Solid electrolytic capacitor and method for manufacturing solid electrolytic capacitor

Abstract

A solid electrolytic capacitor (10) is provided with: a laminate (20) in which a plurality of capacitor elements (21) each having an anode foil (22) and a plurality of cathode foils (26) are laminated; an exterior resin (30) that covers the laminate (20) and has a first end surface (31) in which a part of each anode foil (22) is exposed and a second end surface (32) in which a part of each cathode foil (26) is exposed; an anode external electrode (40) electrically connected to each of the anode foils (22) at the first end surface (31); and a cathode external electrode (50) electrically connected to each of the cathode foils (26) at the second end surface (32). A first end point (P1) is defined as an end point on the mounting surface (33) side of the exterior resin (30) on the second end surface (32), and a first average distance from the first end point (P1) to each of the cathode foils (26) in the second end surface (32) is smaller than a second average distance from the first end point (P1) to each of the cathode foils (26) in a region (R1) in which the capacitor element (21) overlaps the cathode foils (26) in the stacking direction LD of the stacked body (20). As a result, ESR can be reduced.

Description

Technical Field

[0001] This disclosure relates to solid electrolytic capacitors and methods for manufacturing solid electrolytic capacitors. Background Technology

[0002] Conventionally, electrolytic capacitors using solid electrolytes (solid electrolytic capacitors) are known (e.g., Patent Document 1). The solid electrolytic capacitor of Patent Document 1 comprises: a laminate consisting of multiple capacitor elements, each having an anode foil, and multiple cathode foils, stacked together; and an outer resin covering the laminate. The outer resin has a first end face exposing a portion of each anode foil and a second end face exposing a portion of each cathode foil. The solid electrolytic capacitor also includes an anode terminal electrically connected to each anode foil at the first end face and a cathode terminal electrically connected to each cathode foil at the second end face.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-86459 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The solid electrolytic capacitor in Patent Document 1 was proposed as a solid electrolytic capacitor with a low equivalent series resistance (ESR), but its ESR is not low enough. Under such circumstances, one of the objectives of this disclosure is to reduce the ESR.

[0008] Methods for solving problems

[0009] One aspect of this disclosure relates to a solid electrolytic capacitor. The solid electrolytic capacitor comprises: a laminate formed by stacking a plurality of capacitor elements, each having an anode foil, and a plurality of cathode foils; an outer resin covering the laminate, having a first end face exposing a portion of each of the anode foils and a second end face exposing a portion of each of the cathode foils; an external anode electrode electrically connected to each of the anode foils at the first end face; and an external cathode electrode electrically connected to each of the cathode foils at the second end face, wherein the endpoint on the mounting surface side of the outer resin at the second end face is designated as the first endpoint, and in the stacking direction of the laminate, a first average distance from the first endpoint to each of the cathode foils in the second end face is less than a second average distance from the first endpoint to each of the cathode foils in the region where the capacitor elements and the cathode foils overlap.

[0010] Another aspect of this disclosure relates to a method for manufacturing a solid electrolytic capacitor. This method comprises: a preparation step for preparing the aforementioned laminate; and a molding step for forming the outer resin by compression molding in a manner that supplies resin material to the laminate from a side opposite to the mounting surface.

[0011] Invention Effects

[0012] According to this disclosure, ESR can be reduced.

[0013] The novel features of the invention are set forth in the appended claims; however, the invention should be more fully understood, in both its structure and content, together with its other objects and features, by referring to the following detailed description of the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view schematically illustrating an example of a solid electrolytic capacitor of the present disclosure.

[0015] Figure 2 This is a cross-sectional view of a solid electrolytic capacitor. Figure 2 (a) is along Figure 1 The cross-sectional view of line AA is shown, and the second end face is also shown. Figure 2 (b) is along Figure 1 The cross-sectional view of the BB line is shown, and the capacitor element is omitted. Figure 2 (c) is along Figure 1 A cross-sectional view of the CC line is shown, and the first end face is also shown. Detailed Implementation

[0016] The following description illustrates embodiments of the solid electrolytic capacitor and its manufacturing method according to the present disclosure. However, the present disclosure is not limited to the examples described below. Specific values ​​and materials are sometimes illustrated in the following description, but other values ​​and materials may be applied as long as the effects of the present disclosure are achieved.

[0017] (Solid electrolytic capacitor)

[0018] The solid electrolytic capacitor disclosed herein is a so-called end-face collector type solid electrolytic capacitor. The solid electrolytic capacitor of this disclosure includes a laminate, an outer resin, an external anode electrode, and an external cathode electrode.

[0019] A laminate is composed of multiple capacitor elements and multiple cathode foils stacked together. Each capacitor element has an anode foil. Each cathode foil may be thinner than each anode foil.

[0020] The anode foil can be made of valve-acting metals such as aluminum, tantalum, niobium, and titanium, or alloys or compounds containing these valve-acting metals. The surface of the anode foil can be roughened by etching or the like. At least a portion of the surface of the anode foil is formed with a dielectric layer (e.g., a layer of oxide of the valve-acting metal), and at least a portion of the dielectric layer is covered by a solid electrolyte layer. At least a portion of the solid electrolyte layer can be covered by a conductive layer.

[0021] The dielectric layer can be composed of an oxide (e.g., aluminum oxide) formed on the surface of the anode foil by liquid phase methods such as anodic oxidation, vapor deposition, atomic layer deposition, etc.

[0022] The solid electrolyte layer may contain conductive polymers. Dopants may be further incorporated into the solid electrolyte layer as needed.

[0023] As the conductive polymer, known conductive polymers used in solid electrolytic capacitors can be used, such as π-conjugated conductive polymers. Examples of conductive polymers include those with a basic backbone of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylidene, polyphenylene oxide, and polythiophene vinylidene. Among these, polymers with a basic backbone of polypyrrole, polythiophene, or polyaniline are preferred. The aforementioned polymers also include homopolymers, copolymers of two or more monomers, and their derivatives (substitutes with substituents, etc.). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). A single conductive polymer can be used, or two or more can be used in combination.

[0024] As dopants, at least one selected from low-molecular-weight anions and polyanions may be used. Examples of low-molecular-weight anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions, without particular limitation. Examples of dopants that generate organic sulfonate ions include benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. Examples of polyanions include high-molecular-weight polysulfonic acids and high-molecular-weight polycarboxylic acids. Examples of high-molecular-weight polysulfonic acids include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polypropylenesulfonic acid, and polymethpropylenesulfonic acid. Examples of high-molecular-weight polycarboxylic acids include polyacrylic acid and polymethacrylic acid. Polyanions also include polyester sulfonic acid and phenol sulfonic acid phenolic resins. However, polyanions are not limited to these.

[0025] The solid electrolyte layer may further include known additives and known conductive materials other than conductive polymers, as needed. Examples of such conductive materials include at least one selected from conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0026] The conductive layer may consist solely of a carbon layer formed on the surface of the solid electrolyte layer, or it may consist of a carbon layer and a conductive layer formed on the surface of the carbon layer. The conductive layer may also be composed of a silver paste. As the silver paste, for example, a composition containing silver particles and a resin component (binder resin) may be used. As the resin component, thermoplastic resins may also be used, but thermosetting resins such as imide resins and epoxy resins are preferred.

[0027] The cathode foil can be made of metals such as gold, silver, copper, aluminum, or nickel. The surface of the cathode foil can be roughened by etching or other methods, or further coated with carbon or the like. The cathode foil can be connected to the conductive layer via a conductive adhesive, for example. The conductivity of the material constituting the cathode foil can be higher than the conductivity of the material constituting the external cathode electrode.

[0028] An outer resin-coated laminate. The outer resin has a first end face exposed on a portion of each anode foil and a second end face exposed on a portion of each cathode foil. The first and second end faces may also be oriented in opposite directions. The shape of each of the first and second end faces is not particularly limited; for example, it may be flat, curved, or at least partially convex or concave. The outer resin may also be composed of an insulating resin material. The outer resin may, for example, be a cured thermosetting resin containing epoxy resin, and may also contain fillers as needed.

[0029] The external anode electrode is electrically connected to each anode foil at the first end face of the outer resin. The external anode electrode can be made of silver, copper, a copper alloy, aluminum, or an aluminum alloy, and can be plated. A plating layer, conductive adhesive, etc., may or may not be sandwiched between the external anode electrode and each anode foil. The external anode electrode can have a single-layer structure or a multi-layer structure. A multi-layer external anode electrode, for example, can have at least one metal layer and at least one plating layer. A portion of the external anode electrode can extend along the mounting surface of the outer resin (the mounting surface of the solid electrolytic capacitor).

[0030] The external cathode electrode is electrically connected to each cathode foil at the second end face of the outer resin. The external cathode electrode can be made of silver, copper, copper alloy, aluminum, or aluminum alloy, and can be plated. The constituent materials of the external cathode electrode can be the same as or different from those of the external anode electrode. A plating layer, conductive adhesive, etc., may or may not be sandwiched between the external cathode electrode and each cathode foil. The external cathode electrode can have a single-layer structure or a multi-layer structure. A multi-layer external cathode electrode, for example, can have at least one metal layer and at least one plating layer. A portion of the external cathode electrode can extend along the mounting surface of the outer resin (the mounting surface of the solid electrolytic capacitor).

[0031] The endpoint on the mounting surface side of the outer resin at the second end face of the outer resin is designated as the first endpoint. In this case, in the stacking direction of the laminate (e.g., the direction perpendicular to the mounting surface), the first average distance from the first endpoint to each cathode foil in the second end face is less than the second average distance from the first endpoint to each cathode foil in the region where the capacitor element overlaps with the cathode foil (e.g., the region including the midpoint between the first and second end faces; hereinafter also referred to as the overlapping region). Here, the average distance from the first endpoint to each cathode foil in the stacking direction is the value obtained by dividing the sum of the shortest distances from the first endpoint to each cathode foil in the stacking direction by the number of cathode foils in the solid electrolytic capacitor.

[0032] Thus, in the solid electrolytic capacitor of this disclosure, the first average distance in the second end face is less than the second average distance in the repeating region. That is, at the second end face, which serves as the connection point between each cathode foil and the external cathode electrode, the plurality of cathode foils are generally arranged close to the mounting surface. Therefore, when the solid electrolytic capacitor of this disclosure is mounted on a substrate, for example, compared to mounting the solid electrolytic capacitor of Patent Document 1 on a substrate, the total current path from the wiring of the substrate to each cathode foil is shortened. Therefore, the ESR of the solid electrolytic capacitor can be reduced. It should be noted that the first average distance is preferably 90% or less of the second average distance, and more preferably 80% or less of the second average distance.

[0033] At least one pair of cathode foils, adjacent to each other and spaced apart in the lamination direction, may be present on the second end face. Such at least one pair of cathode foils may exist on the mounting surface side among multiple cathode foils. For example, in the case of 8 cathode foils, 3 to 5 cathode foils on the mounting surface side may be spaced apart from each other. With this configuration, when the laminate is coated with an external resin, structural damage to the laminate caused by excessive force applied to the cathode foils can be suppressed.

[0034] At least one pair of anode foils, adjacent to each other and spaced apart in the lamination direction, may be present on the first end face. Such a pair of anode foils may exist on the mounting surface side among a plurality of anode foils. The ratio of the number of spaced-apart anode foils to the total number of anode foils may be higher than the ratio of the number of spaced-apart cathode foils to the total number of cathode foils. For example, in the case of seven anode foils, five to seven anode foils on the mounting surface side may be spaced apart from each other. With this configuration, when the laminate is coated with an external resin, damage to the anode foils due to excessive force can be suppressed.

[0035] The outer resin may contain fillers. The filler content in the outer resin may be 85% by weight or more and 95% by weight or less. With this configuration, the physical properties of the outer resin can be achieved that are particularly suitable for realizing the structure of the solid electrolytic capacitor of this disclosure.

[0036] The flexural modulus of the outer resin at 25°C can be 20 GPa or higher. This configuration enables the achievement of outer resin properties that are particularly suitable for realizing the structure of the solid electrolytic capacitor disclosed herein.

[0037] The glass transition temperature of the outer resin can be 135°C or higher. This configuration enables the achievement of outer resin properties particularly suitable for realizing the structure of the solid electrolytic capacitor disclosed herein.

[0038] (Manufacturing method of solid electrolytic capacitor)

[0039] The method for manufacturing the solid electrolytic capacitor disclosed herein is a method for manufacturing the aforementioned solid electrolytic capacitor, the method comprising a preparation step and a molding step.

[0040] In the preparation step, the above-mentioned laminate is prepared. In the preparation step, for example, the laminate can be prepared by alternately laminating multiple anode foils and multiple cathode foils.

[0041] In the molding process, the outer casing resin is formed by compression molding, in which resin material is supplied to the laminate from the side opposite to the mounting surface. Through compression molding, for example, after granular resin material is placed in the mold, pressure is applied while the heated mold is closed to fill and form the outer casing resin, allowing the resin material to melt. Because the resin material is supplied to the laminate from the side opposite to the mounting surface, a pressure is applied to the laminate, pressing it towards the mounting surface. This pressure causes deformation of the area near the second end face of at least one cathode foil, pressing it towards the mounting surface. As a result, the first average distance becomes smaller than the second average distance, and even a solid electrolytic capacitor with low ESR can be obtained.

[0042] The outer resin may contain fillers. The content of the fillers in the outer resin may be 85% by weight or more and 95% by weight or less. With this configuration, the characteristics of the outer resin, which are particularly suitable for realizing the structure of the solid electrolytic capacitor of this disclosure by the compression molding method described above, can be achieved.

[0043] The flexural modulus of the outer resin at 25°C can be 20 GPa or higher. This configuration enables the achievement of properties in the outer resin that are particularly suitable for realizing the structure of the solid electrolytic capacitor of this disclosure via the compression molding method described above.

[0044] The glass transition temperature of the outer resin can be 135°C or higher. This configuration enables the achievement of outer resin properties particularly suitable for realizing the structure of the solid electrolytic capacitor of this disclosure via the compression molding method described above.

[0045] As described above, according to this disclosure, the ESR of a solid electrolytic capacitor can be reduced by making the first average distance in the second end face smaller than the second average distance in the repeating region.

[0046] Hereinafter, an example of a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor according to the present disclosure will be specifically described with reference to the accompanying drawings. The constituent elements and processes of the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor in the example described below can be applied using the aforementioned constituent elements and processes. The constituent elements and processes of the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor in the example described below can be modified based on the above description. Furthermore, the matters described below can be applied to the above embodiments. Constituent elements and processes in the constituent elements and processes of the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor in the example described below that are not essential for the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor according to the present disclosure may also be omitted. It should be noted that the figures shown below are schematic and do not accurately reflect the actual shape and number of components.

[0047] (Solid electrolytic capacitor)

[0048] The solid electrolytic capacitor 10 in this embodiment is a so-called end-face collector type solid electrolytic capacitor, such as... Figure 1 and Figure 2 As shown, it comprises a laminate 20, an outer resin 30, an external anode electrode 40, and an external cathode electrode 50.

[0049] The stack 20 is composed of multiple (three in this example) capacitor elements 21 and multiple (four in this example) cathode foils 26 stacked alternately. Each of the multiple capacitor elements 21 has an anode foil 22.

[0050] In this embodiment, the anode foil 22 is formed in a rectangular sheet shape, and its surface is roughened. A dielectric layer 23 is formed on at least a portion of the surface of the anode foil 22, and at least a portion of the dielectric layer 23 is covered by a solid electrolyte layer 24. At least a portion of the solid electrolyte layer 24 is covered by a conductive layer 25.

[0051] In this embodiment, the cathode foil 26 is formed into a rectangular sheet with a roughened surface. The cathode foil 26 is electrically connected to the conductive layer 25 of the anode foil 22 via a conductive adhesive (not shown). The cathode foil 26 is made of a material with a higher conductivity than the constituent material of the cathode external electrode 50.

[0052] The outer resin 30 is coated with the laminate 20. The outer resin 30 has a first end face 31 exposed on a portion of each anode foil 22 (in Figure 1 The right end face (in the middle) and a portion of the second end face 32 exposed on each cathode foil 26 (in Figure 1 (The left end face is shown in the middle). The outer resin 30 is composed of an insulating resin material. The outer resin 30 contains filler (not shown) at a content of 85% to 95% by weight. The flexural modulus of the outer resin 30 at 25°C is 20 GPa or more, for example, 20 GPa or more and 35 GPa or less. The glass transition temperature of the outer resin 30 is 135°C or more, for example, 135°C or more and 160°C or less.

[0053] The external anode electrode 40 is electrically connected to each anode foil 22 at the first end face 31 of the outer resin 30. In this embodiment, the external anode electrode 40 is electrically connected to each anode foil 22 via a conductive adhesive 60, but is not limited thereto. The external anode electrode 40 has a first portion 41 extending along the first end face 31, and a mounting surface 33 continuous with the first portion 41 and extending along the outer resin 30. Figure 1 The second part 42 extends from the lower surface of the middle.

[0054] The external cathode electrode 50 is electrically connected to each cathode foil 26 at the second end face 32 of the outer resin 30. In this embodiment, the external cathode electrode 50 is electrically connected to each cathode foil 26 via a conductive adhesive 60, but is not limited thereto. The external cathode electrode 50 has a third portion 51 extending along the second end face 32 and a fourth portion 52 that is continuous with the third portion 51 and extends along the mounting surface 33 of the outer resin 30.

[0055] The endpoint on the mounting surface 33 side of the outer resin 30 at the second end face 32 of the outer resin 30 is designated as the first endpoint P1. At this time, in the lamination direction LD of the laminate 20, the first average distance AD1 from the first endpoint P1 to each cathode foil 26 in the second end face 32 is less than the second average distance AD2 from the first endpoint P1 to each cathode foil 26 in the overlapping region R1 (i.e., the region where the capacitor element 21 and the cathode foil 26 overlap). The relationship between this first average distance AD1 and the second average distance AD2 is as follows: Figure 1 As shown, this is because, as it moves from the repeating region R1 toward the second end face 32, at least a portion of the cathode foil 26 is shaped to be inclined toward the mounting surface 33.

[0056] In this embodiment, the shortest distance from the first endpoint P1 to each cathode foil 26 on the second end face 32 is set as D11 to D14 respectively (refer to...). Figure 2(a) Based on the formula AD1 = (D11 + D12 + D13 + D14) / 4, the first average distance AD1 is calculated. Similarly, the shortest distances from the first endpoint P1 to each cathode foil 26 in the repeating region R1 are set as D21 to D24 respectively (refer to...). Figure 2 (b) The second average distance AD2 is calculated based on the formula AD2 = (D21 + D22 + D23 + D24) / 4. Here, of course, the two formulas can be appropriately modified according to the number of cathode foils 26. It should be noted that in... Figure 2 (b) shows the first endpoint P1, which is in the opposite direction of the first end face 31 and the second end face 32. Figure 1 The first endpoint P1 is projected onto the cross-sectional position of the figure in the left-right direction.

[0057] like Figure 2 As shown in (a), at least one pair of cathode foils 26 are present on the second end face 32, adjacent to each other and spaced apart in the stacking direction LD. In this example, the pair of cathode foils 26 on the mounting surface 33 side corresponds to this. Additionally, as... Figure 2 As shown in (c), there is at least one pair of anode foils 22 that are adjacent to each other and spaced apart in the stacking direction LD on the first end face 31. In this example, all the cathode foils 26 correspond to this.

[0058] (Manufacturing method of solid electrolytic capacitor)

[0059] The manufacturing method of the solid electrolytic capacitor in this embodiment is a method for manufacturing the solid electrolytic capacitor 10 described above, and the manufacturing method includes a preparation step and a molding step.

[0060] In the preparation process, the aforementioned laminate 20 is prepared. In the preparation process, the laminate 20 is prepared by alternately laminating multiple anode foils 22 and multiple cathode foils 26.

[0061] In the molding process, from the side opposite to the mounting surface 33 ( Figure 1 The outer resin 30 is formed by compression molding, in which resin material is supplied to the laminate 20 from the upper side. It should be noted that, in practice, because molten resin material is added to a predetermined mold for supply, the laminate 20 is formed with... Figure 1 The orientation shown is opposite to the top and bottom for use in the molding process.

[0062] Postscript

[0063] The following technology has been disclosed through the above description of the embodiments.

[0064] (Technology 1)

[0065] A solid electrolytic capacitor, comprising:

[0066] A laminate is formed by stacking multiple capacitor elements, each having an anode foil, and multiple cathode foils.

[0067] The outer resin covers the laminate and has a first end face exposed in a portion of each of the anode foils and a second end face exposed in a portion of each of the cathode foils;

[0068] An external anode electrode, electrically connected to each of the aforementioned anode foils at the first end face; and

[0069] The external cathode electrode is electrically connected to each of the aforementioned cathode foils at the second end face.

[0070] The endpoint of the mounting surface of the outer resin at the second end face is designated as the first endpoint. In the stacking direction of the laminate, the first average distance from the first endpoint to each cathode foil in the second end face is less than the second average distance from the first endpoint to each cathode foil in the area where the capacitor element overlaps with the cathode foil.

[0071] (Technology 2)

[0072] According to the solid electrolytic capacitor described in Technique 1, at least one pair of cathode foils are present at the second end face, which are adjacent to each other and spaced apart in the stacking direction.

[0073] (Technology 3)

[0074] According to the solid electrolytic capacitor described in technique 1 or 2, at the first end face there are at least one pair of anode foils that are adjacent to each other and spaced apart in the stacking direction.

[0075] (Technology 4)

[0076] According to any one of the techniques 1 to 3, in the solid electrolytic capacitor, the outer resin contains filler.

[0077] The content of the filler in the aforementioned outer resin is 85% by weight or more and 95% by weight or less.

[0078] (Technology 5)

[0079] According to any one of the techniques 1 to 4, the solid electrolytic capacitor wherein the flexural modulus of the outer resin at 25°C is 20 GPa or more.

[0080] (Technology 6)

[0081] According to any one of the techniques 1 to 5, the glass transition temperature of the outer resin is 135°C or higher.

[0082] (Technology 7)

[0083] A method for manufacturing a solid electrolytic capacitor, which is a method for manufacturing a solid electrolytic capacitor according to any one of techniques 1 to 6, wherein the manufacturing method comprises:

[0084] Preparation process, including preparing the above-mentioned laminated body; and

[0085] The molding process involves forming the outer resin by compression molding, in which resin material is supplied to the laminate from the side opposite to the mounting surface.

[0086] (Technology 8)

[0087] According to the manufacturing method of the solid electrolytic capacitor described in Technique 7, the aforementioned outer resin contains filler.

[0088] The content of the filler in the aforementioned outer resin is 85% by weight or more and 95% by weight or less.

[0089] (Technology 9)

[0090] According to the manufacturing method of the solid electrolytic capacitor described in Technique 7 or 8, the flexural modulus of the outer resin at 25°C is 20 GPa or more.

[0091] (Technology 10)

[0092] According to any one of the technical methods 7 to 9, the glass transition temperature of the outer resin is 135°C or higher.

[0093] Example

[0094] The ESR of the solid electrolytic capacitors of Examples 1 and 2 and Comparative Examples 1 and 2 shown below was evaluated.

[0095] Example 1

[0096] A laminate is constructed by alternately stacking seven capacitor elements and eight cathode foils. The laminate is coated with an outer resin. A portion of each anode foil is exposed from the first end face of the outer resin. In the first end face, all anode foils are spaced apart from each other. An external anode electrode is electrically connected to each anode foil at the first end face. A portion of each cathode foil is exposed from the second end face of the outer resin. In the second end face, four cathode foils on the mounting surface are spaced apart from each other, while the remaining four cathode foils are in contact with each other. An external cathode electrode is electrically connected to each cathode foil at the second end face. The first average distance in the second end face is set to 76% of the second average distance in the repeating region. The ESR of the solid electrolytic capacitor of Example 1 is 90% of the ESR of the solid electrolytic capacitor of Comparative Example 1.

[0097] Example 2

[0098] A laminate is constructed by alternately stacking seven capacitor elements and eight cathode foils. The laminate is coated with an outer resin. A portion of each anode foil is exposed from the first end face of the outer resin. In the first end face, all anode foils are spaced apart from each other. An external anode electrode is electrically connected to each anode foil at the first end face. A portion of each cathode foil is exposed from the second end face of the outer resin. In the second end face, all cathode foils are in contact with each other on the mounting surface side. An external cathode electrode is electrically connected to each cathode foil at the second end face. The first average distance in the second end face is set to 33% of the second average distance in the repeating region. The ESR of the solid electrolytic capacitor of Example 2 is 78% of the ESR of the solid electrolytic capacitor of Comparative Example 1.

[0099] Comparative Example 1

[0100] A laminate is constructed by alternately stacking seven capacitor elements and eight cathode foils. The laminate is coated with an outer resin. A portion of each anode foil is exposed from the first end face of the outer resin. All anode foils are spaced apart from each other on the first end face. An external anode electrode is electrically connected to each anode foil at the first end face. A portion of each cathode foil is exposed from the second end face of the outer resin. All cathode foils are spaced apart from each other on the second end face. An external cathode electrode is electrically connected to each cathode foil at the second end face. It should be noted that in Comparative Example 1, the anode and cathode foils extend parallel to each other throughout the entire structure. That is, in the solid electrolytic capacitor of Comparative Example 1, the first average distance and the second average distance are equal to each other.

[0101] Comparative Example 2

[0102] A laminate is constructed by alternately stacking seven capacitor elements and eight cathode foils. The laminate is coated with an outer resin. A portion of each anode foil is exposed from the first end face of the outer resin. In the first end face, all anode foils are spaced apart from each other. An external anode electrode is electrically connected to each anode foil at the first end face. A portion of each cathode foil is exposed from the second end face of the outer resin. In the second end face, all cathode foils are in contact with each other on the side opposite to the mounting surface. An external cathode electrode is electrically connected to each cathode foil at the second end face. The first average distance in the second end face is set to 167% of the second average distance in the repeating region. The ESR of the solid electrolytic capacitor of Comparative Example 2 is 152% of the ESR of the solid electrolytic capacitor of Comparative Example 1.

[0103] As described above, the solid electrolytic capacitors of Comparative Examples 1 and 2 have lower ESRs compared to those of Comparative Examples 1 and 2. Therefore, it can be said that each embodiment demonstrates superiority.

[0104] The invention has been described through the present preferred embodiments, but such disclosure should not be interpreted as restrictive. Various modifications and alterations will undoubtedly be apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the scope of the appended claims should be interpreted to include all modifications and alterations without departing from the true spirit and scope of the invention.

[0105] Industrial availability

[0106] This disclosure can be used for solid electrolytic capacitors and methods for manufacturing solid electrolytic capacitors.

[0107] Symbol Explanation

[0108] 10: Solid electrolytic capacitors

[0109] 20: Layered bodies

[0110] 21: Capacitor Components

[0111] 22: Anode foil

[0112] 23: Dielectric layer

[0113] 24: Solid electrolyte layer

[0114] 25: Conductive layer

[0115] 26: Cathode foil

[0116] 30: Outer resin

[0117] 31: First end face

[0118] 32: Second end face

[0119] 33: Mounting surface

[0120] 40: External electrode of anode

[0121] 41: Part 1

[0122] 42: Part 2

[0123] 50: External electrode of cathode

[0124] 51: Part 3

[0125] 52: Part 4

[0126] 60: Conductive adhesives

[0127] AD1: First Average Distance

[0128] AD2: Second average distance

[0129] D11~D14: The shortest distance from the first endpoint to each cathode foil on the second end face.

[0130] D21~D24: The shortest distance from the first endpoint to each cathode foil in the repeating region.

[0131] LD: Stacking direction

[0132] P1: First endpoint

[0133] R1: Repeating region

Claims

1. A solid electrolytic capacitor comprising: a laminate obtained by stacking a plurality of capacitor elements each having an anode foil and a plurality of cathode foils; an encapsulating resin covering the laminate and having a first end surface from which a part of each of the anode foils is exposed and a second end surface from which a part of each of the cathode foils is exposed; an anode external electrode electrically connected to each of the anode foils at the first end surface; and a cathode external electrode electrically connected to each of the cathode foils at the second end surface, wherein an end point of a mounting surface side of the encapsulating resin at the second end surface is set as a first end point, and a first average distance from the first end point to each of the cathode foils in the second end surface in a stacking direction of the laminate is smaller than a second average distance from the first end point to each of the cathode foils in a region where the capacitor elements overlap with the cathode foils.

2. The solid electrolytic capacitor according to claim 1, wherein at least one pair of the cathode foils adjacent to each other and spaced apart in the stacking direction is present at the second end surface.

3. The solid electrolytic capacitor according to claim 1 or 2, wherein at least one pair of the anode foils adjacent to each other and spaced apart in the stacking direction is present at the first end surface. the encapsulating resin contains a filler, a content rate of the filler in the encapsulating resin is 85% by weight or more and 95% by weight or less. a bending elastic modulus of the encapsulating resin at 25°C is 20 GPa or more. a glass transition temperature of the encapsulating resin is 135°C or more.

7. A manufacturing method of a solid electrolytic capacitor, which is a method of manufacturing the solid electrolytic capacitor according to claim 1 or 2, the manufacturing method comprising: a preparation step of preparing the laminate; and a molding step of forming the encapsulating resin using a compression molding method in a manner that a resin material is supplied to the laminate from a side opposite to the mounting surface.

4. The solid electrolytic capacitor according to claim 1 or 2, wherein the encapsulating resin contains a filler, a content rate of the filler in the encapsulating resin is 85% by weight or more and 95% by weight or less.

5. The solid electrolytic capacitor according to claim 1 or 2, wherein a bending elastic modulus of the encapsulating resin at 25°C is 20 GPa or more.

6. The solid electrolytic capacitor according to claim 1 or 2, wherein a glass transition temperature of the encapsulating resin is 135°C or more. ​ ​ ​ 8. The method of producing a solid electrolytic capacitor according to claim 7, wherein ​ ​ 9. The method of producing a solid electrolytic capacitor according to claim 7, wherein ​ 10. The method of producing a solid electrolytic capacitor according to claim 7, wherein ​

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