JP3522294B2 - 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 solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor using an aluminum winding element.

[0002]

2. Description of the Related Art Generally, solid electrolytic capacitors are made of Al or Ta.
An oxide film is formed on the surface of a metal electrode such as to form a dielectric, and a solid electrolyte is attached to the dielectric, graphite,
The cathode is led out through a cathode conductive layer such as silver. This type of capacitor is used as a solid electrolyte such as manganese dioxide, metal oxides such as lead oxide, and organic semiconductor TCN.
Q complex, conductive polymer polypyrrole, etc. are used. Of these, manganese dioxide is generally used for Ta electrolytic capacitors, but it is quite difficult to use for Al electrolytic capacitors. Impregnation of manganese dioxide is carried out by immersing it in a manganese nitrate solution and then subjecting it to thermal decomposition.
A method is used in which it is attached to the electrode as manganese dioxide. According to this method, in the case of Al during the thermal decomposition treatment, the aluminum oxide film which is a dielectric is damaged, resulting in a large decrease in breakdown voltage. Further, as a method of impregnating the TCNQ complex which is an organic semiconductor, a melt impregnation method is generally adopted. In this, impregnation is performed when the TCNQ complex is melted by heating and liquefied. However, the TCNQ complex is weak to heat, and in particular, the TCNQ complex capable of being melt-impregnated must have a melting point. Since the decomposition point of the TCNQ complex is around 290 ° C, the melting point is preferably 270 ° C or lower. However, if this is done, the solder heat resistance will be insufficient.

On the other hand, in recent years, polypyrrole, which is a functional polymer having heat resistance and good conductivity, has come to be used.
With respect to the impregnation of this polypyrrole, a significant decrease in withstand voltage of the dielectric oxide film as seen in the above-mentioned manganese dioxide does not occur, and due to the improvement of the donor material, a much stronger heat resistance than the TCNQ complex has appeared. The conductivity is also much better than that of manganese dioxide and TCNQ complex.
It will be excellent in SR, high frequency impedance, etc. However, the impregnation of the above-mentioned polypyrrole is not sufficient unless the plate structure is used as the form of the electrode, and various attempts were made to apply it to the wound element, but none of them was suitable.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a study to impregnate a conventionally wound element (hereinafter referred to as a wound element) with an aluminum electrode foil with a conductive polymer as a solid electrolyte. It was found from inside. That is, in the conventional method of impregnating a conductive polymer such as polypyrrole, in order to generate it on the dielectric oxide film which is an insulator by electrolytic polymerization, a conductive polymer film or manganese dioxide which is changed to the conductive polymer film is previously formed in the film. In this system, pre-coating was performed and electric power was supplied through the pre-coating film to carry out electrolytic polymerization. This method is good when the electrode is a flat plate, but when it becomes a wound element, the precoat cannot be uniformly formed on the oxide film, and the subsequent electrolytic polymerization becomes extremely uneven, resulting in product characteristics, Satisfactory products such as yield have not been obtained.

A typical method of precoating is, for example, oxidative polymerization of pyrrole. This is to polymerize the pyrrole with an oxidizing agent. Oxidation polymerization is carried out in a solution in which the pyrrole and the oxidant are dissolved, but the dispersion of the concentration distribution of the pyrrole and the oxidant greatly affects the degree of polymerization, and the vicinity of the surface where the polymerization is carried out is constantly maintained under constant conditions. I have to hit. In the case of a flat plate electrode, it is easy to supply sufficient pyrrole and oxidant to control under certain conditions.However, in the wound type, it is not possible to supply the pill and oxidant inside the element during oxidative polymerization. This is sufficient, and a large variation occurs in the oxidatively polymerized pyrrole polymerization.

[0006]

Means for Solving the Problems The skeleton of the present invention focuses on a soluble conductive polymer, impregnates a wound element with a conductive polymer solution, and after impregnation, precoating is performed by removing the solvent, By this treatment, the inside of the wound element is uniformly pre-coated, and then electrolytic polymerization of pyrrole or the like is performed so that the wound element can be impregnated. Various investigations have been carried out, and as a result, a soluble polyaniline solution has been found. Soluble polyaniline is soluble in N-methylpyrrolidone solution even if it has a considerably high molecular weight when it is dedoped by alkali treatment. Therefore, after impregnating the wound element with the solution, N-methylpyrrolidone
It is scattered by heating from 0 ° C. to 250 ° C. Since it has no conductivity as it is, it is oxidized to give a conductive polyaniline by doping. If electrolytic polymerization is carried out thereafter, it has become possible to stably obtain a solid electrolytic capacitor using a conductive polymer in a wound element, which has heretofore been unavailable.

The temperature at which N-methylpyrrolidone is vaporized and scattered varies depending on the size and the time of the element, but at least 100 ° C. or higher is necessary, and polyaniline deteriorates at a temperature higher than 250 ° C., which is not suitable. Is. In addition, when impregnating polyaniline, in order to sufficiently impregnate the soluble polyaniline solution, reduced pressure injection was performed, and after impregnation in a reduced pressure atmosphere, any element could be impregnated by performing pressure treatment. The depressurization condition and pressurization condition cannot be specified depending on the element size used and the number of elements impregnated at one time,
Generally, the larger the pressure reduction and the pressure increase, the better.

After impregnation with polyaniline as described above,
Electrolytic polymerization of polypyrrole, polyaniline, polythiophene, etc. is performed, but when performing electrolytic polymerization, if the power is supplied from the electrode foil itself, the dielectric film will be deteriorated and the leakage current characteristics of the capacitor will be greatly affected. . Therefore, power is supplied through the previously impregnated polyaniline. Therefore, the winding of the wound anode foil is used as the power supply unit.
It is a method of attaching polyaniline to the battery part and supplying power from there. As a result of studying an appropriate range to be attached to the anode lead, the polyaniline including the depth A of 0.5 mm to 3 mm from the root of the lead terminal 1 made of CP wire as shown in FIG. It was good to immerse in and to impregnate. If it is less than 0.5 mm, it is extremely difficult to supply power, and if it exceeds 3 mm, polyaniline impregnated during product assembly may protrude to the outside of the product. In FIG. 1, 2 is an aluminum tab connected to the electrode foil by crimping, welding, etc., 3 is an aluminum tab 2
And a lead terminal 1 are welded, 4 is a polyaniline immersion position, and 5 is a capacitor element.

[0009]

EXAMPLES Specific examples of the present invention will be described below.
A wound element was produced by using an aluminum etching foil formed at 14 V and a cathode foil as a separator of 50 μm Manila paper. The following impregnation was performed using this element. (Example 1) The above device was immersed in a solution of soluble polyaniline 5 wt% N-methylpyrrolidone up to a lead terminal of 1 mm. 150mm at a speed of 1mm / min
It was dried at ℃ for 15 minutes. Then, it was dipped in a 3% solution of ammonium persulfate as an oxidant for 5 minutes, and further dipped in a 5% solution of paratoluenesulfonic acid as a dopant for 3 minutes to perform a doping treatment. After impregnation with polyaniline as described above, 2 m in a solution prepared by dissolving pyrol 0.05 mol, paratoluenesulfonic acid 0.025 mol, and tri-n-butylamine in acetonitrile.
Electrolytic polymerization was performed at A / cm ² for 1 hour. Then, after washing and drying, it was inserted into an aluminum case and sealed with an epoxy resin to prepare a solid electrolytic capacitor.

Example 2 The same chemicals as in Example 1 were used. The operation was different from that at the time of impregnation with polyaniline, and was performed by the following method. The element is set at a predetermined position, and the pressure in the impregnation container is reduced to 1/10 atmospheric pressure. Then, the polyaniline solution was injected under reduced pressure, and the reduced pressure was maintained for 10 minutes. After that, air was injected, the pressure was increased to 5 atm, and the pressure was maintained for 60 minutes. The polyaniline impregnation was completed as described above, and after the electrolytic polymerization, the same procedure as in Example 1 was carried out to produce a solid electrolytic capacitor.

Comparative Example Using the same element as above, a pyrrole solution and an ammonium persulfate solution were prepared,
Alternately dipping the device in a pyrrole solution and a persulfuric acid solution,
A polypropylene precoat layer was formed. Thereafter, after electrolytic polymerization, the solid electrolytic capacitor was manufactured in the same manner as in Example 1 and Example 2. Table 1 shows the results of the characteristic evaluations of Examples 1 and 2 and Comparative Example. The rating was targeted at 6.3V-33μF product.

[0012]

As shown in Table 1, according to the present invention, it is possible to reasonably impregnate a conventionally used wound element with a conductive polymer as a solid electrolyte, and to improve the impregnation rate as compared with a conventional comparative example. Of course, tan δ, ESR, leakage current characteristics, etc. are also greatly improved. Further, the characteristics can be further improved by performing pressure reduction and pressure treatment during impregnation with polyaniline. In addition, the manufacturing method is simpler than that of the conventional method, the product reliability and yield are improved accordingly, and the manufacturing cost is also reduced, which is of great practical value.

[Brief description of drawings]

FIG. 1 is a perspective view of a winding element according to the present invention.

[Explanation of symbols]

1 lead terminal 2 Aluminum tab 3 welds 4 Immersion position 5 Capacitor element

[Table 1]

Continued front page       (56) References JP-A-4-48710 (JP, A)                 JP-A-3-35516 (JP, A)                 JP-A-2-303017 (JP, A)

Claims (2)

(57) [Claims] 1. An element for an aluminum electrolytic capacitor, in which an anode foil and a cathode foil are wound with a separator interposed therebetween,
0.5 to 3m from the root of the lead terminal connected to the anode foil
Soaked in soluble polyaniline as the first impregnation up to m,
Next, heat treatment is performed in the range of 100 ° C. to 250 ° C. to impregnate polyaniline, and thereafter, oxidation treatment and doping treatment are performed. Then, as the second impregnation, power is supplied from the polyaniline formed on the lead portion, and any of pyrrole, thiophene, and aniline is supplied. A method for producing a solid electrolytic capacitor, characterized in that the electrolytic polymerization is performed. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the dipping in the soluble polyaniline at the time of the first impregnation is carried out by applying a pressure reduction treatment and then a pressure treatment.