Solid electrolytic capacitor and method for manufacturing solid electrolytic capacitor

Abstract

A solid electrolytic capacitor 10 comprises: 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 covering the laminate 20 and having a first end surface 31 exposing a part of each anode foil 22 and a second end surface 32 exposing a part of each cathode foil 26; an anode external electrode 40 electrically connected to each anode foil 22 on the first end surface 31; and a cathode external electrode 50 electrically connected to each cathode foil 26 on the second end surface 32. When an end point on the second end surface 32 on the mounting surface 33 side of the exterior resin 30 is a first end point P1, a first average distance from the first end point P1 to each cathode foil 26 on the second end surface 32 in a lamination direction LD of the laminate 20 is smaller than a second average distance from the first end point P1 to each cathode foil 26 in a region R1 where the capacitor elements 21 and the cathode foils 26 overlap. Thus, ESR can be reduced.

Description

Solid electrolytic capacitor and method for manufacturing the same

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

[0002] Electrolytic capacitors using a solid electrolyte (solid electrolytic capacitors) have been known (see, for example, Patent Document 1). The solid electrolytic capacitor in Patent Document 1 includes a laminate including multiple capacitor elements, each having an anode foil, and multiple cathode foils, and an exterior resin covering the laminate. The exterior resin has a first end surface from which a portion of each anode foil is exposed and a second end surface from which a portion of each cathode foil is exposed. The solid electrolytic capacitor further includes an anode terminal electrically connected to each anode foil at the first end surface and a cathode terminal electrically connected to each cathode foil at the second end surface.

[0003] Japanese Patent Application Laid-Open No. 2003-86459

[0004] Although the solid electrolytic capacitor of Patent Document 1 is proposed as having a low equivalent series resistance (ESR), the ESR is not sufficiently low. In this situation, one of the objectives of the present disclosure is to reduce the ESR.

[0005] One aspect of the present disclosure relates to a solid electrolytic capacitor, the solid electrolytic capacitor comprising: a laminate including a plurality of capacitor elements each having an anode foil and a plurality of cathode foils stacked together; an exterior resin covering the laminate and having a first end face at which a portion of each anode foil is exposed and a second end face at which a portion of each cathode foil is exposed; an anode external electrode electrically connected to each anode foil at the first end face; and a cathode external electrode electrically connected to each cathode foil at the second end face, wherein a first end point of the exterior resin on a mounting surface side of the second end face is defined as a first end point, and a first average distance from the first end point on the second end face to each of the cathode foils in a stacking direction of the laminate is shorter than a second average distance from the first end point to each of the cathode foils in a region where the capacitor element and the cathode foil overlap.

[0006] Another aspect of the present disclosure relates to a method for manufacturing the solid electrolytic capacitor described above, the method including: a preparation step of preparing the laminate; and a molding step of forming the exterior resin by a compression molding method in which a resin material is supplied to the laminate from the side opposite the mounting surface.

[0007] According to the present disclosure, the ESR can be reduced.

[0008] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present application, will be better understood from the following detailed description taken in conjunction with the drawings.

[0009] 1A is a cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure, showing a second end face along line A-A in FIG. 1 , a cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure along line B-B in FIG. 1 , with the capacitor element omitted, and a cross-sectional view of a first end face along line C-C in FIG. 1 .

[0010] The following describes examples of embodiments of a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor according to the present disclosure. However, the present disclosure is not limited to the examples described below. While the following description may use specific numerical values ​​and materials, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0011] (Solid Electrolytic Capacitor) The solid electrolytic capacitor according to the present disclosure is a so-called end-collection type solid electrolytic capacitor, and includes a laminate, an exterior resin, an anode external electrode, and a cathode external electrode.

[0012] The laminate includes a plurality of capacitor elements and a plurality of cathode foils stacked together, each of the plurality of capacitor elements having an anode foil, and each of the cathode foils may be thinner than each of the anode foils.

[0013] The anode foil may be made of a valve metal such as aluminum, tantalum, niobium, or titanium, or an alloy or compound containing such a valve metal. The surface of the anode foil may be roughened by etching or the like. A dielectric layer (e.g., a layer of an oxide of the valve metal) is formed on at least a portion of the surface of the anode foil, and at least a portion of the dielectric layer is covered with a solid electrolyte layer. At least a portion of the solid electrolyte layer may be covered with a conductive layer.

[0014] The dielectric layer may be made of an oxide (for example, aluminum oxide) formed on the surface of the anode foil by a liquid phase method such as anodization, or a gas phase method such as vapor deposition or atomic layer deposition.

[0015] The solid electrolyte layer may contain a conductive polymer and, if necessary, may further contain a dopant.

[0016] Conductive polymers that can be used include known polymers used in solid electrolytic capacitors, such as π-conjugated conductive polymers. Examples of conductive polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. Of these, polymers with a basic skeleton of polypyrrole, polythiophene, or polyaniline are preferred. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (e.g., substituted products having substituents). For example, polythiophenes include poly(3,4-ethylenedioxythiophene). Conductive polymers may be used alone or in combination.

[0017] The dopant may be, for example, at least one selected from the group consisting of low molecular weight anions and polyanions. Examples of low molecular weight anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Examples of dopants that generate organic sulfonate ions include benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. Examples of polyanions include polymeric polysulfonic acids and polymeric polycarboxylic acids. Examples of polymeric polysulfonic acids include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylicsulfonic acid, and polymethacrylicsulfonic acid. Examples of polymeric polycarboxylic acids include polyacrylic acid and polymethacrylic acid. Examples of polyanions include polyestersulfonic acid and phenolsulfonic acid novolac resin. However, the polyanions are not limited to these.

[0018] The solid electrolyte layer may further contain, as necessary, known additives and known conductive materials other than conductive polymers, such as at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0019] The conductive layer may be composed of only a carbon layer formed on the surface of the solid electrolyte layer, or may be composed of a carbon layer and a conductive layer formed on the surface of the carbon layer. The conductive layer may 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, a thermoplastic resin may be used, but it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.

[0020] The cathode foil may be made of a metal such as gold, silver, copper, aluminum, or nickel. The surface of the cathode foil may be roughened by etching or the like, and may further be coated with carbon or the like. The cathode foil may be connected to the conductive layer via, for example, a conductive adhesive. The conductivity of the material constituting the cathode foil may be higher than the conductivity of the material constituting the cathode external electrode.

[0021] The exterior resin covers the laminate. The exterior resin has a first end face from which a portion of each anode foil is exposed and a second end face from which a portion of each cathode foil is exposed. The first end face and the second end face may face in opposite directions. The shapes of the first end face and the second end face are not particularly limited, and may be, for example, flat, curved, or have at least a portion with irregularities. The exterior resin may be made of an insulating resin material. The exterior resin may be, for example, a cured product of a thermosetting resin containing an epoxy resin, and may contain a filler as necessary.

[0022] The anode external electrode is electrically connected to each anode foil at a first end surface of the exterior resin. The anode external electrode may be made of silver, copper, a copper alloy, aluminum, or an aluminum alloy, and may be plated. A plating layer, a conductive adhesive, or the like may or may not be interposed between the anode external electrode and each anode foil. The anode external electrode may have a single-layer structure or a multi-layer structure. An anode external electrode with a multi-layer structure may have, for example, at least one metal layer and at least one plating layer. A portion of the anode external electrode may extend along the mounting surface of the exterior resin (the mounting surface of the solid electrolytic capacitor).

[0023] The cathode external electrode is electrically connected to each cathode foil at the second end surface of the exterior resin. The cathode external electrode may be made of silver, copper, a copper alloy, aluminum, or an aluminum alloy, and may be plated. The constituent material of the cathode external electrode may be the same as or different from the constituent material of the anode external electrode. A plating layer, a conductive adhesive, or the like may or may not be interposed between the cathode external electrode and each cathode foil. The cathode external electrode may have a single-layer structure or a multi-layer structure. A multi-layer cathode external electrode may have, for example, at least one metal layer and at least one plating layer. A portion of the cathode external electrode may extend along the mounting surface of the exterior resin (the mounting surface of the solid electrolytic capacitor).

[0024] An end point of the second end face of the exterior resin on the mounting surface side of the exterior resin is defined as a first end point. In this case, a first average distance from the first end point on the second end face to each cathode foil in the stacking direction of the laminate (e.g., a direction perpendicular to the mounting surface) is shorter than a second average distance from the first end point to each cathode foil in a region where the capacitor element and the cathode foil overlap (e.g., a region including a midpoint between the first end face and the second end face; hereinafter, also referred to as an overlap region). Here, the average distance from the first end point to each cathode foil in the stacking direction refers to the sum of the shortest distances from the first end point to each cathode foil in the stacking direction divided by the number of cathode foils included in the solid electrolytic capacitor.

[0025] Thus, in the solid electrolytic capacitor according to the present disclosure, the first average distance at the second end face is shorter than the second average distance at the overlapping region. In other words, the multiple cathode foils are generally arranged closer to the mounting surface at the second end face, which is the connection point between each cathode foil and the cathode external electrode. Therefore, when the solid electrolytic capacitor according to the present disclosure is mounted on a substrate, the total current path from the wiring on the substrate to each cathode foil is shorter than when, for example, the solid electrolytic capacitor of Patent Document 1 is mounted on a substrate. This reduces the ESR of the solid electrolytic capacitor. 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.

[0026] At least one pair of cathode foils may be present on the second end surface, adjacent to each other in the stacking direction and spaced apart from each other. Such at least one pair of cathode foils may be present on the mounting surface side of the plurality of cathode foils. For example, in a case where eight cathode foils are present, three to five of the cathode foils on the mounting surface side may be spaced apart from each other. This configuration can prevent damage to the structure of the stack from being caused by excessive force acting on the cathode foils when the stack is covered with an exterior resin.

[0027] At least one pair of anode foils may be present on the first end surface, adjacent to each other in the stacking direction and spaced apart from each other. Such at least one pair of anode foils may be present on the mounting surface side of the multiple anode foils. The ratio of the number of spaced anode foils to the total number of anode foils may be higher than the ratio of the number of spaced cathode foils to the total number of cathode foils. For example, if there are seven anode foils, five to seven anode foils on the mounting surface side may be spaced apart from each other. This configuration can prevent damage to the anode foils due to excessive force acting on the anode foils when the laminate is covered with an exterior resin.

[0028] The exterior resin may contain a filler. The filler content in the exterior resin may be 85% by weight or more and 95% by weight or less. This configuration allows the exterior resin to have physical properties that are particularly suitable for achieving the structure of the solid electrolytic capacitor according to the present disclosure.

[0029] The exterior resin may have a flexural modulus of 20 GPa or more at 25° C. This configuration makes it possible to achieve physical properties of the exterior resin that are particularly suitable for realizing the structure of the solid electrolytic capacitor according to the present disclosure.

[0030] The glass transition temperature of the exterior resin may be equal to or higher than 135° C. This configuration makes it possible to achieve physical properties of the exterior resin that are particularly suitable for realizing the structure of the solid electrolytic capacitor according to the present disclosure.

[0031] (Method for Manufacturing Solid Electrolytic Capacitor) A method for manufacturing a solid electrolytic capacitor according to the present disclosure is a method for manufacturing the above-described solid electrolytic capacitor, and includes a preparation step and a molding step.

[0032] In the preparation step, the laminate is prepared. In the preparation step, for example, the laminate may be prepared by alternately stacking a plurality of anode foils and a plurality of cathode foils.

[0033] In the molding process, a compression molding method is used to form the exterior resin by supplying a resin material to the laminate from the side opposite the mounting surface. Using the compression molding method, for example, granular resin material is placed in a mold, and then the heated mold is closed to apply pressure while melting the resin material, thereby filling and forming the exterior resin. Because the resin material is supplied to the laminate from the side opposite the mounting surface, pressure acts on the laminate to press it toward the mounting surface. This pressure presses and deforms a region of at least one cathode foil near the second end face toward the mounting surface, thereby making the first average distance smaller than the second average distance, resulting in a solid electrolytic capacitor with a low ESR.

[0034] The exterior resin may contain a filler. The filler content in the exterior resin may be 85% by weight or more and 95% by weight or less. This configuration allows the exterior resin to have properties that are particularly suitable for realizing the structure of the solid electrolytic capacitor according to the present disclosure using the above-mentioned compression molding method.

[0035] The exterior resin may have a flexural modulus of 20 GPa or more at 25° C. This configuration makes it possible to achieve exterior resin properties that are particularly suitable for realizing the structure of the solid electrolytic capacitor according to the present disclosure using the above-described compression molding method.

[0036] The glass transition temperature of the exterior resin may be equal to or higher than 135° C. This configuration makes it possible to achieve exterior resin properties that are particularly suitable for realizing the structure of the solid electrolytic capacitor according to the present disclosure using the above-described compression molding method.

[0037] As described above, according to the present disclosure, the ESR of the solid electrolytic capacitor can be reduced by making the first average distance at the second end face smaller than the second average distance in the overlap region.

[0038] An example of a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor according to the present disclosure will be described in detail below with reference to the drawings. The components and steps described above can be applied to the components and steps of the example solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor described below. The components and steps of the example solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Among the components and steps of the example solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor described below, components and steps that are not essential to the solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0039] (Solid Electrolytic Capacitor) The solid electrolytic capacitor 10 of this embodiment is a so-called end-face current collection type solid electrolytic capacitor, and as shown in Figures 1 and 2, it includes a laminate 20, an exterior resin 30, an anode external electrode 40, and a cathode external electrode 50.

[0040] The laminate 20 is formed by alternately stacking a plurality of (three in this example) capacitor elements 21 and a plurality of (four in this example) cathode foils 26. Each of the plurality of capacitor elements 21 has an anode foil 22.

[0041] In this embodiment, the anode foil 22 is formed in a rectangular sheet shape and has a roughened surface. 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 with a solid electrolyte layer 24. At least a portion of the solid electrolyte layer 24 is covered with a conductive layer 25.

[0042] In this embodiment, the cathode foil 26 is formed in a rectangular sheet shape and has 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 having a higher conductivity than the material of the cathode external electrode 50.

[0043] The exterior resin 30 covers the laminate 20. The exterior resin 30 has a first end surface 31 (the end surface on the right side in FIG. 1 ) from which a portion of each anode foil 22 is exposed, and a second end surface 32 (the end surface on the left side in FIG. 1 ) from which a portion of each cathode foil 26 is exposed. The exterior resin 30 is made of an insulating resin material. The exterior resin 30 contains a filler (not shown) at a content of 85 wt % or more and 95 wt % or less. The flexural modulus of the exterior resin 30 at 25°C is 20 GPa or more, and may be, for example, 20 GPa or more and 35 GPa or less. The glass transition temperature of the exterior resin 30 is 135°C or more, and may be, for example, 135°C or more and 160°C or less.

[0044] The anode external electrode 40 is electrically connected to each anode foil 22 at the first end surface 31 of the exterior resin 30. In the present embodiment, the anode external electrode 40 is electrically connected to each anode foil 22 via a conductive adhesive 60, but this is not limiting. The anode external electrode 40 has a first portion 41 extending along the first end surface 31 and a second portion 42 that is continuous with the first portion 41 and extends along the mounting surface 33 (the lower surface in FIG. 1 ) of the exterior resin 30.

[0045] The cathode external electrode 50 is electrically connected to each cathode foil 26 at the second end surface 32 of the exterior resin 30. In the present embodiment, the cathode external electrode 50 is electrically connected to each cathode foil 26 via a conductive adhesive 60, but this is not limiting. The cathode external electrode 50 has a third portion 51 extending along the second end surface 32, and a fourth portion 52 continuing from the third portion 51 and extending along the mounting surface 33 of the exterior resin 30.

[0046] An end point of second end surface 32 of exterior resin 30 on the mounting surface 33 side of exterior resin 30 is defined as first end point P1. In this case, in stacking direction LD of laminate 20, a first average distance AD1 from first end point P1 on second end surface 32 to each cathode foil 26 is smaller than a second average distance AD2 from first end point P1 to each cathode foil 26 in overlapping region R1, which is a region where capacitor elements 21 and cathode foil 26 overlap. Such a magnitude relationship between first average distance AD1 and second average distance AD2 results from the fact that, as shown in FIG. 1 , at least a portion of cathode foil 26 is shaped to point toward mounting surface 33 as it extends from overlapping region R1 toward second end surface 32.

[0047] In this embodiment, the first average distance AD1 is calculated based on the formula AD1 = (D11 + D12 + D13 + D14) / 4, where D11 to D14 are the shortest distances from the first end point P1 on the second end face 32 to each cathode foil 26 (see FIG. 2( a)). Similarly, the second average distance AD2 is calculated based on the formula AD2 = (D21 + D22 + D23 + D24) / 4, where D21 to D24 are the shortest distances from the first end point P1 to each cathode foil 26 in the overlap region R1 (see FIG. 2( b)). Needless to say, both formulas can be modified appropriately depending on the number of cathode foils 26. Note that while the first end point P1 is shown in FIG. 2( b), this is a projection of the first end point P1 onto the cross-sectional position shown in the figure in the opposing direction between the first end face 31 and the second end face 32 (the left-right direction in FIG. 1).

[0048] As shown in Fig. 2(a) , at least one pair of cathode foils 26 that are adjacent to but spaced apart from each other in the stacking direction LD are present on the second end surface 32. In this example, this corresponds to the pair of cathode foils 26 on the mounting surface 33 side. Also, as shown in Fig. 2(c) , at least one pair of anode foils 22 that are adjacent to but spaced apart from each other in the stacking direction LD are present on the first end surface 31. In this example, all of the cathode foils 26 correspond to this pair.

[0049] (Method for Manufacturing Solid Electrolytic Capacitor) The method for manufacturing a solid electrolytic capacitor according to this embodiment is a method for manufacturing the above-described solid electrolytic capacitor 10, and includes a preparation step and a molding step.

[0050] In the preparation step, the above-described laminate 20 is prepared. In the preparation step, the laminate 20 is prepared by alternately stacking a plurality of anode foils 22 and a plurality of cathode foils 26.

[0051] In the molding process, the exterior resin 30 is formed using a compression molding method so that the resin material is supplied to the laminate 20 from the side opposite the mounting surface 33 (the upper side in FIG. 1 ). In practice, the molten resin material is supplied into a predetermined mold, so the laminate 20 is supplied to the molding process in an orientation upside down from the orientation shown in FIG.

[0052] <<Supplementary Note>> The above embodiments disclose the following technology: (Technology 1) A solid electrolytic capacitor comprising: a laminate in which a plurality of capacitor elements, each having an anode foil, and a plurality of cathode foils are stacked together; an exterior resin covering the laminate and having a first end face from which a portion of each of the anode foils is exposed and a second end face from which a portion of each of the cathode foils is exposed; an anode external electrode electrically connected to each of the anode foils at the first end face; and a cathode external electrode electrically connected to each of the cathode foils at the second end face, wherein an end point of the exterior resin on a mounting surface side is defined as a first end point, and a first average distance from the first end point on the second end face to each of the cathode foils in a stacking direction of the laminate is shorter than a second average distance from the first end point to each of the cathode foils in a region where the capacitor elements and the cathode foils overlap. (Technology 2) The solid electrolytic capacitor according to Technology 1, wherein at least one pair of the cathode foils is adjacent to and spaced apart from each other in the stacking direction on the second end surface. (Technology 3) The solid electrolytic capacitor according to Technology 1 or 2, wherein at least one pair of the anode foils is adjacent to and spaced apart from each other in the stacking direction on the first end surface. (Technology 4) The solid electrolytic capacitor according to any one of Technology 1 to 3, wherein the exterior resin contains a filler, and the filler content in the exterior resin is 85% by weight or more and 95% by weight or less. (Technology 5) The solid electrolytic capacitor according to any one of Technology 1 to 4, wherein the exterior resin has a flexural modulus of elasticity of 20 GPa or more at 25°C. (Technology 6) The solid electrolytic capacitor according to any one of Technology 1 to 5, wherein the exterior resin has a glass transition temperature of 135°C or more. (Technology 7) A method for manufacturing the solid electrolytic capacitor according to any one of Technologies 1 to 6, comprising: a preparation step of preparing the laminate; and a molding step of forming the exterior resin by using a compression molding method so as to supply a resin material to the laminate from the side opposite to the mounting surface.(Technology 8) The method for manufacturing a solid electrolytic capacitor according to Technology 7, wherein the exterior resin contains a filler, and the filler content in the exterior resin is 85% by weight or more and 95% by weight or less. (Technology 9) The method for manufacturing a solid electrolytic capacitor according to Technology 7 or 8, wherein the exterior resin has a flexural modulus of elasticity at 25°C of 20 GPa or more. (Technology 10) The method for manufacturing a solid electrolytic capacitor according to any one of Technology 7 to 9, wherein the exterior resin has a glass transition temperature of 135°C or more.

[0053] The ESR of the solid electrolytic capacitors of Examples 1 and 2 and Comparative Examples 1 and 2 shown below was evaluated.

[0054] Example 1 Seven capacitor elements and eight cathode foils were alternately stacked to form a laminate. The laminate was covered with an exterior resin. A portion of each anode foil was exposed from a first end surface of the exterior resin. All of the anode foils were spaced apart from each other at the first end surface. Anode external electrodes were electrically connected to each anode foil at the first end surface. A portion of each cathode foil was exposed from a second end surface of the exterior resin. At the second end surface, the four cathode foils on the mounting surface were spaced apart from each other, while the remaining four cathode foils were in contact with each other. Cathode external electrodes were electrically connected to each cathode foil at the second end surface. The first average distance at the second end surface was 76% of the second average distance in the overlapping region. The ESR of the solid electrolytic capacitor of Example 1 was 90% of the ESR of the solid electrolytic capacitor of Comparative Example 1.

[0055] Example 2 Seven capacitor elements and eight cathode foils were alternately stacked to form a laminate. The laminate was covered with an exterior resin. A portion of each anode foil was exposed from a first end face of the exterior resin. All of the anode foils were spaced apart from each other at the first end face. An anode external electrode was electrically connected to each anode foil at the first end face. A portion of each cathode foil was exposed from a second end face of the exterior resin. All of the cathode foils were in contact with each other on the mounting surface side at the second end face. A cathode external electrode was electrically connected to each cathode foil at the second end face. The first average distance at the second end face was 33% of the second average distance in the overlapping region. The ESR of the solid electrolytic capacitor of Example 2 was 78% of the ESR of the solid electrolytic capacitor of Comparative Example 1.

[0056] Comparative Example 1 Seven capacitor elements and eight cathode foils were alternately stacked to form a laminate. The laminate was covered with an exterior resin. A portion of each anode foil was exposed from a first end surface of the exterior resin. All of the anode foils were spaced apart from one another at the first end surface. An anode external electrode was electrically connected to each anode foil at the first end surface. A portion of each cathode foil was exposed from a second end surface of the exterior resin. All of the cathode foils were spaced apart from one another at the second end surface. A cathode external electrode was electrically connected to each cathode foil at the second end surface. The anode foils and cathode foils of Comparative Example 1 extended in parallel throughout. That is, in the solid electrolytic capacitor of Comparative Example 1, the first average distance and the second average distance were equal to each other.

[0057] Comparative Example 2 Seven capacitor elements and eight cathode foils were alternately stacked to form a laminate. The laminate was covered with an exterior resin. A portion of each anode foil was exposed from a first end surface of the exterior resin. All of the anode foils were spaced apart from each other at the first end surface. An anode external electrode was electrically connected to each anode foil at the first end surface. A portion of each cathode foil was exposed from a second end surface of the exterior resin. All of the cathode foils were in contact with each other at the second end surface opposite the mounting surface. A cathode external electrode was electrically connected to each cathode foil at the second end surface. The first average distance at the second end surface was 167% of the second average distance in the overlapping region. The ESR of the solid electrolytic capacitor of Comparative Example 2 was 152% of the ESR of the solid electrolytic capacitor of Comparative Example 1.

[0058] As described above, the solid electrolytic capacitors of Comparative Examples 1 and 2 had lower ESR than the solid electrolytic capacitors of Comparative Examples 1 and 2. Therefore, it can be said that the superiority of each example was demonstrated.

[0059] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0060] The present disclosure can be used for a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor.

[0061] 10: Solid electrolytic capacitor 20: Laminate 21: Capacitor element 22: Anode foil 23: Dielectric layer 24: Solid electrolyte layer 25: Conductive layer 26: Cathode foil 30: Exterior resin 31: First end face 32: Second end face 33: Mounting surface 40: Anode external electrode 41: First portion 42: Second portion 50: Cathode external electrode 51: Third portion 52: Fourth portion 60: Conductive adhesive AD1: First average distance AD2: Second average distance D11 to D14: Shortest distance from the first end point to each cathode foil on the second end face D21 to D24: Shortest distance from the first end point to each cathode foil in the overlapping region LD: Stacking direction P1: First end point R1: Overlapping region

Claims

1. A solid electrolytic capacitor comprising: a laminate in which a plurality of capacitor elements, each having an anode foil, and a plurality of cathode foils are laminated together; an exterior resin covering the laminate and having a first end face at which a portion of each of the anode foils is exposed and a second end face at which a portion of each of the cathode foils is exposed; an anode external electrode electrically connected to each of the anode foils at the first end face; and a cathode external electrode electrically connected to each of the cathode foils at the second end face, wherein an end point of the exterior resin on the mounting surface side of the second end face is defined as a first end point, and a first average distance from the first end point at the second end face to each of the cathode foils in a stacking direction of the laminate is shorter than a second average distance from the first end point to each of the cathode foils in a region where the capacitor elements and the cathode foils overlap.

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

3. The solid electrolytic capacitor according to claim 1, wherein at least one pair of the anode foils is adjacent to and spaced apart from each other in the stacking direction on the first end surface.

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

5. The solid electrolytic capacitor according to claim 1, wherein the exterior resin has a flexural modulus at 25° C. of 20 GPa or more.

6. The solid electrolytic capacitor according to claim 1, wherein the exterior resin has a glass transition temperature of 135° C. or higher.

7. A method for producing the solid electrolytic capacitor according to claim 1 or 2, comprising: a preparation step of preparing the laminate; and a molding step of forming the exterior resin by using a compression molding method so as to supply a resin material to the laminate from the opposite side to the mounting surface.

8. The method for producing a solid electrolytic capacitor according to claim 7, wherein the exterior resin contains a filler, and a content of the filler in the exterior resin is 85% by weight or more and 95% by weight or less.

9. The method for producing a solid electrolytic capacitor according to claim 7, wherein the exterior resin has a flexural modulus of elasticity at 25° C. of 20 GPa or more.

10. The method for producing a solid electrolytic capacitor according to claim 7, wherein the exterior resin has a glass transition temperature of 135° C. or higher.

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