JP3490868B2 - 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 suitable for miniaturization and large capacity.

[0002]

2. Description of the Related Art With the digitization of electronic equipment, capacitors used therefor have low ESR in the high frequency range.
There is an increasing demand for smaller size and larger capacity. Here, ESR means equivalent series resistance.

As a small-sized, large-capacity, low-ESR capacitor, a solid electrolytic capacitor using an electron conductive solid such as manganese dioxide or TCNQ complex salt as an electrolyte is put to practical use. Here, TCNQ means 7,7,8,8-tetracyanoquinodimethane. In addition, solid electrolytic capacitors using conductive polymers such as polypyrrole, polythiophene, polyfuran, and polyaniline as electrolytes have also attracted attention.

[0004]

However, even though the conductive polymer has an electric conductivity about 10 times or more that of the TCNQ complex salt, the ESR of the solid electrolytic capacitor using the conductive polymer as an electrolyte is However, in comparison with the solid electrolytic capacitor in which the electrolyte portion is replaced with the TCNQ complex salt, it is often large.

The present invention is to elucidate a method for producing a solid electrolytic capacitor which uses a conductive polymer as an electrolyte and which can bring out excellent material properties of the conductive polymer.

[0006]

According to the method for producing a solid electrolytic capacitor of the present invention, a capacitor element in which an anodized foil and a counter cathode foil are wound via separator paper is impregnated with a conductive polymer as a cathode electrolyte. In the method for producing a solid electrolytic capacitor, a chemical polymerization liquid containing a monomer to be a conductive polymer by oxidative polymerization and an oxidizing agent is prepared, and the capacitor element is preheated to a temperature not lower than the liquid temperature of the chemical polymerization liquid. A step of forming a conductive polymer layer in the capacitor element by immersing the capacitor element in the chemical polymerization solution until the temperature of the capacitor element becomes equal to or lower than the temperature of the chemical polymerization solution. It is characterized by.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the present invention, a winding type capacitor element 7 as shown in FIG. 1 is used. In this capacitor element, an anode chemical conversion foil 1 obtained by etching and chemical conversion of a foil made of a valve metal such as aluminum, tantalum, niobium, titanium, etc., and a counter cathode foil 2 are wound with a separator paper 3 interposed therebetween. Is formed by. Lead terminals 51 and 52 are attached to the anodized foil 1 and the counter cathode foil 2 via lead tabs 61 and 62, respectively. 4 is a winding stop tape.

In the method for producing a solid electrolytic capacitor according to a preferred embodiment of the present invention, first, 3,4-ethylenedioxythiophene: 33 wt% as a monomer which becomes a conductive polymer by oxidative polymerization and 33% by weight as an oxidizing agent. Iron (III) paratoluenesulfonate: 27wt%
And n-butyl alcohol as a diluent: 40 wt%
A chemical polymerization liquid containing and is prepared.

Then, after the capacitor element is preheated to a temperature higher than the liquid temperature of the chemical polymerization liquid, the capacitor element is subjected to the chemical polymerization until the temperature of the capacitor element becomes lower than the liquid temperature of the chemical polymerization liquid. By immersing in liquid,
A polymer layer of 3,4-ethylenedioxythiophene is formed in the capacitor element.

A preferable liquid temperature of the chemical polymerization liquid is about 50 ° C.
And the preferred preheat temperature of the capacitor element is about 100 ° C to about 300 ° C.

Instead of the 3,4-ethylenedioxythiophene, a monomer such as pyrrole, thiophene, furan, aniline and their derivatives, which becomes a conductive polymer by oxidative polymerization, may be used.

Then, as shown in FIG. 2, the capacitor element 7 is housed in a cylindrical aluminum case 8 having a bottom, the opening is sealed with an epoxy resin 9, and an aging treatment is performed to obtain a desired solid. The electrolytic capacitor is completed. Instead of the epoxy resin as the sealing material, low permeability and high heat resistance butyl rubber or the like may be used.

Here, in comparison with Examples 1 to 5, which were made by trial production according to the above-described preferred manufacturing method, except that the aluminum wound type capacitor element having φ6.3 mm × H5.5 mm and a rating of 4V-47 μF was used, except for the matters noted in Table 1. Regarding the solid electrolytic capacitor of the example, 1 at 105 ° C while applying the rated voltage.
A high temperature load test of holding for 000 hours was performed, and electrical characteristics were measured before and after the high temperature load test. The results are shown in Table 2.

[0014]

[Table 1]

[0015]

[Table 2]

In Table 2, C is the capacitance at 120 Hz, tan δ is the tangent of the loss angle at 120 Hz, ESR is the equivalent series resistance at 100 kHz, LC is the leakage current 30 seconds after the rated voltage is applied, ΔC / C represents the rate of change of C by the high temperature load test, and each characteristic value is an average of 10 samples.

As can be seen by comparing Table 1 and Table 2,
In Examples 1 to 5 in which the capacitor element was preheated, ESR and L before the high temperature load test were compared with Comparative Examples in which preheating was not performed.
C and ΔC / C and ESR after the high temperature load test are small, and especially in Example 3 of 200 ° C. preheating, the reduction of ESR, LC and ΔC / C is remarkable.

In the embodiments of the present invention, the above-mentioned effects are obtained because the moisture in the capacitor element is removed by preheating the capacitor element, so that the moisture does not mix into the reaction system of chemical polymerization and the adhesion with the chemical conversion film is improved. It is considered that the conductive polymer layer having excellent properties is formed.

Further, by immersing the capacitor element in the chemical polymerization liquid after the capacitor element is preheated and cooled to a temperature below the temperature of the chemical polymerization liquid, the chemical polymerization liquid penetrates into the separator paper in the capacitor element. The formation of a uniform conductive polymer layer in the capacitor element is also considered to contribute to the above effect.

[0020]

INDUSTRIAL APPLICABILITY According to the present invention, in a solid electrolytic capacitor using a conductive polymer as an electrolyte, a conductive polymer layer excellent in adhesion to a chemical conversion film is uniformly formed in a capacitor element, Provided is a solid electrolytic capacitor in which excellent material characteristics (electrical conductivity, etc.) are sufficiently obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a capacitor element used in an embodiment of the present invention.

FIG. 2 is a sectional view of a solid electrolytic capacitor according to an embodiment of the present invention.

[Explanation of symbols]

1 Anodized foil 2 Opposite cathode foil 3 separator paper 4 winding stop tape 51 Anode lead terminal 52 Cathode lead terminal 61 Anode lead tab 62 cathode lead tab 7 Capacitor element 8 exterior case 9 Sealing resin

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01G 9/028 H01G 9/00

Claims (3)

(57) [Claims] 1. A method for producing a solid electrolytic capacitor, comprising a conductive element as a cathode electrolyte impregnated in a capacitor element in which an anodized foil and a counter cathode foil are wound with separator paper in between, and a conductive polymer is formed by oxidative polymerization. A chemical polymerization liquid containing a monomer and an oxidant to be prepared is prepared, and after the capacitor element is preheated to the liquid temperature of the chemical polymerization liquid or higher, the temperature of the capacitor element becomes equal to or lower than the liquid temperature of the chemical polymerization liquid. In the meantime, the method for producing a solid electrolytic capacitor, comprising the step of forming a conductive polymer layer in the capacitor element by immersing the capacitor element in the chemical polymerization liquid. 2. The solid electrolytic capacitor according to claim 1, wherein the temperature of the chemical polymerization liquid is about 50 ° C. or lower, and the preheating temperature of the capacitor element is about 100 ° C. to about 300 ° C. Method. 3. The method for producing a solid electrolytic capacitor according to claim 2, wherein a thiophene derivative is used as the monomer, and a salt containing an ion of a sulfonic acid compound is used as the oxidizing agent.