Electrolytic capacitor and method for manufacturing electrolytic capacitor

Abstract

The electrolytic capacitor (1) comprises: a rectangular parallelepiped resin molded body (9) having a laminate (30) and a sealing resin (8) for sealing the periphery of the laminate (30), the laminate having a capacitor element (20), the capacitor element including an anode (3) having a dielectric layer (5) on its surface and a cathode (7) opposite to the anode (3); a first external electrode (11) provided on a first end face (9a) of the resin molded body (9) and in contact with the anode (20) exposed from the first end face (9a). 3) electrical connection; and a second external electrode (13), which is arranged on the second end face (9b) of the resin molded body (9) and is electrically connected to the cathode (7) exposed from the second end face (9b), and the first external electrode (11) has a first sprayed electrode layer (11a) and a second sprayed electrode layer (11b) in sequence from the first end face (9a) side of the resin molded body (9), and the second sprayed electrode layer is connected to the first sprayed electrode layer (11a) and has a higher porosity than the first sprayed electrode layer (11a).

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor and a method for manufacturing an electrolytic capacitor. Background Art

[0002] An electrolytic capacitor such as a solid electrolytic capacitor can be produced, for example, by forming a dielectric layer on the surface of an anode made of a valve-acting metal and then forming a cathode facing the anode.

[0003] For example, Patent Document 1 discloses a stacked solid electrolytic capacitor in which a plurality of solid electrolytic capacitor units each having a dielectric coating and a solid electrolyte are stacked between a pair of electrodes, the connection ends of each of the pair of electrodes being aligned on one side of the stack and bonded to a facing conductor, and the connection ends of each of the other of the pair of electrodes being aligned on the other side of the stack and bonded to a facing conductor, and at least one of the conductor bonded to each of the one electrodes and the conductor bonded to each of the other electrodes being formed by spraying a conductive material.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 4-188814 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] In the laminated solid electrolytic capacitor described in Patent Document 1, since the conductor to which the electrode of the unit is joined is formed by spraying, the electrode and the conductor are very firmly bonded, and the contact resistance between the electrode and the conductor is low, so the impedance in the high-frequency region becomes low, so that even if the number of units is large and the number of contact points increases, the ESR (equivalent series resistance) does not increase. However, in the laminated solid electrolytic capacitor described in Patent Document 1, it can be said that there is room for further improvement in the following aspects, that is, the structure of the conductor formed by spraying is studied to reduce the ESR.

[0009] The present invention has been made to solve the above-mentioned problems, and its object is to provide an electrolytic capacitor having a low ESR. In addition, the present invention is to provide a method for manufacturing the electrolytic capacitor.

[0010] Technical solutions to solve problems

[0011] The electrolytic capacitor of the present invention is characterized in that it comprises: a rectangular parallelepiped resin molded body having a laminate and a sealing resin for sealing the periphery of the laminate, the laminate having a capacitor element, the capacitor element including an anode having a dielectric layer on the surface and a cathode opposite to the anode; a first external electrode provided on a first end face of the resin molded body and electrically connected to the anode exposed from the first end face; and a second external electrode provided on a second end face of the resin molded body and electrically connected to the cathode exposed from the second end face, the first external electrode having a first sprayed electrode layer and a second sprayed electrode layer in order from the first end face side of the resin molded body, the second sprayed electrode layer being in contact with the first sprayed electrode layer and having a higher porosity than the first sprayed electrode layer.

[0012] The method for manufacturing an electrolytic capacitor of the present invention is characterized by comprising: a step of preparing a rectangular parallelepiped resin molded body, the rectangular parallelepiped resin molded body having a laminated body and a sealing resin for sealing the periphery of the laminated body, the laminated body having a capacitor element, the capacitor element including an anode having a dielectric layer on a surface and a cathode facing the anode; a step of forming a first external electrode on a first end surface of the resin molded body, the first external electrode being electrically connected to the anode exposed from the first end surface; and a step of forming a second external electrode on a second end surface of the resin molded body, the second external electrode being electrically connected to the cathode exposed from the second end surface, wherein in the step of forming the first external electrode, a first sprayed electrode layer and a second sprayed electrode layer are formed in order from the first end surface side by spraying the first end surface of the resin molded body, the second sprayed electrode layer being in contact with the first sprayed electrode layer and having a higher porosity than the first sprayed electrode layer.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide an electrolytic capacitor having a low ESR. In addition, according to the present invention, it is possible to provide a method for manufacturing the electrolytic capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a perspective schematic diagram showing the electrolytic capacitor according to the first embodiment of the present invention.

[0016] Figure 2 It is shown Figure 1 A schematic cross-sectional view of the portion corresponding to the line segment A1 - A2 in FIG.

[0017] Figure 3 It is shown Figure 2 Schematic diagram of an example of the WT surface of the first sprayed electrode layer in.

[0018] Figure 4 It is shown Figure 2 Schematic diagram of an example of the WT surface of the second sprayed electrode layer.

[0019] Figure 5 1 is a schematic cross-sectional view showing an electrolytic capacitor according to Modification 1 of Embodiment 1 of the present invention.

[0020] Figure 6 1 is a schematic cross-sectional view showing an electrolytic capacitor according to a second embodiment of the present invention.

[0021] Figure 7 1 is a schematic cross-sectional view showing an electrolytic capacitor according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0022] The electrolytic capacitor of the present invention and the method for manufacturing the electrolytic capacitor of the present invention are described below. In addition, the present invention is not limited to the following structure, and can also be appropriately changed within the scope of the main purpose of the present invention. In addition, a structure combining multiple preferred structures described below is also the present invention.

[0023] The embodiments shown below are for illustration only. It is self-evident that partial replacement or combination of the structures shown in different embodiments can be performed. After Embodiment 2, the description of matters common to Embodiment 1 is omitted, and the description is mainly based on the differences. In particular, the same effects brought about by the same structure will not be mentioned one by one in each embodiment. In the following description, when the embodiments are not particularly distinguished, they are simply referred to as "electrolytic capacitors of the present invention".

[0024] [Implementation Method 1]

[0025] The electrolytic capacitor of the present invention is characterized in that it comprises: a rectangular parallelepiped resin molded body having a laminate and a sealing resin for sealing the periphery of the laminate, the laminate having a capacitor element, the capacitor element including an anode having a dielectric layer on the surface and a cathode opposite to the anode; a first external electrode provided on a first end face of the resin molded body and electrically connected to the anode exposed from the first end face; and a second external electrode provided on a second end face of the resin molded body and electrically connected to the cathode exposed from the second end face, the first external electrode having a first sprayed electrode layer and a second sprayed electrode layer in order from the first end face side of the resin molded body, the second sprayed electrode layer being in contact with the first sprayed electrode layer and having a higher porosity than the first sprayed electrode layer. In addition, in the electrolytic capacitor of the present invention, the second external electrode may include a first sprayed electrode layer and a second sprayed electrode layer in order from the second end surface side of the resin molded body, the second sprayed electrode layer is in contact with the first sprayed electrode layer, and has a higher porosity than the first sprayed electrode layer. Furthermore, in the electrolytic capacitor of the present invention, the first external electrode and the second external electrode each include an outer plating layer, and the outer plating layer is provided on the surface of the second sprayed electrode layer on the opposite side of the first sprayed electrode layer. Hereinafter, such an example will be described as an electrolytic capacitor according to Embodiment 1 of the present invention.

[0026] Figure 1 1 is a perspective schematic diagram showing an electrolytic capacitor according to Embodiment 1 of the present invention. Figure 1 As shown, the electrolytic capacitor 1 includes a resin molded body 9 , a first external electrode 11 , and a second external electrode 13 .

[0027] In this manual, if Figure 1 As shown in the figures, the length direction, width direction, and thickness direction of the electrolytic capacitor (resin molded body, first external electrode, or second external electrode) are respectively set to directions defined by arrows L, W, and T. Here, the length direction L, the width direction W, and the thickness direction T are orthogonal to each other.

[0028] In this specification, in an electrolytic capacitor (resin molded body, first external electrode, or second external electrode), the surface along the length direction L and the thickness direction T is called an LT surface, the surface along the length direction L and the width direction W is called an LW surface, and the surface along the width direction W and the thickness direction T is called a WT surface.

[0029] The resin molded body 9 is in the shape of a rectangular parallelepiped, having a first end face 9a and a second end face 9b (both WT faces) opposite to each other in the length direction L, a bottom face 9c and an upper surface 9d (both LW faces) opposite to each other in the thickness direction T, and a first side face 9e and a second side face 9f (both LT faces) opposite to each other in the width direction W.

[0030] The first external electrode 11 is provided on the first end surface 9 a of the resin molded body 9 , and extends over a portion of the bottom surface 9 c , the upper surface 9 d , the first side surface 9 e , and the second side surface 9 f .

[0031] The second external electrode 13 is provided on the second end surface 9 b of the resin molded body 9 , and extends over a portion of the bottom surface 9 c , the upper surface 9 d , the first side surface 9 e , and the second side surface 9 f .

[0032] Figure 2 It is shown Figure 1 The cross-sectional view of the portion corresponding to the line segment A1-A2 in FIG. Figure 2 As shown, the resin molded body 9 includes a laminate 30 and a sealing resin 8 that seals the periphery of the laminate 30, and the laminate 30 includes a plurality of capacitor elements 20. The capacitor elements 20 may be bonded to each other via a conductive adhesive.

[0033] Laminated body 30 preferably includes a plurality of capacitor elements 20 , but may also include a single capacitor element 20 .

[0034] Capacitor element 20 includes anode 3 having dielectric layer 5 on its surface and cathode 7 facing anode 3. More specifically, in capacitor element 20, cathode 7 faces anode 3 with dielectric layer 5 interposed therebetween.

[0035] The anode 3 is exposed from the first end surface 9 a of the resin molded body 9 , and is electrically connected to the first external electrode 11 .

[0036] The anode 3 has a valve metal substrate 3a at the center and a porous layer (not shown) on the surface. A dielectric layer 5 is provided on the surface of the porous layer.

[0037] Examples of the valve metal constituting the valve metal substrate 3a include simple metals such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, and silicon, or alloys containing at least one of these metals. Among them, aluminum or an aluminum alloy is particularly preferred.

[0038] The shape of the valve-acting metal substrate 3a is preferably a flat plate, and more preferably a foil.

[0039] The porous layer is preferably an etching layer that has been etched with hydrochloric acid or the like.

[0040] The thickness of the valve metal substrate 3a before etching is preferably 60 μm or more, and preferably 180 μm or less. In the state after etching, the thickness of the core of the valve metal substrate 3a that has not been etched is preferably 10 μm or more, and preferably 70 μm or less. The thickness of the porous layer can be designed according to the withstand voltage and electrostatic capacitance required by the electrolytic capacitor 1. Figure 2 In the LT plane shown, the total thickness of the porous layers provided on both sides of the valve metal substrate 3 a is preferably 10 μm or more and preferably 120 μm or less.

[0041] The dielectric layer 5 is preferably composed of an oxide film of the above-mentioned valve metal. For example, when the valve metal substrate 3a is an aluminum foil, the valve metal substrate 3a is anodized in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts, ammonium salts, etc., to form an oxide film that becomes the dielectric layer 5. The dielectric layer 5 is formed along the surface of the porous layer, so that, as a result, pores (recesses) are provided in the dielectric layer 5.

[0042] The thickness of dielectric layer 5 can be designed according to the withstand voltage, electrostatic capacitance, etc. required for electrolytic capacitor 1, and is preferably 10 nm or more and preferably 100 nm or less.

[0043] The cathode 7 (here, a cathode lead layer 7 c described later) is exposed from the second end surface 9 b of the resin molded body 9 and is electrically connected to the second external electrode 13 .

[0044] Cathode 7 includes solid electrolyte layer 7a disposed on dielectric layer 5, conductive layer 7b disposed on solid electrolyte layer 7a, and cathode lead layer 7c disposed on conductive layer 7b. Electrolytic capacitor 1 includes solid electrolyte layer 7a as part of cathode 7 and can be considered a solid electrolytic capacitor.

[0045] Furthermore, the electrolytic capacitor of the present invention may include an electrolytic solution instead of a solid electrolyte, or may include both a solid electrolyte and an electrolytic solution.

[0046] As the constituent material of the solid electrolyte layer 7a, for example, there can be cited conductive polymers with pyrrole, thiophene, aniline, etc. as the skeleton. As the conductive polymer with thiophene as the skeleton, for example, there can be cited poly (3, 4-ethylenedioxythiophene) (PEDOT), and it can also be PEDOT:PSS compounded with polystyrene sulfonic acid (PSS) as a dopant.

[0047] The solid electrolyte layer 7a 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 5 using a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene, or by 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 5 and then drying it. The solid electrolyte layer 7a is formed in a given area by applying the above-mentioned treatment liquid or dispersion to the surface of the dielectric layer 5 by a method such as sponge transfer, screen printing, spraying, dispenser coating, inkjet printing, etc. In addition, as the solid electrolyte layer 7a, it is preferable to form an outer layer solid electrolyte layer for covering the entire dielectric layer 5 after forming an inner layer solid electrolyte layer for filling the pores (recesses) of the dielectric layer 5.

[0048] The thickness of the solid electrolyte layer 7a is preferably 2 μm or more and preferably 20 μm or less.

[0049] The conductive layer 7 b is provided to electrically and mechanically connect the solid electrolyte layer 7 a and the cathode lead layer 7 c .

[0050] The conductive layer 7b is formed, for example, by applying a conductive paste such as carbon paste, graphene paste, or silver paste to the surface of the solid electrolyte layer 7a by dipping, sponge transfer, screen printing, spraying, dispenser coating, inkjet printing, or the like.

[0051] The conductive layer 7b is preferably a carbon layer, a graphene layer, or a silver layer formed as described above. Alternatively, the conductive layer 7b 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.

[0052] The thickness of the conductive layer 7b is preferably not less than 2 μm and is preferably not more than 20 μm.

[0053] The cathode lead layer 7c is composed of, for example, a metal foil, a printed electrode layer, a coated electrode layer, or the like.

[0054] When the cathode lead layer 7c is a metal foil, the metal foil contains at least one metal selected from the group consisting of aluminum, copper, silver, and an alloy containing at least one of these metals as a main component. If the metal foil contains the above metal, the resistance of the metal foil becomes low, so the ESR of the electrolytic capacitor 1 is likely to be low.

[0055] As the metal foil, a metal foil coated with carbon, titanium, or the like by a film forming method such as sputtering or vapor deposition may be used. Among them, it is particularly preferable to use carbon-coated aluminum foil.

[0056] From the viewpoint of improving workability in the production process, miniaturization, and reducing ESR, the thickness of the metal foil is preferably 20 μm or more and preferably 50 μm or less.

[0057] When the cathode lead layer 7c is a printed electrode layer, the printed electrode layer is formed in a given area by applying an electrode paste to the surface of the conductive layer 7b by a method such as sponge transfer, screen printing, or inkjet printing.

[0058] When the cathode lead layer 7c is a coating electrode layer, the coating electrode layer is formed in a predetermined area by applying an electrode paste to the surface of the conductive layer 7b by dipping, spraying, dispenser coating or the like.

[0059] The electrode paste preferably contains silver, copper, or nickel as a main component.

[0060] The printed electrode layer can be made thinner than the metal foil. For example, when the printed electrode layer is formed by screen printing, the thickness can be made 20 μm or less.

[0061] The cathode lead layer 7c is preferably provided on the conductive layer 7b in a sticky state before the conductive layer 7b is dried.

[0062] The end of the valve-acting metal substrate 3a located on the second end face 9b side of the resin molded body 9 in the capacitor element 20 is sealed by the sealing resin 8. Therefore, the valve-acting metal substrate 3a is not directly in contact with the solid electrolyte layer 7a or the conductive layer 7b. On the other hand, the end of the valve-acting metal substrate 3a located on the second end face 9b side of the resin molded body 9 may be covered by the solid electrolyte layer 7a and the conductive layer 7b in the case of performing an insulation treatment such as being covered by the dielectric layer 5.

[0063] The sealing resin 8 contains at least resin, and preferably contains resin and filler.

[0064] As the resin, epoxy resin, phenol resin, polyimide resin, silicone resin, polyamide resin, liquid crystal polymer, etc. are preferably used.

[0065] As the filler, silica particles, alumina particles, metal particles, etc. are preferably used.

[0066] The sealing resin 8 may be in a solid state or in a liquid state. As the sealing resin 8, it is preferable to use a material containing solid epoxy resin, phenol resin, and silica particles.

[0067] As a molding method of the resin molded body 9, when using a solid sealing resin 8, it is preferable to use resin molding such as compression molding and transfer molding, and compression molding is more preferable. In addition, when using a liquid sealing resin 8, it is preferable to use a molding method such as a dispensing method and a printing method. Among them, it is particularly preferable to seal the periphery of the stacked body 30 with the sealing resin 8 by compression molding to make the resin molded body 9.

[0068] The corners of the resin molded body 9 may also be rounded. As a method for rounding the corners of the resin molded body 9, for example, drum grinding or the like may be used. Since the resin molded body is softer than the ceramic body, it is difficult to round the corners by drum grinding, but by adjusting the specifications of the medium such as the composition, particle size, shape, and the drum processing time, etc., it is possible to make the corners even smaller.

[0069] The first external electrode 11 is provided on the first end surface 9 a of the resin molded body 9 , and is electrically connected to the anode 3 exposed from the first end surface 9 a .

[0070] The first external electrode 11 includes a first sprayed electrode layer 11 a and a second sprayed electrode layer 11 b in this order from the first end surface 9 a side of the resin molded body 9 .

[0071] The first spray-plated electrode layer 11a is provided to cover the entire first end surface 9a of the resin molded body 9. Since the first spray-plated electrode layer 11a is formed by spraying, the body resistance (internal resistance) of the first external electrode 11 becomes low, and when the electrolytic capacitor 1 is mounted on a wiring substrate, the contact resistance between the first external electrode 11 and the electrode of the wiring substrate becomes low. In addition, the adhesion between the first spray-plated electrode layer 11a and the resin molded body 9 is improved, and in particular, the adhesion with the anode 3 is improved, and the contact resistance between the two becomes low. Based on the above, the ESR of the electrolytic capacitor 1 becomes low.

[0072] The second spray-plated electrode layer 11b is in contact with the first spray-plated electrode layer 11a, and has a higher porosity than the first spray-plated electrode layer 11a. That is, the surface area of ​​the second spray-plated electrode layer 11b is larger than the surface area of ​​the first spray-plated electrode layer 11a. Therefore, by providing the second spray-plated electrode layer 11b, the contact area with the outer layer plating layer 11c described later becomes larger, so that the outer layer plating layer 11c becomes easy to adhere to the second spray-plated electrode layer 11b, and the adhesion between the two is improved. Based on the above, the ESR of the electrolytic capacitor 1 becomes lower.

[0073] The second external electrode 13 is provided on the second end surface 9 b of the resin molded body 9 , and is electrically connected to the cathode 7 exposed from the second end surface 9 b .

[0074] The second external electrode 13 includes a first sprayed electrode layer 13 a and a second sprayed electrode layer 13 b in this order from the second end surface 9 b side of the resin molded body 9 .

[0075] The first spray-plated electrode layer 13a is provided to cover the entire second end surface 9b of the resin molded body 9. Since the first spray-plated electrode layer 13a is formed by spraying, the body resistance (internal resistance) of the second external electrode 13 becomes low, and when the electrolytic capacitor 1 is mounted on a wiring substrate, the contact resistance between the second external electrode 13 and the electrode of the wiring substrate becomes low. In addition, the adhesion between the first spray-plated electrode layer 13a and the resin molded body 9 is improved, and in particular, the adhesion with the cathode 7 is improved, and the contact resistance between the two becomes low. Based on the above, the ESR of the electrolytic capacitor 1 becomes low.

[0076] The second spray-plated electrode layer 13b is in contact with the first spray-plated electrode layer 13a, and has a higher porosity than the first spray-plated electrode layer 13a. That is, the surface area of ​​the second spray-plated electrode layer 13b is larger than the surface area of ​​the first spray-plated electrode layer 13a. Therefore, by providing the second spray-plated electrode layer 13b, the contact area with the outer layer plating layer 13c described later becomes larger, so that the outer layer plating layer 13c becomes easy to adhere to the second spray-plated electrode layer 13b, and the adhesion between the two is improved. Based on the above, the ESR of the electrolytic capacitor 1 becomes lower.

[0077] Figure 3 It is shown Figure 2 A schematic diagram of an example of the WT surface of the first sprayed electrode layer in FIG. The first sprayed electrode layer 11a and the first sprayed electrode layer 13a refer to sprayed electrode layers that are continuously arranged in the length direction L in a state in which the porosity in the WT surface is greater than 0% and less than 5%, preferably 0%. In the first sprayed electrode layer 11a and the first sprayed electrode layer 13a, respectively, the porosity in the WT surface may be greater than 0% and less than 5% and the layers are continuously arranged in the length direction L while the porosity changes, or the layers are continuously arranged in the length direction L without changing the porosity. The voids in the first sprayed electrode layer 11a and the first sprayed electrode layer 13a refer to regions where the constituent materials derived from the first sprayed electrode layer 11a and the first sprayed electrode layer 13a do not exist. The porosity in the WT surface of the first sprayed electrode layer 11a and the first sprayed electrode layer 13a refers to the area ratio of the voids relative to the entire first sprayed electrode layer 11a (including the voids) and the entire first sprayed electrode layer 13a (including the voids), respectively, and can be calculated based on the image of the WT surface obtained by CT scanning.

[0078] Figure 4 It is shown Figure 2A schematic diagram of an example of the WT surface of the second sprayed electrode layer in FIG. The second sprayed electrode layer 11b and the second sprayed electrode layer 13b refer to sprayed electrode layers that are continuously arranged in the length direction L in a state in which the porosity in the WT surface is greater than 5% and less than 100%, preferably greater than 30% and less than 90%. In the second sprayed electrode layer 11b and the second sprayed electrode layer 13b, the WT surface may be arranged continuously in the length direction L while the porosity changes in a state in which the porosity is greater than 5% and less than 100%, or may be arranged continuously in the length direction L without changing the porosity. In the second sprayed electrode layer 11b and the second sprayed electrode layer 13b, it is preferred that the porosity in the WT surface increases continuously from the resin molded body 9 side toward the opposite side of the resin molded body 9. The voids 40 of the second sprayed electrode layer 11b and the second sprayed electrode layer 13b refer to regions where the constituent materials of the second sprayed electrode layer 11b and the second sprayed electrode layer 13b do not exist, respectively. The void ratios in the WT surface of the second sprayed electrode layer 11b and the second sprayed electrode layer 13b refer to the area ratios of the voids 40 relative to the entire second sprayed electrode layer 11b (including the voids) and the entire second sprayed electrode layer 13b (including the voids), respectively, and can be calculated based on an image of the WT surface obtained by CT scanning.

[0079] The images of the WT surfaces of the first sprayed electrode layer 11a, the first sprayed electrode layer 13a, the second sprayed electrode layer 11b, and the second sprayed electrode layer 13b are captured using, for example, a CT scanner "inspeXio SMX-225CT" manufactured by Shimadzu Corporation.

[0080] Sprayed electrode layers such as the first sprayed electrode layer 11a, the first sprayed electrode layer 13a, the second sprayed electrode layer 11b, and the second sprayed electrode layer 13b can be distinguished from electrode layers formed by methods other than spraying based on the following information, namely, the outer edge is concave-convex in the image of the WT surface obtained by CT scanning, oxygen (i.e., oxidation) is detected by energy dispersive X-ray analysis (EDX), etc.

[0081] The first sprayed electrode layer 11a and the second sprayed electrode layer 11b preferably contain the same metal as a main component. This reduces the contact resistance between the first sprayed electrode layer 11a and the second sprayed electrode layer 11b, and thus the ESR of the electrolytic capacitor 1 is likely to be reduced.

[0082] The first sprayed electrode layer 11a and the second sprayed electrode layer 11b each preferably contain copper, nickel, or a nickel-aluminum alloy as a main component. Thus, compared with the case where the first sprayed electrode layer 11a contains other metals as a main component, the contact resistance between the first sprayed electrode layer 11a and the anode 3 is likely to be lower, and thus the ESR of the electrolytic capacitor 1 is likely to be lower.

[0083] The first sprayed electrode layer 13a and the second sprayed electrode layer 13b preferably contain the same metal as a main component. This reduces the contact resistance between the first sprayed electrode layer 13a and the second sprayed electrode layer 13b, and thus the ESR of the electrolytic capacitor 1 is likely to be reduced.

[0084] The first sprayed electrode layer 13a and the second sprayed electrode layer 13b each preferably contain copper, nickel, or a nickel-aluminum alloy as a main component. Thus, compared with the case where the first sprayed electrode layer 13a contains other metals as a main component, the contact resistance between the first sprayed electrode layer 13a and the cathode 7 is likely to be lowered, and thus the ESR of the electrolytic capacitor 1 is likely to be lowered.

[0085] The metal as the main component of the first sprayed electrode layer 11a and the second sprayed electrode layer 11b and the metal as the main component of the first sprayed electrode layer 13a and the second sprayed electrode layer 13b may be different, but are preferably the same.

[0086] In this specification, the main component of each layer or each electrode refers to the component with the largest content in each layer or each electrode. The main component of each layer or each electrode can be confirmed by the following method, that is, when using Figure 2 After the LT surface shown is exposed, element analysis such as energy dispersive X-ray analysis is performed.

[0087] The total thickness of the first spray-plated electrode layer 11a and the second spray-plated electrode layer 11b is preferably 40 μm or more and 120 μm or less. This makes it easier to reduce the ESR of the electrolytic capacitor 1. In addition, the adhesion between the first spray-plated electrode layer 11a and the resin molded body 9 is improved, and in particular, the adhesion between the first spray-plated electrode layer 11a and the anode 3 is improved, so that the appearance defects such as peeling and scratching of the first spray-plated electrode layer 11a are reduced.

[0088] The total thickness of the first spray-plated electrode layer 13a and the second spray-plated electrode layer 13b is preferably 40 μm or more and 120 μm or less. This makes it easier to reduce the ESR of the electrolytic capacitor 1. In addition, the adhesion between the first spray-plated electrode layer 13a and the resin molded body 9 is improved, and in particular, the adhesion between the first spray-plated electrode layer 13a and the cathode 7 is improved, so that the appearance defects such as peeling and scratching of the first spray-plated electrode layer 13a are reduced.

[0089] The total thickness of the first sprayed electrode layer 11 a and the second sprayed electrode layer 11 b and the total thickness of the first sprayed electrode layer 13 a and the second sprayed electrode layer 13 b may be different from or the same as each other.

[0090] The first external electrode 11 has an outer plating layer 11c provided on the surface of the second sprayed electrode layer 11b on the opposite side to the first sprayed electrode layer 11a. By providing the outer plating layer 11c, the second sprayed electrode layer 11b having a higher porosity than the first sprayed electrode layer 11a is covered by the relatively dense outer plating layer 11c, so that the ESR of the electrolytic capacitor 1 is easily reduced.

[0091] The outer plating layer 11c and the second sprayed electrode layer 11b preferably contain the same metal as a main component. This reduces the contact resistance between the outer plating layer 11c and the second sprayed electrode layer 11b, and thus the ESR of the electrolytic capacitor 1 is likely to be reduced.

[0092] The outer plating layer 11c preferably contains copper, nickel, or tin as a main component. As a result, the ESR of the electrolytic capacitor 1 is likely to be lowered. Here, the outer plating layer 11c may be a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, it is preferred that the layer in contact with the second sprayed electrode layer 11b among the multiple layers constituting the outer plating layer 11c contains copper, nickel, or tin as a main component.

[0093] When the outer plating layer 11c has a multi-layer structure, the outer plating layer 11c may include a first outer plating layer 11ca and a second outer plating layer 11cb in this order from the second sprayed electrode layer 11b side.

[0094] The first outer plating layer 11ca is preferably a so-called nickel plating layer containing nickel as a main component.

[0095] The second outer plating layer 11cb is preferably a so-called tin plating layer containing tin as a main component.

[0096] The second external electrode 13 has an outer plating layer 13c provided on the surface of the second sprayed electrode layer 13b on the opposite side to the first sprayed electrode layer 13a. By providing the outer plating layer 13c, the second sprayed electrode layer 13b having a higher porosity than the first sprayed electrode layer 13a is covered with the relatively dense outer plating layer 13c, so that the ESR of the electrolytic capacitor 1 is easily reduced.

[0097] The outer plating layer 13c and the second sprayed electrode layer 13b preferably contain the same metal as a main component. This reduces the contact resistance between the outer plating layer 13c and the second sprayed electrode layer 13b, and thus the ESR of the electrolytic capacitor 1 is likely to be reduced.

[0098] The outer plating layer 13c preferably contains copper, nickel, or tin as a main component. As a result, the ESR of the electrolytic capacitor 1 is easily reduced. Here, the outer plating layer 13c may be a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, it is preferred that the layer in contact with the second sprayed electrode layer 13b among the multiple layers constituting the outer plating layer 13c contains copper, nickel, or tin as a main component.

[0099] When the outer plating layer 13c has a multi-layer structure, the outer plating layer 13c may include a first outer plating layer 13ca and a second outer plating layer 13cb in this order from the second sprayed electrode layer 13b side.

[0100] The first outer plating layer 13ca is preferably a so-called nickel plating layer containing nickel as a main component.

[0101] The second outer plating layer 13cb is preferably a so-called tin plating layer containing tin as a main component.

[0102] exist Figure 2 In the LT surface shown, the deviation of the thickness of the first external electrode 11 measured from the first end surface 9a of the resin molded body 9, and the deviation of the thickness of the second external electrode 13 measured from the second end surface 9b of the resin molded body 9 are preferably less than 30 μm, more preferably less than 20 μm, and further preferably less than 5 μm.

[0103] The thickness deviation of the first external electrode 11 can be specified as follows. Figure 2 The thickness of the first external electrode 11 is measured at five locations, namely, the bottom surface, the top surface, and three locations where the bottom surface to the top surface are divided into four equal parts, of the laminate 30, with the LT surface shown in FIG. 1 exposed. Then, the difference between the maximum value and the minimum value obtained from the measured values ​​of the thickness of the first external electrode 11 at these five locations is defined as the deviation of the thickness of the first external electrode 11. Figure 2 Even in the non-destructive state in which the LT surface is exposed as shown, the thickness of the first external electrode 11 can be measured at a plurality of locations using a fluorescent X-ray film thickness meter, a laser displacement meter, or the like.

[0104] The variation in thickness of the second external electrode 13 can also be specified in the same manner as the variation in thickness of the first external electrode 11 .

[0105] Preferred ranges of the dimensions of the electrolytic capacitor 1 are as follows.

[0106] · Dimension in the length direction L: 3.4 mm or more and 3.8 mm or less

[0107] Dimension in width direction W: 2.7 mm or more and 3.0 mm or less

[0108] Dimension in thickness direction T: 1.8 mm or more and 2.0 mm or less

[0109] The method for manufacturing an electrolytic capacitor of the present invention is characterized by comprising: a step of preparing a rectangular parallelepiped resin molded body, the rectangular parallelepiped resin molded body having a laminated body and a sealing resin for sealing the periphery of the laminated body, the laminated body having a capacitor element, the capacitor element including an anode having a dielectric layer on a surface and a cathode facing the anode; a step of forming a first external electrode on a first end surface of the resin molded body, the first external electrode being electrically connected to the anode exposed from the first end surface; and a step of forming a second external electrode on a second end surface of the resin molded body, the second external electrode being electrically connected to the cathode exposed from the second end surface, wherein in the step of forming the first external electrode, a first sprayed electrode layer and a second sprayed electrode layer are formed in order from the first end surface side by spraying the first end surface of the resin molded body, the second sprayed electrode layer being in contact with the first sprayed electrode layer and having a higher porosity than the first sprayed electrode layer. Furthermore, it may also be that in the manufacturing method of the electrolytic capacitor of the present invention, in the process of forming the above-mentioned second external electrode, by performing spraying on the above-mentioned second end face of the above-mentioned resin molded body, a first sprayed electrode layer and a second sprayed electrode layer are formed in sequence from the above-mentioned second end face side, and the above-mentioned second sprayed electrode layer is in contact with the above-mentioned first sprayed electrode layer, and has a higher porosity than the above-mentioned first sprayed electrode layer. Furthermore, it may also be that in the manufacturing method of the electrolytic capacitor of the present invention, in the process of forming the above-mentioned first external electrode and the process of forming the above-mentioned second external electrode, by performing plating treatment after performing the above-mentioned spraying on the above-mentioned first end face and the above-mentioned second end face of the above-mentioned resin molded body, respectively, an outer layer plating layer is formed on the surface of the above-mentioned second sprayed electrode layer on the opposite side of the above-mentioned first sprayed electrode layer. Hereinafter, such an example is taken as the manufacturing method of the electrolytic capacitor of embodiment 1 of the present invention, that is, Figure 1 as well as Figure 2 A method for manufacturing the electrolytic capacitor 1 shown in FIG. 1 will be described.

[0110] <Step of Manufacturing Resin Molded Body>

[0111] First, a valve-acting metal substrate 3a having a porous layer on the surface, that is, an anode 3 is prepared. Then, the surface of the porous layer is anodized to form a dielectric layer 5.

[0112] Next, a solid electrolyte layer 7a is formed on the dielectric layer 5 by screen printing or the like. Then, a conductive layer 7b is formed on the solid electrolyte layer 7a by screen printing or the like. Furthermore, a cathode lead layer 7c is formed on the conductive layer 7b by sheet lamination, screen printing or the like. Thus, a cathode 7 having a solid electrolyte layer 7a, a conductive layer 7b and a cathode lead layer 7c is formed.

[0113] As described above, capacitor element 20 including anode 3 having dielectric layer 5 on its surface and cathode 7 facing anode 3 is manufactured.

[0114] Next, a plurality of capacitor elements 20 are stacked to produce a stacked body 30. The stacked body 30 is then sealed with a sealing resin 8 by compression molding or the like to produce a resin molded body 9. In the resin molded body 9, the anode 3 is exposed from the first end face 9a, and the cathode 7 is exposed from the second end face 9b.

[0115] <Step of Forming the First External Electrode>

[0116] First, a sprayed electrode layer is formed by spraying on the first end face 9a of the resin molded body 9. At this time, for example, by adjusting various conditions of the spraying, as the sprayed electrode layer, a first sprayed electrode layer 11a and a second sprayed electrode layer 11b can be formed in sequence from the first end face 9a side, and the second sprayed electrode layer 11b is in contact with the first sprayed electrode layer 11a and has a higher porosity than the first sprayed electrode layer 11a.

[0117] As the spraying material, for example, copper, nickel, nickel-aluminum alloy (95Ni-5Al, Ni-20Al), phosphor bronze (Cu-9Sn), nickel-chromium alloy (Ni-20Cr), nickel-aluminum-molybdenum alloy (Ni-5Al-5Mo), etc. can be cited. Among them, copper, nickel, or nickel-aluminum alloy is particularly preferred. When copper is used as the spraying material, the porosity of the second sprayed electrode layer 11b is easily increased compared to the case of using nickel.

[0118] Examples of the thermal spraying method include plasma spraying, arc spraying, cold spraying, and aerosol deposition (AD) method. Among them, thermal spraying is industrially useful, and therefore, it is particularly preferable to perform the thermal spraying by plasma spraying.

[0119] In the case of plasma spraying, the first sprayed electrode layer 11a and the second sprayed electrode layer 11b can be formed separately by adjusting various conditions such as the spraying process before spraying, the particle velocity, the working gas temperature, the number of scans (number of paths), etc. For example, the number of scans is set to 2, and in the second scan, the particle velocity is reduced or the gas temperature is reduced compared to the first scan, thereby forming the second sprayed electrode layer 11b having a higher porosity than the first sprayed electrode layer 11a in the second scan.

[0120] Next, after the first end face 9a of the resin molded body 9 is sprayed, a plating treatment such as electrolytic plating is performed to form an outer plating layer 11c on the surface of the second sprayed electrode layer 11b on the opposite side to the first sprayed electrode layer 11a. At this time, as the outer plating layer 11c, the first outer plating layer 11ca and the second outer plating layer 11cb may be formed in order from the second sprayed electrode layer 11b side.

[0121] Based on the above, the first external electrode 11 electrically connected to the anode 3 exposed from the first end face 9a is formed on the first end face 9a of the resin molded body 9. More specifically, the first external electrode 11 having the first sprayed electrode layer 11a, the second sprayed electrode layer 11b, and the outer plating layer 11c in order from the first end face 9a side of the resin molded body 9 is formed.

[0122] In the case where a natural oxide film (passive state) is easily formed on the exposed surface of the anode 3, in the past, when an external electrode is formed on the anode 3, it is necessary to remove the natural oxide film in advance by pretreatment such as zincate treatment. In contrast, if spraying is directly performed on the first end surface 9a of the resin molded body 9 as in the present embodiment, the natural oxide film of the anode 3 can be physically destroyed, thereby directly connecting the anode 3 and the first sprayed electrode layer 11a, so pretreatment such as zincate treatment is not required.

[0123] <Step of Forming the Second External Electrode>

[0124] First, a sprayed electrode layer is formed by spraying on the second end face 9b of the resin molded body 9. At this time, similarly to the process of forming the first external electrode, for example, by adjusting various conditions of the spraying, as the sprayed electrode layer, a first sprayed electrode layer 13a and a second sprayed electrode layer 13b can be formed in sequence from the second end face 9b side, and the second sprayed electrode layer 13b is in contact with the first sprayed electrode layer 13a and has a higher porosity than the first sprayed electrode layer 13a.

[0125] As the spraying material, the same spraying materials as those used to form the first spraying electrode layer 11a and the second spraying electrode layer 11b can be cited. Among them, copper, nickel, or a nickel-aluminum alloy is particularly preferred. When copper is used as the spraying material, the porosity of the second spraying electrode layer 13b is easily increased compared to the case of using nickel.

[0126] As the thermal spraying method, the same thermal spraying method as that used in forming the first thermal spraying electrode layer 11a and the second thermal spraying electrode layer 11b can be used. Among them, thermal spraying is industrially useful, and therefore, it is particularly preferable to perform the thermal spraying by plasma spraying.

[0127] In the case of plasma spraying, the first sprayed electrode layer 13a and the second sprayed electrode layer 13b can be formed separately by adjusting various conditions such as the spraying process before spraying, the particle velocity, the working gas temperature, the number of scans (number of paths), etc. For example, the number of scans is set to 2 times, and in the second scan, the particle velocity is reduced or the gas temperature is reduced compared to the first scan, thereby forming the second sprayed electrode layer 13b having a higher porosity than the first sprayed electrode layer 13a in the second scan.

[0128] Next, after the second end face 9b of the resin molded body 9 is sprayed, a plating treatment such as electrolytic plating is performed to form an outer plating layer 13c on the surface of the second sprayed electrode layer 13b on the opposite side to the first sprayed electrode layer 13a. At this time, as the outer plating layer 13c, the first outer plating layer 13ca and the second outer plating layer 13cb may be formed in order from the second sprayed electrode layer 13b side.

[0129] Based on the above, the second external electrode 13 electrically connected to the cathode 7 exposed from the second end face 9b is formed on the second end face 9b of the resin molded body 9. More specifically, the second external electrode 13 having the first sprayed electrode layer 13a, the second sprayed electrode layer 13b, and the outer plating layer 13c in order from the second end face 9b side of the resin molded body 9 is formed.

[0130] In the case where a natural oxide film is easily formed on the exposed surface of the cathode 7, in the past, when an external electrode is formed on the cathode 7, it is necessary to remove the natural oxide film in advance by pretreatment such as zincate treatment. In contrast, if spraying is directly performed on the second end surface 9b of the resin molded body 9 as in the present embodiment, the natural oxide film of the cathode 7 can be physically destroyed, thereby directly connecting the cathode 7 and the first sprayed electrode layer 13a, so pretreatment such as zincate treatment is not required.

[0131] The step of forming the first external electrode and the step of forming the second external electrode may be performed at different timings or at the same timing. When the two steps are performed at different timings, their order is not particularly limited.

[0132] Based on the above, it can be manufactured Figure 1 as well as Figure 2 The electrolytic capacitor 1 is shown.

[0133] [Variation 1 of Implementation Example 1]

[0134] Alternatively, in the electrolytic capacitor of the first embodiment of the present invention, in each of the first external electrode and the second external electrode, a composite layer of the second sprayed electrode layer and the outer plating layer is provided inside the second sprayed electrode layer. Hereinafter, such an example will be described as an electrolytic capacitor of a modification 1 of the first embodiment of the present invention. The electrolytic capacitor of the modification 1 of the first embodiment of the present invention is the same as the electrolytic capacitor of the first embodiment of the present invention except for the structure of the second sprayed electrode layer.

[0135] Figure 5 FIG. 1 is a schematic cross-sectional view showing an electrolytic capacitor according to a first variation of the first embodiment of the present invention. Figure 5 As shown, in the first external electrode 11 of the electrolytic capacitor 1a, a composite layer 11ba of the second sprayed electrode layer 11b and the outer layer plating layer 11c (here, the first outer layer plating layer 11ca) is provided inside the second sprayed electrode layer 11b. More specifically, the composite layer 11ba is provided in a state where the constituent material derived from the first outer layer plating layer 11ca exists in the gaps of the second sprayed electrode layer 11b. By providing the composite layer 11ba, the second sprayed electrode layer 11b is densified, so that the ESR of the electrolytic capacitor 1a is easily reduced.

[0136] The composite layer 11ba may be provided on a portion of the second sprayed electrode layer 11b or on the entire second sprayed electrode layer 11b. When the composite layer 11ba is provided on a portion of the second sprayed electrode layer 11b, the composite layer 11ba is preferably provided in a region of the second sprayed electrode layer 11b that is in contact with the outer plating layer 11c.

[0137] In the second external electrode 13 of the electrolytic capacitor 1a, a composite layer 13ba of the second sprayed electrode layer 13b and the outer layer plating layer 13c (here, the first outer layer plating layer 13ca) is provided inside the second sprayed electrode layer 13b. More specifically, the composite layer 13ba is provided in a state where the constituent material derived from the first outer layer plating layer 13ca exists in the gaps of the second sprayed electrode layer 13b. By providing the composite layer 13ba, the second sprayed electrode layer 13b is densified, so that the ESR of the electrolytic capacitor 1a is easily reduced.

[0138] The composite layer 13ba may be provided on a portion of the second sprayed electrode layer 13b or on the entire second sprayed electrode layer 13b. When the composite layer 13ba is provided on a portion of the second sprayed electrode layer 13b, the composite layer 13ba is preferably provided in a region of the second sprayed electrode layer 13b that is in contact with the outer plating layer 13c.

[0139] In the method for manufacturing an electrolytic capacitor according to the first modification of the first embodiment of the present invention, that is, Figure 5 In the manufacturing method of the electrolytic capacitor 1a shown in the figure, by increasing the porosity in the WT surface of the second spray-plated electrode layer 11b, preferably to 30% or more and 90% or less, a part of the first outer plating layer 11ca is immersed in the voids of the second spray-plated electrode layer 11b, and a composite layer 11ba is formed. In addition, by increasing the porosity in the WT surface of the second spray-plated electrode layer 13b, preferably to 30% or more and 90% or less, a part of the first outer plating layer 13ca is immersed in the voids of the second spray-plated electrode layer 13b, and a composite layer 13ba is formed.

[0140] [Implementation Method 2]

[0141] Alternatively, in the electrolytic capacitor of the present invention, the first external electrode and the second external electrode each have an inner plating layer, and the inner plating layer is provided between the anode and the first sprayed electrode layer, and between the cathode and the first sprayed electrode layer. Hereinafter, such an example will be described as an electrolytic capacitor according to a second embodiment of the present invention. The electrolytic capacitor according to the second embodiment of the present invention is the same as the electrolytic capacitor according to the first embodiment of the present invention except for the structure of the first external electrode and the second external electrode.

[0142] Figure 6 2 is a schematic cross-sectional view showing an electrolytic capacitor according to Embodiment 2 of the present invention. Figure 6 As shown, the first external electrode 11 of the electrolytic capacitor 2 has an inner plating layer 11d provided between the anode 3 and the first sprayed electrode layer 11a. The inner plating layer 11d is in contact with the anode 3. In addition, the inner plating layer 11d is in contact with the first sprayed electrode layer 11a. In the case where the contact resistance between the anode 3 and the first sprayed electrode layer 11a is high, the inner plating layer 11d is provided, so that the resistance between the anode 3 and the first sprayed electrode layer 11a becomes low, and thus the ESR of the electrolytic capacitor 2 is easily reduced.

[0143] The second external electrode 13 of the electrolytic capacitor 2 has an inner plating layer 13d provided between the cathode 7 and the first sprayed electrode layer 13a. The inner plating layer 13d is in contact with the cathode 7 (here, the cathode lead layer 7c). In addition, the inner plating layer 13d is in contact with the first sprayed electrode layer 13a. In the case where the contact resistance between the cathode 7 and the first sprayed electrode layer 13a is high, the inner plating layer 13d is provided, so that the resistance between the cathode 7 and the first sprayed electrode layer 13a becomes low, and thus the ESR of the electrolytic capacitor 2 is easily reduced.

[0144] It is preferable that each of the inner plating layer 11d and the inner plating layer 13d contains copper, nickel, or silver as a main component. This tends to reduce the ESR of the electrolytic capacitor 2.

[0145] If the inner plating layer 11d and the inner plating layer 13d are each a so-called copper plating layer containing copper as a main component, or a so-called silver plating layer containing silver as a main component, the inner plating layer 11d and the inner plating layer 13d each have a single-layer structure. In the case where the inner plating layer 11d and the inner plating layer 13d are each a single-layer structure of a copper plating layer or a silver plating layer, compared with the case of a two-layer structure of a nickel plating layer and a silver plating layer, the number of interfaces becomes less, and thus the interface resistance becomes lower, so the ESR of the electrolytic capacitor 2 is likely to be lowered. In addition, if the inner plating layer 11d and the inner plating layer 13d are each a copper plating layer or a silver plating layer, the ESR of the electrolytic capacitor 2 is likely to be lowered compared with the case of a nickel plating layer.

[0146] The copper plating layer or the silver plating layer as the inner plating layer 11d is preferably formed by performing a displacement plating treatment by electroless copper plating or electroless silver plating after performing a zincate treatment on the first end surface 9a of the resin molded body 9. The zincate treatment is a treatment for removing oxides on the surface of a metal to be plated and forming a zinc film on the surface of the metal.

[0147] The copper plating layer or silver plating layer as the inner plating layer 13d can also be formed by the same method as the copper plating layer or silver plating layer as the inner plating layer 11d, but zincate treatment is not required. However, when the cathode lead layer 7c of the cathode 7 contains aluminum as a main component, zincate treatment is preferably performed.

[0148] When the inner plating layer 11d and the inner plating layer 13d are each a copper plating layer, the thickness of the copper plating layer is preferably 0.2 μm to 4.0 μm, and more preferably 0.5 μm to 2.0 μm. By setting the thickness of the copper plating layer to be within the above range, a sufficient thickness as the plating layer can be ensured, and the ESR of the electrolytic capacitor 2 is easily reduced.

[0149] When the inner plating layer 11d and the inner plating layer 13d are each a silver plating layer, the thickness of the silver plating layer is preferably 0.1 μm to 2.0 μm, and more preferably 0.2 μm to 1.0 μm. By setting the thickness of the silver plating layer to be within the above range, the ESR of the electrolytic capacitor 2 is easily reduced even if the thickness is relatively small.

[0150] The thickness of the copper plating layer or the silver plating layer as the inner plating layer 11d can be specified as follows. Figure 6 A microscope photograph is taken with the LT surface shown in FIG. 1 exposed, and then a perpendicular line is drawn in the microscope photograph relative to the first end surface 9a of the resin molded body 9. Next, the thickness specified by the size of the perpendicular line is measured for each copper plating layer or silver plating layer provided corresponding to each anode 3. Then, the average value calculated from the measured values ​​of the thickness at least 5 places is specified as the thickness of the copper plating layer or silver plating layer as the inner plating layer 11d.

[0151] The thickness of the copper plating layer or the silver plating layer as the inner plating layer 13d can be specified as follows. Figure 6 A microscope photograph is taken with the LT surface shown in FIG. 1 exposed, and then a perpendicular line is drawn in the microscope photograph relative to the second end surface 9b of the resin molded body 9. Next, the thickness specified by the dimension of the perpendicular line is measured for each copper plating layer or silver plating layer provided corresponding to each cathode 7. Then, the average value calculated from the measured values ​​of the thickness at least 5 places is specified as the thickness of the copper plating layer or silver plating layer as the inner plating layer 13d.

[0152] The inner plating layer 11d may also be formed by performing electroless nickel plating and electrolytic silver plating in sequence after performing zincate treatment on the first end face 9a of the resin molded body 9. In addition, the inner plating layer 13d may also be formed by performing electroless nickel plating and electrolytic silver plating in sequence after performing zincate treatment on the second end face 9b of the resin molded body 9.

[0153] When the anode 3 (here, the valve metal substrate 3a) contains aluminum as a main component and the first sprayed electrode layer 11a and the second sprayed electrode layer 11b of the first external electrode 11 each contain copper as a main component, the first external electrode 11 preferably has an inner plating layer 11d containing silver as a main component provided between the anode 3 and the first sprayed electrode layer 11a. The contact resistance between copper and silver is lower than the contact resistance between copper and aluminum. Therefore, when the first sprayed electrode layer 11a and the second sprayed electrode layer 11b each contain copper as a main component, if the inner plating layer 11d containing silver as a main component is provided between the anode 3 and the first sprayed electrode layer 11a, the ESR of the electrolytic capacitor 2 is easily reduced.

[0154] On the other hand, when the first sprayed electrode layer 11a and the second sprayed electrode layer 11b of the first external electrode 11 each contain nickel or a nickel-aluminum alloy as a main component, it is preferable not to provide an inner plating layer 11d containing silver as a main component. More specifically, when the anode 3 (here, the valve-acting metal substrate 3a) contains aluminum as a main component and the first sprayed electrode layer 11a and the second sprayed electrode layer 11b of the first external electrode 11 each contain nickel or a nickel-aluminum alloy as a main component, it is preferable that the anode 3 and the first sprayed electrode layer 11a are in contact with each other. The contact resistance between nickel or a nickel-aluminum alloy and aluminum is lower than the contact resistance between nickel or a nickel-aluminum alloy and silver. Therefore, when the first sprayed electrode layer 11a and the second sprayed electrode layer 11b each contain nickel or a nickel-aluminum alloy as a main component, it is preferable not to provide an inner plating layer 11d containing silver as a main component. Figure 2 As shown, when the anode 3 and the first sprayed electrode layer 11a are in contact with each other, the ESR of the electrolytic capacitor 1 is likely to be lowered.

[0155] In the first external electrode 11 of the electrolytic capacitor 2, a composite layer 11ba of the second sprayed electrode layer 11b and the outer plating layer 11c (here, the first outer plating layer 11ca) may be provided inside the second sprayed electrode layer 11b, as in the first variant of the first embodiment. In addition, in the second external electrode 13 of the electrolytic capacitor 2, a composite layer 13ba of the second sprayed electrode layer 13b and the outer plating layer 13c (here, the first outer plating layer 13ca) may be provided inside the second sprayed electrode layer 13b, as in the first variant of the first embodiment.

[0156] A method for manufacturing an electrolytic capacitor according to a second embodiment of the present invention, namely, Figure 6 The manufacturing method of the electrolytic capacitor 2 shown in the figure is similar to the method of manufacturing the electrolytic capacitor 2 shown in the figure, except that the inner plating layer 11d and the inner plating layer 13d are formed. Figure 2 The manufacturing method of the electrolytic capacitor 1 shown is the same.

[0157] In the step of forming the first external electrode 11 , the inner plated layer 11 d is formed between the anode 3 and the first sprayed electrode layer 11 a by performing a plating process before spraying the first end surface 9 a of the resin molded body 9 .

[0158] When forming the inner plating layer 11 d , it is preferred that the first end surface 9 a of the resin molded body 9 be subjected to zincate treatment and then subjected to displacement plating treatment using electroless copper plating or electroless silver plating to form a copper plating layer or a silver plating layer.

[0159] For example, when the valve metal substrate 3a of the anode 3 is an aluminum foil, first, the surface of the anode 3 exposed from the first end face 9a of the resin molded body 9 is etched with an acid mainly composed of nitric acid, and then a zinc film is formed on the surface, thereby performing zincate treatment. As zincate treatment, it is preferred to perform both primary zincate treatment (pickling) and secondary zincate treatment (stripping). Then, a copper plating layer or a silver plating layer is formed as the inner plating layer 11d by performing displacement plating treatment based on electroless copper plating or electroless silver plating.

[0160] The plating solution for forming the copper plating layer is preferably a neutral electroless copper plating solution, and the pH is preferably 7.0 to 8.5.

[0161] The plating solution for forming the silver plating layer is preferably a cyanide-containing electroless silver plating solution, and the pH is preferably 8.0 to 9.0.

[0162] Furthermore, the thickness of the copper plating layer or the silver plating layer can be adjusted by adjusting the conditions such as the concentration of the plating solution and the plating time in the electroless copper plating or the electroless silver plating.

[0163] In the step of forming the second external electrode 13, the inner plated layer 13d is formed between the cathode 7 and the first sprayed electrode layer 13a by performing a plating process before spraying the second end surface 9b of the resin molded body 9.

[0164] When a copper plating layer or a silver plating layer is formed as the inner layer plating layer 13 d , it can be formed by the same method and conditions as when a copper plating layer or a silver plating layer is formed as the inner layer plating layer 11 d .

[0165] The inner plating layer 11d may be formed by performing zincate treatment on the first end face 9a of the resin molded body 9, and then performing electroless nickel plating and electrolytic silver plating in sequence, thereby forming a two-layer structure of a nickel plating layer and a silver plating layer. In addition, the inner plating layer 13d may be formed by performing zincate treatment on the second end face 9b of the resin molded body 9, and then performing electroless nickel plating and electrolytic silver plating in sequence, thereby forming a two-layer structure of a nickel plating layer and a silver plating layer.

[0166] Although the outer plating layer is provided in each of the above-mentioned embodiments, the outer plating layer may not be provided. Figure 2 The electrolytic capacitor shown in 1, Figure 5 The electrolytic capacitor 1a shown, or Figure 6The outer plating layer 11c and the outer plating layer 13c may not be provided in the electrolytic capacitor 2 shown. In this case, when the second spray-plated electrode layer 11b and the second spray-plated electrode layer 13b are soldered when mounted on a wiring substrate, the second spray-plated electrode layer 11b and the second spray-plated electrode layer 13b have a high porosity, that is, a large surface area, so the wettability of the solder is improved.

[0167] [Implementation method 3]

[0168] Alternatively, in the electrolytic capacitor of the present invention, the second external electrode has a printed electrode layer, and the printed electrode layer is disposed on the second end face of the resin molded body. Furthermore, in the electrolytic capacitor of the present invention, the first external electrode and the second external electrode each have an outer plating layer, and the outer plating layer is disposed on the surface of the second sprayed electrode layer on the opposite side to the first sprayed electrode layer, and on the surface of the printed electrode layer on the opposite side to the resin molded body. Hereinafter, such an example will be described as an electrolytic capacitor according to embodiment 3 of the present invention. The electrolytic capacitor according to embodiment 3 of the present invention is the same as the electrolytic capacitor according to embodiment 1 of the present invention, except for the structure of the second external electrode.

[0169] Figure 7 1 is a schematic cross-sectional view showing an electrolytic capacitor according to Embodiment 3 of the present invention. Figure 7 As shown, the second external electrode 13 of the electrolytic capacitor 4 includes a printed electrode layer 13 e and an outer plating layer 13 c in this order from the second end surface 9 b side of the resin molded body 9 .

[0170] The printed electrode layer 13 e is provided on the second end surface 9 b of the resin molded body 9 , and is in contact with the cathode 7 (here, the cathode lead layer 7 c ).

[0171] The outer plating layer 13 c is provided on the surface of the printed electrode layer 13 e on the opposite side to the resin molded body 9 .

[0172] The structure of the second external electrode 13 of the electrolytic capacitor 4 is effective when the main component of the cathode lead layer 7c is other than the valve action metal. More specifically, in the second end surface 9b of the resin molded body 9, no natural oxide film is formed on the exposed surface of the cathode lead layer 7c, so the cathode lead layer 7c and the printed electrode layer 13e are directly connected. As a result, the ESR of the electrolytic capacitor 4 is likely to be lowered. In the electrolytic capacitor 4, the main component of the cathode lead layer 7c is preferably silver, copper, nickel, or an alloy containing at least one of these metals.

[0173] In the first external electrode 11 of the electrolytic capacitor 4, as in the first modification of the first embodiment, a composite layer 11ba of the second sprayed electrode layer 11b and an outer plating layer 11c (here, the first outer plating layer 11ca) may be provided inside the second sprayed electrode layer 11b.

[0174] In the first external electrode 11 of the electrolytic capacitor 4, an inner plating layer 11d as in Embodiment 2 may be provided between the anode 3 and the first sprayed electrode layer 11a. In addition, in the second external electrode 13 of the electrolytic capacitor 4, an inner plating layer 13d as in Embodiment 2 may be provided between the cathode 7 and the printed electrode layer 13e.

[0175] A method for manufacturing an electrolytic capacitor according to a third embodiment of the present invention, namely, Figure 7 The method for manufacturing the electrolytic capacitor 4 shown in FIG. 1 is similar to the method for manufacturing the electrolytic capacitor 4 shown in FIG. 1 except that a printed electrode layer 13e is formed instead of the first spray-deposited electrode layer 13a and the second spray-deposited electrode layer 13b. Figure 2 The manufacturing method of the electrolytic capacitor 1 shown is the same.

[0176] In the step of forming the second external electrode 13 , an electrode paste is applied to the second end surface 9 b of the resin molded body 9 by a method such as sponge transfer, screen printing, or inkjet printing, thereby forming a printed electrode layer 13 e .

[0177] The electrode paste used when forming the printed electrode layer 13 e preferably contains silver, copper, or nickel as a main component.

[0178] [Example]

[0179] Hereinafter, examples of the electrolytic capacitor of the present invention will be described in more detail. In the following examples, a solid electrolytic capacitor is described as the electrolytic capacitor of the present invention. In addition, the present invention is not limited to these examples.

[0180] [Example 1]

[0181] The solid electrolytic capacitor of Example 1 was manufactured by the following method.

[0182] <Step of Manufacturing Resin Molded Body>

[0183] The sealing resin containing epoxy resin and silica particles is used to seal the Figure 6 The laminated body having the structure shown was sealed to produce a resin molded body.

[0184] <Step of Forming the First External Electrode and Step of Forming the Second External Electrode>

[0185] First, the first end face and the second end face of the resin molded body were etched with an acid mainly composed of nitric acid, and then zinc films were formed on the end faces, thereby performing zincate treatment. Then, the first end face and the second end face were sequentially subjected to electroless nickel plating and electrolytic silver plating, thereby forming a two-layer structure of a nickel plating layer and a silver plating layer as an inner plating layer.

[0186] Next, a mask is set on the resin molded body so that the first end face and the second end face are exposed, and then plasma spraying is performed to form a sprayed electrode layer covering the inner layer plating layer. Copper is used as a spraying material. At this time, by adjusting various conditions such as the spraying treatment before spraying (alumina spraying treatment), particle velocity, working gas temperature, scanning number (number of paths), etc., the first sprayed electrode layer and the second sprayed electrode layer are formed in sequence from the first end face side and the second end face side, respectively, and the second sprayed electrode layer is connected to the first sprayed electrode layer, and the porosity is higher than that of the first sprayed electrode layer.

[0187] Next, after plasma spraying the first end face and the second end face of the resin molded body, electrolytic nickel plating and electrolytic tin plating are performed in sequence, thereby forming a nickel plating layer as the first outer plating layer and a tin plating layer as the second outer plating layer in sequence on the surface of the second sprayed electrode layer on the opposite side of the first sprayed electrode layer.

[0188] Based on the above, the solid electrolytic capacitor of Example 1 was manufactured.

[0189] In the solid electrolytic capacitor of Example 1, the thickness of the sprayed electrode layer, that is, the total thickness of the first sprayed electrode layer and the second sprayed electrode layer is 15 μm. The thickness of the sprayed electrode layer was measured using a field emission scanning electron microscope "JSM-7100F" manufactured by JEOL Ltd. in a state where the LT surface was exposed by polishing the solid electrolytic capacitor.

[0190] [Examples 2 to 54]

[0191] The solid electrolytic capacitors of Examples 2 to 54 were manufactured in the same manner as the solid electrolytic capacitor of Example 1, except that the specifications were changed to those shown in Tables 1 to 3 regarding the presence or absence of an inner layer plating layer, the sprayed material, and the thickness of the sprayed electrode layer (the total thickness of the first sprayed electrode layer and the second sprayed electrode layer).

[0192] [evaluate]

[0193] The following evaluations were performed on the solid electrolytic capacitors of Examples 1 to 54. The results are shown in Tables 1 to 3.

[0194] <esr>

[0195] The ESR at 100 kHz was measured using an LCR meter "E4980A" manufactured by KEYSIGHT Co., Ltd. The ESR was measured after forming the thermally sprayed electrode layer and after forming the outer plating layer.

[0196] <Tightness>

[0197] The first external electrode and the second external electrode were each subjected to a cross-cut test in accordance with "JIS K 5600-5-6" to evaluate the adhesion between the first external electrode and the anode and the adhesion between the second external electrode and the cathode. The evaluation criteria were as follows, with all the cross-cuts drawn on the first external electrode and the second external electrode as the object.

[0198] ○: All grids were not peeled off.

[0199] △: The number of cells peeling off is more than 0% and less than 5% of the total.

[0200] ×: The number of cells peeling off is greater than 5% of the total.

[0201] [Table 1]

[0202]

[0203] [Table 2]

[0204]

[0205] [Table 3]

[0206]

[0207] As shown in Tables 1 to 3, the solid electrolytic capacitors of Examples 1 to 54 had low ESR and high adhesion.

[0208] When copper is used as a thermal spraying material when forming a thermal spraying electrode layer as in the solid electrolytic capacitors of Examples 1 to 18, the following is found.

[0209] · When the thickness of the thermal sprayed electrode layer is the same, the ESR of the specification "with inner layer plating layer" is lower than that of the specification "without inner layer plating layer".

[0210] Compared with the case where other thermal spraying materials are used, the ESR is likely to decrease after the outer layer plating layer is formed, that is, the difference between the ESR after the thermal spraying electrode layer is formed and the ESR after the outer layer plating layer is formed is likely to become larger.

[0211] When nickel is used as a thermal spraying material when forming a thermal spraying electrode layer as in the solid electrolytic capacitors of Examples 19 to 36, the following is found.

[0212] · When the thickness of the thermal sprayed electrode layer is the same, the ESR of the specification "Inner layer plating: No" is lower than that of the specification "Inner layer plating: Yes".

[0213] When a nickel-aluminum alloy is used as a thermal spraying material when forming a thermal spraying electrode layer as in the solid electrolytic capacitors of Examples 37 to 54, the following is found.

[0214] · When the thickness of the thermal sprayed electrode layer is the same, the ESR of the specification "Inner layer plating: No" is lower than that of the specification "Inner layer plating: Yes".

[0215] Description of Reference Numerals

[0216] 1, 1a, 2, 4: electrolytic capacitors;

[0217] 3: anode;

[0218] 3a: Valve action metal substrate;

[0219] 5: dielectric layer;

[0220] 7: cathode;

[0221] 7a: solid electrolyte layer;

[0222] 7b: conductive layer;

[0223] 7c: cathode lead layer;

[0224] 8: Sealing resin;

[0225] 9: Resin molded body;

[0226] 9a: 1st end surface of the resin molded body;

[0227] 9b: The second end surface of the resin molded body;

[0228] 9c: bottom surface of the resin molded body;

[0229] 9d: upper surface of the resin molded body;

[0230] 9e: The first side surface of the resin molded body;

[0231] 9f: The second side of the resin molded body;

[0232] 11: 1st external electrode;

[0233] 11a, 13a: first sprayed electrode layer;

[0234] 11b, 13b: second sprayed electrode layer;

[0235] 11ba, 13ba: composite layer;

[0236] 11c, 13c: outer plating layer;

[0237] 11ca, 13ca: first outer plating layer;

[0238] 11cb, 13cb: second outer plating layer;

[0239] 11d, 13d: inner plating layer;

[0240] 13: second external electrode;

[0241] 13e: printed electrode layer;

[0242] 20: Capacitor element;

[0243] 30: laminate;

[0244] 40: Gap.< / esr>

Claims

1. An electrolytic capacitor, characterized in that: have: A rectangular parallelepiped resin molded body having a laminate and a sealing resin for sealing the periphery of the laminate, wherein the laminate has a capacitor element including an anode having a dielectric layer on its surface and a cathode facing the anode; a first external electrode disposed 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 provided on the second end surface of the resin molded body and electrically connected to the cathode exposed from the second end surface; The first external electrode includes a first sprayed electrode layer and a second sprayed electrode layer in order from the first end surface side of the resin molded body, the second sprayed electrode layer is in contact with the first sprayed electrode layer and has a higher porosity than the first sprayed electrode layer. The second external electrode includes a first sprayed electrode layer and a second sprayed electrode layer in order from the second end surface side of the resin molded body, the second sprayed electrode layer is in contact with the first sprayed electrode layer and has a higher porosity than the first sprayed electrode layer. The first external electrode and the second external electrode each have an outer plating layer, and the outer plating layer is provided on a surface of the second sprayed electrode layer on the opposite side to the first sprayed electrode layer. In each of the first external electrode and the second external electrode, a composite layer of the second sprayed electrode layer and the outer plating layer is provided inside the second sprayed electrode layer.

2. The electrolytic capacitor according to claim 1, characterized in that: The outer plating layer and the second sprayed electrode layer contain the same metal as a main component.

3. The electrolytic capacitor according to claim 1 or 2, characterized in that: The outer plating layer contains copper, nickel, or tin as a main component.

4. The electrolytic capacitor according to claim 1 or 2, characterized in that: The first external electrode and the second external electrode each have an inner plating layer, and the inner plating layer is provided between the anode and the first sprayed electrode layer, and between the cathode and the first sprayed electrode layer.

5. The electrolytic capacitor according to claim 4, characterized in that: The inner plating layer contains copper, nickel, or silver as a main component.

6. The electrolytic capacitor according to claim 1 or 2, characterized in that: The first sprayed electrode layer and the second sprayed electrode layer contain the same metal as a main component.

7. The electrolytic capacitor according to claim 6, characterized in that: The first sprayed electrode layer and the second sprayed electrode layer each contain copper, nickel, or a nickel-aluminum alloy as a main component.

8. The electrolytic capacitor according to claim 1 or 2, characterized in that: The total thickness of the first sprayed electrode layer and the second sprayed electrode layer is 40 μm or more and 120 μm or less.

9. The electrolytic capacitor according to claim 1, characterized in that: The anode contains aluminum as a main component, The first sprayed electrode layer and the second sprayed electrode layer of the first external electrode each contain copper as a main component. The first external electrode has an inner plating layer provided between the anode and the first sprayed electrode layer and containing silver as a main component.

10. The electrolytic capacitor according to claim 1, characterized in that: The anode contains aluminum as a main component, The first sprayed electrode layer and the second sprayed electrode layer of the first external electrode each contain nickel or a nickel-aluminum alloy as a main component. The anode is in contact with the first sprayed electrode layer.

11. A method for manufacturing an electrolytic capacitor, characterized in that: have: A step of manufacturing a rectangular parallelepiped resin molded body, the rectangular parallelepiped resin molded body having a laminate and a sealing resin for sealing the periphery of the laminate, the laminate having a capacitor element, the capacitor element including an anode having a dielectric layer on a surface and a cathode facing the anode; forming a first external electrode on a first end surface of the resin molded body, the first external electrode being electrically connected to the anode exposed from the first end surface; as well as forming a second external electrode on a second end surface of the resin molded body, the second external electrode being electrically connected to the cathode exposed from the second end surface, In the step of forming the first external electrode, the first end face of the resin molded body is subjected to spraying, thereby forming a first sprayed electrode layer and a second sprayed electrode layer in sequence from the first end face side, the second sprayed electrode layer being in contact with the first sprayed electrode layer and having a higher porosity than the first sprayed electrode layer, In the step of forming the second external electrode, the second end face of the resin molded body is subjected to spraying, thereby forming a first sprayed electrode layer and a second sprayed electrode layer in sequence from the second end face side, the second sprayed electrode layer being in contact with the first sprayed electrode layer and having a higher porosity than the first sprayed electrode layer, In the process of forming the first external electrode and the process of forming the second external electrode, the first end face and the second end face of the resin molded body are respectively subjected to plating treatment after the spraying, thereby forming an outer layer plating layer on the surface of the second sprayed electrode layer on the opposite side of the first sprayed electrode layer, and forming a composite layer of the second sprayed electrode layer and the outer layer plating layer inside the second sprayed electrode layer.

12. The method for manufacturing an electrolytic capacitor according to claim 11, wherein: In the process of forming the first external electrode and the process of forming the second external electrode, inner plating layers are formed between the anode and the first sprayed electrode layer, and between the cathode and the first sprayed electrode layer, respectively, by performing plating treatment on the first end face and the second end face of the resin molded body before the spraying.

13. The method for manufacturing an electrolytic capacitor according to claim 11 or 12, characterized in that: The spraying is performed by plasma spraying.

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