Electrolytic capacitor

Abstract

This electrolytic capacitor is provided with a laminated element. The laminated element has a plurality of anode foils (23), a plurality of cathode foils, and spacers interposed between the anode foils (23) and the cathode foils, each of the anode foils (23) and the cathode foils including a metal part (25) and an oxide film (26) formed on the surface of the metal part (25). Part of each of the anode foils (23) is a joint part (24a) that is joined to each other by joining the metal parts (25). The ratio of the bonding portion (24a) of the anode foil (23) to the oxide film (26) of the metal portion (25) is smaller than that of the remaining portion of the anode foil (23). As a result, ESR can be reduced.

Description

Technical Field

[0001] This invention relates to an electrolytic capacitor. Background Technology

[0002] Conventionally, there are known stacked electrolytic capacitors that have stacked elements consisting of multiple stacked electrode foils (e.g., Patent Document 1). The manufacturing method of the electrolytic capacitor in Patent Document 1 includes: a step of arranging metal foils for electrical connection in the stacked elements, a step of inserting a piercing needle through them, and a step of connecting each electrode foil to the lead frame by arranging a lead frame at the location of the through hole formed therein and performing resistance welding.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 5854510 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In recent years, there has been a desire to further reduce the equivalent series resistance (ESR) in multilayer electrolytic capacitors. Under these circumstances, one of the objectives of this invention is to reduce the ESR.

[0008] Methods for solving problems

[0009] One aspect of the present invention relates to an electrolytic capacitor. The electrolytic capacitor includes a stacked element having a plurality of anode foils, a plurality of cathode foils, each comprising a metal portion and an oxide film formed on the surface of the metal portion, and a spacer sandwiched between the anode foils and the cathode foils. A portion of each anode foil is a joint portion joined together by a bonding between the metal portions, and the ratio of the joint portion of the anode foil to the oxide film on the metal portion is smaller than that of the remaining portion of the anode foil.

[0010] Another aspect of the present invention relates to an electrolytic capacitor. The electrolytic capacitor includes an anode foil comprising a metal portion and an oxide film formed on the surface of the metal portion, and an anode lead connected to the anode foil. A portion of the anode foil is a joint portion joined to the anode lead via the metal portion. The ratio of the joint portion of the anode foil to the oxide film of the metal portion is smaller than that of the remaining portion of the anode foil.

[0011] Invention Effects

[0012] According to the present invention, ESR can be reduced.

[0013] The novel features of the invention are set forth in the appended scope of the claims, and the invention, in both its structure and content, should be more fully understood, together with other objects and features of this application, by referring to the following detailed description of the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view schematically illustrating an example of the configuration of the stacked elements of the present invention.

[0015] Figure 2 yes Figure 1 A top view of the stacked components.

[0016] Figure 3 It has Figure 2 A top view of an electrolytic capacitor with stacked components.

[0017] Figure 4 It is a schematic cross-sectional view of the first anode junction and its surrounding area, omitting the common anode lead.

[0018] Figure 5 This is an enlarged cross-sectional view schematically showing the first anode joint. Detailed Implementation

[0019] Embodiments of the electrolytic capacitor of the present invention are illustrated below. However, the present invention is not limited to the examples described below. In the following description, specific values ​​and materials are sometimes illustrated; however, other values ​​and materials may be applied as long as the effects of the present invention can be obtained.

[0020] An electrolytic capacitor (hereinafter also referred to as electrolytic capacitor A) according to one embodiment of the present invention comprises a laminate. The laminate has a plurality of anode foils, a plurality of cathode foils, and spacers. The plurality of anode foils and the plurality of cathode foils are alternately laminated with spacers sandwiched between the anode foils and the cathode foils. It should be noted that "electrolytic capacitor" may also be referred to as "solid electrolytic capacitor" or "solid-liquid hybrid electrolytic capacitor", and "capacitor" may also be referred to as "capacitance".

[0021] Multiple anode foils each comprise a metal portion and an oxide film formed on the surface of the metal portion. The anode foils may be formed in sheet form. The oxide film may be composed of an oxide of the metal constituting the metal portion. The oxide film may constitute a dielectric layer. At least a portion of the oxide film (dielectric layer) may be covered by a solid electrolyte.

[0022] The material for the metal part can be, for example, a valve-acting metal, or an alloy or compound containing a valve-acting metal. The valve-acting metal can be aluminum, tantalum, or niobium, etc.

[0023] For example, a foil containing a metal portion is immersed in a forming solution such as ammonium adipate solution, and the foil is subjected to a forming treatment under a voltage applied as needed, thereby forming an oxide film (dielectric layer).

[0024] Solid electrolytes may contain, for example, manganese compounds or conductive polymers. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. Solid electrolytes containing conductive polymers can be formed, for example, by chemically polymerizing and / or electrolytically polymerizing the raw material monomers on a dielectric layer. Alternatively, solid electrolytes can be formed, for example, by attaching a solution containing dissolved conductive polymers or a dispersion of conductive polymers to a dielectric layer.

[0025] Multiple cathode foils can be individually composed of metal foils. The aforementioned valve-acting metal can be used as the material for the metal foils. The surface of the cathode foil can be roughened. An oxide film can be formed on the surface of the cathode foil as needed. A conductive layer such as a carbon layer can also be formed on the surface of the cathode foil as needed.

[0026] A spacer is sandwiched between the anode foil and the cathode foil. The spacer electrically insulates the anode foil from the cathode foil. The spacer can be made of non-woven fabric. The non-woven fabric can be made of fibers such as cellulose, polyethylene terephthalate, vinylon, and polyamides (aliphatic polyamides, aromatic polyamides, etc.). A solid electrolyte can be impregnated into the spacer.

[0027] Each of the aforementioned anode foils has a joint portion that is joined together by the joining of metal parts. The joint portion may be provided in a region of each anode foil that does not overlap with the cathode foil or spacer in the stacking direction of the laminate. Alternatively, the regions of each anode foil that do not overlap with the cathode foil may be joined together, for example by ultrasonic joining or laser welding, thereby forming the joint portion.

[0028] The ratio of the oxide film on the metal portion to the joint portion of the anode foil is smaller than that on the remaining portion of the anode foil. Here, the ratio of the oxide film to the metal portion can be directly calculated, for example, as the ratio of the area of ​​the oxide film to the area of ​​the metal portion in a cross-section of the anode foil passing through the joint portion, or it can be indirectly calculated as the content of oxygen atoms per unit volume.

[0029] Such a joint has a very low connection resistance because it is joined together by the metal parts. Furthermore, the small ratio of oxide film relative to the metal parts at the joint also contributes to reducing the connection resistance. This reduced connection resistance at the joint, i.e., the reduced connection resistance between the multiple anode foils, leads to a decrease in the ESR of the electrolytic capacitor A.

[0030] In at least a portion of the joint, the metal portion and the oxide film can exist in a layered mixture. In this case, an adhesive effect caused by the oxide film is generated, and the bonding strength between the metal portions can be improved. Furthermore, because of the presence of the oxide film, which is more fragile than the metal portion, even if vibration is transmitted to the joint, the oxide film can absorb or mitigate the vibration. Thus, according to this configuration, the bonding damage at the joint can be suppressed, thereby improving the reliability of the electrolytic capacitor A.

[0031] The joint may also not have a through hole along the stacking direction of the laminated elements. In this case, the strength of the joint can be sufficiently ensured, while the metal resistance of the joint can be reduced. In addition, if a through hole is formed, cracks may occur in the anode foil around it; however, since no through hole is formed in this configuration, cracks are less likely to occur in the anode foil.

[0032] The ratio of the oxide film in the thinnest portion of the joint to the metal portion can be 0% or more and 50% or less. By keeping this ratio within this range, the ESR of the electrolytic capacitor A can be sufficiently reduced, while ensuring sufficient joint strength. This ratio can also be 0% or more and 20% or less. It should be noted that the ratio of the oxide film to the metal portion can also be a ratio related to the respective areas in the cross-section through the joint. This ratio can also be calculated, for example, as an average value over the entire bottom of the joint.

[0033] Viewed from the stacking direction of the stacked components, the area at the bottom of the joint can be 0.2 mm. 2 Above and 20mm 2 The following applies. By ensuring the area of ​​the bottom of the joint is within this range, the ESR of the electrolytic capacitor A can be sufficiently reduced, while simultaneously ensuring sufficient joint strength. The area of ​​the bottom of the joint can also be 0.7 mm². 2 Above and 5mm 2 The following should be noted: The so-called bottom of the joint refers to the region within the joint that is 10 μm or less from its thinnest part toward the opening of the joint in the depth direction of the joint (or the stacking direction of the stacked elements).

[0034] The ratio of the thickness of the thinnest portion of the anode foil relative to the thickness of the portion outside the joint can be 20% or more and 60% or less. The former thickness can be the sum of the thickness of the metal portion and the thickness of the oxide film, and can be calculated, for example, as the average thickness of any five points of the portion of the anode foil outside the joint. By keeping this ratio within this range, the connection resistance between multiple anode foils can be further reduced.

[0035] An electrolytic capacitor (hereinafter also referred to as electrolytic capacitor B) according to another embodiment of the present invention includes an anode foil and an anode lead.

[0036] The anode foil can be the same as the anode foil of electrolytic capacitor A.

[0037] The anode lead is connected to the anode foil. The anode lead can be electrically or mechanically connected to the anode foil. The anode lead can be made of metal (e.g., copper or a copper alloy). The anode lead can also function as an external terminal of electrolytic capacitor B.

[0038] A portion of the anode foil is a joint that is bonded to the anode lead via a metal section. The joint can also be formed by overlapping a given area of ​​the anode foil onto the anode lead, for example, by ultrasonic bonding or laser welding.

[0039] The ratio of oxide film on the metal portion to the bonding portion of the anode foil is smaller compared to the remaining portion of the anode foil. Because this bonding portion is connected to the anode lead via the metal portion, the connection resistance is very low. Furthermore, the small ratio of oxide film on the metal portion at the bonding portion also contributes to reducing the connection resistance at the bonding portion. This reduced connection resistance at the bonding portion, i.e., the reduced connection resistance between the multiple anode foils, leads to a decrease in the ESR of the electrolytic capacitor B.

[0040] An oxide film can be formed on the surface of the anode lead. When ultrasonic bonding is used to form the joint, the joint can be formed efficiently while removing the oxide film on the surface of the anode lead. That is, if an oxide film is formed on the surface of the anode lead, the connection resistance between the anode lead and the anode foil tends to increase. However, since the oxide film ratio is reduced in the joint of the present invention, the connection resistance between the anode lead and the anode foil can be sufficiently reduced.

[0041] The thickness of the oxide film on the surface of the anode lead can be 1 nm or more, or it can be 10 nm or more. Even when the thickness of the oxide film on the surface of the anode lead is 10 nm or more, the connection resistance between the anode lead and the anode foil can be sufficiently reduced because the oxide film ratio in the joint of the present invention is small.

[0042] In at least a portion of the joint, the metal portion and the oxide film may be present in a layered mixture. In this case, an adhesion effect caused by the oxide film is generated, and the bonding strength between the anode foil and the anode lead is improved. Furthermore, because of the presence of the oxide film, which is more fragile than the metal portion, even if vibration is transmitted to the joint, the oxide film can absorb or mitigate the vibration. Thus, according to this configuration, the possibility of joint damage can be suppressed, thereby improving the reliability of the electrolytic capacitor B.

[0043] The ratio of the oxide film in the thinnest part of the joint to the metal part can be 0% or more and 50% or less. By keeping this ratio within this range, the ESR of the electrolytic capacitor B can be sufficiently reduced, while ensuring sufficient joint strength. This ratio can also be 0% or more and 20% or less. It should be noted that the ratio of the oxide film to the metal part can be a ratio related to the respective areas in the cross-section through the joint.

[0044] As shown above, according to the present invention, in the joint where multiple anode foils are joined, the ESR of the electrolytic capacitor can be reduced by reducing the amount of oxide film while joining the metal parts.

[0045] Hereinafter, an example of the electrolytic capacitor of the present invention will be specifically described with reference to the accompanying drawings. The constituent elements of the electrolytic capacitor of the example described below can be applied using the constituent elements described above. The constituent elements of the electrolytic capacitor of the example described below can be modified based on the above description. Furthermore, the matters described below can also be applied to the above-described embodiments. Constituent elements in the electrolytic capacitor of the example described below that are not essential to the electrolytic capacitor of the present invention can be omitted. It should be noted that the figures shown below are schematic diagrams and do not accurately reflect the shape and number of actual components.

[0046] like Figures 1-3 As shown, the electrolytic capacitor 10 of this embodiment includes a stacked element 20 and a housing 40.

[0047] like Figure 1 As shown, the stacked element 20 has multiple units 21 connected in parallel. Each unit 21 has multiple capacitor elements 22 connected in parallel.

[0048] Each capacitor element 22 includes an anode foil 23, a cathode foil 27, and a spacer 29 sandwiched between them. The anode foil 23 and the cathode foil 27 are made of a valve-acting metal or an alloy or compound containing a valve-acting metal. The spacer 29 is made of, for example, non-woven fabric. Liquid components or electrolytes are impregnated in the spacer 29.

[0049] The anode foil 23 is in the form of a foil or sheet, and its shape is rectangular. Along the length of the anode foil 23 ( Figure 1 An anode lead-out portion 24 is provided on one end side (in the left-right direction). The anode foil 23 has a metal portion 25 (see reference). Figure 4 The surface of the metal part 25 is roughened to become porous. An oxide film (dielectric layer) 26 is formed on the surface of the porous part (the surface of the metal part 25). Figure 4 At least a portion of the oxide film 26 is covered by a solid electrolyte.

[0050] The cathode foil 27 is foil-shaped or sheet-shaped, and its shape is rectangular. Along the length of the anode foil 23 ( Figure 1 A cathode lead-out portion 28 is provided on one end side (in the left-right direction). The portion of the cathode foil 27 other than the cathode lead-out portion 28 is in contact with the solid electrolyte.

[0051] In this embodiment, three anode foils 23 and four cathode foils 27 are overlapped with spacers 29 to form one unit 21. Furthermore, two units 21 are overlapped to form a stacked element 20. Based on the number of anode foils 23, one unit 21 is composed of three capacitor elements 22, and the stacked element 20 is composed of six capacitor elements 22.

[0052] The stacked element 20 further includes a common anode lead 31 made of metal. In this embodiment, two common anode leads 31 are provided. The anode leads 24 of the three capacitor elements 22 constituting each unit 21 are overlapped and joined together with the common anode leads 31. This joining can be performed, for example, by ultrasonic joining. By using ultrasonic joining, the removal of the oxide film 26 and the joining between the metal parts 25 can be performed simultaneously. The part of each anode foil 23 to be joined is the joining part 24a that is joined to each other by the joining between the metal parts 25. Moreover, each joining part 24a is joined to the common anode lead 31 to form a first anode joining part 32. An oxide film (not shown) with a thickness of 10 nm or more can be formed on the surface of the common anode lead 31. The common anode lead 31 is an example of an anode lead.

[0053] The ratio of the bonding portion 24a of the anode foil 23 to the oxide film 26 of the metal portion 25 is smaller compared to the remaining portion of the anode foil 23. The ratio of the thinnest portion of the bonding portion 24a to the oxide film 26 of the metal portion 25 is preferably 0% or more and 50% or less, more preferably 0% or more and 20% or less, and even more preferably 0% or more and 10% or less. From the lamination direction of the laminated element 20 ( Figure 1 When viewed from above and below, the area of ​​the bottom of the joint 24a is preferably 0.2 mm². 2 Above and 20mm 2 The following is more preferably 0.7mm 2 Above and 1.7mm 2 The following applies. The ratio of the thickness of the thinnest portion of the anode foil 23 to the thickness of the portion other than the joint 24a is preferably 20% or more and 60% or less. The joint 24a does not have a through hole along the stacking direction of the laminated element 20.

[0054] like Figure 5As shown, preferably in at least a portion of the junction 24a (or at least a portion of the first anode junction 32), the metal portion 25 and the oxide film 26 are present in a layered mixture.

[0055] like Figure 1 As shown, the two common anode leads 31 overlap and join together to form a second anode junction 33. When the common anode leads 31 are sheet-like, the shape of the second anode junction 33 is generally flat. In addition, the second anode junction 33 is arranged without overlapping the first anode junction 32 in the stacking direction of the laminated element 20.

[0056] The stacked element 20 further includes a metallic cathode common lead 34. In this embodiment, two cathode common leads 34 are provided. The cathode leads 28 of the three capacitor elements 22 constituting each unit 21 are overlapped and joined together with the cathode common leads 34. This joining can be performed, for example, using ultrasonic bonding. The portion of each cathode foil 27 and the cathode common lead 34 to be joined constitutes a first cathode bonding portion 35.

[0057] Two cathode common leads 34 are joined together in an overlapping manner to form a second cathode junction 36. When the cathode common leads 34 are sheet-like, the shape of the second cathode junction 36 is generally flat. In addition, the second cathode junction 36 is arranged without overlapping the first cathode junction 35 in the stacking direction of the stacked element 20.

[0058] like Figure 3 As shown, the housing 40 houses the stacked element 20. From one side of the housing 40 ( Figure 3 (Left side of the middle) Anode common lead 31 is led out. From the other side of the housing 40 ( Figure 3 (Right side of the image) A cathode lead 34 is provided. The laminated element 20 can be housed together with the liquid component or electrolyte in the housing 40. The housing 40 can be made of a laminate with a metal shielding layer, but is not limited thereto. For example, the housing 40 can be made of metals such as aluminum, stainless steel, copper, iron, brass, or their alloys.

[0059] Postscript

[0060] Based on the description of the above embodiments, the following technology is disclosed.

[0061] (Technology 1)

[0062] An electrolytic capacitor comprising stacked elements,

[0063] The above-mentioned stacked elements have:

[0064] Multiple anode foils, each comprising a metal portion and an oxide film formed on the surface of the metal portion,

[0065] Multiple cathode foils, and

[0066] A spacer sandwiched between the anode foil and the cathode foil.

[0067] A portion of each of the aforementioned anode foils is a joint portion that is joined together by the joining of the aforementioned metal parts.

[0068] The ratio of the oxide film on the metal portion to the joint portion of the anode foil is smaller than that to the remaining portion of the anode foil.

[0069] (Technology 2)

[0070] According to the electrolytic capacitor described in Technique 1, in at least a portion of the aforementioned junction, the metal portion and the aforementioned oxide film are present in a layered mixture.

[0071] (Technology 3)

[0072] According to the electrolytic capacitor described in Technique 1 or 2, the aforementioned joint does not have a through hole along the stacking direction of the aforementioned stacked elements.

[0073] (Technology 4)

[0074] According to any one of the techniques 1 to 3, in the thinnest part of the aforementioned joint, the ratio of the aforementioned oxide film to the aforementioned metal part is 0% or more and 50% or less.

[0075] (Technology 5)

[0076] According to any one of the techniques 1 to 4, in the electrolytic capacitor, when viewed from the stacking direction of the stacked elements, the area of ​​the bottom of the junction is 0.2 mm². 2 Above and 20mm 2 the following.

[0077] (Technology 6)

[0078] According to any one of the techniques 1 to 5, in the electrolytic capacitor, the ratio of the thickness of the thinnest portion of the anode foil to the thickness of the portion other than the joint is 20% or more and 60% or less.

[0079] (Technology 7)

[0080] An electrolytic capacitor comprising:

[0081] An anode foil comprising a metal portion and an oxide film formed on the surface of the metal portion; and

[0082] The anode lead connected to the aforementioned anode foil,

[0083] A portion of the aforementioned anode foil is a joint portion that is joined to the aforementioned anode lead via the aforementioned metal portion.

[0084] The ratio of the oxide film on the metal portion to the joint portion of the anode foil is smaller than that to the remaining portion of the anode foil.

[0085] (Technology 8)

[0086] According to the electrolytic capacitor described in Technique 7, an oxide film is formed on the surface of the anode lead.

[0087] (Technology 9)

[0088] According to the electrolytic capacitor described in Technology 8, the thickness of the oxide film on the surface of the anode lead is 10 nm or more.

[0089] (Technology 10)

[0090] According to any one of the techniques 7 to 9, in the electrolytic capacitor, the metal portion and the oxide film are present in a layered mixture in at least a portion of the junction.

[0091] (Technology 11)

[0092] According to any one of the techniques 7 to 10, in the thinnest part of the joint, the ratio of the oxide film on the metal part is 0% or more and 50% or less.

[0093] While the invention has been described with respect to preferred embodiments, such disclosure should not be interpreted as restrictive. Various modifications and alterations will be readily apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the additional scope of the claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0094] Industrial availability

[0095] This invention can be used in electrolytic capacitors.

[0096] Explanation of reference numerals in the attached figures

[0097] 10 Electrolytic capacitor, 20 Stacked element, 21 Unit, 22 Capacitor element, 23 Anode foil, 24 Anode lead, 24a Joint, 25 Metal part, 26 Oxide film, 27 Cathode foil, 28 Cathode lead, 29 Spacer, 31 Common anode lead (anode lead), 32 First anode joint, 33 Second anode joint, 34 Common cathode lead, 35 First cathode joint, 36 Second cathode joint, 40 Housing.

Claims

1. An electrolytic capacitor comprising stacked elements, The stacked element has: A plurality of anode foils, each comprising a metal portion and an oxide film formed on the surface of the metal portion; Multiple cathode foils; and A spacer sandwiched between the anode foil and the cathode foil. A portion of each of the anode foils is a joint portion that is joined together by the bonding between the metal parts. The ratio of the junction of the anode foil to the remaining portion of the anode foil relative to the oxide film on the metal portion is smaller.

2. The electrolytic capacitor according to claim 1, wherein, In at least a portion of the joint, the metal portion and the oxide film exist in a layered mixture.

3. The electrolytic capacitor according to claim 1 or 2, wherein, The joint does not have a through hole along the stacking direction of the stacked elements.

4. The electrolytic capacitor according to claim 1 or 2, wherein, In the thinnest part of the joint, the ratio of the oxide film relative to the metal part is more than 0% and less than 50%.

5. The electrolytic capacitor according to claim 1 or 2, wherein, Viewed from the stacking direction of the stacked elements, the area of ​​the bottom of the joint is 0.2 mm. 2 Above and 20mm 2 the following.

6. The electrolytic capacitor according to claim 1 or 2, wherein, The ratio of the thickness of the thinnest portion of the anode foil to the thickness of the portion other than the joint is 20% or more and 60% or less.

7. An electrolytic capacitor comprising an anode foil including a metal portion and an oxide film formed on the surface of the metal portion, and an anode lead connected to the anode foil. A portion of the anode foil is a joint that is bonded to the anode lead via the metal portion. The ratio of the junction of the anode foil to the remaining portion of the anode foil relative to the oxide film on the metal portion is smaller.

8. The electrolytic capacitor according to claim 7, wherein, An oxide film is formed on the surface of the anode lead.

9. The electrolytic capacitor according to claim 8, wherein, The thickness of the oxide film on the surface of the anode lead is 10 nm or more.

10. The electrolytic capacitor according to any one of claims 7 to 9, wherein, In at least a portion of the joint, the metal portion and the oxide film exist in a layered mixture.

11. The electrolytic capacitor according to any one of claims 7 to 9, wherein, In the thinnest part of the joint, the ratio of the oxide film relative to the metal part is more than 0% and less than 50%.

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