JPS617619A - 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 [Industrial Application Field] The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and particularly to an improvement in a method for forming a solid electrolyte layer made of an organic semiconductor.

[Conventional technology]

Solid electrolytic capacitors use a film-forming metal such as aluminum or tantalum for the anode, and in order to make the anode corrugated, it is made porous by etching or sintering, and an oxide film layer that becomes a dielectric is formed on the surface. Then, a solid electrolyte layer is formed on the surface of the solid electrolyte layer, and a conductive cathode extraction layer is further formed on the outside of the 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 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 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 enough TCNQ complex salt in one impregnation, and this process is repeated several to ten times, similar to the formation of the manganese dioxide layer. was necessary, and the complexity of the manufacturing process could not be avoided.

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 crystallizes after the solvent evaporates, or the TCNQ complex salt is dispersed in a crystalline state, so that the dielectric oxide film on the surface of the anode body, which has been subjected to a corrugation treatment and has complex irregularities, is There was a drawback that sufficient contact could not be obtained between them, and a predetermined capacitance could not be obtained.

Recently, T
Only the CNQ complex salt is heated above its melting point and melted, impregnating the anode body, and then taken out and cooled to form a 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 salt is sensitive to heat, and if kept in a molten state, it decomposes in a very short time and turns into an insulator. For this reason, the above impregnation process must be completed within an extremely short period of time, and then rapid cooling must be performed.
Rapid processing requires complicated equipment, and productivity is also low. Further, after cooling, the TCNQ complex salt crystallizes, resulting in poor contact with the dielectric oxide film, resulting in the drawback that sufficient capacitance cannot be drawn out.

[Problem that the invention seeks to solve]

This invention improves on these conventional drawbacks.
The purpose is to simplify the work process of impregnating a solid electrolyte layer made of TCNQ complex salt onto the dielectric oxide film of the anode body of a solid electrolytic capacitor, and to improve the impregnation rate and the characteristics of the solid electrolytic capacitor. .

[Means for solving problems]

This invention provides methylisoquinolinium TCNQ complex salt,
A mixture obtained by adding a quinoline compound is used as a solid electrolyte, and the solid electrolyte layer is formed by heating to a temperature lower than the melting point or decomposition temperature of the methylisoquinolinium TCNQ complex salt to liquefy it. It is characterized by impregnating the capacitor element and cooling and solidifying it after impregnation. Focusing on the phenomenon that the melting point (freezing point) of a mixture falls compared to that of a pure substance, TCNQ
A mixture of a complex salt and an additive is heated and melted to impregnate the anode body. The present invention will be explained in detail based on the following examples.

〔Example〕

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

FIG. 1 is a cross-sectional view of a completed solid electrolytic capacitor manufactured by the method of the present invention, 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. This anode 2 is first subjected to an etching process to form a wave surface, and a dielectric oxide film is formed on its surface by anodizing process.

This strip-shaped anode 2 has collector electrodes 3 having approximately the same area disposed opposite each other, and a separator paper 4 slightly wider than the 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 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 11 on the top surface.
is provided, and the capacitor element 1 is placed in the recess 11, and the capacitor element I 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 beater embedded therein and a recess 13 formed in its upper surface. Then, a powder mixture 14 consisting of a TCNQ complex salt and an additive is injected into the recess 13, and the mixture 14 is melted by heating.

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 way 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 protrude from the through hole provided in the elastic sealing body 21 to the outside, 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. As a conventional example, a normal dry electrolytic capacitor using a liquid electrolyte and a solid electrolytic capacitor made by melting and impregnating only methylisoquinolinium TCNQ complex salt are shown in comparison with the present invention.

One eyebrow” I (L- First, the width of the capacitor element is 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.
Winding with a separator paper made of manila hemp fiber mixed in between,
A cylindrical capacitor element was used. (The same capacitor element is used in both the conventional example and the inventive example below.) Next, this capacitor element is impregnated with an ethylene glycol-ammonium adipate electrolyte and placed inside an aluminum exterior case. The element was housed in the capacitor, the opening was closed with a rubber sealing body, and the open end of the outer case was tightly rolled up and sealed to complete an electrolytic capacitor with a rated voltage of 6.3 μF and a rated capacity of 10 μF. At this time, the external dimensions of the main body were 3 mm in diameter and 5 mm in length.

When this electrolytic capacitor was aged by applying the rated voltage for 15 minutes and its electrical characteristics were investigated, the following results were obtained.

Capacitance 9.2μF Tangent of loss angle 0.3°Equivalent series resistance value (100KHz) 25Ω Leakage current (
2 minute value) 0.10μA - harvested rice ± 1 - The same capacitor element as in Conventional Example 1 was used, and this capacitor element was preheated at 250°C in a preheating block.
It was heated up and left to standby. Next, only methylisoquinolinium TCNQ complex salt was injected into the block for heating impregnation,
When I heated it to impregnate it, methyl isoki, ? The linium TCNQ complex thermally decomposed while producing smoke, making impregnation impossible.

The capacitor element used is the same as the conventional example, heated and maintained at 170°C in a preheating block, and the impregnation block contains 1 methylisoquinolinium TCNQ complex salt.
A mixture of 0.8 parts by weight of isoquinoline was poured into the mixture and heated. This mixture melted at 170°C. Therefore, the capacitor element was removed from the preheating block, immersed in the melting bath for 10 seconds, and then taken out and allowed to cool naturally.

The exterior treatment after solid electrolyte impregnation was carried out under exactly the same conditions as in the conventional example.

The characteristics of this solid electrolytic capacitor were as follows.

Capacitance 8.3μF Tangent of loss angle 0.101 Equivalent series resistance value (100KHz) 1.8Ω Leakage current (2
Minute value) 0.19 μA - Ikukori W cross - The capacitor element used was the same as in the conventional example, and the preheating block was heated and maintained at 190°C. For the impregnation block, methylisoquinolinium T CN Q 1!
A mixture of 1 part by weight of normal quinoline and 1 part by weight of salt was injected and heated.

This mixture melted at 190°C. Therefore, the capacitor element was removed from the preheating block, immersed in the melting bath for 10 seconds, and then taken out and allowed to cool naturally.

The exterior treatment after solid electrolyte impregnation was carried out under exactly the same conditions as in the conventional example.

The characteristics of this solid electrolytic capacitor were as follows.

Capacitance 8.8μF Tangent of loss angle 0.081 Equivalent series resistance value (100KHz) 1. 3Ω leakage current (2 minute value) 0.09μA - The capacitor element used was the same as the conventional example, and the preheating block was heated and maintained at 150°C.The impregnation block had: A mixture of 1 part by weight of methylisoquinolinium TCNQ complex salt and 2 parts by weight of 8-oxyquinoline was injected and heated. This mixture melted at 150°C. The capacitor element was then moved from the preheating block. The sample was soaked in the melting tank for 10 seconds, and then taken out and allowed to cool naturally.

The exterior treatment after solid electrolyte impregnation was carried out under exactly the same conditions as in the conventional example.

The characteristics of this solid electrolytic capacitor were as follows.

Capacitance 7.9 μF Tangent of loss angle 0.131 Equivalent series resistance value (100 KHz > 2. OΩ Leakage current (2-minute value) 0.38 μA - Yosato Yosato ↓ - The capacitor element used is the same as the conventional example The preheating block was heated and maintained at 170°C.The impregnation block contained 1 part by weight of methylisoquinolinium TCNQ complex salt, 0.5 parts by weight of T-butyrolactone, and further 0.8 parts by weight of isoquinoline. The additive mixture was injected and heated. The mixture melted at 170° C. The capacitor element was then removed from the preheating block and immersed in the melting bath for 10 seconds, then removed and allowed to cool naturally.

The exterior treatment after solid electrolyte impregnation was carried out under exactly the same conditions as in the conventional example.

The characteristics of this solid electrolytic capacitor were as follows.

Capacitance 9.0μF Tangent of loss angle 0.04B Equivalent series resistance value (100KHz) 1. 3Ω leakage current (2 minute value) 0.09μA [Function] Looking at the results of these examples, it can be seen that in a normal electrolytic capacitor using a liquid electrolyte as shown in Conventional Example 1, the electrolyte is in a liquid state inside the electrolytic capacitor element. The electrolyte penetrates into the deepest part of the fine etching holes (pits) created by the etching process to expand the anode.
It has sufficient contact with the dielectric oxide film and exhibits a high capacitance value.

However, the specific resistance value of the electrolytic solution is as high as 100-200 Ω·mark, whereas that of the methylisoquinolinium TCNQ complex salt is several tens of Ω·1 or less, resulting in product loss or other problems. The series resistance value is higher than that of the solid electrolytic capacitor of the present invention.

Furthermore, as shown in Conventional Example 2, the method of heating and melting only the methylisoquinolinium TCNQ complex salt and impregnating it into the capacitor element causes thermal decomposition of the methylisoquinolinium TCNQ complex salt before it reaches its melting temperature. , impregnation work is not possible.

On the other hand, the solid electrolytic capacitors manufactured by the method of the present invention have small losses, high capacitance values, and excellent impedance characteristics in all of Examples 1 to 4 of the present invention. This is because the solid electrolyte of the present invention is a mixture of a methylisoquinolinium TCNQ complex salt and a quinoline compound, so the crystallization of the methylisoquinolinium TCNQ complex salt is prevented during cooling after melting and impregnation, resulting in an amorphous state. It is thought that this is because the contact with the dielectric oxide film is maintained sufficiently because it remains in the etching bit in this state. In addition, even if some methylisoquinolinium TCNQ complex salts crystallize, the presence of the quinoline compound between the crystals provides intercrystal conductivity and ensures capacitance. it is conceivable that.

In this example, a capacitor element is constructed by using foil-shaped aluminum as an anode, and forming a dielectric oxide film on the surface after enlarging the anode, and winding a current collecting electrode with a separator paper interposed therebetween. 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. 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.

Incidentally, quinoline compounds other than those exemplified in the examples also show similar results. In addition, in the example,
Although only one type of quinoline compound was added, the same effect can be expected even if two or more types of quinoline compounds are mixed and added.

〔Effect of the invention〕

As described above, the solid electrolytic capacitor obtained by the present invention has a high impregnation rate, that is, it can have a large capacitance per unit volume.

Moreover, since the impregnated solid and heavy electrolytes have high electrical conductivity,
Low loss and excellent impedance characteristics.

Furthermore, in the formation of the electrolyte, melting point depression occurs in order to melt the mixture of the methylisoquinolinium TCNQ complex salt and the quinoline compound, and the mixture melts and liquefies at a temperature lower than the melting point of the methylisoquinolinium TCNQ complex salt itself. Therefore, it is now possible to melt and impregnate methylisoquinolinium TCNQ complex salt, which was conventionally impossible to do alone.

Furthermore, since the melting temperature is low, deterioration of the TCNQ complex salt due to heating can be prevented, the substantial impregnation time can be extended, and the impregnation operation can be facilitated.

Furthermore, since sufficient properties can be obtained in a single impregnation process, the electrolyte layer forming process can be simplified, and expensive TCNQ complex salt can be used without wasting it. Moreover, the present invention has the advantage that a simple manufacturing apparatus is required, and the present invention is extremely useful for improving the characteristics of solid electrolytic capacitors and improving workability.

[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 solid electrolyte impregnation device of the present invention. l...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 (4)

[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 contains tetracyanoquinodimethane and methylisoquinolinium. 1. A solid electrolytic capacitor comprising a mixture obtained by melting and solidifying a mixture obtained by adding a quinoline compound to a complex salt of (2) The solid electrolytic capacitor according to claim (1), wherein the quinoline compound is one or more compounds selected from the group of isoquinoline, normal quinoline, and 8-oxyquinoline. (3) 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 formed with tetracyanoquinodimethane and methyl isochloride. A mixture obtained by adding a quinoline compound to a complex salt with nolinium is liquefied by heating to a temperature lower than the melting point or thermal decomposition temperature of the complex salt of tetracyanoquinodimethane and methylisoquinolinium, 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) The solid electrolytic capacitor according to claim (3), wherein the quinoline compound is one or more compounds selected from the group of isoquinoline, normal quinoline, and 8-oxyquinoline. Production method.