JPS6151910A - 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 solid electrolytic capacitors, and particularly to improvements in solid electrolytes made of mobile semiconductors.

[Conventional technology]

Solid electrolytic capacitors use a film-forming metal such as aluminum or tanker as an anode, and the surface of the foil anode body is etched to make the anode corrugated, or a porous material is formed by sintering a powder of the metal. Then, an oxide film layer to serve as a dielectric is formed on this surface by means such as anodizing treatment, a solid electrolyte layer is further formed on this upper surface, and an electrical connection for drawing out the cathode is made from this solid electrolyte layer. It is configured with means.

Conventionally, manganese dioxide has been used for 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, in this method of electrolyte formation, only a small amount of manganese dioxide is deposited in one step, so it is necessary to repeat the same process several times or more times.

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

Recently, it has been proposed to use a conductive organic substance as an electrolyte instead of manganese dioxide.

This is known as a carrier electrolyte that uses various complex salts of tetracyanoquinodimethane (hereinafter referred to as TcNQ).

Although TCNQ complex salt is an organic substance, it has appropriate conductivity, and its use has been attempted as suitable for the electrolyte layer of solid electrolytic capacitors.

Since the TCNQ complex salt is a solid substance at room temperature, the problem is how to make it adhere to the dielectric oxide film as an electrolyte.

For example, as seen in (US Patent No. 321.4648), TCNQ salts in an organic 7 medium have been proposed. It is known that the anode body is dissolved, the anode body is impregnated in this 7-volume solution, and then the anode body is taken out from the solution and the organic solvent is evaporated to form a TCNQ complex salt layer on the surface of the anode body. However, in this method, TCN in the solvent
Because the concentration of Q complex salt is low, one-time impregnation is sufficient for T.
The CN Q complex salt could not be deposited, and this step, like the formation of the manganese dioxide layer, had to be repeated several times or more times, making the manufacturing process unavoidably complicated.

In addition, as in (Special Publication No. 51-32303), polymer substances and T CN Q! A method has also been proposed in which a dispersion consisting of fine powder of 7F salt is attached to the electrode surface.

However, in these methods, the TCNQ complex salt crystallizes after evaporation of the solvent, or the TCNQ complex salt is dispersed in a crystalline state, so that the dielectric oxide film on the anode surface, which has been wave-treated and has complex irregularities, is There was a drawback that sufficient contact could not be obtained between the capacitors and the desired capacitance could not be obtained.

Recently, (Unexamined Japanese Patent Publication No. 57-173928) Nodoto (, T
A solid electrolytic capacitor has been proposed in which only the CNQ complex salt is heated and melted above its melting point, an anode body is impregnated therein, and then the anode body is pulled up and cooled to adhere the TCNQ complex salt.

In the solid electrolytic capacitor produced by this method, the highly concentrated TCNQ complex salt itself is deposited on the anode body, so that a sufficient TCNQ complex salt layer can be formed in a single impregnation operation.

However, in the solid electrolyte layer formed by this method, the TCNQ complex salt is crystallized, as described above, and the desired capacitance cannot be obtained because sufficient contact with the dielectric oxide film layer cannot be established.

Moreover, the TCNQ complex salt itself is extremely sensitive to heating, and if kept in a molten state, it will undergo thermal decomposition in a short period of time, turning into an insulator. Furthermore, some TCNQ complex salts undergo thermal decomposition at temperatures below their melting point, making it virtually impossible to form a solid electrolyte layer by this method. For example, isopropyl-isoquinolinium TCNQ complex salt can be impregnated by heating and melting, but the time that the molten state can be maintained is extremely short. In addition, methylisoquinolinium TCNQ complex salt, 4,4'-dimethylbipyridinium TCNct complex salt, 4,4'-isopropylbipyridinium TCNQ complex salt, etc. undergo thermal decomposition from the heating stage before melting, and electrolyte impregnation due to melting is substantially reduced. It's impossible.

(Problems to be solved by the invention) This invention improves on these conventional drawbacks.
Conventionally, TCNQ complex salts that cannot be melt-impregnated or TCNQ complex salts that can be melt-impregnated but have to be impregnated in a very short period of time can be used as solid electrolytes.
The purpose is to obtain a solid electrolytic capacitor with high impregnation efficiency and excellent characteristics by forming on the surface of the anode body and improving insufficient contact with the dielectric oxide film due to crystallization after TCNQ complex salt impregnation. That is.

[Means for solving problems]

This invention forms a dielectric oxide film on the anode metal surface,
Furthermore, in this solid electrolytic capacitor in which a solid electrolyte layer is formed on the upper surface, the solid electrolyte N is isopropyl-isoquinolinium, methylisoquinolinium, 4.4
3-methyl-
A solid electrolytic capacitor characterized in that it is formed by melting and solidifying a mixture to which 2-oxazolidinone is added.

The present invention will be described in detail below based on examples.

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

FIG. 1 is a cross-sectional view of a completed solid electrolytic capacitor manufactured according to this example, and FIG. 2 is a cross-sectional view of the anode body, ie, the capacitor element, used in this example.

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 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 impregnating the capacitor element 1 with a solid electrolyte layer, and a preheating block 10 is placed on the left side of the figure. The heating block 10 has a heating heater embedded therein, a recess 11 on the top surface, and a heating block 10 for heating the capacitor element 1 in the recess 11.
The capacitor element 1 is heated in advance by being placed inside the capacitor and maintained at a high temperature.

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. The recess 13 contains the TCNQ complex salt and the additive 3-
A powder mixture 14 consisting of methyl-2-oxazolidinone is injected and the mixture 14 is melted by heating. Then, 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.
Thereafter, 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.

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.

First, as a capacitor element, width 2.2fl and length 101
A high-purity (99.99%) aluminum foil with 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 alternating current, and then dielectric oxidation with a withstand voltage of 9 μm is applied to the surface. The film was formed by anodizing. Then, aluminum foil (purity 99.94%) of the same size as the anode was placed oppositely as a current collecting electrode, and an aluminum tab for external extraction was cold welded approximately in the center of both electrodes. A cylindrical product was commonly used in the examples by connecting and winding it as shown in FIG. 2 with a separator paper mixed with Manila hemp fiber interposed therebetween.

Next, as Comparative Example 1, this capacitor element was impregnated with an ethylene glycol-ammonium adipate electrolyte. In addition, as Comparative Examples 2 to 5, isopropyl-
Isoquinolinium complex salt, methylisoquinolinium complex salt,
4. For four types of TCNQ complex salts, 4'-dimethylbipyridinium complex salt and 4,4'-isopropylbipyridinium complex salt, only each complex salt was heated and melted, and the above-mentioned capacitor element was impregnated with this using the above-mentioned impregnation device. .

Next, as invention examples 1 to 4, the above four types of TCNQ
A mixture obtained by adding 3-methyl-2-oxazolidinone to a complex salt was impregnated using the above-mentioned impregnation apparatus while changing the heating temperature.

Then, the capacitor element that has been impregnated is stored in a cylindrical aluminum outer case, the case opening is closed with a rubber sealing body, and the outer case opening end is wrapped and sealed. Rated voltage 6.3■, rated capacity 10μF
completed an electrolytic capacitor.

Among these electrolytic capacitors, Comparative Example 1 using a liquid electrolyte was tested for 15 minutes, and other Comparative Examples that could be impregnated and this invention example were tested for 1 hour. After aging the capacitor by applying the rated voltage, its electrical characteristics were investigated.

The equivalent series resistance value of LOOKIIz and the leakage current after 2 minutes of applying the rated voltage were measured, and each 1. +
I compared the characteristics.

The results are shown in the table below.

(Margins below this page) [Operation] Looking at the results of these examples, the ordinary dry electrolytic capacitor using a liquid electrolyte shown in Comparative Example 1 shows that the electrolyte is held in a liquid state inside the capacitor element. As a result, the electrolyte penetrates into the fine etching holes (focuses) formed by the etching process to make the anode corrugated, and makes sufficient contact with the dielectric oxide film, resulting in a high capacitance value. show.

However, the specific resistance value of the electrolyte is 200-300Ω, whereas the specific resistance value of the TCNQ complex salt is about several tens of Ωcm.
・The loss value or equivalent series resistance value is high because it is marked as high.

In addition, in comparison example 2, only the isopropyl-isoquinolinium TCNQ complex salt can be impregnated by heating and melting.
1, those using other TCNQ complex salts of Comparative Examples 3 to 5 caused thermal decomposition before reaching the molten state,
Impregnation was not possible. In addition, looking at the characteristics of Comparative Example 2, which was able to be impregnated, excellent characteristics were obtained in terms of loss and equal series resistance because the specific resistance value of the TCNQ complex salt is lower than that of the electrolytic solution, as described above. However, sufficient capacitance values have not been obtained.

The reason for this is not clear, but when only the TCNQ complex salt is heated and melted, the TCNQ complex penetrates into the etching focus of the anode. This is thought to be because contact with the dielectric oxide film within the etched bit, which forms capacitance, is not made in some parts.

On the other hand, as is clear from the characteristics of Invention Examples 1 to 4, the solid electrolytic capacitor of the present invention has the following characteristics in all cases:
It shows a larger capacitance value than Comparative Example 2. This is because the solid electrolyte of this invention has a TCNQ complex salt and 3-methyl-2-
This is thought to be because the mixture with oxazolidinone prevents crystallization during cooling after melting and impregnation, and remains in the etching bit in an amorphous state, maintaining sufficient contact with the dielectric oxide film. It will be done.

Furthermore, even if some of the TCNQtM salt crystallizes, it is thought that the presence of 3-methyl-2-oxazolidinone between the crystals provides electrical conduction between the crystals and ensures capacitance.

For the same reason, excellent electric power can be obtained in contact with the collector electrode side, contributing to improved characteristics.

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, but 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, resin dipped or molded,
/Lz)L? , = b (7)・US′i′−17g
tz"608 exterior, etc., does not depart from the scope of this invention.

〔effect〕

As described above, according to the present invention, the solid electrolyte layer is
Since it can be formed by heat-melting and impregnating CN with a mixture of l salt and 3-methyl-2-oxazolidinone, it is possible to use TCNQ complex salt, which conventionally could not be impregnated by heat-melting.

Furthermore, since the melting temperature of the TCNQ complex salt, which can be impregnated by heating and melting, is lowered, the time required for thermal decomposition is extended, and deterioration of properties can be prevented and impregnation becomes easier.

Further, according to the present invention, the impregnation rate of the TCNQ complex salt can be improved and the capacitance value per unit volume can be increased, thus contributing to miniaturization of the solid electrolytic capacitor.

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 a completed solid electrolytic capacitor of the present invention, FIG. 2 is a perspective view of the structure of a capacitor element used in an embodiment of the present invention, and FIG. 1 is a cross-sectional view showing a solid electrolyte impregnation device used in an example of the present invention. l...Capacitor element, 2...Anode, 3...Collector electrode, 4
・・Separate paper, 5.6・・Tab, 7° 8・・External lead, 10・・Preheating block, 11.13・・Recessed part, 12・・・Professional impregnation 7-ri, 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 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 is composed of a complex salt of tetracyanoquinodimethane, 3-methyl-2 - A solid electrolytic capacitor characterized in that it is made of a melted and solidified mixture to which oxazolidinone is added. (2) Complex salts of tetracyanoquinodimethane include isopropyl-isoquinolinium, methylisoquinolinium, 4,
Claim No. 1, which is a complex salt consisting of one or more selected from the group of 4'-dimethylbipyridinium and 4,4'-isopropylbipyridinium.
Solid electrolytic capacitors listed in ).