JPH01282812A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To hold solder heat resistance, and to obtain excellent high-frequency characteristics by combining an inorganic matter and an inorganic compound having specific physical properties together with a TCNQ complex salt. CONSTITUTION:A solid electrolyte composed of the complex of a tetracyanoquinodimethane (TCNQ) complex salt and the particulates of an inorganic matter or an inorganic compound, a linear expansion coefficient of which is brought to 5X10<-5>(K-1) or less and the melting point of which is brought to 260 deg.C or higher, is used. The complex salt, etc., of isoquinolium, an N order of which is replaced with an alkyl group, and TCNQ is cited as the TCNQ complex salt. Carbon represented by graphite, a semimetal such as boron, silicon, etc., and various metals such as aluminum are quoted as the inorganic matter. Various oxides such as silica and alumina are cited as the inorganic compound. Accordingly, solder heat resistance is held, and excellent high-frequency characteristics are maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a solid electrolytic capacitor, particularly a solid electrolytic capacitor that maintains excellent high frequency characteristics and has solder heat resistance.

[Prior Art] For example, JP-A-58-17609 discloses a 7,7,8.8 tetracyanoquinodimethane complex salt as an organic solid electrolyte that has excellent repairability for anodic oxide films and good transconductivity. (
A capacitor using TCNQi salt (hereinafter abbreviated as TCNQi salt) as a solid electrolyte has been proposed.

According to the above publication, an organic semiconductor consisting of a complex salt of isoquinoline substituted with alkyl at the N-position and TCNQ is used as a solid electrolyte, this TCNQ complex salt is heated and melted to impregnate a capacitor element, and before the complex salt is decomposed, it is cooled and solidified. It is disclosed that the electrolytic capacitor is made into a homogeneous electrolyte, and an object of the present invention is to provide an identified electrolytic capacitor with excellent high frequency characteristics.

[if%i to be solved by the invention] However, in the above capacitor, the TCNQ complex salt is heated and melted and impregnated into the capacitor element, and then cooled and solidified, so that shrinkage occurs and contact with the dielectric oxide film occurs. This results in a disadvantage that only about 70% of the rated capacity can be obtained.

Furthermore, capacitors using such τCNQ salt had the disadvantage that leakage current increased extremely in a soldering heat resistance test (260° C. x 10 seconds), making it difficult to make them into chips.

[Means for Solving the Problems] The present inventors believe that if the above-mentioned drawbacks of TCNQCN, which inherently has high performance, can be eliminated, a truly high-performance capacitor can be obtained, and therefore, the above-mentioned drawbacks can be effectively eliminated. As a result of various studies and examinations aimed at this purpose, it has been found that the above object can be achieved by using an inorganic substance or an inorganic compound having specific physical properties in combination with TCNQfl salt.

Thus, the present invention provides a tetracyanoquinodimethane complex salt,
The object of the present invention is to provide a solid electrolytic capacitor using a solid electrolyte made of a composite with fine particles of an inorganic substance or compound having a coefficient of linear expansion of 5 x 10-5 (K-') or less and a melting point of 260°C or more.

Tetracyanoquinodimethane complex salt (T
Examples of CNQCN include complex salts of isoquinolinium substituted with an alkyl group at the N-position and TCNQ, and more specifically used complex salts include those listed in JP-A-58-191414. .

In addition, the coefficient of linear expansion used in the present invention is defined by the chemical society of Japan,
According to the definition shown on page 685 of Chemical Handbook, Revised 2nd Edition, Iililin.

The fine particles of the inorganic substance or inorganic compound used in the present invention must have a coefficient of linear expansion of 5 x 10-5 (K"1) or less. If the coefficient of linear expansion is greater than the above value, it is necessary to form a complex with TCNQ rust salt. This is inappropriate because it becomes impossible to effectively reduce the coefficient of linear expansion.

Further, the substance needs to have such a coefficient of linear expansion and a melting point of 260° C. or higher. If the melting point is lower than this value, it is unsuitable because it will melt when immersed in a molten solder bath and increase in volume, resulting in an increase in leakage current of the capacitor.

In addition, in the case of a wound type capacitor, etc., it is necessary to fill the composite between the anode foil and the cathode foil, so these substances should be in the form of fine particles with an average particle size of 30μ or less, preferably 10μ or less. is necessary.

Among these substances, examples of inorganic substances include carbon such as graphite, semimetals such as boron and silicon, and various metals such as aluminum, and examples of inorganic compounds include various oxides such as silica and alumina. , nitrides such as silicon nitride, carbides such as silicon carbide, various borides such as zirconium boride, etc., and these may be used alone or in combination of two or more.

The ratio of these fine particles used on TCNQCN tends to be smaller and more effective as the coefficient of linear expansion of the fine particles used is smaller, but in general, about 5 to 10% by weight based on TCNQCN is adopted. is appropriate. However, when the fine particles are non-electronic conductive, if the amount exceeds 50% by weight, the specific resistance as a composite on TCNQCN increases significantly, which is not preferable.

In this way, a complex is formed between the TCNQCN and the fine particles.

As a means of forming the complex, for example, the two are sufficiently mixed and dissolved in a solvent that dissolves the TCNQI salt,
Alternatively, the mixture may be melted, but it is particularly practical to use melting means. In this case, it is appropriate to adopt a melting temperature of 260 to 350°C.

The thus obtained molten material is impregnated into a capacitor element, and then cooled and solidified to form a solid electrolyte xNI.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

[Comparative Example] Using the isoquinolinium-TCNQ complex salt substituted with isoamyl at the N position disclosed in JP-A No. 62-92424,
This was filled into an aluminum can case and melted on a hot plate kept at 290°C. Next, a well-known wound aluminum electrolytic capacitor element (rated capacity 0.33 μF, rated voltage 2
5V) quickly into the aluminum can case and connect the TCN.
After being impregnated with the Q complex salt, the case was pulled up together with the case and cooled with water to solidify the TCNQ complex salt. Next, the opening was sealed with epoxy resin, and the capacitor was then molded with epoxy resin to fabricate a prototype chip-type aluminum solid electrolytic capacitor. The characteristics of this capacitor after aging by applying a rated voltage at 105° C. for 1 hour are shown below.

Capacitance (120) 1z) 0.22u Ft
an δ (120Hz) 0.010E
S P (100KHz) 0.25Ω Leakage current (1 minute value) 0.01μA Next, perform a solder heat resistance test by immersing this capacitor in a solder bath melting at 260℃ for 10 seconds, and then measure the leakage current. Then,
The value was 3.5mA, and the capacitor had lost its function.

Example 1 Purity 99, 99% with respect to TCNQ complex salt used in comparative example
, alumina powder with an average particle size of 0.2 μ (a expansion coefficient 2
10 wt. 10-5 (K-')) was added and thoroughly mixed with a bean milk drumstick. Next, using this mixture, Comparative Example 1
A chip-type aluminum solid electrolytic capacitor was fabricated using the same procedure as above. The characteristics after aging and the results of the soldering heat resistance test are shown in the table.

Example 2 Purity 99.98% with respect to TCNQ complex salt used in comparative example
A capacitor was prototyped in the same manner as in Example 1 using a mixture to which 15 wt% of silicone carbide (linear expansion coefficient 4 x 10-5 (K-1)) with an average particle size of 0.5 μ was added, and a soldering heat resistance test was conducted. Ta. The results are shown in the table.

Example 3 Purity 99 with respect to T CN Q W4 salt used in comparative example
．． 99% silicon nitride with an average particle size of 0.4μ (linear expansion coefficient 2
．． A capacitor was prototyped in the same manner as in Example 1 using a mixture to which 10 wt% of 5Xl0-5(K-1)) was added, and a soldering heat resistance test was conducted. The results are shown in the table.

[Effects of the Invention] As is clear from the examples above, the capacitor of the present invention maintains remarkable soldering heat resistance, and can be made into a chip while maintaining excellent high frequency characteristics based on the good conductivity of the TCNQ complex salt. It becomes possible. Moreover, the capacity achievement rate can also be improved compared to the case of only TCNQ complex salt.

Claims (2)

[Claims] 1. Tetracyanoquinodimethane complex salt and linear expansion coefficient of 5×
A solid electrolytic capacitor using a solid electrolyte made of a composite with fine particles of an inorganic substance or inorganic compound having a temperature of 10^-^5 (K^-^1) or less and a melting point of 260°C or more. 2. The solid electrolyte is a tetracyanoquinodimethane complex salt,
After heating a mixture with fine particles of an inorganic substance or inorganic compound having a coefficient of linear expansion of 5 x 10^-^5 (K^-^1) or less and a melting point of 260°C or more to melt the tetracyanoquinodimethane complex salt. 2. The solid electrolytic capacitor according to claim 1, which is solidified by cooling.