JP2814502B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor using a conductive polymer as a solid electrolyte and a method for producing the same.

2. Description of the Related Art In recent years, as a power supply circuit of an electronic device has been increased in frequency, an electrolytic capacitor used therein has also been required to have excellent high frequency characteristics. Therefore, in order to realize low impedance in a high frequency region, a solid electrolytic capacitor using a conductive polymer having high conductivity as a solid electrolyte has been proposed. In conventional solid electrolytic capacitors, the conductive polymer used is pyrrole, thiophene, or furan as a monomer, and perchloric acid, boron tetrafluoride, and toluenesulfonic acid are used to add conductivity to those polymers. And so on. (See JP-A-60-37114 and JP-A-63-158829) Problems to be Solved by the Invention However, when a halide such as perchloric acid or boron tetrafluoride is used as a dopant, When aluminum is used as the anode valve metal, the anodic oxide film, which is a dielectric, is easily corroded and deteriorated. Therefore, there is a problem that the leakage current of the product is large and the capacitance changes with time at a high temperature.

On the other hand, when toluene sulfonic acid is used as the dopant, although the aggressiveness to the anodic oxide film is smaller than that of the halide, at high temperatures, the presence of moisture tends to cause undoping, and the conductivity of the polymer film is reduced. Therefore, the deterioration of the product characteristics under high temperature and high humidity is large. As mentioned above,
It has been difficult to obtain a highly reliable solid electrolytic capacitor with the conventionally proposed dopants.

The present invention has been made to solve such problems, and has as its object to provide a solid electrolytic capacitor having excellent characteristics and reliability.

Means for Solving the Problems In order to solve this problem, the present invention uses an oxide film of an anode body made of a valve metal as a dielectric, and a manganese dioxide layer formed on the surface of the oxide film of the dielectric. Any of the conductive polymers of polypyrrole, polythiophene, and polyfuran doped with polyvinyl sulfonic acid or sulfonated polyvinyl alcohol formed as described above is used as a solid electrolyte. Further, as a method for producing the same, a monomer such as pyrrole, thiophene or furan, a supporting electrolyte in which polyvinyl sulfonic acid or sulfonated polyvinyl alcohol is an anion, and water, acetonitrile, propylene carbonate, or γ-butyl lactone are used. An auxiliary anode is placed in contact with a manganese dioxide layer formed on an oxide film on the surface of an anode body made of a valve metal in a polymerization solution comprising any one of the above solvents, and the manganese dioxide layer is placed through the auxiliary anode. A conductive polymer used as a solid electrolyte is formed on the manganese dioxide layer by electrolytic polymerization of applying a voltage to the manganese dioxide layer.

Function In the present invention, since a conductive polymer of any of polypyrrole, polythiophene, and polyfuran using polyvinyl sulfonic acid or sulfonated polyvinyl alcohol as a dopant is used as a solid electrolyte, the dopant does not attack the anodic oxide film. An excellent solid electrolytic capacitor with less characteristic deterioration can be realized.

Embodiment An embodiment of the present invention will be described below with reference to the drawings and tables.

FIG. 1 is a sectional view of a solid electrolytic capacitor using the conductive polymer of the present invention as a solid electrolyte. The anode body 1 uses an etched aluminum plate.
An anodic oxide film is formed on the surface of the anode body 1 made of an aluminum plate in advance at a formation voltage of 35 V in a chemical conversion solution. The conductive polymer layer 3 is formed later by electrolytic polymerization, but no current flows because the surface of the anode body 1 is covered with an oxide film. Therefore, a manganese dioxide layer 2 having conductivity is formed on the surface of the anode body 1. The manganese dioxide layer 2 is formed on the anodic oxide film of the anode body 1 by immersing and impregnating the anode body 1 in a manganese nitrate solution having a specific gravity of 1.3 and then thermally decomposing at a temperature of 250 ° C. After the formation of the manganese dioxide layer 2, restoration chemical conversion is performed again in a chemical conversion solution. Further, as shown in FIG. 2, the conductive polymer layer 3 is formed as a conductive polymer monomer in a polymerization solution 9 of an aqueous solution of pyrrole 0.5 mol / l and supporting electrolyte 0.1 mol / l in an auxiliary cathode. A constant voltage of 5 V is applied to the manganese dioxide layer 2 for 10 minutes through an auxiliary anode 10 placed in contact with the manganese dioxide layer 2 using the cathode 11 as a cathode, and is formed on the manganese dioxide layer 2 by electrolytic polymerization. Is done. Sodium polyvinyl sulfonate is used as a supporting electrolyte.

As the supporting electrolyte, a sodium salt of sulfonated polyvinyl alcohol may be used instead of using the above-mentioned sodium polyvinyl sulfonate.

The surface of the conductive polymer layer 3 has a carbon coating layer 4,
The silver paint layer 5 is formed by coating, and the cathode lead 6 is drawn out by soldering. An anode lead 8 is connected to the anode body 1.

The capacitor element thus configured is covered with the exterior material 7 made of epoxy resin.

Table 1 shows the capacitance (C), loss angle tangent (tan δ), and leakage current (L) of the capacitors of the present invention and the conventional example.
C) Initial characteristics of (10 V applied, 2 minutes value) and time-dependent change in characteristics in a high-temperature and high-humidity atmosphere (85 ° C, 90% relative humidity, 500 hours without load) The loss angle tangent (tan δ) and leakage current (LC) are shown in comparison.
Examples of the present invention include those using sodium polyvinyl sulfonate as the supporting electrolyte (the present invention product 1) and those using the sodium salt of sulfonated polyvinyl alcohol (the present invention product 2). Electrolytes using lithium perchlorate (conventional example 1), those using tetrabutylammonium boron tetrafluoride (conventional example 2), and those using tetraethylammonium p-toluenesulfonate (conventional example) 3) is raised.

As is clear from Table 1, in the present invention, the leakage current (LC) is smaller than in the conventional example. The rate of change of capacitance over time (ΔC) in a high-temperature and high-humidity atmosphere is also very small. In the conventional example, when the device is left in a high-temperature and high-humidity atmosphere, the tangent of the loss angle (ta
nδ) and leakage current (LC) are considerably increased, but in the present invention, the loss angle tangent (tanδ) and leakage current (LC)
In both cases, there was almost no change, and no deterioration in product characteristics was observed.

As described above, according to the present invention, the leakage current is small,
It is possible to provide a solid electrolytic capacitor having a small characteristic deterioration even at high temperature and high humidity and having excellent reliability.

In the above examples, the case where pyrrole is used as the conductive polymer monomer will be described, but the same can be applied to thiophene, furan and their dielectrics. In addition, although examples have been described in which sodium polyvinyl sulfonate and sodium salt of sulfonated polyvinyl alcohol are used as the supporting electrolyte, the cation may be an alkali metal cation such as lithium or potassium, or a quaternary ammonium cation. The solvent of the supporting electrolyte solution is not only water but also acetonitrile, propylene carbonate, γ-
Any of butyl lactone may be used.

Effect of the Invention As described above, according to the present invention, the use of a conductive polymer such as polypyrrole, polythiophene, or polyfuran using polyvinyl sulfonic acid or sulfonated polyvinyl alcohol as a dopant as a solid electrolyte reduces leakage current. It is possible to obtain a small and reliable solid electrolyte capacitor with small characteristic deterioration even in high temperature and high humidity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an aluminum solid electrolytic capacitor according to one embodiment of the present invention, and FIG. 2 is a schematic view showing a configuration of an electrolytic polymerization tank for forming a conductive polymer layer. DESCRIPTION OF SYMBOLS 1 ... Anode body, 2 ... Manganese dioxide layer, 3 ... Conductive polymer layer, 4 ... Carbon paint layer, 5 ... Silver paint layer, 9
... Polymerization liquid, 10 ... Auxiliary anode.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshikuni Kojima 3-10-1, Higashi-Mita, Tama-ku, Kawasaki City, Kanagawa Prefecture Inside Matsushita Giken Co., Ltd. Mita 3-chome No. 1 Matsushita Giken Co., Ltd. (72) Inventor Kenji Kawamura 1006 Oji Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-314824 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01G 9/028

Claims (4)

(57) [Claims] An oxide film of an anode body made of a valve metal is used as a dielectric, and polyvinyl sulfonic acid or sulfonated polyvinyl alcohol formed via a manganese dioxide layer formed on the surface of the oxide film of the dielectric is used as a dielectric. A solid electrolytic capacitor using a conductive polymer such as polypyrrole, polythiophene, or polyfuran as a dopant as a solid electrolyte. 2. The solid electrolytic capacitor according to claim 1, wherein aluminum is used as the anode body made of a valve metal. (3) a monomer selected from the group consisting of pyrrole, thiophene and furan, and a supporting electrolyte in which polyvinyl sulfonic acid or sulfonated polyvinyl alcohol is an anion;
An auxiliary anode was disposed on a manganese dioxide layer formed on an oxide film on the surface of an anode body made of a valve metal in a polymerization solution comprising a solvent of water, acetonitrile, propylene carbonate, or γ-butyl lactone. A method for producing a solid electrolytic capacitor in which a conductive polymer used as a solid electrolyte is formed on a manganese dioxide layer by electrolytic polymerization in which a voltage is applied to the manganese dioxide layer via the auxiliary anode. 4. The method for manufacturing a solid electrolytic capacitor according to claim 3, wherein aluminum is used as the anode body made of a valve metal.