Solid electrolytic capacitor and manufacturing method

Abstract

The invention provides a manufacturing method for improving the capacitance occurrence rate of a solid electrolytic capacitor and the solid electrolytic capacitor with the improved capacitance occurrence rate. A wound body (1) in which an anode foil and a cathode foil on which a dielectric film is formed are wound so as to face each other is wound with a hydrophobic adhesive tape (2). The conductive polymer is formed using a conductive polymer liquid that disperses or dissolves the conductive polymer and has a viscosity of 10-60 mPa * s (inclusive). In other words, a wound body 1 wound with an adhesive tape 2 is immersed in a conductive polymer liquid having a viscosity of 10-60 mPa * s, and the conductive polymer is adhered to the inside of the wound body 1.

Description

Technical Field

[0001] The present invention relates to a wound solid electrolytic capacitor containing a conductive polymer as an electrolyte and a manufacturing method thereof. Background Art

[0002] Electrolytic capacitors include valve metals such as tantalum or aluminum as anode foil and cathode foil. The anode foil is expanded by forming the valve metal into a sintered body or an etched foil, and has a dielectric film on the expanded surface. An electrolyte is present between the anode foil and the cathode foil. The electrolyte is in close contact with the concave and convex surface of the anode foil and functions as a true cathode.

[0003] As a form of electrolytic capacitor, a wound type is known. A wound electrolytic capacitor includes a wound body including an anode foil, a cathode foil and a separator. The anode foil and the cathode foil are strip-shaped foil bodies. The cathode foil and the anode foil face each other with the separator between them. Moreover, the winding is made so that the width direction of the strip is consistent with the winding axis and the length direction of the strip is bent. A strip-shaped adhesive tape is wrapped around the outer periphery of the wound body, and the wound body is wound in a manner that the wound body is not unwound (for example, refer to patent document 1).

[0004] In recent years, solid electrolytic capacitors with conductive polymers as electrolytes filled in the winding body have rapidly become popular. Conductive polymers are derived from monomers with π conjugated double bonds. Conductive polymers, for example, are poly(3,4-ethylenedioxythiophene) (PEDOT), which has excellent adhesion to the dielectric film. In conductive polymers, polyanions such as organic sulfonic acids are used as dopants during chemical oxidation polymerization or electrolytic oxidation polymerization to exhibit high conductivity.

[0005] In addition to low equivalent series resistance, solid electrolytic capacitors also have the following advantages: there is no need to worry about the electrolyte drying out due to evaporation over time, and the life is long. However, in order to give the dielectric film a defect repair function and reduce the leakage current of the solid electrolytic capacitor, the so-called hybrid solid electrolytic capacitor using a conductive polymer and an electrolyte has also become popular (for example, see Patent Document 2).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 1-201911

[0009] Patent Document 2: Japanese Patent Application Publication No. 2006-114540 Summary of the invention

[0010] Problems to be solved by the invention

[0011] The conductive polymer is attached to the wound body by immersing the wound body in a conductive polymer liquid. The conductive polymer liquid is a dispersion or solution prepared by dispersing or dissolving the conductive polymer in water as the main solvent. Compared with electrolytic polymerization and oxidative polymerization in which the wound body is immersed in a polymerization liquid to cause a polymerization reaction, the method of impregnating the wound body with a conductive polymer liquid does not expose the wound body to high heat, and no impurities remain in the wound body.

[0012] However, the adhesive tape used to wrap the outer circumference of the winding body often uses water in the manufacturing process of the solid electrolytic capacitor, so it has a hydrophobic base material such as polypropylene. The hydrophobic adhesive tape ejects the conductive polymer liquid and prevents the conductive polymer liquid from penetrating into the winding body. Therefore, there is room for further improving the adhesion between the conductive polymer and the dielectric film and improving the characteristics such as increasing the electrostatic capacitance of the solid electrolytic capacitor.

[0013] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor with improved capacitance appearance rate, and a solid electrolytic capacitor with improved capacitance appearance rate.

[0014] Technical means of solving problems

[0015] In order to solve the above-mentioned problem, the manufacturing method of the solid electrolytic capacitor of the present embodiment includes: a winding step of winding an anode foil and a cathode foil formed with a dielectric film facing each other to form a wound body; a winding step of winding the circumferential surface of the wound body with a hydrophobic adhesive tape; and a solid electrolyte forming step of immersing the wound body wound with the adhesive tape in a conductive polymer liquid in which the conductive polymer is dispersed or dissolved, so that the conductive polymer is attached to the wound body, and in the solid electrolyte forming step, the wound body is immersed in the conductive polymer liquid having a viscosity of not less than 10 mPa·s and not more than 60 mPa·s.

[0016] In addition, in order to solve the above-mentioned problem, the solid electrolytic capacitor of the present embodiment includes: a winding body, in which an anode foil and a cathode foil having a dielectric film formed thereon are wound facing each other; an adhesive tape, which is hydrophobic and is wound around the circumference of the winding body; and a conductive polymer, which is attached to at least the dielectric film, and the conductive polymer is formed using a conductive polymer liquid in which the conductive polymer is dispersed or dissolved and has a viscosity of not less than 10 mPa·s and not more than 60 mPa·s.

[0017] The conductive polymer may be impregnated with the conductive polymer liquid and attached to the wound body. The conductive polymer liquid may contain water as a solvent. The conductive polymer may be formed using the conductive polymer liquid containing water as a solvent. The conductive polymer liquid may further contain a high boiling point solvent.

[0018] In the winding process, a separator having an air resistance of 5.5 [s / 100 mL] or less may be interposed between the anode foil and the cathode foil and the winding may be performed. A separator having an air resistance of 5.5 [s / 100 mL] or less may be interposed between the anode foil and the cathode foil in the winding body.

[0019] The lead terminal formed by connecting a flat portion, a round rod portion and a lead wire in series is connected to the anode foil and the cathode foil through the flat portion, so that the round rod portion extends from one end face of the wound body and the lead wire is led out. In the solid electrolyte formation step, the wound body is immersed in the conductive polymer liquid to at least a height above one end face of the wound body.

[0020] It may include a lead terminal, which is composed of a flat portion, a round rod portion and a lead wire connected in series, and is connected to the anode foil and the cathode foil through the flat portion, so that the round rod portion extends from one end surface of the winding body and the lead wire is led out, and the conductive polymer is attached above the height of one end surface of the winding body.

[0021] Effects of the Invention

[0022] According to the present invention, the capacitance appearance rate of the solid electrolytic capacitor is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] [ Figure 1 ] is a schematic diagram of a solid electrolytic capacitor according to this embodiment.

[0024] [ Figure 2 ] is a schematic diagram showing a state in which a lead terminal and an electrode foil included in the solid electrolytic capacitor of the present embodiment are connected.

[0025] [ Figure 3 ] is a schematic diagram showing the liquid surface position of the conductive polymer liquid or the attachment position of the conductive polymer.

[0026] [ Figure 4 ] is a graph showing the relationship between ESR and capacitance appearance rate and the viscosity of the conductive polymer liquid.

[0027] [ Figure 5 ] is a graph showing the relationship between the immersion liquid surface height of the conductive polymer liquid and the adhesion amount of the conductive polymer.

[0028] [ Figure 6 ] is a graph showing the relationship between the immersion liquid level height of the conductive polymer liquid and tanδ of the solid electrolytic capacitor.

[0029] [ Figure 7 ] is a graph showing the relationship between the immersion liquid level height of the conductive polymer liquid and the capacitance appearance rate of the solid electrolytic capacitor.

[0030] [ Figure 8 ] is a scatter diagram showing the relationship between ESR and capacitance appearance rate and the viscosity of the conductive polymer liquid. DETAILED DESCRIPTION

[0031] The following describes a solid electrolytic capacitor and a manufacturing method according to an embodiment of the present invention. In addition, the present invention is not limited to the embodiment described below. In addition, in each figure, for easy understanding, thickness, size, positional relationship, ratio, quantity or shape are sometimes emphasized, but the present invention is not limited to these emphases.

[0032] (Overall structure and manufacturing method)

[0033] A solid electrolytic capacitor is a passive component that obtains electrostatic capacitance through the dielectric polarization of a dielectric film and performs charge storage and discharge. The solid electrolytic capacitor includes an anode foil and a cathode foil with a dielectric film formed on the surface. The anode foil and the cathode foil are arranged facing each other. In order to prevent the anode foil and the cathode foil from short-circuiting, a partition is provided between the anode foil and the cathode foil.

[0034] Conductive polymer is attached to the dielectric film of the anode foil. Conductive polymer is the electrolyte of solid electrolytic capacitors. It is arranged in a way that it connects between the dielectric film and the cathode body to create a conductive path and becomes a true cathode. Electrolyte can be used in solid electrolytic capacitors. The electrolyte fills the gap between the dielectric film and the conductive polymer.

[0035] Figure 1 Schematic diagram of a winding body included in a solid electrolytic capacitor. The solid electrolytic capacitor is in a winding shape. That is, the solid electrolytic capacitor includes a winding body 1. The winding body 1 is formed by spirally winding a stack of an anode foil, a cathode foil and a separator multiple times, and has a cylindrical shape. The anode foil and the cathode foil are strip-shaped foil bodies. The winding is performed in a manner such that the strip width direction is consistent with the central axis of the winding body 1 and the strip length direction is circular. The process of winding the anode foil, the cathode foil and the separator to form the winding body 1 is called a winding process.

[0036] Before the winding process, lead terminals 3 are connected to the anode foil and the cathode foil, respectively. The lead terminals 3 are electrically and mechanically connected to the anode foil and the cathode foil by cold welding, ultrasonic welding, laser welding, etc. The lead terminals 3 are electrical conductors that protrude from the lead-out end surface 1a on one side of the winding body 1 and electrically connect the solid electrolytic capacitor and the mounting substrate.

[0037] After the winding process, a tape-shaped adhesive tape 2 is wound around the outer periphery of the winding body 1. The adhesive tape 2 is wound around at least the outer end of the tape so that the winding body 1 does not unwind. The process of winding the circumference of the winding body 1 with the adhesive tape 2 is called a winding process. In order to achieve water resistance to moisture in the manufacturing process of the solid electrolytic capacitor, the adhesive tape 2 has a hydrophobic base material such as polypropylene. An adhesive layer is stacked on the hydrophobic base material, and the adhesive tape 2 is hydrophobic.

[0038] The width of the adhesive tape 2 in the tape width direction is the same length or substantially the same length as the axial length of the roll 1. The adhesive tape 2 is wound around the roll 1 so as to cover at least the tape outer end of the roll 1. In addition, the adhesive tape 2 is wound around the roll 1 so that the edge of the adhesive tape 2 in the tape length direction is coplanar or substantially coplanar with the lead-out end face 1a and the opposite end face 1b of the roll 1.

[0039] After the winding process, the solid electrolyte forming process is transferred. However, the solid electrolyte forming process may not be transferred immediately after the winding process, but may be interposed with, for example, a rechemical conversion process or other processes for repairing damage to the dielectric film caused by the winding process. In the solid electrolyte forming process, the conductive polymer is attached to the inside of the winding body 1. The conductive polymer covers at least a portion of the dielectric film.

[0040] The conductive polymer is formed in the wound body 1 using a conductive polymer liquid. The conductive polymer liquid is a dispersion or solution in which the conductive polymer is dispersed or dissolved. The main solvent of the conductive polymer liquid is water, and the powder or particles of the conductive polymer are dispersed or dissolved in the water. In the solid electrolyte formation process, the wound body 1 is immersed in the conductive polymer liquid, and the conductive polymer liquid is impregnated in the wound body 1. The wound body 1 can be immersed in the conductive polymer liquid once or multiple times. The conductive polymer liquid can also be impregnated in the wound body 1 under reduced pressure.

[0041] After the conductive polymer liquid is impregnated into the winding body 1, the solvent of the conductive polymer liquid is removed by drying. The temperature environment is, for example, 40°C to 200°C, and the drying time is, for example, 3 minutes to 180 minutes. The drying process can be repeated multiple times. Drying can also be performed under reduced pressure, for example, under a pressure of 5 kPa to 100 kPa.

[0042] In the case of impregnation with electrolyte, after the solid electrolyte formation step, the process is transferred to the impregnation step of impregnation with electrolyte. The wound body 1 with the conductive polymer attached is impregnated with electrolyte once or multiple times in an atmospheric pressure environment or a reduced pressure environment. Then, after the solid electrolyte formation step or the electrolyte impregnation step, the wound body 1 filled with both the conductive polymer and the electrolyte, that is, the capacitor element, is inserted into the outer casing 41 with a bottomed cylindrical shape and sealed with a sealing member 42.

[0043] The sealing member 42 is an elastic body for sealing the capacitor element in the outer casing, and has an insertion hole 43 through which the lead terminal 3 passes. The lead terminal 3 is pressed into the insertion hole 43 and led out from the sealing member 42. The solid electrolytic capacitor is manufactured through an aging process. In the aging process, a DC voltage is applied to the solid electrolytic capacitor to repair defective parts such as the dielectric film layer.

[0044] In addition, the capacitor element may be covered with a laminate film instead of an outer casing. In addition, the capacitor element may be molded with a resin such as a heat-resistant resin or an insulating resin. The capacitor element may also be sealed by forming the resin into a thin film using a method such as dip coating or printing.

[0045] (Detailed structure and manufacturing method)

[0046] (Electrode Foil)

[0047] Anode foil is a long strip of foil made of valve metal. Valve metals include aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth and antimony. Cathode foil is a long strip of foil made of the same valve metal as the anode foil, silver or other metals. Cathode foil can also be a layered foil made of a carbon layer stacked on a silver layer. Regarding purity, the anode foil is ideally 99.9% or more, and the cathode foil is ideally 99% or more, and may also contain silicon, iron, copper, magnesium, zinc, etc.

[0048] The long strip foil can be formed by stretching valve metal or the like, or by sintering valve metal powder. A surface expansion layer is formed on one or both sides of the anode foil. The surface expansion layer is an etching layer obtained by etching the foil, a sintering layer obtained by sintering valve metal powder, or a vapor deposition layer obtained by vapor deposition of valve metal particles on the foil. That is, the surface expansion layer has a porous structure, including tunnel-shaped pits, sponge-shaped pits, or dense powders or gaps between particles.

[0049] The tunnel-shaped etch pit is a hole dug in the thickness direction of the foil. The tunnel-shaped etch pit is typically formed by passing a direct current through an acidic aqueous solution such as hydrochloric acid in which halogen ions exist. The tunnel-shaped etch pit is further expanded by passing a direct current through an acidic aqueous solution such as nitric acid. Through the sponge-shaped etch pit, the expanded layer becomes a sponge-shaped layer that is expanded by connecting fine gaps into a space. The sponge-shaped etch pit is formed by passing an alternating current through an acidic aqueous solution such as hydrochloric acid in which halogen ions exist.

[0050] The sintered layer is made by the following method: a powder of a valve metal of the same or different species as the foil is obtained by a pulverization method, an atomization method, a melt spinning method, a rotating disk method, a rotating electrode method, etc., and a paste is made by using an adhesive or a solvent, applied to the foil and dried, and heated and sintered in a vacuum or a reducing environment. The atomization method can be any one of a water atomization method, a gas atomization method, and a water gas atomization method. The vapor-deposited layer is made, for example, by a resistance heating vapor deposition method or an electron beam heating vapor deposition method. The vapor-deposited layer is heated and evaporated by using resistance heat or electron beam energy to heat and evaporate the valve metal of the same or different species as the foil, so that the vapor of the valve metal particles is deposited on the surface of the foil to form a film.

[0051] The dielectric film is formed on the concavo-convex surface of the expansion layer. The dielectric film is typically an oxide film formed on the concavo-convex surface of the expansion layer. If the anode foil is made of aluminum, it is an aluminum oxide layer that oxidizes the concavo-convex surface of the expansion layer. In the chemical conversion treatment for forming the dielectric film, a voltage is applied to the anode foil in a chemical conversion solution with the desired withstand voltage as the target. The chemical conversion solution is a solution without halogen ions, for example, a phosphoric acid-based chemical conversion solution such as ammonium dihydrogen phosphate, a boric acid-based chemical conversion solution such as ammonium borate, and an adipic acid-based chemical conversion solution such as ammonium adipate.

[0052] As for the cathode foil, a surface expansion layer may be formed as needed in the same manner as the anode foil. A flat foil without a surface expansion layer may also be used as the cathode foil. The cathode foil may also be formed with a dielectric film in the same manner as the anode foil. A natural oxide film or a thin oxide film (about 1V to 10V) formed by chemical conversion treatment may also be formed as the dielectric film. The natural oxide film is formed by the reaction of the cathode foil with oxygen in the air.

[0053] In addition, for the cathode foil, a conductive layer may be laminated on the foil surface. The conductive layer is, for example, a layer containing metal nitrides, metal carbides, metal carbonitrides, or carbon such as titanium, zirconium, tantalum, or niobium. The metal nitrides, metal carbides, metal carbonitrides, and carbon are formed by a vapor deposition method or a slurry coating method.

[0054] (Lead terminal)

[0055] Figure 2Schematic diagram of the lead terminal 3. The lead terminal 3 is led out through the sealing member 4, and is composed of a lead wire 31, a round rod portion 32 and a flat portion 33 arranged in a series. The sealing member 42 is an elastic body used to seal the capacitor element in the outer casing, and has an insertion hole 43 through which the lead terminal 3 passes. The lead wire 31 is an electric wire that extends further to the outside than the sealing member 42 and electrically connects the solid electrolytic capacitor to the mounting substrate. The lead wire 31 is usually a copper-clad steel wire called a copper-clad steel (CP) wire, and solder plating such as lead or tin is implemented on the surface.

[0056] The round rod portion 32 is typically made of aluminum and is a roughly cylindrical round rod. Among them, the cross-sectional shape of the round rod portion 32 is not limited to a perfect circle, and can also be an ellipse, a polygonal shape such as a triangle or a quadrilateral, or other shapes. The lead wire 31 and the round rod portion 32 are connected by arc welding or the like, and the connecting portion 34 formed by welding intervenes between the lead wire 31 and the round rod portion 32. Alternatively, the lead wire 31 can also be formed by a part of the round rod portion 32. The round rod portion 32 is set to be one circle larger than the insertion hole 43 of the sealing member 42. The round rod portion 32 is pressed into the insertion hole 43, and is in close contact with the inner wall of the insertion hole 43 due to the increase in the internal pressure of the sealing member 42 after riveting.

[0057] The flat portion 33 is formed into a flat plate shape by flattening the side of the round bar portion 32 opposite to the lead wire 31 by pressing or the like. The boundary between the round bar portion 32 and the flat portion 33 is an inclined portion whose thickness decreases linearly to the thickness of the flat portion 33. The inclined portion is included in the round bar portion 32.

[0058] The flat portion 33 is electrically and mechanically connected to each electrode foil 5, which is a general term for anode foil and cathode foil, by using one of various connection methods such as suture connection, cold rolling, ultrasonic welding or laser welding. The flat portion 33 is brought into contact with one side of the long side and one side of the electrode foil 5, and the round rod portion 32 and the lead wire 31 are extended from the electrode foil 5 in a manner orthogonal to the long side of the electrode foil 5, thereby connecting the flat portion 33 and the electrode foil 5. The winding process is performed after the lead terminal 3 is connected to each electrode foil 5.

[0059] (Partition)

[0060] The separator prevents the short circuit between the anode foil and the cathode foil and holds the conductive polymer and the electrolyte. The separator is made of kraft paper, Manila hemp, esparto, hemp, cellulose such as rayon and mixed paper thereof, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and derivatives thereof, polytetrafluoroethylene resins, polyvinylidene fluoride resins, vinylon resins, polyamide resins such as aliphatic polyamides, semi-aromatic polyamides, and fully aromatic polyamides, polyimide resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, and polyvinyl alcohol resins, etc. These resins can be used alone or in combination.

[0061] The separator can be fibrillated by generating fine fibers branching from the surface of the original fiber, such as fibrillated cellulose. Fibrillation can be formed, for example, by beating. The fibrillated fibers are entangled with each other using the fibrillated fine fibers, and the strength of the separator is improved. Therefore, the separator can be made thinner.

[0062] In addition, it is preferred to use a separator having an air resistance of 5.5 [s / 100 mL] or less in the wound body 1. If the air resistance of the separator is 5.5 [s / 100 mL] or less, the conductive polymer liquid can easily penetrate into the wound body 1 in the solid electrolyte formation step. Therefore, the amount of conductive polymer liquid impregnated into the wound body 1 and the amount of conductive polymer attached to the wound body 1 increase, thereby increasing the appearance rate of the solid electrolytic capacitor.

[0063] Here, air resistance is also called Gurley value, which is the time required for 100 mL of air to pass through the partition. The air resistance is measured by the Gurley method based on Japanese Industrial Standards (JIS) P8117:2009. A gasket with an inner diameter of 28.6 mm is used for the measurement. Among them, the air resistance within 1 [s / 100 mL] is measured using a gasket with an inner diameter of 6 mm, and converted to the value when measured with an inner diameter of 28.6 mm. Specifically, the value obtained with an inner diameter of 6 mm is multiplied by 6. 2 / 28.6 2 Conversion formula.

[0064] (Conductive polymer)

[0065] Conductive polymers are self-doped conjugated polymers doped with intramolecular dopants or conjugated polymers doped with external dopant molecules. Conjugated polymers are obtained by chemical oxidation polymerization or electrolytic oxidation polymerization of monomers or derivatives having π conjugated double bonds. Dopants or external dopant molecules are acceptors that easily accept electrons from conjugated polymers or donors that easily donate electrons to conjugated polymers, thereby making conductive polymers exhibit high conductivity.

[0066] As the conjugated polymer, known polymers can be used without particular limitation. For example, polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene vinylene, etc. can be mentioned. These conjugated polymers can be used alone, or in combination of two or more, and can also be copolymers of two or more monomers.

[0067] Among the conjugated polymers, a conjugated polymer obtained by polymerizing thiophene or its derivatives is preferred, and a conjugated polymer obtained by polymerizing 3,4-ethylenedioxythiophene (i.e., 2,3-dihydrothieno[3,4-b][1,4]dioxin), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, or derivatives thereof is preferred. As a thiophene derivative, a compound selected from thiophenes having substituents at the 3- and 4-positions is preferred, and the substituents at the 3- and 4-positions of the thiophene ring can form a ring together with the carbons at the 3- and 4-positions. The number of carbon atoms in the alkyl or alkoxy group is preferably 1 to 16.

[0068] In particular, a polymer of 3,4-ethylenedioxythiophene called EDOT, that is, poly(3,4-ethylenedioxythiophene) called PEDOT is preferred. In addition, a substituent may be added to 3,4-ethylenedioxythiophene. For example, an alkylated ethylenedioxythiophene to which an alkyl group having 1 to 5 carbon atoms is added as a substituent may be used. Examples of the alkylated ethylenedioxythiophene include methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxin), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxin), butylated ethylenedioxythiophene (i.e., 2-butyl-2,3-dihydro-thieno〔3,4-b〕〔1,4〕dioxin), and 2-alkyl-3,4-ethylenedioxythiophene.

[0069] The dopant may be a known one without particular limitation. The dopant may be used alone or in combination of two or more. In addition, a polymer or a monomer may be used. For example, as a dopant, inorganic acids such as polyanions, boric acid, nitric acid, and phosphoric acid; organic acids 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, bisoxalylboric acid, sulfonylimide acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, and butylnaphthalenesulfonic acid may be cited.

[0070] The polyanion is, for example, a substituted or unsubstituted polyalkylene, a substituted or unsubstituted polyalkenylene, a substituted or unsubstituted polyimide, a substituted or unsubstituted polyamide, or a substituted or unsubstituted polyester, and examples thereof include a polymer containing only a structural unit having an anionic group, and a polymer containing a structural unit having an anionic group and a structural unit not having an anionic group. Specifically, examples of the polyanion include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid sulfonic acid, polymethacrylic acid sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0071] Examples of such conductive polymers include poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid. Hereinafter, such conductive polymers are referred to as PEDOT / PSS (polystyrene sulfonicacid).

[0072] In the solid electrolyte formation step, the wound body 1 is immersed in a conductive polymer liquid so that the conductive polymer is attached to the wound body 1. The conductive polymer liquid is a dispersion or a dissolved solution in which the conductive polymer is dispersed. The conductive polymer liquid is prepared by purifying a solution after electrolytic polymerization or chemical polymerization by ultrafiltration, cation exchange, anion exchange, etc., removing residual monomers or impurities, and dispersing or dissolving the solution in a solvent, or by adding particles or powder of the conductive polymer to a solvent to disperse or dissolve the conductive polymer.

[0073] The main solvent of the conductive polymer liquid is water. The conductive polymer liquid is adjusted to a viscosity of 10 mPa·s or more and 60 mPa·s or less by, for example, the processing time of a dispersion method such as an ultrasonic homogenizer or jet mixing, the type and amount of the dispersion medium, the type and amount of the additive, the degree of polymerization of the polymer, the polymer concentration, etc. If the viscosity is within the range, the solid electrolytic capacitor can be maintained at a good equivalent series resistance (ESR), and the conductive polymer liquid can easily penetrate into the winding body 1, so that the capacitance appearance rate of the solid electrolytic capacitor is good. Among them, if the viscosity is less than 10 mPa·s, the ESR will increase sharply. In addition, if the viscosity exceeds 60 mPa·s, the capacitance appearance rate will decrease sharply.

[0074] The capacitance appearance rate is the ratio of the electrostatic capacitance of the solid electrolytic capacitor to the combined capacitance of the anode foil and the cathode foil, and is the percentage of the result obtained by dividing the electrostatic capacitance of the solid electrolytic capacitor by the combined capacitance of the anode foil and the cathode foil. The combined capacitance of the anode foil and the cathode foil is the combined capacitance of the solid electrolytic capacitor as a capacitor with the anode side and the cathode side connected in series. In the case where the cathode foil has a conductive layer, or in the case where the electrostatic capacitance of the cathode body converges to infinity, the combined capacitance of the anode foil and the cathode foil is the electrostatic capacitance of the anode foil.

[0075] In addition, the main solvent of the conductive polymer liquid is water. If the particles or powder of the conductive polymer are dispersed or dissolved, the solvent of the conductive polymer dispersion liquid can be a mixed solution of water and an organic solvent. As the organic solvent, polar solvents, alcohols, esters, hydrocarbons, carbonate compounds, ether compounds, chain ethers, heterocyclic compounds, nitrile compounds, etc. can be preferably exemplified.

[0076] As polar solvents, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, etc. can be listed. As alcohols, methanol, ethanol, propanol, butanol, etc. can be listed. As esters, ethyl acetate, propyl acetate, butyl acetate, etc. can be listed. As hydrocarbons, hexane, heptane, benzene, toluene, xylene, etc. can be listed. As carbonate compounds, ethylene carbonate, propylene carbonate, etc. can be listed. As ether compounds, dioxane, diethyl ether, etc. can be listed. As chain ethers, ethylene glycol dialkyl ethers, propylene glycol dialkyl ethers, polyethylene glycol dialkyl ethers, polypropylene glycol dialkyl ethers, etc. can be listed. As heterocyclic compounds, 3-methyl-2-oxazolidinone, etc. can be listed. As nitrile compounds, acetonitrile, glutaronitrile, methoxyacetonitrile, propionitrile, benzonitrile, etc. can be listed.

[0077] The pH of the conductive polymer liquid can be adjusted, and polyols and various additives can be added as needed. As pH adjusters, for example, ammonia water, sodium hydroxide, primary amines, secondary amines, tertiary amines, etc. can be listed. As polyols, sorbitol, ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, glycerol, polyglycerol, polyoxyethylene glycerol, xylitol, erythritol, mannitol, dipentaerythritol, pentaerythritol, or a combination of two or more of these. Since polyols are high-boiling-point solvents with high boiling points, they will remain in the winding body 1 even after the conductive polymer liquid is impregnated in the winding body 1 and dried. In addition, polyols can obtain the effect of reducing the ESR or improving the withstand voltage of the solid electrolytic capacitor. As additives, for example, organic binders, surfactants, dispersants, defoamers, coupling agents, antioxidants, ultraviolet absorbers, etc. can be listed.

[0078] In the solid electrolyte forming step, the wound body 1 is immersed in a conductive polymer liquid with the opposite end faces 1 b of the wound body 1 facing downward. Figure 3 It is a schematic diagram showing the liquid surface position of the conductive polymer liquid or the attachment position of the conductive polymer. Figure 3 As shown, the boundary position between the lead wire 31 of the lead terminal 3 and the upper end of the connection part 34 is set as the connection part upper end A1. The boundary position between the lower end of the connection part 34 of the lead terminal 3 and the round rod part 32 is set as the connection part lower end A2. The position 1 mm or more from the lead-out end face 1a of the winding body 1 is set as A3. A3 is, for example, a half height position in the length direction of the round rod part 32. And, the lead-out end face 1a of the winding body 1 is set as the end face position A4.

[0079] At this time, the winding body 1 is preferably immersed in the conductive polymer liquid in such a manner that the liquid level of the conductive polymer liquid is located at least at the lead-out end face 1a of the winding body 1. In addition, it is preferred that the winding body 1 is immersed in the conductive polymer liquid in such a manner that the liquid level of the conductive polymer liquid is located between a height position A3 of more than 1 mm from the lead-out end face 1a of the winding body 1 and the upper end A1 of the connection portion, for example, at a half position A3 of a round rod. In other words, it is preferred that in addition to attaching the conductive polymer to the inside of the winding body 1, the conductive polymer is attached to at least the range between the position A3 of the lead terminal 3 and the upper end A1 of the connection portion. Since the contact angle between the hydrophobic adhesive tape and the conductive polymer liquid is large, a curved liquid surface is formed. Therefore, the winding body 1 needs to be immersed in the conductive polymer liquid beyond the upper edge of the hydrophobic adhesive tape 2.

[0080] The conductive polymer liquid is sucked up from the opposite end surface 1b and drops from the lead-out end surface 1a. By using a separator with an air permeability resistance of 5.5 [s / 100mL] or less, the conductive polymer liquid entering from the lead-out end surface 1a and the opposite end surface 1b penetrates into the wound body 1 through the separator.

[0081] Therefore, in the solid electrolyte forming process, by immersing at least the height of position A3 of the round rod portion 32 in the conductive polymer liquid, the conductive polymer is included in addition to being attached to the winding body 1 and also attached to at least the height of position A3 of the round rod portion 32, so that the capacitance occurrence rate of the solid electrolytic capacitor is improved and the dielectric loss tangent (tanδ) is reduced.

[0082] The impregnation time of the conductive polymer liquid can be appropriately set according to the size of the winding body 1. Even if the impregnation is carried out for a long time, there is no disadvantage in the characteristics. When impregnating the winding body 1, in order to promote the impregnation, a decompression treatment or a pressurization treatment can be carried out as needed. The solid electrolyte formation process can also be repeated multiple times. The solvent of the conductive polymer liquid is evaporated and removed by drying as needed. In order to remove the solvent, heating drying or decompression drying can also be carried out as needed.

[0083] In addition, between the winding process and the solid electrolyte forming process, a repair chemical conversion treatment may be performed to repair defects such as pores, cracks or scars in various parts of the dielectric film caused by insufficient formation of the dielectric film and bending stress caused by winding. As a chemical conversion liquid for repairing chemical conversion, an aqueous solution is used in which phosphoric acid systems such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, boric acid systems such as ammonium borate, and adipic acid systems such as ammonium adipate are dissolved in water. The voltage is preferably set to a value of, for example, 0.1 to 1.2 times the chemical conversion voltage. Then, in order to remove the chemical conversion liquid from the winding body 1, the winding body 1 immersed in the chemical conversion liquid is cleaned using a chemical conversion liquid cleaning liquid such as pure water.

[0084] (Electrolyte)

[0085] When an electrolyte is used in a solid electrolytic capacitor, after the solid electrolyte forming process, the electrolyte impregnation process is transferred. The electrolyte is a mixed solution in which a solute is dissolved in a solvent and additives are added as needed. The electrolyte may not dissolve the solute, may be only a solvent, or may contain a solvent and additives. As the solvent of the electrolyte, protic organic polar solvents or non-protic organic polar solvents can be listed, which can be used alone or in combination of two or more. In addition, as a solute of the electrolyte, an anion component or a cationic component is included. The solute is typically a salt of an organic acid, a salt of an inorganic acid, or a salt of a composite compound of an organic acid and an inorganic acid, which can be used alone or in combination of two or more. The acid as an anion and the base as a cation can also be added to the solvent separately.

[0086] Examples of protonic organic polar solvents as solvents include monohydric alcohols, polyhydric alcohols, and oxyhydric alcohol compounds. Examples of monohydric alcohols include ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, and the like. Examples of polyhydric alcohols and oxyhydric alcohol compounds include ethylene glycol, propylene glycol, glycerol, polyglycerol, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, polyethylene glycol, or polyoxyethylene glycerol, etc., alkylene oxide adducts of polyhydric alcohols. Among them, the solvent is preferably a polyhydric alcohol, and ethylene glycol and glycerol are particularly preferred. Due to ethylene glycol or glycerol, the higher-order structure of the conductive polymer changes, and the initial ESR characteristics are good, and the high-temperature characteristics also become good. It is more preferred if ethylene glycol is 30wt% or more in the solvent.

[0087] As a non-protonic organic polar solvent of the solvent, sulfone series, amide series, lactone series, cyclic amide series, nitrile series, sulfoxide series, etc. can be listed as representatives. As sulfone series, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, cyclopentane, 3-methylcyclopentane, 2,4-dimethylcyclopentane, etc. can be listed. As amide series, N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, hexamethylphosphoramide, etc. can be listed. As lactone series and cyclic amide series, γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, isobutylene carbonate, etc. can be listed. As nitrile series, acetonitrile, 3-methoxypropionitrile, glutaronitrile, etc. can be listed. Examples of the sulfoxide-based compounds include dimethyl sulfoxide and the like.

[0088] Examples of organic acids that serve as anion components as solutes 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, heptanoic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, tert-butyladipic acid, 11-vinyl-8-octadecenedicarboxylic acid, resorcinolic acid, pyrogallolic acid, gallic acid, gentisic acid, protocatechuic acid, catecholcarboxylic acid, trimellitic acid, and pyromellitic acid, or phenols and sulfonic acids.

[0089] Inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid. Composite compounds of organic acids and inorganic acids include boron disalicylic acid, boron dioxalic acid, boron diglycolic acid, boron dimalonic acid, boron disuccinic acid, boron diadipic acid, boron diazelaic acid, boron dibenzoic acid, boron dimaleic acid, boron dilactic acid, boron dimalic acid, boron ditartaric acid, boron dicitric acid, boron diphthalic acid, boron di(2-hydroxy)isobutyric acid, boron diresorcinolic acid, boron dimethylsalicylic acid, boron dinaphthoic acid, boron dimandelic acid, and boron di(3-hydroxy)propionic acid.

[0090] In addition, as at least one salt of an organic acid, an inorganic acid, and a composite compound of an organic acid and an inorganic acid, for example, 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 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.

[0091] Furthermore, other additives may also be added to the electrolyte. Examples of additives include complex compounds of boric acid and polysaccharides (mannitol, sorbitol, etc.), complex compounds of boric acid and polyols, 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, etc. These may be used alone or in combination of two or more. The amount of additive added is not particularly limited, and is preferably added to a degree that does not deteriorate the characteristics of the solid electrolytic capacitor, for example, less than 60wt% in the electrolyte.

[0092] Example

[0093] Hereinafter, the solid electrolytic capacitor and the manufacturing method of the present invention will be described in more detail based on examples. In addition, the present invention is not limited to the following examples.

[0094] (Example 1-Example 7)

[0095] Solid electrolytic capacitors of Examples 1 to 7 and Comparative Examples 1 and 2 were prepared as follows. The solid electrolytic capacitors of Examples 1 to 7 and Comparative Examples 1 and 2 were common except that the viscosity of the conductive polymer liquid used for preparation was different.

[0096] First, the anode foil and the cathode foil are made into strip-shaped aluminum foils extending in a long strip. The anode foil and the cathode foil are expanded by direct current etching. After the expansion, the anode foil is subjected to chemical conversion treatment to form a dielectric film.

[0097] The lead terminal 3 is attached to each of the anode foil and the cathode foil by sewing. The winding body 1 is formed by interposing a fibrillated cellulose separator between the anode foil and the cathode foil connected with the lead terminal 3, and winding in a circular manner in the tape length direction. In the solid electrolytic capacitor of Example 1, a separator made of fibrillated cellulose and having an air permeability resistance of 5.48 [s / 100mL] is used.

[0098] An adhesive tape 2 having the same width as the entire axial length of the wound body 1 was prepared, and the outer circumference of the wound body 1 was wrapped with the adhesive tape 2. A voltage of 57 V was applied to the wound body 1 in the chemical conversion solution to perform repair chemical conversion.

[0099] The winding body 1 is impregnated with a conductive polymer liquid. The conductive polymer liquid has poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) doped with polystyrene sulfonic acid (PSS) dispersed in water. PEDOT / PSS is added at a ratio of 1.2 wt% relative to the entire conductive polymer liquid. In addition, ethylene glycol is added to the conductive polymer liquid at a ratio of 10 wt% relative to the conductive polymer liquid. In the solid electrolytic capacitor of Example 1, the viscosity of the conductive polymer liquid is adjusted by dispersing using an ultrasonic homogenizer.

[0100] The conductive polymer liquid is impregnated in the wound body 1 for 10 minutes at room temperature and a reduced pressure environment of 80 kPa or less. Figure 3 After each impregnation step, the wound body 1 was left standing at room temperature for 10 minutes and further at 110° C. for 30 minutes to dry.

[0101] The wound body 1 impregnated with a conductive polymer and dried is contained in an outer casing 41, and the outer casing 41 is sealed with a sealing member 42. The sealing member 42 and the outer casing 41 are in close contact by riveting. The lead terminal 3 is pressed into the insertion hole 43 of the sealing member 42, so that the outer circumference of the round rod portion 32 is in close contact with the inner circumference of the insertion hole 43. The manufactured solid electrolytic capacitor is subjected to an aging treatment in which a voltage of 40V is applied for 1 hour. As a result, an electrolytic capacitor of Example 1 with a diameter of 10mm and a height of 10mm, a rated voltage of 35WV and a rated electrostatic capacitance of 270μF is manufactured.

[0102] (Capacitor Characteristics)

[0103] The equivalent series resistance (ESR) and capacitance appearance rate (%) of the solid electrolytic capacitors of Examples 1 to 7 and Comparative Examples 1 and 2 were measured. ESR is expressed based on Comparative Example 2 (100%). The results are shown in Table 1 together with the viscosity of the conductive polymer liquid used in Examples 1 to 7 and Comparative Examples 1 and 2. In addition, the relationship between ESR and capacitance appearance rate and the viscosity of the conductive polymer liquid is shown in Table 1. Figure 4 In. Figure 4 In the figure, the white plot is the capacitance occurrence rate and the black plot is the ESR.

[0104] In addition, the equivalent series resistance (ESR) was measured at room temperature using an inductance capacitance resistance (LCR) meter with a sine wave having a frequency of 100 kHz and an AC amplitude of 0.5 Vms.

[0105] Regarding the capacitance appearance rate, the capacitance of the anode foil or cathode foil is measured by cutting a test piece of a specified area from the anode foil or cathode foil, immersing a platinum plate as the opposite electrode in the electrostatic capacitance measurement liquid in a glass measurement tank, and using an electrostatic capacitance meter. The specified area is set to 1 cm 2 The capacitance measurement liquid was set to an aqueous solution of ammonium adipate at 30° C., the capacitance meter was set to an LCR meter, and as measurement conditions, the AC amplitude was set to 0.5 Vms.

[0106] (Table 1)

[0107]

[0108]

[0109] As shown in Table 1 and Figure 4 As shown, the solid electrolytic capacitors of Comparative Example 1 and Examples 1 to 7 are formed with conductive polymers using a conductive polymer liquid having a viscosity of 60 mPa·s or less. The capacitance appearance rate of the solid electrolytic capacitors of Comparative Example 1 and Examples 1 to 7 becomes good. However, in Comparative Example 1 in which a conductive polymer is formed using a conductive polymer liquid having a viscosity of less than 10 mPa·s, the ESR becomes high. On the other hand, in Examples 1 to 7 in which a conductive polymer is formed using a conductive polymer liquid having a viscosity of 10 mPa·s or more and 60 mPa·s or less, the capacitance appearance rate is good and the ESR also becomes good.

[0110] This confirmed that even when the film is wrapped with the hydrophobic adhesive tape 2 , the capacitance appearance ratio is improved and the ESR is reduced by setting the viscosity of the conductive polymer liquid to 10 mPa·s or more and 60 mPa·s or less.

[0111] (Example 8)

[0112] A solid electrolytic capacitor of Example 8 was prepared. Example 8 is the same as Example 4 in the following respects. That is, in the solid electrolytic capacitor of Example 8, a conductive polymer liquid with a viscosity of 30 mPa·s was impregnated into the winding body 1 as in Example 4. The winding body 1 was placed such that the liquid level of the conductive polymer liquid was at Figure 3 The conductive polymer is immersed in a conductive polymer liquid in a manner such that the conductive polymer is attached to the lower end A2 of the connection portion as shown. The so-called lower end A2 of the connection portion is a position 2 mm from the lead-out end surface 1a of the winding body 1. Among them, Example 8 is different from Example 4 in that a partition with an air permeability resistance of 5.76 [s / 100mL] is used. In other respects, Example 8 has the same structure as Example 4 and is manufactured under the same manufacturing method and manufacturing conditions.

[0113] (Capacitance occurrence rate)

[0114] The capacitance appearance ratio (%) of the solid electrolytic capacitors of Example 4 and Example 8 was measured. The results are shown in Table 2 below.

[0115] (Table 2)

[0116]

[0117] As shown in Table 2, although the capacitance appearance rate of Example 8 in which the air permeability resistance of the separator is 5.76 [s / 100mL] is good unlike Comparative Example 2, it is a lower value than that of Example 4. In other words, it was confirmed that when the viscosity of the conductive polymer liquid was set to 10 mPa·s or more and 60 mPa·s or less, and the air permeability resistance of the separator was set to 5.5 [s / 100mL] or less, which is within the range of Examples 1 to 8, the capacitance appearance rate of the solid electrolytic capacitor became better.

[0118] (Example 9)

[0119] A solid electrolytic capacitor of Example 9 was prepared. Example 9 is the same as Example 4 in the following aspects. That is, in the solid electrolytic capacitor of Example 9, as in Example 4, a fibrillated cellulose having an air permeability resistance of 5.48 [s / 100mL] was used as a separator. A conductive polymer liquid having a viscosity of 30 mPa·s was impregnated into the winding body 1. However, unlike Example 4, the winding body 1 of Example 9 has a liquid level of the conductive polymer liquid at a height of Figure 3 The conductive polymer is attached to the upper end A1 of the connection portion shown in the figure, and is immersed in the conductive polymer liquid. In other respects, Example 9 has the same structure as Example 4 and is manufactured under the same manufacturing method and manufacturing conditions. The so-called upper end A1 of the connection portion is a position 2.7 mm from the lead-out end surface 1a of the winding body 1.

[0120] (Example 10)

[0121] A solid electrolytic capacitor of Example 10 was prepared. Example 10 is the same as Example 4 in the following aspects. That is, in the solid electrolytic capacitor of Example 10, as in Example 4, a fibrillated cellulose having an air permeability resistance of 5.48 [s / 100 mL] was used as a separator. A conductive polymer liquid having a viscosity of 30 mPa·s was impregnated into the winding body 1. However, unlike Example 4, the winding body 1 of Example 10 has a liquid level of the conductive polymer liquid at a height of Figure 3 The conductive polymer is attached to the height of the upper end A1 of the connection portion and immersed in the conductive polymer liquid. In other respects, Example 10 has the same structure as Example 4 and is manufactured under the same manufacturing method and manufacturing conditions. The so-called position A3 is a position 1 mm from the lead-out end surface 1a of the winding body 1.

[0122] (Example 11)

[0123] A solid electrolytic capacitor of Example 11 was prepared. Example 11 is the same as Example 4 in the following aspects. That is, in the solid electrolytic capacitor of Example 11, as in Example 4, a fibrillated cellulose having an air permeability resistance of 5.48 [s / 100mL] was used as a separator. A conductive polymer liquid having a viscosity of 30 mPa·s was impregnated into the winding body 1. However, unlike Example 4, the winding body 1 of Example 11 has a conductive polymer liquid level at a height of 1.000 mm / s. Figure 3 The conductive polymer was immersed in a conductive polymer liquid until the end surface position A4 was shown and the conductive polymer was attached to the height of the end surface position A4. In other respects, Example 11 had the same structure as Example 4 and was manufactured by the same manufacturing method and manufacturing conditions.

[0124] (Adhesion test)

[0125] The amount of the conductive polymer liquid impregnated in the wound body 1 of Examples 4 and Examples 9 to 11 was measured. The adhesion amount was calculated from the weight change of the wound body 1 before and after the solid electrolyte formation step. The adhesion amount of Examples 4 and Examples 9 to 10 is shown with the adhesion amount of Example 11 as the reference (100%).

[0126] The relationship between the weight of the conductive polymer liquid attached to the wound body 1 and the height of the conductive polymer liquid immersion liquid surface in Examples 4 and 9 to 11 is shown in FIG. Figure 5 middle.

[0127] like Figure 5 As shown, it was confirmed that the conductive polymer liquid adhesion amount was significantly improved at position A3 which is half the height in the longitudinal direction of the round rod portion 32, compared with the case where the conductive polymer liquid immersion liquid surface height and the conductive polymer adhesion height were set at end surface position A4.

[0128] In addition, it was confirmed that: in the height range of the connection portion 34 between the round rod portion 32 and the lead wire 31, namely, the lower end A2 of the connection portion and the upper end A1 of the connection portion, the adhesion amount of the conductive polymer liquid was further improved compared to the case where the immersion liquid surface height of the conductive polymer liquid and the adhesion height of the conductive polymer were set to the end surface position A4.

[0129] (Capacitor Characteristics)

[0130] The dielectric loss tangent (tan δ) and capacitance appearance rate (%) of the solid electrolytic capacitors of Example 4 and Example 9 to Example 11 were measured. The results are shown in Figure 6 and Figure 7 In addition, the measurement results of the capacitance appearance rate (%) are shown in the following Table 3, and the measurement results of the dielectric loss tangent (tanδ) are shown in the following Table 4. The dielectric loss tangent (tanδ) was measured at room temperature using an LCR meter. The measurement frequency of tanδ was 120 Hz, and the AC amplitude was a sine wave of 0.5 Vms.

[0131] (Table 3)

[0132]

[0133] (Table 4)

[0134]

[0135] As shown in Table 3 and Table 4, Figure 6 and Figure 7 As shown in the figure, it can be confirmed that tanδ and capacitance appearance rate follow Figure 5 The amount of conductive polymer attached is improved.

[0136] That is, when the hydrophobic adhesive tape 2 is used for winding, the viscosity of the conductive polymer liquid is set to 10 mPa·s or more and 60 mPa·s or less, so that the conductive polymer is easily distributed in the wound body 1. Then, the immersion liquid surface of the conductive polymer liquid is located at the half position of the round rod, which is half the height position in the length direction of the round rod portion 32, or at a position 1 mm from the lead-out end surface 1a of the wound body 1, that is, A3 or more, and the conductive polymer is attached, thereby increasing the amount of conductive polymer liquid attached. As a result, it was confirmed that the capacitance appearance rate of the solid electrolytic capacitor became better and tanδ also became better.

[0137] (Example 12 to Example 14)

[0138] Solid electrolytic capacitors of Examples 12 to 14 were prepared. Examples 12 to 14 were the same as Example 1 in the following respects. That is, in the solid electrolytic capacitors of Examples 12 to 14, a conductive polymer liquid with a viscosity of 13 mPa·s was impregnated into the winding body 1 in the same manner as in Example 1. The liquid level of the conductive polymer liquid was at Figure 3 The wound body 1 is immersed in a conductive polymer liquid so that the conductive polymer is attached to the height of the connecting portion lower end A2 shown in the figure. The connecting portion lower end A2 is a position 2 mm from the lead-out end surface 1 a of the wound body 1 .

[0139] Among them, the solid electrolytic capacitors of Examples 12 to 14 are different from those of Example 1 in that a separator made of natural cellulose and having an air permeability resistance of 0.03 [s / 100 mL] is used. In Examples 12 to 14, the viscosity of the conductive polymer liquid impregnated in the winding body 1 is different from each other. Example 12 is the same as Example 1, and a conductive polymer liquid with a viscosity of 13 mPa·s is impregnated in the winding body 1. Example 13 is different from Example 12, and a conductive polymer liquid with a viscosity of 25 mPa·s is impregnated in the winding body 1. Example 14 is different from Example 12, and a conductive polymer liquid with a viscosity of 60 mPa·s is impregnated in the winding body 1.

[0140] Regarding other aspects, Examples 12 to 14 have the same structure as Example 1 and are manufactured using the same manufacturing method and under the same manufacturing conditions.

[0141] In addition, a solid electrolytic capacitor of Comparative Example 3 was prepared. The solid electrolytic capacitor of Comparative Example 3 had the same structure as Examples 12 to 14, and was prepared by the same manufacturing method and manufacturing conditions, except that the wound body 1 was impregnated with a conductive polymer liquid having a viscosity of 125 mPa·s.

[0142] (Capacitor characteristics)

[0143] The equivalent series resistance (ESR) and capacitance appearance rate (%) of the solid electrolytic capacitors of Examples 12 to 14 and Comparative Example 3 were measured. The determination method and conditions of ESR and capacitance appearance rate were the same as those of Examples 1 to 8. The results are shown in Table 5 below together with the viscosity of the conductive polymer liquid used in Examples 12 to 14 and Comparative Example 3. ESR is expressed based on Comparative Example 3 (100%).

[0144] (Table 5)

[0145]

[0146] Based on Table 5, the relationship between ESR and capacitance appearance rate and the viscosity of the conductive polymer liquid is shown in Figure 8 In. Figure 8 In the figure, the white plot is the capacitance occurrence rate and the black plot is the ESR.

[0147] As shown in Table 5 and Figure 8 As shown, even when using natural cellulose with an air permeability resistance value of 0.03 [s / 100mL], the capacitance appearance rate of Examples 12 to 14 in which the conductive polymer is formed using a conductive polymer liquid with a viscosity of 10 mPa·s to 60 mPa·s is good, and the ESR also becomes good.

[0148] Description of Figure Numbers

[0149] 1: Winding body

[0150] 1a: Export end face

[0151] 1b: Opposite end face

[0152] 2: Adhesive tape

[0153] 3: Lead terminal

[0154] 31: Lead wire

[0155] 32: Round rod

[0156] 33: Flat part

[0157] 34: Connection

[0158] 41: External shell

[0159] 42: Sealing components

[0160] 43: Insert hole

[0161] 5: Electrode foil

Claims

1. A method for manufacturing a solid electrolytic capacitor, characterized in that: include: A winding step of winding the anode foil and the cathode foil formed with the dielectric film so as to face each other to form a winding body; A winding step of winding the circumference of the wound body with a hydrophobic adhesive tape; as well as The solid electrolyte forming step comprises immersing the wound body wound with the adhesive tape in a conductive polymer liquid in which the conductive polymer is dispersed or dissolved, so that the conductive polymer is attached to the wound body. In the solid electrolyte forming step, the wound body is immersed in the conductive polymer liquid having a viscosity of 10 mPa·s or more and 60 mPa·s or less.

2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein: The conductive polymer liquid contains water as a solvent.

3. The method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, characterized in that: In the winding step, the anode foil and the cathode foil are wound with a separator having an air permeability resistance of 5.5 [s / 100 mL] or less interposed therebetween.

4. The method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, characterized in that: A lead terminal formed by connecting a flat portion, a round rod portion and a lead wire in series is connected to the anode foil and the cathode foil through the flat portion, the round rod portion is extended from one end surface of the winding body, and the lead wire is led out. In the solid electrolyte forming step, the wound body is immersed in the conductive polymer solution to a height at least equal to or higher than one end surface of the wound body.

5. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein: The conductive polymer liquid further includes a high boiling point solvent.

6. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein: The method further includes an electrolyte impregnation step of impregnating the wound body with an electrolyte.

7. A solid electrolytic capacitor, characterized in that: include: The wound body is formed by winding the anode foil and the cathode foil formed with the dielectric film so as to face each other; An adhesive tape is hydrophobic and is wound around the circumference of the winding body; as well as A conductive polymer is attached to at least the dielectric film. The conductive polymer is formed using a conductive polymer liquid in which the conductive polymer is dispersed or dissolved and has a viscosity of 10 mPa·s or more and 60 mPa·s or less.

8. The solid electrolytic capacitor according to claim 7, characterized in that: The invention also includes a separator which is interposed between the anode foil and the cathode foil in the wound body and has an air permeation resistance of 5.5 [s / 100 mL] or less.

9. The solid electrolytic capacitor according to claim 7, characterized in that: The lead terminal includes a flat portion, a round rod portion and a lead wire connected in series, connected to the anode foil and the cathode foil through the flat portion, and the round rod portion extends from one end surface of the winding body to lead out the lead wire. The conductive polymer is attached to a height higher than one end surface of the wound body.

10. The solid electrolytic capacitor according to claim 7, characterized in that: Also included is an electrolyte solution impregnated in the wound body.

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