JP6537105B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor and a method of manufacturing the same.

  As a solid electrolytic capacitor, one in which a conductive polymer layer is formed on an anode foil of a capacitor element in which an anode foil having a dielectric oxide film formed on the surface and a cathode foil is wound via a separator, The conductive polymer layer is formed on the anode foil on which the body oxide film is formed, and then the laminated capacitor element or the capacitor element on which the dielectric oxide film is formed after sintering the valve metal powder is used as the conductive polymer. What formed the layer is known.

  A solid electrolytic capacitor is generally made of a valve metal such as aluminum, tantalum or niobium, and is provided with an anode body (anode foil or sintered body) having etching pits and micropores formed on the surface. A dielectric oxide film is formed on the surface, a conductive polymer layer is formed on the dielectric oxide film, and an electrode is drawn out. The conductive polymer layer plays a role as a true cathode in the electrolytic capacitor, and greatly affects the electrical characteristics of the electrolytic capacitor.

  The conductive polymer layer is a layer containing a solid electrolyte that is electronically conductive, and is a derivative of polythiophene, such as polyethylene dioxythiophene (PEDOT), polythiophene, polyaniline, polypyrrole, etc. It is known to use as (patent document 1).

As a method of forming such a conductive polymer layer, a mixed solution of an oxidizing agent and a monomer is prepared in advance, and a method of immersing and impregnating a capacitor element in this mixed solution, or separately oxidizing agent and monomer There is a method of impregnating the capacitor element sequentially. For example, in the solid electrolytic capacitor described in Patent Document 2, the capacitor element is immersed in a mixed solution of a polymerizable monomer and an oxidizing agent to generate a polymerization reaction of the conductive polymer in the capacitor element. Then, after forming the solid electrolyte layer, the capacitor element is immersed in a predetermined ion conductive material, and the void portion in the capacitor element is filled with the ion conductive material, so that the withstand voltage characteristics under high temperature reflow can be obtained. It prevents deterioration.
In any of the above methods, the conductive polymer layer is formed while the polymerization reaction proceeds on the capacitor element, but in these methods, the change in solution viscosity with the progress of the polymerization, the oxidizing agent It has also been known that there are process control problems such as insufficient mixing with the monomer.

  On the other hand, there is also known a method of forming a conductive polymer layer by impregnating a capacitor element with a dispersion containing a conductive polymer that has been subjected to a polymerization reaction in advance and drying it to form a coating. This method is characterized in that it is relatively easy to control the process and advantageous in mass productivity since it is not necessary to carry out a polymerization reaction on the dielectric oxide film (Patent Document 3).

  The invention of Patent Document 3 is an aqueous dispersion of a conductive polymer polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) under the trade name Baytron-P (BAYTRON is a registered trademark, manufactured by Starck GmbH, Germany) ) Is used to form the conductive polymer layer, and the purpose is to improve the conductivity of the conductive polymer layer (avoid increase in equivalent series resistance (ESR)) and to improve the long-term reliability of the electrical characteristics. In the invention of Patent Document 3, first, an anodic oxide film is formed, and on the surface thereof, a precoat layer (a layer obtained by applying and drying polystyrene sulfonic acid) and an internal conductive polymer layer (formed by chemical oxidation polymerization) have a relative molecular weight. An anode body on which a film of a small conductive polymer is formed is prepared. Next, a solution containing naphthalenesulfonic acids, high molecular weight PSS, boric acid, mannitol, glycols and water is mixed with an aqueous dispersion containing PEDOT and PSS, to thereby produce a high molecular polymerization solution. Then, the polymer solution is applied or impregnated to the above anode body and dried to provide a conductive polymer layer.

By the way, as the use of a solid electrolytic capacitor is expanded, a capacitor that can be used without problems even in a more severe environment is required.
Therefore, it has been proposed to impregnate the capacitor element with a high boiling point solvent such as polyethylene glycol (boiling point: about 250 ° C.) in order to reduce the change in electrical characteristics under high temperature and high humidity. However, when only polyethylene glycol is impregnated as a high boiling point solvent, it exhibits good characteristics in a high humidity atmosphere such as 85 ° C.-85% RH, but the high temperature atmosphere and temperature of 125 ° C. or more required recently have been required. Under the severe conditions of the cycle test, there is a problem that the characteristic change due to the oxidation deterioration becomes large.

JP-A-2-15611 Patent No. 4779277 gazette JP, 2008-311582, A

  The present invention solves such problems in the prior art, and provides a solid electrolytic capacitor excellent in temperature cycle characteristics, in which the change in capacitance is small even in a high temperature atmosphere of 125 ° C. or higher, low ESR is maintained. To be a task.

The solid electrolytic capacitor according to the present invention, which can solve the above-mentioned problems, impregnates and dries, at least once, a dispersion containing polyethylenedioxythiophene / polystyrene sulfonic acid as a basic composition in a capacitor element having a dielectric oxide film formed thereon. In the solid electrolytic capacitor in which the electrolyte is formed on the surface of the dielectric oxide film by
With polyethylene glycol,
Polyoxypropylene glyceryl ether, polyoxypropylene, characterized in that it contains polyoxypropylene trimethylolpropane ether, and one or more compounds selected from the group consisting of polyoxypropylene sorbitol ethers and are.

Furthermore, the present invention is also characterized in that, in the solid electrolytic capacitor having the above-mentioned characteristics, the compound is contained at a weight of 0.5 to 5 times a weight of polyethylene glycol.

Further, the present invention provides a solid electrolytic capacitor having the above characteristics, the number average molecular weight of said compound, is also characterized by that it is 400 to 4000.

The present invention is also a method for producing a solid electrolytic capacitor having the above features, and the production method is
Impregnating and drying a capacitor element having a dielectric oxide film formed thereon in a dispersion solution having a basic composition of PEDOT / PSS;
Impregnating a mixed solution containing polyethylene glycol and one or more compounds selected from the group consisting of polyoxypropylene glyceryl ether, polyoxypropylene, polyoxypropylene trimethylol propane ether, and polyoxypropylene sorbitol ether ; It is characterized by including.

  In the solid electrolytic capacitor of the present invention, polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) is added to a capacitor element in which an anode foil on which a dielectric oxide film is formed and a cathode foil are wound via a separator. The conductive polymer layer is formed by impregnating and drying the dispersion having the basic composition at least once, and the conductive polymer layer composed of the layer composed of PEDOT / PSS makes it possible to conduct solid electrolyte with high conductivity. A capacitor is obtained.

In the present invention, polythiophene, polypyrrole, polyaniline or polyaniline on the dielectric oxide film is previously formed to suppress the above-mentioned conductive polymer layer from swelling due to the influence of moisture and to improve the moisture resistance of the solid electrolytic capacitor. It is preferable to form a first conductive polymer layer by impregnating and drying a solution containing the derivative, and a PEDOT / PSS layer is formed thereon as a second conductive polymer layer.
The separator in the solid electrolytic capacitor of the present invention is preferably a separator having no hydrolyzability, for example, a separator mainly composed of polyacrylonitrile and aramid, and by using such a separator, particularly high temperature In the area, it is possible to obtain a solid electrolytic capacitor more excellent in durability.

In the solid electrolytic capacitor of the present invention, it is selected from the group consisting of polyethylene glycol, polyoxypropylene glyceryl ether, polyoxypropylene, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether in the capacitor element. and it has one or more impregnated mixed solution containing the compound. Examples of the preferred compounds in the present invention, and polyoxypropylene glyceryl ether, polyoxypropylene, and the like. In the present invention, more preferably, the compounds are mixed at a weight of 0.5 to 5 times the weight of polyethylene glycol.

Next, the process of the present invention for producing the solid electrolytic capacitor of the present invention will be described. In the first step of the production method of the present invention, a capacitor element in which an anode foil on which a dielectric oxide film is formed and a cathode foil are wound via a separator is impregnated with a solution in which a conductive polymer is dissolved, It is dried to form a first conductive polymer layer on the dielectric oxide film. At this time, the solution in which the conductive polymer is dissolved is preferably a solution in which either polythiophene, polypyrrole, polyaniline or a derivative thereof is dissolved, and the separator of the solid electrolytic capacitor is hydrolyzable. It is preferable that there is no separator.
In the present invention, by using the above-described solution as a solution in which a conductive polymer is dissolved, it is possible to form a conductive polymer layer on the surface of the anode foil by a general method. In addition, by using a solution of a conductive polymer, it is possible to form a conductive polymer layer more uniformly than in the case of carrying out a polymerization reaction on an anodic oxide film, and also to use unreacted monomers in the capacitor element. In addition, since unnecessary substances such as an oxidizing agent do not remain, it is possible to improve the moisture resistance of the solid electrolytic capacitor and to improve the electrical characteristics.

  Then, in the next step of the production method of the present invention, the dispersion containing polyethylenedioxythiophene and polystyrene sulfonic acid is impregnated into the capacitor element and dried to form the second conductive polymer layer on the first conductive polymer layer. The conductive polymer layer (PEDOT / PSS layer) is formed. When such a dispersion of polyethylenedioxythiophene and polystyrene sulfonic acid is used, the oxidizing agent and the monomer component are less likely to remain in the capacitor element, and the dielectric film is particularly deteriorated at high temperatures. As a result, it is possible to obtain a solid electrolytic capacitor having a small change in capacitance in a low temperature range and a small change in characteristics of the capacitor even at high temperatures.

In the final step of the production method of the present invention, polyethylene glycol and one or more compounds selected from the group consisting of polyoxypropylene glyceryl ether, polyoxypropylene, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether And impregnating the capacitor element under reduced pressure for a fixed time. When polyethylene glycol is impregnated alone, the characteristics deteriorate in a short time due to autoxidation deterioration in a high temperature atmosphere and temperature cycle test, but the reactivity with thermal oxidation deterioration is suppressed by mixing with the above compound , High temperature resistance characteristics and temperature cycle characteristics are improved.

  According to the present invention, it is possible to obtain a solid electrolytic capacitor excellent in temperature cycle characteristics, in which a change in capacitance is small even in a high temperature atmosphere of 125 ° C. or higher, a low ESR is maintained, and the like.

It is a disassembled perspective view which shows the outline | summary of a capacitor | condenser element.

  FIG. 1 is an exploded perspective view showing an outline of a capacitor element. The anode foil 1 and the cathode foil 3 are wound and stored in the capacitor element 4 with the separator 2 interposed therebetween, and the anode lead wire 5 connected to the anode foil and the cathode lead wire 6 connected to the cathode foil Is pulled out.

  In the anode foil of the solid electrolytic capacitor according to the present invention, the surface of a flat plate-like valve metal having a predetermined width was roughened by etching and then subjected to chemical conversion to form a dielectric oxide film on the surface. Use the one. As the valve metal action, a metal containing at least one selected from aluminum, tantalum, niobium and titanium is preferable, and among them, aluminum is preferable.

  The etching treatment and the formation oxidation treatment can be performed by known methods, and purchased products can also be used. For example, as a chemical conversion solution used for chemical conversion oxidation treatment, a chemical conversion solution can be used in which a solute of an organic acid salt having a carboxylic acid group or an inorganic acid salt such as phosphoric acid is dissolved in an organic solvent or an inorganic solvent.

  The anode foil is wound together with the separator and the cathode foil as described above, but after winding, a restoration formation is carried out in order to repair the dielectric oxide film which is lost at the time of attachment of the cut edge of the anode foil or the external lead electrode. As a chemical conversion solution for restoration chemical formation, a chemical conversion solution in which a solute of an organic acid salt having a carboxylic acid group or an inorganic acid salt such as phosphoric acid is dissolved in an organic solvent or an inorganic solvent can be used.

  Then, a first conductive polymer layer is formed on the dielectric oxide film. The first conductive polymer layer is preferably formed by impregnating and drying a solution type conductive polymer solution. The first conductive polymer layer is formed using a solution mainly composed of polythiophene, polypyrrole, polyaniline or a derivative thereof, that is, a conductive polymer layer mainly composed of polythiophene, polypyrrole, polyaniline or a derivative thereof Is preferred. The concentration of the conductive polymer in the solution is preferably 0.1 to 2.0 wt%, and the solvent dissolves the conductive polymer regardless of alcohol, ether or aromatic type, and the drying temperature is less than 250 ° C. Solvents capable of transpiration can be used. The drying conditions are not limited as long as they can remove the solvent and do not adversely affect the capacitor element, but can be dried, for example, at 100 to 250 ° C. for 30 to 120 minutes. As a solution for forming a 1st conductive polymer layer, it can form by making it dry at 150 degreeC for 30 minutes especially using 0.5-1.5 wt% polyaniline / ethanol solution. For example, sulfosuccinic acid ester can be used as the polyaniline dopant.

  A second conductive polymer layer is formed on the first conductive polymer layer thus formed. The second conductive polymer layer is formed by immersing and impregnating the capacitor element in a polymer dispersion containing polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS), and then removing water by drying. Preferably it is formed. As a PEDOT / PSS dispersion liquid, what used water as a solvent is preferable, and what was produced as the density | concentration of PEDOT / PSS in a dispersion liquid is 0.5-3.0 wt% may be used. When forming the second conductive polymer layer, the impregnation may be carried out under normal pressure, but it is also preferable to carry out under reduced pressure. In addition, impregnation and drying can be repeated twice or more. The drying conditions are not limited as long as they can remove the solvent and do not adversely affect the capacitor element, but can be dried, for example, at 85 to 150 ° C. for 30 to 120 minutes. Particularly preferably, the process of immersion and impregnation for 15 minutes under a reduced pressure of 10 kPa and drying for 60 minutes at 100 ° C. is repeated three times using a polymer dispersion solution containing 1.0 wt% of PEDOT / PSS. A second conductive polymer layer can be formed.

Then, the capacitor element in which the conductive polymer layer is formed by the above process is a group comprising polyethylene glycol, polyoxypropylene glyceryl ether, polyoxypropylene, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether. A mixed solution containing one or more selected compounds is impregnated into a capacitor element under reduced pressure (eg, 10 kPa) for a fixed time (eg, 30 minutes), and then the capacitor element is housed in a metal case, and the metal case is The solid electrolytic capacitor of the present invention is obtained by curling the opening portion of the above and applying a rated voltage to the capacitor under a temperature condition of about 150 ° C. to perform an aging treatment.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to the following examples.

Example 1
A tab terminal for an external lead-out electrode was connected to the anode foil and the cathode foil cut to a predetermined width. As the anode foil, an aluminum foil was used as a valve metal, and the surface of the valve metal was subjected to an etching treatment and a chemical conversion treatment to form a dielectric oxide film.
The above-mentioned anode foil and a cathode foil having titanium oxide formed on the surface thereof were wound via a separator mainly composed of polyacrylonitrile to complete a wound element.
Subsequently, the so-called chemical conversion treatment was performed to repair the dielectric oxide film which was lost when the anode foil was cut or when the external lead electrode was attached. Using a 0.5 to 3 wt% conversion solution in which ammonium adipate was dissolved in a water solvent, a voltage close to the formation voltage value of the dielectric oxide film was applied to perform conversion treatment.

Next, a conductive polymer layer, which is a cathode layer of a solid electrolytic capacitor, was formed.
First, the wound element was impregnated with a 1.0 wt% polyaniline / ethanol solution, and dried at 150 ° C. for 30 minutes to form a first conductive polymer layer.
Thereafter, the polymer dispersion solution containing 1.0 wt% of PEDOT / PSS was dipped and impregnated for 15 minutes under a reduced pressure of 10 kPa, and the water was removed by heating at 100 ° C. for 60 minutes. This impregnation and drying were repeated three times to form a second conductive polymer layer.
Further, polyethylene glycol (PEG-600 manufactured by Sanyo Chemical Industries, Ltd., number average molecular weight determined from hydroxyl value: 600) and polyoxypropylene glyceryl ether (Sannix GP-400 manufactured by Sanyo Chemical Industries, Ltd., calculated from hydroxyl value Number average molecular weight: 400) was mixed at a weight ratio of 40:60, and the above wound element was impregnated with this mixed solution for 30 minutes under a reduced pressure of 10 kPa.

  The capacitor element on which the conductive polymer layer was formed by the above method was housed in a metal case, and the opening of the metal case was curled. Subsequently, a rated voltage was applied to the capacitor under a temperature condition of about 150 ° C. to perform an aging treatment, and a solid electrolytic capacitor was completed.

Example 2
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that a solution in which PEG-600 and GP-400 were mixed at a weight ratio of 30:70 was used as a post-treatment solution for impregnating the capacitor element.

[Example 3]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that a solution in which PEG-600 and GP-400 were mixed at a weight ratio of 70:30 was used as a post-treatment solution for impregnating the capacitor element.

Example 4
A solid electrolytic capacitor was prepared in the same manner as in Example 1 except that a solution in which PEG-600, GP-400 and pure water were mixed at a weight ratio of 30: 20: 50 was used as a post-treatment solution to impregnate the capacitor element. did.

[Conventional example]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that a 50% aqueous solution of PEG-600 was used as a post-treatment solution for impregnating the capacitor element.

[Evaluation of solid electrolytic capacitors of Examples and Conventional Examples]
The solid electrolytic capacitors of Examples and Conventional Examples were evaluated by the following evaluation methods.
Study product: φ 8 × 10 L 35 WV-150 μF
1. Temperature cycle test Test conditions: −55 ° C./+125° C. Each cycle is 30 minutes, and after 1,000 cycles, the capacitance (Cap), tan δ and equivalent series resistance (ESR) are measured. Rate of change was calculated. The results are shown in Table 1 below.
2. Reliability test Test conditions: Test atmosphere: 145 ° C
Applied voltage · Elapsed time: 35 V applied, 2,000 hours 145 ° C, 35 V applied, capacitance after 2000 hours (Cap), tan δ, equivalent series resistance (ESR) was measured and changed from the value before the test The rate was calculated. The results are shown in Table 2 below.

Polymer Solutions Used in Examples 1 to 4 and Conventional Example Conventional Example: Post-Treatment Solution of PEG-600 50% aq Example 1: Post-Treatment Solution in which 40% of PEG-600 and 60% of GP-400 were mixed Example 2 : Post-treatment solution mixed with PEG-600 30%, GP-400 70% Example 3: Post-treatment solution mixed with PEG-600 70%, GP-400 30% Example 4: PEG-600 30%, GP Post-treatment solution with a mixture of -400 20% and pure water 50%

As shown in the experimental results in Tables 1 and 2 above, the rate of change of the capacitance (Cap), tan δ and equivalent series resistance (ESR) in the above-described temperature cycle test and high temperature reliability test is the same as in Examples 1 to 4. Is smaller and more stable than the prior art. Further, Table 2 shows that in the high temperature reliability test, the change rate of the capacitance (Cap), tan δ, equivalent series resistance (ESR) of Examples 1 to 4 is smaller than that of the conventional example and the high temperature region (145). It is also shown that the stability is excellent also in ° C.), particularly when the weight of GP-400 exceeds 0.5 times the weight of PEG-600 (Examples 1, 2 and 4). It was found that good high temperature stability was obtained. In addition, since the withstand voltage characteristics are improved by setting the weight of GP-400 to 5 times or less of the weight of PEG-600, from the viewpoint of achieving both high temperature stability and withstand voltage characteristics, the weight of GP-400 is More preferably, it is 0.5 to 5 times the weight of PEG-600. Further, the number average molecular weight of the compound result as 400 to 4000, it is possible to improve the impregnation of the capacitor element.

And, in the present invention, polyoxypropylene glyceryl ether is used as the compound in the above-mentioned example, but other polyoxypropylene, polyoxypropylene trimethylol propane ether, polyoxypropylene sorbitol ether may be used similarly. An effect is obtained.

Furthermore, according to the present invention, the wound element is impregnated with a mixed solution of polyethylene glycol and polyoxypropylene glyceryl ether after the formation of the conductive polymer layer in the above embodiment, but the dielectric oxide film is formed and then wound. element, polyethylene glycol and polyoxypropylene glyceryl ether compound and impregnated with a solution obtained by mixing the same effect even if such is obtained polymer dispersion solution containing the PEDOT / PSS.

  In the above embodiment, the capacitor element is formed by winding the anode foil on which the dielectric oxide film is formed and the cathode foil with a separator interposed, but a capacitor in which the anode foil on which the dielectric oxide film is formed is laminated After sintering the element or the powder of the valve metal, a capacitor element having a dielectric oxide film may be used.

1 anode foil 2 separator 3 cathode foil 4 capacitor element 5 anode lead wire 6 cathode lead wire

Claims (4)

In a solid electrolytic capacitor in which an electrolyte is formed on the surface of a dielectric oxide film by impregnating and drying a dispersion solution having a basic composition of polyethylenedioxythiophene / polystyrene sulfonic acid in a capacitor element on which a dielectric oxide film is formed , In the capacitor element,
With polyethylene glycol,
A solid electrolytic capacitor comprising: one or more compounds selected from the group consisting of polyoxypropylene glyceryl ether, polyoxypropylene, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether . The solid electrolytic capacitor according to claim 1, wherein the compound is contained at a weight of 0.5 to 5 times a weight of polyethylene glycol . The number average molecular weight of the said compound is 400-4000, The solid electrolytic capacitor of Claim 1 or 2 characterized by the above-mentioned. Impregnating and drying a capacitor element having a dielectric oxide film formed thereon in a dispersion solution containing polyethylene dioxythiophene / polystyrene sulfonic acid as a basic composition;
Impregnating a mixed solution containing polyethylene glycol and one or more compounds selected from the group consisting of polyoxypropylene glyceryl ether, polyoxypropylene, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether
A method of manufacturing a solid electrolytic capacitor, comprising:

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