Method for manufacturing electrolytic capacitor

Abstract

To provide a method for manufacturing an electrolytic capacitor having small variation of characteristics.SOLUTION: A manufacturing method to be disclosed includes a process (iii) for oxidizing at least a portion of the surface of an anode body to form a dielectric layer by applying a direct current voltage between a first electrode 210 and a second electrode 220 in a state in which the anode body is immersed in a chemical conversion liquid 202. In the process (iii), at least one selected between a distance between first and second anode bodies 113a and 113b and the second electrode 220, and the area of the second electrode 220 facing the first and second anode bodies 113a and 113b is made different between the first anode body 113a and the second anode boy 113b so as to reduce difference between conversion current flowing to the first anode body 113a existing at an end and conversion current flowing to the second anode body 113b existing on an inner side of the first anode body 113a.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] An electrolytic capacitor includes an anode body and a dielectric layer formed on the surface of the anode body. Generally, the dielectric layer is formed by anodizing (forming treatment) the surface of the anode body.

[0003] Conventionally, various anodizing methods have been proposed. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-327899) discloses "In a manufacturing apparatus for a valve-acting metal element for a solid electrolytic capacitor, a plurality of valve-acting metal elements for a solid electrolytic capacitor are fixed to a metal horizontal bar by the anode lead-out wires of the elements, and a direct current is applied between the horizontal bar and the cathode-side electrode to perform anodization. The cathode-side electrode is composed of an electrode parallel to the bottom surface of the element and an electrode parallel to the side surface, and the cathode-side electrode is characterized by being in a mesh shape."

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of investigations, the inventors of the present application newly found that in the conventional method, there is a large variation in the thickness of the dielectric layer formed on each of the plurality of anode bodies. One object of the present disclosure is to provide a method for manufacturing an electrolytic capacitor with reduced variation in the thickness of the dielectric layer and reduced variation in characteristics.

Means for Solving the Problems

[0006] One aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method includes: step (i) of preparing a plurality of anode parts each including an anode body and an anode wire protruding from a first end face of the anode body; step (ii) of connecting a plurality of the anode wires connected to the plurality of anode bodies to a first electrode for formation in a state where the plurality of anode bodies are arranged at intervals along a predetermined direction to form an anode body group; and step (iii) of oxidizing at least a part of the surface of the anode body through applying a DC voltage between the first electrode and a second electrode while immersing the plurality of anode bodies connected to the first electrode through the anode wires in a formation solution to form a dielectric layer. In step (iii), the second electrode contacts the formation solution and is arranged along the anode body group. Among the anode body group, when a plurality of the anode bodies existing at the ends are defined as first anode bodies and the anode bodies existing inside the first anode bodies are defined as second anode bodies, in step (iii), at least one selected from the distances between the first and second anode bodies and the second electrode, and the areas of the second electrode facing the first and second anode bodies is made different between the first anode bodies and the second anode bodies so that the difference between the formation current flowing through the first anode bodies and the formation current flowing through the second anode bodies becomes small.

Advantages of the Invention

[0007] According to the present disclosure, an electrolytic capacitor with small variation in characteristics can be manufactured.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 10

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Figure 12

[0009] Hereinafter, embodiments of the manufacturing method according to the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "numerical value A or more and numerical value B or less".

[0010] (Method for Manufacturing an Electrolytic Capacitor) The method of the present embodiment for manufacturing an electrolytic capacitor includes the following steps (i) to (iii) in this order. In addition, from another perspective, the following manufacturing method is a manufacturing method of a member of an electrolytic capacitor (an anode body having a dielectric layer formed on its surface).

[0011] (Step (i)) Step (i) is a step of preparing a plurality of anode parts each including an anode body and an anode wire protruding from a first end face of the anode body. There is no limitation to the anode body and the anode wire, and known anode bodies and anode wires may be used. Alternatively, the anode part may be fabricated by a known method. Examples of the anode body and the anode wire and examples of their forming methods will be described later. (Step (ii)) Step (ii) is a step of connecting a plurality of anode wires connected to a plurality of anode bodies to a first electrode for formation in a state where the plurality of anode bodies are arranged at intervals along a predetermined direction to form an anode body group. That is, in step (ii), in a state where the plurality of anode parts are arranged at intervals along a predetermined direction, a plurality of anode wires connected to the plurality of anode bodies are connected to the first electrode for formation. The plurality of anode bodies may be arranged in a row or in a matrix.

[0012] The shape of the first electrode is selected according to the arrangement of the anode body group. For example, when the plurality of anode bodies are arranged in a row, the first electrode may have a linear shape (for example, rod-shaped or plate-shaped). When the plurality of anode bodies are arranged in a matrix, the first electrode may be composed of a plurality of linear electrodes or may be a grid-shaped electrode. The first electrode and the anode wire are electrically connected. Usually, the anode wire is fixed to the first electrode by a method such as welding. There is no particular limitation on the material of the first electrode, and it may be a conductive metal (for example, iron, iron alloy, copper, copper alloy, aluminum, etc.).

[0013] There is no limitation on the number of anode bodies included in the anode body group, and it may be in the range of 10 to 200 (for example, in the range of 40 to 100). The interval between adjacent anode bodies is not particularly limited either. The interval may be in the range of 1 to 20 mm (for example, in the range of 2 to 6 mm). Usually, the interval is constant, but the interval may not be constant.

[0014] (Step (iii)) Step (iii) is to immerse a plurality of anode bodies connected to the first electrode via anode wires in a formation solution In a step of forming a dielectric layer by oxidizing at least a part of the surface of the anode body (anodic oxidation) by applying a DC voltage between the first electrode and the second electrode in a dipped state. In step (iii), the second electrode is arranged so as to be in contact with the forming solution and along the anode body group. Here, among the anode body group, a plurality of anode bodies existing at the ends are defined as the first anode bodies, and anode bodies existing inside the first anode bodies are defined as the second anode bodies. In step (iii), At least one selected from the distances between the first and second anode bodies and the second electrode, and the area of the second electrode facing the first and second anode bodies is made different between the first anode body and the second anode body so that the difference between the forming current flowing through the first anode body and the forming current flowing through the second anode body becomes small.

[0015] According to the method of the present disclosure, as described in the examples, the difference between the forming current flowing through the first anode body and the forming current flowing through the second anode body can be reduced. As a result, the variation in the thickness of the dielectric layer formed on the surface of the anode body can be reduced. Therefore, according to the method of the present disclosure, an electrolytic capacitor with high reliability and characteristics can be manufactured with a high yield.

[0016] The first anode body may be composed only of the anode body existing at the outermost end, or may be composed of the anode body existing at the outermost end and a plurality of anode bodies in its vicinity. For example, when a plurality of anode bodies are arranged in a row, the two anode bodies at both ends may be defined as the first anode bodies. Alternatively, the anode bodies at both ends and a plurality of anode bodies in their vicinity may be defined as the first anode bodies. When a plurality of anode bodies are arranged in a matrix, the anode bodies existing at the outermost edge may be defined as the first anode bodies. Alternatively, the anode bodies at the outermost edge and a plurality of anode bodies in their vicinity may be defined as the first anode bodies. The second anode body is an anode body other than the first anode body and is arranged between the first anode bodies.

[0017] In step (iii), the surface of the anode body is oxidized and changed into a dielectric layer. For example, the anode body is When it is made of tantalum, a tantalum oxide layer is formed on the surface of the anode body. There is no particular limitation on the formation solution, and a known formation solution used for the formation treatment of the anode body of an electrolytic capacitor may be used. For example, any of an acidic aqueous solution, a neutral aqueous solution, and a basic aqueous solution may be used as the formation solution. Examples of the acidic aqueous solution include a phosphoric acid aqueous solution, a nitric acid aqueous solution, an acetic acid aqueous solution, and a sulfuric acid aqueous solution. Other examples of the formation solution include an aqueous solution of tartrate, an aqueous solution of oxalate, and an aqueous solution of tetraborate.

[0018] The second electrode is arranged so as to be in contact with the formation solution. For example, the second electrode may be immersed in the formation solution. Alternatively, at least a part of the electrolytic cell in which the formation solution is arranged may be used as the second electrode. It is preferable to use a metal that is stable during formation as the material of the second electrode. Examples of the material of the second electrode include ferroalloy, nickel, chromium, gold, platinum, tantalum, titanium, and carbon. The second electrode may be plate-shaped or mesh-shaped.

[0019] The manufacturing method of the present embodiment may satisfy the following condition (1). By satisfying the condition (1), in the formation treatment of step (iii), the difference between the formation current flowing through the first anode body and the formation current flowing through the second anode body can be reduced. An example of this configuration will be described later. (1) In step (iii), the shortest distance between the first anode body and the second electrode is made longer than the shortest distance between the second anode body and the second electrode.

[0020] The shortest distance L1 between the first anode body and the second electrode is greater than 1 times and not more than 10 times (for example, in the range of 1.05 to 2.3 times) the shortest distance L2 between the second anode body and the second electrode. When the shortest distance L1 and / or the shortest distance L2 take a plurality of values, any of those values satisfies the above relationship.

[0021] The first example (1a) and the second example (1b) that satisfy condition (1) will be described below. In the first example (1a), the second electrode is bent and / or curved so as to move away from the first anode body. In the second example (1b), the length De2 of the second electrode in the above-mentioned predetermined direction (the direction in which the anode bodies are arranged) is shorter than the length Dp of the anode body group in the predetermined direction. In the second example (1b), the length De2 (mm) is less than 1 times the length Dp (mm) and may be in the range of 0.85 to 0.97 times.

[0022] The manufacturing method of the present embodiment may satisfy the following condition (2). By satisfying condition (2), in the formation process of step (iii), the difference between the formation current flowing through the first anode body and the formation current flowing through the second anode body can be reduced. An example of this configuration will be described later. (2) In step (iii), the area of the second electrode of the portion facing the first anode body is smaller than the area of the second electrode of the portion facing the second anode body. For example, a through hole may be formed in the second electrode of the portion facing the first anode body.

[0023] When condition (2) is satisfied, the area S1 of the second electrode of the portion facing the first anode body is less than 1 times the area S2 of the second electrode of the portion facing the second anode body, and may be 0.01 times or more and less than 1 times the area S2, or may be in the range of 0.01 to 0.3 times the area S2 (for example, in the range of 0.03 to 0.15 times).

[0024] The manufacturing method of the present embodiment may satisfy the following condition (3). (3) The second electrode is disposed so as to face at least one surface selected from the second end surface of the anode body (the end surface from which the anode wire protrudes) and the side surface connecting the first end surface and the second end surface. For example, the second electrode may be disposed so as to face only the second end surface of the anode body, or may be disposed so as to face only the side surface of the anode body, or may be disposed so as to face both the second end surface and the side surface of the anode body. When the second electrode is disposed so as to face the side surface of the anode body, the second electrode may be disposed so as to face only one side surface of the aligned anode body group. Alternatively, two second electrodes may be disposed so as to sandwich the anode body group. When the electrode (counter electrode) paired with the first electrode is composed of two or more electrodes, at least one of those electrodes is the second electrode having the above characteristics.

[0025] The manufacturing method of the present embodiment may satisfy two selected from the above conditions (1) to (3). For example, it may satisfy conditions (1) and (2), may satisfy conditions (1) and (3), or may satisfy conditions (2) and (3). Alternatively, the manufacturing method of the present embodiment may satisfy all of the above conditions (1) to (3).

[0026] Through the steps including steps (i) to (iii), an anode part with a dielectric layer formed on its surface is obtained. Therefore, from one perspective, the present disclosure provides a method for manufacturing an anode part with a dielectric layer formed on its surface. The manufacturing method includes the above-described steps (i) to (iii).

[0027] After steps (i) to (iii), a step of forming parts necessary for the electrolytic capacitor is performed to obtain an electrolytic capacitor. There is no limitation to those steps, and known methods may be applied.

[0028] In an example of a manufacturing method of an electrolytic capacitor in which the anode body is a sintered body, an electrolyte layer is formed on the dielectric layer Form it and form a cathode lead layer on the electrolyte layer. In this way, a capacitor element is fabricated. Next, connect an anode lead terminal to the anode wire and connect a cathode lead terminal to the cathode lead layer. Then, form an exterior body so as to cover the capacitor element, a part of the anode lead terminal, and a part of the cathode lead terminal. In this way, an electrolytic capacitor is obtained.

[0029] In an example of a manufacturing method of an electrolytic capacitor in which the anode body is a wound body of a metal foil, in step (i), prepare a wound body obtained by winding an anode body (metal foil), a separator, and a cathode foil. The wound body includes an anode portion. The anode portion includes the anode body (metal foil) and an anode wire protruding from a first end face of the anode body (the first end face of the wound anode body). Usually, a dielectric layer is formed on the surface of the anode body (metal foil), but the dielectric layer is not formed on at least a part of the end face of the anode body. Therefore, a dielectric layer is formed on the portion where the dielectric layer is not formed by the above step (ii) and step (iii). After forming the dielectric layer, an electrolyte layer is formed inside the wound body to fabricate a capacitor element. By encapsulating the fabricated capacitor element in a case, a wound electrolytic capacitor is obtained. The electrolyte layer may be a solid electrolyte layer or an electrolyte layer containing a liquid component. There are no particular limitations on those components and formation methods, and known components and formation methods may be used.

[0030] As an example of the configuration and components of an electrolytic capacitor manufactured by the manufacturing method of the present disclosure, an example in the case of using a sintered anode body will be described below. An example of an electrolytic capacitor described below includes a capacitor element, an exterior body, an anode lead terminal, and a cathode lead terminal. Note that the configuration and components of the electrolytic capacitor manufactured by the method of the present disclosure are not limited to the following examples.

[0031] (Capacitor element) The capacitor element includes an anode portion, a dielectric layer, and a cathode portion. There are no particular limitations on the capacitor element, and a capacitor element used in a known solid electrolytic capacitor may be used.

[0032] The anode part includes an anode body and an anode wire. The anode body may be a porous sintered body or a metal foil with a porous surface. The dielectric layer is formed on the surface of the anode body. The cathode part includes an electrolyte layer and a cathode lead-out layer. The electrolyte layer is disposed between the dielectric layer formed on the surface of the anode body and the cathode lead-out layer. There are no particular limitations on these components, and components used in known solid electrolytic capacitors may be applied. Examples of these components will be described below.

[0033] (Anode body) For the material of the anode body, valve metal can be used. As the valve metal, titanium (Ti), tantalum (Ta), niobium (Nb), aluminum (Al), etc. or alloys containing them are used. The anode body may be formed by sintering particles serving as the material (for example, particles of valve metal) or by etching the metal serving as the material. The dielectric layer formed on the surface of the anode body is formed by the above-described process.

[0034] (Anode wire) The anode wire may be a wire made of metal. Examples of the material of the anode wire include the above-mentioned valve metal and copper. A part of the anode wire is embedded in the anode body, and the remaining part protrudes from the end face of the anode body.

[0035] (Electrolyte layer) There are no particular limitations on the electrolyte layer, and an electrolyte layer used in a known solid electrolytic capacitor may be applied. In this specification, the electrolyte layer may be read as a solid electrolyte layer, and the electrolytic capacitor may be read as a solid electrolytic capacitor. The electrolyte layer may be a laminate of two or more different electrolyte layers.

[0036] The electrolyte layer is arranged to cover at least a part of the dielectric layer. The electrolyte layer may be formed using a manganese compound or a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and their derivatives. These may be used alone or in combination of multiple types. Further, the conductive polymer may be a copolymer of two or more monomers. Note that the derivative of the conductive polymer means a polymer having the conductive polymer as a basic skeleton. For example, examples of the derivative of polythiophene include poly(3,4-ethylenedioxythiophene).

[0037] It is preferable that a dopant is added to the conductive polymer. The dopant can be selected according to the conductive polymer, and known dopants may be used. Examples of the dopant include naphthalenesulfonic acid, p-toluenesulfonic acid, polystyrenesulfonic acid, and their salts. An example of the electrolyte layer is formed using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonic acid (PSS).

[0038] The electrolyte layer containing the conductive polymer may be formed by polymerizing a raw material monomer on the dielectric layer. Alternatively, it may be formed by applying a liquid containing the conductive polymer (and a dopant if necessary) to the dielectric layer and then drying it.

[0039] (Cathode extraction layer) The cathode extraction layer is a conductive layer and is arranged to cover at least a part of the electrolyte layer. The cathode extraction layer may include a carbon layer formed on the electrolyte layer and a metal paste layer formed on the carbon layer. The carbon layer may be formed of a conductive carbon material such as graphite and a resin. The metal paste layer may be formed of metal particles (e.g., silver particles) and a resin, and may be formed of, for example, a known silver paste.

[0040] (Cathode lead terminal and anode lead terminal) The cathode lead terminal includes a cathode terminal portion exposed on the bottom surface of the electrolytic capacitor and a connection portion connected to the cathode terminal portion. The connection portion is electrically connected to the cathode portion. For example, the connection portion may be connected to the cathode lead layer by a conductive layer (such as a silver paste layer). The anode lead terminal includes an anode terminal portion exposed on the bottom surface of the electrolytic capacitor and a wire connection portion connected to the anode terminal portion. The wire connection portion is connected to the anode wire. The lead terminal may be formed by processing a metal sheet (including a metal plate and a metal foil) made of a metal (such as copper or a copper alloy) by a known metal processing method.

[0041] (Outer package) The outer package is arranged around the capacitor element so that the capacitor element is not exposed on the surface of the electrolytic capacitor. Further, the outer package insulates the anode lead terminal and the cathode lead terminal. Therefore, the outer package is made of an insulating material. There is no limitation on the formation method of the outer package, and it may be formed by a known method. For example, the outer package may be formed by arranging and curing the material of the outer package so as to cover a part of the lead terminal and the capacitor element. In this way, an electrolytic capacitor is obtained.

[0042] An example of a wound electrolytic capacitor includes a group of electrode plates, an electrolyte, and a case. The group of electrode plates includes a wound body, an anode wire, and a cathode wire. The wound body is formed by winding an anode body (metal foil), a separator, and a cathode foil. The anode wire is connected to the anode body (metal foil), and the cathode wire is connected to the cathode foil. The anode body is formed of a metal including the valve action metal described above. The surface of the anode body is porous, and a dielectric layer is formed on the surface. The separator is impregnated with an electrolyte. The electrolyte of the wound electrolytic capacitor may contain a liquid component. There is no particular limitation on these components, and known components used in wound electrolytic capacitors may be used.

[0043] In one aspect, the present disclosure provides a forming treatment method and a forming treatment apparatus for forming a dielectric layer on the surface of an anode body. The forming treatment method includes the above-described steps (i) to (iii). The forming treatment apparatus includes a tank in which a forming treatment liquid is disposed, a first electrode, and a second electrode, and further includes a DC power source as necessary. The tank is not particularly limited, and a known tank used for forming treatment may be used. Since the first electrode and the second electrode have been described above, redundant descriptions are omitted.

[0044] Hereinafter, an example of the method of the present disclosure for manufacturing an electrolytic capacitor will be specifically described with reference to the drawings. The above-described configuration can be applied to the example of the method described below. Also, the example of the method described below can be changed based on the above-described description. Further, the matters described below may be applied to the above-described embodiments. Also, in the embodiments described below, components that are not essential to the method of the present disclosure may be omitted.

[0045] (Embodiment 1) In Embodiment 1, an example of the manufacturing method according to the present disclosure will be described. A cross-sectional view of an example of an electrolytic capacitor manufactured by the manufacturing method of Embodiment 1 is schematically shown in FIG. 1. The electrolytic capacitor 100 shown in FIG. 1 includes a capacitor element 110, an anode lead terminal 120, a cathode lead terminal 130, an exterior body 101, and a conductive layer 141. The capacitor element 110 includes an anode portion 111, a dielectric layer 114, and a cathode portion 115. The anode portion 111 includes an anode body 113 and an anode wire 112. The anode body 113 is a rectangular parallelepiped-shaped porous sintered body, and a dielectric layer 114 is formed on the surface. A part of the anode wire 112 protrudes from one end face of the anode body 113 toward the front face 100f of the electrolytic capacitor 100. The other part of the anode wire 112 is embedded in the anode body 113.

[0046] The cathode part 115 includes an electrolyte layer 116 disposed to cover at least a part of the dielectric layer 114, and a cathode lead-out layer 117 formed on the electrolyte layer 116. The cathode lead-out layer 117 includes, for example, a carbon layer formed on the electrolyte layer 116 and a metal particle layer formed on the carbon layer. The metal particle layer is, for example, a metal paste layer (e.g., a silver paste layer) formed using a metal paste.

[0047] The anode lead terminal 120 includes an anode terminal part 121 and a wire connection part 122. The anode terminal part 121 is exposed on the bottom surface 100b of the electrolytic capacitor 100. The wire connection part 122 is connected to the anode wire 112. The cathode lead terminal 130 includes a cathode terminal part 131 and a connection part 132. The cathode terminal part 131 is exposed on the bottom surface 100b of the electrolytic capacitor 100. The connection part 132 is electrically connected to the cathode lead-out layer 117 by a conductive layer 141.

[0048] In the manufacturing method of Embodiment 1, first, a plurality of anode parts 111 are prepared. As shown in FIG. 2, the anode part 111 includes an anode body 113 and an anode wire 112 protruding from a first end face 113e1 of the anode body 113. The anode body 113 has a second end face on the side opposite to the first end face 113e1, and side faces 113s connecting the first end face 113e1 and the second end face 113e2. An example of the anode body 113 shown in FIG. 2 is substantially rectangular parallelepiped-shaped and has four side faces 113s.

[0049] Next, as shown in FIG. 3, with a plurality of anode bodies 113 arranged at intervals along a predetermined direction D to form an anode body group 113G, a plurality of anode wires 112 connected to the plurality of anode bodies 113 are connected to a first electrode 210 for formation. In Embodiment 1, the plurality of anode bodies 113 are arranged in a row. The first electrode 210 is an elongated plate-shaped electrode extending linearly. The anode wire 112 is fixed and electrically connected to the first electrode 210 by, for example, welding.

[0050] Next, as shown in FIG. 4, while a plurality of anode bodies 113 connected to the first electrode 210 via the anode wire 112 are immersed in the formation solution 202, a DC voltage is applied between the first electrode 210 and the second electrode 220. Thereby, at least a part of the surface of the anode body 113 is oxidized to form the dielectric layer 114. At this time, a part of the surface of the anode wire 112 may also be oxidized. In FIG. 4, an example is shown in which the second electrode 220 is formed only at a position facing the second end face 113e2 of the anode bodies 113 (the first anode body 113a and the second anode body 113b). The formation solution 202 is disposed in the tank 201. The second electrode 220 is also immersed in the formation solution 202.

[0051] In step (iii), the second electrode 220 contacts the formation solution 202 and is arranged along the anode body group 113G. Here, among the anode body group 113G, a plurality of anode bodies 113 existing at the ends are defined as the first anode body 113a, and the anode bodies 113 existing inside the first anode body 113a are defined as the second anode body 113b. In FIG. 4, an example is shown in which two anode bodies 113 at both ends are defined as the first anode body 113a, but a plurality of anode bodies 113 at both ends and in the vicinity thereof may be defined as the first anode body 113a (the same applies to other embodiments).

[0052] The second electrode 220 is an elongated plate-shaped electrode, but as shown in FIG. 4, it is bent at the central bent portion 220a. In the example shown in FIG. 4, among the second electrodes 220, the portion facing the first anode body 113a is bent such that the second electrode 220 moves away from the anode body group. Therefore, the shortest distance L1 between the first anode body 113a and the second electrode is longer than the shortest distance L2 between the second anode body 113b and the second electrode 220. According to this configuration, in step (iii), the difference between the formation current flowing through the first anode body 113a and the formation current flowing through the second anode body 113b can be reduced.

[0053] The second electrode 220 may be curved from the center toward the outside such that the shortest distance L1 between the first anode body 113a and the second electrode is longer than the shortest distance L2 between the second anode body 113b and the second electrode 220. A diagram of such a second electrode 220 is schematically shown in FIG. 5. The second electrode 220 is curved so as to move away from the anode body group 113G as it approaches the end.

[0054] The second electrode 220 may be bent at the end portion such that the shortest distance L1 between the first anode body 113a and the second electrode is longer than the shortest distance L2 between the second anode body 113b and the second electrode 220. A diagram of such a second electrode 220 is schematically shown in FIG. 6. The second electrode 220 shown in FIG. 6 is bent at two bent portions 220a located at positions corresponding to between the first anode body 113a and the second anode body 113b. The second electrode 220 between the two bent portions 220a is in a flat plate shape.

[0055] The length of the second electrode 220 in the direction D (the direction D in which the anode bodies 113 are arranged) may be shorter than the length of the anode body group 113G in the direction D. A cross-sectional view of such a second electrode 220 is shown in FIG. 7. In an example shown in FIG. 7, the length De2 of the second electrode 220 in the direction D is shorter than the length Dp of the anode body group 113G in the direction D. Also, the second electrode 220 does not exist in a portion of the anode body group 113G that faces the first anode body 113a existing at the end. As a result, the shortest distance L1 between the first anode body 113a and the second electrode 220 is longer than the shortest distance L2 between the second anode body 113b and the second electrode 220. Note that the distance between the second electrode 220 and the anode body group 113G in the direction D is, for example, (Dp - De2) / 2.

[0056] From another perspective, the embodiment shown in FIG. 7 is an example in which the areas of the second electrode 220 of the portions facing the first anode body 113a and the second anode body 113b are different. Specifically, the area S1 (not shown) of the second electrode 220 of the portion facing the first anode body 113a is smaller than the area S2 (not shown) of the second electrode 220 of the portion facing the second anode body 113b. Here, the area of the second electrode 220 of the portion facing the anode body 113 is the following area. First, the surface of the anode body 113 that faces the second electrode 220 (the second end face 113e2 of the anode body 113 in the example of FIG. 7) is projected in a direction perpendicular to the surface and toward the second electrode 220. At this time, the area of the portion where the projected surface and the surface of the second electrode 220 overlap is the area of the second electrode 220 of the portion facing the anode body 113. In the case of the example shown in FIG. 7, the area S1 of the second electrode 220 of the portion facing the first anode body 113a is zero. The area S2 of the second electrode 220 of the portion facing the second anode body 113b is equal to the area of the second end face 113e2.

[0057] A cross-sectional view of an example of another method for making the areas of the second electrode 220 of the portions facing the first anode body 113a and the second anode body 113b different is schematically shown in FIG. 8. In the example shown in FIG. 8, through holes 220h are formed in the second electrode 220 of the portion facing the second anode body 113b. As a result, the area S1 of the second electrode 220 of the portion facing the first anode body 113a is smaller than the area S2 of the second electrode 220 of the portion facing the second anode body 113b. The second electrode 220 shown in FIG. 8 is plate-shaped, and the shortest distance L1 and the shortest distance L2 are equal, but they do not have to be equal.

[0058] When the second electrode is mesh-shaped, the surface density of the second electrode 220 of the portion facing the first anode body 113a may be made smaller than the surface density of the second electrode 220 of the portion facing the second anode body 113b. Also in this case, the area of the second electrode 220 of the portion facing the first anode body 113a can be made smaller than the area of the second electrode 220 of the portion facing the second anode body 113b.

[0059] In the above figure, an example is shown in which the second electrode 220 is disposed only in a portion facing the second end face 113e2 of the anode body 113. However, as shown in FIG. 9, the second electrode 220 may be disposed in a portion facing the second end face 113e2 of the anode body 113 and a portion facing the side face 113s. FIG. 9 is a schematic diagram when viewing the arrangement of the electrodes from the second end face 113e2 side. In an example shown in FIG. 9, three second electrodes 220 are used as counter electrodes. FIG. 9 shows an example using the second electrode 220 shown in FIG. 4, but other second electrodes may be used. Further, any one or two of the three second electrodes 220 shown in FIG. 9 may be omitted. For example, one or two second electrodes 220 disposed in a portion facing the second end face 113e2 of the anode body 113 may be used as counter electrodes. Also, only one of the plurality of electrodes constituting the counter electrode may be the second electrode 220, and the other electrodes may be normal electrodes.

[0060] In Embodiment 1, an example in which the anode body is a sintered body has been described. However, as described above, the anode body may be a metal foil. In that case, a perspective view of an example of the electrode plate group including the anode portion prepared in step (i) is shown in FIG. 10. The electrode plate group 300 shown in FIG. 10 includes a wound body 310, an anode wire (anode lead) 322, and a cathode wire 323. The wound body 310 includes an anode body (metal foil), a cathode foil, and a separator. They are stacked and wound so that a separator is disposed between the anode body and the cathode foil. The surface of the metal foil that is the anode body is porous. A dielectric layer is formed on at least a part of the porous surface. Usually, no dielectric layer is formed on the end face of the metal foil. An example of the anode portion shown in FIG. 11 includes the wound anode body (metal foil) and the anode wire 322 protruding from the first end face 313e1 of the wound anode body. The anode wire 322 is connected to the anode body, and the cathode wire 323 is connected to the cathode foil.

[0061] The wound anode body includes a first end face 313e1, a second end face 313e2 opposite to the first end face 313e1, and a side face 313s connecting them. By replacing the electrode plate group 300 (including the anode part) shown in FIG. 10 with the anode part 111 in the above-described embodiment and performing steps (ii) and (iii), the surface of the anode body included in the electrode plate group shown in FIG. 10 A dielectric layer can be formed on at least a part of the. Specifically, the anode wires 312 of a plurality of electrode plate groups 300 (a plurality of anode parts) may be connected to the first electrode 210 to perform step (iii). Wo By step (iii), a dielectric layer can be formed on the end face of the anode body on which the dielectric layer is not formed . Even in this case, variations in the thickness of the formed dielectric layer can be reduced.

[0062] As described above, steps (i) to (iii) can be performed. After that, an electrolytic capacitor may be manufactured by the above-described steps.

Example

[0063] The present disclosure will be described in more detail with reference to the following examples.

[0064] In this example, the formation treatment was performed by changing the shape of the electrode (counter electrode) used during the formation treatment to form a dielectric layer. Then, an electrolytic capacitor was manufactured using the anode body on which the dielectric layer was formed.

[0065] Specifically, first, a plurality of anode parts including an anode body (tantalum sintered body) and an anode wire embedded therein were manufactured. Then, 106 anode parts were arranged in a row at regular intervals, and the anode wires were welded to a long and narrow plate-shaped first electrode.

[0066] ​Next, the anode body welded to the first electrode and the second electrode were immersed in a formation solution. An aqueous phosphoric acid solution was used as the formation solution. In the production of the electrolytic capacitor A1, formation treatment was performed using an electrode having the same shape as the second electrode 220 shown in FIG. 4. Further, in the production of the electrolytic capacitor C1 of the comparative example, formation treatment was performed using a flat plate-shaped electrode as in the conventional case.

[0067] Then, a dielectric layer was formed on the surfaces of 106 anode bodies by applying a DC voltage between the first electrode and the second electrode to perform formation treatment. In this way, an anode portion with a dielectric layer formed thereon was obtained. Using the obtained anode portion, 106 electrolytic capacitors A1 and 106 electrolytic capacitors C1 were manufactured. A polymer electrolyte layer containing a dopant was used for the electrolyte layer.

[0068] Among the manufactured electrolytic capacitors A1, the capacitance was measured for the electrolytic capacitors A1 manufactured using 53 anode portions in which the position fixed to the first electrode was on one side from the center. Similarly, among the manufactured electrolytic capacitors C1, the capacitance was measured for the electrolytic capacitors C1 manufactured using 53 anode portions in which the position fixed to the first electrode was on one side from the center.

[0069] For the electrolytic capacitor A1, the relationship between the position fixed to the first electrode and the capacitance is shown in FIG. 11. For the electrolytic capacitor C1, the relationship between the position fixed to the first electrode and the capacitance is shown in FIG. 12. The numbers on the horizontal axis in FIGS. 11 and 12 indicate the numbers assigned in the order of arrangement from the end of the first electrode. 1 on the horizontal axis is an electrolytic capacitor using the anode portion arranged at the outermost end of the first electrode. 53 on the horizontal axis is an electrolytic capacitor using the anode portion arranged at the position closest to the center of the first electrode. As shown in FIG. 11, in the electrolytic capacitor A1, the capacitance was almost constant regardless of the position where the anode portion was fixed to the first electrode. On the other hand, as shown in FIG. 12, in the electrolytic capacitor C1, the capacitance of the electrolytic capacitor using the anode portion fixed to the end of the first electrode decreased significantly. This is considered to be due to the following reasons.

[0070] Consider the case where, in formation processing, a plurality of anode bodies are arranged in a row to form an anode body group. In this case, the first anode body existing at the end of the anode body group mainly shares the current supplied from the second electrode with one adjacent anode body. On the other hand, the second anode body existing inside the first anode body mainly shares the current supplied from the second electrode with two anode bodies existing around it. Therefore, when using a conventional counter electrode, the formation current flowing through the first anode body becomes larger than the formation current flowing through the second anode body. As a result, when using a conventional counter electrode, the dielectric layer formed on the surface of the first anode body becomes thick, and the capacitance of the electrolytic capacitor using the same decreases. On the other hand, in the manufacturing method according to the present disclosure, the difference between the formation current flowing through the first anode body and the formation current flowing through the second anode body can be reduced. As a result, an electrolytic capacitor with high characteristics and small variation in characteristics can be manufactured regardless of the position where the anode body is fixed to the first electrode.

[0071] Note that the increase in the formation current at the end when using a conventional counter electrode does not occur only in the outermost anode body, and may also occur in the anode body near the anode body.

Industrial Applicability

[0072] The present disclosure can be used in a method for manufacturing an electrolytic capacitor.

Explanation of Signs

[0073] 100: Electrolytic capacitor 110: Capacitor element 111: Anode part 112: Anode wire 113: Anode body 113a: First anode body 113b: Second anode body 113e1: First end face 113e2: Second end face 113G: Anode body group 113s: Side face 114: Dielectric layer 202: Formation liquid 210: First electrode 220: Second electrode 220h: Through-hole

Claims

1. (i) preparing a plurality of anode parts each including an anode body and an anode wire protruding from a first end surface of the anode body; (ii) connecting a plurality of the anode wires connected to the anode bodies to a first electrode for chemical conversion in a state in which the plurality of the anode bodies are arranged at intervals along a predetermined direction to form an anode body group; and (iii) applying a DC voltage between the first electrode and the second electrode while the plurality of anode bodies connected to the first electrode via the anode wire are immersed in a chemical conversion solution to oxidize at least a portion of a surface of the anode bodies to form a dielectric layer, In the step (iii), the second electrode is in contact with the chemical conversion solution and is They are arranged along the polar body group, When the anode bodies at the ends of the anode body group are defined as first anode bodies and the anode body located more inward than the first anode bodies is defined as a second anode body, In the step (iii), the formation current flowing through the first anode body and the second anode body a first anode body and a second anode body, the first anode body and the second anode body being different from each other in at least one selected from a distance between the first and second anode bodies and the second electrode, and an area of ​​the second electrode facing the first and second anode bodies, so that a difference in a chemical formation current flowing through the first anode body and the second anode body is small.

2. In the step (iii), the shortest distance between the first anode body and the second electrode is The method according to claim 1 , wherein the distance is longer than the shortest distance between the second anode body and the second electrode.

3. The method of claim 2 , wherein the second electrode is bent and / or curved away from the first anode body.

4. The manufacturing method according to claim 2 , wherein a length of the second electrode in the predetermined direction is shorter than a length of the anode body group in the predetermined direction.

5. In the step (iii), the area of ​​the second electrode facing the first anode body is smaller than an area of ​​the second electrode that faces the second anode body.

6. The method according to claim 5 , wherein a through hole is formed in the second electrode in a portion facing the first anode body.

7. The manufacturing method according to any one of claims 1 to 6, wherein the second electrode is disposed to face at least one surface selected from a second end surface of the anode body opposite to the first end surface and a side surface connecting the first end surface and the second end surface.

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