solid electrolytic capacitor

Abstract

This disclosed solid electrolytic capacitor 10 comprises: a layered unit 20 formed by layering a plurality of capacitor units 21 each of which includes a capacitor element 22 having an anode section 23a and a cathode section 25, and cathode foil 27 that is connected to the cathode section 25 via a first electrically conductive paste 28; and a cathode lead terminal 30 that is electrically connected to the cathode section 25. The cathode lead terminal 30 has at least one side-wall section 31 that faces a side surface of the cathode section 25 and is electrically connected to the cathode foil 27. This configuration makes it possible to decrease the ESR of the solid electrolytic capacitor.

Description

[Technical Field]

[0001] The present disclosure relates to solid electrolytic capacitors. [Background technology]

[0002] Conventionally, solid electrolytic capacitors that use a solid electrolyte are known (for example, Patent Document 1). The solid electrolytic capacitor of Patent Document 1 includes a capacitor element having a solid electrolyte layer that serves as a cathode, a metal electrode lead member that is connected to the solid electrolyte layer via a conductive paste and that contains carbon on its surface, and a cathode lead connected to the electrode lead member. The electrode lead member is made of, for example, aluminum foil that contains carbon on its surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-176219 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the solid electrolytic capacitor of Patent Document 1 has a low capacitance storage efficiency relative to the package (i.e., the ratio of the volume of the portion that contributes to capacitance generation to the total volume of the solid electrolytic capacitor), and also tends to have a high ESR value. In this situation, one of the objectives of the present disclosure is to reduce the ESR of solid electrolytic capacitors. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a solid electrolytic capacitor including a laminated unit formed by laminating a plurality of capacitor units, each of which has a capacitor element including an anode portion and a cathode portion and a cathode foil connected to the cathode portion via a first conductive paste, and a cathode lead terminal electrically connected to the cathode portion, the cathode lead terminal having at least one sidewall portion facing a side surface of the cathode portion and electrically connected to the cathode foil. [Effects of the Invention]

[0006] According to the present disclosure, the ESR of a solid electrolytic capacitor can be reduced.

[0007] 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. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically showing a solid electrolytic capacitor according to a first embodiment. [Figure 2] 1 is a cross-sectional view schematically showing a capacitor unit according to a first embodiment. [Figure 3] FIG. 2 is a perspective view schematically showing each lead terminal. [Figure 4] FIG. 10 is a perspective view showing a state in which a plurality of capacitor units are stacked on each lead terminal. [Figure 5] 10 is a cross-sectional view schematically showing a solid electrolytic capacitor according to a second embodiment, in which a side wall portion is indicated by a two-dot chain line. [Figure 6] FIG. 10 is a cross-sectional view schematically showing a capacitor unit according to a second embodiment. [Figure 7] 10 is a cross-sectional view schematically showing a solid electrolytic capacitor according to a third embodiment, in which a side wall portion is indicated by a two-dot chain line. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes an embodiment of 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.

[0010] A solid electrolytic capacitor according to the present disclosure includes a multilayer unit and a cathode lead terminal.

[0011] The laminated unit is formed by stacking a plurality of capacitor units. Each capacitor unit has a capacitor element and a cathode foil. The capacitor element includes an anode portion and a cathode portion. An insulating portion may be provided between the anode portion and the cathode portion to electrically insulate them from each other. The insulating portion may be formed of, for example, insulating tape or insulating resin.

[0012] The anode section may be configured to include a portion of the anode body (a portion on one side of the insulating section) made of a valve metal contained in the capacitor element. The cathode section may have a solid electrolyte layer formed on the surface of the cathode-forming section, which is the remaining portion of the anode body (a portion on the other side of the insulating section). A carbon layer may or may not be formed on the surface of the solid electrolyte layer. In the solid electrolytic capacitor of the present disclosure, no silver paste layer is formed on the surface of the solid electrolyte layer or the carbon layer. The carbon layer may contain a resin or binder, but the amount is usually small. A dielectric layer is provided between the anode body and the solid electrolyte layer.

[0013] Examples of the valve metal constituting the anode body include aluminum, tantalum, niobium, titanium, etc. The anode body may be a foil of the valve metal or a sintered body of valve metal particles.

[0014] The dielectric layer is formed on the surface of at least the cathode-forming portion, which is the remaining portion of the anode body. The dielectric layer may be made of an oxide (e.g., aluminum oxide) formed on the surface of the anode body by anodization or a gas phase method such as vapor deposition or atomic layer deposition.

[0015] The solid electrolyte layer is formed on the surface of the dielectric layer. The solid electrolyte layer may include a conductive polymer. The solid electrolyte layer may further include a dopant, if necessary.

[0016] The conductive polymer may be a known one used in solid electrolytic capacitors, such as a π-conjugated conductive polymer. Examples of conductive polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. Among these, polymers with a basic skeleton of polypyrrole, polythiophene, or polyaniline are preferred. The above polymers 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). The conductive polymers may be used alone or in combination of two or more.

[0017] The dopant may be at least one selected from the group consisting of low molecular weight anions and polyanions. Examples of 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 cathode foil is connected to the cathode section via the first conductive paste. In other words, the cathode foil and the cathode section are electrically connected to each other. The cathode foil may be a sheet-like member containing metal. The shape of the cathode foil may be the same as or different from the shape of the cathode section. The thickness of the cathode foil may be, for example, 15 μm or more and 25 μm or less. The first conductive paste may contain carbon, or may contain carbon and a resin or binder. The carbon may be graphite powder or carbon black as long as it is conductive. The resin contained in the first conductive paste is usually greater in amount than the resin contained in the carbon layer and has adhesive properties.

[0020] The cathode lead terminal is electrically connected to the cathode portion. The cathode lead terminal may be connected to the cathode portion via a second conductive paste. The cathode lead terminal has at least one side wall portion facing a side surface of the cathode portion and electrically connected to the cathode foil. Each side wall portion may be formed by bending a part of a plate-like member constituting the cathode lead terminal. Each side wall portion may face side surfaces of all or some of the cathode portions. Note that the side surface of the cathode portion refers to a surface connecting two main surfaces of the cathode portion. Each side wall portion may be electrically connected to all or some of the cathode foils. However, it is preferable that all of the cathode foils are electrically connected to at least one of the side wall portions.

[0021] The sidewalls shorten the conductive path between the cathode lead terminal and each cathode portion, thereby reducing the ESR of the solid electrolytic capacitor even when the first conductive paste contains carbon instead of silver. Furthermore, as described above, no silver paste layer is formed on the surface of the solid electrolyte layer or the carbon layer, thereby reducing the manufacturing cost of the solid electrolytic capacitor.

[0022] The solid electrolytic capacitor may further include an anode lead terminal electrically connected to the anode portion, and an exterior resin covering each component such that a portion of each of the cathode lead terminal and the anode lead terminal is exposed to the outside. The anode lead terminal may be connected to the anode portion by, for example, welding (e.g., resistance welding or laser welding).

[0023] In each capacitor unit, a pair of cathode foils may be provided to sandwich the capacitor element. In this configuration, the capacitor unit is provided with twice the number of cathode foils as the number of capacitor elements. Compared to providing one cathode foil for each capacitor element or sharing one cathode foil between two capacitor elements, this allows for a thicker conduction path to each capacitor element, further reducing the ESR of the solid electrolytic capacitor.

[0024] The sidewall portion may be connected to the cathode foil via a second conductive paste different from the first conductive paste, the first conductive paste may include carbon, and the second conductive paste may include silver.

[0025] The second conductive paste may contact both the main surface and the side surface of the cathode foil. With this configuration, the second conductive paste contacts a wide area of ​​the cathode foil, thereby reducing the resistance between the side wall portion and the cathode foil, and therefore the cathode portion, and further reducing the ESR of the solid electrolytic capacitor. Note that the side surface of the cathode foil refers to the surface connecting the two main surfaces of the cathode foil.

[0026] The sidewalls may be connected to the cathode foil by laser welding, which reduces the amount of expensive materials (e.g., silver) used, thereby reducing the manufacturing cost of the solid electrolytic capacitor.

[0027] The cathode section may have a solid electrolyte layer and a carbon layer provided on the surface of the solid electrolyte layer. The carbon layer may be in contact with the first conductive paste. With this configuration, the affinity between the carbon layer and the first conductive paste is high, making it possible to reduce the ESR of the solid electrolytic capacitor more than when the first conductive paste is provided on the surface of the solid electrolyte layer. The first conductive paste may contain carbon.

[0028] The thickness of the carbon layer may be 3 μm or less. With this configuration, the resistance of the carbon layer can be made extremely small, and the ESR of the solid electrolytic capacitor can be further reduced. Note that the thickness T1 of the carbon layer may be greater than 3 μm.

[0029] The thickness T2 of the first conductive paste may be 40 μm or less. With this configuration, the resistance of the first conductive paste can be made extremely small, and the ESR of the solid electrolytic capacitor can be further reduced. The thickness of the first conductive paste may be greater than 40 μm. The thickness T2 may be greater than the thickness T1, and for example, the value of T2 / T1 may be 1 or more and 100 or less, or T2 / T1>1.

[0030] At least one of the cathode foils may be made of copper or copper alloy foil. All of the cathode foils may be made of copper or copper alloy foil.

[0031] At least one of the cathode foils may be made of aluminum foil having a surface layer containing carbon. All of the cathode foils may be made of aluminum foil having a surface layer containing carbon.

[0032] The capacitor element may be free of silver, which can reduce the manufacturing cost of the solid electrolytic capacitor.

[0033] As described above, the present disclosure makes it possible to reduce the ESR of a solid electrolytic capacitor, and further reduces the manufacturing cost of the solid electrolytic capacitor.

[0034] An example of a solid electrolytic capacitor according to the present disclosure will be described in detail below with reference to the drawings. The components described above can be applied to the components of the example solid electrolytic capacitor described below. The components of the example solid electrolytic capacitor described below can be modified based on the above description. The matters described below may also be applied to the above-described embodiment. Among the components of the example solid electrolytic capacitor described below, components that are not essential to the solid electrolytic capacitor according to the present disclosure may be omitted. Note that the drawings shown below are schematic and do not accurately reflect the shapes or number of actual components. Furthermore, although terms indicating directions such as "up" and "down" may be used in the following description, these are used for convenience of explanation and do not limit the scope of the present disclosure in any way.

[0035] First Embodiment A first embodiment of the present disclosure will be described. The solid electrolytic capacitor 10 of this embodiment is a so-called gull-wing type (in which each lead terminal extends from the side surface along the underside of the exterior resin), but is not limited thereto. For example, the solid electrolytic capacitor 10 may be a so-called bottom electrode type (in which each lead terminal is exposed from the underside of the exterior resin) or a so-called edge current collection type (in which the lead terminals that collect current from each capacitor element are provided on the edge surface of the exterior resin). Furthermore, while the solid electrolytic capacitor 10 of this embodiment has each capacitor element facing in the same direction, this is not limiting, and some capacitor elements may face in opposite directions to the remaining capacitor elements. In the latter case, the currents flowing through some capacitor elements and the remaining capacitor elements are in opposite directions, and the magnetic fields of the two currents cancel each other out, thereby reducing the ESL of the solid electrolytic capacitor 10.

[0036] 1 to 4, the solid electrolytic capacitor 10 of this embodiment has a double-sided laminated structure (a structure in which capacitor elements are laminated on both sides of each lead terminal). The solid electrolytic capacitor 10 includes a laminated unit 20, a cathode lead terminal 30, an anode lead terminal 40, and an exterior resin 50.

[0037] The laminated unit 20 is formed by laminating a plurality of capacitor units 21. The lamination direction here is the vertical direction in FIG. 1. The plurality of capacitor units 21 are laminated via a conductive paste (e.g., silver paste) not shown. Each capacitor unit 21 has one capacitor element 22 and a pair of cathode foils 27.

[0038] As shown in FIG. 2, capacitor element 22 has anode portion 23a, cathode portion 25, and insulating portion 26. Capacitor element 22 does not contain silver. Anode portion 23a is formed from a portion of anode body 23 made of a valve metal (e.g., aluminum). Cathode portion 25 is formed from solid electrolyte layer 25a and carbon layer 25b, which are sequentially formed on the surface of the cathode-forming portion, which is the remaining portion of anode body 23. The thickness of carbon layer 25b is 3 μm or less, but is not limited to this. Insulating portion 26 is formed from insulating tape and electrically insulates anode portion 23a from cathode portion 25. Dielectric layer 24 is provided between anode body 23 and solid electrolyte layer 25a.

[0039] A pair of cathode foils 27 are disposed to sandwich capacitor element 22. Each cathode foil 27 is made of, but is not limited to, a copper alloy foil. Each cathode foil 27 is connected to cathode portion 25 via a first conductive paste 28 containing carbon. The shape of cathode foil 27 is substantially the same as the shape of cathode portion 25. First conductive paste 28 is in contact with cathode foil 27 and carbon layer 25b of cathode portion 25. The thickness of first conductive paste 28 is, but is not limited to, 40 μm or less.

[0040] Cathode lead terminal 30 is electrically connected to cathode portion 25. Cathode lead terminal 30 is connected to cathode portion 25 via a conductive paste (not shown). Cathode lead terminal 30 has a plurality of side wall portions 31 (four in this example) that face the side surface of cathode portion 25 (or the side surface of each capacitor unit 21) and are electrically connected to cathode foil 27. Side wall portions 31 are connected to cathode foil 27 via a second conductive paste (not shown) containing silver. The second conductive paste is in contact with both the main surface and the side surface of cathode foil 27.

[0041] The anode lead terminal 40 is electrically connected to the anode portion 23a by, for example, resistance welding.

[0042] The exterior resin 50 covers the laminate unit 20, the cathode lead terminal 30, and the anode lead terminal 40 so that a portion of each of the cathode lead terminal 30 and the anode lead terminal 40 is exposed to the outside. The exterior resin 50 is made of an insulating resin material. The exposed portions of the cathode lead terminal 30 and the anode lead terminal 40 form the external terminals of the solid electrolytic capacitor 10.

[0043] Second Embodiment A second embodiment of the present disclosure will be described. Solid electrolytic capacitor 10 of this embodiment differs from the first embodiment in its basic structure and the number of cathode foils 27 in each capacitor unit 21. The following mainly describes the differences from the first embodiment.

[0044] As shown in FIG. 5, the solid electrolytic capacitor 10 of this embodiment has a single-surface layer structure (a structure in which a capacitor element is layered on one side of each lead terminal).

[0045] As shown in Fig. 6, each capacitor unit 21 has one capacitor element 22 and one cathode foil 27. Capacitor element 22 does not have a carbon layer, and solid electrolyte layer 25a is in contact with first conductive paste 28. Each cathode foil 27 is made of aluminum foil having a surface layer containing carbon. In the illustrated example, in each capacitor unit 21, cathode foil 27 is arranged on the side farther from cathode lead terminal 30 (upper side in Fig. 6), but it may also be arranged on the side closer to cathode lead terminal 30 (lower side in Fig. 6).

[0046] The cathode lead terminal 30 has a pair of side walls 31 (one on the front side and one on the back side in FIG. 5). The pair of side walls 31 are arranged to sandwich the laminated unit 20 from the sides. The length of each side wall 31 (the dimension in the vertical direction in FIG. 5) may be less than the dimension of the laminated unit 20 in the stacking direction, may be the same as the dimension in the stacking direction, or may be greater than the dimension in the stacking direction. Each side wall 31 is connected to the cathode foil 27 by laser welding.

[0047] Third Embodiment A third embodiment of the present disclosure will be described. The solid electrolytic capacitor 10 of this embodiment differs in its basic structure from that of the first embodiment. The following mainly describes the differences from the first embodiment.

[0048] As shown in FIG. 7, solid electrolytic capacitor 10 of this embodiment is a bottom electrode type solid electrolytic capacitor (a type in which each lead terminal is exposed from the bottom surface of the exterior resin).

[0049] The cathode lead terminal 30 has a shape that generally follows the shape of the lower surface of the exterior resin 50, and a portion thereof extends to the side surface of the exterior resin 50. The anode lead terminal 40 has a portion that is arranged to sandwich the multiple anode portions 23a from above and below, and a portion that has a shape that generally follows the shape of the lower surface of the exterior resin 50. A portion of the anode lead terminal 40 extends along the side surface of the exterior resin 50. [Example]

[0050] The ESR values ​​of the solid electrolytic capacitors 10 of Examples 1 to 6 and Comparative Example shown below were evaluated.

[0051] Example 1 A gull-wing type solid electrolytic capacitor 10 with a single-sided laminate structure was evaluated. The capacitor element 22 of each capacitor unit 21 was configured to include a cathode portion 25 consisting of a solid electrolyte layer 25a and a carbon layer 25b provided on the surface of the solid electrolyte layer 25a. Each capacitor unit 21 was configured to include a pair of cathode foils 27 made of copper foil and arranged to sandwich the capacitor element 22. The side wall portion 31 was configured to be connected to the cathode foils 27 by laser welding. The ESR of the solid electrolytic capacitor 10 of Example 1 was 2.91 mΩ.

[0052] Example 2 A Cu-wing type solid electrolytic capacitor 10 with a single-sided laminated structure was evaluated. The capacitor element 22 of each capacitor unit 21 was configured to include a cathode portion 25 consisting of a solid electrolyte layer 25a and a carbon layer 25b provided on the surface of the solid electrolyte layer 25a. Each capacitor unit 21 was configured to include a pair of cathode foils 27 made of copper foil and arranged to sandwich the capacitor element 22. The side wall portion 31 was configured to be connected to the cathode foil 27 via silver paste. The ESR of the solid electrolytic capacitor 10 of Example 2 was 2.94 mΩ.

[0053] Example 3 A solid electrolytic capacitor 10 with a single-sided laminated structure and a bottom electrode type was evaluated. The capacitor element 22 of each capacitor unit 21 was configured to include a cathode portion 25 consisting of a solid electrolyte layer 25a and a carbon layer 25b provided on the surface of the solid electrolyte layer 25a. Each capacitor unit 21 was configured to include a pair of cathode foils 27 made of copper foil and arranged to sandwich the capacitor element 22. The side wall portion 31 was configured to be connected to the cathode foil 27 via silver paste. The ESR of the solid electrolytic capacitor 10 of Example 3 was 2.07 mΩ.

[0054] Example 4 A double-sided laminated gull-wing type solid electrolytic capacitor 10 was evaluated. The capacitor element 22 of each capacitor unit 21 was configured to include a cathode portion 25 consisting of a solid electrolyte layer 25a and a carbon layer 25b provided on the surface of the solid electrolyte layer 25a. Each capacitor unit 21 was configured to include a pair of cathode foils 27 made of copper foil and arranged to sandwich the capacitor element 22. The side wall portion 31 was configured to be connected to the cathode foil 27 via silver paste. The ESR of the solid electrolytic capacitor 10 of Example 4 was 1.74 mΩ.

[0055] Example 5 A double-sided laminated gull-wing type solid electrolytic capacitor 10 was evaluated. The capacitor element 22 of each capacitor unit 21 was configured to include a cathode portion 25 consisting of a solid electrolyte layer 25a and a carbon layer 25b provided on the surface of the solid electrolyte layer 25a. Each capacitor unit 21 was configured to include one cathode foil 27 made of copper foil and disposed on one side of the capacitor element 22. The side wall portion 31 was configured to be connected to the cathode foil 27 via silver paste. The ESR of the solid electrolytic capacitor 10 of Example 5 was 1.80 mΩ.

[0056] Example 6 A double-sided laminated gull-wing type solid electrolytic capacitor 10 was evaluated. The capacitor element 22 of each capacitor unit 21 was configured to include a cathode portion 25 consisting of a solid electrolyte layer 25a and a carbon layer 25b provided on the surface thereof. Each capacitor unit 21 was configured to include a pair of cathode foils 27, each composed of aluminum foil with a surface layer containing carbon, arranged to sandwich the capacitor element 22. The side wall portion 31 was configured to be connected to the cathode foil 27 via silver paste. The ESR of the solid electrolytic capacitor 10 of Example 6 was 1.95 mΩ.

[0057] Comparative Example A gull-wing type solid electrolytic capacitor with a single-sided laminated structure was evaluated. Each capacitor element was configured with a cathode layer formed on the surface of the solid electrolyte layer and consisting of a carbon layer and a silver paste layer. Adjacent cathode sections were connected to each other via a conductive adhesive. The sidewall section was connected to the cathode section via silver paste. The ESR of the comparative solid electrolytic capacitor was 3.15 mΩ.

[0058] As described above, the ESR of the solid electrolytic capacitors 10 of Examples 1 to 6 was smaller than the ESR of the solid electrolytic capacitor of the comparative example. This demonstrates the superiority of Examples 1 to 6.

[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. [Industrial Applicability]

[0060] The present disclosure can be used for solid electrolytic capacitors. [Explanation of symbols]

[0061] 10: Solid electrolytic capacitor 20: Stacking unit 21: Capacitor unit 22: Capacitor element 23: Anode body 23a: Anode section 24: Dielectric layer 25: Cathode 25a: Solid electrolyte layer 25b: Carbon layer 26: Insulation section 27: Cathode foil 28: First conductive paste 30: Cathode lead terminal 31: Side wall 40: Anode lead terminal 50: Exterior resin

Claims

1. a laminated unit formed by laminating a plurality of capacitor units, each of which has a capacitor element including an anode portion and a cathode portion, and a cathode foil connected to the cathode portion via a first conductive paste; a cathode lead terminal electrically connected to the cathode portion; Equipped with the cathode lead terminal has at least one side wall portion that faces a side surface of the cathode portion and is electrically connected to the cathode foil.

2. 2. The solid electrolytic capacitor according to claim 1, wherein in each of the capacitor units, a pair of the cathode foils are provided to sandwich the capacitor element.

3. the side wall portion is connected to the cathode foil via a second conductive paste different from the first conductive paste; the first conductive paste contains carbon; The solid electrolytic capacitor according to claim 1 , wherein the second conductive paste contains silver.

4. The solid electrolytic capacitor according to claim 3 , wherein the second conductive paste is in contact with both the main surface and the side surface of the cathode foil.

5. 3. The solid electrolytic capacitor according to claim 1, wherein the side wall portion is connected to the cathode foil by laser welding.

6. the cathode portion has a solid electrolyte layer and a carbon layer provided on a surface of the solid electrolyte layer, 3. The solid electrolytic capacitor according to claim 1, wherein the carbon layer is in contact with the first conductive paste.

7. 7. The solid electrolytic capacitor according to claim 6, wherein the carbon layer has a thickness of 3 [mu]m or less.

8. 3. The solid electrolytic capacitor according to claim 1, wherein the first conductive paste has a thickness of 40 [mu]m or less.

9. 3. The solid electrolytic capacitor according to claim 1, wherein at least one of the cathode foils is made of a foil of copper or a copper alloy.

10. 3. The solid electrolytic capacitor according to claim 1, wherein at least one of the cathode foils is made of an aluminum foil having a surface layer containing carbon.

11. 3. The solid electrolytic capacitor according to claim 1, wherein the capacitor element does not contain silver.

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