JPH0252848B2 - - Google Patents

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 enlarge the area of the anode, it is made porous by etching or sintering, and an oxide film layer that serves as a dielectric is applied to the surface of the anode. , 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 layer is to impregnate the anode metal into liquid manganese nitrate, and then
Manganese nitrate was thermally decomposed at a temperature of around 300°C and denatured into manganese dioxide.

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.

As a result, 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, instead of this manganese dioxide,
It has been proposed to use conductive organic materials in this electrolyte layer.

This organic electrolyte is known as tetracyanoquinodimethane (hereinafter referred to as TCNQ).
This method uses various complex salts of

Since TCNQ complex salt is a solid substance at room temperature, conventionally proposed methods for attaching it to capacitor elements using it as an electrolyte include (US Pat. No. 3,214,648), in which TCNQ complex salt is dissolved in an organic solvent. A TCNQ complex salt layer is formed on the surface of the anode body by impregnating the anode body in a solution containing TCNQ, then pulling it out of the solution, and evaporating the organic solvent. But with this method,
Due to the low concentration of TCNQ complex salt in the solvent, it is not possible to deposit enough TCNQ complex salt in one impregnation, and it is necessary to repeat this process several times to more than 10 times, similar to the formation of the manganese dioxide layer. Process complexity was unavoidable.

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

However, in these methods, the solvent is
Because the TCNQ complex salt crystallizes or is dispersed in a crystalline state, sufficient contact cannot be obtained with the dielectric oxide film on the surface of the anode body, which has been enlarged and has complex irregularities. There was a drawback that a predetermined capacitance could not be obtained.

Recently, as in (Unexamined Japanese Patent Publication No. 57-173928)
A method has been proposed in which only the TCNQ complex salt is heated above its melting point to melt, the anode body is impregnated therein, and then the anode body is pulled up and cooled to adhere the TCNQ complex salt.

According to this method, since the highly concentrated TCNQ complex salt itself is deposited on the anode body, sufficient TCNQ complex salt can be deposited in one impregnation step.
However, TCNQ complex salts are sensitive to heat, and if kept in a molten state, they decompose in an extremely short period of time, turning into an insulator. For this reason, the above-mentioned impregnation treatment must be completed within a very short period of time, and then rapid cooling must be performed, which results in a complicated apparatus and poor productivity due to the rapid treatment. Furthermore, after cooling, the TCNQ complex crystallized, resulting in poor contact with the dielectric oxide film, which resulted in the drawback that sufficient capacitance could not be extracted.

[Problem that the invention seeks to solve]

This invention improves on these conventional drawbacks, and simplifies 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 also improves the impregnation rate. The purpose is to improve the characteristics of solid electrolytic capacitors.

[Means for solving problems]

This invention relates to methylisoquinolinium TCNQ
A mixture obtained by adding a quinoline compound to a complex salt is used as a solid electrolyte, and the formation of the solid electrolyte layer is performed using the methylisoquinolinium compound.
It is characterized by heating the TCNQ complex salt to a temperature lower than its melting point or decomposition temperature to liquefy it, impregnating the capacitor element in this liquid mixture, and cooling and solidifying it after impregnation. Focusing on the phenomenon that the freezing point (freezing point) falls,
Heat and melt a mixture of TCNQ complex salt and additives,
This impregnates the anode body. This 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 sectional view showing the completed state of a 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 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 etching treatment to enlarge its surface.
A dielectric oxide film is formed on the surface by anodizing.

This strip-shaped anode 2 is arranged with collector electrodes 3 having approximately the same area facing each other, and the anode 2 and the collector electrode 3 are arranged opposite each other.
A separator paper 4, which is slightly wider than the electrodes 2 and 3, is sandwiched between the electrodes 2 and 3 and wound from one end 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. Further, external leads 7 and 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.
The capacitor element 1 is placed in the recess 11, 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. And in this recess 13,
Powder mixture 1 consisting of TCNQ complex salt and additives
4 is injected 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.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. Closed, outer case 2
Tighten the open end of 0 to seal it. Note that the external leads 7 and 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. 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.

Conventional example 1 First, as a capacitor element, a width of 2.2 mm and a length of
10mm, 80μm thick high purity aluminum (purity
99.99%) was prepared as an anode, and after enlarging the surface of this anode by electrolytic etching using alternating current, a dielectric oxide film with a withstand voltage of 9 V was formed on the surface by anodizing treatment. Aluminum (purity 99.94%) of the same size as the anode is placed oppositely as a current collecting electrode, and an aluminum tab for external extraction is connected approximately at the center of both electrodes by cold welding. A cylindrical capacitor element was obtained by winding the capacitor with a separator paper interposed therebetween. (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 is housed in the case, the opening is closed with a rubber sealing body, the opening end of the outer case is wrapped tightly and sealed, and the rated voltage is 6.3V.
We have completed an electrolytic capacitor with a rated capacity of 10μF.
At this time, the external dimensions of the main body are 3 mm in diameter and 5 mm in length.
It was warm in mm.

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 0.30 Equivalent series resistance value (100KHz) 25Ω Leakage current (2-minute value) 0.10μA Conventional example 2 The same capacitor element as in Conventional example 1 is used, and this capacitor element is placed in a preheating block. It was heated to 250°C in advance and kept on standby. Next, methylisoquinolinium was added to the hot impregnation block.
When only the TCNQ complex salt was injected and heated for impregnation, the methylisoquinolinium TCNQ complex salt thermally decomposed while emitting smoke before melting, making impregnation impossible.

Example 1 of the present invention The capacitor element used was the same as the conventional example, heated and maintained at 170°C in a preheating block, and the impregnation block contained 1 part by weight of methylisoquinolinium TCNQ complex salt and isoquinoline. 0.8 parts by weight was added and heated. This mixture melted at 170°C. Therefore, the capacitor element was removed from the preheating block and placed in the melting tank.
It was soaked for 10 seconds, then pulled out and allowed to cool naturally.

Regarding the exterior treatment after solid electrolyte impregnation,
The test was carried out under exactly the same conditions as 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) 0.19μA Invention example 2 The capacitor element used is the same as the conventional example, and the preheating block is It was heated and maintained at 190°C.
For the impregnation block, methylisoquinolinium
A mixture of 1 part by weight of normal quinoline and 1 part by weight of TCNQ complex 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.

Regarding the exterior treatment after solid electrolyte impregnation,
The test was carried out under exactly the same conditions as 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 Invention example 3 The capacitor element used is the same as the conventional example, and the preheating block is It was heated and maintained at 150°C.
For the impregnation block, methylisoquinolinium
To 1 part by weight of TCNQ complex salt, 8-oxyquinoline 2
A mixture of parts by weight was injected and heated. This mixture melted at 150°C. Therefore, the capacitor element was moved from the preheating block and
It was immersed in the melting tank for 10 seconds, then taken out and allowed to cool naturally.

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

The characteristics of this solid electrolytic capacitor were as follows.

Capacitance 7.9μF Tangent of loss angle 0.131 Equivalent series resistance value (100KHz) 2.0Ω Leakage current (2-minute value) 0.38μA Invention example 4 The capacitor element used is the same as the conventional example, and the preheating block is It was heated and maintained at 170°C.
For the impregnation block, methylisoquinolinium
A mixture of 1 part by weight of TCNQ complex salt, 0.5 part by weight of γ-butyrolactone, and 0.8 part by weight of isoquinoline was injected and heated. This mixture is
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.

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

The characteristics of this solid electrolytic capacitor were as follows.

Capacitance 9.0μF Tangent of loss angle 0.048 Equivalent series resistance value (100KHz) 1.3Ω Leakage current (2-minute value) 0.09μA [Function] Looking at the results of these examples, we can see that the liquid electrolyte shown in Conventional Example 1 In the ordinary electrolytic capacitor used, the electrolyte is held in a liquid state inside the electrolytic capacitor element, so in order to enlarge the surface of the anode, fine etching holes (pits) are formed by etching.
The electrolyte penetrates to the deepest part of the capacitor, making sufficient contact with the dielectric oxide film and exhibiting a high capacitance value.

However, the specific resistance value of the electrolyte is as high as 100-200 Ω·cm, whereas the resistivity value of the methylisoquinolinium TCNQ complex salt is several tens of Ω·cm or less, resulting in product loss or equivalent series resistance. The 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 the methylisoquinolinium TCNQ complex salt to undergo thermal decomposition before reaching 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 low loss, 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.
This is thought to be because the oxide remains in the etching pit in an amorphous state, so that sufficient contact with the dielectric oxide film is maintained. In addition, even if some methylisoquinolinium TCNQ complex salts crystallize, the presence of quinoline compounds 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 obtained by sintering film-forming metal powder. Moreover, even if it is a wound structure, the separator paper may be omitted, the collecting electrode may be made of a metal other than aluminum, or a heat-resistant conductive resin film may be used.

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 dip or mold, a laminate film exterior, etc. However, this does not deviate from the scope of this invention.

Note that similar results are obtained even when the quinoline compound is other than those exemplified in the examples. Further, in the examples, only one kind of quinoline compound was added, but the same effect can be expected even if two or more kinds 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 electrolyte has high conductivity, loss is small and impedance characteristics are also excellent.

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

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

Furthermore, since sufficient properties can be obtained in a single impregnation process, the electrolyte layer formation process can be simplified, and expensive TCNQ complex salts can be used without wasting them. 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 state of the solid electrolytic capacitor of this invention, FIG. 2 is an exploded perspective view showing the structure of a capacitor element used in an embodiment of this invention, and FIG. FIG. 1 is a cross-sectional view showing a solid electrolyte layer impregnation device of the invention. 1... Capacitor element, 2... Anode, 3... Collector electrode,
4... Separator paper, 5, 6... Tab, 7, 8... External lead, 10... Preheating block, 11, 13...
Recessed portion, 12... Impregnation block, 14... Mixture, 2
0...Exterior case, 21...Elastic sealing body.

Claims (1)

[Scope of Claims] 1. A solid electrolytic capacitor in which a dielectric oxide film is formed on the surface of an anode metal, and a solid electrolyte layer is further formed on the upper surface of the solid electrolyte layer, the solid electrolyte layer comprising tetracyanoquinodimethane and methyl isochloride. A solid electrolytic capacitor comprising a mixture obtained by melting and solidifying a mixture obtained by adding a quinoline compound to a complex salt with quinolinium. 2. The solid electrolytic capacitor according to claim 1, wherein the quinoline compound is one or more selected from the group of isoquinoline, normal quinoline, and 8-oxyquinoline. 3. In a solid electrolytic capacitor formed by forming a dielectric oxide film on the surface of the anode metal and further forming a solid electrolyte layer on the upper surface thereof, the solid electrolyte layer is formed using tetracyanoquinodimethane and methylisoquinolinium. A mixture obtained by adding a quinoline compound to a complex salt of tetracyanoquinodimethane and methylisoquinolinium 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, which comprises impregnating a capacitor element in a mixture and cooling and solidifying the mixture. 4. The method for producing a solid electrolytic capacitor according to claim 3, wherein the quinoline compound is one or more selected from the group of isoquinoline, normal quinoline, and 8-oxyquinoline.