JP3267311B2 - Solid electrolytic capacitor and method of manufacturing the same - 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 which is inexpensive and has a simple manufacturing process, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the digitization of electronic devices,
There is an increasing demand for capacitors having good high-frequency characteristics. However, in the case of an aluminum electrolytic capacitor using a general electrolytic solution, the capacitance at high frequencies is extremely reduced due to ionic conduction, and the specific resistance cannot be extremely reduced. There is. On the other hand, a solid electrolytic capacitor does not have the above-mentioned disadvantages, but the impedance at high frequencies is still insufficient because the specific resistance of manganese which is a solid electrolyte is not so low. Thus, recently, solid electrolytic capacitors using organic semiconductors have been widely studied.

[0003]

Among the solid electrolytic capacitors using an organic semiconductor as a solid electrolyte, various techniques using a pyrrole-based conductive polymer as a plate-like electrode foil have been disclosed. However, there is a problem that the volume efficiency is poor and the cost is high because the manufacturing process is completely different from that of the conventional electrolytic capacitor using an electrolytic solution.

Some techniques using a capacitor element in which an anode foil and a cathode foil are wound are also disclosed. For example, in JP-A-64-24410, a wound aluminum electrolytic capacitor element is immersed in a monomer solution of a conductive polymer compound and then immersed in an oxidizing agent solution coexisting with an organic acid or a salt thereof to polymerize. There is disclosed a method for causing this to occur. However, in this method, when the temperature is high, polymerization by an oxidation reaction is promoted, so that a conductive polymer is preferentially formed and solidified near the surface of the device, and it is difficult to uniformly polymerize the inside of the device. Further, when the temperature is lowered, there is a problem that a long time is required for polymerization.

In Japanese Patent Application Laid-Open No. 2-186616, an element wound with a porous separator interposed between an anode foil and a cathode foil is used, impregnated with a pyrrole solution for impregnation, and immersed in an oxidant solution. A method is disclosed in which, after performing chemical polymerization of pyrrole, electrolytic polymerization is further performed. However, this method has a problem that the steps are complicated and that the monomer is not sufficiently supplied to the inside of the device during the electrolytic polymerization.

Further, Japanese Patent Application Laid-Open No. 2-62028 discloses that
Also disclosed is a method of immersing a wound capacitor element in an electrolytic polymerization solution to perform electrolytic polymerization using a cathode foil as a positive electrode and an anode foil as a negative electrode. However, not only is the electrolytic polymerization apparatus and conditions complicated, but also the anode foil may be damaged during the electrolytic polymerization, and the conductive polymer is formed from the positive electrode side. It is difficult to form evenly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a simple electrolytic process utilizing conventional electrolytic capacitor equipment, and to provide a solid electrolytic device having good characteristics at low cost. The purpose is to provide a capacitor.

[0008]

According to the present invention, there is provided a method for manufacturing a solid electrolytic capacitor using a capacitor element in which an anode foil having an oxide film formed by anodic oxidation and a cathode foil are wound via a separator. In the above, the capacitor element is finally impregnated with the polymerization solution in a metal case, and then a conductive polymer is formed by performing electrolytic polymerization using the cathode foil of the capacitor element as a positive electrode and the metal case as a negative electrode. And As the polymerization solution, it is desirable to use a mixed solution containing an oxidizing agent and a conductive polymer monomer cooled to −30 ° C. or lower. The polymer monomer may be pyrrole or a derivative thereof, and the oxidizing agent may be an organic sulfonic acid, a carboxylic acid, or a transition metal salt of an organic sulfate compound. The electrolytic polymerization is preferably performed at a temperature of -20 ° C or higher. The capacitor element may be pre-impregnated with a polymerization solution before being inserted into the metal case.

[0009]

According to the present invention, up to the capacitor element can be manufactured in the same manufacturing process as the conventional electrolytic capacitor using the electrolytic solution, so that it can be mass-produced at very low cost. Further, by combining the oxidative polymerization and the electrolytic polymerization, the filling rate of the conductive polymer into the capacitor element is increased, so that the frequency characteristics are improved, and the capacitance change rate and the ESR at a high frequency can be suppressed low.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. Example 1 A high-purity aluminum foil was electrochemically roughened, followed by anodic oxidation to form a dielectric film, and a roughened cathode foil having a density of 0.5 g / cm. ^3. Winding through a separator mainly composed of Manila hemp, 25V 47μF (5φ
× 11 l) was produced (not shown). Next, this capacitor element was immersed in a chemical conversion solution such as an ammonium phosphate aqueous solution, and the anode foil cut section, the anode lead lead-out portion, and the like were subjected to re-chemical treatment. Subsequently, 25 wt% of iron (III) dodecylbenzenesulfonate and pyrrole in an amount 3 times the number of moles of the iron (III) dodecylbenzenesulfonate were added.
After injecting the above element into an aluminum case (5φ × 11 l), impregnating and impregnating the element, a constant current of 5 mA was applied in a 25 ° C. atmosphere with the cathode foil of the capacitor element as the positive electrode and the aluminum case as the negative electrode for 1 hour. Was electrolytically polymerized. Thereafter, the capacitor was dried at 90 ° C. for 10 minutes, and sealed with a resin to form a capacitor (not shown).

Example 2 The same wound type capacitor element as in Example 1 was subjected to re-chemical treatment, and then iron (III) dodecylbenzenesulfonate 2
It was pre-impregnated by immersion in a methanol solution at -50 ° C to which 5% by weight and 6 moles of pyrrole of the iron (III) dodecylbenzenesulfonate were added. Next, 0.15 ml of the methanol solution was placed in an aluminum case, and the capacitor element was inserted thereinto for impregnation.
, And then allowed to stand for 20 minutes to perform chemical oxidative polymerization. Further, electrolytic polymerization was performed in the same manner as in Example 1. Then 90 ° C
After drying for 10 minutes, it was sealed with resin to obtain a capacitor (not shown).

Comparative Example 1 The same wound type capacitor element as used in Example 1 was used for re-chemical formation, and then impregnated with a solution of pyrrole 4: tetraethylammonium paratoluenesulfonate 6: methanol 2, and 20% by weight of ammonium persulfate. The polymer was immersed in an aqueous solution containing 10% by weight of tetraethylammonium paratoluenesulfonate for 1 hour to carry out polymerization. After completion of the polymerization, the mixture was dried at 90 ° C. for 10 minutes, and then sealed in a metal case to obtain a capacitor.

Comparative Example 2 The same wound type capacitor element as used in Example 1 was used for re-chemical formation, and then impregnated with a solution of pyrrole 4: tetraethylammonium paratoluenesulfonate 6: methanol 2, followed by a cathode lead and an anode. A voltage of 5 V was applied between the leads so that the cathode lead was positive, and electrolytic polymerization was performed for 1 hour. After completion of the polymerization, the mixture was dried at 90 ° C. for 10 minutes, and then sealed in a metal case to obtain a capacitor.

The capacitor manufactured as described above is
After applying 10 V in a 5 ° C. atmosphere and performing aging for 3 hours, various characteristics were measured at a rated voltage of 10 V. Table 1 shows the results.

[0015]

[Table 1]

As is clear from Table 1, in the embodiment according to the present invention, since the conductive polymer can be effectively filled into the etching pits of the anode foil, the capacity appearance ratio is extremely high. Also, a low value of the ESR at a high frequency can be realized.

Although the present invention has been described in various embodiments with reference to preferred embodiments, the present invention is not limited to these embodiments. For example, the anode foil has a spongy etching structure by AC etching in the embodiment, but a tunnel type structure by DC etching can also be used. The cathode foil does not need to be etched because a solid electrolytic capacitor does not require a cathode capacity. In the separator, not only natural fibers but also synthetic fibers can be used.

[0018]

According to the present invention, since a device for an aluminum dry electrolytic capacitor can be used, the manufacturing process is simplified, and a solid electrolytic capacitor having good characteristics at low cost can be provided.

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

Claims (6)

(57) [Claims] 1. A method for manufacturing a solid electrolytic capacitor using a capacitor element obtained by winding an anode foil having an oxide film formed by anodization and a cathode foil through a separator, wherein the capacitor element is impregnated with a polymerization solution. Is performed in a metal case, and then a conductive polymer is formed by performing electrolytic polymerization using the cathode foil of the capacitor element as the positive electrode and the metal case as the negative electrode to form a conductive polymer. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein said polymerization solution is a mixed solution containing an oxidizing agent cooled to -30 ° C. or lower and a conductive polymer monomer. . 3. The method according to claim 1, wherein the electrolytic polymerization is performed at a temperature of −20 ° C. or higher. 4. The method for producing a solid electrolytic capacitor according to claim 1, wherein said polymerization solution is pre-impregnated before inserting said capacitor element into a metal case. 5. The method according to claim 1, wherein the polymer monomer is pyrrole or a derivative thereof, and the oxidizing agent is a transition metal salt of an organic sulfonic acid, a carboxylic acid or an organic sulfate compound. Or a method for manufacturing a solid electrolytic capacitor according to item 4. 6. A solid electrolytic capacitor manufactured by the manufacturing method according to claim 1, 2, 3, 4, or 5.