Electrolytic Capacitor Manufacturing Method
By arranging anode bodies in a group and varying the second electrode's distance and area relative to the anodes during the chemical conversion process, the method addresses the issue of dielectric layer thickness variations, resulting in more reliable and consistent electrolytic capacitors.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
- Filing Date
- 2025-03-10
- Publication Date
- 2026-05-22
AI Technical Summary
Conventional methods for manufacturing electrolytic capacitors result in significant variations in the thickness of the dielectric layer, leading to inconsistent capacitor characteristics.
A manufacturing method involving the arrangement of anode bodies in a group, connecting them to a first electrode, and applying a DC voltage with a second electrode in a chemical conversion process, where the distance and area of the second electrode relative to the anodes are varied to minimize current differences, thereby reducing dielectric layer thickness variations.
This approach enables the production of electrolytic capacitors with reduced variations in characteristics, enhancing reliability and yield.
Smart Images
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Abstract
Description
Technical Field
[0006] , , , ,
[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 (chemical conversion 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 action metal element for a solid electrolytic capacitor, in which a plurality of valve action metal elements for a solid electrolytic capacitor are fixed to a metal horizontal bar by the anode lead-out wires of the elements, and anodic oxidation is performed by applying a direct current between the horizontal bar and the cathode-side electrode, 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, the variation in the thickness of the dielectric layer formed on each of the plurality of anode bodies is large. One object of the present disclosure is to provide a method for manufacturing an electrolytic capacitor with small variations in characteristics by reducing the variation in the thickness of the dielectric layer.
Means for Solving the Problems
[0006] One aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method includes the steps of (i) preparing a plurality of anode portions, each comprising an anode body and an anode wire protruding from a first end face of the anode body; (ii) arranging the plurality of anode bodies at intervals along a predetermined direction to form an anode body group, and connecting a plurality of anode wires connected to the plurality of anode bodies to a first electrode for chemical conversion; and (iii) immersing the plurality of anode bodies connected to the first electrode via the anode wires in a chemical conversion solution, and applying a DC voltage between the first electrode and a second electrode to oxidize at least a portion of the surface of the anode bodies to form a dielectric layer. The process includes the above, and in step (iii), the second electrode comes into contact with the chemical solution and The anodes are arranged along the anode group, and among the anode group, the multiple anodes located at the ends are designated as the first anodes, and the anodes located inside the first anodes are designated as the second anodes. In step (iii), the chemical energy flowing through the first anodes To minimize the difference between the current and the formation current flowing through the second anode, at least one of the distances between the first and second anodes and the second electrode, and the area of the second electrode facing the first and second anodes, is made different for the first and second anodes. [Effects of the Invention]
[0007] According to this disclosure, electrolytic capacitors with small variations in characteristics can be manufactured. [Brief explanation of the drawing]
[0008] [Figure 1] This is a schematic cross-sectional view showing an example of an electrolytic capacitor manufactured by the manufacturing method disclosed herein. [Figure 2] This is a schematic perspective view showing an example of an anode used in the manufacturing method disclosed herein. [Figure 3] This figure schematically illustrates an example of one step in the manufacturing method of the present disclosure. [Figure 4]This diagram schematically shows an example of a process that follows the process shown in Figure 3. [Figure 5] This figure schematically shows another example of a process that follows the process shown in Figure 3. [Figure 6] This figure schematically shows another example of a process that follows the process shown in Figure 3. [Figure 7] This figure schematically shows another example of a process that follows the process shown in Figure 3. [Figure 8] This figure schematically shows another example of a process that follows the process shown in Figure 3. [Figure 9] This figure schematically shows another example of a process that follows the process shown in Figure 3. [Figure 10] This figure schematically illustrates another example of one step in the manufacturing method of the present disclosure. [Figure 11] This graph shows an example of the evaluation results of an electrolytic capacitor manufactured using the method described in the example. [Figure 12] This graph shows an example of the evaluation results of an electrolytic capacitor manufactured using the comparative example method. [Modes for carrying out the invention]
[0009] The following describes embodiments of the manufacturing method relating to this disclosure with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be given as examples, but other numerical values and materials may be applied as long as the effects of this disclosure are 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 "greater than or equal to numerical value A and less than or equal to numerical value B".
[0010] (Manufacturing method for electrolytic capacitors) The method of this embodiment for manufacturing an electrolytic capacitor comprises the following steps (i) to (iii): The following are included in this order. Furthermore, from another perspective, the following manufacturing methods are for manufacturing components of electrolytic capacitors (anodes with a dielectric layer formed on their 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 parts 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 chemical conversion 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), a plurality of anode wires connected to a plurality of anode bodies are connected to a first electrode for chemical conversion in a state where the plurality of anode parts are arranged at intervals along a predetermined direction. 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 (such as a rod shape or a plate shape). 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 (such as 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 also not particularly limited. 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 a first electrode via anode wires in a chemical conversion solution This process involves oxidizing (anodic oxidation) at least a portion of the surface of the anode body by applying a DC voltage between the first electrode and the second electrode while the anode body is immersed, thereby forming a dielectric layer. In step (iii), the second electrode is positioned in contact with the conversion solution and along the anode body group. Here, among the group of anodes, the multiple anodes located at the ends are designated as the first anodes, and the anodes located inside the first anodes are designated as the second anodes. In step (iii), To minimize the difference between the conversion current flowing through the first anode and the conversion current flowing through the second anode, at least one of the following is made different for the first and second anodes: the distance between the first and second anodes and the second electrode, and the area of the second electrode facing the first and second anodes.
[0015] According to the method of this disclosure, as described in the examples, the difference between the conversion current flowing through the first anode and the conversion current flowing through the second anode can be reduced. As a result, variations in the thickness of the dielectric layer formed on the surface of the anode can be reduced. Therefore, according to the method of this disclosure, electrolytic capacitors with high reliability and characteristics can be manufactured with a high yield.
[0016] The first anode body may consist only of the anode body located at the outermost edge, or it may consist of the anode body located at the outermost edge and multiple anode bodies in its vicinity. For example, if multiple anode bodies are arranged in a row, the two anode bodies at both ends may be considered the first anode body. Alternatively, multiple anode bodies at both ends and in their vicinity may be considered the first anode body. If multiple anode bodies are arranged in a matrix, the anode body located at the outermost edge may be considered the first anode body. Alternatively, multiple anode bodies at the outermost edge and in its vicinity may be considered the first anode body. The second anode body is an anode body other than the first anode body, and is located between the first anode bodies.
[0017] In step (iii), the surface of the anode is oxidized and transformed into a dielectric layer. For example, the anode is If the anode is made of tantalum, a tantalum oxide layer is formed on the surface of the anode. There are no particular limitations on the conversion solution, and known conversion solutions used for the conversion treatment of anodes of electrolytic capacitors may be used. For example, any of acidic aqueous solutions, neutral aqueous solutions, or basic aqueous solutions may be used as the conversion solution. Examples of acidic aqueous solutions include phosphoric acid aqueous solutions, nitric acid aqueous solutions, acetic acid aqueous solutions, and sulfuric acid aqueous solutions. Other examples of conversion solutions include aqueous solutions of tartrate, oxalate, and tetraborate.
[0018] The second electrode is positioned to be in contact with the chemical conversion solution. For example, the second electrode may be immersed in the chemical conversion solution. Alternatively, at least a portion of the electrolytic cell in which the chemical conversion solution is contained may be used as the second electrode. It is preferable to use a metal that is stable during the chemical conversion process as the material of the second electrode. Examples of materials for the second electrode include iron alloys, nickel, chromium, gold, platinum, tantalum, titanium, and carbon. The second electrode may be in the form of a plate or a mesh.
[0019] The manufacturing method of this embodiment may satisfy the following condition (1). By satisfying condition (1), in the chemical treatment of step (iii), the chemical current flowing through the first anode and the second This allows for a reduction in the difference between the current flowing through the anode and the conversion current. An example of this configuration will be discussed later. (1) In step (iii), the shortest distance between the first anode and the second electrode is the second anode The distance between the polar body and the second electrode should be longer than the shortest distance between them.
[0020] The shortest distance L1 between the first anode and the second electrode may be greater than 1 times the shortest distance L2 between the second anode and the second electrode, and greater than 1 times but less than or equal to 10 times (for example, in the range of 1.05 to 2.3 times). When the shortest distances L1 and / or L2 take multiple values, any of them satisfies the above relationship.
[0021] The first example (1a) and the second example (1b) that satisfy condition (1) are described below. In the first example (1a), the second electrode is bent and / or curved away from the first anode. In the second example (1b), the length De2 of the second electrode in the predetermined direction (the direction in which the anodes are aligned) is shorter than the length Dp of the anode group in the same 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 this embodiment may also satisfy the following condition (2). By satisfying condition (2), in the chemical treatment of step (iii), the chemical current flowing through the first anode and the second This allows for a reduction in the difference between the current flowing through the anode and the conversion current. An example of this configuration will be discussed later. (2) In step (iii), the area of the second electrode in the portion facing the first anode is the second It is smaller than the area of the second electrode in the portion facing the anode. For example, a through hole may be formed in the second electrode in the portion facing the first anode.
[0023] If condition (2) is met, the area S1 of the second electrode in the portion facing the first anode is less than 1 times the area S2 of the second electrode in the portion facing the second anode, and may be 0.01 times or more but less than 1 times the area S2, and 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 this embodiment may satisfy the following condition (3). (3) The second electrode is positioned to face at least one of the following faces: the second end face of the anode body opposite to the first end face (the end face from which the anode wire protrudes), and the side face connecting the first and second end faces. For example, the second electrode may be positioned to face only the second end face of the anode body, or only the side face of the anode body, or both the second end face and the side face of the anode body. If the second electrode is positioned to face the side face of the anode body, the second electrode may be positioned to face only one side face of the group of anode bodies. Alternatively, two second electrodes may be positioned so as to sandwich the group of anode bodies. If the electrode paired with the first electrode (counter electrode) consists of two or more electrodes, at least one of them is a second electrode having the above characteristics.
[0025] The manufacturing method of this embodiment may satisfy two of the above conditions (1) to (3). For example, it may satisfy conditions (1) and (2), or conditions (1) and (3), or conditions (2) and (3). Alternatively, the manufacturing method of this embodiment may satisfy all of the above conditions (1) to (3).
[0026] The anode portion, in which a dielectric layer is formed on its surface by the process including steps (i) to (iii) Therefore, in one respect, the present disclosure provides a method for manufacturing an anode portion having a dielectric layer formed on its surface. The manufacturing method comprises steps (i) to (iii) described above.
[0027] After steps (i) to (iii), a process is carried out to form the necessary parts for the electrolytic capacitor. An electrolytic capacitor can be obtained by this process. There are no limitations on these steps, and known methods may be applied.
[0028] In one example of a manufacturing method for an electrolytic capacitor in which the anode is a sintered body, an electrolyte layer is placed on a dielectric layer. A cathode lead layer is formed on the electrolyte layer. In this way, a capacitor element is fabricated. Next, the anode lead terminals are connected to the anode wire, and the cathode lead terminals are connected to the cathode lead layer. Then, an outer casing is formed to cover the capacitor element, a portion of the anode lead terminals, and a portion of the cathode lead terminals. In this way, an electrolytic capacitor is obtained.
[0029] In a manufacturing method for an example of an electrolytic capacitor in which the anode is a wound metal foil, step (i) prepares a wound body in which the anode (metal foil), separator, and cathode foil are wound. The wound body includes an anode portion. The anode portion includes the anode (metal foil) and an anode wire protruding from the first end face of the anode (the first end face of the wound anode). Normally, a dielectric layer is formed on the surface of the anode (metal foil), but at least a portion of the end face of the anode does not have a dielectric layer. Therefore, a dielectric layer is formed in the portion where the dielectric layer is not formed by steps (ii) and (iii) above. After the dielectric layer is formed, electrolytic capacitors are introduced into the interior of the wound body. Capacitor elements are fabricated by forming a solid layer. A wound electrolytic capacitor is obtained by enclosing the fabricated capacitor elements in a case. The electrolyte layer may be a solid electrolyte layer or an electrolyte layer containing a liquid component. There are no particular limitations on the components and formation methods, and known components and formation methods may be used.
[0030] An example of the configuration and components of an electrolytic capacitor manufactured by the manufacturing method of this disclosure is described below, specifically in the case where a sintered anode is used. The example electrolytic capacitor described below includes a capacitor element, an outer casing, anode lead terminals, and cathode lead terminals. However, the configuration and components of an electrolytic capacitor manufactured by the method of this disclosure are not limited to the example below.
[0031] (Capacitor element) The capacitor element includes an anode, a dielectric layer, and a cathode. There are no particular limitations on the capacitor element, and capacitor elements used in known solid electrolytic capacitors may be used.
[0032] The anode portion 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. A dielectric layer is formed on the surface of the anode body. The cathode portion includes an electrolyte layer and a cathode extraction layer. The electrolyte layer is disposed between the dielectric layer formed on the surface of the anode body and the cathode extraction layer. These components are not particularly limited, and components used in known solid electrolytic capacitors may be used. Examples of these components are described below.
[0033] (Anode) Valve metals can be used as the material for the anode. Suitable valve metals include titanium (Ti), tantalum (Ta), niobium (Nb), aluminum (Al), and alloys containing these materials. The anode may be formed by sintering material particles (e.g., valve metal particles) or by etching the material metal. The dielectric layer formed on the surface of the anode is formed by the process described above.
[0034] (Anode wire) The anode wire may be a wire made of metal. Examples of materials for the anode wire include the valve metals and copper mentioned above. 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 known solid electrolytic capacitors may be applied. In this specification, "electrolyte layer" may be read as "solid electrolyte layer," and "electrolytic capacitor" may be read as "solid electrolytic capacitor." The electrolyte layer consists of two or more different layers. It may also be a laminate of electrolyte layers.
[0036] The electrolyte layer is positioned to cover at least a portion of the dielectric layer. The electrolyte layer may be formed using manganese compounds or conductive polymers. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. These may be used individually or in combination. The conductive polymer may also be a copolymer of two or more monomers. A derivative of a conductive polymer refers to a polymer that uses a conductive polymer as its basic skeleton. For example, an example of a derivative of polythiophene is 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 dopants include naphthalene sulfonic acid, p-toluenesulfonic acid, polystyrene sulfonic acid, and salts thereof. One example of an electrolyte layer is formed using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS).
[0038] The electrolyte layer containing the conductive polymer may be formed by polymerizing the raw material monomers on the dielectric layer. Alternatively, it may be formed by coating the dielectric layer with a liquid containing the conductive polymer (and optionally a dopant) and then drying it.
[0039] (Cathode extraction layer) The cathode extraction layer is a conductive layer and is arranged to cover at least a portion 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 (e.g., 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 terminals may be formed by processing a metal sheet (including metal plates and metal foils) made of metal (copper, copper alloy, etc.) using known metalworking methods.
[0041] (Exterior) The outer casing is positioned around the capacitor element so that the capacitor element is not exposed on the surface of the electrolytic capacitor. Furthermore, the outer casing insulates the anode lead terminal from the cathode lead terminal. For this reason, the outer casing is made of an insulating material. There are no limitations on the method of forming the outer casing, and it may be formed by known methods. For example, the outer casing may be formed by arranging the outer casing material so as to cover a part of the lead terminals and the capacitor element, and then curing it. In this way, an electrolytic capacitor is obtained.
[0042] An example of a wound electrolytic capacitor includes a plate group, an electrolyte, and a case. The plate group includes a winding, an anode wire, and a cathode wire. The winding is formed by winding an anode (metal foil), a separator, and a cathode foil. The anode wire is connected to the anode (metal foil), and the cathode wire is connected to the cathode foil. The anode is made of a metal including the valve metal described above. The surface of the anode is porous, and a dielectric layer is formed on its surface. The separator is impregnated with an electrolyte. The electrolyte of a wound electrolytic capacitor is liquid. The components may include certain elements. These components are not particularly limited, and known components used in wound electrolytic capacitors may be used.
[0043] In one respect, this disclosure provides a chemical conversion treatment method and a chemical conversion apparatus for forming a dielectric layer on the surface of an anode. The chemical conversion treatment method comprises steps (i) to (iii) described above. The chemical treatment apparatus includes a tank in which the chemical treatment liquid is placed, a first electrode, and a second electrode, and optionally further includes a DC power supply. The tank is not particularly limited, and a known tank used for chemical treatment may be used. The first electrode and the second electrode have been described above, so a redundant explanation will be omitted.
[0044] Hereinafter, an example of the method of the present disclosure for manufacturing electrolytic capacitors will be specifically described with reference to the drawings. The configuration described above can be applied to the example of the method described below. Furthermore, the example of the method described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiments. Furthermore, in the embodiments described below, components that are not essential to the method of the present disclosure may be omitted.
[0045] (Embodiment 1) Embodiment 1 describes an example of a manufacturing method according to the present disclosure. A schematic cross-sectional view of an example of an electrolytic capacitor manufactured by the manufacturing method of Embodiment 1 is shown in Figure 1. The electrolytic capacitor 100 shown in Figure 1 includes a capacitor element 110, anode lead terminals 120, cathode lead terminals 130, an outer casing 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 porous sintered body with a dielectric layer 114 formed on its surface. A portion of the anode wire 112 protrudes from one end face of the anode body 113 toward the front surface 100f of the electrolytic capacitor 100. The other portion of the anode wire 112 is embedded in the anode body 113.
[0046] The cathode portion 115 includes an electrolyte layer 116 disposed to cover at least a portion of the dielectric layer 114, and a cathode extraction layer 117 formed on the electrolyte layer 116. The cathode extraction 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 portion 121 and a wire connection portion 122. The anode terminal portion 121 is exposed on the bottom surface 100b of the electrolytic capacitor 100. The wire connection portion 122 is connected to the anode wire 112. The cathode lead terminal 130 includes a cathode terminal portion 131 and a connection portion 132. The cathode terminal portion 131 is exposed on the bottom surface 100b of the electrolytic capacitor 100. The connection portion 132 is electrically connected to the cathode lead layer 117 by a conductive layer 141.
[0048] In the manufacturing method of Embodiment 1, first, a plurality of anode portions 111 are prepared. As shown in Figure 2, the anode portion 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 a side surface 113s connecting the first end face 113e1 and the second end face 113e2. An example of the anode body 113 shown in Figure 2 is substantially rectangular parallelepiped and has four side surfaces 113s.
[0049] Next, as shown in Figure 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 the first electrode 210 for chemical formation. In Embodiment 1, the plurality of anode bodies 113 are They are arranged in a row. The first electrode 210 is a long, narrow, plate-shaped electrode that extends in a straight line. The anode wire 112 is fixed and electrically connected to the first electrode 210, for example by welding.
[0050] Next, as shown in Figure 4, with multiple anode bodies 113 connected to the first electrode 210 via an anode wire 112 immersed in the conversion solution 202, a DC voltage is applied between the first electrode 210 and the second electrode 220. This oxidizes at least a portion of the surface of the anode bodies 113 to form a dielectric layer 114. At this time, a portion of the surface of the anode wire 112 may also be oxidized. Figure 4 shows an example in which the second electrode 220 is formed only at a position facing the second end face 113e2 of the anode body 113 (first anode body 113a and second anode body 113b). The conversion solution 202 is placed in a tank 201. The second electrode 220 is also immersed in the conversion solution 202.
[0051] In step (iii), the second electrode 220 comes into contact with the chemical solution 202 and the anode body The anodes are arranged along group 113G. Here, among the anode group 113G, the multiple anodes 113 located at the ends are designated as the first anodes 113a, and the anodes 113 located inside the first anodes 113a are designated as the second anodes 113b. Note that Figure 4 shows an example in which the two anodes 113 at both ends are designated as the first anodes 113a, but the multiple anodes 113 at both ends and in their vicinity may also be designated as the first anodes 113a (the same applies to other embodiments).
[0052] The second electrode 220 is an elongated plate-shaped electrode, but as shown in Figure 4, it is bent at the central bent portion 220a. In the example shown in Figure 4, the second electrode 220 is bent such that the portion of the second electrode 220 facing the first anode 113a moves away from the anode group. Therefore, the shortest distance L1 between the first anode 113a and the second electrode is longer than the shortest distance L2 between the second anode 113b and the second electrode 220. With this configuration, in process (iii), the conversion current flowing through the first anode 113a and the current flowing through the second anode 113b The difference with the chemical conversion current can be reduced.
[0053] The second electrode 220 may be curved outward from the center such that the shortest distance L1 between the first anode 113a and the second electrode is longer than the shortest distance L2 between the second anode 113b and the second electrode 220. A schematic diagram of such a second electrode 220 is shown in Figure 5. The second electrode 220 is curved so that it moves away from the anode group 113G as it approaches its ends.
[0054] The second electrode 220 may be bent at its end portion such that the shortest distance L1 between the first anode 113a and the second electrode is longer than the shortest distance L2 between the second anode 113b and the second electrode 220. A schematic diagram of such a second electrode 220 is shown in Figure 6. The second electrode 220 shown in Figure 6 is bent at two bent portions 220a located at corresponding positions between the first anode 113a and the second anode 113b. The second electrode 220 between the two bent portions 220a is flat and plate-like.
[0055] The length of the second electrode 220 in direction D (the direction D in which the anodes 113 are aligned) may be shorter than the length of the anode group 113G in direction D. A cross-sectional view of such a second electrode 220 is shown in Figure 7. In the example shown in Figure 7, the length De2 of the second electrode 220 in direction D is shorter than the length Dp of the anode group 113G in direction D. Also, the second electrode 220 does not exist in the portion of the anode group 113G that is located at the end and facing the first anode 113a. As a result, the shortest distance L1 between the first anode 113a and the second electrode 220 is longer than the shortest distance L2 between the second anode 113b and the second electrode 220. Note that the distance between the second electrode 220 and the anode group 113G in direction D is, for example, (Dp-De2). It is / 2.
[0056] From another perspective, the embodiment shown in Figure 7 is an example in which the areas of the second electrode 220 differ in the portion facing the first anode 113a and the second anode 113b. Specifically, the area S1 (not shown) of the portion of the second electrode 220 facing the first anode 113a is smaller than the area S2 (not shown) of the portion of the second electrode 220 facing the second anode 113b. Here, the area of the second electrode 220 facing the anode 113 is as follows: First, the surface of the anode 113 facing the second electrode 220 (the second end face 113e2 of the anode 113 in the example of Figure 7) is projected perpendicular to that surface and toward the second electrode 220. At that time, the area of the portion where the projected surface and the surface of the second electrode 220 overlap is the area of the portion of the second electrode 220 facing the anode 113. In the example shown in Figure 7, the area S1 of the portion of the second electrode 220 facing the first anode 113a is zero. The area S2 of the portion of the second electrode 220 facing the second anode 113b is equal to the area of the second end face 113e2.
[0057] Figure 8 schematically shows a cross-sectional view of an example of another method for making the areas of the second electrode 220 different in the portions facing the first anode 113a and the second anode 113b. In the example shown in Figure 8, a through hole 220h is formed in the portion of the second electrode 220 facing the second anode 113b. As a result, the area S1 of the portion of the second electrode 220 facing the first anode 113a is smaller than the area S2 of the portion of the second electrode 220 facing the second anode 113b. The second electrode 220 shown in Figure 8 is plate-shaped, and the shortest distances L1 and L2 are equal, but they do not have to be equal.
[0058] If the second electrode is mesh-like, the surface density of the portion of the second electrode 220 facing the first anode 113a may be made smaller than the surface density of the portion of the second electrode 220 facing the second anode 113b. In this case as well, the area of the portion of the second electrode 220 facing the first anode 113a can be made smaller than the area of the portion of the second electrode 220 facing the second anode 113b.
[0059] The above figure shows an example in which the second electrode 220 is located only on the portion of the anode body 113 facing the second end face 113e2. However, the second electrode 220 may be located on both the portion of the anode body 113 facing the second end face 113e2 and the portion facing the side surface 113s, as shown in Figure 9. Figure 9 is a schematic diagram of the electrode arrangement as viewed from the second end face 113e2 side. In the example shown in Figure 9, three second electrodes 220 are used as counter electrodes. Figure 9 shows an example using the second electrodes 220 shown in Figure 4, but other second electrodes may be used. Also, one or two of the three second electrodes 220 shown in Figure 9 may be omitted. For example, one or two second electrodes 220 located on the portion of the anode body 113 facing the second end face 113e2 may be used as counter electrodes. Alternatively, one of the multiple electrodes constituting the counter electrode may be designated as the second electrode 220, while the other electrodes are ordinary electrodes.
[0060] In Embodiment 1, an example was described in which the anode body is a sintered body. However, as mentioned above, the anode body may be a metal foil. In that case, Figure 10 shows a perspective view of an example of an electrode plate group including the anode portion prepared in step (i). The electrode plate group 300 shown in Figure 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 wound together so that a separator is placed between the anode body and the cathode foil. The metal foil that is the anode body has a porous surface. A dielectric layer is formed on at least a part of the porous surface. Normally, a dielectric layer is not formed on the end face of the metal foil. The anode portion of an example shown in Figure 11 includes a wound anode body (metal foil) and a protruding part from the first end face 313e1 of the wound anode body. It includes an anode wire 322. 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 surface 313s connecting them. By replacing the anode portion 111 in the above-described embodiment with the electrode plate group 300 (including the anode portion) shown in Figure 10 and performing steps (ii) and (iii), the surface of the anode body included in the electrode plate group shown in Figure 10 A dielectric layer can be formed on at least a portion of it. Specifically, the anode wires 312 of the multiple electrode plate groups 300 (multiple anode portions) can be connected to the first electrode 210 and step (iii) can be performed. By method (iii), a dielectric layer can be formed on the end face of the anode body where no dielectric layer is formed. Even in this case, variations in the thickness of the dielectric layer formed can be reduced.
[0062] As described above, steps (i) to (iii) can be carried out. After that, the process described above can be followed. We just need to manufacture electrolytic capacitors. [Examples]
[0063] The present disclosure will be further described by the following embodiments.
[0064] In this embodiment, the shape of the electrode (counter electrode) used during the chemical conversion treatment was changed, and a dielectric layer was formed. Then, an electrolytic capacitor was fabricated using the anode body on which the dielectric layer was formed.
[0065] Specifically, first, multiple anode sections were fabricated, each containing an anode body (tantalum sintered body) and an embedded anode wire. Then, 106 anode sections were arranged in a line at regular intervals, and the anode wires were welded to a long, narrow, plate-shaped first electrode.
[0066] Next, the anode welded to the first electrode and the second electrode were immersed in a chemical conversion solution. A phosphoric acid aqueous solution was used as the chemical conversion solution. In the manufacture of electrolytic capacitor A1, the chemical conversion treatment was performed using an electrode having the same shape as the second electrode 220 shown in Figure 4. In the manufacture of the comparative example electrolytic capacitor C1, the chemical conversion treatment was performed using a straight plate-shaped electrode, as in the conventional method.
[0067] Then, by applying a DC voltage between the first electrode and the second electrode and performing a chemical conversion treatment, a dielectric layer was formed on the surface of 106 anode bodies. In this way, an anode portion with a dielectric layer formed 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] The capacitance of electrolytic capacitor A1 was measured for electrolytic capacitor A1 that was fabricated using 53 anode portions fixed to the first electrode at a position to one side of the center. Similarly, the capacitance of electrolytic capacitor C1 was measured for electrolytic capacitor C1 that was fabricated using 53 anode portions fixed to the first electrode at a position to one side of the center.
[0069] Figure 11 shows the relationship between the fixed position of the first electrode and the capacitance for electrolytic capacitor A1. Figure 12 shows the relationship between the fixed position of the first electrode and the capacitance for electrolytic capacitor C1. The numbers on the horizontal axis in Figures 11 and 12 indicate the order in which the first electrode is positioned from the edge. 1 on the horizontal axis represents an electrolytic capacitor using the anode positioned at the very edge of the first electrode. 53 on the horizontal axis represents an electrolytic capacitor using the anode positioned closest to the center of the first electrode. As shown in Figure 11, in electrolytic capacitor A1, the capacitance was almost constant regardless of the position of the anode fixed to the first electrode. On the other hand, as shown in Figure 12, in the electrolytic capacitor C1, the capacitance of the electrolytic capacitor using the anode fixed to the end of the first electrode decreased significantly. This is thought to be due to the following reasons.
[0070] Consider the case where multiple anodes are arranged in a line to form an anode group during a chemical conversion process. In this case, the first anode located at the end of the anode group shares the current supplied from the second electrode mainly with one adjacent anode. On the other hand, the second anode located inside the first anode shares the current supplied from the second electrode mainly with two surrounding anodes. Therefore, when using a conventional counter electrode, the conversion current flowing through the first anode is greater than the conversion current flowing through the second anode. As a result, when using a conventional counter electrode, the dielectric layer formed on the surface of the first anode becomes thicker, and the capacitance of the electrolytic capacitor using it decreases. On the other hand, the manufacturing method according to this disclosure can reduce the difference between the conversion current flowing through the first anode and the conversion current flowing through the second anode. As a result, electrolytic capacitors with high performance and low variation in characteristics can be manufactured regardless of the position in which the anode is fixed to the first electrode.
[0071] Furthermore, the increase in the chemical current at the end when using a conventional counter electrode does not necessarily occur only at the outermost anode, but may also occur at anodes in the vicinity of that anode. [Industrial applicability]
[0072] This disclosure can be used in a method for manufacturing electrolytic capacitors. [Explanation of symbols]
[0073] 100: Electrolytic capacitor 110: Capacitor element 111: Anode section 112: Anode wire 113: Anode 113a: First anode 113b: Second anode 113e1: First end face 113e2: Second end face 113G:Anode body group 113s :Side 114: Dielectric layer 202:Chemical liquid 210: First electrode 220: Second electrode 220h: Through hole
Claims
1. (i) A step of preparing a plurality of anode portions, each including an anode body and an anode wire protruding from a first end face of the anode body, (ii) A step of connecting a plurality of anode wires connected to a plurality of anode bodies to a first electrode for chemical formation, with a plurality of anode bodies arranged at intervals along a predetermined direction to form an anode body group, (iii) A step in which a plurality of anode bodies connected to the first electrode via the anode wire are immersed in a conversion solution, and a DC voltage is applied between the first electrode and the second electrode to oxidize at least a portion of the surface of the anode bodies and form a dielectric layer, In step (iii) above, the second electrode is in contact with the chemical solution and is positioned along the anode group, When, among the group of anodes, a plurality of anodes located at the ends are designated as the first anodes, and the anodes located inside the first anodes are designated as the second anodes, In step (iii) above, in order to reduce the difference between the conversion current flowing through the first anode and the conversion current flowing through the second anode, at least one of the distance between the first and second anodes and the second electrode, and the area of the second electrode facing the first and second anodes, is made different for the first anode and the second anode. In step (iii) above, the shortest distance between the first anode and the second electrode is longer than the shortest distance between the second anode and the second electrode. The length of the second electrode in the predetermined direction is shorter than the length of the anode group in the predetermined direction. A method for manufacturing an electrolytic capacitor, wherein in step (iii), the area of the second electrode in the portion facing the first anode is smaller than the area of the second electrode in the portion facing the second anode.
2. (i) A step of preparing a plurality of anode portions, each including an anode body and an anode wire protruding from a first end face of the anode body, (ii) A step of connecting a plurality of anode wires connected to a plurality of anode bodies to a first electrode for chemical formation, with a plurality of anode bodies arranged at intervals along a predetermined direction to form an anode body group, (iii) A step in which a plurality of anode bodies connected to the first electrode via the anode wire are immersed in a conversion solution, and a DC voltage is applied between the first electrode and the second electrode to oxidize at least a portion of the surface of the anode bodies and form a dielectric layer, In step (iii) above, the second electrode is in contact with the chemical solution and is positioned along the anode group, The second electrode is positioned to face at least one of the following surfaces selected from the second end face of the anode body opposite to the first end face and the side surface connecting the first end face and the second end face. When, among the group of anodes, a plurality of anodes located at the ends are designated as the first anodes, and the anodes located inside the first anodes are designated as the second anodes, In step (iii) above, in order to reduce the difference between the conversion current flowing through the first anode and the conversion current flowing through the second anode, at least one of the distance between the first and second anodes and the second electrode, and the area of the second electrode facing the first and second anodes, is made different for the first anode and the second anode. A method for manufacturing an electrolytic capacitor, wherein in step (iii), the area of the second electrode in the portion facing the first anode is smaller than the area of the second electrode in the portion facing the second anode.
3. The manufacturing method according to claim 2, wherein in step (iii), the shortest distance between the first anode and the second electrode is longer than the shortest distance between the second anode and the second electrode.
4. The manufacturing method according to claim 1 or 2, wherein the second electrode is bent and / or curved so as to move away from the first anode.
5. The manufacturing method according to claim 2, wherein the length of the second electrode in the predetermined direction is shorter than the length of the anode group in the predetermined direction.
6. The manufacturing method according to claim 1, wherein the second electrode is positioned to face at least one of the second end face of the anode body opposite to the first end face, and the side surface connecting the first end face and the second end face.