JP2001267184A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid electrolytic capacitor capable of solving a problem of not uniformly covering a surface of a dielectric oxide film with a manganese oxide and largely improving productivity. SOLUTION: A manganese oxide layer is formed by twice of the step of forming first/second manganese oxide layers. Thus, a coating area of the manganese oxide layer can be improved. Accordingly, a coating speed of a conductive polymer by an electrolytic polymerization of the later step is remarkably decelerated. Thus, a production efficiency can be remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor, which is mainly based on a method for forming a solid electrolyte using a conductive polymer.

[0002]

2. Description of the Related Art With the recent digitization of electronic devices, capacitors used in these devices also have low impedance in a high-frequency region, and there is an increasing demand for small-sized and large-capacity capacitors. Examples of the capacitor include an aluminum dry electrolytic capacitor and an aluminum or tantalum solid electrolytic capacitor in addition to a plastic film capacitor, a mica capacitor, a multilayer ceramic capacitor and the like.

In the above-mentioned aluminum dry electrolytic capacitor, an etched anode / cathode aluminum foil is wound up through a separator and impregnated with a liquid electrolyte, and in an aluminum or tantalum solid electrolytic capacitor, the above-mentioned aluminum is used. The electrolyte is solidified to improve the characteristics of the dry electrolytic capacitor. The solid electrolyte is formed by immersing the anode body in a manganese nitrate solution and then thermally decomposing the anode body in a high-temperature furnace at about 250 ° C. to 350 ° C. to form a manganese oxide layer. In the case of such a solid electrolytic capacitor, since the electrolyte is solid, there are no disadvantages such as a decrease in capacity due to outflow or dry-up of the electrolyte at a high temperature, a decrease in function caused by solidification in a low temperature range, and a liquid electrolyte. It is known to show better frequency characteristics and temperature characteristics in comparison.

Further, according to the techniques disclosed in JP-A-60-37114 and JP-A-60-244017, electrolytic polymerization of a heterocyclic monomer such as pyrrole or thiophene using a supporting electrolyte is disclosed. It describes that a solid electrolytic capacitor having excellent frequency characteristics and temperature characteristics can be obtained using a conductive polymer containing an anion of a supporting electrolyte as a dopant as a solid electrolyte.

[0005]

However, in a conventional solid electrolytic capacitor using a conductive polymer as a solid electrolyte, a method for forming a conductive polymer on an electrode is disclosed in, for example, JP-A-63-173313. First, a conductive polymer layer is formed on a dielectric oxide film by chemical polymerization using an oxidizing agent, and the conductive polymer becomes a true electrolyte through the polymer of the conductive polymer layer. There is a method in which a conductive polymer is formed by electrolytic polymerization, but in such a method, the conductive polymer layer formed by the above chemical polymerization is used as a power supply portion in a later step of electrolytic polymerization. However, there has been a problem that productivity is remarkably inferior, cost is increased, and yield is poor.

A method of using manganese oxide as a conductive layer necessary for forming a conductive polymer layer on the surface of a dielectric oxide film by electrolytic polymerization has been widely adopted. The formation of manganese nitrate is performed by thermal decomposition of a manganese nitrate solution at a high temperature. In this method, the dielectric oxide film generated during the thermal decomposition is greatly damaged. Since the amount of oxides generated is small and the oxides are dispersed like islands, multiple thermal decomposition reactions are required to cover the surface of the dielectric oxide film evenly, which further damages the dielectric oxide film However, there is a problem that the number increases.

For the purpose of suppressing such damage to the dielectric oxide film, the technique described in JP-A-6-124858 does not produce manganese oxide by a thermal decomposition reaction, but uses an aqueous solution of permanganate. In a method of obtaining manganese oxide by adhering and reducing this by heating, and in the technique described in JP-A-6-84706, manganese oxide is produced by a chemical oxidation-reduction reaction of acetate and permanganate. Although a method for producing an object is disclosed, it has been difficult to drastically solve the above-mentioned conventional problems even by such a technique.

The present invention solves such a conventional problem,
It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor which can greatly improve productivity by forming a conductive polymer layer in an extremely short time.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is particularly directed to a method in which an anode body having a dielectric oxide film layer formed thereon is immersed in a manganese nitrate solution and then thermally decomposed. Forming a first manganese oxide layer on the dielectric oxide film layer in the form of islands, followed by immersing the anode body in an aqueous permanganate solution, followed by washing and drying to form a second manganese oxide layer. This is a method for manufacturing a solid electrolytic capacitor in which a conductive polymer layer is formed by electrolytic polymerization on these after forming the oxide layers, and this method improves the coverage area of the manganese oxide layer. Therefore, there is an operational effect that the coating speed of the conductive polymer by the subsequent step of electrolytic polymerization can be greatly reduced.

[0010] The invention described in claim 2 of the present invention is, in particular,
The second manganese oxide layer is formed by immersing the anode body in an aqueous solution of permanganate and then drying the anode body. This method eliminates the cleaning step and thus increases the amount of permanganese. Since a large number of manganese oxide layers can be formed while the acid salt remains, there is an effect that the coating speed of the conductive polymer by electrolytic polymerization can be further reduced.

[0011] The invention described in claim 3 of the present invention is, in particular,
The step of forming the second manganese oxide layer is repeated twice or more. According to this method, more manganese oxide layers can be formed to increase the covering area. This has the effect that the coating speed of the conductive polymer by polymerization can be further reduced.

The invention described in claim 4 of the present invention particularly provides
A step of repairing the dielectric oxide film layer is provided before the step of forming the conductive polymer layer, and this method has an effect of improving the leakage current characteristics.

The invention according to claim 5 of the present invention particularly provides
According to this method, the pH of the aqueous solution of permanganate is adjusted to 3 or less. According to this method, the use of the aqueous solution of permanganate having a higher oxidizing property leads to high reactivity and formation of more manganese oxide layers. Thus, the coating area can be increased, and therefore, the effect that the coating speed of the conductive polymer by the electrolytic polymerization can be further reduced.

[0014] The invention according to claim 6 of the present invention particularly provides
The concentration of the aqueous solution of permanganate is from 0.2 mol / L to 0.1 mol / L.
5 mol / L. According to this method, more manganese oxide layers can be formed and the covering area can be increased, so that the coating speed of the conductive polymer by electrolytic polymerization can be further reduced. It has the effect of being able to do. If the concentration of the aqueous solution of permanganate is 0.2 mol / L or less, the manganese oxide layer cannot be sufficiently covered due to poor reactivity. Is not preferred because it becomes supersaturated beyond the permissible amount of permanganate aqueous solution at room temperature.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a conceptual diagram schematically showing the structure of a solid electrolytic capacitor. In FIG. 1, reference numeral 1 denotes an anode body, and this anode body 1 uses an aluminum foil which is a valve action metal and has a surface thereof. Are roughened by etching.
Reference numeral 2 denotes a dielectric oxide film layer formed by anodizing the surface of the anode body 1, and 3 denotes a dielectric oxide film layer 2
The solid electrolyte layer 3 is composed of a manganese oxide layer and a conductive polymer layer. 4 is a carbon layer formed on the solid electrolyte layer 3 and 5 is a silver layer formed on the carbon layer 4. The carbon layer 4 and the silver layer 5 constitute a cathode layer. It is. In addition, + and-in the figure are an anode lead and a cathode lead respectively drawn from the anode body 1 and the cathode layer.

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described with reference to Embodiment 1.

First, as in the solid electrolytic capacitor shown in FIG. 1, an anode body 1 of 3 mm × 4 mm made of aluminum having an anode lead connected to one end is prepared.
The anode body 1 was subjected to anodization using a 3% aqueous solution of ammonium adipate at an applied voltage of 12 V and an aqueous solution temperature of 70 ° C. for 60 minutes to form a dielectric oxide film layer 2 on the surface of the anode body 1.

Next, the anode body 1 on which the dielectric oxide film layer 2 is formed is immersed in a 30% manganese nitrate solution, pulled up, air-dried, and then thermally decomposed at 300 ° C. for 10 minutes. Thereby, the first manganese oxide layer 6 which became a part of the solid electrolyte layer 3 was formed. FIG. 2 shows a state of the first manganese oxide layer 6 formed on the dielectric oxide film layer 2 in this state. In this state, the first manganese oxide layer 6 is It is only formed in an island shape on top.

Subsequently, the anode body 1 in which the first manganese oxide layer 6 is formed in an island shape is removed by a concentration of 0.2 mol / L.
After dipping in a potassium permanganate solution having a pH of 3 for 10 minutes and pulling it up, thoroughly washing it with running water and drying it, the dielectric containing the island-shaped first manganese oxide layer 6 is formed. The second manganese oxide layer 7 was formed on the oxide film layer 2. FIG. 3 shows the state of the dielectric oxide film layer 2 and the second manganese oxide layer 7 formed on the first manganese oxide layer 6 in this state. It can be confirmed that the coverage area of the manganese oxide layer is improved as compared with FIG.

Next, the pyrrole monomer 0.5 mol / L
And sodium propylnaphthalenesulfonate 0.1mo
The anode body 1 on which the first and second manganese oxide layers 6 and 7 are formed is immersed in a polymerization solution for forming a solid electrolyte prepared by adding water as a solvent after mixing 1 / L in advance. A conductive polymer layer is formed by bringing a polymerization initiation electrode close to the surface of the anode body 1 in the polymerization solution and performing electrolytic polymerization at a polymerization solution temperature of 30 ° C. and a polymerization voltage of 3 V, thereby forming a solid electrolyte. Layer 3 was formed.

Thereafter, a colloidal carbon suspension is applied as a cathode extraction layer to the anode body 1 on which the solid electrolyte layer 3 is formed, and the suspension is dried to form a carbon layer 4.
Is formed, a silver paste is applied, and the silver paste is dried to form a silver layer 5 to provide a cathode layer. After connecting a cathode lead to this cathode layer, the anode body 1 is made of epoxy resin.
Was coated (not shown) to complete a solid electrolytic capacitor.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to Embodiment 2.

The second embodiment is different from the first embodiment in that the method of forming the second manganese oxide layer 7 is different from that of the first embodiment. The description of the portions will be omitted, and only different portions will be described.

The method for forming the second manganese oxide layer 7 in the present embodiment is as follows. The anode body 1 in which the first manganese oxide layer 6 is formed in an island shape is formed by adding 0.2 mol / L potassium permanganate. After being immersed in the solution for 10 minutes and pulled up, it is immediately dried to form a second layer on the dielectric oxide film layer 2 including the island-shaped first manganese oxide layer 6.
The manganese oxide layer 7 was formed. That is, by omitting the running water washing performed in the first embodiment, the anode body 1 that has been dipped in the aqueous solution of permanganate and then pulled up is immediately dried.

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described with reference to Embodiment 3.

The third embodiment is different from the first embodiment in that the method of forming the second manganese oxide layer 7 is different from that of the first embodiment. The description of the portions will be omitted, and only different portions will be described.

The method of forming the second manganese oxide layer 7 in the third embodiment is the same as that of the first embodiment.
The step of forming the manganese oxide layer 7 was repeated twice.

(Embodiment 4) Hereinafter, a fourth embodiment of the present invention will be described with reference to Embodiment 4.

The fourth embodiment is different from the first embodiment in that a step of repairing the dielectric oxide film layer 2 is provided before the step of forming the conductive polymer layer in the first embodiment. Since the configuration is the same as that of the first embodiment, the description of the same portions will be omitted, and only different portions will be described.

In the fourth embodiment, the anode body 1 on which the first / second manganese oxide layers 6 and 7 are formed is immersed in a 3% aqueous solution of ammonium adipate. The dielectric oxide film layer 2 was repaired by performing anodic oxidation for minutes.

(Embodiment 5) Hereinafter, a fifth embodiment of the present invention will be described with reference to Embodiment 5.

The fifth embodiment is different from the first embodiment in that the second manganese oxide layer 7 is formed by a different method. The description of the portions will be omitted, and only different portions will be described.

In the method of forming the second manganese oxide layer 7 in the fifth embodiment, the anode body 1 in which the first manganese oxide layer 6 is formed in the shape of an island is prepared by adjusting the pH of the anode body 1 to 0.2 mol / L. 1. A dielectric oxide film layer including the first manganese oxide layer 6 formed in an island shape by immersing in the potassium permanganate solution for 10 minutes, pulling it up, thoroughly washing it with running water, and drying it. 2 on the second manganese oxide layer 7
Was formed. That is, the pH of the potassium permanganate solution of the first embodiment is adjusted from 3 to 1.

(Embodiment 6) Hereinafter, a sixth embodiment of the present invention will be described with reference to FIG.

The sixth embodiment differs from the first embodiment in the method of forming the second manganese oxide layer 7, and is the same as the first embodiment except for the other points. The description of the portions will be omitted, and only different portions will be described.

In the method for forming the second manganese oxide layer 7 in the sixth embodiment, the anode body 1 in which the first manganese oxide layer 6 is formed in the shape of an island is prepared by adjusting the pH of the anode body 1 to 0.5 mol / L. 3 is immersed in the potassium permanganate solution for 10 minutes, pulled up, thoroughly washed with running water, and dried to form a dielectric oxide film layer including the first manganese oxide layer 6 formed in an island shape. 2 on the second manganese oxide layer 7
Was formed. That is, the concentration of the potassium permanganate solution of the first embodiment is adjusted from 0.2 mol / L to 0.1 mol / L.
It was changed to 5 mol / L.

(Comparative Example) Using a conventional product as a comparative example, first,
3m made of aluminum with anode lead connected to one end
An anode body having a size of mx 4 mm is prepared.
12% aqueous solution of ammonium adipate
V. Anodizing was performed at an aqueous solution temperature of 70 ° C. for 60 minutes to form a dielectric oxide film layer on the surface of the anode body.

Next, the anode body on which the dielectric oxide film layer was formed was immersed in a 30% manganese nitrate solution and pulled up.
This was air-dried, and then subjected to a thermal decomposition treatment at 300 ° C. for 10 minutes to form a manganese oxide layer that became a part of the solid electrolyte layer. Next, the pyrrole monomer 0.5
mol / L and sodium propylnaphthalenesulfonate 0.1 mol / L are mixed in advance, and then the anode body on which the manganese oxide layer is formed is immersed in a polymerization solution for forming a solid electrolyte prepared by adding water as a solvent. Then, in the polymerization solution, an electrode for initiating polymerization is brought close to the surface of the anode body, and electropolymerization is performed at a polymerization solution temperature of 30 ° C. and a polymerization voltage of 3 V to form a conductive polymer layer. A layer was formed.

Thereafter, a colloidal carbon suspension is applied as a cathode extraction layer to the anode body having the solid electrolyte layer formed thereon, and the suspension is dried to form a carbon layer, and further, a silver paste is applied and dried. Then, a cathode layer was formed by forming a silver layer, and a cathode lead was connected to the cathode layer. Then, an outer surface of the anode body was covered with an epoxy resin to complete a solid electrolytic capacitor.

Embodiments 1 to 6 manufactured as described above
And the solid electrolytic capacitors according to the comparative examples (the number of each is 10), the time required to completely cover the surface of the anode body with a conductive polymer by electrolytic polymerization, the capacitance at 120 Hz, tan δ, the rated voltage (2 V ) Was measured for each one minute leakage current, and the average value is shown in Table 1 below.

[0042]

[Table 1]

As is clear from Table 1, the solid electrolytic capacitor according to the present invention has a longer coating time with the conductive polymer on the surface of the anode body while maintaining the same characteristics as the comparative example which is a conventional product. This can significantly reduce the production time, and can greatly improve the production efficiency.

The surface after forming the first / second manganese oxide layers 6 and 7 as in the present embodiment and the surface after forming only the first manganese oxide layer as in the comparative example. The results of the elemental analysis are shown in (Table 2).

[0045]

[Table 2]

As is clear from Table 2, the solid electrolytic capacitor according to the present invention has an improved coverage on the surface of the anode body.

In the present embodiment, the case where aluminum is used as the material of the anode body has been described. However, the present invention is not limited to this, and other valve action metals such as tantalum and niobium may be used. May be.

Further, in this embodiment, an example using polypyrrole as the conductive polymer material has been described. However, the present invention is not limited to this, and compounds obtained from aniline, thiophene and derivatives thereof are used. It may be.

Further, in the present embodiment, the description has been given of the case where a potassium permanganate solution is used as the aqueous solution of permanganate. However, the present invention is not limited to this, and includes a permanganate ion as an anion. Any other salt may be used as long as it is a salt.

Further, in the present embodiment, the case where sodium propylnaphthalenesulfonate is used as the supporting electrolyte has been described. However, the present invention is not limited to this, as long as it shows high conductivity by doping. However, other than this may be used.

[0051]

As described above, according to the present invention, the formation area of the manganese oxide layer is reduced by performing the formation of the manganese oxide layer twice in the first / second manganese oxide layer forming step. Therefore, the coating speed of the conductive polymer by electrolytic polymerization, which is a subsequent step, can be greatly reduced, and the production efficiency can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram schematically showing a configuration of a solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing a covering state of the manganese oxide layer after a first manganese oxide layer forming step according to the embodiment.

FIG. 3 is a plan view schematically showing a covering state of the manganese oxide layer after a second manganese oxide layer forming step according to the embodiment.

[Explanation of symbols]

 Reference Signs List 1 anode body 2 dielectric oxide film layer 3 solid electrolyte layer 4 carbon layer 5 silver layer 6 first manganese oxide layer 7 second manganese oxide layer

Claims (6)

[Claims] 1. A dielectric oxide film layer is formed by anodic oxidation on the outer surface of an anode body made of a valve metal, and then the anode body is immersed in a manganese nitrate solution and then thermally decomposed. The first manganese oxide layer is formed on the coating layer in the form of islands, and then the anode body is immersed in an aqueous solution of permanganate, washed and dried to include the first manganese oxide layer. After a second manganese oxide layer is formed on the dielectric oxide film layer, the conductive oxide film is formed on the dielectric oxide film layer and the first and second manganese oxide layers formed thereon by electropolymerization. A method for manufacturing a solid electrolytic capacitor in which a molecular layer is formed. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the formation of the second manganese oxide layer is performed by immersing the anode body in an aqueous solution of permanganate and then drying. 3. The method according to claim 1, wherein the step of forming the second manganese oxide layer is repeated twice or more. 4. Prior to the step of forming a conductive polymer layer,
The method for manufacturing a solid electrolytic capacitor according to claim 1, further comprising a step of repairing the dielectric oxide film layer. 5. The method for producing a solid electrolytic capacitor according to claim 1, wherein the pH of the aqueous solution of permanganate is 3 or less. 6. The concentration of the aqueous solution of permanganate is 0.2 m
The method for producing a solid electrolytic capacitor according to claim 1, wherein the amount is from ol / L to 0.5 mol / L.