JP4858667B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

【発明の効果】
以上説明したように、本発明によれば、固体電解コンデンサにおけるポリ３，４-エチレンジオキシチオフェンと反応残留物との総量を、ある特定の量、すなわち０．２５〜０．７ｍｇ/ｍｍ^２とすることにより、誘電体酸化皮膜層の再化成性が顕著に向上した固体電解コンデンサを製造することが可能となった。
【図面の簡単な説明】
【図１】本発明で用いる平板型コンデンサ素子の分解斜視図である。
【図２】本発明で用いる巻回型コンデンサ素子の分解斜視図である。
【符号の説明】
１ 陽極電極箔
２ 陰極電極箔
３ セパレータ
４，５ リード線
６ コンデンサ素子[0001]
[Industrial application fields]
The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and more particularly to a solid electrolytic capacitor that has been improved to improve the repairability of a defective portion of a dielectric oxide film layer and a method for manufacturing the same.
[0002]
[Prior art]
An electrolytic capacitor has a structure in which an oxide film layer serving as a dielectric is formed on the surface of an anode electrode having fine holes and etching pits made of a valve metal such as tantalum and aluminum, and the electrode is drawn from the oxide film layer. Become.
[0003]
And extraction of the electrode from an oxide film layer is performed by the electrolyte layer which has electroconductivity. Therefore, in the electrolytic capacitor, the electrolyte layer serves as a true cathode. For example, in an aluminum electrolytic capacitor, a liquid electrolyte is used as a true electrode, and a cathode electrode is merely responsible for electrical connection between the liquid electrolyte layer and an external terminal.
[0004]
The electrolyte layer that functions as a true cathode is required to have adhesiveness, denseness, and uniformity with the oxide film layer. In particular, the adhesion within the fine holes of the anode electrode and the etching pits has a great influence on the electrical characteristics, and a number of electrolyte layers have been proposed in the past.
[0005]
Solid electrolytic capacitors use conductive solid electrolytes instead of liquid electrolyte layers. Among them, manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes are known. However, there were problems with the electrical characteristics and heat resistance of the product.
[0006]
In order to solve the disadvantages of the manganese dioxide and the TCNQ complex, it has been attempted to use a conductive polymer typified by polypyrrole as a solid electrolyte layer. However, when these conductive polymers are produced by a chemical polymerization method, it is difficult to densely produce a strong coating layer, and when produced by an electrolytic polymerization method, the production process becomes complicated. In many cases, it was very difficult to continuously produce a conductive polymer film having a uniform thickness.
[0007]
Accordingly, the present inventors focused on polyethylene dioxythiophene having a slow reaction rate and excellent adhesion to the oxide film layer of the anode electrode (Japanese Patent Laid-Open No. 2-15611), and the anode electrode foil and the cathode electrode A capacitor element in which a foil is wound through a separator is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent, and then poly 3,4-ethylene which is a solid electrolyte by a chemical polymerization reaction that proceeds slowly thereafter. An application was filed for an invention characterized in that dioxythiophene was produced inside a capacitor element (Japanese Patent Application No. 8-131374).
[0008]
Further, the applicants of the present invention are characterized in that poly 3,4-ethylenedioxythiophene is generated inside a flat-plate type capacitor element, and is a solid having excellent high-frequency characteristics, high withstand voltage, and high capacity. An invention for an electrolytic capacitor was filed (Japanese Patent Application No. 2000-251702).
[0009]
[Problems to be solved by the invention]
However, compared with electrolytic capacitors using an electrolytic solution, solid electrolytic capacitors are generally inferior in repairability of defects in the dielectric oxide film layer, that is, re-formability. There was room for further study on re-chemical conversion.
[0010]
An object of the present invention is to provide a solid electrolytic capacitor excellent in re-formability and a method for producing the same.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have intensively studied a solid electrolytic capacitor excellent in re-formability and a manufacturing method thereof, and as a result, completed the present invention.
[0012]
That is, the present inventors have disclosed a 3,4-ethylenedioxythio in a solid electrolytic capacitor comprising a cathode electrode foil, an anode electrode foil having a dielectric oxide film layer formed on the surface thereof, and a separator holding a solid electrolyte. the solid electrolytic capacitor total and Fe ting oxidant poly 3,4-ethylenedioxythiophene formed by thermal polymerization followed impregnated in the separator and the reaction residue is 0.25~0.7mg / mm ² The above object was achieved.
[0013]
This solid electrolytic capacitor has a capacitor element composed of a cathode electrode foil, an anode electrode foil having a dielectric oxide film layer formed on the surface thereof, and a separator for holding a solid electrolyte, and 3,4-ethylenedioxythiophene and In a method for producing a solid electrolytic capacitor in which an oxidant is impregnated and then heat polymerization is performed, the total amount of poly 3,4-ethylenedioxythiophene formed by heat polymerization and the reaction residue is 0.25 to 0. It can be produced by a method for producing a solid electrolytic capacitor, characterized in that the amount is 7 mg / mm ² .
[0014]
In the above method for producing a solid electrolytic capacitor, the total amount of poly 3,4-ethylenedioxythiophene formed by heat polymerization and the reaction residue is 0.25 to 0.7 mg / mm by tightening at the time of heat polymerization. ² is also acceptable.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be specifically described. The solid electrolytic capacitor of the present invention is obtained by the steps of roughening the surface of the bipolar foil → chemical conversion treatment of the anode electrode foil → capacitor element formation → impregnation with 3,4-ethylenedioxythiophene and an oxidant → polymerization → reformation → drying. The product is manufactured and sealed after insertion into the outer case.
[0016]
Here, the anode electrode foil may be any valve metal such as aluminum or tantalum, but usually aluminum is used. A large number of etching pits are formed on the surface of the anode electrode foil by, for example, electrochemical etching treatment (roughening) in an aqueous chloride solution, and then a voltage is applied in an aqueous solution such as ammonium borate. Then, an oxide film layer serving as a dielectric is formed (chemical conversion treatment).
[0017]
The cathode electrode foil may be any material that electrically connects the lead wire and the electrolyte layer, and aluminum is used in one embodiment of the present invention. Note that the surface of the cathode electrode foil is also subjected to etching treatment and chemical conversion treatment. Furthermore, in order to increase the capacitance, a titanium nitride film may be formed on the surface of the cathode electrode foil.
[0018]
Note that lead wires for connecting the respective electrodes to the outside are connected to the anode electrode foil and the cathode electrode foil by known means such as stitching or ultrasonic welding. The lead wire is made of aluminum or the like, and includes a connection portion with the anode electrode foil or the cathode electrode foil and an external connection portion that is responsible for electrical connection with the outside, and is led out from the end portion of the capacitor element.
[0019]
Note that the anode electrode foil and the cathode electrode foil are subjected to repair formation in the chemical liquid after the processing in order to repair the damaged portion of the film and the cut surface received in the processing stage.
[0020]
As the separator, a glass separator is usually used, but as another embodiment, other electrolytic paper used for a normal electrolytic capacitor can be used. That is, synthetic fibers, those obtained by mixing these, and nonwoven fabrics obtained by mixing synthetic fibers and fibers for electrolytic paper or glass fibers can be used. Examples of the synthetic fiber include vinylon fiber, polyester fiber, nylon fiber, and rayon fiber. Furthermore, a porous separator made of synthetic resin can be used. Examples of these synthetic resins include polyamide, polyimide, and aramid. The separator is 10 to 3000 [mu] m, preferably 20 to 1500 [mu] m thick. When the total amount of poly3,4-ethylenedioxythiophene and reaction residue is adjusted to an optimum amount, a thickness within this range may be used.
[0021]
The dimensions of the cathode electrode foil and the anode electrode foil may be such that 3,4-ethylenedioxythiophene and the oxidizing agent penetrate into the center of the capacitor element. Further, the anode electrode foil may be sandwiched between the cathode electrode foils, or may be rolled up, and is arbitrarily selected according to the specifications of the solid electrolytic capacitor to be manufactured. A separator having a slightly larger width than the cathode electrode foil may be used depending on the dimensions of the cathode electrode foil and the anode electrode foil.
[0022]
Next, the anode electrode foil and the cathode electrode foil that have been subjected to the above treatment are laminated via a separator as shown in FIG. 1 to form a capacitor element. The shape of the solid electrolytic capacitor element of the present invention is not limited to the flat plate type as shown in FIG. 1, but may be a winding type as shown in FIG. In this case, the anode electrode foil and the cathode electrode foil are wound through a separator as shown in FIG. 2 to form a capacitor element.
[0023]
Then, by impregnating these capacitor elements with 3,4-ethylenedioxythiophene and an oxidizing agent, 3,4-ethylenedioxythiophene and the oxidizing agent penetrate into the capacitor elements, and the subsequent chemical polymerization reaction Thus, poly 3,4-ethylenedioxythiophene is produced while being held by the separator inside the capacitor element.
[0024]
3,4-ethylenedioxythiophene can be obtained by a known production method disclosed in JP-A-2-15611.
[0025]
As the oxidizing agent, a solution obtained by dissolving ferric p-toluenesulfonate, which is an iron salt of aromatic sulfonic acid, in a butanol solvent is used. As the oxidant solvent, a common organic solvent such as alcohols such as ethanol and butanol can be used.
[0026]
As a method of impregnating the capacitor element with 3,4-ethylenedioxythiophene and an oxidizing agent, not only a method of immersing the capacitor element in a liquid in which 3,4-ethylenedioxythiophene and an oxidizing agent are mixed in advance, but also other methods. As an embodiment, a method of immersing a capacitor element immersed in 3,4-ethylenedioxythiophene in an oxidizing agent, or a method of immersing a capacitor element immersed in an oxidizing agent in 3,4-ethylenedioxythiophene, Furthermore, a method of replacing the dipping operation with the discharge of the solution from the syringe is also possible.
[0027]
The heating condition during the polymerization reaction is preferably 20 to 180 ° C. When the polymerization temperature is less than 20 ° C., the production of poly3,4-ethylenedioxythiophene does not proceed well. On the other hand, a temperature higher than 180 ° C. is not preferable because decomposition of 3,4-ethylenedioxythiophene occurs.
[0028]
In addition, as a method for adjusting the total amount of poly 3,4-ethylenedioxythiophene and reaction residue to an optimum amount, an oxidizing agent and 3,4-ethylenedioxy can be used by impregnation under reduced pressure or impregnation by quantitative discharge during impregnation Adjust the amount of thiophene by adjusting the amount of thiophene impregnation or applying pressure, such as pressurization (clamping) for flat plate type or pressure for winding type for winding type capacitors during polymerization reaction. be able to.
[0029]
Under the above polymerization conditions, a solid electrolyte layer is obtained by allowing the polymerization reaction to proceed for 30 minutes or more. The reaction time of this polymerization reaction is preferably 30 minutes or longer so that the polymerization reaction can be completed completely.
[0030]
After the formation of the solid electrolyte layer by the polymerization reaction, re-chemical conversion is performed under high-humidity conditions at room temperature or higher in order to repair the dielectric oxide film layer. In re-forming, the temperature condition is 40 ° C. or higher, particularly 50 to 120 ° C., more preferably 60 to 90 ° C. If it is less than 40 ° C., the re-forming voltage does not increase, and the re-forming process cannot be performed. The humidity condition is preferably 20 to 60% RH. If the humidity is less than 20% RH, the water necessary for re-forming is insufficient and the voltage does not rise stably. If it exceeds 60% RH, the water will be excessive and the voltage will not rise stably.
[0031]
The total amount of poly 3,4-ethylenedioxythiophene formed and the reaction residue during the re-chemical conversion treatment is preferably 0.25 to 0.7 mg / mm ² , more preferably 0.3 to 0.6 mg / mm ^2. a mm ^2. That is, when the total amount of poly 3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitor is the appropriate amount described above, a rapid and stable increase in the re-forming voltage occurs, and as a result, The chemical conversion treatment proceeds well in a short time.
[0032]
After the re-chemical conversion treatment, a voltage is applied as a water removal step. This suppresses gas generation and swelling of the capacitor due to deterioration of the electrode foil due to residual moisture. As another embodiment of removing moisture, it is possible to leave it under high temperature and low humidity conditions.
[0033]
According to the above-described embodiment, a solid electrolytic capacitor excellent in repairability of a defective portion of the dielectric oxide film layer, that is, re-formability can be obtained.
[0034]
【Example】
Next, although the manufacturing method of the solid electrolytic capacitor in this invention and the solid electrolytic capacitor obtained by the method are concretely demonstrated using drawing based on an Example, this invention is limited to these Examples. is not.
[0035]
[Example 1]
FIG. 1 is an exploded perspective view of an element of a flat plate type solid electrolytic capacitor of the present invention. The anode electrode foil 1 is made of an aluminum foil having a vertical dimension of 30 mm and a horizontal dimension of 40 mm, and is subjected to etching treatment and chemical conversion treatment to form an oxide film layer made of aluminum oxide on the surface thereof. Next, the cathode electrode foil 2 is made of an aluminum foil having a vertical dimension of 30 mm and a horizontal dimension of 85 mm, and after performing etching treatment and chemical conversion treatment, a titanium nitride film is formed on the surface by a cathode arc plasma deposition method. . In order to repair the damaged part of the electrode foil and the cut surface of the electrode foil received in the processing stage, by performing restoration conversion in an aqueous ammonium phosphate solution, an oxide film is formed again, and further boric acid is added to stabilize the oxide film. It was dried after being immersed in an aqueous solution. A glass separator 3 having a thickness of 300 μm, a vertical dimension of 35 mm, and a horizontal dimension of 90 mm is stacked on the cathode electrode foil 2 and laminated so as to sandwich the anode electrode 1 with the separator 3 interposed therebetween to obtain a capacitor element 6. . Lead wires 4 and 5 are electrically connected in advance to the anode electrode foil 1 and the cathode electrode foil 2 of the capacitor element 6, respectively, and protrude from the end of the capacitor element 6.
[0036]
The capacitor element 6 having the above configuration was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent. As the oxidizing agent, ferric p-toluenesulfonate dissolved in butanol was used to prepare a mixed solution thereof. The impregnation was performed by a method in which the capacitor element 6 was immersed in an impregnation tank in which a certain amount of the mixed solution was stored. Next, the capacitor element 6 impregnated with the mixed solution is pulled up from the impregnation tank, and in a pressurized (tightened) state, the polymerization reaction is proceeded for 2 hours under heating at 60 ° C. and for another 2 hours under heating at 150 ° C. A combined body was produced, and the total amount of poly 3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitor was 0.84 g, converted to electrode area, and was 0.47 mg / mm ² .
[0037]
Furthermore, re-chemical conversion was performed by applying a voltage under a current condition of 400 μA under the conditions of 90 ° C. and 20% RH. Following this re-chemical conversion treatment, after applying the voltage and removing the moisture in the solid electrolyte, the solid electrolytic capacitor is inserted into a bag formed of a laminate sheet with the lead wires protruding out of the bag. A series of manufacturing steps was completed through a process of sealing and sealing the opening by thermocompression bonding by melting polypropylene. The solid electrolytic capacitor of the present invention was prepared from the above manufacturing process, and this capacitor was referred to as Example 1.
[0038]
[Example 2]
In the solid electrolytic capacitor as described in Example 1, the total amount of the reaction residues and poly 3,4-ethylenedioxythiophene in the solid electrolytic capacitor to create an electrolytic capacitor to be 0.69 mg / mm ^2, Example 2 It was.
[0039]
[Example 3]
In the solid electrolytic capacitor described in Example 1, an electrolytic capacitor in which the total amount of poly3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitor was 0.38 mg / mm ² was prepared, and Example 3 It was.
[0040]
[Example 4]
In the solid electrolytic capacitor described in Example 1, an electrolytic capacitor was prepared in which the total amount of poly3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitor was 0.28 mg / mm ^2. It was.
[0041]
[Comparative Example 1]
In the solid electrolytic capacitor described in Example 1, an electrolytic capacitor was prepared in which the total amount of poly 3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitor was 0.75 mg / mm ^2. It was.
[0042]
[Comparative Example 2]
In the solid electrolytic capacitor as described in Example 1, the total amount of the reaction residues and poly 3,4-ethylenedioxythiophene in the solid electrolytic capacitor to create an electrolytic capacitor to be 0.23 mg / mm ^2, Comparative Example 2 It was.
[0043]
[Test Example 1]
The total amount of poly 3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitors prepared in Example 1, Example 2, Example 3, Example 4, Comparative Example 1 and Comparative Example 2, The relationship between the time required for re-formation with a current of 400 μA, that is, the time until the voltage reaches 33 V was confirmed. The results are shown in Table 1.
[0044]
In Example 1, the voltage suddenly and stably increased, and the voltage reached 33 V in about 30 seconds. In Example 2, Example 3, and Example 4, it was also confirmed that the voltage increased stably, and the voltage reached 33 V in 30 minutes, 15 minutes, and 25 minutes, respectively. On the other hand, in Comparative Examples 1 and 2, a short circuit occurred during the voltage increase, and the product could not be produced.
[0045]
[Table 1]

【Effect of the invention】
As described above, according to the present invention, the total amount of poly 3,4-ethylenedioxythiophene and reaction residue in the solid electrolytic capacitor is set to a specific amount, that is, 0.25 to 0.7 mg / mm ^2. By doing so, it became possible to manufacture a solid electrolytic capacitor in which the re-formability of the dielectric oxide film layer was remarkably improved.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a flat capacitor element used in the present invention.
FIG. 2 is an exploded perspective view of a wound capacitor element used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Anode electrode foil 2 Cathode electrode foil 3 Separator 4,5 Lead wire 6 Capacitor element

Claims (3)

Separator and cathode foil, and the anode foil having a dielectric oxide layer on the surface, in the solid electrolytic capacitor comprising a separator which holds the solid electrolyte, and a 3,4-ethylenedioxy thiophenium ting oxidant A solid electrolytic capacitor obtained by reforming the total amount of poly 3,4-ethylenedioxythiophene and reaction residue formed by heat polymerization after impregnation into 0.25 to 0.7 mg / mm ² . A capacitor element composed of a cathode electrode foil, an anode electrode foil having a dielectric oxide film layer formed on the surface, and a separator for holding a solid electrolyte is impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent. Then, after carrying out heat polymerization and forming a solid electrolyte layer by polymerization reaction , poly 3,4-ethylenedioxythiophene formed by heat polymerization and reaction residue in a method for producing a solid electrolytic capacitor produced by re- forming The manufacturing method of the solid electrolytic capacitor characterized by making a total amount with a thing into 0.25-0.7 mg / mm < ² >. 3. The total amount of poly 3,4-ethylenedioxythiophene formed by heat polymerization and the reaction residue is set to 0.25 to 0.7 mg / mm ² by tightening at the time of heat polymerization. The manufacturing method of the solid electrolytic capacitor of description.

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