JP4822362B2 - Method for manufacturing element for solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a method for manufacturing an element for a solid electrolytic capacitor.

In recent years, with the digitization of electronic devices, solid electrolytic capacitors are required to have excellent high frequency characteristics, and a conductive polymer layer is used as the solid electrolyte layer. The purpose is to realize low ESR. Examples of the conductive polymer include polythiophene, polypyrrole, polyaniline, or derivatives thereof, but polythiophene, particularly polyethylene dioxythiophene, is often used because of its high conductivity and excellent thermal stability.

  As a method for forming the conductive polymer layer, there is a method by electrolytic polymerization or chemical oxidation polymerization. In the case of electrolytic polymerization, it is necessary to install a polymerization electrode on each capacitor element, which is disadvantageous for mass production. On the other hand, chemical oxidative polymerization is widely used among those skilled in the art as a technique that can be easily mass-produced.

  In chemical oxidative polymerization, first, an anode body is formed with a valve metal, and a dielectric oxide film is formed on the surface of the anode body. Thereafter, when the anode body is immersed in a mixed solution of an oxidant and a monomer and pulled up from the solution, a conductive polymer layer can be formed on the surface of the oxide film by chemical oxidative polymerization (see, for example, Patent Document 1). ). Alternatively, the anode body may be immersed in the oxidant solution and the monomer solution and pulled up from the solution.

Further, it is necessary to form a conductive polymer layer having a certain thickness so that the dielectric oxide film on the surface of the anode body is not subjected to mechanical stress when forming the exterior resin. For example, when the thickness of the conductive polymer layer on the outer surface of the anode body is 10 μm or less, the leakage current defect rate increases rapidly.
On the other hand, when the thickness of the conductive polymer layer is increased, the element exposure failure rate and the equivalent series resistance (ESR) are deteriorated. And the equivalent series resistance (ESR) deteriorates rapidly. Therefore, the thickness of the conductive polymer layer is desirably in the range of 10 to 50 μm, and more desirably in the range of 15 to 25 μm (see, for example, Patent Documents 2 and 3).

Japanese Patent No. 3040113 Japanese Patent Laid-Open No. 2001-143968 JP 2003-188052 A

  By the way, when a conductive polymer layer is formed on the surface of an oxide film by chemical oxidative polymerization, one end of the capacitor element is welded to a metal bar, the anode body is immersed in a processing solution, and then pulled up from the solution. Because of the gravity, the treatment solution accumulates in the lower part of the anode body, and the thickness of the conductive polymer layer decreases at the upper part of the anode body (welding side of the metal bar) and increases at the lower part. There was a problem that it was difficult to give the molecular layer a uniform thickness. If the conductive polymer layer is formed with a non-uniform thickness, there is a problem that the equivalent series resistance and the leakage current increase.

  The present invention solves the above-described problems, and an object thereof is to form a conductive polymer layer of a solid electrolytic capacitor element with a uniform thickness.

In order to solve the above problems, according to the present invention, a dielectric oxide film is formed on the surface of an anode body made of a valve action metal, the anode body is immersed in a treatment solution, pulled up from the solution, and subjected to chemical oxidative polymerization. In the method for producing a solid electrolytic capacitor element in which a conductive polymer layer is formed on the surface of the oxide film,
A method for producing an element for a solid electrolytic capacitor, characterized in that the conductive polymer layer is formed by rotating the anode body at a speed of 1 to 12 rpm in the lead-down direction with one end of the anode body as an axis. Is provided.

  Further, after the anode body is welded to the metal bar, the conductive polymer layer is preferably formed by rotating the anode body at a speed of 1 to 12 rpm in the lead droop direction around the metal bar.

  The treatment solution is preferably a mixed solution of an oxidizing agent and a monomer.

  According to the present invention, when the conductive polymer layer is formed, the anode body is slowly rotated in the direction of lead droop so that the treatment solution does not accumulate under the anode body due to gravity. A conductive polymer layer can be formed.

  Examples of the present invention will be described below.

[Example 1]
In this example, aluminum was used as the valve action metal, and this aluminum foil was etched to form a porous aluminum foil having a large specific surface area, and then cut into a size of 10 mm × 20 mm. The anode body 1 is made of this cut aluminum foil.
Thereafter, as shown in FIG. 1, one end of the anode body 1 was connected to a metal bar by resistance welding. Further, a dielectric oxide film made of aluminum oxide was formed on the surface of the anode body 1 by anodic oxidation.

  Thereafter, the anode body 1 was immersed in a mixed solution composed of an alcohol solvent using ferric dodecylbenzenesulfonate as an oxidant and polythiophene as a monomer, and then pulled up from the solution.

  Furthermore, in an atmosphere at a temperature of 25 ° C. and a humidity of 60%, as shown in FIG. 1, it is dried for 20 minutes while rotating at a speed of 1 rpm around the metal bar 3, and is subjected to chemical oxidation polymerization to form an oxide film. The conductive polymer layer 2 was formed on the surface.

  Further, the steps of dipping, pulling up and drying were repeated 5 times, and the conductive polymer layer 2 was gradually increased to a desired thickness. The anode body 1 was rotated at a speed of 1 rpm around the metal bar 3 every time it was dried. A schematic cross-sectional view of a solid electrolytic capacitor element on which a conductive polymer layer is formed is shown in FIG.

  Thereafter, a carbon paste and a silver paste were sequentially applied on the conductive polymer layer 2 and dried to form a carbon layer and a silver layer. The element for solid electrolytic capacitors was produced by the above process.

[Example 2]
At the time of drying for performing the chemical oxidative polymerization, the anode body 1 was rotated at a speed of 12 rpm with the metal bar 3 as an axis. Other than that was carried out similarly to Example 1, and produced the element for solid electrolytic capacitors.

(Comparative Example 1)
At the time of drying for performing the chemical oxidative polymerization, the anode body 1 was rotated at a speed of 15 rpm around the metal bar 3. Other than that was carried out similarly to Example 1, and produced the element for solid electrolytic capacitors. A schematic cross-sectional view of a solid electrolytic capacitor element according to Comparative Example 1 is shown in FIG.

(Comparative Example 2)
At the time of drying for performing the chemical oxidative polymerization, the anode body 1 was rotated at a speed of 0.1 rpm around the metal bar 3. Other than that was carried out similarly to Example 1, and produced the element for solid electrolytic capacitors. A schematic cross-sectional view of a solid electrolytic capacitor element according to Comparative Example 2 is shown in FIG.

[Conventional example]
At the time of drying for performing the chemical oxidative polymerization, the anode body 1 was kept vertical without being rotated and dried in that state. Other than that was carried out similarly to Example 1, and produced the element for solid electrolytic capacitors.

  The thickness of the minimum part and the thickness of the maximum part of the conductive polymer layer 2 of the element for a solid electrolytic capacitor produced according to the above-mentioned examples, comparative examples and conventional examples were measured. Thereafter, the element was connected to a lead frame and covered with an exterior resin to produce a solid electrolytic capacitor with a rated voltage of 2.5 V, and leakage current and equivalent series resistance (ESR) at 100 kHz were measured. The results are shown in Table 1.

  As is clear from Table 1, in Examples 1 and 2, compared to the comparative example and the conventional example, the conductive polymer layer 2 as a whole has a substantially uniform thickness, and the leakage current value, equivalent series Both resistance is low. This is because when the conductive polymer layer 2 is formed, the anode body 1 is rotated at a speed of 1 to 12 rpm around the metal bar 3 so that the treatment solution does not accumulate under the anode body due to gravity. Because.

  Here, when the anode body 1 is rotated at a speed of 15 rpm, the conductive polymer layer 2 cannot be formed uniformly, and both the leakage current value and the equivalent series resistance increase (Comparative Example 1). This is because the rotational speed is too high, and the treatment liquid moves to the lower part of the anode body due to centrifugal force. As in the conventional example, as shown in FIG. This is due to the fact that the conductive polymer layer 2 cannot have a uniform thickness.

  On the contrary, when the anode body 1 is rotated at a speed of 0.1 rpm, the conductive polymer layer 2 cannot be formed uniformly, and both the leakage current value and the equivalent series resistance increase (Comparative Example 2). This is because the rotational speed is too slow, and as shown in FIG. 4, the thickness of the conductive polymer layer 2 increases at the upper part (metal bar welding side) or the lower part of the anode body 1, and the conductive polymer layer 2 This is because it cannot have a uniform thickness.

  Further, in the conventional example, when the conductive polymer layer 2 is formed, the anode body 1 is kept vertical and is dried in that state, so that the treatment solution falls below the anode body due to gravity. For this reason, the thickness of the conductive polymer layer 2 decreases at the upper part (metal bar welding side) of the anode body 1 and increases at the lower part, so that the conductive polymer layer 2 cannot have a uniform thickness.

  In the above embodiment, the anode body 1 is dried in an atmosphere having a temperature of 25 ° C. and a humidity of 60%. However, the anode body 1 may be dried in another temperature / humidity atmosphere.

  In addition, thiophene and ferric dodecylbenzene sulfonate were used as monomers and oxidizing agents, but monomers such as pyrrole and aniline as monomers, ferric butylnaphthalene sulfonate and ferric paratoluene sulfonate as oxidizing agents, etc. An oxidizing agent may be used. Further, the anode body 1 may be pulled up from the solution after being separately dipped in the oxidant solution and the monomer solution instead of the oxidant and monomer mixed solution.

  Moreover, although aluminum was used as the valve action metal, tantalum or niobium may be used.

It is a figure which shows the rotation direction of the Example of this invention. 1 is a schematic cross-sectional view of a solid electrolytic capacitor element produced in Examples 1 and 2. FIG. 6 is a schematic cross-sectional view of a solid electrolytic capacitor element produced in Comparative Example 1. FIG. 5 is an example of a schematic cross-sectional view of a solid electrolytic capacitor element produced in Comparative Example 2. FIG.

Explanation of symbols

1 Anode body 2 Conductive polymer layer 3 Metal bar

Claims (3)

A dielectric oxide film is formed on the surface of an anode body made of a valve metal, the anode body is immersed in a treatment solution, pulled up from the solution, and a conductive polymer layer is formed on the surface of the oxide film by chemical oxidative polymerization. In the method of manufacturing a solid electrolytic capacitor element to be formed,
A method for producing an element for a solid electrolytic capacitor, wherein an electroconductive polymer layer is formed by rotating the anode body in the lead-down direction at a speed of 1 to 12 rpm with one end of the anode body as an axis.   2. The conductive polymer layer is formed by welding the anode body to a metal bar and then rotating the anode body at a speed of 1 to 12 rpm around the metal bar in the lead-down direction. The manufacturing method of the element for solid electrolytic capacitors of description.   The method for manufacturing a solid electrolytic capacitor element according to claim 1, wherein the treatment solution is a mixed solution of an oxidizing agent and a monomer.

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