JP2005197314A - Method of manufacturing solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having good leakage current characteristics. <P>SOLUTION: A method of manufacturing the solid electrolytic capacitor includes steps of: performing restoration and formation of a capacitor element in which an anode electrode foil and a cathode electrode foil are wound through a separator; impregnating with a 3, 4-ethylenedioxythiophene and an oxidizing agent solution; generating a polyethylenedioxythiophene in the capacitor element by a chemical polymerization; and then housing the capacitor element in a sheathing case. In the method, after the capacitor element performs the restoration and the formation, the capacitor element is immersed in a boric acid compound solution, heated and again subjected to the restoration and the formation. Accordingly, the leakage current characteristics are improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor using a conductive polymer as an electrolyte.

  An electrolytic capacitor is made of a valve action metal such as tantalum or aluminum, and has a structure in which an oxide film layer serving as a dielectric is formed on the surface of an anode electrode having fine holes and etching pits, and an electrode is drawn from the oxide film layer. Become. And extraction of the electrode from an oxide film layer is performed by the electrolyte layer which has electroconductivity. Therefore, in the electrolytic capacitor, the electrolyte layer serves as a true cathode. Such an electrolyte layer functioning as a true cathode is required to have adhesion, denseness, and uniformity with the oxide film layer. In particular, the adhesion within the fine holes of the anode electrode and the etching pits has a great influence on the electrical characteristics, and a number of electrolyte layers have been proposed in the past.

  By the way, in recent years, with the digitization and high frequency of electronic equipment, a capacitor having a small size and a large capacity and a low impedance in a high frequency region is required.

In response to these requirements, a capacitor element in which a cathode foil and an anode foil are wound through a separator is housed in a metal case, and a small and large capacity is realized by a wound type electrolytic capacitor that is sealed with a sealing rubber. Can do. And it can respond to low impedance by using a solid electrolyte as an electrolyte. As such a solid electrolyte, conductive polymers having high conductivity such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex, polypyrrole, polythiophene and the like are known. Attention is now focused on polyethylenedioxythiophene (PEDT), which has a slow reaction rate and excellent adhesion to the oxide film layer of the anode electrode (see Patent Document 1), and as a result, the anode electrode foil and the cathode electrode Capacitor element wound with foil through a separator is impregnated with monomer and oxidant, and then polyethylenedioxythiophene, which is a solid electrolyte, is generated by a chemical polymerization reaction between the monomer and oxidant that occurs slowly. (See Patent Document 2).
JP-A-2-15611 Japanese Patent Laid-Open No. 10-340829

By the way, in recent years, electronic information devices have been digitized, and the driving frequency of the microprocessor which is the heart of these electronic information devices has been increased. Along with this, the power consumption has been increasing and the problem of reliability due to heat generation has become obvious. Therefore, the drive voltage has been reduced as a countermeasure.

In order to reduce the drive voltage, a large number of capacitors having low ESR are used as output-side capacitors of a power supply that supplies highly accurate power to the microprocessor. As the capacitor having such a low ESR characteristic, the solid electrolytic capacitor as described above is used.

However, in such a solid electrolytic capacitor having low ESR characteristics, there is a problem that the leakage current characteristics may be increased and the yield rate is reduced.

Therefore, an object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor that improves the leakage current characteristics and improves the yield rate in order to solve the above-described problems.

The method for producing a solid electrolytic capacitor according to the present invention comprises restoring and forming a capacitor element in which an anode electrode foil and a cathode electrode foil are wound through a separator, and impregnating 3,4-ethylenedioxythiophene and an oxidizing agent solution. In the method of manufacturing a solid electrolytic capacitor in which polyethylene dioxythiophene is produced in the capacitor element by chemical polymerization and then the capacitor element is housed in the outer case, the capacitor element is repaired and then immersed in a boric acid compound solution and pulled up It is characterized in that it is heated and then repaired again.
And it is characterized in that the repair conversion is performed in an ammonium dihydrogen phosphate A solution.

  The solid electrolytic capacitor of the present invention will be described. An anode electrode foil made of a valve action metal such as aluminum and having an oxide film layer formed on the surface thereof and a cathode electrode foil are wound through a separator to form a capacitor element. The conductive polymer is held in the separator of the capacitor element.

  The anode electrode foil is made of a valve action metal such as aluminum, and an oxide film layer serving as a dielectric is formed on the surface of the anode electrode foil by applying a voltage in an aqueous solution of ammonium adipate or the like. The cathode electrode foil is made of aluminum or the like like the anode electrode foil, and the surface is subjected to etching treatment.

  Anode extraction means and cathode extraction means for connecting the respective electrodes to the outside are connected to the anode electrode foil and the cathode electrode foil by known means such as stitching and ultrasonic welding. These electrode lead-out means are led out from the end face of the wound capacitor element.

  The capacitor element is formed by winding the anode electrode foil and the cathode electrode foil with a separator interposed therebetween. The dimensions of the bipolar electrode foil are arbitrary depending on the specifications of the solid electrolytic capacitor to be manufactured, and the separator having a slightly larger width may be used depending on the dimensions of the bipolar electrode foil.

  Polyethylenedioxythiophene (PEDT) is formed in the capacitor element. This PEDT can be obtained by polymerizing 3,4-ethylenedioxythiophene (EDT) as a monomer with ferric p-toluenesulfonate as an oxidizing agent. Polymerization is performed by impregnating the capacitor element with an EDT solution, then impregnating with an oxidant solution, and then heating.

  Then, the capacitor element in which the conductive polymer is formed is housed in a bottomed cylindrical metal case, and is swaged and sealed with a sealing rubber to form a solid electrolytic capacitor.

  Here, in the present invention, after the capacitor element is repaired and formed, it is immersed in a boric acid compound solution and heated, and then repaired and formed again. As the chemical solution for restoration chemical conversion, phosphoric acid-based chemicals such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate; boric acid-based chemicals such as ammonium borate; and adipic acid-based chemicals such as ammonium adipate. Although a liquid can be used, it is preferable to use ammonium dihydrogen phosphate or ammonium adipate. As the boric acid compound, boric acid, borax, ammonium salts of boric acid, boric acid salts such as metal salts, boric acid esters such as triethyl boric acid, etc. can be used, among which boric acid is used. Is desirable. Moreover, as a solvent of these boric acid compounds, what is necessary is just to melt | dissolve these compounds, and water, glycerol, etc. can be mainly used. The heating temperature is preferably 150 to 200 ° C.

According to the method for producing a solid electrolytic capacitor of the present invention as described above, after performing repair conversion, when immersed in a boric acid compound, pulled up and heated, the boric acid compound adheres to the oxide film and the film characteristics are improved. However, it is considered that the film characteristics are further improved and the leakage current characteristics are improved by performing the restoration conversion again. Further, when an ammonium dihydrogen phosphate solution is used as the repairing chemical, the repairing is performed satisfactorily and the leakage current characteristics are further improved.

    The method for producing a solid electrolytic capacitor according to the present invention involves restoration-forming a capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator, and impregnating 3,4-ethylenedioxythiophene and an oxidizing agent solution. In a method for producing a solid electrolytic capacitor in which polyethylene dioxythiophene is produced in a capacitor element by chemical polymerization, and then the capacitor element is housed in an outer case, the capacitor element is repaired and formed, then immersed in a boric acid compound solution and pulled up Heating is then performed again, and the repair formation is performed again, so that the leakage current characteristics are improved.

Next, the manufacturing method of the solid electrolytic capacitor of this invention is demonstrated concretely.
The anode electrode foil and the cathode electrode foil are made of a valve metal, such as aluminum or tantalum, and the surface thereof is preliminarily etched to increase the surface area. The anode electrode foil is further subjected to chemical conversion treatment, and an oxide film layer made of aluminum oxide is formed on the surface. These electrode foils are connected to aluminum tab terminals to which lead wires are attached. The anode electrode foil and the cathode electrode foil are wound through a separator to obtain a capacitor element.

  Thereafter, the capacitor element was repaired and formed in an ammonium dihydrogen phosphate solution.

  Next, the capacitor element is impregnated with EDT and an oxidizing agent. As the oxidizing agent, a butanol solution of ferric p-toluenesulfonate is used and polymerized by heating at 150 ° C. for 1 hour to produce PEDT which is a conductive polymer.

  Thus, the capacitor element in which the conductive polymer layer is formed on the separator interposed between the anode electrode foil and the cathode electrode foil is housed in a bottomed cylindrical case and sealed with a sealing rubber made of butyl rubber. A solid electrolytic capacitor is formed. The rating is 25 WV-68 μF.

  The above-mentioned solid electrolytic capacitor was used as a comparative example, and after repair formation as an example, after being immersed in a boric acid solution and heated at 160 ° C., repair conversion was performed again.

  Next, initial characteristics of these solid electrolytic capacitors are shown in (Table 1).

(Table 1)

┌───────┬──────────────────┐
│ │ Leakage current failure rate (%) │
├───────┼──────────────────┤
│ Examples │ 5 │
├───────┼──────────────────┤
│ Comparative example │ 15 │
└───────┴──────────────────┘

As described above, the defect rate of the leakage current is reduced in the example compared with the conventional example, and the effect of the present invention can be understood.

Claims (2)

  A capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator is subjected to restoration conversion, impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent solution, and polyethylenedioxy in the capacitor element by chemical polymerization. In the method of manufacturing a solid electrolytic capacitor in which a capacitor element is housed in an outer case after producing thiophene, the capacitor element is repaired and formed, then immersed in a boric acid compound solution, heated up, and then subjected to repairing and forming again. Capacitor manufacturing method. The method for producing a solid electrolytic capacitor according to claim 1, wherein the repair conversion is performed in an ammonium dihydrogen phosphate solution.