JPS617620A - Solid electrolytic condenser and method of producing same - 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 C. Industrial Application Field The present invention relates to a face-shaped electrolytic capacitor and a method for manufacturing the same, and particularly to improvements in a solid electrolyte layer made of an organic semiconductor and a method for forming the same.

[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, it is made porous by etching legs or sintering, and an oxide film layer that becomes a dielectric is formed on the surface. However, it has a structure in which a solid electrolyte layer is formed on this surface, and a conductive cathode extraction layer is further formed on the outside of this solid electrolyte layer.

Conventionally, manganese dioxide has been used as 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, according to this method, only a small amount of manganese dioxide is deposited in one process, so it is necessary to repeat the same process several to more than ten 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 Pat. No. 321
It is possible to form a TCNQ complex salt layer on the surface of the anode body by impregnating the anode body in a solution of TCNQ complex salt dissolved in an organic solvent, and then removing it from the solution and evaporating the organic solvent, as in No. 4648). It is being done. However, in this method, since the concentration of TCNQ complex salt in the solvent is low, it is not possible to deposit sufficient TCNQ complex salt in one impregnation, and this process is repeated several times to more than 10 times, similar to the formation of the 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 solvent is TCNQCN after evaporation.
Because the TCNQ complex salt is dispersed in a crystalline state, it is not possible to obtain sufficient contact with the dielectric oxide film on the surface of the anode body, which has been subjected to a wave surface treatment and has complex irregularities. The drawback was that it was not possible to obtain a capacitance of .

Recently, T
Only the CNQ complex salt is heated above its melting point to liquefy, the anode body is impregnated into it, and then it is pulled up and cooled to form TCN
A method of attaching Q 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. Examples of this include complex salts of bipyridinium and TCNQ such as 4,4'-dimethylbipyridinium or 4,4'-dimethylbipyridinium.
If heated above 0°C, it will emit smoke and decompose before melting, becoming an insulator.

[Problem that the invention seeks to solve]

This invention improves on these drawbacks, and aims to make it possible to heat-melt and impregnate TCNQ complex salts, which were conventionally impossible to heat-melt and impregnate, and also to obtain a solid electrolytic capacitor with excellent characteristics. There is.

[Means for solving problems]

This invention relates to 4,4'-dimethylbipyridinium TCN
A mixture obtained by adding a quinoline compound to Q complex salt or 4,4'-isopropylbipyridinium TCNQ complex salt is heated to a temperature lower than the decomposition temperature of the TCNQ complex salt to liquefy it, and a capacitor element is placed in this liquid mixture. This method is characterized by impregnation and cooling and solidification after impregnation. Focusing on the phenomenon that the melting point (freezing point) of a mixture is lower than that of a pure substance, a mixture of TCNQ complex salt and additives is heated and melted to form an anode body. It is used to impregnate.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

First, the manufacturing procedure of the solid electrolytic capacitor according to the present invention will be explained.

FIG. 1 is a sectional view of a completed solid electrolytic capacitor manufactured by the method of the present invention, and FIG. 2 shows the anode body, ie, the capacitor element, used in this embodiment.

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 between the anode 2 and the collector electrode 3, a separator paper 4 slightly wider than the electrodes 2.3 is placed. 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 a method of 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 embedded inside and a recess 1) on the top surface.
is provided, and the capacitor element 1 is placed in the recess 1), and the capacitor element 1 is heated in advance to maintain a high temperature state.

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.

In addition, as a conventional example, a normal dry electrolytic capacitor using a liquid electrolyte and a solid electrolytic capacitor made using an isopropyl-isoquinolinium TCNQ complex salt that can be melted and impregnated only with a TCNQ complex salt are compared with this invention as a conventional example. Let me show you.

First, the capacitor element used had a width of 2.2 mm.

A high-purity aluminum (purity 99.99%) with a length of 10 mm and a thickness of 80 μm is prepared as an anode, and the surface of this anode is made into a corrugated surface by electrolytic etching using an alternating current. A body oxide film was formed by anodizing. Then, 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.
Wrapped with separate paper mixed with manila hemp fiber,
It is cylindrical.

Next, in Conventional Example 1, this capacitor element was impregnated with an ethylene glycol-ammonium adipate based electrolyte. In addition, for conventional example 2, T
The isopropyl-isoquinolinium TCNQ complex salt, which can be heated and melted only with the CNQ complex salt, was heated and melted at 240°C and impregnated into the capacitor element.
, 4'-dimethylbipyridinium TCNQ complex salt; 4.
An attempt was made to impregnate 4'-isopropyl bipyridinium TCNQ complex salts by heating only these complex salts.

Regarding Examples 1 to 6 of the present invention, the capacitor element was heated to 200°C in a preheating block using the impregnation apparatus shown in FIG.
A Q complex salt or a mixture of this and an additive was injected, heated and melted, and the capacitor element was immersed in this for 10 seconds, 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 to seal the rated voltage of 6.3V. We have 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.

Electrical characteristics are capacitance (μF), tangent of loss angle, 100
Equivalent Series Resistance (ESR) at KHz.

(Ω) and leakage current value (μA/2 minute value) were measured, and the results shown in the following table were obtained. In addition, regarding the number of layers to 3 of the present invention, 4,4'-dimethylbipyridinium TCNQ
An example using a mixture of a complex salt and a quinoline compound. Examples 4 to 6 of the present invention use a mixture of 4,4'-isopropylbipyridinium TCNQ complex salt and a quinoline compound. Furthermore, in Inventive Example 1 and Inventive Example 4, 0.2 parts by weight of γ-butyrolactone (per 1 part by weight of TCNQ complex salt) were each contained in addition to the listed components.

−Table 1 Cold sword D? I'm sorry for the dissection of l (N weight ratio).

[Effect]

Looking at the results of these examples, as shown in Conventional Example 3 or Conventional Example 4, 4,4'-dimethyl, which could not be used as a solid electrolyte because of thermal decomposition before melting when heated and melted, It can be seen that by adding a quinoline compound and heating the bipyridinium TCNQ complex salt or the 4,4'-isopropylbipyridinium TCNQ complex salt, it can be liquefied at a temperature that does not lead to decomposition and can be impregnated into a capacitor element.

4.4'-dimethylbipyridinium or 4.4'
-The complex salt of isopropyl bipyridinium and TCNQ is
As mentioned above, when this salt alone is heated and the temperature exceeds 260°C, it is observed that it turns into an insulator while emitting smoke.

However, as can be seen from the examples, the types of additives,
Although there are differences depending on the mixing ratio, it can be seen that in all Examples, melting and liquefaction occurred at a temperature of 200° C. or lower, making it possible to impregnate capacitor elements.

Furthermore, when examining the characteristics of solid electrolytic capacitors after being impregnated with electrolyte, we found that in conventional dry electrolytic capacitors using a liquid electrolyte as shown in Conventional Example 1, the electrolyte is held in a liquid state inside the capacitor element, so the anode The electrolyte penetrates into the fine etched holes (bits) created by the etching process to create a wave surface, and makes sufficient contact with the dielectric oxide film, resulting in a high capacitance value. However, the specific resistance value of the electrolyte is as high as 200-300 Ω・cm, whereas the specific resistance value of the TCNQ complex salt is about several tens of Ω・ω, so the loss value or equivalent series resistance value is high. .

In addition, the solid electrolytic capacitor manufactured by heating and melting only the isopropyl-isoquinolinium TCNQ complex salt and impregnating it into the capacitor element shown in Conventional Example 2 has a loss and an equivalent series resistance value 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 the capacitance value is not sufficiently obtained.

The reason for this is not clear, but although the molten isopropyl-isoquinolinium TCN QR salt penetrates into the etching pit of the anode,
This is believed to be because the isopropyl-isoquinolinium TCNQ complex crystallizes into needle-like crystals during the subsequent cooling and solidification, and only a portion of the isopropyl-isoquinolinium TCNQ complex comes into contact with the dielectric oxide film within the etching focus.

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. In this case, the solid electrolyte of the present invention is TCN
Since it is a mixture of Q complex salt and quinoline compound, crystallization is prevented during cooling after melting and impregnation, and it remains in the etching pin 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.
Even if the CNQ complex salt crystallizes, it is thought that the presence of the quinoline compound between the crystals provides intercrystalline conductivity and ensures capacitance.

This example uses a capacitor element in which foil-shaped aluminum is used for the anode, the surface of which is enlarged and then a dielectric oxide film is formed, and a current collecting electrode is wound with separator paper interposed. However, the capacitor element is not limited to such a structure, and 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, and may be a porous body made by sintering film-forming metal powder. In addition, even if the structure is wound, separator paper may be omitted, the collector electrode may be made of a metal other than aluminum, or
A heat-resistant conductive resin film or the like 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.

Furthermore, the quinoline compound to be added may be a quinoline compound other than those exemplified in this example. Furthermore, in the examples, only one type of additive was used, but the same effect can be expected even if two or more types of quinoline compounds are mixed and added.

C Effects of the Invention] As described above, according to the present invention, 4,4'-dimethylbipyridinium TCNQ complex salt or 4,4'-isopropylbipyridinium TC
It is possible to impregnate the capacitor element by heating and melting the NQ complex salt.

Further, according to the present invention, it is possible to improve the impregnation rate of TCNQ complex salt, increase the capacitance value per unit volume, reduce loss, and have excellent impedance characteristics, so that the characteristics of solid electrolytic capacitors can be improved and It also contributes to miniaturization.

Furthermore, since the concentration of the TCNQ complex salt itself is much higher than that of the TCNQ complex salt dissolved in a conventional solvent, sufficient characteristics can be brought out in a single impregnation process.

Furthermore, since it becomes liquid at a temperature lower than the decomposition temperature of TCNQ complex salt, sufficient time can be secured for the properties of TCNQ complex salt to change due to heating, making impregnation work easier and allowing the use of expensive TCNQ complex salt without wasting it. This has the effect of improving the characteristics of solid electrolytic capacitors,
This is extremely useful for improving work efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the completed solid electrolytic capacitor of the present invention, FIG. 2 is an exploded perspective view showing the structure of a capacitor element used in an embodiment of the invention, and FIG.
The figure is a cross-sectional view of the apparatus used for impregnating the solid electrolyte of the present invention. 1. Capacitor element, 2. Anode, 3. Collector electrode, 4
... Separator paper, 5, 6... Tab, 7° 8... External lead, 10... Preheating block, 1). 13... Concavity, 12... Impregnation block, 14... Mixture, 20...
Exterior case, 21... Elastic sealing body.

Claims (4)

[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 tetracyanoquinodimethane and 4,4'- A solid electrolytic capacitor, characterized in that it is a mixture obtained by melting and solidifying a mixture of a complex salt consisting of dimethylbipyridinium or 4,4'-isopropylbipyridinium and a quinoline compound added thereto. (2) Claim No. 2, wherein the quinoline compound is one or more selected from the group of isoquinoline, normal quinoline, and 8-oxyquinoline.
The solid electrolytic capacitor described in item 1). (3) 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 with tetracyanoquinodimethane, 4, 4 A mixture obtained by adding a quinoline compound to a complex salt consisting of '-dimethylbipyridinium or 4,4'-isopropylbipyridinium is liquefied by heating to a temperature lower than the decomposition temperature of the tetracyanoquinodimethane complex salt, A method for manufacturing a solid electrolytic capacitor, characterized in that a capacitor element is impregnated into this liquid mixture, and after the impregnation, the solid electrolytic capacitor is cooled and solidified. (4) Claim No. 1 in which the quinoline compound is one or more selected from the group of isoquinoline, normal quinoline, and 8-oxyquinoline.
3) The method for manufacturing a solid electrolytic capacitor as described in section 3).