JPH04307917A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To materialize a solid electrolytic capacitor which is low in short circuiting defective and is excellent in LC(leaked current) property, concerning the manufacture of the small-sized but large capacity of soild electrolytic capacitor wherein a conductive polymer is used as a solid electrolyte and which is excellent in frequency characteristic. CONSTITUTION:An electrolytically polymerized conductive polymer film 5 is formed all over the surface of a valve metal, with the metal as the starting part of growth, by welding the metal to the valve metal which has an oxide film and a manganese oxide layer 4, and performing electrolytic polymerization in the solution consisting of a pyrrole or its derivative and a supporting electrolyte. Then, the section which includes at least the welded metal is removed by nonshearing method so as to complete a capacitor element, and since the conductive layer, which constitutes a cathode, such as said electrolytically polymerized conductive polymer film 5, a carbon paint film 6, a silver paint film 7, etc., never contacts directly with an anode valve metallic foil being in the insulated condition through a dielectric film 3, a solid electrolytic capacitor, where there is no short circuiting inferiority and a leak current is small, can be gotten.

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 uses a conductive polymer membrane as a solid electrolyte and has low leakage current characteristics and excellent productivity.

0002

2. Description of the Related Art Recently, with the digitization of electrical equipment, the capacitors used therein have low impedance in the high frequency range, and there is an increasing demand for smaller capacitors with larger capacitance. Conventionally, plastic film capacitors, mica capacitors, multilayer ceramic capacitors, etc. have been used as high frequency capacitors.

Other types include aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. In aluminum dry type solid electrolytic capacitors, etched anode and cathode aluminum foils are wound up with a paper separator in between, and a liquid electrolyte is used.

In aluminum or tantalum solid electrolytic capacitors, the electrolyte is solidified in order to improve the characteristics of the aluminum electrolytic capacitor. To form this solid electrolyte, an anode foil is immersed in a manganese nitrate solution and thermally decomposed in a high temperature furnace at around 350°C to form a manganese dioxide layer. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as volatilization of the electrolyte at high temperatures or functional deterioration caused by solidification at low temperatures, and it exhibits better frequency and temperature characteristics than liquid electrolytes. Aluminum electrolytic capacitors, like tantalum electrolytic capacitors, can achieve large capacitance because the oxide film that serves as the dielectric can be made very thin.

Furthermore, in recent years, solid electrolytic capacitors using organic semiconductors such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) salts as solid electrolytes have been developed (Japanese Patent Application Laid-open No. 17609/1983). Public bulletin). Also pyrrole,
There is also a method of electrolytically polymerizing a polymerizable monomer such as furan to form a conductive polymer and using this as a solid electrolyte (Japanese Unexamined Patent Publication No. 60-244017).

[0006]

[Problems to be Solved by the Invention] Various types of capacitors are used in this way, but film capacitors and mica capacitors have a large shape, making it difficult to increase the capacity, and multilayer ceramic capacitors have a small size and large capacity. However, it has disadvantages such as extremely high price and poor temperature characteristics. Furthermore, since the oxide film of aluminum electrolytic capacitors is easily damaged, it is necessary to apply an electrolyte between the oxide film and the cathode to repair the damage as needed. For this reason, products that use liquid electrolytes tend to suffer from a decrease in capacitance and an increase in loss over time due to electrolyte leakage and ionic conductivity, as well as high frequency characteristics and low temperature range. It has drawbacks such as large losses.

Next, regarding solid electrolytes,
The loss in the high frequency range cannot be said to be sufficiently small because of the damage to the oxide film caused by thermal decomposition several times at high temperatures and the high resistivity of manganese dioxide. Also, TCN
Solid electrolytic capacitors using organic semiconductors such as Q salt are
It shows superior high frequency characteristics compared to those using manganese dioxide, but due to the increase in specific resistance when applying the organic semiconductor and weak adhesion to the anode foil, it may not show ideal characteristics. I can't say that.

Furthermore, when a conductive polymer thin film is used as a solid electrolyte, frequency characteristics, temperature characteristics, life characteristics, etc. are excellent. However, in this solid electrolytic capacitor, in order to form a conductive polymer thin film as a solid electrolyte on the anode valve metal, a polymerization-initiating conductive part is provided on the anode valve metal foil having a dielectric film, and this polymerization-initiating conductive part In order to carry out electrolytic polymerization using the material as an anode, stack a conductive polymer film, and then shear and remove the part containing at least the conductive part that became the polymerization initiation part.
When a conductive layer such as an electropolymerized conductive polymer film, a carbon paint film, or a silver paint film is sheared, the shear or cross-sectional chips easily come into direct contact with the insulating anode valve metal foil through the dielectric film. However, the problem is that solid electrolytic capacitors with large leakage current are easily formed.

[0009]

[Means for Solving the Problems] A method for manufacturing a solid electrolytic capacitor according to the present invention includes providing a manganese oxide layer on an anode valve metal foil on which a dielectric film is formed on the surface by anodizing, and then forming a manganese oxide layer on the anode valve metal foil. The dielectric film is removed from at least one part of the metal foil to expose the metal part, electrolytic polymerization is performed using the conductive part provided in contact with the metal part as a polymerization initiation site, and electrolytic polymerization is performed on the manganese oxide layer. A polymerized conductive polymer film is laminated, and then a portion including at least a conductive portion that has become the polymerization initiation portion is removed by a non-shearing method. The conductive portion that has become the polymerization initiation portion can be removed after lamination of the electropolymerized conductive polymer film, after lamination of the carbon paint film, or after lamination of the silver paint film.

0010

[Operation] According to the present invention, as described above, after a manganese oxide layer is provided on the anode valve metal foil on which a dielectric film is formed,
The dielectric film is removed from at least one location on the anode valve metal foil, and electrolytic polymerization is performed using a conductive portion provided in contact with the exposed metal portion as a polymerization initiation site, and electrolytic polymerization is performed on the manganese oxide layer. Conductive polymer films are laminated, and then the part containing at least the conductive part that has become the polymerization initiation part is removed by a non-shear removal method. The conductive layer does not come into direct contact with the insulated anode valve metal foil via the dielectric film, and a solid electrolytic capacitor with low leakage current can be obtained.

[0011]

Embodiments (Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are manufacturing process diagrams in this embodiment. Valve metal foil 2 (aluminum etched foil) is anodized using a 7% ammonium adipate aqueous solution at approximately 70°C for 40 minutes with an applied voltage of 42V to form dielectric film 3, and then nitric acid A manganese aqueous solution is applied and thermally decomposed at 300°C for 20 minutes to form a conductive layer consisting of a manganese oxide film 4, and then a polymerization initiation conductive part 10 (a piece of nickel foil in the example, 1 mm in diameter,
(thickness: 50 μm) was placed on the manganese oxide film 4 by welding. Valve metal foil is immersed in an electrolytic polymerization solution consisting of pyrrole (0.25M), triisopropylnaphthalene sulfonate (0.1M), and water, and a nickel foil piece is used as the polymerization initiation conductive part 10, and a constant voltage of 2.5V is applied. was applied for 30 minutes to form a conductive polymer film 5 (polypyrrole film) for solid electrolyte on the manganese oxide 4, as shown in FIG. 1(a), a partially crushed side view, and FIG. 1(b), a front view. did.

Subsequently, as shown in FIG. 2(a) a side view and FIG. 2(b) a front view, nitrogen gas was pressurized to 3 kgf/cm2 to a portion containing at least the polymerization initiation conductive portion 10 to a diameter of 1 mm.
The film was applied at high speed through a nozzle, and the film was bent and removed together with the valve metal foil 2, dielectric film 3, manganese oxide film 4, and conductive polymer film 5 above and below.

Next, as shown in the partially fragmented side view of FIG. 3 and the front view of FIG.
Subsequently, a silver paint film 7 was formed, and finally, as shown in FIG. 4, an anode lead 1 and a cathode lead 8 were provided and covered with resin to obtain a solid electrolytic capacitor.

Table 1 shows the characteristics of a solid electrolytic capacitor obtained by bending and removing the portion containing at least the conductive portion that became the polymerization initiation portion according to this example, and the initial characteristics of a solid electrolytic capacitor removed by shearing as a comparative example. It is shown in As is clear from these (Table 1), the solid electrolytic capacitor according to the present example has excellent effects in that the short-circuit failure rate is low and the leakage current is small.

[0016]

[Table 1]

As described above, according to this embodiment, after the polymerization initiation conductive portion is provided on the anode foil and the conductive polymer film is formed on the anode foil, the portion containing at least the polymerization initiation conductive portion is bent. Since the leakage current is removed by removing the leakage current, there is no short-circuit failure and low leakage current can be realized. In this example, the polymerization initiation site was removed using nitrogen gas at high speed, but it is also possible to remove the polymerization initiation site using other gases such as argon or air if the speed is increased.
It is also possible to use liquids such as water and alcohol if the speed is increased.

(Example 2) Valve metal foil 2 (aluminum etched foil) was anodized using a 7% ammonium adipate aqueous solution at about 70° C. for 40 minutes at an applied voltage of 42 V to form dielectric film 3. Next, a manganese nitrate aqueous solution is applied and thermally decomposed at 300° C. for 20 minutes to form a conductive layer consisting of the manganese oxide film 4. Next, a conductive layer 4 consisting of a polymerization initiation conductive portion 10 (in the example, a piece of nickel foil) is formed. , diameter 1mm
, 50 μm thick) was placed on the manganese oxide film 4 by welding. Valve metal foil is immersed in an electrolytic polymerization solution consisting of pyrrole (0.25M), triisopropylnaphthalene sulfonate (0.1M), and water, and a nickel foil piece is used as the polymerization initiation conductive part 10, and a constant voltage of 2.5V is applied. was applied for 30 minutes to form a conductive polymer film 5 (polypyrrole film) for solid electrolyte on the manganese oxide 4. Subsequently, after forming a carbon paint film 6 and then a silver paint film 7, nitrogen gas is applied to a portion including at least the polymerization initiation conductive portion 10.
The pressure is applied to kgf/cm2 through a nozzle with a diameter of 1 mm at high speed, and the valve metal foil 2 and dielectric film 3 above and below are applied.
, the manganese oxide film 4, the conductive polymer film 5, the carbon paint film 6, and the silver paint film 7 were bent and removed. Next, an anode lead 1 and a cathode lead 8 were provided and covered with resin to obtain a solid electrolytic capacitor.

The initial characteristics of the solid electrolytic capacitor according to this example are shown in Table 1. As is clear from these (Table 1), the solid electrolytic capacitor according to the present example, in which the polymerization initiation conductive part is removed after the formation of the silver paint film, has a low short-circuit failure rate and a small leakage current as in the first example. Excellent effects can be obtained in this respect.

[0020] In the above example, only the case where manganese oxide was formed using manganese nitrate was described, but other materials can be used as long as they can form manganese oxide, not limited to manganese nitrate. be. Further, in the above embodiment, it was described that nickel foil was welded and brought into contact with the anode and used as the polymerization initiation part, but it is not limited to nickel, and other conductive materials that are not anodized can also be used.

[0021] The contact method is not limited to welding, but other methods such as caulking can also be used. Further, in the above embodiment, only the method of bending and removing using high-speed gas or the like was described, but it is also possible to remove by pulling.

[0022]

[Effects of the Invention] As described above, in the present invention, after a manganese oxide layer is formed on a dielectric film, a conductive part that is not anodized is brought into contact with an anode metal foil to provide a polymerization initiation part and conduct electrolytic polymerization. This is a method for producing a solid electrolytic capacitor, in which an electrolytically polymerized conductive polymer film is laminated on the manganese oxide layer, and then a portion including at least the conductive portion that has become the polymerization initiation portion is removed by a non-shearing method. , the electropolymerized conductive polymer film, carbon paint film, or silver paint film does not come into direct contact with the insulated anode valve metal foil through the dielectric film, resulting in a solid electrolytic capacitor with no short circuit defects and low leakage current. can be produced efficiently.

[Brief explanation of drawings]

FIG. 1: A dielectric film, a valve metal foil, and a dielectric film,
Process diagram for forming manganese oxide film, polymerization initiation conductive part, and conductive polymer film

[Figure 2] Process diagram with the polymerization initiation conductive part removed in the same example

[Figure 3] Process diagram of forming a carbon paint film and a silver paint film on a conductive polymer film in the same example

[Fig. 4] Plan view of the solid electrolytic capacitor manufactured in the same example.

[Explanation of symbols]

1 Anode lead 2 Valve action metal foil 3 Dielectric film 4 Manganese oxide film 5 Electropolymerized conductive polymer membrane 6 Carbon paint film 7 Silver paint film 8 Cathode lead 10 Polymerization initiation conductive part

Claims (4)

[Claims] 1. After forming a manganese oxide layer on an anode valve metal foil on which a dielectric film has been formed on the surface by anodizing, the dielectric film is removed at at least one location on the anode valve metal foil. After exposing the metal part and performing electrolytic polymerization using the conductive part provided in contact with the exposed metal part as a polymerization initiation part, and laminating an electrolytically polymerized conductive polymer film on the manganese oxide layer. A method for manufacturing a solid electrolytic capacitor, characterized in that the portion containing at least the polymerization initiation portion is removed by a non-shearing method. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the non-shearing removal method is at least one of bending cutting and tension cutting. 3. The solid electrolyte according to claim 1 or 2, wherein the electropolymerized conductive polymer film is formed in a solution containing at least one of pyrrole, thiophene, or a derivative thereof and a supporting electrolyte. Method of manufacturing capacitors. 4. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the anode valve metal is one selected from aluminum and tantalum.