Solid electrolytic capacitor and manufacturing method

Abstract

To provide a manufacturing method for enhancing the capacitance appearance rate of a solid electrolytic capacitor and a solid electrolytic capacitor with an enhanced capacitance appearance rate.SOLUTION: A wound body 1 made by winding an anode foil and a cathode foil with a dielectric film formed facing each other is wound and fastened with a hydrophobic adhesive tape 2. A conductive polymer is formed using a conductive polymer solution, having a viscosity greater or equal to 10 mPa s and less than or equal to 60 mPa s, in which the conductive polymer is dispersed or dissolved. That is, by immersing the wound body 1, which is wound and fastened with the adhesive tape 2, in the conductive polymer solution with a viscosity of greater than or equal to 10 mPa s and less than or equal to 60 mPa s, the conductive polymer is made to adhere to the wound body 1.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a wound type solid electrolytic capacitor containing a conductive polymer as an electrolyte, and a method for producing the same. [Background technology]

[0002] An electrolytic capacitor has valve metals such as tantalum or aluminum as anode and cathode foils. The anode foil is enlarged by forming the valve metal into a sintered or etched foil, etc., and has a dielectric coating layer on the enlarged surface. An electrolyte is interposed between the anode foil and the cathode foil. The electrolyte is in close contact with the uneven surface of the anode foil and functions as a true cathode.

[0003] A wound type electrolytic capacitor is known. A wound type electrolytic capacitor has a wound body made up of 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 are opposed to each other via the separator. The strip is then wound so that the short side of the strip coincides with the winding axis and the strip is curved in the long side. A strip-shaped adhesive tape is wound around the outer periphery of the wound body to prevent the wound body from unwinding (see Patent Document 1, for example).

[0004] In recent years, solid electrolytic capacitors in which a conductive polymer is filled in the wound body as an electrolyte have rapidly become popular. Conductive polymers are derived from monomers with π-conjugated double bonds. An example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT), which has excellent adhesion to dielectric films. Polyanions such as organic sulfonic acid are used as dopants during chemical oxidation polymerization or electrolytic oxidation polymerization to produce conductive polymers with high conductivity.

[0005] In addition to having a low equivalent series resistance, solid electrolytic capacitors have the advantage of being long-lived, since there is no risk of the electrolyte drying up due to evaporation to the outside over time. However, so-called hybrid-type solid electrolytic capacitors that use a conductive polymer and an electrolyte in combination to provide a repair function for defective parts of the dielectric film and reduce leakage current of the solid electrolytic capacitor are also becoming popular (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Publication No. 1-201911 [Patent Document 2] JP 2006-114540 A Summary of the Invention [Problem to be solved by the invention]

[0007] The conductive polymer is attached to the inside of 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 a conductive polymer in water, using water as the main solvent. Compared to electrical 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 the conductive polymer liquid does not expose the wound body to high heat and does not leave impurities on the wound body.

[0008] However, the adhesive tape used to fasten the outer periphery of the wound body has a hydrophobic base material such as polypropylene because water is often used in the manufacturing process of solid electrolytic capacitors. The hydrophobic adhesive tape repels the conductive polymer liquid and prevents the conductive polymer liquid from penetrating into the inside of the wound body. Therefore, there is room for further improvement in the adhesion between the conductive polymer and the dielectric film, and for example, improvement in the characteristics such as increasing the capacitance of the solid electrolytic capacitor.

[0009] The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a manufacturing method for increasing the capacitance appearance rate of a solid electrolytic capacitor, and a solid electrolytic capacitor with an increased capacitance appearance rate. [Means for solving the problem]

[0010] In order to solve the above problems, a method for manufacturing a solid electrolytic capacitor according to the present embodiment includes a winding step of winding an anode foil and a cathode foil, each having a dielectric film formed thereon, facing each other to form a wound body, a winding stop step of winding a circumferential surface of the wound body with a hydrophobic adhesive tape, and a solid electrolyte formation step of immersing the wound body wound and stopped with the adhesive tape in a conductive polymer liquid in which a conductive polymer is dispersed or dissolved, thereby adhering the conductive polymer to the inside of the wound body, and in the solid electrolyte formation 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.

[0011] In order to solve the above-mentioned problems, the solid electrolytic capacitor of this embodiment includes a wound body in which an anode foil and a cathode foil, each having a dielectric coating, are wound facing each other, a hydrophobic adhesive tape that fastens the circumferential surface of the wound body, and a conductive polymer that adheres to at least the dielectric coating, wherein 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.

[0012] The conductive polymer may be attached to the wound body by impregnating the wound body with the conductive polymer liquid. The conductive polymer liquid may contain water as a solvent. The conductive polymer liquid may further contain a high boiling point solvent. The method may further include an electrolyte impregnation step of impregnating the wound body with an electrolyte. The wound body may further contain an electrolyte to be impregnated therein.

[0013] In the winding step, 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 wound. 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 wound body.

[0014] A lead terminal, in which a flat portion, a round bar portion, and a lead wire are connected in series to the anode foil and the cathode foil, is connected to the flat portion, the round bar portion is caused to protrude from one end face of the wound body, and the lead wire is drawn out, and in the solid electrolyte forming step, the wound body may be immersed in the conductive polymer liquid to a height at least equal to or greater than the height of one end face of the wound body.

[0015] The winding body may include a flat portion, a round bar portion, and a lead wire that are connected to the anode foil and the cathode foil at the flat portion, the round bar portion protruding from one end face of the winding, and a lead terminal from which the lead wire is drawn out, and the conductive polymer may be attached to a height equal to or higher than the height of the one end face of the winding. Effect of the Invention

[0016] According to the present invention, the capacitance appearance rate of the solid electrolytic capacitor is increased. [Brief description of the drawings]

[0017] [Figure 1] 2 is a schematic diagram of a wound body included in the solid electrolytic capacitor according to the embodiment. FIG. [Diagram 2] 2 is a schematic diagram of a lead terminal included in the solid electrolytic capacitor according to the embodiment. FIG. [Diagram 3] 3A and 3B are schematic diagrams showing the liquid level position of a conductive polymer liquid or the adhesion position of a conductive polymer. [Figure 4] FIG. 1 is a scatter diagram showing the relationship between the ESR and the capacitance appearance rate versus the viscosity of a conductive polymer liquid. [Diagram 5] 1 is a graph showing the relationship between the height of the immersion liquid surface of the conductive polymer liquid and the amount of the conductive polymer adhered. [Figure 6]1 is a graph showing the relationship between the height of the immersion liquid surface of the conductive polymer liquid and tan δ of the solid electrolytic capacitor. [Figure 7] 1 is a graph showing the relationship between the height of the immersion liquid surface of the conductive polymer liquid and the capacitance appearance rate of the solid electrolytic capacitor. [Figure 8] FIG. 1 is a scatter diagram showing the relationship between the ESR and the capacitance appearance rate versus the viscosity of a conductive polymer liquid. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, a solid electrolytic capacitor and a manufacturing method thereof according to an embodiment of the present invention will be described. Note that the present invention is not limited to the embodiment described below. In addition, in each drawing, thickness, dimensions, positional relationship, ratio, number, shape, etc. may be emphasized for ease of understanding, but the present invention is not limited to such emphasis.

[0019] (Overall structure and manufacturing method) A solid electrolytic capacitor is a passive device that obtains capacitance through the dielectric polarization of a dielectric film and stores and discharges electric charge. This 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 opposite each other. A separator is interposed between the anode foil and the cathode foil to prevent the anode foil and the cathode foil from shorting out.

[0020] A conductive polymer is attached to the dielectric film of the anode foil. The conductive polymer is the electrolyte of the solid electrolytic capacitor, and is arranged in a continuous manner between the dielectric film and the cathode body to create a conductive path, making it the true cathode. A liquid electrolyte can be used in conjunction with the solid electrolytic capacitor. The liquid electrolyte fills the gap between the dielectric film and the conductive polymer.

[0021] FIG. 1 is a schematic diagram of a wound body provided in a solid electrolytic capacitor. The solid electrolytic capacitor is of a wound type. That is, the solid electrolytic capacitor is provided with a wound body 1. The wound body 1 is formed by winding a laminate of an anode foil, a cathode foil, and a separator in a spiral shape multiple times, and has a cylindrical shape. The anode foil and the cathode foil are strip-shaped foil bodies. The strip is wound so that the short side direction is aligned with the central axis of the wound body 1 and the strip is rolled in the long side direction. The process of winding the anode foil, the cathode foil, and the separator to form the wound body 1 is called the winding process.

[0022] Prior to the winding process, the anode foil and the cathode foil are connected to respective lead terminals 3. The lead terminals 3 are electrically and mechanically connected to the anode foil and the cathode foil by cold welding, ultrasonic welding, laser welding, or the like. The lead terminals 3 protrude from one of the lead-out end faces 1a of the wound body 1 and are conductors that electrically connect the solid electrolytic capacitor to the mounting board.

[0023] After the winding process, a strip-shaped adhesive tape 2 is wound around the outer circumference of the wound body 1. At least the outer end of the strip of the adhesive tape 2 is secured to prevent the wound body 1 from unraveling. The process of securing the outer circumference of the wound body 1 with the adhesive tape 2 is called the winding securing process. The adhesive tape 2 has a hydrophobic base material such as polypropylene to provide water resistance against moisture during the manufacturing process of the solid electrolytic capacitor. An adhesive layer is laminated on this hydrophobic base material, and the adhesive tape 2 is hydrophobic.

[0024] The width of this adhesive tape 2 in the band short-side direction is the same or approximately the same 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 outer end of the roll 1. The adhesive tape 2 is also wound around the roll 1 so that the edges of the adhesive tape 2 in the band long-side direction are flush or approximately flush with the lead-out end face 1a and the opposite end face 1b of the roll 1.

[0025] After the winding process, the process proceeds to a solid electrolyte forming process. However, instead of immediately proceeding to the solid electrolyte forming process after the winding process, for example, a chemical conversion re-treatment for repairing damage to the dielectric film caused by the winding process and other treatments may be performed in between. In the solid electrolyte forming process, a conductive polymer is applied to the inside of the wound body 1. The conductive polymer covers at least a part of the dielectric film.

[0026] The conductive polymer is formed in the wound body 1 using a conductive polymer liquid. The conductive polymer liquid is a dispersion liquid or solution in which a conductive polymer is dispersed or dissolved. The main solvent of the conductive polymer liquid is water, in which conductive polymer powder or particles are dispersed or dissolved. In the solid electrolyte formation step, the wound body 1 is immersed in the conductive polymer liquid to impregnate the wound body 1 with the conductive polymer liquid. The wound body 1 may be immersed in the conductive polymer liquid once or multiple times. The wound body 1 may be impregnated with the conductive polymer liquid in a reduced pressure environment.

[0027] After the conductive polymer solution is impregnated into the wound body 1, the solvent of the conductive polymer solution is removed by drying. The temperature environment is, for example, 40°C or higher and 200°C or lower, and the drying time is, for example, in the range of 3 minutes or higher and 180 minutes or lower. The drying process may be repeated multiple times. Drying may be performed in a reduced pressure environment, for example, by reducing the pressure to 5 kPa or higher and 100 kPa or lower.

[0028] When impregnating with the electrolyte, the solid electrolyte forming step is followed by an impregnation step in which the electrolyte is impregnated. The wound body 1 with the conductive polymer attached is impregnated with the electrolyte once or multiple times in an atmospheric pressure environment or a reduced pressure environment. Then, after the solid electrolyte forming step or the electrolyte impregnation step, the wound body 1 filled with the conductive polymer or both the conductive polymer and the electrolyte, i.e., the capacitor element, is inserted into a cylindrical exterior case 41 with a bottom and sealed with a sealing member 42.

[0029] The sealing member 42 is an elastic body for sealing the capacitor element in the exterior case, and has an insertion hole 43 through which the lead terminal 3 passes. The lead terminal 3 is press-fitted into the insertion hole 43 and pulled out from the sealing member 42. The manufacture of the solid electrolytic capacitor is completed after an aging process. In the aging process, a DC voltage is applied to the solid electrolytic capacitor to repair defects in the dielectric coating layer, etc.

[0030] The capacitor element may be covered with a laminate film instead of an exterior case. The capacitor element may be molded with a resin such as a heat-resistant resin or an insulating resin. The capacitor element may be sealed by forming the resin into a thin film by a method such as dip coating or printing.

[0031] (Detailed composition and manufacturing method) (electrode foil) The anode foil is a long foil made of a valve metal. The valve metal is aluminum, tantalum, niobium, niobium oxide, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc. The cathode foil is a long foil made of the same valve metal as the anode foil or other metal such as silver. The cathode foil may be a layered foil made of a silver layer and a carbon layer laminated thereon. The purity of the anode foil is preferably 99.9% or more, and that of the cathode foil is preferably 99% or more, but may contain silicon, iron, copper, magnesium, zinc, etc.

[0032] The long foil may be formed by stretching a valve metal or the like, or by sintering a powder of the valve metal. A surface-expanding layer is formed on one or both sides of the anode foil. The surface-expanding layer may be an etching layer formed by etching the foil, a sintered layer formed by sintering a powder of the valve metal, or a deposition layer formed by depositing valve metal particles onto the foil. That is, the surface-expanding layer has a porous structure and is composed of tunnel-like pits, spongy pits, or voids between densely packed powder or particles.

[0033] The tunnel-shaped etching pit is a hole dug in the foil thickness direction. This tunnel-shaped etching pit is typically formed by passing a direct current in an acidic aqueous solution containing halogen ions such as hydrochloric acid. The tunnel-shaped etching pit is further enlarged by passing a direct current in an acidic aqueous solution such as nitric acid. The spongy etching pit makes the surface-enlarged layer into a sponge-like layer with fine voids extending in a space. This spongy etching pit is formed by passing an alternating current in an acidic aqueous solution containing halogen ions such as hydrochloric acid.

[0034] The sintered layer is produced by obtaining a powder of a valve metal of the same or different type as the foil body by a pulverization method, an atomization method, a melt spinning method, a rotating disk method, a rotating electrode method, or the like, forming a paste with a binder or a solvent, applying it to the foil body, drying it, and heating and sintering it in a vacuum or a reducing atmosphere, or the like. The atomization method may be any of a water atomization method, a gas atomization method, and a water gas atomization method. The vapor deposition layer is produced by, for example, a resistance heating vapor deposition method or an electron beam heating vapor deposition method. This vapor deposition layer is formed by heating and evaporating a valve metal of the same or different type as the foil body by resistance heat or electron beam energy, and depositing the vapor of the valve metal particles on the surface of the foil body.

[0035] The dielectric film is formed on the uneven surface of the surface-expanding layer. The dielectric film is typically an oxide film formed on the uneven surface of the surface-expanding layer, and if the anode foil is made of aluminum, it is an aluminum oxide layer formed by oxidizing the uneven surface of the surface-expanding layer. In the chemical conversion treatment for forming the dielectric film, a voltage is applied to the anode foil in a chemical conversion solution so as to achieve a desired withstand voltage. The chemical conversion solution is a solution that does not contain halogen ions, and is, 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, or an adipic acid-based chemical conversion solution such as ammonium adipate.

[0036] A surface enlarging layer may be formed on the cathode foil as required, in the same manner as the anode foil. A plain foil without a surface enlarging layer may be used as the cathode foil. The cathode foil may have a dielectric film formed thereon, in the same manner as the anode foil. The dielectric film may be a natural oxide film or a thin oxide film (about 1 to 10 V) formed by chemical conversion treatment. The natural oxide film is formed by the reaction of the cathode body with oxygen in the air.

[0037] The cathode foil may have a conductive layer laminated on the foil surface. The conductive layer is, for example, a layer containing a metal nitride such as titanium, zirconium, tantalum, or niobium, a metal carbide, a metal carbonitride, or carbon. The metal nitride, metal carbide, metal carbonitride, and carbon are formed by a deposition method, a slurry coating method, or the like.

[0038] (Lead terminal) 2 is a schematic diagram of a lead terminal 3. The lead terminal 3 is drawn through a sealing member 4, and is configured with a lead wire 31, a round bar portion 32, and a flat portion 33 arranged in a series. The sealing member 42 is an elastic body for sealing the capacitor element in an exterior case, and has an insertion hole 43 through which the lead terminal 3 passes. The lead wire 31 is an electric wire that extends outside beyond the sealing member 42 and electrically connects the solid electrolytic capacitor to a mounting board. This lead wire 31 is generally a copper-coated steel wire called a CP wire, and its surface is plated with solder such as lead or tin.

[0039] The round bar portion 32 is typically made of aluminum and is a round bar having a substantially cylindrical shape. However, the cross-sectional shape of the round bar portion 32 is not limited to a perfect circle, and may be an ellipse, a polygonal shape such as a triangle or a rectangle, or other shapes. The lead wire 31 and the round bar portion 32 are connected by arc welding or the like, and a connection portion 34 by welding is interposed between the lead wire 31 and the round bar portion 32. Alternatively, the lead wire 31 may be formed from a part of the round bar portion 32. The round bar portion 32 is set to be one size larger than the insertion hole 43 of the plugging member 42. The round bar portion 32 is press-fitted into the insertion hole 43, and is in close contact with the inner wall of the insertion hole 43 due to an increase in the internal pressure of the plugging member 4 after it is crimped.

[0040] The flat portion 33 is formed by crushing the side of the round bar portion 32 opposite to the lead wire 31 by pressing or the like into a flat plate shape. The boundary between the round bar portion 32 and the flat portion 33 is an inclined portion whose thickness linearly decreases to the thickness of the flat portion 33. This inclined portion is included in the round bar portion 32.

[0041] The flat portion 33 is electrically and mechanically connected to each electrode foil 5, which is a collective term for anode foil and cathode foil, by one of various connection means such as stitch connection, cold pressure welding, ultrasonic welding, or laser welding. The flat portion 33 is brought into contact with one surface and one side of the long side of the electrode foil 5, and the round bar portion 32 and the lead wire 31 are allowed to protrude from the electrode foil 5 so as to be perpendicular 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 terminals 3 are connected to each electrode foil 5.

[0042] (Separator) The separator prevents short-circuiting between the anode foil and the cathode foil, and also holds the conductive polymer and the electrolyte. The separator may be made of cellulose such as kraft, Manila hemp, esparto, hemp, rayon, or a mixture of these, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or derivatives thereof, polytetrafluoroethylene resins, polyvinylidene fluoride resins, vinylon resins, polyamide resins such as aliphatic polyamides, semi-aromatic polyamides, or fully aromatic polyamides, polyimide resins, polyethylene resins, polypropylene resins, trimethylpentene resins, polyphenylene sulfide resins, acrylic resins, polyvinyl alcohol resins, or the like, which may be used alone or in combination.

[0043] The separator may be fibrillated by generating thin fibers that branch out from the surface of the original fibers, such as fibrillated cellulose. The fibrillation can be achieved, for example, by beating. The fibrillated fibers are entangled with each other using the fibrillated thin fibers, improving the strength of the separator. This allows the separator to be made thinner.

[0044] In addition, it is preferable to use a separator with an air resistance of 5.5 [s / 100 mL] or less for the wound body 1. If the separator has an air resistance of 5.5 [s / 100 mL] or less, the conductive polymer liquid will easily permeate into the wound body 1 in the solid electrolyte formation process. This increases the amount of conductive polymer liquid impregnated into the wound body 1 and the amount of conductive polymer attached to the wound body 1, improving the appearance rate of solid electrolytic capacitors.

[0045] Here, air resistance is also called the Gurley value, and is the time required for 100 mL of air to permeate the separator. Air resistance is measured by the Gurley method in accordance with JIS P8117:2009. A gasket with an inner diameter of 28.6 mm is used for the measurement. However, for air resistances of 1s / 100 mL or less, measurements are made using a gasket with an inner diameter of 6 mm and converted to values ​​measured with an inner diameter of 28.6 mm. Specifically, the value obtained with an inner diameter of 6 mm is multiplied by 28.6. 2 / 6 2 Use the conversion formula to multiply the above.

[0046] (conductive polymer) Conductive polymers are self-doped conjugated polymers doped with an intramolecular dopant, or conjugated polymers doped with an external dopant molecule. Conjugated polymers are obtained by chemical oxidative polymerization or electrolytic oxidative polymerization of a monomer having a π-conjugated double bond or a derivative thereof. The dopant or external dopant molecule is an acceptor that easily accepts electrons into the conjugated polymer, or a donor that easily gives electrons to the conjugated polymer, which allows the conductive polymer to exhibit high conductivity.

[0047] The conjugated polymer may be any known polymer without any particular limitation. For example, polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, polythiophenevinylene, etc. These conjugated polymers may be used alone, or in combination of two or more kinds, or may be a copolymer of two or more kinds of monomers.

[0048] Among the above conjugated polymers, preferred are conjugated polymers obtained by polymerizing thiophene or its derivatives, and preferred are conjugated polymers obtained by polymerizing 3,4-ethylenedioxythiophene (i.e., 2,3-dihydrothieno[3,4-b][1,4]dioxine), 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4-alkylthiophene, 3,4-alkoxythiophene, or derivatives thereof. As the thiophene derivative, a compound selected from thiophenes having substituents at the 3rd and 4th positions is preferred, and the substituents at the 3rd and 4th positions of the thiophene ring may form a ring together with the carbons at the 3rd and 4th positions. The number of carbon atoms of the alkyl group or alkoxy group is preferably 1 to 16.

[0049] In particular, a polymer of 3,4-ethylenedioxythiophene called EDOT, that is, poly(3,4-ethylenedioxythiophene) called PEDOT, is preferred. A substituent may be added to 3,4-ethylenedioxythiophene. For example, an alkylated ethylenedioxythiophene having an alkyl group having 1 to 5 carbon atoms added as a substituent may be used. Examples of alkylated ethylenedioxythiophene include methylated ethylenedioxythiophene (i.e., 2-methyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), ethylated ethylenedioxythiophene (i.e., 2-ethyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), butylated ethylenedioxythiophene (i.e., 2-butyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine), and 2-alkyl-3,4-ethylenedioxythiophene.

[0050] The dopant may be any known dopant without any particular limitation. The dopant may be used alone or in combination of two or more. A polymer or monomer may also be used. For example, the dopant may be an inorganic acid such as a polyanion, boric acid, nitric acid, or phosphoric acid, or an organic acid such as acetic acid, oxalic acid, citric acid, tartaric acid, squaric acid, rhodizonic acid, croconic acid, salicylic acid, p-toluenesulfonic acid, 1,2-dihydroxy-3,5-benzenedisulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, borodisalicylic acid, bisoxalate borate acid, sulfonylimide acid, dodecylbenzenesulfonic acid, propylnaphthalenesulfonic acid, or butylnaphthalenesulfonic acid.

[0051] Examples of the polyanion include substituted or unsubstituted polyalkylene, substituted or unsubstituted polyalkenylene, substituted or unsubstituted polyimide, substituted or unsubstituted polyamide, and substituted or unsubstituted polyester, and include polymers consisting of only structural units having an anionic group, and polymers consisting of structural units having an anionic group and structural units not having an anionic group.Specific examples of the polyanion include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacryl sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0052] An example of such a conductive polymer is poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonic acid, and hereinafter this conductive polymer is referred to as PEDOT / PSS.

[0053] In the solid electrolyte formation process, the wound body 1 is immersed in a conductive polymer liquid to adhere the conductive polymer to the inside of the wound body 1. The conductive polymer liquid is a dispersion liquid in which a conductive polymer is dispersed or a solution in which a conductive polymer is dissolved. The conductive polymer liquid is prepared by purifying a solution after electrolytic polymerization or chemical polymerization by ultrafiltration, cation exchange, anion exchange, or the like to remove residual monomers and impurities, and dispersing or dissolving the conductive polymer in a solvent, or by adding particles or powder of the conductive polymer to a solvent and dispersing or dissolving the conductive polymer in the solvent.

[0054] The main solvent of the conductive polymer liquid is water. The viscosity of the conductive polymer liquid is adjusted to 10 mPa·s or more and 60 mPa·s or less by, for example, the processing time by 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 this range, the conductive polymer liquid can easily permeate the wound body 1 while maintaining a good ESR of the solid electrolytic capacitor, thereby improving the capacitance appearance rate of the solid electrolytic capacitor. However, if the viscosity is less than 10 mPa·s, the ESR will increase rapidly. Also, if the viscosity exceeds 60 mPa·s, the capacitance appearance rate will decrease rapidly.

[0055] The capacitance appearance rate is the ratio of the capacitance of the solid electrolytic capacitor to the combined capacitance of the anode foil and the cathode foil, and is a percentage obtained by dividing the 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 when the solid electrolytic capacitor is regarded as a capacitor with an anode side and a cathode side connected in series. When the cathode foil has a conductive layer, or when the capacitance of the cathode body can be said to converge to infinity, the combined capacitance of the anode foil and the cathode foil is the capacitance of the anode foil.

[0056] The solvent for the conductive polymer dispersion may be a mixture of water and an organic solvent, as long as the conductive polymer particles or powder can be dispersed or dissolved in the solvent. Suitable examples of the organic solvent include polar solvents, alcohols, esters, hydrocarbons, carbonate compounds, ether compounds, chain ethers, heterocyclic compounds, and nitrile compounds.

[0057] Examples of polar solvents include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. Examples of alcohols include methanol, ethanol, propanol, and butanol. Examples of esters include ethyl acetate, propyl acetate, and butyl acetate. Examples of hydrocarbons include hexane, heptane, benzene, toluene, and xylene. Examples of carbonate compounds include ethylene carbonate and propylene carbonate. Examples of ether compounds include dioxane and diethyl ether. Examples of chain ethers include ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether. Examples of heterocyclic compounds include 3-methyl-2-oxazolidinone. Examples of nitrile compounds include acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile.

[0058] The conductive polymer liquid may have a pH adjusted, and may contain polyhydric alcohol and various additives as necessary. Examples of pH adjusters include ammonia water, sodium hydroxide, primary amines, secondary amines, and tertiary amines. Examples of polyhydric alcohols include sorbitol, ethylene glycol, diethylene glycol, triethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, glycerin, polyglycerin, polyoxyethylene glycerin, xylitol, erythritol, mannitol, dipentaerythritol, pentaerythritol, and combinations of two or more of these. Polyhydric alcohols are high-boiling point solvents, and remain in the wound body 1 even after the wound body 1 is impregnated with the conductive polymer liquid and dried. The polyhydric alcohols can reduce the ESR of the solid electrolytic capacitor and improve the withstand voltage. Examples of additives include organic binders, surfactants, dispersants, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers.

[0059] In the solid electrolyte forming process, the wound body 1 is immersed in the conductive polymer liquid with the opposite end surface 1b of the wound body 1 facing downward. FIG. 3 is a schematic diagram showing the liquid level of the conductive polymer liquid or the position where the conductive polymer is attached. As shown in FIG. 3, the boundary position between the lead wire 31 of the lead terminal 3 and the upper end of the connection portion 34 is defined as the upper end A1 of the connection portion. The boundary position between the lower end of the connection portion 34 of the lead terminal 3 and the round bar portion 32 is defined as the lower end A2 of the connection portion. The position at half the height in the length direction of the round bar portion 32 or a position 1 mm or more away from the lead end surface 1a of the wound body 1 is defined as A3. The lead end surface 1a of the wound body 1 is defined as the end surface position A4.

[0060] At this time, it is preferable to immerse the wound body 1 in the conductive polymer liquid so that the liquid level of the conductive polymer liquid is located at least on the lead-out end surface 1a of the wound body 1. It is also preferable to immerse the wound body 1 in the conductive polymer liquid so that the liquid level of the conductive polymer liquid is located between the position A3, which is 1 mm from the half position of the round bar or the lead-out end surface 1a of the wound body 1, and the upper end A1 of the connection part. In other words, it is preferable to attach the conductive polymer to the lead terminal 3 in the range between at least the position A3 and the upper end A1 of the connection part, in addition to the inside of the wound body 1. Since the contact angle between the hydrophobic adhesive tape and the conductive polymer liquid is large, a meniscus is formed. Therefore, it is necessary to immerse the wound body 1 in the conductive polymer liquid beyond the upper end edge of the hydrophobic adhesive tape 2.

[0061] The conductive polymer liquid is absorbed from the opposite end face 1b and drips down from the outlet end face 1a. By using a separator with an air resistance of 5.5 [s / 100 mL] or less, the conductive polymer liquid that has entered from the outlet end face 1a and the opposite end face 1b permeates through the separator and into the wound body 1.

[0062] Therefore, in the solid electrolyte formation process, the round bar portion 32 is immersed in the conductive polymer liquid at least to a height equal to or greater than the height of position A3, and in addition to the wound body 1, a conductive polymer is provided that adheres to the round bar portion 32 at least to a height equal to or greater than the height of position A3, thereby increasing the capacitance appearance rate of the solid electrolytic capacitor and reducing the dielectric tangent (tan δ).

[0063] The impregnation time of the conductive polymer liquid can be set appropriately depending on the size of the wound body 1. There is no adverse effect on the characteristics even if the impregnation is performed for a long time. When impregnating the wound body 1, a decompression treatment or a pressurization treatment may be performed as necessary to promote the impregnation. The solid electrolyte formation process may be repeated multiple times. The solvent of the conductive polymer liquid is evaporated and removed by drying as necessary. Heat drying or reduced pressure drying may be performed as necessary to remove the solvent.

[0064] Between the winding step and the solid electrolyte forming step, a repair chemical treatment may be performed to repair defects such as voids, cracks, or scratches in various parts of the dielectric film caused by insufficient formation of the dielectric film and bending stress due to winding. As the chemical solution for the repair chemical conversion, an aqueous solution of phosphoric acid such as ammonium dihydrogen phosphate or diammonium hydrogen phosphate, boric acid such as ammonium borate, or adipic acid such as ammonium adipate dissolved in water is used. The voltage is preferably set to, for example, 0.1 to 1.2 times the chemical conversion voltage. Thereafter, in order to remove the chemical conversion solution from the wound body 1, the wound body 1 immersed in the chemical conversion solution is washed with a chemical conversion solution washing solution such as pure water.

[0065] (electrolyte) When an electrolyte is used in the solid electrolytic capacitor, the solid electrolyte forming step is followed by the electrolyte impregnation step. The electrolyte is a mixed solution in which a solute is dissolved in a solvent and an additive is added as necessary. The electrolyte does not need to dissolve a solute, and may be a solvent only, or may contain a solvent and an additive. The solvent for the electrolyte may be a protic organic polar solvent or an aprotic organic polar solvent, which may be used alone or in combination of two or more. The solute for the electrolyte may include an anion component or a cation component. The solute is typically a salt of an organic acid, a salt of an inorganic acid, or a salt of a complex compound of an organic acid and an inorganic acid, which may be used alone or in combination of two or more. An acid that becomes an anion and a base that becomes a cation may be added separately to the solvent.

[0066] Examples of the protic organic polar solvent that is the solvent include monohydric alcohols, polyhydric alcohols, and oxyalcohol compounds. Examples of the monohydric alcohols include ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, and benzyl alcohol. Examples of the polyhydric alcohols and oxyalcohol compounds include ethylene glycol, propylene glycol, glycerin, polyglycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, and alkylene oxide adducts of polyhydric alcohols such as polyethylene glycol and polyoxyethylene glycerin. Among these, the solvent is preferably a polyhydric alcohol, and particularly preferably ethylene glycol or glycerin. Ethylene glycol or glycerin causes a change in the higher-order structure of the conductive polymer, resulting in good initial ESR characteristics and good high-temperature characteristics. It is even better if the ethylene glycol is 30 wt% or more in the solvent.

[0067] Representative examples of aprotic organic polar solvents that serve as solvents include sulfones, amides, lactones, cyclic amides, nitriles, and sulfoxides. Examples of sulfones include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane. Examples of amides include N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, and hexamethylphosphoric amide. Examples of lactones and cyclic amides include γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, and isobutylene carbonate. Examples of the nitriles include acetonitrile, 3-methoxypropionitrile, glutaronitrile, etc. Examples of the sulfoxides include dimethyl sulfoxide, etc.

[0068] 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, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedioic acid, azelaic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, t-butyl adipic acid, 11-vinyl-8-octadecenedioic acid, resorcylic acid, phloroglucinic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, and pyromellitic acid, as well as phenols and sulfonic acids.

[0069] Examples of inorganic acids include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, silicic acid, etc. Examples of composite compounds of organic acids and inorganic acids include borodisalicylic acid, borodioxalic acid, borodiglycolic acid, borodimalonic acid, borodisuccinic acid, borodiadipic acid, borodiazelaic acid, borodibenzoic acid, borodimaleic acid, borodilactic acid, borodimalic acid, boroditartaric acid, borodicitric acid, borodiphthalic acid, borodi(2-hydroxy)isobutyric acid, borodiresorcinic acid, borodimethylsalicylic acid, borodinaphthoic acid, borodimandelic acid, and borodi(3-hydroxy)propionic acid, etc.

[0070] In addition, examples of at least one salt of an organic acid, an inorganic acid, and a complex compound of an organic acid and an inorganic acid include, for example, an ammonium salt, a quaternary ammonium salt, a quaternary amidinium salt, an amine salt, a sodium salt, and a potassium salt. Examples of the quaternary ammonium ion of the quaternary ammonium salt include tetramethylammonium, triethylmethylammonium, and tetraethylammonium. Examples of the quaternary amidinium include ethyldimethylimidazolinium and tetramethylimidazolinium. Examples of the amine salt include salts of primary amines, secondary amines, and tertiary amines. Examples of the primary amines include methylamine, ethylamine, and propylamine, and examples of the secondary amines include dimethylamine, diethylamine, ethylmethylamine, and dibutylamine, and examples of the tertiary amines include trimethylamine, triethylamine, tributylamine, ethyldimethylamine, and ethyldiisopropylamine.

[0071] Further, other additives can 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 polyhydric alcohols, boric acid esters, nitro compounds (o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, p-nitrobenzyl alcohol, etc.), and phosphoric acid esters. These may be used alone or in combination of two or more. The amount of additives added is not particularly limited, but it is preferable to add them to an extent that does not deteriorate the characteristics of the solid electrolytic capacitor, for example, 60 wt% or less in the electrolyte. EXAMPLES

[0072] The solid electrolytic capacitor and the manufacturing method thereof according to the present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0073] (Examples 1 to 7) As described below, solid electrolytic capacitors of Examples 1 to 7 and Comparative Examples 1 and 2 were fabricated. The solid electrolytic capacitors of Examples 1 to 7 and Comparative Examples 1 and 2 are common to all but the viscosities of the conductive polymer solutions used in the fabrication were different.

[0074] First, the anode foil and the cathode foil were strip-shaped aluminum foil stretched to a long length. The anode foil and the cathode foil were enlarged in surface area by direct current etching. After the enlargement, the anode foil was subjected to chemical conversion treatment to form a dielectric film.

[0075] A lead terminal 3 was attached to each of the anode foil and the cathode foil by stitch connection. A separator made of fibrillated cellulose was interposed between the anode foil and the cathode foil to which the lead terminal 3 was connected, and the strip was wound so that the strip was curled in the longitudinal direction to form a wound body 1. In the solid electrolytic capacitor of Example 1, a separator made of fibrillated cellulose and having an air resistance of 5.48 [s / 100 mL] was used.

[0076] An adhesive tape 2 having the same width as the entire axial length of the wound body 1 was prepared, and the outer periphery of the wound body 1 was wound and secured with this adhesive tape 2. A voltage of 57 V was applied to the wound body 1 in the chemical conversion solution, and a repair chemical conversion was performed.

[0077] The wound body 1 was impregnated with a conductive polymer liquid. The conductive polymer liquid was prepared by dispersing poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) doped with polystyrene sulfonic acid (PSS) in water. PEDOT / PSS was added at a ratio of 1.2 wt% to the entire conductive polymer liquid. Ethylene glycol was also added to the conductive polymer liquid, and the ethylene glycol was added at a ratio of 10 wt% to the conductive polymer liquid. In the solid electrolytic capacitor of Example 1, the viscosity of the conductive polymer liquid was adjusted by dispersing the conductive polymer liquid with an ultrasonic homogenizer.

[0078] The wound body 1 was impregnated with the conductive polymer liquid for 10 minutes at room temperature and in a reduced pressure environment of 80 kPa or less. The wound body 1 was immersed in the conductive polymer liquid so that the liquid level of the conductive polymer liquid was located at the lower end A2 of the connection part shown in Figure 3 and the conductive polymer was attached up to the height of the lower end A2 of the connection part. After each impregnation process, the wound body 1 was left to stand at room temperature for 10 minutes and then left to stand in a temperature environment of 110°C for 30 minutes to dry it.

[0079] After being impregnated with the conductive polymer and dried, the wound body 1 was housed in an exterior case 41, and the exterior case 41 was sealed with a sealing member 42. The sealing member 42 and the exterior case 41 were tightly attached by crimping. The lead terminal 3 was press-fitted into the insertion hole 43 of the sealing member 42, and the outer peripheral surface of the round bar portion 32 was tightly attached to the inner peripheral surface of the insertion hole 43. The completed solid electrolytic capacitor was subjected to an aging treatment in which a voltage of 40 V was applied for 1 hour. As a result, the electrolytic capacitor of Example 1 was produced, having a diameter of 10 mm, a height of 10 mm, a rated voltage of 35 WV, and a rated capacitance of 270 μF.

[0080] (Capacitor characteristics) 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. The ESR was expressed with Comparative Example 2 as the standard (100%). The results are shown in Table 1 together with the viscosities of the conductive polymer liquids used in Examples 1 to 7 and Comparative Examples 1 and 2. The relationship of the ESR and capacitance appearance rate to the viscosity of the conductive polymer liquid is shown in the scatter diagram of FIG. 4. In FIG. 4, the white plots represent the capacitance appearance rate, and the black plots represent the ESR.

[0081] The equivalent series resistance (ESR) was measured at room temperature using an LCR meter at a measurement frequency of 100 kHz and a sine wave with an AC amplitude of 0.5 Vms.

[0082] Regarding the capacitance appearance rate, the capacitance of the anode foil or cathode foil was measured by cutting a test piece of a specified area from the anode foil or cathode foil, immersing it in a capacitance measurement solution in a glass measurement tank with a platinum plate as the counter electrode, and measuring it with a capacitance meter. The specified area was 1 cm 2The capacitance measurement liquid was an aqueous solution of ammonium adipate at 30°C, the capacitance meter was an LCR meter, and the measurement conditions were an AC amplitude of 0.5 Vms.

[0083] (Table 1) TIFF2024052276000002.tif106161

[0084] As shown in Table 1 and Fig. 4, in the solid electrolytic capacitors of Comparative Example 1 and Examples 1 to 7, a conductive polymer is formed using a conductive polymer solution having a viscosity of 60 mPa·s or less. The solid electrolytic capacitors of Comparative Example 1 and Examples 1 to 7 had a good capacitance appearance rate. However, Comparative Example 1, in which a conductive polymer is formed using a conductive polymer solution having a viscosity of less than 10 mPa·s, had a high ESR. On the other hand, Examples 1 to 7, in which a conductive polymer is formed using a conductive polymer solution having a viscosity of 10 mPa·s or more and 60 mPa·s or less, had a good capacitance appearance rate and a good ESR.

[0085] This confirmed that even when the capacitor was wound with hydrophobic adhesive tape 2, by setting the viscosity of the conductive polymer liquid to 10 mPa s or more and 60 mPa s or less, the capacitance appearance rate was good and the ESR was also low.

[0086] Example 8 A solid electrolytic capacitor of Example 8 was produced. Example 8 is common to Example 4 in the following respects. That is, in the solid electrolytic capacitor of Example 8, a conductive polymer liquid having a viscosity of 30 mPa·s was impregnated into the wound body 1, as in Example 4. The wound body 1 was immersed in the conductive polymer liquid so that the liquid level of the conductive polymer liquid was located at the lower end A2 of the connection part shown in FIG. 3, and the conductive polymer was attached up to the height of the lower end A2 of the connection part. The lower end A2 of the connection part is a position 2 mm from the lead-out end surface 1a of the wound body 1. However, Example 8 is different from Example 4, and a separator with an air resistance of 5.76 [s / 100 mL] was used in Example 8. In other respects, Example 8 has the same configuration as Example 4, and was produced by the same production method and production conditions.

[0087] (Capacity appearance rate) The capacitance appearance rate (%) was measured for the solid electrolytic capacitors of Examples 4 and 8. The results are shown in Table 2 below. (Table 2) TIFF2024052276000003.tif36163

[0088] As shown in Table 2, the capacitance appearance rate of Example 8, in which the separator had an air resistance of 5.76 [s / 100 mL], was good, unlike Comparative Example 2, but was lower than that of Example 4. In other words, it was confirmed that when the viscosity of the conductive polymer liquid was 10 mPa s or more and 60 mPa s or less, and the separator had an air resistance of 5.5 [s / 100 mL] or less, which includes the range of Examples 1 to 8, the capacitance appearance rate of the solid electrolytic capacitor was further improved.

[0089] Example 9 A solid electrolytic capacitor of Example 9 was produced. Example 9 is common to Example 4 in the following respects. That is, in the solid electrolytic capacitor of Example 9, as in Example 4, a filuryl cellulose having an air 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 wound body 1. However, unlike Example 4, the wound body 1 of Example 9 was immersed in the conductive polymer liquid so that the liquid level of the conductive polymer liquid was located at the upper end A1 of the connection part shown in FIG. 3, and the conductive polymer was attached up to the height of the upper end A1 of the connection part. In other respects, Example 9 has the same configuration as Example 4, and was produced by the same manufacturing method and manufacturing conditions. The upper end A1 of the connection part is located 2.7 mm from the lead-out end surface 1a of the wound body 1.

[0090] Example 10 A solid electrolytic capacitor of Example 10 was produced. Example 11 has the following in common with Example 4. That is, in the solid electrolytic capacitor of Example 11, a filuryl cellulose having an air resistance of 5.48 [s / 100 mL] was used as a separator, as in Example 4. A conductive polymer liquid having a viscosity of 30 mPa·s was impregnated into the wound body 1. However, unlike Example 4, the wound body 1 of Example 11 was immersed in the conductive polymer liquid so that the liquid level of the conductive polymer liquid was located at position A3 shown in FIG. 3 and the conductive polymer was attached up to the height of the upper end A1 of the connection part. In other respects, Example 11 has the same configuration as Example 4, and was produced by the same manufacturing method and manufacturing conditions. Position A3 is a position 1 mm from the lead-out end surface 1a of the wound body 1.

[0091] Example 11 A solid electrolytic capacitor of Example 11 was produced. Example 11 has the following in common with Example 4. That is, in the solid electrolytic capacitor of Example 12, a filuryl cellulose having an air resistance of 5.48 [s / 100 mL] was used as a separator, as in Example 4. A conductive polymer liquid having a viscosity of 30 mPa·s was impregnated into the wound body 1. However, unlike Example 4, the wound body 1 of Example 11 was immersed in the conductive polymer liquid so that the liquid level of the conductive polymer liquid was located at the end face position A4 shown in FIG. 3 and the conductive polymer was attached up to the height of the end face position A4. In other respects, Example 11 has the same configuration as Example 4 and was produced by the same production method and production conditions.

[0092] (Adhesion test) The amount of the conductive polymer solution impregnated in the wound body 1 of Example 4 and Examples 9 to 11 was measured. The adhesion amount was calculated from the change in weight of the wound body 1 before and after the solid electrolyte formation step. The adhesion amount of Example 4 and Examples 9 to 10 is shown with the adhesion amount of Example 11 as the reference (100%).

[0093] FIG. 5 shows the relationship between the weight of the conductive polymer liquid attached to the wound body 1 in each of Examples 4 and 9 to 11 and the immersion liquid level of the conductive polymer liquid.

[0094] As shown in FIG. 5, it was confirmed that the amount of conductive polymer liquid adhered was significantly improved at A3, which is half the height in the longitudinal direction of the round bar portion 32, compared to when the immersion liquid level of the conductive polymer liquid and the conductive polymer adhesion height were set at end face position A4.

[0095] Furthermore, it was confirmed that at the lower end A2 and upper end A1 of the connection portion, which are in the height range of the connection portion 34 between the round bar portion 32 and the lead wire 31, the amount of conductive polymer liquid adhered thereto was further improved compared to when the immersion liquid level height of the conductive polymer liquid and the conductive polymer adhesion height were set at the end face position A4.

[0096] (Capacitor characteristics) The dielectric loss tangent (tan δ) and capacitance appearance rate (%) of the solid electrolytic capacitors of Example 4 and Examples 9 to 11 were measured. The results are shown in Figures 6 and 7. The measurement results of the capacitance appearance rate (%) are shown in Table 3 below, and the measurement results of the dielectric loss tangent (tan δ) are shown in Table 4 below. The dielectric loss tangent (tan δ) was measured at room temperature using an LCR meter. The measurement frequency of tan δ was 120 Hz, and the AC amplitude was a sine wave of 0.5 Vms.

[0097] (Table 3) TIFF2024052276000004.tif56167

[0098] (Table 4) TIFF2024052276000005.tif56167

[0099] As shown in Tables 3 and 4 and FIGS. 6 and 7, it can be confirmed that tan δ and the capacitance appearance rate are improved in accordance with the amount of conductive polymer attached in FIG.

[0100] That is, when the conductive polymer is wound with hydrophobic adhesive tape 2, the viscosity of the conductive polymer liquid is set to 10 mPa·s or more and 60 mPa·s or less to facilitate the spreading of the conductive polymer inside the wound body 1. The immersion liquid surface of the conductive polymer liquid is positioned at the halfway position of the round bar, which is half the height in the longitudinal direction of the round bar portion 32, or above A3, which is 1 mm from the leading end face 1a of the wound body 1, and the conductive polymer is adhered, thereby increasing the amount of the conductive polymer liquid adhered. It has been confirmed that this further improves the capacitance appearance rate of the solid electrolytic capacitor, and also improves tan δ.

[0101] (Examples 12 to 14) Solid electrolytic capacitors of Examples 12 to 14 were produced. Examples 12 to 14 are common to Example 1 in the following respects. That is, in the solid electrolytic capacitors of Examples 12 to 14, as in Example 1, the wound body 1 was impregnated with a conductive polymer liquid having a viscosity of 13 mPa s. The wound body 1 was immersed in the conductive polymer liquid so that the liquid level of the conductive polymer liquid was located at the lower end A2 of the connection part shown in FIG. 3, and the conductive polymer was attached up to the height of the lower end A2 of the connection part. The lower end A2 of the connection part is located 2 mm from the lead-out end surface 1a of the wound body 1.

[0102] However, the solid electrolytic capacitors of Examples 12 to 14 use a separator made of natural cellulose with an air resistance of 0.03 [s / 100 mL], unlike Example 1. Examples 12 to 14 differ from each other in the viscosity of the conductive polymer liquid impregnated into the wound body 1. In Example 12, like Example 1, the wound body 1 was impregnated with a conductive polymer liquid with a viscosity of 13 mPa·s. In Example 13, unlike Example 12, the wound body 1 was impregnated with a conductive polymer liquid with a viscosity of 25 mPa·s. In Example 14, unlike Example 12, the wound body 1 was impregnated with a conductive polymer liquid with a viscosity of 60 mPa·s.

[0103] In other respects, Examples 12 to 14 have the same configuration as Example 1, and were produced by the same manufacturing method and under the same manufacturing conditions.

[0104] A solid electrolytic capacitor of Comparative Example 3 was also produced. The solid electrolytic capacitor of Comparative Example 3 had the same configuration as Examples 12 to 14, except that the wound body 1 was impregnated with a conductive polymer liquid having a viscosity of 125 mPa s, and was produced by the same production method and under the same production conditions.

[0105] (Capacitor characteristics) 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 measurement method and conditions for 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. The ESR is shown with Comparative Example 3 as the standard (100%).

[0106] (Table 5) TIFF2024052276000006.tif57164

[0107] Based on this Table 5, the relationship between the viscosity of the conductive polymer liquid and the ESR and the capacitance appearance rate is shown in the scatter diagram of Figure 8. In Figure 8, the white plots indicate the capacitance appearance rate, and the black plots indicate the ESR.

[0108] As shown in Table 5 and FIG. 8, even when natural cellulose with an air resistance value of 0.03 [s / 100 mL] was used, Examples 12 to 14 in which the conductive polymer was formed using a conductive polymer solution with a viscosity of 10 mPa s or more and 60 mPa s or less showed a good capacitance appearance rate and a good ESR. [Explanation of symbols]

[0109] 1 roll 1a Leading end face 1b Opposite end face 2. Adhesive tape 3 Lead terminal 31 Leader 32 Round bar section 33 Flat area 34 Welding 41 Outer case 42 Sealing member 43 Insertion hole 5 Electrode foil

Claims

1. A winding step of forming a wound body by winding an anode foil and a cathode foil having a dielectric film formed thereon so as to face each other; A winding prevention step of winding the circumferential surface of the wound body with a hydrophobic adhesive tape; A solid electrolyte forming step of attaching the conductive polymer to the wound body by immersing the wound body wound with the adhesive tape in a conductive polymer solution in which the conductive polymer is dispersed or dissolved; comprising: In the solid electrolyte forming step, immersing the wound body in the conductive polymer solution containing a high-boiling solvent and having a viscosity of 10 mPa·s or more and 60 mPa·s or less; A method for manufacturing a solid electrolytic capacitor, characterized in that.

2. The conductive polymer solution contains water as a solvent; The method for manufacturing a solid electrolytic capacitor according to claim 1, characterized in that.

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

4. A lead terminal in which a flat portion, a round bar portion, and a lead wire are continuously connected in series is connected to the anode foil and the cathode foil at the flat portion, the round bar portion protrudes from one end surface of the wound body, and the lead wire is drawn out. In the solid electrolyte forming step, immersing the wound body in the conductive polymer solution to a height of at least one end surface of the wound body; The method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, characterized in that.

5. Further comprising an electrolytic solution impregnation step of impregnating the wound body with an electrolytic solution; The method for manufacturing a solid electrolytic capacitor according to claim 1, characterized in that.

6. A wound body obtained by winding an anode foil and a cathode foil having a dielectric film formed thereon so as to face each other; A hydrophobic adhesive tape for winding the circumferential surface of the wound body; At least a conductive polymer attached to the dielectric film; A separator interposed between the anode foil and the cathode foil in the wound body and having an air permeability resistance of 5.5 [s / 100 mL] or less; comprising: The conductive polymer is formed by using a conductive polymer solution 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; A solid electrolytic capacitor, characterized in that.

7. Comprising a lead terminal in which a flat portion, a round bar portion, and a lead wire are continuously connected in series, the flat portion is connected to the anode foil and the cathode foil, the round bar portion protrudes from one end surface of the wound body, and the lead wire is drawn out. The conductive polymer adheres to a height equal to or greater than that of one end surface of the wound body. The solid electrolytic capacitor according to claim 6, characterized in that.

8. Further comprising an electrolytic solution impregnated in the wound body. The solid electrolytic capacitor according to claim 6, characterized in that.

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