Electrolytic capacitors

Abstract

The electrolytic capacitor (1) of the present invention comprises: a rectangular parallelepiped resin molded body (9), a laminated body (30) including a capacitor element (20) including an anode (3) having a dielectric layer (5) on its surface and a cathode (7) facing the anode (3); a first external electrode (11) formed on a first end surface (9a) of the resin molded body (9) and electrically connected to the anode (3) exposed from the first end surface (9a); and a second external electrode (13) formed on a second end surface (9b) of the resin molded body (9) and electrically connected to the cathode (7) exposed from the second end surface (9b). The cathode (7) is electrically connected, characterized in that at least one of the first external electrode (11) and the second external electrode (12) is a multilayer structure having an inner plating layer (11a, 13a) formed on the surface of the anode (3) exposed from the first end face (9a) or the surface of the cathode (7) exposed from the second end face (9b) and a resin electrode layer (11b, 13b) formed on the surface of the inner plating layer (11a, 13a) and containing one or more metals selected from the group consisting of Ni, Cu and Ag and a resin component, and the total number of layers constituting the first external electrode (11) and the second external electrode (13) is less than four.

Description

Technical Field

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

[0002] Patent Document 1 discloses a multilayer ceramic capacitor.

[0003] The stacked ceramic capacitor is manufactured in the following manner: after the first and second surfaces of the capacitor body are respectively impregnated with electrode paste and dried, a sintering treatment is performed to form a base film for external electrodes, and after the electrode paste is printed on the two ends in the length direction of the fifth surface of the capacitor body and dried, a sintering treatment is performed to form another base film for external electrodes to be continuous with the base film.

[0004] In addition, Patent Document 2 describes a method for forming external electrodes on a ceramic capacitor. Specifically, the method includes a first paste layer forming step of screen printing on the end surface of a green body and a second paste layer forming step of screen printing on the main surface of the green body, a first sintering step after the first paste layer forming step, and a second sintering step after the second paste layer forming step.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-152620

[0008] Patent Document 2: Japanese Patent Application Publication No. 2012-4480 Summary of the invention

[0009] Problems to be solved by the invention

[0010] The techniques described in Patent Documents 1 and 2 are to perform a sintering treatment at a high temperature of 600 to 800° C. after screen-printing the electrode paste on the ceramic body. The composition, rheology or printing conditions of the electrode paste are suitable for the sintering treatment.

[0011] On the other hand, an electrolytic capacitor such as a solid electrolytic capacitor may have a laminated body including a capacitor element including an anode having a dielectric layer on its surface and a cathode facing the anode sealed by a resin molded body, and external electrodes formed on the resin molded body.

[0012] When the external electrode is formed by a resin molded body, the electrode layer cannot be formed by a high temperature sintering process, etc., so it is difficult to improve the adhesion between the resin molded body and the electrode layer. Therefore, the external electrode forming method disclosed in Patent Documents 1 and 2 cannot be used directly.

[0013] Therefore, as a method for forming external electrodes on the surface of a resin molded body, a structure is considered to provide an inner plating layer that is in direct contact with the cathode and the anode, an outer plating layer that is in direct contact with the solder, and a resin electrode layer for preventing cracks in the external electrodes. The resin electrode layer is arranged between the inner plating layer and the outer plating layer.

[0014] For the inner layer plating layer, it is required to have high adhesion to the anode or cathode. Although Ni plating has excellent adhesion to the anode and cathode, it is easily oxidized. Therefore, it is considered that the inner layer plating layer is formed into a double-layer structure of a Ni plating layer and a plating layer (such as an Ag plating layer) for preventing oxidation of the Ni plating.

[0015] The outer plating layer requires high solder wettability. However, when the Sn plating layer with high solder wettability is directly provided on the surface of the resin electrode layer, the adhesion will decrease. Therefore, for the outer plating layer, it is necessary to first form a Ni plating layer on the surface of the resin electrode layer, and then provide a Sn plating layer on the surface of the Ni plating layer.

[0016] Thus, the external electrode has a five-layer structure of two inner plating layers (Ni / Ag), a resin electrode layer, and two outer plating layers (Ni / Sn).

[0017] However, in the above structure, there is a concern that the number of electrode layers is too large, which may lead to an increase in manufacturing cost.

[0018] Furthermore, since the number of interfaces between electrode layers is large, there is a concern that the ESR may increase due to interface resistance.

[0019] Therefore, an object of the present invention is to provide an electrolytic capacitor capable of suppressing increases in manufacturing cost and ESR.

[0020] Means for solving problems

[0021] The electrolytic capacitor of the present invention comprises: a rectangular parallelepiped resin molded body, which comprises a laminated body including a capacitor element and a sealing resin that seals the periphery of the laminated body, wherein the capacitor element comprises an anode having a dielectric layer on its surface and a cathode facing the anode; a first external electrode formed on a first end surface of the resin molded body and electrically connected to the anode exposed from the first end surface; and a second external electrode formed on a second end surface of the resin molded body and electrically connected to the cathode exposed from the second end surface, characterized in that at least one of the first external electrode and the second external electrode has a multilayer structure having an inner plating layer and a resin electrode layer, the inner plating layer being formed on a surface of the anode exposed from the first end surface or a surface of the cathode exposed from the second end surface, the resin electrode layer being formed on a surface of the inner plating layer and comprising one or more metals selected from the group consisting of Ni, Cu and Ag and a resin component, and the total number of layers constituting the first external electrode and the second external electrode is four or less.

[0022] Effects of the Invention

[0023] According to the present invention, it is possible to provide an electrolytic capacitor capable of suppressing increases in manufacturing cost and ESR. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a perspective view schematically showing an example of the electrolytic capacitor of the present invention.

[0025] Figure 2 yes Figure 1 AA line cross-sectional view of the electrolytic capacitor shown. DETAILED DESCRIPTION

[0026] Hereinafter, the electrolytic capacitor of the present invention will be described.

[0027] However, the present invention is not limited to the following configurations, and can be applied with appropriate changes within the scope of the present invention. It should be noted that an embodiment composed of combining two or more preferred configurations of the embodiments of the present invention described below is also the present invention.

[0028] Figure 1 It is a perspective view schematically showing an example of the electrolytic capacitor of the present invention.

[0029] exist Figure 1 2 shows a rectangular parallelepiped resin molded body 9 constituting the electrolytic capacitor 1 .

[0030] The resin molded body 9 has a length direction (L direction), a width direction (W direction), and a thickness direction (T direction), and has a first end face 9a and a second end face 9b that are opposite to each other in the length direction. A first external electrode 11 is formed on the first end face 9a, and a second external electrode 13 is formed on the second end face 9b.

[0031] The resin molded body 9 includes a bottom surface 9c and an upper surface 9d which are opposed to each other in the thickness direction.

[0032] Furthermore, the resin molded body 9 includes a first side surface 9e and a second side surface 9f that are opposed to each other in the width direction.

[0033] It should be noted that in this specification, the surface along the length direction (L direction) and thickness direction (T direction) of the electrolytic capacitor or resin molded body is called LT surface, the surface along the length direction (L direction) and width direction (W direction) is called LW surface, and the surface along the thickness direction (T direction) and width direction (W direction) is called WT surface.

[0034] Figure 2 yes Figure 1 AA line cross-sectional view of the electrolytic capacitor shown.

[0035] Capacitor element 20 includes anode 3 having dielectric layer 5 on its surface and cathode 7 facing anode 3 .

[0036] A plurality of capacitor elements 20 are stacked to form a stacked body 30, and the periphery of the stacked body 30 is sealed with a sealing resin 8 to form a resin molded body 9. In the stacked body 30, the stacked capacitor elements 20 may be bonded to each other via a conductive adhesive (not shown).

[0037] A first external electrode 11 is formed on the first end surface 9 a of the resin molded body 9 , and the first external electrode 11 is electrically connected to the anode 3 exposed from the first end surface 9 a .

[0038] A second external electrode 13 is formed on the second end surface 9 b of the resin molded body 9 , and the second external electrode 13 is electrically connected to the cathode 7 exposed from the second end surface 9 b .

[0039] The end portion of the second end face 9b side of the valve metal foil 3a constituting the capacitor element 20 is sealed by the sealing resin 8, and the valve metal foil 3a is not in direct contact with the solid electrolyte layer 7a or the conductive layer 7b. On the other hand, in the case where the end portion of the second end face 9b side of the valve metal foil 3a is covered with the dielectric layer 5 or other insulating treatment, the end portion of the second end face 9b side of the valve metal foil 3a may be covered with the solid electrolyte layer 7a and the conductive layer 7b.

[0040] Anode 3 constituting capacitor element 20 has valve metal foil 3a at the center and a porous layer (not shown) such as an etching layer on the surface. Dielectric layer 5 is provided on the surface of the porous layer.

[0041] Examples of the valve-acting metal include simple metals such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, and silicon, or alloys containing these metals, etc. Among these, aluminum or an aluminum alloy is preferred.

[0042] The shape of the valve metal is not particularly limited, but is preferably a flat plate, and more preferably a foil. In addition, the porous layer is preferably an etching layer that has been etched with hydrochloric acid or the like.

[0043] The thickness of the valve metal foil before etching is preferably 60 μm or more and preferably 180 μm or less. In addition, the thickness of the valve metal foil (core) that is not etched after the etching process is preferably 10 μm or more and preferably 70 μm or less. The thickness of the porous layer is designed in accordance with the withstand voltage and electrostatic capacitance required by the electrolytic capacitor, but it is preferably 10 μm or more and preferably 120 μm or less when combined with the porous layers on both sides of the valve metal foil.

[0044] The anode 3 is led out to the first end surface 9 a of the resin molded body 9 and is electrically connected to the first external electrode 11 .

[0045] The dielectric layer is preferably composed of an oxide film of the valve metal. For example, when aluminum foil is used as the valve metal substrate, an oxide film that becomes the dielectric layer can be formed by anodizing in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts, ammonium salts, etc.

[0046] The dielectric layer is formed along the surface of the porous layer to form fine pores (recesses). The thickness of the dielectric layer is designed in accordance with the withstand voltage and electrostatic capacitance required of the electrolytic capacitor, but is preferably 10 nm or more and preferably 100 nm or less.

[0047] Cathode 7 constituting capacitor element 20 is formed by laminating solid electrolyte layer 7a formed on dielectric layer 5, conductive layer 7b formed on solid electrolyte layer 7a, and cathode lead layer 7c formed on conductive layer 7b.

[0048] An electrolytic capacitor having a solid electrolyte layer as a part of a cathode can also be called a solid electrolytic capacitor.

[0049] As materials constituting the solid electrolyte layer, for example, conductive polymers having a skeleton of pyrrole, thiophene, aniline, etc. are cited. As conductive polymers having a skeleton of thiophene, for example, PEDOT [poly (3, 4-ethylenedioxythiophene)] is cited, and PEDOT:PSS composited with polystyrene sulfonic acid (PSS) as a dopant is also exemplified.

[0050] The solid electrolyte layer is formed, for example, by a method of forming a polymer film of poly(3,4-ethylenedioxythiophene) or the like on the surface of the dielectric layer using a treatment solution containing a monomer such as 3,4-ethylenedioxythiophene, a method of applying a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) or the like to the surface of the dielectric layer and drying it, etc. It should be noted that it is preferred that after forming a solid electrolyte layer for an inner layer that fills the pores (recesses), a solid electrolyte layer for an outer layer that covers the entire dielectric layer is formed.

[0051] The solid electrolyte layer can be formed in a predetermined area by applying the above-mentioned treatment liquid or dispersion liquid to the dielectric layer by sponge transfer, screen printing, spraying, dispenser, inkjet printing, etc. The thickness of the solid electrolyte layer is preferably 2 μm or more and preferably 20 μm or less.

[0052] The conductive layer is provided to electrically and mechanically connect the solid electrolyte layer to the cathode lead layer. For example, it is preferably a carbon layer, a graphene layer or a silver layer formed by applying a conductive paste such as a carbon paste, a graphene paste or a silver paste. In addition, it may be a composite layer in which a silver layer is provided on a carbon layer or a graphene layer, or a mixed layer in which a carbon paste or a graphene paste is mixed with a silver paste.

[0053] The conductive layer can be formed by forming a conductive paste such as a carbon paste on the solid electrolyte layer by sponge transfer, screen printing, spraying, dispenser, inkjet printing, etc. It should be noted that it is preferred to laminate the cathode lead layer of the next process while the conductive layer has a viscosity before drying. The thickness of the conductive layer is preferably 2 μm or more and preferably 20 μm or less.

[0054] The cathode lead layer can be formed of a metal foil or a printed electrode layer.

[0055] In the case of metal foil, it is preferable to contain at least one metal selected from the group consisting of Al, Cu, Ag, and alloys containing these metals as main components. When the metal foil contains the above metals, the resistance value of the metal foil can be reduced, and the ESR can be reduced.

[0056] In addition, as the metal foil, a metal foil with a carbon coating or a titanium coating applied to the surface by a film forming method such as sputtering or evaporation can also be used. More preferably, an Al foil with a carbon coating is used. The thickness of the metal foil is not particularly limited, but from the viewpoint of handling in the manufacturing process, miniaturization, and reduction of ESR, it is preferably 20 μm or more and preferably 50 μm or less.

[0057] In the case of a printed electrode layer, an electrode paste is formed on the conductive layer by sponge transfer, screen printing, spraying, dispenser, inkjet printing, etc., so that the cathode lead layer can be formed in a predetermined area. As the electrode paste, an electrode paste with Ag, Cu or Ni as the main component is preferably used. In the case of setting the cathode lead layer as a printed electrode layer, the thickness of the printed electrode layer can be reduced compared to the case of using a metal foil, and in the case of screen printing, a thickness of 2 μm or more and 20 μm or less can also be used.

[0058] The cathode lead layer 7 c is led out to the second end surface 9 b of the resin molded body 9 and is electrically connected to the second external electrode 13 .

[0059] The sealing resin 8 constituting the resin molded body 9 contains at least a resin, preferably a resin and a filler. As the resin, for example, epoxy resin, phenolic resin, polyimide resin, silicone resin, polyamide resin, liquid crystal polymer, etc. are preferably used. As the form of the sealing resin 8, any of a solid resin and a liquid resin can be used. In addition, as the filler, for example, silica particles, alumina particles, metal particles, etc. are preferably used. It is more preferable to use a material containing silica particles in a solid epoxy resin and a phenolic resin.

[0060] As a forming method of the resin molded body, when a solid sealing material is used, it is preferred to use resin molding such as compression molding and transfer molding, and compression molding is more preferred. In addition, when a liquid sealing material is used, it is preferred to use a forming method such as a dispensing method or a printing method. It is preferred to form a resin molded body 9 by sealing the laminated body 30 of the capacitor element 20 including the anode 3, the dielectric layer 5 and the cathode 7 with the sealing resin 8 by compression molding.

[0061] The resin molded body 9 has a rectangular parallelepiped shape, and has an upper surface 9d serving as an LW plane, a bottom surface 9c, a first side surface 9e serving as an LT plane, a second side surface 9f, a first end surface 9a serving as a WT plane, and a second end surface 9b.

[0062] The resin molded body 9 is formed with a chamfered R (radius of curvature) at the corner by roller grinding after resin molding. In the case of a resin molded body, it is softer than a ceramic body and it is difficult to form R at the corner by roller grinding, but it can be formed smaller by adjusting the composition, particle size, shape, roller processing time, etc. of the medium.

[0063] Hereinafter, the structure of the external electrodes included in the electrolytic capacitor of the present invention will be described in detail.

[0064] At least one of the first external electrode and the second external electrode in the electrolytic capacitor of the present invention is a multilayer structure having an inner plating layer and a resin electrode layer, wherein the resin electrode layer is formed on the surface of the inner plating layer and contains one or more metals selected from the group consisting of Ni, Cu and Ag and a resin component.

[0065] Preferably, the first external electrode has an inner plating layer and a resin electrode layer, wherein the inner plating layer is formed on the surface of the anode exposed from the first end face, and the resin electrode layer is formed on the surface of the inner plating layer and contains one or more metals selected from the group consisting of Ni, Cu and Ag and a resin component.

[0066] The structure of the coating layer other than this is not essential, but the following reference Figure 2 The first external electrode and the second external electrode including the inner plating layer, the resin electrode layer, and the outer plating layer will be described.

[0067] in addition, Figure 2 The resin electrode layer shown is a printed resin electrode layer formed by screen printing of an electrode paste.

[0068] exist Figure 2 2 shows the layer structure of the first external electrode 11 and the second external electrode 13 included in the electrolytic capacitor 1 .

[0069] The first external electrode 11 includes an inner plating layer 11a, a resin electrode layer 11b, and an outer plating layer 11c. The resin electrode layer 11b is a printed resin electrode layer.

[0070] The second external electrode 13 includes an inner plating layer 13a, a resin electrode layer 13b, and an outer plating layer 13c. The resin electrode layer 13b is a printed resin electrode layer.

[0071] Therefore, in Figure 2 In the electrolytic capacitor 1 shown, the first external electrode 11 and the second external electrode 13 are both multilayer structures having an inner plating layer and a resin electrode layer, and the resin electrode layer is formed on the surface of the inner plating layer and contains one or more metals selected from the group consisting of Ni, Cu and Ag and a resin component.

[0072] In the electrolytic capacitor of the present invention, the total number of layers constituting the first external electrode and the second external electrode is four or less.

[0073] Since the total number of layers constituting the first external electrode and the second external electrode is four or less, the electrolytic capacitor of the present invention can suppress increases in manufacturing cost and ESR.

[0074] As long as the total number of layers of the first external electrode and the second external electrode is four or less, the inner plating layer may be two or more layers, and the outer plating layer may be two or more layers.

[0075] The inner plating layer is preferably formed by zincate treatment. That is, the surface of the aluminum foil of the anode 3 exposed from the first end surface of the resin molded body 9 is subjected to alkaline etching to remove the oxide film of the anode 3, and then Zn plating is performed. Then, displacement plating based on electroless Ni plating is performed to form the inner plating layer 11a.

[0076] The inner plating layer formed on the surface of the cathode lead layer 7c can also be formed by the same method as the inner plating layer formed on the surface of the anode 3, but zincate treatment is not necessary. However, when the cathode lead layer 7c contains Al, zincate treatment is preferably performed.

[0077] The inner plating layer is preferably a Ni plating layer, a Cu plating layer or an Ag plating layer, and more preferably a Ni plating layer.

[0078] When the inner layer plating layer is two layers, the inner layer plating layer may also have a first inner layer plating layer formed on the surface of the anode exposed from the first end surface of the resin molded body or the surface of the cathode exposed from the second end surface, and a second inner layer plating layer formed on the surface of the first inner layer plating layer.

[0079] When the inner layer plating layer includes a first inner layer plating layer and a second inner layer plating layer, it is preferable that the first inner layer plating layer is a Ni plating layer and the second inner layer plating layer is an Ag plating layer.

[0080] When the inner plating layer is a Ni plating layer, the thickness of the Ni plating layer is preferably 3 μm to 10 μm. Also, when the first inner plating layer is a Ni plating layer, the thickness of the Ni plating layer is preferably 3 μm to 10 μm.

[0081] By setting the thickness of the Ni plating layer to be 3 μm or more, the valve metal foil and the dielectric layer can be prevented from being corroded by the plating solution when the second inner plating layer is formed. In addition, by setting the thickness of the Ni plating layer to be 10 μm or less, the surface unevenness of the external electrode can be suppressed, ensuring solder mounting performance.

[0082] Regarding the thickness of the Ni plating layer, Figure 2The thickness of the Ni plating layer is determined by measuring the dimension of a line perpendicular to the first end face or the second end face in a cross-sectional microscope photograph taken at a cross-sectional plane (LT plane). The thickness of each Ni plating layer formed corresponding to each anode or cathode lead layer is measured, and the average thickness of the Ni plating layer at least five locations is measured to determine the thickness of the Ni plating layer.

[0083] The resin electrode layers 11 b and 13 b contain a conductive component and a resin component.

[0084] As the resin component, it is preferable to contain epoxy resin, phenol resin or the like as a main component.

[0085] The resin electrode layer preferably contains 67% by weight or more and 97% by weight or less of a conductive component, and preferably contains 3% by weight or more and 33% by weight or less of a resin component.

[0086] In addition, it is more preferable that the conductive component is contained in an amount of 72% by weight or more and 95% by weight or less, and it is more preferable that the resin component is contained in an amount of 5% by weight or more and 28% by weight or less.

[0087] Furthermore, it is more preferable that the conductive component is contained in an amount of 78% by weight or more and 95% by weight or less, and it is more preferable that the resin component is contained in an amount of 5% by weight or more and 22% by weight or less.

[0088] In addition, it is particularly preferable that the conductive component is contained in an amount of 79% by weight or more and 89% by weight or less, and it is particularly preferable that the resin component is contained in an amount of 11% by weight or more and 21% by weight or less.

[0089] The conductive component constituting the resin electrode layer is one or more metals selected from the group consisting of Ni, Cu, and Ag.

[0090] The conductive component constituting the resin electrode layer may be an alloy.

[0091] Examples of the alloy containing one or more metals selected from the group consisting of Ni, Cu, and Ag include Ag-Ni alloys, Cu-Ni alloys, and Sn-Ni alloys.

[0092] The composition of each alloy is not particularly limited, but examples of the composition of the Sn-Ni alloy include Ni3Sn, Ni3Sn2, and Ni3Sn4.

[0093] As the conductive component constituting the resin electrode layer, Ni and a Ni alloy are preferred, and Ni is more preferred.

[0094] In addition, the resin electrode layer is preferably a printed resin electrode layer formed by screen printing of an electrode paste. Here, it is more preferred that the electrode paste is an electrode paste containing a conductive filler and a resin, the conductive filler containing one or more metals selected from the group consisting of Ni, Cu and Ag as a conductive component, and the resin electrode layer is a printed resin electrode layer formed by screen printing.

[0095] When the resin electrode layer is a printed resin electrode layer, the external electrodes can be made flatter than when the electrode paste is formed by dipping. That is, the uniformity of the film thickness of the first external electrode and the second external electrode is improved.

[0096] exist Figure 2 When the flatness of the first external electrode and the second external electrode is measured in the cross-sectional view shown, the deviation of the thickness of the first external electrode measured from the first end surface of the resin molded body and the deviation of the thickness of the second external electrode measured from the second end surface of the resin molded body are preferably 30 μm or less. In addition, the deviation of the thickness is more preferably 20 μm or less. In addition, the deviation of the thickness is further preferably 5 μm or less.

[0097] can be achieved through Figure 2 The thickness deviation is obtained by taking the difference between the maximum and minimum values ​​of the thickness of the first external electrode and the second external electrode at three locations where the stack is divided into four equal parts from the top surface to the bottom surface in the cross-sectional view shown and at a total of five locations on the top surface and the bottom surface. Alternatively, the thickness of multiple locations can be measured in a non-destructive manner using a fluorescent X-ray film thickness meter or a laser displacement meter.

[0098] In addition, when the resin electrode layer is a printed resin electrode layer formed by screen printing of an electrode paste, the electrode paste preferably contains 60 wt % to 95 wt % of a conductive component and preferably contains 3 wt % to 30 wt % of a resin component.

[0099] In addition, it is more preferable that the conductive component is contained in an amount of 65% by weight or more and 90% by weight or less, and it is more preferable that the resin component is contained in an amount of 5% by weight or more and 25% by weight or less.

[0100] Furthermore, it is more preferable that the conductive component is contained in an amount of 70% by weight or more and 90% by weight or less, and it is more preferable that the resin component is contained in an amount of 5% by weight or more and 20% by weight or less.

[0101] In addition, it is particularly preferable that the conductive component is contained in an amount of 75% by weight or more and 85% by weight or less, and it is particularly preferable that the resin component is contained in an amount of 10% by weight or more and 20% by weight or less.

[0102] The electrode paste may contain an organic solvent, and as the organic solvent, a glycol ether-based solvent is preferably used, for example, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, and the like.

[0103] In addition, additives may be used as needed. Additives are useful for adjusting the rheological properties, especially the thixotropy, of the electrode paste. The content of the additives is preferably less than 5% by weight relative to the weight of the electrode paste.

[0104] An outer plating layer may be further provided on the surface of the resin electrode layer.

[0105] As the outer plating layer, a Ni plating layer or a Sn plating layer is preferable.

[0106] When the outer plating layer is two layers, the outer plating layer may include a first outer plating layer formed on the surface of the resin electrode layer and a second outer plating layer formed on the surface of the first outer plating layer.

[0107] The first outer plating layer is preferably a Ni plating layer, and the second outer plating layer is preferably a Sn plating layer.

[0108] Examples of preferred ranges of the dimensions of the electrolytic capacitor of the present invention are as follows.

[0109] Size of electrolytic capacitors

[0110] L size: 3.4mm or more and 3.8mm or less, representative value is 3.5mm

[0111] W size: 2.7mm or more and 3.0mm or less, the typical value is 2.8mm

[0112] T size: 1.8mm or more and 2.0mm or less, the typical value is 1.9mm

[0113] The electrolytic capacitor of the present invention described so far can be manufactured by the following method, for example.

[0114] [Fabrication of capacitor elements]

[0115] A valve-acting metal foil such as aluminum foil having a porous layer such as an etching layer on the surface is prepared, and the surface of the porous layer is anodized to form a dielectric layer.

[0116] A solid electrolyte layer is formed on the dielectric layer by screen printing, and then a carbon layer is formed on the solid electrolyte layer by screen printing. Furthermore, a cathode lead layer is formed on the carbon layer by sheet lamination or screen printing.

[0117] Through the above steps, a capacitor element is obtained.

[0118] [Lamination and resin sealing of capacitor elements]

[0119] A plurality of capacitor elements are stacked as a layered body, compression molded, and sealed with a sealing resin to form a resin molded body.

[0120] [Formation of external electrodes]

[0121] The first end surface and the second end surface of the resin molded body are subjected to zincate treatment and displacement plating to form an inner plated layer.

[0122] The inner plating layer is preferably, for example, a Ni plating layer, a Cu plating layer, or an Ag plating layer, and more preferably a Ni plating layer.

[0123] It should be noted that the inner plating layer may be formed on at least one of the surface of the anode exposed from the first end surface and the surface of the cathode exposed from the second end surface.

[0124] Next, the electrode paste is screen-printed on the first end surface of the resin molded body and then thermally cured to form the first external electrode.

[0125] Furthermore, the electrode paste is screen-printed on the second end surface of the resin molded body and then thermally cured to form the second external electrode.

[0126] The electrode paste contains a conductive component and a resin component, and the resin electrode layer formed in this way is a printed resin electrode layer.

[0127] The electrode paste used in this step preferably contains 67% by weight or more and 97% by weight or less of a conductive component, and preferably contains 3% by weight or more and 33% by weight or less of a resin component.

[0128] In addition, it is more preferable that the conductive component is contained in an amount of 72% by weight or more and 95% by weight or less, and it is more preferable that the resin component is contained in an amount of 5% by weight or more and 28% by weight or less.

[0129] In addition, it is more preferable that the conductive component is contained in an amount of 78% by weight or more and 95% by weight or less, and it is more preferable that the resin component is contained in an amount of 5% by weight or more and 22% by weight or less.

[0130] Furthermore, it is more preferable that the conductive component is contained in an amount of 79% by weight or more and 89% by weight or less, and it is more preferable that the resin component is contained in an amount of 11% by weight or more and 21% by weight or less.

[0131] The electrode paste may contain an organic solvent, and as the organic solvent, a glycol ether-based solvent is preferably used, for example, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, and the like.

[0132] In addition, additives may be used as necessary, and the amount of the additives added is preferably less than 5% by weight relative to the weight of the electrode paste.

[0133] Next, an outer plating layer is formed.

[0134] When the inner plating layer is one layer, as the outer plating layers, it is preferable to form a Ni plating layer as a first outer plating layer and a Sn plating layer as a second outer plating layer.

[0135] The outer plating layer is formed on the printed resin electrode layer as the first external electrode and the second external electrode.

[0136] Through the above steps, the electrolytic capacitor of the present invention can be obtained.

[0137] The total number of layers of the first external electrode and the second external electrode in the electrolytic capacitor obtained through the above steps is four.

[0138] In addition, the laminate including the capacitor element preferably includes a plurality of capacitor elements, but the capacitor element may be one.

[0139] Example

[0140] Examples in which ESR of the electrolytic capacitor of the present invention was evaluated are shown below. It should be noted that the present invention is not limited to these examples.

[0141] The relationship between the total number of layers constituting the external electrodes and the ESR was evaluated by the following procedure.

[0142] [Preparation of Sample 1]

[0143] The sealing resin containing epoxy resin and silica particles is used to seal the Figure 1 and Figure 2 After the laminated body of the structure shown in the figure is sealed to obtain a resin molded body, a Ni plating layer (in Table 1, for convenience, it is recorded as the first inner plating layer) is applied as an inner plating layer, and an electrode paste is applied to the end faces (the first end face and the second end face) of the resin molded body by screen printing, and thermally cured at a drying temperature of 150° C. to 200° C. to form a resin electrode layer. Furthermore, a Ni plating layer as a first outer plating layer and a Sn plating layer as a second outer plating layer are formed on the surface of the resin electrode layer to produce a sample 1.

[0144] The electrode paste contained 50 wt % of Ni powder, 17 wt % of phenolic resin, 6 wt % of additives, 20 wt % of diethylene glycol monobutyl ether as a solvent, and 7 wt % of diethylene glycol monophenyl ether as a solvent.

[0145] [Sample 2]

[0146] Sample 2 was produced by the same procedure as Sample 1 except that the structures of the first external electrode and the second external electrode were changed as shown in Table 1.

[0147] It should be noted that the composition of the Ag paste used to prepare Sample 2 is 50 wt% of Ag powder, 17 wt% of phenolic resin, 6 wt% of additives, 20 wt% of diethylene glycol monobutyl ether as a solvent, and 7 wt% of diethylene glycol monophenyl ether as a solvent.

[0148] [ESR measurement]

[0149] Using an impedance analyzer, the ESR of Sample 1 and Sample 2 was measured. Table 1 shows the results.

[0150] [Table 1]

[0151]

[0152] * This is a sample that does not correspond to the electrolytic capacitor of the present invention

[0153] As shown in Table 1, it is found that the ESR can be reduced by using one or more metals selected from the group consisting of Ni, Cu and Ag as the conductive material constituting the resin electrode layer and by setting the total number of external electrode layers to four or less.

[0154] Description of Reference Numerals

[0155] 1 electrolytic capacitor;

[0156] 3 Anode;

[0157] 3a Valve action metal foil;

[0158] 5 Dielectric layer;

[0159] 7 cathode;

[0160] 7a Solid electrolyte layer;

[0161] 7b conductive layer;

[0162] 7c cathode lead layer;

[0163] 8 Sealing resin;

[0164] 9. Resin molded body;

[0165] 9a: a first end surface of the resin molded body;

[0166] 9b a second end surface of the resin molded body;

[0167] 9c: bottom surface of the resin molded body;

[0168] 9d: upper surface of the resin molded body;

[0169] 9e: a first side surface of the resin molded body;

[0170] 9f a second side surface of the resin molded body;

[0171] 11 a first external electrode;

[0172] 11a, 13a inner coating layer;

[0173] 11b, 13b resin electrode layer (printed resin electrode layer);

[0174] 11c, 13c outer coating layer;

[0175] 13 a second external electrode;

[0176] 20 capacitor elements;

[0177] 30 laminates.

Claims

1. An electrolytic capacitor comprising: A rectangular parallelepiped resin molded body comprising a laminate including a capacitor element and a sealing resin that seals the periphery of the laminate, wherein the capacitor element includes an anode having a dielectric layer on its surface and a cathode facing the anode; a first external electrode formed on a first end surface of the resin molded body and electrically connected to the anode exposed from the first end surface; as well as a second external electrode formed on a second end surface of the resin molded body and electrically connected to the cathode exposed from the second end surface; It is characterized in that The first external electrode and the second external electrode are multilayer structures having an inner plating layer and a resin electrode layer, the inner plating layer being formed only near the surface of the anode exposed from the first end surface and near the surface of the cathode exposed from the second end surface, the resin electrode layer being formed on the surface of the inner plating layer and containing a metal and a resin component, the metal containing Ni or a Ni alloy, The inner plating layer is a Ni plating layer, The thickness of the Ni plating layer is 3 μm or more and 10 μm or less, The total number of layers constituting the first external electrode and the second external electrode is four or less.

2. The electrolytic capacitor according to claim 1, in, The resin electrode layer contains 3 wt % or more and 33 wt % or less of the resin component.

3. The electrolytic capacitor according to claim 1 or 2, in, An outer plating layer is also provided on the surface of the resin electrode layer.

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