Electrolytic capacitor and its manufacturing method

Abstract

To enhance reliability of an electrolytic capacitor.SOLUTION: An electrolytic capacitor comprises a capacitor element that includes a porous anode body, a dielectric layer formed on a surface of the anode body, a solid electrolyte layer for at least partially coating the dielectric layer, and a carbon layer for at least partially coating the solid electrolyte layer. At least a part of an exposed region, in which at least one of the solid electrolyte layer and the carbon layer is exposed on a surface of the capacitor element, is coated with a resin protective layer including a luminescent material.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Electrolytic capacitors are used in a variety of electronic devices due to their low equivalent series resistance (ESR) and excellent frequency characteristics. An electrolytic capacitor typically includes a capacitor element having an anode portion and a cathode portion. The anode portion includes a porous anode body, and a dielectric layer is formed on the surface of the anode body. The dielectric layer is in contact with the electrolyte. Some electrolytic capacitors use a solid electrolyte such as a conductive polymer as the electrolyte (see, for example, Patent Document 1).

[0003] The capacitor element is usually sealed in an exterior case. In an electrolytic capacitor, the exterior case covers the capacitor element and a portion of the lead terminal electrically connected to the capacitor element. The remaining portion of the lead terminal is exposed from the exterior case and is used for connection to an external terminal.

[0004] If the sealing performance of the exterior packaging is poor, air (oxygen and moisture) may enter the electrolytic capacitor. If the air that has entered the electrolytic capacitor comes into contact with the solid electrolyte layer contained in the capacitor element, the conductive polymer contained in the solid electrolyte layer may deteriorate.

[0005] Furthermore, although not directly related to sealing of the exterior body, Patent Document 2 discloses a capacitor including an anode body, a dielectric layer on the anode body, a solid organic electrolyte layer on the dielectric layer, and a light-reflecting layer on the solid organic electrolyte layer. According to the capacitor described in Patent Document 2, the light-reflecting layer reflects light directed toward the capacitor element during laser welding, thereby suppressing the formation of defects due to carbonization of the solid electrolyte layer, enabling a relatively low ESR and leakage current. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-182157 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-65179 Summary of the Invention [Problem to be solved by the invention]

[0007] To prevent air (oxygen and moisture) from entering the inside of an electrolytic capacitor, it is possible to cover the surface of the capacitor element with a barrier layer that prevents air from entering before sealing it with an exterior body. The barrier layer can be made of a resin material. However, because resin materials are generally transparent, it is difficult to confirm whether the barrier layer has been properly formed in the desired area on the surface of the capacitor element. [Means for solving the problem]

[0008] One aspect of the present disclosure relates to an electrolytic capacitor including a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a carbon layer covering at least a portion of the solid electrolyte layer, wherein at least a portion of an exposed region on the surface of the capacitor element where at least one of the solid electrolyte layer and the carbon layer is exposed is covered with a resin protective layer, and the resin protective layer contains a luminescent material.

[0009] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor, including: preparing a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a carbon layer covering at least a portion of the solid electrolyte layer; electrically connecting the anode body to an anode lead terminal and electrically connecting the carbon layer to a cathode lead terminal; and covering at least a portion of an exposed region on a surface of the capacitor element, where at least one of the solid electrolyte layer and the carbon layer is exposed, with a resin protective layer, wherein the resin protective layer contains a luminescent material. [Effects of the Invention]

[0010] Since it is possible to accurately confirm whether a barrier layer (resin protective layer) is formed in a desired region on the surface of the capacitor element, the reliability of electrolytic capacitors equipped with a solid electrolyte layer is improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of a capacitor element according to an embodiment of the present disclosure. [Figure 2] 1 is a cross-sectional view schematically illustrating an electrolytic capacitor manufactured by a manufacturing method according to an embodiment of the present disclosure. [Figure 3] FIG. 10 is a cross-sectional view schematically illustrating another example of an electrolytic capacitor manufactured by a manufacturing method according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] An electrolytic capacitor according to an embodiment of the present disclosure includes a capacitor element including a porous anode body, a dielectric layer formed on the surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a carbon layer covering at least a portion of the solid electrolyte layer. The capacitor element may further include a conductive resin layer covering at least a portion of the carbon layer. The carbon layer (and the conductive resin layer) constitute a cathode portion of the electrolytic capacitor.

[0013] The surface of the capacitor element has an exposed region that is not covered with a conductive resin layer or the like, and in which at least one of the solid electrolyte layer and the carbon layer is exposed. At least a portion of the exposed region is covered with a resin protective layer. The resin protective layer acts as a barrier layer that prevents air and the like from penetrating into the capacitor element. Covering the exposed region with the resin protective layer prevents air from penetrating through the exposed region. This prevents deterioration of the solid electrolyte layer and improves the reliability of the electrolytic capacitor.

[0014] The resin protective layer contains a luminescent material, which allows accurate confirmation of whether the exposed area is covered with the resin protective layer.

[0015] To check whether the exposed region is covered with the resin protective layer, one possible method is to color the resin protective layer by adding a pigment or the like to the resin protective layer, thereby identifying the region covered with the resin protective layer. However, even when a pigment-containing resin protective layer is used, it is difficult to distinguish the region where the solid electrolyte layer is exposed from the region covered with the resin protective layer based on the difference in color. In addition, heat generated during the manufacturing process (e.g., the process of electrically connecting the anode body to the anode lead terminal) may cause discoloration of the solid electrolyte layer, making it even more difficult to identify the boundary of the region covered with the resin protective layer.

[0016] In contrast, according to one embodiment of the present disclosure, the capacitor element is irradiated with light (excitation light) having a wavelength corresponding to the luminescent material, and the spatial distribution of the luminescence intensity is measured, thereby easily identifying the area covered with the resin protective layer. Therefore, it is possible to accurately confirm whether the desired area of ​​the exposed area is covered with the resin protective layer, making it easy to identify defective products and improving the reliability of the electrolytic capacitor.

[0017] The capacitor element may have an anode wire implanted from an implantation surface, which is one main surface of the anode body. As described above, in the capacitor element, the solid electrolyte layer is covered with a carbon layer. Typically, the carbon layer can be covered with a conductive resin layer (e.g., a silver paste layer). The conductive resin layer has a certain degree of barrier property for preventing the intrusion of air and the like, and can prevent air from infiltrating from the area of ​​the capacitor element covered with the conductive resin layer. However, to avoid contact between the anode wire and the carbon layer or the conductive resin layer and a short circuit, the implantation surface of the anode wire is not covered with the carbon layer or the conductive resin layer, and an exposed area where the solid electrolyte layer is exposed or an exposed area where the carbon layer is exposed may be provided around the anode wire. On the other hand, in a capacitor element having an anode wire, air and the like are likely to infiltrate through the contact area between the anode wire and the anode body, so it is necessary to sufficiently cover the exposed area of ​​the solid electrolyte layer or the carbon layer on the implantation surface with a resin protective layer. According to the electrolytic capacitor according to the embodiment of the present disclosure, it is possible to accurately confirm whether the exposed region of the solid electrolyte layer on the implantation surface is covered with the resin protective layer, thereby improving the reliability of the electrolytic capacitor.

[0018] When a conductive resin layer that covers at least a portion of the carbon layer is provided in the capacitor element, the resin protective layer can cover at least a portion of the exposed area of ​​the surface of the carbon layer that is not covered with the conductive resin layer. The resin protective layer may cover a portion of the conductive resin layer in addition to covering the exposed area.

[0019] The resin protective layer may cover not only the implantation surface of the anode wire, but also a portion of the surface of the capacitor element corresponding to the side surface adjacent to the implantation surface. The resin protective layer may cover the surface of the electrolytic capacitor in a region on the side surface of the anode body adjacent to the implantation surface, where the distance from the implantation surface (including an imaginary plane extending outward from the implantation surface) is 30% or less of the width W of the side surface in the extension direction of the anode wire (i.e., the region from the connection point between the implantation surface and the side surface to a position where the distance to the implantation surface is 30% of the width W). It is sufficient that the exposed region within the region where the distance from the implantation surface is 30% or less of the width W is covered by the resin protective layer.

[0020] The resin component constituting the resin protective layer is not limited, but is preferably a water-repellent resin, and examples thereof include fluorocarbon resins such as (PTFE), polyvinylidene fluoride (PVDF), perfluoroalkoxyalkane (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and vinylidene fluoride-hexafluoropropylene copolymer, silicone, and siloxane compounds, and thermosetting resins containing silicone or siloxane compounds (e.g., epoxy resins) may also be used.

[0021] The light-emitting material contained in the resin protective layer can be, for example, 3',6'-bis(diethylamino)spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one (CI Solvent Red 49). This material absorbs green or yellow light with a wavelength of 480 nm to 580 nm and then emits fluorescent light with a wavelength of 560 nm to 680 nm. Therefore, by observing the luminescent state, the area where the resin protective layer is formed can be visually confirmed. However, the light-emitting material is not limited to the above materials, and any material that absorbs excitation light and induces luminescence can be used. The luminescence mechanism is also not particularly limited. The light-emitting material may be a fluorescent material or a phosphorescent material. Furthermore, the light-emitting material may be an organic material or an inorganic material. Examples of luminescent materials other than those mentioned above include CI Solvent Red 35, CI Solvent Red 36, CI Solvent Red 42, CI Solvent Red 43, CI Solvent Red 44, CI Solvent Red 45, CI Solvent Red 46, CI Solvent Red 47, CI Solvent Red 48, CI Solvent Red 72, CI Solvent Red 73, CI Solvent Red 109, CI Solvent Red 140, CI Solvent Red 141, CI Solvent Red 237, CI Solvent Red 246, CI Solvent Violet 2, and CI Solvent Violet 10.

[0022] The wavelengths of the excitation light and the emitted light of the light-emitting material are not particularly limited. The region where the resin protective layer is formed may be confirmed by photographing the luminescent state and analyzing the photographed image by a computer. In this case, the wavelength of the emitted light is not limited to visible light, but may be infrared light or ultraviolet light.

[0023] The content of the luminescent material in the resin protective layer is preferably within a range of content in which the luminescent intensity changes linearly with changes in the content of the luminescent material (hereinafter also referred to as the "linear region"). When the content of the luminescent material in the resin protective layer is below a predetermined value, the luminescent intensity, when the intensity of the excitation light is constant, increases roughly in proportion to the content as the content of the luminescent material in the resin protective layer increases from zero. On the other hand, when the content of the luminescent material in the resin protective layer exceeds a predetermined value, the luminescent intensity plateaus and begins to decrease. This is thought to be because when the content of the luminescent material is excessive, the excitation light is easily absorbed and converted into collision energy between molecules or energy transfer between excited and unexcited molecules.

[0024] By keeping the content of the luminescent material in the resin protective layer within the linear region, the conversion of the excitation light energy into energy other than luminescence is suppressed, thereby improving the luminescence efficiency. In other words, the luminescent material contained in the resin protective layer can be made to emit light without waste. In addition, in this case, since the luminescence intensity is considered to depend on the film thickness of the resin protective layer, it is possible to measure the variation in the film thickness of the resin protective layer by measuring the distribution of the luminescence intensity in the formation region of the resin protective layer.

[0025] The content of the luminescent material in the resin protective layer is preferably 0.1% by mass or more, from the viewpoints of obtaining sufficient luminescence intensity and making it easy to confirm the area where the resin protective layer is formed. On the other hand, the higher the content of the luminescent material in the resin protective layer, the more difficult it becomes to harden the resin and form the resin protective layer in the desired area. The content of the luminescent material in the resin protective layer is preferably 5% by mass or less, from the viewpoints of keeping the content within the linear range and making it easy to harden the resin protective layer. For these reasons, the content of the luminescent material in the resin protective layer is preferably in the range of 0.1% to 5% by mass.

[0026] The electrolytic capacitor and the method for manufacturing the electrolytic capacitor according to this embodiment will be described below with reference to the accompanying drawings. However, the present invention is not limited thereto. FIG. 1 is a cross-sectional view schematically showing an example of a capacitor element according to this embodiment. FIG. 2 is a cross-sectional view of an electrolytic capacitor manufactured by the manufacturing method according to this embodiment.

[0027] Electrolytic capacitor 20 includes capacitor element 10 having anode portion 6 and cathode portion 7, exterior body 11 that seals capacitor element 10, anode lead terminal 13 electrically connected to anode portion 6 and partially exposed from exterior body 11, and cathode lead terminal 14 electrically connected to cathode portion 7 and partially exposed from exterior body 11. Anode portion 6 includes anode body 1 and anode wire 2. Dielectric layer 3 is formed on the surface of the anode body. Cathode portion 7 includes solid electrolyte layer 4 covering at least a portion of dielectric layer 3, and cathode layer 5 covering at least a portion of the surface of solid electrolyte layer 4.

[0028] <Capacitor element> Hereinafter, capacitor element 10 will be described in detail, taking as an example a case where a solid electrolyte layer is provided as the electrolyte.

[0029] The anode part 6 has an anode body 1 and an anode wire 2 that extends from one surface of the anode body 1 and is electrically connected to an anode lead terminal 13 . The anode body 1 is, for example, a rectangular parallelepiped porous sintered body obtained by sintering metal particles. The metal particles used are particles of a valve metal such as titanium (Ti), tantalum (Ta), or niobium (Nb). The anode body 1 uses one or more types of metal particles. The metal particles may be an alloy made of two or more types of metal. For example, an alloy containing a valve metal and silicon, vanadium, boron, or the like may be used. Alternatively, a compound containing a valve metal and a typical element such as nitrogen may be used. The valve metal alloy contains the valve metal as the main component, for example, at least 50 atomic % of the valve metal.

[0030] The anode wire 2 is made of a conductive material. The material of the anode wire 2 is not particularly limited and includes, for example, copper, aluminum, aluminum alloys, and the like, in addition to the valve metals mentioned above. The anode body 1 and the anode wire 2 may be made of the same or different materials. The anode wire 2 has a first portion 2a that is embedded inside the anode body 1 from one surface of the anode body 1, and a second portion 2b that extends from the above surface of the anode body 1. The cross-sectional shape of the anode wire 2 is not particularly limited and includes, for example, a circle, a track shape (a shape consisting of parallel straight lines and two curved lines connecting the ends of these straight lines), an ellipse, a rectangle, a polygon, and the like.

[0031] The anode part 6 is produced, for example, by embedding the first portion 2a in a powder of particles of the first metal, press-molding the first portion 2a into a rectangular parallelepiped shape, and then sintering the resulting product. This causes the second portion 2b of the anode wire 2 to extend from one surface of the anode body 1 in an upright manner. The second portion 2b is joined to the anode lead terminal 13 by welding or the like, thereby electrically connecting the anode wire 2 and the anode lead terminal 13. The welding method is not particularly limited, and examples include resistance welding and laser welding.

[0032] A dielectric layer 3 is formed on the surface of the anode body 1. The dielectric layer 3 is made of, for example, a metal oxide. Methods for forming a layer containing a metal oxide on the surface of the anode body 1 include, for example, a method of anodizing the surface of the anode body 1 by immersing the anode body 1 in a chemical conversion solution, and a method of heating the anode body 1 in an oxygen-containing atmosphere. The dielectric layer 3 is not limited to the above-mentioned layer containing a metal oxide, and may be any layer that is insulating.

[0033] (cathode) The cathode section 7 has a solid electrolyte layer 4 and a cathode layer 5 that covers the solid electrolyte layer 4. The solid electrolyte layer 4 is formed so as to cover at least a portion of the dielectric layer 3.

[0034] For example, a manganese compound or a conductive polymer is used for the solid electrolyte layer 4. Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene. These may be used alone or in combination. The conductive polymer may also be a copolymer of two or more monomers. In terms of excellent conductivity, polythiophene, polyaniline, and polypyrrole may be used. In particular, in terms of excellent water repellency, polypyrrole may be used.

[0035] The solid electrolyte layer 4 containing the conductive polymer is formed, for example, by polymerizing a raw material monomer on the dielectric layer 3. Alternatively, it is formed by applying a liquid containing the conductive polymer to the dielectric layer 3. The solid electrolyte layer 4 is composed of one or more solid electrolyte layers. When the solid electrolyte layer 4 is composed of two or more layers, the composition and formation method (polymerization method) of the conductive polymer used in each layer may be different.

[0036] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0037] Various dopants may be added to the polymerization solution for forming the conductive polymer, or the solution or dispersion of the conductive polymer in order to improve the conductivity of the conductive polymer. The dopant is not particularly limited, but examples thereof include naphthalenesulfonic acid, p-toluenesulfonic acid, and polystyrenesulfonic acid.

[0038] When the conductive polymer is dispersed in the dispersion medium in the form of particles, the particles have an average particle size D50 of, for example, 0.01 μm or more and 0.5 μm or less. If the average particle size D50 of the particles is within this range, the particles can easily penetrate into the interior of anode body 1.

[0039] The cathode layer 5 has, for example, a carbon layer 5a formed to cover the solid electrolyte layer 4, and a metal paste layer 5b (conductive resin layer) formed on the surface of the carbon layer 5a. The carbon layer 5a contains a conductive carbon material such as graphite and a resin. The metal paste layer 5b contains, for example, metal particles (e.g., silver) and a resin. The configuration of the cathode layer 5 is not limited to this configuration. The configuration of the cathode layer 5 may be any configuration that has a current collecting function.

[0040] (resin protective layer) The resin protective layer 12 covers a portion of the surface of the capacitor element 10. In the example of FIG. 2, the surface of the capacitor element corresponding to the implantation surface of the anode body 1 on which the anode wire 2 is implanted is not covered with the metal paste layer 5b, and an exposed region exists where the solid electrolyte layer 4 or the carbon layer 5a is exposed. The resin protective layer 12 is formed to cover this exposed region. The resin protective layer 12 serves to prevent air and the like from entering the capacitor element through the exposed region (particularly the contact portion between the anode wire and the anode body 1), thereby suppressing deterioration of the conductive polymer that constitutes the solid electrolyte layer. The thickness of the resin protective layer 12 is, for example, in the range of 0.1 μm to 30 μm.

[0041] As shown in FIG. 2, resin protective layer 12 may cover a portion of the surface of the capacitor element corresponding to the side surface adjacent to the implantation surface. The size of the region on the side surface adjacent to the implantation surface where resin protective layer 12 is formed may include, for example, a region whose distance from the implantation surface is 30% or less of the width W of the side surface in the extension direction of the anode wire. It is sufficient that the exposed region within the region whose distance from the implantation surface is 30% or less of the width W is covered with the resin protective layer. For example, the maximum distance d from the implantation surface of the region covered with resin protective layer 12 shown in FIG. 2 may be 30% or more of the width W. On the side surface adjacent to the implantation surface, resin protective layer 12 may be formed so as to cover silver paste layer 5b that covers the exposed region.

[0042] Fig. 3 is a cross-sectional schematic diagram showing another example of an electrolytic capacitor manufactured by the manufacturing method according to this embodiment. Unlike Fig. 2, the electrolytic capacitor 21 shown in Fig. 3 does not entirely cover the side surface adjacent to the implantation surface with the silver paste layer 5b, and there is an exposed area where the carbon layer 5a is exposed on the implantation surface side of the side surface adjacent to the implantation surface. Even in this case, the resin protective layer 12 covers the exposed area of ​​the carbon layer 5a, thereby preventing air and other contaminants from entering the capacitor element through the exposed area of ​​the carbon layer 5a and suppressing deterioration of the solid electrolyte layer.

[0043] <Anode lead terminal> The anode lead terminal 13 is electrically connected to the anode body 1 via the second portion 2b of the anode wire 2. The material of the anode lead terminal 13 is not particularly limited as long as it is electrochemically and chemically stable and conductive. The anode lead terminal 13 may be made of a metal such as copper, or a non-metal. The shape of the anode lead terminal 13 is not particularly limited as long as it is flat. The thickness of the anode lead terminal 13 (the distance between the main surfaces of the anode lead terminal 13) may be 25 μm or more and 200 μm or less, or 25 μm or more and 100 μm or less, from the viewpoint of reducing the height.

[0044] One end of the anode lead terminal 13 may be joined to the anode wire 2 with a conductive adhesive or solder, or may be joined to the anode wire 2 by resistance welding or laser welding. The other end of the anode lead terminal 13 is led out of the exterior body 11 and exposed from the exterior body 11. The conductive adhesive is, for example, a mixture of a thermosetting resin (described later) with carbon particles or metal particles.

[0045] <Cathode lead terminal> Cathode lead terminal 14 is electrically connected to cathode portion 7 at joint portion 14a. Joint portion 14a is a portion of cathode lead terminal 14 that overlaps with cathode layer 5 when cathode layer 5 and cathode lead terminal 14 joined to cathode layer 5 are viewed from the normal direction of cathode layer 5.

[0046] Cathode lead terminal 14 is joined to cathode layer 5 via, for example, conductive adhesive 8. One end of cathode lead terminal 14 constitutes, for example, part of joint portion 14a and is disposed inside exterior body 11. The other end of cathode lead terminal 14 is led out to the outside. Therefore, a part of cathode lead terminal 14, including the other end, is exposed from exterior body 11.

[0047] The material of the cathode lead terminal 14 is not particularly limited as long as it is electrochemically and chemically stable and conductive. The cathode lead terminal 14 may be made of a metal such as copper, or a non-metal. The shape of the cathode lead terminal 14 is also not particularly limited, and may be, for example, a long, flat plate. From the viewpoint of reducing the height, the thickness of the cathode lead terminal 14 may be 25 μm or more and 200 μm or less, or 25 μm or more and 100 μm or less.

[0048] <Exterior body> The exterior body 11 is provided to electrically insulate the anode lead terminal 13 and the cathode lead terminal 14, and is made of an insulating material (exterior body material). The exterior body material includes, for example, a thermosetting resin. Examples of thermosetting resins include epoxy resin, phenol resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane, polyimide, and unsaturated polyester.

[0049] <Manufacturing method of electrolytic capacitors> An example of a method for manufacturing the electrolytic capacitor according to this embodiment will be described below.

[0050] A method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure includes the steps of: preparing a capacitor element including a porous anode body, a dielectric layer formed on the surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a carbon layer covering at least a portion of the solid electrolyte layer; electrically connecting the anode body to an anode lead terminal and electrically connecting the solid electrolyte layer to a cathode lead terminal; and covering at least a portion of an exposed region of the surface of the capacitor element, where at least one of the solid electrolyte layer and the carbon layer is exposed, with a resin protective layer. The resin protective layer contains a luminescent material.

[0051] (1) Capacitor element preparation process First, a capacitor element is prepared. The step of preparing the capacitor element includes, for example, a step of preparing an anode body, a step of covering at least a portion of the anode body with a dielectric layer, a step of covering at least a portion of the dielectric layer with a solid electrolyte layer, and a step of covering at least a portion of the solid electrolyte layer with a carbon layer. The step of preparing the capacitor element may further include a step of covering at least a portion of the carbon layer with a conductive resin layer.

[0052] (1a) Anode body preparation process A porous sintered body can be used as the anode body 1. Valve metal particles and an anode wire 2 are placed in a mold so that the first portion 2a is embedded in the valve metal particles, and then press-molded and sintered to obtain an anode part 6 including the anode body 1, which is a porous body of valve metal. The first portion 2a of the anode wire is embedded inside the porous sintered body from one surface. The pressure used in press-molding is not particularly limited. Sintering is preferably carried out under reduced pressure. A binder such as polyacrylic carbonate may be mixed with the valve metal particles as needed.

[0053] Valve metal particles are usually pressure-molded using a mold having a rectangular parallelepiped internal space, and then sintered. In this case, the shape of the sintered anode body 1 is also rectangular parallelepiped and has multiple main surfaces.

[0054] (1b) Dielectric layer formation process Next, the anode body 1 is subjected to a chemical conversion treatment, and at least a portion of the anode body 1 is covered with a dielectric layer 3. Specifically, the anode body 1 is immersed in a chemical conversion tank filled with an aqueous electrolytic solution (for example, an aqueous phosphoric acid solution), the second portion 2b of the anode wire 2 is connected to the anode body in the chemical conversion tank, and anodization is performed, thereby forming the dielectric layer 3 made of an oxide film of a valve metal on the surface of the porous portion. The aqueous electrolytic solution is not limited to an aqueous phosphoric acid solution, and nitric acid, acetic acid, sulfuric acid, etc. can also be used.

[0055] (1c) Solid electrolyte layer formation process Subsequently, at least a portion of dielectric layer 3 is covered with solid electrolyte layer 4. In this way, capacitor element 10 including anode body 1, dielectric layer 3, and solid electrolyte layer 4 is obtained. Solid electrolyte layer 4 containing a conductive polymer is formed on at least a portion of dielectric layer 3, for example, by impregnating anode body 1 on which dielectric layer 3 has been formed with a monomer or oligomer, and then polymerizing the monomer or oligomer by chemical polymerization or electrolytic polymerization, or by impregnating anode body 1 on which dielectric layer 3 has been formed with a solution or dispersion of a conductive polymer and drying it.

[0056] The solid electrolyte layer 4 can be formed, for example, by immersing the anode body 1 having the dielectric layer 3 formed thereon in a dispersion liquid containing a conductive polymer, a binder, and a dispersion medium, removing the anode body 1, and drying the anode body 1. The dispersion liquid may contain a binder and / or conductive inorganic particles (e.g., a conductive carbon material such as carbon black). The conductive polymer may also contain a dopant. The conductive polymer and the dopant may each be selected from those exemplified for the solid electrolyte layer 4. Known binders can be used. The dispersion liquid may contain known additives used in forming the solid electrolyte layer.

[0057] (1d) Formation process of carbon layer and conductive resin layer Next, a carbon paste and a metal paste are applied in this order to the surface of the solid electrolyte layer 4 to form a cathode layer 5 composed of a carbon layer 5a and a metal paste layer 5b. The configuration of the cathode layer 5 is not limited to this, and any configuration having a current collecting function may be used.

[0058] (2) Electrical connection process between capacitor element and lead terminal Next, an anode lead terminal 13 and a cathode lead terminal 14 are prepared. A second portion 2b of the anode wire 2 extending from the anode body 1 is joined to the anode lead terminal 13 by laser welding, resistance welding, or the like. After applying a conductive adhesive 8 to the cathode layer 5, the cathode lead terminal 14 is joined to the cathode part 7 via the conductive adhesive 8.

[0059] (3) Resin protective layer formation process Next, a predetermined region on the surface of the capacitor element is covered with a resin protective layer 12. The resin protective layer 12 is formed so as to cover at least a portion of an exposed region on the surface of the capacitor element that is not covered with the metal paste layer 5b and in which at least one of the solid electrolyte layer 4 and the carbon layer 5a is exposed (for example, the implantation surface of the anode body 1 in which the anode wire 2 is implanted). The resin protective layer 12 may be formed so as to cover a portion of the metal paste layer 5b in addition to covering the exposed region of the carbon layer 5a.

[0060] (4) Light irradiation process Next, excitation light corresponding to the luminescent material contained in resin protective layer 12 is irradiated. By measuring the intensity of the luminescence from the excitation light, the area on the surface of the capacitor element that is covered with resin protective layer 12 is identified. This confirms whether the exposed area is covered with resin protective layer 12. Since the luminescence intensity is thought to depend on the film thickness of resin protective layer 12, by measuring the distribution of the luminescence intensity on the surface of the capacitor element, the variation in the film thickness of resin protective layer 12 can be measured.

[0061] If no luminescence is observed in the exposed region or the luminescence intensity is less than a predetermined threshold, it is determined that the resin protective layer 12 has not been formed to the desired thickness in the exposed region. If the luminescence intensity in the exposed region is equal to or greater than a predetermined threshold, the sealing process described below is performed.

[0062] The excitation light irradiation step may be performed on the capacitor element before the anode lead terminal 13 and / or the cathode lead terminal 14 are electrically connected. However, if the anode wire 2 is welded to the anode lead terminal 13 of a capacitor element on which the resin protective layer 12 has been formed, there is a risk that the resin protective layer 12 may be deteriorated due to heat generated in the joining step. In order to prevent deterioration of the resin protective layer 12, it is preferable to perform the resin protective layer 12 formation step after the anode lead terminal 13 is electrically connected to the anode body of the capacitor element, and then irradiate the capacitor element with excitation light.

[0063] Next, the capacitor element 10 and the materials for the exterior body 11 (for example, uncured thermosetting resin and filler) are placed in a mold, and the capacitor element 10 is sealed by transfer molding, compression molding, or the like. At this time, anode lead terminal 13 and cathode lead terminal 14 are partially exposed from the mold. The molding conditions are not particularly limited, and the time and temperature conditions may be set appropriately taking into consideration the curing temperature of the thermosetting resin used, etc.

[0064] Finally, the exposed portions of anode lead terminal 13 and cathode lead terminal 14 are bent along package 11 to form bent portions. As a result, a portion of anode lead terminal 13 and a portion of cathode lead terminal 14 are disposed on the mounting surface of package 11. By the above method, the electrolytic capacitor 20 is manufactured. [Industrial Applicability]

[0065] The present invention can be used in electrolytic capacitors, and preferably in electrolytic capacitors that use a porous body as an anode body. [Explanation of symbols]

[0066] 20, 21: Electrolytic capacitors 10: Capacitor element 1: Anode body 2: Anode wire 2a:First part 2b:Second part 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode layer 5a: Carbon layer 5b: Metal paste layer 6: Anode part 7: Cathode 8: Conductive adhesive 11: Exterior body 12: Resin protective layer 13: Anode lead terminal 14: Cathode lead terminal 14a: Joint

Claims

1. preparing a capacitor element including a porous anode body, a dielectric layer formed on a surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a carbon layer covering at least a portion of the solid electrolyte layer; electrically connecting the anode body to an anode lead terminal and electrically connecting the carbon layer to a cathode lead terminal; and covering, with a resin protective layer, at least a portion of an exposed region where at least one of the solid electrolyte layer and the carbon layer is exposed on the surface of the capacitor element, the resin protective layer contains a light-emitting material, the step of covering with the resin protective layer is performed after the step of electrically connecting the anode body to the anode lead terminal.

2. 2. The method for manufacturing an electrolytic capacitor according to claim 1, further comprising, after the step of covering with the resin protective layer, a light irradiation step of irradiating the capacitor element with excitation light corresponding to the luminescent material to identify the region covered with the resin protective layer.

3. The method for manufacturing an electrolytic capacitor according to claim 2 , wherein the light irradiation step measures a distribution of luminescence intensity that depends on the film thickness of the resin protective layer.

4. the capacitor element has an anode wire that is implanted from an implantation surface that is one main surface of the anode body, 4. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the step of covering with a resin protective layer, at least the exposed region of the implanted surface of the anode wire is covered with the resin protective layer.

5. 5. The method for manufacturing an electrolytic capacitor according to claim 1, wherein the content of the luminescent material in the resin protective layer is in a content range in which the luminescent intensity changes linearly with the change in the content of the luminescent material.

6. 6. The method for manufacturing an electrolytic capacitor according to claim 5, wherein the content of the luminescent material in the resin protective layer is in the range of 0.1% by mass to 5% by mass.

7. further comprising a step of covering at least a portion of the carbon layer with a conductive resin layer; 7. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the covering with a resin protective layer, at least a part of a surface of the carbon layer that is not covered with the conductive resin layer is covered with the resin protective layer.

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