Manufacturing method for solid electrolytic capacitors

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] This disclosure relates to a method for manufacturing solid electrolytic capacitors. [Background technology]

[0002] A solid electrolytic capacitor comprises a solid electrolytic capacitor element, an outer casing that encloses the solid electrolytic capacitor element, and external electrodes electrically connected to the solid electrolytic capacitor element. The solid electrolytic capacitor element comprises an anode, a dielectric layer formed on at least the surface of the cathode-forming portion of the anode, and a cathode portion that covers at least a part of the dielectric layer. The cathode portion comprises a solid electrolyte layer containing a conductive polymer that covers at least a part of the dielectric layer and a cathode extraction layer that covers at least a part of the solid electrolyte layer. The solid electrolyte layer can be formed, for example, by coating an anode having a dielectric layer with a liquid mixture (dispersion or solution) containing a conductive polymer. Alternatively, the solid electrolyte layer can be formed by chemical polymerization or electrolytic polymerization of a precursor of a conductive polymer.

[0003] For example, Patent Document 1 proposes forming an internal conductive polymer layer on the surface of a porous valve metal having an anodic oxide film formed on its surface, and providing a liquid phase portion on the surface of the internal conductive polymer layer, which is a polymer polymerization solution obtained by mixing polyethylenedioxythiophene and polystyrene sulfonic acid as conductive polymers, naphthalene sulfonic acids, high molecular weight polystyrene sulfonic acid, boric acid, mannitol, and glycols, and drying and solidifying the liquid phase portion of the polymer polymerization solution to form a solid electrolyte layer.

[0004] Furthermore, from the perspective of improving productivity, a technique has been proposed in which multiple solid electrolytic capacitors are formed in an aggregate state using an aggregate having multiple anode regions, and then separated into individual solid electrolytic capacitors. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-311582 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] From the standpoint of easily manufacturing solid electrolytic capacitors and ensuring higher productivity, it is advantageous to form the solid electrolyte layer using a liquid mixture containing a conductive polymer (for example, a liquid dispersion containing a liquid medium and particulate conductive polymer dispersed in the liquid medium), as described in Patent Document 1. However, when forming a solid electrolyte layer using an assembly having multiple anode regions, if a liquid mixture containing a conductive polymer is used, it is necessary to form a solid electrolyte layer of a certain thickness in order to keep leakage current low. 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 this disclosure is a method for manufacturing a solid electrolytic capacitor element including an anode, a dielectric layer covering at least a portion of the anode, and a solid electrolyte layer covering at least a portion of the dielectric layer, A first assembly having a dielectric layer and a plurality of anode regions corresponding to a plurality of anodes arranged in the planar direction, a step of forming the solid electrolyte layer so as to cover at least a portion of the dielectric layer to form a second assembly having a plurality of solid electrolytic capacitor elements, The process includes the step of separating the second assembly into individual solid electrolytic capacitor elements, The process of forming the aforementioned two aggregates is as follows: A first step of forming a film containing manganese oxide that covers at least a portion of the dielectric layer, A second step involves contacting a liquid mixture containing a conjugated polymer precursor, a dopant, and a polyhydric alcohol with the coating to chemically polymerize the precursor using manganese oxide as an oxidizing agent, thereby forming the solid electrolyte layer containing the conjugated polymer and the dopant. This invention relates to a method for manufacturing solid electrolytic capacitors, including [specific components / features]. [Effects of the Invention]

[0008] When forming multiple solid electrolytic capacitors using an assembly comprising multiple anode regions, a more uniform solid electrolyte layer can be formed. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic plan view of a second assembly used in a method for manufacturing a solid electrolytic capacitor according to one embodiment of the present disclosure. [Figure 2] This is a schematic cross-sectional view of the second aggregate in Figure 1, taken by cutting along line II-II, as seen from the direction of the arrow. [Figure 3] This is a process diagram showing a method for manufacturing a solid electrolytic capacitor according to the first embodiment. [Figure 4] This is a schematic cross-sectional view of a solid electrolytic capacitor obtained by a method for manufacturing a solid electrolytic capacitor according to the second embodiment of this disclosure. [Figure 5] This is a schematic cross-sectional view of a solid electrolytic capacitor obtained by a method for manufacturing a solid electrolytic capacitor according to the third embodiment of this disclosure. [Figure 6A] This is a schematic cross-sectional view of a solid electrolytic capacitor obtained by the manufacturing method of a solid electrolytic capacitor according to the fourth embodiment of this disclosure, when the anode body is cut in a direction parallel to the longitudinal direction (first direction) and the stacking direction of the solid electrolytic capacitor elements. [Figure 6B] Figure 6A is a schematic cross-sectional view of the solid electrolytic capacitor when it is cut in the width direction of the anode (second direction) and in a direction parallel to the stacking direction of the solid electrolytic capacitor elements. [Modes for carrying out the invention]

[0010] When manufacturing solid electrolytic capacitors by forming a solid electrolyte layer using an assembly with multiple anode regions and then separating it into individual components, it becomes significantly more difficult to form a more uniform solid electrolyte layer compared to manufacturing solid electrolytic capacitors individually. In the former case, since the solid electrolyte layer is formed simultaneously on multiple anode regions, variations in the rate and extent of solid electrolyte layer formation tend to occur in each anode region. Although the solid electrolyte layer can also be formed by chemical polymerization or electrolytic polymerization, controlling the reaction is more difficult compared to forming the solid electrolyte layer using a liquid mixture containing a conductive polymer. In particular, since chemical polymerization proceeds around the oxidizing agent, it is extremely difficult to proceed with uniform polymerization on the anode region when using a liquid mixture containing a conductive polymer precursor and an oxidizing agent. Even when the oxidizing agent is applied to the anode 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 perform stable and uniform polymerization on the anode region. Theoretically, it is possible to form a solid electrolyte layer on the anode region by repeatedly applying an oxidizing agent and polymerizing it using a liquid mixture. However, because the position where the oxidizing agent adheres cannot be controlled, the film quality and thickness of the solid electrolyte layer are expected to become even more non-uniform. In particular, when forming a solid electrolyte layer using an assembly with multiple anode regions, it is extremely difficult to make the distribution of the oxidizing agent uniform throughout the anode region of the assembly, and the difficulty of reaction control increases dramatically. Therefore, it is difficult to suppress variations in the state, thickness, and film quality of the solid electrolyte layer formed in each anode region, and the product defect rate increases dramatically. From this perspective, when using an assembly, forming a solid electrolyte layer by chemical polymerization is not practical, and it is common to form a solid electrolyte layer using a liquid mixture containing a conductive polymer. When using a liquid mixture containing a conductive polymer, it is necessary to form a solid electrolyte layer of a certain thickness in order to keep the leakage current low. However, when using a liquid mixture containing a conductive polymer, it is not possible to form a solid electrolyte layer of an appropriate thickness without repeating the application and drying of the liquid mixture multiple times. Repeated drying processes cause the solid electrolyte layer to expand, making it difficult to reduce variations in the thickness of the solid electrolyte layer.

[0011] The present disclosure provides a method for manufacturing a solid electrolytic capacitor, comprising the steps of: forming a solid electrolyte layer covering at least a portion of the dielectric layer using an assembly (first assembly) each having a dielectric layer and a plurality of anode regions arranged in the planar direction, thereby forming an assembly (second assembly) having a plurality of solid electrolytic capacitor elements; and separating the second assembly into individual solid electrolytic capacitor elements. In the step of forming the second assembly, a film containing manganese oxide is formed covering at least a portion of the dielectric layer (first step); a liquid mixture containing a precursor of a conjugated polymer, a dopant, and a polyhydric alcohol is brought into contact with the film containing manganese oxide, and the manganese oxide is used as an oxidizing agent to chemically polymerize the precursor, thereby forming a solid electrolyte layer containing the conjugated polymer and the dopant (second step). By forming the film containing manganese oxide covering at least a portion of the dielectric layer in the first step, the manganese oxide, which is the oxidizing agent, is immobilized on the surface of the dielectric. Since the immobilized manganese oxide does not dissolve in the liquid mixture, in the second step, the chemical polymerization of the precursor can proceed more uniformly and efficiently with the manganese oxide relatively uniformly dispersed on the surface of the dielectric layer. Therefore, a more uniform solid electrolyte layer can be stably formed across the entire area where the coating is formed, in multiple anode regions simultaneously. In each anode region, the formed solid electrolyte layer is moderately porous and has excellent film quality, and because there is no need to repeat drying multiple times, expansion is suppressed and it has a more uniform thickness. As a result, high capacitance can be obtained, the equivalent series resistance (ESR) can be kept low, and leakage current can be reduced. Despite being able to manufacture multiple solid electrolytic capacitors simultaneously, the product defect rate (such as the leakage current defect rate) is reduced, thus increasing productivity.

[0012] Since the thickness of the solid electrolyte layer can be made more uniform, the accuracy in forming a laminate of a plurality of second aggregates can be improved. Further, since the polymerization reaction occurs efficiently in the portion of the film containing manganese oxide, a solid electrolyte layer can be formed for anode body regions of various shapes, and the degree of freedom in the shape of the solid electrolytic capacitor element is large. The solid electrolyte layer can be formed in the state of an aggregate, and since the polymerization rate is high, productivity can be greatly improved. In addition, since polymerization proceeds if a liquid mixture containing a precursor is present around the film, the amount of the liquid mixture used can be reduced compared with the conventional case. Unlike electrolytic polymerization, no electrode is required, so the manufacturing apparatus can be made more space-saving. Further, since the formed solid electrolyte layer is moderately porous, when a cathode lead-out layer is formed so as to cover the solid electrolyte layer, the constituent components of the cathode lead-out layer also penetrate into the voids of the solid electrolyte layer, ensuring high adhesion and conductivity and enabling the ESR to be kept low.

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

[0014] The 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 part of the anode body, and a cathode portion covering at least a part of the dielectric layer. The cathode portion includes a solid electrolyte layer covering at least a part of the dielectric layer. The cathode portion may further include a cathode lead-out layer covering at least a part of the solid electrolyte layer. The solid electrolytic capacitor includes at least one solid electrolytic capacitor element, and may include a laminate in which a plurality of solid electrolytic capacitor elements are laminated. Hereinafter, the solid electrolytic capacitor element may be simply referred to as a capacitor element.

[0015] In this disclosure, a solid electrolytic capacitor is formed using a first assembly having a dielectric layer and a plurality of anode regions arranged in the planar direction. The anode regions correspond to the anodes in a solid electrolytic capacitor. More specifically, a method for manufacturing a solid electrolytic capacitor includes the steps of forming a solid electrolyte layer in the first assembly so as to cover at least a portion of the dielectric layer to form a second assembly having a plurality of capacitor elements, and the steps of separating the second assembly into individual capacitor elements. The method for manufacturing a solid electrolytic capacitor may further include the step of forming a stack of a plurality of second assemblies, each containing a stack of a plurality of capacitor elements. In this case, the separation step separates each stack of capacitor elements. The manufacturing method may further include the step of sealing the second assembly or its stack with a resin to form a resin portion covering the second assembly or its stack. In this case, the separation step separates the resin portion together with the second assembly or its stack, forming a solid electrolytic capacitor comprising a capacitor element or its stack and a resin outer casing that seals the capacitor element or its stack. The manufacturing method may include a step of forming grooves in the laminate of the second assembly prior to resin sealing. 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 leads to at least one of the cathode and anode portions of the capacitor element, a step of forming electrodes, and so on. The manufacturing method may include a step of preparing the first assembly. Each step will be described in more detail below.

[0016] (Steps to prepare the first assembly) The first assembly may be a state in which multiple anode regions are connected in a planar arrangement, or a state in which a large anode (for example, a raw anode roll or a long strip of anode) is divided into multiple anode regions. For example, the first assembly can be prepared by connecting multiple anode regions in a planar arrangement, arranging multiple anode regions on a substrate, or processing a large anode to form multiple anode regions. For example, the first assembly can be prepared by punching a large anode foil into a predetermined shape to form multiple anode regions. Alternatively, for example, an insulating region (hereinafter sometimes referred to as the first insulating region) can be formed on the surface of a large anode (such as an anode foil), and the first assembly can be prepared by dividing (or partitioning) the anode (such as an anode foil) into multiple regions (corresponding to anode regions) using the first insulating region.

[0017] In particular, when using a first assembly having multiple anode regions formed by dividing a large anode into multiple regions, it is possible to form more anode regions compared to other methods. As the density of anode regions in the first assembly increases, it becomes particularly difficult to form a more uniform solid electrolyte layer in each anode region. However, according to this disclosure, since the solid electrolyte layer is formed by the first and second steps, even when using a first assembly with a high density of anode regions, a more uniform solid electrolyte layer can be formed all at once, and the product defect rate can be reduced. Furthermore, compared to using a first assembly in which multiple anode regions are formed by punching a large anode foil into a predetermined shape, using a first assembly having multiple partitioned anode regions is particularly advantageous in forming a more uniform solid electrolyte layer because the unevenness in the depth direction when polymerization is performed while immersed in a liquid mixture is reduced. In addition, when using a first assembly having multiple partitioned anode regions, a large number of capacitor elements can be formed all at once with a small amount of liquid mixture. Therefore, the efficiency of using liquid mixtures is dramatically improved, and productivity can be significantly increased, making it extremely cost-effective.

[0018] In the first assembly, the multiple anode regions may be arranged in a matrix, for example, with multiple rows of multiple anode regions 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 region. The dielectric layer is formed, for example, by anodizing the valve metal on the surface of the anode region. Anodizing can be carried out, for example, by a chemical conversion treatment.

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

[0021] The anode region may include valve metals, alloys containing valve metals, and compounds containing valve metals. The anode region may contain one of these materials or a combination of two or more. As valve metals, aluminum, tantalum, niobium, and titanium are preferably used.

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

[0023] Each anode 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 usually formed in the cathode-forming portion of the anode 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, formed to cover at least a portion of the surface of the anode region. The dielectric layer contains an oxide of the 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 these; any material that functions as a dielectric is acceptable.

[0025] The dielectric layer only needs to be formed to cover at least a portion of the anode region. The dielectric layer is usually formed on the surface of the anode region (e.g., the porous region). The dielectric layer is usually formed along the surface irregularities of the anode region and the inner walls of the voids in the porous region.

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

[0027] Examples of insulating materials constituting the first insulating region (first insulating material) include resin materials. Using a water-repellent resin material as the insulating material makes it easier to suppress the adhesion of the cathode component material to areas other than the intended area. From the viewpoint of increasing productivity, the width of the first insulating region tends to decrease, 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 this disclosure, since manganese oxide is fixed to the surface of the dielectric layer, if even a small amount of manganese oxide is fixed to the surface of the first insulating region, a solid electrolyte layer is formed on the surface of the first insulating region, making it difficult to ensure insulation. When the first insulating region includes a water-repellent resin material, the effect of suppressing the fixation of manganese oxide on the surface of the first insulating region is enhanced, making it even easier to ensure insulation. The resin material may be either a thermoplastic resin or a curable resin (thermosetting resin, photocurable resin, etc.).

[0028] Examples of curable resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, furan resins, alkyd resins, curable polyurethanes, curable polyimides, polyamide-imides, unsaturated polyesters, allyl resins, and curable acrylic resins.

[0029] Examples of thermoplastic resins include polyester, polyamide, polycarbonate, polyacetal, polyphenylene ether, polyphenylene sulfide, polyetheretherketone, polyacryletherketone, polyamide, polyamideimide, polyimide, polyetherimide, polysulfone, polyethersulfone, 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. Preferably, the first insulating region contains a water-repellent material such as silicone resin or fluororesin. The first insulating region may also contain a water-repellent material and other resin materials.

[0031] The step of preparing the first assembly may further include the step of forming an insulating region (hereinafter sometimes referred to as the second insulating region) in the anode region, at the end of the anode portion on the cathode forming portion side and in its vicinity. The second insulating region may be formed in the step of forming the first insulating region, or it may be formed separately from the step of forming the first insulating region. Providing the second insulating region makes it easier to further ensure insulation between the anode portion and the cathode portion. The second insulating region is formed by applying an insulating material (second insulating material) to the anode 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 can be carried out in accordance with the case of the first insulating material.

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

[0033] (Process for forming the second assembly) A second assembly having multiple capacitor elements is formed by forming cathode portions in each of the anode regions 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 region. If 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] (Process for forming a solid electrolyte layer) The process for forming a solid electrolyte layer includes a first step of forming a film containing manganese oxide that covers at least a portion of the dielectric layer, and a second step of contacting the film with a liquid mixture containing a conjugated polymer precursor, a dopant, and a polyhydric alcohol, and chemically polymerizing the precursor with manganese oxide as an oxidizing agent to form a solid electrolyte layer containing the conjugated polymer and the dopant. By forming a solid electrolyte layer by the first and second steps, a more uniform solid electrolyte layer can be formed when forming a solid electrolyte layer on multiple anode regions simultaneously.

[0035] (1st step) The manganese oxide contained in the film 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 film with a more uniform thickness, it is preferable that the manganese oxide contains at least dimanganese trioxide, and more preferably that 50% by mass or more of the manganese oxide is dimanganese trioxide. A more uniform film thickness is advantageous in improving the uniformity of the solid electrolyte layer. The film containing manganese oxide is formed to cover at least a portion of the surface of the dielectric layer.

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

[0037] An aqueous solution containing manganese nitrate may be applied to the surface of the dielectric layer by means of 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 concentration of manganese nitrate is within this range, it is easy to control the amount of manganese oxide film that adheres. The concentration of manganese nitrate in the aqueous solution is, for example, 10% by mass or more, and may be 20% by mass or more, or 30% by mass or more.

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

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

[0041] The amount of manganese oxide deposited on the anode region is, for example, 5 μg / mm³. 2 More than 20μg / mm 2 The following is true: When the amount of adhesion is within this range, a more uniform solid electrolyte layer is more easily obtained, and a solid electrolyte layer of 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 precursor of the conjugated polymer, a dopant, and a polyhydric alcohol is brought into contact with the manganese oxide film formed in the first step, and the conjugated polymer precursor is chemically polymerized to form the solid electrolyte layer. Since the manganese oxide acts as an oxidizing agent, the chemical polymerization of the precursor proceeds selectively at and near the interface between the manganese oxide film and the liquid mixture, forming the conjugated polymer. Therefore, even though a first assembly with multiple anode regions is used, a more uniform solid electrolyte layer is formed in the portion of the anode region where the manganese oxide film is formed. The manganese oxide itself is reduced to divalent manganese ions and dissolves in the liquid mixture, but 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 typically contains a solvent. The liquid mixture may also contain additives as needed.

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

[0045] Examples of conjugated polymers include known conjugated polymers used in solid electrolytic capacitors, such as π-conjugated polymers. Examples of conjugated polymers include polymers based on polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene as the basic skeleton. The above polymers only need to contain at least one monomer unit that constitutes the basic skeleton. Monomer units include monomer units having substituents. The above polymers also include homopolymers and copolymers of two or more monomers.

[0046] Among conjugated polymers, those containing monomer units corresponding to thiophene compounds are preferred. Precursors of such conjugated polymers readily undergo polymerization reactions using manganese oxide as an oxidizing agent. Furthermore, such conjugated polymers are resistant to oxidative degradation, making it easier to ensure high heat resistance in solid electrolytic capacitors. Examples of thiophene compounds include compounds having a thiophene ring and capable of forming a repeating structure of the corresponding monomer units.

[0047] Thiophene compounds may, for example, have substituents at least one of the 3rd and 4th positions of the thiophene ring. The substituent at the 3rd position and the substituent at the 4th position may be linked to form a ring fused to the thiophene ring. Examples of thiophene compounds include thiophenes which may have substituents at least one of the 3rd and 4th positions, alkylenedioxythiophene compounds (such as ethylenedioxythiophene compounds), and C 2-4 Examples include alkylenedioxythiophene compounds. Alkylenedioxythiophene compounds also include those that have substituents on the alkylene group.

[0048] The substituents include alkyl groups (such as methyl and ethyl groups). 1-4 Alkyl groups (such as alkyl groups), alkoxy groups (such as methoxy groups and ethoxy groups), etc. 1-4Alkoxy groups, hydroxyl groups, hydroxyalkyl groups (such as hydroxymethyl groups and other hydroxyC groups) 1-4 While alkyl groups are preferred, the compound is not limited to these. If the thiophene compound has two or more substituents, the substituents may be the same or different.

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

[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 this case, the yield of the chemical polymerization reaction is high, and a solid electrolyte layer can be stably formed.

[0051] Examples of dopants include at least one selected from the group consisting of anions and polyanions.

[0052] Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions, but are not particularly limited. 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, sulfisophthalic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid, alkylnaphthalenesulfonic acid, polyalkylnaphthalenesulfonic acid, anthraquinonesulfonic acid, anthraquinonedisulfonic acid, biphenylsulfonic acid, and their derivatives. Examples of derivatives include substituted products having substituents (e.g., hydrocarbon groups (alkyl groups, aryl groups, etc.), hydroxyl groups, carboxyl groups, alkoxy groups, nitro groups). In particular, it is preferable to use an aromatic sulfonic acid having at least one selected from the group consisting of a hydroxyl group bonded to an aromatic ring and a carboxyl group bonded to an aromatic ring. Using such aromatic sulfonic acids allows for the smooth chemical polymerization of the precursor of the conjugated polymer. Using a dopant containing sulfosalicylic acid increases the conductivity of the solid electrolyte layer, allowing for higher capacitance and lower ESR. Furthermore, it allows for a thicker solid electrolyte layer, thus reducing leakage current.

[0054] Examples of polyanions include polymer anions. The solid electrolyte layer may, for example, contain a conjugated polymer containing monomer units corresponding to the 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 anionic groups include sulfonic acid groups and carboxyl groups.

[0056] Examples of polymer anions having a carboxyl 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 a sulfonic acid group include, but are not limited to, polymer-type 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 phenol sulfonic acid novolac resin.

[0058] In the solid electrolyte layer formed, the anionic group of the dopant may be present in free form, anionic form, or salt form, or in a form bonded to or interacting with a conjugated polymer system. In this specification, all of these forms may be simply referred to as "anionic group," "sulfonic acid group," or "carboxyl group."

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

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

[0061] The polyhydric alcohol is not particularly limited as long as it is a polyhydric alcohol that coordinates to the divalent manganese ion. Aliphatic alcohols are preferred as polyhydric alcohols. Aliphatic alcohols may have an aliphatic ring, an aromatic ring, or a heterocycle, but it is preferable that they do not have such rings, considering their coordination to the manganese ion. 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 hydroxyl groups in the polyhydric alcohol is, for example, 2 to 6, or 2 to 4. From the viewpoint of easily keeping the viscosity of the liquid mixture low, it is preferable to use at least ethylene glycol.

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

[0063] Examples of solvents include at least one selected from the group consisting of water and organic solvents (excluding polyhydric alcohols). The liquid mixture may contain water and an organic solvent. Examples of organic solvents include aliphatic alcohols, aliphatic ketones (such as acetone), nitriles (such as acetonitrile and benzonitrile), amides (such as N,N-dimethylformamide), and sulfoxides (such as dimethyl sulfoxide). The solvent may contain one organic solvent or a combination of two or more. Aliphatic monools are used as aliphatic alcohols. Aliphatic alcohols having 1 to 5 carbon atoms are preferred. Examples of aliphatic alcohols include methanol, ethanol, 1-propanol, 2-propanol, and butanol. The type and amount of solvent used should be determined by considering, for example, the solubility of the conjugated polymer precursor and dopant in the liquid mixture. For example, water and an aliphatic alcohol (such as 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 range.

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

[0065] The polymerization temperature is, for example, between 5°C and 60°C, or between 15°C and 35°C.

[0066] In the second step, chemical polymerization may be repeated two or more times. However, since the second step is performed after the first step has formed a manganese oxide film, the thickness of the solid electrolyte layer can be made relatively large even if chemical polymerization is performed only once.

[0067] The solid electrolyte layer may be a single layer or composed of multiple layers. If the solid electrolyte layer is composed of multiple layers, the components contained in each layer (e.g., conjugated polymer, dopant, polyhydric alcohol, and additive) may be the same or different. For example, a first solid electrolyte layer may be formed in a second step, and then a second solid electrolyte layer may be formed so as 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 electropolymerization using a treatment solution containing a precursor and dopant of a conjugated polymer. Such a treatment solution may optionally contain at least one selected from the group consisting of oxidizing agents and additives. Alternatively, the second solid electrolyte layer may be formed using a treatment solution (such as a solution or dispersion) containing a conjugated polymer and dopant. After applying these treatment solutions to the first solid electrolyte layer, drying, heat treatment, etc., may be performed as needed. The treatment solution may be applied, for example, by immersion, coating (such as coating using a dispenser), dropping, screen printing, or transfer.

[0069] (Process for forming the cathode extraction layer) The cathode extraction layer includes, for example, 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 also 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 a metal foil. Examples of conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may be composed of a layer containing conductive carbon as the first layer (also referred to as a carbon layer) and a layer containing metal powder or a metal foil as the second layer. When a metal foil is used as the first layer, the cathode extraction layer may be composed 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 composition may be applied using, for example, screen printing or transfer.

[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 portion of the solid electrolyte layer, or the first layer may be formed by laminating a large metal foil onto a second assembly in which a solid electrolyte layer is formed in each anode region. When a metal foil is used as the first layer, the type of metal is not particularly limited. Examples of metal foils include aluminum, aluminum alloys, copper, or copper alloys. Valve metals (such as aluminum, tantalum, or niobium) or alloys containing valve metals may also be used for the metal foil. The surface of the metal foil may be roughened as needed. 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 onto the first layer. The surface of the metal foil may be provided with a chemical conversion coating, and a coating of a different metal (dissimilar metal) or a nonmetal may be provided on the surface of the metal foil. Examples of dissimilar metals or nonmetals include metals such as titanium or nonmetals such as carbon (such as conductive carbon). The above-mentioned dissimilar metal or nonmetal (for example, conductive carbon) coating may be used as the first layer, and the above-mentioned metal foil may be used as the second layer. In this case, after forming the first layer on the surface of the metal foil which is the second layer, the cathode extraction layer may be formed by laminating the resulting laminate with a solid electrolyte layer (or a second assembly with the solid electrolyte layer formed on it) such that the first layer is in contact with the solid electrolyte layer.

[0073] When using metal foil, an insulating region such as a first insulating region may be formed, similar to the case of the first assembly, and the cathode lead layer may be partitioned (or divided) into multiple regions. Alternatively, similar to the case of the first assembly, a metal foil divided into multiple regions by punching out 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, in which the solid electrolyte layer is formed, such that each region is in contact with each of the solid electrolyte layers. When using large metal foil, holes may be provided in the metal foil for filling with sealing resin as needed.

[0074] When using metal foil, a second assembly without metal foil may be formed, and in the lamination process of the second assembly, the second assembly without 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 as needed.

[0075] The second layer, which contains metal powder, 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 using a composition (slurry, paste, etc.) containing, for example, metal powder such as silver particles and a resin (binder resin). The composition may be applied using, for example, screen printing or transfer. As the resin, a thermoplastic resin can be used, but typically thermosetting resins such as imide resins and epoxy resins are used.

[0076] In the process of forming the cathode extraction layer, drying or heat treatment may be performed at an appropriate stage.

[0077] (Steps to form the laminate of the second assembly) When stacking multiple second assemblies, the second assemblies are stacked such that the capacitor elements in each second assembly overlap in the thickness direction of the second assembly. Positioning members (such as guide pins) may be used to ensure that the multiple capacitor elements overlap accurately in the thickness direction. A stacking jig may be used for stacking as needed. The stacking jig may also be equipped with positioning members. Furthermore, when forming a cathode extraction layer containing metal foil as described above, the cathode extraction layer (and second assemblies) may be completed by stacking a second assembly without metal foil and the metal foil in this process.

[0078] A laminate may be formed by forming or fixing a second assembly located at the bottom of the lamination onto a substrate, and then stacking other second assemblies on top of this second assembly. Examples of substrates include insulating substrates (for example, insulating substrates containing a substrate made of glass cloth impregnated with epoxy resin). Lamination may be performed by fixing adjacent capacitor elements in the lamination direction with a conductive adhesive. As the conductive adhesive, for example, a composition containing metal powder as described for the second layer of the cathode extraction layer (such as a silver particle-containing paste) may be used. Such a conductive adhesive may also be used to fix metal foils and second assemblies without metal foils (more specifically, the first layer (such as a carbon layer)).

[0079] The direction from the anode-side end (first end) of the anode region of the capacitor element toward the cathode-forming end (second end) 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. The ends of the second direction are defined as the third and fourth ends. In this case, adjacent capacitor elements in the stacking direction may overlap so that the first directions of each capacitor element are parallel. In this case, adjacent capacitor elements in the stacking direction may overlap at their first ends and their second ends, or at their first and second ends. Also, adjacent capacitor elements in the stacking direction may overlap so that the first and second directions of each capacitor element are parallel. In this case, the first end of one capacitor element (first capacitor element) and the third (or fourth) end of an adjacent capacitor element (second capacitor element) in the stacking direction of the first capacitor element are located close together. Also, the second end of the first capacitor element and the fourth (or third) end of the second capacitor element are located close together. The orientation of each capacitor element in the laminate should be determined according to the design of the solid electrolytic capacitor.

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

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

[0082] The grooves can be formed, for example, using a dicing blade such as a diamond blade. Alternatively, the grooves may be formed by other grooving techniques (e.g., laser processing).

[0083] (The process of connecting the leads) When drawing current from a capacitor element 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 part of the cathode portion of a capacitor element included in the second assembly or to a part of the cathode portion of a capacitor element included in the laminate of the second assembly. One end of the lead may also be connected to a part of the anode region included in the first assembly. Lead connections are usually made before the resin sealing process. The other end of the lead is configured to be exposed from the resin casing after individualization.

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

[0085] The lead can be made of a metal such as copper or a copper alloy.

[0086] (Process for forming the resin part (resin sealing process)) The second assembly or laminate is sealed with resin. More specifically, it is sealed by covering the perimeter of the second assembly or laminate with resin and molding it into a predetermined shape. This forms a resin portion that covers the second assembly or laminate. If grooves are formed in the laminate of the second assembly, the grooves are also filled with resin during 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] Examples of resins used include curable resin compositions, thermoplastic resins, or compositions thereof. The resin composition may optionally contain fillers (such as inorganic fillers).

[0089] (Singulation process) In the individualization process, the second assembly is individualized for each capacitor element. When forming a laminate of the second assembly, each laminate of multiple capacitor elements is individualized. If the second assembly or the laminate is covered with a resin portion, the second assembly or the laminate is individualized together with the resin portion. The solid electrolytic capacitor thus obtained comprises capacitor elements or their laminates, and a resin outer casing that seals the capacitor elements or their laminates.

[0090] Fragmentation is performed, for example, by cutting the second aggregate or its stack using a dicing blade such as a diamond blade.

[0091] In the individualization process, capacitor elements (or their stacks) are separated from adjacent capacitor elements (or their stacks). Individualization may be carried out in stages. For example, multiple capacitor elements or their stacks may be separated row by row, and after other processes are carried out (for example, after electrodes are formed by the electrode formation process described later), the individual capacitor elements or their stacks may be separated.

[0092] In the individualization process, the second assembly or its laminate may be cut to divide the resin portion. In the individualization process, the second assembly or its laminate may be cut so that at least one part of the anode portion and cathode portion of the capacitor element is exposed from the resin casing. Alternatively, the second assembly or its laminate may be cut so that the other end of a lead electrically connected to the anode portion or cathode portion is exposed from the resin 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 that is exposed from the resin casing. External electrodes may be electrically connected to the exposed portion in the electrode formation process described later.

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

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

[0095] (Electrode formation process) Solid electrolytic capacitors may be provided with external electrodes. The external electrode on the anode side may be referred to as the first external electrode, and the external electrode on the cathode side may be referred to as the second external electrode.

[0096] For example, the first external electrode is electrically connected to the anode-side exposed portion, and the second external electrode is electrically connected to the cathode-side exposed portion. The first and second external electrodes are provided at a distance from each other so as not to short-circuit. The connection between each exposed portion and the external electrode may be made by at least one 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. An intermediate electrode layer may be provided between the exposed portion or contact layer and the external electrode, if necessary.

[0098] Figure 1 is a schematic plan view of a second assembly used in the manufacturing method of a solid electrolytic capacitor of this disclosure. Figure 2 is a schematic cross-sectional view of the second assembly of Figure 1 when it is cut along line II-II, viewed from the direction of the arrow. In the illustrated example, in the second assembly 12, a grid-like first insulating region 13 is provided on both main surfaces of the large anode body (anodide foil) 6A. The large anode body 6A is divided into a plurality of anode body regions 6 by the first insulating region 13. Each anode body region 6 corresponds to the anode body of the capacitor element after it has been separated into individual components. 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 laminate of the second assemblies 12 is formed by stacking a plurality of second assemblies 12 in the thickness direction. The plurality of second assemblies 12 are stacked, for example, so that the cathode portions 10 of adjacent second assemblies 12 overlap. The second assembly 12 or its laminate is separated into individual capacitor elements or its laminate by, for example, cutting along the first insulating region 13.

[0099] Figure 3 is a process diagram showing a manufacturing method of the first embodiment of the present disclosure. In the illustrated example, first, a second assembly having a plurality of capacitor elements is formed by first and second steps. In the first step, a film containing manganese oxide is formed to cover at least a portion of the dielectric layer in each anode 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 film formed in the first step, and the manganese oxide is used as an oxidizing agent to chemically polymerize the conjugated polymer precursor, thereby forming a solid electrolyte layer containing the conjugated polymer and the dopant (S2). Next, a laminate of a plurality of second assemblies is formed (S3). The resulting laminate is further sealed with resin (S4). By separating the laminate of the second assemblies together with the resin portion formed by sealing, a solid electrolytic capacitor comprising a laminate of capacitor elements and a resin outer casing that seals it is obtained (S5).

[0100] Figure 4 is a schematic cross-sectional view of a solid electrolytic capacitor formed by the manufacturing method of the second embodiment of the present disclosure. The solid electrolytic capacitor 1 comprises a capacitor element 2, a substrate S supporting the capacitor element 2, a resin casing 3 enclosing 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 casing 3 has a substantially rectangular parallelepiped shape, and the solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped shape.

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

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

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

[0104] Figure 5 is a schematic cross-sectional view of a solid electrolytic capacitor obtained by a manufacturing method according to the third embodiment of the present disclosure. The solid electrolytic capacitor 21 comprises a laminate L of a plurality of capacitor elements 22, a substrate S supporting the laminate L, a resin casing 3 sealing the laminate L, a first external electrode 4a, and a second external electrode 5a. The laminate L comprises a plurality of laminated elements (precursors of capacitor elements) 22A and a metal foil (second layer) 9B arranged between adjacent elements 22A. The elements 22A and the metal foil (second layer) 9B are bonded together via a conductive adhesive 16. The elements 22A correspond to capacitor elements before the formation of the second layer 9B, and a solid electrolyte layer 8 is formed on the surface of the anode region 6 via a dielectric layer 7, and a carbon layer (first layer) 9A is formed so as to cover the solid electrolyte layer 8. In the laminate L, the cathode extraction layer 9 is composed of a carbon layer (first layer) 9A, a metal foil (second layer) 9B, and a conductive adhesive 16 interposed between them. In the laminate L, each capacitor element 22 is stacked in the thickness direction of the capacitor element 22 (or anode region 6) such that the direction from the first end e1 to the second end e2 of each anode region 6 (first direction) is parallel. In the anode region 6 of each element 32A, the first end e1 is exposed from the first main surface m1 of the resin casing 3 and 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 region 6 is exposed from the second main surface m2 opposite to the first main surface m1 and electrically connected to the second external electrode 5a. In Figure 5, the configuration of some elements 22A is omitted. Figure 5 shows the stacking direction D of the capacitor element 22, parallel to the first direction in which the pair of first ends e1 of the anode region 6 face each other. LIt is a schematic cross-sectional view when the solid electrolytic capacitor 21 is cut in a direction parallel thereto. For the configuration of FIG. 5 other than these, reference can be made to the description of FIG. 3.

[0105] When the solid electrolytic capacitor includes a laminate of a plurality of capacitor elements, the first end portions of the anode body regions of each capacitor element may be alternately exposed from the resin exterior body on the first main surface and the second main surface in the stacking direction of the laminate and electrically connected to the first external electrode.

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

[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 exterior body 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 element 32A and the metal foil (second layer) 9B are adhered via a conductive adhesive 16.

[0108] In the anode body region 6 of each element 32A, the first end portion e1 is in the stacking direction D LIn this configuration, the first main surface m1 and the second main surface m2 opposite to the first main surface m1 of the resin casing 3 are alternately exposed and electrically connected to the first external electrode 4a. In addition, one end of each metal foil (second layer) 9B is exposed from the third main surface m3 of the resin casing 3 and electrically connected to the second external electrode 5a. The other end of the metal foil (second layer) 9B is exposed from the fourth main surface m4 opposite to the third main surface m3 of the resin casing and electrically connected to the second external electrode 5a. In this case, the first and second directions intersect. For the configuration of Figures 6A and 6B other than those described above, please refer to the explanations in Figures 4 and 5. Note that the configuration of some elements 32A is omitted in Figures 6A and 6B.

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

[0110] Examples 1-6 Solid electrolytic capacitors were fabricated and their characteristics evaluated according to the following procedure.

[0111] (1) Preparation of the first assembly An anode body with a porous surface was fabricated by roughening both surfaces of a large sheet of electrolytic aluminum foil (100 μm thick) used as a substrate through etching.

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

[0113] A grid-like first insulating region was formed on both surfaces of the anode body using an inkjet method with an ink containing silicone resin and ethyl methyl ketone as a solvent. On each surface, the grid-like first insulating region was formed at positions opposite the anode body, as shown in Figure 2. In this way, multiple anode body regions, demarcated by the first insulating region, were formed on each surface of the anode body. On each surface of the anode body, 36 anode body regions were arranged in 10 rows in a matrix, and the size of each anode body region (capacitive effective area portion) was 2.7 mm vertically × 2.3 mm horizontally. In this way, the first assembly was prepared.

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

[0115] (2-2) Second process A polymerization solution (liquid composition) was prepared by adding 3,4-ethylenedioxythiophene monomer, a dopant, and ethylene glycol to a mixed solvent of deionized water and isopropyl alcohol, and then mixing. The monomer concentration in the polymerization solution 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 sulfisophthalic acid was used in Examples 3 and 6.

[0116] Chemical polymerization was carried out by immersing the first assembly, which had a 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 the cathode extraction layer and the formation of the second assembly stack A carbon layer, which is the first layer, was formed by screen printing a dispersion of graphite particles dispersed in water onto the surface of the solid electrolyte layer formed in (2) above, and then drying it. Drying was carried out at 130-180°C for 10-30 minutes. In this way, a precursor of the second assembly (the second assembly in which the solid electrolyte and the first layer were formed) was created.

[0118] A laminate was formed on a glass epoxy substrate by sequentially layering metal foil (electrolytic aluminum foil) punched into a predetermined pattern and a precursor of the second assembly via a conductive adhesive. This laminate was filled with a silver particle-containing paste containing silver particles and a binder resin (epoxy resin), and the binder resin was cured by heating at 150-200°C for 10-60 minutes to fix the laminate. In this way, a cathode extraction layer containing a carbon layer as the first layer and 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) Sealing with resin The laminate of the second assembly obtained in (3) above was placed in a mold, and the resin portion was formed by filling it with insulating resin by compression molding and sealing the laminate with insulating resin.

[0120] (5) Separation and formation of external electrodes The laminate of the second assembly, sealed with the insulating resin obtained in (4) above, was separated into individual capacitor element laminates using a diamond blade. This separation resulted in a state where a portion of the anode foil (anode portion) and a portion of the cathode foil (cathode portion) were exposed on the cut surface. External electrodes were joined to the exposed portions of the anode and cathode. In this way, a total of 360 solid electrolytic capacitors, including the capacitor element laminates and the resin casings sealing these laminates, were formed in one unit. The rated voltages of the solid electrolytic capacitors are the values ​​shown in Table 1 or Table 2.

[0121] Comparative Examples 1-4 In Examples 1-6 (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 as shown in Table 1 or Table 2 were formed in the same manner as in Examples 1-6. 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 and dried at 120°C for 5-10 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 and dried at 120°C for 5-10 minutes, repeating the application and drying of the second liquid dispersion alternately. In Comparative Examples 1 and 3, the application and drying of the second liquid dispersion was repeated four times. In Comparative Examples 2 and 4, the application and drying of the second liquid dispersion was repeated twice. In this way, a solid electrolyte layer was formed.

[0122] "evaluation" The following evaluations were performed using the second assembly with the solid electrolyte layer formed in Example and Comparative Example (2), or the solid electrolytic capacitor obtained in (5).

[0123] (a) Measurement of the thickness of the solid electrolyte layer In the second assembly obtained in (2) above, with the solid electrolyte layer formed, the thickness of the second assembly with the solid electrolyte layer was measured, and the thickness of the solid electrolyte layer per surface was determined by subtracting the thickness of the anode foil and multiplying by 0.5. The thickness of the solid electrolyte layer was measured at a total of nine locations on both surfaces of each anode region: the center of the anode region, the four ends of the anode, and the four midpoints between adjacent ends, and the measurement was averaged. Similarly, the thickness of the solid electrolyte layer was determined and averaged for 20 arbitrarily selected anode regions. In this way, the mean and standard deviation of the solid electrolyte layer thickness were obtained.

[0124] (b) Initial capacitance and ESR Under conditions of 20°C, the initial capacitance (μF) at 120 Hz and the initial ESR (mΩ) at 100 kHz were measured for each of 20 arbitrarily selected solid electrolytic capacitors using a 4-terminal LCR meter, and the average values ​​were calculated. For the initial capacitance, Examples 1-3 and Comparative Example 2 were evaluated using the ratio with the initial capacitance of Comparative Example 1 set to 1, while Examples 4-6 and Comparative Example 3 were evaluated using the ratio with the initial capacitance of Comparative Example 3 set to 1.

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

[0126] Solid electrolytic capacitors that did not show a leakage current exceeding 1 mA as described above were heated to 260°C, simulating a reflow process. More specifically, the solid electrolytic capacitors were heated from 25°C to 260°C over 2.5 minutes and 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 showing a leakage current exceeding 1 mA 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 represent Examples 1 to 6, and C1 to C4 represent Comparative Examples 1 to 4.

[0128] [Table 1]

[0129] [Table 2]

[0130] As shown in Tables 1 and 2, when forming a solid electrolyte layer using a liquid dispersion, it is necessary to repeat the application and drying of the liquid dispersion to some extent in order to suppress the leakage current failure rate (comparison of C1 and C2, comparison of C3 and C4). However, in C1 and C3, the variation in the thickness of the solid electrolyte layer also increases, and the ESR tends to be higher (comparison of C1 and C2, comparison of C3 and C4). In contrast, in the examples, a solid electrolyte layer of appropriate thickness is formed in a single chemical polymerization, and the variation in thickness is also reduced to some extent (comparison of E1-E3 and C1-C2, comparison of E4-E6 and 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 failure rate is significantly reduced, and the leakage current failure rate after reflow is also reduced to 0%. Furthermore, in the examples, a large capacitance is obtained and the ESR is kept low compared to C1 and C3. [Industrial applicability]

[0131] According to this disclosure, variations in the thickness of the solid electrolyte layer are suppressed, and solid electrolytic capacitors with superior capacitor performance can be manufactured in large quantities in a single batch. Furthermore, the manufacturing method according to this disclosure can also reduce the leakage current failure rate. Therefore, the manufacturing method according to this disclosure is suitable, for example, for the industrial manufacture 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) in a state where the second layer has not yet been formed), 3: Resin casing, 4a: First external electrode, 4b: Intermediate electrode layer, 4c: Contact layer, 5a: Second external electrode, 5b: Intermediate electrode layer, 6: Anode region (anode), 6A: Large anode (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: Laminate of solid electrolytic capacitor elements, S: Substrate, e1: First end of anode region 6, e2: Second end of anode 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

1. A method for manufacturing a solid electrolytic capacitor including a solid electrolytic capacitor element comprising an anode, a dielectric layer covering at least a portion of the anode, and a solid electrolyte layer covering at least a portion of the dielectric layer, A first assembly having a dielectric layer and a plurality of anode regions corresponding to a plurality of anodes arranged in the planar direction, a step of forming the solid electrolyte layer so as to cover at least a portion of the dielectric layer to form a second assembly having a plurality of solid electrolytic capacitor elements, The process includes separating the second assembly into individual solid electrolytic capacitor elements, The step of forming the aforementioned second aggregate is: A first step of forming a film containing manganese oxide that covers at least a portion of the dielectric layer, A second step involves 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, such that the thickness is uniform across all of the multiple anodes arranged in the planar direction. Includes, The aforementioned conjugated polymer contains monomer units corresponding to the thiophene compound, The dopant contains an aromatic sulfonic acid, and the method for manufacturing a solid electrolytic capacitor.

2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the dopant comprises sulfoisophthalic acid or sulfophthalic acid.

3. A method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, wherein in the first step, an aqueous solution containing manganese nitrate is deposited on the surface of the dielectric layer, and the coating is formed by thermally decomposing the manganese nitrate in a humidified atmosphere to produce the manganese oxide.

4. Furthermore, the process includes forming a stack of the second assembly, which includes a stack of the multiple solid electrolytic capacitor elements, A method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 3, wherein in the step of separating the second assembly into individual pieces, the laminate of the solid electrolytic capacitor elements is separated into individual pieces for each laminate of solid electrolytic capacitor elements.

5. Furthermore, the process includes a step of forming a resin portion that covers the laminate of the second assembly by sealing the laminate of the second assembly with resin. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein in the step of separating the pieces, the laminate of the second assembly is separated together with the resin portion to form the solid electrolytic capacitor comprising the laminate of solid electrolytic capacitor elements and the resin outer casing containing the resin that seals the laminate of solid electrolytic capacitor elements.

6. The method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 5, wherein the first assembly includes an insulating region that demarcates adjacent anode regions.

7. The method for manufacturing a solid electrolytic capacitor according to claim 6, wherein the insulating region includes a water-repellent material.

8. A method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 7, wherein the chemical polymerization is carried out in one step in the second step.

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