阅读说明：本技术 电解电容器及其制造方法 (Electrolytic capacitor and method for manufacturing the same ) 是由 大形德彦 矢野佑磨 后藤和秀 杉原之康 凤桐将之 上田政弘 小田根和仁 于 2020-02-26 设计创作，主要内容包括：电解电容器(20)具备电容器元件(10),该电容器元件(10)包含多孔质的阳极体(1)、形成于阳极体(1)的表面的电介质层(3)、以及覆盖电介质层(3)的至少一部分的固体电解质层(4)。阳极体(1)具有多个主面、和角部分,所述角部分包含将多个主面彼此连结的多个边部分和将多个主面彼此连结的1个或多个顶点部分。角部分的至少一部分的表层X比与表层X邻接的主面的表层Y致密。(An electrolytic capacitor (20) is provided with a capacitor element (10), and the capacitor element (10) comprises a porous anode body (1), a dielectric layer (3) formed on the surface of the anode body (1), and a solid electrolyte layer (4) covering at least a part of the dielectric layer (3). The anode body (1) has a plurality of main surfaces, and an angle portion including a plurality of edge portions connecting the main surfaces to each other and 1 or more apex portions connecting the main surfaces to each other. The surface layer X of at least a part of the corner portion is denser than the surface layer Y of the main surface adjacent to the surface layer X.)

1. An electrolytic capacitor provided with a capacitor element, the capacitor element comprising:

a porous anode body;

a dielectric layer formed on a surface of the anode body; and

a solid electrolyte layer covering at least a portion of the dielectric layer,

the anode body has a plurality of main surfaces and corner portions,

the corner portion includes a plurality of edge portions and an apex portion that join the plurality of main faces to each other,

the surface layer X of at least a part of the corner portion is denser than the surface layer Y of the main surface adjacent to the surface layer X.

2. The electrolytic capacitor according to claim 1, wherein at least a part of the corner portion including the surface layer X has a curved surface shape or a chamfered surface shape.

3. The electrolytic capacitor according to claim 2, wherein the surface layer Y is adjacent to the portion having the curved surface shape or the chamfered shape in the corner portion.

4. The electrolytic capacitor as recited in claim 2 or 3, wherein the corner portion, the portion having the curved surface shape or the chamfered shape includes a portion having a radius of curvature R of 20 μm to 500 μm.

5. The electrolytic capacitor according to any one of claims 2 to 4, wherein the corner portion includes portions having the curved surface shape or the chamfered shape, the portions having different radii of curvature R from each other, and a difference between a maximum value and a minimum value of the different radii of curvature is 350 μm or less.

6. The electrolytic capacitor according to any one of claims 1 to 5, wherein the porosity P in the surface layer X₁Less than the porosity P in the surface layer Y₂。

7. The electrolytic capacitor of claim 6, wherein the surface layer X has the porosity P₁A fraction of 10% or less.

8. The electrolytic capacitor as recited in claim 6 or 7, wherein the surface layer X and the surface layer Y have a porosity satisfying the porosity P₂Relative to the porosity P₁Ratio P₂/P₁A fraction of 5 or more.

9. The electrolytic capacitor according to any one of claims 1 to 8, wherein the solid electrolyte layer contains a conductive polymer.

10. The electrolytic capacitor as recited in any one of claims 1 to 9, wherein the anode body is a sintered body of metal particles having a valve action.

11. A method for manufacturing a solid electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method comprising:

preparing the anode body;

covering at least a part of the anode body with the dielectric layer; and

a step of covering at least a part of the dielectric layer with the solid electrolyte layer,

the anode body has a plurality of main surfaces, and an angle portion including a plurality of edge portions and apex portions that join the main surfaces to each other,

the step of preparing the anode body includes a step of irradiating at least a part of the corner portion with a laser beam.

12. The method of manufacturing an electrolytic capacitor according to claim 11, wherein at least a part of a main surface of the anode body adjacent to the corner portion is not irradiated with laser light.

13. The method for manufacturing an electrolytic capacitor as claimed in claim 11 or 12, wherein the anode body is a sintered body of metal powder,

the laser irradiation is performed after sintering the metal powder.

14. A method for manufacturing a solid electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method comprising:

preparing the anode body;

covering at least a part of the anode body with the dielectric layer; and

a step of covering at least a part of the dielectric layer with the solid electrolyte layer,

the anode body has a plurality of main surfaces, and a corner portion including an edge portion and a vertex portion that join the plurality of main surfaces to each other,

the step of preparing the anode body includes a step of causing the dielectric particles to collide with at least a part of the corner portion.

15. The method for manufacturing an electrolytic capacitor as claimed in claim 14, wherein the average particle diameter of the dielectric particles is 0.1mm to 3 mm.

16. A method for manufacturing a solid electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method comprising:

preparing the anode body;

covering at least a part of the anode body with the dielectric layer; and

a step of covering at least a part of the dielectric layer with the solid electrolyte layer,

the anode body has a plurality of main surfaces, and a corner portion including an edge portion and a vertex portion that join the plurality of main surfaces to each other,

the step of preparing the anode body includes a step of vibrating the anode body together with a vibrating member.

17. The method of manufacturing an electrolytic capacitor as recited in claim 16, wherein the vibrating member is a screen.

Technical Field

The present invention relates to an electrolytic capacitor and a method for manufacturing the same.

Background

Electrolytic capacitors have a small Equivalent Series Resistance (ESR) and excellent frequency characteristics, and are therefore mounted in various electronic devices. An electrolytic capacitor generally includes a capacitor element having an anode portion and a cathode portion. The anode portion includes a porous anode body, and a dielectric layer is formed on a surface of the anode body. The dielectric layer is in contact with the electrolyte. There is an electrolytic capacitor using a solid electrolyte such as a conductive polymer as an electrolyte (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2009-182157

Disclosure of Invention

Problems to be solved by the invention

The reliability of an electrolytic capacitor using a solid electrolyte is improved.

Means for solving the problems

An aspect of the present invention relates to an electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, wherein the anode body has a plurality of main surfaces, and a corner portion including a plurality of side portions and vertex portions connecting the main surfaces to each other, and a surface layer X of at least a part of the corner portion is denser than a surface layer Y of the main surface adjacent to the surface layer X.

Another aspect of the present invention relates to a method for manufacturing a solid electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method including: preparing the anode body; covering at least a part of the anode body with the dielectric layer; and a step of covering at least a part of the dielectric layer with the solid electrolyte layer, wherein the anode body has a plurality of main surfaces, and a corner portion including a plurality of side portions and a vertex portion connecting the main surfaces, and the step of preparing the anode body includes a step of irradiating at least a part of the corner portion with a laser beam.

Another aspect of the present invention relates to a method for manufacturing a solid electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method including: preparing the anode body; covering at least a part of the anode body with the dielectric layer; and a step of covering at least a part of the dielectric layer with the solid electrolyte layer, wherein the anode body has a plurality of main surfaces, and a corner portion including a side portion and a vertex portion connecting the main surfaces, and the step of preparing the anode body includes a step of causing a dielectric particle to collide with at least a part of the corner portion.

Another aspect of the present invention relates to a method for manufacturing a solid electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method including: preparing the anode body; covering at least a part of the anode body with the dielectric layer; and a step of covering at least a part of the dielectric layer with the solid electrolyte layer, wherein the anode body has a plurality of main surfaces, and a corner portion including a side portion and a vertex portion connecting the plurality of main surfaces to each other, and the step of preparing the anode body includes a step of vibrating the anode body together with a vibrating member.

Effects of the invention

The reliability of the electrolytic capacitor is improved.

The present invention relates to both the structure and the content, and can be better understood by the following detailed description with reference to the drawings together with other objects and features of the present invention.

Drawings

Fig. 1 is a perspective view schematically showing the shape of an anode body used in an electrolytic capacitor according to an embodiment of the present invention.

Fig. 2 is a sectional view schematically showing an electrolytic capacitor according to an embodiment of the present invention.

Fig. 3 is an electron micrograph of a cross section of an angle portion of the anode body after laser irradiation.

Detailed Description

[ electrolytic capacitor ]

An electrolytic capacitor according to one embodiment of the present invention includes a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer. The anode body has a plurality of main surfaces and corner portions. The corner portion includes, for example, a plurality of edge portions that join the plurality of main surfaces to each other, and 1 or more vertex portions that join the plurality of main surfaces to each other. At least a portion of the corner portion has a curved surface or is chamfered.

In the anode body, by providing a curved surface or chamfering at least a part of the side portion and/or the apex portion, damage of the dielectric layer in the corner portion is suppressed, and an electrolytic capacitor with a small leakage current can be realized. Therefore, the reliability of the electrolytic capacitor can be improved.

The side portion refers to a side where 2 main surfaces of the anode body intersect and a region in the vicinity thereof. The apex portion refers to an apex where 3 main surfaces of the anode body intersect and a region in the vicinity thereof. Here, the edge portion and the vertex portion are collectively referred to as "angle portion". At least a part of the corner portion has a curved surface or is chamfered means that for example at least one edge portion and/or at least one vertex portion has a curved surface or is chamfered. In addition, a case where a part of one edge portion has a curved surface or is chamfered is included.

In addition, the "curved surface" of at least a part of the corner portion is not limited to the case where the cross-sectional shape of the corner portion is a curved line. For example, the cross-sectional shape of the corner portion may be a polygonal line having a plurality of obtuse angles. When the cross-sectional shape is a convex shape and a straight line corresponding to one main surface and a straight line corresponding to the other adjacent main surface are connected to each other via at least one straight line and/or curved line in the cross-sectional shape, it can be said that the corner portion has a curved surface. In other words, having a "curved surface" at the corner portion also means: in the cross-sectional shape of the corner portion in the cross section perpendicular to the adjacent 2 main surfaces, there is no sharp region of 90 ° or less.

The dielectric layer is generally formed by subjecting the anode body to chemical conversion treatment to grow an oxide film on the surface of the anode body. Therefore, the properties of the dielectric layer formed by the chemical conversion are affected by the surface state of the anode body before the chemical conversion treatment.

The anode body generally has a rectangular parallelepiped shape. In this case, the surface of the anode body is microscopically uneven in the vicinity of the side connecting the 2 orthogonal principal surfaces of the rectangular parallelepiped and/or in the vicinity of the vertex (corner portion) where the 3 orthogonal principal surfaces of the rectangular parallelepiped intersect, and the surface has a large roughness, and is likely to have a shape having unevenness. If the dielectric layer is grown by chemical conversion treatment in this state, defects are likely to occur in the dielectric layer in the concave-convex portions. If a defect is generated in the dielectric layer, there are the following cases: a path is created in which current flows between the solid electrolyte and the valve-acting metal via the defective portion, and the leakage current increases.

Further, the anode body is porous and therefore fragile and easily broken. In particular, the corner portion of the anode body has lower mechanical strength than the portions other than the corner portion, and thermal stress is likely to concentrate. There are the following situations: since the porous portion is damaged, the dielectric layer covering the porous portion is damaged. There are cases where leakage current increases due to damage of the dielectric layer.

In the electrolytic capacitor of the present embodiment, by forming at least a part of the corner portion of the anode body into a curved surface in advance, defects at the time of chemical conversion of the dielectric layer can be reduced. As a result, the leakage current can be reduced. In addition, the mechanical strength can be improved and the thermal stress can be relaxed. This can suppress damage to the dielectric layer after chemical conversion. As a result, an increase in leakage current can be suppressed.

The solid electrolyte layer is formed so as to cover the dielectric layer. In the case where the corner portion of the anode body does not have a curved surface, the thickness of the solid electrolyte layer at the corner portion is easily formed thin. In particular, when the solid electrolyte layer contains a conductive polymer and the conductive polymer is formed by chemical polymerization, the thickness of the solid electrolyte layer tends to be thin in the corner portion. However, by forming at least a part of the corner portion into a curved surface, the thinning of the solid electrolyte layer at the corner portion can be suppressed, and the solid electrolyte layer can be formed with a uniform thickness. This strengthens the electrolytic capacitor against external stress, and suppresses an increase in leakage current and the occurrence of short-circuit defects. In addition, the withstand voltage is improved.

The surface layer X of at least a part of the corner portion may be denser than the surface layer Y of the main surface adjacent to the surface layer X. The surface layer Y is a surface layer of the main surface adjacent to the corner portion, and usually the porous anode body is exposed. By densely forming the surface layer X of the corner portion, the mechanical strength of the corner portion can be further improved. Therefore, the effect of suppressing an increase in leakage current through the corner portion can be improved.

In the case where at least a part of the surface layer X of the corner portion is densely formed, the dense surface layer X may not be a curved surface or may not be a chamfered surface. Even when the corner portion does not have a curved surface and is not chamfered, sufficient mechanical strength can be obtained by densely forming the surface layer X of the corner portion. Therefore, an increase in leakage current via the corner portion can be suppressed. However, if at least a part of the portion including the surface layer X has a curved surface shape or a chamfered shape, leakage current can be further suppressed, which is preferable. In this case, the top sheet Y may be a region adjacent to the portion of the top sheet X having the curved surface shape or the chamfered shape.

The surface layer X being denser than the surface layer Y means, for example, the porosity P in the surface layer X₁Less than porosity P in surface layer Y₂. The surface layer X may have a porosity P₁A fraction of 10% or less. In contrast, the porosity P in the surface layer Y₂Usually 20% or more.

The surface layer X and the surface layer Y may have a porosity P₂Relative porosity P₁Ratio P₂/P₁Satisfying, for example, a portion of 5 or more. P₂/P₁May be 10 or more or 50 or more. Any part of the surface layer X and any part of the surface layer Y may satisfy P₂/P₁Is 5 or more.

When at least a part of the angle portion has a curved surface, the curvature of the curved surface is, for example, 0.002(1/μm) to 0.05(1/μm), and more preferably 0.005(1/μm) to 0.02(1/μm).

The curvature and porosity were obtained by image analysis of a cross-sectional photograph of the anode body in a predetermined region. In the sectional electron micrograph, the area of the void portion in an arbitrary region a in the surface layer X is obtained, and the ratio of the area of the void portion to the region a is defined as the porosity P₁. Similarly, the area of the void portion in an arbitrary region B in the top sheet Y is obtained, and the ratio of the area of the void portion to the region B is defined as the porosity P₂。

The corner portion having the curved surface can be formed by pressing the anode body using a mold formed with the curved surfaceThe anode can be formed by removing a part of the corner portion of the anode body. However, by irradiating the corner portions with laser light, the surface layer in which the corner portions are formed can be curved and/or densely formed. By the irradiation of the laser, the surface layer X at the corner portion is melted. The surface layer X after laser irradiation is a molten layer formed by melting the porous portion of the anode body, and can be formed more densely than the porous surface layer Y. Porosity P of surface layer X formed by laser irradiation₁The minimum value may be, for example, 1% or less.

Alternatively, the anode body may be placed on a vibrating member such as a screen or a medium particle, and the vibrating member may be vibrated to form the corner portion into a curved surface. In this case, the corner portion of the anode body collides with the vibration member due to vibration, the corner portion is compressed due to collision, and the corner portion can be formed in a curved surface shape. This makes it possible to form the surface layer X at the corner portion more densely (with a higher density) than the surface layer Y maintaining the porous main surface.

In the corner portion, the portion having a curved surface shape or a chamfered shape includes, for example, a portion having a radius of curvature R of 20 μm to 500 μm, and more preferably a portion having a radius of curvature R of 50 μm to 200 μm. Here, the radius of curvature of the corner portion is calculated by taking a picture of the anode body from a certain principal surface side and analyzing the obtained outline shape in the vicinity of the corner portion (vertex). In the contour line of the anode body, the distance from the boundary between the region where the curved surface is formed (chamfered portion) and the edge portion where the curved surface is not formed (not chamfered) to the vertex position before the curved surface is formed (before the chamfer) (the position of the intersection of the edge portion and the edge portion) is obtained and regarded as the radius of curvature R. The curvature radius R may be obtained for each side portion of the anode body, and an average value may be calculated. For example, when the anode body is a substantially rectangular parallelepiped, the curvature radius R is obtained at both ends of the 12 side portions, and the average value of the total of 24 curvature radii R is obtained. By using the vibrating member, the anode body having the average value of the curvature radius R in the above range can be easily obtained.

In the corner portion of the anode body, the portion having the curved surface shape or the chamfered shape may include portions having different radii of curvature R from each other. In this case, the variation in the radius of curvature R at a plurality of corners in the anode body may be, for example, 350 μm or less, and more preferably 150 μm or less. The variation of the radius of curvature R is the difference between the maximum value and the minimum value of the radius of curvature R of the corner portion calculated by the above-described method (in the case where the anode body is a substantially rectangular parallelepiped, the difference between the maximum value and the minimum value of the calculated 24 radii of curvature).

Fig. 1 is a schematic perspective view showing an example of an anode body used in the electrolytic capacitor according to the present embodiment. As shown in fig. 1, anode element 1 has a substantially rectangular parallelepiped shape, and 6 main surfaces 101A to 101F are exposed. Note that 101D to 101F are not shown because they are located at positions hidden from the paper.

In the main surfaces 101A to 101F, a connection surface is formed by removing corners of edge portions in the vicinity of edges where two adjacent main surfaces intersect with each other. In the example of fig. 1, the connection surface 102C is interposed between the main surfaces 101A and 101B, the connection surface 102A is interposed between the main surfaces 101B and 101C, and the connection surface 102A is interposed between the main surfaces 101B and 101C. In addition, in the vicinity of the vertex where the 3 main surfaces intersect, a second connection surface is formed by removing the corner of the vertex portion. In the example of fig. 1, a second connection surface 103A is provided at an apex portion where the main surfaces 101A to 101C intersect. The second connection surface 103A connects the connection surfaces 102A to 102C to each other. The connection surfaces 102A to 102C and the second connection surface 103A are curved surfaces with rounded corners. The connection surfaces 102A to 102C and the second connection surface 103A may be curved surfaces or may be formed of one or more flat surfaces (for example, corner portions may be chamfered).

By providing anode element 1 with a shape from which the sharp portions have been removed in this way, a dielectric layer with few defects can be formed on the surface of anode element 1. As a result, the leakage current can be reduced. In addition, the mechanical strength of the anode body is improved, and the concentration of thermal stress is relaxed. As a result, damage to the dielectric layer can be suppressed, an increase in leakage current due to damage to the dielectric layer can be suppressed, and the leakage current can be kept small.

The surface layers of the connection surfaces 102A to 102C and/or the second connection surface 103A may be formed denser than the surface layers of the porous main surfaces 101A to 101F. I.e. the connection faces 102A-102C and/orPorosity P in surface layer of second joint surface 103A₁The porosity P in the surface layer may be smaller than the porosities P in the main surfaces 101A to 101F₂. In this case, the mechanical strength of the corner portion of the anode body can be further improved.

The anode wire 2 extends from the main surface 101B of the anode body 1. The anode body 1 and the anode wire 2 constitute an anode portion 6.

Hereinafter, the structure of the electrolytic capacitor according to the present embodiment will be described with reference to the drawings as appropriate. However, the present invention is not limited thereto. Fig. 2 is a schematic cross-sectional view of the electrolytic capacitor of the present embodiment.

The electrolytic capacitor 20 includes: capacitor element 10 including anode portion 6 and cathode portion 7, package 11 sealing capacitor element 10, anode lead terminal 13 electrically connected to anode portion 6 and partially exposed from package 11, and cathode lead terminal 14 electrically connected to cathode portion 7 and partially exposed from package 11. The anode portion 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 portion 7 includes a solid electrolyte layer 4 covering at least a part of the dielectric layer 3, and a cathode layer 5 covering a surface of the solid electrolyte layer 4.

< capacitor element >

The capacitor element 10 will be described in detail below with reference to the case where a solid electrolyte layer is provided as an electrolyte.

The anode portion 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 a valve metal such as titanium (Ti), tantalum (Ta), niobium (Nb), or the like are used. 1 or 2 or more kinds of metal particles can be used for the anode body 1. The metal particles may be an alloy composed of 2 or more metals. For example, an alloy containing a valve-acting metal and silicon, vanadium, boron, or the like may be used. In addition, a compound containing a valve metal and a typical element such as nitrogen may be used. The alloy of the valve metal contains the valve metal as a main component, and contains 50 atomic% or more of the valve metal, for example.

The anode wire 2 is made of a conductive material. The material of the anode wire 2 is not particularly limited, and examples thereof include copper, aluminum, and aluminum alloy in addition to the valve metal. The anode body 1 and the anode wire 2 may be made of the same material or different materials. The anode wire 2 has: a first portion 2a embedded in the anode body 1 from one surface of the anode body 1, and a second portion 2b 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 circular shape, a loop shape (a shape composed of straight lines parallel to each other and 2 curved lines connecting end portions of the straight lines to each other), an oval shape, a rectangular shape, a polygonal shape, and the like.

The anode portion 6 is manufactured by, for example, pressing and sintering the first portion 2a in a rectangular parallelepiped shape in a state of being embedded in the powder of the metal particles. Thereby, the second portion 2b of the anode wire 2 is drawn out from one surface of the anode body 1 in an extending manner. The second portion 2b is joined to the anode lead terminal 13 by welding or the like, and the anode wire 2 is electrically connected to the anode lead terminal 13. The welding method is not particularly limited, and examples thereof include resistance welding and laser welding. Thereafter, the corner portions of the rectangular parallelepiped can be processed to form curved surfaces.

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. Examples of the method of forming the layer containing the metal oxide on the surface of the anode body 1 include a method of immersing the anode body 1 in a chemical conversion solution to anodize the surface of the anode body 1, and a method of heating the anode body 1 in an atmosphere containing oxygen. The dielectric layer 3 is not limited to a layer containing the metal oxide, and may have any insulating property.

(cathode part)

The cathode portion 7 has a solid electrolyte layer 4 and a cathode layer 5 covering the solid electrolyte layer 4. The solid electrolyte layer 4 is formed to cover at least a part of the dielectric layer 3.

The solid electrolyte layer 4 is made of, for example, a manganese compound or a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene. These may be used alone or in combination of two or more. The conductive polymer may be a copolymer of 2 or more monomers. In view of excellent conductivity, polythiophene, polyaniline, and polypyrrole may be used. In particular, polypyrrole can be used because of its excellent hydrophobicity.

The solid electrolyte layer 4 containing the conductive polymer is formed by polymerizing a raw material monomer on the dielectric layer 3, for example. Alternatively, the dielectric layer 3 is formed by applying a liquid containing the conductive polymer to the dielectric layer. The solid electrolyte layer 4 is composed of 1 or 2 or more solid electrolyte layers. When the solid electrolyte layer 4 is composed of 2 or more layers, the composition, the formation method (polymerization method), and the like of the conductive polymer used in each layer may be different.

In the present specification, polypyrrole, polythiophene, polyfuran, polyaniline, and the like respectively mean a polymer having polypyrrole, polythiophene, polyfuran, polyaniline, and the like as a basic skeleton. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, and the like may contain their respective derivatives. For example, polythiophenes include poly (3, 4-ethylenedioxythiophene) and the like.

In the polymerization liquid for forming the conductive polymer, the solution or dispersion liquid of the conductive polymer, various dopants may be added for improving the conductivity of the conductive polymer. The dopant is not particularly limited, and examples thereof include naphthalene sulfonic acid, p-toluenesulfonic acid, polystyrene sulfonic acid, and the like.

When the conductive polymer is dispersed in the 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 easily penetrate into 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 5 a. The carbon layer 5a includes a conductive carbon material such as graphite and a resin. The metal paste layer 5b contains, for example, metal particles (e.g., silver) and a resin. The structure of the cathode layer 5 is not limited to this structure. The cathode layer 5 may be configured to have 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 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 nonmetal. The shape is not particularly limited as long as it is a flat plate. From the viewpoint of thinning, the thickness of anode lead terminal 13 (the distance between the principal surfaces of anode lead terminal 13) may be 25 μm or more and 200 μm or less, or may be 25 μm or more and 100 μm or less.

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

< cathode lead terminal >

Cathode lead terminal 14 is electrically connected to cathode portion 7 at junction 14 a. The joint 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, for example, the conductive adhesive 8. One end of cathode lead terminal 14 constitutes, for example, a part of bonding portion 14a, and is disposed inside package 11. The other end of cathode lead terminal 14 is led out to the outside. Therefore, a part of cathode lead terminal 14 including the other end is exposed from package 11.

The material of cathode lead terminal 14 is 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 nonmetal. The shape is also not particularly limited, and is, for example, a long and flat plate. From the viewpoint of reduction in thickness, the thickness of 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.

< outer Package >

Package 11 is provided to electrically insulate anode lead terminals 13 and cathode lead terminals 14, and is made of an insulating material (package material). The exterior material contains, 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, unsaturated polyester, and the like.

Method for manufacturing electrolytic capacitor

An example of the method for manufacturing the electrolytic capacitor according to the present embodiment will be described below.

A method for manufacturing a solid electrolytic capacitor having a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the method for manufacturing the electrolytic capacitor including a step of preparing the anode body, a step of covering at least a part of the anode body with the dielectric layer, and a step of covering at least a part of the dielectric layer with the solid electrolyte layer, wherein the anode body has a plurality of main surfaces and a corner portion including a plurality of side portions and a vertex portion connecting the plurality of main surfaces, and the step of preparing the anode body includes a step of forming a curved surface in at least a part of the corner portion or chamfering at least a part of the corner portion.

(1) Preparation of anode body

As the anode body 1, a porous sintered body can be used. The valve-acting metal particles and the anode wire 2 are placed in a mold so that the first portions 2a are embedded in the valve-acting metal particles, and after press molding, sintering is performed, thereby obtaining the anode portion 6 of the anode body 1 including the porous body of the valve-acting metal. The first portion 2a of the anode wire is embedded in the porous sintered body from one surface thereof. The pressure at the time of press molding is not particularly limited. The sintering is preferably carried out under reduced pressure. The valve-acting metal particles may be mixed with a binder such as a polyacrylate carbonate, if necessary.

The valve-acting metal particles are generally press-molded and sintered using a mold having a rectangular parallelepiped inner space. In this case, the sintered anode body 1 is also rectangular parallelepiped in shape and has a plurality of main surfaces. In this case, the plurality of main surfaces are directly connected to each other to form a side and a vertex, and the edge portion and/or the vertex portion connecting the plurality of main surfaces, that is, the tip end portion of the corner portion, is in a sharp state.

The anode body having a sharp tip end may be subjected to a process of forming a curved surface at least in a part of a corner portion or a process of chamfering at least in a part of a corner portion. This removes corners of the tip portion, and can be formed into a rounded shape, for example. The processing of forming the curved surface in the corner portion may be performed by removing the tip portion by cutting off a part of the corner portion, for example.

In the processing step of forming a curved surface in at least a part of the corner portion or chamfering at least a part of the corner portion, at least a part of the corner portion can be formed with high density. For example, by irradiating the angle portion with laser light, the angle portion is formed into a curved surface, and at least a part of the angle portion can be formed with high density. Alternatively, the anode body may be vibrated together with the vibration member. Accompanying the vibration, particularly the corner portion of the anode body collides with the vibration member, the corner portion is compressed, thereby forming a curved surface, and at least a part of the corner portion can be formed with high density.

The curved surface may be formed at the corner portion by irradiating the corner portion with laser light. By irradiating the corner portion with laser light, the corner portion is melted, and the tip portion can be changed from a sharp shape to a shape having a curved surface. The molten layer formed after melting is denser than the porous portion of the anode body, and the porosity is extremely small. Therefore, the mechanical strength of the corner portion can be significantly improved, and the effect of suppressing damage to the dielectric layer in the corner portion is large. The thickness of the molten layer may be, for example, 1 μm to 100 μm.

The laser used for laser irradiation is not limited, and for example, a YAG (Yttrium Aluminum Garnet) laser (wavelength 1064nm) can be used.

In the formation of the solid electrolyte layer, it is preferable that the corner portion is irradiated with the laser light and the principal surface of the anode body adjacent to the corner portion is not substantially irradiated with the laser light, from the viewpoint that air present in the pores of the anode body is easily discharged. The above description is intended to exclude the case where laser light is not irradiated to most of the main surface, and irradiation of laser light to a part of the main surface (for example, a region on the main surface adjacent to the corner portion) is not excluded.

The laser irradiation may be performed on the anode body after sintering, or may be performed on the valve-acting metal particles subjected to pressure forming before sintering. However, if considering the deformation accompanying the volume shrinkage after sintering, it is preferable to irradiate the sintered anode body with laser light.

When the anode body is vibrated together with the vibrating member, for example, the anode body can be removed by placing the anode body on a base (vibrating member) having irregularities on the surface, such as a screen (sieve) or a file, and vibrating the base in the vertical direction and/or the horizontal direction. The anode body rolls on the base while jumping with the vibration of the base. Accordingly, a part of the tip end of the corner portion is cut off, and a curved surface is formed at the corner portion. However, most of the distal end portion can remain in a compressed state on the surface layer of the corner portion without being shaved off. As a result, the surface layer having the corner portion of the curved surface can be formed with high density. The base may be a sieve in order to facilitate the downward falling and removal of the residue scraped off at the tip, to reduce the static friction coefficient appropriately, and to facilitate the rolling movement of the anode body. The mesh of the screen may be smaller than the minimum value of the outer diameter of the anode body so that the anode body does not fall through the openings of the screen. The mesh of the sieve may be 1mm or more, or 2mm or more and 3.4mm or less. When the mesh size is 1mm or more, the variation in the radius of curvature R at the corner portions is easily reduced to a constant value or less.

The anode body may be vibrated together with the dielectric particles by applying an external force to the dielectric particles in a state where the anode body is placed on the dielectric particles. For example, the anode body and the dielectric particles are mixed, and the anode body and the dielectric particles are put into an oscillator together to operate the oscillator. The oscillator is preferably capable of applying vibration in the vertical direction in addition to vibration in the horizontal direction. Alumina particles, zirconia particles, and the like can be used as the dielectric particles. The particle diameter (average particle diameter) of the medium particles may be, for example, 0.1mm to 3mm, or 0.5mm to 2 mm.

The dielectric particles put into the oscillator together with the anode body vibrate by the operation of the oscillator and collide with the anode body. Since the corner portion of the anode body has low mechanical strength, it is easily deformed by collision, and the porous portion of the corner portion is easily crushed and compressed. Therefore, the skin layer of the corner portion can be formed at high density.

The density of the dielectric particles may be 0.15 to 0.4 times the density (true density) of the anode body. In the case where the density of the dielectric particles is in the above range, the energy generated by the collision of the dielectric particles can be effectively used for the compression deformation of the corner portion. In addition, the rate of the corner portion being chipped off by the collision can be reduced.

In the method of vibrating the dielectric particles in a state in which the anode body and the dielectric particles are mixed, the curved surface can be formed or the chamfer can be performed at the corner portion in a shorter time than in the method of vibrating the sieve on which the anode body is placed. Therefore, the deviation of the curvature radius R at the corner portion is easily reduced.

In the case where the vibration member is used to form or chamfer the curved surface of the corner portion, it is preferable to form or chamfer the curved surface of the corner portion on the porous body before sintering because the mechanical strength is improved by sintering and the corner portion is hard to be compressed.

The valve-acting metal particles are pressure-molded using a die from which corners have been removed in advance, and sintered to obtain an anode body having a curved surface formed at the corner portion.

(2) Dielectric layer formation process

Next, the anode body 1 is subjected to chemical conversion treatment, and at least a part of the anode body 1 is covered with the dielectric layer 3. Specifically, the dielectric layer 3 composed of an oxide film of a valve metal can be formed on the surface of the porous portion by immersing the anode body 1 in a chemical conversion vessel filled with an electrolytic aqueous solution (for example, an aqueous phosphoric acid solution), connecting the second portion 2b of the anode wire 2 to the anode body of the chemical conversion vessel, and anodizing the second portion. The electrolytic aqueous solution is not limited to the phosphoric acid aqueous solution, and nitric acid, acetic acid, sulfuric acid, or the like can be used.

(3) Process for Forming solid electrolyte layer

Next, at least a part of the dielectric layer 3 is covered with the solid electrolyte layer 4. Thus, capacitor element 10 including anode element 1, dielectric layer 3, and solid electrolyte layer 4 was obtained.

The solid electrolyte layer 4 containing a conductive polymer is formed on at least a part of the dielectric layer 3 by, for example, a method of impregnating the anode element 1 having the dielectric layer 3 with a monomer or oligomer and then polymerizing the monomer or oligomer by chemical polymerization or electrolytic polymerization, or a method of impregnating the anode element 1 having the dielectric layer 3 with a solution or dispersion of a conductive polymer and drying the solution or dispersion.

The solid electrolyte layer 4 can be formed, for example, by impregnating the anode element 1 on which the dielectric layer 3 is formed with a dispersion liquid containing a conductive polymer, a binder and a dispersion medium, taking out the dispersion liquid, and drying the dispersion liquid. The dispersion liquid may contain a binder and/or conductive inorganic particles (for example, a conductive carbon material such as carbon black). The conductive polymer may contain a dopant. The conductive polymer and the dopant may be selected from those exemplified for the solid electrolyte layer 4. The adhesive may be a known adhesive. The dispersion liquid may contain known additives used in forming the solid electrolyte layer.

Next, a carbon paste and a metal paste are sequentially applied to the surface of the solid electrolyte layer 4, thereby forming a cathode layer 5 including a carbon layer 5a and a metal paste layer 5 b. The structure of the cathode layer 5 is not limited to this, and may be any structure having a current collecting function.

Next, anode lead terminal 13 and cathode lead terminal 14 were prepared. The second portion 2b of the anode wire 2 extending from the anode body 1 is joined to the anode lead terminal 13 by laser welding, resistance welding, or the like. After the conductive adhesive 8 is applied to the cathode layer 5, the cathode lead terminal 14 is bonded to the cathode portion 7 via the conductive adhesive 8.

Next, the materials (for example, uncured thermosetting resin and filler) of capacitor element 10 and package 11 are housed in a mold, and capacitor element 10 is sealed by a transfer molding method, a compression molding method, or the like. At this time, a part of anode lead terminal 13 and cathode lead terminal 14 was exposed from the mold. The molding conditions are not particularly limited, and time and temperature conditions may be appropriately set in consideration of the curing temperature of the thermosetting resin used.

Finally, the exposed portions of anode lead terminal 13 and cathode lead terminal 14 are bent along package 11 to form bent portions. Thus, anode lead terminal 13 and cathode lead terminal 14 are partially disposed on the mounting surface of package 11.

The electrolytic capacitor 20 is manufactured by the above method.

Fig. 3 shows an electron micrograph of a cross section of the corner portion of the anode body after laser irradiation. In fig. 3, the valve metal (Ta) is present in the white portion, and the black portion is a void. It was found that the corner portions had curved surfaces, and the surface layer X having the corner portions of the curved surfaces was densely formed. On the other hand, the inside of the top sheet X is kept porous.

Industrial applicability

The present invention can be used for an electrolytic capacitor, and can be suitably used for an electrolytic capacitor using a porous body as an anode body.

The present invention has been described in terms of the presently preferred embodiments, but such disclosure should not be construed as limiting. Various modifications and alterations will no doubt become apparent to those skilled in the art to which this invention pertains from a reading of the above disclosure. Accordingly, the appended claims should be construed to include all such modifications and changes as fall within the true spirit and scope of the invention.

Description of the reference numerals

20: electrolytic capacitor

10: capacitor element

1: anode body

2: anode line

2 a: the first part

2 b: the second part

3: dielectric layer

4: solid electrolyte layer

5: cathode layer

5 a: carbon layer

5 b: metal paste layer

6: anode section

7: cathode part

8: conductive adhesive material

11: exterior body

13: anode lead terminal

14: cathode lead terminal

14 a: joint part

101A to 101C: main surface of anode body

102A to 102C: connecting surface

103A: second connecting surface