JPH05304055A - Manufacture of solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To impregnate a roll-type aluminum electrolytic capacitor element with conductive high molecular compound of solid electrolyte without wasting it by a method wherein the element is dipped into soluble polyaniline and subjected to an oxidation and a doping treatment to be impregnated with conductive polyaniline, and then polypyrrole or the like is electrolytically polymerized. CONSTITUTION:A positive foil and a negative foil are rolled up interposing a separator between them to form an aluminum electrolytic capacitor element 5, and the element 5 is dipped into soluble polyaniline including parts A of the lead terminals 1 as long as 0.5 to 3mm from their roots. Then, the element 5 is thermally treated in a temperature range of 100-250 deg.C to be impregnated with polyaniline and then subjected to an oxidation treatment and a doping treatment. Then, the element is secondarily impregnated with pyrrole, thyophene, or aniline electrolytically polymerized. By this setup, a capacitive element can be easily impregnated with conductive high molecular compound as solid electrolyte and enhanced in impregnation rate. Furthermore, a solid electrolytic capacitor is enhanced in tandelta, leakage current characteristics, and the like.

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 of 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 for solid electrolytes 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 is considerably difficult to use for Al electrolytic capacitors. Impregnation of manganese dioxide is carried out by heat decomposition treatment after immersing in manganese nitrate solution.
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. As a method of impregnating a TCNQ complex which is an organic semiconductor, a melt impregnation method is generally adopted. In this method, 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 reduction in withstand voltage of the dielectric oxide film as seen in the above manganese dioxide does not occur, and the improvement of the donor material reveals that it is much more heat-resistant than the TCNQ complex. The conductivity is also much better than that of manganese dioxide and TCNQ complex.
It will be excellent for 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 the application to the wound element was examined from various directions, but none of them was suitable.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a study to impregnate a conventionally wound element with an aluminum electrode foil (hereinafter referred to as a wound element) with a conductive polymer as a solid electrolyte without difficulty. 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. Oxidative polymerization is carried out in a solution in which pyrrole and an oxidant are dissolved, but variations in the concentration distribution of the pyrrole and oxidant have a great influence on 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, but 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 an 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 treatment. 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 of the device, time, etc., but at least 100 ° C. or higher is necessary, and polyaniline deteriorates at temperatures 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. Depressurization conditions and pressurization conditions 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 a power supply.
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, as shown in FIG. 1, the polyaniline including the depth A from 0.5 mm to 3 mm from the root of the lead terminal 1 made of CP wire or the like is included. It was good to carry out the impregnation by immersing in. If it is less than 0.5 mm, it is extremely difficult to supply power, and if it exceeds 3 mm, the 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 to each other, 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 manufactured by using an aluminum etching foil formed at 14V 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 5% by weight of soluble polyaniline in N-methylpyrrolidone up to a lead terminal of 1 mm. Pull up at a speed of 1 mm / min 150
It was dried at ℃ for 15 minutes. Then, it was dipped in a 3% solution of ammonium persulfate as an oxidizing agent for 5 minutes, and further dipped in a 5% solution of para-toluenesulfonic acid as a dopant for 3 minutes to perform a doping treatment. After impregnation with polyaniline as described above, 2 m in a solution of 0.05 mol of pyrrole, 0.025 mol of paratoluenesulfonic acid, and tri-n-butylamine dissolved 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 produce 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 state 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. Then, 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, which improves 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 the yield are improved accordingly, and the manufacturing cost can be reduced, and its practical value is great.

[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 Welding part 4 Immersion position 5 Capacitor element

[Table 1]

Claims (2)

[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, the element is dipped in soluble polyaniline, and then 1
It is characterized in that it is subjected to a heat treatment in the range of 00 ° C. to 250 ° C. to impregnate polyaniline, followed by an oxidation treatment and a doping treatment, and then as a second impregnation, electrolytic polymerization with pyrrole, thiophene, aniline and the like. Method for manufacturing solid electrolytic capacitor. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein a pressure treatment is carried out after a pressure reduction treatment during the immersion in the soluble polyaniline during the first impregnation.