JPH0274016A - Solid electrolytic condenser - Google Patents

Abstract

PURPOSE:To contrive improvement in high frequency characteristics, the irregularity both in a leakage current and withstand voltage characteristics, and also in the yield of production by a method wherein a first layer consisting of manganese dioxide formed on valve metal through an anodic oxide film, a second layer consisting of an electrolytic reduction polymerized high molecule, and a third layer consisting of a conductivity electrolytic oxide polymerized high molecule are provided. CONSTITUTION:An oxide film 3 is formed on a Al foil which is valve metal, they are dipped into a manganese nitrate aqueous solution, and an MnO2 film 4 is formed. Then, the above-mentioned materials are dipped into a polymerized solution 8 such as acrylamide and the like, an electrolytic reduction polymerized high molecular film is grown by applying electric potential, and cation is doped thereon. Then, the above- mentioned material are dipped into the polymerized solution 8 of pyrrole, thiophene and their derivative, voltage exceeding the polymerized electric potential is applied, and first, a polymerized film is formed on an electrode 5, and then a polymerized film is grown on the manganese dioxide film 4 in its surface direction. As a result, the title solid electrolytic condenser, having excellent high frequency characteristics, a low leakage current and high withstand voltage, can be manufactured with excellent yield of production.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a solid electrolytic capacitor with excellent capacitor characteristics, particularly high frequency characteristics.

BACKGROUND OF THE INVENTION In recent years, with the digitization of electrical equipment circuits, there has been an increasing demand for capacitors used therein that have low impedance in the high frequency range and are small and large in capacity.

Conventionally, plastic film capacitors, mica capacitors, and multilayer ceramic capacitors have been used as capacitors for high frequency ranges, but film capacitors and mica capacitors have large shapes, making it difficult to increase the capacity, and multilayer ceramic capacitors Capacitors have the disadvantage that the smaller and larger the capacitance, the worse the temperature characteristics and the higher the price.

On the other hand, known high-capacity type capacitors include aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. These capacitors can achieve large capacitance because the anodic oxide film that serves as the dielectric can be made very thin, but on the other hand, the oxide film is easily damaged, so damage must be repaired between the oxide film and the cathode. It is necessary to provide an electrolyte for this purpose. In an aluminum dry electrolytic capacitor, etched positive and negative electrode aluminum foils are wound up with a paper separator in between, and the separator is impregnated with a liquid electrolyte. For this reason, capacitance decreases and losses (ta++J) occur over time due to electrolyte leakage, evaporation, etc.
At the same time as the increase in K occurs, there are disadvantages such as extremely poor high frequency characteristics and low temperature characteristics due to the ionic conductivity of the electrolyte.

In addition, for aluminum and tantalum solid electrolytic capacitors,
Manogan dioxide has been used as a solid electrolyte to improve the drawbacks of the above-mentioned aluminum dry electrolytic capacitors. This solid electrolyte is obtained by immersing an anode element in a manganese nitrate aqueous solution and thermally decomposing it at a temperature of around 350°C. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as electrolyte leakage at high temperatures or performance deterioration caused by coagulation at low temperatures, and it has better frequency characteristics and characteristics than capacitors using liquid electrolytes. However, due to damage to the oxide film due to thermal decomposition of manganese nitrate and the high specific resistance of manganese dioxide, the impedance or loss in the high frequency range is 1% compared to multilayer ceramic capacitors or glass film capacitors. The value is more than an order of magnitude higher.

In order to solve the above problems, organic semiconductors (7, 7, 8
, 8-tetracyanoquinodimethane complex). This organic semiconductor can be applied to the oxide film by dissolving it in an organic solvent or melting it by heating, and can prevent damage to the oxide film due to thermal decomposition that occurs when impregnating MnQt. can.

TCNQCN has high conductivity and excellent anodic oxidation properties, and has good high frequency characteristics, making it possible to manufacture large capacity capacitors.

For example, an application has been filed for an invention in which an organic semiconductor consisting of N-n-propyl or N-1so-propylisoquinoline and TCNQ is used as a solid electrolyte (Japanese Patent Laid-Open No. 58
-17609). According to the invention, impregnation of a wound aluminum electrolytic capacitor with TCNQ salt
This is done by heating and melting the salt, which results in TCN
A strong bond between the Q salt and the oxide film is achieved, and the high conductivity of the TCNQ salt helps to produce an aluminum capacitor with significantly improved frequency and temperature characteristics. The use of an organic semiconductor based on TCNQ salt as a solid electrolyte has already been proposed by the same applicant (Japanese Patent Application Laid-Open No. 17609/1983).
As shown in , TCNQ salt has higher conductivity and higher anodic oxidation ability (repairing action) than manganese dioxide, so it has better frequency characteristics and temperature characteristics than solid electrolytic capacitors using manganese dioxide. enable superior performance. According to this invention, the oxide film is impregnated with a TCNQ salt having a cation of inquiturium substituted with an alkyl group at the N position by heating and melting the oxide film.

Furthermore, in recent years, proposals have been made to form polymers of heterocyclic compounds such as pyrrole and thiophene on an anode body and to utilize the polymers by solid electrolysis.

Problems to be Solved by the Invention However, in the electrolytic polymerization reaction, it is not possible to form a polymer film on the oxide film that serves as a dielectric without destroying the film due to the reaction process of electrolytic oxidation of monomers. Furthermore, before forming the oxide film, it is possible to apply an electrolytic polymer film on the valve metal and then perform a chemical conversion reaction to form the oxide film. As a result, the quality of the electropolymerized membrane may be altered, and its adhesion to the valve metal may be reduced. Therefore, until now, it has been considered difficult to form a good electrolytically polymerized film on a valve metal.

The present invention solves the above-mentioned conventional problems and aims to provide a solid electrolytic capacitor with excellent high frequency characteristics, less variation in leakage current and withstand voltage characteristics, and high yield.

Means for Solving the Problems The present invention achieves the above object, and its technical means includes: a fourth layer made of manganese dioxide formed on the valve metal via an anodized film; A second layer made of an electrolytically reduced polymer formed on at least a portion of the layer, and a third layer made of a conductive electrolytically oxidized polymer.

Effect of the present invention: Manganese dioxide treatment is applied to the oxide film on the At or Ta valve metal, and then electrolytic reduction polymerization polymer is formed on the defective parts of the oxide film, and then the electrolytic oxidation polymer film is oxidized. By forming it over the entire surface of the film, a solid electrolytic capacitor with high frequency characteristics, low leakage current, and high withstand voltage can be obtained.

The electrolytically reduced polymer of the present invention is preferably acrylic ester, methacrylic ester, acrylonitrile, or acrylamide. It is desirable that the polymer be a polymer that can be used.

Example The present invention will be explained in detail below.

FIG. 1 shows a manufacturing schematic diagram illustrating the structure of a solid electrolytic capacitor in an embodiment of the present invention. As shown in Fig. 1 (a+), a capacitor anode lead electrode 2 is attached to a foil l of At, which is a valve metal, and is first subjected to an etching treatment to increase the surface area.Next, as shown in Fig. 1 (b
), using an adipic acid aqueous solution etc.
An oxidation degree M3 consisting of The oxide film 3 is formed by a conventional method using electrochemical means. Thereafter, it is immersed in a manganese nitrate aqueous solution and thermally decomposed in air at 250 to 300°C to form a MnQ film 4. Next, an electrolytic polymer film is formed on this surface, but even if a voltage is applied using the anode 2 of the capacitor as a polymerizing electrode, electrolytic polymerization does not occur and film growth does not occur because the dielectric film is present. . Therefore, as shown in FIG. 2, an electrode 5 for electrolytic polymerization that initiates polymerization is provided externally so as to be in contact with the MnO membrane 4, and a counter electrode 6 for electrolytic polymerization is further provided separated from the electrode 5 for electrolytic polymerization. Ta. However, if there is a defect in the oxide film, a polymeric film will grow from there, or the film will grow deep into the oxide layer. Such locations cause an increase in leakage current and a decrease in withstand voltage. Therefore, in this example, before forming a film of an electrolytically oxidized polymer having excellent conductivity, an electrolytically reduced polymer film is previously formed on the defect.

That is, a polymerization solution 8 made of acrylic acid ester, methacrylic acid ester, methacrycentrile, methacrylamide, acrylonitrile, or acrylamide is prepared in the polymerization reaction container 7 shown in FIG. By immersing the formed At foil 1 and applying a positive potential to the counter electrode 6 for electrolytic polymerization and a negative potential to the electrode 5 for electrolytic polymerization, the electrolytically reduced polymer film grows and is doped with cation/.

Next, a polymerization solution 8 consisting of an electrolytically polymerizable monomer selected from pyrrole, thiophene, and derivatives thereof, a supporting electrolyte, and a solvent was placed in a polymerization reaction vessel 7 as shown in FIG. In this, the above At foil 1 is placed 5' as shown in the figure.
By immersing the IC and applying a voltage higher than the polymerization potential between the counter electrode 6 for electrolytic polymerization and the electrode 5 for electrolytic polymerization, a polymer film (not shown) is first formed on the electrode 5, and then, gradually starting from this point, a polymer film (not shown) is formed on the electrode 5. Then, a polymer film is grown in the direction of the surface of the manganese dioxide film 4. After the polymer film completely covers the surface of the manganese dioxide film 4, the electrolytic polymerization reaction is terminated.

In this process, cations are dedoped from the electrolytically reduced polymer, resulting in higher electrical conductivity and resistance. Therefore, an electrolytically polymerized film with excellent conductivity is formed at the defective portion of the oxide film, and an increase in leakage current and a decrease in withstand voltage are significantly reduced. Finally, the surface of the trap and polymeric membrane is washed and dried. Thereafter, although not shown, a lead electrode of a capacitor cathode is attached in contact with the polymer film using carbon paste, silver paste, or the like. Finally, the exterior is treated using epoxy wood and resin. A plurality of electrodes 5 for electrolytic polymerization may be provided. Further, the counter electrode 6 for electrolytic polymerization may be located anywhere as long as it is located apart from the electrode 5 for electrolytic polymerization, and it is desirable that the electrode 5 for electrolytic polymerization has a smaller shape than the counter electrode 6 for electrolytic polymerization.

More details are provided below.

The At foil used was one that had been normally etched and had a rating of 16 V and 16 μF. After applying a chemical conversion film using an adipic acid aqueous solution, it was immersed in a 30% manganese nitrate aqueous solution and thermally decomposed in air at 270°C for 15 minutes.

Electrolytic reduction polymerization solution was mixed with methyl methacrylate (05M/l)
, tetraethylammonium barchlorate (01M
/l), prepared from acetonitrile.

The electrolytic oxidation polymerization solution contains pyrrole (0.5M/l), tetraethylammonium valatoluenesulfonate (0.
, 1M/l) and acetonitrile.

First, an electrolytic reduction polymerization reaction is carried out using a platinum wire as an electrode at the starting point of electrolytic polymerization and a platinum plate as a counter electrode.
was applied for 5 minutes. Thereafter, after washing with alcohol, an electrolytic oxidation polymerization reaction was performed for 30 minutes using the same electrode configuration. Then, wash with alcohol and dry. Next, attach the cathode lead electrode using Aquaduck and silver paste. Finally, the exterior was covered with epoxy resin. Next, 8
Etching treatment was performed by applying 20V at 0°C for 2 hours.

Next, the characteristics of this capacitor are shown in the table. The results in the table represent the average value of 10 samples, with a liquid volume of 10 pF.
(120Hz).

As is clear from the capacitor characteristics table, the capacitance value at 120 Hz, for example, is very high at 95 μF (normal solid capacitors, such as TCNQ salt, have a value of 37 μF) and 500 KH2.
The series resistance (ESR) at K is also very small at 30 mfl among At electrolytic capacitors, and the high frequency characteristics are excellent. The leakage current also showed a very small value of 0.2μ8 or less. Furthermore, if the electrolytically reduced polymer polymer is not treated, the leakage current will be on the order of mA or more.
There were 2 to 3 out of 0, and some were destroyed at a withstand voltage of 16V or less, but by processing,
Such defects were no longer observed, and the yield was improved.

Effects of the Invention In short, the present invention provides a first layer formed on an oxide film by manganese dioxide treatment, and a second layer made of an electrolytically reduced polymeric polymer provided covering at least a portion of the first layer. , and a third layer made of an electrolytically oxidized polymer with excellent conductivity, the solid electrolytic capacitor has excellent high frequency characteristics, low leakage current, and high withstand voltage, which can be manufactured with high yield. has advantages.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing the steps of a method for manufacturing a solid electrolytic capacitor in an embodiment of the present invention. 1... At foil, 2... anode lead electrode, 3... oxide film, 4... MnO snow film, 5... electrode for electrolytic polymerization,
6... Counter electrode for electrolytic polymerization, 7... Polymerization reaction vessel, 8...
...Polymerization solution. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1

Claims (2)

[Claims] (1) A first layer made of manganese dioxide formed on the valve metal through its anodic oxide film, and a second layer made of an electrolytically reduced polymer provided on at least a portion of the first layer. and a third layer made of a conductive electrolytically oxidized polymer. (2) The electrolytically reduced polymer is a polymer obtained from a monomer selected from acrylic acid ester metal ester, acrylonitrile, acrylamide, and the conductive electrolytically oxidized polymer is selected from pyrrole, thiophene, or their derivatives. The solid electrolytic capacitor according to claim 1, characterized in that: