Solid electrolytic capacitor

Abstract

To provide a solid electrolytic capacitor capable of sufficiently improving heat resistance reliability.SOLUTION: A solid electrolytic capacitor according to an embodiment of the present disclosure includes a capacitor element including an anode body extending in a first direction, a dielectric layer covering at least a portion of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer. The solid electrolyte layer includes a conductive polymer. The anode body has a first anode body portion having no solid electrolyte layer disposed on one side in a first direction and a second anode body portion having a solid electrolyte layer disposed on the other side in the first direction. Both the first anode body portion and the second anode body portion have a roughened portion extending from at least one outer surface toward a center portion in a thickness direction, and a core portion continuous with a roughened portion in the thickness direction. The roughened portion of the first anode body portion has a thinner thickness than the roughened portion of the second anode body portion, and the thinner portion has a porosity of 30% or less.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to a solid electrolytic capacitor. [Background technology]

[0002] The solid electrolytic capacitor has a capacitor element including, for example, an anode body extending in a first direction, a dielectric layer covering at least a portion of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer. In the capacitor element, the anode body has, for example, a first anode body portion not including a solid electrolyte layer and a second anode body portion including a solid electrolyte layer. The first anode body and the second anode body portion each have, for example, a roughened portion extending from at least one outer surface toward the center in the thickness direction and a core portion continuous with the roughened portion in the thickness direction. The first anode body has, for example, a separator (thin portion), and this separator has a separator member disposed in the separator to prevent contact between the first anode body and the cathode extraction layer formed on the second anode body. It is known that such capacitor elements use a solid electrolyte layer containing a conductive polymer.

[0003] The following Patent Document 1 describes a solid electrolytic capacitor having an anode lead portion (corresponding to the first anode body portion) and a capacitor element portion (corresponding to the second anode body portion) separated from each other by a forbidden band (corresponding to the separating portion) provided on a porous layer (corresponding to the roughened portion) formed on the surface of a valve metal. Patent Document 1 also describes that in the solid electrolytic capacitor, a dielectric oxide film layer, a conductive polymer layer, and a conductor layer are further laminated in this order on the porous layer to form the capacitor element portion. Patent Document 1 also describes that the solid electrolytic capacitor has a groove portion where the porous portion is removed on the capacitor element portion side from the forbidden band. That is, the solid electrolytic capacitor describes providing a groove portion between the forbidden band and the capacitor element portion that makes the porous portion discontinuous in the thickness direction. Patent Document 1 also describes that a dielectric oxide film completely fills the groove portion, blocking the path of oxygen penetration from the anode lead portion. Patent Document 1 below describes that in a solid electrolytic capacitor configured as described above, the grooves can prevent oxygen that has penetrated through the porous portion of the anode lead-out portion from reaching the conductive polymer layer, thereby preventing loss of conductivity and hence capacity reduction due to oxidation of the conductive polymer layer and improving long-term reliability.

[0004] Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-102663) describes a solid electrolytic capacitor comprising a capacitor element including a cathode portion (corresponding to the second anode portion) formed by sequentially forming a dielectric oxide film layer, a solid electrolyte layer, and a conductor layer on a portion of the outer surface of an anode body made of a valve-acting metal and having a roughened surface layer formed by roughening the surface, and an anode lead portion (corresponding to the first anode portion) formed on the remaining portion of the outer surface of the anode body, lead terminals connected to the cathode portion and the anode lead portion of the capacitor element, respectively, and an exterior resin covering the capacitor element with portions of the lead terminals exposed to the outside. Patent Document 2 also describes that in the solid electrolytic capacitor, a first forbidden band and a second forbidden band (corresponding to the separating portion) for separating the anode body from the cathode portion (corresponding to the separating portion) are provided in a portion of the roughened surface layer, and that insulating members (corresponding to the separating member) are provided on the surfaces of the first and second forbidden bands. Furthermore, Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-102663) describes forming the first and second forbidden bands by pressing a portion of the anode body. Patent Document 2 below describes that in a solid electrolytic capacitor configured as described above, the first and second forbidden bands and the insulating member can prevent penetration of the conductive polymer material, and the probability that the solid electrolyte layer will reach the anode lead portion, causing insulation failure or insulation breakdown, is significantly reduced.

[0005] Patent Document 3 listed below describes a solid electrolytic capacitor in which a forbidden zone (corresponding to the above-mentioned separator) is provided in a roughened or porous layer formed on the surface of a valve metal to prevent penetration of a conductive polymer material so as to form at least a boundary between an anode lead portion (corresponding to the above-mentioned first anode body portion) and a capacitor element portion (corresponding to the above-mentioned second anode body portion), and a dielectric oxide film layer, a conductive polymer layer, and a conductor layer are sequentially formed on the surface of the capacitor element portion separated by this forbidden zone, with terminals attached to the surface of the anode lead portion and to the conductor layer, respectively. Patent Document 3 also describes that in a solid electrolytic capacitor configured as described above, the probability that the conductive polymer layer will reach the anode lead portion and cause insulation failure or insulation breakdown is significantly reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-112360 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-7571 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-243665 Summary of the Invention [Problem to be solved by the invention]

[0007] Recently, there has been an increasing demand for improved heat resistance reliability in solid electrolytic capacitors. The decline in heat resistance reliability is often caused by degradation of the solid electrolyte layer when exposed to high temperatures for a long period of time, which in turn leads to a decrease in capacitance. Such degradation of the solid electrolyte layer occurs, for example, when oxygen penetrates the solid electrolyte layer, causing oxidative degradation of the conductive polymer contained in the solid electrolyte layer.

[0008] The above Patent Documents 2 and 3 consider dramatically reducing the probability of poor insulation or breakdown caused by the solid electrolyte layer containing a conductive polymer and the conductive polymer layer reaching the anode lead portion (corresponding to the above-mentioned first anode body portion), but do not consider at all how to suppress the penetration of oxygen into the solid electrolyte layer.

[0009] Furthermore, Patent Document 1 also studies preventing a decrease in capacitance due to oxidation of the conductive polymer layer by providing a groove between the forbidden band and the capacitor element (corresponding to the second anode body) that discontinuities the porous portion in the thickness direction and completely filling the groove with a dielectric oxide film. However, in the capacitor element, the region closer to the anode lead portion than the groove formation position does not benefit from the effect of the groove in suppressing oxygen penetration. Therefore, the conductive polymer film in such region is still subject to oxidative degradation, which is disadvantageous in terms of heat resistance reliability. Therefore, there is room for further study on how to sufficiently suppress oxygen penetration into a solid electrolyte layer containing a conductive polymer and sufficiently improve heat resistance reliability.

[0010] Therefore, the present disclosure provides a solid electrolytic capacitor that can sufficiently improve heat resistance reliability. [Means for solving the problem]

[0011] One aspect of the present invention relates to a solid electrolytic capacitor having a capacitor element including an anode body extending in a first direction, a dielectric layer covering at least a portion of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer, wherein the solid electrolyte layer contains a conductive polymer, the anode body has a first anode body part that does not have the solid electrolyte layer and is arranged on one side in the first direction, and a second anode body part that has the solid electrolyte layer and is arranged on the other side in the first direction, each of the first anode body part and the second anode body part has a roughened portion extending from at least one outer surface toward a center in a thickness direction and a core portion that is continuous with the roughened portion in the thickness direction, the roughened portion of the first anode body part has a thin portion that is thinner than the roughened portion of the second anode body part, and the roughened portion of the thin portion has a porosity of 30% or less. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a solid electrolytic capacitor that can sufficiently improve heat resistance reliability. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a side cross-sectional view showing the configuration of a capacitor element according to an embodiment of the present disclosure. [Figure 1B] 10 is a side cross-sectional view illustrating another mode of attaching the separating member to the capacitor element. FIG. [Figure 1C] FIG. 4 is a plan view illustrating an example of the configuration of a first anode body. [Figure 1D] FIG. 10 is a plan view illustrating another example of the configuration of the first anode body. [Figure 2A] 1 is a side cross-sectional view showing a configuration of a solid electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2B] 2B is a plan view of the solid electrolytic capacitor when viewed from above in FIG. 2A. FIG. [Figure 3] FIG. 2 is a plan view showing a comb-shaped metal foil. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure are obtained. Note that known components may be applied to components characteristic of the present disclosure. In this specification, when a "range between numerical value A and numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0015] In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties, conditions, etc. are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of them can be selected and used alone, or two or more can be used in combination, unless otherwise specified.

[0016] The present disclosure encompasses any combination of two or more claims arbitrarily selected from the appended claims, i.e., any combination of two or more claims arbitrarily selected from the appended claims may be combined unless a technical contradiction arises.

[0017] A solid electrolytic capacitor according to an embodiment of the present disclosure has a capacitor element including an anode body extending in a first direction, a dielectric layer covering at least a portion of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer.

[0018] In the capacitor element, the solid electrolyte layer includes a conductive polymer, and the anode body has a first anode body that does not have a solid electrolyte layer and is arranged on one side in a first direction, and a second anode body that has a solid electrolyte layer and is arranged on the other side in the first direction. In the capacitor element, the first anode body and the second anode body both have a roughened portion that extends from at least one outer surface toward the center in the thickness direction, and a core portion that is continuous with the roughened portion in the thickness direction. In the capacitor element, the roughened portion of the first anode body has a thin-walled portion that is thinner than the roughened portion of the second anode body, and the thin-walled portion has a porosity of 30% or less.

[0019] In the solid electrolytic capacitor according to the embodiment of the present disclosure, it is important that the first anode body included in the capacitor element has a specific configuration. Specifically, it is important that the roughened surface portion of the first anode body has a thin-walled portion that is thinner than the roughened surface portion of the second anode body, and that the thin-walled portion has a porosity of 30% or less. The reason for this is explained below.

[0020] When the anode body has a first anode body that does not have a solid electrolyte layer and is arranged on one side in the first direction, and a second anode body that has a solid electrolyte layer and is arranged on the other side in the first direction, and the first anode body and the second anode body both have a roughened portion that extends from at least one outer surface toward the center in the thickness direction and a core portion that is continuous with the roughened portion in the thickness direction, oxygen contained in the air passes through voids formed in the roughened portion of the first anode body and then enters the inside of the solid electrolyte layer via voids formed in the roughened portion of the second anode body.

[0021] When the solid electrolyte layer contains a conductive polymer, if the solid electrolytic capacitor is exposed to high temperatures for a long period of time (for example, 145°C for 400 hours), the conductive polymer will be significantly oxidized and deteriorated by oxygen that has penetrated into the solid electrolyte layer. The oxidative deterioration of the conductive polymer will cause the solid electrolyte layer to have poor conductivity, which will result in a decrease in the heat resistance reliability of the solid electrolytic capacitor (for example, capacity retention at high temperatures).

[0022] However, in the solid electrolytic capacitor according to the embodiment of the present disclosure, the roughened surface of the first anode body has a thin portion that is thinner than the roughened surface of the second anode body, and the thin portion has a porosity of 30% or less. That is, the roughened surface of the first anode body has a thin portion with an extremely low porosity. This significantly reduces the amount of oxygen that passes through the roughened surface of the first anode body and reaches the roughened surface of the second anode body. Consequently, the amount of oxygen that penetrates into the solid electrolyte layer via the roughened surface of the second anode body can also be significantly reduced. This sufficiently prevents significant oxidative degradation of the conductive polymer contained in the solid electrolyte layer, even when the solid electrolytic capacitor according to the embodiment of the present disclosure is exposed to high temperatures for a long period of time. As a result, the heat resistance reliability of the solid electrolytic capacitor according to the embodiment of the present disclosure is significantly improved.

[0023] Furthermore, when the roughened portions are formed in the thickness direction from each of the outer surfaces of the first anode body toward the center, i.e., when the first anode body is configured so that the core is sandwiched between a pair of roughened portions in the thickness direction, each of the thin-walled portions formed in the pair of roughened portions will have a porosity of 30% or less.

[0024] The porosity of the thin-walled portion can be determined using a cross-sectional image of the anode body including the thin-walled portion. Specifically, the anode body is first cut in the thickness direction to obtain a cross-section including the thin-walled portion, and then an electron microscope photograph of this cross-section is taken. Next, the image of the cross-section (hereinafter also referred to as a cross-sectional image) is binarized to distinguish between metal portions and void portions. Next, the thin-walled portion in the captured image is divided into multiple regions (e.g., regions spaced 0.1 μm apart in the thickness direction) along a path parallel to the thickness direction from the first surface on the outer surface side to the second surface on the core side, and the porosity of each divided region is determined. The arithmetic average of the porosities of each region is then obtained as the porosity of the thin-walled portion. Note that the porosity is a value obtained by regarding the value obtained on an area basis in the cross-sectional image as a volume basis. Therefore, in the porosity, "%" means "volume %."

[0025] The porosity of the thin portion can be adjusted by the degree to which the roughened portion of the first anode body is compressed. Specifically, the porosity of the thin portion can be reduced by increasing the degree to which the roughened portion of the first anode body is compressed, and the porosity of the thin portion can be increased by decreasing the degree to which the roughened portion of the first anode body is compressed.

[0026] The porosity of the thin-walled portion is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less. The smaller the porosity of the thin-walled portion, the more effectively the amount of oxygen that reaches the roughened portion of the second anode body via the roughened portion of the first anode body. This further reduces the amount of oxygen that penetrates into the solid electrolyte layer via the roughened portion of the second anode body. This further effectively prevents the conductive polymer contained in the solid electrolyte layer from undergoing significant oxidative degradation, even when the solid electrolytic capacitor is exposed to high temperatures for a long period of time. As a result, the heat resistance reliability of the solid electrolytic capacitor is further improved. The first anode body does not have a solid electrolyte layer and therefore contributes little to the capacitance of the solid electrolytic capacitor. Therefore, to prevent oxidative degradation of the conductive polymer contained in the solid electrolyte, it is desirable to minimize the porosity of the thin-walled portion. However, excessive compression of the first anode body to reduce the porosity of the thin-walled portion may result in an excessive decrease in the mechanical strength of the first anode body. Therefore, the lower limit of the porosity of the thin-walled portion is preferably 1% or more, more preferably 3% or more, and even more preferably 5% or more.

[0027] Hereinafter, the configuration of a capacitor element and the configuration of a solid electrolytic capacitor according to an embodiment of the present disclosure will be described with reference to the drawings.

[0028] 1A, capacitor element 10 includes anode body 11 extending in first direction D1, a dielectric layer (not shown) covering at least a portion of anode body 11, solid electrolyte layer 12 covering at least a portion of the dielectric layer, and cathode extraction layer 13 covering at least a portion of solid electrolyte layer 12. In capacitor element 10, for example, solid electrolyte layer 12 and cathode extraction layer 13 form cathode portion 14. Note that first direction D1 is a direction parallel to a main surface of anode body 11 and also the length direction of anode body 11.

[0029] In capacitor element 10, anode body 11 has a first anode body 11a that does not have solid electrolyte layer 12 and is arranged on one side in first direction D1, and a second anode body 11b that has solid electrolyte layer 12 and is arranged on the other side in first direction D1. First anode body 11a functions as an anode lead. For convenience, in FIG. 1A, the boundary between first anode body 11a and second anode body 11b is indicated by a solid line.

[0030] In the capacitor element 10, the first anode body 11a and the second anode body 11b each have a roughened portion 11c extending from at least one outer surface toward the center in the thickness direction, and a core portion 11d continuous with the roughened portion 11c in the thickness direction. In the first anode body 11a and the second anode body 11b shown in FIG. 1A, the roughened portion 11c is formed so as to extend from each of the outer surfaces toward the center in the thickness direction. That is, in the first anode body 11a and the second anode body 11b shown in FIG. 1A, the core portion 11d is sandwiched between a pair of roughened portions 11c in the thickness direction. The outer surfaces of the first anode body 11a and the second anode body 11b refer to the main surfaces of the first anode body 11a and the second anode body 11b.

[0031] In capacitor element 10, roughened surface portion 11c of first anode body 11a has thin-walled portion 11c1 that is thinner than roughened surface portion 11c of second anode body 11b, and thin-walled portion 11c1 has a porosity of 30% or less. In first anode body 11a shown in FIG. 1A, each of the pair of roughened surface portions 11c has thin-walled portion 11c1 that is thinner than each of the pair of roughened surface portions 11c of second anode body 11b. In such a case, each of thin-walled portions 11c1 has a porosity of 30% or less. Note that the thickness of roughened surface portion 11c of second anode body 11b refers to the thickness of the portion of roughened surface portion 11c of second anode body 11b that is not compressed in the thickness direction. Furthermore, roughened surface portion 11c of second anode body portion 11b and roughened surface portion 11c other than thin portion 11c1 of first anode body portion 11a typically have a porosity of 60% or more and 80% or less.

[0032] 1A, separating member 15 is disposed in thin portion 11c1. By disposing separating member 15 in thin portion 11c1 in this manner, contact between first anode body portion 11a and cathode portion 14 is restricted. This makes it possible to suppress the occurrence of a short circuit between first anode body portion 11a and cathode portion 14.

[0033] As shown in FIG. 1A, separating member 15 may be arranged to cover the entire exposed surface of thin-walled portion 11c1. Specifically, separating member 15 may be arranged to cover the entire main surface (surface along the first direction D1) of thin-walled portion 11c1 and the entire side surface (surface along the thickness direction) of thin-walled portion 11c1. Arranging separating member 15 in this manner can prevent a gap from being formed between thin-walled portion 11c1 and second anode body 11b in the first direction D1. In this case, separating member 15 is preferably arranged on thin-walled portion 11c1 so as to have a dimension in the thickness direction that is larger than the distance between the main surface of second anode body 11b and the main surface of thin-walled portion 11c1 (see FIG. 1A). This further prevents oxygen contained in the air from penetrating into solid electrolyte layer 12 from the boundary with thin-walled portion 11c1 through roughened surface portion 11c of second anode body 11b. Therefore, even when the solid electrolytic capacitor is exposed to high temperatures for a long period of time, the conductive polymer contained in the solid electrolyte layer can be further prevented from being significantly oxidized and deteriorated, resulting in a further substantial improvement in the heat resistance reliability of the solid electrolytic capacitor.

[0034] As shown in FIG. 1A, thin portion 11c1 is preferably adjacent to second anode body 11b in first direction D1. Thin portion 11c1 is preferably in contact with second anode body 11b at the boundary between first anode body 11a and second anode body 11b, specifically, at the boundary in first direction D1. In other words, thin portion 11c1 is preferably disposed closer to first anode body 11a than the boundary in first direction D1, but not closer to second anode body 11b. That is, roughened portion 11c of second anode body 11b preferably does not have thin portion 11c1. This ensures a sufficient surface area for forming a dielectric layer and solid electrolyte layer 12 in second anode body 11b, thereby enabling sufficient capacitance to be generated. Furthermore, since thin portion 11c1 is disposed in first anode body 11a at the boundary with second anode body 11b in first direction D1, the flow path through which oxygen contained in the air enters roughened portion 11c of second anode body 11b can be sufficiently narrowed. This further sufficiently prevents oxygen contained in the air from entering solid electrolyte layer 12 through roughened surface portion 11c of second anode body 11b. Note that, in second anode body 11b, the surface on which the dielectric layer and solid electrolyte layer 12 are formed refers to the outer surface of roughened surface portion 11c of second anode body 11b and the inner wall surfaces of a plurality of fine pores in roughened surface portion 11c of second anode body 11b.

[0035] Furthermore, roughened surface portion 11c of first anode body 11a may have only thin portion 11c1. That is, the entire roughened surface portion 11c of first anode body 11a may be configured as thin portion 11c1. In this case, the flow path through which oxygen contained in the air passes can be sufficiently narrowed throughout roughened surface portion 11c of first anode body 11a, thereby more sufficiently preventing oxygen contained in the air from passing through roughened surface portion 11c of second anode body 11b and entering solid electrolyte layer 12. Furthermore, when roughened surface portion 11c of first anode body 11a is configured as described above, the dimension of first anode body 11a in first direction D1 can be made smaller than when roughened surface portion 11c of first anode body 11a has two regions in first direction D1, that is, a region having thin portion 11c1 and a region not having thin portion 11c1, as shown in FIG. 1A . This allows a larger proportion of second anode body 11b, which has solid electrolyte layer 12, in anode body 11. Therefore, when a capacitor element in which the roughened surface portion of the first anode body has two regions, one with a thin portion and one without a thin portion, and a capacitor element in which the roughened surface portion of the first anode body has only a thin portion (i.e., one region), have the same dimensions in first direction D1, the dimension in first direction D1 of second anode body 11b can be made larger. As a result, a solid electrolytic capacitor having such a capacitor element has a sufficiently increased capacitance.

[0036] As shown in FIG. 1B , when the separating member 15 is disposed on the thin-walled portion 11c1 so as to form a gap between the thin-walled portion 11c1 and the second anode body 11b in the first direction D1, the gap is preferably filled with a conductive polymer 16. In this case, the conductive polymer 16 can sufficiently prevent oxygen contained in the air from penetrating the gap through the roughened portion 11c of the second anode body 11b into the solid electrolyte layer 12. This sufficiently prevents the conductive polymer contained in the solid electrolyte layer 12 from being significantly oxidized and deteriorated, even when the solid electrolytic capacitor is exposed to high temperatures for a long period of time. As a result, the heat resistance reliability of the solid electrolytic capacitor is further improved. The conductive polymer 16 may be filled in the gap by a portion of the solid electrolyte layer 12 penetrating the gap. Note that the conductive polymer 16 filled in the gap formed between the thin-walled portion 11c1 and the second anode body 11b hardly contributes to the capacitance development of the solid electrolytic capacitor. Therefore, even if the conductive polymer 16 filling these gaps is oxidized and deteriorated, the heat resistance reliability of the solid electrolytic capacitor is not significantly affected.

[0037] First anode body 11a has cutout portion 11A on at least one side in second direction D2 orthogonal to first direction D1, and cutout portion 11A preferably includes thin-walled portion 11c1. This cuts out at least a portion of roughened surface portion 11c in first anode body 11a, thereby reducing the number of oxygen flow paths (flow paths in second direction D2) in roughened surface portion 11c of first anode body 11a. This further reduces the amount of oxygen that penetrates into solid electrolyte layer 12 through roughened surface portion 11c of second anode body 11b, further preventing oxidative degradation of solid electrolyte layer 12 and a decrease in capacitance when the solid electrolytic capacitor is exposed to high temperatures for a long period of time. From the viewpoint of further reducing the number of flow paths through which oxygen passes in the roughened portion 11c of the first anode body 11a, the first anode body 11a preferably has cutout portions 11A in both the first direction D1 and a second direction D2 perpendicular to the first direction D1, as shown in Figures 1C and 1D. The second direction D2 is the width direction of the anode body 11. In Figures 1C and 1D, the roughened portion 11c, the thin-walled portion 11c1, the separating member 15, and the like are not shown.

[0038] As shown in FIGS. 1C and 1D , the cutout 11A is preferably formed in the first anode body 11a so as to extend to the first end 11B opposite the second anode body 11b. This reduces the flow path in the second direction D2 at the first end 11B, thereby reducing the amount of oxygen that penetrates from the first end 11B into the interior of the roughened surface portion 11c of the first anode body 11a. As a result, the amount of oxygen that penetrates into the interior of the solid electrolyte layer 12 through the roughened surface portion 11c of the second anode body 11b is further reduced, further suppressing oxidative degradation of the solid electrolyte layer 12 and a decrease in capacitance when the solid electrolytic capacitor is exposed to high temperatures for a long period of time. The cutout 11A is preferably formed in the first anode body 11a so as to include the thin-walled portion 11c1 of the roughened surface portion 11c.

[0039] The shape of the cutout portion 11A is not particularly limited. When the capacitor element 10 is viewed in plan, the cutout portion 11A may be formed by cutting out an arc-shaped portion of at least one side of the first anode body portion 11a in the second direction D2, as shown in FIG. 1C. When the capacitor element 10 is viewed in plan, the cutout portion 11A may be formed by cutting out a rectangular portion of at least one side of the first anode body portion 11a in the second direction D2, as shown in FIG. 1D. When the cutout portions 11A are formed on both sides in the second direction D2, it is preferable that these cutout portions 11A be line-symmetrical with respect to a line segment L that passes through the center of the second direction D2 and extends in the first direction D1.

[0040] 1C and 1D, the second anode body 11b may have a first end 11C on the side of the first anode body 11a in the first direction D1, and the cutout portion 11A may be formed spaced apart from the first end 11C of the second anode body 11b. Although not shown in FIGS. 1C and 1D, the first anode body 11a has a thin-walled portion 11c1. For example, as shown in FIG. 1A, in the first anode body 11a, the thin-walled portion 11c1 is adjacent to the second anode body 11b in the first direction D1. In this case, as shown in FIGS. 1C and 1D, a rectangular region R having approximately the same dimension (width) as the dimension (width) of the second anode body 11b in the second direction D2 is formed between the first end 11C of the second anode body 11b and the cutout portion 11A of the first anode body 11a. That is, first anode body 11a may have rectangular region R as described above on the side of first end 11C of second anode body 11b.

[0041] If the dimension (length) of first anode body 11a in first direction D1 is L1 and the dimension (length) of rectangular region R in first direction D1 is LR, from the viewpoint of ensuring a sufficient adhesive surface for the insulating tape, LR is preferably 0.2L1 or more, more preferably 0.3L1 or more, and still more preferably 0.4L1 or more. Furthermore, from the viewpoint of sufficiently reducing the flow paths through which oxygen penetrates in first anode body 11a (flow paths in second direction D2), LR is preferably 0.8L1 or less, and more preferably 0.6L1 or less.

[0042] In the second direction D2, the ratio RW (= W1 / W2 × 100) of the narrowest dimension W1 of the first anode body 11a to the widest dimension (width) W2 of the second anode body 11b is preferably 60% or less. When the ratio RW is 60% or less, the flow paths (flow paths in the second direction D2) through which oxygen passes in the roughened portion 11c of the first anode body 11a can be reduced. As a result, the amount of oxygen that penetrates into the inside of the solid electrolyte layer 12 through the roughened portion 11c of the second anode body 11b is further reduced. The ratio RW may be 50% or less, or may be 40% or less.

[0043] The ratio RW is preferably 20% or more. The ratio RW may be 25% or more, or may be 30% or more. As will be described later, the capacitor element 10 is provided in a solid electrolytic capacitor in a state where it is covered with an exterior body (e.g., a resin sealant). In such a solid electrolytic capacitor, on the side of the first anode body 11a, a part of the exterior body may be cut so that at least a part of the first anode body 11a is exposed, thereby ensuring electrical continuity between the first anode body 11a and the outside. In order to further ensure electrical continuity between the first anode body 11a and the outside, a conductive coating (e.g., a copper (Cu) coating) may be formed on the exposed end surface of the first anode body 11a (the end surface of the first anode body 11a) by cold spray processing or the like. In such a case, when the ratio RW is within the above range, a conductive coating can be sufficiently formed on the exposed end surface of the first anode body 11a. This makes it possible to more sufficiently ensure electrical continuity between the first anode body 11a and the outside, and therefore to sufficiently prevent the ESR of the solid electrolytic capacitor from increasing due to poor electrical continuity between the first anode body 11a and the outside.

[0044] 1C and 1D, in the second anode body portion 11b, the second end 11D located on the opposite side of the first end 11C in the first direction D1 preferably has both ends in the second direction D2 that are rounded. In other words, it is preferable that neither end side of the second end 11D in the second direction D2 has a corner. It is preferable that both end sides of the second end 11D in the second direction D2 have an arc shape that bulges outward, for example. This makes it possible to prevent stress from concentrating on both end sides of the second end 11D in the second direction D2, thereby preventing damage to both end sides of the second end 11D due to stress concentration.

[0045] Anode body 11 is formed using a metal containing a valve metal. For example, a foil (metal foil) containing a valve metal can be used for anode body 11. Examples of valve metals include aluminum, tantalum, niobium, and titanium. Anode body 11 contains one or more valve metals. Anode body 11 may contain the valve metal in the form of an alloy or an intermetallic compound. The thickness of anode body 11 is not particularly limited. The thickness of anode body 11 other than thin portion 11c1 is, for example, 15 μm to 300 μm, and may be 80 μm to 250 μm. As described above, the anode body 11 has the first anode body 11a and the second anode body 11b, and each of the first anode body 11a and the second anode body 11b has a roughened portion 11c extending from each of the outer surfaces of the first anode body 11a and the second anode body 11b toward the center in the thickness direction, and a core portion 11d continuous with the roughened portion 11c in the thickness direction. In the anode body 11, the roughened portion 11c may be formed by an etching process such as electrolytic etching. That is, the roughened portion 11c may be an etched layer. The roughened portion 11c is a region having a plurality of fine pores. On the other hand, the core portion 11d is, for example, a region that has not been electrolytically etched.

[0046] It is preferable that the separating member 15 has high insulating properties. The separating member 15 may be a conventionally known insulating tape (resist tape). For example, polyimide tape (PI tape) can be used as such an insulating tape.

[0047] The separation member 15 may be formed by applying a resin composition containing a curable resin to at least a portion of the surface of the separation section. The curable resin may be a thermosetting resin or a photocurable resin. The photocurable resin may be a resin that cures under visible light or ultraviolet light. Examples of curable resins include epoxy resins, polyimide resins, silicone resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, furan resins, polyurethane resins, curable acrylic resins, and photoresist resins. The resin composition may contain a curing agent, a curing accelerator, a flame retardant, a filler, a coupling agent, a colorant, a mold release agent, and an inorganic ion scavenger, as needed. Various known agents may be used. The resin composition may contain a thermoplastic resin (e.g., polyamide resin, polyamideimide resin, polyolefin resin, polyester resin, etc.) in addition to the curable resin.

[0048] As described above, the dielectric layer covers at least a portion of the anode body 11. The dielectric layer may be formed, for example, by anodizing the surface of the anode body 11 using a chemical conversion treatment or the like. Therefore, the dielectric layer may contain an oxide of a valve metal. For example, when aluminum is used as the valve metal, the dielectric layer may contain Al2O3. Note that the dielectric layer is not limited to this and may be any material that functions as a dielectric. The dielectric layer is preferably formed on at least a portion of the surface of the roughened portion 11c of the first anode body 11a and the roughened portion 11c of the second anode body 11b. The dielectric layer is preferably formed on the outer surface of the roughened portion 11c of the first anode body 11a and the second anode body 11b, and more preferably formed along the inner wall surfaces of the multiple fine pores in the roughened portion 11c.

[0049] As described above, solid electrolyte layer 12 covers at least a portion of the dielectric layer. Solid electrolyte layer 12 is also disposed on second anode body 11b. That is, solid electrolyte layer 12 covers at least a portion of the dielectric layer in second anode body 11b. Solid electrolyte layer 12 may also cover the entire surface of the dielectric layer in second anode body 11b.

[0050] As described above, the solid electrolyte layer 12 contains a conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylvinylene, polyacene, and polythiophenevinylene. These may be used alone or in combination of two or more. The conductive polymer may also be a copolymer of two or more monomers.

[0051] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0052] The conductive polymer may be contained in the solid electrolyte layer together with a dopant. The dopant may be a monomolecular anion or a polymeric anion. Examples of monomolecular anions include paratoluenesulfonic acid and naphthalenesulfonic acid. Examples of polymeric anions include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylicsulfonic acid, polymethacrylicsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, and polyacrylic acid. The above dopants may be used alone or in combination of two or more. Furthermore, the polymeric anion may be a polymer of a single monomer or a copolymer of two or more monomers.

[0053] The solid electrolyte layer 12 may further contain known additives and known conductive materials other than conductive polymers, as needed. Examples of the conductive materials include at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ (tetracyanoxydimethane) complex salts.

[0054] A conductive polymer can be obtained by chemical oxidative polymerization or electrolytic polymerization of a monomer that constitutes the conductive polymer (hereinafter, also simply referred to as a monomer).

[0055] Chemical oxidative polymerization can be carried out by chemically oxidizing a monomer using a solvent, an oxidizing agent, a monomer, and, if necessary, a dopant. Examples of solvents that can be used include water, sulfuric acid, methanol, ethanol, propanol, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, chloroform, dichloromethane, carbon tetrachloride, benzene, toluene, xylene, tetrahydrofuran, N-methyl-2-pyrrolidone, and propylene carbonate. The monomer and dopant can be appropriately selected depending on the desired conductive polymer. Examples of oxidizing agents that can be used include ferric oxide, iron(III) tri(p-toluenesulfonate), sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, and potassium permanganate. The polymerization conditions for chemical oxidative polymerization can be appropriately selected depending on the types of solvent, oxidizing agent, monomer, and, if necessary, dopant used.

[0056] In electropolymerization, a monomer is polymerized in a solvent to obtain a conductive polymer. In electropolymerization, a dopant may be used as needed. As the solvent, those exemplified above can be used. The monomer and dopant may be appropriately selected depending on the desired conductive polymer.

[0057] Examples of electrolytic polymerization include a method in which a monomer and, if necessary, a dopant compound are dissolved in a solvent (hereinafter referred to as a monomer-containing solvent) by applying a potential sweep method or a constant voltage method using a potentiostat to polymerize the monomer, and a method in which a constant current method is applied to a monomer-containing solvent by using a galvanostat to polymerize the monomer. The dopant compound functions as an electrolyte in the monomer-containing solvent. The conditions for the potential sweep method, constant voltage method, and constant current method can be appropriately selected depending on the type of solvent, monomer, and, if necessary, dopant used.

[0058] As described above, cathode extraction layer 13 covers at least a portion of solid electrolyte layer 12. Cathode extraction layer 13 may cover the entire surface of solid electrolyte layer 12. Cathode extraction layer 13 may include, for example, a carbon layer and a metal (e.g., silver) paste layer formed on the surface of the carbon layer. The configuration of cathode extraction layer 13 is not limited thereto, and may be any configuration that has a current collecting function. Note that when cathode extraction layer 13 includes a carbon layer and a paste layer, the carbon layer is laminated on solid electrolyte layer 12.

[0059] The carbon layer contains a carbon material and has electrical conductivity. The carbon material is not particularly limited. Examples of the carbon material include graphite, carbon black, graphene flakes, and carbon nanotubes.

[0060] The carbon layer may contain at least one of a binder resin and an additive, as needed. The binder resin is not particularly limited, and known binder resins used in the manufacture of capacitor elements can be used. Examples of binder resins include thermosetting resins and thermoplastic resins. Examples of thermosetting resins include epoxy resins, polyimide resins, silicone resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, and curable acrylic resins. Examples of thermoplastic resins include polyamide resins, polyamideimide resins, polyolefin resins, and polyester resins. Examples of additives include dispersants, surfactants, antioxidants, preservatives, bases, and acids.

[0061] The metal paste layer contains a metal material. The metal material is not particularly limited. From the viewpoint of enhancing electrical conductivity, the metal material preferably contains silver.

[0062] The volume ratio of the metal material in the metal paste layer is not particularly limited as long as it exceeds 0% by volume. From the viewpoint of reducing electrical resistance, the volume ratio of the metal material is preferably 60% by volume or more, more preferably 70% by volume or more, and even more preferably 80% by volume or more.

[0063] The metal paste layer may further contain a binder resin. The volume ratio of the binder resin in the metal paste layer is not particularly limited. From the viewpoint of reducing electrical resistance, the volume ratio of the binder resin is preferably 60% by volume or less, more preferably 20% by volume or less, and even more preferably 10% by volume or less. The volume ratio of the binder resin may be 0.1% by volume or more, or may be 0% by volume. The volume ratio of the binder resin can be confirmed, for example, by energy dispersive X-ray spectroscopy (SEM-EDX).

[0064] The thickness of the metal paste layer is not particularly limited. For example, the thickness of the metal paste layer may be 0.1 μm or more and 50 μm or less, or 1 μm or more and 20 μm or less. The thickness of the metal paste layer is the average value of five arbitrary points on the cross section in the thickness direction.

[0065] Next, a solid electrolytic capacitor according to an embodiment of the present disclosure will be described with reference to Figures 2A and 2B. A solid electrolytic capacitor according to an embodiment of the present disclosure may include at least one of the above-described capacitor elements. For example, when a solid electrolytic capacitor according to an embodiment of the present disclosure includes multiple capacitor elements, at least one of the multiple capacitor elements may be the above-described capacitor element, and the remaining capacitor elements may be conventionally known capacitor elements. In such a case, however, it is preferable that all of the multiple capacitor elements be the above-described capacitor elements.

[0066] 2A and 2B, the solid electrolytic capacitor 100 includes a plurality of capacitor elements 10. All of the plurality of capacitor elements 10 are the above-described capacitor elements. As shown in FIG. 2A, in the solid electrolytic capacitor 100, the plurality of capacitor elements 10 are stacked in the height direction with their main surfaces overlapping each other. As shown in FIG. 2A, in the solid electrolytic capacitor 100, the plurality of capacitor elements 10 are stacked in the first direction D1 such that the protruding end surfaces S1 of the first anode body portions 11a and the terminal end surfaces S2 of the cathode portions 14 face the same direction.

[0067] There is no particular limitation on the number of stacked capacitor elements 10. The number of stacked capacitor elements 10 is, for example, between 2 and 20. Note that Fig. 2A shows an example in which six capacitor elements 10 are stacked.

[0068] A solid electrolytic capacitor 100 according to one embodiment of the present disclosure comprises a lead frame 110 electrically connected to each of the cathode portions 14 of a plurality of capacitor elements 10, an outer casing 120 that seals the plurality of capacitor elements 10 and the lead frame 110, a first external electrode 130 electrically connected to each of the first anode portions of the plurality of capacitor elements 10 at a first end face E1 on one side of the outer casing 120 in the first direction D1, and a second external electrode 140 electrically connected to the lead frame 110 at a second end face E2 on the other side of the outer casing 120 in the first direction D1.

[0069] 2A and 2B, in the plurality of capacitor elements 10, the protruding end surface S1 of each of the first anode body portions 11a is exposed from the first end surface E1 of the exterior body 120. In addition, in the plurality of capacitor elements 10, the terminal end surface S2 of each of the cathode portions 14 is arranged on the second end surface E2 side of the exterior body 120.

[0070] 2A and 2B, in the plurality of capacitor elements 10, each roughened portion 11c of the first anode body portion 11a has only a thin portion 11c1. Also, in FIGS. 2A and 2B, a separating member 15 is arranged to cover the entire exposed surface of each thin portion 11c1. Furthermore, in FIGS. 2A and 2B, in the plurality of capacitor elements 10, each separating member 15 has an end face Es that is flush with the respective protruding end face S1 of the first anode body portion 11a and is exposed from the first end face E1 of the exterior body 120.

[0071] 2A and 2B, in the plurality of capacitor elements 10, each of the first anode bodies 11a has a cutout portion 11A in both of the first direction D1 and the second direction D2 orthogonal to each other. Note that each of the first anode bodies 11a may have a cutout portion 11A in either one of the second directions D2. That is, each of the first anode bodies 11a only needs to have a cutout portion 11A in at least one of the second directions D2. The shape of the cutout portion 11A is not particularly limited. Although FIG. 2B shows an example in which the cutout portion 11A has an arc shape when the capacitor element 10 is viewed in a plan view, the shape of the cutout portion 11A when the capacitor element 10 is viewed in a plan view may also be rectangular (see FIG. 1D).

[0072] 2B also shows an example in which both ends of second end 11D of second anode body 11b in second direction D2 have corners. That is, FIG. 2B shows an example in which second anode body 11b has a rectangular shape when capacitor element 10 is viewed in a plan view. Note that both ends of second end 11D of second anode body 11b in second direction D2 may be rounded when capacitor element 10 is viewed in a plan view, as shown in FIGS. 1C and 1D. Both ends of second end 11D of second anode body 11b in second direction D2 may have, for example, an arc shape that bulges outward.

[0073] The exterior body 120 protects the plurality of capacitor elements 10 from impact, moisture, and the like. The exterior body 120 is configured to cover the entire plurality of capacitor elements 10. The exterior body 120 may be a resin exterior body or another exterior body. The exterior body 120 is preferably a resin exterior body. For example, epoxy resin can be used as the material for the resin exterior body.

[0074] The first external electrode 130 and the second external electrode 140 can be obtained by applying a conductive paste containing conductive particles (e.g., silver particles) to the first end face E1 and the second end face E2 of the exterior body 120, drying it to form a conductive paste layer, and then plating a metal (e.g., nickel) on the conductive paste layer to form a metal plating layer. In the solid electrolytic capacitor 100, the first external electrode 130 is configured to cover the first end face E1 of the exterior body 120, and the second external electrode 140 is configured to cover the second end face E2 of the exterior body 120.

[0075] In the solid electrolytic capacitor 100 according to the embodiment of the present disclosure, the lead frame 110 has a sidewall 111 that extends along the second end face E2 of the package 120 and faces the terminal end face S2 of the cathode portion 14 in the first direction D1, and an overhang 112 that intersects the sidewall 111, extends toward the second end face E2 of the package 120, and is exposed at the second end face E2. The lead frame 110 is electrically connected to the second external electrode 140 via the overhang 112. In other words, at the second end face E2 of the package 120, the protruding end face S3 of the overhang 112 of the lead frame 110 is exposed and electrically connected to the second external electrode 140. By configuring the lead frame 110 as described above, the length L of the overhang 112 can be designed to be as small as possible. This reduces the excess space formed between the second end face E2 of the package 120 and the side wall 111 of the lead frame 110, allowing for a larger size of the capacitor element 10 to be placed inside the package 120. As a result, the capacitance of the solid electrolytic capacitor 100 can be increased. Furthermore, since the lead frame 110 has the side wall 111, it is possible to prevent the end face S2 of the cathode portion 14 from coming too close to the second end face E2 of the package 120.

[0076] The side wall portion 111 of the lead frame 110 and the plurality of capacitor elements 10 are connected by a first conductive paste layer (not shown). This allows electrical connection between each of the cathode portions 14 of the plurality of capacitor elements 10 and the side wall portion 111 of the lead frame 110. More specifically, the side wall portion 111 of the lead frame 110 can be electrically connected to each of the end faces S2 of the cathode portions 14 of the plurality of capacitor elements 10. The second end face E2 of the outer casing 120 and the second external electrode 140 are also connected by a second conductive paste layer. This allows electrical connection between the second external electrode 140 and the protruding portion 112 of the lead frame 110. The first conductive paste layer and the second conductive paste layer can be formed using any of various known conductive adhesives.

[0077] As described above, in the multiple capacitor elements 10, the protruding end faces S1 of the multiple first anode bodies 11a are exposed from the first end face E1 of the exterior housing 120. The multiple first anode bodies 11a are electrically connected to the first external electrode 130 via their respective protruding end faces S1. In other words, the protruding end faces S1 of the multiple first anode bodies 11a are exposed from the first end face E1 of the exterior housing 120 and are electrically connected to the first external electrode 130. Specifically, the first end face E1 of the exterior housing 120 and the first external electrode 130 are connected by a third conductive paste layer (not shown). When the solid electrolytic capacitor 100 is configured as described above, it is possible to prevent excess space from being formed between the protruding end faces S1 of the multiple first anode bodies 11a and the first end face E1 of the exterior housing 120. This allows the size of the capacitor elements 10 to be placed inside the exterior housing 120 to be further increased. As a result, the capacitance of solid electrolytic capacitor 100 can be further increased.

[0078] In solid electrolytic capacitor 100 according to an embodiment of the present disclosure, lead frame 110 includes a pair of protruding portions 112 spaced apart from each other (see FIG. 2B ), and side wall portion 111 extends from between the pair of protruding portions 112 along second end face E2 of exterior body 120 toward end face S2 of cathode portion 14. When solid electrolytic capacitor 100 is configured as described above, the contact area between second external electrode 140 and lead frame 110 can be increased, thereby enabling more optimal electrical connection between lead frame 110 and second external electrode 140.

[0079] In solid electrolytic capacitor 100 according to an embodiment of the present disclosure, lead frame 110 further includes bottom plate portion 113 that extends in first direction D1 along the lower end surface of cathode portion 14 and is connected to side wall portion 111 and protruding portion 112. When lead frame 110 is configured as described above, bottom plate portion 113 can adequately support multiple capacitor elements 10 from below. In FIG. 2A , the boundary between protruding portion 112 and bottom plate portion 113 is indicated by reference numeral B1.

[0080] In solid electrolytic capacitor 100 according to an embodiment of the present disclosure, bottom plate portion 113 of lead frame 110 is connected to the lower end surface of cathode portion 14 of capacitor element 10 by a fourth conductive paste layer (not shown). With this configuration, the lower end surface of capacitor element 10 can also be electrically connected to lead frame 110. That is, bottom plate portion 113 of lead frame 110 can be electrically connected so as to contact the lower end surface of cathode portion 14.

[0081] In solid electrolytic capacitor 100 according to an embodiment of the present disclosure, length L of protruding portion 112 in lead frame 110 may be, for example, 0.60 mm or less, or 0.40 mm or less. The lower limit of length L of protruding portion 112 is typically 0.15 mm. In lead frame 110, thickness of side wall portion 111 and protruding portion 112 may be, for example, 0.08 mm or more and 0.30 mm or less.

[0082] In solid electrolytic capacitor 100 according to an embodiment of the present disclosure, lead frame 110 may have notches C formed between a pair of overhanging portions 112 and side wall portions 111 (see FIG. 2B ). In lead frame 110, side wall portions 111 are typically formed by bending a portion of a flat plate. Therefore, if the region corresponding to side wall portions 111 and the region corresponding to overhanging portion 112 are in contact with each other in the flat plate, the region corresponding to side wall portions 111 is likely to be obstructed by the region corresponding to overhanging portion 112 when the flat plate is bent. However, by forming notches C as described above, the region corresponding to side wall portions 111 and the region corresponding to overhanging portion 112 can be kept out of contact with each other in the flat plate. This makes it less likely that the region corresponding to side wall portions 111 will be obstructed by the region corresponding to overhanging portion 112 when the flat plate is bent. In other words, the region corresponding to side wall portions 111 can be easily bent to any desired position.

[0083] Next, a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure will be described.

[0084] A method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure includes a first step of preparing an anode body having a roughened portion extending from at least one outer surface toward a center in a thickness direction and a core portion continuous with the roughened portion in the thickness direction; a second step of forming a dielectric layer so as to cover at least a portion of the anode body; a third step of compressing the portion of the anode body having the roughened portion in the thickness direction to form a thin portion; a fourth step of covering at least a portion of the dielectric layer so as to expose the thin portion to form a cathode portion, thereby obtaining a laminate in which the anode body, the dielectric layer, and the cathode portion are laminated in this order; a fifth step of placing the laminate on a lead frame having a protruding portion extending toward the cathode while electrically connecting a side wall portion of the lead frame to an end face of the cathode portion, and sealing the lead frame and the laminate to obtain a sealed body; a sixth step of exposing the protruding end face of the anode body from a first end face of the sealed body and exposing the protruding end face of the protruding portion of the lead frame from a second end face of the sealed body; and a seventh step of arranging a first external electrode so as to be electrically connected to the protruding end face of the anode body exposed from the first end face of the sealed body, and arranging a second external electrode so as to be electrically connected to the protruding portion of the lead frame exposed from the second end face of the sealed body.

[0085] In the first step, the roughened portion can be formed by performing an etching process or the like on at least one outer surface of the anode body. The outer surface of the anode body refers to the main surface of the anode body. In the first step, it is preferable to perform an etching process or the like on each of the outer surfaces of the anode body, thereby forming a roughened portion on the anode body from each of the outer surfaces toward the center in the thickness direction. In the anode body, the region not subjected to the etching process or the like may be the core portion. The etching process may also be electrolytic etching.

[0086] In the second step, the dielectric layer can be formed by various known methods. The dielectric layer can be formed by oxidizing the valve metal contained in the anode body through chemical conversion treatment or the like. For example, the dielectric layer may be formed by immersing the anode body in a chemical conversion solution and applying a voltage. In the method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure, as described above, the anode body has a roughened portion. Therefore, the dielectric layer may be formed on the outer surface of the roughened portion or along the inner wall surfaces of multiple fine holes in the roughened portion. The dielectric layer is typically formed over almost the entire area of ​​the anode body. That is, the dielectric layer is typically formed on both the first anode body and the second anode body.

[0087] In the third step, the thin-walled portion is formed by compressing a portion of the anode body having the roughened portion in the thickness direction. The pressure applied when compressing the portion of the anode body in the thickness direction can be appropriately adjusted taking into account the porosity of the roughened portion before compression and the porosity of the desired thin-walled portion. In a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure, the portion of the anode body is compressed in the thickness direction so that the porosity of the thin-walled portion is 30% or less. In the second step, the anode body is divided into a first anode body portion having the thin-walled portion and a second anode body portion not having the thin-walled portion. The first anode body portion is a region of the anode body that does not have a cathode portion including a solid electrolyte layer, and the second anode body portion is a region of the anode body that has a cathode portion including a solid electrolyte layer.

[0088] In the fourth step, the cathode part can be formed by various known methods. The solid electrolyte layer in the cathode part can be formed, for example, by attaching a monomer of a conductive polymer (hereinafter simply referred to as a monomer) to at least a portion of the dielectric layer, and then chemically oxidizing or electrolytically polymerizing the monomer on at least a portion of the dielectric layer to form a conductive polymer layer. The attachment of the monomer to at least a portion of the dielectric layer can be performed by immersing at least a portion of the anode body on which the dielectric layer has been formed in a polymerization solution containing the monomer. In a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure, the monomer is attached to the dielectric layer formed on the second anode body to form a conductive polymer layer on the second anode body. When electrolytically polymerizing the monomer, a voltage in the range of 1 V to 5 V may be applied to the anode body as electrical energy.

[0089] The solid electrolyte layer in the cathode section may be formed by applying a treatment liquid containing a conductive polymer onto the dielectric layer to form a coating film, and then drying the coating film. The conductive polymer may be, for example, poly(3,4-ethylenedioxythiophene) (PEDOT). The dopant may be, for example, polystyrene sulfonic acid (PSS). The treatment liquid is a dispersion or solution of the conductive polymer. Examples of the dispersion medium (solvent) include water, an organic solvent, or a mixture thereof.

[0090] The cathode extraction layer in the cathode section can be obtained, for example, by applying a carbon dispersion liquid in which carbon is dispersed so as to cover at least a portion of the solid electrolyte layer, drying the liquid to form a carbon layer, and then applying a composition containing metal particles (e.g., silver particles) and a resin component (binder resin) to cover at least a portion of the carbon layer, and then heating and drying the composition to form a conductive layer. Note that if the binder resin is a thermosetting resin, the binder resin can be thermally cured by the above-mentioned heating and drying. In this manner, a laminate in which the anode body, the dielectric layer, and the cathode section are laminated in this order can be obtained.

[0091] In the fifth step, a lead frame having sidewall portions and protruding portions extending in a direction intersecting the sidewall portions can be obtained by processing a metal plate into a predetermined shape. In addition to the sidewall portions and protruding portions, the lead frame preferably further includes a bottom plate portion connected to the sidewall portions and the protruding portions. By including the bottom plate portion in the lead frame, the laminate obtained as described above can be sufficiently supported from the lower surface side. The bottom plate portion preferably extends in the same direction as the extending direction of the protruding portions. In other words, the bottom plate portion preferably extends in a direction intersecting the sidewall portions.

[0092] The side wall portion of the lead frame and the end surface of the cathode portion can be electrically connected, for example, by interposing a conductive paste layer therebetween. The lead frame and the laminate are sealed, for example, by using a sealing resin or the like to embed the entire lead frame and the laminate. When the sealing resin is a thermosetting resin, it is preferable that the sealing resin be thermally cured after embedding the lead frame and the laminate. For sealing with the sealing resin, conventionally known techniques such as transfer molding or compression molding can be applied.

[0093] In the sixth step, the first and second end faces of the sealing body are cut to a predetermined size by, for example, blade dicing or using an ultrasonic cutter, so that the protruding end face of the anode body and the protruding end face of the protruding portion of the lead frame are exposed. In the method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure, the protruding end face of the anode body refers to the protruding end face of the first anode body. Furthermore, the protruding end face of the anode body is exposed from the first end face of the sealing body after cutting, and the protruding portion of the lead frame is exposed from the second end face of the sealing body after cutting. A coating may be formed on the first and second end faces of the sealing body after cutting by cold spraying. This can prevent natural oxidation of the protruding end face of the anode body (i.e., the protruding end face of the first anode body) and the protruding end face of the protruding portion exposed by cutting. For cold spray processing, metal particles such as copper (Cu), aluminum (Al), titanium (Ti), silver (Ag), nickel (Ni), zinc (Zn), tin (Sn), molybdenum (Mo), iron (Fe), tantalum (Ta), niobium (Nb), silicon (Si), and chromium (Cr) can be used.

[0094] In the seventh step, the first external electrode can be obtained by applying a conductive paste containing conductive particles (e.g., silver particles) to the first end face of the cut sealing body to form a conductive paste layer, and then plating a metal (e.g., nickel) on the conductive paste layer to form a metal plating layer. The second external electrode can also be obtained in the same manner as above, by forming a conductive paste layer and a metal plating layer in this order on the second end face of the cut sealing body. The first external electrode obtained as described above is electrically connected to the protruding end face of the anode body (i.e., the protruding end face of the first anode body portion), and the second external electrode obtained as described above is electrically connected to the protruding end face of the protruding portion of the lead frame.

[0095] As described above, by carrying out the first to seventh steps, a solid electrolytic capacitor according to an embodiment of the present disclosure can be obtained.

[0096] In a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present disclosure, the first to fourth steps may be performed using a foil (metal foil) containing a valve metal and having a comb-like shape. For example, as shown in FIG. 3 , the first to fourth steps may be performed using a metal foil 200 having a main body portion 210 and a plurality of extension portions 220 extending outward from both ends of the main body portion 210 in the width direction. The extension portions 220 each have a narrow first region 220a whose one end is connected to the main body portion 210 and a wide second region 220b whose other end is connected to the first region 220a. At least a portion of the first region 220a of the extension portion 220 is used as a first anode portion, and a cathode portion is formed in the second region 220b. After the cathode portion is formed in the second region 220b, the extension portion 220 is cut at a predetermined location in the first region 220a. This allows for the production of a laminate in which the anode body, dielectric layer, and cathode portion are stacked in this order. Also, in Fig. 3, the boundary between the first region 220a and the second region 220b is indicated by a dashed line. Such a comb-shaped metal foil 200 is particularly useful when producing multiple laminates at once.

[0097] Although the present specification has described an example in which the solid electrolytic capacitor 100 includes a plurality of capacitor elements 10 as an embodiment, the solid electrolytic capacitor 100 may include only one capacitor element 10. Furthermore, the present specification has described an example in which the protruding end surface S1 of the first anode body 11a is exposed and electrically connected to the first external electrode 130 in the solid electrolytic capacitor 100 as an embodiment, but the electrical connection between the first anode body 11a and the first external electrode 130 is not limited to this. The first anode body 11a and the first external electrode 130 may be electrically connected via a lead frame. Furthermore, the present specification has described an example in which the solid electrolytic capacitor 100 includes an example in which the cathode portion 14 and the second external electrode 140 are electrically connected via a lead frame 110 having a side wall portion 111 and a protruding portion 112 extending intersecting with the side wall portion 111, but the configuration of the lead frame is not limited to this. The lead frame may have an extension that extends from the inside to the outside of package 120, and may be electrically connected to second external electrode 140 by this extension.

[0098] (Addendum) The above description discloses the following techniques. (Technology 1) a solid electrolytic capacitor having a capacitor element including an anode body extending in a first direction, a dielectric layer covering at least a portion of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer, the solid electrolyte layer contains a conductive polymer, the anode body includes a first anode body portion that does not have the solid electrolyte layer and is arranged on one side in the first direction, and a second anode body portion that has the solid electrolyte layer and is arranged on the other side in the first direction, each of the first anode body and the second anode body has a roughened portion extending from at least one outer surface toward a center in a thickness direction, and a core portion continuous with the roughened portion in the thickness direction; the roughened surface portion of the first anode body portion has a thin portion that is thinner than the roughened surface portion of the second anode body portion, The thin-walled portion has a porosity of 30% or less. Solid electrolytic capacitor. (Technology 2) A separating member is disposed in the thin-walled portion. The solid electrolytic capacitor according to claim 1. (Technology 3) an exterior body covering at least a portion of the capacitor element; a protruding end surface of the first anode body portion exposed from one end surface of the exterior body; The solid electrolytic capacitor according to claim 1 or 2. (Technology 4) the roughened portion of the first anode body portion has only the thin portion, The solid electrolytic capacitor according to any one of the first to third aspects. (Technology 5) the thin-walled portion is adjacent to the second anode body portion in the first direction. 5. The solid electrolytic capacitor according to any one of the first to fourth aspects. (Technology 6) a gap is present between the separating member and the second anode body, and the conductive polymer is filled in the gap; 6. The solid electrolytic capacitor according to any one of claims 2 to 5. (Technology 7) the anode end portion has a notch portion on at least one side in a second direction perpendicular to the first direction, The cutout portion includes the thin-walled portion. 7. The solid electrolytic capacitor according to any one of the first to sixth aspects. (Technology 8) the second anode body has a first end on the first anode body side in the first direction, the notch portion is formed spaced apart from the first end portion of the second anode portion. The solid electrolytic capacitor according to claim 7. (Technology 9) In the second direction, the ratio of the narrowest dimension of the first anode body to the widest dimension of the second anode body is 60% or less. 9. The solid electrolytic capacitor according to claim 7 or 8. (Technology 10) In the second direction, the ratio of the narrowest dimension of the first anode body to the widest dimension of the second anode body is 20% or more. The solid electrolytic capacitor according to claim 9.

[0099] While the present invention has been described with respect to presently preferred embodiments, such disclosure should not be interpreted as limiting. Various variations and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all variations and modifications that do not depart from the true spirit and scope of the invention. [Example]

[0100] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0101] Example 1 (1) Fabrication of capacitor elements An aluminum foil (thickness: 100 μm) was prepared as an anode body. Then, both main surfaces of this aluminum foil were etched to obtain an anode body having a roughened portion (thickness: 35 μm on each main surface) extending from each main surface toward the center. The roughened portion was formed over the entire area of ​​both main surfaces of the anode body. A direct current voltage of 70 V was applied for 20 minutes while the anode body was immersed in a 0.3 mass% phosphoric acid solution (liquid temperature: 70°C), forming a dielectric layer containing aluminum oxide (Al2O3) on both main surfaces of the anode body.

[0102] After dividing the anode body on which the dielectric layer was formed into a first anode body and a second anode body, a portion of the first anode body adjacent to the second anode body was compressed by press working to form a thin-walled portion (thickness 10 μm). The press working was performed so that the porosity of the thin-walled portion was 10%. The porosity of the roughened portion before pressing was 70%. The press working was also performed on both main surfaces of the first anode body. That is, a thin-walled portion having a porosity of 10% was formed on each of both main surfaces of the first anode body. Then, an insulating resist tape (separating member) was attached to the thin-walled portion. The porosity of the thin-walled portion and the roughened portion was determined according to the method described in the above embodiment section.

[0103] The second anode body of the anode was immersed in a liquid composition containing a conductive material (polyaniline) to form a precoat layer on the second anode body. A polymerization solution containing pyrrole (a monomer for conductive polymers), naphthalenesulfonic acid (a dopant), and water was prepared. The second anode body with the precoat layer formed thereon was then immersed in the resulting polymerization solution, followed by electrolytic polymerization at an applied voltage of 3 V to form a solid electrolyte layer on the precoat layer. The voltage was applied from the thin-walled portion using a power supply tape.

[0104] A dispersion of graphite particles dispersed in water was applied to the surface of the solid electrolyte layer to form a coating, and the coating was then dried. This resulted in a carbon layer being formed on the solid electrolyte layer. Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer to form a coating, and the coating was then heated to harden the binder resin. This resulted in a silver paste layer (15 μm thick) being formed on the carbon layer. In this way, a cathode extraction layer composed of a carbon layer and a silver paste layer was formed so as to cover a portion of the solid electrolyte layer, thereby obtaining a capacitor element according to Example 1.

[0105] The above procedure was repeated to produce seven capacitor elements according to Example 1, and then these seven capacitor elements were stacked so that the ends of the anode bodies (specifically, the ends of the first anode bodies) and the ends of the cathode extraction layers were aligned to obtain a stack of capacitor elements. The seven first anode bodies in this stack of capacitor elements were then joined together by laser welding.

[0106] (2) Assembly of solid electrolytic capacitors Two lead frames (Sn-plated copper lead frames) were bonded to the laminate of the capacitor elements. Next, the entire laminate of the capacitor elements and parts of each lead frame were sealed with a sealing material containing a biphenyl-type epoxy resin to form an exterior housing. This resulted in the solid electrolytic capacitor of Example 1.

[0107] Example 2 A solid electrolytic capacitor according to Example 2 was obtained in the same manner as in Example 1, except that the press working was carried out so that the porosity of the thin-walled portion was 20%.

[0108] (Comparative Example 1) A solid electrolytic capacitor according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the press working was carried out so that the porosity of the thin-walled portion was 35%.

[0109] <Evaluation> Capacitance change rate The initial capacitance C0 (μF) of each solid electrolytic capacitor at a frequency of 120 Hz was measured using a four-terminal LCR meter in an environment of 20°C. The arithmetic average value for 20 solid electrolytic capacitors was then calculated. Next, a heat resistance test was performed by applying a rated voltage to each solid electrolytic capacitor in an environment of 145°C for 400 hours. Thereafter, the capacitance C1 (μF) after the accelerated heat resistance test was measured in an environment of 20°C using the same procedure as for the initial capacitance, and the arithmetic average value for the 20 solid electrolytic capacitors was then calculated. The capacitance change rate (%) for each solid electrolytic capacitor was then calculated using the following formula: Capacitance change rate (%) = (C1-C0) / C0 x 100

[0110] The capacitance change rate (%) of the solid electrolytic capacitor according to each example is shown in Table 1 below.

[0111] [Table 1]

[0112] From Table 1, it can be seen that the capacitance change rate of the solid electrolytic capacitor according to Example 1 is -15%, and the capacitance change rate of the solid electrolytic capacitor according to Example 2 is -30%. In other words, when the porosity of the thin-walled portion is 30% or less, the decrease in capacitance is suppressed even when the solid electrolytic capacitor is exposed to high temperatures. On the other hand, it can be seen that the capacitance change rate of the solid electrolytic capacitor according to Comparative Example 1 is -65%. In other words, when the porosity of the thin-walled portion exceeds 30%, the decrease in capacitance becomes significant when the solid electrolytic capacitor is exposed to high temperatures. These results show that the heat resistance reliability of the solid electrolytic capacitor can be sufficiently improved by setting the porosity of the thin-walled portion to 30% or less. [Industrial Applicability]

[0113] The solid electrolytic capacitor according to the present disclosure can be used in applications that require sufficient improvement in heat resistance reliability. [Explanation of symbols]

[0114] 10: capacitor element, 11: anode body, 11a: first anode body portion, 11b: second anode body portion, 11c: roughened portion, 11c1: thin portion, 11d: core portion, 11A: notch portion, 11B: first end portion, 11C: first end portion, 11D: second end portion, 12: solid electrolyte layer, 13: cathode lead layer, 14: cathode portion, 15: separation member, 16: conductive polymer, 100: solid electrolytic capacitor, 111: side wall portion, 112: protruding portion, 113: bottom plate portion, 120: exterior body, 130: first external electrode, 140: second external electrode, C: notch, D1: first direction, D2: second direction, E1: first end face, E2: second end face, S1: tip face, S2: terminal face, S3: tip face

Claims

1. a solid electrolytic capacitor having a capacitor element including an anode body extending in a first direction, a dielectric layer covering at least a portion of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer, the solid electrolyte layer contains a conductive polymer, the anode body includes a first anode body portion that does not have the solid electrolyte layer and is arranged on one side in the first direction, and a second anode body portion that has the solid electrolyte layer and is arranged on the other side in the first direction, each of the first anode body and the second anode body has a roughened portion extending from at least one outer surface toward a center in a thickness direction, and a core portion continuous with the roughened portion in the thickness direction; the roughened portion of the first anode body has a thin portion that is thinner than the roughened portion of the second anode body, The thin-walled portion has a porosity of 30% or less. Solid electrolytic capacitor.

2. A separating member is disposed in the thin-walled portion. The solid electrolytic capacitor according to claim 1 .

3. an exterior body covering at least a portion of the capacitor element; a protruding end surface of the first anode body portion exposed from one end surface of the exterior body; The solid electrolytic capacitor according to claim 1 or 2.

4. the roughened portion of the first anode body portion has only the thin-walled portion, The solid electrolytic capacitor according to claim 1 or 2.

5. the thin-walled portion is adjacent to the second anode body portion in the first direction; The solid electrolytic capacitor according to claim 1 or 2.

6. a gap is provided between the separating member and the second anode body, and the conductive polymer is filled in the gap; The solid electrolytic capacitor according to claim 2 .

7. the first anode body has a notch portion on at least one side in a second direction perpendicular to the first direction, The cutout portion includes the thin-walled portion. The solid electrolytic capacitor according to claim 1 or 2.

8. the second anode body has a first end on the first anode body side in the first direction, the notch portion is formed spaced apart from the first end portion of the second anode body portion. The solid electrolytic capacitor according to claim 7.

9. In the second direction, a ratio of the narrowest dimension of the first anode body portion to the widest dimension of the second anode body portion is 60% or less. The solid electrolytic capacitor according to claim 7.

10. In the second direction, a ratio of the narrowest dimension of the first anode body portion to the widest dimension of the second anode body portion is 20% or more. The solid electrolytic capacitor according to claim 9.

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