JP2924251B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid electrolytic capacitor having a conductive polymer film as a solid electrolyte and having 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 and larger capacitors. Conventionally, plastic film capacitors, mica capacitors, multilayer ceramic capacitors, and the like have been used as high-frequency capacitors. Other examples include an aluminum dry electrolytic capacitor and an aluminum or tantalum solid electrolytic capacitor. In an aluminum dry-type solid electrolytic capacitor, an etched positive and negative aluminum foil is wound up through a paper separator, and a liquid electrolyte is used.

Further, in the case of aluminum or tantalum solid electrolytic capacitors, the electrolyte is solidified in order to improve the characteristics of the aluminum electrolytic capacitors. To form this solid electrolyte, immerse the anode foil in a manganese nitrate solution,
Decomposes in a high-temperature furnace at around ℃ 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 a high temperature and functional deterioration caused by solidification in a low temperature range, and the capacitor exhibits better frequency characteristics and temperature characteristics than a liquid electrolyte. Aluminum electrolytic capacitors, like tantalum electrolytic capacitors, can achieve a large capacity because an oxide film serving as a dielectric can be made very thin.

Further, in recent years, a solid electrolytic capacitor using an organic semiconductor such as a 7,7,8,8-tetracyanoquinodimethane (TCNQ) salt as a solid electrolyte has been developed (Japanese Patent Laid-Open No. Sho 58-17609). Gazette). Furthermore, 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).

[0005]

As described above, various types of capacitors are used. However, film capacitors and mica capacitors have large shapes because of their large shapes. However, it has disadvantages such as extremely high price and poor temperature characteristics. In addition, since the aluminum electrolytic capacitor is easily damaged by the oxide film, it is necessary to repair the damage by applying an electrolyte between the oxide film and the cathode as needed. For this reason, those using a liquid electrolyte for the electrolyte cause a decrease in capacitance or an increase in loss over time due to electrolyte leakage or ionic conductivity, etc. It has disadvantages such as a large loss.

Next, the solid electrolyte will be described.
The loss in the high frequency range cannot be said to be sufficiently small because the oxide film is damaged by thermal decomposition several times at a high temperature and the specific resistance of manganese dioxide is high. Also, TCN
Solid electrolytic capacitors using organic semiconductors such as Q salt
It shows excellent high-frequency characteristics compared to those using manganese dioxide, but shows ideal characteristics due to the increase in specific resistance when applying organic semiconductors, weak adhesion to anode foil, etc. I can't say.

Further, when a conductive polymer thin film is used as a solid electrolyte, frequency characteristics, temperature characteristics, life characteristics and the like 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, an external electrode is brought into contact with an anode valve metal foil having a dielectric film, and this external electrode is used as an anode. Since the electrolytic polymerization is performed, the dielectric film may be damaged, and there is a problem that the entire apparatus becomes large and the productivity is poor.

[0008]

The method of manufacturing a solid electrolytic capacitor according to the present invention comprises the steps of: providing a manganese oxide layer on an anode valve metal foil having a dielectric film formed on the surface by anodic oxidation; The dielectric film is removed in at least one portion of the metal foil to expose the metal portion, and the conductive portion provided in contact with the metal portion is subjected to electrolytic polymerization using the polymerization as a polymerization initiation portion, and the electrolytic polymerization is performed on the manganese oxide layer. A conductive polymer film is laminated, and thereafter, the conductive portion serving as the polymerization initiation portion is cut and removed, and a dielectric film is formed by anodic oxidation on the anode valve metal foil exposed at the cut surface of the capacitor element. Is what you do. There is no problem in coating another insulator after forming this dielectric. The removal of the conductive portion serving as the polymerization start portion, after the electropolymerized conductive polymer film laminated, or after the carbon paint film laminated,
Alternatively, it may be any one after the silver paint film is laminated.

[0009]

According to the present invention, a manganese oxide layer is provided on an anode valve metal foil on which a dielectric film is formed, as described above.
Electrolytic polymerization is performed using a conductive part provided in contact with the metal part from which the dielectric film has been removed in at least one place on the anode valve metal foil as a polymerization initiation part, and an electrolytically polymerized conductive polymer is formed on the manganese oxide layer. The dielectric layer is formed by anodic oxidation on the anode valve metal foil exposed on the cut surface of the capacitor element by cutting and removing the conductive portion serving as the polymerization start portion after laminating the film, The polymerization reaction is performed stably at the polymerization initiation part, the electropolymerization conductive polymer film layer grows quickly, and after the completion of the electropolymerization, the polymerization initiation part in contact with the anode valve metal foil is cut off and short-circuited. Part is eliminated, and since a dielectric film is formed on the anode valve action metal foil exposed at the cut surface, the withstand voltage is improved, the leakage current can be reduced without a short-circuited portion due to temperature change, and Dress The whole can be improved productivity can be miniaturized.

[0010]

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

(Embodiment 1) FIG. 1 (a) side view, FIG.
(B) The valve action metal foil 2 (aluminum etched foil) shown in the front view was prepared using a 7% ammonium adipate aqueous solution.
Anodization was performed at about 70 ° C. for 40 minutes at an applied voltage of 42 V to form a dielectric film 3 as shown in FIG. 2 (a), a partially crushed side view, and FIG. 2 (b), a front view. Next, an aqueous solution of manganese nitrate was applied and thermally decomposed at 300 ° C. for 20 minutes.
(A) A conductive layer composed of a manganese oxide film 4 was formed as shown in a partially crushed side view and FIG. 3 (b) front view.

Next, as shown in FIG. 4 (a) side view and FIG. 4 (b) front view, the polymerization initiation conductive part 10 (in the embodiment, a nickel foil piece, diameter 1 mm, thickness 50 μm) is manganese oxide by welding. It was set on the material film 4. The polymerization initiation conductive part 10 is shown in FIG. 5 (a cross-sectional view taken along line AA ′ in FIG.
As shown in the figure, the dielectric film 3 penetrates through the manganese oxide film 4 and is in contact with the valve metal foil 2. Pyrrole (0.
25M), triisopropyl naphthalene sulphonate (0.1 M), and an electrolytic polymerization solution composed of water.
A constant voltage of 5 V is applied for 30 minutes, and a conductive polymer film 5 (polypyrrole) for the solid electrolyte is formed on the manganese oxide 4 as shown in FIG. film)
Was formed.

Next, FIG. 7A is a partially broken side view, and FIG.
(B) As shown in the front view, the polymerization initiation conductive portion 10 was bent and removed together with the upper and lower valve action metal foils 2, the dielectric film 3, the manganese oxide film 4, and the conductive polymer film 5. Next, as shown in FIG. 8A, a partially crushed side view, and FIG. 8B, a front view, the valve action metal foil 2 (aluminum etched foil) exposed at the cut surface of this element from which the polymerization initiation portion has been removed ) Using a 7% aqueous solution of ammonium adipate,
Anodize at 0 ° C. for 20 minutes at an applied voltage of 42 V,
A dielectric film 9 was formed. Thereafter, as shown in FIGS. 9 and 10 (each (a) is a partially crushed side view, and (b) is a front view), a carbon paint film 6 and subsequently a silver paint film 7 were formed. Finally, as shown in FIG. 11, the anode lead 1 and the cathode lead 8 were provided and covered with a resin to obtain a solid electrolytic capacitor.

The characteristics of the solid electrolytic capacitor having the dielectric film 3 formed on the valve metal foil 2 exposed at the cut surface according to the present embodiment and the solid electrolytic capacitor without the dielectric film 3 as a comparative example are shown as initial characteristics. , Heat cycle test LC yield characteristics (Table 1) and (Table 2)
Is shown in As is clear from Tables 1 and 2, the solid electrolytic capacitor according to the present embodiment has excellent effects in terms of withstand voltage characteristics and reliability.

[0015]

[Table 1]

[0016]

[Table 2]

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 including at least the polymerization initiation conductive portion is removed. Then, since a dielectric film is formed on the removed cross-section by anodic oxidation, the withstand voltage characteristics and reliability can be improved.

(Example 2) The process up to the formation of the electropolymerized conductive polymer film 5 is the same as in Example 1. That is, after the conductive polymer film 5 is formed as shown in FIG.
(A) A carbon paint film 6 was formed as shown in a partially crushed side view and FIG. 12 (b) front view. Subsequently, FIG.
(A) As shown in the partially crushed side view and FIG. 13 (b) front view, the polymerization initiating conductive part 10 is formed of a valve metal foil 2, a dielectric film 3, a manganese oxide film 4, and a conductive polymer above and below it. Membrane 5,
It was bent and removed together with the carbon paint film 6.

Next, FIG. 14 (a) is a partially crushed side view, and FIG.
4 (b) As shown in the front view, a 7% aqueous solution of ammonium adipate was used on the valve-acting metal foil 2 (aluminum-etched foil) exposed at the cut surface where the polymerization initiation portion of the element was removed. , About 70 ° C, 20 minutes, applied voltage 42V
Anodizing was performed under the conditions described above to form a dielectric film 9. Thereafter, a silver paint film 7 was formed as shown in FIG. 15 (a), a partially crushed side view, and FIG. 15 (b), a front view. Finally, FIG.
As shown in FIG. 2, an anode lead 1 and a cathode lead 8 were provided and covered with a resin to obtain a solid electrolytic capacitor.

With respect to the solid electrolytic capacitor of this embodiment, the initial characteristics and the heat cycle test LC yield characteristics are shown in (Table 1) and (Table 2), respectively. As is clear from Tables 1 and 2, the solid electrolytic capacitor according to the present embodiment has excellent effects in terms of withstand voltage characteristics and reliability as in the first embodiment.

Example 3 The procedure up to the formation of the electropolymerized conductive polymer film 5 is the same as that of Example 1. After the formation of the conductive polymer film 5 as shown in FIG. 6, FIG.
As shown in the partially crushed side view and FIG. 17 (b) front view, the carbon paint film 6 is formed, and then as shown in FIG. 18 (a) partially crushed side view and FIG. 18 (b) front view. A silver paint film 7 was formed. Subsequently, as shown in FIG. 19A, a partially crushed side view, and FIG. 19B, a front view, the polymerization initiating conductive part 10 is provided with a valve metal foil 2, a dielectric film 3, a manganese oxide film 4 above and below it. And the conductive polymer film 5, the carbon paint film 6, and the silver paint film 7 were bent and removed. Next, as shown in FIG. 20 (a) a partially crushed side view and FIG. 20 (b) front view, the valve action metal foil 2 (aluminum etched foil) exposed at the cut surface of the element from which the polymerization initiation portion has been removed is shown. ) Was anodized using a 7% aqueous solution of ammonium adipate at about 70 ° C. for 20 minutes at an applied voltage of 42 V to form a dielectric film 9. Finally, as shown in FIG. 21, the anode lead 1 and the cathode lead 8 were provided, and were packaged with resin to obtain a solid electrolytic capacitor.

With respect to the solid electrolytic capacitor according to this embodiment, the initial characteristics and the LC yield characteristics of the heat cycle test are shown in (Table 1) and (Table 2), respectively. As is clear from Tables 1 and 2, the solid electrolytic capacitor according to the present embodiment has excellent effects in terms of withstand voltage characteristics and reliability as in the first embodiment.

In the above embodiment, only the case where manganese oxide was formed using manganese nitrate was described. However, the present invention is not limited to manganese nitrate, and any other material capable of forming manganese oxide can be used. is there. In the above embodiment, the nickel foil was welded to the anode and brought into contact with the anode to be used for the polymerization initiation part. However, the conductive member is not limited to nickel, and any other conductive material that is not anodized may be used. Also, the contact method is not limited to welding, and other methods such as caulking can be used.

[0024]

As described above, according to the present invention, after a manganese oxide layer is formed on a dielectric film, a conductive portion which is not anodized is brought into contact with an anode metal foil to provide a polymerization initiation portion to perform electrolytic polymerization. By laminating an electropolymerized conductive polymer film on the manganese oxide layer by cutting and then removing the polymerization initiation portion, by anodic oxidation on the anode valve metal foil exposed at the cut surface of the capacitor element By the method of forming the dielectric film, it is possible to form the electropolymerized conductive polymer film stably and faster than the polymerization start part, and to form the dielectric film on the cut surface after removing the polymerization start part, so that the pressure resistance characteristics And the reliability of the solid electrolytic capacitor with reduced leakage current can be suppressed, and a solid electrolytic capacitor with low leakage current can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 shows a valve metal (aluminum etched foil) used in a method for manufacturing a solid electrolytic capacitor according to a first embodiment of the present invention.

FIG. 2 is a process chart of forming a dielectric film on a valve metal in the embodiment.

FIG. 3 is a process chart of forming a manganese oxide film on a dielectric film in the example.

FIG. 4 is a process diagram of forming a polymerization initiation conductive part on a manganese oxide film in the same example.

FIG. 5 is a sectional view showing a contact state of a polymerization initiation conductive portion in the example.

FIG. 6 is a process chart of forming a conductive polymer film on a manganese oxide film in the example.

FIG. 7 is a process diagram in which the polymerization initiation conductive portion is removed in the same example.

FIG. 8 is a process diagram in which a dielectric film is formed on the valve action metal foil exposed at the cut surface in the same example.

FIG. 9 is a process chart of forming a carbon paint film on a conductive polymer film in the example.

FIG. 10 is a process chart of forming a silver paint film on a carbon paint film in the example.

FIG. 11 is a plan view of the capacitor manufactured in the same example.

FIG. 12 is a process diagram showing a method for manufacturing a solid electrolytic capacitor according to a second embodiment of the present invention, in which a carbon paint film is formed on a conductive polymer film.

FIG. 13 is a process diagram in which the polymerization initiation conductive portion is removed in the same example.

FIG. 14 is a process chart of forming a dielectric film on the valve action metal foil exposed at the cut surface in the example.

FIG. 15 is a process chart of forming a silver paint film on a carbon paint film in the example.

FIG. 16 is a plan view of the capacitor manufactured in the same example.

FIG. 17 is a process diagram showing a method of manufacturing a solid electrolytic capacitor according to a third embodiment of the present invention, in which a carbon paint film is formed on a conductive polymer film.

FIG. 18 is a process chart of forming a silver paint film on a carbon paint film in the example.

FIG. 19 is a process diagram in which the polymerization initiation conductive portion is removed in the same example.

FIG. 20 is a process chart of forming a dielectric film on the valve action metal foil exposed at the cut surface in the example.

FIG. 21 is a plan view of the capacitor manufactured in the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode lead 2 Valve action metal foil 3 Dielectric film 4 Manganese oxide film 5 Electropolymerized conductive polymer film 6 Carbon paint film 7 Silver paint film 8 Cathode lead 9 Dielectric film 10 Polymerization start conductive part

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshinari Nanai 3-1-1 Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture Matsushita Giken Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) H01G 9/02 H01G 9/24

Claims (3)

(57) [Claims] A manganese oxide layer is formed on an anode valve metal foil having a dielectric film formed on the surface by anodic oxidation, and then the dielectric film is removed at least at one portion of the anode valve metal foil. The metal part is exposed, and the conductive part provided in contact with the exposed metal part is subjected to electrolytic polymerization as a polymerization initiation part, and after the electrolytic polymerization conductive polymer film is laminated on the manganese oxide layer, A method for producing a solid electrolytic capacitor, comprising cutting off a polymerization initiation portion and forming a dielectric film by anodic oxidation on an anode valve metal foil exposed on the cut surface. 2. The solid electrolytic capacitor according to claim 1, 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. Production method. 3. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the anode valve metal is one selected from aluminum or tantalum.