic capacitor is completed.

[0005]

In general, an electrolytic capacitor is subjected to an aging process after a product is completely assembled in order to reduce a leakage current which is increased due to a damage of a dielectric oxide film in a manufacturing process. The aging process is performed by applying a DC voltage to the capacitor in an environment at the maximum operating temperature of the capacitor (or a higher temperature), and the aging process repairs the damage of the dielectric oxide film and causes leakage. The current is reduced. However, when a solid conductive material such as MnO _{2 or} a conductive organic material is used for the cathode layer, it is more difficult to repair the dielectric oxide film by aging treatment than when using an electrolytic solution. The effect of reducing the leakage current is low. For this reason, the occurrence rate of defective products whose leakage current value does not satisfy the required specifications could not be suppressed.

[0006]

The inventors of the present invention have conducted various experiments on an organic solid electrolytic capacitor. As a result, they have found that leakage current can be significantly reduced by performing aging treatment before forming an outer shell. Devised. An object of the present invention is to provide a method for manufacturing an organic solid electrolytic capacitor having low leakage current.

[0007]

According to a method of manufacturing an organic solid electrolytic capacitor of the present invention, an aging process is performed, an outer shell is formed, and after the formation of the outer shell and assembly of the capacitor are completed, the aging process is performed again. Is performed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, embodiments and examples of the present invention will be described. In the solid electrolytic capacitor element of the present embodiment, an anode lead wire is attached to an anode body made of a valve metal such as Al or Ta, and a surface of the anode body and a part of the anode lead wire is subjected to a dielectric oxidation treatment by electrolytic oxidation. An oxide film is formed, a cathode layer made of a conductive organic material such as a conductive polymer or an organic semiconductor is formed, and a carbon and silver paste layer is formed on the cathode layer. In this embodiment, after the capacitor element is subjected to an aging treatment, a metal terminal plate is attached to each of the anode lead wire of the capacitor element and the carbon and silver paste layers, and the capacitor element and the metal terminal plate are formed by injection molding or the like. And a part of it is covered with resin,
The solid electrolytic capacitor is completed by forming the outer shell and then performing the aging process again. A foil, a sintered body, or the like is used for the anode body. In the following examples and comparative examples, a Ta sintered body using Ta as a valve metal is used. The conductive organic material forming the cathode layer includes:
Conductive polymers such as polypyrrole, polyaniline, and polythiophene, and organic semiconductors such as TCNQ complex salts are used. In the following examples, polypyrrole is used.

[0009]

EXAMPLES Examples of the present invention and comparative examples will be described below.

(Example) Ta having an anode lead wire attached
The sintered body was subjected to electrolytic oxidation in a phosphoric acid aqueous solution to form a dielectric oxide film on the surface of the Ta sintered body and a part of the anode lead wire. Next, a cathode layer made of polypyrrole was formed on the dielectric oxide film using a known chemical polymerization method, electrolytic polymerization method, or the like. Then, a carbon and silver paste layer was formed on the cathode layer to complete a capacitor element.

Next, the plate-like carbon felt (3) is heated on a hot plate to adjust the surface temperature to 125 ° C., and then, as shown in FIG. The capacitor element (1) is placed on the carbon felt (3) so that the carbon and silver paste layers (11) of (1) are in contact with each other, and the positive electrode of the power supply (6) is connected to the anode of the capacitor element (1). Connect the negative electrode to the lead wire (10) with carbon felt
Each was connected to (3) and a rated voltage was applied for 2 hours to perform aging treatment before forming the outer shell. As a result of this aging treatment, the leakage current was significantly reduced as shown by the solid line in FIG. The carbon felt (3) has a thickness of 5 from the viewpoint of heat conduction and electric resistance.
~ 20mm, bulk density 0.1 ~ 0.2g / cm ³ and volume resistivity 7
It is desirable that it be Ωcm or less. In this embodiment, a carbon felt (3) having a thickness of 7 mm, a bulk density of 0.12 g / cm ³ and a volume resistivity of 6.3 Ωcm was used. Next, a metal terminal plate is welded or bonded to the anode lead wire (10) and the carbon and silver paste layers (11) of the capacitor element (1) subjected to the aging treatment, respectively. Then, an epoxy resin was injection-molded to a part of the metal terminal plate to form an outer shell, and a rated voltage was applied at a temperature of 125 ° C. for 2 hours to complete aging treatment. As shown by the solid line in FIG. 3, the leakage current at this time was slightly smaller than the leakage current reached by the aging process before the outer shell was formed. Then, the metal terminal plate exposed from the outer shell was bent along the outer shell to complete a chip-shaped solid electrolytic capacitor.

As shown in FIG. 2, instead of the carbon felt (3), the aging treatment before forming the outer shell is performed by laying granular carbon (4) in a metal tank (5). ) And the carbon and silver paste layers (11) of the capacitor element (1) should be in sufficient contact with each other.
Of the power supply (6) is connected to the anode lead wire (10) of the capacitor element (1), and the negative electrode is connected to the metal tank (5). When the aging treatment was performed before the outer shell was formed by applying the time, the same result as described above was obtained.

Comparative Example As a comparative example of the above embodiment, a solid electrolytic capacitor was completed in the same manner as in the embodiment except that only the aging treatment with the carbon felt (3) before forming the outer shell was omitted. The leakage current in the completed aging process at this time only slightly decreases as shown by the dashed line in FIG. 3, and the leakage current reached by the completed aging process is much larger than the leakage current of the embodiment. It became. Table 1 shows the inspection results in the above Examples and Comparative Examples.

[0014]

[Table 1]

[0015] In Table 1, short-circuit defective products are those in which the current flowing between the anode body and the cathode layer becomes several mA during the aging treatment, and the dielectric oxide film is irreversibly damaged. Be excluded before you.
Therefore, the short-circuit defective product is not included in the target of the good leakage current product, the defective leakage current product, and the average value of the leakage current.
It should be noted that short-circuit defective products are generated to the same extent in both the examples and comparative examples. A good leakage current product is one in which the leakage current after applying a voltage to the completed capacitor for 10 seconds satisfies the required specifications, and a defective leakage current product has the specifications in which the leakage current is required. It is not satisfied. Further, the average value of the leakage current is an average value for both good leakage current products and defective leakage current products. From Table 1, it can be seen that the average value of the leakage current is significantly smaller in the example than in the comparative example, and the number of non-defective products of the leakage current is significantly greater in the example than in the comparative example.

[0016]

Generally, the mechanism by which the leakage current is reduced by the aging process is that the damaged dielectric oxide film has a low withstand voltage, so that when a voltage is applied during the aging process, the current concentrates in a region with a low withstand voltage. It is oxidized by an electric current to repair the dielectric oxide film.
However, in the case of an organic solid electrolytic capacitor using an organic conductive material such as a conductive polymer or an organic semiconductor for the cathode layer, the organic conductive material is insulated by Joule heat generated by the current, thereby causing leakage. It is believed that the current will be smaller. From the results of the above examples and comparative examples,
In the aging treatment before the formation of the outer shell, it is considered that by reacting with some substance in the atmosphere, the insulation of the organic conductive material is promoted, and the leakage current is greatly reduced.

[0017]

As described above, according to the present invention, since the leakage current can be significantly reduced, the occurrence rate of defective products whose leakage current value does not satisfy the required specifications can be suppressed.
Product yield can be increased.

The description of the above embodiments is for the purpose of describing the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof.
Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims. For example, in the present embodiment, the metal terminal plate is attached to the capacitor element after performing the aging process before forming the outer shell, but the aging process may be performed in a state where the capacitor element is exposed to the outside air. The aging process may be performed after attaching the metal terminal plate.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an aging process before forming an outer shell in an embodiment of the present invention.

FIG. 2 is a perspective view showing an aging process before forming an outer shell in another embodiment of the present invention.

FIG. 3 is a graph qualitatively showing a change in leakage current due to aging processing in Examples and Comparative Examples.

[Explanation of symbols]

 (1) Capacitor element (3) Carbon felt (4) Granular carbon (10) Anode lead wire (11) Carbon and silver paste layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoichi Kojima 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (4)

[Claims] 1. A dielectric oxide film is formed on the surface of an anode body made of a valve metal such as Al or Ta, and the dielectric oxide film is formed on the dielectric oxide film.
A method for manufacturing a solid electrolytic capacitor in which a capacitor element is completed by forming a cathode layer made of a solid conductive organic material such as a conductive polymer and an organic semiconductor, and forming an outer shell on the capacitor element by injection molding or the like. In the above, after the aging process is performed,
A method for manufacturing a solid electrolytic capacitor, wherein an outer shell is formed and an aging process is performed again after the outer shell is formed. 2. An anode lead wire (10) is attached to an anode body, which is a sintered body made of a valve metal such as Al or Ta, and a dielectric oxide film is formed on the surface of the anode body. By forming a cathode layer made of a solid conductive organic material such as a conductive polymer and an organic semiconductor on the film, and forming a carbon and silver paste layer (11) on the cathode layer, a capacitor element is formed.
(1) is completed, and the capacitor element (1) is subjected to an aging process in a method for manufacturing a solid electrolytic capacitor in which an outer shell is formed by injection molding or the like. The outer shell is formed, and the aging process is performed again after the outer shell is formed. The first aging process is the completed capacitor element (1).
Is placed on a carbon felt (3) or in granular carbon (4), the anode lead wire (10) of the capacitor element (1) is used as an anode electrode, and the carbon and silver paste layers (11) of the capacitor element (1) are used. A method for producing a solid electrolytic capacitor, which is performed by applying a voltage using carbon felt (3) or granular carbon (4) in contact with a cathode as a cathode electrode. 3. The first aging process is to reduce the ambient temperature.
125 ° C or the contact surface between the capacitor element (1) and the carbon felt (3) or granular carbon (4)
Done by maintaining at 125 ° C by heating,
A method for manufacturing a solid electrolytic capacitor according to claim 2. 4. The carbon felt (3) has a thickness of 5 to 5.
20mm, bulk density 0.1 ~ 0.2g / cm ³ and volume resistivity 7
The method for producing a solid electrolytic capacitor according to claim 2, wherein the value is Ωcm or less. 5.