Solid electrolytic capacitor element, solid electrolytic capacitor, and solid electrolytic capacitor element manufacturing method

Abstract

A solid electrolytic capacitor element 1 comprising: a valve metal substrate 10 that has a metal substrate layer 11 and a porous layer 12 on the metal substrate layer 11, and has an anode terminal region 13 and a cathode formation region 14; a dielectric layer 20 that is provided on the surface of the porous layer 12 in the cathode formation region 14; a solid electrolyte layer 30 that is provided on the porous layer 12 in the cathode formation region 14 with the dielectric layer 20 therebetween; a conductive layer 40 that is formed on the solid electrolyte layer 30; and a mask 50 that has a first portion 51 and a second portion 52, wherein the first portion 51 separates the anode terminal region 13 and the cathode formation region 14 and is in contact with the porous layer 12 either via the dielectric layer 20 or directly, the second portion 52 covers the solid electrolyte layer 30 provided on the porous layer 12, and the mask 50 does not cover the conductive layer 40.

Description

Solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing solid electrolytic capacitor element

[0001] The present invention relates to a solid electrolytic capacitor element, a solid electrolytic capacitor, and a method for manufacturing a solid electrolytic capacitor element.

[0002] Patent Document 1 describes a solid electrolytic capacitor that includes a capacitor element including an anode foil having a first portion whose surface is etched and a second portion whose surface other than the first portion is not etched, a dielectric layer formed on the surface of the first portion of the anode foil, a solid electrolyte layer formed on the surface of the dielectric layer, and a cathode extraction layer formed on part of the surface of the solid electrolyte layer, wherein a boundary between the first portion and the second portion and the vicinity of the boundary, together with an end of the cathode extraction layer and an end of the solid electrolyte layer, are covered with an insulating protective layer.

[0003] International Publication No. 2017 / 154374

[0004] The solid electrolytic capacitor described in Patent Document 1 can reduce stress near the insulating protective layer, but cannot prevent defects caused by intrusion of conductive paste during cathode extraction layer formation. Specifically, the solid electrolyte layer near the boundary between the first and second portions is thin and prone to defects. If the conductive paste for the cathode extraction layer intrudes into this area, it can lead to leakage current defects and unstable quality. Possible methods to prevent this include highly improving the processing precision of the conductive paste or reducing the area where the conductive paste is applied. However, the former increases equipment costs and management costs, while the latter sacrifices equivalent series resistance (ESR).

[0005] The present invention has been made to solve the above problems, and aims to provide a solid electrolytic capacitor element that can suppress leakage current defects. It is also an object of the present invention to provide a solid electrolytic capacitor including the solid electrolytic capacitor element. It is still another object of the present invention to provide a method for manufacturing a solid electrolytic capacitor element that can realize a solid electrolytic capacitor element that can suppress leakage current defects.

[0006] The solid electrolytic capacitor element of the present invention comprises: a valve action metal substrate having a metal substrate layer and a porous layer on the metal substrate layer, the valve action metal substrate having an anode terminal region and a cathode formation region; a dielectric layer provided on the surface of the porous layer in the cathode formation region; a solid electrolyte layer provided on the porous layer in the cathode formation region with the dielectric layer interposed therebetween; a conductive layer formed on the solid electrolyte layer; and a mask having a first portion and a second portion, wherein the first portion separates the anode terminal region from the cathode formation region and contacts the porous layer directly or via the dielectric layer; the second portion covers the solid electrolyte layer provided on the porous layer; and the mask does not cover the conductive layer.

[0007] The solid electrolytic capacitor of the present invention includes a plurality of solid electrolytic capacitor elements of the present invention.

[0008] The method for manufacturing a solid electrolytic capacitor element of the present invention includes the steps of: forming a first portion of a mask, which separates an anode terminal region and a cathode formation region of the valve metal substrate, on a porous layer of the valve metal substrate, either directly or via a dielectric layer; after forming the first portion, forming a solid electrolyte layer on the porous layer in the cathode formation region, via the dielectric layer; and, after forming the solid electrolyte layer, forming a second portion of the mask to cover the solid electrolyte layer.

[0009] According to the present invention, a solid electrolytic capacitor element capable of suppressing leakage current defects can be provided. Also, according to the present invention, a solid electrolytic capacitor including the solid electrolytic capacitor element can be provided. Furthermore, according to the present invention, a method for manufacturing a solid electrolytic capacitor element capable of realizing a solid electrolytic capacitor element capable of suppressing leakage current defects can be provided.

[0010] FIG. 1 is a plan view schematically illustrating an example of a solid electrolytic capacitor element according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line X-X of the solid electrolytic capacitor element shown in FIG. 1. FIG. 3 is a cross-sectional view enlarging a mask portion of the solid electrolytic capacitor element shown in FIG. 2. FIG. 4 is a cross-sectional view enlarging a mask portion of a solid electrolytic capacitor element having a configuration different from that of the solid electrolytic capacitor element shown in FIG. 2. FIG. 5 is a schematic view illustrating an example of a step of forming a first portion of a mask on a porous layer of a valve metal substrate. FIG. 6 is a schematic view illustrating an example of a step of forming a solid electrolyte layer. FIG. 7 is a schematic view illustrating an example of a step of immersing a valve metal substrate having a first portion of a mask formed thereon in a treatment liquid containing a solid electrolyte. FIG. 8 is a schematic view illustrating an example of a step of forming a second portion of a mask on a solid electrolyte layer. FIG. 9 is a perspective view schematically illustrating an example of a solid electrolytic capacitor according to an embodiment of the present invention. FIG. 10 is a cross-sectional view taken along line A-A of the solid electrolytic capacitor shown in FIG. 9. FIG. 11 is a perspective view schematically illustrating another example of a solid electrolytic capacitor according to an embodiment of the present invention. FIG. 12 is a cross-sectional view taken along line B-B of the solid electrolytic capacitor shown in FIG. 11. FIG. 13 is a perspective view schematically illustrating an example of a first portion of an exterior body, showing a state in which some of the through holes are seen through. FIG. 14 is a plan view schematically illustrating an example of a workpiece. FIG. 15 is a diagram schematically illustrating an example of a process for preparing a stack in which multiple solid electrolytic capacitor elements are stacked on top of each other. FIG. 16 is a diagram schematically illustrating an example of a process for attaching an adhesive sheet to the first portion of the exterior body. FIG. 17 is a diagram schematically illustrating an example of a process for supplying conductive paste onto the adhesive sheet. FIG. 18A is a diagram schematically illustrating an example of a process for inserting the stack into the through holes. FIG. 18B is a diagram schematically illustrating an example of a process for embedding the tip portions of each element in the conductive paste. FIG. 18C is a diagram schematically illustrating an example of a process for filling a liquid material around each element inserted into the through holes. FIG. 19 is a diagram schematically illustrating an example of a process for cutting the first portion of the exterior body around the through holes. FIG. 20 is a graph showing the results of measuring leakage current for the solid electrolytic capacitors of the example and comparative example.

[0011] The solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing a solid electrolytic capacitor element of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual desirable configurations described below also constitutes the present invention.

[0012] [Solid Electrolytic Capacitor Element] Fig. 1 is a plan view schematically showing an example of a solid electrolytic capacitor element according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line X-X of the solid electrolytic capacitor element shown in Fig. 1. Fig. 3 is an enlarged cross-sectional view of the masked portion of the solid electrolytic capacitor element shown in Fig. 2. In Fig. 1, the outer peripheries of the valve metal substrate 10 and solid electrolyte layer 30 covered with the conductive layer 40 are indicated by dashed lines.

[0013] The solid electrolytic capacitor element 1 shown in FIGS. 1 to 3 includes a valve metal substrate 10 having a metal substrate layer 11 and a porous layer 12 on the metal substrate layer 11, and having an anode terminal region 13 and a cathode formation region 14; a dielectric layer 20 (see FIG. 3 , not shown in FIGS. 1 and 2 ) provided on the surface of the porous layer 12 in the cathode formation region 14; a solid electrolyte layer 30 provided on the porous layer 12 in the cathode formation region 14 with the dielectric layer 20 interposed therebetween; a conductive layer 40 formed on the solid electrolyte layer 30; and a mask 50 having a first portion 51 and a second portion 52.

[0014] The first portion 51 separates the anode terminal region 13 from the cathode formation region 14 and contacts the porous layer 12 via the dielectric layer 20, the second portion 52 covers the solid electrolyte layer 30 provided on the porous layer 12, and the mask 50 does not cover the conductive layer 40.

[0015] In this manner, the first portion 51 of the mask 50 separates the anode terminal region 13 from the cathode formation region 14 and contacts the porous layer 12 via the dielectric layer 20. The second portion 52 of the mask 50 covers the solid electrolyte layer 30 provided on the porous layer 12, but the mask 50 does not cover the conductive layer 40. Therefore, the first portion 51 of the mask 50 can be formed first, the solid electrolyte layer 30 can be formed in the cathode formation region 14, the second portion 52 of the mask 50 can be formed, and then the conductive layer 40 can be formed on the solid electrolyte layer 30. Therefore, even if the solid electrolyte layer 30 is thin near the first portion 51 of the mask 50 and a defect occurs, the thin film portion and the defect can be covered and protected by the second portion 52 of the mask 50 before the conductive layer 40 is formed. Therefore, even if the conductive layer 40 is subsequently formed, the conductive layer 40 can be prevented from contacting the valve metal substrate 10 via the dielectric layer 20 at the thin film portion and the defect portion. As a result, leakage current defects caused by such contact can be suppressed.

[0016] 3, from the viewpoint of more effectively suppressing leakage current defects, it is preferable that second portion 52 cover solid electrolyte layer 30 up to a point at least 50 μm (more preferably 100 μm, and even more preferably 300 μm) away from end 51 a of first portion 51 on the cathode formation region 14 side. That is, the width W of second portion 52 when taken from end 51 a of first portion 51 on the cathode formation region 14 side as the starting point is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 300 μm or more.

[0017] From the viewpoint of reducing ESR, it is preferable that second portion 52 does not cover solid electrolyte layer 30 at a point more than 500 μm (more preferably 300 μm, and even more preferably 100 μm) from end 51 a of first portion 51 on the cathode formation region 14 side. That is, the width W of second portion 52 when taken from end 51 a of first portion 51 on the cathode formation region 14 side as the starting point is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 100 μm or less.

[0018] The second portion 52 preferably covers at least a part of the first portion 51. This creates a gap between the first portion 51 and the second portion 52, which exposes a thin film portion or a defect portion of the solid electrolyte layer 30, and prevents the conductive layer 40 from contacting the valve metal base 10 via the dielectric layer 20 at the exposed thin film portion or defect portion. In other words, leakage current defects can be more effectively suppressed.

[0019] 2, the thickness T1 of the solid electrolyte layer 30 in the vicinity of the first portion 51 may be smaller than the thickness T2 of the solid electrolyte layer 30 in the central portion of the solid electrolyte layer 30. In such a case, leakage current defects can be more effectively suppressed as described above.

[0020] In this case, the thickness T1 of the solid electrolyte layer 30 may be smaller than the thickness T2 of the solid electrolyte layer 30 on each main surface of the valve metal substrate 10. Furthermore, the thickness of the solid electrolyte layer 30 may gradually decrease on each main surface of the valve metal substrate 10 from near one end of the valve metal substrate 10 (the end farthest from the mask 50) toward the other end (the first portion 51 of the mask 50).

[0021] 2 shows the case where the first portion 51 and the second portion 52 are provided on each main surface of the valve metal base 10, but it is preferable that the first portion 51 and the second portion 52 are provided on at least one main surface of the valve metal base 10. The valve metal base 10 has a pair of main surfaces facing each other and a plurality of side surfaces (usually four) connecting the pair of main surfaces, and since the area of ​​the pair of main surfaces is large, leakage current defects can be more effectively suppressed by providing the first portion 51 and the second portion 52 on at least one main surface (more preferably each main surface) of the valve metal base 10.

[0022] From the same viewpoint, the first portion 51 and the second portion 52 are preferably provided in an annular shape (e.g., a square ring shape) so as to surround the valve metal base 10. That is, the first portion 51 and the second portion 52 are preferably provided on a pair of main surfaces and a pair of side surfaces of the valve metal base 10.

[0023] Although Figure 3 shows a configuration in which the first portion 51 of the mask 50 is in contact with the porous layer 12 via the dielectric layer 20, the first portion 51 of the mask 50 may be in direct contact with the porous layer 12.

[0024] Fig. 4 is an enlarged cross-sectional view of a mask portion of a solid electrolytic capacitor element having a different configuration from the solid electrolytic capacitor element shown in Fig. 2. Fig. 4 shows a configuration in which a first portion 51 of a mask 50 is in direct contact with a porous layer 12 without a dielectric layer 20 therebetween. The other configurations are the same as those of the mask portion shown in Fig. 3. The effects achieved by providing the mask 50 are the same as those achieved in the solid electrolytic capacitor elements having the configurations shown in Figs. 2 and 3.

[0025] Each component of the solid electrolytic capacitor element 1 will be described in detail below.

[0026] The valve metal substrate 10 is a thin film (foil) having a quadrangular shape in plan view, and preferably has a rectangular shape (strip shape) having a pair of long sides and a pair of short sides in plan view. The valve metal substrate 10 functions as the anode 60 of the solid electrolytic capacitor element 1.

[0027] In this specification, the term "plan view" means a view from the normal direction of the main surface of the valve metal substrate.

[0028] As shown in Figures 3 and 4, the valve metal substrate 10 has a metal substrate layer 11 and a porous layer 12 provided with a plurality of recesses. Therefore, each main surface of the valve metal substrate 10 is porous. This increases the surface area of ​​the valve metal substrate 10. Note that both main surfaces of the valve metal substrate 10 are not limited to being porous (porous layers 12), and only one of the main surfaces of the valve metal substrate 10 may be porous (porous layer 12).

[0029] The metal substrate layer 11 is the core metal portion of the valve metal substrate 10, and as shown in FIG. 2, its thickness is approximately constant.

[0030] The valve metal substrate 10 is made of a valve metal such as an elemental metal such as aluminum, tantalum, niobium, titanium, or zirconium, or an alloy containing these metals. An oxide film can be formed on the surface of the valve metal.

[0031] The valve action metal substrate 10 may be formed of a metal substrate layer and a porous layer provided on at least one of the main surfaces of the metal substrate layer, and may be formed by etching the surface of a metal foil, forming a porous fine powder sintered body on the surface of a metal foil, or the like.

[0032] In this embodiment, the dielectric layer 20 is provided on the surface of the porous layer 12 of the valve metal substrate 10 (see FIG. 3). In the embodiment shown in FIG. 3, the dielectric layer 20 is provided over the entire surface of the valve metal substrate 10 except for one end face 11a of the metal substrate layer 11 (see FIG. 2). In the embodiment shown in FIG. 4, the dielectric layer 20 is provided over the entire surface of the valve metal substrate 10 except for one end face 11a of the metal substrate layer 11 (see FIG. 2) and an area directly below the first portion 51 of the mask 50. However, it is sufficient that the dielectric layer 20 is provided on at least one of the two main surfaces of the valve metal substrate 10 except for at least the end face 11a.

[0033] The dielectric layer 20 is preferably formed of an oxide film provided on the surface of the porous layer 12 of the valve metal substrate 10. For example, the dielectric layer 20 is formed of an aluminum oxide. As will be described later, the aluminum oxide is formed by anodizing the surface of the valve metal substrate.

[0034] The mask 50 is an insulating member provided along one side 10a (preferably a short side) of the valve metal substrate 10, and separates the anode 60 and the cathode 70 of the solid electrolytic capacitor element 1, ensuring insulation between the anode 60 and the cathode 70 of the solid electrolytic capacitor element 1. A first portion 51 of the mask 50 divides the valve metal substrate 10 into an anode terminal region 13 and a cathode formation region 14. The mask 50 is provided linearly (extending in a strip shape) along the side 10a of the valve metal substrate 10.

[0035] Here, the mask 50 (first portion 51) is disposed at a predetermined distance from the edge 10a of the valve metal base 10, but it may also be disposed up to the edge of the edge 10a. In that case, the end face located on the edge 10a of the valve metal base 10 corresponds to the anode terminal region 13. The mask 50 is provided on the pair of main surfaces and the pair of side surfaces of the valve metal base 10 via the dielectric layer 20, but like the dielectric layer 20, it may also be provided on at least one of the pair of main surfaces of the valve metal base 10 (the main surface on which the dielectric layer 20 is provided).

[0036] As described above, the mask 50 has a first portion 51 that contacts the porous layer 12 via the dielectric layer 20, and a second portion 52 that covers the solid electrolyte layer 30 provided on the porous layer 12. The first portion 51 separates the anode terminal region 13 and the cathode formation region 14 and primarily functions as an insulating mask that prevents the solid electrolyte layer 30 from penetrating into the anode terminal region 13, while the second portion 52 primarily functions as a protective mask that covers and protects thin-film portions and defective portions of the solid electrolyte layer 30. The second portion 52 also limits the application area of ​​the conductive layer 40. The second portion 52 covers only a portion of the solid electrolyte layer 30, particularly only a portion of the solid electrolyte layer 30 adjacent to the first portion 51.

[0037] 3 and 4 , the first portion 51 of the mask 50 is preferably provided so as to fill a plurality of pores (recesses) in the valve metal substrate 10 (porous layer 12). However, it is sufficient that the first portion 51 of the mask 50 covers a part of the outer surface of the dielectric layer 20, and there may be pores (recesses) in the porous layer 12 that are not filled with the first portion 51 of the mask 50.

[0038] Furthermore, the first portion 51 of the mask 50 exists continuously from the portion where the pores of the porous layer 12 are filled toward the opposite side of the metal substrate layer 11, and the solid electrolyte layer 30 does not exist between the first portion 51 of the mask 50 and the outermost surface 12a of the porous layer 12 (the surface that appears outermost of the porous layer 12; see the bold dashed lines in Figures 3 and 4 ). However, if a plurality of pores of the porous layer 12 that are not filled with the first portion 51 of the mask 50 are present on the metal substrate layer 11 side, those pores may be filled with the solid electrolyte layer 30.

[0039] 3 and 4 , the second portion 52 of the mask 50 further covers the solid electrolyte layer 30 that covers the outermost surface 12 a of the porous layer 12. That is, the solid electrolyte exists in a layer form between the second portion 52 of the mask 50 and the outermost surface 12 a of the porous layer 12, and the second portion 52 of the mask 50 does not fill the pores (recesses) of the valve metal substrate 10 (porous layer 12).

[0040] The mask 50 (first portion 51 and second portion 52) is made of an insulating material. The mask 50 is formed by applying a mask material such as a composition containing an insulating resin. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.), a composition consisting of soluble polyimide siloxane and epoxy resin, polyimide resin, polyamide-imide resin, and derivatives or precursors thereof.

[0041] The first portion 51 and the second portion 52 of the mask 50 may be made of the same insulating material, or may be made of different insulating materials. In the former case, an interface as shown in Figures 3 and 4 does not need to exist between the first portion 51 and the second portion 52. In this case, too, the portion that contacts the porous layer 12 directly or via the dielectric layer 20 is defined as the first portion 51, and the portion that covers the solid electrolyte layer 30 provided on the porous layer 12 is defined as the second portion 52.

[0042] The mask material can be applied by, for example, screen printing, roller transfer, dispenser, inkjet printing, or the like.

[0043] The solid electrolytic capacitor element 1 has a solid electrolyte layer 30 provided on a dielectric layer 20 and a conductive layer 40 provided on the solid electrolyte layer 30, which function as a cathode 70 of the solid electrolytic capacitor element 1. The cathode 70 is provided on the dielectric layer 20 in a cathode formation region 14 of the valve metal substrate 10 defined by a first portion 51 of a mask 50.

[0044] The solid electrolyte layer 30 is provided on the dielectric layer 20. As shown in Figures 3 and 4, the solid electrolyte layer 30 is preferably provided so as to fill a plurality of pores (recesses) in the valve metal substrate 10 (porous layer 12). However, it is sufficient that the solid electrolyte layer 30 covers a portion of the outer surface of the dielectric layer 20, and there may be pores (recesses) in the porous layer 12 that are not filled with the solid electrolyte layer 30.

[0045] The solid electrolyte layer 30 is provided on the dielectric layer 20 in the cathode forming region 14 of the valve metal substrate 10 defined by the first portion 51 of the mask 50 .

[0046] Examples of materials that can be used to form the solid electrolyte layer 30 include conductive polymers such as polypyrroles, polythiophenes, and polyanilines. Among these, polythiophenes are preferred, and poly(3,4-ethylenedioxythiophene), also known as PEDOT, is particularly preferred. The conductive polymers may also contain dopants such as polystyrene sulfonate (PSS).

[0047] The solid electrolyte layer 30 is formed, for example, by a method of forming a polymerized film of a conductive polymer such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer 20 using a liquid containing a polymerizable monomer such as 3,4-ethylenedioxythiophene, or by a method of applying a dispersion liquid of a conductive polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric layer 20 and drying it.

[0048] It is preferable to form an outer layer that covers the entire dielectric layer 20 after forming an inner layer that fills the pores (recesses) of the valve metal substrate 10. The inner layer can be formed by, for example, a dipping method, electrolytic polymerization, sponge transfer, screen printing, a dispenser, inkjet printing, etc. Similarly, the outer layer can be formed by, for example, a dipping method, electrolytic polymerization, sponge transfer, screen printing, a dispenser, inkjet printing, etc.

[0049] The conductive layer 40 is provided on the solid electrolyte layer 30. The conductive layer 40 covers substantially the entire area of ​​the solid electrolyte layer 30 except for the area covered by the second portion 52 of the mask 50, and is in contact with the second portion 52 of the mask 50. The conductive layer 40 may be disposed so as to cover at least a portion of the second portion 52 of the mask 50, or may be disposed up to the second portion 52 of the mask 50 without contacting the second portion 52 of the mask 50. The conductive layer 40 has a substantially constant thickness.

[0050] The conductive layer 40 includes, for example, a carbon layer or a cathode conductor layer. Alternatively, the conductive layer 40 may be a composite layer in which a cathode conductor layer is provided on the outer surface of a carbon layer, or a mixed layer containing carbon and a cathode conductor layer material.

[0051] The carbon layer is formed, for example, by applying a carbon paste containing carbon particles and resin to the surface of the solid electrolyte layer 30 and drying it.

[0052] The carbon paste can be applied by, for example, a dipping method, sponge transfer, screen printing, spray application, a dispenser, inkjet printing, or the like.

[0053] The cathode conductor layer is formed, for example, by a method of applying a conductive paste containing metal particles such as gold, silver, copper, or platinum and a resin to the surface of the solid electrolyte layer or the carbon layer and drying the paste. The cathode conductor layer is preferably a silver layer.

[0054] The conductive paste can be applied by, for example, a dipping method, sponge transfer, screen printing, spray application, a dispenser, inkjet printing, or the like.

[0055] [Method for Manufacturing Solid Electrolytic Capacitor Element] The following describes a method for manufacturing the solid electrolytic capacitor element 1. In the following example, a method for simultaneously manufacturing a plurality of solid electrolytic capacitor elements using a large valve metal substrate will be described.

[0056] FIG. 5 is a schematic diagram showing an example of a step of forming a first portion of a mask on the porous layer of a valve metal substrate.

[0057] As shown in FIG. 5, a first portion 51 of a mask 50 that defines an anode terminal region 13 and a cathode formation region 14 of the valve metal substrate 10A is formed on the porous layer (not shown) of the valve metal substrate 10A with a dielectric layer (not shown) interposed therebetween.

[0058] More specifically, first, the valve action metal substrate 10A, which has a metal substrate layer (not shown) and a porous layer on the metal substrate layer, is cut by laser processing, punching, or the like, to form a shape including a plurality of element portions 15 and support portions 16. Each element portion 15 is rectangular and protrudes from the support portion 16.

[0059] Next, first portions 51 of the mask 50 are formed on both main surfaces and both side surfaces of each element portion 15 so as to follow the short sides of the element portion 15 .

[0060] The first portion 51 of the mask 50 is formed by applying a mask material such as a composition containing an insulating resin by screen printing, roller transfer, dispenser, inkjet printing, etc. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.), a composition consisting of soluble polyimide siloxane and epoxy resin, polyimide resin, polyamide-imide resin, and derivatives or precursors thereof.

[0061] The valve metal substrate 10A is then anodized to form an oxide film serving as a dielectric layer on the surface of the valve metal substrate 10A (porous layer). During this process, an oxide film is also formed on the side surfaces of the element portions 15 cut by laser processing, punching, or the like. In this process, no dielectric layer is formed on the portion of the surface of the valve metal substrate 10A (porous layer) covered by the first portion 51 of the mask 50. Therefore, the first portion 51 of the mask 50 directly contacts the porous layer without a dielectric layer. A chemically processed foil on which an oxide of the valve metal has already been formed may also be used as the valve metal substrate 10A. In this case, an oxide film is also formed on the side surfaces of the cut element portions 15 by anodizing the valve metal substrate 10A after cutting. When such a chemically processed foil is used as the valve metal substrate 10A, the first portion 51 of the mask 50 contacts the porous layer via the dielectric layer.

[0062] Fig. 6 is a schematic view showing an example of a step of forming a solid electrolyte layer, and Fig. 7 is a schematic view showing an example of a step of immersing the valve metal substrate on which the first portion of the mask has been formed in a treatment liquid containing a solid electrolyte.

[0063] After the first portion 51 is formed, as shown in FIG. 6, the solid electrolyte layer 30 is formed on the porous layer in the cathode formation region 14 via the dielectric layer.

[0064] 7 , the element portion 15 is immersed in a treatment liquid 80 containing a solid electrolyte from the tip side until it contacts the first portion 51 of the mask 50, thereby impregnating the treatment liquid 80 into the porous layer of the valve action metal substrate 10A. The treatment liquid 80 is supplied to a treatment tank 85. After immersion for a predetermined time, the element portion 15 is pulled out of the treatment liquid 80 and dried at a predetermined temperature for a predetermined time. The process of immersion in the treatment liquid 80, pulling out, and drying is repeated a predetermined number of times to form the solid electrolyte layer 30.

[0065] As the treatment liquid 80 containing a solid electrolyte, for example, a dispersion liquid of a conductive polymer such as polypyrroles, polythiophenes, or polyanilines is used. A conductive polymer film can be formed by applying the dispersion liquid of a conductive polymer to the outer surface of the dielectric layer 20 and drying it. Alternatively, a liquid containing a polymerizable monomer, for example, 3,4-ethylenedioxythiophene, and an oxidizing agent may be used as the treatment liquid 80 containing a solid electrolyte. A conductive polymer film can be formed by applying the liquid containing the polymerizable monomer to the outer surface of the dielectric layer 20 and chemically polymerizing it. This conductive polymer film becomes the solid electrolyte layer 30.

[0066] FIG. 8 is a schematic diagram showing an example of a step of forming a second portion of the mask on the solid electrolyte layer.

[0067] 8 , after the solid electrolyte layer 30 is formed, a second portion 52 of a mask 50 is formed to cover the solid electrolyte layer 30. More specifically, the second portion 52 of the mask 50 is formed on both main surfaces and both side surfaces of the element portion 15 so as to follow the first portion 51 of the mask 50.

[0068] By forming the second portion 52 of the mask 50, even if the solid electrolyte layer 30 is thin and defects occur near the first portion 51 of the mask 50, the thin film portion and the defective portion can be covered and protected by the second portion 52 of the mask 50 before the formation of the conductive layer 40. Therefore, the occurrence of leakage current defects as described above can be suppressed.

[0069] The second portion 52 of the mask 50 is formed by applying a mask material such as a composition containing an insulating resin by screen printing, roller transfer, dispenser, inkjet printing, etc. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.), a composition consisting of soluble polyimide siloxane and epoxy resin, polyimide resin, polyamide-imide resin, and derivatives or precursors thereof.

[0070] Thereafter, a carbon paste is applied to the surface of the solid electrolyte layer 30 and dried to form a carbon layer in the cathode formation region 14. For example, the carbon layer is formed by immersing the element portion 15 in the carbon paste, lifting it out, and drying it. In addition to the immersion method, the carbon paste may also be applied by sponge transfer, screen printing, spray application, a dispenser, inkjet printing, or the like. The carbon paste is a conductive paste containing carbon particles as a conductive component and a resin component such as an epoxy resin or a phenolic resin.

[0071] Then, a conductive paste is applied to the surface of the carbon layer and dried to form a cathode conductor layer in the cathode formation region 14. For example, the cathode conductor layer is formed by immersing the element portion 15 in the conductive paste, lifting it out, and drying it. The conductive paste may be applied by sponge transfer, screen printing, spray coating, a dispenser, inkjet printing, or other methods, in addition to the immersion method. Examples of conductive pastes for forming the cathode conductor layer include those containing metal particles as a conductive component and a resin component such as an epoxy resin or a phenolic resin. Examples of metal particles include gold, silver, copper, and platinum. Among these, a silver paste containing silver particles as a conductive component is preferred as the conductive paste for forming the cathode conductor layer.

[0072] Finally, the valve metal substrate 10A is cut to separate the element portions 15, thereby forming strip-shaped valve metal substrates 10A.

[0073] Through the above steps, the solid electrolytic capacitor element 1 is obtained.

[0074] [Solid Electrolytic Capacitor] FIG. 9 is a perspective view schematically showing an example of a solid electrolytic capacitor according to an embodiment of the present invention.

[0075] The solid electrolytic capacitor 100A shown in FIG. 9 has a sealing body 160 formed by sealing a plurality of solid electrolytic capacitor elements 1 with a sealing material, and includes a lead frame 170 connected to the anode of the solid electrolytic capacitor element 1 and a lead frame 180 connected to the cathode of the solid electrolytic capacitor element 1.

[0076] 9 and 10, the length direction (longitudinal direction) of the solid electrolytic capacitor 100A is indicated by L, the width direction by W, and the height direction by T. Here, the length direction L, the width direction W, and the height direction T are perpendicular to one another. The length direction of the solid electrolytic capacitor is also the length direction of the lead frame.

[0077] Fig. 10 is a cross-sectional view taken along line A-A of the solid electrolytic capacitor shown in Fig. 9. The solid electrolytic capacitor 100A shown in Fig. 10 includes the above-described plurality of solid electrolytic capacitor elements 1, a lead frame 170 connected to the valve metal substrate 10 functioning as the anode 60 of the solid electrolytic capacitor elements 1, a lead frame 180 connected to the conductive layer 40 functioning as the cathode 70 of the solid electrolytic capacitor elements 1, and a sealing body 160 formed from a sealing material.

[0078] The sealing body 160 (sealing material) seals the plurality of solid electrolytic capacitor elements 1. The sealing body 160 is formed so as to cover the entirety of each solid electrolytic capacitor element 1, a part of the lead frame 170, and a part of the lead frame 180. Examples of materials for the sealing body 160 (sealing material) include epoxy resin.

[0079] As described above, the solid electrolytic capacitor element 1 includes a valve metal substrate 10, a dielectric layer (not shown), a solid electrolyte layer 30, a conductive layer 40, and a mask 50. The valve metal substrate 10 has a metal substrate layer 11 and a porous layer 12 on the metal substrate layer 11, and has an anode terminal region 13 and a cathode formation region 14. The mask 50 has a first portion 51 that contacts the porous layer 12 directly or via the dielectric layer, and a second portion 52 that covers the solid electrolyte layer 30 provided on the porous layer 12, but does not cover the conductive layer 40.

[0080] On the anode terminal region 13 side, the valve metal substrates 10 of the solid electrolytic capacitor elements 1 are gathered together by a lead frame 170 and drawn out to the outside of the sealing material (sealant 160).

[0081] On the cathode forming region 14 side, the conductive layers 40 of the solid electrolytic capacitor elements 1 are electrically connected, and further electrically connected to the lead frame 180, and are drawn out to the outside of the sealing material (sealant 160).

[0082] Fig. 11 is a perspective view schematically showing another example of the solid electrolytic capacitor according to the embodiment of the present invention, and Fig. 12 is a cross-sectional view taken along line BB of the solid electrolytic capacitor shown in Fig. 11.

[0083] 11 and 12, the length direction (longitudinal direction) of solid electrolytic capacitor 100B and element body 110 is indicated by L, the width direction is indicated by W, and the height direction is indicated by T. Here, the length direction L, the width direction W, and the height direction T are perpendicular to each other.

[0084] 11 and 12 has a substantially rectangular parallelepiped outer shape. The solid electrolytic capacitor 100B includes an element body 110, a first external electrode 130, and a second external electrode 140.

[0085] The element body 110 includes solid electrolytic capacitor elements 1 (hereinafter sometimes simply referred to as "elements 1") and a stack 101 in which a plurality of elements 1 are stacked. The element body 110 further includes an exterior body 120 and a collecting electrode 102. The number of elements 1 included in the stack 101 is not particularly limited as long as it is two or more, and can be set appropriately.

[0086] The element body 110 has a substantially rectangular parallelepiped outer shape. The element body 110 has a first main surface 110a and a second main surface 110b that face each other in a height direction T, a first side surface 110c and a second side surface 110d that face each other in a width direction W, and a first end surface 110e and a second end surface 110f that face each other in a length direction L.

[0087] As described above, the element body 110 has a substantially rectangular parallelepiped outer shape, but the corners and ridges may be rounded. A corner is a portion where three faces of the element body 110 intersect, and a ridge is a portion where two faces of the element body 110 intersect.

[0088] The first external electrode 130 is formed on a first end surface 110 e of the element body 110 , and the second external electrode 140 is formed on a second end surface 110 f of the element body 110 .

[0089] The multiple elements 1 are arranged stacked in the height direction T. The extending direction of each of the multiple elements 1 is substantially parallel to the first main surface 110a and the second main surface 110b of the base body 110. The elements 1 adjacent to each other in the height direction T may be joined to each other via a conductive adhesive (not shown).

[0090] As described above, the solid electrolytic capacitor element 1 includes a valve metal substrate 10, a dielectric layer (not shown), a solid electrolyte layer 30, a conductive layer 40, and a mask 50. The valve metal substrate 10 has a metal substrate layer 11 and a porous layer 12 on the metal substrate layer 11, and has an anode terminal region 13 and a cathode formation region 14. The mask 50 has a first portion 51 that contacts the porous layer 12 directly or via the dielectric layer, and a second portion 52 that covers the solid electrolyte layer 30 provided on the porous layer 12, but does not cover the conductive layer 40.

[0091] 12 , the exterior body 120 encapsulates a plurality of elements 1. That is, a stack 101 of a plurality of elements 1 is embedded in the exterior body 120. The exterior body 120 also encapsulates the collecting electrodes 102. The exterior body 120 has a first portion 121 containing a first resin material and a second portion 122 containing a second resin material.

[0092] The first portion 121 is a tubular structure (e.g., a rectangular tubular structure) having a through hole 123, and houses a plurality of elements 1 (stacked body 101) inside the through hole 123. The second portion 122 is present inside the through hole 123 that houses the plurality of elements 1 (stacked body 101). Note that here, the "rectangular tubular structure" refers to a structure in which the outer peripheral surface of the tubular structure includes four flat surfaces, and any two adjacent surfaces of the four flat surfaces intersect (preferably orthogonal to) each other, and the shape of the through hole 123 is not particularly limited.

[0093] The second portion 122 is filled in the through-hole 123 in which the plurality of elements 1 (superimposed body 101) are housed. That is, the second portion 122 is filled inside the first portion 121 and around the plurality of elements 1 (superimposed body 101). Note that, here, the state in which the second portion 122 is filled in the through-hole 123 in which the plurality of elements 1 (superimposed body 101) are housed may mean that the second portion 122 completely fills the space inside the first portion 121 and around the plurality of elements 1 (superimposed body 101), or may not completely fill it. In the latter case, for example, a small amount of air bubbles may remain in the second portion 122, a small gap may remain between the second portion 122 and the first portion 121, or a small gap may remain between the second portion 122 and at least one element 1.

[0094] The first resin material may be the same as the second resin material, but is preferably a material different from the second resin material.

[0095] The first resin material of the first portion 121 is preferably an injection-moldable resin, specifically, a thermoplastic resin such as PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PBT (polybutylene terephthalate), polyimide, polyamide, etc. The first resin material may contain, as a reinforcing material, a filler such as silica particles, alumina particles, or metal particles, or fibers such as ceramic fibers.

[0096] The second resin material of the second portion 122 is preferably a thermosetting resin such as an epoxy resin, a silicone resin, or a urethane resin. The second resin material may contain, as a reinforcing material, a filler such as silica particles, alumina particles, or metal particles, or fibers such as ceramic fibers.

[0097] 12 , the collecting electrode 102 is electrically connected to the plurality of cathodes 70 of the plurality of elements 1. The collecting electrode 102 is exposed at the first end face 110e of the element body 110, and is provided at least on the first end face 110e side of the element body 110. The collecting electrode 102 is formed in a shape with a certain thickness at a position recessed from the first end face 110e.

[0098] As shown in FIG. 12 , at least the portion of each cathode 70 on the first external electrode 130 side is embedded in the collecting electrode 102, thereby ensuring electrical connection between each cathode 70 and the collecting electrode 102.

[0099] The collecting electrode 102 is a composite material of a conductive component (conductive material) and a resin component (resin material). The conductive component preferably contains, as a main component, a metal such as silver, copper, nickel, or tin, or an alloy containing at least one of these metals. The resin component preferably contains, as a main component, an epoxy resin, a phenolic resin, or the like. The collecting electrode 102 can be formed using, for example, a conductive paste such as silver paste.

[0100] As shown in Fig. 12 , the first external electrode 130 is provided on the first end surface 110e of the element body 110. In Fig. 11 , the first external electrode 130 is provided from the first end surface 110e of the element body 110 to each of the first main surface 110a, the second main surface 110b, the first side surface 110c, and the second side surface 110d. The first external electrode 130 is electrically connected to the collecting electrode 102 exposed from the element body 110 at the first end surface 110e. That is, the first external electrode 130 is electrically connected to each cathode 70 via the collecting electrode 102.

[0101] Furthermore, the collecting electrode 102 is present in the through-hole 123 that houses the multiple elements 1 (superimposed body 101), and the collecting electrode 102 and the first portion 121 of the exterior body 120 form the first end surface 110e of the element body 110, so the first external electrode 130 can be formed on this first end surface 110e. This makes it easy to electrically connect the first external electrode 130 and the collecting electrode 102, and also makes it possible to form the first external electrode 130 with a small thickness.

[0102] Specifically, the first external electrode 130 may have a so-called sputtered film formed by sputtering. Examples of materials for the sputtered film include Ni, Sn, Ag, Cu, and Ag.

[0103] The first external electrode 130 may also have a so-called vapor-deposited film formed by vapor deposition, for example, Ni, Sn, Ag, Cu, or the like.

[0104] In this way, since the first external electrode 130 can be formed from a sputtered film and / or a vapor-deposited film, the film thickness of the first external electrode 130 may be thinner than the film thickness of the second external electrode 140. Specifically, the film thickness of the first external electrode 130 is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and even more preferably 10 μm or more and 30 μm or less.

[0105] As shown in Fig. 12, the second external electrode 140 is provided on the second end surface 110f of the element body 110. In Fig. 11, the second external electrode 140 is provided from the second end surface 110f of the element body 110 to each of the first main surface 110a, the second main surface 110b, the first side surface 110c, and the second side surface 110d. The second external electrode 140 is electrically connected to the anode 60 of the element 1 exposed from the element body 110 at the second end surface 110f. The second external electrode 140 may be directly or indirectly connected to the anode 60 at the second end surface 110f of the element body 110.

[0106] At least one of the first external electrode 130 and the second external electrode 140 may have a resin electrode layer containing a conductive component and a resin component. The conductive component preferably contains, as a main component, a metal such as silver, copper, nickel, or tin, or an alloy containing at least one of these metals. The resin component preferably contains, as a main component, an epoxy resin, a phenolic resin, or the like. The resin electrode layer can be formed using, for example, a conductive paste such as silver paste.

[0107] At least one of the first external electrode 130 and the second external electrode 140 may have a so-called plating layer formed by a plating method. Examples of the plating layer include a zinc-silver-nickel layer, a silver-nickel layer, a nickel layer, a zinc-nickel-gold layer, a nickel-gold layer, a zinc-nickel-copper layer, and a nickel-copper layer. On these plating layers, for example, a copper plating layer, a nickel plating layer, and a tin plating layer are preferably provided in this order (or with the exception of some plating layers).

[0108] At least one of the first external electrode 130 and the second external electrode 140 may have both a resin electrode layer and a plating layer. For example, the first external electrode 130 may have a resin electrode layer connected to the collecting electrode 102 and an outer plating layer provided on the surface of the resin electrode layer. The first external electrode 130 may also have an inner plating layer connected to the collecting electrode 102, a resin electrode layer provided so as to cover the inner plating layer, and an outer plating layer provided on the surface of the resin electrode layer. The second external electrode 140 may also have a resin electrode layer connected to the anode 60 and an outer plating layer provided on the surface of the resin electrode layer. The second external electrode 140 may also have an inner plating layer connected to the anode 60, a resin electrode layer provided so as to cover the inner plating layer, and an outer plating layer provided on the surface of the resin electrode layer.

[0109] [Method for manufacturing solid electrolytic capacitor] The solid electrolytic capacitor 100A shown in Figures 9 and 10 can be manufactured, for example, by connecting lead frames 170 and 180 to multiple solid electrolytic capacitor elements 1, and then sealing the periphery of the multiple solid electrolytic capacitor elements 1 with a sealing material using a resin mold such as compression molding or transfer molding to form the sealed body 160.

[0110] 11 and 12 can be manufactured by the following method. In the following example, a method for simultaneously manufacturing a plurality of solid electrolytic capacitor elements using a large valve metal substrate will be described.

[0111] FIG. 13 is a perspective view schematically illustrating an example of the first part of the exterior body, showing some through-holes in a see-through state.

[0112] First, as shown in FIG. 13 , a first portion 221 of an exterior body 220 (a component that will become the first portion 121 of the exterior body 120) containing the first resin material and having a plurality of through holes 223 is prepared. The first portion 221 is a flat plate having a predetermined thickness and a rectangular shape in a plan view, with a plurality of through holes 223 formed vertically and horizontally. Each through hole 223 is formed in a direction perpendicular to the main surface of the first portion 221, and both ends are open. The first portion 221 can be produced by injection molding. The first resin material used for the first portion 221 is preferably an injection-moldable resin, specifically, a thermoplastic resin such as PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PBT (polybutylene terephthalate), polyimide, or polyamide. The first resin material may contain a filler such as silica particles, alumina particles, or metal particles, or a fiber such as ceramic fiber, as a reinforcing material. The inner corners of each through-hole 223 of the first portion 221 may be rounded or corner-processed (formed into an inclined surface).

[0113] Next, the stack 101 is prepared.

[0114] FIG. 14 is a plan view schematically illustrating an example of a workpiece.

[0115] 14, a workpiece 210 is prepared in which element portions 212 (plurality of solid electrolytic capacitor elements 1) are connected in strips at regular intervals to a band-shaped holding portion 211. A mask 50 is formed on each element portion 212. The workpiece 210 can be produced by the method described above in the method for producing a solid electrolytic capacitor element.

[0116] Here, the first portion 221 has substantially rectangular parallelepiped through holes 223 formed in the same number and at the same pitch as the elements 1 of the strip-shaped workpiece 210, and has a plurality of rows of such through holes 223.

[0117] FIG. 15 is a diagram schematically illustrating an example of a process for preparing a stack in which a plurality of solid electrolytic capacitor elements are stacked on top of each other.

[0118] Next, as shown in Fig. 15, a plurality of workpieces 210 each having a plurality of elements 1 formed in a strip shape are prepared, and a predetermined number of workpieces 210 are bundled together so that the plurality of elements 1 overlap each other and fixed with a jig such as a clamp (not shown). This creates a plurality of stacks 101 in which the plurality of elements 1 overlap each other. The plurality of stacks 101 are arranged in a row (a row aligned perpendicular to the plane of Fig. 15).

[0119] FIG. 16 is a diagram schematically illustrating an example of a step of attaching an adhesive sheet to the first portion of the exterior body.

[0120] 16 , an adhesive sheet 250 (hereinafter sometimes simply referred to as “sheet 250”) is attached to the first portion 221 so as to close the first openings 223a of each through-hole 223. That is, the adhesive sheet 250 is attached to the entire surface of one side of the first portion 221 so as to close one side of each through-hole 223. This makes it possible to easily expose the collecting electrode 102 at the first end surface 110e of the element body 110 by peeling off the sheet 250 after sealing.

[0121] In addition, it is sufficient for each through hole 223 that the first opening 223a (lower opening) is covered, and instead of attaching the adhesive sheet 250, the first opening 223a may be covered, for example, by placing the first part 221 on a flat table.

[0122] FIG. 17 is a diagram schematically illustrating an example of a step of supplying a conductive paste onto an adhesive sheet.

[0123] Next, as shown in FIG. 17 , with the first opening 223a of each through hole 223 covered with an adhesive sheet 250, conductive paste 230 is supplied onto the sheet 250 through the second opening 223b (upper opening) of each through hole 223. As a result, the conductive paste 230 is applied onto the sheet 250 within each through hole 223. Examples of conductive paste 230 include those containing metal particles as a conductive component and a resin component such as epoxy resin or phenolic resin. Examples of metal particles include silver, copper, nickel, and tin. Of these, silver paste containing silver particles as a conductive component is preferred as the conductive paste 230. Furthermore, the conductive paste 230 can be supplied using, for example, a dispenser.

[0124] 18A is a diagram schematically illustrating an example of a process for inserting a stack into a through-hole, FIG. 18B is a diagram schematically illustrating an example of a process for embedding the tip of each element in a conductive paste, and FIG. 18C is a diagram schematically illustrating an example of a process for filling a liquid material around each element inserted into a through-hole.

[0125] Next, as shown in FIG. 18A, the fixed plurality of workpieces 210 are moved relative to the first portion 221, and the stack 101 is inserted into the through-holes 223 in the same row from the second openings 223b.

[0126] In this way, by using a workpiece 210 in which multiple elements 1 are connected in the form of strips at regular intervals in the holding portion 211, the elements 1 can be inserted into the first part 221 in strip units, which significantly improves productivity compared to inserting elements 1 one by one or stacks 101 one by one into the first part 221.

[0127] 18B , the conductive paste 230 is spread by the tip of each element 1, i.e., the tip of the cathode 70, and the tip of the cathode 70 of each element 1 is embedded in the conductive paste 230. In other words, the conductive paste 230 is connected to all elements 1.

[0128] Then, with each cathode 70 embedded, the conductive paste 230 is hardened on the sheet 250 by, for example, heating, so that the current collecting electrode 102 is formed with at least the tip of the cathode 70 of each element 1 embedded in the current collecting electrode 102 (see FIG. 12 ).

[0129] Next, as shown in FIG. 18C , the liquid material 222 is filled around each element 1 inserted into each through-hole 223, i.e., the gaps between adjacent elements 1 and the gaps between the stack 101 and the first portion 221. For example, the liquid material 222 is injected into each through-hole 223 using a dispenser or the like, followed by vacuum degassing to fill the liquid material 222 around each element 1. Here, the liquid material 222 is also filled between adjacent masks 50. However, if the adjacent masks 50 are in contact with each other, the liquid material 222 does not need to be filled between them. Furthermore, the viscosity of the liquid material 222 may be reduced by heating during injection or vacuum degassing. The liquid material 222 contains the second resin material described above (however, in a liquid state before hardening). The resin contained in the liquid second resin material is preferably a thermosetting resin such as epoxy resin, silicone resin, or urethane resin. The liquid second resin material may contain, as a reinforcing material, fillers such as silica particles, alumina particles, or metal particles, or fibers such as ceramic fibers.

[0130] The liquid material 222 before curing preferably has a viscosity of 100 Pa·s or less at 25° C. A viscosity of 100 Pa·s or less allows for easy filling by simply degassing and heating in a vacuum oven, thereby increasing productivity. The viscosity of the liquid material 222 before curing is more preferably 30 Pa·s or less at 25° C., and even more preferably 5 Pa·s or less.

[0131] Although there is no lower limit to the viscosity of the liquid material 222 before hardening, it is preferable that the viscosity is not too low so that the liquid material 222 does not leak from the gap between the first portion 221 and the sheet 250 after the liquid material 222 is filled and before it is heated and hardened. More specifically, the viscosity of the liquid material 222 before hardening at 25° C. is usually 0.01 Pa·s or more, preferably 0.1 Pa·s or more, and more preferably 0.3 Pa·s or more.

[0132] Then, the liquid material 222 filled in each through-hole 223 is cured. For example, the liquid material 222 is heated and cured in a vacuum oven to form the second portion 222a of the exterior body 220 (the portion that will become the second portion 122 of the exterior body 120). Note that a small amount of air bubbles may remain in the second portion 222a, which is the cured product of the liquid material 222. Also, a small gap may remain between the second portion 222a and the first portion 221, and / or between the second portion 222a and at least one element 1.

[0133] Then, for each of the other rows of through holes 223, the conductive paste 230 is supplied, multiple elements 1 (superimposed body 101) are inserted, the conductive paste 230 is hardened, the liquid material 222 is filled, and the liquid material 222 is hardened, so that multiple elements 1 (superimposed body 101) and second portions 222a are stored in all of the through holes 223.

[0134] Next, after the liquid material 222 has hardened, the sheet 250 is peeled off from the first portion 221. The collector electrodes 102 to which the elements 1 are connected are exposed on the peeled surface, and this peeled surface becomes the first end surface 110e of the element body 110. Note that an end surface of at least one cathode 70 may also be exposed on this peeled surface.

[0135] On the other hand, the upper portion of the first portion 221 contains unnecessary portions of each element 1, unnecessary portions of the liquid material 222, and the holder 211 of the workpiece 210. Furthermore, the height of the first portion 221 corresponds to the longitudinal length of the chip, and therefore must be trimmed to a predetermined length. Therefore, first, the unnecessary portions of the upper portion of the first portion 221 are removed using a grinder or the like along a predetermined cutting line (e.g., the dashed line in FIG. 18C ). The surface exposed after the unnecessary portions have been removed becomes the second end face 110f of the element body 110. The anode 60 (a foil made of a valve metal substrate) of each element 1 is exposed on the second end face 110f.

[0136] Next, cutting is performed to separate the substrate into individual pieces.

[0137] FIG. 19 is a diagram schematically illustrating an example of a step of cutting the first portion of the exterior body around the through hole.

[0138] 19 , the first portion 221 is cut around each through-hole 223. This makes it possible to easily form the first portion 121 of the tubular structure from the first portion 221. For example, predetermined cut lines (e.g., dashed lines in FIG. 19 ) on the outside of each through-hole 223 are cut using a dicer or the like.

[0139] In this way, an element body 110 including a stack 101 of elements 1 is obtained.

[0140] Thereafter, the element body 110 may be subjected to barrel polishing. Specifically, the element body 110 may be polished by sealing the element body 110 together with an abrasive in a barrel tank and rotating the barrel tank. This allows the corners and ridges of the element body 110 to be rounded.

[0141] If necessary, metal particles (e.g., Cu particles) may be sprayed by an aerosol deposition method and collided with the second end face 110 f (anode end face) of the barrel-polished element body 110. This may form a metal film (contact layer) on the anode 60 exposed at the second end face 110 f (anode end face) of the element body 110.

[0142] Next, the first external electrode 130 and the second external electrode 140 are formed on the first end face 110e (cathode end face) and the second end face 110f (anode end face) of the element body 110, respectively. For example, a conductive paste is applied by screen printing or the like and cured to form resin electrode layers as the first external electrode 130 and the second external electrode 140. A silver paste containing silver particles as a conductive component is suitable as the conductive paste for forming the resin electrode layers. A plating layer may then be formed on the resin electrode layers by plating.

[0143] At this time, the first external electrode 130 may be formed as a thin sputtered film and / or vapor-deposited film having a thickness of, for example, several micrometers by sputtering or vapor deposition.

[0144] The solid electrolytic capacitor 100B can be obtained by the above method.

[0145] Although the case where the current collecting electrode 102 is provided has been described above, the cathode 70 of each solid electrolytic capacitor element 1 may be directly connected to the first external electrode 130 without providing the current collecting electrode 102. In this case, for example, after peeling off the adhesive sheet 250, the lower portion of the first portion 221 to which the sheet 250 was attached may be scraped off with a grinder or the like to expose each cathode 70 at the first end surface 110e (cathode end surface) of the element body 110, and the first external electrode 130 may then be formed on each cathode 70 exposed at the first end surface 110e.

[0146] Furthermore, when the collecting electrode 102 is not provided, the second portion 222a of the exterior body 220 may be formed according to the following process. That is, first, the liquid material 222 is injected into each of the through-holes 223 of the first portion 221 using a dispenser or the like to fill them. Next, multiple solid electrolytic capacitor elements 1 (superimposed body 101) are inserted into each of the through-holes 223 filled with the liquid material 222, and the liquid material 222 is filled around each of the inserted elements 1. For example, after the multiple elements 1 are inserted, vacuum degassing is performed to fill the liquid material 222 around each of the elements 1. Then, the liquid material 222 filled in each of the through-holes 223 is hardened by heating, for example, in a vacuum oven.

[0147] Furthermore, in the above embodiment (particularly FIGS. 11 and 12 ), the case where the exterior body 120 is composed of only two types of resin material, i.e., the first portion 121 and the second portion 122, has been described. However, the exterior body 120 may be composed of three types of resin material. For example, one or more intermediate resin layers made of a resin material may be provided between the first and second portions of the exterior body. Such an intermediate resin layer may be formed, for example, by forming the second portion that seals the stack of multiple solid electrolytic capacitor elements by transfer molding or the like to a size smaller than the through hole of the first portion, then inserting the stack of solid electrolytic capacitor elements together with the second portion into the through hole of the first portion, and finally filling the gap between the second portion and the first portion with a liquid resin material and curing it.

[0148] Conversely, exterior body 120 may be made of only one type of resin material. For example, first portion 121 may not be provided, and only second portion 122 may be provided. Such a solid electrolytic capacitor can be manufactured, for example, by setting a cut line inside each through hole 223 in a cutting process for individualization, and cutting and removing all of first portion 221.

[0149] Furthermore, in the above embodiment (particularly Figures 11 and 12), a case has been described in which a substantially rectangular parallelepiped element body 110 is used. However, in the solid electrolytic capacitor 100B shown in Figures 11 and 12, the element body is not particularly limited to any particular shape as long as it has opposing first and second end faces, and may be, for example, cylindrical in shape in addition to a substantially rectangular parallelepiped shape.

[0150] Furthermore, in the above embodiment (particularly Figures 13 to 19), a case has been described in which multiple element bodies 110 are simultaneously produced using a first part 221 having multiple through holes 223, but element bodies may also be produced one by one using a first part of an outer casing having only one through hole.

[0151] EXAMPLES Hereinafter, examples will be given that more specifically disclose the solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing a solid electrolytic capacitor of the present invention, but the present invention is not limited to these examples.

[0152] (Example) A plurality of solid electrolytic capacitors similar to solid electrolytic capacitor 100A shown in Figures 9 and 10 were fabricated. However, in each of the solid electrolytic capacitors, defects were generated in the solid electrolyte layer near the first portion of the mask.

[0153] Comparative Examples: A plurality of solid electrolytic capacitors were fabricated in the same manner as in the Examples, except that the second portion of the mask was not formed. All of the solid electrolytic capacitors used in the Comparative Examples had defects in the solid electrolyte layer near the first portion of the mask.

[0154] 20 is a graph showing the results of measuring the leakage current of the solid electrolytic capacitors of the example and comparative examples, where the vertical axis represents the magnitude (logarithm) of the leakage current and the horizontal axis represents the number of solid electrolytic capacitors that exhibited the leakage current on the vertical axis.

[0155] As shown in FIG. 20 , in the example provided with a mask having a first portion and a second portion, even if a defect occurs in the solid electrolyte layer, the leakage current was kept below the standard value (see the standard line in the figure), and the occurrence of leakage current defects was prevented.

[0156] On the other hand, in the comparative example provided with a mask having only the first portion, solid electrolytic capacitors exhibited leakage currents exceeding the standard value (see the standard line in the figure).

[0157] The present specification discloses the following:

[0158] <1> A solid electrolytic capacitor element comprising: a valve metal substrate having a metal substrate layer and a porous layer on the metal substrate layer, the valve metal substrate having an anode terminal region and a cathode formation region; a dielectric layer provided on a surface of the porous layer in the cathode formation region; a solid electrolyte layer provided on the porous layer with the dielectric layer interposed therebetween in the cathode formation region; a conductive layer formed on the solid electrolyte layer; and a mask having a first portion and a second portion, wherein the first portion separates the anode terminal region from the cathode formation region and contacts the porous layer directly or via the dielectric layer, the second portion covers the solid electrolyte layer provided on the porous layer, and the mask does not cover the conductive layer.

[0159] <2> The solid electrolytic capacitor element according to <1>, wherein the second portion covers the solid electrolyte layer up to a point at least 50 μm away from an end of the first portion on the cathode formation region side.

[0160] <3> The solid electrolytic capacitor element according to <1> or <2>, wherein the second portion does not cover the solid electrolyte layer at a point more than 500 μm from the end of the first portion on the cathode formation region side.

[0161] <4> The solid electrolytic capacitor element according to any one of <1> to <3>, wherein the second portion covers at least a part of the first portion.

[0162] <5> The solid electrolytic capacitor element according to any one of <1> to <4>, wherein the thickness of the solid electrolyte layer in the vicinity of the first portion is smaller than the thickness of the solid electrolyte layer in a central portion of the solid electrolyte layer.

[0163] <6> The solid electrolytic capacitor element according to any one of <1> to <5>, wherein the first portion and the second portion are provided on at least one main surface of the valve metal substrate.

[0164] <7> The solid electrolytic capacitor element according to <6>, wherein the first portion and the second portion are annularly provided so as to surround the valve metal substrate.

[0165] <8> A solid electrolytic capacitor comprising a plurality of the solid electrolytic capacitor elements according to any one of <1> to <7>.

[0166] <9> A method for manufacturing a solid electrolytic capacitor element, comprising: forming a first portion of a mask, which separates an anode terminal region and a cathode formation region of the valve metal base, on a porous layer of the valve metal base, either directly or via a dielectric layer; forming a solid electrolyte layer on the porous layer in the cathode formation region, via the dielectric layer, after forming the first portion; and forming a second portion of the mask, which covers the solid electrolyte layer, after forming the solid electrolyte layer.

[0167] 1 Solid electrolytic capacitor element 10, 10A Valve action metal substrate 10a Side of valve action metal substrate 11 Metal substrate layer 11a One end surface of metal substrate layer 12 Porous layer 12a Outermost surface of porous layer 13 Anode terminal region 14 Cathode formation region 15 Element portion 16 Support portion 20 Dielectric layer 30 Solid electrolyte layer 40 Conductive layer 50 Mask 51 First portion of mask 51a End of first portion of mask on cathode formation region side 52 Second portion of mask 60 Anode 70 Cathode 80 Treatment liquid 85 Treatment tank 100A, 100B Solid electrolytic capacitor 101 Stack 102 Collecting electrode 110 Element body 110a First main surface 110b Second main surface 110c First side surface 110d Second side surface DESCRIPTION OF SYMBOLS 110e First end surface 110f Second end surface 120 Exterior body 121 First portion of exterior body 122 Second portion of exterior body 123 Through hole 130 First external electrode 140 Second external electrode 160 Sealing body 170, 180 Lead frame 210 Work 211 Holding portion 212 Element portion 220 Exterior body 221 First portion of exterior body 222 Liquid material 222a Second portion of exterior body 223 Through hole 223a First opening 223b Second opening 230 Conductive paste 250 Adhesive sheet W Width of second portion of mask T1 Thickness of solid electrolyte layer in the vicinity of first portion of mask T2 Thickness of solid electrolyte layer at center portion of solid electrolyte layer

Claims

1. a valve metal substrate having a metal substrate layer and a porous layer on the metal substrate layer, the valve metal substrate having an anode terminal region and a cathode forming region; a dielectric layer provided on a surface of the porous layer in the cathode formation region; a solid electrolyte layer provided on the porous layer via the dielectric layer in the cathode formation region; a conductive layer formed on the solid electrolyte layer; a mask having a first portion and a second portion; the first portion separates the anode terminal region from the cathode formation region, and is in contact with the porous layer directly or via the dielectric layer; the second portion covers the solid electrolyte layer provided on the porous layer, the mask does not cover the conductive layer; the solid electrolyte layer contacts the first portion, and a thickness of the solid electrolyte layer in the vicinity of the first portion is smaller than a thickness of the solid electrolyte layer in a central portion of the solid electrolyte layer.

2. The solid electrolytic capacitor element according to claim 1 , wherein the second portion covers the solid electrolyte layer up to a point at least 50 μm away from an end of the first portion on the cathode formation region side.

3. 3 . The solid electrolytic capacitor element according to claim 1 , wherein the second portion does not cover the solid electrolyte layer at a point that is more than 500 μm from an end of the first portion on the cathode formation region side.

4. The solid electrolytic capacitor element according to claim 1 , wherein the second portion covers at least a part of the first portion.

5. A solid electrolytic capacitor element as described in claim 1 or 2, wherein the second part continuously covers at least a portion of the first part and the solid electrolyte layer in a range of 50 μm or more and 500 μm or less from the end of the first part on the cathode formation region side.

6. 3. The solid electrolytic capacitor element according to claim 1, wherein the first portion and the second portion are provided on at least one of the main surfaces of the valve metal base.

7. 7. The solid electrolytic capacitor element according to claim 6, wherein the first portion and the second portion are provided in an annular shape so as to surround the valve metal base.

8. A solid electrolytic capacitor comprising a plurality of the solid electrolytic capacitor elements according to claim 1 or 2.

9. forming a first portion of a mask on a porous layer of a valve metal substrate, either directly or through a dielectric layer, the first portion defining an anode terminal region and a cathode forming region of the valve metal substrate; forming a solid electrolyte layer on the porous layer via the dielectric layer in the cathode formation region after forming the first portion; forming a second portion of the mask overlying the solid electrolyte layer after forming the solid electrolyte layer; the solid electrolyte layer contacts the first portion, and a thickness of the solid electrolyte layer in the vicinity of the first portion is smaller than a thickness of the solid electrolyte layer in a central portion of the solid electrolyte layer.