JPH0883735A - Manufacture of capacitor - Google Patents

Abstract

PURPOSE: To realize a capacitor which is small in leakage current by a method wherein a conductive high-molecular layer obtained by chemical oxidation polymerization is formed on a valve-action metal. CONSTITUTION: The corners of an anode valve metal 2 molded like a rectangular parallelepiped, a regular hexahedron, or a cylinder are chamfered or rounded, a dielectric film 5 is formed surrounding the anode valve metal 2 by anodization, and a conductive high-molecular layer 6 is formed thereon through chemical oxidation polymerization for the formation of a capacitor. The conductive high-molecular layer 6 is capable of being uniformly laminated on all the surface of the capacitor formed as mentioned above, so that the capacitor is small in leakage current and loss, and chemical oxidation polymerization processes can be lessened in number of times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a capacitor using a conductive polymer film as a solid electrolyte, and particularly to a solid electrolytic capacitor having excellent high frequency characteristics and leakage current characteristics.

[0002]

2. Description of the Related Art Recently, with the digitalization of electric equipment, the capacitors used therein have low impedance in the high frequency region, and there is an increasing demand for miniaturization and large capacity. Conventionally, plastic film capacitors, mica capacitors, laminated ceramic capacitors, etc. have been used as high frequency capacitors. In addition, there are aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. In the aluminum dry electrolytic capacitor, the positive and negative aluminum foils subjected to etching are wound around a paper separator and a liquid electrolyte is used. In the case of aluminum or tantalum solid electrolytic capacitors, the electrolyte is solidified in order to improve the characteristics of the aluminum dry electrolytic capacitors. To form this solid electrolyte, the anode foil is dipped in a manganese nitrate solution and pyrolyzed in a high temperature furnace at about 350 ° C. to form a manganese dioxide layer. In the case of this capacitor, since the electrolyte is a solid, there are no drawbacks such as volatilization of the electrolytic solution at high temperature and deterioration of the function caused by solidification at low temperature, and the frequency characteristics and temperature characteristics are better than those of the liquid electrolyte. Further, the aluminum electrolytic capacitor can realize a large capacity because the oxide film serving as a dielectric can be made very thin like the tantalum electrolytic capacitor. Further, in recent years, solid electrolytic capacitors using an organic semiconductor such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) salt as a solid electrolyte have been developed.
(JP-A-58-17609) Further, there is a method in which a polymerizable monomer such as pyrrole or furan is electrolytically polymerized to form a conductive polymer, which is used as a solid electrolyte. (JP-A-60-244017)

[0003]

Various types of capacitors are used in this way, but it is difficult to increase the capacity of film capacitors and mica capacitors due to their large size, and monolithic ceramic capacitors are small and large in capacity. However, it has drawbacks such as an extremely high price and poor temperature characteristics. Further, since the aluminum electrolytic capacitor is apt to be damaged by the oxide film, it is necessary to apply an electrolyte between the oxide film and the cathode to repair the damage at any time. The one that uses a liquid as this electrolyte causes a decrease in capacitance and an increase in loss over time due to electrolyte leakage and ionic conductivity, and has a large loss in the high frequency region and low temperature region. It has drawbacks such as Next, the solid electrolyte cannot be said to have a small loss in the high frequency region because of damage to the oxide film due to thermal decomposition several times at high temperature and high resistivity of manganese dioxide. Also, solid electrolytic capacitors using organic semiconductors such as TCNQ salt show superior high frequency characteristics compared to those using manganese dioxide, but increase in resistivity when applying organic semiconductors, It cannot be said that it exhibits ideal characteristics due to weak adhesion. Furthermore, when using a conductive polymer thin film as a solid electrolyte,
It has excellent frequency characteristics, temperature characteristics, life characteristics, etc.
In order to form a conductive polymer thin film as a solid electrolyte on the anode valve metal, the anode valve metal is alternately immersed in a polymerizable monomer solution and an oxidizer solution to perform chemical oxidative polymerization. The solution impregnated at the sharp corners is more likely to diffuse than the corners. From this, even if the solid electrolyte is sufficiently formed on the flat surface, the number of repetitive treatments increases because the vicinity of the corner is still unformed, and therefore the film on the flat surface becomes too thick and the solid loss is large. There is a problem that an electrolytic capacitor is easily formed. Furthermore, since the pH of the oxidant solution is in the strongly acidic range, there is a problem that the dielectric film deteriorates.

[0004]

According to the method of manufacturing a capacitor of the present invention, first, a corner of an anode valve metal, which is a solid having at least one corner, is chamfered, and then the surface of the anode valve metal is cut. A dielectric film is formed by anodic oxidation, and a chemical oxidative polymerization conductive polymer layer is laminated on the dielectric film by further performing chemical oxidative polymerization using a solution of a heterocyclic five-membered ring compound and an oxidant solution. is there.

Secondly, a dielectric film is formed on the surface of the anode valve metal by anodic oxidation, and then chemical oxidative polymerization is carried out by using a solution of a hetero five-membered ring compound and steam and an oxidant solution, and the dielectric The chemical oxidation polymerization conductive polymer layer is laminated on the body film.

Thirdly, a dielectric film is formed on the surface of the anode valve metal by anodic oxidation, and then the anode valve metal is dipped in a solution of a hetero five-membered ring compound, and then the anode valve metal and a conductive material. The counter electrode consisting of the above is immersed in an oxidant solution, and the anode valve material is used as an anode to apply a voltage between the anode valve metal and the counter electrode to repair the dielectric film and to chemically oxidize the dielectric film on the dielectric film. The polymerized conductive polymer layer is laminated.

[0007]

By this manufacturing method, firstly, the electrode shape of the capacitor does not have an acute angle portion, so that a uniform conductive polymer can be laminated on the entire surface at the same time, and the number of times of chemical oxidative polymerization is small and the loss is low. You can get a small capacitor. Secondly, since the chemical oxidative polymerization is carried out in a combination of a monomer solution and a vapor, it is possible to fill the inside of the pores by polymerizing in a solution, and by polymerizing in the vapor, the surface is evenly distributed. It is possible to obtain a capacitor with a small loss because the number of times of chemical oxidative polymerization is small. Thirdly, a chemical conversion reaction occurs by applying a predetermined voltage during the immersion in the oxidant solution, and the conductive polymer can be laminated simultaneously with the repair of the dielectric film, and the number of chemical oxidative polymerization treatments is small, resulting in loss. You can get a small capacitor.

[0008]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIG.
Will be described with reference to. FIG. 1 is a sectional view of a capacitor manufactured in the first embodiment of the present invention. In FIG.
Reference numeral 1 is an anode lead, 2 is an anode valve metal serving as an anode of a capacitor, 3 is a slope of a portion where the corner of the anode valve metal 3 is chamfered, 4 is chamfered of a corner of the anode valve metal 3. Is a chamfered length of a portion, 5 is a dielectric film that serves as a dielectric layer of a capacitor, 6 is a conductive polymer layer that serves as an electrolyte layer that corrects deterioration of the dielectric film, and 7 is a conductive layer. A carbon paint film that enhances the adhesion between the polymer layer 5 and the silver paint film, 8 is a silver paint film that serves as the capacitor cathode, and 9 is a cathode lead.

First, an anode valve metal 2 (size (mm): length 2, which is a rectangular parallelepiped tantalum sintered body with an anode lead 1 attached thereto).
Chamfer each corner of height 1.5, width 1) so that the slope 3 is 50 ° and the chamfer length 4 is 0.2 mm, and the anode valve metal 2 is treated with 0.05% phosphoric acid aqueous solution. Dielectric coating 5 was formed by anodic oxidation under conditions of an applied voltage of 33.9 V at about 85 ° C. for 60 minutes. This device was immersed in an aqueous solution in which pyrrole was dissolved in 0.75 mol / l for 2 minutes, and then ferric sulfate 0.1mo
It was immersed for 10 minutes in an oxidizing agent aqueous solution in which 1 / l was dissolved. This operation was repeated several times, and when it was visually judged that the entire element was covered with the conductive polymer layer 6 (polypyrrole) by chemical oxidative polymerization, this operation was terminated. Next, a carbon paint film 7 and then a silver paint film 8 are formed by a usual method,
A cathode lead 9 was provided on the silver paint film 8, aging was performed at an applied voltage of 12.5 V, and the package was covered with a resin to obtain a solid electrolytic capacitor.

The operation of the capacitor manufactured in the first embodiment of the present invention will be described below with reference to FIG.
FIG. 2 is a completed view of the capacitor manufactured in the first embodiment of the present invention. In FIG. 2, 21 is an anode lead,
22 is a cathode lead. By applying a positive voltage to the anode lead 21 and a negative voltage to the cathode lead 22,
Operates as a capacitor.

The characteristics of the solid electrolytic capacitor manufactured by the method for manufacturing a capacitor according to this embodiment are shown in Table 1-1 as in Example 1-1.
Shown in As Comparative Example 1, the characteristics of a solid electrolytic capacitor using a rectangular parallelepiped non-chamfered anode valve metal (tantalum sintered body, length 2, height 1.5, width 1 (mm)) are shown (Table 1).
Shown in

As is clear from these (Table 1), the solid electrolytic capacitor according to this example is excellent in that the short circuit defect rate is low, the leakage current is small, and the number of times of chemical oxidative polymerization is small. The effect was obtained.

Next, at each corner of the rectangular parallelepiped, the inclination 3 is 50 °,
Anode valve metal 2 (tantalum sintered body, length 4, height 3, width 2.5 (mm)) chamfered so that the chamfer length 4 becomes 1.5 mm
Is used, and each corner is chamfered so that the inclination 3 is 40 ° and the chamfering length 4 is 0.2 mm (tantalum sintered body, length 2, height 1.5, The characteristics of the solid electrolytic capacitor when a width of 1 (mm) is used are shown in Example 1-2 and Example 1-3 of Table 1, respectively. In addition, Comparative Example 2
As a comparative example, an anode valve metal (tantalum sintered body, length 2, height 1.5, width 1 (mm)) whose corners are chamfered with a slope of 50 ° and a chamfer length of 0.1 mm is used. 3 and each corner has a slope of 5
A 5 ° chamfered 0.2 mm chamfered anode valve metal (tantalum sintered body, length 2, height 1.5, width 1 (mm)) was used. 50 ° chamfer length 1.6 mm
The characteristics of the solid electrolytic capacitor using the anode valve metal chamfered in Example 1 and the solid electrolytic capacitor using the anode valve metal chamfered at the corner portion of 35 degrees and 0.2 mm in length as Comparative Example 5 are shown in Table 1.

As is clear from these (Table 1), in the solid electrolytic capacitors of Examples 1-2 and 1-3, the short-circuit defect rate was low, the leakage current was small, and the number of chemical oxidative polymerization was repeated. An excellent effect was obtained in that it can be reduced.

Next, when chamfering a corner portion of a rectangular parallelepiped anode valve metal 2 (tantalum sintered body, length 2, height 1.5, width 1 (mm)) with a curved surface having a radius of curvature R0.05 mm, And the characteristics of the solid electrolytic capacitor when each corner of a rectangular parallelepiped anode valve metal 2 (tantalum sintered body, length 4, height 3, width 2.5 (mm)) is chamfered with a curved surface with a radius of curvature R1 mm. These are shown in Examples 1-4 and 1-5 of (Table 1), respectively. Further, as Comparative Example 6, an anode valve metal having a rounded corner of R 0.04 mm was used, and as Comparative Example 7, the corner was R.
The characteristics of the solid electrolytic capacitor produced by using the anode valve metal having a roundness of 1.1 mm are shown in (Table 1).

As is clear from these (Table 1), in the solid electrolytic capacitors of Examples 1-4 and 1-5, the short-circuit failure rate was low, the leakage current was low, and the number of repetitions of chemical oxidative polymerization was low. An excellent effect was obtained in that it was completed.

Furthermore, the anode valve metal 2 formed into a cylindrical shape
(Tantalum sintered body, 1φ1H) has a slope of 3
° When chamfering so that the chamfer length 4 becomes 0.2 mm,
And the characteristics of the solid electrolytic capacitor when chamfered with a curved surface having a radius of curvature R0.05 mm are shown in Table 1 of Example 1 respectively.
-6 and Example 1-7. Further, as Comparative Example 8, the characteristics when a cylindrical anode valve metal (tantalum sintered body, 1φ1H) is not chamfered are shown in (Table 1).

As is clear from these (Table 1), in the solid electrolytic capacitors of Examples 1-6 and 1-7, the short-circuit defect rate was low, the leakage current was low, and the number of repetitions of chemical oxidative polymerization was low. An excellent effect was obtained in that it was completed.

Although tantalum is shown as an example of the anode valve metal, other metals such as aluminum may be used.

Although pyrrole was shown as an example of a monomer, a hetero five-membered ring compound such as thiophene or furan may be used in addition to this.

Although an aqueous solution of ferric sulfate was shown as an example of the oxidizing agent, any aqueous solution of ferric sulfate, such as hydrogen peroxide solution, ammonium persulfate, or iron benzenesulfonate, can be used as long as it can oxidize the polymerizable monomer. Such an oxidant may be used.

The carbon paint film 6 enhances the adhesion between the conductive polymer layer 5 and the silver paint film 7, and when the adhesion between the conductive polymer layer 5 and the silver paint film 7 is high. You don't have to.

(Embodiment 2) A second embodiment of the present invention will be described below with reference to FIG. FIG. 3 is a sectional view of a capacitor manufactured in the second embodiment of the present invention. In FIG. 3, 31 is an anode lead, 32 is an anode valve metal that serves as a capacitor anode, 33 is a dielectric film that serves as a capacitor dielectric layer, and 34 is an electrolyte that repairs deterioration of the dielectric film. It is a conductive polymer layer to be a layer,
Reference numeral 35 is a carbon paint film that enhances the adhesion between the conductive polymer layer 4 and the silver paint film, 36 is a silver paint film that serves as the cathode of the capacitor, and 37 is a cathode lead.

First, 0.05% of an anode valve metal 32 (size (mm): length 2, height 1.5, width 1 (mm)), which is a rectangular parallelepiped tantalum sintered body with the anode lead 31 attached, is used. The dielectric film 33 was formed by anodic oxidation with a phosphoric acid aqueous solution at about 85 ° C. for 60 minutes under an applied voltage of 33.9V. This device was immersed in an aqueous solution in which pyrrole was dissolved at 0.75 mol / l for 2 minutes,
Then, it was immersed for 10 minutes in an oxidizing agent aqueous solution in which ferric sulfate 0.1 mol / l was dissolved. After repeating this operation 5 times,
It was washed with water and dried. Then, reimmerse in the oxidant solution,
Subsequently, the conductive polymer layer 34 was formed by chemical oxidative polymerization over the entire element by exposing it to pyrrole vapor. Next, a carbon paint film 35 and then a silver paint film 36 are formed by a usual method, a cathode lead 37 is provided on the silver paint film 36, and aging is performed at an applied voltage of 12.5 V. I got a capacitor.

The characteristics of the solid electrolytic capacitor manufactured by the method for manufacturing a capacitor of this example are shown as Example 2 (Table 1).
Shown in As is clear from these (Table 1), the solid electrolytic capacitor according to this example has an excellent effect in that the short circuit defect rate is low, the leakage current is small, and the number of times of chemical oxidative polymerization is extremely small. It was

Although tantalum is shown as an example of the anode valve metal, other metals such as aluminum may be used.

Although pyrrole was shown as an example of a monomer, a hetero five-membered ring compound such as thiophene or furan may be used in addition to this.

Although an aqueous solution of ferric sulfate was shown as an example of the oxidizing agent, any aqueous solution of ferric sulfate, such as hydrogen peroxide solution, ammonium persulfate, or iron benzenesulfonate, can be used as long as it can oxidize the polymerizable monomer. Such an oxidant may be used.

The carbon paint film 6 enhances the adhesion between the conductive polymer layer 5 and the silver paint film 7, and when the adhesion between the conductive polymer layer 5 and the silver paint film 7 is high. You don't have to.

It goes without saying that this embodiment is effective even if it is combined with the first embodiment.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to FIG. Since the description of FIG. 3 is the same as that of the second embodiment, the description thereof is omitted. First, an anode valve metal 32 (size (mm): length 2, height 1.5, width 1 (mm)), which is a rectangular parallelepiped tantalum sintered body to which the anode lead 31 is attached, is set to 0.05.
% Phosphoric acid aqueous solution at about 85 ° C. for 60 minutes, applied voltage 33.9
Anodization was performed under the condition of V to form the dielectric film 33. This device was immersed for 2 minutes in an aqueous solution in which pyrrole was dissolved in 0.75 mol / l, and then for 10 minutes in an oxidant aqueous solution in which 0.1 mol / l ferric sulfate was dissolved. While being immersed in the oxidant aqueous solution, a counter electrode was provided separately from the anode valve metal 32, and a voltage of 27.1 V (formation voltage × 0.8) was applied with the anode valve metal 32 as an anode to apply dielectric by anodic oxidation. The repair of the body film 33 and the chemical oxidative polymerization were performed at the same time. This operation was repeated several times, and when it was visually judged that the entire element was covered with the conductive polymer layer 34 (polypyrrole) by chemical oxidative polymerization, this operation was terminated. Next, a carbon paint film 35 and then a silver paint film 36 are formed by a normal method,
A cathode lead 37 was provided on the silver paint film 36, aging was performed at an applied voltage of 12.5 V, and the package was covered with a resin to obtain a solid electrolytic capacitor.

The characteristics of the solid electrolytic capacitor manufactured by the method for manufacturing a capacitor of this example are shown as Example 3 (Table 1).
Shown in As is clear from these (Table 1), the solid electrolytic capacitor according to this example has an excellent effect in that the short-circuit defect rate is low, the leakage current is small, and the number of times of chemical oxidative polymerization is small. .

Although tantalum is shown as an example of the anode valve metal, other metals such as aluminum may be used.

Although pyrrole is shown as an example of a monomer, a hetero five-membered ring compound such as thiophene or furan may be used instead.

Although an aqueous solution of ferric sulfate is shown as an example of the oxidizing agent, any oxidizing agent such as hydrogen peroxide solution, ammonium persulfate, or iron benzenesulfonate can be used as long as it can oxidize the polymerizable monomer. Such an oxidant may be used.

The carbon paint film 6 enhances the adhesion between the conductive polymer layer 5 and the silver paint film 7, and when the adhesion between the conductive polymer layer 5 and the silver paint film 7 is high. You don't have to.

In this embodiment, 80% of the formation voltage is shown as an example of the voltage during the chemical oxidative polymerization, but other than that, it is possible to apply a voltage in the range of 100% to 40% of the formation voltage. It is also possible to apply a current.

It goes without saying that this embodiment is effective even if it is combined with the first or second embodiment.

[0039]

[Table 1]

[0040]

As described above, according to the present invention, first, since the corners of the three-dimensional anode valve metal having at least one corner are chamfered and used, they are alternately immersed in the monomer solution and the oxidant solution. Even though it is possible to suppress the diffusion of monomers or oxidants at the corners in the solution, a capacitor manufacturing method that can manufacture capacitors with a low short circuit defect rate and small leakage current with a small number of chemical oxidative polymerization treatments is realized. It is possible.

Secondly, since the chemical oxidative polymerization is carried out in a combination of a solution and a vapor, the conductive polymer layer is filled up to the back of the pores by the polymerization in the solution, and the polymerization is performed in the vapor. A conductive polymer layer can be uniformly laminated on the surface,
A capacitor with a low short circuit defect rate and a small leakage current,
It is possible to realize a method of manufacturing a capacitor that can be manufactured with a small number of chemical oxidative polymerization treatments.

Thirdly, since a counter electrode is provided separately from the anode valve metal during the chemical oxidative polymerization and a voltage or current is applied using the anode valve metal as an anode, repair of the dielectric film and chemical oxidative polymerization can be carried out at the same time. Thus, it is possible to realize a capacitor manufacturing method capable of manufacturing a capacitor having a low short circuit defect rate and a small leakage current with a small number of chemical oxidation polymerization treatments.

[Brief description of drawings]

FIG. 1 is a structural sectional view of a capacitor manufactured by a manufacturing method according to a first embodiment of the present invention.

FIG. 2 is a completed view of a capacitor manufactured by the manufacturing method according to the first embodiment of the present invention.

FIG. 3 is a structural cross-sectional view of a capacitor manufactured by a manufacturing method according to second and third embodiments of the present invention.

[Explanation of symbols]

 1, 21, 31 Anode lead 2, 32 Anode valve metal 3 Gradient 4 Chamfer length 5, 33 Dielectric film 6, 34 Conductive polymer layer 7, 35 Carbon paint film 8, 36 Silver paint film 9, 22, 37 Cathode lead

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mutsumi Murakami 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (7)

[Claims] 1. A chamfered corner of an anode valve metal that is a solid having at least one corner, and then a dielectric film is formed on the surface of the anode valve metal by anodic oxidation. A method for producing a capacitor, characterized in that a chemical oxidative polymerization conductive polymer layer is laminated on the dielectric film by performing chemical oxidative polymerization using a solution and an oxidant solution. 2. The chamfered surface has an inclination of 40 ° to 50 °.
2. The method for manufacturing a capacitor according to claim 1, wherein the flat surface has a length of 0.2 mm to 1.5 mm. 3. The chamfered surface has a radius of curvature R of 0.05.
The method of manufacturing a capacitor according to claim 1, wherein the curved surface has a diameter of mm to 1 mm. 4. The dielectric film is formed by forming a dielectric film on the surface of an anode valve metal by anodic oxidation, and then performing chemical oxidative polymerization using a solution of a five-membered heterocyclic compound and steam and an oxidant solution. A method of manufacturing a capacitor, which comprises laminating a chemically oxidatively polymerized conductive polymer layer on top. 5. A dielectric film is formed on the surface of an anode valve metal by anodic oxidation, and then the anode valve metal is immersed in a solution of a five-membered heterocyclic compound, after which the anode valve metal and a conductive material are formed. The dielectric film is repaired by immersing the counter electrode in an oxidant solution and applying a voltage between the anode valve metal and the counter electrode using the anode valve material as an anode, and at the same time, the chemical oxidation polymerization on the dielectric film is conducted. A method for manufacturing a capacitor, which comprises laminating conductive polymer layers. 6. The method for producing a capacitor according to claim 1, wherein the five-membered heterocyclic compound is at least one selected from pyrrole, thiophene, and furan. 7. The method of manufacturing a capacitor according to claim 1, wherein the anode valve metal is aluminum or tantalum.