JPH08203783A - Solid electrolytic capacitor and its manufacture - Google Patents

Abstract

PURPOSE: To provide a solid electrolytic capacitor of a large capacity and good high frequency characteristic by realizing hybrid solid-state electrolyte of a mixture layer of mangane dioxide and yttrium oxide-ruthenium oxide layer. CONSTITUTION: Water solution which is formed by mixing yttrium nitrate with manganese nitrate is impregnated onto an anode oxide film 2 of a valve metal and is thermally decomposed. Thereby, an inside of even a smaller fine hole can be covered with a mixture layer 3 of mixture electrolyte of manganese, dioxide and yttrium oxide. Furthermore, since hybrid structure is realized as electrolyte for connecting a ruthenium oxide layer 4 to an external extraction electrode 5 for sharing roles and each characteristic is effectively used, a solid- state electrolytic capacitor of good capacitor characteristic, especially a large capacity and high frequency characteristic and good leak current characteristic can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same. More specifically, the present invention relates to a solid electrolytic capacitor having excellent capacitor characteristics, particularly high frequency characteristics, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Aluminum electrolytic capacitors or tantalum electrolytic capacitors are large-capacity type capacitors. Since the dielectrics of these capacitors were made by the anodic oxidation method, a very uniform thin film was obtained, and the capacity could be increased simply by increasing the surface area of the electrode body.

These capacitors have a thin oxide film,
Moreover, since it has a large area, there is a possibility that the leakage current may increase due to the damage of the oxide film. In order to repair the damage on the oxide film, an electrolyte is provided to bring about a repairing action.
As this electrolyte, in an aluminum electrolytic capacitor, an electrolyte in which an electrolyte is dissolved in an organic solvent (for example, γ-butyrolactone) is used.

In the case of such a liquid electrolyte, there is a problem that the high frequency characteristics and the low temperature characteristics are inferior because the ionic conductivity of the electrolyte is utilized. Therefore, tantalum electrolytic capacitors and aluminum electrolytic capacitors are being made into solid electrolytes, and manganese dioxide is used as one of the electrolytes. However, the specific resistance of manganese dioxide is about 10 Ω · cm, which is not so low.
Therefore, the impedance in the high frequency region is higher than that of the monolithic ceramic capacitor by one order or more.

A manganese dioxide-ruthenium oxide composite solid electrolyte (for example, Japanese Patent Application No. 4-301959 etc.) has been proposed as a method for increasing the electric conductivity of the electrolyte for solving the above-mentioned problems.

[0006]

On the other hand, these electrolytic capacitors are also required to be smaller and have a larger capacity. For example, aluminum electrolytic capacitors have a high etching ratio and are intended to be used in fine holes. In tantalum electrolytic capacitors, efforts are being made to utilize a fine powder sintered body to increase the specific surface area and extract the capacitance from the pores.

Therefore, the specific surface area of the powder per gram is expressed by using the CV product obtained from the chemical conversion voltage × capacitance,
We considered increasing the capacity of electrolytic capacitors. For example 3000
In order to extract the capacitance equivalent to that of a tantalum electrolytic capacitor made of a sintered body of 0 CV / g of fine powder and 50000 CV / g of a sintered body of a fine powder of manganese dioxide, In the case of using the electrolyte as an electrolyte in the same manner as in the prior art, there was a problem that tan δ and impedance increased.

Further, in the above-mentioned structure of the solid electrolytic capacitor using the manganese dioxide-ruthenium oxide composite solid electrolyte, since ruthenium oxide is an oxide of a substance having a good conductivity, the anodic oxide film of the aluminum electrolytic capacitor or the tantalum electrolytic capacitor is formed. It is a substance that is easy to put on. However, when only ruthenium oxide is directly used as the electrolyte of these capacitors, the leakage current increases and there is a problem that it is difficult to put the capacitors into practical use as capacitors.

Further, manganese dioxide produced by the conventional method has a problem that the resistance is not so low as a conductor and it is difficult to enter the inside of the electrode body. The present invention solves the above-mentioned conventional problems, and has a higher anodic oxide film repair ability with fine particles than conventional manganese dioxide,
Moreover, while utilizing a mixed solid electrolyte layer of low-resistance manganese dioxide and yttrium oxide, the conductivity of the electrolyte as a whole is improved, making it possible to improve the high frequency characteristics as well as the small size and large capacity, and at the same time reduce the leakage current. This is intended to be achieved.

[0010]

In order to achieve the above object, the present invention provides a mixed layer of manganese dioxide and yttrium oxide on an anodic oxide film formed on a valve metal such as tantalum, aluminum or titanium. It is characterized in that a ruthenium oxide layer is formed on the mixed layer and is joined to an external extraction electrode via the ruthenium oxide layer.

According to the method for producing a solid electrolytic capacitor of the present invention, a mixed layer of manganese dioxide and yttrium oxide is formed from a solution containing manganese and yttrium ions on an anodic oxide film formed on a valve metal, and this mixed layer is formed. It is characterized in that a ruthenium oxide layer is formed via the layer, and the ruthenium oxide layer is bonded to the extraction electrode via the ruthenium oxide layer.

Further, in the method of manufacturing the solid electrolytic capacitor having the above structure, the mixed solution of manganese nitrate and yttrium nitrate is impregnated on the anodic oxide film, and then pyrolyzed to form a mixed layer of manganese dioxide and yttrium oxide. It is preferably formed.

[0013]

The solid electrolytic capacitor configured as described above can have a low resistance because the mixed layer of manganese dioxide and yttrium oxide is formed on the anodic oxide film, and the impedance in the high frequency region can be reduced. The frequency characteristic and the leakage current characteristic can be improved. Further, since the conductive ruthenium oxide layer is formed on the mixed layer, it is possible to draw out the capacitance from the inside of the fine pores and reduce the internal structure of the electrode body. Therefore, the solid electrolytic capacitor can have a low resistance, a small size and a large capacity, and high frequency characteristics and leakage current characteristics can be improved.

In the method of manufacturing a solid electrolytic capacitor having the above-described structure, manganese dioxide as a conductive solid electrolyte is likely to be clogged inside the electrode body, so manganese dioxide and yttrium oxide are deposited on the anodic oxide film of the valve metal. The mixed solid electrolyte layer with can be easily attached. After that, by forming a low resistance ruthenium oxide layer and using it as a composite solid electrolyte, it is possible to easily manufacture a high-quality solid electrolytic capacitor having a small size and large capacity, high frequency characteristics, and improved leakage current characteristics. it can.

In the method for producing a solid electrolytic capacitor having the above-mentioned structure, a mixed solution of manganese nitrate and yttrium nitrate is impregnated on the anodic oxide film and then pyrolyzed to form a mixture of manganese dioxide and yttrium oxide. According to a preferable example of forming the mixed layer, by adding yttrium nitrate to the manganese nitrate aqueous solution, a large amount of β-manganese dioxide, which is a conductor, is produced, and manganese dioxide having a small particle size is obtained. As a result, manganese dioxide is easily deposited inside the electrode body, that is, the mixed solid electrolyte layer of manganese dioxide and yttrium oxide is easily attached on the anodic oxide film. As a result, small size and large capacity,
It is possible to easily manufacture a high-quality solid electrolytic capacitor with improved high frequency characteristics and leakage current characteristics.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows the structure of a solid electrolytic capacitor of this embodiment. In the figure, 1 is a valve metal electrode body. The anodic oxide film is formed by entering the pores of the electrode body 1, and the mixed layer 3 is formed by entering the pores on the anodic oxide film 2. A ruthenium oxide layer 4 is formed by penetrating into the pores on the mixed layer 3 and is joined to the ruthenium oxide layer 4 to provide an external extraction electrode 5 to form a solid electrolytic capacitor.

The method of manufacturing the solid electrolytic capacitor of this embodiment will be described below. The valve metal is formed by forming a fine powder of tantalum of 50,000 CV / g into a predetermined shape.
It is prepared by firing at 0 ° C.

Next, the sintered body produced from this fine powder is subjected to chemical conversion in a phosphoric acid solution at 50 V to form an oxide film 2. Next, the mixed layer 3 of manganese dioxide and yttrium oxide is mixed with 0.1 mol% (m
(mol%) yttrium ion-containing manganese nitrate 3 mol / l (mol / l) solution of manganese nitrate and yttrium nitrate is impregnated into the electrode body 1 at 250 ° C.
It is formed by carrying out thermal decomposition at. This process is repeated 4 times to form the mixed layer 3. Next, the ruthenium oxide layer 4 is formed by thermally decomposing a 1 mol / l ruthenium nitrate aqueous solution three times. Then, the cathode extraction electrode 5 composed of a carbon layer and a silver conductive resin layer was provided by coating, printing or the like.

The results of measuring the capacitance, tan δ, impedance and leakage current of the tantalum solid electrolytic capacitor according to this embodiment are shown in Table 1 and FIG. Further, a tantalum solid electrolytic capacitor having a manganese dioxide layer in place of the mixed layer of manganese dioxide and yttrium oxide was prepared as a comparative example, and its characteristics are also shown in Table 1 and FIG.

[0020]

[Table 1]

The capacitance and tan δ were measured at 120 Hz, the impedance was measured at 100 Hz to 10 MHz, and the leakage current was measured at a value 60 seconds after 20 V was applied.
The theoretical capacitance of this capacitor is 7.4 μF.

According to this embodiment, as shown in Table 1 and FIG.
For example, manganese nitrate with yttrium nitrate 0.1 mol%
By adding and pyrolyzing,
The characteristics of the gun change and the capacitor characteristics, especially in the high frequency range
Frequency characteristics of impedance and leakage current characteristics
It can be seen that a solid electrolytic capacitor with excellent properties can be obtained.
It That is, by adding yttrium nitrate
Yttrium oxide formation affects manganese dioxide formation
The produced manganese dioxide has a small particle size, β type
You can get This forms an anodized film
Electrolyte inside the pores formed by small powder of valve metal
Can be covered with. Further low resistance (10 ^-3Ω / cm)
Electrolysis for Connecting Ruthenium Oxide to External Extraction Electrode
Since it is provided as a quality and has a hybrid structure, it is smaller
For capacitors with an internal electrode body
Quantity, excellent high frequency characteristics and leakage current characteristics can be obtained.
It

Further, according to the present invention, although the capacitor characteristics vary depending on the film thickness of the mixed layer of manganese dioxide and yttrium oxide and the type of valve metal, excellent high frequency characteristics can be obtained by the hybrid structure of manganese dioxide-ruthenium oxide. Can be inferred.

According to the present invention, by adding yttrium nitrate to an aqueous solution of manganese nitrate, a large amount of β-manganese dioxide, which is a conductor, is produced, manganese dioxide having a small particle size is obtained, and the ability to restore the anodized film is high. Become. Utilizing this property, once the repair ability is given to the electrolyte,
A hybrid structure was used as an electrolyte for connecting ruthenium oxide to the external extraction electrode, the roles were shared, and by utilizing each characteristic efficiently, high-frequency characteristics and leakage current characteristics were improved along with miniaturization and large capacity. .

[0025]

As is apparent from the above description of the embodiments, the solid electrolytic capacitor of the present invention and the method for manufacturing the same are
A large amount of β-manganese dioxide having high conductivity is produced by impregnating an aqueous solution of manganese nitrate with yttrium nitrate on the anodic oxide film of the valve metal and thermally decomposing it.
In addition, since small particles are obtained, the inside of smaller pores can be covered with an electrolyte, which enhances the anodic oxide film repair ability, and as an electrolyte for connecting low resistance ruthenium oxide to the external extraction electrode. Since the structure is hybrid, the roles are shared and the respective characteristics are efficiently utilized, the solid electrolytic capacitor has excellent capacitor characteristics, particularly large capacity and high frequency characteristics and leakage current characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a solid electrolyte layer according to an embodiment of the present invention.

FIG. 2 is a graph showing frequency characteristics of impedance according to an example of the present invention and a comparative example.

[Explanation of symbols]

 1 tantalum electrode body 2 oxide film 3 mixed layer of manganese dioxide and yttrium oxide 4 ruthenium oxide layer 5 external extraction electrode

Claims (3)

[Claims] 1. A mixed layer of manganese dioxide and yttrium oxide is formed on an anodized film formed on a valve metal, and a ruthenium oxide layer is formed on this mixed layer.
A solid electrolytic capacitor, characterized in that it is joined to an external extraction electrode through the ruthenium oxide layer. 2. A mixed layer of manganese dioxide and yttrium oxide is formed from a solution containing manganese and yttrium ions on an anodized film formed on a valve metal, and a ruthenium oxide layer is formed through this mixed layer. Then, the method for producing a solid electrolytic capacitor is characterized in that it is joined to the extraction electrode through the ruthenium oxide layer. 3. The solid electrolytic capacitor according to claim 2, wherein a mixed solution of manganese nitrate and yttrium nitrate is impregnated on the anodic oxide film and then pyrolyzed to form a mixed layer of manganese dioxide and yttrium oxide. Manufacturing method.