JPH0266922A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To realize satisfactory frequency characteristic and wide temperature characteristic in a high frequency range by growing electrolytically polymerizable conductive polymer on a compounded film. CONSTITUTION:Semiconductor 4 made of metal oxide selected from lead dioxide, vanadium trioxide, triiron tetraoxide or mixture is insularly adhered uniformly to a layer on a whole for leading a cathode on a compounded film 3 as a dielectric of a capacitor. Then, polymer solution 5 is prepared by employing 0.5mol/l as monomer, 0.1mol/l of paratoluenesulfonic acid tetraethylammonium salt as supporting electrolyte and acetonitrile as solvent, and an auxiliary anode 6 made of an aluminum rod is brought into light contact with the semiconductor layer 4 in the solution 5. When 5V is applied between the anode 6 and an auxiliary cathode 7, a conductive polymer film 8 is also formed on the layer 4. Then, the film 8 is coated with a graphite layer 9, where silver paint is deposited as a conductive layer 10, and a cathode lead 11 is then extracted, and sheathed with epoxy resin 12 to form a capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a solid electrolytic capacitor suitable for miniaturization and increase in capacity.

2. Description of the Related Art Recently, with the digitalization of electronic devices, there has been an increasing demand for capacitors used therein that have low impedance in the high frequency range and are smaller in size and larger in capacity.

Conventionally, glass film capacitors, mica capacitors, multilayer ceramic capacitors, and the like have been used as capacitors for high frequency regions. Other types include aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. In aluminum dry electrolytic capacitors, etched anode and cathode aluminum foils are wound up with a separator in between, and a liquid electrolyte is used. In addition, in aluminum and mental solid electrolytic capacitors, the electrolyte is solidified in order to improve the characteristics of the aluminum dry electrolytic capacitor. To form this solid electrolyte, the anode body is immersed in a manganese nitrate solution.
It is thermally decomposed in a high-temperature furnace at around 60 to 360°C to form a manganese dioxide layer. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as electrolyte leakage at high temperatures or functional deterioration caused by solidification at low temperatures, and it exhibits better frequency and temperature characteristics than liquid electrolytes. Also, like tantalum electrolytic capacitors, aluminum electrolytic capacitors can achieve large capacitance because the chemical conversion film that serves as the dielectric can be made very thin.

However, in recent years, 7. Solid electrolytic capacitors using organic semiconductors such as 8,8-tetracyanoquinodimethane salts as solid electrolytes have been developed.

Furthermore, what about pyrrole, thiophene, furan, etc. to improve the conductivity of solid electrolytes? A method has been proposed in which a conductive polymer is produced by depolymerizing the conductive polymer and this is used as a solid electrolyte.

Problems to be Solved by the Invention Regarding conductive polymers, the conductive dust is approximately 1 to 10
It is possible to construct a capacitor using oS@cm, and it is possible to realize good frequency characteristics in a high frequency region and temperature characteristics over a wide range by taking advantage of the merits of a solid state. In the electrolytic polymerization reaction, it is necessary to apply a polymer film onto the chemical conversion film that serves as a dielectric without destroying the film through a reaction process called electrolytic oxidation of monomers.

As a method for this, Japanese Patent Application Laid-Open No. 62-165313 discloses that a conductive substance is provided in a part of the chemical conversion film as a starting point for polymerization.
A method of depositing and growing on a chemical conversion film has been proposed.

In the example of JP-A-62-165313, a conductive film in which metal is vapor-deposited on a polyester film is attached to the outer periphery of the chemical conversion film (0.001 to 50% of the total area of the chemical conversion film).
%) and conduct electrolytic polymerization using that point as the polymerization starting point. However, in this method, an electrolytic polymer film grows very close to the conductive substance, but when the chemical conversion film is made to have a large area, the electrolytic polymer film cannot be grown over the entire surface of the chemical conversion film, which is a drawback. However, there are still problems such as short circuits when a highly conductive material such as metal powder or graphite is directly used as a conductive material on the entire chemical conversion coating.

Before forming the chemical conversion film, it is possible to apply an electrolytic polymer film on the valve metal and then form the chemical film by anodic chemical formation in a chemical solution, but in this case, the chemical reaction is not carried out through the electrolytic polymer film. As a result, the quality of the electrolytically polymerized membrane deteriorates and its adhesion to the valve metal deteriorates. Therefore, it has been difficult to provide large capacity capacitors using these methods.

The present invention solves these problems, and in the production of electrolytic polymer solid electrolytic capacitors, an electrolytic polymer conductive polymer is effectively applied to the entire area from which the cathode is taken out on the chemical conversion film that serves as the dielectric of the capacitor. The object of the present invention is to provide a large-capacity electrolytic capacitor that can be grown and has good frequency characteristics in a high frequency region and temperature characteristics over a wide range.

Means for Solving the Problems In order to solve these problems, the present invention forms an anode chemical coating on the surface of an anode body made of a valve metal, and then applies an anode chemical coating to the entire portion of the anode chemical coating from which the cathode is taken out. , a metal oxide semiconductor selected from lead dioxide, vanadium trioxide, and triiron tetroxide, or a mixture thereof, is uniformly deposited in the form of an island or a layer, and furthermore, at least one electrode is placed in contact with the semiconductor. A conductive polymer film is formed on the anode chemical conversion film by electrolytic polymerization.

Effect The effect of the present invention is that, according to the method of the present invention, lead dioxide, trioxide, etc. After uniformly depositing a semiconductor made of a metal oxide selected from vanadium, triiron tetroxide, or a mixture in the form of islands or layers, an electrolytic polymerization reaction is once initiated from an electrode placed in contact with the semiconductor layer. Then, they discovered that the polymer grows over the entire surface of the semiconductor from this point, and this phenomenon is utilized to effectively deposit electropolymerized conductive polymers onto chemical conversion coatings. This makes it possible to provide a large-capacity electrolytic capacitor that achieves good frequency characteristics in a high frequency region and temperature characteristics over a wide range.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

An anode lead wire 2 is welded to a part of an anode body 1 made of aluminum foil that has been electrolytically etched with hydrochloric acid or the like, and after a chemical conversion reaction is performed in an aqueous solution of ammonium adipate or the like, metal is formed by the method described below. Oxide semiconductor layer 4
was formed.

(1) Method of forming lead dioxide Lead dioxide is formed by immersing the anode body in a reaction mother liquor containing lead ions and thermally decomposing it at a high temperature of 200 to 300°C (Japanese Patent Publication No. 58-21414). ), a method of chemically precipitating lead dioxide using silver ions as a catalyst (
(Japanese Patent Publication No. 49-29374), a method of immersing it in an aqueous solution of sodium leadate and leaving it at 60°C under reduced pressure for 30 hours to decompose and form a lead dioxide layer (Japanese Patent Publication No. 62-12662).
No. 5).

(2) Formation method of vanadium trioxide To form vanadium trioxide, the anode body is immersed in an aqueous solution of ammonium metavanadate and sodium borono-hydride as a reducing agent, and left under reduced pressure for 3 hours to form vanadium trioxide. Method for forming a vanadium layer (Japanese Unexamined Patent Publication No. 62-12
No. 6624).

(3) Formation method of triiron tetroxide To form triiron tetroxide, the anode body is immersed in a reaction mother liquor containing iron ions, for example, a saturated ferric sulfate aqueous solution whose pH has been adjusted to 4.5 with ammonium sulfate. Method of forming triiron tetroxide by leaving it for 3 hours at
Publication No. 3).

For electrolytic polymerization, an electrolytic polymerization tank as shown in FIG.
l. Prepared using paratoluenesulfonic acid tetraethylammonium salt 01 mol/l as a supporting electrolyte and acetonitrile as a solvent, and lightly contacting the auxiliary anode 6 made of an aluminum rod with a diameter of 0.2 with the semiconductor layer 4 in the polymerization solution 5. . The tip of this aluminum rod is round and the contact area with the semiconductor layer 4 is 0.2- or less. This aluminum rod is used as the auxiliary anode 6, while the auxiliary cathode 7 has a thickness of 100 mm.
μm aluminum ξ foil was used. When a constant voltage of 5V is applied between the auxiliary anode 6 and the auxiliary cathode 70 in this configuration,
A conductive polymer film is immediately formed on the entire surface of the aluminum rod, which is the auxiliary anode 6, in the polymerization solution 6. If the voltage continues to be applied after that, a conductive polymer film 8 is also formed on the semiconductor layer 4 and gradually grows, and after 10 to 30 minutes, the KFi 112a
A conductive polymer film of f was formed. Next, as shown in FIG. 2, a graphite layer 9 is coated on the conductive polymer film 8, and silver paint is coated on top of it as a conductive layer 10.
Take out ゜. A capacitor was then produced by covering the cap with epoxy resin 12.

The characteristics of the solid electrolytic capacitor prototyped using the method described above were measured and are shown in Table 1.

Table 1 The liquid capacity of the aluminum anode foil used this time is 16.1
Since it was μF, the capacity achievement rate was 662 to 83.9%. Furthermore, we were able to obtain a relatively large-capacity, high-performance capacitor with extremely low impedance at a high frequency of 1 MHz.

In this example, an electrolytically polymerized membrane is formed using pyrrole and thiophene as conductive polymer monomers and paratoluenesulfonic acid tetraethylammonium salt as a supporting electrolyte. An electrolytically polymerized membrane may be formed using a polymerization solution using a derivative as a monomer and another supporting electrolyte. Further, although aluminum is used as the auxiliary anode and auxiliary cathode of the electrolytic polymerization tank in the example shown, the effect remains the same even if metals such as stainless steel, iron, nickel, etc. are used.

Effects of the Invention According to the present invention, in the production of electropolymerized polymer solid electrolytic capacitors, any of lead dioxide, vanadium trioxide, and triiron tetroxide is added to the entire portion from which the cathode is taken out on the chemical conversion film that serves as the dielectric of the capacitor. After uniformly depositing a metal oxide semiconductor in the form of an island or a layer, an electrolytic polymerization reaction is initiated from an electrode placed in contact with the semiconductor layer. Using this method, it is possible to effectively grow electropolymerized conductive polymers on chemical conversion coatings, and it has good frequency characteristics in the high frequency range and a wide temperature range. It becomes possible to provide a large-capacity electrolytic capacitor that achieves these characteristics, and the effect is significant.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an electrolytic polymerization tank in one embodiment of the present invention, and FIG. 2 is a general view of a solid electrolytic C capacitor obtained in the same embodiment. DESCRIPTION OF SYMBOLS 1... Anode body, 2... Anode lead wire, 3... Chemical conversion film, 4... Semiconductor layer, 6... Polymerization liquid , 6... Auxiliary anode, 7
..... Auxiliary cathode, 8 .... Conductive polymer film, 9 .... Graphite layer, 1o .... Conductive layer, 11 .... Cathode Lead wire, 12...
·Epoxy resin. ″$g rib yang yang

Claims (1)

[Claims] An anode chemical coating is formed on the surface of the anode body made of valve metal,
Thereafter, a metal oxide semiconductor selected from lead dioxide, vanadium trioxide, triiron tetroxide, or a mixture thereof is uniformly adhered to the entire portion of the anode chemical conversion coating from which the cathode is to be taken out, in the form of islands or layers; A method for manufacturing a solid electrolytic capacitor, comprising forming a conductive polymer film on the anode chemical film by electrolytic polymerization using at least one electrode placed in contact with the semiconductor.