Manufacturing method of solid electrolytic capacitor

Abstract

To form a more uniform solid electrolyte layer in the manufacture of a solid electrolytic capacitor using an assembly including a plurality of anode body regions.SOLUTION: A manufacturing method of a solid electrolytic capacitor includes the steps of forming a solid electrolyte layer so as to cover at least a portion of a dielectric layer and forming a second assembly having a plurality of solid electrolytic capacitor elements in a first assembly having a plurality of anode body regions each having a dielectric layer and arranged in a plane direction, and singulating the second assembly into individual solid electrolytic capacitor elements. The step of forming the second assembly includes a first step of forming a coating including manganese oxide covering at least a portion of the dielectric layer, and a second step of forming the solid electrolyte layer containing a conjugated polymer precursor and a dopant by bringing a liquid mixture containing the conjugated polymer precursor, the dopant, and a polyhydric alcohol into contact with the coating, and chemically polymerizing the precursor using the manganese oxide as an oxidizing agent.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a solid electrolytic capacitor. [Background technology]

[0002] A solid electrolytic capacitor includes a solid electrolytic capacitor element, an exterior body that seals the solid electrolytic capacitor element, and an external electrode electrically connected to the solid electrolytic capacitor element. The solid electrolytic capacitor element includes an anode body, a dielectric layer formed on the surface of at least the cathode-forming portion of the anode body, and a cathode portion that covers at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer containing a conductive polymer that covers at least a portion of the dielectric layer, and a cathode extraction layer that covers at least a portion of the solid electrolyte layer. The solid electrolyte layer can be formed, for example, by applying a liquid mixture (dispersion or solution) containing the conductive polymer to an anode body having a dielectric layer. Alternatively, the solid electrolyte layer can be formed by chemically or electrolytically polymerizing a precursor of the conductive polymer.

[0003] For example, Patent Document 1 proposes forming an internal conductive polymer layer made of a conductive polymer on the surface of a porous valve metal having an anodized film formed on its surface, providing a liquid phase part made of a polymer polymerization solution obtained by mixing an aqueous dispersion containing polyethylenedioxythiophene and polystyrenesulfonic acid as conductive polymers, naphthalenesulfonic acids, high-molecular-weight polystyrenesulfonic acid, boric acid, mannitol, and glycols on the surface of the internal conductive polymer layer, and drying and solidifying the liquid phase part made of the polymer polymerization solution to form a solid electrolyte layer.

[0004] Furthermore, from the viewpoint of improving productivity, a technique has been proposed in which an assembly having a plurality of anode body regions is used to form a plurality of solid electrolytic capacitors in the state of the assembly, and then the solid electrolytic capacitors are separated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-311582 Summary of the Invention [Problem to be solved by the invention]

[0006] From the viewpoint of easily manufacturing solid electrolytic capacitors and ensuring higher productivity, it is advantageous to form a solid electrolyte layer using a liquid mixture containing a conductive polymer (e.g., a liquid dispersion containing a liquid medium and a particulate conductive polymer dispersed in the liquid medium), as in Patent Document 1. However, when forming a solid electrolyte layer using an assembly having multiple anode body regions, if a liquid mixture containing a conductive polymer is used, it is necessary to form a solid electrolyte layer with a certain thickness in order to reduce leakage current. In this case, it is difficult to form a uniform solid electrolyte layer throughout the entire assembly. [Means for solving the problem]

[0007] A first aspect of the present disclosure is a method for manufacturing a solid electrolytic capacitor including a solid electrolytic capacitor element including an anode body, a dielectric layer covering at least a portion of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer, the method comprising: forming a second assembly having a plurality of the solid electrolytic capacitor elements by forming the solid electrolyte layer so as to cover at least a portion of the dielectric layer in a first assembly having anode body regions corresponding to the plurality of the anode bodies arranged in a planar direction, the first assembly each having the dielectric layer; and dividing the second assembly into individual solid electrolytic capacitor elements, The step of forming the second assembly includes: a first step of forming a coating containing manganese oxide that covers at least a portion of the dielectric layer; a second step of contacting the coating with a liquid mixture containing a precursor of a conjugated polymer, a dopant, and a polyhydric alcohol, and chemically polymerizing the precursor using the manganese oxide as an oxidizing agent to form the solid electrolyte layer containing the conjugated polymer and the dopant; The present invention relates to a method for manufacturing a solid electrolytic capacitor, including: [Effects of the Invention]

[0008] When a plurality of solid electrolytic capacitors are formed using an assembly having a plurality of anode body regions, a more uniform solid electrolyte layer can be formed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 3 is a schematic plan view of a second assembly used in a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2] 2 is a schematic cross-sectional view of the second assembly of FIG. 1 taken along line II-II, viewed from the direction of the arrows. FIG. [Figure 3] 2A to 2C are process diagrams illustrating a method for manufacturing the solid electrolytic capacitor according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of a solid electrolytic capacitor obtained by a method for manufacturing a solid electrolytic capacitor according to a second embodiment of the present disclosure. [Figure 5] FIG. 10 is a schematic cross-sectional view of a solid electrolytic capacitor obtained by a method for manufacturing a solid electrolytic capacitor according to a third embodiment of the present disclosure. [Figure 6A] 10 is a cross-sectional view schematically illustrating a solid electrolytic capacitor obtained by a method for manufacturing a solid electrolytic capacitor according to a fourth embodiment of the present disclosure, taken in a direction parallel to the length direction (first direction) of an anode body and the stacking direction of solid electrolytic capacitor elements. FIG. [Figure 6B] 6B is a schematic cross-sectional view of the solid electrolytic capacitor of FIG. 6A cut in the width direction (second direction) of the anode body and in a direction parallel to the stacking direction of the solid electrolytic capacitor elements. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] When a solid electrolytic capacitor is manufactured by forming a solid electrolyte layer using an assembly having multiple anode body regions and then singulating the assembly, it is significantly more difficult to form a more uniform solid electrolyte layer than when the solid electrolytic capacitors are manufactured individually. In the former case, the solid electrolyte layer is formed simultaneously on multiple anode body regions, which tends to result in variations in the rate and extent of solid electrolyte layer formation in each anode body region. Although a solid electrolyte layer can also be formed by chemical polymerization or electrolytic polymerization, controlling the reaction is more difficult than when a solid electrolyte layer is formed using a liquid mixture containing a conductive polymer. In particular, because chemical polymerization proceeds around an oxidizing agent, it is extremely difficult to achieve uniform polymerization on the anode body region when a liquid mixture containing a conductive polymer precursor and an oxidizing agent is used. Even if an oxidizing agent is applied to the anode body region and then brought into contact with a liquid mixture containing a conductive polymer precursor, the oxidizing agent dissolves in the liquid mixture, making it difficult to achieve stable and uniform polymerization on the anode body region. It is theoretically possible to form a solid electrolyte layer on an anode region by repeatedly applying an oxidizing agent and polymerizing the liquid mixture. However, because the location of the oxidizing agent deposition cannot be controlled, the film quality and thickness of the solid electrolyte layer are thought to be even more nonuniform. In particular, when forming a solid electrolyte layer using an assembly with multiple anode regions, it is extremely difficult to achieve a uniform oxidizing agent distribution across the entire anode region of the assembly, significantly increasing the difficulty of reaction control. Therefore, it is difficult to suppress variations in the state, thickness, and film quality of the solid electrolyte layer formed on each anode region, resulting in a significant increase in the product defect rate. From this perspective, forming a solid electrolyte layer by chemical polymerization is not practical when using an assembly, and a solid electrolyte layer is generally formed using a liquid mixture containing a conductive polymer. When using a liquid mixture containing a conductive polymer, a solid electrolyte layer of a certain thickness is required to suppress leakage current. However, when using a liquid mixture containing a conductive polymer, the application and drying of the liquid mixture must be repeated multiple times to form a solid electrolyte layer of appropriate thickness. If drying is performed multiple times, the solid electrolyte layer expands, making it difficult to reduce variations in the thickness of the solid electrolyte layer.

[0011] The method for manufacturing a solid electrolytic capacitor according to the present disclosure includes the steps of: forming an assembly (second assembly) having a plurality of solid electrolytic capacitor elements by forming a solid electrolyte layer covering at least a portion of the dielectric layer using an assembly (first assembly) having a plurality of anode body regions arranged in the plane direction, each having a dielectric layer; and singulating the second assembly into individual solid electrolytic capacitor elements. In the step of forming the second assembly, a coating containing manganese oxide is formed to cover at least a portion of the dielectric layer (first step), and a liquid mixture containing a precursor of a conjugated polymer, a dopant, and a polyhydric alcohol is contacted with the coating containing manganese oxide to chemically polymerize the precursor using manganese oxide as an oxidizing agent, thereby forming a solid electrolyte layer containing the conjugated polymer and the dopant (second step). By forming the coating containing manganese oxide to cover at least a portion of the dielectric layer in the first step, the oxidizing agent manganese oxide is immobilized on the surface of the dielectric. Because the immobilized manganese oxide does not dissolve in the liquid mixture, the chemical polymerization of the precursor can proceed more uniformly and efficiently in the second step, with the manganese oxide dispersed relatively uniformly on the surface of the dielectric layer. This allows for the stable formation of a uniform solid electrolyte layer across the entire coating area in multiple anode body regions. The solid electrolyte layer formed in each anode body region is moderately porous and has excellent film quality. Since multiple drying cycles are not required, expansion is suppressed and the thickness is more uniform. This results in high capacitance, low equivalent series resistance (ESR), and reduced leakage current. Despite the ability to manufacture multiple solid electrolytic capacitors simultaneously, productivity is improved due to reduced product defect rates (e.g., leakage current defect rates).

[0012] This method allows for a more uniform thickness of the solid electrolyte layer, improving the precision of forming a stack of multiple second assemblies. Furthermore, because the polymerization reaction occurs efficiently in the manganese oxide-containing coating, the solid electrolyte layer can be formed on anode regions of various shapes, providing greater flexibility in the shape of solid electrolytic capacitor elements. The solid electrolyte layer can be formed in the aggregate state, and the polymerization rate is fast, significantly improving productivity. Furthermore, because polymerization proceeds simply by having a liquid mixture containing the precursor surrounding the coating, the amount of liquid mixture used can be reduced compared to conventional methods. Unlike electropolymerization, no electrodes are required, thereby reducing the space required for manufacturing equipment. Furthermore, because the solid electrolyte layer is moderately porous, when a cathode extraction layer is formed to cover the solid electrolyte layer, the components of the cathode extraction layer can penetrate into the pores of the solid electrolyte layer, ensuring high adhesion and conductivity and reducing ESR.

[0013] Hereinafter, the method for manufacturing a solid electrolytic capacitor according to the present disclosure will be described in more detail with reference to the drawings as necessary.

[0014] A solid electrolytic capacitor obtained by the manufacturing method of the present disclosure includes a solid electrolytic capacitor element including an anode body, a dielectric layer covering at least a portion of the anode body, and a cathode portion covering at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer. The cathode portion may further include a cathode extraction layer covering at least a portion of the solid electrolyte layer. The solid electrolytic capacitor includes at least one solid electrolytic capacitor element, and may include a laminate in which multiple solid electrolytic capacitor elements are stacked. Hereinafter, the solid electrolytic capacitor element may be simply referred to as a capacitor element.

[0015] In the present disclosure, a solid electrolytic capacitor is formed using a first assembly having a plurality of anode regions, each having a dielectric layer and arranged in a planar direction. The anode regions correspond to the anode bodies in the solid electrolytic capacitor. More specifically, a method for manufacturing a solid electrolytic capacitor includes forming a second assembly having a plurality of capacitor elements by forming a solid electrolyte layer in the first assembly so as to cover at least a portion of the dielectric layer, and singulating the second assembly into individual capacitor elements. The method for manufacturing a solid electrolytic capacitor may further include forming a laminate of a plurality of second assemblies, each comprising a laminate of a plurality of capacitor elements. In this case, the singulation step involves singulating into individual laminates of a plurality of capacitor elements. The manufacturing method may further include sealing the second assembly or its laminate with resin to form a resin portion covering the second assembly or its laminate. In this case, the singulation step involves singulating the resin portion together with the second assembly or its laminate, thereby forming a solid electrolytic capacitor comprising capacitor elements or its laminate and a resin outer package sealing the capacitor elements or its laminate. The manufacturing method may include a step of forming a groove in the laminate of the second assembly prior to sealing with resin. The manufacturing method may include a step of forming a cathode extraction layer so as to cover at least a portion of the solid electrolyte layer. The manufacturing method may include a step of connecting a lead to at least one of the cathode portion and the anode portion of the capacitor element, a step of forming an electrode, etc. The manufacturing method may include a step of preparing a first assembly. Each step will be described in more detail below.

[0016] (Step of Preparing a First Assembly) The first assembly may be in a state in which a plurality of anode body regions are connected in a planar arrangement, or in a state in which a large anode body (e.g., a raw anode body or a long strip-shaped anode body) is partitioned into a plurality of anode body regions. For example, the first assembly is prepared by connecting a plurality of anode body regions in a planar arrangement, arranging a plurality of anode body regions on a substrate, or processing a large anode body to form a plurality of anode body regions. For example, the first assembly may be prepared by punching a large anode foil into a predetermined shape to form a plurality of anode body regions. Alternatively, for example, the first assembly may be prepared by forming an insulating region (hereinafter sometimes referred to as a first insulating region) on the surface of a large anode body (e.g., anode foil) and partitioning (or dividing) the anode body (e.g., anode foil) into a plurality of regions (corresponding to the anode body regions) by the first insulating region.

[0017] In particular, when a first assembly having multiple anode body regions formed by partitioning a large anode foil into multiple regions is used, more anode body regions can be formed than when using other methods. When the density of the anode body regions in the first assembly increases, it becomes particularly difficult to form a more uniform solid electrolyte layer in each anode body region. However, according to the present disclosure, since the solid electrolyte layer is formed through the first and second steps, a more uniform solid electrolyte layer can be formed collectively even using a first assembly in which the anode body regions are formed densely, and the product defect rate can also be reduced. Furthermore, compared to using a first assembly in which multiple anode body regions are formed by punching a large anode foil into a predetermined shape, using a first assembly having multiple partitioned anode body regions reduces unevenness in the depth direction when polymerization is performed while the anode foil is immersed in the liquid mixture, which is particularly advantageous for forming a more uniform solid electrolyte layer. Furthermore, when a first assembly having multiple partitioned anode body regions is used, a large number of capacitor elements can be formed collectively using a small amount of liquid mixture. Therefore, the efficiency of using the liquid mixture is dramatically improved, and productivity can be significantly improved, which is extremely advantageous in terms of cost.

[0018] In the first assembly, the plurality of anode body regions may be, for example, in a matrix form in which a plurality of rows of anode body regions are arranged side by side.

[0019] At an appropriate stage in preparing the first assembly, a dielectric layer is formed on at least a portion of the surface of the anode body region. The dielectric layer is formed, for example, by anodizing the valve metal on the surface of the anode body region. Anodization can be performed, for example, by chemical conversion treatment.

[0020] The dielectric layer may be formed before arranging or forming the multiple anode body regions or before partitioning the multiple anode body regions, or may be formed after the multiple anode body regions have been arranged or formed. For example, after forming a dielectric layer on at least a portion of the surface of a large anode foil, the anode foil may be punched to form the multiple anode body regions or partitioned into the multiple anode body regions. Alternatively, after punching a large anode foil to form the multiple anode body regions or partition the anode foil into the multiple anode body regions, the dielectric layer may be formed on at least a portion of the surface of the anode body regions. The formation of the dielectric layer may be performed in one step or multiple steps.

[0021] The anode body region can contain a valve metal, an alloy containing a valve metal, or a compound containing a valve metal. The anode body region can contain one of these materials or a combination of two or more of them. Preferred valve metals include aluminum, tantalum, niobium, and titanium.

[0022] The anode region (anode in a solid electrolytic capacitor) preferably has a porous portion at least in its surface layer. The porous portion can be obtained, for example, by roughening the surface of a substrate (such as a sheet-like (e.g., foil-like, plate-like) substrate) containing a valve metal. The roughening can be performed, for example, by etching (such as electrolytic etching). The anode region may also be composed of a compact or sintered body of particles containing a valve metal. The compact and sintered body each have a porous structure. The compact and sintered body each may be in the form of a sheet, a rectangular parallelepiped, a cube, or a similar shape.

[0023] Each anode body region typically has a cathode forming portion where a cathode portion is formed and an anode portion where no cathode portion is formed. The cathode portion is typically formed on the cathode forming portion of the anode body region via a dielectric layer. An anode terminal is connected to at least a portion of the anode portion.

[0024] The dielectric layer is an insulating layer that functions as a dielectric and is formed to cover at least a portion of the surface of the anode body region. The dielectric layer contains an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains Al2O3. However, the dielectric layer is not limited to this, as long as it functions as a dielectric.

[0025] The dielectric layer may be formed so as to cover at least a portion of the anode body region. The dielectric layer is usually formed on the surface of the anode body region (e.g., the porous portion). The dielectric layer is usually formed along the irregularities on the surface of the anode body region and the inner wall surfaces of the voids in the porous portion.

[0026] In the first assembly, the first insulating region is formed to separate adjacent anode body regions. The first insulating region may be, for example, lattice-shaped. The shape of the anode body region is determined by the shape of the first insulating region, thereby increasing design flexibility. The first insulating region is formed, for example, by applying an insulating material to a predetermined region of a large anode body (such as an anode foil). The insulating material is applied to the anode body by, for example, inkjet printing, screen printing, or transfer printing. When a fluid insulating material is applied to the anode body, it penetrates into the irregularities on the surface of the anode body and the voids in the porous portion, thereby suppressing the formation of a solid electrolyte layer in the voids in the porous portion. This further facilitates ensuring insulation between the anode and cathode portions, thereby improving the reliability of the solid electrolytic capacitor. The fluid insulating material only needs to be fluid when applied to the anode body and may be fluid at room temperature (e.g., 20°C or higher and 35°C or lower). A solution or dispersion containing the insulating material may be used as the fluid insulating material. Alternatively, the insulating material may be applied by attaching a tape-shaped insulating material to the surface of the anode body. These methods may also be combined.

[0027] Examples of the insulating material (first insulating material) constituting the first insulating region include resin materials. Using a water-repellent resin material as the insulating material makes it easier to prevent the constituent material of the cathode section from adhering to areas other than the intended area. The width of the first insulating region tends to be narrower from the standpoint of increasing productivity, but if a solid electrolyte layer is formed on the surface of the first insulating region, it becomes difficult to ensure insulation. In particular, in the present disclosure, manganese oxide is fixed on the surface of the dielectric layer. Therefore, even if even a small amount of manganese oxide is fixed on the surface of the first insulating region, a solid electrolyte layer is also formed on the surface of the first insulating region, which tends to make it difficult to ensure insulation. When the first insulating region includes a water-repellent resin material, the effect of preventing the fixation of manganese oxide on the surface of the first insulating region is enhanced, making it easier to ensure insulation. The resin material may be either a thermoplastic resin or a curable resin (such as a thermosetting resin or a photocurable resin).

[0028] Examples of the curable resin include epoxy resin, phenolic resin, silicone resin, melamine resin, urea resin, furan resin, alkyd resin, curable polyurethane, curable polyimide, polyamideimide, unsaturated polyester, allylic resin, and curable acrylic resin.

[0029] Examples of thermoplastic resins include polyester, polyamide, polycarbonate, polyacetal, polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyacryl ether ketone, polyamide, polyamide imide, polyimide, polyether imide, polysulfone, polyether sulfone, polyolefin, fluororesin, and silicone resin.

[0030] The first insulating region may contain one type of resin material or a combination of two or more types. The first insulating region preferably contains a water-repellent material such as silicone resin or fluororesin. The first insulating region may contain a water-repellent material and another resin material.

[0031] The step of preparing the first assembly may further include a step of forming an insulating region (hereinafter sometimes referred to as a second insulating region) in the anode body region at and near the end of the anode part on the cathode-forming part side. The second insulating region may be formed in the step of forming the first insulating region, or may be formed separately from the step of forming the first insulating region. Providing the second insulating region makes it easier to ensure insulation between the anode part and the cathode part. The second insulating region is formed by applying an insulating material (second insulating material) to the anode body region. Examples of the second insulating material include the resin materials exemplified for the first insulating material. The second insulating region may contain one type of second insulating material or a combination of two or more types. The application of the second insulating material may be performed in a manner similar to that of the first insulating material.

[0032] When a large anode body (such as an anode foil) is used to form the first assembly, a hole may be formed in part of the anode body at an appropriate stage in the step of forming the first assembly, as necessary. For example, a resin for sealing the capacitor element may be filled around the capacitor element through the hole. Furthermore, when a long strip-shaped anode body is used to form the first assembly, the anode body may be cut to a predetermined length at an appropriate stage. For example, after forming the first assembly using a long strip-shaped anode body, the anode body may be cut to a predetermined length, and the cut first assembly may be subjected to the step of forming the second assembly.

[0033] (Step of forming a second assembly) A second assembly having a plurality of capacitor elements is formed by forming a cathode portion in each anode body region of the first assembly. The step of forming the second assembly includes at least the step of forming a solid electrolyte layer so as to cover at least a portion of the dielectric layer of the anode body region. When the cathode portion includes a cathode extraction layer in addition to the solid electrolyte layer, the step of forming the second assembly further includes the step of forming the cathode extraction layer.

[0034] (Step of forming a solid electrolyte layer) The process for forming the solid electrolyte layer includes a first step of forming a coating containing manganese oxide that covers at least a portion of the dielectric layer, and a second step of contacting the coating with a liquid mixture containing a precursor of a conjugated polymer, a dopant, and a polyhydric alcohol, and chemically polymerizing the precursor using manganese oxide as an oxidizing agent to form a solid electrolyte layer containing the conjugated polymer and the dopant. By forming the solid electrolyte layer through the first and second steps, a more uniform solid electrolyte layer can be formed when forming solid electrolyte layers simultaneously on multiple anode body regions.

[0035] (1st step) The manganese oxide contained in the coating formed in the first step includes, for example, at least one of manganese dioxide and dimanganese trioxide. From the viewpoint of facilitating the formation of a coating with a more uniform thickness, the manganese oxide preferably includes at least dimanganese trioxide, and more preferably, 50 mass % or more of the manganese oxide is dimanganese trioxide. A more uniform coating thickness is more advantageous in terms of improving the uniformity of the solid electrolyte layer. The coating containing manganese oxide is formed so as to cover at least a portion of the surface of the dielectric layer.

[0036] The coating is formed, for example, by applying an aqueous solution containing manganese nitrate to the surface of the dielectric layer and then thermally decomposing the manganese nitrate in a humid atmosphere to produce manganese oxide.

[0037] The aqueous solution containing manganese nitrate may be applied to the surface of the dielectric layer by, for example, coating (such as coating using a dispenser), dropping, screen printing, or transfer.

[0038] The concentration of manganese nitrate in the aqueous solution is, for example, 50% by mass or less. When the manganese nitrate concentration is in this range, it is easy to control the amount of manganese oxide coating that is deposited. The concentration of manganese nitrate in the aqueous solution may be, for example, 10% by mass or more, 20% by mass or more, or 30% by mass or more.

[0039] The humidified atmosphere used in the thermal decomposition of manganese nitrate contains, for example, 30% or more by volume of water. From the viewpoint of increasing the content of manganese trioxide in the coating and making it easier to obtain a more uniform solid electrolyte layer, the humidified atmosphere preferably contains 40% or more by volume of water. The humidified atmosphere may contain, for example, 90% or less by volume of water.

[0040] The thermal decomposition of manganese nitrate can be carried out in a humid atmosphere by heating at a temperature of, for example, 200° C. to 350° C. The heating time is, for example, 1 minute to 15 minutes, and may be 2 minutes to 10 minutes.

[0041] The amount of manganese oxide attached to the anode body region is, for example, 5 μg / mm 2 More than 20μg / mm 2 When the deposition amount is within this range, a more uniform solid electrolyte layer is easily obtained, and a solid electrolyte layer with an appropriate density is formed, thereby ensuring a higher capacitance.

[0042] (2nd process) In the second step, a solid electrolyte layer containing a conjugated polymer and a dopant is formed by chemical polymerization. More specifically, a liquid mixture containing a conjugated polymer precursor, a dopant, and a polyhydric alcohol is brought into contact with the coating containing manganese oxide formed in the first step, and the conjugated polymer precursor is chemically polymerized to form the solid electrolyte layer. Because manganese oxide acts as an oxidizing agent, chemical polymerization of the precursor selectively proceeds at and near the interface between the manganese oxide coating and the liquid mixture, resulting in the formation of a conjugated polymer. Therefore, even when a first assembly including multiple anode body regions is used, a more uniform solid electrolyte layer is formed in the portions of the anode body regions where the coating containing manganese oxide is formed. Although manganese oxide itself is reduced to divalent manganese ions and dissolved in the liquid mixture, some manganese oxide may remain on the surface of the dielectric layer. Therefore, a portion of the solid electrolyte layer may be formed to cover the manganese oxide.

[0043] The liquid mixture contains a precursor of a conjugated polymer, a dopant, and a polyhydric alcohol. The liquid mixture usually contains a solvent. The liquid mixture may contain an additive, if necessary.

[0044] Examples of precursors of conjugated polymers include raw material monomers of conjugated polymers, and oligomers and prepolymers in which multiple molecular chains of raw material monomers are linked together. The liquid mixture may contain one type of precursor of the conjugated polymer, or a combination of two or more types. From the viewpoint of facilitating more uniform polymerization of the conjugated polymer, it is preferable to use at least one type (particularly a monomer) selected from the group consisting of monomers and oligomers as the precursor.

[0045] Conjugated polymers include known conjugated polymers used in solid electrolytic capacitors, such as π-conjugated polymers. Examples of conjugated polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. The above polymers may contain at least one monomer unit constituting the basic skeleton. The monomer unit may also include a monomer unit having a substituent. The above polymers also include homopolymers and copolymers of two or more monomers.

[0046] Among conjugated polymers, preferred are those containing monomer units corresponding to thiophene compounds. Such conjugated polymer precursors are prone to polymerization using manganese oxide as an oxidizing agent. Furthermore, such conjugated polymers are resistant to oxidative degradation, making it easy to ensure high heat resistance in solid electrolytic capacitors. Examples of thiophene compounds include compounds that have a thiophene ring and can form a repeating structure of the corresponding monomer units.

[0047] The thiophene compound may have a substituent at, for example, at least one of the 3- and 4-positions of the thiophene ring. The substituent at the 3-position and the substituent at the 4-position may be linked to form a ring fused to the thiophene ring. Examples of the thiophene compound include thiophenes that may have a substituent at, for example, the 3- and 4-positions, alkylenedioxythiophene compounds (C thiophenes such as ethylenedioxythiophene compounds), and the like. 2-4 Alkylenedioxythiophene compounds include those having a substituent in the alkylene group portion.

[0048] The substituents include alkyl groups (C such as methyl and ethyl groups) 1-4 alkyl groups, alkoxy groups (methoxy groups, ethoxy groups, etc.) 1-4Alkoxy groups, hydroxy groups, hydroxyalkyl groups (hydroxy C groups such as hydroxymethyl groups) 1-4 Preferred are, but not limited to, alkyl groups, etc. When the thiophene compound has two or more substituents, the respective substituents may be the same or different.

[0049] Conjugated polymers (such as PEDOT) containing at least monomer units corresponding to 3,4-ethylenedioxythiophene compounds (such as 3,4-ethylenedioxythiophene (EDOT)) may be used. The conjugated polymer containing at least monomer units corresponding to EDOT may contain only monomer units corresponding to EDOT, or may contain, in addition to the monomer units, monomer units corresponding to thiophene compounds other than EDOT.

[0050] The content of the conjugated polymer precursor in the liquid mixture may be 0.3% by mass or more and 2% by mass or less, in which case the yield of the chemical polymerization reaction is high and the solid electrolyte layer can be stably formed.

[0051] The dopant may be, for example, at least one selected from the group consisting of anions and polyanions.

[0052] Examples of anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, carboxylate ions, etc. Aromatic sulfonic acids are preferred as dopants that generate sulfonate ions.

[0053] Examples of aromatic sulfonic acids include toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, hydroxybenzenesulfonic acid, nitrobenzenesulfonic acid, sulfosalicylic acid, sulfophthalic acid, sulfoisophthalic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid, alkylnaphthalenesulfonic acid, polyalkylnaphthalenesulfonic acid, anthraquinonesulfonic acid, anthraquinonedisulfonic acid, biphenylsulfonic acid, and derivatives thereof. Derivatives include, for example, substituted derivatives having a substituent (e.g., a hydrocarbon group (e.g., an alkyl group, an aryl group), a hydroxy group, a carboxy group, an alkoxy group, or a nitro group). Among these, aromatic sulfonic acids having at least one group selected from the group consisting of a hydroxy group bonded to an aromatic ring and a carboxy group bonded to an aromatic ring are preferred. The use of such aromatic sulfonic acids allows for smooth chemical polymerization of conjugated polymer precursors. The use of a dopant containing sulfosalicylic acid increases the conductivity of the solid electrolyte layer, ensuring higher capacitance and lowering the ESR. It also allows the thickness of the solid electrolyte layer to be increased, reducing leakage current.

[0054] Examples of the polyanion include a polymer anion, etc. The solid electrolyte layer may include, for example, a conjugated polymer including a monomer unit corresponding to a thiophene compound and a polymer anion.

[0055] Examples of polymer anions include polymers having multiple anionic groups. Such polymers include polymers containing monomer units having anionic groups. Examples of the anionic groups include sulfonic acid groups and carboxyl groups.

[0056] Examples of polymer anions having a carboxy group include, but are not limited to, polyacrylic acid, polymethacrylic acid, and copolymers using at least one of acrylic acid and methacrylic acid.

[0057] Specific examples of polymer anions having sulfonic acid groups include, but are not limited to, polymeric polysulfonic acids such as polyvinyl sulfonic acid, polystyrene sulfonic acid (including copolymers and substituted products having substituents), polyacrylic sulfonic acid, polyester sulfonic acid (such as aromatic polyester sulfonic acid), and phenolsulfonic acid novolac resin.

[0058] In the solid electrolyte layer formed, the anionic group of the dopant may be contained in a free form, an anion form, or a salt form, or may be contained in a form bound to or interacting with the conjugated polymer. In this specification, all of these forms may be simply referred to as an "anionic group," "sulfonic acid group," "carboxy group," or the like.

[0059] The amount of the dopant contained in the liquid mixture is, for example, 10 to 500 parts by mass, or may be 50 to 200 parts by mass, relative to 100 parts by mass of the precursor of the conjugated polymer.

[0060] The polyhydric alcohol contained in the liquid mixture is thought to coordinate with the divalent manganese ions produced by the reduction of manganese oxide, reducing the localized increase in the concentration of divalent manganese ions, which is thought to allow oxidation by manganese oxide and chemical polymerization of the conjugated polymer precursor to proceed smoothly and stably.

[0061] The polyhydric alcohol is not particularly limited as long as it coordinates with divalent manganese ions. An aliphatic alcohol is preferred as the polyhydric alcohol. The aliphatic alcohol may have an aliphatic ring, an aromatic ring, or a heterocyclic ring, but in consideration of its coordination with manganese ions, it is preferable that the aliphatic alcohol does not have such a ring. Examples of polyhydric alcohols include alkylene glycols (ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, etc.), polyalkylene glycols (diethylene glycol, triethylene glycol, etc.), glycerin, polyglycerin (diglycerin, etc.), trimethylolpropane, pentaerythritol, and sugar alcohols (erythritol, xylitol, mannitol, sorbitol, etc.). The number of hydroxy groups contained in the polyhydric alcohol is, for example, 2 to 6, or may be 2 to 4. From the viewpoint of easily maintaining a low viscosity of the liquid mixture, it is preferable to use at least ethylene glycol.

[0062] From the viewpoints of facilitating smooth polymerization of the conjugated polymer precursor and stably forming a solid electrolyte layer, the content of the polyhydric alcohol in the liquid mixture is preferably 10% by mass or less, and may be more than 0% by mass and 1% by mass or more.

[0063] The solvent may be, for example, at least one selected from the group consisting of water and organic solvents (excluding polyhydric alcohols). The liquid mixture may contain both water and an organic solvent. Examples of organic solvents include aliphatic alcohols, aliphatic ketones (e.g., acetone), nitriles (e.g., acetonitrile, benzonitrile), amides (e.g., N,N-dimethylformamide), and sulfoxides (e.g., dimethyl sulfoxide). The solvent may contain one organic solvent or a combination of two or more organic solvents. As the aliphatic alcohol, an aliphatic monool is used. As the aliphatic alcohol, an aliphatic alcohol having 1 to 5 carbon atoms is preferred. Examples of the aliphatic alcohol include methanol, ethanol, 1-propanol, 2-propanol, and butanol. The type and amount of solvent used may be determined, for example, taking into consideration the solubility of the conjugated polymer precursor and the dopant in the liquid mixture. For example, water and an aliphatic alcohol (e.g., 2-propanol) may be used in combination. For example, the amount of solvent used is adjusted so that the concentration of the conjugated polymer precursor in the liquid mixture falls within the above-mentioned range.

[0064] The chemical polymerization may be carried out, for example, by immersing the first assembly, on which the coating containing manganese oxide has been formed, in a liquid mixture.

[0065] The temperature at which the polymerization is carried out may be, for example, 5°C or higher and 60°C or lower, and may be 15°C or higher and 35°C or lower.

[0066] In the second step, chemical polymerization may be repeated two or more times. However, because the second step is carried out after the manganese oxide coating is formed in the first step, the thickness of the solid electrolyte layer can be made relatively large even if chemical polymerization is carried out only in one stage (one time).

[0067] The solid electrolyte layer may be a single layer or may be composed of multiple layers. When the solid electrolyte layer is composed of multiple layers, the components (e.g., conjugated polymer, dopant, polyhydric alcohol, and additive) contained in each layer may be the same or different. For example, a first solid electrolyte layer may be formed in the second step, and then a second solid electrolyte layer may be formed to cover the first solid electrolyte layer (third step).

[0068] (3rd step) In the third step, the second solid electrolyte layer may be formed by chemical polymerization or electrolytic polymerization using a treatment liquid containing a precursor of a conjugated polymer and a dopant. Such a treatment liquid may contain at least one selected from the group consisting of an oxidizing agent and an additive, as needed. The second solid electrolyte layer may also be formed using a treatment liquid (such as a solution or dispersion) containing a conjugated polymer and a dopant. After applying these treatment liquids to the first solid electrolyte layer, drying treatment, heating treatment, or the like may be performed as needed. The treatment liquid may be applied by, for example, immersion, coating (such as coating using a dispenser), dropping, screen printing, or transfer.

[0069] (Step of forming cathode extraction layer) The cathode extraction layer includes, for example, at least a first layer that is in contact with the solid electrolyte layer and covers at least a portion of the solid electrolyte layer. The cathode extraction layer may include a first layer and a second layer that covers the first layer. Examples of the first layer include a layer containing conductive particles and metal foil. Examples of the conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may include a first layer containing conductive carbon (also referred to as a carbon layer) and a second layer containing metal powder or metal foil. When metal foil is used as the first layer, the cathode extraction layer may be formed of this metal foil.

[0070] Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0071] The first layer containing conductive particles is formed, for example, by applying a composition (slurry, paste, etc.) containing conductive particles to the surface of the solid electrolyte layer. The application of the composition may be performed, for example, by screen printing, transfer, etc.

[0072] When the first layer is a metal foil, for example, the first layer is formed by laminating the metal foil so as to cover the surface of the solid electrolyte layer. The metal foil may be laminated only on the solid electrolyte layer portion, or the first layer may be formed by laminating a larger metal foil on the second assembly in which the solid electrolyte layer is formed in each anode body region. When a metal foil is used as the first layer, the type of metal is not particularly limited. For example, aluminum, an aluminum alloy, copper, or a copper alloy may be used as the metal foil. The metal foil may be a valve metal (aluminum, tantalum, niobium, etc.) or an alloy containing a valve metal. If necessary, the surface of the metal foil may be roughened. The cathode extraction layer may be formed by forming the first layer so as to cover the solid electrolyte layer and then laminating the second layer on the first layer. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a non-metal different from the metal constituting the metal foil. Examples of dissimilar metals and non-metals include metals such as titanium and non-metals such as carbon (e.g., conductive carbon). The coating of the dissimilar metal or nonmetal (e.g., conductive carbon) may be used as the first layer, and the metal foil may be used as the second layer. In this case, the cathode extraction layer may be formed by forming the first layer on the surface of the metal foil, which is the second layer, and then laminating the resulting laminate with the solid electrolyte layer (or the second assembly with the solid electrolyte layer formed thereon) so that the first layer contacts the solid electrolyte layer.

[0073] When a metal foil is used, an insulating region such as the first insulating region may be formed, as in the case of the first assembly, to partition (or divide) the cathode extraction layer into multiple regions. Alternatively, similar to the case of the first assembly, a metal foil divided into multiple regions by punching a large metal foil into a predetermined shape (predetermined pattern) may be used. In these cases, the metal foil is laminated with the second assembly on which the solid electrolyte layer has been formed so that each region contacts the solid electrolyte layer. When a large metal foil is used, the metal foil may be provided with holes for filling with sealing resin, if necessary.

[0074] When a metal foil is used, a second assembly not including the metal foil may be formed, and in the step of laminating the second assembly, the second assembly not including the metal foil and the metal foil may be sequentially laminated to complete the cathode extraction layer (and the second assembly) and obtain a laminate of the second assembly. A conductive adhesive may be used for lamination, if necessary.

[0075] The layer containing metal powder as the second layer is formed, for example, by applying a composition (slurry, paste, etc.) containing metal powder to the surface of the first layer. Such a second layer is formed, for example, using a composition (slurry, paste, etc.) containing metal powder such as silver particles and a resin (binder resin). The composition may be applied by, for example, screen printing, transfer printing, etc. Although a thermoplastic resin can also be used as the resin, a thermosetting resin such as an imide resin or an epoxy resin is usually used.

[0076] In the step of forming the cathode extraction layer, a drying treatment or a heating treatment may be carried out at an appropriate stage.

[0077] (Step of forming a laminate of second assemblies) When stacking multiple second assemblies, the second assemblies are stacked so that the capacitor elements in each second assemblies overlap in the thickness direction of the second assemblies. A positioning member (such as a guide pin) may be used to accurately overlap the multiple capacitor elements in the thickness direction. A stacking jig may be used for stacking, if necessary. The stacking jig may be equipped with a positioning member. Note that, when forming a cathode extraction layer containing metal foil as described above, the cathode extraction layer (and second assemblies) may be completed in this step by stacking second assemblies that do not have the metal foil and the metal foil.

[0078] The lowermost second assembly in the stack may be formed or fixed on a substrate, and other second assemblies may be stacked on top of this second assembly to form a laminate. Examples of the substrate include an insulating substrate (e.g., an insulating substrate including a substrate in which glass cloth is impregnated with epoxy resin). Stacking may be performed by fixing adjacent capacitor elements in the stacking direction with a conductive adhesive. Examples of the conductive adhesive include a composition containing metal powder (e.g., a silver particle-containing paste) as described for the second layer of the cathode extraction layer. Such a conductive adhesive may also be used to fix a metal foil to a second assembly (more specifically, a first layer (e.g., a carbon layer)) that does not have a metal foil.

[0079] The direction from the end (first end) of the anode body region of the capacitor element on the anode portion side to the end (second end) on the cathode forming portion side is defined as the first direction, and the direction perpendicular to the first direction and the thickness direction of the capacitor element is defined as the second direction. Both ends in the second direction are defined as the third end and the fourth end. In this case, adjacent capacitor elements in the stacking direction may overlap so that the first direction of each capacitor element is parallel. In this case, adjacent capacitor elements in the stacking direction may overlap so that the first end and the second end of each capacitor element overlap, or so that the first end and the second end of each capacitor element overlap. Furthermore, adjacent capacitor elements in the stacking direction may overlap so that the first direction and the second direction of each capacitor element are parallel. In this case, the first end of one capacitor element (first capacitor element) and the third end (or fourth end) of the capacitor element (second capacitor element) adjacent to the first capacitor element in the stacking direction are located close to each other. Furthermore, the second end of the first capacitor element and the fourth end (or third end) of the second capacitor element are located close to each other. The orientation of each capacitor element in the laminate may be determined according to the design of the solid electrolytic capacitor.

[0080] When each second assembly has a first insulating region, the second assemblies may be stacked so that the first insulating regions of adjacent second assemblies in the thickness direction overlap.

[0081] (Groove forming process) When forming the laminate of the second assembly, a groove may be formed in a portion of the laminate of the second assembly prior to sealing with resin. The formed groove is filled with sealing resin in a subsequent process. The shape, position, depth, etc. of the groove are determined according to the design of the solid electrolytic capacitor. For example, when the laminate of the second assembly is formed on a substrate, the groove is formed to a depth that cuts through the laminate of the second assembly but does not cut through the substrate. If a hole is formed in the first assembly, resin can be smoothly filled around the laminate of the capacitor element without forming such a groove.

[0082] The grooves can be formed using, for example, a dicing blade such as a diamond blade, or by other groove processing techniques (for example, laser processing).

[0083] (Lead connection process) When current is drawn from the capacitor elements using leads such as lead frames, one end of the lead may be electrically connected to at least one of the anode and cathode portions at an appropriate stage. For example, one end of the lead may be connected to a portion of the cathode portion of a capacitor element included in the second assembly or to a portion of the cathode portion of a capacitor element included in a laminate of the second assembly. One end of the lead may also be connected to a portion of the anode body region included in the first assembly. The lead connection is usually performed before the resin sealing process. The other end of the lead is configured to be exposed from the resin exterior body after singulation.

[0084] The lead and the anode or cathode may be connected by welding or by using a conductive adhesive, such as a composition containing metal powder (e.g., a silver particle-containing paste) for forming the second layer of the cathode extraction layer.

[0085] The leads may be constructed of a metal such as, for example, copper or a copper alloy.

[0086] (Process for forming the resin part (sealing process with resin)) The second assembly or its laminate is sealed with resin. More specifically, the second assembly or its laminate is sealed by covering the periphery of the second assembly or its laminate with resin and molding it into a predetermined shape. This forms a resin portion that covers the second assembly or its laminate. If a groove is formed in the laminate of the second assembly, the groove is also filled with resin in the sealing process.

[0087] The resin portion can be formed using molding techniques such as injection molding, compression molding, insert molding, compression molding, and transfer molding.

[0088] The resin may be, for example, a curable resin composition, a thermoplastic resin, or a composition thereof. The resin composition may contain a filler (such as an inorganic filler) as needed.

[0089] (Singulation process) In the singulation process, the second assembly is singulated into individual capacitor elements. When forming a laminate of the second assembly, the second assembly is singulated into individual laminates of multiple capacitor elements. When the second assembly or its laminate is covered with a resin portion, the second assembly or its laminate is singulated together with the resin portion. The solid electrolytic capacitor obtained in this manner includes a capacitor element or its laminate, and a resin outer casing that encapsulates the capacitor element or its laminate.

[0090] The individual pieces are separated by cutting the second assembly or the laminate using a dicing blade such as a diamond blade.

[0091] In the singulation process, the capacitor element (or its laminate) is separated from adjacent capacitor elements (or its laminate). The singulation may be performed in stages. For example, a plurality of capacitor elements or their laminates may be separated row by row, and then the individual capacitor elements or their laminates may be separated after other processes are performed (for example, after electrodes are formed in the electrode formation process described below).

[0092] In the singulation, the second assembly or its laminate may be cut so as to separate the resin portion. In the singulation, the second assembly or its laminate may be cut so that a portion of at least one of the anode portion and the cathode portion of the capacitor element is exposed from the resin outer casing. Also, the second assembly or its laminate may be cut so that the other end of the lead electrically connected to the anode portion or the cathode portion is exposed from the resin outer casing. Current can be drawn from the capacitor element or its laminate through the exposed portion (exposed portion) of the anode portion, cathode portion, or lead from the resin outer casing. An external electrode may be electrically connected to the exposed portion in the electrode formation process described below.

[0093] The exposed portion on the anode side (the exposed portion of the anode part and the exposed portion of the lead connected to the anode part) may be exposed on one main surface or two or more main surfaces of the resin outer casing. Similarly, the exposed portion on the cathode side (the exposed portion of the cathode part and the exposed portion of the lead connected to the cathode part) may be exposed on one main surface or two or more main surfaces of the resin outer casing. From the viewpoint of suppressing short circuits, it is usually preferable that the exposed portion on the cathode side and the exposed portion on the anode side are exposed on different main surfaces.

[0094] For example, the resin outer casing has a first main surface, a second main surface opposite the first main surface, a third main surface intersecting the first and second main surfaces, and a fourth main surface opposite the third main surface. The fourth main surface intersects the first and second main surfaces. In this case, the exposed portion on the anode component side may be exposed from the resin outer casing at the first main surface, and the exposed portion on the cathode component side may be exposed from the resin outer casing at any of the second to fourth main surfaces. Furthermore, when the exposed portion on the anode component side is exposed at both the first and second main surfaces, the exposed portion on the cathode component side may be exposed at least at one of the third and fourth main surfaces from the viewpoint of preventing short circuits.

[0095] (Electrode formation process) The solid electrolytic capacitor may have external electrodes. The external electrode on the anode side may be referred to as a first external electrode, and the external electrode on the cathode side may be referred to as a second external electrode.

[0096] For example, the first external electrode is electrically connected to the exposed portion on the anode side, and the second external electrode is electrically connected to the exposed portion on the cathode side. The first external electrode and the second external electrode are provided apart from each other so as not to short-circuit each other. The connection between each exposed portion and the external electrode may be performed by at least one method selected from the group consisting of bonding, plating, vapor deposition, cold spraying, and thermal spraying.

[0097] Each exposed portion and the external electrode may be connected via a conductive contact layer, and an intermediate electrode layer may be provided between the exposed portion or the contact layer and the external electrode, if necessary.

[0098] FIG. 1 is a schematic plan view of a second assembly used in the manufacturing method of a solid electrolytic capacitor according to the present disclosure. FIG. 2 is a schematic cross-sectional view of the second assembly of FIG. 1 taken along line II-II and viewed from the direction of the arrow. In the illustrated example, in the second assembly 12, a lattice-shaped first insulating region 13 is provided on both main surfaces of a large anode body (anode foil) 6A. The large anode body 6A is partitioned by the first insulating region 13 into multiple anode body regions 6. Each anode body region 6 corresponds to an anode body included in a capacitor element after singulation. A dielectric layer (not shown) is formed on the surface of each anode body region 6, and a cathode portion 10 including at least a solid electrolyte layer is formed so as to cover the surface of the dielectric layer. A stack of multiple second assemblies 12 is formed by stacking multiple second assemblies 12 in the thickness direction. The multiple second assemblies 12 are stacked, for example, so that the cathode portions 10 of adjacent second assemblies 12 overlap. The second assembly 12 or the stack thereof is singulated into individual capacitor elements or stacks thereof, for example, by cutting along the first insulating regions 13.

[0099] FIG. 3 is a process diagram illustrating a manufacturing method of the first embodiment of the present disclosure. In the illustrated example, a second assembly having a plurality of capacitor elements is first formed through a first step and a second step. In the first step, a coating containing manganese oxide is formed to cover at least a portion of the dielectric layer in each anode body region of the first assembly (S1). In the second step, a liquid mixture containing a conjugated polymer precursor, a dopant, and a polyhydric alcohol is brought into contact with the coating formed in the first step, and the conjugated polymer precursor is chemically polymerized using manganese oxide as an oxidizing agent to form a solid electrolyte layer containing the conjugated polymer and the dopant (S2). Next, a stack of a plurality of second assemblies is formed (S3). The resulting stack is further sealed with resin (S4). The stack of second assemblies is singulated together with the resin portions formed by sealing to obtain a solid electrolytic capacitor comprising a stack of capacitor elements and a resin outer package sealing it (S5).

[0100] 4 is a cross-sectional schematic diagram of a solid electrolytic capacitor formed by the manufacturing method of the second embodiment of the present disclosure. The solid electrolytic capacitor 1 includes a capacitor element 2, a substrate S that supports the capacitor element 2, a resin outer casing 3 that seals the capacitor element 2, a first external electrode 4a on the anode side, and a second external electrode 5a on the cathode side. The resin outer casing 3 has a substantially rectangular parallelepiped outer shape, and the solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0101] The capacitor element 2 includes an anode body region 6 (an anode body corresponding to the anode body region 6 in the first or second assembly), a dielectric layer 7 covering the anode body region 6, and a cathode portion 10 covering the dielectric layer 7. The cathode portion 10 includes a solid electrolyte layer 8 covering the dielectric layer 7 and a cathode extraction layer 9 covering the solid electrolyte layer 8. The anode body region 6 has a first end e1 on the side of the region (anode portion) not facing the cathode portion 10, and a second end e2 opposite to the first end. A first insulating region 13 is formed in a region of the anode body region 6 not facing the cathode portion 10 so as to cover the surface of the anode body region 6 in a strip shape. The first insulating region 13 restricts contact between the cathode portion 10 and the anode body region 6. A second insulating region may be provided instead of the first insulating region 13. Instead of these insulating regions, a resin outer casing 3 may be filled in these regions.

[0102] A first end e1 of the anode body region 6 is exposed from the first main surface of the resin outer casing 3 and is electrically connected to the first external electrode 4a. An intermediate electrode layer 4b is provided between the first external electrode 4a and the first main surface of the resin outer casing 3. A contact layer 4c is provided between the intermediate electrode layer 4b and the first end e1 of the anode body region 6 exposed from the first main surface. The first end e1 of the anode body region 6 exposed from the resin outer casing 3 is electrically connected to the first external electrode 4a via the contact layer 4c and the intermediate electrode layer 4b.

[0103] One end of cathode lead 15 is connected to at least a portion of cathode section 10 via conductive adhesive 16. The other end of cathode lead 15 is exposed from a second main surface of resin outer casing 3 opposite to the first main surface, and is electrically connected to second external electrode 5a. An intermediate electrode layer 5b is provided between second external electrode 5a and the second main surface of the resin outer casing. The end of cathode lead 15 exposed from resin outer casing 3 (exposed portion) is electrically connected to second external electrode 5a via intermediate electrode layer 5b.

[0104] 5 is a cross-sectional schematic diagram of a solid electrolytic capacitor obtained by the manufacturing method of the third embodiment of the present disclosure. The solid electrolytic capacitor 21 includes a laminate L of multiple capacitor elements 22, a substrate S supporting the laminate L, a resin outer casing 3 sealing the laminate L, a first external electrode 4a, and a second external electrode 5a. The laminate L includes multiple stacked elements (precursors of the capacitor elements) 22A and a metal foil (second layer) 9B disposed between adjacent elements 22A. The elements 22A and the metal foil (second layer) 9B are bonded via a conductive adhesive 16. The element 22A corresponds to the capacitor element before the second layer 9B is formed. A solid electrolyte layer 8 is formed on the surface of the anode body region 6 via a dielectric layer 7, and a carbon layer (first layer) 9A is formed to cover the solid electrolyte layer 8. In the laminate L, the carbon layer (first layer) 9A and the metal foil (second layer) 9B (and the conductive adhesive 16 interposed therebetween) form a cathode extraction layer 9. In the laminate L, the capacitor elements 22 are stacked in the thickness direction of the capacitor elements 22 (or anode body regions 6) so that the direction (first direction) from the first end e1 to the second end e2 of each anode body region 6 is parallel. In the anode body region 6 of each element 32A, the first end e1 is exposed from the first main surface m1 of the resin outer casing 3 and is electrically connected to the first external electrode 4a. In addition, in each metal foil (second layer) 9B, the end on the second end e2 side of the anode body region 6 is exposed from the second main surface m2 opposite the first main surface m1 and is electrically connected to the second external electrode 5a. The configuration of some of the elements 22A is omitted in FIG. 5. 5, a pair of first ends e1 of the anode body region 6 are parallel to the first direction in which they face each other, and the stacking direction D of the capacitor element 22 is parallel to the first direction. L5 is a schematic cross-sectional view of solid electrolytic capacitor 21 cut in a direction parallel to the arrows 21. For other configurations of FIG. 5, the description of FIG.

[0105] When the solid electrolytic capacitor includes a stack of multiple capacitor elements, the first ends of the anode body regions of each capacitor element may be exposed from the resin outer casing on the first and second main surfaces alternately in the stacking direction of the stack and electrically connected to the first external electrode.

[0106] FIG. 6A shows a solid electrolytic capacitor obtained by a manufacturing method according to a fourth embodiment of the present disclosure, viewed in a first direction D1 and a stacking direction D2. L 6B is a schematic cross-sectional view of the solid electrolytic capacitor of FIG. 6A cut in a direction parallel to the second direction D2 and the stacking direction D L 1 is a cross-sectional view taken in a direction parallel to FIG.

[0107] The solid electrolytic capacitor 31 includes a laminate L of a plurality of capacitor elements 32, a substrate S that supports the laminate L, a resin outer casing 3 that seals the laminate L, a first external electrode 4a, and a second external electrode 5a. The laminate L includes a plurality of stacked elements 32A and a metal foil (second layer) 9B disposed between adjacent elements 32A. The elements 32A and the metal foil (second layer) 9B are bonded via a conductive adhesive 16.

[0108] In the anode body region 6 of each element 32A, the first end e1 is L6A and 6B, the metal foils 32A are alternately exposed from the first main surface m1 of the resin outer casing 3 and the second main surface m2 opposite the first main surface m1, and are electrically connected to the first external electrode 4a. Furthermore, one end of each metal foil (second layer) 9B is exposed from the third main surface m3 of the resin outer casing 3 and is electrically connected to the second external electrode 5a. Furthermore, the other end of the metal foil (second layer) 9B is exposed from the fourth main surface m4 opposite the third main surface m3 of the resin outer casing 3 and is electrically connected to the second external electrode 5a. In this case, the first direction and the second direction intersect. For the rest of the configuration in FIGS. 6A and 6B, please refer to the descriptions of FIGS. 4 and 5. Note that the configuration of some elements 32A is omitted in FIGS. 6A and 6B.

[0109] [Example] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0110] Examples 1 to 6 A solid electrolytic capacitor was fabricated in the following manner, and its characteristics were evaluated.

[0111] (1) Preparation of the first assembly Anode bodies having porous portions on the surface were fabricated by roughening both surfaces of a large electrolytic aluminum foil (thickness: 100 μm) used as a substrate by etching.

[0112] The anode body was then immersed in a chemical conversion solution, and a DC voltage was applied for 20 minutes at 70°C to form a dielectric layer containing aluminum oxide. The DC voltage applied was 5 V in Examples 1 to 3, and 15 V in Examples 4 to 6.

[0113] A grid-shaped first insulating region was formed on both surfaces of the anode body by inkjet printing using an ink containing silicone resin and ethyl methyl ketone as a solvent. On each surface, the grid-shaped first insulating regions were formed at opposing positions across the anode body, as shown in Figure 2. In this way, multiple anode body regions separated by the first insulating regions were formed on each surface of the anode body. On each surface of the anode body, 10 rows of 36 anode body regions were arranged in a matrix, and the size of each anode body region (capacitive effective area) was 2.7 mm long x 2.3 mm wide. In this way, a first assembly was prepared.

[0114] (2) Formation of the second aggregate (2-1) First step An aqueous solution containing manganese nitrate (manganese nitrate concentration 30% by mass) was applied to the anode body region of the first assembly using a dispenser, and the mixture was dried at a temperature of 100°C or less until moisture was no longer visible to the naked eye. The first assembly with manganese nitrate attached to the surface of the anode body region was heated at 250°C for 10 minutes in a humidified atmosphere containing 50% moisture by volume. In this way, a coating containing manganese oxide was formed on the surface of the anode body region.

[0115] (2-2) Second process A polymerization liquid (liquid composition) was prepared by adding 3,4-ethylenedioxythiophene monomer, a dopant, and ethylene glycol to a mixed solvent of ion-exchanged water and isopropyl alcohol and mixing them. The monomer concentration in the polymerization liquid was 1% by mass, the dopant concentration was 13% by mass, the ethylene glycol concentration was 10% by mass, and the isopropyl alcohol concentration was 15% by mass. As the dopant, sulfosalicylic acid was used in Examples 1, 2, 4, and 5, and sulfoisophthalic acid was used in Examples 3 and 6.

[0116] Chemical polymerization was carried out by immersing the first assembly having the coating containing manganese oxide obtained in the first step in a polymerization solution maintained at a temperature of 20°C to 25°C for 20 minutes. In this way, a solid electrolyte layer containing poly(3,4-ethylenedioxythiophene) (PEDOT) and a dopant was formed.

[0117] (3) Formation of a cathode extraction layer and formation of a laminate of the second assembly A dispersion of graphite particles dispersed in water was applied by screen printing to the surface of the solid electrolyte layer formed in (2) above, and then dried to form a carbon layer as the first layer. Drying was carried out at 130 to 180°C for 10 to 30 minutes. In this way, a precursor of the second assembly (a second assembly having a solid electrolyte and a first layer formed thereon) was formed.

[0118] A laminate was formed by sequentially laminating a metal foil (electrolytic aluminum foil) punched into a predetermined pattern and a precursor of the second assembly on a glass epoxy substrate via a conductive adhesive. This laminate was filled with a silver particle-containing paste containing silver particles and a binder resin (epoxy resin), and heated at 150 to 200°C for 10 to 60 minutes to harden the binder resin and fix the laminate. In this way, a cathode extraction layer containing a carbon layer as the first layer and a metal foil (aluminum foil) as the second layer was formed (completing the second assembly), and a laminate of the second assembly was obtained.

[0119] (4) Resin sealing The laminate of the second assembly obtained in (3) above was placed in a mold, and an insulating resin was filled in by compression molding, and the laminate was sealed with the insulating resin to form a resin portion.

[0120] (5) Slicing and formation of external electrodes The laminate of the second assembly sealed with insulating resin obtained in (4) above was cut into individual capacitor element laminates using a diamond blade. As a result of the cutting process, a portion of the anode foil (anode portion) and a portion of the cathode foil (cathode portion) were exposed on the cut surfaces. External electrodes were bonded to the exposed portions of the anode and cathode, respectively. In this way, a total of 360 solid electrolytic capacitors were formed, each including a capacitor element laminate and a resin outer casing that sealed the laminate. The rated voltages of the solid electrolytic capacitors are shown in Table 1 or Table 2.

[0121] Comparative Examples 1 to 4 In Examples 1 to 6 (2), the solid electrolyte layer was formed using a liquid dispersion containing PEDOT and a dopant. A total of 360 solid electrolytic capacitors with rated voltages shown in Table 1 or Table 2 were formed in the same manner as in Examples 1 to 6, except for this. More specifically, an aqueous dispersion containing PEDOT and polystyrene sulfonic acid (PSS) at a concentration of 1.8% by mass (first liquid dispersion) was applied to the first assembly using a dispenser, followed by drying at 120°C for 5 to 10 minutes. Next, an aqueous dispersion containing PEDOT and PSS at a concentration of 5.5% by mass (second liquid dispersion) was applied to the resulting first assembly using a dispenser, followed by drying at 120°C for 5 to 10 minutes, with the application and drying of the second liquid dispersion being repeated alternately. In Comparative Examples 1 and 3, the application and drying of the second liquid dispersion were repeated four times. In Comparative Examples 2 and 4, the application and drying of the second liquid dispersion was repeated twice, thus forming a solid electrolyte layer.

[0122] "evaluation" The second assemblies with the solid electrolyte layers formed thereon obtained in (2) of the Examples and Comparative Examples, or the solid electrolytic capacitors obtained in (5) were used to carry out the following evaluations.

[0123] (a) Measurement of the thickness of the solid electrolyte layer For the second assembly with the solid electrolyte layer formed as obtained in (2) above, the thickness of the second assembly with the solid electrolyte layer formed was measured, subtracted from the thickness of the anode foil, and multiplied by 0.5 to determine the thickness of the solid electrolyte layer per surface on one side. The thickness of the solid electrolyte layer was measured at nine locations on both surfaces of each anode body region: the center of the anode body region, the four edges of the anode body, and the four midpoints between adjacent edges, and then averaged. In the same manner, the thickness of the solid electrolyte layer was measured and averaged for 20 randomly selected anode body regions. In this way, the average value and standard deviation of the thickness of the solid electrolyte layer were determined.

[0124] (b) Initial capacitance and ESR For each of 20 randomly selected solid electrolytic capacitors, the initial capacitance (μF) at a frequency of 120 Hz and the initial ESR (mΩ) at a frequency of 100 kHz were measured using a four-terminal LCR meter in an environment of 20°C, and the average values ​​were calculated. The initial capacitances of Examples 1 to 3 and Comparative Example 2 were evaluated as a ratio when the initial capacitance of Comparative Example 1 was set to 1, and the initial capacitances of Examples 4 to 6 and Comparative Example 3 were evaluated as a ratio when the initial capacitance of Comparative Example 3 was set to 1.

[0125] (c) Leakage current defect rate (LC defect rate) At 25°C, a 1 kΩ resistor was connected in series to the solid electrolytic capacitor, and a rated voltage of 25 V was applied from a DC power supply for 1 minute, after which the leakage current (μA) was measured. The leakage current was measured for 20 randomly selected solid electrolytic capacitors, and the percentage (%) of solid electrolytic capacitors with a leakage current exceeding 1 mA was calculated. This percentage was taken as the initial LC defect rate.

[0126] The solid electrolytic capacitors for which no leakage current exceeding 1 mA was measured were heated to 260°C to simulate the reflow process. More specifically, the solid electrolytic capacitors were heated from 25°C to 260°C over 2.5 minutes and then maintained at 260°C for 1 minute. The leakage current after heating (reflow) was measured in the same manner as for the initial leakage current, and the percentage of solid electrolytic capacitors for which a leakage current exceeding 1 mA was measured was calculated. This percentage was defined as the LC defect rate after reflow.

[0127] The evaluation results are shown in Tables 1 and 2. In the tables, E1 to E6 are Examples 1 to 6, and C1 to C4 are Comparative Examples 1 to 4.

[0128] [Table 1]

[0129] [Table 2]

[0130] As shown in Tables 1 and 2, when a solid electrolyte layer is formed using a liquid dispersion, repeated application and drying of the liquid dispersion is necessary to reduce the leakage current defect rate (compare C1 with C2, compare C3 with C4). However, in C1 and C3, the thickness variation of the solid electrolyte layer also increases, and the ESR also tends to increase (compare C1 with C2, compare C3 with C4). In contrast, in the Examples, a solid electrolyte layer of appropriate thickness is formed with a single chemical polymerization, and the thickness variation is reduced to a certain extent (compare E1-E3 with C1-C2, compare E4-E6 with C3-C4). In the Examples, the thickness of the solid electrolyte layer is not significantly different from that of C2 or C4, but the leakage current defect rate is significantly reduced, and the leakage current defect rate after reflow is also reduced to 0%. Furthermore, in the Examples, a larger capacitance is obtained and the ESR is also reduced compared to C1 and C3. [Industrial Applicability]

[0131] According to the present disclosure, it is possible to mass-produce solid electrolytic capacitors with excellent capacitor performance by suppressing variations in the thickness of the solid electrolyte layer. Furthermore, the manufacturing method according to the present disclosure can also reduce the leakage current defect rate. Therefore, the manufacturing method according to the present disclosure is suitable for, for example, industrial production of solid electrolytic capacitors. [Explanation of symbols]

[0132] 1, 21, 31: solid electrolytic capacitor, 2, 22, 32: solid electrolytic capacitor element, 22A, 32A: element (solid electrolytic capacitor element (or capacitor element precursor) without second layer formed), 3: resin outer casing, 4a: first external electrode, 4b: intermediate electrode layer, 4c: contact layer, 5a: second external electrode, 5b: intermediate electrode layer, 6: anode body region (anode body), 6A: large-sized anode body (anode foil), 7: dielectric layer, 8: solid electrolyte layer, 9: cathode lead layer, 9A: first layer (carbon layer), 9B: second layer (metal foil), 10: cathode part, 12: second assembly, 13: first insulating region, 15: cathode lead, 16: conductive adhesive, L: stack of solid electrolytic capacitor elements, S: substrate, e1: first end of anode body region 6, e2: second end of anode body region 6, D L :Stacking direction, D1: 1st direction, D2: 2nd direction, m1: 1st main surface, m2: 2nd main surface, m3: 3rd main surface, m4: 4th main surface

Claims

[Claim 1] A method for manufacturing a solid electrolytic capacitor including a solid electrolytic capacitor element including an anode body, a dielectric layer covering at least a portion of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer, comprising: forming a second assembly having a plurality of the solid electrolytic capacitor elements by forming the solid electrolyte layer so as to cover at least a portion of the dielectric layer in a first assembly having anode body regions corresponding to the plurality of the anode bodies arranged in a plane direction, the first assembly each having the dielectric layer; and dividing the second assembly into individual solid electrolytic capacitor elements, The step of forming the second assembly includes: a first step of forming a coating containing manganese oxide that covers at least a portion of the dielectric layer; a second step of contacting the coating with a liquid mixture containing a precursor of a conjugated polymer, a dopant, and a polyhydric alcohol, and chemically polymerizing the precursor using the manganese oxide as an oxidizing agent to form the solid electrolyte layer containing the conjugated polymer and the dopant; A method for manufacturing a solid electrolytic capacitor, comprising:

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