JP2023150735A - Manufacturing method of capacitor and cathode electrode for chemical treatment - Google Patents

Abstract

To form a dielectric layer with less fault by a chemical treatment when manufacturing an electrolytic capacitor.SOLUTION: A method of manufacturing a capacitor element in which a dielectric layer is formed onto a front surface of a positive electrode substance constructed by a valve action metal, contains: a step (i) of electrically connecting a plurality of positive electrode substances to a first electrode provided along a first direction; and a step (ii) of forming the dielectric layer by oxidizing at least one part of a front surface of the positive electrode substance by flowing a current between a first electrode and a second plate-like electrode arranged along a bottom surface of a chemical treatment in a state where the positive electrode substance connected to the first electrode is immersed in chemical treatment liquid in a chemical treatment tank. The second electrode includes: a pair of convex parts by adjacent two each other or one concave part to an opposite surface opposite to the first electrode in each of the plurality of positive electrode substances. Each of the plurality of positive electrode substances is arranged at a position of the pair of concave parts or at the concave part in a second direction orthogonal to the first direction.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a capacitor manufacturing method and a cathode electrode for chemical formation.

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.

For example, as shown in Patent Document 1, chemical conversion treatment involves suspending a solid electrolytic capacitor element from a band-shaped fixing plate via a wire made of valve metal, and immersing the solid electrolytic capacitor element in a chemical solution in a chemical conversion tank. This is done by applying a voltage between the cathode placed in the chemical solution and the fixed plate. The cathode is usually a flat plate.

Japanese Patent Application Publication No. 11-150044

The larger the size of the anode body and the larger the surface area of a porous body used for the anode body, the greater the current required to uniformly form a dielectric layer on the porous surface of the anode, and the larger the area of the cathode. Become. In the case of a flat cathode, the area of the cathode required for chemical conversion treatment of the anode body may be insufficient, resulting in insufficient chemical conversion, or a long time chemical conversion treatment may be required.

If the chemical conversion treatment is insufficient, defects are likely to occur in the formed dielectric layer, and leakage current is likely to increase. On the other hand, by performing chemical conversion treatment for a long time, productivity decreases.

One aspect of the present disclosure is a method for manufacturing a capacitor element in which a dielectric layer is formed on the surface of an anode body made of a valve metal, wherein a plurality of the anode bodies are provided along a first direction. a step (i) of electrically connecting the anode body connected to the first electrode to the chemical conversion solution in the chemical conversion tank; forming the dielectric layer by oxidizing at least a portion of the surface of the anode body by passing an electric current between it and a plate-shaped second electrode disposed along the bottom surface of the chemical conversion tank ( ii), wherein the second electrode has a pair of adjacent convex portions or one concave portion on the opposing surface facing the first electrode, and the plurality of anode bodies and each of the plurality of anode bodies is disposed at a position of the recess or a position between two adjacent convex parts in a second direction perpendicular to the first direction. The present invention relates to a method for manufacturing an element.

Another aspect of the present disclosure is to immerse an anode body made of a valve metal in a chemical conversion liquid in a chemical conversion tank with the anode body connected to an anode electrode, and to apply an electric current to the anode body. , a plate-shaped chemical formation cathode electrode disposed along the bottom surface of the chemical conversion tank to oxidize at least a part of the surface of the anode body to form a dielectric layer, the plate-shaped chemical formation cathode electrode facing the anode electrode; The present invention relates to a cathode electrode for chemical formation having a pair of two adjacent convex portions on a surface thereof.

According to the present disclosure, a dielectric layer with few defects can be formed by chemical conversion treatment, and leakage current of an electrolytic capacitor can be reduced.

FIG. 2 is a diagram schematically showing the state inside a chemical conversion tank during chemical conversion treatment, illustrating an example of the manufacturing method of the present disclosure. FIG. 2 is a perspective view showing a schematic configuration of a second electrode for chemical conversion (cathode electrode) used in the manufacturing method of the present disclosure. FIG. 2 is a diagram schematically showing the state inside a chemical conversion tank during chemical conversion treatment, illustrating an example of the manufacturing method of the present disclosure. FIG. 7 is a diagram showing another example of the second electrode (cathode electrode). FIG. 7 is a diagram showing another example of the second electrode (cathode electrode). FIG. 7 is a diagram showing another example of the second electrode (cathode electrode). FIG. 7 is a diagram showing another example of the second electrode (cathode electrode). FIG. 7 is a diagram showing another example of the second electrode (cathode electrode). FIG. 7 is a diagram showing another example of the second electrode (cathode electrode). 1 is a cross-sectional view schematically showing an example of a capacitor element manufactured by the manufacturing method of the present disclosure. 1 is a cross-sectional view schematically showing an example of an electrolytic capacitor using a capacitor element manufactured by the manufacturing method of the present disclosure.

Hereinafter, embodiments of the manufacturing method according to the present disclosure will be described using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be illustrated, 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 expression "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "more than or equal to numerical value A and less than or equal to numerical value B."

<Method for manufacturing capacitor elements>
A method for manufacturing a capacitor element according to an embodiment of the present disclosure is a method for manufacturing a capacitor element in which a dielectric layer is formed on the surface of an anode body made of a valve metal, the method comprising: a plurality of anode bodies; Step (i) of electrically connecting to a first electrode (anode electrode) provided along the first direction, and a state in which the anode body connected to the first electrode is immersed in a chemical solution in a chemical conversion tank. At least a part of the surface of the anode body is oxidized by passing a current between the first electrode and a plate-shaped second electrode (cathode electrode) arranged along the bottom of the chemical conversion tank. (ii) forming a dielectric layer.

The second electrode has a plate-like overall shape, but has a pair of convex portions or one concave portion in two adjacent to each other on the opposing surface facing the first electrode, respectively of the anode body. have against.
The surface area of the second electrode is increased by the hole shape, which is a groove or a recess formed between two adjacent protrusions. This increases the current density flowing through the anode body during the chemical conversion treatment, making it possible to speed up the growth of the dielectric layer. As a result, the occurrence of defects in the dielectric layer is suppressed and leakage current is reduced. This groove shape or hole shape allows the anode body to be brought close to the second electrode without coming into contact with it. Furthermore, by fixing the position of the anode body in the height direction perpendicular to the liquid level of the chemical liquid near the apex height of the convex part or near the hole-shaped opening in the concave part, vibration and displacement of the first electrode can be prevented. If the position of the anode body shifts in the second direction through the anode body, it is possible to prevent the anode body from coming into contact with the second electrode.

Each of the plurality of anode bodies is arranged at a position between a pair of protrusions or at a position of one recess in a second direction perpendicular to the first direction. By placing the anode body close to the space between the pair of protrusions, the anode body can be placed close to the cathode electrode, and the current density flowing through the anode body during chemical conversion treatment can be further increased. . Similarly, by arranging the anode body close to the concave space formed by the recess, the anode body can be disposed close to the cathode electrode, and the current density during chemical conversion treatment can be further increased.

In the second electrode having at least one pair of protrusions, a space is formed between the pair of protrusions. This space can be thought of in the same way as a recessed space. In the following, the space formed by two adjacent convex portions will be referred to as a gap, and will be distinguished from the recessed space of the concave portion.

For example, the convex portion is formed to include a portion that protrudes toward the outside of the second electrode (that is, in the direction approaching the first electrode) with respect to the reference plane. Similarly, the recessed portion may be formed, for example, to include a portion recessed toward the inside of the second electrode (that is, in the direction away from the first electrode) with respect to the reference plane. The reference surface of the convex portion is the part of the facing surface facing the first electrode (hereinafter also referred to as "element facing surface") farthest from the first electrode (excluding the inner circumferential surface of the circulation hole described later). ). The reference surface in the recess may be a portion of the element facing surface closest to the first electrode (an opening portion in which a hole shape is formed).

Alternatively, a hole passing through the second electrode may be formed between the facing surface and the surface opposite to the facing surface, and the anode body may be arranged so as to overlap the through hole. In this case, this hole also has the function of allowing the chemical solution to flow and circulate.

In addition, when the anode body is disposed at a position between a pair of convex portions, it means that the anode body and the anode body are disposed at a position in a certain first direction in a plane parallel to a second direction and a direction perpendicular to the liquid level of the chemical liquid. Considering the cross section of the second electrode, the range of the position occupied by the anode body in the second direction is limited between one apex part and the other apex part of the pair of convex parts, and does not overlap with either apex part. It means not to be.

When the anode body is placed at the position of the convex part, the end of the anode body on the second electrode side is placed close to the convex part, so the current density at the end of the anode body on the second electrode side is On the other hand, it is difficult to increase the current density at the end of the anode body on the first electrode side away from the convex portion. For this reason, a difference occurs in the current density during the chemical conversion treatment between the first electrode side and the second electrode side of the anode body, and the dielectric layer tends to be formed non-uniformly. On the other hand, by arranging the anode body between the pair of convex portions, the current density can be increased while suppressing the difference in current density during the chemical conversion treatment inside the anode body. As a result, a uniform dielectric layer with few defects can be formed, and the characteristics of the electrolytic capacitor such as leakage current can be improved.

In one embodiment, a convex portion may be formed in a line shape along the first direction of the opposing surface (that is, the direction in which the first electrode (anode electrode) extends). The two protrusions extending in the first direction may form a groove extending in the first direction between the two protrusions. In this case, by arranging a plurality of anode bodies side by side along the groove between the two convex parts, it becomes easier to arrange the anode body and the second electrode closer to each other, and the flow to the anode body during chemical conversion treatment is reduced. Easy to increase current density.

In another embodiment, the second electrode may have a plurality of pairs of convex portions along the first direction of the opposing surface. In this case, the plurality of pairs of convex portions may be arranged along the first direction, corresponding to each of the plurality of anode bodies. Each of the plurality of anode bodies is arranged at a position between a corresponding pair of protrusions in the second direction. In this case, it is easy to increase the surface area of the second electrode, and it is easy to increase the current density flowing through the anode body during the chemical conversion treatment. The same applies when the second electrode has a plurality of recesses along the first direction of the opposing surface.
When the second electrode has a plurality of pairs of protrusions or a plurality of recesses, the pair of protrusions or recesses may correspond to each of the plurality of anode bodies. Furthermore, one anode body may share two pairs of convex portions or two concave portions that are adjacent to each other in the first direction.

In another embodiment, the recess may be in the shape of a hole penetrating the back surface of the opposing surface. The hole-shaped recesses may be arranged in a row for each anode body along the first direction. When the first electrodes are arranged in multiple rows, the entire hole shape of the second electrodes may be arranged in a mesh shape. Each of the anode bodies may be placed at a location of an opening in the mesh.

The height of the anode body (distance to the second electrode) in the chemical conversion tank is preferably as low as possible, as long as contact between the second electrode and the anode body is suppressed. When the second electrode has at least one pair of convex parts, the height of the anode body in the chemical conversion bath is such that the height at its lowest position (minimum height) is equal to the maximum height of the convex parts (for example, the apex of the convex parts). It may be higher or lower than the height of

If the minimum height of the anode body in the chemical conversion tank is lower than the maximum height of the convex part, a part of the anode body is placed in the gap between the two convex parts, making it easier to increase the current density during the chemical conversion treatment. . When the minimum height of the anode body in the chemical conversion tank is higher than the maximum height of the convex part, the difference between the maximum height of the convex part and the minimum height of the anode body is preferably 2 mm or less.

Similarly, when the second electrode has a recess, the height of the anode body in the chemical conversion bath may be higher than the height of the reference plane of the recess (minimum height) or may be lower than the height of the reference surface of the recess. It's okay. When the minimum height of the anode body in the chemical conversion bath is higher than the height of the reference surface of the recess, the difference between the height of the reference surface of the recess and the minimum height of the anode body is preferably 2 mm or less.

The height in the chemical conversion tank means the height in the direction (vertical direction) perpendicular to the liquid level of the chemical liquid. The maximum height of the convex portion is also the height of the part closest to the liquid level of the chemical liquid within the surface of the convex portion. The height of the reference plane of the recess is also the height of the point closest to the liquid level of the chemical liquid within the reference plane of the recess.

The maximum height of the anode body within the chemical conversion bath may be higher than the maximum height at the apex of the convex portion. That is, at least a portion of the anode body may not be accommodated within the gap between the two protrusions, but may be placed above the gap between the two protrusions. Thereby, when the anode body is immersed in the chemical solution, contact between the anode body and the second electrode is suppressed, and productivity is improved. Similarly, when the second electrode has a recess, the maximum height of the anode body within the chemical conversion bath may be higher than the height of the reference plane of the recess.

There are no particular limitations on the shape of the protrusions or recesses. In one embodiment, the cross-sectional shape of the convex portion in a cross section perpendicular to the first direction may be triangular, trapezoidal, or rectangular. When the cross-sectional shape is triangular, the shape of the convex portion may be a cone or a polygonal pyramid. When the cross-sectional shape is a trapezoid, the shape of the convex portion may be a truncated cone or a truncated polygonal pyramid. When the cross-sectional shape is rectangular, the shape of the convex portion may be a cylinder or a polygonal prism. The convex portion or the concave portion may have a curved surface.

The second electrode may have a circulation hole penetrating from the opposing surface to the opposite surface through which the chemical liquid flows and circulates. The circulation hole may be formed on the surface adjacent to the hole shape of the recess, or may be formed on the concave surface of the hole shape. A circulation hole may be formed in the groove portion between the two protrusions. The circulation hole may be formed at a position that overlaps with the anode body, or may be formed at a position that does not overlap with the anode body, when viewed from a direction perpendicular to the liquid level of the chemical liquid.

The chemical conversion treatment process will be explained in detail below.

(Step (i))
First, the anode body is electrically connected to the first electrode. For example, in the case where the anode part has a porous anode body and an anode wire planted from a planting surface that is one main surface of the anode body, the anode wire is connected to the first electrode. Thereby, the anode body is electrically connected to the first electrode via the anode wire. There are no limitations on the anode body and anode wire, and known anode bodies and anode wires may be used. Alternatively, the anode portion may be manufactured using a known method. Examples of the anode body and anode wire, and examples of methods for forming the same will be described later.

At this time, a plurality of anode bodies are arranged at intervals along a predetermined direction (herein referred to as the first direction) to form an anode body group, and each of the anode bodies in the anode body group is connected to the first electrode. electrically connected to. For example, when the anode part has an anode wire, each of the plurality of anode wires connected to the plurality of anode bodies is connected to the first electrode with the plurality of anode parts arranged at intervals along the first direction. Connect to. The plurality of anode bodies may be arranged in a line, or when the plurality of first electrodes are arranged in a line, they may be arranged in a matrix. The intervals at which the plurality of anode parts are arranged may be the same for all the anode parts, or the intervals between one anode part and an adjacent anode part may be different from others.

The shape of the first electrode is selected depending on the arrangement of the anode body group. For example, the first electrode has a linear shape (for example, a rod shape or a plate shape), and a plurality of anode bodies are arranged in a line along the first electrode. When a plurality of anode bodies are arranged in a matrix, the first electrode is formed by arranging a plurality of linear electrodes in a plurality of rows. The first electrode and the anode wire are electrically connected. Typically, the anode wire is secured to the first electrode by a method such as welding. The material of the first electrode is not particularly limited, and may be a conductive metal (for example, iron, iron alloy, aluminum, etc.). A plurality of second electrodes are formed corresponding to a plurality of first electrodes arranged in a plurality of rows, and the plurality of second electrodes are coupled in a second direction to form an integral second electrode. Two electrodes may be formed.

As the first electrode, metal aluminum and its alloys can be preferably used because they are lightweight and have excellent workability.

The number of anode bodies included in the anode body group is not limited, and may be in the range of 10 to 200 (for example, in the range of 40 to 100). The distance between adjacent anode bodies is also not particularly limited. The spacing may be in the range 1-20 mm (for example in the range 2-6 mm). Usually, the interval is constant, but the interval does not have to be constant.

(Step (ii))
Next, with the anode body electrically connected to the first electrode immersed in the chemical solution in the chemical conversion tank, a DC voltage is applied between the first electrode and the second electrode to generate a current. Flow. As a result, at least a portion of the surface of the anode body is oxidized (anodized) to form a dielectric layer.

In step (ii), the surface of the anode body is oxidized and transformed into a dielectric layer. For example, when the anode body is made of tantalum, a tantalum oxide layer is formed on the surface of the anode body. The chemical conversion liquid is not particularly limited, and any known chemical conversion liquid used for chemical conversion treatment of anode bodies of electrolytic capacitors may be used. For example, the chemical solution may be an acidic aqueous solution, a neutral aqueous solution, or a basic aqueous solution. Examples of acidic aqueous solutions include phosphoric acid aqueous solution, nitric acid aqueous solution, acetic acid aqueous solution, sulfuric acid aqueous solution, and the like. Other examples of chemical liquids include aqueous tartrate solutions, aqueous oxalate solutions, aqueous tetraborate solutions, and the like.

The second electrode is arranged along the bottom surface of the chemical conversion tank and is immersed in the chemical conversion liquid. As the material of the second electrode, it is preferable to use a metal that is stable during chemical formation. Examples of the material of the second electrode include iron alloy, nickel, chromium, gold, platinum, tantalum, titanium, carbon, and the like. The second electrode is created, for example, by cutting the surface of a thick plate-shaped material or by making a hole. If the plate portion of the second electrode is made of a mesh of metal wires, the circulation of the chemical liquid will be improved, but the current density will be low and it will be difficult to increase the current density.

A pair of convex portions or one concave portion is provided on the surface of the second electrode facing the first electrode. A plurality of anode bodies (anode body group) electrically connected to the first electrode each correspond to the position of a pair of convex portions of the second electrode or one position when viewed from a direction perpendicular to the liquid surface. It is immersed in the chemical solution so as to be located at the position of the recess.

After step (ii), a capacitor element is obtained by performing a step of forming parts necessary for an electrolytic capacitor, and an electrolytic capacitor can be manufactured. There are no limitations to these steps, and known methods may be applied.

In one example of a manufacturing method for an electrolytic capacitor in which the anode body is a sintered body, an electrolyte layer is formed on a dielectric layer, and a cathode portion is formed on the electrolyte layer. A capacitor element is produced in this way. Next, an anode lead terminal is connected to the anode wire, and a cathode lead terminal is connected to the cathode portion. Then, an exterior body is formed to cover the capacitor element, a portion of the anode lead terminal, and a portion of the cathode lead terminal. In this way, an electrolytic capacitor is obtained.

In an exemplary method for manufacturing an electrolytic capacitor in which the anode body is a wound body of metal foil, in step (i), a wound body in which an anode body (metal foil), a separator, and a cathode foil are wound is prepared. The wound body includes an anode portion. The anode section includes an anode body (metal foil) and an anode wire protruding from a first end surface of the anode body (a first end surface 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 portion of the end face of the anode body. Therefore, in order to form a dielectric layer even in the portion where the dielectric layer is not formed, the dielectric layer is formed by the above step (ii). After forming the dielectric layer, a capacitor element is manufactured by forming an electrolyte layer inside the wound body. A wound type electrolytic capacitor is obtained by enclosing the manufactured capacitor element 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 those components and formation methods, and known components and formation methods may be used.

[First embodiment]
In the following, an example will be described with reference to the drawings in which a capacitor element is manufactured by performing a chemical conversion treatment on an anode body using a second electrode provided with at least one pair of convex portions.

FIG. 1 is a schematic diagram illustrating the chemical conversion treatment step of the method for manufacturing a capacitor element according to the present embodiment, and shows the gap between a plurality of first electrodes (anode electrode) 104 and second electrodes (cathode electrode) 105. FIG. 3 is a diagram schematically showing the state inside the chemical conversion tank 101 when chemical conversion treatment is performed by flowing a direct current to the chemical conversion tank 101 . The plurality of first electrodes 104 extend in a first direction parallel to the liquid surface 102a of the chemical liquid 102 (in FIG. 1, a direction perpendicular to the paper surface), and are also called carrier bars. A plurality of first electrodes 104 are arranged side by side in a second direction orthogonal to the first direction. FIG. 1 shows a cross-sectional view of the chemical conversion tank 101 in a plane perpendicular to the first direction (a plane parallel to the second direction and a direction perpendicular to the liquid level). FIG. 2 is a perspective view showing a schematic configuration of the second electrode 105 arranged along the bottom surface of the chemical conversion tank 101.

A plurality of anode parts each having an anode body 1 and an anode wire 2 are arranged at regular intervals along the carrier bar of one first electrode 104 at predetermined intervals, and are connected to the first electrode via the anode wire 2. It is electrically connected to 104. Therefore, although it is not clear from FIG. 1, the plurality of anode parts are arranged in a matrix along the first direction and the second direction. Each of the anode bodies 1 in the plurality of anode parts is immersed in the chemical conversion liquid 102 and is in contact with the chemical conversion liquid 102 .

The second electrode 105 has a plurality of convex portions on the surface facing the first electrode 104. In the example of FIG. 2, a plurality of square pyramid-shaped convex portions 110 are two-dimensionally arranged along the first direction and the second direction on the opposing surface of the second electrode 105. The cross-sectional shape of the convex portion 110 in a cross section perpendicular to the first direction is triangular.

A gap 112 is formed between two pyramid-shaped convex portions 110 adjacent in the second direction. By arranging a plurality of convex portions 110 two-dimensionally, a plurality of gaps 112 are also formed. As shown in FIG. 1, each of the anode bodies 1 is arranged so as to be located within one of these gaps 112 when viewed from a direction perpendicular to the liquid level 102a.

The protrusion height H of the convex portion 110 in FIG. 1 is, for example, in the range of 1 to 20 mm. The interval between the convex portions 110 in the second direction (in other words, the interval between the plurality of second electrodes 105 arranged side by side in the second direction) is, for example, 5 to 20 mm.

In the example shown in FIG. 1, the minimum height h1 of each anode body 1 immersed in the chemical conversion liquid 102 is higher than the height h2 of the apex of the convex portion 110 (h1>h2), and the difference is less than 2 mm. Yes (h1-h2<2mm). This results in high current density.

However, as shown in FIG. 3, the minimum height h1 of each anode body 1 immersed in the chemical conversion liquid 102 may be lower than the height h2 of the apex of the convex portion 110 (h1<h2). In that case, a portion of the anode body 1 is accommodated within the gap 112 formed by the two adjacent convex portions 110. In this case, higher current densities are obtained.

In either case of FIGS. 1 and 3, the maximum height h3 of each anode body 1 immersed in the chemical solution 102 is higher than the height h2 of the apex of the convex portion 110. That is, at least a portion of the anode body 1 on the first electrode side may not be accommodated within the gap 112 but may be located above the gap 112.

4A to 4D show other examples of the second electrode 105 in which a convex portion is provided on the opposing surface. Each of the figures in FIGS. 4A to 4D corresponds to a case in which only one row of first electrodes 104 is arranged, and the periphery of the region facing one anode body 1 in the second electrode 105 is enlarged. FIG. 3 is a perspective view showing a cross section of the second electrode 105 in a plane perpendicular to the first direction (a plane parallel to the second direction and a direction perpendicular to the liquid surface).

FIG. 4A is an example of the second electrode 105 shown in FIG. 2 in which the apex portion of the pyramid-shaped convex portion 110 is cut off to form the convex portion 110 into a quadrangular truncated pyramid shape. In this case, the cross-sectional shape of the convex portion 110 in a cross section perpendicular to the first direction is a trapezoid.

FIG. 4B is an example in which a plurality of convex portions 110 extending in the first direction are arranged. A groove is formed between two adjacent protrusions 110. The plurality of anode bodies 1 may be arranged in the first direction along this groove. The cross-sectional shape of the convex portion 110 in a cross section perpendicular to the first direction is triangular.

Similar to FIG. 4B, FIG. 4C is an example in which a plurality of convex portions 110 extending in the first direction are arranged and a groove is formed between two adjacent convex portions 110. In FIG. 4C, the cross-sectional shape of the convex portion 110 in a cross section perpendicular to the first direction is a trapezoid.

Similar to FIGS. 4B and 4C, FIG. 4D is an example in which a plurality of convex portions 110 extending in the first direction are arranged. A groove is formed between two adjacent protrusions 110. In FIG. 4D, the cross-sectional shape of the convex portion 110 in a cross section perpendicular to the first direction is a rectangle that is long in the protruding direction of the convex portion. As a result, a U-shaped groove is formed between two adjacent convex portions 110. A plurality of anode bodies 1 may be arranged along this groove.

In FIGS. 4A to 4D, circulation holes 113, through which the chemical solution flows, are provided at predetermined positions on the opposing surface of the second electrode 105 from the opposing surface to the opposite surface to promote circulation of the chemical solution. It is provided for. The position where the circulation hole for chemical liquid circulation is provided is not particularly limited. From the point of view of increasing the current density flowing through the anode body, it is desirable that the circulation hole be disposed at a position that does not overlap with the anode body, but it may be disposed so as to overlap the anode body.

[Second embodiment]
A capacitor element may be manufactured by performing a chemical conversion treatment on the anode body using the second electrode provided with the recessed portion. FIGS. 5A and 5B show an example of the second electrode 105 in which a recess is provided on the opposing surface. 5A and 5B each show an enlarged view of the periphery of the region facing one anode body 1 within the second electrode 105, and also show a surface perpendicular to the first direction (the second direction and the liquid level). FIG. 3 is a cutaway perspective view showing a cross section of the second electrode 105 in a plane parallel to a direction perpendicular to .

FIG. 5A shows an example in which a recess 114 is formed on the opposing surface of the second electrode 105. In the example of FIG. 5A, the recess 114 is a hole having a circular opening. The depth of the hole is not particularly limited, and the hole may penetrate to the surface opposite to the facing surface. A plurality of recesses 114 may be arranged along the first direction. Each of the plurality of anode bodies 1 is arranged at a position overlapping with any one of the recesses 114 when viewed from a direction perpendicular to the liquid level of the chemical liquid.

In FIG. 5B, the recess 114 in FIG. 5A is a penetrating hole having a square opening. By arranging square-shaped through holes along the first direction, a second electrode 105 in which a plurality of through holes are arranged in a row is formed.

In FIG. 5B, the penetrating hole forming the recess 114 functions to allow the chemical liquid to flow. In FIG. 5A, a penetrating hole (circulation hole) for circulating the chemical solution may be provided separately. The circulation hole for chemical liquid distribution may be provided on the opposing surface (reference surface) on which the recess 114 is not formed, or may be provided on the recessed surface of the recess 114.

<Capacitor elements and electrolytic capacitors>
As an example of the structure and components of a capacitor element and an electrolytic capacitor manufactured by the manufacturing method of the present disclosure, an example in which a sintered anode body is used will be described below. An example 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.

FIG. 6 is a cross-sectional view schematically showing an example of a capacitor element manufactured by the manufacturing method according to the present embodiment. FIG. 7 is a schematic cross-sectional view of an electrolytic capacitor using a capacitor element manufactured by the manufacturing method according to the present embodiment. However, the present invention is not limited to the configurations shown in these drawings.

The electrolytic capacitor 20 includes a capacitor element 10 having an anode part 6 and a cathode part 7 , an exterior body 11 that seals the capacitor element 10 , and an electrically connected to the anode part 6 , with a part of the exterior body 11 being electrically connected to the anode part 6 . It includes an exposed anode lead terminal 13 and a cathode lead terminal 14 electrically connected to the cathode section 7 and partially exposed from the exterior body 11. The anode section 6 includes an anode body 1 and an anode wire 2. A dielectric layer 3 is formed on the surface of the anode body. The cathode section 7 includes a solid electrolyte layer 4 that covers at least a portion of the dielectric layer 3 and a cathode layer 5 that covers at least a portion of the surface of the solid electrolyte layer 4 .

(capacitor element)
Hereinafter, the capacitor element 10 will be described in detail, taking as an example a case where the capacitor element 10 is provided with a solid electrolyte layer as an electrolyte.

(Anode part)
The anode section 6 includes an anode body 1 and an anode wire 2 extending from one surface of the anode body 1 and electrically connected to an anode lead terminal 13 .
The anode body 1 is, for example, a rectangular parallelepiped porous sintered body obtained by sintering metal particles. As the metal particles, particles of valve metal such as titanium (Ti), tantalum (Ta), and niobium (Nb) are used. The anode body 1 uses one or more types of metal particles. The metal particles may be an alloy of two or more metals. For example, an alloy containing a valve metal and silicon, vanadium, boron, etc. can be used. Further, a compound containing a valve metal and a typical element such as nitrogen may be used. The valve metal alloy has a valve metal as a main component, and contains, for example, 50 atomic percent or more of the valve metal.

The anode wire 2 is made of a conductive material. The material of the anode wire 2 is not particularly limited, and includes, for example, niobium, aluminum, aluminum alloy, etc. in addition to the above-mentioned valve metals. The materials constituting the anode body 1 and the anode wire 2 may be the same or different. The anode wire 2 has a first portion 2 a buried inside the anode body 1 from one surface of the anode body 1 and a second portion 2 b extending from the one surface of the anode body 1 . The cross-sectional shape of the anode wire 2 is not particularly limited, and examples thereof include a circle, a track shape (a shape consisting of mutually parallel straight lines and two curved lines connecting the ends of these straight lines), an ellipse, a rectangle, a polygon, etc. It will be done.

The anode portion 6 is produced, for example, by pressing and forming the first portion 2a into a rectangular parallelepiped shape while embedding the first portion 2a in powder of particles of the first metal, and sintering the first portion 2a. Thereby, the second portion 2b of the anode wire 2 is pulled out from one surface of the anode body 1 so as to stand up. The second portion 2b is joined to the anode lead terminal 13 by welding or the like, so that the anode wire 2 and the anode lead terminal 13 are electrically connected. The welding method is not particularly limited, and examples thereof include resistance welding, laser welding, and the like.

A dielectric layer 3 is formed on the surface of the anode body 1 . The dielectric layer 3 is made of, for example, a metal oxide. The dielectric layer 3 is formed by performing the above-mentioned chemical conversion treatment step, by immersing the anode body 1 in a chemical solution and anodizing the surface of the anode body 1.

(Cathode part)
The cathode section 7 includes a solid electrolyte layer 4 and a cathode layer 5 covering the solid electrolyte layer 4 . Solid electrolyte layer 4 is formed to cover at least a portion of dielectric layer 3 .

For example, a manganese compound or a conductive polymer is used for the solid electrolyte layer 4. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene. These may be used alone or in combination. Further, the conductive polymer may be a copolymer of two or more types of monomers. Polythiophene, polyaniline, and polypyrrole may be used since they have excellent conductivity. In particular, polypyrrole may be used since it has excellent water repellency.

The solid electrolyte layer 4 containing the conductive polymer is formed, for example, by polymerizing raw material monomers on the dielectric layer 3. Alternatively, it is formed by applying a liquid containing the conductive polymer to the dielectric layer 3. The solid electrolyte layer 4 is composed of one or more solid electrolyte layers. When the solid electrolyte layer 4 is composed of two or more layers, the composition, formation method (polymerization method), etc. of the conductive polymer used in each layer may be different.

In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. each mean a polymer having a basic skeleton of polypyrrole, polythiophene, polyfuran, polyaniline, etc. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene) and the like.

Various dopants may be added to the polymerization solution, solution or dispersion of the conductive polymer for forming the conductive polymer in order to improve the conductivity of the conductive polymer. The dopant is not particularly limited, and examples thereof include naphthalenesulfonic acid, p-toluenesulfonic acid, polystyrenesulfonic acid, and the like.

When the conductive polymer is dispersed in a dispersion medium in the form of particles, the average particle diameter D50 of the particles is, for example, 0.01 μm or more and 0.5 μm or less. If the average particle diameter D50 of the particles is within this range, the particles will easily penetrate into the inside of the anode body 1.

The cathode layer 5 includes, for example, a carbon layer 5a formed to cover the solid electrolyte layer 4, and a metal paste layer 5b formed on the surface of the carbon layer 5a. The carbon layer 5a contains a conductive carbon material such as graphite and resin. The metal paste layer 5b includes, for example, metal particles (eg, silver) and resin. Note that the configuration of the cathode layer 5 is not limited to this configuration. The structure of the cathode layer 5 may be any structure as long as it has a current collecting function.

(Anode lead terminal)
The anode lead terminal 13 is electrically connected to the anode body 1 via the second portion 2b of the anode wire 2. The material of the anode lead terminal 13 is not particularly limited as long as it is electrochemically and chemically stable and has conductivity. The anode lead terminal 13 may be made of metal such as copper, or may be made of non-metal. Its shape is not particularly limited as long as it is flat. The thickness of the anode lead terminal 13 (the distance between the main surfaces of the anode lead terminal 13) may be 25 μm or more and 200 μm or less, or 25 μm or more and 100 μm or less, from the viewpoint of reducing the height.

One end of the anode lead terminal 13 may be joined to the anode wire 2 with a conductive adhesive or solder, or may be joined to the anode wire 2 by resistance welding or laser welding. The other end of the anode lead terminal 13 is led out of the exterior body 11 and exposed from the exterior body 11 . The conductive adhesive is, for example, a mixture of a thermosetting resin and carbon particles or metal particles, which will be described later.

(Cathode lead terminal)
The cathode lead terminal 14 is electrically connected to the cathode portion 7 at the joint portion 14a. The joint portion 14a is a portion of the cathode lead terminal 14 that overlaps the cathode layer 5 when the cathode layer 5 and the cathode lead terminal 14 joined to the cathode layer 5 are viewed from the normal direction of the cathode layer 5.

The cathode lead terminal 14 is bonded to the cathode layer 5 via the conductive adhesive 8, for example. One end of the cathode lead terminal 14 constitutes, for example, a part of the joint portion 14a, and is arranged inside the exterior body 11. The other end of the cathode lead terminal 14 is led out. Therefore, a portion of the cathode lead terminal 14 including the other end is exposed from the exterior body 11.

The material of the cathode lead terminal 14 is also not particularly limited as long as it is electrochemically and chemically stable and has conductivity. The cathode lead terminal 14 may be made of metal such as copper, or may be made of a non-metal. The shape is also not particularly limited, and may be elongated and flat, for example. The thickness of the cathode lead terminal 14 may be 25 μm or more and 200 μm or less, or 25 μm or more and 100 μm or less, from the viewpoint of reducing the height.

(exterior body)
The exterior body 11 is provided to electrically insulate the anode lead terminal 13 and the cathode lead terminal 14, and is made of an insulating material (exterior body material). The exterior body material includes, for example, a thermosetting resin. Examples of the thermosetting resin include epoxy resin, phenol resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane, polyimide, and unsaturated polyester.

[Example]
EXAMPLES Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The anode body was subjected to chemical conversion treatment in the following manner.
Tantalum metal particles were used as the valve metal. The tantalum metal particles were formed into a rectangular parallelepiped so that one end of the anode wire made of tantalum metal was embedded in the tantalum metal particles, and then the formed body was sintered in a vacuum. As a result, an anode body (1.7 mm x 3.3 mm x 4.4 mm) made of porous sintered tantalum and an anode with one end buried in the anode body and the remaining part planted from one side of the anode body. An anode section including a wire was obtained. The anode wire is planted from a 1.7 mm x 3.3 mm surface.

Fifty-five anode parts were arranged in a line at regular intervals (5 mm), and the anode wire was welded to the elongated plate-shaped first electrode. Next, the anode body welded to the first electrode and the second electrode were immersed in a chemical solution. A phosphoric acid aqueous solution was used as the chemical solution. Then, by applying a DC voltage (90V) between the first electrode and the second electrode and performing a chemical conversion treatment, a dielectric material of tantalum oxide (Ta ₂ O ₅ ) is formed on the surface of the 55 anode bodies. formed a layer.

The following cathode electrode made of pure copper was prepared as a second electrode corresponding to the first electrode arranged in only one row, the height of the anode body relative to the cathode electrode was changed appropriately, and chemical conversion treatment was performed. Ta.

(Example 1)
A second electrode having two adjacent convex portions shown in FIG. 4A was prepared, and was used as a cathode electrode A1. The protrusion height H of the truncated quadrangular pyramid-shaped convex portion 110 in the cathode electrode A1 was set to 10 mm. The truncated quadrangular pyramid has an upper base of a square with a side of 1 mm, and a lower base of a square with a side of 5 mm. The spacing between the convex portions 110 arranged in the first direction and the second direction was 10 mm in the first direction in which the first electrode extends, and 10 mm in the second direction perpendicular to the first direction. In the second direction, the anode body was immersed in the chemical solution so that the anode body was disposed between the protrusions 110.

In Example 1, the anode body is immersed in the chemical solution so that the minimum height h1 of the anode body in the chemical conversion tank is at the same position as the maximum height h2 at the apex of the convex portion 110 (upper base surface of the truncated square pyramid). Soaked.

(Examples 2 to 4)
A second electrode having two adjacent convex portions shown in FIG. 4B was prepared, and was designated as cathode electrode A2. The protrusion height H of the convex portion 110 in the cathode electrode A2 was set to 2 mm. The arrangement interval in the second direction of the convex portions 110 extending in the first direction was 10 mm. In the second direction, the anode body was immersed in the chemical solution so that the anode body was disposed between the protrusions 110.

In Example 2, the cathode electrode A2 is used, and the anode body is chemically formed so that the minimum height h1 of the anode body in the chemical conversion tank is at the same position as the maximum height h2 at the apex (ridge line portion) of the convex portion 110. Immersed in liquid.

In Example 3, the cathode electrode A2 was used, and the anode body was immersed in a chemical solution such that the minimum height h1 of the anode body was 1 mm higher than the maximum height h2 of the convex portion 110.

In Example 4, a cathode electrode A2 with a protrusion height H of 5 mm was used as a cathode electrode A3, and the other aspects were the same as in Example 2.

(Examples 5 and 6)
A second electrode having two adjacent convex portions shown in FIG. 4C was prepared, and was designated as cathode electrode A4. The protruding height H of the convex portion 110 in the cathode electrode A4 was set to 10 mm. The cross-sectional shape of the convex portion 110 perpendicular to the first direction is an isosceles trapezoid with an upper base of 1 mm and a lower base of 3 mm. The arrangement interval in the second direction of the convex portions 110 extending in the first direction was 10 mm. In the second direction, the anode body was immersed in the chemical solution so that the anode body was disposed between the protrusions 110.

In Example 5, the cathode electrode A4 was used, and the anode body was immersed in the chemical solution so that the minimum height h1 of the anode body in the chemical conversion tank was at the same position as the maximum height h2 at the apex of the convex portion 110. .

In Example 6, the cathode electrode A4 was used, and the anode body was immersed in a chemical solution such that the minimum height h1 of the anode body was 1 mm higher than the maximum height h2 of the convex portion 110.

(Example 7)
A second electrode having two adjacent convex portions shown in FIG. 4D was prepared, and was designated as cathode electrode A5. The protruding height H of the convex portion 110 in the cathode electrode A5 was set to 15 mm. The arrangement interval of the convex portions 110 in the second direction was 10 mm. In the second direction, the anode body was immersed in the chemical solution so that the anode body was disposed between the protrusions 110.

In Example 7, the cathode electrode A5 was used, and the anode body was immersed in the chemical conversion solution such that the minimum height h1 of the anode body in the chemical conversion tank was at the same position as the maximum height h2 at the apex of the convex portion 110. .

Note that in the cathode electrodes A1 to A5, the thickness of the second electrode excluding the convex portion 110 was 3 mm.

(Example 8)
A second electrode having a cylindrical hole shape and a concave shape as shown in FIG. 5A was prepared, and was used as a cathode electrode A6. The thickness of the cathode electrode A6 is 10 mm, and a hole with a diameter of 4 mm is arranged as the recess 114. The arrangement interval of the recesses 114 in the first direction was 10 mm. In the second direction, the anode body was immersed in the chemical solution so that the anode body was placed at the position of the recess 114 .

In Example 8, the cathode electrode A6 was used, and the anode body was immersed in the chemical conversion solution such that the minimum height h1 of the anode body in the chemical conversion tank was at the same position as the height of the reference plane of the recess.

(Example 9)
A second electrode having a rectangular prism-like hole shape and a concave shape as shown in FIG. 5B was prepared, and was used as a cathode electrode A7. The cathode electrode A7 has a thickness of 5 mm, and a 3 mm x 3 mm square hole passing through the cathode electrode A7 is arranged as a recess 114. The arrangement interval (distance between centers) of the recesses in the first direction was 10 mm. The anode body was immersed in the chemical solution so that the anode body was placed at the position of the recess 114 in the first direction and the second direction.

In Example 9, the cathode electrode A7 was used, and the anode body was immersed in the chemical conversion solution so that the minimum height h1 of the anode body in the chemical conversion tank was at the same position as the height of the reference plane of the recess.

(Comparative example 1)
As the second electrode, a flat plate with a thickness of 3 mm was prepared and used as the cathode electrode B1. The anode body was immersed in the chemical conversion solution so that the minimum height h1 of the anode body in the chemical conversion tank was 1 mm away from the cathode electrode B1.

During the chemical conversion treatment, the current density of the anode body located approximately at the 30th position in the center among the 55 anode bodies arranged in the first direction was measured using an ammeter. On the 3.3 mm x 4.4 mm surface of the anode body, the current density distribution along the center line perpendicular to the 1.7 mm x 3.3 mm surface was determined, and the average value _IA of the current density was determined. Table 1 shows the measurement results for Examples 1 to 9 and Comparative Example 1.

The present disclosure can be used in a method of manufacturing an electrolytic capacitor.

20: Electrolytic capacitor 10: Capacitor element 1: Anode body 2: Anode wire 2a: First part 2b: Second part 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode layer 5a: Carbon layer 5b: Metal paste layer 6: Anode part 7: Cathode part 8: Conductive adhesive material 11: Exterior body 12: Resin protective layer 13: Anode lead terminal 14: Cathode lead terminal 14a: Joint part 101: Chemical conversion tank 102: Chemical liquid 102a: Liquid surface 103: Air bubbles 104: First electrode (anode electrode)
105: Second electrode (cathode electrode)
110: Convex portion 112: Gap formed by the convex portion 113: Circulation hole 114: Concave portion

Claims (14)

A method for manufacturing a capacitor element in which a dielectric layer is formed on the surface of an anode body made of a valve metal, the method comprising:
a step (i) of electrically connecting the plurality of anode bodies to a first electrode provided along a first direction;
In a state where the anode body connected to the first electrode is immersed in a chemical conversion liquid in a chemical conversion tank, the first electrode and a plate-shaped second electrode arranged along the bottom surface of the chemical conversion tank are connected to the first electrode. (ii) oxidizing at least a portion of the surface of the anode body to form the dielectric layer by passing a current between;
The second electrode has, for each of the plurality of anode bodies, a pair of convex portions or one concave portion adjacent to each other on an opposing surface facing the first electrode,
The method for manufacturing a capacitor element, wherein each of the plurality of anode bodies is disposed at a position between the pair of convex portions or at a position of the concave portion in a second direction perpendicular to the first direction. The method for manufacturing a capacitor element according to claim 1, wherein the convex portion is formed along the first direction of the opposing surface. having a plurality of pairs of the convex portions or a plurality of the concave portions along the first direction of the opposing surface;
The method for manufacturing a capacitor element according to claim 1, wherein a plurality of pairs of the convex portions or a plurality of the concave portions are arranged along the first direction, corresponding to each of the plurality of anode bodies. 4. The method for manufacturing a capacitor element according to claim 3, wherein the plurality of recesses have a hole shape penetrating the back surface of the opposing surface. having the convex portion on the opposing surface;
The height of the lowest position of the anode body in the chemical conversion bath is higher than the maximum height at the apex of the convex portion projecting toward the first electrode, and the height is greater than the maximum height and the lowest position of the anode body. 4. The method for manufacturing a capacitor element according to claim 1, wherein the difference between the height and the height of the capacitor element is 2 mm or less. having the convex portion on the opposing surface;
According to any one of claims 1 to 3, the height of the lowest position of the anode body in the chemical conversion bath is lower than the maximum height at the apex of the convex portion protruding toward the first electrode. A method for manufacturing a capacitor element. having the recess on the opposing surface;
The height of the lowest position of the anode body in the chemical conversion tank is higher than the height of the reference plane of the recess on the opposing surface, and the difference between the height of the reference plane and the height of the lowest position of the anode body The method for manufacturing a capacitor element according to claim 3 or 4, wherein the diameter is 2 mm or less. having the recess on the opposing surface;
5. The method for manufacturing a capacitor element according to claim 3, wherein the height of the lowest position of the anode body in the chemical conversion tank is lower than the height of the reference plane of the recess on the opposing surface. 7. The method for manufacturing a capacitor element according to claim 1, wherein the cross-sectional shape of the convex portion in a cross section perpendicular to the first direction is triangular. 7. The method for manufacturing a capacitor element according to claim 1, wherein the cross-sectional shape of the convex portion in a cross section perpendicular to the first direction is trapezoidal. 7. The method for manufacturing a capacitor element according to claim 1, wherein the cross-sectional shape of the convex portion in a cross section perpendicular to the first direction is rectangular. 12. The method for manufacturing a capacitor element according to claim 1, wherein the second electrode has a circulation hole penetrating from the opposing surface to the opposite surface through which the chemical conversion liquid circulates. The capacitor element according to any one of claims 1 to 12, wherein a plurality of said second electrodes are formed and integrated in correspondence with a plurality of said first electrodes arranged in a plurality of columns. manufacturing method. An anode body made of a valve metal is immersed in a chemical conversion solution in a chemical conversion bath with the anode body connected to an anode electrode, and a current is passed through the anode body to remove at least the surface of the anode body. A plate-shaped chemical conversion cathode electrode disposed along the bottom surface of the chemical conversion tank to partially oxidize and form a dielectric layer,
A cathode electrode for chemical formation, which has a pair of protrusions adjacent to each other on a surface facing the anode electrode.

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