JPH0770441B2 - Solid electrolytic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a solid electrolytic capacitor using a solid electrolyte.

BACKGROUND OF THE INVENTION A solid electrolytic capacitor has a structure in which a solid electrolyte is attached to a dielectric film-forming metal such as aluminum having an anodized film. Until now, manganese dioxide has mostly been used as a solid electrolyte in this type of capacitor.

However, when manganese dioxide is formed on the electrode, it is generally soaked in a manganese nitrate solution and then thermally decomposed. There was a drawback.

Organic semiconductors, mainly 7,7,8,8-tetracyanoquinodimethane (T
It has been proposed to use CNQ) salts.

The TCNQ complex uses TCNQ as an acceptor and quinoline (Q _n ), tetrathiafulvalene (TTF), N as a donor material.
-Methylphenazine (NMP), tetraselenafulvalene (TSF), etc. have been studied so far, and research on new donor materials has been energetically conducted, but satisfactory results have not been obtained yet. .

In particular, in terms of heat resistance, all TCNQ complexes that have been studied so far have problems. In other words, solid electrolytic capacitors are often exposed to heat such as soldering in the manufacturing process of capacitors and that they are placed near the transformer in the power supply circuit. Therefore, the electrolyte must be thermally stable, but all conventional TCNQ complexes have anxiety in this respect.

[Object of the Invention]

The present invention is to provide a new and useful solid electrolytic capacitor which does not have the above-mentioned problems of the solid electrolytic capacitor at all.

[Outline of Invention]

The present invention provides an N-alkyl-based electrolyte as an electrolyte interposed between an electrode for an anode made of a valve metal having an anodized film on the surface and an electrode for a cathode arranged to face the electrode.
TC with 4-phenylpyridinium cation as donor material
A solid electrolytic capacitor characterized by using an NQ complex.

The characteristics of the donor material are that the ionization potential is appropriately small, the π-electron system spreads widely, the ions are stabilized, and the polarizability is high.

Satisfying all of these conditions is an important factor in molecular design, but it is extremely difficult to satisfy all of them. Further, in order to apply TCNQ complexes composed of various donor materials to electrolytic capacitors, there is a problem in adhesion to electrodes, and TCNQ complexes having extremely fine crystal grains and having good compatibility with metal oxides are desirable.

In addition, the TCNQ complex that does not change its electric conductivity from low temperature to high temperature and decomposes even at high temperature is required.

The inventors of the present invention have conducted extensive studies, and have newly found a donor material for a TCNQ complex that can sufficiently satisfy the above requirements, and arrived at the present invention. That is, the present invention is characterized in that an organic semiconductor that can be used even when it is reflowed at a sufficiently high temperature when it is soldered to a printed circuit board after being commercialized is used.

The N-alkyl-4-phenylpyridinium TCNQ complex is
For example, it is represented as follows.

(In the formula, n represents an arbitrary number of 0.5 ≦ n ≦ 2.) The N-alkyl-4-phenylpyridinium TCNQ complex is
It has a relatively high melting point and decomposition point. For example, N-isobutyl-4-phenylpyridinium TCNQ complex has a melting start point of 250 ° C. and a decomposition point of 281 ° C.
Melting point of n-butylisoquinoline TCNQ complex 217.5
Both values are higher than the ℃ and decomposition point of 267.1 ℃. Thus, the N-alkyl-4-phenylpyridinium TCNQ complex is an extremely thermally stable complex.

Also, the N-alkyl-4-phenylpyridinium TCNQ complex can be sufficiently applied as a solid electrolyte for electrolytic capacitors in terms of electrical conductivity. For example, 400k N-isobutyl-4-phenylpyridinium TCNQ complex powder
The specific resistance value when pressed into pellets is 1 to 12Ω.
・ It was cm.

The complex of TCNQ and N-alkyl-4-phenylpyridinium cations is stable up to high temperature and thus provides an advantageous advantage in the bonding technique with electrodes. That is, it can be dissolved in a solvent having a high boiling point and a high polarity, and recrystallization on the electrode surface occurs very quickly during immersion and drying. Also, it is reasonably impregnated into the unevenness of the electrode surface that is finely etched like an aluminum electrolytic capacitor. Although this has a problem in that the conditions such as the crystallization rate are not taken into consideration, it goes without saying that the impregnation state becomes better as the crystal becomes finer and the density becomes higher.

The anode electrode used in the solid electrolytic capacitor of the present invention is not limited to the aluminum foil, and other metal for lunch can be used as a matter of course, and the same effect can be obtained by using the powder sintered electrode. It goes without saying that you can get it.

The carbon number of the alkyl group at the N-position of the 4-phenylpyridinium cation used in the solid electrolytic capacitor of the present invention is preferably 1 to 10 and is higher than that, it is unstable, and in terms of cost. However, there are many disadvantages.

Hereinafter, specific examples of the present invention will be described.

Example 1 N-isoamyl-4-phenylpyridinium TCHQ complex
It was supersaturated in a nitrobenzene solution heated to 180 ° C. Next, 50 times the aluminum foil that has been etched 40 times
v It was formed into a cathode electrode. The electrode is charged with the above solution 180
It was immersed in the solution kept at ℃, slowly pulled up, and dried at 230 ℃. This operation was repeated 4 times to complete the impregnation. Next, carbon was applied as a cathode, silver paste was applied thereon, and lead wires were soldered to prepare a capacitor sample (sample group A).

For comparison, as a conventional example, Nn-butylisoquinoline TCNQ complex was similarly supersaturated and dissolved in nitrobenzene heated to 180 ° C., and the same operation was repeated.
The attachment of the cathode and the lead wire was performed in the same manner as above to prepare a capacitor sample (sample group B).

Further, as a conventional example, a saturated aqueous solution of manganese nitrate is used,
Immersion at 220 ° C. for 60 seconds and heat treatment were repeated 6 times. Then, the cathode and the lead wire were attached in the same manner as above to prepare a capacitor sample (Sample C).

All samples are solid electrolytic capacitors rated at 25v and 47μF.

Table 1 shows the initial characteristics. Capacitance and tanδ are 1 at room temperature
The value at 20Hz and the leakage current are the values at room temperature and 1 minute after the rated voltage was applied.

Table 2 shows the results of a high temperature load test for up to 2000 hours with a rated voltage applied in an atmosphere of 105 ° C.

As is clear from Tables 1 and 2 above, it was proved that the solid electrolytic capacitor of the present invention is thermally stable.

Example 2 The same electrode as in Example 1 was used as an anode foil, an aluminum foil opposite to which was etched by about 10 times was used as a cathode, and electrolytic paper was used as a separator. A wound type capacitor (rated 25wv-33).
A device of μF) was produced. After heat-treating the above element and carbonizing the separator, N-isobutyl-4 was added thereto.
-Impregnated with a phenylpyridinium TCNQ complex, packaged,
A capacitor sample group D was produced.

For comparison, Nn-butylisoquinoline TCNQ complex was similarly dipped to prepare sample group E.

Table 3 shows the initial characteristics and the characteristics after 1 minute of solder reflow at 250 ° C.

As is clear from the results in Table 3, the products using the N-n-butylisoquinoline TCNQ complex had a large decrease in capacitance and tan δ on the contrary. Indicates that the complex has deteriorated. On the other hand, the N-isobutyl-4-phenylpyridinium TCNQ complex shows extremely small changes in both capacitance and tan δ and is extremely stable.

[Effects of the Invention] As described above, the solid electrolyte composed of the TCNQ complex of N-alkyl-4-phenylpyridinium cation is extremely stable thermally, and the bondability between the electrode and the solid electrolyte is good. The solid electrolytic capacitor of the present invention used as above has a remarkable effect in that its electric characteristics are significantly improved and stabilized as compared with the conventional one, and is of great industrial and practical value. There is.

Claims (2)

[Claims] 1. An N-alkyl-4-electrolyte is used as an electrolyte interposed between an electrode for an anode made of a valve metal having an anodized film on the surface thereof and an electrode for a cathode arranged facing the electrode. Phenylpyridinium cation as donor material
A solid electrolytic capacitor characterized by using a TCNQ complex. 2. The solid electrolytic capacitor according to claim 1, wherein the alkyl group of the donor material has 1 to 10 carbon atoms.