Capacitor element and electrolytic capacitor

Abstract

This capacitor element comprises a metal foil that includes a valve action metal and has two main surfaces. The metal foil has a first portion that is a cathode-forming part, a second portion that includes an anode lead-out part, and a separation portion between the first portion and the second portion. Each of the first portion, the separation portion, and the second portion has porous parts having the main surfaces and a core part connected to the porous parts. The metal foil has a projection / recess region having a plurality of recesses on the main surfaces. At least a part of the separation portion overlaps the projection / recess region.

Description

Capacitor elements and electrolytic capacitors CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-011349, filed on January 29, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a capacitor element and an electrolytic capacitor.

[0003] Patent Document 1 discloses a "substrate for a solid electrolytic capacitor having a porous layer on its surface, characterized in that at least a portion of the porous layer between the anode region and the cathode region is reduced."

[0004] Patent Document 2 discloses "an electrode foil before being incorporated into a wound capacitor, the electrode foil being made of a strip-shaped foil, and comprising: an enlarged surface portion formed on the surface of the foil and consisting of a large number of tunnel-shaped pits; a core portion which is the remainder of the foil excluding the enlarged surface portion; a plurality of dividing portions which divide the enlarged surface portion; and a dielectric coating formed on the surface of the enlarged surface portion or on the surfaces of the enlarged surface portion and the dividing portions; and the electrode foil being wound in a state in which the dividing portions are present when incorporated into the wound capacitor."

[0005] Patent Document 3 discloses "an electrode foil for an electrolytic capacitor, the electrode foil extending in a longitudinal direction and having a width direction perpendicular to the longitudinal direction, the electrode foil having an enlarged surface portion on a surface of the electrode foil, and a crack formed in the enlarged surface portion in a direction oblique to the width direction."

[0006] Patent Document 4 discloses a solid electrolytic capacitor comprising: "a capacitor element including a cathode portion formed by sequentially forming a dielectric oxide film layer, a solid electrolyte layer, and a conductor layer on a portion of the outer surface of an anode body made of a valve action metal having a roughened surface layer formed by roughening the surface; an anode lead portion formed on the remaining portion of the outer surface of the anode body; lead terminals connected to the cathode portion and the anode lead portion of the capacitor element, respectively; and an exterior resin covering the capacitor element in a state where portions of the lead terminals are exposed to the outside, wherein the solid electrolytic capacitor comprises: a first forbidden band separating the anode body from the anode lead portion; and a second forbidden band having a smaller surface area than the first forbidden band, the first forbidden band comprising a compressed layer or a molten condensed layer formed by processing so as to have a smaller surface area than the surface area of ​​the roughened surface layer of the valve action metal; and an insulating member provided so as to cover the surfaces of the first and second forbidden bands."

[0007] International Publication No. 2006 / 137482 Pamphlet Japanese Patent Application Laid-Open No. 2023-015261 Japanese Patent Application Laid-Open No. 2022-099215 Japanese Patent No. 4547835

[0008] Electrode foils for capacitor elements of electrolytic capacitors are subjected to various processes, such as slitting, crimping, punching, welding, etc. During the processes, stresses such as bending stress, tension, and heat are applied to the electrode foils.

[0009] For example, if a portion of the porous layer is reduced as in Patent Document 1, or if a divided portion is formed in the foil as in Patent Document 2, the tensile strength decreases and it becomes difficult to distribute stress, which can cause defects such as cracks.

[0010] One aspect of the present disclosure relates to a capacitor element comprising a metal foil containing a valve metal and having two main surfaces, the metal foil having a first portion that is a cathode forming portion, a second portion that includes an anode lead portion, and a separation portion between the first portion and the second portion, the first portion, the separation portion, and the second portion each having a porous portion having the main surface and a core portion continuous with the porous portion, the metal foil having an uneven region having a plurality of recesses on the main surface, and at least a portion of the separation portion overlapping the uneven region.

[0011] Another aspect of the present disclosure relates to an electrolytic capacitor including the above capacitor element, in which the porous portion of at least the first portion has a dielectric layer, and a cathode portion covering at least a portion of the dielectric layer, wherein the cathode portion includes a conductive polymer.

[0012] According to the present disclosure, in a capacitor element having a first portion that is a cathode forming portion, a second portion that includes an anode lead portion, and a separation portion between the first portion and the second portion, the strength of the separation portion is improved.

[0013] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0014] FIG. 2 is a cross-sectional schematic diagram of a capacitor element according to an embodiment of the present disclosure. FIG. 3 is a plan view schematic diagram of a portion of the capacitor element of FIG. 1. FIG. 4 is a cross-sectional schematic diagram of a detail of the capacitor element of FIG. 1. FIG. 5 is a plan view schematic diagram of a portion of another capacitor element. FIG. 6 is a plan view schematic diagram of a portion of yet another capacitor element. FIG. 7 is a cross-sectional schematic diagram showing an electrolytic capacitor according to an embodiment of the present disclosure. FIG. 8 is a SEM photograph of the top surface of an example of a concave-convex region. FIG. 9 is a cross-sectional SEM photograph of an example of a concave-convex region.

[0015] The following describes embodiments of the present disclosure 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 exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits are exemplified for numerical values ​​of specific physical properties or conditions, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one may be selected from them and used alone, or two or more may be used in combination.

[0016] The present disclosure encompasses any combination of two or more claims arbitrarily selected from the appended claims, i.e., any combination of two or more claims arbitrarily selected from the appended claims may be combined unless a technical contradiction arises.

[0017] The present disclosure does not limit the type of electrolytic capacitor. The present disclosure is applicable to all electrolytic capacitors that include a metal foil having a first portion that is a cathode forming portion, a second portion that includes an anode lead portion, and a separation portion between the first and second portions. The electrolytic capacitor may be a solid electrolytic capacitor, a solid-liquid hybrid electrolytic capacitor, or the like. In any electrolytic capacitor, the strength of the separation portion is improved, and phenomena caused by foil tearing and cracking in the separation portion can be suppressed. In particular, in solid electrolytic capacitors that use a conductive polymer as a solid electrolyte, the strength of the separation portion is significantly improved by using a capacitor element according to the present disclosure.

[0018] (Capacitor Element) A capacitor element according to an embodiment of the present disclosure includes a metal foil containing a valve metal and having two main surfaces. The metal foil has a first portion that is a cathode forming portion, a second portion that includes an anode lead portion, and a separation portion between the first and second portions. The material of the electrode foil may be a valve metal such as aluminum, tantalum, niobium, or titanium.

[0019] The first portion, the separation portion, and the second portion each have a porous portion having the above-mentioned main surface and a core portion continuous with the porous portion. That is, the main surface is the main surface of the porous portion, and the metal foil is an electrode foil or an etched foil.

[0020] The separation portion is a region that insulates the cathode portion formed in the first portion from the anode lead portion in the second portion. At least a portion of the porous portion in the separation portion may be impregnated with an insulating resin (e.g., a resist resin). An insulating tape may be attached to the surface of the porous portion in the separation portion.

[0021] Here, the metal foil has an "irregular region" having a plurality of recesses on its main surface. At least a portion of the separation portion overlaps with the irregular region. At least a portion of the first portion may overlap with the irregular region. At least a portion of the second portion may overlap with the irregular region. That is, at least the main surface of the separation portion (porous portion thereof) is provided with an "irregular region" having a plurality of recesses. The irregular region may also be formed on at least a portion of the main surface of the first portion. The irregular region may also be formed on at least a portion of the main surface of the second portion. The irregular region of the first portion or the second portion may be continuous with the irregular region of the separation portion.

[0022] When the metal foil (electrode foil) is viewed from the normal direction of the main surface, 70% or more of the projected area of ​​the separated portion may be the projected area of ​​the concave-convex region, or the entire separated portion may be the concave-convex region. The concave-convex region may be formed on only one main surface of the separated portion, or may be formed on both main surfaces.

[0023] When the metal foil (electrode foil) is viewed in the normal direction of the main surface, 70% or more of the projected area of ​​the first portion may be the projected area of ​​the concave-convex region, or the entire first portion may be the concave-convex region.

[0024] When the metal foil (electrode foil) is viewed in the normal direction of the main surface, 70% or more of the projected area of ​​the second portion may be the projected area of ​​the concave-convex region, or the entire second portion may be the concave-convex region.

[0025] In the concave-convex region, by controlling parameters such as the shape, depth, and spacing of the multiple recesses, stress during processing can be highly dispersed, resulting in a significant improvement in folding strength in particular. The separated portion may be subjected to compression processing, embossing processing, imprinting processing, etc. In this case, the tensile strength can be further improved by reducing voids.

[0026] By providing the separation portion with an uneven region, it is possible to suppress cracks and foil breaks that reach the first portion or the second portion in various processes.

[0027] When multiple recesses are regularly arranged, stress is particularly easily dispersed, significantly improving the strength of the separated portion and making it easier to prevent foil breakage and cracks during processes such as cutting (slitting), foil transport, lamination, punching, welding, crimping, and winding.

[0028] The width of the uneven region in the direction from the first portion to the second portion (hereinafter also referred to as "direction D12") (hereinafter also referred to as "width W3") may be 10% or more, or may be 15% to 80% of the length of the first portion in direction D12 (hereinafter also referred to as "length L1"). When the ratio of the width W3 of the uneven region to the length L1 of the first portion is within the above range, foil tearing and cracking in the separation portion are significantly suppressed. The width W3 of the uneven region may be the same as the width of the separation portion in direction D12 or may be smaller than the width of the separation portion. However, the width W3 of the uneven region is preferably equal to or larger than the width of the separation portion. When the width W3 of the uneven region is larger than the width of the separation portion, the uneven region may extend to at least one of the first portion and the second portion adjacent to the separation portion.

[0029] In the separated portion and other portions, the concave-convex region may satisfy at least one of the following conditions (A) and (B): (A) the depth H of the concave portion is 5% or more and 80% or less (preferably 20% or more and 40% or less) of the distance from the non-convex surface where no concave portion is formed to the core portion, and (B) the projected area ratio Ras of the concave portion in the concave-convex region is 3% or more and 65% or less (preferably 10% or more and 50% or less).

[0030] Condition (A) may be satisfied on only one main surface of the separation portion, or on both main surfaces. Condition (A) is preferably satisfied on both of the two main surfaces. Condition (B) may be satisfied on only one main surface of the separation portion, or on both main surfaces. Condition (B) is preferably satisfied on both of the two main surfaces.

[0031] When the uneven regions are provided on both main surfaces of the separation portion, the depth H of the recesses and the ratio of the projected area of ​​the recesses to the main surface region may be the same or different in both main surfaces. When the separation portion is viewed from the normal direction of the main surfaces, the recesses constituting the uneven region on one main surface and the recesses constituting the uneven region on the other main surface may overlap each other, but preferably do not overlap each other.

[0032] When the first portion has a concave-convex region, the concave-convex region of the separation portion and the concave-convex region of the first portion may be different from each other. For example, the concave-convex region of the separation portion and the concave-convex region of the first portion may be the same or different in terms of the shape, arrangement, size, depth, and projected area ratio of the recesses.

[0033] When the second portion has a concave-convex region, the concave-convex region of the separation portion and the concave-convex region of the second portion may be different from each other. For example, the concave-convex region of the separation portion and the concave-convex region of the second portion may be the same or different in terms of the shape, arrangement, size, depth H, and projected area ratio Ras of the concaves.

[0034] The depth H of the recess under condition (A) can be measured in a cross section (hereinafter simply referred to as the "cross section of the foil") parallel to the thickness direction of the metal foil (electrode foil) or separation portion (hereinafter simply referred to as the "foil"). The cross section of the foil is formed so that the deepest parts of at least two mutually adjacent recesses can be observed, and observed with a scanning electron microscope (SEM). The depth H of the recess is the average of two distances (distances parallel to the thickness direction of the foil) between the highest point of a non-recess between the two mutually adjacent recesses and the deepest parts of the two mutually adjacent recesses sandwiching the non-recess. The depth H of the recess is measured at at least five points on the foil and calculated as the average value. Note that when the recesses extend linearly, the "cross section of the foil" is a cross section parallel to the thickness direction and intersecting the extension direction of the linear recesses at an angle of 80° to 100° (for example, 90°).

[0035] The "proportion of the projected area of ​​the recesses in the concave-convex region" in condition (B) is the ratio of the total projected area of ​​the plurality of recesses onto the main surface region to the projected area of ​​the concave-convex region as viewed from the normal direction of the concave-convex region (hereinafter also referred to as "convex projected area ratio Ras"). The projected area of ​​the concave-convex region for measuring the concave-convex projected area ratio Ras is, for example, 1 mm ２ When the concave-convex region is observed with an SEM from the normal direction of the concave-convex region, the concave and non-convex regions can be distinguished from each other based on their color tones. The concave and non-convex regions may also be distinguished from each other by binarizing the SEM image based on common technical knowledge.

[0036] The ratio (H / F) of the depth H (μm) of the recess to the thickness F (μm) of the separated portion is preferably 0.03 or more and 0.45 or less, more preferably 0.05 or more and 0.3 or less, and even more preferably 0.1 or more and 0.25 or less. When H / F is within the above range, the folding endurance of the separated portion is easily ensured. The thickness F (μm) of the separated portion is measured at at least five locations in the non-recessed portion and calculated as the average value. The thickness F (μm) of the separated portion may be measured at any five locations as twice the distance from the center of the core portion to the non-recessed surface of the porous portion.

[0037] The ratio (H / T) of the depth H of the recess to the thickness T of the porous portion is preferably 0.15 or more and 0.75 or less, more preferably 0.20 or more and 0.40 or less. When H / T is within the above range, the folding strength of the separated portion is likely to be ensured.

[0038] Hereinafter, a case where the concave-convex region has a plurality of concave portions scattered like islands will be described.

[0039] When viewed from the normal direction of the concave and convex region, the shape of each of the recesses constituting the plurality of recesses (the shape of the opening of the recess) is not particularly limited.

[0040] Some of the parameters that define the recesses scattered like islands will be described below. Recesses that satisfy any of the following conditions are particularly effective in increasing the folding strength and tensile strength of the separated portions.

[0041] The number density Nd of the recesses in the uneven region is 4 / mm ２ Above, 1200 pieces / mm ２ The number density Nd may be 10 pieces / mm or less. ２ More than 300 pieces / mm ２ The area of ​​the concave and convex region for measuring the number density Nd may be, for example, 1 mm ２ The "number density" refers to the number of recesses formed per unit area of ​​the recessed / protruding region. When recessed / protruding regions are provided on both main surfaces of the foil, the number densities Nd of the recesses in both recessed / protruding regions may be the same or different.

[0042] The projection area Sn per recess (the projection area of ​​the recess onto the recessed area as viewed from the normal direction of the recessed area) is 150 μm ２ More than 13000μm ２ The projection area Sn per recess may be 500 μm or less. ２ 7000 μm or more ２ The projected area Sn per recess is calculated as the average value of the projected areas Sn of at least five arbitrarily selected recesses. When the recessed and projected areas are provided on both main surfaces of the foil, the projected areas Sn per recess in both recessed and projected areas may be the same or different.

[0043] The ratio of the long side Lmax to the short side Lmin of the smallest rectangle enclosing the recess (hereinafter also referred to as the "aspect ratio") may be 1.0 to 2.5. Such recesses have low anisotropy, so the tensile strength of the separated portion or foil is less dependent on the tensile direction, making it easier to ensure isotropy of the tensile strength. The aspect ratio is calculated as the average aspect ratio of at least five arbitrarily selected recesses. When textured regions are provided on both main surfaces of the foil, the aspect ratios of the recesses in both textured regions may be the same or different.

[0044] The short side Lmin may be 15 μm or more and 110 μm or less. The dimension of the short side Lmin may be 25 μm or more and 80 μm or less. The dimension of the short side Lmin is determined as the average dimension of the short side Lmin of at least five arbitrarily selected recesses. When a concave-convex region is provided on both main surfaces of the foil, the dimensions of the short side Lmin of the recesses in both concave-convex regions may be the same or different.

[0045] The shortest distance Dmin between the edges of the closest recesses may be 1 to 10 times the short side Lmin. The shortest distance Dmin may be 15 μm or more and 300 μm or less. The shortest distance Dmin is calculated as the average value of the shortest distances between the edges of at least five arbitrarily selected pairs of the closest recesses. Note that "edge of recess" refers to a point on the contour line that defines the shape of the recess opening. When a textured region is provided on both main surfaces of the foil, the shortest distance between the edges of the closest recesses in both textured regions may be the same or different.

[0046] The ratio (Lmin / F) of the short side Lmin (μm) of the recess to the thickness F (μm) of the isolation portion is preferably less than 0.5. The Lmin / F ratio may be 0.1 or more.

[0047] The ratio (Lmin / H) of the short side Lmin (μm) of the recess to the depth H (μm) of the recess is preferably 1 or more and 5 or less.

[0048] Next, a case where the concave-convex region has a plurality of linearly extending concave portions will be described.

[0049] When viewed from the normal direction of the concave-convex region, the form of each of the recesses constituting the plurality of recesses extending linearly is not particularly limited. The direction in which the plurality of recesses extend may be, independently of one another, parallel, perpendicular, or oblique to the direction from the first portion to the second portion (direction D12). The plurality of recesses may all extend in roughly one direction without intersecting with one another. Alternatively, some of the recesses may extend in one direction and the remaining recesses may extend in another direction. The recesses may also intersect with one another.

[0050] Some of the parameters that define the recesses extending in a line shape will be described below. Recesses that satisfy any of the following conditions are particularly effective in increasing the folding strength and tensile strength of the separated portion.

[0051] Each linearly extending recess may be formed continuously in the extending direction of the recess. For example, each recess may be formed so as to cross the uneven region (or separated portion) from one end to the other end on the opposite side, and may be continuous without interruption over a length L of 1 mm or more, for example.

[0052] Each linearly extending recess may be formed discontinuously (e.g., in a dashed line) in the extending direction of the recess. For example, each recess may be formed intermittently so that the length L of each recess is less than 0.1 mm.

[0053] When textured regions are provided on both main surfaces of the foil, the recesses in both textured regions may be continuous, or only one of the recessed regions may be continuous.

[0054] The length L of each linear recess is, for example, 20 μm or more, or may be 80 μm or more, or 300 μm or more. The length L of the recess is calculated as the average length of at least five arbitrarily selected recesses. When a textured region is provided on both main surfaces of the foil, the lengths L of the recesses in both textured regions may be the same or different.

[0055] The width W of the linear recess (the dimension perpendicular to the length of the recess) may be 15 μm or more and 110 μm or less. The width W of the recess may be 25 μm or more and 80 μm or less. The width W of the recess is determined as the average value of the widths of at least five recesses selected arbitrarily. When an uneven region is provided on both main surfaces of the foil, the width W of the recess in both uneven regions may be the same or different.

[0056] The ratio (L / W) of the length L of the recess to the width W of the recess may be 2 or more, or may be 40 or more.

[0057] The ratio (W / F) of the width W (μm) of the recess to the thickness F (μm) of the separation portion (or foil) is preferably less than 0.5, and the W / F ratio is preferably 0.1 or more.

[0058] In a typical example where all of the recesses extend in approximately the same direction without intersecting each other (including cases where the recesses may intersect at angles of -20° to 20° when extended in the longitudinal direction), the recesses extend in a stripe pattern. In this case, the shortest distance Dmin between the edges of the closest recesses may be 10 μm or more and 300 μm or less. The shortest distance Dmin may be 30 μm or more and 200 μm or less. The shortest distance Dmin is calculated as the average value of the shortest distances Dmin between the edges of at least five arbitrarily selected pairs of the closest recesses. However, the shortest distance Dmin is the distance between horizontally adjacent lines facing the same direction (the distance in the width direction of the recesses). When a textured region is provided on both main surfaces of the foil, the shortest distance Dmin between the edges of the closest recesses in both textured regions may be the same or different.

[0059] The recesses may be in a mesh (or lattice) pattern. In this case, the shortest distance Dmin between opposing sides of the squares surrounded by the recesses may be 10 μm or more and 300 μm or less. The shortest distance Dmin may be 30 μm or more and 200 μm or less. The shortest distance Dmin is calculated as the average value of the shortest distances Dmin between the edges of the recesses in at least five arbitrarily selected squares. When a textured region is provided on both main surfaces of the foil, the shortest distances Dmin in both textured regions may be the same or different.

[0060] In the capacitor element, the uneven region may be formed on the main surface of the second portion in addition to the separation portion. Furthermore, the uneven region may be formed on the main surface of the second portion and the main surface of the portion extending from the second portion (the portion to be removed in a later process) in addition to the separation portion. Such a capacitor element is easier to manufacture than one in which the uneven region is formed only in the separation portion (or in the separation portion and the first portion). The first portion of the capacitor element may also have an uneven region.

[0061] The following description will be made with reference to the drawings. However, the capacitor element and electrolytic capacitor according to the present disclosure are not limited to the embodiments shown in the drawings. Each drawing is a schematic diagram, and the shape or characteristics of each component in each drawing do not necessarily reflect the actual dimensions, and are not necessarily depicted to the same scale.

[0062] Fig. 1 is a schematic cross-sectional view of a capacitor element 110. Fig. 2 is a schematic plan view of the capacitor element 110. Fig. 3 is a schematic cross-sectional view of the capacitor element 110 in detail, showing the details at a larger scale than Fig. 1.

[0063] Capacitor element 110 is formed using a metal foil (electrode foil) as a base and has a generally sheet-like shape. Capacitor element 110 includes anode body 11 based on the electrode foil, dielectric layer 12 covering at least a portion of anode body 11, solid electrolyte layer 13 covering at least a portion of the dielectric layer, and cathode extraction layer 14 covering at least a portion of solid electrolyte layer 13. Solid electrolyte layer 13 and cathode extraction layer 14 form cathode portion 134. Cathode extraction layer 14 is formed by sequentially forming, for example, a carbon layer and a metal paste layer.

[0064] The anode body 11 has a first portion (R1) which is a cathode formation portion 11b, a second portion (R2) which includes an anode lead portion 11a, and a separation portion 11c (R3) between the first portion (R1) and the second portion (R2). The first portion (R1), the separation portion (R3), and the second portion (R2) each have a porous portion 112 having a main surface and a core portion 111 continuous with the porous portion 112. The separation portion (R3) has an uneven region AS with a plurality of recesses 113 on its main surface.

[0065] The width W3 of the concave-convex region AS in the direction D12 from the first portion (R1) to the second portion (R2) is 10% or more of the length of the first portion (R1) in the direction D12. An insulating resin 15 is attached to the surface of the separation portion (R3) so as to cover at least a part of the concave-convex region AS.

[0066] In the capacitor element 110, the uneven region AS is formed on the surface of at least the porous portion 112 of the separation portion (R3). A plurality of linear recesses 113 are formed in the uneven region AS. The linear recesses are striped. The extending direction of the recesses is preferably generally parallel to the direction D12, but for convenience, they are depicted as being generally perpendicular to the direction D12. Although not shown, the uneven region AS may also be formed on the main surface of the second portion (R2).

[0067] Variations of the capacitor element will be described below. In the following Figures 4 to 7, the concave-convex region AS is formed on the main surface of each of the separation portion (R3) and the second portion (R2). The recess 113 formed in the separation portion (R3) is covered with insulating resin 15.

[0068] In the uneven region AS shown in FIG. 4, a plurality of linear recesses 113 are formed in a stripe pattern. The extending direction of the recesses is generally parallel to the direction D12. In the uneven region AS shown in FIG. 5, a plurality of rectangular recesses 113 are provided scattered in an island-like pattern. In the uneven region AS shown in FIG. 6, a plurality of flat recesses 113 are provided scattered in an island-like pattern. The flat recesses 113 are formed alternately at 90° angles in the vertical and horizontal directions of the page. In the uneven region AS shown in FIG. 7, a plurality of linear recesses 113 are provided in a mesh (lattice) pattern. The recesses that intersect with each other intersect with the direction D12 at an angle of approximately 60 to 70°.

[0069] 8 is a cross-sectional view schematically illustrating an electrolytic capacitor according to this embodiment. The electrolytic capacitor 100 includes a laminate of a plurality of capacitor elements 110, an anode lead terminal 120A joined to the anode lead portion 11a of the capacitor elements 110, a cathode lead terminal 120B joined to the cathode portion, and a sealing resin 130 that seals the capacitor elements 110.

[0070] The solid electrolyte layer 13 preferably contains a conductive polymer. Examples of the conductive polymer include π-conjugated polymers. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, and polyaniline. The conductive polymer may be used alone or in combination of two or more types, or may be a copolymer of two or more types of monomers. The weight-average molecular weight of the conductive polymer is, for example, 1,000 to 100,000.

[0071] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene), etc.

[0072] The conductive polymer may be doped with a dopant. The solid electrolyte layer 13 may contain a dopant together with the conductive polymer. Examples of the dopant include polystyrene sulfonic acid.

[0073] A method for manufacturing an electrolytic capacitor includes, for example, a step of stacking capacitor elements as necessary and electrically connecting the lead terminals, and a step of covering the capacitor elements and a portion of the lead terminals with an exterior body. An example will be described below, but the method for manufacturing an electrolytic capacitor is not limited to the following example.

[0074] The capacitor element includes, for example, the steps of: (a-1) preparing a raw foil (plain foil); (a-2) roughening the surface of the raw foil to form a porous portion and thereby forming an electrode foil; (a-3) forming a dielectric layer in the porous portion; (a-4) cutting an anode body from the electrode foil having the dielectric layer; and (a-5) forming a cathode portion in a first portion of the anode body.

[0075] The raw foil is a metal foil containing a valve metal and does not have a porous portion. The surface of the raw foil is roughened to form a porous portion, thereby obtaining an electrode foil. When the surface of the raw foil is etched (e.g., electrolytically etched), an etched foil is obtained.

[0076] The dielectric layer is formed by anodizing the electrode foil (etching foil). The anodization can be performed by a known chemical conversion treatment. The chemical conversion treatment can be performed by immersing the electrode foil in a chemical conversion solution and applying a voltage between the electrode foil as an anode and a counter electrode, a cathode. For example, an aqueous phosphoric acid solution can be used as the chemical conversion solution. The dielectric layer can also be formed by other methods (for example, atomic layer deposition (ALD)).

[0077] The electrode foil having the dielectric layer is usually in the form of a wide, simple strip from which the anode body can be cut out, and the capacitor element is cut out from such an electrode foil by processing such as slitting or punching.

[0078] The anode body has a first portion (R1) which is a cathode forming portion, a second portion (R2) which includes an anode lead portion, and a separation portion (R3) between the first portion (R1) and the second portion (R2).

[0079] Here, a concave-convex region is formed at least in the separated portion (R3) at some timing. For example, a concave-convex region may be formed at a predetermined location on a wide, simple, strip-shaped electrode foil before the anode body is cut out. Alternatively, a concave-convex region may be formed at a predetermined location on the anode body after it has been cut out.

[0080] The uneven region may be formed by pressing a jig having a plurality of protrusions against the electrode foil or the anode body. Alternatively, the uneven region may be formed by pressing the electrode foil or the anode body with a pair of rollers having a plurality of protrusions. The uneven region may also be formed by laser processing, blast processing, etching, or the like.

[0081] Next, a cathode portion is formed on the first portion of the anode body. Before the step of forming the cathode portion, a step of applying an insulating resin to the separated portion of the anode body may be included.

[0082] The insulating resin can be applied by a known method, such as a coating method or a dispensing method using various coaters or dispensers, immersion, transfer (roller transfer, etc.), etc. As the insulating resin, insulating tape or resist tape may be attached to the separated portion.

[0083] The step of forming the cathode portion includes, for example, a step of forming a solid electrolyte layer so as to cover at least a portion of the dielectric layer, and a step of forming a cathode extraction layer on the surface of the solid electrolyte layer.

[0084] The solid electrolyte layer may be formed, for example, by using a treatment liquid containing a precursor of a conductive polymer and polymerizing the precursor on the dielectric layer (so-called "in-situ polymerization"). The polymerization may be performed by either chemical polymerization or electrolytic polymerization. Alternatively, the solid electrolyte layer may be formed by applying a dispersion or solution containing the conductive polymer to the dielectric layer and then drying it.

[0085] The cathode extraction layer is formed, for example, by a process including a step of forming a carbon layer containing conductive carbon and a step of forming a metal paste layer containing metal powder.

[0086] The carbon layer can be formed by immersing the anode body on which the solid electrolyte layer has been formed in a dispersion liquid containing conductive carbon, or by applying a paste containing conductive carbon to the surface of the solid electrolyte layer.

[0087] The metal paste layer can be formed by laminating a paste composition containing metal powder, such as silver particles and a binder resin, on the surface of the carbon layer.

[0088] A capacitor element is obtained through the above process.

[0089] (b) Lead Terminal Connection Step If necessary, multiple capacitor elements are stacked to form a laminate, and each anode lead portion is electrically connected to an anode lead terminal. A cathode lead terminal is electrically connected to the cathode lead layer of the cathode portion. The anode lead portion and the anode lead terminal are electrically connected by, for example, welding. The cathode lead layer and the cathode lead terminal are electrically connected by, for example, a conductive adhesive.

[0090] (c) Encapsulation process: The capacitor element and a portion of each lead terminal are then encapsulated with encapsulating resin using a molding technique such as injection molding, insert molding, or compression molding. The encapsulating resin is the material of the exterior body.

[0091] <<Supplementary Notes>> The above embodiments disclose the following technologies. (Technology 1) A capacitor element comprising a metal foil containing a valve metal and having two main surfaces, wherein the metal foil has a first portion that is a cathode formation portion, a second portion that includes an anode lead portion, and a separation portion between the first portion and the second portion, wherein the first portion, the separation portion, and the second portion each have a porous portion having the main surface and a core portion continuous with the porous portion, wherein the metal foil has a textured region having a plurality of recesses on the main surface, and at least a portion of the separation portion overlaps with the textured region. (Technology 2) The capacitor element according to Technology 1, wherein a width of the textured region in a direction from the first portion to the second portion is 10% or more of a length of the first portion in a direction from the first portion to the second portion. (Technology 3) A capacitor element according to Technology 1 or 2, wherein (A) the depth of the recess is 5% or more and 80% or less of the distance from the non-recessed surface where the recess is not formed to the core, or (B) the proportion of the projected area of ​​the recess in the uneven region is 3% or more and 65% or less. (Technology 4) A capacitor element according to any one of Technology 1 to 3, wherein the uneven region has the recesses scattered like a plurality of islands. (Technology 5) A capacitor element according to Technology 1, wherein the number density of the recesses is 4 / mm ２ Above, 1200 pieces / mm ２The capacitor element according to Technology 4, wherein the projection area of ​​each recess is 150 μm or less. ２ More than 13000μm ２or less. (Technology 7) A capacitor element according to any one of Techniques 4 to 6, wherein the ratio of the long side Lmax to the short side Lmin of the smallest rectangle enclosing the recess is 1.0 to 2.5. (Technology 8) A capacitor element according to Technique 7, wherein the short side is 15 μm or more and 110 μm or less. (Technology 9) A capacitor element according to Technique 7 or 8, wherein the shortest distance between the edges of the most adjacent recesses is 1 time or more and 10 times or less the short side. (Technology 10) A capacitor element according to any one of Techniques 1 to 3, wherein the concave-convex region has the recesses extending in a plurality of lines. (Technology 11) A capacitor element according to Technique 10, wherein the width of the recess is 15 μm or more and 110 μm or less. (Technology 12) A capacitor element according to Technique 10 or 11, wherein the ratio of the length of the recess to the width of the recess is 40 or more. (Technology 13) A capacitor element according to any one of Techniques 10 to 12, wherein the plurality of recesses are striped, and the shortest distance between edges of the recesses that are closest to each other in the width direction of the recesses is 10 μm or more and 300 μm or less, or the plurality of recesses are mesh-shaped, and the shortest distance between opposing sides of squares surrounded by the recesses is 10 μm or more and 300 μm or less. (Technology 14) A capacitor element according to any one of Techniques 10 to 13, wherein the extension directions of the plurality of recesses are each independently parallel, perpendicular, or oblique to the direction from the first portion to the second portion. (Technology 15) A capacitor element according to any one of Techniques 1 to 13, wherein the uneven region overlaps with at least a portion of the second portion in addition to the separated portion. (Technology 16) A capacitor element according to any one of Techniques 1 to 14, wherein the uneven region overlaps with at least a portion of the first portion in addition to the separated portion. (Technology 17) An electrolytic capacitor comprising: the capacitor element according to any one of Technologies 1 to 16, in which the porous portion of at least the first portion has a dielectric layer; and a cathode portion covering at least a portion of the dielectric layer, wherein the cathode portion includes a conductive polymer.

[0092] [Examples] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the examples.

[0093] Examples 1 to 15 (Preparation of Electrode Foil) A strip of Al foil (plain foil, thickness F: 120 μm) was etched as the raw foil. This resulted in porous portions with spongy etching pits on both main surfaces of the raw foil. The etched foil was then subjected to a chemical conversion treatment at 49 V to form a dielectric layer in the porous portion, thereby obtaining a chemically converted foil. In this manner, foils A1 to A15 were obtained.

[0094] (Formation of Concave and Convex Region) A predetermined concave and convex region was formed in the region (R3) corresponding to the separation portion of the chemical foil so as to satisfy the parameters shown in Table 1. The concave and convex region was formed by pressing the separation portion (R3) with a roller having predetermined convex portions. The linear pressure (kg / cm) applied at that time is shown in Table 1.

[0095] The island-like recesses A13 to A15 in Examples 13 to 15 are rectangular recesses arranged in a matrix as shown in FIG.

[0096] The ratio (H / T) of the depth H of each recess on both sides to the thickness T of the porous portion is shown in Table 1 in percentage (%).

[0097] Comparative Example 1 A foil B1 was produced in the same manner as in Example 1, except that no concave-convex region was formed in the region (R3) corresponding to the separated portion of the chemically formed foil.

[0098] [Evaluation 1] The foils obtained in the examples and comparative examples were evaluated as follows.

[0099] [Measurement of folding endurance] The folding endurance of the chemical foil in the D12 direction was measured. The measurement was performed in accordance with the test method for electrode foil for aluminum electrolytic capacitors of the Electronic Industry Standards of Japan (EIAJ RC-2364A). The dimensions of the test piece were 100 mm in the length direction and 10 mm in the width direction. The radius of curvature of the bent portion was set to 3.5 mm (R3.5).

[0100] The folding endurance was expressed as a relative value when the folding endurance of the foil B1 of Comparative Example 1 was set to 100. The larger the value, the better. The results are shown in Table 1.

[0101]

[0102] Foils A1 to A15 exhibited higher folding strength than foil B1.

[0103] Examples 16 to 30 Chemical foils were obtained by changing the chemical voltage of the etched foil as shown in Table 2. In addition, a predetermined uneven area was formed so as to satisfy the parameters shown in Table 2. The linear pressure (kg / cm) and H / T ratio at that time are also shown in Table 2.

[0104] Comparative Examples 2 to 6 Foils B2, 3, 4, 5 and 6 were produced in the same manner as in Examples 16, 19, 22, 25 and 28, except that no textured region was formed in the region (R3) corresponding to the separated portion of the chemically formed foil.

[0105] [Evaluation 2] [Measurement of folding endurance] The foils of the examples and comparative examples were evaluated in the same manner as above. The results are shown in Table 2.

[0106] The folding strengths of Examples 16 to 18 were expressed as relative values ​​when the folding strength of Foil B2 of Comparative Example 2 was set to 100. The folding strengths of Examples 19 to 21 were expressed as relative values ​​when the folding strength of Foil B3 of Comparative Example 3 was set to 100. The folding strengths of Examples 22 to 24 were expressed as relative values ​​when the folding strength of Foil B4 of Comparative Example 4 was set to 100. The folding strengths of Examples 25 to 27 were expressed as relative values ​​when the folding strength of Foil B5 of Comparative Example 5 was set to 100. The folding strengths of Examples 28 to 30 were expressed as relative values ​​when the folding strength of Foil B6 of Comparative Example 6 was set to 100.

[0107] The larger the value, the better. The results are shown in Table 2.

[0108]

[0109] The foils A16 to A30 had higher folding strength than the foils B2 to B6, respectively.

[0110] Examples 31 to 33 The chemical conversion voltage of the etched foil was changed to 5 V, and predetermined concave-convex regions were formed so as to satisfy the parameters shown in Table 3. Table 3 also shows the linear pressure (kg / cm) and H / T ratio when forming the concave-convex regions.

[0111] The island-like recesses A31 to A33 of Examples 31 to 33 are flat recesses arranged in a matrix, with the directions alternately shifted by 90° as shown in Fig. 6. Fig. 9 shows an SEM photograph of the top surface of the concave-convex region, and Fig. 10 shows an SEM photograph of a cross section of the concave-convex region.

[0112] Comparative Example 7 Foil B7 was produced in the same manner as in Example 31, except that no concave-convex region was formed in the region (R3) corresponding to the separated portion of the chemically formed foil.

[0113] [Evaluation 3] [Measurement of Tensile Strength] The tensile strength in the D12 direction was measured for the foils of the Examples and Comparative Examples. The measurement was performed in accordance with the test method for electrode foils for aluminum electrolytic capacitors of the Electronic Industry Standards of Japan (EIAJ RC-2364A). The dimensions of the test specimen were 65 mm in the length direction and 10 mm in the width direction. The results are shown in Table 3.

[0114] [Measurement of folding endurance] The foils of the examples and comparative examples were evaluated in the same manner as above. The results are shown in Table 3.

[0115] The tensile strength and folding endurance of Examples 31 to 33 were expressed as relative values ​​when the tensile strength and folding endurance of Foil B7 of Comparative Example 7 were set at 100.

[0116]

[0117] Each of the foils A31 to A33 had a higher tensile strength and folding endurance than the foil B7.

[0118] The capacitor element according to the present disclosure is suitable for use in electrolytic capacitors that require high reliability.

[0119] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0120] REFERENCE SIGNS LIST 100 Electrolytic capacitor 110 Capacitor element 11 Anode body 111 Core portion 112 Porous portion 134 Cathode portion 12 Dielectric layer 13 Solid electrolyte layer 14 Cathode extraction layer 15 Insulating resin 120A: Anode lead terminal 120B: Cathode lead terminal 130: Sealing resin 134: Cathode portion

Claims

1. A capacitor element comprising a metal foil containing a valve metal and having two main surfaces, wherein the metal foil has a first portion which is a cathode forming portion, a second portion which includes an anode lead portion, and a separation portion between the first portion and the second portion, wherein the first portion, the separation portion, and the second portion each have a porous portion having the main surface and a core portion continuous with the porous portion, wherein the metal foil has an uneven region having a plurality of recesses on the main surface, and at least a portion of the separation portion overlaps with the uneven region.

2. A capacitor element as described in claim 1, wherein the width of the uneven area in the direction from the first portion to the second portion is 10% or more of the length of the first portion in the direction from the first portion to the second portion.

3. A capacitor element as described in claim 1, wherein (A) the depth of the recess is 5% or more and 80% or less of the distance from the non-recessed surface where the recess is not formed to the core, or (B) the projected area ratio of the recess in the uneven region is 3% or more and 65% or less.

4. The capacitor element according to claim 1, wherein the concave and convex region has the concave portions scattered in a plurality of island shapes.

5. The number density of the recesses is 4 / mm ２ Above, 1200 pieces / mm ２ 5. The capacitor element of claim 4, wherein:

6. The projected area of each recess is 150 μm ２ More than 13000μm ２ 5. The capacitor element of claim 4, wherein:

7. The capacitor element according to claim 4, wherein the ratio of the long side Lmax to the short side Lmin of the smallest rectangle enclosing the recess is 1.0 to 2.

5.

8. The capacitor element according to claim 7, wherein the dimension of the short side Lmin is 15 μm or more and 110 μm or less.

9. The capacitor element according to claim 7, wherein the shortest distance between the edges of the recesses that are closest to each other is not less than 1 time and not more than 10 times the length of the short side.

10. The capacitor element according to claim 1, wherein the uneven area has the recesses extending in a plurality of lines.

11. The capacitor element according to claim 10, wherein the width of the recess is 15 μm or more and 110 μm or less.

12. The capacitor element according to claim 10, wherein the ratio of the length of the recess to the width of the recess is 40 or greater.

13. A capacitor element according to claim 10, wherein the plurality of recesses are in a stripe pattern, and the shortest distance between the edges of the recesses that are closest to each other in the width direction of the recesses is 10 μm or more and 300 μm or less, or the plurality of recesses are in a mesh pattern, and the shortest distance between opposing sides of squares surrounded by the recesses is 10 μm or more and 300 μm or less.

14. The capacitor element according to claim 10, wherein the extending directions of the plurality of recesses are each independently parallel, perpendicular, or oblique to the direction from the first portion toward the second portion.

15. The capacitor element of claim 1, wherein the textured region overlaps at least a portion of the second portion in addition to the separating portion.

16. An electrolytic capacitor comprising: the capacitor element according to claim 1, wherein the porous portion of at least the first portion has a dielectric layer; and a cathode portion covering at least a portion of the dielectric layer, wherein the cathode portion includes a conductive polymer.

Images