WO2024135668A1 - 固体電解コンデンサ素子および固体電解コンデンサ - Google Patents

固体電解コンデンサ素子および固体電解コンデンサ Download PDF

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WO2024135668A1
WO2024135668A1 PCT/JP2023/045459 JP2023045459W WO2024135668A1 WO 2024135668 A1 WO2024135668 A1 WO 2024135668A1 JP 2023045459 W JP2023045459 W JP 2023045459W WO 2024135668 A1 WO2024135668 A1 WO 2024135668A1
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Prior art keywords
layer
solid electrolytic
electrolytic capacitor
anode body
cathode
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English (en)
French (fr)
Japanese (ja)
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直貴 馬橋
兄 廣田
孝拓 吉井
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to CN202380086779.0A priority Critical patent/CN120380561A/zh
Priority to JP2024566073A priority patent/JPWO2024135668A1/ja
Publication of WO2024135668A1 publication Critical patent/WO2024135668A1/ja
Priority to US19/229,074 priority patent/US20250299889A1/en
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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
    • H01G9/004—Details
    • H01G9/022—Electrolytes; Absorbents
    • H01G9/025—Solid electrolytes
    • H01G9/028—Organic semiconducting electrolytes, e.g. TCNQ
    • 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
    • H01G9/0029—Processes of manufacture
    • H01G9/0036—Formation of the solid electrolyte layer
    • 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
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
    • H01G9/0425—Electrodes or formation of dielectric layers thereon characterised by the material specially adapted for cathode
    • 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
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
    • H01G9/055—Etched foil electrodes
    • 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
    • H01G9/07—Dielectric layers
    • 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

  • This disclosure relates to solid electrolytic capacitor elements and solid electrolytic capacitors.
  • a solid electrolytic capacitor comprises a solid electrolytic capacitor element, a resin exterior body or case that seals the solid electrolytic capacitor element, and an external electrode that is electrically connected to the solid electrolytic capacitor element.
  • the solid electrolytic capacitor element comprises, for example, an anode body, a dielectric layer formed on the surface of the anode body, and a cathode portion that covers at least a portion of the dielectric layer.
  • the cathode portion includes a conductive polymer (e.g., a conjugated polymer and a dopant) that covers at least a portion of the dielectric layer.
  • the conductive polymer is also referred to as a solid electrolyte.
  • Patent Document 1 proposes a method for manufacturing a solid electrolytic capacitor equipped with a capacitor element having a dielectric layer and a solid electrolyte layer, in which the formation of the solid electrolyte layer is carried out in the following order: a first step of applying a first conductive polymer solution in which conductive polymer particles are dispersed and drying to form a first conductive polymer layer; a second step of applying a coating solution containing at least one selected from aromatic sulfonic acid or its salt having a carboxyl group and a hydroxyl group or two carboxyl groups in one molecule to the first conductive polymer layer and drying; and a third step of applying a second conductive polymer solution in which conductive polymer particles are dispersed and drying to form a second conductive polymer layer.
  • a solution containing a cation of an amine compound is used as the coating solution.
  • Patent Document 2 proposes a conductive polymer capacitor characterized in that the ratio of the number of atoms in the electrode cross section, ⁇ /(Al+N+S+ ⁇ ), is 0.01 or less ( ⁇ is the number of cationic atoms that make up the oxidizer, and Al, N, and S are the numbers of aluminum, nitrogen, and sulfur atoms, respectively).
  • the equivalent series resistance may increase after the solid electrolytic capacitor is exposed to a high temperature and high humidity environment.
  • a first aspect of the present disclosure includes an anode body having a porous portion at least on a surface layer, a dielectric layer covering at least a portion of the anode body; a cathode portion covering at least a portion of the dielectric layer, the cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer, the solid electrolyte layer contains a nitrogen element N, a sulfur element S, a carbon element C, and an oxygen element O, and has a first portion filled in voids of the porous portion in the anode body having the dielectric layer, and a second portion protruding from a main surface of the anode body having the dielectric layer,
  • the solid electrolytic capacitor element relates to a mass ratio of elemental nitrogen N to elemental sulfur S in the second portion: N/S, which is 0.30 or more and 1.00 or less.
  • the second aspect of the present disclosure relates to a solid electrolytic capacitor that includes at least one of the solid electrolytic capacitor elements described above.
  • FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure.
  • FIG. 2 is a schematic front view of a solid electrolytic capacitor element as viewed from one main surface side.
  • 3 is a schematic cross-sectional view of the solid electrolytic capacitor element taken along line III-III in FIG. 2, viewed in the direction of the arrows.
  • the solid electrolyte layer formed in this way contains N element derived from the cationic agent and S element derived from the anionic agent.
  • N/S the balance of N/S, the mass ratio of nitrogen element N to sulfur element S in the solid electrolyte layer, affects the ESR of the solid electrolytic capacitor.
  • the cathode part may include a solid electrolyte layer and a cathode extraction layer that covers the solid electrolyte layer.
  • the specific resistance of the cathode extraction layer may increase due to the action of components derived from the anionic agent in the solid electrolyte layer. This is also thought to increase the ESR of the solid electrolytic capacitor.
  • a solid electrolytic capacitor element includes an anode body having a porous portion at least on its surface, a dielectric layer covering at least a portion of the anode body, and a cathode portion covering at least a portion of the dielectric layer.
  • the cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer.
  • the solid electrolyte layer includes nitrogen element N, sulfur element S, carbon element C, and oxygen element O, and has a first portion filled in the voids of the porous portion in the anode body having the dielectric layer, and a second portion protruding from the main surface of the anode body having the dielectric layer.
  • the mass ratio of nitrogen element N to sulfur element S in the second portion: N/S is 0.30 or more and 1.00 or less.
  • the solid electrolytic capacitor element may be referred to as a capacitor element.
  • the N/S ratio within the above range, the amount of moisture absorption of the solid electrolyte layer when the solid electrolytic capacitor is exposed to a high temperature and high humidity environment can be reduced, and an increase in the specific resistance can be suppressed.
  • an increase in the specific resistance of the cathode lead layer (metal particle-containing layer, etc.) due to components derived from an anionic agent such as a sulfonic acid compound can be suppressed. Therefore, an increase in the ESR of the solid electrolytic capacitor when exposed to a high temperature and high humidity environment can be suppressed.
  • the reason why the increase in the specific resistance is suppressed is thought to be that the N element-containing component derived from the cationic agent and the S element-containing component derived from the anionic agent interact to reduce the amount of moisture absorption and reduce the effect on the cathode lead layer.
  • the N/S ratio is less than 0.30, the specific resistance of the cathode lead layer (metal particle-containing layer, etc.) increases.
  • the N/S ratio exceeds 1.00, the amount of moisture absorption of the solid electrolyte layer increases, and the specific resistance increases. Therefore, in either case, the ESR increases when the solid electrolytic capacitor is exposed to a high temperature and high humidity environment.
  • the mass ratio of the nitrogen element N to the total amount of the carbon element C, the oxygen element O, and the sulfur element S in the second portion: N/(C+O+S) may be 0.033 or more and 0.050 or less.
  • the maximum thickness of the second portion may be 15 ⁇ m or more and 42 ⁇ m or less.
  • the conductive polymer deteriorates or dedoping occurs, and the conductivity is likely to decrease. Such a decrease in conductivity is likely to occur from the outside of the solid electrolyte layer.
  • the maximum thickness of the second portion be 15 ⁇ m or more, even if the conductivity of the outer part of the solid electrolyte layer decreases, the inner part maintains high conductivity and the increase in ESR can be suppressed.
  • the maximum thickness of the second portion be 42 ⁇ m or less, a higher capacity can be obtained.
  • the anode body has an anode lead-out portion including a first end and a cathode forming portion including a second end.
  • the ratio T1/T2 of the thickness T1 of the second portion formed at the corner of the anode body to the thickness T2 of the second portion formed at the center of the anode body may be 0.8 or more and 1.7 or less.
  • the variation in the thickness of the solid electrolyte layer over the entire surface of the cathode forming portion of the anode body is suppressed, and an increase in ESR, a decrease in electrostatic capacitance, etc. are suppressed, and the quality of the solid electrolytic capacitor is more stabilized.
  • the cathode portion includes a conductive carbon layer that covers at least a portion of the solid electrolyte layer.
  • the cathode lead layer (particularly the metal particle-containing layer) is prone to degradation and reduced conductivity due to components derived from the sulfonic acid compound contained in the solid electrolyte layer.
  • the N/S ratio of the second portion is within a specific range, which suppresses degradation of the cathode lead layer (such as the metal particle-containing layer) and ensures high conductivity, thereby making it possible to keep the ESR low.
  • the second portion may include a conjugated polymer and a dopant.
  • the conjugated polymer may include a monomer unit corresponding to a thiophene compound, and the dopant may have a sulfo group.
  • the second portion includes such a conjugated polymer and a dopant, the increase in ESR in a high temperature and high humidity environment can be further suppressed by setting the N/S ratio within the above range.
  • the present disclosure also includes a solid electrolytic capacitor that includes at least one capacitor element described in any one of (1) to (6) above.
  • the solid electrolytic capacitor and capacitor element of the present disclosure will be described in more detail below, including the above (1) to (7). At least one selected from the components described below can be arbitrarily combined with at least one of the above (1) to (7) related to the solid electrolytic capacitor of the present disclosure, as long as such combination is technically possible.
  • a solid electrolytic capacitor includes one or more capacitor elements.
  • the capacitor element includes an anode body, a dielectric layer covering at least a portion of the anode body, and a cathode portion covering at least a portion of the dielectric layer.
  • the cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer.
  • the anode body may contain, for example, a valve metal, an alloy containing a valve metal, or a compound containing a valve metal (such as an intermetallic compound). These materials may be used alone or in combination of two or more.
  • the valve metal include aluminum, tantalum, niobium, and titanium.
  • the anode body may be a foil (anode foil) of a valve metal, an alloy containing a valve metal, or a compound containing a valve metal, or it may be a compact (porous compact) or a sintered body (porous sintered body) of particles of a valve metal, an alloy containing a valve metal, or a compound containing a valve metal.
  • the anode body has an anode lead portion including a first end, and a cathode forming portion including a second end opposite the first end.
  • a cathode portion including a solid electrolyte layer is formed on the surface of the cathode forming portion of the anode body.
  • the anode lead portion is used, for example, for electrical connection with an external electrode on the anode side.
  • An anode lead terminal may be connected to the anode lead portion.
  • the anode body has a porous portion at least on the surface.
  • the porous portion contains many fine voids.
  • the porous portion gives the anode body at least a finely uneven shape on the surface, increasing the surface area and providing a high capacity.
  • the porous portion may be formed on a part of the surface of the anode body, or on the entire surface.
  • the porous portion may be formed, for example, on at least the surface of the cathode forming portion, or may be formed on at least a part of the surface of the anode lead-out portion in addition to the surface of the cathode forming portion.
  • the anode body is a porous molded body or a porous sintered body, the entire anode body may constitute the porous portion.
  • the porous portion is formed by roughening the surface of at least the portion of the base material (e.g., metal foil) containing the valve metal that corresponds to the cathode-forming portion.
  • the roughening may be performed by an etching process or the like.
  • the etching process may be performed by electrolytic etching or chemical etching.
  • An anode body usually has six faces that determine the external shape of the anode body. Of these faces, the face that occupies the largest area (usually a pair of faces) is called the main face, and the faces other than the main faces are sometimes called end faces. There are corners between adjacent faces. For example, if the anode body is an anode foil, it has a pair of main faces that occupy most of the area of the anode foil, and end faces that exist between the pair of main faces.
  • the direction from the first end to the second end when the anode body (such as an anode foil) is flat is sometimes referred to as the length direction of the anode body.
  • the direction from the first end side to the second end side is a direction parallel to the line connecting the center of the end face of the first end and the center of the end face of the second end. This direction is sometimes referred to as the length direction of the anode body or capacitor element.
  • the direction perpendicular to the length direction and thickness direction of the anode body (or capacitor element) is sometimes referred to as the width direction of the anode body (or capacitor element).
  • the dielectric layer is an insulating layer that functions as a dielectric.
  • the dielectric layer is formed by anodizing the valve metal on the surface of the anode body by chemical conversion treatment or the like.
  • the surface of the dielectric layer has a fine uneven shape according to the shape of the surface of the porous portion.
  • the dielectric layer may be formed of a material that functions as a dielectric layer.
  • examples of such materials include oxides of valve metals.
  • the dielectric layer may include Ta2O5 when tantalum is used as the valve metal, and may include Al2O3 when aluminum is used as the valve metal .
  • the dielectric layer is not limited to these specific examples.
  • the cathode portion includes at least a solid electrolyte layer covering at least a portion of the dielectric layer.
  • the solid electrolyte layer is formed on the portion of the anode body on the second end side (in other words, the cathode formation portion) via a dielectric layer.
  • the cathode portion usually includes a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer.
  • the solid electrolyte layer and the cathode extraction layer will be described below.
  • the solid electrolyte layer contains N, S, C, and O elements.
  • the solid electrolyte layer is divided into a first portion filled in the voids of the porous portion and a second portion protruding from the main surface of the anode body having the dielectric layer.
  • the mass ratio of N to S in the second portion: N/S is 0.30 or more and 1.00 or less. With the N/S ratio in this range, it is possible to reduce an increase in ESR after the solid electrolytic capacitor is exposed to a high temperature and high humidity environment.
  • the solid electrolyte layer is composed of a solid electrolyte (in other words, a conductive polymer).
  • the conductive polymer includes a conjugated polymer and a dopant.
  • the conductive polymer may further include an additive, if necessary.
  • the solid electrolyte layer also includes at least one selected from the group consisting of components derived from the cationic agent and components derived from the anionic agent as described above.
  • the N element may be derived from the conjugated polymer, but most of the N element is derived from the cationic agent contained in the treatment liquid.
  • the S element may be derived from the conjugated polymer or the dopant, but most of the S element is derived from the anionic agent contained in the treatment liquid.
  • the N/S ratio represents the balance between the cationic agent and the anionic agent in the second part of the solid electrolyte layer.
  • the N element and the S element may be included in the first part.
  • the N/S ratio in the above range can provide a significant effect of suppressing the increase in ESR.
  • the N/S ratio is 0.30 or more, and may be 0.35 or more, or 0.40 or more, or 0.41 or more.
  • the N/S ratio is 1.00 or less, or 0.97 or less, or 0.95 or less. From the viewpoint of further reducing the ESR after the solid electrolytic capacitor is exposed to a high temperature and high humidity environment, the N/S ratio may be 0.80 or less, or 0.77 or less.
  • the N/S ratio may be, for example, 0.30 or more and 1.00 or less, 0.35 or more and 0.97 or less, or 0.40 or more and 0.95 or less.
  • the C and O elements contained in the solid electrolyte layer are mostly derived from the conductive polymer.
  • the N/(C+O+S) ratio may be 0.033 or more, or may be 0.034 or more. From the viewpoint of further reducing the ESR after the solid electrolytic capacitor is exposed to a high temperature and high humidity environment, the N/(C+O+S) ratio may be 0.035 or more.
  • the N/(C+O+S) ratio may be 0.050 or less, or may be 0.046 or less.
  • the N/(C+O+S) ratio may be 0.033 or more and 0.050 or less, 0.034 or more and 0.050 or less, or 0.035 or more and 0.050 or less.
  • the mass content of each element in the second portion is determined by performing element mapping using energy dispersive X-ray spectroscopy (EDX) based on an image of the capacitor element or solid electrolytic capacitor with the second portion exposed, taken with a scanning electron microscope (SEM).
  • EDX energy dispersive X-ray spectroscopy
  • SEM scanning electron microscope
  • the N/S ratio and N/(C+O+S) ratio are determined from the obtained content.
  • the element mapping is performed on a rectangular region (region A) having a first side with a length of 10 ⁇ m or more and 20 ⁇ m or less, and a second side perpendicular to the first side with a length of 12 ⁇ m or more and 25 ⁇ m or less.
  • the first side of region A may or may not be parallel to the width direction or thickness direction of the capacitor element.
  • the second side of region A may or may not be parallel to the thickness direction or width direction of the capacitor element.
  • the shortest distance between region A and the main surface of the anode body may be 0 ⁇ m or more and 5 ⁇ m or less.
  • the shortest distance between region A and the main surface of the anode body is the shortest distance between the average main surface of the anode body determined in the above cross-sectional image and region A.
  • the content of each element is determined by measuring and averaging multiple regions A of the exposed cross-section. It is preferable that both of the shortest distances between each region A and the main surface of the anode body satisfy the above range.
  • a sample for taking an SEM image is prepared by the following procedure.
  • a capacitor element or solid electrolytic capacitor is embedded in a curable resin, and the curable resin is cured.
  • the cured product is wet or dry polished to expose a cross section parallel to the thickness direction of the cathode part (a cross section where the stacking state of each layer of the cathode part can be confirmed).
  • the exposed cross section is smoothed by ion milling to obtain a sample for imaging.
  • the cross section is taken at a position 0 to 0.05 (0 or more and 0.05 or less) from the end on the first end side of the area where the solid electrolyte layer is formed, where the length of the area where the solid electrolyte layer is formed in the direction parallel to the longitudinal direction of the capacitor element is taken as 1.
  • the maximum thickness of the second portion may be 15 ⁇ m or more, or 16 ⁇ m or more.
  • the maximum thickness of the second portion may be 42 ⁇ m or less, or 40 ⁇ m or less.
  • the maximum thickness of the second portion may be, for example, 15 ⁇ m or more and 42 ⁇ m or less, or 16 ⁇ m or more and 42 ⁇ m or less.
  • T1/T2 In a cross section of the solid electrolyte layer perpendicular to the direction from the first end to the second end of the capacitor element at any position on the part on the first end side of the anode body, the ratio of the thickness T1 of the second part formed at the corner of the anode body to the thickness T2 of the second part formed at the center of the anode body: T1/T2 may be 0.8 or more, or 0.9 or more.
  • the T1/T2 ratio may be 1.7 or less, 1.5 or less, or 1.2 or less.
  • the T1/T2 ratio may be, for example, 0.8 or more and 1.7 or less, or 0.9 or more and 1.7 or less.
  • the T1/T2 ratio is in such a range, the variation in the conductivity of the solid electrolyte layer when the solid electrolytic capacitor is exposed to a high temperature and high humidity environment is suppressed, and the increase in ESR is further suppressed.
  • the thickness of the solid electrolyte layer at the corner is suppressed from becoming thinner, thereby suppressing the occurrence of product defects due to short circuits.
  • the first part includes at least a first conductive polymer layer, and may include a first conductive polymer layer and a second conductive polymer layer.
  • the first part may be a single layer, or may be composed of multiple layers.
  • the types, compositions, contents, etc. of the conductive polymers and additives contained in each layer may be the same or different.
  • each of the first conductive polymer layer and the second conductive polymer layer does not necessarily have to be in a layered form.
  • the first conductive polymer may be attached to the surface of the dielectric layer.
  • the first conductive polymer and the second conductive polymer contained in each conductive polymer layer include known conductive polymers used in solid electrolytic capacitors, such as conjugated polymers (such as ⁇ -conjugated polymers) and dopants.
  • the first conductive polymer may include a self-doped conductive polymer.
  • Conjugated polymers include, for example, polymers having a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene.
  • the above polymers need only contain at least one type of monomer unit that constitutes the basic skeleton.
  • Monomer units also include monomer units having a substituent.
  • the above polymers also include homopolymers and copolymers of two or more types of monomers.
  • polythiophenes include poly3,4-ethylenedioxythiophene (PEDOT).
  • thiophene compounds include compounds that have a thiophene ring and can form a repeating structure of the corresponding monomer unit.
  • Thiophene compounds can form a repeating structure of the monomer unit by linking at the 2- and 5-positions of the thiophene ring.
  • the thiophene compound may have a substituent at least at the 3rd and 4th positions of the thiophene ring.
  • the substituent at the 3rd position and the substituent at the 4th position may be linked to form a ring condensed to the thiophene ring.
  • Examples of the thiophene compound include thiophenes and alkylenedioxythiophene compounds (C 2-4 alkylenedioxythiophene compounds such as ethylenedioxythiophene compounds) that may have a substituent at least at the 3rd and 4th positions.
  • the alkylenedioxythiophene compound also includes those having a substituent in the alkylene group portion.
  • substituents include, but are not limited to, alkyl groups (e.g., C 1-4 alkyl groups such as methyl and ethyl groups), alkoxy groups (e.g., C 1-4 alkoxy groups such as methoxy and ethoxy groups), hydroxy groups, hydroxyalkyl groups (e.g., hydroxy C 1-4 alkyl groups such as hydroxymethyl groups), etc.
  • alkyl groups e.g., C 1-4 alkyl groups such as methyl and ethyl groups
  • alkoxy groups e.g., C 1-4 alkoxy groups such as methoxy and ethoxy groups
  • hydroxy groups e.g., hydroxyalkyl groups (e.g., hydroxy C 1-4 alkyl groups such as hydroxymethyl groups), etc.
  • the respective substituents may be the same or different.
  • the conjugated polymer may be used alone or in combination of two or more types.
  • the weight average molecular weight (Mw) of the conjugated polymer is not particularly limited, but is, for example, 1,000 or more and 1,000,000 or less.
  • the weight average molecular weight (Mw) is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC). GPC is usually measured using a polystyrene gel column and water/methanol (volume ratio 8/2) as the mobile phase.
  • a dopant for example, at least one selected from the group consisting of anions and polyanions is used.
  • anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions.
  • dopants that generate sulfonate ions include aromatic sulfonic acid compounds (such as paratoluenesulfonic acid and naphthalenesulfonic acid).
  • polyanions examples include polymeric polysulfonic acids and polymeric polycarboxylic acids.
  • Polymeric polysulfonic acids include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, and polymethacrylic sulfonic acid.
  • Polymeric polycarboxylic acids include polyacrylic acid and polymethacrylic acid.
  • Polyanions also include polyester sulfonic acid and phenol sulfonic acid novolac resin. However, polyanions are not limited to these.
  • polyanions that have relatively high heat resistance and electron-withdrawing properties (e.g., polymeric polysulfonic acid).
  • the amount of dopant contained in the first conductive polymer layer or the second conductive polymer layer may be, for example, 10 parts by mass or more and 1,000 parts by mass or less, and may be 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the conjugated polymer.
  • the first conductive polymer layer and the second conductive polymer layer may each be formed by applying a treatment liquid (e.g., a dispersion liquid or solution) containing a conductive polymer (conjugated polymer) to the dielectric layer and then drying.
  • a treatment liquid e.g., a dispersion liquid or solution
  • the dispersion medium (or solvent) may be at least one selected from the group consisting of water and organic solvents.
  • the treatment liquid may further contain other components (additives, etc.).
  • a solid electrolyte layer may be formed using a treatment liquid containing a conductive polymer (e.g., PEDOT), a dopant (e.g., a polyanion such as polystyrene sulfonate), and additives as necessary.
  • the first conductive polymer layer may be formed by polymerizing a precursor on the dielectric layer using a treatment liquid containing a precursor of a conjugated polymer and a dopant.
  • the polymerization can be performed by at least one of chemical polymerization and electrolytic polymerization.
  • the precursor of the conjugated polymer include a monomer, an oligomer, and a prepolymer.
  • an oxidizing agent is used to polymerize the precursor.
  • the oxidizing agent may be included in the treatment liquid as an additive.
  • the oxidizing agent may be applied to the anode body before or after contacting the treatment liquid with the anode body on which the dielectric layer is formed.
  • oxidizing agents examples include compounds capable of generating Fe 3+ (such as ferric sulfate), persulfates (such as sodium persulfate and ammonium persulfate), and hydrogen peroxide.
  • the oxidizing agents can be used alone or in combination of two or more.
  • the treatment liquid that forms the first portion may be referred to as the first treatment liquid.
  • the process of forming the first conductive polymer layer by immersion in the first treatment liquid and polymerization (or drying) may be performed once, or may be repeated multiple times.
  • the process of forming the second conductive polymer layer may be performed once, or may be repeated multiple times.
  • the conditions such as the composition and viscosity of the treatment liquid may be the same each time, or at least one of the conditions may be changed.
  • Each of the first conductive polymer layer and the second conductive polymer layer may be a single layer or may be composed of multiple layers.
  • the conductive polymers contained in each layer may be the same or different.
  • the second portion includes, for example, a second conductive polymer (such as a conjugated polymer and a dopant). It may include at least a second conductive polymer layer.
  • the second portion (or the second conductive polymer layer) may be a single layer or may be composed of multiple layers. When the second portion (or the second conductive polymer layer) is composed of multiple layers, the types, compositions, contents, etc. of the conductive polymer, additives, etc. included in each layer may be the same or different.
  • the conjugated polymer contained in the second portion preferably contains a monomer unit corresponding to a thiophene compound.
  • the dopant preferably has a sulfo group.
  • the amount of dopant contained in the second layer may be, for example, 10 parts by mass or more and 1,000 parts by mass or less, and may be 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the conjugated polymer.
  • the second portion (or the second conductive polymer layer) is formed, for example, by treating the anode body formed via the dielectric layer of the first portion (or the first conductive polymer layer) with a treatment liquid (second treatment liquid) containing an anionic agent and a cationic agent, or salts thereof, and then with a treatment liquid (third treatment liquid) containing the second conductive polymer.
  • a treatment liquid containing an anionic agent and a cationic agent, or salts thereof
  • a treatment liquid third treatment liquid containing the second conductive polymer.
  • At least one of the anionic agent and the cationic agent contains an N element.
  • At least one of the anionic agent and the cationic agent contains an S element.
  • the second treatment liquid may further contain a surface conditioner.
  • the second portion is formed by treating the above-mentioned anode body with the second treatment liquid, drying, and then treating it with the third treatment liquid and drying.
  • Step A in which the anode body is treated with the second treatment liquid and dried
  • step B in which the anode body is treated with the third treatment liquid and dried
  • the pattern e.g., the repeated pattern
  • steps A and B may be repeated alternately.
  • Step A may be performed once or multiple times, and then step B may be performed once or multiple times.
  • Step A may be performed multiple times, and then step B may be performed multiple times, and these may be repeated alternately.
  • the anode body may be further washed with water and dried.
  • the N/S ratio and the N/(C+O+S) ratio can be adjusted by, for example, selecting or adjusting at least one selected from the group consisting of the use of a surface conditioner, the concentration of the surface conditioner in the second treatment liquid, the concentration of the anionic agent, the cationic agent or its salt in the second treatment liquid, the number of times of each of steps A and B, the implementation of water washing in step A, and the repetition pattern of steps A and B.
  • N/(C+O+S) may also be adjusted by the type of the second conductive polymer, the quantitative ratio of the dopant to the conjugated polymer, and the like.
  • the maximum thickness of the second portion can be adjusted by, for example, selecting or adjusting at least one selected from the concentration of the anionic agent, the cationic agent or its salt in the second treatment liquid, the number of times of each of steps A and B, and the implementation of water washing in step A.
  • the T1/T2 ratio can be adjusted by, for example, adjusting the type and concentration of the surface conditioner, the type of liquid medium used in the second treatment liquid, the drying conditions of the coating of the second treatment liquid, and the like.
  • the cationic agent and the anionic agent are different from the surface conditioner.
  • An example of the surface conditioner is a surfactant.
  • the cationic agent and the anionic agent are each a component that is not a surfactant.
  • Each of the first conductive polymer layer and the layer formed by the third treatment liquid usually contains an anionic dopant, and this dopant is likely to be present on the surface of each layer. In other words, since the surface of each layer is likely to be negatively charged, it is difficult to form a layer containing a second conductive polymer on each layer.
  • the second treatment liquid containing a cationic agent to the first conductive polymer layer or the layer formed by the third treatment liquid, the film-forming properties of the second conductive polymer layer can be improved.
  • the second treatment liquid contain an anionic agent, the film repair properties of the dielectric layer can be improved and the dissociation properties of the cationic agent can be increased, which is advantageous in terms of improving film-forming properties.
  • the cationic agent having a cationic group is not particularly limited as long as it can generate cations in a dissociated state.
  • the cationic agent may be, for example, a metal compound (such as an inorganic base such as a metal hydroxide), but is preferably an organic compound containing an N element (such as an organic base).
  • an amino group such as a primary amino group, a secondary amino group, and a tertiary amino group
  • Such cationic groups also include salts of amino groups and salts of quaternary ammonium groups.
  • the second portion or the second conductive polymer layer may contain one type of cationic agent, or may contain two or more types of cationic agents.
  • cationic agents having an amino group as a cationic group are preferred.
  • amine compounds include amines having one to three substituents on the nitrogen atom (primary amines, secondary amines, and tertiary amines), and diamines that may have one or two alkyl groups on the nitrogen atom.
  • the substituents are, for example, selected from the group consisting of alkyl groups, cycloalkyl groups, and aryl groups.
  • Each of the alkyl groups, cycloalkyl groups, and aryl groups may further have a substituent (for example, at least one selected from the group consisting of hydroxy groups and alkoxy groups).
  • diamine examples include diaminoalkanes, diaminocycloalkanes (diamino C5-8 cycloalkanes such as diaminocyclohexane), and diaminoarenes (diamino C6-14 arenes such as diaminobenzene and diaminonaphthalene).
  • diaminoalkanes examples include diamino C2-14 alkanes and diamino C4-12 alkanes. Specific examples of the diaminoalkanes include 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, and 1,10-diaminodecane.
  • the amine may be at least one selected from the group consisting of primary amines and tertiary amines.
  • tertiary amines include N,N- diC1-10 alkyl-N- C4-16 alkylamines (N,N-dimethylhexylamine, N,N-dimethyloctylamine, N,N-diethyloctylamine, etc.), N,N- diC4-16 alkyl-N- C1-10 alkylamines, triC4-16 alkylamines, etc.
  • the second portion or the second conductive polymer layer may contain the cationic agent in any of the following forms: an amine compound, a cation corresponding to an amine compound, a quaternary ammonium compound, and a salt of a cation.
  • the cationic agent may form a salt with the anionic agent, or may interact with the dopant.
  • the anion agent for example, at least one selected from the group consisting of anions and polyanions exemplified as the dopants of the first conductive polymer and the second conductive polymer may be used. In particular, it is preferable to use an anion agent containing an S element. In addition, from the viewpoint of suppressing dedoping from the first conductive polymer and the second conductive polymer, it is preferable to use an anion agent different from the dopant of the first conductive polymer and the dopant of the second conductive polymer. From the same viewpoint, it is also possible to use an anion agent having a lower electron-withdrawing ability than the dopants of each conductive polymer.
  • the anionic group of the anionic agent may be contained in any form selected from the above anionic groups, anions corresponding to the above anionic groups, and salts of anions.
  • a sulfonic acid compound (aliphatic sulfonic acid, alicyclic sulfonic acid, aromatic sulfonic acid, etc.) may be used.
  • an anionic agent (first anionic agent) containing a sulfo group (first anionic group) and a second anionic group having a lower electron-withdrawing ability than the sulfo group
  • first anionic agent include an anionic agent having a sulfo group and a carboxy group, and an anionic agent having a sulfo group and a hydroxy group.
  • the first anionic agent examples include aliphatic compounds (such as sulfosuccinic acid) and aromatic compounds (such as sulfobenzoic acid, sulfosalicylic acid, disulfosalicylic acid, sulfophthalic acid, sulfoisophthalic acid, sulfoterephthalic acid, and naphtholsulfonic acid).
  • aromatic compounds such as sulfobenzoic acid, sulfosalicylic acid, disulfosalicylic acid, sulfophthalic acid, sulfoisophthalic acid, sulfoterephthalic acid, and naphtholsulfonic acid.
  • a polymer containing a sulfo group and a second anionic group may be used as the first anionic agent.
  • Examples of the first anionic agent that is a polymer (polymer compound) include a copolymer (p1) that contains at least a monomer unit having a first anionic group and a monomer unit having a second anionic group, and a polymer (p2) that contains at least a monomer unit having a first anionic group and a second anionic group. These polymerizable agents may further contain other copolymerizable monomer units.
  • monomer units that serve as the base for the above monomer units include aliphatic vinyl monomer units such as ethylene and propylene, aromatic vinyl monomer units such as styrene, and diene monomer units such as butadiene and isoprene.
  • the Mw of the polymer may be, for example, 5,000 or more and 500,000 or less, or 10,000 or more and 200,000 or less.
  • the first anionic agent can be used alone or in combination of two or more.
  • the first anionic agent may be used in combination with a second anionic agent, if necessary.
  • a second anionic agent for example, a monomer compound among the anions and polyanions described as the dopants of the first layer may be used.
  • the second anionic agent may be any of an aliphatic compound, an alicyclic compound, and an aromatic compound.
  • the second anionic agent may be used alone or in combination of two or more types.
  • sulfonic acid compound examples include aliphatic sulfonic acids (C 1-6 alkane sulfonic acids such as methanesulfonic acid), alicyclic sulfonic acids (C 5-8 cycloalkane sulfonic acids such as cyclohexanesulfonic acid), and aromatic sulfonic acids (C 6-14 arenesulfonic acids such as benzenesulfonic acid and styrenesulfonic acid).
  • C aliphatic sulfonic acids C 1-6 alkane sulfonic acids such as methanesulfonic acid
  • alicyclic sulfonic acids C 5-8 cycloalkane sulfonic acids such as cyclohexanesulfonic acid
  • aromatic sulfonic acids C 6-14 arenesulfonic acids such as benzenesulfonic acid and styrenesulfonic acid.
  • the second anionic agent may have two or more types of anionic groups.
  • second anionic agents include second anionic agents having a phosphate group and a carboxy group (e.g., 2-(dihydroxyphosphinyloxy)acrylic acid), second anionic agents having a phosphonic acid group and a carboxy group (e.g., phosphonoacrylic acid, 2-methyl-3-phosphonoacrylic acid), etc.
  • the surface conditioner includes, for example, a leveling agent and an antifoaming agent. From the viewpoint of spreading the second treatment liquid containing the surface conditioner over the entire surface of the cathode forming portion of the anode body, the surface conditioner is preferably one having a leveling effect. As the surface conditioner, a surfactant is preferably used.
  • the surfactant may be either a nonionic surfactant or an ionic surfactant.
  • the surfactant has a hydrophilic group and a hydrophobic group.
  • Ionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants.
  • the surfactant may be used alone or in combination of two or more types.
  • Nonionic surfactants include ether type (polyether type, etc.), ester ether type (fatty acid polyethylene glycol, fatty acid polyoxyethylene sorbitan, etc.), ester type (glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, etc.), and alkanolamide type (fatty acid alkanolamide, etc.) nonionic surfactants.
  • Polyether type nonionic surfactants include those having a polyoxyalkylene chain such as a polyoxyethylene chain (polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, etc.).
  • the nonionic surfactant may have a halogen atom. Halogen atoms include fluorine, chlorine, bromine, and iodine atoms. Of these, fluorine atoms are preferred.
  • cationic surfactants include alkylamine salt type (monoalkylamine salt, dialkylamine salt, trialkylamine salt, etc.) and quaternary ammonium salt type (alkyltrimethylammonium halide, dialkyldimethylammonium halide, alkylbenzalkonium chloride, etc.).
  • anionic surfactants include carboxylic acid type, sulfonic acid type, sulfate type, and phosphate type anionic surfactants.
  • carboxylic acid type anionic surfactants include aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acylsarcosine salts, and N-acylglutamates.
  • sulfonic acid type anionic surfactants include dialkyl sulfosuccinates, alkanesulfonates, ⁇ -olefinsulfonates, alkylbenzenesulfonates, naphthalenesulfonic acid-formaldehyde condensates, alkylnaphthalenesulfonates, and N-methyl-N-acyltaurate salts.
  • sulfate type anionic surfactants include alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fat sulfates.
  • phosphate type anionic surfactants include alkyl phosphates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkyl phenyl ether phosphates.
  • amphoteric surfactants include carboxybetaine type (alkylbetaine, fatty acid amidopropylbetaine, etc.), 2-alkylimidazoline derivative type (2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, etc.), glycine type (alkyldiethylenetriaminoacetic acid, dialkyldiethylenetriaminoacetic acid, etc.), and amine oxide type (alkylamine oxide, etc.).
  • carboxybetaine type alkylbetaine, fatty acid amidopropylbetaine, etc.
  • 2-alkylimidazoline derivative type (2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, etc.
  • glycine type alkyldiethylenetriaminoacetic acid, dialkyldiethylenetriaminoacetic acid, etc.
  • amine oxide type alkylamine oxide, etc.
  • a nonionic surfactant can prevent the pot life of the second treatment liquid from becoming shorter and can also prevent dedoping of the conductive polymer.
  • a cationic surfactant or an amphoteric surfactant may be used from the viewpoint of more easily promoting adhesion of the conductive polymer to the anode body surface.
  • An anionic surfactant may be used from the viewpoint of more easily preventing volatilization of the cationic agent described below.
  • the content of the surface conditioner in the second portion may be 0.01% by mass or more and 30% by mass or less, or 0.10% by mass or more and 15% by mass or less.
  • the surface conditioner can be distributed more uniformly over the entire surface of the cathode forming portion, making it easier to reduce variation in the thickness of the second portion.
  • the specific resistance of the second portion can be kept low, which is advantageous in suppressing an increase in ESR.
  • Each of the first and second parts may further include at least one selected from the group consisting of known additives and known conductive materials other than conductive polymers, as necessary.
  • the conductive material include at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.
  • a layer for enhancing adhesion may be interposed between the dielectric layer and the first part (or the first conductive polymer layer).
  • the cathode extraction layer needs to include at least a first layer that is in contact with the solid electrolyte layer and covers at least a portion of the solid electrolyte layer, and may include the first layer and a second layer that covers at least a portion of the first layer.
  • the first layer may be, for example, a layer containing conductive particles, metal foil, etc.
  • the conductive particles may be, for example, at least one selected from conductive carbon and metal powder.
  • the cathode part (more specifically, the cathode lead layer) may include a layer containing metal powder (such as a metal particle-containing layer).
  • the resistivity of the cathode lead layer (such as a metal particle-containing layer) is likely to increase due to components derived from the anion agent in a high-temperature and high-humidity environment.
  • the N/S ratio of the second part is set to a specific range, so that the high conductivity of the cathode lead layer (such as a metal particle-containing layer) can be ensured and the increase in ESR in a high-temperature and high-humidity environment can be suppressed.
  • the cathode lead layer may be, for example, composed of a layer containing conductive carbon (carbon layer) as the first layer and a layer containing metal powder (such as a metal particle-containing layer) or metal foil as the second layer.
  • the cathode lead layer includes a metal foil or a metal particle-containing layer
  • the entire cathode lead layer may be composed of the metal foil or the metal particle-containing layer.
  • at least one of the first layer and the second layer may be composed of the metal particle-containing layer.
  • Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).
  • the type of metal is not particularly limited. It is preferable to use a valve metal (aluminum, tantalum, niobium, etc.) or an alloy containing a valve metal for the metal foil. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (heterogeneous metal) different from the metal constituting the metal foil or a nonmetal. Examples of heterogeneous metals and nonmetals include metals such as titanium and nonmetals such as carbon (conductive carbon, etc.).
  • the coating of the dissimilar metal or nonmetal may be the first layer, and the metal foil may be the second layer.
  • the cathode extraction layer is formed by a known method according to its layer structure.
  • the first or second layer is formed by laminating the metal foil so as to cover at least a part of the solid electrolyte layer or the first layer.
  • the first layer including conductive particles is formed, for example, by applying a conductive paste or liquid dispersion including conductive particles and, if necessary, a resin binder (water-soluble resin, curable resin, etc.) to the surface of the solid electrolyte layer.
  • the second layer including metal powder is formed, for example, by applying a paste including metal powder and a resin binder to the surface of the first layer.
  • a drying process, a heating process, etc. may be performed as necessary.
  • a separator When a metal foil is used for the cathode extraction layer, a separator may be disposed between the metal foil and the anode foil.
  • the separator is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).
  • the solid electrolytic capacitor includes at least one capacitor element.
  • the solid electrolytic capacitor may be of a wound type, and may be either a chip type or a stacked type.
  • the solid electrolytic capacitor may include a plurality of stacked capacitor elements.
  • the solid electrolytic capacitor may also include two or more wound capacitor elements. The configuration of the capacitor element may be selected according to the type of the solid electrolytic capacitor.
  • one end of the cathode lead terminal may be electrically connected to the cathode lead layer.
  • the cathode lead terminal is bonded to the cathode lead layer via the conductive adhesive, for example, by applying a conductive adhesive to the cathode lead layer.
  • One end of the anode lead terminal may be electrically connected to the anode lead portion of the anode body.
  • the other end of the anode lead terminal and the other end of the cathode lead terminal are each drawn out from the resin exterior body or case.
  • the other end of each terminal exposed from the resin exterior body or case is used for solder connection with the substrate on which the solid electrolytic capacitor is to be mounted.
  • at least one end face of the anode portion and the cathode portion may be exposed from the outer surface of the sealing body and electrically connected to an external electrode.
  • the solid electrolytic capacitor 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure.
  • the solid electrolytic capacitor 1 includes a capacitor element 11, a resin outer casing 12 that seals the capacitor element 11, and an anode terminal 13 and a cathode terminal 14 that are exposed to the outside of the resin outer casing 12.
  • the capacitor element 11 includes an anode body 2, a dielectric layer 3 that covers the second end side of the anode body 2, and a cathode portion 15 that covers the dielectric layer 3.
  • the portion of the anode body 2 where the cathode portion 15 (particularly the solid electrolyte layer 4) is formed is the cathode forming portion, and the portion where the cathode portion 15 is not formed is the anode lead portion.
  • the anode terminal 13 is electrically connected to the anode lead portion of the anode body 2.
  • the cathode terminal 14 is electrically connected to the cathode portion 15.
  • the resin outer casing 12 has an outer shape that is approximately rectangular, and as a result, the solid electrolytic capacitor 1 also has an outer shape that is approximately rectangular.
  • the anode body 2 and the cathode section 15 face each other via the dielectric layer 3.
  • the cathode section 15 has a solid electrolyte layer 4 covering the dielectric layer 3, and a cathode lead layer 5 covering the solid electrolyte layer 4.
  • the cathode lead layer 5 in the illustrated example has a two-layer structure and has a carbon layer 5a in contact with the solid electrolyte layer 4, and a metal particle-containing layer 5b covering the surface of the carbon layer 5a.
  • the anode lead portion of the anode body 2 protruding from the cathode portion 15 has an insulating separator 16 formed in the cathode portion 15 side region so as to cover the surface of the anode body 2 in a band shape, and contact between the cathode portion 15 and the anode body 2 is restricted.
  • the first end of the anode body 2 protruding from the cathode portion 15 is electrically connected to one end 13a of the anode terminal 13 by welding or the like.
  • the cathode lead layer 5 formed on the outermost layer of the cathode portion 15 is electrically connected to one end 14a of the cathode terminal 14 via a conductive adhesive 17 (e.g., a mixture of thermosetting resin and metal particles).
  • a conductive adhesive 17 e.g., a mixture of thermosetting resin and metal particles.
  • the other end 13b of the anode terminal 13 and the other end 14b of the cathode terminal 14 are each drawn out from different side surfaces of the resin outer casing 12 and extend in an exposed state to one of the main flat surfaces (the lower surface in FIG. 1).
  • the exposed parts of each terminal on this flat surface are used for soldering to a substrate (not shown) on which the solid electrolytic capacitor 1 is to be mounted.
  • the dielectric layer 3 is formed on part of the surface of the conductive material that constitutes the anode body 2. Specifically, the dielectric layer 3 can be formed by anodizing the surface of the conductive material that constitutes the anode body 2. Therefore, the dielectric layer 3 is formed along the surface of the anode body 2 (including the inner wall surfaces of the holes and depressions on the inner surface).
  • FIG. 2 is a schematic front view of the capacitor element as viewed from one of its main surfaces.
  • FIG. 3 is a schematic cross-sectional view of the capacitor element in FIG. 2 taken along line III-III (cross-section G) as viewed in the direction of the arrow.
  • the thicknesses T1 and T2 of the solid electrolyte layer can be determined, for example, by the following procedure.
  • the ratio T1/T2 is determined in a cross section G of the cathode portion 15 perpendicular to the direction from the first end E1 to the second end E2 of the capacitor element 11 (sometimes referred to as the length direction of the anode body 2 or the capacitor element 11).
  • the cross section G is formed at an arbitrary position on the portion on the first end E1 side of the anode body 2.
  • the portion on the first end E1 side of the cathode portion 15 is the portion from the end on the first end E1 side of the cathode portion 15 to a position of length L/2, where L is the length of the cathode portion 15 in the length direction of the capacitor element 11.
  • L is the length of the cathode portion 15 in the length direction of the capacitor element 11.
  • the portion on the first end E1 side of the cathode portion 15 corresponds to the upper half of the cathode portion 15.
  • FIG. 3 shows a cross section G perpendicular to the length direction of the capacitor element 11 at line III-III of the portion on the first end E1 side of the cathode portion 15.
  • Line III-III corresponds to an arbitrarily selected position on the portion on the first end E1 side of the cathode portion 15. Note that hatching indicating that this is a cross section has been omitted in FIG. 3.
  • a center line CL is drawn at a position W/2 from each end face Es.
  • the center line CL passes through the midpoint of the line segment corresponding to each main surface Ms of the anode body 2.
  • the distances D21 and D22 between the intersection of the center line CL with the outer edge of the solid electrolyte layer 4 and the midpoint of the above line segment are respectively defined as the thickness of the solid electrolyte layer at the center of the main surface Ms. T2 is found by averaging the values of these two distances.
  • Step of forming a solid electrolyte layer 3,4-ethylenedioxythiophene monomer was added to an aqueous solution of polystyrene sulfonic acid (Mw: 75,000) under stirring, and then an oxidizing agent (iron (III) sulfate and sodium persulfate) was added to carry out chemical oxidation polymerization.
  • the obtained polymerization liquid was filtered with an ion exchange device to remove impurities, thereby obtaining a solution containing PEDOT as a first conductive polymer and polystyrene sulfonic acid (PSS) as a dopant.
  • Pure water was added to the resulting solution, which was then homogenized using a high-pressure homogenizer and filtered to prepare a first treatment liquid in the form of a dispersion.
  • the anode body on which the dielectric layer obtained in (2) was formed was immersed in the first treatment liquid, then removed from the first treatment liquid and dried at 120°C for 10 to 30 minutes. The immersion in the first treatment liquid and drying were repeated once more to form a first conductive polymer layer covering the surface of the dielectric layer 3.
  • a second treatment liquid was prepared by dissolving an ester-type nonionic surfactant (surface conditioner) and a salt of a cationic agent (N,N-dimethyloctylamine) and an anionic agent (sulfoisophthalic acid) in distilled water.
  • the amount of the surface conditioner in the second treatment liquid was 0.5 mass%, and the concentration of the salt was 2.5 mass%.
  • the anode body on which the first layer was formed was immersed in the second treatment liquid, removed, and dried at 100°C for 3 minutes. Next, the dried anode body was immersed in a third treatment liquid having the same composition as the first treatment liquid, removed, and dried at 120°C for 10 to 30 minutes.
  • a silver paste containing silver particles and a binder resin epoxy resin
  • the binder resin was cured by heating at a temperature of 150° C. to 200° C. for 10 minutes to 60 minutes to form metal particle-containing layer 5 b.
  • cathode extraction layer 5 composed of carbon layer 5 a and metal particle-containing layer 5 b was formed.
  • the capacitor element 11 was produced.
  • the anode body on which the first layer was formed was immersed in the second treatment liquid, removed, dried at 100°C for 3 minutes, washed by immersing in distilled water for 5 minutes, and further dried at 100°C for 3 minutes.
  • the dried anode body was immersed in a third treatment liquid having the same composition as the first treatment liquid, removed, and dried at 120°C for 10 to 30 minutes. Immersion in the second treatment liquid and drying, washing with water and drying, and immersion in the third treatment liquid and drying were repeated four times in this order.
  • the salt concentration in the second treatment liquid was 3.8 mass%.
  • Solid electrolytic capacitors E4 to E6> A total of 20 solid electrolytic capacitors E4, E5, and E6 were fabricated in the same manner as the solid electrolytic capacitor E1, and were evaluated in the same manner. However, the number of times that the immersion in the second treatment liquid and drying were alternately repeated, and the number of times that the immersion in the third treatment liquid and drying were alternately repeated, was 4 times for E4, 3 times for E5, and 2 times for E6. The salt concentration in the second treatment liquid was 3.8% by mass for E4, and 7.5% by mass for E5 and E6.
  • Solid electrolytic capacitors C1 and C2 A total of 20 solid electrolytic capacitors C1 and C2 were fabricated in the same manner as in the case of the solid electrolytic capacitor E6, and similar evaluations were performed. However, in the case of C1 and C2, no surface conditioner was used in the preparation of the second treatment liquid. In addition, the number of times that the immersion in the second treatment liquid and drying, the water washing and drying, and the immersion in the third treatment liquid and drying were alternately repeated was two times for C1 and four times for C2.
  • E1 to E6 and C1 to C2 are shown in Table 1.
  • E1 to E6 are working examples, and C1 to C2 are comparative examples.
  • the ESR evaluation after the high temperature and high humidity test was expressed as a relative value with the measured value for solid electrolytic capacitor C2 set at 100.
  • E1 to E6 which have N/S ratios of 0.30 or more and 1.00 or less, show a marked suppression of the increase in ESR after the high-temperature, high-humidity test.
  • the N/(C+O+S) ratio is preferably 0.033 or more and 0.050 or less.
  • the maximum thickness of the second portion is preferably 15 ⁇ m or more and 42 ⁇ m or less.
  • the solid electrolytic capacitor according to the present disclosure can suppress an increase in ESR when exposed to high temperature and high humidity environments. Therefore, the solid electrolytic capacitor according to the present disclosure can be used in a variety of applications that require high reliability, and is also useful for applications that require high heat resistance and applications in high humidity environments. However, the applications of the solid electrolytic capacitor are not limited to these.

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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