JPS6151907A - Solid electrolytic condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to solid electrolytic capacitors, and particularly to improvements in solid electrolytes made of organic semiconductors.

[Conventional technology]

Solid electrolytic capacitors use film-forming metals such as aluminum and tantalum for the anode, and in order to make the anode corrugated, the surface of the foil-shaped anode body is etched, or powder of the metal is sintered to form a porous material. Then, an oxide film layer to serve as a dielectric is formed on this surface by means such as anodizing treatment, a solid electrolyte layer is further formed on this upper surface, and an electrical connection for drawing out the cathode is made from this solid electrolyte layer. It is constructed by means of jiff L/.

Conventionally, manganese dioxide has been used for this solid electrolyte layer. The method for forming this manganese dioxide on the dielectric oxide film layer is to impregnate the anode electrode in liquid manganese nitrate, and then thermally decompose the manganese nitrate at a temperature of around 300°C to denature it into manganese dioxide. Ta.

However, with this method of electrolyte formation, only a small amount of manganese dioxide is deposited in a single process, so it is necessary to repeat the same process repeatedly.

Therefore, the manufacturing process becomes extremely complicated, and the dielectric oxide film deteriorates due to the same temperature and generated gas during thermal decomposition.

Recently, it has been proposed to use a conductive organic substance as an electrolyte instead of manganese dioxide.

As this organic electrolyte, various complex salts of tetracyanoquinodimethane (hereinafter referred to as TCNQ) are known.

Although TCNQ complex salt is an organic substance, it has appropriate conductivity, and its use has been attempted as suitable for the electrolyte layer of solid electrolytic capacitors.

Since the TCNQ complex salt is a solid substance at room temperature, the problem is how to make it adhere to the dielectric oxide film as an electrolyte.

For example, as shown in (U.S. Pat. No. 3,214,648), TCNQ salts are dissolved in an organic solvent, the anode body is impregnated in this solution, and then the anode body is pulled out of the solution. It is known that a TCNQ complex salt layer is formed on the surface of the anode body by evaporating the organic solvent. However, with this method, since the concentration of TCNQ complex salt in the solvent is low, it is not possible to deposit enough TCNQ complex salt in one impregnation, and this process, as well as the formation of the manganese dioxide layer, has to be canceled. It required repeated political changes, and the complexity of the manufacturing process could not be avoided.

Furthermore, as in (Japanese Patent Publication No. 51-32303), a method has been proposed in which a dispersion consisting of a polymer substance and fine powder of TCNQ complex salt is adhered to the electrode surface.

However, in these methods, the TCNQ complex salt crystallizes after evaporation of the solvent, or the TCNQ complex salt is dispersed in a crystalline state, so that the dielectric oxide film on the anode surface, which has been wave-treated and has complex irregularities, is There was a drawback that sufficient contact could not be obtained between the capacitors and the desired capacitance could not be obtained.

Recently, T.
A solid electrolytic capacitor has been proposed in which only the CNQ complex salt is heated and melted above its melting point, an anode body is impregnated therein, and then the anode body is pulled up and cooled to adhere the TCNQ complex salt.

In the solid electrolytic capacitor produced by this method, the highly concentrated TCNQ complex salt itself is adhered to the anode body, so that a sufficient TCNQ complex salt layer can be formed in a single impregnation operation.

However, as described above, in the solid electrolyte layer produced by this method, the TCNQ halide salt is crystallized, and sufficient contact with the dielectric oxide film layer cannot be established, making it impossible to obtain the desired capacitance.

Moreover, the TCNQ complex salt itself is extremely sensitive to heating, and if kept in a molten state, it will undergo thermal decomposition in a short period of time, turning into an insulator. Furthermore, some TCNQ complex salts undergo thermal decomposition at temperatures below their melting point, making it virtually impossible to form a solid electrolyte layer by this method. For example, isopropyl-isoquinolinium TCNQ complex salt can be impregnated by heating and melting, but the time that the molten state can be maintained is extremely short. Also, methylisoquinolinium 'TCNQ
Sa salt, 4,4'-dimethylbipyridinium TCNQ complex salt, 4,4'-isopropylbipyridinium TCNQ complex salt, etc. undergo thermal decomposition from the heating stage before melting, and electrolyte soaking by melting is virtually impossible.

[Problem that the invention seeks to solve]

This invention improves on these conventional drawbacks.
Conventionally, TCNQ complex salts that cannot be melt-impregnated or TCNQ complex salts that can be melt-impregnated but have to be impregnated in a very short period of time can be used as solid electrolytes.
In addition to forming the TCNQ complex salt on the surface of the anode body, the insufficiency of contact with the dielectric oxide layer 11 caused by crystallization after impregnation is improved, and the solid electrolytic capacitor has high impregnation efficiency. The purpose is to rise above 1.

[Means for solving problems]

This invention forms a dielectric oxide film on the anode metal surface,
Furthermore, in this solid electrolytic capacitor in which a solid electrolyte layer is formed on the upper surface, the solid type f'+*IT 5 may be isopropyl-isoquinolinium, methylisogynolinium, 4,4'-dimethylbipyridinium, 4,4'- It is characterized by being formed by melting and solidifying a mixture in which T-butyrolactam is added to a complex salt consisting of one or more selected from the group of isoprobil bipyridinium and T CN Q. It is a solid electrolytic capacitor.

The present invention will be described in detail below based on examples.

〔Example〕

First, the solid electrolytic capacitor according to the present invention will be explained along with an example of its manufacturing procedure.

FIG. 1 is a cross-sectional view of a completed solid electrolytic capacitor manufactured according to this example, and FIG. 2 is a cross-sectional view of the anode body, ie, the capacitor element, used in this example.

The capacitor element 1 shown in FIG. 2 is formed by winding a band-shaped electrode body, and the anode 2 is made of high-purity aluminum foil. A dielectric oxide film is formed on the surface of this anode 2 by anodizing treatment.

This strip-shaped anode 2 has collector electrodes 3 of approximately the same size disposed opposite each other, and a separator paper 4 slightly wider than these electrodes 2.3 is placed between the anode 2 and the collector electrode 3. What is sandwiched is 1n1 from -mandan to form a cylindrical capacitor element 1. Note that tabs 5 and 6 for obtaining electrical connection with the outside are connected to each of the anode 2 and the collector electrode 3 by means such as welding, and protrude in parallel from one end surface. Furthermore, external leads 7.8 are connected to the tips of these tabs by welding.

FIG. 3 shows an example of impregnating the solid electrolyte layer into the capacitor element 1. A preheating block 10 is placed on the left side of the figure. A heater is buried therein, a recess 11 is provided on the top surface, and the capacitor element 1 is placed in the recess 11.
The capacitor element 1 is heated in advance by being placed inside the capacitor and maintained at a high temperature.

Next, an impregnating block 12 is placed on the right side of the figure, and this impregnating block 12 also has a heating heater embedded therein and a recess 13 formed in its upper surface. This recess 13 contains TCNQtM salt and additive γ.
- Ptyrolaccum is injected, and heating melts said mixture 14. The capacitor element 1, which has been kept on standby in the preheating block 10, is moved here and impregnated for a predetermined period of time.Then, the capacitor element 1 is pulled up from the recess 13, and the liquid mixture 14 is solidified by natural cooling to form a solid electrolyte. form a layer.

The capacitor element 1 on which the solid electrolyte layer has been formed in this manner is housed in a bottomed cylindrical outer case 20, as shown in FIG. The outer case 20 is closed and the σfTD end of the outer case 20 is rolled up and sealed. Note that the external leads 7.8 drawn out from the capacitor element 1 protrude to the outside from the through hole provided in the elastic sealing body 21, so that an electrical connection between the capacitor element 1 and the outside can be established.

Next, we will show the results of fabricating an actual solid electrolytic capacitor using the procedure described above and determining its characteristics.

First, as a capacitor element, width 2.2fl, length 10+
am, a high-purity (99.99%) aluminum foil with a thickness of 80 μm is provided as an anode, and after the surface of this anode is made into a corrugated surface by electrolytic etching using an alternating current, a dielectric with a withstand voltage of 9 μm is applied to the surface. A body oxide film was formed by anodizing. Then, as a current collecting electrode, aluminum foil (99.94% purity) of the same size as the anode is placed oppositely, and an aluminum tab for external extraction is connected to the approximate center of both electrodes by cold welding. A cylindrical shape obtained by winding a separator paper mixed with manila hemp fiber as shown in FIG. 2 was used in all the examples.

Next, as Comparative Example 1, this capacitor element was impregnated with an ethylene glycol-ammonium adipate based electrolyte. Further, as Comparative Examples 2 to 5, isopropyl-isoquinolinium complex salt, methylisoquinolinium complex salt, 4,4'-dimethylbipyridinium complex salt, 4,4'-
Four types of TCNQ complex salts, including isopropyl bipyridinium complex salts, were heated and melted, and the capacitor element was impregnated with the complex salts using the impregnating apparatus described above.

Next, as invention examples 1 to 4, the above four types of TCNQ
A mixture in which γ-butyrolactum was added to a complex salt was impregnated using the above impregnating apparatus while changing the heating temperature.

Then, the capacitor element that has been impregnated is stored in a cylindrical aluminum outer case, the case opening is closed with a rubber sealing body, and the outer case opening end is wrapped and sealed. Rated voltage 6.3■, rated capacity 10μF
completed an electrolytic capacitor.

Among these electrolytic capacitors, Comparative Example 1 using a liquid electrolyte was tested for 15 minutes, and other Comparative Examples that could be impregnated and this invention example were tested for 1 hour. After aging the capacitor by applying the rated voltage, its electrical characteristics were investigated.

Regarding electrical properties, capacitance, tangent of loss angle, 100
Equivalent series resistance values in KII2 and leakage current 2 minutes after application of the rated voltage were measured, and each characteristic was compared.

The results are shown in the table below.

(Left space on wooden page) [Operation] Looking at the results of these examples, it is found that in the normal dry electrolytic capacitor using a liquid electrolyte shown in Comparative Example 1, the electrolyte is held in a liquid state inside the capacitor element. As a result, the electrolyte penetrates into the fine etching holes (focuses) formed by the etching process to make the anode corrugated, and makes sufficient contact with the dielectric oxide film, resulting in a high capacitance value. show.

However, the specific resistance value of the electrolyte is 200-300 Ω・while the specific resistance value of the TCNQ complex salt is about several tens of Ω・marks.
cm, the loss value or equal series resistance value is high.

In addition, in Comparative Example 2, the isopropyl-
Only isoquinolinium T CN Q tH salt can be impregnated by heating and melting, and other TCNQ of Comparative Examples 3 to 5
In all cases using complex salts, thermal decomposition occurred before reaching a molten state, making impregnation impossible. In addition, looking at the characteristics of Comparative Example 2, which was able to be impregnated, excellent characteristics were obtained in terms of loss and equal series resistance because the specific resistance value of the TCNQ complex salt is lower than that of the electrolytic solution, as described above. However, a sufficient value for capacitance (1) has not been obtained.

The reason for this is not clear, but when only the TCNQ complex salt is heated and melted, the TCNQ complex penetrates into the etching focus of the anode. This is thought to be because contact with the dielectric oxide film within the etching focus, which forms capacitance, is not made in some parts.

On the other hand, the solid electrolytic capacitor of the present invention has the following characteristics in each case, as is clear from the characteristics of Invention Examples Work to 4.
It shows a larger capacitance value than Comparative Example 2. This is because the solid electrolyte of this invention is a mixture of TCNQtR salt and γ-butyrolactam, so crystallization is prevented during cooling after melting and impregnation, and it remains in the etching pin in an amorphous state. This is thought to be because sufficient contact with the body's oxidized film is maintained.

Furthermore, even if some of the TCNQ complex salt crystallizes, it is thought that the presence of T-butyrolactam between the crystals provides electrical conductivity between the crystals and maintains the capacitance.

For the same reason, excellent electric power can be obtained in contact with the collecting electrode side, contributing to improved characteristics.

In this example, foil-like aluminum is used for the recessed part, and after the surface is enlarged, a dielectric oxide layer is formed.
Although we used a capacitor element in which the current collecting electrode and the current collecting electrode were wound with a separator paper interposed therebetween, the capacitor element is not limited to such a structure (the metal constituting the anode may be tantalum or other metal). It may be a film-forming metal or an alloy thereof.In addition, it is not limited to such a wound + IJ structure, but may also be a porous body obtained by sintering a film-forming metal powder. Even if it has a circular structure, the separator paper may be omitted, the collecting electrode may be made of a metal other than aluminum, or a heat-resistant conductive resin film may be used.

In addition, regarding the exterior structure, in this example, the case is housed in a metal exterior case, but the exterior body may be a resin case, one made by dipping or molding resin, or an exterior device made of a laminated film. However, this does not depart from the scope of this invention.

〔effect〕

As described above, according to the present invention, the solid electrolyte layer is
Since it can be formed by heating and melting impregnation of a mixture of CNQ complex salt and γ-butyrolactam, it is possible to form the mixture by heating and melting it. A'! A TCNQ complex salt that could not be impregnated by melting can be used.

Furthermore, since the melting temperature of the TCNQ complex salt, which can be impregnated by heating and melting, is lowered, the time required for thermal decomposition is extended, and deterioration of properties can be prevented and impregnation becomes easier.

Further, according to the present invention, the impregnation rate of TCNJQ salt is improved and the capacitance value per unit volume can be increased, which contributes to miniaturization of solid electrolytic capacitors.

Furthermore, since the TCNQ complex salt is in sufficient contact with the dielectric oxide layer, it is possible to obtain a solid electrolytic capacitor with low loss and excellent impedance characteristics, which is extremely useful for improving the characteristics of solid electrolytic capacitors. be.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the completed solid electrolytic capacitor of the present invention, FIG. 2 is an exploded perspective view of the structure of a capacitor element used in an embodiment of the present invention, and FIG. 3 is a cross-sectional view of the solid electrolytic capacitor of the present invention. FIG. 2 is a cross-sectional view of a solid electrolyte impregnation device used in Examples. 1. Capacitor element, 2. Anode, 3. Collector electrode, 4
Separate paper, 5, 6... Tab, 7° 8... External lead, 10... Preheating block, 11.13... Concavity, 12... Impregnation block, 14... Mixture, 20...
Exterior case, 21... Elastic sealing body. Patent application Nippon Chemi-Con Co., Ltd. Figure 1 Figure 2

Claims (2)

[Claims] (1) In a solid electrolytic capacitor in which a dielectric oxide film is formed on the surface of the anode metal, and a solid electrolyte layer is further formed on the upper surface of the solid electrolyte layer, the solid electrolyte layer contains γ-butyrolactam added to a complex salt of tetracyanoquinodimethane. A solid electrolytic capacitor is characterized in that it is made of a mixture obtained by melting and solidifying the mixture. (2) Complex salts of tetracyanoquinodimethane include isopropyl-isoquinolinium, methylisoquinolinium, 4,
Claim No. 1, which is a complex salt consisting of one or more selected from the group of 4'-dimethylbipyridinium and 4,4'-isopropylbipyridinium.
Solid electrolytic capacitors listed in ).