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

Abstract

To provide a solid electrolytic capacitor that suppresses ESR changes, is reduced in size, and is improved in volumetric efficiency.SOLUTION: A solid electrolytic capacitor includes a capacitor element, a sealed body, and first and second external electrodes. The capacitor element includes an anode body (electrode foil 111), a dielectric layer 112, a solid electrolyte layer 113, and a conductor layer. The anode body includes a valve-action metal and has an anode terminal area and a cathode formation area arranged along a first direction. The solid electrolyte layer is formed on the dielectric layer in the cathode formation area, and has a first end portion, a second end portion facing the first end portion in the first direction, a first side portion and a second side portion connecting the first end portion and the second end portion, and a central portion surrounded by the first end portion, the second end portion, the first side portion, and the second side portion. The central portion is approximately flat, and a first uneven portion having an uneven shape is formed at the first end portion and the second end portion from the central portion.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, solid electrolytic capacitors are formed by stacking multiple capacitor elements. Various structures have been studied for solid electrolytic capacitors that suppress changes in ESR, reduce size, and improve volumetric efficiency.

[0003] The solid electrolytic capacitor of Patent Document 1 includes a capacitor element, a dielectric layer formed on the surface of the capacitor element, a solid electrolyte layer, a cathode conductor layer, and an insulating resin covering the outer peripheral surface of the capacitor element. Manganese dioxide, which is a conductive powder, is attached to the bottom surface and edge of the capacitor element to form an uneven portion. By forming the uneven portion, the conductive layer on the edge of the bottom surface can be made thicker. This configuration ensures a conductive path and suppresses deterioration of the ESR.

[0004] The solid electrolytic capacitor described in Patent Document 2 forms a dielectric by forming an oxide film of a valve metal on the metal. A conductive polymer compound as a solid electrolyte and a cathode conductor layer are formed on the oxide film. The entire surface of the conductive polymer compound is formed with projections and recesses. This improves the adhesion between the conductive polymer compound and the cathode conductor layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4452141 [Patent Document 2] Japanese Patent Application Publication No. 7-94368 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, the unevenness is formed only on the bottom surface and the edge of the capacitor element. Therefore, in the capacitor element of Patent Document 1, it can be presumed that the carbon layer and the silver layer are sufficiently attached to the bottom surface and the edge of the capacitor element. On the other hand, there is a risk that the carbon layer and the silver layer are not sufficiently attached to other parts. In addition, a process of applying a conductive powder is required to form the unevenness.

[0007] In addition, in Patent Document 2, the entire surface of the solid electrolyte layer is uneven. When a capacitor element having an uneven solid electrolyte layer is laminated using a conductive adhesive, the solid electrolytic capacitor becomes thick. Therefore, the solid electrolytic capacitor cannot be made small, and there is a risk that the volumetric efficiency will deteriorate.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a solid electrolytic capacitor which suppresses changes in ESR, is miniaturized, and has improved volumetric efficiency. [Means for solving the problem]

[0009] The solid electrolytic capacitor of the present invention includes a capacitor element, a sealing body, a first external electrode, and a second external electrode. The capacitor element includes an anode body, a dielectric layer, a solid electrolyte layer, and a conductor layer. The anode body includes a valve metal, has a porous layer having a plurality of holes on the surface of the valve metal, and has an anode terminal region and a cathode formation region arranged along a first direction. The anode body is in the form of a flat film. The dielectric layer is formed on at least the cathode formation region. The solid electrolyte layer is formed on the dielectric layer in the cathode formation region. The conductor layer is formed so as to cover the solid electrolyte layer.

[0010] The sealing body seals a laminate in which a plurality of capacitor elements are stacked with an insulating resin. The first external electrode is connected to an end of the anode terminal region. The second external electrode is connected to the cathode formation region.

[0011] The solid electrolyte layer has a first end, a second end facing the first end in a first direction, a first side and a second side connecting the first end and the second end, and a central portion surrounded by the first end, the second end, the first side and the second side. The central portion is substantially flat, and a first uneven portion having an uneven shape from the central portion is formed at the first end and the second end.

[0012] In this configuration, the first uneven portion is formed at the first end and the second end of the solid electrolyte layer. That is, the area where the solid electrolyte layer and the carbon layer and the carbon layer and the metal layer contact each other is increased. Therefore, the adhesion between the solid electrolyte layer and the carbon layer and between the carbon layer and the metal layer is improved, and it is possible to suppress the increase in ESR. In addition, when using a dip method (a wet coating method in which an object to be coated is immersed (dipped) in a coating liquid in a direction from the first end to the second end to form a coating film), the carbon paste flows in a direction from the first end to the second end according to gravity. Therefore, if the first uneven portion is not formed at the first end, the carbon paste does not remain sufficiently at the first end, and the carbon layer formed at the first end becomes thin. On the other hand, if the first uneven portion is formed at the first end, the carbon paste is caught by the uneven portion and the flow is suppressed, so that the carbon paste remains sufficiently at the first end, and the carbon layer is formed at the first end with a sufficient thickness. As a result, in this configuration, the carbon layer is formed uniformly from the first end to the second end. That is, when the carbon layer sags due to gravity, the carbon paste attached to the first end region becomes thin, but the first uneven portion prevents the carbon paste from becoming thin by trapping the carbon liquid. Therefore, the current conduction path is sufficiently secured, making it possible to suppress an increase in ESR.

[0013] A method for manufacturing a solid electrolytic capacitor according to the present invention includes a capacitor element forming step, a first external electrode forming step, a second external electrode forming step, and a sealing body forming step. The capacitor element forming step forms a capacitor element. The capacitor element forming step further includes a pressurizing step.

[0014] The capacitor element has an anode body, a dielectric layer, a first end, a second end, a solid electrolyte layer, a carbon layer, and a conductor layer. The anode body includes a valve metal, has a porous layer having a plurality of holes on the surface of the valve metal, and has an anode terminal region and a cathode formation region arranged along a first direction. The anode body is in the form of a flat film. The dielectric layer is formed at least on the cathode formation region. The solid electrolyte layer has a first end, a second end, a first side portion, a second side portion, and a central portion. The first end is formed on the dielectric layer in the cathode formation region. The second end faces the first end in the first direction. The first side portion and the second side portion connect the first end and the second end. The central portion is surrounded by the first end, the second end, the first side portion, and the second side portion. The conductor layer is formed so as to cover the solid electrolyte layer.

[0015] The first external electrode forming step forms a first external electrode connected to an end of the anode terminal region. The second external electrode forming step forms a second external electrode connected to the cathode formation region. The sealing body forming step forms a sealing body by stacking a plurality of capacitor elements and sealing them with an insulating resin, the sealing body having a first surface from which the end of the anode terminal region is linearly exposed.

[0016] The capacitor element forming process further includes a pressurizing process for applying pressure to the vicinity of the central portion of the solid electrolyte layer to form a flat shape so that the first end portion and the second end portion of the solid electrolyte layer become a first uneven portion having an uneven shape relative to the central portion.

[0017] In this manufacturing method, the first unevenness is formed at the first end and the second end of the solid electrolyte layer. That is, the area where the solid electrolyte layer and the carbon layer, and the carbon layer and the metal layer contact each other is increased. Therefore, the adhesion between the solid electrolyte layer and the carbon layer, and between the carbon layer and the metal layer is improved, and it is possible to suppress the increase in ESR. In addition, when the Dip method is used, by forming an uneven portion at the first end, the carbon paste is caught on this first uneven portion to suppress the flow, so that the carbon paste is sufficiently left at the first end, and the carbon layer can be formed with a sufficient thickness at the first end. As a result, the carbon layer can be formed uniformly from the first end to the second end. That is, when the carbon layer sags due to gravity, the carbon paste attached to the first end region becomes thin, whereas the carbon paste is caught by the carbon liquid due to the presence of the first uneven portion, and the carbon paste can be prevented from becoming thin. Therefore, the conductive path of the current is sufficiently secured, and it is possible to suppress the increase in ESR.

[0018] The capacitor element of the present invention has an anode body, a dielectric layer, a solid electrolyte layer, and a conductor layer. The anode body includes a valve metal, has a porous layer having a plurality of holes on the surface of the valve metal, and has an anode terminal region and a cathode formation region arranged along a first direction. The anode body is in the form of a flat film. The dielectric layer is formed on at least the cathode formation region. The solid electrolyte layer is formed on the dielectric layer in the cathode formation region. The conductor layer is formed so as to cover the solid electrolyte layer.

[0019] The solid electrolyte layer has a first end, a second end, a first side, a second side, and a central portion. The second end faces the first end in a first direction. The first and second side portions connect the first and second end portions. The central portion is surrounded by the first and second end portions and the first and second side portions. The central portion is substantially flat, and a first uneven portion having an uneven shape from the central portion is formed at the first and second end portions.

[0020] In this configuration, a first unevenness is formed at the first end and the second end of the solid electrolyte layer. That is, the area where the solid electrolyte layer and the carbon layer and the carbon layer and the metal layer contact each other is increased. This improves the adhesion between the solid electrolyte layer and the carbon layer and between the carbon layer and the metal layer, making it possible to suppress an increase in ESR. Effect of the Invention

[0021] According to the present invention, it is possible to provide a solid electrolytic capacitor that suppresses changes in ESR, has a smaller size, and has improved volumetric efficiency. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a side cross-sectional view of the solid electrolytic capacitor according to the first embodiment. [Diagram 2] FIG. 2(A) is an enlarged view of a portion of the capacitor element according to the first embodiment, FIG. 2(B) is a side cross-sectional view of the capacitor element, and FIG. 2(C) is a cross-sectional view of the uneven portion as viewed from the fourth surface side of the capacitor element. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of the capacitor element according to the first embodiment. [Figure 4] FIG. 4A is a diagram showing the configuration of an end portion of a capacitor element according to the first embodiment, and FIG. 4B is a diagram showing the configuration of an end portion of a capacitor element according to a conventional configuration. [Diagram 5] FIG. 5 is an enlarged view showing a configuration in which the capacitor element according to the first embodiment is laminated using a conductive adhesive. [Figure 6] FIG. 6 is a flow chart showing the steps of forming a capacitor element. [Figure 7] FIG. 7 is a flow chart showing the steps of forming a solid electrolytic capacitor. [Figure 8] FIG. 8 is an enlarged view of a portion of the capacitor element according to the second embodiment. [Figure 9]FIG. 9 is a table comparing the relative ESR values ​​and the thicknesses of the laminates of the capacitor element and Comparative Examples 1, 2, and 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] [First embodiment] A solid electrolytic capacitor 1 according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a side cross-sectional view of the solid electrolytic capacitor 1 according to the first embodiment.

[0024] (Structure of solid electrolytic capacitor) The solid electrolytic capacitor 1 includes a capacitor assembly 10, a first external electrode 20, a second external electrode 30, and an insulating resin body 40.

[0025] The capacitor assembly 10 includes a plurality of capacitor elements 11 and a conductive member 19. The conductive member 19 is preferably an electrode paste containing, for example, nickel, silver, or copper as a main component. The maximum thickness of the conductive member 19 is preferably 2 μm or more and 20 μm or less. Note that if a conductivity equal to or higher than a desired conductivity is obtained between the plurality of capacitor elements 11, the conductive member 19 may be omitted. A more detailed structure of the conductive member 19 will be described later.

[0026] In this embodiment, the number of capacitor elements 11 constituting capacitor assembly 10 is not limited as long as it is plural. The structure of capacitor element 11 will be described in detail later.

[0027] The plurality of capacitor elements 11 are stacked. A capacitor assembly 10 (laminate) is formed by stacking the plurality of capacitor elements 11. At this time, the plurality of capacitor elements 11 are formed so as to be approximately parallel to each other.

[0028] The capacitor assembly 10 is sealed with an insulating resin body 40. This forms a sealing body 400. The sealing body 400 has a generally rectangular parallelepiped shape having a top surface 401, a bottom surface 402, a first surface 403, a second surface 404, and side surfaces connecting these surfaces. As described below, the surface on which the first external electrode 20 is formed by extending from the first surface 403 and the surface on which the second external electrode 30 is formed by extending from the second surface 404 are referred to as the bottom surface 402 for the sake of convenience, and the surface facing away from the bottom surface 402 is referred to as the top surface 401.

[0029] At this time, some of the multiple capacitor elements 11 are exposed from first surface 403 of sealing body 400. The surface (first surface 403) where the multiple capacitor elements 11 are linearly exposed from insulating resin body 40 is connected to first external electrode 20.

[0030] The first external electrode 20 is formed along the sealing body 400. Specifically, the first external electrode 20 is disposed across the first surface 403 and the bottom surface 402.

[0031] The first external electrode 20 is made of, for example, a copper alloy material or an iron alloy material, and is formed of, for example, a material cut out from a metal plate.

[0032] The first external electrode 20 is preferably made of a metal material that is easy to bend and has high conductivity. In this case, the first external electrode 20 is preferably arranged so as to be bent along the first surface 403 and the bottom surface 402 of the sealing body 400.

[0033] The second external electrode 30 is formed along the sealing body 400. Specifically, the second external electrode 30 is disposed across the second surface 404 and the bottom surface 402. The capacitor element 11 and the second external electrode are joined by a conductive adhesive 50 made of silver paste or the like.

[0034] The connection layers (conductive layers including solid electrolyte layer 113) of the multiple capacitor elements 11 are electrically and physically connected to second external electrode 30 by conductive adhesive 50.

[0035] The second external electrode 30 is preferably formed of a metal material that is easy to bend and has high conductivity, such as a copper alloy material or an iron alloy material. The second external electrode 30 is formed of a material cut out from a metal plate, for example. The first external electrode 20 and the second external electrode 30 may be made of the same material or different materials.

[0036] The insulating resin body 40 is mainly made of resin and may contain a filler. As the resin, for example, epoxy resin, phenol resin, polyimide resin, silicone resin, polyamide resin, liquid crystal polymer, etc. are preferable. The resin may be in the form of either solid resin or liquid resin. It is preferable that the corners are rounded by barrel polishing after the resin sealing. As the filler, for example, silica particles, alumina particles, etc. are preferable. The maximum diameter of the filler is preferably, for example, 30 μm or more and 40 μm or less. It is more preferable that the material contains silica particles in solid epoxy resin and phenol resin.

[0037] (Capacitor element structure) The structure of capacitor element 11 will be described in more detail with reference to Figures 2(A), 2(B), 2(C), and 3. In Figures 2(A), 2(B), 2(C), and 3, the structures are exaggerated in order to clearly explain the characteristics of each structure, and the structure in the Z-axis direction in particular is exaggerated.

[0038] Fig. 2(A) is an external perspective view of the capacitor element according to the first embodiment, Fig. 2(B) is a side cross-sectional view of the capacitor element, and Fig. 2(C) is a cross-sectional view of the uneven portion of the capacitor element viewed from the fourth surface side. Fig. 3 is an enlarged view of the cross-sectional view of the capacitor element according to the first embodiment. Note that the carbon layer and the metal layer are omitted in Fig. 3.

[0039] Capacitor element 11 includes electrode foil 111, dielectric layer 112, solid electrolyte layer 113, carbon layer 114, and metal layer 115. Electrode foil 111 includes electrode layer 111F and porous layer 111L.

[0040] A more specific structure of the electrode foil 111 is as follows. The electrode layer 111F is made of, for example, a simple metal such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, silicon, or an alloy containing these metals. The electrode layer 111F is preferably made of aluminum or an aluminum alloy. A porous layer 111L is formed on the surface portion of the electrode layer 111F. The porous layer 111L is formed by etching the surface of the electrode layer 111F. This makes the porous layer 111L a porous body. The electrode foil 111 may be a valve action metal that exhibits a so-called valve action. A more detailed structure of the electrode foil 111 will be described later.

[0041] The electrode foil 111 has a dielectric layer 112 formed thereon. The dielectric layer 112 is formed on the entire surface of the porous layer 111L, which is a porous body. As shown in FIG. 2(A) and FIG. 2(B), the electrode foil 111 has a first face F1 and a second face F2 that face each other in the Z-axis direction. The electrode foil 111 further has a third face F3, a fourth face F4, a fifth face F5, and a sixth face F6 that are connected to the first face F1 and the second face F2 and are parallel to the Z-axis direction. The third face F3 and the fourth face F4 are parallel to the Y-axis direction. The fifth face F5 and the sixth face F6 are parallel to the X-axis. The dielectric layer 112 covers the first face F1, the second face F2, the fourth face F4, the fifth face F5, and the sixth face F6 of the electrode foil 111.

[0042] The dielectric layer 112 is preferably made of an oxide film of the electrode foil 111 (porous layer 111L). When an aluminum foil is used for the electrode layer 111F, the dielectric layer 112 is formed by applying a voltage in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or a sodium salt or ammonium salt thereof, and anodizing the same. The thickness of the dielectric layer 112 is preferably 1 nm or more and 100 nm or less.

[0043] Solid electrolyte layer 113 covers the outer surface of dielectric layer 112 (at least the surface opposite to the surface in contact with electrode foil 111). Solid electrolyte layer 113 is also filled in a large number of pores covered with dielectric layer 112.

[0044] More specifically, the solid electrolyte layer 113 includes, for example, an inner layer and an outer layer.

[0045] The inner layer is a layer on the dielectric layer 112 side of the solid electrolyte layer 113, and is realized by, for example, a conductive polymer having a skeleton of pyrroles, thiophenes, anilines, or the like, or a conductive polymer having a skeleton of thiophenes, such as PEDOT [poly(3,4-ethylenedioxythiophene)]. The inner layer may also be a layer of a conductive polymer obtained by compounding PEDOT with a dopant such as polystyrene sulfonic acid (PSS), paratoluene sulfonic acid (PTS), or anthraquinone sulfonic acid (AQS). The inner layer is formed by a method of forming a polymer film such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer 112 using an electrolyte solution serving as a base for forming the solid electrolyte layer 113, for example, a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene, or a method of applying a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric part and drying it.

[0046] The outer layer is a layer formed on the outside of the inner layer. For example, the outer layer is a layer formed so as to cover the entire surface of the inner layer after the inner layer is formed to fill the fine recesses of the porous portion. The thickness of the outer layer is preferably 2 μm or more and 20 μm or less. The outer layer is formed by immersing the inner layer in an aqueous ammonium persulfate solution after the inner layer is formed, followed by drying, or the like.

[0047] When the solid electrolyte layer 113 is formed in the order of the inner layer and the outer layer, a reaction selectively occurs on the surface of the solid electrolyte layer 113 due to the presence of by-products generated during the formation of the solid electrolyte layer. At this time, the reaction proceeds so that the surface of the solid electrolyte layer 113 has irregularities. By repeating this reaction, irregularities having a thickness are formed on the surface of the solid electrolyte layer 113. Note that the conductive polymer constituting the solid electrolyte layer 113 is one example, and other combinations may be used.

[0048] The carbon layer 114 is formed so as to cover the outer layer (solid electrolyte layer 113). The carbon layer 114 is formed by applying a conductive paste in which an insulating resin such as a phenolic resin is mixed with carbon or graphene particles.

[0049] Metal layer 115 is formed so as to cover carbon layer 114. Metal layer 115 is formed, for example, by applying a silver paste containing silver particles and polypropylene resin.

[0050] With this configuration, capacitor element 11 becomes a flat-film solid electrolytic capacitor. In this capacitor element 11, electrode foil 111 corresponds to the anode, and metal layer 115 corresponds to the cathode. A region of electrode foil 111 where solid electrolyte layer 113, carbon layer 114, and metal layer 115 are not formed corresponds to the "anode terminal region" of the present invention, and a region where solid electrolyte layer 113, carbon layer 114, and metal layer 115 are formed corresponds to the "cathode formation region" of the present invention. Electrode foil 111 corresponds to the "anode body" of the present invention. The direction in which the "anode terminal region" and the "cathode formation region" are aligned is referred to as the "first direction" of the present invention.

[0051] (Structure of solid electrolyte layer) The structure of the solid electrolyte layer 113 will be described. The thickness of the capacitor element 11 in which the unevenness is formed on the solid electrolyte layer 113 is about 180 μm. The surface of the solid electrolyte layer 113 on the first surface F1 side of the electrode foil 111 is the first surface F11. The surface of the solid electrolyte layer 113 on the second surface F2 side of the electrode foil 111 is the second surface F12. The surface of the solid electrolyte layer 113 on the third surface F3 side of the electrode foil 111 is the third surface F13. The surface of the solid electrolyte layer 113 on the fourth surface F4 side of the electrode foil 111 is the fourth surface F14. The surface of the solid electrolyte layer 113 on the fifth surface F5 side of the electrode foil 111 is the fifth surface F15. The surface of the solid electrolyte layer 113 on the sixth surface F6 side of the electrode foil 111 is the sixth surface F16.

[0052] Furthermore, the solid electrolyte layer 113 has a first end close to the third face F13 and a second end opposite the first end and close to the fourth face F14. The solid electrolyte layer 113 has a first side and a second side connecting the first end and the second end. The solid electrolyte layer 113 has the first end, the second end, and a central portion surrounded by the first side and the second side.

[0053] Next, in the XY plane, the solid electrolyte layer 113 is heated and pressed with the first face F11 and the second face F12 sandwiched between them. More specifically, a press is disposed so as to straddle the fifth face F15 and the sixth face F16 of the solid electrolyte layer 113 and to abut against the first face F11 and the second face F12, except for predetermined regions at both ends including the third face F13 and the fourth face F14 of the solid electrolyte layer 113. In this state, the solid electrolyte layer 113 is heated and pressed.

[0054] By carrying out such processing, unevenness is formed (unevenness remains) in the parts of solid electrolyte layer 113 that are not heated and pressed by the press.

[0055] More specifically, the uneven portion 113a is formed at a first end portion close to the third face F13 of the solid electrolyte layer 113. In other words, the uneven portion 113a (see FIG. 2(A)) is formed at a first end portion of the solid electrolyte layer 113 that is not heated and pressed by a press machine. This first end portion is an end portion on the third face F13 side of the solid electrolyte layer 113. This portion includes a part of the first face F11, a part of the second face F12, a part of the fifth face F15, and a part of the sixth face F16 of the solid electrolyte layer 113. That is, each part here is a part including a ridge portion formed by an end face of the third face F13 of the solid electrolyte layer 113.

[0056] Similarly, the uneven portion 113b is formed at a second end portion close to the fourth face F14 of the solid electrolyte layer 113. In other words, the uneven portion 113b (see FIG. 2(A) and FIG. 3) is formed at a second end portion of the solid electrolyte layer 113 that is not heated and pressed by a press machine. This second end portion is an end portion of the fourth face F14 of the solid electrolyte layer 113. This portion includes a part of the first face F11, a part of the second face F12, a part of the fourth face F14, a part of the fifth face F15, and a part of the sixth face F16 of the solid electrolyte layer 113. That is, each of the parts is a portion including a ridge portion formed by an end face of the fourth face F14 of the solid electrolyte layer 113.

[0057] The uneven portion 113a and the uneven portion 113b correspond to a "first uneven portion" according to the present invention.

[0058] Meanwhile, the first surface F11 and the second surface F12 on which the press is disposed are heated and pressurized to become substantially flat at their central portions, so that the thickness of the solid electrolyte layer 113 in the Z-axis direction at the flat portion (the portion where the concave and convex portions 113a and 113b are not formed) becomes approximately 160 μm.

[0059] Fig. 2(C) is a cross-sectional view of the fourth surface F14 at the second end portion along the YZ plane. The cross-sectional view in Fig. 2(C) shows a structure in which the uneven portion 113b is divided into six portions. As can be seen from Fig. 2(C), the uneven portion 113b has unevenness, which increases the contact area between the solid electrolyte layer 113, the carbon layer 114, and the metal layer 115. The first end portion has a similar configuration.

[0060] FIG. 3 is an enlarged view of the second end portion on the fourth surface F4 side in FIG. 2(B). FIG. 3 shows the concave-convex portion 113b in a schematic manner. The thickness of the first surface F11 of the solid electrolyte layer 113 and the concave-convex portion 113b at the position where the thickness is the largest (corresponding to the convex portion) is defined as dmax. The thickness of the first surface F11 of the solid electrolyte layer 113 and the concave-convex portion 113b at the position where the thickness is the smallest (corresponding to the concave portion) is defined as dmin. These thicknesses dmax and dmin are thicknesses from the surface of the flat portion. That is, the thicknesses dmax and dmin are larger than the thickness of the flat portion. The difference between the thickness dmax and the thickness dmin (dmax-dmin) is preferably 1 μm or more and 100 μm or less.

[0061] The thickness of the uneven portions 113a and 113b can be calculated by measuring the surface of the solid electrolyte layer 113 with a micrometer or a laser microscope. Alternatively, the thickness of the uneven portions 113a and 113b may be calculated by observing a cross section.

[0062] Next, a more detailed structure in which solid electrolyte layer 113, carbon layer 114, and metal layer 115 are in contact with each other will be described with reference to Fig. 4(A) and Fig. 4(B). Fig. 4(A) is a diagram showing a capacitor element having a conventional configuration. At the end of the capacitor element having the conventional configuration, the thickness of solid electrolyte layer 113G is extremely small, and the contact area between solid electrolyte layer 113G, carbon layer 114G, and metal layer 115G is small. In other words, at the end of the capacitor element, the thickness at which solid electrolyte layer 113G, carbon layer 114G, and metal layer 115G are formed is small. This makes it impossible to ensure a conductive path for current, and the ESR increases.

[0063] On the other hand, as shown in FIG. 4(B), in the configuration of the present invention, uneven portion 113b (uneven portion 113a) is formed. Therefore, the surface area at the first end and the second end is large. Carbon layer 114 and metal layer 115 are formed so as to cover solid electrolyte layer 113 on which uneven portions 113a and 113b are formed. That is, the contact area between solid electrolyte layer 113, carbon layer 114, and metal layer 115 at the first end and the second end is large. That is, a conductive path for current is secured, and an increase in ESR can be suppressed.

[0064] (Arrangement of conductive members) FIG. 5 is an enlarged view showing a configuration in which the capacitor element according to the first embodiment is laminated using the conductive member 19. As shown in FIG. 5, the conductive member 19 is preferably formed in a region surrounded by the first end and the second end. In other words, it is preferably formed in a region surrounded by the uneven portion 113a and the uneven portion 113b. By arranging the conductive member 19 in this manner, the uneven portion 113a and the uneven portion 113b do not overlap with the conductive member 19 in the Z-axis direction. Therefore, it is possible to more reliably physically join the adjacent capacitor elements 11 and electrically conduct them without increasing the thickness of the solid electrolytic capacitor 1. In addition, the volumetric efficiency is improved while realizing a miniaturization of the solid electrolytic capacitor 1. The volumetric efficiency indicates, for example, the volume required to realize a predetermined capacity (capacitance), and is defined as the smaller the volume, the higher the volumetric efficiency.

[0065] (Method of manufacturing capacitor element) The capacitor element having the above-mentioned structure is formed as follows: The steps for manufacturing the capacitor element will be described with reference to the flow chart of FIG.

[0066] A dielectric layer 112 is formed on the electrode foil 111 (S11).

[0067] A solid electrolyte layer 113 is formed so as to cover the dielectric layer 112 (S12).

[0068] The central portion of the solid electrolyte layer 113 is heated and pressed by a press (S13). This central portion refers to the vicinity of the central portion when the first face F11 and the second face F12 of the solid electrolyte layer 113 are viewed in plan (more specifically, the region excluding a region of a predetermined length from both ends including the third face F13 and the fourth face F14 of the solid electrolyte layer 113). By using this step S13, the uneven portion 113a is formed at the first end (the end of the third face F13) of the solid electrolyte layer 113, and the uneven portion 113b is formed at the second end (the end of the fourth face F14). Meanwhile, the vicinity of the central portion of the solid electrolyte layer 113 has an approximately flat shape.

[0069] Next, carbon layer 114 is formed (S14) so ​​as to cover solid electrolyte layer 113. At this time, carbon layer 114 is formed so as to conform to uneven portions 113a and 113b.

[0070] The metal layer 115 is formed so as to cover the carbon layer 114 (S15). At this time, the metal layer 115 is formed so as to fit along the carbon layer 114.

[0071] Through the above-mentioned steps, capacitor element 11 is formed in which uneven portion 113a is formed at a first end portion of solid electrolyte layer 113 and uneven portion 113b is formed at a second end portion of solid electrolyte layer 113. Thus, capacitor element 11 is formed in which the contact areas between solid electrolyte layer 113, carbon layer 114, and metal layer 115 are improved.

[0072] In the above-mentioned step S13, a press is used to flatten the central portion of the solid electrolyte layer 113. However, the process may be a process in which a sheet is arranged so that the central portion of the solid electrolyte layer 113 is flat, and the uneven portions 113a and 113b are formed by additionally applying, for example, a paste-like solid electrolyte layer to the first end portion and the second end portion.

[0073] (Method of manufacturing solid electrolytic capacitor) Solid electrolytic capacitor 1 using capacitor element 11 having the above-mentioned configuration is formed as follows. Solid electrolytic capacitor 1 is manufactured, for example, as follows. Fig. 7 is a flow chart showing an example of a schematic flow of the method for manufacturing the solid electrolytic capacitor according to this embodiment.

[0074] 1, capacitor elements 11 are stacked and each capacitor element 11 is bonded using conductive member 19. This forms capacitor assembly 10 (S21). When forming capacitor assembly 10, stacked capacitor elements 11 are heated and pressurized. At this time, conductive member 19 is preferably disposed in an area surrounded by concave-convex portions 113a, 113b when capacitor assembly 10 is viewed in plan on the XY plane.

[0075] Next, as shown in FIG. 1, the capacitor assembly 10 is sealed with an insulating resin body 40 (S22).

[0076] Next, sealing body 400 is ground to expose electrode foil 111. A first external electrode 20 is formed on the end face (first surface 403) in the anode terminal region of capacitor assembly 10 (S23).

[0077] Next, as shown in FIG. 1, the end face (second surface 404) of the capacitor assembly 10 in the cathode formation region is joined to the second external electrode 30 using a conductive adhesive 50 such as silver paste (S24).

[0078] Next, the first external electrode 20 is bent along the first surface 403 and the bottom surface 402 of the sealing body 400. More specifically, the first external electrode 20 is bent along the bottom surface 402 of the sealing body 400. Similarly, the second external electrode 30 is bent along the second surface 404 and the bottom surface 402 of the sealing body 400 (S25).

[0079] In the above-described configuration, the lead frame (a configuration in which the terminal is drawn out to the outside by a conductive plate material) is formed after forming the sealing body 400. However, the sealing body 400 may be formed after forming the first external electrode 20 in step S23 and the second external electrode 30 in step S24.

[0080] In this way, by using capacitor element 11 having uneven portions 113a and 113b, it is possible to increase the contact area between solid electrolyte layer 113, carbon layer 114, and metal layer 115. In other words, a current conduction path is secured, and an increase in ESR can be suppressed.

[0081] Moreover, the structure of solid electrolyte layer 113 having a flat shape and uneven portions 113a and 113b can be formed using a press. That is, the structure of solid electrolyte layer 113 can be formed by a simple method.

[0082] [Second embodiment] A solid electrolytic capacitor 1A according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 8 is an enlarged view of a portion of the capacitor element according to the second embodiment.

[0083] 8, the solid electrolytic capacitor 1A according to the second embodiment differs from the solid electrolytic capacitor 1 according to the first embodiment in the location where the concave and convex portions are formed. The other configuration of the solid electrolytic capacitor according to the second embodiment is similar to that of the solid electrolytic capacitor according to the first embodiment, and a description of similar parts will be omitted.

[0084] As shown in Fig. 8, uneven portion 113a is formed at the first end, and uneven portion 113b is formed at the second end. Furthermore, uneven portion 113c and uneven portion 113d are formed at the ends of the side surfaces (fifth face F15 and sixth face F16) connecting the first end and the second end. The end of the fifth face F15 and the end of the sixth face F16 correspond to the "first side" and "second side" in the present invention.

[0085] This end is a region including the fifth face F15 and the sixth face F16 of the solid electrolyte layer 113 and the ridges of the fifth face F15 and the sixth face F16 of the solid electrolyte layer 113. The end on the fifth face F15 is defined as a third end, and the end on the sixth face F16 is defined as a fourth end. That is, the third end is formed with an uneven portion 113c, and the fourth end is formed with an uneven portion 113d. The uneven portion 113c and the uneven portion 113d correspond to the "second uneven portion" in the present invention.

[0086] 6, the uneven portions 113a, 113b, 113c, and 113d are heated and pressed only near the center of the solid electrolyte layer 113. As a result, the center of the surface of the solid electrolyte layer 113 becomes substantially flat.

[0087] More specifically, the press machine heats and presses the portions of the first face F11 and the second face F12 of the solid electrolyte layer 113, which are the centers of gravity of the solid electrolyte layer 113, without spanning the fifth face F15 and the sixth face F16 of the solid electrolyte layer 113. As a result, the vicinity of the center of the surface of the solid electrolyte layer 113 becomes substantially flat. Furthermore, in the portion not heated and pressed, the solid electrolyte layer 113 is formed (remains) at the first end, the second end, the third end (the end of the fifth face F15), and the fourth end (the end of the sixth face F16). As a result, the uneven portions 113a, 113b, 113c, and 113d are formed. Therefore, the uneven portions 113a, 113b, 113c, and 113d are formed in a frame shape (picture frame shape) except for the vicinity of the center of the first face F11 and the second face F12 of the solid electrolyte layer 113.

[0088] By forming the uneven portions 113a, 113b, 113c, and 113d, the surface areas at the first end, the second end, the third end, and the fourth end are increased. The carbon layer 114 and the metal layer 115 are formed so as to cover the solid electrolyte layer 113 on which the uneven portions 113a, 113b, 113c, and 113d are formed. That is, the contact areas between the solid electrolyte layer 113, the carbon layer 114, and the metal layer 115 at the first end, the second end, the third end, and the fourth end are increased. That is, the conductive path of the current is secured over a larger area, and the increase in the ESR can be further suppressed.

[0089] [Comparison of specific numerical examples] Next, a solid electrolytic capacitor formed using the above-mentioned configuration will be compared with a solid electrolytic capacitor having a conventional configuration using specific numerical examples. Fig. 9 is a table comparing the relative ESR values ​​and the thickness of the laminate of the capacitor element and Comparative Example 1, Comparative Example 2, and Comparative Example 3. Note that in the table shown in Fig. 9, the comparison is made based on the condition that four capacitor elements are laminated.

[0090] The configuration of the first embodiment is that of solid electrolytic capacitor 1. The thickness of the solid electrolyte layer in the first embodiment is about 180 μm. A conductive member is formed on this solid electrolyte layer to form a laminate. Since four capacitor elements each having a thickness of 180 μm are provided, the thickness of the laminate is 720 μm. At this time, concave-convex portions 113a and 113b are formed in solid electrolyte layer 113, and conductive member 19 is formed in the area surrounded by these concave-convex portions 113a and 113b. Therefore, the thickness of the conductive member is not added.

[0091] The configuration of the second embodiment is the configuration of the solid electrolytic capacitor 1A. The thickness of the solid electrolyte layer in the second embodiment is about 180 μm. A conductive member is formed on this solid electrolyte layer to form a laminate. Since four capacitor elements each having a thickness of 180 μm are provided, the thickness of the laminate is 720 μm. At this time, uneven portions 113a, 113b, 113c, and 113d are formed in the solid electrolyte layer 113, and the conductive member 19 is formed in the area surrounded by the uneven portions 113a, 113b, 113c, and 113d. Therefore, the thickness of the conductive member is not added.

[0092] In Comparative Example 1, the solid electrolyte layer is heated and pressed using a press machine to make the entire surface of the solid electrolyte layer into a substantially flat shape. That is, no unevenness is formed in the solid electrolyte layer of Comparative Example 1. In this case, the thickness of the solid electrolyte layer is 160 μm. The configuration of Comparative Example 1 includes four capacitor elements having a thickness of 160 μm and a conductive member having a thickness of 60 μm. Therefore, the thickness of the laminate is 700 μm. Compared with the first and second embodiments, since no unevenness is formed, the thickness of the conductive member is added to the thickness of the laminate.

[0093] In Comparative Example 2, the solid electrolyte layer is heated and pressurized using a press machine to form a recess only at the second end of the solid electrolyte layer (the second end in the first embodiment). At this time, the thickness of the solid electrolyte layer is 180 μm. A conductive member is formed on this solid electrolyte layer to form a laminate. Since four capacitor elements each having a thickness of 180 μm are provided, the thickness of the laminate is 720 μm. At this time, since uneven portions are formed in solid electrolytic capacitor 1, the thickness of the conductive member is not added.

[0094] In Comparative Example 3, the solid electrolyte layer is not heated and pressed using a press. In this case, the thickness of the solid electrolyte layer is 180 μm. A conductive member is formed on this solid electrolyte layer to form a laminate. Four capacitor elements each having a thickness of 180 μm and a conductive member having a thickness of 60 μm are provided. Thus, the thickness of the laminate is 780 μm. Compared to the first and second embodiments, since no unevenness is formed, the thickness of the conductive member is added to the thickness of the laminate.

[0095] The ESR and thickness of the above-mentioned configurations are compared. Note that the ESR of the configuration of the first embodiment is set to 100 for comparison. In the second embodiment, by providing the uneven portions 113a, 113b, 113c, and 113d, the relative value of the ESR becomes 103, which is as low as the first embodiment.

[0096] On the other hand, in the configuration of Comparative Example 1, no unevenness is formed compared to the first and second embodiments. This reduces the thickness of the laminate. However, since no unevenness is formed, the relative value of ESR is 112, which is higher than the first and second embodiments. Furthermore, in Comparative Example 1, the carbon layer and metal layer are not sufficiently formed at the end of the solid electrolyte layer. Therefore, the contact area of ​​the solid electrolyte layer, the carbon layer, and the metal layer is smaller than the first and second embodiments. That is, the conductive path of the current is not secured, and the ESR is likely to increase.

[0097] In addition, in the configuration of Comparative Example 2, the uneven portion is formed only at the second end portion, compared to the first and second embodiments. This allows the thickness of the entire laminate to be thin without adding the thickness of the conductive member to the thickness of the laminate. However, there are parts at the ends of the solid electrolyte layer where the carbon layer and the metal layer are not sufficiently formed. Therefore, the relative value of ESR is 109, which is higher than the first and second embodiments. In addition, there are parts where the contact area of ​​the solid electrolyte layer, the carbon layer, and the metal layer is smaller than the first and second embodiments. In other words, the conductive path of the current is not sufficiently secured, and the ESR is likely to increase.

[0098] In addition, in the configuration of Comparative Example 3, compared to the first and second embodiments, the uneven portion is formed on the entire surface of the solid electrolyte layer. As a result, the thickness of the conductive member is added to the thickness of the laminate, and the thickness of the entire laminate becomes thicker. On the other hand, since the uneven portion is formed on the entire surface of the solid electrolyte layer, a conductive path for current is sufficiently secured, and an increase in ESR can be suppressed. However, since the thickness of the laminate becomes thicker, the volumetric efficiency decreases. Therefore, it is difficult to miniaturize the solid electrolytic capacitor.

[0099] From the above, by forming the uneven portion at the end of the solid electrolyte layer as in the first and second embodiments, the contact area between the solid electrolyte layer, the carbon layer, and the metal layer can be increased, that is, the conductive path of the current is secured, and the increase in ESR can be suppressed.

[0100] Furthermore, conductive member 19 is formed in the region surrounded by the uneven portion. That is, the uneven portion and conductive member 19 do not overlap in the Z-axis direction. This makes it possible to more reliably physically bond and electrically connect the capacitor elements without increasing the thickness of solid electrolytic capacitor 1. That is, the solid electrolytic capacitor can be made smaller while improving its capacitance efficiency.

[0101] Furthermore, the configurations and various derivative examples shown in the above-described embodiments can be combined as appropriate, and effects according to each combination can be achieved. [Explanation of symbols]

[0102] F11,F1…1st page F12,F2…Second side F13,F3…Third side F14,F4…Fourth side F15,F5…5th side F16,F6…Side 6 1,1A...Solid electrolytic capacitor 10...Capacitor assembly 11...Capacitor element 19...Conductive material 20…First external electrode 30…Second external electrode 40...Insulating resin body 50...Conductive adhesive 111...Electrode foil 111F…electrode layer 111L…Porous layer 112...Dielectric layer 113,113G…Solid electrolyte layer 113a, 113b, 113c, 113d...Uneven parts 114,114G…Carbon layer 115,115G…Metal layer 400...Sealing body 401…Ceiling 402…Bottom 403...Side 1 404…Second side

Claims

1. a flat membrane-like anode body including a valve metal, a porous layer having a plurality of holes on a surface of the valve metal, and an anode terminal region and a cathode formation region that are arranged along a first direction; a dielectric layer formed on at least the cathode forming region; a solid electrolyte layer formed on the dielectric layer in the cathode formation region; a conductor layer formed so as to cover the solid electrolyte layer; and a capacitor element having a sealing body that seals a laminate in which a plurality of the capacitor elements are laminated with an insulating resin; a first external electrode connected to an end of the anode terminal region; a second external electrode connected to the cathode forming region; Further equipped with the solid electrolyte layer has a first end, a second end facing the first end in the first direction, a first side portion and a second side portion connecting the first end and the second end, and a central portion surrounded by the first end, the second end, the first side portion, and the second side portion, the central portion is substantially flat, and a first uneven portion having an uneven shape greater than that of the central portion is formed at the first end portion and the second end portion; Solid electrolytic capacitor.

2. The solid electrolytic capacitor according to claim 1 , wherein a second uneven portion is formed on the first side portion and the second side portion.

3. 2. The solid electrolytic capacitor according to claim 1, wherein a difference in thickness between a portion of the solid electrolyte layer where the first unevenness is the thickest and a portion of the solid electrolyte layer where the first unevenness is the thinnest is 1 μm or more and 100 μm or less.

4. 3. The solid electrolytic capacitor according to claim 2, wherein a difference in thickness between a portion of the second unevenness in the solid electrolyte layer that is the thickest and a portion of the second unevenness that is the thinnest is 1 μm or more and 100 μm or less.

5. a capacitor element forming step of forming a capacitor element having: a flat membrane-like anode body including a valve metal, the anode body having a porous layer having a plurality of holes on a surface of the valve metal, and the anode terminal region and a cathode formation region that are arranged along a first direction; a dielectric layer formed on at least the cathode formation region; a solid electrolyte layer formed on the dielectric layer in the cathode formation region, the solid electrolyte layer having a first end and a second end facing the first end in the first direction, a first side portion and a second side portion connecting the first end and the second end, a central portion surrounded by the first end, the second end, the first side portion and the second side portion; and a conductor layer formed so as to cover the solid electrolyte layer; a first external electrode forming step of forming a first external electrode connected to an end portion of the anode terminal region; a second external electrode forming step of forming a second external electrode connected to the cathode formation region; a sealing body forming step of laminating a plurality of the capacitor elements and sealing the laminate with an insulating resin to form a sealing body having a first surface from which an end of the anode terminal region is linearly exposed; having In the capacitor element forming step, The method further includes a pressurizing step of applying pressure to the vicinity of a central portion of the solid electrolyte layer to form a flat shape such that the first end portion and the second end portion of the solid electrolyte layer become a first uneven portion having an uneven shape relative to the central portion. A method for manufacturing a solid electrolytic capacitor.

6. The pressurizing step includes: the solid electrolyte layer is pushed out toward the first side portion and the second side portion by the pressurization, thereby forming a second uneven portion. The method for producing the solid electrolytic capacitor according to claim 5 .

7. 6. The method for manufacturing a solid electrolytic capacitor according to claim 5, wherein a difference in thickness between a portion of the first unevenness in the solid electrolyte layer that is the thickest and a portion of the first unevenness that is the thinnest is 1 μm or more and 100 μm or less.

8. 7. The method for manufacturing a solid electrolytic capacitor according to claim 6, wherein a difference in thickness between a portion of the second unevenness in the solid electrolyte layer that is thickest and a portion of the second unevenness that is thinnest is 1 μm or more and 100 μm or less.

9. a flat membrane-like anode body including a valve metal, a porous layer having a plurality of holes on a surface of the valve metal, and an anode terminal region and a cathode forming region that are arranged along a first direction; a dielectric layer formed on at least the cathode forming region; a solid electrolyte layer formed on the dielectric layer in the cathode formation region; a conductor layer formed so as to cover the solid electrolyte layer; having the solid electrolyte layer has a first end, a second end facing the first end in the first direction, a first side portion and a second side portion connecting the first end and the second end, and a central portion surrounded by the first end, the second end, the first side portion, and the second side portion, the central portion is substantially flat, and a first uneven portion having an uneven shape greater than that of the central portion is formed at the first end portion and the second end portion; Capacitor element.

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