JPS63239911A - Solid electrolytic capacitor - 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 (Field of Industrial Application) The present invention relates to a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor using an organic semiconductor as a solid electrolyte.

(Prior Art) In recent years, as electronic devices have become smaller and lighter, there has been a demand for small, large-capacity capacitors with low impedance in a high frequency range.

Conventionally, mica capacitors, film capacitors, ceramic capacitors, etc. have been used as capacitors for such high frequencies, but none of these capacitors are suitable for increasing the capacity.

On the other hand, small-sized, large-capacity capacitors include aluminum electrolytic capacitors and tantalum capacitors.

Aluminum electrolytic capacitors have the advantage of being able to provide large capacity at low cost, but because they use an electrolyte, their capacity deteriorates as the electrolyte evaporates over time, and their high frequency characteristics are poor. There was a drawback.

On the other hand, tantalum solid electrolytic capacitors overcome the drawbacks of aluminum electrolytic capacitors, such as capacity deterioration, by using solid manganese dioxide or the like as an electrolyte. However, this solid electrolyte is formed by impregnating and adhering an aqueous solution of manganese nitrate to the valve metal body, and then thermally decomposing the manganese nitrate at around 350°C.It is usually heated several times or more to increase the amount of manganese dioxide deposited. Impregnation of more than 10 figures
Since it is necessary to repeat the thermal decomposition process, there are drawbacks such as damage to the oxide film as a dielectric during thermal decomposition and low repair ability of the manganese dioxide film.

Therefore, in order to improve these shortcomings, Japanese Unexamined Patent Publication No. 58-17
No. 609, etc., as an organic solid electrolyte with excellent repairability of anodized film and good conductivity, 7, 7, 8.
A method using a 8-tetracyanoquinodimethane complex salt (hereinafter abbreviated as TCNQ complex salt) has been proposed. In JP-A-58-17609, an organic semiconductor consisting of inquinoline in which the N position is substituted with an alkyl group and a TCNQ complex salt is used as a solid electrolyte, and before the TCNQ complex salt decomposes, it is cooled and solidified to form a solid state. It is disclosed that it is used as an electrolyte.

(Problems to be Solved by the Invention) However, in the solid electrolyte layer formed by such a method, the TCNQ complex salt crystallizes during cooling and solidification after the impregnation and does not adhere sufficiently to the dielectric oxide film. ,
There was a problem in that the desired capacitance could not be obtained.

Furthermore, since TCNQ complex salt has insufficient thermal stability, if it is kept in a molten state at a high temperature, it will thermally decompose in a short time and become an electrical insulator. Therefore, after performing the impregnation treatment in an extremely short period of time, a rapid cooling operation and a complicated apparatus for the same are required, resulting in problems of high manufacturing costs and poor workability.

The present invention solves the above-mentioned problems and improves workability when impregnating a solid electrolyte made of TCNQjf salt onto the dielectric oxide film formed on the surface of the anode metal, and also prevents the adhesion of TCNQ complex salt to the capacitor element. The purpose of this invention is to provide a solid electrolytic capacitor with high capacitance by improving the capacitance.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides 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 this film. The solid electrolyte layer has the general formula R-3Ox R' (R,R
' indicates an alkyl group or an aryl group) A liquid obtained by heating and melting one type or a mixture of two or more sulfone compounds, and a liquid obtained by dissolving a tetracyanoquinodimethane complex salt and cooling and solidifying it. The present invention provides a solid electrolytic capacitor characterized by comprising:

The present invention enables the TCNQ complex salt to be melted and liquefied at a temperature below the melting point or thermal decomposition temperature of the TCNQtff salt by adding a specific sulfone compound to the TCNQ complex salt, and furthermore, these sulfone compounds can be cooled and solidified. This is based on the fact that the electrical conductivity is the same or higher than that of the TCNQ complex salt.

In the present invention, the sulfone compound added to the TCNQ complex salt has the general formula R-502-R' (R.

R' represents an alkyl group or an aryl group), and R and R' in the general formula are an alkyl group having 1 to 10 carbon atoms,
Alternatively, a phenyl group, tolyl group or xylyl group is preferable, and R and R' may be the same group or different groups. Further, the alkyl group having 1 to 10 carbon atoms may be linear or may have a side chain.

Particularly preferred examples of these sulfone compounds include those in which R and R' are an alkyl group having 1 to 6 carbon atoms or a phenyl group.

The above-mentioned sulfone compounds are suitably used alone or in combination of two or more.

The TCNQ complex salts used in the present invention are not particularly limited, but include pyridine substituted with a hydrocarbon group at the N position, benzothiazole, acridine, phenazine, phenanthridine, quinoline, isoquinoline, α
- TCNQ of naphthoquinoline or β-naphthoquinoline
Complex salts, particularly TCNQ complex salts of quinoline or isoquinoline in which the N position is substituted with a hydrocarbon group, are preferably used.

The solid electrolytic capacitor according to the present invention includes TCNQ complex salt 1.
0.05 to 3 parts by weight of the above sulfone compound
．． 0 parts by weight, preferably 0.1 to 2.0 parts by weight, are added and mixed at a temperature below the melting point or thermal decomposition temperature of the TCNQ complex, for example 120 to 200°C, preferably 150 to 2.
A step of dissolving the TCNQ complex salt into a solution by heating to 00°C to liquefy the additive, and a step of impregnating a capacitor element with this solution and then cooling and solidifying it to form a solid electrolyte layer. It is produced through the process.

(Example) Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

Comparative Example 1 TC disclosed in JP-A-58-191414
N-n with the lowest specific resistance (3.4 Ωcm) among NQ complex salts
- Using butylisoquinolinium (TCNQ) z complex salt,
This was filled into an aluminum can case and melted on a hot plate kept at 260°C. Next, a wound aluminum electrolytic capacitor element (rated capacity 5 μF, rated voltage 25 μF), which had been preheated to the same temperature, was quickly placed in the aluminum can case, impregnated with TCNQ complex salt, and held for 10 seconds, then the case was At the same time, it was pulled up from the hot plate and allowed to cool naturally. Next, the opening was sealed using epoxy resin to produce a solid electrolytic capacitor. The characteristics of this solid electrolytic capacitor after aging by applying the rated voltage for one hour are shown below.

Capacitance (120Hz) 3.2 u
Tangent of F loss angle (tan δ, 120Hz) 0
．． 08 equivalent equivalent side resistance (ESR, 100KHz)
0.65Ω leakage current (after 2 minutes) 0.0
9 μA Example 1 N-n-butylisoquinolinium (T
CN Q) When a mixture of 1.0 parts by weight of z complex salt and 1.0 parts by weight of diethyl sulfone (Cz Hs Sow Cz Hs) was added and mixed into an aluminum can case and heated, a uniform solution was formed at 180°C. Then, as in Comparative Example 1, a capacitor element preheated to the same temperature was placed in the aluminum can case and impregnated, held for 10 seconds, and then allowed to cool naturally together with the can case. Furthermore, sealing with resin was performed under the same conditions as in Comparative Example 1 to produce a solid electrolytic capacitor. The characteristics of this solid electrolytic capacitor after aging by applying the rated voltage for one hour are shown below.

Capacitance! (120Hz) 5.3p
Ftan δ (120)1z)
0.01 equivalent series resistance (100KHz) 0
．． 45Ω leakage current (after 2 minutes) 0.08μA Examples 2 to 13 Based on 1.0 parts by weight of N-n-butylisoquinolinium (TCNQ) z complex salt used in Comparative Example 1 and Example 1 Additives consisting of sulfone compounds shown in Table 1 (Examples 2 to 13) were mixed and impregnated and adhered to the same capacitor element as in Example 1 at the impregnation temperature shown in Table 1 in the same manner as in Example 1. A solid electrolytic capacitor was manufactured using the same method, and the characteristics of the capacitor after aging are shown in Table 1.

Comparative Example 2 N-methylisoquinolinium (T
An attempt was made to fabricate a solid electrolytic capacitor using a complex salt of CNQ) in the same manner as in Comparative Example 1, but this TCNQ complex salt did not melt at 260°C and simultaneously melted and decomposed at 280°C. It was not possible to impregnate the capacitor element.

Example 14 N-methylisoquinolinium (TCN) used in Comparative Example 2
Q) When a mixture of 1.0 parts by weight of Z complex salt and 1.0 parts by weight of diphenyl sulfone (C6H5SOZ Cb Hs) was added and mixed into an aluminum can case and heated, a uniform solution was formed at 240°C. It became. Next, a solid electrolytic capacitor was produced in the same manner as in Example I, and the characteristics of the capacitor after aging are shown below.

Capacitance (120Hz) 5.1 u
Ftan δ (12011z)
0.02 equivalent series resistance (100KHz) 0
．． 61Ω leakage current (after 2 minutes) 0.07μA (this page, below margin) (Functions and effects) In Comparative Example 1, the values of equal series resistance (ESR), leakage current, etc. are relatively good. Despite this, the capacitance is 3.2 μF, which is far lower than the rated value of 5 μF. The reason for this is not clear, but when the molten TCNQ complex salt is cooled and solidified, it becomes needle-shaped crystals or shrinks in volume, and the TCNQtV salt solidified inside the etching pit of the anode. This is thought to be because the dielectric film or bulk contacts the TCNQ complex salt only partially.

On the other hand, the solid electrolytic capacitors according to the present invention in Examples 1 to 14 all have approximately the rated capacitance (4,9 to 5
．． 4) is shown. Although the reason for this is not clear, the crystallization of the TCNQ complex salt is prevented during cooling after impregnation and solidifies in an amorphous state, so that the TCNQ complex salt remaining in the etching bit does not come into sufficient contact with the oxide film. It is assumed that this will be retained. That is, according to the present invention, the first
By adding the additives shown in the table to the TCNQ complex salt,
It is possible to reduce costs by reducing the amount of expensive TCNQ complex salt used, and to improve the adhesion rate of TCNQtI salt to capacitor elements, thereby providing a solid electrolytic capacitor with high capacitance.

Furthermore, in the present invention, the additives (specific sulfone compounds) shown in Table 1 melt at a temperature below the melting point or decomposition temperature of the TCNQ complex salt, and the additives have the ability to dissolve the TCNQ complex salt. , the impregnation temperature of the solid electrolyte can be set lower than the melting temperature of the TCNQ complex salt. Therefore, the time required for thermal decomposition of the TCNQ complex salt can be significantly extended and the workability in the impregnation process can be significantly improved. is about 220℃
At 260°C, it decomposes and becomes an insulator in around 70 seconds, whereas according to the present invention, it is possible to liquefy the TCNQ complex salt at around 1°C, and at this temperature
Since it can be maintained in a stable state without decomposing for more than a minute, the workability of the impregnation and cooling/solidification processes can be significantly improved.

Furthermore, as shown in Example 14, even TCNQ complex salts that cannot be melted and impregnated alone can be impregnated into capacitor elements according to the present invention.
It becomes possible to use the Q complex salt as a solid electrolyte.

(Effects of the Invention) As explained above, according to the present invention, it is possible to impregnate TCNQ complex salt at a temperature lower than its melting point or thermal decomposition temperature, thereby significantly improving the workability of the impregnation and cooling/solidification steps. At the same time, the adhesion rate of TCNQ complex salt to the capacitor element can be improved, and a solid electrolytic capacitor with high capacitance can be obtained.

Claims (3)

[Claims] (1) In a solid electrolytic capacitor in which a dielectric oxide film is formed on the anode metal surface and a solid electrolyte layer is further formed on this film, the solid electrolyte layer has the general formula R-SO_
A tetracyanoquinodimethane complex salt is added to a liquid obtained by heating and melting one type of sulfone compound or a mixture of two or more types of sulfone compounds represented by 2-R' (R and R' represent an alkyl group or an aryl group). A solid electrolytic capacitor characterized by being made of melted, cooled and solidified solid electrolytic capacitor. (2) The solid electrolytic capacitor according to claim 1, wherein R and R' in the sulfone compound are an alkyl group having 1 to 10 carbon atoms, a phenyl group, a tolyl group, or a xylyl group. (3) The tetracyanoquinodimethane complex is a tetra of pyridine, benzothiazole, acridine, phenazine, phenanthridine, quinoline, isoquinoline, α-naphthoquinoline or β-naphthoquinoline obtained by substituting the N position with a hydrocarbon group. The solid electrolytic capacitor according to claim 1 or 2, which is a cyanoquinodimethane complex salt.