Solid electrolytic capacitors and methods for manufacturing solid electrolytic capacitors

Abstract

This invention provides a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor. The solid electrolytic capacitor (100) comprises: a columnar metal core (19) having a valve function; first external terminals (14, 15) connected to one end face and the other end face of the metal core (19), respectively; and a second external terminal (16) with a polarity different from the first external terminals (14, 15). The area of ​​the end face of the metal core (19) is greater than the area of ​​the cross-section in the direction orthogonal to the axial direction at the center along the length direction. A porous layer (19b) having an oxide film is disposed on a portion of the surface of the metal core (19), and the porous layer (19b) is connected to the second external terminal (16) via a cathode layer (22), which is a conductive layer containing a conductive polymer.

Description

[0001] This application is a divisional application of the invention patent application filed on March 7, 2019, with application number 201980018782.2 and invention title "Solid Electrolytic Capacitor and Method for Manufacturing Solid Electrolytic Capacitor". Technical Field

[0002] This invention relates to solid electrolytic capacitors and methods for manufacturing them. Background Technology

[0003] Solid electrolytic capacitors are not only used as ordinary capacitors in decoupling circuits and power supply circuits, but also advantageously used as noise filters to remove high-frequency noise.

[0004] As an example of a solid electrolytic capacitor, Patent Document 1 describes a solid electrolytic capacitor having the following structure: an anode lead wire extends to the end face of a capacitor element, and an external electrode is formed on the end face of the capacitor element, connecting to the anode lead wire. The external electrode is connected to the end face of the anode lead wire.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-94475 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, in the solid electrolytic capacitor described in Patent Document 1, the connection area between the anode lead wire and the external electrode is small, resulting in a large connection resistance and a large ESR (equivalent series resistance).

[0010] The present invention addresses the aforementioned problems and aims to provide a solid electrolytic capacitor with reduced ESR and a method for manufacturing such a solid electrolytic capacitor.

[0011] Methods for solving problems

[0012] The solid electrolytic capacitor of the present invention is characterized by comprising:

[0013] A columnar metal core material with valve function;

[0014] The first external terminal is connected to one end face and the other end face of the metal core material, respectively; and

[0015] The second external terminal has a different polarity than the first external terminal.

[0016] The area of ​​the end face of the metal core is greater than the area of ​​the cross-section of the central portion of the metal core in the direction orthogonal to the axial direction along its length.

[0017] A porous layer with an oxide film is disposed on a portion of the surface of the metal core material.

[0018] The porous layer is connected to the second external terminal via a cathode layer, the cathode layer being a conductive layer containing a conductive polymer.

[0019] The area of ​​the end face of the metal core material can also be more than 1% larger than the area of ​​the cross-section of the central part.

[0020] Alternatively, a resist film may be provided on the portion of the surface of the metal core material where the porous layer is not provided.

[0021] The resist film may also be a resin containing at least one of polyimide and epoxy.

[0022] The method for manufacturing the solid electrolytic capacitor of the present invention is characterized by comprising:

[0023] The process of preparing columnar metal core material with valve function;

[0024] The process of depositing a resist film on the surface of the metal core material;

[0025] The process of removing the resist film in the longitudinal direction of the metal core material in a manner in which the resist film is arranged at given intervals;

[0026] The process of forming a porous layer on the surface of the metal core material where the resist film is not disposed;

[0027] The process of performing a chemical formation treatment on the porous layer;

[0028] The process of coating a conductive polymer layer onto the surface of the metal core material after the formation treatment.

[0029] The process of segmenting the metal core material at the location where the resist film is disposed, thereby performing monolithic assembly; and

[0030] For each monolithized unit, the process of setting external terminals on both ends of the metal core material.

[0031] The method for manufacturing the solid electrolytic capacitor of the present invention is characterized by comprising:

[0032] The process of preparing columnar metal core material with valve function;

[0033] The process of depositing a resist film on the surface of the metal core material at given intervals along its length;

[0034] The process of forming a porous layer on the surface of the metal core material where the resist film is not disposed;

[0035] The process of performing a chemical formation treatment on the porous layer;

[0036] The process of coating a conductive polymer layer onto the surface of the metal core material after the formation treatment.

[0037] The process of segmenting the metal core material at the location where the resist film is disposed, thereby performing monolithic assembly; and

[0038] For each monolithized unit, the process of setting external terminals on both ends of the metal core material.

[0039] The resist film may also be a resin containing at least one of polyimide and epoxy.

[0040] The above-mentioned method for manufacturing solid electrolytic capacitors can further include:

[0041] The process of forming a carbon layer on the conductive polymer layer; and

[0042] The process of forming a silver layer on the carbon layer.

[0043] Invention Effects

[0044] The solid electrolytic capacitor according to the present invention has a structure in which the first external terminal is connected to both ends of a metal core, and the area of ​​the end faces of the metal core is larger than the area of ​​the cross-section of the central portion along the length of the metal core, thereby increasing the connection area between the metal core and the first external terminal. This structure reduces ESR.

[0045] In the manufacturing method of the solid electrolytic capacitor of the present invention, after a resist film is disposed on the surface of a metal core, the resist film is removed in a manner where it is disposed at given intervals, and a porous layer is formed on the portion of the metal core surface where no resist film is disposed. Then, the metal core is segmented at the locations where the resist film was disposed to form monolithic units, and for each monolithized unit, external terminals are provided on both end faces of the metal core. As a result, the area of ​​the end faces of the metal core becomes larger than the area of ​​the cross-section of the central portion in the length direction, thereby increasing the connection area between the metal core and the first external terminal and reducing ESR.

[0046] Furthermore, in the method for manufacturing the solid electrolytic capacitor of the present invention, a resist film is disposed at given intervals along the length direction on the surface of the metal core, and a porous layer is formed on the portion of the metal core surface where the resist film is not disposed. Then, the metal core is segmented at the locations where the resist film is disposed to achieve monolithic assembly, and for each monolithized unit, external terminals are provided at both end faces of the metal core. As a result, the area of ​​the end faces of the metal core becomes larger than the area of ​​the cross-section at the center along the length direction, thereby increasing the connection area between the metal core and the first external terminal and reducing ESR. Attached Figure Description

[0047] Figure 1 This is a perspective view showing the appearance of a solid electrolytic capacitor in one embodiment.

[0048] Figure 2 It is Figure 1 The diagram shows a cross-sectional view of a solid electrolytic capacitor cut at the cut line II-II.

[0049] Figure 3 It is Figure 2 The diagram shows a cross-sectional view of a solid electrolytic capacitor cut at cut line III-III.

[0050] Figure 4 yes Figure 1 The image shows a bottom view of a solid electrolytic capacitor.

[0051] Figure 5 It is Figure 2 A cross-sectional view of part V shown schematically with magnification.

[0052] Figure 6 This is a flowchart illustrating the manufacturing process of a solid electrolytic capacitor in one embodiment.

[0053] Figure 7 This is a diagram used to illustrate the manufacturing process of solid electrolytic capacitors.

[0054] Explanation of reference numerals in the attached figures

[0055] 10: Main body;

[0056] 11: One end face of the main body;

[0057] 12: The other end face of the main body;

[0058] 13: The bottom surface of the main body;

[0059] 14: First anode terminal;

[0060] 15: Second anode terminal;

[0061] 16: Cathode terminal;

[0062] 17: Sealing material;

[0063] 18: Capacitor components;

[0064] 19: Metal core material;

[0065] 19a: Core;

[0066] 19b: Porous layer;

[0067] 20: Fine pores;

[0068] 21: Dielectric layer;

[0069] 22: Cathode layer;

[0070] 23: Conductive polymer layer;

[0071] 24: Carbon layer;

[0072] 25: Silver layer;

[0073] 26: Conductive adhesives;

[0074] 30: Resist film;

[0075] 100: Solid electrolytic capacitor. Detailed Implementation

[0076] The following describes embodiments of the present invention, specifically illustrating the features of the invention.

[0077] Figure 1 This is a perspective view showing the appearance of a solid electrolytic capacitor 100 in one embodiment. Figure 2 It is Figure 1 The solid electrolytic capacitor 100 shown is a cross-sectional view of the capacitor when it is cut at the cutting line II-II. Figure 3 It is Figure 2 The solid electrolytic capacitor 100 shown is a cross-sectional view of the capacitor cut at cut line III-III. Furthermore, Figure 4 yes Figure 1 The bottom view of the solid electrolytic capacitor 100 shown.

[0078] In one embodiment, a solid electrolytic capacitor 100 includes: a cuboid-shaped body 10, a first anode terminal 14 disposed on an end face 11 on one side of the body 10, a second anode terminal 15 disposed on an end face 12 on the other side, and a cathode terminal 16 disposed on a bottom surface 13 of the body 10. The first anode terminal 14 and the second anode terminal 15 constitute a first external terminal, and the cathode terminal 16 constitutes a second external terminal.

[0079] The main body 10 has a capacitor element 18 and a sealing material 17 covering the capacitor element 18.

[0080] The capacitor element 18 has a columnar metal core 19 with a valve function. The valve-acting metal constituting the metal core 19 may be, for example, aluminum, tantalum, niobium, titanium, or an alloy containing at least one of them.

[0081] In this embodiment, the metal core 19 is cylindrical. However, the shape of the metal core 19 is not limited to cylindrical; for example, it can also be a square prism. It is preferable to use aluminum wire as the metal core 19 because it is inexpensive and readily available.

[0082] The metal core 19 includes a core 19a extending in the axial direction of the metal core 19, and a porous layer 19b disposed on a portion of the surface of the core 19a.

[0083] The porous layer 19b is formed, for example, by etching the surface of the metal core 19, which includes aluminum wire, thereby roughening the surface.

[0084] like Figure 5 As schematically shown, a plurality of fine pores 20 with outwardly facing openings are formed in the porous layer 19b. The pore size of the porous layer 19b is, for example, 0.01 μm or more and 100 μm or less. Furthermore, in Figure 3 In the diagram, the porous layer 19b is the shaded area enclosed by the dashed line.

[0085] In this embodiment, the area C1 of the end face of the metal core 19 is greater than the area C2 of the cross section of the central portion of the metal core 19 in the direction orthogonal to the axial direction along its length (see reference). Figure 2 Preferably, the area C1 of the end face of the metal core 19 is at least 1% larger than the area C2 of the cross-section of the central portion of the metal core 19 along its length. Because the area C1 of the end face of the metal core 19 is larger than the area C2 of the cross-section of the central portion, the connection area between the metal core 19 and the first anode terminal 14, and between the metal core 19 and the second anode terminal 15, is increased, thereby reducing ESR. Furthermore, because the area C1 of the end face of the metal core 19 is at least 1% larger than the area C2 of the cross-section of the central portion, ESR can be effectively reduced.

[0086] like Figure 5 As shown, a dielectric layer 21, which is an oxide film, is disposed on the surface of the porous layer 19b. More specifically, the dielectric layer 21 is formed along the inner peripheral surface of the pores 20 of the porous layer 19b. Furthermore, in Figure 5 In the diagram, dielectric layer 21 is shown by thick lines.

[0087] The dielectric layer 21 is formed, for example, by oxidizing the surface of the metal core 19 to which the porous layer 19b is formed. The thickness of the oxide film constituting the dielectric layer 21 is, for example, 0.003 μm or more and 5 μm or less.

[0088] The capacitor element 18 also includes a cathode layer 22 on the dielectric layer 21. The cathode layer 22 includes a conductive polymer layer 23 as a solid electrolyte, a carbon layer 24 on the conductive polymer layer 23, and a silver layer 25 on the carbon layer 24. The cathode layer 22 is a conductive layer.

[0089] As the conductive polymer contained in the conductive polymer layer 23, a π-conjugated conductive polymer can be used. Examples of π-conjugated conductive polymers include substituted or unsubstituted polypyrrole, polythiophene, polyaniline, polyacetylene, poly(p-phenylene), poly(p-phenylenevinylene), and poly(thienylenevinylene), as well as their derivatives.

[0090] Examples of substituents include hydrogen atoms, hydroxyl groups, carboxyl groups, nitro groups, phenyl groups, vinyl groups, halogen atoms, acyl groups, amino groups, sulfonic acid groups, sulfonyl groups, carboxylic acid ester groups, sulfonate groups, alkoxy groups, alkylthio groups, arylthio groups, C1 to C18 alkyl groups having these substituents, C5 to C12 cycloalkyl groups having these substituents, C6 to C14 aryl groups having these substituents, and C7 to C18 aralkyl groups having these substituents.

[0091] Among these, the conductive polymer is preferably one comprising at least one selected from the group consisting of polypyrrole, polythiophene, and polyaniline and their derivatives. Furthermore, from the viewpoint of thermal stability, the conductive polymer is more preferably composed of repeating units of 3,4-ethylenedioxythiophene or its derivatives. The conductive polymer can be either a homopolymer or a copolymer. Moreover, these conductive polymers can be used individually or in combination of two or more.

[0092] There is no particular limitation on the thickness of the conductive polymer layer 23, but for example, when low resistance is required, a thin film is preferred from the viewpoint of the volume resistivity of each layer, and the thickness is preferably adjusted to any value according to the required characteristics.

[0093] like Figure 5As shown, the conductive polymer layer 23 is configured to fill at least a portion of the pores 20 of the porous layer 19b. The conductive polymer layer 23 does not need to cover the entire periphery of the porous layer 19b, but by covering the entire periphery, the conductive polymer layer 23 and the dielectric layer 21 can be made into contact over a large area. Alternatively, the conductive polymer adhering to the resist film 30 (described later) can be removed using a laser or the like, or the conductive polymer can be prevented from being coated on the resist film 30 by using a mask or the like. This ensures insulation between the anode terminals 14, 15 and the cathode terminal 16.

[0094] Furthermore, the carbon layer 24 and silver layer 25 in the cathode layer 22 function as the cathode layer of the capacitor element 18. The cathode layer only needs to be a conductive layer. In this embodiment, the cathode layer is provided as multiple layers of carbon layer 24 and silver layer 25, but the cathode layer may also consist of only silver layer 25.

[0095] The porous layer 19b is electrically connected to the cathode terminal 16 via the cathode layer 22. The cathode layer 22, and more specifically the silver layer 25, are connected via a conductive adhesive 26 (see reference). Figure 3 It is connected to the cathode terminal 16.

[0096] The two end faces of the core portion 19a of the metal core 19 are exposed from the sealing material 17. One end face of the metal core 19 is connected to the first anode terminal 14, and the other end face is connected to the second anode terminal 15.

[0097] The first anode terminal 14 and the second anode terminal 15 include a plated film or a conductive resin film formed on the end face of the core 19a of the metal core material 19. The plated film may contain, for example, metals such as nickel, zinc, copper, tin, gold, silver, palladium, or lead, or alloys containing at least one of these metals. The conductive resin film contains at least one metal particle, such as silver, copper, nickel, tin, or palladium, as a conductive component within a resin such as epoxy.

[0098] The first anode terminal 14 and the second anode terminal 15 may also be configured as a multilayer structure including a plating film and a conductive resin film. For example, the first anode terminal 14 and the second anode terminal 15 may also have two plating layers and a conductive resin layer between these plating layers.

[0099] A resist film 30 comprising an electrically insulating resin is disposed on the surface of the metal core 19 in the area where the porous layer 19b is not formed. The resist film 30 is, for example, a resin comprising at least one of polyimide and epoxy. Furthermore, a height difference between the resist film 30 and the cathode layer 22 is not necessary. The cathode layer 22 may also be thicker than the resist film 30. Additionally, a portion of the resist film 30 may cover the cathode layer 22.

[0100] The sealing material 17 comprises resin. In addition to resin, the sealing material 17 may also contain fillers such as bauxite or silica, and magnetic materials. By including the aforementioned fillers in the sealing material 17, the mechanical strength and processability of the sealing material 17 can be adjusted. Furthermore, by selecting fillers with a desired coefficient of linear expansion, thermal shrinkage can be adjusted.

[0101] When the sealing material 17 contains a magnetic material, the impedance of the capacitor can be intentionally increased. For example, when multiple capacitors with low impedance are connected in parallel, anti-resonance may occur. In this case, if the sealing material contains a magnetic material, anti-resonance can be suppressed. As a magnetic material, for example, iron powder, iron-containing alloy powder, or ferrite powder can be used. The magnetic material can also be a mixture of two or more powders with different particle sizes or different compositions. As described above, the sealing material 17 is preferably selected according to the desired function, using the desired filler and magnetic material.

[0102] (Manufacturing method of solid electrolytic capacitors)

[0103] For the manufacturing method of the solid electrolytic capacitor 100 having the above structure, refer to Figure 6 as well as Figure 7 Please provide an explanation.

[0104] Prepare aluminum wire as a columnar metal core material with valve function 19 ( Figure 6 Step S1). The diameter of the aluminum wire is, for example, 0.02 mm or more and 5.0 mm or less. As mentioned above, there are no particular restrictions on the shape of the aluminum wire; it can be cylindrical or prismatic.

[0105] Next, as Figure 7 As shown in (a), along the length of the aluminum wire serving as the metal core 19, a resist film 30 is disposed at given intervals L1. Figure 6 (Step S2). As the resist film 30, for example, one of polyimide resin and epoxy resin can be used. Thus, on the surface of the aluminum wire, the resist film 30 is disposed in a given area at a given interval L1.

[0106] Here, the given interval L1 is, for example, 0.1 mm or more and 3.0 mm or less. Furthermore, the length of a given area where the resist film 30 is disposed is, for example, 0.1 mm or more and 3.0 mm or less.

[0107] Alternatively, it can also replace Figure 6The process of step S2 is to apply a resist film 30 to the entire surface of the aluminum wire, which serves as the metal core material 19, and to remove the resist film 30 in the form of a given area of ​​resist film 30 remaining at a given interval L1 along the length direction of the aluminum wire.

[0108] Next, a porous layer 19b is formed by etching the surface of the aluminum wire. Figure 6 Step S3). Figure 7 As shown in (b), a porous layer 19b is formed in the area where the resist film 30 is not disposed. As an etching process, methods such as AC electrolytic etching, DC electrolytic etching, and chemical etching can be used.

[0109] As described above, a porous layer 19b is formed in the area where the resist film 30 is not disposed by etching the surface of the aluminum wire. In subsequent processes, the aluminum wire is segmented at the locations where the resist film 30 is disposed, thus becoming a single piece. Therefore, in the final solid electrolytic capacitor, the locations where the resist film 30 is disposed become the ends of the metal core 19. Thus, through the above processes, the area C1 of the end face of the metal core 19 becomes larger than the area C2 of the central cross-section.

[0110] Next, a dielectric layer 21 is formed on the surface of the aluminum wire through a chemical formation process. Figure 6 Step S4). In the forming process, ammonium adipate is used as the forming solution, for example. That is, the surface of the aluminum wire is electrochemically oxidized in an aqueous solution of ammonium adipate, thereby forming an oxide film constituting the dielectric layer 21. The area where the resist film 30 is disposed does not come into contact with the forming solution, and therefore no oxide film is formed.

[0111] Alternatively, a chemical formation process can be performed after removing the resist film 30 using a laser or the like. In this case, the oxide film formed in the area where the resist film 30 is disposed can be removed using a laser or the like, or it can remain directly without removal.

[0112] Next, a material containing a conductive polymer is coated onto the surface of the aluminum wire. Figure 6 Step S5). Specifically, as a solid electrolyte, a conductive polymer solution dispersing poly(3,4-ethylenedioxythiophene) is applied to the porous layer 19b while being impregnated, and then dried to form a conductive polymer layer 23 (see step S5). Figure 7 (c)).

[0113] Here, in order to fill the pores 20 of the porous layer 19b with a material containing a conductive polymer, the aluminum wire is immersed in a conductive polymer solution. The conductive polymer layer 23 does not form in the areas on the surface of the aluminum wire where the resist film 30 is disposed.

[0114] Alternatively, a conductive polymer solution can be selectively coated onto the porous layer 19b.

[0115] Furthermore, if a material containing conductive polymers adheres to a region on the surface of the metal core 19 where a porous layer 19b has not been formed, the adhered material containing conductive polymers can be removed using a laser or the like.

[0116] Next, a carbon layer 24 is formed on the conductive polymer layer 23. Figure 6 Step S6). The carbon layer 24 can be formed, for example, using carbon paste, by methods such as coating, impregnation, printing, or transfer.

[0117] Next, a silver layer 25 is formed on the carbon layer 24. Figure 6 Step S7). The silver layer 25 can be formed, for example, using silver paste, by methods such as coating, dipping, printing, or transfer.

[0118] As described above, the conductive polymer layer 23, the carbon layer 24, and the silver layer 25 constitute the cathode layer 22 (see reference). Figure 5 ).

[0119] Next, a substrate with electrodes configured as cathode terminals 16 is prepared, and conductive adhesive 26 is used to bond the electrodes as cathode terminals 16 and the cathode layer 22. Figure 6 Step S8).

[0120] Then, with the outer surface of the cathode terminal 16 and both end faces of the metal core 19 exposed, resin is used to mold the area around the metal core 19. Figure 6 Step S9). The resin constitutes the sealing material 17.

[0121] Next, the aluminum wire is segmented at the location where the resist film 30 is applied, thus achieving monolithic processing. Figure 6 Step S10). More specifically, through... Figure 7 The dashed line in (c) indicates that the aluminum wire is segmented at the center of the resist film 30 along its length direction to achieve monolithic processing (see reference). Figure 7 (d)). Monolithization can be achieved by any method, such as cutting, pressing, or slits on the surface.

[0122] Next, for each monolithized unit, a first anode terminal 14 and a second anode terminal 15 are formed, such that they are connected to the two end faces of the metal core 19 exposed from the sealing material 17. Figure 6Step S1 1). The first anode terminal 14 and the second anode terminal 15 are formed, for example, by plating the two end faces of the metal core 19. The plating process can be performed, for example, by electrolytic plating or electroless plating.

[0123] Here, aluminum readily forms an oxide film, but this oxide film can be a major obstacle to the adhesion of the coated film. In this embodiment, aluminum wire is used as the metal core 19, and therefore, in order to form a highly adhesive coated film, a zincate treatment is performed before the coating process. Specifically, a solution containing Pd is coated onto the metal core 19, and Ni is precipitated by a displacement reaction through zincate treatment, thereby performing Sn coating on the Ni coating.

[0124] Through the above-described process, a solid electrolytic capacitor 100 (refer to...) can be manufactured. Figure 7 (e)).

[0125] (ESR measurement)

[0126] Using the method described above, several types of solid electrolytic capacitors with different ratios K between the end face area C1 and the central cross-sectional area C2 of the metal core 19 were manufactured. Then, the ESR of these various types of solid electrolytic capacitors was measured using a measuring instrument (E4980A) manufactured by Keysight Technologies.

[0127] Furthermore, after the ESR was measured, the ratio K (K=C1 / C2) of the area C1 of the end face of the metal core 19 to the area C2 of the cross-section at the center was determined.

[0128] Here, for each type of solid electrolytic capacitor with different ratios K, 10 solid electrolytic capacitors are prepared and their respective ESRs and ratios K are calculated. The average value of the ESRs and the average value of ratio K of the 10 solid electrolytic capacitors are also calculated.

[0129] The relationship between the ratio K of the end face area C1 of the metal core 19 to the cross-sectional area C2 of the central part and ESR is shown in Table 1.

[0130] [Table 1]

[0131]

[0132] As shown in Table 1, if we take the case where the area C2 of the cross-section at the center of the metal core 19 and the area C1 of the end face are the same (i.e., the ratio K is 1) as a baseline, the ESR decreases if the ratio K becomes greater than 1. For example, the ESR is 270 mΩ when the ratio K is 1, but the ESR becomes 253 mΩ when the ratio K is 1.01 (i.e., the area C1 of the end face of the metal core 19 is 1% larger than the area C2 of the cross-section at the center). Furthermore, the larger the ratio K becomes (i.e., the larger the area C1 of the end face relative to the area C2 of the cross-section at the center of the metal core 19), the lower the ESR becomes.

[0133] This invention is not limited to the above-described embodiments, and can be applied and modified in various ways within the scope of this invention.

Claims

1. A solid electrolytic capacitor, characterized in that, have: A columnar metal core material with valve function; The first external terminal is configured to cover one end face and the other end face of the metal core material, respectively; and The second external terminal has a different polarity than the first external terminal. The area of ​​each of the one end face and the other end face of the metal core is greater than the area of ​​the cross-section of the central portion of the metal core in the direction orthogonal to the length direction. A porous layer with an oxide film is disposed on a portion of the surface of the metal core material. The porous layer is connected to the second external terminal via a cathode layer, the cathode layer being a conductive layer containing a conductive polymer.

2. The solid electrolytic capacitor according to claim 1, characterized in that, The area of ​​each of the two end faces of the metal core is more than 1% larger than the area of ​​the cross-section of the central portion.

3. The solid electrolytic capacitor according to claim 1 or 2, characterized in that, A resist film is disposed on the portion of the surface of the metal core material where the porous layer is not formed.

4. The solid electrolytic capacitor according to claim 3, characterized in that, The resist film is a resin comprising at least one of polyimide and epoxy.

5. A method for manufacturing a solid electrolytic capacitor, characterized in that, have: The process of preparing columnar metal core material with valve function; The process of depositing a resist film on the surface of the metal core material; The process of removing the resist film in the longitudinal direction of the metal core material in a manner in which the resist film is arranged at given intervals; The process of forming a porous layer on the surface of the metal core material where the resist film is not disposed; The process of performing a chemical formation treatment on the porous layer; The process of coating a conductive polymer layer onto the surface of the metal core material after the formation treatment. The process of dividing the metal core material into individual pieces at the locations where the resist film is disposed; and The process of providing external terminals for each monolithically formed unit to cover both ends of the metal core material. In the metal core material that has been monolithized through the monolithization process, the area of ​​each of the two end faces of the metal core material is greater than the area of ​​the cross section of the central portion of the metal core material in the direction orthogonal to the length direction.

6. A method for manufacturing a solid electrolytic capacitor, characterized in that, have: The process of preparing columnar metal core material with valve function; The process of depositing a resist film on the surface of the metal core material at given intervals along its length; The process of forming a porous layer on the surface of the metal core material where the resist film is not disposed; The process of performing a chemical formation treatment on the porous layer; The process of coating a conductive polymer layer onto the surface of the metal core material after the formation treatment. The process of dividing the metal core material into individual pieces at the locations where the resist film is disposed; and The process of providing external terminals for each monolithically formed unit to cover both ends of the metal core material. In the metal core material that has been monolithized through the monolithization process, the area of ​​each of the two end faces of the metal core material is greater than the area of ​​the cross section of the central portion of the metal core material in the direction orthogonal to the length direction.

7. The method for manufacturing a solid electrolytic capacitor according to claim 5 or 6, characterized in that, The resist film is a resin comprising at least one of polyimide and epoxy.

8. The method for manufacturing a solid electrolytic capacitor according to claim 5 or 6, characterized in that, It also has: The process of forming a carbon layer on the conductive polymer layer; and The process of forming a silver layer on the carbon layer.

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