JP2020057816A - Electrolytic capacitor and method of manufacturing the same - Google Patents

Abstract

To provide an electrolytic capacitor with high withstand voltage, which prevents deterioration in withstand voltage characteristics due to lead-free reflow or the like and can be improved in ESR characteristics, and a method of manufacturing the same.SOLUTION: An electrolytic capacitor is formed by: impregnating a capacitor element, in which an anode electrode foil and a cathode electrode foil are wound via a separator, with a dispersion containing conductive polymer particles, sorbitol or both the sorbitol and polyhydric alcohol, and a solvent to form a solid electrolyte layer containing 60-92 wt.% of the sorbitol or both the sorbitol and the polyhydric alcohol; and filling a space in the capacitor element having the solid electrolyte layer formed therein with an electrolytic solution containing ethylene glycol.SELECTED DRAWING: None

Description

  The present invention relates to an electrolytic capacitor and a method for manufacturing the same, and more particularly, to an electrolytic capacitor having good ESR characteristics and withstand voltage characteristics and a method for manufacturing the same.

  Electrolytic capacitors using a metal having a valve action such as tantalum or aluminum, the valve action metal as the anode-side counter electrode is formed into a sintered body or an etching foil or the like to expand the dielectric, Since it is small and can obtain a large capacity, it is widely and generally used. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has characteristics that it is small, large-capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization, high performance, and low cost of electronic devices.

  In this type of solid electrolytic capacitor, for small size and large capacity applications, generally, an anode foil and a cathode foil made of a valve metal such as aluminum are wound with a separator interposed therebetween to form a capacitor element. A solid electrolyte layer is formed, and the capacitor element is housed in a case made of metal such as aluminum or a case made of synthetic resin, and has a sealed structure. Note that as the anode material, aluminum, tantalum, niobium, titanium, or the like is used, and as the cathode material, the same kind of metal as the anode material is used.

  In addition, manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex are known as solid electrolytes used for solid electrolytic capacitors. There is a technique (Patent Document 1) that focuses on a conductive polymer such as polyethylene dioxythiophene (hereinafter, referred to as PEDOT) having excellent adhesion to an oxide film layer of an electrode.

  A solid electrolytic capacitor of a type in which a solid electrolyte layer made of a conductive polymer such as PEDOT is formed on such a wound-type capacitor element is manufactured as follows. First, the surface of the anode foil made of a valve metal such as aluminum is roughened by electrochemical etching treatment in a chloride aqueous solution to form a large number of etching pits, and then, in an aqueous solution such as ammonium borate. A voltage is applied to form an oxide film layer serving as a dielectric (chemical formation). Like the anode foil, the cathode foil is also made of a valve metal such as aluminum, but its surface is only subjected to etching.

  The anode foil having the oxide film layer formed on the surface and the cathode foil having only the etching pits formed thereon are wound through a separator to form a capacitor element. Subsequently, a polymerizable monomer such as 3,4-ethylenedioxythiophene (hereinafter referred to as EDOT) and an oxidizing agent solution are respectively discharged onto the capacitor element subjected to the repair formation, or immersed in a mixed solution of both. And promotes the polymerization reaction in the capacitor element to generate a solid electrolyte layer made of a conductive polymer such as PEDOT. Thereafter, the capacitor element is housed in a bottomed cylindrical outer case to produce a solid electrolytic capacitor.

JP-A-2-15611

  By the way, in recent years, the above-mentioned solid electrolytic capacitors have been used for in-vehicle use and general power supply circuits, and high withstand voltage of about 35 V or 63 V has been required. For use in such applications, there is a demand for a solid electrolytic capacitor that satisfies requirements such as thermal stability at high temperatures, charge / discharge performance at low temperatures, and further reduction in ESR.

  In recent years, lead-free solder having a high melting point has been used due to environmental problems, and the solder reflow temperature has been further increased from 200 to 220 ° C. to 230 to 270 ° C. When solder reflow is performed at such a high temperature, it is considered that this is due to thermal degradation or crystallization of the electrolyte layer, but the withstand voltage is reduced. Note that such a problem occurs not only when EDOT is used as the polymerizable monomer but also when other thiophene derivatives, pyrrole, and aniline are used.

  The present invention has been proposed to solve the above problems, and an object of the present invention is to provide an electrolytic capacitor which reduces ESR while ensuring charge / discharge performance at a low temperature, has a long life at a high temperature, and a method for manufacturing the same. To provide.

  Another object of the present invention is to provide a high withstand voltage electrolytic capacitor capable of preventing deterioration of withstand voltage characteristics due to lead-free reflow or the like, and a method of manufacturing the same.

  The present inventors have made various studies in order to solve the above-mentioned problems, and as a result, have reached the following conclusions.

  Usually, in the capacitor element after the formation of the conductive polymer, in addition to the conductive polymer, a monomer, an oxidizing agent, and other reaction residues not involved in the polymerization reaction are present. Since the withstand voltage of these substances other than the conductive polymer is lower than the withstand voltage of the conductive polymer, it is considered that these substances lower the withstand voltage of the electrolytic capacitor. Therefore, the present inventors have developed an electrolyte layer containing a conductive polymer by impregnating a capacitor element with a dispersion obtained by dispersing a predetermined conductive polymer compound containing particles of a conductive polymer and at least sorbitol in a solvent. Formed and filled with an electrolytic solution containing ethylene glycol, it was found that these reaction residues themselves could not be mixed, and further studies were conducted to prevent deterioration of withstand voltage characteristics due to lead-free reflow. As a result, the present invention has been completed.

  That is, the electrolytic capacitor of the present invention is a conductive polymer containing conductive polymer particles, sorbitol and a polyhydric alcohol, in a capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator. A solid electrolyte layer using a compound dispersion, the solid electrolyte layer containing the sorbitol and the polyhydric alcohol in an amount of 60 to 92 wt% is formed, and ethylene is formed in a void portion in the capacitor element in which the solid electrolyte layer is formed. It is characterized by being filled with an electrolytic solution containing 10% by weight or more of glycol in a solvent.

  Further, the method for manufacturing an electrolytic capacitor of the present invention is a capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator, particles of a conductive polymer, sorbitol and a polyhydric alcohol, and a solvent. A solid electrolyte layer containing 60 to 92 wt% of the sorbitol and the polyhydric alcohol in a capacitor element through an impregnation step of impregnating a conductive polymer compound dispersion containing: and a drying step after the impregnation step The method includes a forming step, and an electrolytic solution filling step of filling a void in the capacitor element in which the solid electrolyte layer is formed with an electrolytic solution containing 10% by weight or more of ethylene glycol in a solvent.

  According to the present invention, it is possible to provide an electrolytic capacitor having a low ESR and a long life even at a high temperature while ensuring charge / discharge performance at a low temperature. Further, according to the present invention, it is possible to prevent deterioration of withstand voltage characteristics due to lead-free reflow or the like.

  Hereinafter, the present invention will be described in more detail while disclosing a typical manufacturing procedure for manufacturing the electrolytic capacitor according to the present invention.

(Method of manufacturing electrolytic capacitors)
An example of the method for manufacturing the electrolytic capacitor according to the present invention is as follows. That is, the anode foil and the cathode foil each having an oxide film layer formed on the surface are wound via a separator to form a capacitor element (element forming step). Note that the capacitor element may be subjected to restoration formation if necessary. Subsequently, the capacitor element is impregnated with a conductive polymer compound dispersion containing particles of a conductive polymer (including a dopant agent as necessary), sorbitol or sorbitol and a polyhydric alcohol, and a solvent. (Impregnation step), and after drying, a solid electrolyte layer containing a conductive polymer, sorbitol or sorbitol and a polyhydric alcohol is formed (solid electrolyte formation step). Thereafter, the capacitor element is immersed in a predetermined electrolytic solution to fill the void in the capacitor element with the electrolytic solution (electrolyte filling step). Then, the capacitor element is inserted into an outer case, a sealing rubber is attached to an opening end, and after sealing by crimping, aging is performed to form an electrolytic capacitor (sealing step).

(Element formation step)
As the anode foil, an etching foil obtained by etching a flat metal foil (for example, a valve metal foil such as aluminum) and forming a dielectric oxide film by a chemical conversion treatment can be used. As the cathode foil, an etching foil in which a flat metal foil is etched similarly to the anode foil and a thin dielectric oxide film (about 1 to 10 V) is formed by a chemical conversion treatment as necessary can be used. For the anode foil and the cathode foil, for example, fine pores (etching pits) are formed by alternating current etching of a 100 μm aluminum foil, and then a chemical conversion treatment is performed in an aqueous solution such as phosphoric acid to form a dielectric oxide film on the surface. I do.

  The anode foil and the cathode foil are connected to electrode lead-out means, respectively, and are wound via a separator to form a capacitor element. Examples of the separator include a nonwoven fabric separator mainly composed of synthetic fibers and a separator mainly composed of cellulose fibers. Examples of the synthetic fibers include polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and derivatives thereof, vinylon fibers, aspirant polyamides, aromatic polyamides, semi-aromatic polyamides, and polyamides such as wholly aromatic polyamides. Examples include fiber, polyimide fiber, polyethylene fiber, polypropylene fiber, trimethylpentene fiber, polyphenylene sulfide fiber, acrylic fiber, and aramid fiber. Examples of the cellulose fiber include kraft, manila hemp, espart, solvent-spun rayon fiber, and cotton fiber. Further, a mixture of a synthetic fiber and a cellulose fiber can also be used.

  The capacitor element formed as described above is subjected to a predetermined restoration formation. As the chemical liquid for restoration chemical formation, there are phosphoric acid-based chemical solutions such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, boric acid-based chemical solutions such as ammonium borate, and adipic acid-based chemical solutions such as ammonium adipate. Although a liquid can be used, it is particularly preferable to use ammonium dihydrogen phosphate. Also, the immersion time is desirably 5 to 120 minutes.

(Conductive polymer compound dispersion)
Examples of the conductive polymer compound dispersion include particles of a conductive polymer compound made of poly- (3,4-ethylenedioxythiophene) (hereinafter, referred to as PEDOT) and a solid content of a dopant made of polystyrenesulfonic acid. It is preferable to use a mixture obtained by dissolving the mixture in water as a solvent. The concentration of the conductive polymer compound can be 1 to 10% based on the aqueous solution. Note that the solvent of the dispersion of the conductive polymer compound may be other than water as long as the solvent dissolves the conductive polymer compound. Here, the particles include primary particles of a conductive polymer, aggregates (secondary particles) in which a conductive polymer compound and a dopant are aggregated, and powders thereof.

  Specifically, as the conductive polymer compound contained in the conductive polymer compound dispersion, a mixture of particles of thiophene or a derivative thereof and a solid content of a dopant made of a polymer sulfonic acid is preferable. The conductive polymer compound dispersion can be obtained by oxidative polymerization of thiophene or a derivative thereof as a polymerizable monomer in water or an aqueous liquid in the presence of a polymer sulfonic acid as a dopant. Examples of the conductive polymer thiophene or a derivative of thiophene in the derivative thereof include, for example, 3,4-ethylenedioxythiophene, 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, and 3,4. -Alkylthiophene, 3,4-alkoxythiophene and the like. The alkyl group or the alkoxy group preferably has 1 to 16 carbon atoms, and 3,4-ethylenedioxythiophene is particularly preferable. Further, not limited to thiophene, pyrrole or a derivative thereof may be used. Particularly preferred conductive polymers obtained from these polymerizable monomers include polythiophene, polyethylenedioxythiophene, and polypyrrole. As the polymer sulfonic acid serving as a dopant, polystyrene sulfonic acid sulfone, paratoluene sulfonic acid, and the like are suitably used.

(Sorbitol, polyhydric alcohol)
The conductive polymer compound dispersion further contains sorbitol or sorbitol and a polyhydric alcohol. By containing sorbitol in the obtained solid electrolyte layer, the initial ESR characteristics are improved, and the withstand voltage is improved. Polyhydric alcohols that can be included with sorbitol include ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, glycerin, xylitol, erythritol, mannitol, dipentaerythritol, and pentaerythritol. Here, any polyhydric alcohol is preferably a polyhydric alcohol having a boiling point of 180 ° C. or higher. This is because, in the step of drying the conductive polymer compound dispersion, the polyhydric alcohol is hardly scattered and can be left on the solid electrolyte layer. Among the above-mentioned polyhydric alcohols, ethylene glycol, which can reduce ESR characteristics, is particularly preferable.

  In addition, in order to improve the impregnating property and electric conductivity of the conductive polymer compound dispersion, various additives (for example, a silane coupling agent and polyvinyl alcohol) are added to the conductive polymer compound dispersion, or a cation is added. Neutralization may be performed.

(Impregnation step of conductive polymer compound dispersion)
The time for impregnating the capacitor element with the conductive polymer compound dispersion is determined by the size of the capacitor element, but is preferably at least 5 seconds for a capacitor element of about φ5 × 3L and at least 10 seconds for a capacitor element of about φ9 × 5L. Impregnation for at least 5 seconds. It should be noted that there is no adverse effect on the characteristics even after long-time impregnation. Further, it is preferable that the impregnation is maintained in a reduced pressure state after the impregnation. It is considered that the reason is that the residual amount of the volatile solvent is reduced.

(Solid electrolyte forming step)
After the capacitor element is impregnated with the conductive polymer compound dispersion, the capacitor element is dried at a predetermined temperature. The drying temperature is preferably from 100 to 160C for 0.5 to 3 hours. Through this drying step, a solid electrolyte layer containing a conductive polymer and sorbitol or sorbitol and a polyhydric alcohol is formed in the capacitor element, particularly on the oxide film layer in the etching pit of the etching foil. The impregnating step and the drying step of the conductive polymer compound dispersion may be performed a plurality of times as necessary.

  Here, the capacitor element is impregnated with the conductive polymer compound dispersion and subjected to a drying step, whereby a solid electrolyte layer containing a conductive polymer is formed in the capacitor element. However, in this solid electrolyte layer, the conductive polymer and the dopant contained in the conductive polymer compound dispersion, sorbitol or sorbitol and a polyhydric alcohol, and other additives added as necessary remain. Will be. The content of sorbitol or sorbitol and polyhydric alcohol contained in the solid electrolyte layer is preferably 60 to 92 wt%. By setting the content of sorbitol or sorbitol and a polyhydric alcohol within this range, the conductivity of the conductive polymer compound is improved by affinity with ethylene glycol contained in the electrolyte solution described later, and oxidation in the etching pit is also performed. A good coating state on the coating layer, that is, stability of the conductive polymer compound is obtained, and ESR characteristics and withstand voltage characteristics are improved. Here, if it is less than 60 wt%, the content of sorbitol or sorbitol and polyhydric alcohol is not sufficient, and the effect of improving the ESR characteristics and the withstand voltage characteristics is small. On the other hand, if the content exceeds 92 wt%, the amount of the conductive polymer compound is not sufficient, and the conductivity decreases due to alcohol entering between particles of the conductive polymer or between the electrode foil and the conductive polymer particles. It is considered that the ESR characteristics deteriorate.

(Electrolyte filling step)
After forming a solid polymer layer containing a conductive polymer compound and sorbitol or sorbitol and a polyhydric alcohol in a capacitor element, an electrolytic solution for an electrolytic capacitor can be used as an electrolytic solution to be filled in the capacitor element. . Examples of the solvent that can be used for the electrolytic solution include, as examples of the solvent, γ-butyrolactone, ethylene glycol, sulfolane, dimethylformamide, water and a mixed solvent thereof, and the like, and the boiling point thereof is a life test temperature of 120 ° C. It is preferable to use the above solvents. In particular, when ethylene glycol is used, the initial ESR characteristics and the withstand voltage characteristics are improved.

  That is, it was found that, when the ethylene glycol solvent was used, as compared with the case where the solvent containing no ethylene glycol was used, the ESR was reduced and the withstand voltage characteristics were improved, as is clear from the examples described later. ing. It is considered that the reason is that ethylene glycol has an effect of promoting the extension of the polymer chain of the conductive polymer, so that the conductivity is improved and the ESR is reduced. Also, it has good affinity with conductive polymer, sorbitol, polyhydric alcohol, etc. contained in the solid electrolyte layer. It is considered that the voltage characteristics are improved. Further, the content of ethylene glycol in the electrolytic solution is preferably 10% by weight or more based on the solvent.

  Further, at least one solvent selected from lactones such as γ-butyrolactone and sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane may be additionally used as the solvent containing ethylene glycol. The lactone-based compound improves the ESR characteristics at low temperatures, and the sulfolane-based solvent has a high boiling point, so that evaporation of the electrolytic solution is suppressed and the high-temperature characteristics are improved.

  As the electrolytic solution, the above solvent, and at least one kind of ammonium salt, quaternary ammonium salt, quaternized amidinium salt, amine salt and the like solute of an organic acid, an inorganic acid and a complex compound of the organic acid and the inorganic acid. Can be mentioned. Examples of the organic acid include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, and azelaic acid. Examples include carboxylic acids such as acids and phenols. Examples of the inorganic acid include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, phosphoric acid ester, carbonic acid, and silicic acid. Examples of the composite compound of an organic acid and an inorganic acid include borosalicylic acid, borodioxalic acid, and boroglycolic acid.

  Examples of the at least one salt of the organic acid, the inorganic acid, and the composite compound of the organic acid and the inorganic acid include an ammonium salt, a quaternary ammonium salt, a quaternized amidinium salt, and an amine salt. Examples of the quaternary ammonium ion of the quaternary ammonium salt include tetramethylammonium, triethylmethylammonium, tetraethylammonium and the like. Examples of the quaternized amidinium include ethyl dimethyl imidazolinium, tetramethyl imidazolinium, and the like. Examples of the amine of the amine salt include primary amine, secondary amine, and tertiary amine. Primary amines include methylamine, ethylamine, propylamine, etc. Secondary amines include dimethylamine, diethylamine, ethylmethylamine, dibutylamine, etc. Tertiary amines include trimethylamine, triethylamine, tributylamine, ethyldiisopropylamine And the like.

  Further, when a salt of borodisalicylic acid is used as a solute of the electrolytic solution, the ESR characteristics after a low-temperature charge / discharge test at −40 ° C. are improved.

  As additives for the electrolytic solution, polyoxyethylene glycol, complex compounds of boric acid and polysaccharides (such as mannitol and sorbitol), complex compounds of boric acid and polyhydric alcohols, and nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, etc.), and phosphate esters.

  Furthermore, sorbitol is mentioned as an additive of the electrolytic solution. By including sorbitol in the electrolyte, the rate of decrease in withstand voltage after reflow is greatly improved by interaction with sorbitol contained in the solid electrolyte. This is because the sorbitol contained in the electrolytic solution makes it difficult for the sorbitol contained in the solid electrolyte to be eluted into the electrolytic solution, so that the sorbitol causes the conductive polymer compound to form on the surface of the oxide film layer in the etching pit. It is considered that a state in which the film is well coated can be maintained, and deterioration of the withstand voltage characteristics can be suppressed. The content of sorbitol in the electrolytic solution is preferably from 1 to 10% by weight based on the solvent of the electrolytic solution.

(Electrolyte filling conditions)
When the electrolytic solution as described above is filled in the capacitor element, the filling amount is arbitrary as long as it can fill the gap in the capacitor element, but is preferably 3 to 100% of the gap in the capacitor element.

(Sealing process)
The capacitor element is inserted into the outer case together with the electrolytic solution, a sealing rubber is attached to the opening end, sealed by caulking, and then aged to produce an electrolytic capacitor. Further, in addition to the outer case, the capacitor element may be covered with an insulating resin such as an epoxy resin to cover the outer case, followed by aging to produce an electrolytic capacitor.

(Action / Effect)
As described above, after forming a solid electrolyte layer containing sorbitol or sorbitol and a polyhydric alcohol in the capacitor element, the capacitor element is immersed in an electrolytic solution containing ethylene glycol, and the electrolytic solution is inserted into a gap in the capacitor element. By filling the liquid, deterioration of the withstand voltage characteristics due to lead-free reflow can be prevented, and the ESR characteristics can be improved.

  Subsequently, the present invention will be described in more detail based on Examples and Comparative Examples manufactured as described below.

  First, an electrode lead-out means is connected to an anode foil having an oxide film layer formed on its surface and a cathode foil having an oxide film of 5 V formed on its surface, and both electrode foils are made of a separator mainly composed of cellulose fiber. To form a capacitor element having an element shape of 6.3 φ × 6.1 L. Then, the capacitor element was immersed in an aqueous solution of ammonium dihydrogen phosphate for 40 minutes to perform repair formation. Thereafter, the capacitor element was immersed in a conductive polymer compound dispersion containing PEDOT fine particles and polystyrenesulfonic acid, sorbitol or sorbitol and a polyhydric alcohol in an aqueous solution, and the capacitor element was pulled up and dried at about 150 ° C. Further, the capacitor element was repeatedly immersed in the conductive polymer compound dispersion-dried twice, and the conductive polymer compound, sorbitol or sorbitol and polyhydric alcohol were added to the capacitor element as shown in Tables 1 and 2. Was formed. Thereafter, the electrolytic solution shown in Tables 1 and 2 was filled in the capacitor element. Then, this capacitor element was inserted into a bottomed cylindrical outer case, and a sealing rubber was attached to the opening end, and sealing was performed by caulking. Thereafter, aging was performed by applying a voltage to form an electrolytic capacitor. The rated voltage of this electrolytic capacitor is 35 WV. Further, a 63 WV electrolytic capacitor was produced by changing the electrode foil and aging conditions of this electrolytic capacitor.

ＥＧ：エチレングリコール
ＧＢＬ：γ−ブチロラクトン
ＴＭＳ：スルホラン
ＢＳａｌＡ：ボロジサリチル酸
ＴＭＡ：トリメチルアミン Tables 1 and 2 show the test results of these electrolytic capacitors. The initial ESR characteristics, the ESR characteristics at the time of performing a no-load standing test at 125 ° C. for 1500 hours, and the ESR characteristics after the low-temperature charge / discharge test at −40 ° C. were evaluated with a 35 WV product. The withstand voltage rise rate before reflow and the withstand voltage drop rate after reflow were evaluated for 63 WV products. The withstand voltage increase rate before reflow was determined by preparing a 63 WV electrolytic capacitor (comparative electrolytic capacitor) in the same manner as in Comparative Example 2 except that the electrolytic solution was not filled. 3 shows the withstand voltage rise rates of the electrolytic capacitors of the examples and comparative examples on the basis of the withstand voltage. On the other hand, the withstand voltage drop rate after reflow refers to the withstand voltage drop rate due to the reflow, based on the withstand voltage before reflow of the electrolytic capacitors of the examples and comparative examples. Hereinafter, the withstand voltage rise rate before reflow and the withstand voltage drop rate after reflow are values indicated by the same method. The peak temperature of the reflow was 260 ° C. Further, in this specification, all the ESR characteristics indicate values at 100 kHz (20 ° C.).

EG: ethylene glycol GBL: γ-butyrolactone TMS: sulfolane BSalA: borodisalicylic acid TMA: trimethylamine

  From the results shown in Table 1, the electrolytic capacitors of Examples 1 to 3 in which sorbitol is contained in the solid electrolyte and ethylene glycol is contained in the electrolytic solution are earlier in comparison with the electrolytic capacitors in Comparative Examples 1 to 4. It was found that the ESR was low and the ESR was low even after the high temperature test. In Comparative Example 4, in which the content of sorbitol in the solid electrolyte was 95 wt%, it can be seen that the ESR characteristics after the charge / discharge test at a low temperature were significantly deteriorated.

  In addition, the electrolytic capacitors of Examples 1 to 3 have a higher withstand voltage increase rate before reflow and a lower withstand voltage drop rate after reflow as compared with the electrolytic capacitors of Comparative Examples 1 to 3, and have the present invention. It has been found that the electrolytic capacitor has a high withstand voltage characteristic and can prevent deterioration of the withstand voltage characteristic even at a high reflow temperature.

  From the above, it was found that the electrolytic capacitor using sorbitol in the solid electrolyte having a content of 60 to 92 wt% and using an electrolytic solution containing ethylene glycol had low ESR characteristics and good withstand voltage characteristics. .

  Also, from the results in Table 2, the electrolytic capacitors of Examples 4 to 6 containing sorbitol and ethylene glycol in the solid electrolyte and containing ethylene glycol in the electrolytic solution were the same as those of Comparative Examples 5 and 6. It was found that the initial ESR was lower than that of the capacitor, and the ESR characteristics were low even after the high temperature test. In Comparative Example 6, in which the content of sorbitol and ethylene glycol in the solid electrolyte was 95 wt%, it can be seen that the ESR characteristics after the charge / discharge test at low temperature were significantly deteriorated.

  Further, the electrolytic capacitors of Examples 4 to 6 have a higher withstand voltage rise rate before reflow and a lower withstand voltage drop rate after reflow as compared with the electrolytic capacitor of Comparative Example 5, and the electrolytic capacitor of the present invention It has been found that it has high withstand voltage characteristics and can prevent deterioration of withstand voltage characteristics even at a high reflow temperature.

  From the above, the electrolytic capacitor using sorbitol and ethylene glycol in the solid electrolyte having a content of 60 to 92 wt% and using an electrolytic solution containing ethylene glycol has low ESR characteristics and good withstand voltage characteristics. I understood.

ＰｈＡ：フタル酸
ＡｚＡ：アゼライン酸
ＴＥＡ：トリエチルアミン Next, in Table 3, the type of polyhydric alcohol contained in the solid electrolyte was changed, and the composition of the electrolytic solution containing ethylene glycol was changed. The ESR characteristic and the ESR characteristic after the low temperature charge / discharge test at −40 ° C. were evaluated with a 35 WV product, and the withstand voltage rise rate before reflow and the withstand voltage fall ratio after reflow were evaluated with a 63 WV product, and the results are shown. .

PhA: phthalic acid AzA: azelaic acid TEA: triethylamine

  The results in Table 3 show that the electrolytic capacitors of Examples 7 and 8 using glycerin or mannitol as the polyhydric alcohol also had better ESR characteristics and withstand voltage characteristics than the electrolytic capacitors of Comparative Example 2. became. Also, in the electrolytic capacitors of Examples 9 to 11 using triethylamine phthalate or triethylamine azelate as a solute of the electrolytic solution, the ESR characteristics and the withstand voltage characteristics were higher than those of the electrolytic capacitors of Comparative Examples 7 to 9. Was a good result.

Next, Table 4 shows the initial ESR characteristics in the electrolytic solution composition when the content of ethylene glycol contained in the electrolytic solution was changed, the ESR characteristics after a no-load storage test at 125 ° C. and 1500 hours, and the temperature at −40 ° C. The ESR characteristics after the low-temperature charge / discharge test were evaluated at 35 WV, the withstand voltage rise rate before reflow and the withstand voltage drop rate after reflow were evaluated at 63 WV, and the results are shown.

  From the results in Table 4, it was found that increasing the content of ethylene glycol improved the initial ESR characteristics and the ESR characteristics at high temperatures. In particular, in the electrolytic capacitors of Examples 13 to 18 in which the content of ethylene glycol in the solvent of the electrolytic solution was 10% by weight or more, the initial ESR characteristics, the ESR characteristics after the high temperature test, and the withstand voltage characteristics showed the ethylene glycol content. Good results were obtained as compared with Example 12 in which the amount was 5 wt%.

Next, in Table 5, sorbitol was contained in the electrolytic solution, and the initial ESR characteristics in the electrolytic solution composition when the content was changed, at 125 ° C., after 1500 hours of no-load storage test, at −40 ° C. The ESR characteristics after the low-temperature charge / discharge test were evaluated with a 35 WV product, the withstand voltage rise rate before reflow and the withstand voltage drop rate after reflow were evaluated with a 63 WV product, and the results are shown.

  From the results in Table 5, it is found that in the electrolytic capacitors of Examples 19 to 24 in which sorbitol and polyhydric alcohol were contained in the solid electrolyte and sorbitol was also contained in the electrolytic solution, 20 wt% was contained in the solid electrolyte. % Sorbitol and good results in the initial ESR characteristics, the ESR characteristics at high temperatures, and the withstand voltage characteristics as compared with the electrolytic capacitor of Comparative Example 10 in which sorbitol was further contained in the electrolytic solution. In particular, it can be seen that when a predetermined amount of sorbitol and a polyhydric alcohol are contained in the solid electrolyte and sorbitol is contained in the electrolytic solution, the withstand voltage drop rate after reflow is greatly improved. The electrolytic capacitor of Example 19 containing 0.5 wt% of sorbitol with respect to the solvent of the electrolytic solution had a low effect of improving the withstand voltage drop rate after reflow, and 12 wt% of sorbitol with respect to the solvent of the electrolytic solution. In the electrolytic capacitor of Example 24 containing, since the ESR characteristics after the low temperature charge / discharge test at −40 ° C. are deteriorated, the content of sorbitol with respect to the solvent of the electrolytic solution is preferably 1 to 10% by weight. I understood.

Further, in the electrolytic capacitors of Examples 25 to 27 in which the composition of the sorbitol and the polyhydric alcohol in the solid electrolyte was changed and the composition of the electrolytic solution containing sorbitol was changed, the solid electrolyte contained a predetermined amount of sorbitol. However, by including sorbitol also in the electrolytic solution, good results were obtained in the ESR characteristics and the withstand voltage characteristics.

That is, the electrolytic capacitor of the present invention is a capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator, particles of a conductive polymer, and sorbitol or sorbitol and a polyhydric alcohol. A solid electrolyte layer using a polymer compound dispersion, the solid electrolyte layer containing the sorbitol or sorbitol and a polyhydric alcohol in an amount of 60 to 92 wt%, and a void in a capacitor element in which the solid electrolyte layer is formed; The part is filled with an electrolytic solution containing 10% by weight or more of ethylene glycol in a solvent, and the polyhydric alcohol is at least one selected from glycerin, mannitol, and ethylene glycol .

Further, the method for producing an electrolytic capacitor of the present invention, a capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator, conductive polymer particles, sorbitol or sorbitol and a polyhydric alcohol, and a solvent. And an impregnating step of impregnating a conductive polymer compound dispersion containing: and a drying step after the impregnating step, to obtain a solid electrolyte layer containing 60 to 92 wt% of the sorbitol or sorbitol and polyhydric alcohol in the capacitor element. a solid electrolyte forming step of forming, in the gap portion of the solid electrolyte layer capacitor element is formed, an electrolytic solution filling step of filling an electrolytic solution containing ethylene glycol or 10 wt% solvent, only contains the multi hydric alcohols are, to characterized glycerin, mannitol, it is at least one selected from ethylene glycol .

Claims (5)

  A capacitor element in which an anode electrode foil and a cathode electrode foil are wound through a separator, a solid using a conductive polymer compound dispersion containing conductive polymer particles, and sorbitol or sorbitol and a polyhydric alcohol. Forming an electrolyte layer containing the sorbitol or sorbitol and a polyhydric alcohol in an amount of 60 to 92 wt%, and filling the solid electrolyte layer with a 10 wt. %. An electrolytic capacitor characterized by being filled with an electrolytic solution containing at least 10% by weight.   The electrolytic capacitor according to claim 1, wherein the content of ethylene glycol contained in the electrolytic solution is 40 wt% or more in a solvent of the electrolytic solution.   The electrolyte further contains γ-butyrolactone as a solvent, and at least one ammonium salt, quaternary ammonium salt, and quaternized amidinium salt of an organic acid, an inorganic acid, and a composite compound of an organic acid and an inorganic acid. The electrolytic capacitor according to claim 1, further comprising a solute selected from the group consisting of an amine salt and an amine salt.   The electrolytic capacitor according to any one of claims 1 to 3, wherein the electrolytic solution further contains at least one solvent selected from sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane. A capacitor element in which an anode electrode foil and a cathode electrode foil are wound via a separator, conductive polymer particles, sorbitol or sorbitol and a polyhydric alcohol, and a solvent, and a conductive polymer compound dispersion containing the solvent. An impregnation step of impregnating;
A solid electrolyte forming step of forming a solid electrolyte layer containing 60 to 92 wt% of the sorbitol or sorbitol and polyhydric alcohol in a capacitor element through a drying step after the impregnation step;
An electrolytic solution filling step of filling an electrolytic solution containing ethylene glycol in a solvent in an amount of 10 wt% or more into a void portion in the capacitor element in which the solid electrolyte layer is formed;
A method for producing an electrolytic capacitor, comprising: