JPS6147622A - 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 Application Field] The present invention relates to a solid electrolytic capacitor, and particularly to an improvement in a capacitor having a solid electrolyte layer made of an organic semiconductor.

[Conventional technology]

Solid electrolytic capacitors use a film-forming metal such as aluminum or tantalum in the form of a foil or block for the anode, and in order to make the anode corrugated, it is made porous by etching or by sintering fine powder. It has a structure in which an oxide film layer serving as a dielectric is formed on this surface, a solid electrolyte layer is formed on this surface, and a means for extracting a conductive cathode is provided externally.

Conventionally, manganese dioxide has been used as this solid electrolyte layer. This manganese dioxide is formed as an electrolyte layer on the dielectric oxide film by impregnating the anode electrode in liquid manganese nitrate, and then thermally decomposing the manganese nitrate at a temperature of around 300°C to transform it into manganese dioxide. I was letting it happen.

However, according to this formation method, only a small amount of manganese dioxide is deposited in one process, so it is necessary to repeat the same process several to several times.

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

Therefore, recently, it has been proposed to use a conductive organic substance in the electrolyte layer instead of manganese dioxide.

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

Since TCNQ complex salt is a solid substance at room temperature, methods for attaching it to capacitor elements as an electrolyte have been proposed, for example (US Patent No. 3214).
No. 648), the anode body is impregnated in a solution of TCNQ complex salt dissolved in an organic solvent, and then removed from the solution, the organic solvent is dispersed, and the entire TCNQ complex salt layer is formed on the surface of the anode body. things are being done. However, in this method, since the concentration of TCNQ complex salt in the solvent is low, it is not possible to deposit a sufficient amount of TCNQ complex salt in one impregnation, and this step is repeated several times or several times, similar to the formation of a manganese dioxide layer. It is necessary to repeat the process, which also complicates the manufacturing process.

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

However, in these methods, the TCNQ complex salt is dispersed in a crystalline state after the solvent evaporates, so that sufficient contact with the dielectric oxide film on the surface of the anode body, which has a complex wave-shaped unevenness, is prevented. There was a drawback that the desired capacitance could not be obtained.

Recently, T
TC
A method of attaching NQ complex salt has been proposed.

According to this method, since the highly concentrated TCNQ complex salt itself is attached to the anode body, sufficient TCNQ can be obtained in one impregnation step.
Complex salts can be attached.

However, TCNQ complex salts are sensitive to heat, and many TCNQ complex salts decompose when heated before reaching their melting point, making it virtually impossible to use this method. For example, if a complex salt of isopropyl-isoquinolinium and TCNQ is heated to 200° C. or higher, it will emit smoke and decompose before melting, becoming an insulator.

[Problem that the invention seeks to solve]

The present invention improves on these drawbacks, and makes it possible to heat-melt and impregnate isopropyl-isoquinolinium TCNQ complex salt, which was previously impossible to heat-melt and impregnate, and also provides a solid electrolytic capacitor with excellent characteristics. It is an object.

[Means for solving problems]

This invention provides isopropyl-isoquinolinium TCNQ
In the complex salt, γ-hexalactone, T-octalactone, γ
- A mixture obtained by adding one or more lactone compounds selected from the group of nonalactone, γ-decalactone, T-undecalactone, and γ-dodecalactone is used as the solid electrolyte forming material, and this mixture is used as the solid electrolyte forming material. T.C.
It is characterized by heating to a temperature lower than the melting point or decomposition temperature of the NQ complex salt to liquefy it, impregnating a capacitor element in this liquid mixture, and cooling and solidifying after impregnation to obtain a desired solid electrolyte layer. is the melting point (
Focusing on the phenomenon that the freezing point (freezing point) decreases, the TCNQ complex salt and additives are heated and melted in a mixed state, and impregnated into the anode body.

The present invention will be explained in detail based on the following examples.

〔Example〕

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

Fig. 1 is a cross-sectional view of a solid electrolytic capacitor made according to the present invention, and Fig. 2 shows the anode body used in this example.
In other words, it damages the capacitor element.

In FIG. 2, a capacitor element 1 is formed by winding a band-shaped electrode body, and an 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. The sandwiched material is wound from all ends 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 a method for impregnating the capacitor element 1 with a solid electrolyte layer, and a preheating block 10 is placed on the left side of the figure.

This preheating block 10 has a heating heater buried inside and a recess 11 on the top surface, and the capacitor element 1 is placed in the recess 11 to preheat the capacitor element 1 and bring it to a high temperature state. I'll keep it.

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. A powder mixture 14 consisting of a TCNQ complex salt and an additive is injected into the recess 13, and the mixture 14 is heated.
4 melts.

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, and 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 layer. form.

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. Then, the open 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.

Conventional examples include a normal dry electrolytic capacitor using a liquid electrolyte, a solid electrolytic capacitor made using isopropyl-isoquinolinium TCNQ complex salt that can be melted and impregnated with only TCNQ complex salt, and isopropyl-isoquinolinium TCNQ complex salt.
In comparison with this invention, an attempt was made to impregnate only isoquinolinium TCNQ complex salt by heating and melting.

First, the capacitor element used had a width of 2.2 mm and a length of 1
0mm, thickness 80μm high purity aluminum (purity 99
．． 99%) was prepared as an anode, and after the surface of this anode was made into a corrugated surface by electrolytic etching using alternating current, a dielectric oxide film having a withstand voltage of 9 V was formed on the surface by anodizing treatment. As a current collecting electrode, aluminum (purity 99.94%) of the same size as the anode is arranged oppositely, and an aluminum tab for external extraction is connected to the approximate center of both electrodes by cold welding. It is wound into a cylindrical shape with a fiber-mixed separate paper interposed in between.

Next, in Conventional Example 1, this capacitor element was impregnated with an ethylene glycol-ammonium adipate based electrolyte. In addition, conventional example 2.3 and present invention example 1
For items 6 to 6, the capacitor element is heated to 300°C in a preheating block using the impregnating apparatus shown in Fig. 3 and kept on standby, and the impregnating block is filled with TCNQ complex salt or a mixture of it and an additive. The capacitor element was immersed in the melt for 10 seconds, and then taken out of the melting tank and allowed to cool naturally to impregnate the solid electrolyte.

Then, the impregnated capacitor element is housed in an aluminum exterior case, the opening is closed with a rubber sealing body, and the opening end of the exterior case is wrapped tightly and sealed, with a rated voltage of 6.3■ , completed an electrolytic capacitor with a rated capacity of 10μF. At this time, the external dimensions of the capacitor body are:
It had a diameter of 3 mm and a length of 5 mm.

Among these capacitors, the conventional example 1 has 15
For capacitors using a solid electrolyte, aging was performed by applying the rated voltage to each capacitor for 1 hour, and then the electrical characteristics were examined.

The electrical characteristics are capacitance (μF), tangent of loss angle at 120H2, and equal series resistance value at 100KHz (E
SR), (Ω), and leakage current value (μA/2 minute value) were measured, and the results shown in the following table were obtained.

(Margins below this page) [Operation] Looking at the results of these examples, first of all, in the conventional dry electrolytic capacitor using a liquid electrolyte shown in Conventional Example 1, the electrolyte is held in a liquid state inside the solid electrolytic capacitor element. As a result, the electrolyte penetrates into the fine etching holes (focuses) created by the etching process to create a corrugated surface on the anode, making sufficient contact with the dielectric oxide film, resulting in a high capacitance value.

However, the specific resistance value of the electrolyte is 200-300Ω・ω while the specific resistance value of the TCNQ complex salt is about several tens of Ω・ω.
Due to the high degree, the product loss or equal series resistance value is high.

Furthermore, in the solid electrolytic capacitor manufactured by heating and melting only the isopropyl-isoquinolinium TCNQ complex salt and impregnating it into the capacitor element, as shown in Conventional Example 2, the loss and the equal series resistance value are lower than that of the TCNQ complex salt as described above. Since the specific resistance value is lower than that of the electrolytic solution, excellent characteristics are obtained, but sufficient capacitance is not obtained.

The reason for this is not clear, but although the molten isopropyl-isoquinolinium TCNQ complex penetrates into the etching focus of the anode, during subsequent cooling and solidification, the isopropyl-isoquinolinium TC
This is thought to be because the NQ complex crystallizes into needle-like crystals and only partially contacts the dielectric oxide film within the etching pit.

On the other hand, all of the solid electrolytic capacitors manufactured by the method of the present invention exhibit larger capacitance values than Conventional Example 2. This means that the solid electrolyte of this invention is TCN
Since it is a mixture of Q complex salt and lactone compound, crystallization is prevented during cooling after melting and impregnation, and it remains in the etching bit in an amorphous state, so it maintains sufficient contact with the dielectric oxide film. This is thought to be due to the Also, some T.
It is thought that even if the CNQ complex salt crystallizes, the presence of the lactone compound between the crystals provides intercrystalline conductivity and ensures capacitance.

Note that in this example, foil-shaped aluminum was used for the anode,
After enlarging the surface, a dielectric oxide film was formed on the surface, and a current collecting electrode was wound around the capacitor element with separator paper interposed between the capacitor elements. Without limitation, the metal constituting the anode may be other film-forming metals such as tantalum, or alloys thereof. Further, the structure is not limited to such a wound structure, but may be a porous body obtained by sintering film-forming metal powder. Moreover, even if it is a wound structure, a separator paper may be omitted, a metal other than aluminum may be used for the collector electrode, a heat-resistant conductive resin film, etc. 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, a resin dipped or molded one, a laminated film exterior, etc. Even if there is, it does not deviate from this invention.

Further, in this example, only one type of lactone compound was added, but the same effect can be expected even if two or more types of lactone compounds are mixed and added.

〔effect〕

As described above, according to the present invention, the impregnation rate of TCNQ complex salt is improved and the capacitance per unit volume is improved compared to the conventional method in which only isopropyl-isoquinolinium TCNQ complex salt is heated and melted to form a solid electrolyte. Since the value can be increased, it also contributes to the miniaturization of solid electrolytic capacitors.

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

[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
Separator paper, 5.6 Tab, 7°8 External lead, 10 Preheating block, 11.13 Recess, 12 Impregnation block, 14 Mixture, 20...
Exterior case, 21... Elastic sealing body.

Claims (2)

[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 the upper surface of the solid electrolyte layer, the solid electrolyte layer is formed of a complex salt of tetracyanoquinodimethane and isopropyl-isoquinolinium. ,
A solid electrolytic capacitor characterized by being made of a mixture containing a lactone compound. (2) The lactone compound is γ-hexalactone, γ-
The solid according to claim (1), which is one or more selected from the group of octalactone, γ-nonalactone, γ-decalactone, γ-undecalactone, and γ-dodecalactone. Electrolytic capacitor.