Method for manufacturing a solid electrolytic capacitor element and solid electrolytic capacitor element

Abstract

To provide a manufacturing method of a solid electrolytic capacitor element of which capacity is large in which formation of an insulation mask layer is not necessary.SOLUTION: A manufacturing method of a solid electrolytic capacitor element, performs: a step of preparing a valve metal base body 10 in which a dielectric layer is formed; a step of preparing a monomer-containing solvent and an oxidant-containing solvent; a first liquid impregnation step of impregnating a first liquid from a lower part 10B of the valve metal base body toward above the valve metal base body 10 by impregnating the lower part 10B of the valve metal base body in the first liquid that is any one of the monomer containing solvent and the oxidant containing solvent; a second liquid impregnation step of impregnating the valve metal base body 10 into which the first liquid is impregnated into the second liquid in a region that is lower than an upper end 10T of the region where the first liquid is impregnated, using an oxidant containing solution as a second liquid 220 in the case where the monomer containing solvent is the first liquid, whereas using the monomer containing solvent as a second liquid in the case where the oxidant containing solvent is the first liquid; and a cleaning step of cleaning the valve metal base body.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a solid electrolytic capacitor, which includes forming a solid electrolyte at a desired position on a metal material having a dielectric film and having a valve action. The method includes a step of applying a masking material solution that penetrates into the dielectric film and forms a masking layer on the penetrated portion, and a step of thermally denaturing and polymerizing the masking material by heat treatment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, a masking layer (hereinafter referred to as an insulating mask layer in this specification) is provided to separate the anode portion and the cathode portion of the valve action metal. When forming the insulating mask layer, the masking material solution not only penetrates in the thickness direction with respect to the valve action metal, but also penetrates in the plane direction, that is, bleeding in the plane direction occurs. In the region where bleeding of the masking material occurs, the liquid for forming the solid electrolyte layer is difficult to be impregnated due to the water repellent action of the masking material. Similarly, the chemical conversion solution used for performing the chemical conversion treatment for forming the dielectric film is also difficult to be impregnated. Therefore, when the insulating mask layer is provided, there is a problem that a part of the dielectric film may not be covered with the solid electrolyte, and it becomes difficult to repair the dielectric film by the chemical conversion treatment.

[0005] Furthermore, since the portion with the insulating mask layer does not contribute to the capacitance of the capacitor, reducing the area of ​​the insulating mask layer can improve the capacitance of the capacitor.

[0006] The present invention was made to solve the above problems, and aims to provide a method for manufacturing a solid electrolytic capacitor element that does not require the formation of an insulating mask layer and makes it possible to manufacture a solid electrolytic capacitor element with a large capacitance. [Means for solving the problem]

[0007] The present invention provides a method for manufacturing a solid electrolytic capacitor element, comprising the steps of: preparing a valve-acting metal substrate having a dielectric layer formed on its surface; preparing a monomer-containing solution having a monomer and a solvent for forming a solid electrolyte layer by a chemical polymerization reaction, and an oxidizing agent-containing solution having an oxidizing agent and a solvent for polymerizing the monomer; a first liquid immersion step in which the lower part of the valve-acting metal substrate is immersed in a first liquid, which is either the monomer-containing solution or the oxidizing agent-containing solution, and the first liquid penetrates from the lower part of the valve-acting metal substrate upwards; a second liquid immersion step in which, if the monomer-containing solution is the first liquid, the oxidizing agent-containing solution is the second liquid, and if the oxidizing agent-containing solution is the first liquid, the monomer-containing solution is the second liquid, and the valve-acting metal substrate that has been permeated with the first liquid is immersed in the second liquid in a region below the upper end of the region where the first liquid has penetrated; and a cleaning step for cleaning the valve-acting metal substrate.

[0008] The solid electrolytic capacitor element of the present invention comprises a valve-acting metal substrate having a dielectric layer on at least one main surface and a first side that becomes the anode portion and a second side that becomes the cathode portion opposite in the longitudinal direction thereof, and a solid electrolyte layer provided on the dielectric layer, wherein when viewed from the direction normal to the main surface of the solid electrolytic capacitor element, the solid electrolyte layer is provided in a part of the region of the valve-acting metal substrate from the second side toward the first side, the solid electrolyte layer is provided so as to approach the first side from both ends of the tip toward the center of the tip, and there is no insulating mask layer separating the valve-acting metal substrate into an anode portion and a cathode portion. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for manufacturing a solid electrolytic capacitor element that does not require the formation of an insulating mask layer and can manufacture a solid electrolytic capacitor element with a large capacitance. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing an example of a valve-acting metal substrate with a dielectric layer formed on its surface. [Figure 2] Figure 2 is a schematic process diagram showing the first liquid immersion process. [Figure 3] Figure 3 is a schematic process diagram showing the second liquid immersion process. [Figure 4] Figure 4 is a schematic process diagram showing the second first liquid immersion step. [Figure 5] Figure 5 is a schematic process diagram showing the second immersion step in the second liquid. [Figure 6] Figure 6 is a schematic process diagram showing the valve-acting metal substrate after the cleaning process. [Figure 7] Figure 7 is a schematic plan view showing an example of a dielectric layer and a solid electrolyte layer that constitute a solid electrolytic capacitor element. [Figure 8] Figure 8 is a cross-sectional view taken along line XX in Figure 7. [Figure 9]FIG. 9 is a plan view schematically showing an example of a solid electrolytic capacitor element. [Figure 10] FIG. 10 is a sectional view taken along the line Y-Y of FIG. 9. [Figure 11] FIG. 11 is a perspective view schematically showing an example of a solid electrolytic capacitor. [Figure 12] FIG. 12 is a sectional view taken along the line Z-Z of the solid electrolytic capacitor shown in FIG. 11. [Figure 13] FIG. 13 is a perspective view schematically showing an example of a solid electrolytic capacitor in which a lead frame is used as an external electrode. [Figure 14] FIG. 14 is a sectional view taken along the line II-II of the solid electrolytic capacitor shown in FIG. 13.

BEST MODE FOR CARRYING OUT THE INVENTION

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

[0012] [Method for Manufacturing Solid Electrolytic Capacitor Element] In the following example, a method for simultaneously manufacturing a plurality of solid electrolytic capacitor elements using a large-sized valve action metal substrate will be described.

[0013] [[ID=३५]]First, prepare a valve action metal substrate having a dielectric layer formed on its surface. FIG. 1 is a schematic view showing an example of a valve action metal substrate having a dielectric layer formed on its surface. As shown in FIG. 1, a valve-acting metal substrate 10 having a dielectric layer 20 on its surface is prepared. The valve-acting metal substrate 10 includes a support portion 11 and a plurality of element portions 12. Each element portion 12 is strip-shaped and protrudes from the support portion 11. Further, a dielectric layer 20 is formed on the surface of the valve-acting metal substrate 10. An insulating mask layer is not formed on the element portion 12 of the valve-acting metal substrate 10. In addition, by joining the pre-cut strip-shaped element portions 12 to a plate-shaped metal member formed of stainless steel or the like that serves as a substitute for the support portion 11 by welding or the like, a configuration similar to the valve-acting metal substrate 10 shown in FIG. 1 may be obtained.

[0014] When preparing the valve-acting metal substrate 10 shown in FIG. 1, the valve-acting metal substrate 10 having a porous portion on its surface is cut by laser processing or punching or the like to be processed into a shape including a plurality of element portions 12 and a support portion 11. The main surface of the valve-acting metal substrate 10 is preferably porous. Since the main surface of the valve-acting metal substrate 10 is porous, the surface area of the valve-acting metal substrate 10 is increased. Note that it is not limited to the case where both the front and back surfaces of the valve-acting metal substrate 10 are porous, and only one of the front and back surfaces of the valve-acting metal substrate 10 may be porous.

[0015] The valve-acting metal substrate 10 is constituted by, for example, a single metal such as aluminum, tantalum, niobium, titanium, zirconium, or a valve-acting metal such as an alloy containing these metals.

[0016] Thereafter, by performing an anodic oxidation treatment (chemical conversion treatment) on the valve-acting metal substrate 10, an oxide film that becomes the dielectric layer 20 is formed on the surface of the valve-acting metal substrate 10. At this time, an oxide film is also formed on the side surface of the element portion 12 cut by laser processing or punching or the like. Note that a chemical conversion foil on which an aluminum oxide is already formed may be used as the valve-acting metal substrate 10. Also in this case, by performing an anodic oxidation treatment on the valve-acting metal substrate 10 after cutting, an oxide film is formed on the side surface of the cut element portion 12.

[0017] The shape of the valve-acting metal substrate 10 as viewed from the direction normal to the main surface of the valve-acting metal substrate 10, that is, the shape of the valve-acting metal substrate 10 as viewed from the thickness direction in plan, is rectangular, and preferably rectangular with long sides and short sides. The shape of the valve-acting metal substrate 10 referred to here is the shape of the element portion 12 excluding the support portion 11, and represents the shape of the valve-acting metal substrate when it becomes a single solid electrolytic capacitor element.

[0018] If the element portion 12 of the valve-acting metal substrate 10 is in the shape of a strip, the tip of the strip is the lower end of the valve-acting metal substrate, and the portion including the tip of the strip is considered the lower part of the valve-acting metal substrate. On the other hand, the base of the strip (the side of the support portion 11) is considered the upper part of the valve-acting metal substrate.

[0019] Furthermore, the shape of the valve-acting metal substrate is not limited to a strip shape; any shape that allows only the lower part of the valve-acting metal substrate to be immersed in the first and second liquid immersion steps described later is acceptable. In other words, any shape with a defined longitudinal direction is acceptable, and in addition to a strip shape, it may also be a prismatic shape, cylindrical shape, etc.

[0020] The valve-acting metal substrate 10 only needs to consist of a core and a porous portion provided on at least one main surface of the core. Appropriately, a metal foil with an etched surface, a metal foil with a porous fine powder sintered body formed on its surface, etc., can be used.

[0021] Next, prepare a monomer-containing solution and an oxidizing agent-containing solution. The monomer-containing solution has monomers and a solvent that form a solid electrolyte layer through a chemical polymerization reaction. Examples of conductive polymers that constitute the solid electrolyte layer include polypyrroles, polythiophenes, polyanilines, and other conductive polymers. Among these, polythiophenes are preferred, and poly(3,4-ethylenedioxythiophene), known as PEDOT, is particularly preferred. Therefore, the monomers contained in the monomer-containing solution are preferably monomers that become the above-mentioned conductive polymers through chemical polymerization reactions, such as pyrrole, thiophene, and aniline. Among these, 3,4-ethylenedioxythiophene is more preferred. The solvent included in the monomer-containing solution may be an aqueous solvent or an alcohol-based solvent, with an alcohol-based solvent being preferred. Furthermore, the monomer-containing solution is preferably low viscosity in order to enhance its impregnation into the valve-acting metal substrate 10, and a small surface tension (contact angle) on the valve-acting metal substrate 10 is also preferable.

[0022] In this specification, examples of aqueous solvents include ion-exchanged water, pure water, and ultrapure water. Examples of alcoholic solvents include methanol, ethanol, n-propanol, and isopropanol.

[0023] The monomer-containing solution may further contain a dopant. Examples of dopants include aromatic sulfonic acids such as polystyrene sulfonic acid (PSS) and anthraquinone sulfonic acid (AQS) salts, and their salts.

[0024] The oxidizing agent-containing solution contains an oxidizing agent and a solvent that polymerize the above monomer. Examples of oxidizing agents for polymerizing monomers include ammonium persulfate and iron p-toluenesulfonic acid (PTSA). The solvent included in the oxidizing agent-containing solution can be an aqueous solvent or an alcohol-based solvent, with an aqueous solvent being preferred. Furthermore, the oxidizing agent-containing solution is preferably low viscosity in order to enhance its impregnation into the valve-acting metal substrate 10, and a small surface tension (contact angle) on the valve-acting metal substrate 10 is also preferable.

[0025] Regarding the first and second liquids described below, it is possible to choose either to use a monomer-containing solution for the first liquid and an oxidizing agent-containing solution for the second liquid, or to use an oxidizing agent-containing solution for the first liquid and a monomer-containing solution for the second liquid. Here, the chemical polymerization reaction proceeds when the monomer-containing solution and the oxidizing agent-containing solution come into contact with each other. Therefore, in either case, by immersing the valve-acting metal substrate 10, which has been permeated with the first liquid, in the second liquid in the region below the upper end of the region permeated with the first liquid, it is possible to control the seepage upward from the region where the chemical polymerization reaction is occurring.

[0026] Next, the first liquid immersion process is performed. In the first liquid immersion step, the lower part of the valve-acting metal substrate is immersed in the first liquid, which is either a monomer-containing solution or an oxidizing agent-containing solution, allowing the first liquid to penetrate from the lower part of the valve-acting metal substrate upwards. The first solution may be either a monomer-containing solution or an oxidizing agent-containing solution. If the first solution is a monomer-containing solution, the second solution, as described later, will be an oxidizing agent-containing solution. The following explanation uses the case where the first solution is a monomer-containing solution and the second solution is an oxidizing agent-containing solution as an example.

[0027] Figure 2 is a schematic process diagram showing the first liquid immersion process. In the first immersion step, the lower part 10B of the valve-acting metal substrate 10 is immersed in the first liquid 210. The first liquid 210 permeates from the lower part 10B of the valve-acting metal substrate 10 upwards. The first liquid 210 seeps up above the liquid level 210S of the first liquid 210 to above the valve-acting metal substrate 10. In Figure 2, the upper end of the region where the first liquid 210 has penetrated above the liquid surface 210S of the first liquid 210, above the valve-acting metal substrate 10, is indicated by reference numeral 10T. In other words, after the first liquid immersion process, the upper end 10T of the region to which the first liquid 210 has penetrated is located above the liquid level 210S of the first liquid.

[0028] In the first liquid immersion step, it is preferable to immerse a region of 60% to 90% of the length of the valve-acting metal substrate in the longitudinal direction (the length indicated by the double arrow A in Figure 2) from the lower end of the valve-acting metal substrate into the first liquid.

[0029] Furthermore, the region that is part of the valve-acting metal substrate and is intended to be the cathode in the manufactured solid electrolytic capacitor is indicated by the double-headed arrow 10C in Figure 2. In the first liquid immersion step, it is preferable to immerse 80% to 100% of the planned cathode region 10C in the first liquid 210, and it is preferable to immerse 100% of the planned cathode region 10C in the first liquid 210. When 100% of the planned cathode region 10C is immersed in the first liquid 210, the first liquid 210 seeps up to above the liquid surface 210S of the first liquid 210, so the area of ​​the region to which the first liquid 210 has penetrated exceeds 100% of the planned cathode region 10C. However, since the excess first liquid 210 can be washed away in the subsequent washing step, a solid electrolyte layer can be formed in the planned cathode region 10C without excess or deficiency. In Figure 2, 100% of the planned cathode region 10C is immersed in the first solution 210.

[0030] After the first immersion step, drying may be performed as needed. If drying is performed, the temperature can be between 25°C and 100°C. Alternatively, drying may be omitted.

[0031] It is preferable that the solvent contained in the first solution is an alcohol-based solvent. This is because an alcohol-based solvent is more likely to leach out compared to an aqueous solvent. It is preferable to use a monomer-containing solution in which the solvent is an alcohol-based solvent as the first solution. Furthermore, it is preferable that the monomer-containing solution, which is the first solution, further contains a dopant.

[0032] Next, the second liquid immersion process is performed. In the second liquid immersion step, the valve-acting metal substrate, which has been permeated with the first liquid, is immersed in the second liquid in the region below the upper end of the area where the first liquid has permeated. If the first solution is a monomer-containing solution, the second solution will be an oxidizing agent-containing solution.

[0033] Figure 3 is a schematic process diagram showing the second liquid immersion process. In the second immersion step, the lower part 10B of the valve-acting metal substrate 10, which has been permeated with the first liquid 210, is immersed in the second liquid 220. In the portion of the valve-acting metal substrate 10 that is in contact with the second liquid 220, the monomer contained in the first liquid 210 that has permeated the valve-acting metal substrate 10 reacts with the oxidizing agent contained in the second liquid 220, and a chemical polymerization reaction of the monomer proceeds, forming a solid electrolyte layer.

[0034] The reaction between the first liquid 210 and the second liquid 220 occurs in the portion of the valve-acting metal substrate 10 that is in contact with the second liquid 220. Near the liquid surface 220S of the second liquid 220, the presence of unreacted first liquid 210 prevents the second liquid 220 from seeping upwards above the valve-acting metal substrate 10, so there is almost no seepage of the second liquid 220 above the liquid surface 220S above the valve-acting metal substrate 10. Figure 3 shows a portion of the solid electrolyte layer that has become convex due to a slight seepage of the second liquid 220, which is represented as the convex portion 220T.

[0035] Since the upward seepage of the second liquid 220 is inhibited by the first liquid 210 which has not reacted with the second liquid 220, the region in which the solid electrolyte layer is formed can be adjusted by adjusting the immersion depth of the valve-acting metal substrate into the second liquid 220. From the viewpoint of adjusting the region where the solid electrolyte layer is formed using this method, immersion in the second liquid 220 is performed in the region below the upper end 10T of the region where the first liquid 210 has permeated. Since there is almost no seepage of the second liquid 220 above the valve-acting metal substrate 10 from the liquid surface 220S, the region where the solid electrolyte layer is formed is adjusted to the region below the upper end 10T of the region where the first liquid 210 has permeated.

[0036] In the second liquid immersion step, it is preferable to immerse a region of 60% to 90% of the length of the valve-acting metal substrate in the longitudinal direction (the length indicated by the double arrow A in Figure 3) from the lower end of the valve-acting metal substrate into the second liquid.

[0037] In the second liquid immersion step, it is preferable to immerse 80% to 100% of the planned cathode region 10C in the second liquid 220, and it is preferable to immerse 100% of the planned cathode region 10C in the second liquid 220. When 100% of the planned cathode region 10C is immersed in the second liquid 220, there is almost no seepage of the second liquid 220 above the liquid level 220S of the second liquid 220 onto the valve-acting metal substrate 10, so that a solid electrolyte layer can be formed in the planned cathode region 10C without excess or deficiency. Furthermore, it is preferable to immerse 80% to 100% of the area immersed in the first liquid 210 in the first liquid immersion step into the second liquid 220, and the area immersed in the first liquid 210 in the first liquid immersion step and the area immersed in the second liquid 220 in the second liquid immersion step may be the same. In Figure 3, 100% of the planned cathode region 10C is immersed in the second solution 220.

[0038] After the second immersion step, drying may be performed as needed. The drying temperature can be between 25°C and 100°C. Furthermore, natural drying is acceptable instead of forced drying using an oven or the like. A semi-dried state is also acceptable.

[0039] It is preferable that the solvent contained in the second solution is an aqueous solvent. While a direct comparison between aqueous and alcoholic solvents is not possible, an aqueous solvent in the second solution tends to penetrate less easily than an alcoholic solvent due to differences in surface tension. From this perspective, it is preferable to use an oxidizing agent-containing solution in which the solvent is aqueous as the second solution. However, since surface tension is altered by additives such as surfactants, even if the second solution is an alcohol-based solvent, it can be adjusted by adding additives to make it less likely to seep up than the first solution.

[0040] During the formation of the solid electrolyte layer, the first liquid immersion step and the second liquid immersion step may be repeated to increase the thickness of the solid electrolyte layer and adjust the thickness of the solid electrolyte layer to a predetermined thickness.

[0041] Figure 4 is a schematic process diagram showing the second immersion in the first liquid, and Figure 5 is a schematic process diagram showing the second immersion in the second liquid. The first liquid 210 shown in Figure 4 is a monomer-containing solution, and the second liquid 220 shown in Figure 5 is an oxidizing agent-containing solution. In Figure 4, the portion of the solid electrolyte layer 40 formed in the first and second liquid immersion steps is immersed in the first liquid 210. When the second liquid immersion step is performed, the first liquid 210 that seeped up in the first liquid immersion step remains above the liquid surface 210S of the first liquid 210 and above the valve-acting metal substrate 10. Therefore, unlike the first liquid immersion step, the first liquid 210 does not seep up above the liquid surface 210S of the first liquid 210 and above the valve-acting metal substrate 10.

[0042] In Figure 5, the portion of the solid electrolyte layer 40 formed in the first and second liquid immersion steps that has been further penetrated by the first liquid 210 is immersed in the second liquid 220. The second liquid 220 does not seep up above the liquid level 220S of the second liquid 220 to the level above the valve-acting metal substrate 10. Therefore, in the second first and second liquid immersion process, a solid electrolyte layer is formed in almost the same region as the solid electrolyte layer formed in the first and second liquid immersion process, thereby increasing the thickness of the solid electrolyte layer.

[0043] Next, the cleaning process is performed. In the cleaning step, the valve-acting metal substrate is cleaned. Cleaning is preferably carried out with an aqueous solvent (such as tap water, pure water, or ultrapure water) or an alcohol-based solvent. The cleaning step washes away any unreacted first and second liquids. From the viewpoint that the solvents contained in the first and second liquids can be washed away by a washing process (water washing) with an aqueous solvent, it is preferable that the solvents contained in the first and second liquids are alcohol-based solvents or aqueous solvents. If the first liquid immersion step and the second liquid immersion step are repeated multiple times, it is preferable to perform a washing step after each of the multiple first liquid immersion steps to wash away the unreacted first and second liquids together.

[0044] Figure 6 is a schematic process diagram showing the valve-acting metal substrate after the cleaning process. Figure 6 shows the solid electrolyte layer 40 formed by the first and second liquid immersion processes. The region where the solid electrolyte layer 40 is formed is the region where the first liquid 210 and the second liquid 220 came into contact during the second liquid immersion process and a chemical polymerization reaction occurred. In Figures 3, 4, and 5, this region extends upward from the lower part 10B of the valve-acting metal substrate 10 to the convex portion 220T of the second liquid 220. In Figures 3, 4, and 5, the unreacted first liquid 210 that had penetrated from the protrusion 220T of the second liquid 220 to the upper end 10T of the region where the first liquid 210 had penetrated is washed away by the cleaning process. As a result, the dielectric layer 20 is exposed in that area after the cleaning process. Furthermore, any unreacted second liquid 220 remaining on the surface of the solid electrolyte layer 40 will be washed away by the washing process.

[0045] The above process forms a solid electrolyte layer. By immersing the valve-acting metal substrate in a first liquid immersion process and a second liquid immersion process, the formation area of ​​the solid electrolyte layer can be adjusted. Therefore, the anode and cathode portions of the valve-acting metal substrate can be separated without providing an insulating mask layer to separate them. Furthermore, the proportion of the cathode portion can be increased in the area corresponding to the insulating mask layer, thereby improving the capacitance of the capacitor.

[0046] Alternatively, the first liquid immersion step, the second liquid immersion step, and the washing step may be treated as a single solid electrolyte layer formation step, and the solid electrolyte layer formation step may be repeated multiple times.

[0047] After forming a solid electrolyte layer, a valve-acting metal substrate is immersed in carbon paste, then withdrawn and dried to form a carbon layer in a predetermined area.

[0048] After forming a carbon layer, a valve-acting metal substrate is immersed in a conductive paste such as silver paste, then withdrawn and dried to form a cathode conductor layer in a predetermined area.

[0049] The valve-acting metal substrate is cut to separate the element portion.

[0050] Through the above process, a solid electrolytic capacitor element is obtained.

[0051] [Solid electrolytic capacitor element] The present invention relates to a solid electrolytic capacitor element comprising: a valve-acting metal substrate having a dielectric layer on at least one main surface and having a first side that becomes the anode portion and a second side that becomes the cathode portion opposite in the longitudinal direction thereof; and a solid electrolyte layer provided on the dielectric layer, wherein, when viewed from the direction normal to the main surface of the solid electrolytic capacitor element, the solid electrolyte layer is provided in a part of the region of the valve-acting metal substrate from the second side toward the first side, the solid electrolyte layer is provided so as to approach the first side from both ends of the tip toward the center of the tip, and the solid electrolytic capacitor element does not have an insulating mask layer that separates the valve-acting metal substrate into an anode portion and a cathode portion.

[0052] Figure 7 is a schematic plan view showing an example of a dielectric layer and a solid electrolyte layer constituting a solid electrolytic capacitor element, and Figure 8 is a cross-sectional view taken along line XX of Figure 7. The plan view shown in Figure 7 is also a view of the solid electrolytic capacitor element from the direction normal to the main surface. The shape of the valve-acting metal substrate 10 as viewed from the direction normal to the main surface of the valve-acting metal substrate 10, that is, the shape of the valve-acting metal substrate 10 as viewed from the thickness direction in plan, is rectangular, and preferably rectangular with long sides and short sides.

[0053] Figure 7 shows a rectangular valve-acting metal substrate 10 with a dielectric layer 20 provided on its main surface. The valve-acting metal substrate 10 has a first side 13 and a second side 14 that are opposite each other in the longitudinal direction (indicated by double arrows L in Figure 7). Both the first side 13 and the second side 14 are the short sides of the valve-acting metal substrate 10.

[0054] The first side 13 of the valve-acting metal substrate 10 is the short side that becomes the anode portion 31, and the second side 14 of the valve-acting metal substrate 10 is the short side that becomes the cathode portion 32. A dielectric layer 20 is provided on the main surface of the valve-acting metal substrate 10, and a solid electrolyte layer 40 is provided in a portion of the region of the valve-acting metal substrate 10 from the second side 14 toward the first side 13. The solid electrolyte layer 40 is provided so as to move toward the first side 13 from both ends 41e of the tip toward the center 41c of the tip.

[0055] The region where the solid electrolyte layer 40 is provided becomes the cathode portion 32, and the portion where the solid electrolyte layer 40 is not provided becomes the anode portion 31. There is no insulating mask layer to separate the valve-acting metal substrate 10 into the anode portion 31 and the cathode portion 32. If an insulating mask layer is not provided, the cathode area can be made larger, which can improve the capacitance of the capacitor. For example, the ratio of the longitudinal length R2 of the solid electrolyte layer to the longitudinal length R1 of the valve-acting metal substrate 10 (R2 / R1) is preferably 0.8 or greater, and preferably 0.9 or greater. The longitudinal length R2 of the solid electrolyte layer should be defined as the length of the solid electrolyte layer in a straight line passing through the central part 41c of the leading edge of the solid electrolyte layer.

[0056] Figure 9 is a schematic plan view showing an example of a solid electrolytic capacitor element, and Figure 10 is a cross-sectional view of Figure 9 along the YY line. In the solid electrolytic capacitor element 1, a carbon layer 50 is provided on top of the solid electrolyte layer 40. Furthermore, a cathode conductor layer 60 is provided on top of the carbon layer 50.

[0057] As shown in Figures 9 and 10, the carbon layer 50 is provided so as to approach the first side 13 from both ends 51e of the tip towards the center 51c of the tip. The cathode conductor layer 60 is also provided so as to approach the first side 13 from both ends 61e of the tip towards the center 61c of the tip. Furthermore, the central portion 51c of the tip of the carbon layer 50 is positioned to cover a location closer to the cathode portion 32 than the central portion 41c of the tip of the solid electrolyte layer 40. Similarly, the central portion 61c of the tip of the cathode conductor layer 60 is positioned to cover a location closer to the cathode portion 32 than the central portion 51c of the tip of the carbon layer 50.

[0058] Although the solid electrolytic capacitor element of the present invention does not have an insulating mask layer, the manufacturing method of the solid electrolytic capacitor element of the present invention allows for adjustment of the formation region of the solid electrolyte layer. Therefore, the anode and cathode can be separated without providing an insulating mask layer to separate the anode and cathode of the valve-acting metal substrate. For this reason, the solid electrolytic capacitor element of the present invention can be manufactured by the manufacturing method of the solid electrolytic capacitor element of the present invention.

[0059] [Solid electrolytic capacitors] An example of a solid electrolytic capacitor including the solid electrolytic capacitor element of the present invention is described below. Note that the solid electrolytic capacitor element of the present invention may be included in solid electrolytic capacitors having other configurations. For example, a lead frame may be used as an external electrode. Furthermore, the solid electrolytic capacitor of the present invention may include solid electrolytic capacitor elements other than the solid electrolytic capacitor element of the present invention.

[0060] Figure 11 is a schematic perspective view showing an example of a solid electrolytic capacitor. Figure 12 is a cross-sectional view of the solid electrolytic capacitor shown in Figure 11 along the ZZ line.

[0061] In Figures 11 and 12, the length direction of the solid electrolytic capacitor 100 and the casing 110 are denoted 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 orthogonal to each other.

[0062] As shown in Figures 11 and 12, the solid electrolytic capacitor 100 has a substantially rectangular parallelepiped shape. The solid electrolytic capacitor 100 comprises an outer casing 110, a first external electrode 120, a second external electrode 130, and a plurality of solid electrolytic capacitor elements 1. The solid electrolytic capacitor elements 1 are examples of the solid electrolytic capacitor elements of the present invention.

[0063] The outer casing 110 encloses multiple solid electrolytic capacitor elements 1. That is, multiple solid electrolytic capacitor elements 1 are embedded in the outer casing 110. Alternatively, the outer casing 110 may enclose only one solid electrolytic capacitor element 1. That is, one solid electrolytic capacitor element 1 may be embedded inside the outer casing 110.

[0064] The outer casing 110 has a roughly rectangular parallelepiped shape. The outer casing 110 has a first main surface 110a and a second main surface 110b that are opposite in the height direction T, a first side surface 110c and a second side surface 110d that are opposite in the width direction W, and a first end surface 110e and a second end surface 110f that are opposite in the length direction L.

[0065] As described above, the outer casing 110 has a roughly rectangular parallelepiped shape, but it is preferable that the corners and edges are rounded. The corners are the parts where three faces of the outer casing 110 intersect, and the edges are the parts where two faces of the outer casing 110 intersect.

[0066] The outer casing 110 is made of, for example, a sealing resin.

[0067] The sealing resin contains at least a resin, and preferably contains both a resin and a filler.

[0068] Preferably used resins include epoxy resins, phenolic resins, polyimide resins, silicone resins, polyamide resins, and liquid crystal polymers.

[0069] As fillers, silica particles, alumina particles, metal particles, etc., are preferably used.

[0070] As the sealing resin, a material containing a solid epoxy resin, a phenolic resin, and silica particles is preferably used.

[0071] When using a solid sealing resin, resin molds such as compression molds and transfer molds are preferably used, with compression molds being more preferably used. When using a liquid sealing resin, molding methods such as dispensing and printing are preferably used. In particular, it is preferable to seal the periphery of the solid electrolytic capacitor element 1 with sealing resin using a compression mold to form the outer casing 110.

[0072] The outer casing 110 may consist of a substrate and a sealing resin provided on the substrate. The substrate is, for example, an insulating resin substrate such as a glass epoxy substrate. In this case, the bottom surface of the substrate constitutes the second main surface 110b of the outer casing 110. The thickness of the substrate is, for example, 100 μm.

[0073] Multiple solid electrolytic capacitor elements 1 are stacked in the height direction T. The extending direction of each of the multiple solid electrolytic capacitor elements 1 is substantially parallel to the first main surface 110a and the second main surface 110b of the outer casing 110. The solid electrolytic capacitor elements 1 may be joined to each other via a conductive adhesive.

[0074] The first external electrode 120 is provided on the first end face 110e of the casing 110. In Figure 11, the first external electrode 120 extends from the first end face 110e of the casing 110 to each of the first main face 110a, the second main face 110b, the first side face 110c, and the second side face 110d. The first external electrode 120 is electrically connected to the valve-acting metal substrate 10 of the solid electrolytic capacitor element 1 that is exposed from the casing 110. The first external electrode 120 may be directly connected to the valve-acting metal substrate 10 at the first end face 110e of the casing 110, or it may be connected indirectly.

[0075] The second external electrode 130 is provided on the second end face 110f of the outer casing 110. In Figure 12, the second external electrode 130 extends from the second end face 110f of the outer casing 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 130 is electrically connected to the cathode conductor layer 60 of the solid electrolytic capacitor element 1 that is exposed from the outer casing 110. The second external electrode 130 may be directly connected to the cathode conductor layer 60 at the second end face 110f of the outer casing 110, or it may be connected indirectly.

[0076] The first external electrode 120 and the second external electrode 130 are preferably formed by at least one method selected from the group consisting of immersion coating, screen printing, transfer, inkjet printing, dispensing, spray coating, brush coating, drop casting, electrostatic coating, plating, and sputtering.

[0077] The first external electrode 120 preferably has a resin electrode layer containing a conductive component and a resin component. The inclusion of a resin component in the first external electrode 120 improves the adhesion between the first external electrode 120 and the sealing resin of the outer casing 110, thereby improving reliability.

[0078] The second external electrode 130 preferably has a resin electrode layer containing a conductive component and a resin component. The inclusion of a resin component in the second external electrode 130 improves the adhesion between the second external electrode 130 and the sealing resin of the outer casing 110, thereby improving reliability.

[0079] The conductive component preferably consists mainly of elemental metals such as silver, copper, nickel, and tin, or alloys containing at least one of these metals.

[0080] The resin component preferably contains epoxy resin, phenolic resin, or the like as its main component.

[0081] The resin electrode layer is formed by methods such as immersion coating, screen printing, transfer, inkjet printing, dispensing, spray coating, brush coating, drop casting, and electrostatic coating. Among these, the resin electrode layer is preferably a printed resin electrode layer formed by applying a conductive paste using the screen printing method. When the resin electrode layer is formed by applying a conductive paste using the screen printing method, the first external electrode 120 and the second external electrode 130 tend to be flatter compared to when the resin electrode layer is formed by applying a conductive paste using the immersion coating method. That is, the thickness of the first external electrode 120 and the second external electrode 130 tends to be more uniform.

[0082] When the second external electrode 130 has a resin electrode layer, the adhesion between the second external electrode 130 and the carbon layer 50 and the cathode conductor layer 60 is improved because the second external electrode 130, the carbon layer 50 and the cathode conductor layer 60 contain resin components, thereby improving reliability.

[0083] At least one of the first external electrode 120 and the second external electrode 130 may have a so-called plating layer formed by a plating method. Examples of plating layers 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, a nickel-copper layer, and the like. Preferably, a copper plating layer, a nickel plating layer, and a tin plating layer are provided on these plating layers in order (or with some of the plating layers excluded).

[0084] At least one of the first external electrode 120 and the second external electrode 130 may have both a resin electrode layer and a plating layer. For example, the first external electrode 120 may have a resin electrode layer connected to the valve-acting metal substrate 10 and an outer plating layer provided on the surface of the resin electrode layer. Alternatively, the first external electrode 120 may have an inner plating layer connected to the valve-acting metal substrate 10, 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.

[0085] Figure 13 is a schematic perspective view showing an example of a solid electrolytic capacitor in which a lead frame is used as an external electrode. Figure 14 is a cross-sectional view of the solid electrolytic capacitor shown in Figure 13, taken along line II-II.

[0086] As shown in Figures 13 and 14, the solid electrolytic capacitor 300 has a substantially rectangular parallelepiped shape. The solid electrolytic capacitor 300 comprises an outer casing 310, a first external electrode 320, a second external electrode 330, and a capacitor element assembly 340 including a plurality of solid electrolytic capacitor elements 1. The solid electrolytic capacitor element 1 is an example of the solid electrolytic capacitor element of the present invention.

[0087] The outer casing 310 has a roughly rectangular parallelepiped shape. Inside the outer casing 310 is a capacitor element assembly 340 containing a plurality of solid electrolytic capacitor elements 1. The outer casing 310 has a first main surface 310a and a second main surface 310b that are opposite in the height direction T, a first side surface 310c and a second side surface 310d that are opposite in the width direction W, and a first end surface 310e and a second end surface 310f that are opposite in the length direction L. Note that one solid electrolytic capacitor element 1 may be provided inside the outer casing 310.

[0088] The capacitor element assembly 340 comprises a plurality of solid electrolytic capacitor elements 1 (solid electrolytic capacitor element 1a, solid electrolytic capacitor element 1b, solid electrolytic capacitor element 1c, solid electrolytic capacitor element 1d) and a conductive member 319. In this embodiment, the number of solid electrolytic capacitor elements constituting the capacitor element assembly 340 is four, but the number of solid electrolytic capacitor elements constituting the capacitor element assembly is not particularly limited.

[0089] Multiple solid electrolytic capacitor elements 1 are stacked. In this stacking, the dimensions in the stacking direction on the second end face 310f side are larger than the dimensions in the stacking direction on the first end face 310e side. That is, when viewed from the side, the multiple solid electrolytic capacitor elements 1 are arranged to spread in the thickness direction from the first end face side to the second end face side.

[0090] The anode-side end of each valve-acting metal substrate in the multiple solid electrolytic capacitor elements 1 is connected to the first external electrode 320.

[0091] The cathode conductor layers of multiple solid electrolytic capacitor elements 1 are electrically and physically connected by a conductive member 319, and these are electrically and physically connected to the second external electrode 330.

[0092] The first external electrode 320 is exposed to the outside from the first end face 310e of the outer casing 310 and is arranged across the first end face 310e and the second main surface 310b. The second external electrode 330 is exposed to the outside from the second end face 310f of the outer casing 310 and is arranged across the second end face 310f and the second main surface 310b.

[0093] The conductive member 319 is preferably an electrode paste mainly composed of nickel, silver, or copper. The maximum thickness of the conductive member 319 is preferably 2 μm or more and 20 μm or less. However, even without using the conductive member 319, if conductivity of a desired level or higher can be obtained between multiple solid electrolytic capacitor elements 1, between solid electrolytic capacitor elements 1b, 1c and the second external electrode 330, etc., the conductive member 319 can be omitted.

[0094] The first external electrode 320 and the second external electrode 330 are preferably made of a metal material that is easy to bend and has high conductivity. The first external electrode 320 and the second external electrode 330 are made of a material cut from, for example, a metal sheet. The first external electrode 320 and the second external electrode 330 may be made of the same material or different materials.

[0095] The outer casing 310 is mainly made of resin and may contain fillers. Preferred resins include epoxy resin, phenolic resin, polyimide resin, silicone resin, polyamide resin, and liquid crystal polymer. The resin can be in solid or liquid form. It is preferable that the corners are rounded by barrel polishing after resin encapsulation. Preferred fillers include silica particles, alumina particles, and metal particles. The maximum diameter of the fillers is preferably 30 μm or more and 40 μm or less. It is more preferable that the material contains silica particles in the solid epoxy resin and phenolic resin.

[0096] This specification discloses the following:

[0097] (1) The present disclosure is a method for manufacturing a solid electrolytic capacitor element, comprising the steps of: preparing a valve metal substrate having a dielectric layer formed on its surface; preparing a monomer-containing solution having a monomer and a solvent for becoming a solid electrolyte layer by a chemical polymerization reaction, and an oxidizing agent-containing solution having an oxidizing agent and a solvent for polymerizing the monomer; a first liquid immersion step in which the lower part of the valve metal substrate is immersed in a first liquid which is either the monomer-containing solution or the oxidizing agent-containing solution, and the first liquid permeates from the lower part of the valve metal substrate toward the upper part of the valve metal substrate; a second liquid immersion step in which, if the monomer-containing solution is the first liquid, the oxidizing agent-containing solution is the second liquid, and if the oxidizing agent-containing solution is the first liquid, the monomer-containing solution is the second liquid, and the valve metal substrate that has been permeated with the first liquid is immersed in the second liquid in a region below the upper end of the region where the first liquid has permeated; and a cleaning step for cleaning the valve metal substrate.

[0098] Disclosure (2) is a method for manufacturing a solid electrolytic capacitor element according to Disclosure (1), wherein the monomer-containing solution further comprises a dopant.

[0099] (3) of this disclosure is a method for manufacturing a solid electrolytic capacitor element according to (1) or (2) of this disclosure, wherein the solvent contained in the first liquid is an alcohol-based solvent or an aqueous solvent, and the solvent contained in the second liquid is an alcohol-based solvent or an aqueous solvent.

[0100] This disclosure (4) is a method for manufacturing a solid electrolytic capacitor element according to this disclosure (3), wherein the solvent contained in the first liquid is an alcohol-based solvent.

[0101] (5) The present disclosure relates to a solid electrolytic capacitor element comprising: a valve-acting metal substrate having a dielectric layer on at least one main surface and having a first side that is the anode side and a second side that is the cathode side opposite each other in the longitudinal direction; and a solid electrolyte layer provided on the dielectric layer, wherein, when viewed from the direction normal to the main surface of the solid electrolytic capacitor element, the solid electrolyte layer is provided in a part of the region of the valve-acting metal substrate from the second side toward the first side, the solid electrolyte layer is provided so as to approach the first side from both ends of the tip toward the center of the tip, and the solid electrolytic capacitor element does not have an insulating mask layer that separates the valve-acting metal substrate into an anode and a cathode. [Explanation of Symbols]

[0102] 1, 1a, 1b, 1c, 1d Solid electrolytic capacitor elements 10 Valve-acting metal substrate 10B Lower part of the valve-acting metal substrate 10C Cathode Planned Area 10T Upper edge of the area where the first liquid has penetrated 11 Support part 12 Element section 13. First side 14. Second side 20 Dielectric layer 31 Anode section 32 Cathode section 40 Solid electrolyte layer 41c Central part of the tip of the solid electrolyte layer 41e Edge of the solid electrolyte layer 50 carbon layer 51c The central part of the tip of the carbon layer 51e The leading edge of the carbon layer 60 Cathode Conductor Layer 61c Central part of the tip of the cathode conductor layer 61e Edge of the cathode conductor layer 100, 300 Solid electrolytic capacitors 110, 310 Exterior 110a, 310a 1st main surface 110b, 310b 2nd principal surface 110c, 310c 1st side 110d, 310d 2nd side 110e, 310e 1st end surface 110f, 310f 2nd end surface 120, 320 1st external electrode 130, 330 2nd external electrode 210 Solution 1 (Monomer-containing solution) 210S Liquid level of the first liquid 220 Second solution (oxidizing agent-containing solution) 220S Liquid level of the second liquid 220T protrusion 319 Conductive member 340 Capacitor Element Assembly

Claims

1. A step of preparing a valve-acting metal substrate which is in the shape of a strip and has a dielectric layer on at least one main surface, and a first side which is on the anode side and a second side which is on the cathode side, facing each other in the longitudinal direction, A step of preparing a monomer-containing solution having monomers and a solvent to form a solid electrolyte layer by a chemical polymerization reaction, and an oxidizing agent-containing solution having an oxidizing agent and a solvent to polymerize the monomers, A first liquid immersion step is to immerse the valve-acting metal substrate in a first liquid, which is either the monomer-containing solution or the oxidizing agent-containing solution, from the second side to the first side, thereby allowing the first liquid to penetrate the valve-acting metal substrate. If the monomer-containing solution is the first liquid, the oxidizing agent-containing solution is the second liquid; if the oxidizing agent-containing solution is the first liquid, the monomer-containing solution is the second liquid; and the valve-acting metal substrate that has been permeated with the first liquid is immersed in the second liquid in the region on the second side of the region where the first liquid has permeated, rather than the region on the first side. A method for manufacturing a solid electrolytic capacitor element, comprising a cleaning step of cleaning the valve-acting metal substrate, A method for manufacturing a solid electrolytic capacitor element, wherein no insulating mask layer is formed to separate the valve-acting metal substrate into an anode portion and a cathode portion.

2. The method for manufacturing a solid electrolytic capacitor element according to claim 1, wherein the monomer-containing solution further comprises a dopant.

3. The solvent contained in the first liquid is an alcohol-based solvent or an aqueous solvent. The method for manufacturing a solid electrolytic capacitor element according to claim 1 or 2, wherein the solvent contained in the second liquid is an alcohol-based solvent or an aqueous solvent.

4. The method for manufacturing a solid electrolytic capacitor element according to claim 3, wherein the solvent contained in the first liquid is an alcohol-based solvent.

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