WO2024225389A1 - 固体電解コンデンサ及びその製造方法 - Google Patents

固体電解コンデンサ及びその製造方法 Download PDF

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Publication number
WO2024225389A1
WO2024225389A1 PCT/JP2024/016279 JP2024016279W WO2024225389A1 WO 2024225389 A1 WO2024225389 A1 WO 2024225389A1 JP 2024016279 W JP2024016279 W JP 2024016279W WO 2024225389 A1 WO2024225389 A1 WO 2024225389A1
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Prior art keywords
electrolyte
acid
electrolytic capacitor
solid electrolytic
resin
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French (fr)
Japanese (ja)
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健太 佐藤
みづき 中村
哲生 前田
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Nippon Chemi Con Corp
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Nippon Chemi Con Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/022—Electrolytes; Absorbents
    • H01G9/035—Liquid electrolytes, e.g. impregnating materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/08—Housing; Encapsulation
    • H01G9/10—Sealing, e.g. of lead-in wires
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/145—Liquid electrolytic capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/15—Solid electrolytic capacitors

Definitions

  • the present invention relates to a solid electrolytic capacitor having a solid electrolyte layer and an electrolyte solution, and a method for manufacturing the same.
  • An electrolytic capacitor has anode and cathode bodies made of valve metals such as tantalum or aluminum.
  • the anode body has an enlarged surface by forming the valve metal into a sintered body or etched foil, and has a dielectric film on the enlarged surface.
  • An electrolyte is placed between the anode foil and the cathode foil.
  • the electrolyte is in close contact with the uneven surface of the anode foil and functions as a true cathode.
  • the electrolyte also has a function of repairing the dielectric film.
  • the electrolyte evaporates and escapes to the outside of the electrolytic capacitor.
  • the capacitance of the electrolytic capacitor decreases over time as it dries up, eventually reaching the end of its life.
  • the anode body, cathode body, and electrolyte are contained in an exterior case with a bottom.
  • the opening of the exterior case is sealed with a sealant.
  • the sealant contains an elastomer such as butyl rubber, and is crimped to fit tightly to the opening of the case. This sealant keeps the electrolyte contained within the case, suppressing the amount of evaporation and extending the life of the electrolytic capacitor.
  • the electrolyte is not completely contained within the case, but gradually permeates the sealing body and volatilizes to the outside of the electrolytic capacitor.
  • the opening of the case may be covered from above the sealing body with a resin layer that has lower electrolyte permeability than the elastomer (see, for example, Patent Document 1). This resin layer further enhances the gas barrier properties.
  • the opening of the case is sealed with a single sealing body in which an elastomer layer and a resin layer are laminated.
  • electrolytic capacitors are increasingly being used in high-temperature environments, such as 170°C, for example in automotive applications.
  • high-temperature environments the electrolyte is more likely to escape from the electrolytic capacitor, so there is a demand for electrolytic capacitors that suppress the amount of electrolyte leakage even in high-temperature environments.
  • the present invention has been proposed to solve the above problems, and its purpose is to provide an electrolytic capacitor and a manufacturing method that have improved effectiveness in preventing electrolyte leakage.
  • the electrolytic capacitor of this embodiment includes an anode body having a dielectric film, a cathode body facing the anode body, an electrolyte layer interposed between the anode body and the cathode body and containing a solid electrolyte layer and an electrolyte solution, a case that contains the anode body, the cathode body, and the electrolyte layer, and a resin member that covers at least a portion of the opening side of the case, and the electrolyte solution contains glycerin that accounts for 30 wt % or more of the total amount of the solvent.
  • the electrolyte may further include ethylene glycol, sulfolane, polyethylene glycol, or a combination thereof.
  • the resin member may include epoxy resin or acrylic resin.
  • the resin member may include an epoxy resin.
  • the resin member may contain the epoxy resin that does not have an ester bond.
  • the resin member may contain an amine-based hardener or a phenol-based hardener in addition to the epoxy resin.
  • the solid electrolyte layer may contain a high-boiling liquid component having a boiling point of 150°C or higher and a hydroxyl group.
  • the high boiling point liquid component may be ethylene glycol, diethylene glycol, glycerin, diglycerin, polyethylene glycol, or a combination of these.
  • the manufacturing method of the electrolytic capacitor of this embodiment includes the steps of forming a dielectric film on the surface of the anode body, forming a solid electrolyte layer between the anode body and the cathode body, housing the anode body, the cathode body, and the solid electrolyte layer in a case, impregnating the anode body, the cathode body, and the solid electrolyte layer with an electrolyte solution containing 30 wt % or more of glycerin based on the total amount of the solvent, and covering at least a portion of the opening side of the case with a resin member.
  • the present invention makes it possible to reduce the amount of electrolyte leaking from a solid electrolytic capacitor.
  • 1 is a graph showing the relationship between the amount of electrolyte loss by solvent composition and the glycerin ratio in the solvent in a solid electrolytic capacitor having a resin member.
  • 1 is a graph showing a partial range of the relationship between the amount of electrolyte loss by solvent composition and the glycerin ratio in the solvent in a solid electrolytic capacitor having a resin member.
  • 1 is a graph showing the relationship between the amount of electrolyte loss by solvent composition and the glycerin ratio in the solvent in a solid electrolytic capacitor without a resin member.
  • FIG. 11 is a scatter diagram showing the correlation between the amount of missing resin members and the rate of weight change.
  • the solid electrolytic capacitor according to this embodiment is a passive element that obtains capacitance by the dielectric polarization action of a dielectric film and stores and discharges electric charge.
  • This solid electrolytic capacitor is a so-called hybrid type that uses both a solid electrolyte layer and an electrolytic solution.
  • the hybrid type solid electrolytic capacitor will be simply referred to as a solid electrolytic capacitor.
  • a solid electrolytic capacitor comprises an anode body, a cathode body, an electrolyte layer, and a separator.
  • the anode body has a dielectric film formed on its surface.
  • the cathode body faces the dielectric film and opposes the anode body.
  • the electrolyte layer is interposed between the anode body and the cathode body, in contact with the dielectric film, and serves as the true cathode of the solid electrolytic capacitor.
  • This electrolyte layer is made of a solid electrolyte layer and an electrolytic solution.
  • the separator is interposed between the anode body and the cathode body, isolating them and preventing short circuits.
  • the solid electrolytic capacitor has a cylindrical exterior case that is open at one end and has a bottom at the other end, and the anode body, cathode body, electrolyte layer, and separator are housed inside the exterior case.
  • the open end of the exterior case is covered with an elastic member and a resin member.
  • An anode lead is connected to the anode body, and a cathode lead is connected to the cathode body, and the anode lead and cathode lead are pulled out through the elastic member and the resin member.
  • the solid electrolytic capacitor is electrically connected to the mounting circuit via these anode lead and cathode lead.
  • the base material of the anode body is made of a valve metal.
  • the anode body is a long strip of valve metal stretched out, while in a laminate type solid electrolytic capacitor, the anode body is a flat plate of valve metal stretched out, a molded body of valve metal powder arranged in a flat plate shape, or a sintered body of valve metal powder sintered out.
  • Valve metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony.
  • the purity of the anode body is preferably 99.9% or more, but impurities such as silicon, iron, copper, and magnesium may be included.
  • a surface-expanding layer is formed on one or both sides of the anode body.
  • the surface-expanding layer is an etching layer formed by etching the substrate, a sintered layer formed by sintering valve metal powder onto the substrate, or a deposition layer formed by depositing valve metal particles onto the substrate.
  • the surface-expanding layer has a porous structure, consisting of tunnel-shaped pits, spongy pits, or gaps between densely packed powder or particles.
  • Tunnel-shaped etching pits are holes dug in the thickness direction of the foil. These tunnel-shaped etching pits are typically formed by passing a direct current in an acidic aqueous solution containing halogen ions, such as hydrochloric acid. The spongy etching pits turn the surface-expanding layer into a sponge-like layer with fine, interspersed gaps. These spongy etching pits are formed by passing an alternating current in an acidic aqueous solution containing halogen ions, such as hydrochloric acid.
  • the sintered layer is produced by obtaining a powder of a valve action metal of the same or different type as the foil body by a milling method, atomization method, melt spinning method, rotating disk method, rotating electrode method, etc., forming it into a paste using a binder or solvent, applying it to the foil body, drying it, and heating and sintering it in a vacuum or reducing atmosphere, etc.
  • the atomization method may be any of water atomization method, gas atomization method, and water gas atomization method.
  • the vapor deposition layer is produced by, for example, resistance heating vapor deposition method or electron beam heating vapor deposition method. This vapor deposition layer is formed by heating and evaporating a valve action metal of the same or different type as the foil body by resistance heat or electron beam energy, and depositing the vapor of the valve action metal particles on the surface of the foil body.
  • the dielectric film is formed on one or both sides of the anode body, following the unevenness of the surface expansion layer.
  • the dielectric film is typically an oxide film formed on the surface layer of the anode body, and if the anode body is made of aluminum, it is an aluminum oxide layer formed by oxidizing the surface of the surface expansion layer.
  • a voltage is applied to the anode body in a chemical conversion solution, aiming for the desired withstand voltage.
  • the chemical conversion solution is a solution that does not contain halogen ions, and examples of such solutions include phosphoric acid-based chemical conversion solutions such as ammonium dihydrogen phosphate, boric acid-based chemical conversion solutions such as ammonium borate, and adipic acid-based chemical conversion solutions such as ammonium adipate.
  • phosphoric acid-based chemical conversion solutions such as ammonium dihydrogen phosphate
  • boric acid-based chemical conversion solutions such as ammonium borate
  • adipic acid-based chemical conversion solutions such as ammonium adipate.
  • the cathode body is preferably a foil made of a valve metal and stretched.
  • the purity of the cathode body is preferably 99% or more.
  • the cathode body may have a surface-expanding layer formed thereon like the anode body, or a plain foil without a surface-expanding layer may be used as the cathode body.
  • the cathode body may have a natural oxide film or a thin oxide film (about 1 to 10 V) formed by chemical conversion treatment. The natural oxide film is formed by the reaction of the cathode body with oxygen in the air.
  • the cathode body may have a layer made of metal nitride, metal carbide, or metal carbonitride formed by vapor deposition, or a layer containing carbon may be formed on the surface.
  • the cathode body is preferably a laminate of a metal layer and a carbon layer.
  • the carbon layer of the cathode body is arranged facing the anode body.
  • the carbon layer is made into a paste, and is formed by applying it onto the electrolyte layer after the electrolyte layer is formed on the anode body, and then curing it by heating.
  • the metal layer is, for example, a silver layer, and is formed by applying it into a paste on the carbon layer, and then curing it by heating.
  • the electrolyte solvent is composed of glycerin at a ratio of 30 wt % or more of the total amount of the solvent.
  • the solvent other than glycerin is not particularly limited, and a protic polar solvent or an aprotic polar solvent can be used.
  • Representative examples of the protic polar solvent include polyhydric alcohols and oxyalcohol compounds, such as ethylene glycol, propylene glycol, diethylene glycol, and polyethylene glycol.
  • Representative examples of the aprotic polar solvent include sulfones and lactones, such as sulfolane, ⁇ -butyrolactone, ⁇ -valerolactone, ethylene carbonate, and propylene carbonate.
  • a solid electrolytic capacitor with a resin layer when the electrolyte solvent contains glycerin at a ratio of 30 wt% or more of the total amount of solvent, the amount of electrolyte that evaporates from the solid electrolytic capacitor is greatly improved compared to when the glycerin content is less than 30 wt% of the total amount of solvent. Furthermore, when the resin layer is omitted from the solid electrolytic capacitor, there is no significant change in the amount of electrolyte that evaporates at the 30 wt% boundary, and measures to make glycerin 30 wt% or more of the total amount of solvent are useful in solid electrolytic capacitors with a resin layer.
  • the solvent type other than glycerin is ethylene glycol, sulfolane, polyethylene glycol, or two or more of these, which further improves the amount of electrolyte that evaporates from the solid electrolytic capacitor.
  • the electrolyte may contain an electrolyte in addition to glycerin and a protic or aprotic polar liquid.
  • the electrolyte is typically a salt of an organic acid, a salt of an inorganic acid, or a salt of a complex compound of an organic acid and an inorganic acid, and may be used alone or in combination of two or more.
  • An acid that serves as an anion and a base that serves as a cation may be added separately to the liquid.
  • Organic acids that can be anionic components include carboxylic acids such as oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, 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, azelaic acid, resorcylic acid, phloroglucic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, and pyromellitic acid, as well as phenols and sulfonic acids.
  • carboxylic acids such as oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, ter
  • Inorganic acids that can be anionic components include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid.
  • An example of a composite compound of an organic acid and an inorganic acid is borodisalicylic acid.
  • examples of at least one salt of an organic acid, an inorganic acid, or a complex compound of an organic acid and an inorganic acid include ammonium salts, quaternary ammonium salts, quaternary amidinium salts, amine salts, sodium salts, potassium salts, etc.
  • examples of quaternary ammonium ions of quaternary ammonium salts include tetramethylammonium, triethylmethylammonium, tetraethylammonium, etc.
  • examples of quaternary amidinium salts include ethyldimethylimidazolinium, tetramethylimidazolinium, etc.
  • Examples of amine salts include salts of primary amines, secondary amines, and tertiary amines.
  • Examples of primary amines include methylamine, ethylamine, propylamine, etc.
  • examples of secondary amines include dimethylamine, diethylamine, ethylmethylamine, dibutylamine, etc.
  • examples of tertiary amines include trimethylamine, triethylamine, tributylamine, ethyldimethylamine, ethyldiisopropylamine, etc.
  • additives can be added to the electrolyte.
  • additives include complex compounds of boric acid and polysaccharides (mannitol, sorbitol, etc.), complex compounds of boric acid and polyhydric alcohols, boric acid esters, nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, p-nitrobenzyl alcohol, etc.), phosphate esters, alkyl phosphate esters, etc. These may be used alone or in combination of two or more.
  • the electrolyte is impregnated into the gaps in the capacitor element formed by the solid electrolyte layer.
  • the capacitor element is an assembly consisting of an anode body, a cathode body, and an electrolyte layer.
  • the electrolyte may be impregnated by immersing the capacitor element in a tank of electrolyte, or the electrolyte may be impregnated into the capacitor element within the exterior case.
  • a pressure reduction process or a pressure increase process may be performed as necessary; for example, the pressure may be reduced inside the capacitor element and the electrolyte may be pressurized.
  • the solid electrolyte layer includes a conductive polymer.
  • the conductive polymer is a self-doped conjugated polymer doped with an intramolecular dopant molecule, or an externally doped conjugated polymer doped with an external dopant molecule.
  • the conjugated polymer is obtained by chemically oxidizing or electrolytically oxidizing a monomer having a ⁇ -conjugated double bond or a derivative thereof.
  • the dopant or external dopant molecule is an acceptor that easily accepts electrons into the conjugated polymer, or a donor that easily gives electrons to the conjugated polymer, and this allows the conductive polymer to exhibit high conductivity.
  • this solid electrolyte layer allows glycerin to account for 30 wt% or more of the total amount of solvent.
  • an electrolyte in which glycerin accounts for 30 wt% or more of the total amount of solvent has high viscosity and therefore high resistivity.
  • the solid electrolyte layer has high conductivity, which offsets the high resistivity of the electrolyte and reduces the effect of the electrolyte on the internal resistance of the solid electrolytic capacitor.
  • conjugated polymers can be used without any particular limitations. Examples include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, polythiophenevinylene, etc. These conjugated polymers may be used alone, or two or more types may be combined, or they may be copolymers of two or more types of monomers.
  • conjugated polymers formed by polymerizing thiophene or its derivatives
  • conjugated polymers formed by polymerizing 3,4-ethylenedioxythiophene i.e., 2,3-dihydrothieno[3,4-b][1,4]dioxine
  • 3-alkylthiophene 3-alkoxythiophene
  • 3-alkyl-4-alkoxythiophene 3,4-alkylthiophene, 3,4-alkoxythiophene, or derivatives thereof.
  • thiophene derivative a compound selected from thiophenes having substituents at the 3rd and 4th positions is preferred, and the substituents at the 3rd and 4th positions of the thiophene ring may form a ring together with the carbons at the 3rd and 4th positions.
  • the alkyl group or alkoxy group preferably has 1 to 16 carbon atoms.
  • a polymer of 3,4-ethylenedioxythiophene called EDOT i.e., poly(3,4-ethylenedioxythiophene) called PEDOT
  • a substituent may be added to 3,4-ethylenedioxythiophene.
  • an alkylated ethylenedioxythiophene having an alkyl group having 1 to 5 carbon atoms added as a substituent may be used.
  • alkylated ethylenedioxythiophene examples include methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), butylated ethylenedioxythiophene (i.e., 2-butyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), and 2-alkyl-3,4-ethylenedioxythiophene.
  • methylated ethylenedioxythiophene i.e., 2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine
  • ethylated ethylenedioxythiophene i
  • the dopant may be an inorganic acid such as a polyanion, boric acid, nitric acid, or phosphoric acid, or an organic acid such as acetic acid, oxalic acid, citric acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzenedisulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylic acid, bisoxalateborate acid, sulfonylimide acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, or butylnaphthalenes
  • Polyanions include, for example, substituted or unsubstituted polyalkylenes, substituted or unsubstituted polyalkenylenes, substituted or unsubstituted polyimides, substituted or unsubstituted polyamides, and substituted or unsubstituted polyesters, and include polymers consisting only of structural units having an anionic group, and polymers consisting of structural units having an anionic group and structural units not having an anionic group.
  • polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid.
  • the solid electrolyte layer may contain a liquid component that has a hydroxy group and a high boiling point of 150°C or higher.
  • This high boiling point liquid component improves the chemical conversion properties of the dielectric film and increases the voltage resistance of the solid electrolytic capacitor.
  • high boiling point liquid components that have a hydroxy group and a boiling point of 150°C or higher include ethylene glycol, diethylene glycol, glycerin, diglycerin, polyethylene glycol, or a combination of two or more of these.
  • the conductive polymer may be attached by impregnating the anode body, the separator, or both of these, or further the cathode body or the capacitor element with a conductive polymer liquid and then drying.
  • the conductive polymer liquid is a dispersion or solution in which the conductive polymer is dispersed or dissolved in a dispersion medium or solvent.
  • a liquid component having a hydroxyl group and a high boiling point of 150°C or higher may also serve as the dispersion medium or solvent for this conductive polymer liquid. Even if the conductive polymer liquid is volatilized in the drying process, this high boiling point liquid component can be left in the solid electrolyte layer.
  • separator examples include cellulose such as kraft, Manila hemp, esparto, hemp, and rayon, and mixed papers thereof, polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and derivatives thereof, polytetrafluoroethylene-based resins, polyvinylidene fluoride-based resins, vinylon-based resins, polyamide-based resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides, polyimide-based resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, and polyvinyl alcohol resins, and these resins can be used alone or in combination. Note that if the anode body and the cathode body can be insulated by the solid electrolyte layer and the solid electrolyte layer can maintain its shape without a separator, the separator
  • the elastic member seals the open end of the exterior case.
  • the exterior case is made of metal, for example, aluminum, an aluminum alloy containing aluminum and manganese, or stainless steel.
  • An elastic member is inserted into the open end of the exterior case, and the elastic member is tightly attached by crimping, which bends the exterior case inward.
  • the elastic member is tightly attached to the crimped exterior case by elastic force, and can prevent the electrolyte from leaking out from between the elastic member and the exterior case. It is also possible to cover the open side of the exterior case with a resin member without using an elastic member.
  • the elastic member includes an elastomer.
  • the elastomer include isobutylene isoprene rubber, also known as butyl rubber, ethylene propylene diene rubber, also known as EPDM, styrene butadiene rubber, isoprene rubber, fluororubber, acrylic rubber, nitrile rubber, and natural rubber.
  • elastomers are produced by vulcanization such as resin vulcanization, peroxide vulcanization, sulfur vulcanization, quinoid vulcanization, and polyol vulcanization, and also include thermoplastic elastomers.
  • One or more types of elastomers may be used.
  • vulcanizing agents include benzoyl peroxide, dicumyl peroxide, 2,5 dimethyl-2,5 bis(t-butylperoxy)hexane, and alkylphenol formaldehyde resins.
  • crosslinking accelerators include zinc oxide, magnesium oxide, lead peroxide, dibenzothiazyl, disulfide, 1,2-polybutadiene, triallyl cyanurate, metal salts of methacrylic acid and acrylic acid, and ester stearate N,N'-metaphenyl dimaleic acid.
  • the elastic member may contain carbon and inorganic fillers in addition to the elastomer. When carbon and inorganic fillers are added, the elastomer is less likely to cleave, and softening of the elastic member is suppressed.
  • inorganic fillers include talc, mica, silica, kaolin, titania, alumina, and mixtures of these, with flat-shaped talc and mica being preferred. Flat-shaped inorganic fillers are suitable for promoting crosslinking and adjusting the crosslink density.
  • the elastic member may also have a hard synthetic resin plate or metal plate in addition to the elastomer layer, and may be a laminate of an elastomer layer and a hard synthetic resin plate or metal plate.
  • the resin member covers the opening side of the exterior case and suppresses evaporation of the electrolyte.
  • the resin member also serves as a heat insulating layer during a reflow process and the like, enhancing the heat resistance of the solid electrolytic capacitor.
  • the resin member is preferably disposed so as to cover the outer surface of the elastic member, and can suppress evaporation of the electrolyte that permeates the elastic member.
  • the resin member may be provided on the elastic member and laminated together with an elastomer layer. This resin member may not cover the entire opening of the exterior case, and may have a partially uncovered region, such as an extraction region for the anode lead and the cathode lead.
  • resin member After the elastic member is placed, this resin member is poured in liquid form onto the outer surface of the elastic member and allowed to solidify, forming the resin member on the opening side of the exterior case.
  • resin materials for the resin member include thermosetting resins, thermoplastic resins, and ultraviolet curing resins.
  • resin materials include epoxy resins, silicone resins, allyl resins, polybutylene terephthalate resins, polycarbonate resins, polyethylene terephthalate resins, acrylic resins, phenolic resins, polyamide resins, alkyd resins, and urethane resins.
  • the epoxy resin may be a two-part epoxy resin using an acid anhydride, or a one-part epoxy resin.
  • epoxy resin is preferred as the resin material for the resin member.
  • Epoxy resin is classified as a thermosetting resin or an ultraviolet-curing resin in the synthetic resin category, and does not soften with heat like thermoplastic resin, nor does it melt even when exposed to a high-temperature environment.
  • thermosetting resins epoxy resin, silicone resin, and allyl resin have a heat resistance of 150°C or more.
  • epoxy resin also has gas barrier properties and suppresses oxidative deterioration of conductive polymers.
  • the resin material for the resin member is preferably an epoxy resin that does not have an ester bond in its chemical structure.
  • Water is present in the electrolyte either intentionally or during the production process. If the epoxy resin has an ester bond in its chemical structure, when the electrolyte comes into contact with the resin member, the ester bond reacts with water, causing the epoxy resin to hydrolyze. In addition, if a compound with a hydroxyl group is present in the electrolyte, the carbonyl group generated by hydrolysis and this compound cause an esterification reaction. Epoxy resin that reacts with water or a compound with a hydroxyl group dissolves into the electrolyte in the solid electrolytic capacitor, increasing the ESR of the solid electrolytic capacitor. Therefore, the resin material for the resin member is preferably an epoxy resin that does not have an ester bond in its chemical structure.
  • Epoxy resins that do not have ester bonds in their chemical structure include amine-cured epoxy resins and phenol-cured epoxy resins.
  • Amine-cured epoxy resins are epoxy resins cured with an amine-curing agent, and contain an amine-curing agent and an epoxy resin in their chemical structure.
  • Phenol-cured epoxy resins are epoxy resins cured with a phenol-based curing agent, and contain a phenol-based curing agent and an epoxy resin in their chemical structure.
  • Amine-cured epoxy resins are produced by the reaction and bonding of amino groups and epoxy groups, and have ether bonds and no ester bonds.
  • Phenol-cured epoxy resins are produced by the reaction and bonding of phenolic hydroxyl groups and epoxy groups, and have ether bonds and no ester bonds.
  • the epoxy resin contained in phenol-based cured epoxy resins and amine-based cured epoxy resins is an epoxy oligomer with two or more reactive epoxy groups at the end. This epoxy resin changes from a liquid to a solid resin by bridging between the epoxy resin molecules through an addition reaction with an acid anhydride curing agent.
  • a typical example of an epoxy resin is bisphenol A diglycidyl ether, which is a condensation product of bisphenol A and epichlorohydrin.
  • Other examples of epoxy resins include other glycidyl-type epoxy resins and alicyclic epoxides such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate.
  • Glycidyl type epoxy resins include bisphenol types in which bisphenols have been glycidylated.
  • bisphenols include bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol AD, tetramethyl bisphenol S, tetrabromobisphenol A, tetrachlorobisphenol A, and tetrafluorobisphenol A.
  • Glycidyl-type epoxy resins include epoxy resins obtained by glycidylating dihydric phenols.
  • dihydric phenols include biphenol, dihydroxynaphthalene, and 9,9-bis(4-hydroxyphenyl)fluorene.
  • Glycidyl-type epoxy resins include epoxy resins obtained by glycidylating trisphenols.
  • triphenols include 1,1,1-tris(4-hydroxyphenyl)methane and 4,4-(1-(4-(1-(4-hydroxyphenyl)-1-methylethyl)phenyl)ethylidene)bisphenol.
  • Glycidyl-type epoxy resins include epoxy resins obtained by glycidylating tetrakisphenols.
  • tetrakisphenols include 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane.
  • Glycidyl type epoxy resins include novolac type epoxy resins obtained by glycidylating novolacs.
  • novolacs include phenol novolac, cresol novolac, bisphenol A novolac, brominated phenol novolac, and brominated bisphenol A novolac.
  • Glycidyl-type epoxy resins include epoxy resins obtained by glycidylating polyhydric phenols, and aliphatic ether-type epoxy resins obtained by glycidylating polyhydric alcohols such as glycerin and polyethylene glycol.
  • Glycidyl type epoxy resins include ether ester type epoxy resins obtained by glycidylating hydroxycarboxylic acids, ester type epoxy resins obtained by glycidylating polycarboxylic acids, glycidyl compounds of amine compounds, and amine type epoxy resins.
  • Hydroxycarboxylic acids include p-oxybenzoic acid and ⁇ -oxynaphthoic acid.
  • Polycarboxylic acids include phthalic acid and terephthalic acid.
  • Amine compounds include 4,4-diaminodiphenylmethane and m-aminophenol.
  • Amine type epoxy resins include triglycidyl isocyanurate.
  • Phenol-based curing agents contained in phenol-based cured epoxy resins include bifunctional phenols and polyfunctional phenols.
  • Bifunctional phenols include hydroquinone, resorcinol, bisphenol F, biphenol, tetrabromobisphenol A, and naphthalene diol.
  • Polyfunctional phenols include, for example, phenol novolac resin.
  • Amine-based curing agents contained in amine-based cured epoxy resins include aliphatic polyamines, aromatic polyamines, and modified amines.
  • Aliphatic polyamines include diethylenetriamine and triethylenetetramine.
  • Aromatic polyamines include metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone.
  • Modified amines include amine adducts and ketimines.
  • Examples 1 to 18 Various solid electrolytic capacitors were produced.
  • the various solid electrolytic capacitors had the following in common.
  • First, an anode body and a cathode body were produced using aluminum foil. Both the anode body and the cathode body were surface-enlarged by AC etching to form spongy etching pits.
  • a dielectric film was formed on the foil surface of the anode body and the cathode body by chemical conversion treatment. In the chemical conversion treatment process for the anode body, the chemical conversion voltage was increased to 66 V and then held for 10 minutes. In the chemical conversion treatment process for the cathode body, the chemical conversion voltage was increased to 3 V and then held for 10 minutes.
  • a lead wire was connected to each of the anode and cathode bodies, and the anode and cathode foils were wound facing each other with a manila paper separator in between.
  • the wound body had a diameter of 10 mm and a height of 10 mm.
  • Repair formation was performed by passing a current through the wound body for 10 minutes in an aqueous solution of ammonium dihydrogen phosphate at a liquid temperature of 90°C under conditions of an applied voltage of 56.5 V and a current density of 10 mA.
  • the wound body was first impregnated with a conductive polymer liquid.
  • the conductive polymer liquid was a dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT/PSS) doped with polystyrene sulfonic acid (PSS).
  • PEDOT/PSS was added at a ratio of 1.2 wt% to the entire conductive polymer liquid.
  • Ethylene glycol was also added to the conductive polymer liquid at a ratio of 10 wt% to the conductive polymer dispersion.
  • the wound body was impregnated with this conductive polymer liquid for 10 minutes at room temperature and in a reduced pressure environment of -0.3 MPa.
  • the wound body was impregnated with the electrolyte.
  • the electrolyte was allowed to soak into the wound body for 10 minutes at room temperature and in a reduced pressure environment of -0.3 MPa.
  • the capacitor element was housed in an exterior case, and the open end of the exterior case was sealed with an elastic member.
  • the elastic member and the exterior case were tightly attached by crimping.
  • the elastic member was made of butyl rubber.
  • resin was poured onto the outer surface of the elastic member and allowed to harden, forming a resin member that covers the outer surface of the elastic member.
  • the poured resin is an amine-based cured epoxy resin that does not have an ester bond in its chemical structure.
  • the various solid electrolytic capacitors have different electrolyte solvents. However, all solid electrolytic capacitors have in common the addition of 5 wt% ammonium azelaate to the total amount of electrolyte.
  • the electrolyte solvent is composed of glycerin and ethylene glycol, and the ratio of glycerin in the solvent is different.
  • the electrolyte solvent is composed of glycerin and sulfolane, and the ratio of glycerin in the solvent is different.
  • the electrolyte solvent is composed of glycerin and polyethylene glycol, and the ratio of glycerin in the solvent is different.
  • the electrolyte solvent is composed of glycerin and gamma-butyrolactone, and the ratio of glycerin in the solvent is different.
  • the various solid electrolytic capacitors were left at a temperature of 170°C for 560 hours, and the amount of electrolyte lost was measured based on the weight difference before and after leaving the capacitors.
  • the amounts of electrolyte lost for the various solid electrolytic capacitors are shown in Tables 1 to 4 below.
  • the amount of electrolyte leakage increases in the range where the glycerin ratio in the electrolyte solvent is low, with the border being 30 wt%, while the amount of electrolyte leakage is suppressed in the range where the glycerin ratio is high, with the border being 30 wt%. It was confirmed that this tendency is prominent when the electrolyte solvent is composed of glycerin and ethylene glycol, sulfolane, or polyethylene glycol.
  • the electrolyte solvent is composed of glycerin and ethylene glycol, sulfolane, or polyethylene glycol, the amount of electrolyte loss is kept particularly low.
  • various solid electrolytic capacitors serving as reference examples were produced and the amount of electrolyte loss was measured.
  • the various solid electrolytic capacitors serving as reference examples were the same as the respective examples and comparative examples, including the composition of the electrolyte, except that the resin member was omitted.
  • the various solid electrolytic capacitors serving as reference examples were left at a temperature of 170°C for 560 hours, and the amount of electrolyte loss was measured based on the weight difference before and after leaving the capacitors. The results are shown in Figure 3.
  • Figure 3 is a graph showing the relationship between the amount of leakage for each solvent composition of the reference electrolyte and the glycerin ratio in the solvent.
  • the square plots are the first group containing ethylene glycol
  • the triangle plots are the second group containing sulfolane
  • the diamond plots are the third group containing polyethylene glycol
  • the circle plots are the fourth group containing gamma-butyrolactone.
  • Example 19 to 24 In Examples 1 to 18, an amine-based cured epoxy resin having no ester bond in its chemical structure was used as the resin member. Next, the type of resin member was changed and the weight change rate was measured for each combination of the resin member and the solvent of the electrolyte.
  • Example 19 to 21 and Comparative Examples 9 and 10 an acid anhydride-based cured epoxy resin having an ester bond in its chemical structure was used as the resin component.
  • the solvent of the electrolyte in Examples 19 to 21 and Comparative Examples 9 and 10 was composed of glycerin and ethylene glycol, and the ratio of glycerin in the solvent was different.
  • the entire solvent was glycerin, in Example 20, the solvent contained 40 wt% glycerin, in Example 21, the solvent contained 30 wt% glycerin, in Comparative Example 9, the solvent contained 25 wt% glycerin, and in Comparative Example 10, the entire solvent was ethylene glycol.
  • Example 22 to 24 and Comparative Examples 11 and 12 acrylic resin was used as the resin member.
  • the solvent of the electrolyte in Examples 22 to 24 and Comparative Examples 11 and 12 was composed of glycerin and ethylene glycol, and the ratio of glycerin in the solvent was different.
  • the entire solvent was glycerin, in Example 23, the solvent contained 40 wt% glycerin, in Example 24, the solvent contained 30 wt% glycerin, in Comparative Example 11, the solvent contained 25 wt% glycerin, and in Comparative Example 12, the entire solvent was ethylene glycol.
  • the weight change rate is the weight of the resin member that has changed due to the electrolyte absorbed into the resin member.
  • a temperature environment of 170°C 0.5 g of the resin member was immersed in 5 mL of electrolyte solvent and left to stand for 48 hours. After 48 hours, the resin member was removed from the electrolyte solvent, excess liquid was wiped off from the surface, and the weight of the resin member after immersion was measured. The initial weight of the resin member was also measured beforehand prior to this 49-hour immersion test. The initial weight was then subtracted from the weight after immersion, and the percentage of the difference relative to the initial weight was calculated as the weight change rate.
  • this weight change rate has a high correlation with the amount of electrolyte lost.
  • Table 1 the weight change rate was measured along with the amount of electrolyte lost for Examples 1, 4, and 5 and Comparative Examples 1 and 2.
  • Figure 4 is a scatter plot of the weight change rate along with the amount of electrolyte lost for Examples 1, 4, and 5 and Comparative Examples 1 and 2.
  • Table 5 shows the weight change rates for Examples 1, 4 and 5, Examples 19 to 24, and Comparative Examples 9 to 12. (Table 5)
  • the weight change rate is high in the range where the glycerin ratio in the solvent is low, with the boundary set at 30 wt%, and the weight change rate is low in the range where the glycerin ratio is high.
  • the amount of electrolyte lost is high in the range where the glycerin ratio in the solvent is low, with the boundary set at 30 wt%, and the amount of electrolyte lost is low in the range where the glycerin ratio is high.
  • the weight change rate of the two types of epoxy resin is approximately one-third of that of acrylic resin. This confirms that when covering at least a portion of the open side of the case with a resin member, the amount of electrolyte loss from the solid electrolytic capacitor can be further suppressed by including 30 wt% or more of glycerin in the electrolyte solvent and using epoxy resin as the resin member.

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016082053A (ja) * 2014-10-16 2016-05-16 パナソニックＩｐマネジメント株式会社 電解コンデンサ
WO2018123525A1 (ja) * 2016-12-27 2018-07-05 パナソニックＩｐマネジメント株式会社 電解コンデンサ
WO2021193291A1 (ja) * 2020-03-27 2021-09-30 日本ケミコン株式会社 電解コンデンサ
WO2023054502A1 (ja) * 2021-09-30 2023-04-06 日本ケミコン株式会社 固体電解コンデンサ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016082053A (ja) * 2014-10-16 2016-05-16 パナソニックＩｐマネジメント株式会社 電解コンデンサ
WO2018123525A1 (ja) * 2016-12-27 2018-07-05 パナソニックＩｐマネジメント株式会社 電解コンデンサ
WO2021193291A1 (ja) * 2020-03-27 2021-09-30 日本ケミコン株式会社 電解コンデンサ
WO2023054502A1 (ja) * 2021-09-30 2023-04-06 日本ケミコン株式会社 固体電解コンデンサ

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