Electrolytic capacitor

Abstract

The invention provides an electrolytic capacitor. This electrolytic capacitor is provided with: a capacitor element having an anode part and a cathode part; an anode lead frame electrically connected to the anode portion; a cathode lead frame electrically connected to the cathode part; and an exterior body covering the capacitor element. The anode lead frame has an anode embedding portion embedded in the exterior body. The cathode lead frame has a cathode embedding part embedded in the exterior body. The first surface of at least one of the anode embedding part and the cathode embedding part is provided with a plurality of concave parts. A convex portion is provided on an outer edge portion of each of the plurality of recesses.

Description

Technical Field

[0001] The present invention relates to electrolytic capacitors. Background Art

[0002] Conventionally, an electrolytic capacitor is known as a capacitor using a metal oxide film as a dielectric (for example, Patent Document 1). The electrolytic capacitor of Patent Document 1 includes a capacitor element having an anode portion and a cathode portion, an anode lead frame electrically connected to the anode portion, a cathode lead frame electrically connected to the cathode portion, and an outer casing covering the capacitor element, wherein the anode lead frame has a first embedded portion embedded in the outer casing, and the cathode lead frame has a second embedded portion embedded in the outer casing, and a plurality of recesses are formed on a surface of at least one of the first embedded portion and the second embedded portion.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2023 / 008185 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] When using an electrolytic capacitor, oxygen and moisture sometimes reach the capacitor element through the interface between the outer casing and each lead frame. If oxygen and moisture reach the capacitor element, the electrolyte will deteriorate and the equivalent series resistance (ESR) of the electrolytic capacitor will increase. Under such circumstances, one of the purposes of the present invention is to suppress the increase of ESR.

[0008] Solutions for solving problems

[0009] A technical solution of the present invention relates to an electrolytic capacitor. The electrolytic capacitor comprises: a capacitor element having an anode portion and a cathode portion; an anode lead frame electrically connected to the anode portion; a cathode lead frame electrically connected to the cathode portion; and an outer casing covering the capacitor element. The anode lead frame has an anode embedded portion buried in the outer casing, and the cathode lead frame has a cathode embedded portion buried in the outer casing. The first surface of at least one of the anode embedded portion and the cathode embedded portion has a plurality of recesses. A convex portion is provided on the outer edge of each of the plurality of recesses.

[0010] Effects of the Invention

[0011] According to the present invention, it is possible to suppress an increase in equivalent series resistance (ESR). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view schematically showing an example of the electrolytic capacitor of the present invention.

[0013] Figure 2 It is a plan view schematically showing an example of the arrangement of the concave portions and the convex portions of each lead frame.

[0014] Figure 3 is a schematic representation of the Figure 2 A cross-sectional view of a cross section taken along line III-III.

[0015] Description of Reference Numerals

[0016] 10: electrolytic capacitor; 20: capacitor element; 21: anode portion; 21a: anode body; 21b: anode wire; 22: dielectric layer; 23: cathode portion; 23a: electrolyte layer; 23b: cathode layer; 30: anode lead frame; 31: anode buried portion; 32: anode exposed portion; 32a: anode terminal portion; 40: cathode lead frame; 41: cathode buried portion; 42: cathode exposed portion; 42a: cathode terminal portion; 43: conductive adhesive layer; 51: recessed portion; 52: protruding portion; 60: outer casing; D: depth of recessed portion; H: height of protruding portion. DETAILED DESCRIPTION

[0017] The following is an example of an embodiment of the electrolytic capacitor of the present invention. However, the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes illustrated, but other numerical values ​​and materials can also be applied as long as the effects of the present invention can be obtained.

[0018] The electrolytic capacitor of the present invention includes a capacitor element, an anode lead frame, a cathode lead frame, and an outer package. In the following description, the anode lead frame and the cathode lead frame may not be distinguished and may be described as lead frames.

[0019] The capacitor element has an anode portion and a cathode portion. The anode portion may be composed of an anode body, or may include an anode body and an anode wire. The anode body may be a porous sintered body or a metal foil with a porous surface. A dielectric layer may be formed on the surface of the anode body. The cathode portion may include an electrolyte layer (solid electrolyte layer) and a cathode layer. The electrolyte layer is arranged between the dielectric layer and the cathode layer formed on the surface of the anode body. These constituent elements are not particularly limited, and constituent elements used in known electrolytic capacitors may also be applied. Examples of these constituent elements are described below.

[0020] The anode body can also be formed by sintering particles of the material. Examples of the particles of the material include particles of valve metals, particles of alloys containing valve metals, and particles of compounds containing valve metals. These particles can be used alone or in a mixture of two or more. Alternatively, a foil of a valve metal can be used as the anode body. Examples of valve metals include titanium (Ti), tantalum (Ta), niobium (Nb), aluminum (Al), etc. A preferred example of the anode body as a sintered body is a sintered body of tantalum. A preferred example of the anode body as a metal foil is aluminum foil.

[0021] The dielectric layer formed on the surface of the anode body is not particularly limited and can be formed by a known method. For example, the dielectric layer can be formed by anodizing the surface of the anode body.

[0022] Anode wires made of metal can be used. Examples of materials for the anode wires include the above-mentioned valve metals, copper, aluminum alloys, etc. A portion of the anode wire is buried in the anode body, and the remaining portion protrudes from the end surface of the anode body.

[0023] The electrolyte layer (solid electrolyte layer) is not particularly limited, and a solid electrolyte layer used in a known electrolytic capacitor can be applied. The electrolyte layer is configured to cover at least a portion of the dielectric layer. The electrolyte layer can also be formed using a manganese compound or a conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and derivatives thereof. They can be used alone or in combination. In addition, the conductive polymer can also be a copolymer of two or more monomers. In addition, a derivative of a conductive polymer refers to a polymer having a conductive polymer as a basic skeleton. For example, examples of derivatives of polythiophene include poly(3,4-ethylenedioxythiophene) and the like.

[0024] Preferably, a dopant is added to the conductive polymer. The dopant can be selected according to the conductive polymer, and a known dopant (e.g., a polymer dopant) can also be used. Examples of dopants include naphthalenesulfonic acid, p-toluenesulfonic acid, polystyrenesulfonic acid, and salts thereof. An example of an electrolyte layer is formed using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonic acid (PSS).

[0025] The electrolyte layer containing the conductive polymer can also be formed by superimposing the monomer as a raw material on the dielectric layer. Alternatively, the electrolyte layer containing the conductive polymer can be formed by placing a liquid containing the conductive polymer (and a dopant as required) on the dielectric layer and then drying it.

[0026] The cathode layer is a conductive layer, and is arranged to cover at least a portion of the electrolyte layer. The cathode layer includes a conductive cathode lead layer. The cathode layer may also include another conductive layer (e.g., a carbon layer) arranged between the electrolyte layer and the cathode lead layer. For example, the cathode layer may also include a carbon layer formed on the electrolyte layer and a cathode lead layer formed on the carbon layer. The cathode lead layer may be formed of a metal paste (e.g., a silver paste) containing metal particles (e.g., silver particles) and a resin, or may be formed of a known silver paste. The carbon layer is a layer containing carbon, and may be formed of a conductive carbon material such as graphite and a resin.

[0027] The anode lead frame is electrically connected to the anode portion. The anode lead frame may have a substrate formed of a metal (copper, copper alloy, etc.). The thickness of the substrate is not particularly limited and may be in the range of 25 μm to 200 μm (e.g., 25 μm to 100 μm). The anode lead frame may also include a substrate and a plating layer formed on the substrate.

[0028] The plating layer is formed by metals (including alloys) such as nickel, gold, palladium, tin, and copper, and may include a nickel layer, a gold layer, a palladium layer, a tin layer, a copper layer, and the like. For example, the plating layer may be stacked in the order of a nickel layer, a gold layer, and a palladium layer on the substrate. The plating layer can be formed by a known plating method. The plating layer may be formed before forming the concave and convex portions described later, or may be formed after forming the concave and convex portions.

[0029] The cathode lead frame is electrically connected to the cathode portion. It may have a substrate formed of a metal (copper, copper alloy, etc.). The thickness of the substrate is not particularly limited and may be in the range of 25 μm to 200 μm (e.g., 25 μm to 100 μm). The cathode lead frame may also include a substrate and a plating layer formed on the substrate. The plating layer of the cathode lead frame may be the same as the above-mentioned plating layer in association with the anode lead frame.

[0030] The outer casing covers the capacitor element. The outer casing can be arranged around the capacitor element in a manner that the capacitor element is not exposed to the surface of the electrolytic capacitor. Furthermore, the outer casing can be arranged in a manner that covers the anode buried portion and the cathode buried portion described later. The outer casing usually contains a resin (insulating resin) and an insulating filler. In addition, in the following description, the anode buried portion and the cathode buried portion are sometimes not distinguished, and they are recorded as buried portions.

[0031] The outer casing can be formed of a resin composition comprising an insulating resin and an insulating filler (e.g., an inorganic filler). The resin composition may also contain a curing agent, a polymerization initiator, and / or a catalyst in addition to the insulating resin and the insulating filler. Examples of insulating resins include insulating thermosetting resins and insulating thermoplastic resins. Specifically, examples of insulating resins include epoxy resins, phenolic resins, urea-formaldehyde resins, polyimides, polyamide-imides, polyurethanes, diallyl phthalate, unsaturated polyesters, polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), and the like.

[0032] Examples of insulating fillers include insulating particles, insulating fibers, etc. As insulating materials constituting the insulating fillers, for example, insulating compounds (oxides, etc.) such as silicon dioxide and aluminum oxide, glass, mineral materials (talc, mica, clay, etc.), etc. can be listed. The insulating fillers contained in the outer casing can be one type or two or more types.

[0033] The anode lead frame has an anode embedded portion embedded in the outer casing. The anode embedded portion of the anode lead frame can be electrically connected to the anode portion of the capacitor element by welding, for example. The anode lead frame can also have an anode exposed portion exposed from the outer casing. At least a portion of the anode exposed portion can function as an anode external terminal.

[0034] The cathode lead frame has a cathode embedded portion embedded in the outer body. The cathode embedded portion of the cathode lead frame can be electrically connected to the cathode portion of the capacitor element via a conductive adhesive layer, for example. The conductive adhesive layer can contain conductive particles (for example, metal particles such as silver particles). The conductive adhesive layer can be formed using a metal paste (for example, a silver paste) containing metal particles and a resin. The cathode lead frame can also have a cathode exposed portion exposed from the outer body. At least a portion of the cathode exposed portion can function as a cathode external terminal.

[0035] The surface (first surface) of at least one of the anode buried portion and the cathode buried portion has a plurality of recesses. A convex portion is provided at the outer edge of each of the plurality of recesses. The surface of at least one of the anode buried portion and the cathode buried portion may be the main surface of at least one of the anode buried portion and the cathode buried portion. The recesses and convex portions may be formed by irradiating each buried portion with a laser. The recesses and convex portions may be formed on the two main surfaces of each buried portion, or may be formed on only one main surface. By providing the recesses and convex portions, the surface area of ​​the anode buried portion and / or the cathode buried portion is increased, and the adhesion is improved by the anchoring effect between the anode buried portion and the outer body and / or the anchoring effect between the cathode buried portion and the outer body. Therefore, oxygen and moisture are not easy to reach the capacitor element via the interface between each lead frame and the outer body, which can suppress the degradation of the electrolyte layer and the increase of the ESR of the electrolytic capacitor.

[0036] The convex portion may be formed in an annular shape along the outer edge of the concave portion. By providing such an annular convex portion, the anchoring effect can be improved by increasing the surface area of ​​the anode buried portion and / or the cathode buried portion, thereby further suppressing the increase in the ESR of the electrolytic capacitor. In addition, the convex portion may be formed intermittently along the outer periphery of the concave portion.

[0037] Alternatively, in the concave portions (the first concave portion and the second concave portion) adjacent to each other along the surface of the anode buried portion and / or the cathode buried portion where the concave portion and the convex portion are formed, the convex portion located at the outer edge of the first concave portion and the convex portion located at the outer edge of the second concave portion are separated from each other. In this structure, the surface exposed area of ​​the anode buried portion and / or the cathode buried portion is between the adjacent convex portions. Compared with the case where the adjacent convex portions are connected to each other, the surface area of ​​each buried portion can be increased, and the reduction of the ESR of the electrolytic capacitor can be further suppressed.

[0038] The depth of the recess may be greater than 10 μm and less than 55 μm. By setting the depth of the recess within this range, the adhesion between each lead frame and the outer casing or between the lead frame and the adhesive can be improved. In addition, the depth of the recess refers to the distance in the depth direction between the surface on which the recess is formed and the deepest part of the recess. In addition, the depth of the recess can be measured by measuring the depth of 10 randomly selected recesses and finding the average value of the measured values ​​as the depth of the recess. The depth of the recess can also be measured in a cross section parallel to the thickness direction of each lead frame.

[0039] The height of the convex portion can be greater than 0.1 μm and less than 50 μm. By setting the height of the convex portion within this range, the adhesion between each lead frame and the outer casing or between the lead frame and the adhesive can be improved. In addition, the height of the convex portion refers to the distance in the height direction between the surface on which the convex portion is formed and the top of the convex portion. In addition, for the height of the convex portion, the height of 10 convex portions selected at random can be measured, and the average value of the measured values ​​can be obtained as the height of the convex portion. The 10 convex portions selected at random can correspond to different concave portions, respectively. The height of the convex portion can also be measured in a cross section parallel to the thickness direction of each lead frame.

[0040] The ratio of the depth of the recess to the height of the projection may be 0.2 to 550. By setting the ratio of the depth of the recess to the height of the projection within this range, the adhesion between each lead frame and the exterior body or the adhesive can be improved.

[0041] When observed from a direction perpendicular to the surface of the anode buried portion and / or the cathode buried portion, the ratio of the total area of ​​the plurality of recesses to the surface area of ​​each buried portion per unit area can be greater than 5% and less than 25%. By setting the ratio of the total area of ​​the plurality of recesses to the surface area of ​​each buried portion within this range, the adhesion between each lead frame and the outer body or between the lead frame and the adhesive can be improved. In addition, the total area of ​​the plurality of recesses per unit area can be calculated based on the load area ratio at the intersection between the load curve corresponding to the defined area of ​​the same measurement surface (in this example, the surface of the anode buried portion and / or the cathode buried portion) and the height of the lower part of the core. The total area of ​​the plurality of recesses per unit area can be calculated using a laser microscope (e.g., VK-X3000 manufactured by Keyence Corporation).

[0042] When observed from a direction perpendicular to the surface of the anode buried portion and / or the cathode buried portion, the ratio of the total area of ​​the plurality of protrusions to the surface area of ​​each buried portion per unit area can be greater than 5% and less than 30%. By setting the ratio of the total area of ​​the plurality of protrusions to the surface area of ​​each buried portion within this range, the adhesion between each lead frame and the outer body or between the lead frame and the adhesive can be improved. In addition, the total area of ​​the plurality of protrusions per unit area can be calculated based on the load area ratio at the intersection between the load curve corresponding to the defined area of ​​the same measurement surface (in this example, the surface of the anode buried portion and / or the cathode buried portion) and the height of the upper part of the core. The total area of ​​the plurality of protrusions per unit area can be calculated using a laser microscope (e.g., VK-X3000 manufactured by Keyence Corporation).

[0043] When viewed from a direction perpendicular to the surface of the anode embedded portion and / or the cathode embedded portion, the ratio of the total area of ​​the plurality of recesses to the total area of ​​the plurality of protrusions per unit area may be greater than 0.16 and less than 5. By setting the ratio of the total area of ​​the plurality of recesses to the total area of ​​the plurality of protrusions within this range, the adhesion between each lead frame and the outer casing or between the lead frame and the adhesive can be improved.

[0044] When observed from a direction perpendicular to the surface of the anode buried portion and / or the cathode buried portion, the average opening diameter of the recess may be greater than 5 μm and less than 200 μm. By setting the average diameter of the opening of the recess within this range, the adhesion between each lead frame and the outer body or between the lead frame and the adhesive can be improved. In addition, for the opening diameter of the recess, the equivalent circle diameter can be used. The equivalent circle diameter is obtained by the following method. First, the opening of the recess is photographed from above. Then, the area of ​​the opening is obtained by performing image processing on the obtained image. Then, the equivalent circle diameter is calculated based on the obtained area. By calculating the diameter (equivalent circle diameter) of the opening for 10 arbitrarily selected recesses, the average opening diameter is obtained by arithmetically averaging the obtained diameters.

[0045] As described above, according to the present invention, by forming the concave portion and the convex portion on the surface of the lead frame, it is possible to suppress an increase in the ESR of the electrolytic capacitor.

[0046] Hereinafter, an example of an electrolytic capacitor of the present invention will be described in detail with reference to the accompanying drawings. The constituent elements of the electrolytic capacitor of the example described below can apply the above-mentioned constituent elements. The constituent elements of the electrolytic capacitor of the example described below can be changed based on the above-mentioned description. In addition, the matters described below can also be applied to the above-mentioned embodiment. The constituent elements of the electrolytic capacitor of the example described below that are not necessary for the electrolytic capacitor of the present invention can also be omitted. In addition, the figures shown below are schematic figures and do not accurately reflect the shape and number of actual components.

[0047] like Figure 1 to Figure 3 As shown, electrolytic capacitor 10 of the present embodiment includes capacitor element 20 , anode lead frame 30 , cathode lead frame 40 , and outer casing 60 .

[0048] The capacitor element 20 has an anode portion 21, a dielectric layer 22, and a cathode portion 23. The anode portion 21 includes an anode body 21a and an anode wire 21b. The anode body 21a is a porous sintered body in a rectangular parallelepiped shape, and a dielectric layer 22 is formed on the surface of the porous sintered body (including the inner surface of the pores in the porous sintered body).

[0049] A portion of the anode wire 21b extends from one end surface of the anode body 21a toward one end surface of the electrolytic capacitor 10 ( Figure 1 The other part of the anode wire 21b is buried in the anode body 21a. The anode wire 21b extends along the long side direction of the anode body 21a ( Figure 1 The cathode portion 23 includes an electrolyte layer 23a arranged to cover at least a portion of the dielectric layer 22 and a cathode layer 23b formed to cover at least a portion of the electrolyte layer 23a.

[0050] The anode lead frame 30 is electrically connected to the anode portion 21. The anode lead frame 30 includes an anode embedded portion 31 embedded in the outer casing 60 and an anode exposed portion 32 exposed from the outer casing 60. The anode embedded portion 31 is electrically connected to the anode portion 21 by welding. The anode exposed portion 32 includes an anode terminal portion 32a that functions as a terminal on the anode side.

[0051] The cathode lead frame 40 is electrically connected to the cathode portion 23. The cathode lead frame 40 includes a cathode embedded portion 41 embedded in the outer casing 60 and a cathode exposed portion 42 exposed from the outer casing 60. The cathode embedded portion 41 is electrically connected to the cathode portion 23 via a conductive adhesive layer 43. The cathode exposed portion 42 includes a cathode terminal portion 42a functioning as a terminal on the cathode side.

[0052] Outer casing 60 covers capacitor element 20, anode embedded portion 31, and cathode embedded portion 41. Outer casing 60 is disposed around capacitor element 20 so that capacitor element 20 is not exposed to the surface of electrolytic capacitor 10. Outer casing 60 contains insulating resin and insulating filler.

[0053] like Figure 2 and Figure 3 As shown, each of the two surfaces (or two main surfaces) of the anode lead frame 30 and the cathode lead frame 40 has a plurality of recesses 51. A convex portion 52 is provided at the outer edge of the recess 51. The convex portion 52 is preferably formed in a ring shape along the outer edge of the recess 51. Among the plurality of recesses 51, in two recesses 51 (the first recess and the second recess) adjacent to each other along the surface, the convex portion 52 located at the outer edge of the first recess 51 and the convex portion 52 located at the outer edge of the second recess 51 are preferably separated from each other.

[0054] The depth D of the concave portion 51 is preferably 2 μm or more and 55 μm or less, more preferably 10 μm or more and 30 μm or less, and further preferably 20 μm or more and 30 μm or less. The height H of the convex portion 52 is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.5 μm or more and 1.0 μm or less. The ratio of the depth D of the concave portion 51 to the height H of the convex portion 52 is preferably 0.2 or more and 550 or less, more preferably 10 times or more and 300 times or less, and further preferably 20 times or more and 150 times or less.

[0055] When observed from a direction perpendicular to the surface of the anode buried portion 31 and / or the cathode buried portion 41, the ratio of the total area of ​​the plurality of recesses 51 to the surface area of ​​each buried portion 31, 41 per unit area is preferably 5% or more and 25% or less, and more preferably 15% or more and 25% or less. In addition, when observed from a direction perpendicular to the surface of the anode buried portion 31 and / or the cathode buried portion 41, the ratio of the total area of ​​the plurality of protrusions 52 to the surface area of ​​each buried portion 31, 41 per unit area is preferably 5% or more and 30% or less, and more preferably 5% or more and 15% or less. In addition, when observed from a direction perpendicular to the surface of the anode buried portion 31 and / or the cathode buried portion 41, the ratio of the total area of ​​the plurality of recesses 51 to the total area of ​​the plurality of protrusions 52 per unit area is preferably 0.16 or more and 5 or less, and more preferably 1 or more and 3 or less. Furthermore, when viewed in a direction perpendicular to the surface of the anode embedded portion 31 and / or cathode embedded portion 41 , the average opening diameter of the recessed portion 51 is preferably 5 μm or more and 200 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0056] Postscript

[0057] The following technology is disclosed through the description of the above embodiments.

[0058] (Technology 1)

[0059] An electrolytic capacitor, wherein

[0060] The electrolytic capacitor has:

[0061] a capacitor element having an anode portion and a cathode portion;

[0062] an anode lead frame electrically connected to the anode portion;

[0063] a cathode lead frame electrically connected to the cathode portion; and

[0064] an outer casing covering the capacitor element,

[0065] The anode lead frame has an anode embedding portion embedded in the outer casing.

[0066] The cathode lead frame has a cathode embedding portion embedded in the outer casing.

[0067] The first surface of at least one of the anode buried portion and the cathode buried portion has a plurality of recessed portions,

[0068] A convex portion is provided on an outer edge portion of each of the plurality of concave portions.

[0069] (Technique 2)

[0070] The electrolytic capacitor according to technology 1, wherein the convex portion is formed in a ring shape along the outer edge of the concave portion.

[0071] (Technique 3)

[0072] The electrolytic capacitor according to technology 1 or 2, wherein, in the first recess and the second recess that are adjacent to each other along the first surface among the plurality of recesses, the convex portion located at the outer edge of the first recess and the convex portion located at the outer edge of the second recess are separated from each other.

[0073] (Technique 4)

[0074] The electrolytic capacitor according to any one of techniques 1 to 3, wherein the depth of each of the plurality of recesses is 10 μm or more and 55 μm or less.

[0075] (Technique 5)

[0076] The electrolytic capacitor according to any one of techniques 1 to 4, wherein the height of the projection is 0.1 μm or more and 50 μm or less.

[0077] (Technique 6)

[0078] The electrolytic capacitor according to any one of techniques 1 to 5, wherein a ratio of the depth of each of the plurality of recesses to the height of the protrusion is 0.2 or more and 550 or less.

[0079] (Technique 7)

[0080] The electrolytic capacitor according to any one of techniques 1 to 6, wherein, when viewed from a direction perpendicular to the first surface, a ratio of a total area of ​​the plurality of recesses to an area of ​​the first surface per unit area is 5% or more and 25% or less.

[0081] (Technology 8)

[0082] The electrolytic capacitor according to any one of techniques 1 to 7, wherein, when viewed from a direction perpendicular to the first surface, a ratio of a total area of ​​a plurality of projections including the projection to an area of ​​the first surface per unit area is 5% to 30%.

[0083] (Technique 9)

[0084] The electrolytic capacitor according to any one of techniques 1 to 8, wherein, when viewed from a direction perpendicular to the first surface, a ratio of a total area of ​​the plurality of recesses to a total area of ​​a plurality of protrusions including the protrusions per unit area is 0.16 to 5.

[0085] (Technology 10)

[0086] The electrolytic capacitor according to any one of techniques 1 to 9, wherein an average opening diameter of the plurality of recesses is 5 μm or more and 200 μm or less when viewed from a direction perpendicular to the first surface.

[0087] [Example]

[0088] For the electrolytic capacitors of Examples 1 to 3 and Comparative Examples 1 and 2 shown below, the rate of change of ESR before and after the thermal cycle test was measured. As a thermal cycle test, the following test was conducted: the electrolytic capacitors were alternately placed in an atmosphere of -55°C and an atmosphere of 125°C for 15 minutes each, and this operation was repeated approximately 1000 times. The rate of change of ESR before and after the thermal cycle test indicates how many times the ESR after the thermal cycle test is the ESR before the thermal cycle test. For example, if the rate of change is 2, it means that the ESR increases by 2 times before and after the thermal cycle test.

[0089] 《Example 1》

[0090] An electrolytic capacitor corresponding to the above-mentioned embodiment was prepared. The concave portion and the convex portion were formed by irradiating the surface of each lead frame with a laser. The depth of the concave portion was 27.5 μm, and the height of the convex portion was 0.69 μm. Per unit area, the ratio of the total area of ​​the plurality of concave portions to the surface area of ​​each lead frame was 20.7%, and the ratio of the total area of ​​the plurality of convex portions to the surface area of ​​each lead frame was 9.9%. The rate of change of ESR before and after the thermal cycle test was 1.2.

[0091] 《Example 2》

[0092] An electrolytic capacitor corresponding to the above-mentioned embodiment was prepared. The concave portion and the convex portion were formed by irradiating the surface of each lead frame with a laser. The depth of the concave portion was 40.9 μm, and the height of the convex portion was 5.45 μm. Per unit area, the ratio of the total area of ​​the plurality of concave portions to the surface area of ​​each lead frame was 7.6%, and the ratio of the total area of ​​the plurality of convex portions to the surface area of ​​each lead frame was 25.3%. The rate of change of ESR before and after the thermal cycle test was 1.5.

[0093] 《Example 3》

[0094] An electrolytic capacitor corresponding to the above-mentioned embodiment was prepared. The concave portion and the convex portion were formed by irradiating the surface of each lead frame with a laser. The depth of the concave portion was 28.9 μm, and the height of the convex portion was 2.66 μm. Per unit area, the ratio of the total area of ​​the plurality of concave portions to the surface area of ​​each lead frame was 15.6%, and the ratio of the total area of ​​the plurality of convex portions to the surface area of ​​each lead frame was 16.7%. The rate of change of ESR before and after the thermal cycle test was 1.3.

[0095] Comparative Example 1

[0096] An electrolytic capacitor having a concave portion but no convex portion in each lead frame was prepared. The concave portion was formed by cutting the surface of each lead frame. The depth of the concave portion was 27.5 μm. The ratio of the total area of ​​the plurality of concave portions to the surface area of ​​each lead frame per unit area was 20.7%. The rate of change of ESR before and after the thermal cycle test was 5.

[0097] 《Comparative Example 2》

[0098] An electrolytic capacitor having no concave or convex portion in each lead frame was prepared. The rate of change in ESR before and after the heat cycle test was 10.

[0099] As described above, the electrolytic capacitors of Examples 1 to 3 have lower rates of change in ESR before and after the heat cycle test than the electrolytic capacitors of Comparative Examples 1 and 2. Therefore, it can be said that the advantages of each Example are demonstrated.

[0100] Industrial Applicability

[0101] The present invention can be used for electrolytic capacitors.

Claims

1. An electrolytic capacitor, wherein: The electrolytic capacitor has: a capacitor element having an anode portion and a cathode portion; an anode lead frame electrically connected to the anode portion; a cathode lead frame electrically connected to the cathode portion; as well as an outer casing covering the capacitor element, The anode lead frame has an anode embedding portion embedded in the outer casing. The cathode lead frame has a cathode embedding portion embedded in the outer casing. The first surface of at least one of the anode buried portion and the cathode buried portion has a plurality of recessed portions, A convex portion is provided on an outer edge portion of each of the plurality of concave portions.

2. The electrolytic capacitor according to claim 1, wherein: The convex portion is formed in an annular shape along the outer edge of the concave portion.

3. The electrolytic capacitor according to claim 1 or 2, wherein: In a first recess and a second recess that are adjacent to each other along the first surface among the plurality of recesses, the convex portion located at an outer edge of the first recess and the convex portion located at an outer edge of the second recess are separated from each other.

4. The electrolytic capacitor according to claim 1 or 2, wherein: The depth of each of the plurality of recesses is greater than or equal to 10 μm and less than or equal to 55 μm.

5. The electrolytic capacitor according to claim 1 or 2, wherein: The height of the convex portion is greater than or equal to 0.1 μm and less than or equal to 50 μm.

6. The electrolytic capacitor according to claim 1 or 2, wherein: A ratio of the depth of each of the plurality of recesses to the height of the protrusion is greater than or equal to 0.2 and less than or equal to 550.

7. The electrolytic capacitor according to claim 1 or 2, wherein: When viewed from a direction perpendicular to the first surface, a ratio of a total area of ​​the plurality of recesses to an area of ​​the first surface per unit area is 5% or more and 25% or less.

8. The electrolytic capacitor according to claim 1 or 2, wherein: When viewed in a direction perpendicular to the first surface, a ratio of a total area of ​​a plurality of convex portions including the convex portion to an area of ​​the first surface per unit area is 5% or more and 30% or less.

9. The electrolytic capacitor according to claim 1 or 2, wherein: When viewed from a direction perpendicular to the first surface, a ratio of a total area of ​​the plurality of recesses to a total area of ​​a plurality of protrusions including the protrusions per unit area is 0.16 or more and 5 or less.

10. The electrolytic capacitor according to claim 1 or 2, wherein: When viewed from a direction perpendicular to the first surface, an average opening diameter of the plurality of recesses is greater than or equal to 5 μm and less than or equal to 200 μm.

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