Solid electrolytic capacitor and connection element of solid electrolytic capacitor

Abstract

This solid electrolytic capacitor comprises: a layered body of solid electrolytic capacitor elements; a sealing body; a first external electrode; and a second external electrode. The solid electrolytic capacitor elements each comprise: a valve action metallic base that has a dielectric layer on at least one main surface and that is divided into an anode terminal region and a cathode formation region; and a solid electrolyte layer provided on the dielectric layer in the cathode formation region. The sealing body seals, by means of an insulating resin, the layered body in which a plurality of the solid electrolytic capacitor elements are layered. The sealing body has a first main surface and a second main surface opposing the first main surface. The first external electrode is connected to the anode terminal region. The second external electrode has a bottom surface electrode portion disposed on the second main surface, and a bent portion continuing to the bottom surface electrode portion. The second external electrode is connected to the cathode formation region. The bent portion of the second external electrode has, in a direction in which the second external electrode extends, a first portion, a second portion continuing to the first portion, and a third portion continuing to the second portion. The second portion is bent so as to have a first angle with respect to the first portion. The third portion is bent so as to have a second angle with respect to the second portion. The third portion is disposed at a position sandwiched between the plurality of solid electrolytic capacitor elements in the layering direction of the layered body. The sealing body has a first region close to the first main surface and a second region close to the second main surface with the third portion as a reference. The solid electrolytic capacitor elements are configured such that a first number of layers of a first capacitor element formed in the first region is different from a second number of layers of a second capacitor element formed in the second region.

Description

Solid electrolytic capacitor and connection element for solid electrolytic capacitor

[0001] The present invention relates to a solid electrolytic capacitor having a plate-shaped metal body as an external electrode (connection element to the outside).

[0002] 2. Description of the Related Art Various techniques have been known for connecting the cathode foil of a laminate formed by stacking a plurality of capacitor elements to a connecting element (lead frame).

[0003] The solid electrolytic capacitor described in Patent Document 1 has stacked capacitor elements sandwiched between a lead frame, connecting the stacked capacitor elements to the lead frame. The stacked capacitor elements are formed of an even number of sheets. The lead frame is sandwiched between two capacitor elements (cathode foils) arranged at the center in the stacking direction.

[0004] Patent Document 2 discloses a configuration in which a cathode connection part is connected to a lead frame. The cathode connection part is a connection electrode having a predetermined area. The cathode connection part has a shape that extends in a direction parallel to the stacking direction of the capacitor elements. The cathode connection part is connected to an end face of the capacitor element that is parallel to the stacking direction.

[0005] JP 2020-205446 A JP 2013-179143 A

[0006] In the configuration of Patent Document 1, when an odd number of capacitor elements are stacked to form a laminate, the position of the lead frame sandwiched between the capacitor elements is biased toward the upper or lower surface side relative to the center position in the stacking direction, which means that the balance of the laminate is lost.

[0007] As described above, when the number of laminated capacitor elements is odd, the balance of the laminate may be lost. In order to solve this problem, the following method may be used.

[0008] The lead frame is bent significantly depending on the number of layers of the capacitor element. In this case, excessive stress is applied to the bending points of the lead frame. As a result, there is a risk that the lead frame may break at these bending points.

[0009] - A mold corresponding to the number of laminated capacitor elements is used. In this case, a new mold must be prepared every time the number of laminated capacitor elements changes, which increases costs.

[0010] Furthermore, if resin sealing is performed when the lead frame is misaligned, there will be a bottleneck where the resin flow path narrows, which can easily cause stress to the capacitor elements. Furthermore, because the capacitor elements on the outermost layer are significantly bent in the stacking direction, they are particularly susceptible to stress. Therefore, there is a risk that the capacitor elements on the outermost layer will break. This can lead to LC defects.

[0011] Furthermore, the imbalance of the laminate can result in narrower resin flow paths, leaving some areas unfilled with resin. This lack of resin filling creates a difference in the thickness of the sealing resin between the top and bottom sides of the laminate. If the resin on the bottom side is too thin, water vapor and oxygen from the outside can penetrate, accelerating the deterioration of the capacitor element.

[0012] Furthermore, the cathode connection portion in the configuration of Patent Document 2 has one end connected to the lead frame and the other end not connected to the lead frame. That is, the other end is spaced farther from the lead frame than the one end. Since the ESR increases with the distance from the lead frame, there is a risk that the ESR of the solid electrolytic capacitor will increase. In this case, it is necessary to apply a conductive paste to prevent the ESR from increasing, but there is a risk that the conductive paste will be costly.

[0013] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a highly reliable solid electrolytic capacitor that improves the bonding strength between the cathode region of the capacitor element and the lead frame, while suppressing deterioration in electrical characteristics.

[0014] The solid electrolytic capacitor of the present invention comprises a laminate of solid electrolytic capacitor elements, a sealing body, a first external electrode, and a second external electrode. The solid electrolytic capacitor element comprises a valve metal substrate having a dielectric layer on at least one main surface thereof and divided into an anode terminal region and a cathode formation region, and a solid electrolyte layer provided on the dielectric layer in the cathode formation region.

[0015] The sealing body seals a laminate of multiple stacked solid electrolytic capacitor elements with an insulating resin. The sealing body has a first main surface and a second main surface opposite the first main surface. The first external electrode is connected to the anode terminal region. The second external electrode has a bottom electrode portion disposed on the second main surface and a bent portion connected to the bottom electrode portion. The second external electrode is connected to the cathode formation region.

[0016] The bent portion of the second external electrode has, in the extension direction of the second external electrode, a first portion, a second portion connected to the first portion, and a third portion connected to the second portion. The second portion is bent at a first angle relative to the first portion. The third portion is bent at a second angle relative to the second portion. The third portion is disposed at a position sandwiched between the plurality of solid electrolytic capacitor elements in the stacking direction of the laminate.

[0017] The sealing body has a first region near the first main surface and a second region near the second main surface, with the third portion as a reference. In the solid electrolytic capacitor element, a first number of first capacitor elements formed in the first region is different from a second number of second capacitor elements formed in the second region.

[0018] With this configuration, the second external electrode can be bent according to the number of stacked capacitor elements. This allows the laminate to be balanced. That is, the fluidity can be made uniform when filling the resin. Therefore, the area where the resin is not filled can be reduced. This makes the permeation speed of water vapor and oxygen from the outside uniform throughout the laminate, stabilizing the rate of deterioration of the capacitor elements. Furthermore, there is no need to bend the second external electrode and the capacitor elements significantly. Since the stress on the outermost capacitor element can be reduced, LC defects are suppressed. Furthermore, there is no need to prepare molds according to the number of stacked capacitor elements, which allows for low costs. Furthermore, the distance between the capacitor element and the second external electrode is not large. Therefore, an increase in ESR can be suppressed.

[0019] The connection element of the solid electrolytic capacitor of the present invention has a first electrode portion and a bent portion connected to the first electrode portion. The bent portion has, in an extending direction, a first portion, a second portion connected to the first portion, and a third portion connected to the second portion. The second portion is bent at a first angle relative to the first portion. The third portion is bent at a second angle relative to the second portion.

[0020] In this configuration, the connecting element can be bent according to the number of capacitor elements. In other words, the connecting element does not need to be bent significantly. In addition, the stress on the outermost capacitor element can be reduced, which makes it possible to suppress LC defects.

[0021] According to the present invention, it is possible to provide a highly reliable solid electrolytic capacitor that improves the bonding strength between the cathode region of the capacitor element and the connection element and suppresses deterioration of electrical characteristics.

[0022] FIG. 1 is an external perspective view of the solid electrolytic capacitor according to the first embodiment. FIG. 2(A) is an enlarged view of a portion of the capacitor element according to the first embodiment, and FIG. 2(B) is a cross-sectional view of the capacitor element. FIG. 3 is a cross-sectional view of the capacitor assembly according to the first embodiment. FIG. 4 is a schematic view of the capacitor element according to the first embodiment. FIG. 5(A) is a cross-sectional view of the solid electrolytic capacitor according to the first embodiment, and FIG. 5(B) is a cross-sectional view of a solid electrolytic capacitor according to a conventional configuration. FIG. 6 is a flowchart showing a procedure for forming the solid electrolytic capacitor according to the first embodiment. FIG. 7 is a view showing an overview of resin sealing according to the first embodiment. FIG. 8 is a cross-sectional view of the solid electrolytic capacitor according to the second embodiment. FIG. 9 is a cross-sectional view of the solid electrolytic capacitor according to the third embodiment. FIG. 10 is a cross-sectional view of the solid electrolytic capacitor according to the fourth embodiment.

[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 perspective view of the appearance of the solid electrolytic capacitor 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. Note that in Fig. 1, for ease of understanding, some components are omitted and the insulating resin body 40 is shown in a see-through manner.

[0025] As shown in FIG. 1 , 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 the conductive member 19 can be omitted if conductivity equal to or greater than the desired conductivity can be obtained between the plurality of capacitor elements 11 without using the conductive member 19. The stacking direction of the plurality of capacitor elements 11 in the capacitor assembly 10 corresponds to the Z-axis direction in FIG. 1 .

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

[0027] The plurality of capacitor elements 11 are stacked. By stacking the plurality of capacitor elements 11, a capacitor assembly 10 (laminate) is formed.

[0028] The capacitor assembly 10 is sealed with an insulating resin body 40. This forms a sealed body 400. The sealed 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, a third surface 405, and a fourth surface 406. The first surface 403 is a surface opposite to the second surface 404, and the third surface 405 is a surface opposite to the fourth surface 406. The top surface 401 of the capacitor assembly 10 corresponds to the "first main surface" in the present invention, and the bottom surface 402 corresponds to the "second main surface" in the present invention.

[0029] The first external electrode 20 is formed along the sealing body 400 and a portion of the capacitor element 11. Specifically, the first external electrode 20 is disposed on a first surface 403 of the sealing body 400, a portion of the side surface of the capacitor element 11, and a bottom surface 402 of the sealing body 400. The anode terminal region and the first external electrode 20 are electrically and physically connected by being sandwiched between the stacked capacitor elements 11 via a conductive adhesive (not shown).

[0030] The first external electrode 20 is preferably formed of a metal material that is easy to bend and has high conductivity, such as a copper alloy or iron alloy material. The first external electrode 20 is formed of a material cut out from a metal plate, for example, and is configured to bend the metal plate at a midpoint in the longitudinal direction.

[0031] 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 30 are joined with a conductive adhesive made of silver paste or the like. A more detailed structure of the second external electrode 30 will be described later. The second external electrode 30 corresponds to the "connection element of the solid electrolytic capacitor" of the present invention.

[0032] The connection layers (conductive layers including the solid electrolyte layer 113) of the plurality of capacitor elements 11 are electrically and physically connected to the second external electrode 30 by a conductive adhesive.

[0033] 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 or iron alloy, similar to the first external electrode 20. The second external electrode 30 is formed of a material cut out from a metal plate (metal sheet), for example, and has a configuration in which the metal sheet is bent midway along its length. Note that the first external electrode 20 and the second external electrode 30 may be made of the same material or different materials.

[0034] The insulating resin body is mainly made of resin and may contain a filler. Examples of preferred resins include epoxy resin, phenol resin, polyimide resin, silicone resin, polyamide resin, and liquid crystal polymer. The resin may be in either solid or liquid form. It is preferred that corners are rounded by barrel polishing after resin sealing. Examples of preferred fillers include silica particles and alumina particles. The maximum diameter of the filler is preferably 30 μm or more and 40 μm or less. A material containing silica particles in a solid epoxy resin and phenol resin is more preferred.

[0035] (Structure of Capacitor Element) The structure of capacitor element 11 will be described in more detail with reference to FIGS. 2(A) and 2(B).

[0036] Fig. 2(A) is an external perspective view of capacitor element 11, and Fig. 2(B) is a cross-sectional view of capacitor element 11. Fig. 2(B) is a cross-sectional view taken along a plane (XZ plane) perpendicular to the flat film surface and end surface of capacitor element 11.

[0037] 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.

[0038] A more specific structure of the electrode foil 111 is as follows. The electrode layer 111F is made of, for example, a metal such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, or 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 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 porous. The electrode foil 111 may be made of a valve metal that exhibits so-called valve action.

[0039] A dielectric layer 112 is formed on the electrode foil 111. As shown in FIGS. 2A and 2B , the electrode foil 111 has a first surface F1 and a second surface F2 that face each other in the Z-axis direction (the stacking direction of the laminate). The electrode foil 111 further includes a third surface F3, a fourth surface F4, a fifth surface F5, and a sixth surface F6 that are connected to the first surface F1 and the second surface F2 and are parallel to the Z-axis direction. The third surface F3 and the fourth surface F4 are parallel to the Y-axis direction. The fifth surface F5 and the sixth surface F6 are parallel to the X-axis. The dielectric layer 112 covers the first surface F1, the second surface F2, the fourth surface F4, the fifth surface F5, and the sixth surface F6 of the electrode foil 111.

[0040] The dielectric layer 112 is preferably made of an oxide film of the electrode foil 111 (porous layer 111L). For example, 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 their sodium salts or ammonium salts, and then anodizing the aluminum foil. The thickness of the dielectric layer 112 is preferably 10 nm or more and 100 nm or less.

[0041] 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 also fills the numerous pores covered with dielectric layer 112.

[0042] More specifically, the solid electrolyte layer 113 includes, for example, an inner layer and an outer layer.

[0043] The inner layer is a layer of solid electrolyte layer 113 that abuts dielectric layer 112, and may be, for example, a PEDOT:PSS layer realized by 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)], and composited with polystyrene sulfonic acid (PSS) as a dopant. The inner layer is formed by a method of forming a polymer film of poly(3,4-ethylenedioxythiophene) or the like on the surface of dielectric layer 112 using an electrolyte solution that serves as the base for forming 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 portion and drying it.

[0044] The outer layer is a layer formed on the outside of the inner layer. For example, the outer layer is formed so as to cover the entire surface of the inner layer after the inner layer is formed to fill the fine recesses in 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 a method of forming a polymer film of poly(3,4-ethylenedioxythiophene) or the like on the surface of the inner layer using an electrolyte solution that serves as the 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 or paste of a polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the inner layer portion and drying it, or the like.

[0045] A conductive member may be provided as a layer subsequent to the outer layer. The conductive member may include, for example, a carbon layer and a silver layer. The carbon layer is preferably formed by applying a conductive paste containing a mixture of an insulating resin such as epoxy resin or phenolic resin and particles of carbon black or graphite. The silver layer is preferably formed by applying a conductive paste containing a mixture of an insulating resin such as epoxy resin or phenolic resin and particles of silver or the like. The materials constituting the conductive member may be appropriately combined, for example, by omitting the carbon layer.

[0046] The carbon layer 114 is formed so as to cover the outer layer (solid electrolyte layer 113). The carbon layer 114 contains a thermosetting resin. More specifically, the carbon layer 114 is formed by applying a carbon paste in which an insulating resin such as a phenolic resin is mixed with particles of carbon black or graphite.

[0047] The metal layer 115 is formed so as to cover the carbon layer 114. The metal layer 115 includes a thermoplastic resin. More specifically, the metal layer 115 is formed by applying a metal paste in which an insulating resin such as a phenolic resin is mixed with silver particles, for example.

[0048] 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 solid electrolyte layer 113 corresponds to the cathode. The region of electrode foil 111 where solid electrolyte layer 113 is not formed corresponds to the "anode terminal region" in the present invention, and solid electrolyte layer 113 corresponds to the "cathode-forming region" in the present invention. Electrode foil 111 corresponds to the "main body" in the present invention.

[0049] (Detailed Structure of Capacitor Assembly and Second External Electrode) Next, the structure of the second external electrode 30 will be described in detail using Figures 3, 4, 5(A), and 5(B). Figure 3 is a cross-sectional view of the capacitor assembly according to the first embodiment. Figure 4 is a schematic diagram of the capacitor element according to the first embodiment. Figure 5(A) is a cross-sectional view of the solid electrolytic capacitor according to the first embodiment, and Figure 5(B) is a cross-sectional view of a solid electrolytic capacitor according to a conventional configuration. Note that the structure of the second external electrode 30 in Figure 5(B) is different from the structure in Figure 5(A). Figures 3, 4, 5(A), and 5(B) are cross-sectional views taken along a plane (XZ plane) perpendicular to the capacitor assembly and the solid electrolytic capacitor.

[0050] First, the detailed structure of the capacitor assembly 10 will be described using FIG. 3 . The capacitor assembly 10 includes a first region R1 and a second region R2. The first region R1 is the region on the top surface 401 side in FIG. 5A , and the second region R2 is the region on the bottom surface 402 side in FIG. 5A . The number of capacitor elements 11 constituting the capacitor assembly 10 is an odd number. In FIGS. 3 and 5A , the number of capacitor elements 11 is assumed to be, for example, five. In this case, there are two capacitor elements 11 (hereinafter referred to as first capacitor elements) formed in the first region R1. On the other hand, there are three capacitor elements (hereinafter referred to as second capacitor elements) formed in the second region R2. That is, the number of second capacitor elements formed in the second region R2 is greater than the number of first capacitor elements formed in the first region R1. The number of first capacitor elements corresponds to the “first number of stacked layers” in the present invention, and the number of second capacitor elements corresponds to the “second number of stacked layers” in the present invention.

[0051] Next, the structure of the second external electrode 30 will be described. As shown in Fig. 4, the second external electrode 30 includes a bottom electrode portion 310 and a bent portion 320. The bottom electrode portion 310 and the bent portion 320 are connected by bending the metal plate at a midpoint in the longitudinal direction. As shown in Fig. 5A, the bottom electrode portion 310 and a portion of the bent portion 320 are bent along the sealing body 400.

[0052] The bent portion 320 includes a first portion 321, a second portion 322, and a third portion 323. That is, in the first embodiment, the bent portion 320 has two bending points. The bottom electrode portion 310 corresponds to the "first electrode portion" of this invention.

[0053] More specifically, the first portion 321 is connected to the bottom electrode portion 310 substantially perpendicularly, so that the first portion 321 and the bottom electrode portion 310 are bent along the encapsulant 400 .

[0054] The first portion 321 and the second portion 322 are connected in a bent shape at a midpoint in the longitudinal direction so as to form a first angle α1 in the longitudinal direction. More specifically, the first angle α1 is preferably 20° or more and 160° or less.

[0055] The second portion 322 and the third portion 323 are connected in a bent shape at a midpoint in the longitudinal direction so as to form a second angle α2 in the longitudinal direction. More specifically, the second angle α2 is preferably equal to or greater than 110° and less than 250°.

[0056] Next, a more specific structure for joining the second external electrode 30 to the capacitor assembly 10 will be described with reference to Fig. 5A. As shown in Fig. 5A, the third portion 323 of the second external electrode 30 is sandwiched between the first capacitor element in the first region R1 and the second capacitor element in the second region R2 of the capacitor assembly 10. In this way, the second external electrode 30 is joined to the cathode formation region of the capacitor element 11.

[0057] In this case, the third portion 323 is disposed in a state substantially parallel to the bottom electrode portion 310 and the capacitor element 11. In other words, the first angle α1 and the second angle α2 may be determined so that the third portion 323 is in a state substantially parallel to the bottom electrode portion 310 and the capacitor element 11.

[0058] In the example shown in FIG. 5A , it is preferable that the second portion 322 bends toward the first region R1. It is also preferable that the third portion 323 bends so as to be substantially parallel to the bottom electrode portion 310 and the capacitor element 11. In the first embodiment, when the first angle α1 is set to be 90° or more and 160° or less, the second angle α2 is preferably set to be 110° or more and less than 180°. Note that the above-described substantially parallel state is not limited to a completely parallel state. In other words, the "substantially parallel state" in the present invention also includes substantial parallelism within a certain manufacturing tolerance range.

[0059] In this way, by bending the bent portion 320 so as to have the first angle α1 and the second angle α2, the third portion 323 is biased toward the first region R1, in other words, the region where the number of stacked capacitor elements 11 is small. As described above, the third portion 323 is arranged so as to be substantially parallel to the bottom electrode portion 310 and the capacitor elements 11. In other words, the plurality of capacitor elements 11 in the first region R1 and the plurality of capacitor elements 11 in the second region R2 can be arranged while maintaining balance with respect to the center of the stacking direction (Z-axis direction) of the plurality of capacitor elements 11. In the present invention, this state is defined as a state in which the first region R1 and the second region R2 are balanced.

[0060] In other words, it is possible to make small or substantially equal the difference between a first total thickness, which is the thickness of the plurality of capacitor elements 11 (first capacitor elements) on the first region R1 side and the thickness of the third portion 323 of the second external electrode 30, and a second total thickness, which is the thickness of the plurality of capacitor elements 11 (second capacitor elements) on the second region R2 side, relative to the center in the height direction (stacking direction) of the sealing body 400. In other words, by achieving a balance between the first region R1 and the second region R2, it is not necessary to use molds corresponding to the number of the plurality of capacitor elements 11.

[0061] 5A, the capacitor assembly 10 is placed in a mold 500 (see FIG. 7, which will be described later). For example, resin sealing is performed by transfer molding.

[0062] By maintaining a balance between the first region R1 and the second region R2, the resin flow path is prevented from narrowing. This makes the resin flow uniform, reducing the area where the resin is not filled. That is, it is possible to make the thickness of the resin uniform in the first region R1 and the second region R2. Furthermore, the distance H1 between the top surface 401 and the capacitor assembly 10 and the distance H2 between the bottom surface 402 and the capacitor assembly 10 can be made approximately the same. It is preferable that the distance H1 and the distance H2 are at least approximately 150 μm.

[0063] This makes the speed at which water vapor and oxygen from the outside permeate the solid electrolytic capacitor uniform, suppressing an increase in the rate of partial deterioration of the capacitor element and stabilizing the rate of deterioration.

[0064] The same effect can be obtained if the difference between the distance H1 and the distance H2 is within about 50 μm. The distance H1 corresponds to the "first distance" of the present invention, and the distance H2 corresponds to the "second distance" of the present invention.

[0065] Furthermore, in the first embodiment, the bent portion 320 has two bent portions. Therefore, the second external electrode 30 does not need to be bent greatly. In other words, the amount of bending per time can be reduced. Therefore, breakage of the second external electrode 30 can be suppressed.

[0066] Furthermore, in the first embodiment, excessive stress is unlikely to be applied to capacitor element 11 located in the outermost layer in the stacking direction. Therefore, it is possible to prevent breakage of the capacitor element located in the outermost layer, which is particularly susceptible to stress. In other words, it is possible to prevent LC defects.

[0067] Furthermore, in the conventional configuration, when the number of laminated capacitor elements is an odd number, it is necessary to use a mold according to the number of laminated capacitor elements 11. However, by using the configuration of the first embodiment, it is not necessary to prepare a separate mold. In other words, low costs can be achieved.

[0068] Furthermore, there is no large distance between each of the plurality of capacitor elements 11 and the second external electrode 30. In other words, there is a small difference in the distance between each of the plurality of capacitor elements 11 and the second external electrode 30. This makes it possible to suppress an increase in ESR.

[0069] Here, the structure of the second external electrode of a conventional solid electrolytic capacitor 1P will be described with reference to FIG. 5B. In the structure of the solid electrolytic capacitor 1P shown in FIG. 5B, the second external electrode 30P has one bending point. That is, the balance between the first region R1 and the second region R2 is not maintained. That is, the distance H1P between the top surface 401 and the capacitor assembly 10 is different from the distance H2P between the bottom surface 402 and the capacitor assembly 10. More specifically, the distance H2P is smaller than the distance H1P.

[0070] This results in an imbalance between the first region R1 and the second region R2, narrowing the resin inflow path. Therefore, the rate at which water vapor and oxygen from the outside penetrate the solid electrolytic capacitor varies, leading to unstable degradation of the capacitor element. This causes variations in the resin's fluidity, increasing the number of areas where the resin is not filled. This can lead to fracture of the capacitor element in the outermost layer, which is particularly susceptible to stress, and can cause LC defects.

[0071] Furthermore, in order to maintain a balance between the first region R1 and the second region R2, it is necessary to prepare molds according to the number of laminated layers of the capacitor element, which increases costs.

[0072] Therefore, by using the structure shown in the first embodiment of the present invention, a balance between the first region R1 and the second region R2 can be maintained, which makes it possible to suppress deterioration of electrical characteristics and provide a more reliable solid electrolytic capacitor 1.

[0073] (Method of Manufacturing Solid Electrolytic Capacitor) The solid electrolytic capacitor 1 having the above-described configuration is manufactured, for example, as follows. Fig. 6 is a flowchart showing the procedure for forming the solid electrolytic capacitor according to the first embodiment. Fig. 7 is a diagram showing an overview of the resin sealing according to the first embodiment.

[0074] The capacitor element 11 is formed (S11). Specifically, as shown in Figures 2(A) and 2(B), a dielectric layer 112, a solid electrolyte layer 113, a carbon layer 114, and a metal layer 115 are formed on a plurality of electrode foils 111.

[0075] Next, as shown in Fig. 3, conductive member 19 is formed on solid electrolyte layer 113 of capacitor element 11. Then, capacitor elements 11 are stacked. At this time, capacitor element 11 is defined as having first region R1 and second region R2. In this way, capacitor assembly 10 is formed (S12).

[0076] 7, one end of the first external electrode 20 is sandwiched between the first region R1 and the second region R2 of the capacitor assembly 10. This allows the anode-forming region of the capacitor assembly 10 to be bonded to the first external electrode 20 using a conductive adhesive such as silver paste (S13).

[0077] 7, the third portion 323 of the second external electrode 30 is sandwiched between the first region R1 and the second region R2 of the capacitor assembly 10. In the cathode forming region of the capacitor assembly 10, the third portion 323 is bonded to the second external electrode 30 using a conductive adhesive such as silver paste (S14). The second portion 322 and the third portion 323 are bonded in a bent state so as to form a second angle α2.

[0078] 7, the capacitor assembly 10 with the first external electrode 20 and the second external electrode 30 joined together is placed in a mold 500 and resin-sealed (S15). More specifically, the capacitor assembly 10 is resin-sealed by transfer molding.

[0079] Next, the first external electrode 20 is bent along the sealing body 400 (S16). More specifically, the first external electrode 20 is bent along the first surface 403 and the bottom surface 402 of the sealing body 400.

[0080] Next, the second external electrode 30 is bent so that the first portion 321 and the second portion 322 form a first angle α1. Next, the first portion 321 is bent along the second surface 404 and the bottom surface 402 of the sealing body 400 (S17).

[0081] In other words, by using such a process, it is possible to provide a highly reliable solid electrolytic capacitor 1 in which the balance between the first region R1 and the second region R2 is maintained.

[0082] In addition, if the number of first capacitor elements formed in the first region R1 is n (n is an integer value), it is preferable that the number of second capacitor elements formed in the second region R2 is n+1.

[0083] In the above-described structure, the number of first capacitor elements formed in the first region R1 is different from the number of second capacitor elements formed in the second region R2. However, the number of first capacitor elements may be the same as the number of second capacitor elements.

[0084] In the above configuration, an example has been described in which the first angle α1 is 90° or more and 160° or less, and the second angle is 110° or more and less than 180°. However, the same effect can be obtained if the first angle α1 is 20° or more and 160° or less, and the second angle α2 is 110° or more and less than 250°.

[0085] 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 a cross-sectional view of the solid electrolytic capacitor 1A according to the second embodiment. Fig. 8 is a cross-sectional view taken along a plane (XZ plane) perpendicular to the solid electrolytic capacitor.

[0086] 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 relationship between the number of first capacitor elements formed in the first region R1 and the number of second capacitor elements formed in the second region R2. The other configuration of the solid electrolytic capacitor according to the second embodiment is the same as that of the solid electrolytic capacitor according to the first embodiment, and a description of similar parts will be omitted.

[0087] 8, the number of capacitor elements 11 in the capacitor assembly 10A is five. In this case, the number of first capacitor elements in the first region R1 is three, and the number of second capacitor elements in the second region R2 is two.

[0088] The first portion 321 and the second portion 322 are connected in a bent shape at a first angle α12 in the longitudinal direction. In the second embodiment, it is preferable that the second portion 322 bends toward the second region R2. More specifically, it is preferable that the first angle α12 be greater than or equal to 20° and less than 90°.

[0089] Furthermore, second portion 322 and third portion 323 are connected in a bent shape at a second angle α22 in the longitudinal direction. In the second embodiment, third portion 323 is preferably bent so as to be substantially parallel to bottom electrode portion 310 and capacitor element 11. More specifically, second angle α22 is preferably equal to or greater than 180° and less than 250°.

[0090] Even with this configuration, the bent portion 320 is bent to have the first angle α12 and the second angle α22, so that the balance between the first region R1 and the second region R2 can be maintained.

[0091] As in the first embodiment, the capacitor assembly 10A is resin-sealed by transfer molding. Because the balance between the first region R1 and the second region R2 is maintained, the resin flow path is prevented from narrowing. This makes the resin flow uniform, reducing the area where the resin is not filled. This allows the resin thickness to be uniform in the first region R1 and the second region R2. This ensures that the permeation speeds of water vapor and oxygen from the outside are uniform in the solid electrolytic capacitor, stabilizing the rate of deterioration of the capacitor element.

[0092] Furthermore, in the second embodiment, the bent portion 320 also has two bent points, so there is no need to bend the second external electrode 30 and the capacitor element 11 significantly.

[0093] Also in the second embodiment, excessive stress is unlikely to be applied to capacitor element 11 in the outermost layer in the stacking direction. Therefore, it is possible to prevent breakage of the capacitor element in the outermost layer, which is particularly susceptible to stress. In other words, it is possible to prevent LC defects.

[0094] Furthermore, since it is not necessary to prepare molds according to the number of laminated capacitor elements 11, low costs can be achieved.

[0095] Furthermore, there is no large distance between the capacitor element 11 and the second external electrode 30. Therefore, an increase in ESR can be suppressed.

[0096] By using a structure in which the balance between the first region R1 and the second region R2 is maintained, as in the structure shown in the second embodiment, it is possible to suppress the deterioration of electrical characteristics and provide a more reliable solid electrolytic capacitor 1A.

[0097] Third Embodiment A solid electrolytic capacitor 1B according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 9 is a cross-sectional view of the solid electrolytic capacitor 1B according to the third embodiment.

[0098] 9, the solid electrolytic capacitor 1B according to the third embodiment differs from the solid electrolytic capacitor 1 according to the first embodiment in the relationship between the number of first capacitor elements formed in the first region R1 and the number of second capacitor elements formed in the second region R2. The other configuration of the solid electrolytic capacitor according to the third embodiment is the same as that of the solid electrolytic capacitor according to the first embodiment, and a description of similar parts will be omitted.

[0099] 9, the number of capacitor elements 11 in the capacitor assembly 10B is five. In this case, the number of first capacitor elements in the first region R1 is one, and the number of second capacitor elements in the second region R2 is four.

[0100] The first portion 321 and the second portion 322 are connected in a bent shape at a first angle α13 in the longitudinal direction. In the second embodiment, it is preferable that the first portion 321 bends toward the first region R1. More specifically, it is preferable that the first angle α13 be greater than or equal to 90° and less than or equal to 160°.

[0101] Furthermore, second portion 322 and third portion 323 are connected in a bent shape at a second angle α23 in the longitudinal direction. In the third embodiment, third portion 323 is preferably bent so as to be substantially parallel to bottom electrode portion 310 and capacitor element 11. More specifically, second angle α23 is preferably equal to or greater than 110° and less than 180°.

[0102] Even with this configuration, the bent portion 320 is bent to have the first angle α13 and the second angle α23, so that the balance between the first region R1 and the second region R2 can be maintained.

[0103] As in the first embodiment, the capacitor assembly 10B is resin-sealed by transfer molding. Because the balance between the first region R1 and the second region R2 is maintained, the resin flow path is prevented from narrowing. This makes the resin flow uniform, reducing the number of regions unfilled with resin. This allows the resin thickness to be uniform in the first region R1 and the second region R2. This ensures that the permeation speeds of water vapor and oxygen from the outside are uniform in the solid electrolytic capacitor, stabilizing the rate of deterioration of the capacitor element.

[0104] Furthermore, in the third embodiment, the bent portion 320 also has two bent points, so there is no need to bend the second external electrode 30 and the capacitor element 11 significantly.

[0105] Also in the third embodiment, excessive stress is unlikely to be applied to capacitor element 11 in the outermost layer in the stacking direction. Therefore, it is possible to prevent breakage of the capacitor element in the outermost layer, which is particularly susceptible to stress. In other words, it is possible to prevent LC defects.

[0106] Furthermore, since it is not necessary to prepare molds according to the number of laminated capacitor elements 11, low costs can be achieved.

[0107] Furthermore, there is no large distance between the capacitor element 11 and the second external electrode 30. Therefore, an increase in ESR can be suppressed.

[0108] By using a structure in which the balance between the first region R1 and the second region R2 is maintained, as in the structure shown in the third embodiment, it is possible to suppress the deterioration of electrical characteristics and provide a more reliable solid electrolytic capacitor 1B.

[0109] Fourth Embodiment A solid electrolytic capacitor 1C according to a fourth embodiment of the present invention will be described with reference to the drawings. Fig. 10 is a cross-sectional view of the solid electrolytic capacitor 1C according to the fourth embodiment.

[0110] 10 , the solid electrolytic capacitor 1C according to the fourth embodiment differs from the solid electrolytic capacitor 1 according to the first embodiment in the relationship between the number of first capacitor elements formed in the first region R1 and the number of second capacitor elements formed in the second region R2. The other configuration of the solid electrolytic capacitor according to the fourth embodiment is the same as that of the solid electrolytic capacitor according to the first embodiment, and a description of similar parts will be omitted.

[0111] 10, the number of capacitor elements 11 in the capacitor assembly 10C is five. In this case, the number of first capacitor elements in the first region R1 is four, and the number of second capacitor elements in the second region R2 is one.

[0112] The first portion 321 and the second portion 322 are connected in a bent shape at a first angle α14 in the longitudinal direction. In the second embodiment, it is preferable that the first portion 321 bends toward the second region R2. More specifically, it is preferable that the first angle α14 be 20° or more and 90° or less.

[0113] Furthermore, second portion 322 and third portion 323 are connected in a bent shape at a second angle α24 in the longitudinal direction. In the second embodiment, third portion 323 is preferably bent so as to be substantially parallel to bottom electrode portion 310 and capacitor element 11. More specifically, second angle α24 is preferably equal to or greater than 180° and less than 250°.

[0114] Even with this configuration, the bent portion 320 is bent to have the first angle α14 and the second angle α24, so that the balance between the first region R1 and the second region R2 can be maintained.

[0115] As in the first embodiment, resin sealing is performed by transfer molding. Because the balance between the first region R1 and the second region R2 is maintained, the resin flow path is prevented from narrowing. This makes the resin flow uniform, reducing the number of regions unfilled with resin. This allows the resin thickness to be uniform in the first region R1 and the second region R2. This ensures that the permeation speeds of water vapor and oxygen from the outside are uniform in the solid electrolytic capacitor, stabilizing the rate of deterioration of the capacitor element.

[0116] Furthermore, in the fourth embodiment, the bent portion 320 also has two bent points, so there is no need to bend the second external electrode 30 and the capacitor element 11 significantly.

[0117] Also in the fourth embodiment, excessive stress is unlikely to be applied to capacitor element 11 in the outermost layer in the stacking direction. Therefore, it is possible to prevent breakage of the capacitor element in the outermost layer, which is particularly susceptible to stress. In other words, it is possible to prevent LC defects.

[0118] Furthermore, since it is not necessary to prepare molds according to the number of laminated capacitor elements 11, low costs can be achieved.

[0119] Furthermore, there is no large distance between the capacitor element 11 and the second external electrode 30. Therefore, an increase in ESR can be suppressed.

[0120] By using a structure in which the balance between the first region R1 and the second region R2 is maintained, as in the structure shown in the fourth embodiment, it is possible to suppress the deterioration of electrical characteristics and provide a more reliable solid electrolytic capacitor 1C.

[0121] In the above-described embodiments, examples having two bending points have been described. However, the number of bending points is not limited to two. In other words, a solid electrolytic capacitor may have three or more bending points as long as the performance of the solid electrolytic capacitor can be maintained.

[0122] In the first and second embodiments described above, an example was shown in which the difference between the number of first stacked layers of the first capacitor element in the first region R1 and the number of second stacked layers of the second capacitor element in the second region R2 was 1. However, as in the third and fourth embodiments, the difference between the number of first stacked layers and the number of second stacked layers (difference in the number of stacked layers) may be 2 or more. However, it is preferable that the difference in the number of stacked layers is small.

[0123] Furthermore, although preferred first and second angles have been exemplified in each embodiment, the effects of the present invention can be obtained as long as the first angle is 20° or greater and 160° or less, and the second angle is 110° or greater and less than 250°. In other words, the same effects can be obtained by appropriately determining the second angle relative to the first angle within the above ranges.

[0124] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1P...Solid electrolytic capacitor 10, 10A, 10B, 10C...Capacitor assembly 11...Capacitor element 19...Conductive member 20...First external electrode 30, 30P...Second external electrode 40...Insulating resin body 111...Electrode foil 111F...Electrode layer 111L...Porous layer 112...Dielectric layer 113...Solid electrolyte layer 114...Carbon layer 115...Metal layer 310...Bottom electrode portion 320...Bent portion 321...First portion 322...Second portion 323...Third portion 400...Sealing body 401...Top surface 402...Bottom surface 403...First surface 404...Second surface 405...Third surface 406...Fourth surface 500...Mold F1...First surface F2...Second surface F3...Third surface F4...Fourth surface F5...Fifth surface F6...Sixth surface R1...First region R2...Second region α1, α12, α13, α14…First angle α2, α22, α23, α24… Second angle

Claims

1. A laminate of solid electrolytic capacitor elements comprising: a valve action metal substrate having a dielectric layer on at least one main surface thereof and divided into an anode terminal region and a cathode formation region; and a solid electrolyte layer provided on the dielectric layer in the cathode formation region; the laminate is sealed with an insulating resin; and the sealing body has a first main surface and a second main surface opposite the first main surface; a first external electrode connected to the anode terminal region; and a second external electrode having a bottom electrode portion disposed on the second main surface and a bent portion connected to the bottom electrode portion, the bent portion of the second external electrode having, in the extension direction of the second external electrode, a first portion, a second portion connected to the first portion, and a third portion connected to the second portion; the second portion is bent at a first angle relative to the first portion; and the third portion is bent at a second angle relative to the second portion; and the third portion is positioned between a plurality of the solid electrolytic capacitor elements in the stacking direction of the laminate; The sealing body has, with respect to the third portion, a first region close to the first main surface and a second region close to the second main surface, and in the solid electrolytic capacitor element, a first number of first capacitor elements formed in the first region is different from a second number of second capacitor elements formed in the second region.

2. The solid electrolytic capacitor according to claim 1, wherein the third portion is disposed so as to be substantially parallel to the solid electrolytic capacitor element.

3. The solid electrolytic capacitor according to claim 1 or 2, wherein the first angle is equal to or greater than 20° and less than 90°, and the second angle is equal to or greater than 180° and less than 250°.

4. The solid electrolytic capacitor according to claim 1 or 2, wherein the first angle is equal to or greater than 90° and equal to or less than 160°, and the second angle is equal to or greater than 110° and less than 180°.

5. A solid electrolytic capacitor according to any one of claims 1 to 4, wherein when the first number of laminated layers is n, the second number of laminated layers is n-1.

6. A solid electrolytic capacitor according to any one of claims 1 to 4, wherein when the number of first laminated layers is n, the number of second laminated layers is n+1.

7. A solid electrolytic capacitor according to any one of claims 1 to 6, wherein a first distance from the first main surface to the laminate is substantially the same as a second distance from the second main surface to the laminate.

8. A solid electrolytic capacitor according to any one of claims 1 to 6, wherein the difference between a first distance from the first main surface to the laminate and a second distance from the second main surface to the laminate is within approximately 50 μm.

9. A connection element for a solid electrolytic capacitor, comprising: a first electrode portion; and a bent portion connected to the first electrode portion, wherein the bent portion has, in an extending direction, a first portion, a second portion connected to the first portion, and a third portion connected to the second portion, wherein the second portion is bent at a first angle relative to the first portion, and the third portion is bent at a second angle relative to the second portion.

10. The connection element of a solid electrolytic capacitor according to claim 9, wherein the first electrode portion and the third portion are disposed in substantially parallel positions.

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