Solid electrolytic capacitor

Abstract

The disclosed solid electrolytic capacitor (100) includes an anode body (113), an anode line (112), a dielectric layer (114), a solid electrolyte layer (116), a carbon layer (117), and a silver particle layer (118). The solid electrolyte layer (116) is formed so as to cover the entirety of the bottom surface (113b), the entirety of the side surface (113s), and at least a part of the end surface (113e) of the anode body (113). The carbon layer (117) is formed so as to cover the entirety of the bottom surface (113b) and a part of the side surface (113s) of the anode body (113) and not cover the end surface (113e). The silver particle layer (118) is formed so as to cover the entirety of the bottom surface (113b) and a part of the side surface (113s) and not cover the end surface (113e). The carbon layer (117) and the silver particle layer (118) are formed in a predetermined region in the side surface (113s).

Description

Technical Field

[0001] The present disclosure relates to a solid electrolytic capacitor. Background Art

[0002] One example of a solid electrolytic capacitor includes an anode body made of a porous sintered body, a dielectric layer formed on the anode body, a solid electrolyte layer formed on the dielectric layer, and a cathode lead-out layer formed on the solid electrolyte layer. Regarding the cathode lead-out layer, various proposals have been made in the past.

[0003] Claim 1 of Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-117034) discloses "a solid electrolytic capacitor, in which a capacitor element formed by sequentially laminating a dielectric oxide film layer, a semiconductor layer, a carbon paste layer, and a conductor layer is externally mounted on the surface of a sintered body of valve metal or conductive oxide to which an anode lead is connected, characterized in that the carbon paste layer is not formed only on the sintered body surface to which the anode lead is connected".

[0004] Claim 1 of Patent Document 2 (International Publication No. 2007 / 004511) describes "a method for manufacturing a capacitor element, characterized in that the manufacturing method includes the following steps: immersing only the top end of the covering treatment force element to be covered with conductive paste of the capacitor element in a conductive paste bath; and immersing the entire area to be covered in the conductive paste bath".

[0005] Prior art documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-117034

[0008] Patent Document 2: International Publication No. 2007 / 004511 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In a solid electrolytic capacitor, it is desired to reduce the equivalent series resistance (ESR) and the leakage current. One object of the present disclosure is to provide a solid electrolytic capacitor with a lower ESR and leakage current.

[0011] Solutions to the Problems

[0012] One technical solution of the present disclosure relates to a solid electrolytic capacitor. The solid electrolytic capacitor includes: an anode body, which is a porous sintered body; an anode lead, which protrudes from an end face of the anode body; a dielectric layer, which is formed on a surface of the anode body; a solid electrolyte layer, which is formed on the dielectric layer; a carbon layer, which is formed on the solid electrolyte layer; and a silver particle layer, at least a part of which is formed on the carbon layer and contains silver particles. The anode body has a bottom surface on a side opposite to the end face and a side surface connecting the end face and the bottom surface. The solid electrolyte layer is formed to cover the entire bottom surface, the entire side surface, and at least a part of the end face. The carbon layer is formed to cover the entire bottom surface and a part of the side surface and does not cover the end face. The silver particle layer is formed to cover the entire bottom surface and a part of the side surface and does not cover the end face. When the distance from a first surface of the solid electrolyte layer formed on the bottom surface to a second surface of the solid electrolyte layer formed on the end face is set as L, the carbon layer is formed to cover a region in the side surface where the distance from the first surface is X (where 0.89 ≤ X / L < 1.00) or less. The silver particle layer is formed to cover a region in the side surface where the distance from the first surface is Y (where 0.90 ≤ Y / L < 1.00) or less.

[0013] Effect of the Invention

[0014] According to the present invention, a solid electrolytic capacitor with lower ESR and leakage current can be obtained.

[0015] The new features of the present invention are described in the appended claims. However, the present invention relates to both the structure and the content. Together with other objects and features of the present application, it should be better understood through the following detailed description with reference to the drawings. Description of the Drawings

[0016] Figure 1 It is a cross-sectional view schematically showing an example of the solid electrolytic capacitor of Embodiment 1.

[0017] Figure 2 It is used to Figure 1 explain an example of the structure of the solid electrolytic capacitor shown.

[0018] Figure 3 It is a cross-sectional view used to explain another example of the structure of the solid capacitor of Embodiment 1. Detailed Embodiment

[0019] Hereinafter, embodiments of the present disclosure will be described by way of examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials are sometimes exemplified, but other numerical values and other materials can also be applied as long as the effects of the present disclosure can be obtained. In this specification, a description such as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can also be referred to as "not less than numerical value A and not more than numerical value B". In the following description, when the lower limit and the upper limit of numerical values related to specific physical properties, conditions, etc. are exemplified, any one of the exemplified lower limits and any one of the exemplified upper limits can be arbitrarily combined as long as the lower limit is not greater than the upper limit. In the following description, when examples of constituent elements are listed, unless otherwise specified, either only one of the listed examples can be used, or a plurality of the listed examples can be used simultaneously.

[0020] (Solid electrolytic capacitor)

[0021] Hereinafter, the solid electrolytic capacitor of the present embodiment may sometimes be referred to as "solid electrolytic capacitor (S)". The solid electrolytic capacitor (S) includes: an anode body, which is a porous sintered body; an anode lead, which protrudes from an end face of the anode body; a dielectric layer, which is formed on the surface of the anode body; a solid electrolyte layer, which is formed on the dielectric layer; a carbon layer, which is formed on the solid electrolyte layer; and a silver particle layer, at least a part of which is formed on the carbon layer and contains silver particles. Hereinafter, the end face of the sintered body from which the anode lead protrudes may sometimes be referred to as "end face (e)". The anode body has a bottom face on the side opposite to the end face (e) and a side face connecting the end face (e) and the bottom face. Hereinafter, the bottom face and the side face may sometimes be referred to as "bottom face (b)" and "side face (s)". The solid electrolyte layer is formed to cover the entire bottom face (b), the entire side face (s), and at least a part of the end face (e). The carbon layer is formed to cover the entire bottom face (b) and a part of the side face (s) and does not cover the end face (e). The silver particle layer is formed to cover the entire bottom face (b) and a part of the side face (s) and does not cover the end face (e). The distance from the first surface of the solid electrolyte layer formed on the bottom face (b) to the second surface of the solid electrolyte layer formed on the end face (e) is set as L. The carbon layer is formed to cover the region in the side face (s) where the distance from the above first surface is X (where 0.89 ≤ X / L < 1.0). The silver particle layer is formed to cover the region in the side face (s) where the distance from the above first surface is Y (where 0.90 ≤ Y / L < 1.0).

[0022] More specifically, the solid electrolyte layer is formed to cover a predetermined surface of the anode body with the dielectric layer therebetween. However, even in this case, the solid electrolyte layer is still formed to cover the predetermined surface of the anode body, and this remains unchanged. Therefore, in this specification, when a specific constituent member A is formed to cover the anode body with a specific layer therebetween, it is sometimes expressed as "constituent member A is formed to cover the anode body".

[0023] In the solid electrolytic capacitor (S), a carbon layer and a silver particle layer are used as the conductive layer (cathode lead-out layer) formed on the solid electrolyte layer. Generally, it is considered that the larger the area of the cathode lead-out layer, the lower the equivalent series resistance (ESR). In the solid electrolytic capacitor of Patent Document 1, a conductive layer is also formed on the end face of the sintered body where the anode lead (anode wire) is connected, in the surface of the sintered body. However, based on the research results, the inventors of the present application newly found that if the cathode lead-out layer is formed on the above-mentioned end face (e), the leakage current increases significantly. The present disclosure is based on this new finding.

[0024] In the solid electrolytic capacitor (S), the carbon layer and the silver particle layer are formed to cover all regions in the side surface (s) of the anode body where the distance from the bottom surface (b) is 0.89L or less, or 0.90L or less. Therefore, the ESR can be reduced. In addition, the carbon layer and the silver particle layer are not formed on the end face (e) of the sintered body. According to this structure, the leakage current can be suppressed to a low level. The reason for this is not clear at present, but it can be considered as follows. The end face (e) as the joint surface between the anode wire and the porous sintered body is a part where materials of different shapes coexist and has stress during formation, so the dielectric layer formed in this part is unstable. Therefore, it is considered that if the cathode lead-out layer (carbon layer, silver particle layer) adheres to the end face (e), leakage current is likely to occur.

[0025] In the solid electrolytic capacitor (S), the cathode lead-out layer is not formed on the end face (e). Therefore, there is no need to form an insulating layer (an insulating layer other than the dielectric layer) for reducing the leakage current on the end face (e).

[0026] X / L is 0.89 or more, and can also be 0.90 or more, or 0.95 or more. X / L is less than 1.00, and can also be 0.99 or less, 0.98 or less, or 0.97 or less. Similarly, Y / L is 0.90 or more, and can also be 0.95 or more. Y / L is less than 1.00, and can also be 0.99 or less, 0.98 or less, or 0.97 or less. By setting X / L and / or Y / L to 0.95 or more, the ESR can be particularly reduced. By setting X / L and / or Y / L to 0.99 or less (for example, 0.98 or less, or 0.97 or less), the formation of the cathode lead-out layer becomes easier.

[0027] The above-mentioned L and the above-mentioned X may also satisfy the relationship of 0.95 ≤ X / L < 1.00 (for example, 0.95 ≤ X / L ≤ 0.99, 0.95 ≤ X / L ≤ 0.98), and the above-mentioned L and the above-mentioned Y may also satisfy the relationship of 0.95 ≤ Y / L < 1.00 (for example, 0.95 ≤ Y / L ≤ 0.99, 0.95 ≤ Y / L ≤ 0.98). According to this structure, the ESR becomes particularly low.

[0028] Most of the silver particle layer is formed on the carbon layer, but a part of the silver particle layer may also be formed on the solid electrolyte layer. The silver particle layer may also be entirely formed on the carbon layer. By having a carbon layer between the solid electrolyte layer and the silver particle layer, the ESR can be particularly reduced. Additionally, the above-mentioned X may be less than the above-mentioned Y.

[0029] From another perspective, the solid electrolytic capacitor (S) includes a cathode lead layer that is formed to cover the entire bottom surface (b) and a part of the side surface (s) of the solid electrolyte layer and does not cover the end surface (e). The cathode lead layer includes a carbon layer formed on the solid electrolyte layer and a silver particle layer at least partially formed on the carbon layer. The cathode lead layer is formed to cover the region in the side surface (s) where the distance from the above-mentioned first surface is Z (where 0.89 ≤ Z / L < 1.00). Z may also be 0.90 or more or 0.95 or more.

[0030] The diameter D of the anode wire and the length W of the short side of the end surface (e) may satisfy 0.5 ≤ D / W. In the solid electrolytic capacitor of Patent Document 1, a conductive layer is also formed on the end surface (e). Therefore, if the diameter of the anode wire (anode lead) is increased, a short circuit is likely to occur. On the other hand, in the solid electrolytic capacitor (S), no cathode lead layer is formed on the end surface (e). Therefore, even if the diameter D of the anode wire is increased, a short circuit is not likely to occur. By increasing the diameter D of the anode wire, the ESR can be reduced. D / W may also be in the range of 0.5 to 0.8 (for example, in the range of 0.5 to 0.7). However, D / W may also be less than 0.5. Additionally, the short side refers to the shortest side of the sides of the end surface (e). In the case where the end surface (e) is a square, the length of one side of the square is the length W of the short side.

[0031] (Method for manufacturing a solid electrolytic capacitor (E))

[0032] An example of the method for manufacturing the solid electrolytic capacitor (E) will be described. However, the solid electrolytic capacitor (E) may also be manufactured by a method other than the method described below. Each of the following steps may also be performed by a known method or a method obtained by modifying a known method in combination with the present disclosure.

[0033] In this manufacturing method, first, an anode body (porous sintered body) with a part of the anode wire embedded therein is fabricated. Next, a dielectric layer is formed on the surface of the anode body. Then, a solid electrolyte layer is formed on the dielectric layer. The solid electrolyte layer can be formed by disposing a liquid containing a material (e.g., a conductive polymer) constituting the solid electrolyte layer on the anode body and then drying it. In an example of the method for forming the solid electrolyte layer, first, the anode body is immersed in the liquid to coat the liquid on the anode body. Next, the coated liquid is dried. In this way, a solid electrolyte layer can be formed on the dielectric layer. Alternatively, the solid electrolyte layer can also be formed by electrolytic polymerization, chemical polymerization, etc. Electrolytic polymerization and chemical polymerization can be carried out under known conditions.

[0034] Next, a carbon layer and a silver particle layer are sequentially formed on the solid electrolyte layer. The carbon layer can be formed by applying a carbon paste containing particles of a carbonaceous material on the solid electrolyte layer and then heating it. The silver particle layer can be formed by applying a silver paste containing silver particles on the carbon layer and then heating it. The carbon paste and the silver paste can use the same materials as those used in the manufacture of known solid electrolytic capacitors. The carbon layer and the silver particle layer are formed in the above-mentioned region.

[0035] The application of the carbon paste can also be carried out by immersing the anode body having the solid electrolyte layer formed thereon in the carbon paste and then lifting it up. By changing which position of the anode body is immersed in the carbon paste, the above-mentioned X / L value can be controlled. In addition, by changing the lifting speed, the thickness of the carbon layer can be controlled.

[0036] The application of the silver paste can also be carried out by immersing the anode body having the carbon layer formed thereon in the silver paste and then lifting it up. By changing which position of the anode body is immersed in the silver paste, the above-mentioned Y / L value can be controlled. In addition, by changing the lifting speed, the thickness of the silver particle layer can be controlled.

[0037] As described above, a capacitor element including an anode body, an anode wire, a dielectric layer, a solid electrolyte layer, and a cathode lead-out layer (carbon layer and silver particle layer) is formed. The subsequent processes are not particularly limited, and the processes required for manufacturing a solid electrolytic capacitor are carried out. For example, the following processes can also be carried out. First, an anode lead terminal is connected to the anode wire, and a cathode lead terminal is connected to the silver particle layer. The anode lead terminal can be connected to the anode wire by welding or the like. The cathode lead terminal can be connected to the cathode lead terminal through a conductive layer (e.g., another silver paste layer or other conductive adhesive layer). Next, an outer package is formed to cover a part of the anode lead terminal, a part of the cathode lead terminal, and the capacitor element. The outer package can be formed of a sealing resin or the like. By doing so, a solid electrolytic capacitor (S) is manufactured.

[0038] Hereinafter, examples of the components of the solid electrolytic capacitor of the present disclosure will be described, but the structure of the solid electrolytic capacitor (S) of the present disclosure is not limited to the structures exemplified below. Except for the parts peculiar to the solid electrolytic capacitor (S), the components of the solid electrolytic capacitor (S) may also use the components used in known solid electrolytic capacitors (S).

[0039] The solid electrolytic capacitor (S) includes a capacitor element, lead terminals (anode lead terminal, cathode lead terminal), and an outer package. The capacitor element includes an anode portion, a dielectric layer, and a cathode portion. The anode portion includes an anode body and an anode wire. The dielectric layer is formed on the surface of the anode body. The dielectric layer may also be formed on a part of the anode wire. The cathode portion includes a solid electrolyte layer and a cathode lead-out layer. The cathode lead-out layer includes a carbon layer and a silver particle layer laminated on the carbon layer.

[0040] (Anode body)

[0041] The anode body is a porous sintered body. The anode body is formed by sintering the particles that are the material. Examples of the above particles include particles of valve metal, particles of an alloy containing valve metal, and particles of a compound containing valve metal. These particles may use only one kind, or two or more kinds may be mixed. As the valve metal, titanium (Ti), tantalum (Ta), niobium (Nb), etc. can be used.

[0042] The anode body has a columnar shape, for example, a rectangular parallelepiped shape. When the anode body is a rectangular parallelepiped shape, the anode body has an end face (e), a bottom face (b), and four side faces (s) connecting the end face (e) and the side face (b).

[0043] The anode body can be manufactured by the following method. First, a part of the anode wire is buried in the powder (for example, metal powder) that is the material of the anode body, and the powder is press-molded into a columnar shape (for example, a rectangular parallelepiped shape). After that, the anode body is formed by sintering the powder. In this way, an anode body in which a part of the anode wire is buried can be manufactured.

[0044] (Dielectric layer)

[0045] The dielectric layer is formed to cover the entire surface of the anode body. The dielectric layer formed on the surface of the anode body is not particularly limited and can be formed by a known method. For example, the dielectric layer can be formed by immersing the anode body in a chemical conversion solution to anodize the surface of the anode body. Or, the dielectric layer can also be formed by heating the anode body in an oxygen-containing atmosphere to oxidize the surface of the anode body. When the anode body is a tantalum sintered body, a dielectric layer composed of tantalum oxide is formed by oxidizing the surface of the tantalum sintered body.

[0046] (Anode wire)

[0047] The anode wire can use a wire made of metal. Examples of the material of the anode wire include the above-mentioned valve metals, copper, aluminum, aluminum alloy, etc. A part of the anode wire is buried in the anode body, and the remaining part protrudes from the end face (e) of the anode body. The anode wire has a rod-like shape.

[0048] (Solid electrolyte layer)

[0049] The solid electrolyte layer is not particularly limited, and a solid electrolyte layer used in a known solid electrolytic capacitor can be used. The solid electrolyte layer can also be a laminate of two or more different solid electrolyte layers.

[0050] The solid electrolyte layer is disposed on the dielectric layer. As described above, the solid electrolyte layer is formed to cover the entire bottom surface (b) of the anode body, the entire side surface (s), and at least a part of the end face (e). The solid electrolyte layer can also be formed to cover the entire end face (e) except for the part where the anode wire protrudes. That is, the solid electrolyte layer can also be formed to cover the entire surface of the anode body.

[0051] The solid electrolyte layer can also be formed using a manganese compound or a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and their derivatives, etc. These substances can be used alone or in combination of multiple kinds. The conductive polymer can also be a copolymer of two or more monomers. In addition, the derivative of the conductive polymer refers to a polymer having the conductive polymer as a basic skeleton. For example, examples of the derivative of polythiophene include poly(3,4-ethylenedioxythiophene), etc.

[0052] Preferably, a dopant is added to the conductive polymer. The dopant can be selected corresponding to the conductive polymer, and a known dopant can also be used. Examples of the dopant include naphthalenesulfonic acid, p-toluenesulfonic acid, polystyrenesulfonic acid, and their salts, etc. An example of the solid electrolyte layer is formed using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonic acid (PSS).

[0053] The solid electrolyte layer containing the conductive polymer can be formed by polymerizing a raw material monomer on the dielectric layer. Alternatively, it can also be formed by coating a liquid containing the conductive polymer (and optionally a dopant) on the dielectric layer and then drying it.

[0054] (Carbon layer)

[0055] The carbon layer contains a carbonaceous material (a carbonaceous material with electrical conductivity) and has electrical conductivity. The carbonaceous material is not particularly limited. Examples of the carbonaceous material include graphite, carbon black, graphene sheets, carbon nanotubes, etc. The carbon layer can contain only one type of carbonaceous material or multiple types of carbonaceous materials. The thickness of the carbon layer can be in the range of 0.2 μm to 20 μm (for example, in the range of 1 μm to 3 μm).

[0056] The carbon layer can contain a binder and / or additives, etc. as required. The binder and additives are not particularly limited, and the binders and additives used in the carbon layers of known solid electrolytic capacitors can be used. Examples of the binder include resins such as thermoplastic resins (polyester resins, etc.) and thermosetting resins (polyimide resins, epoxy resins, etc.). Examples of the additives include dispersants, surfactants, antioxidants, preservatives, alkalis, and acids.

[0057] (Silver particle layer)

[0058] The silver particle layer contains silver particles and has electrical conductivity. The thickness of the silver particle layer can be in the range of 5 μm to 100 μm (for example, in the range of 10 μm to 60 μm).

[0059] The silver particle layer can contain a binder and / or additives, etc. as required. The binder and additives are not particularly limited, and the binders and additives used in the silver particle layers of known solid electrolytic capacitors can be used. Examples of the binder include resins such as thermoplastic resins (polyester resins, etc.) and thermosetting resins (phenolic resins, polyimide resins, epoxy resins, etc.). Examples of the additives include dispersants, surfactants, antioxidants, preservatives, alkalis, and acids.

[0060] The carbon layer can also contain particles of a carbonaceous material with an average particle size of 1 μm or less. The silver particle layer can also contain silver particles with an average particle size of 1 μm or less. When applying conductive particles with a smaller average particle size (particles of a carbonaceous material, silver particles) to the end face (e), the applied conductive particles are likely to reach the dielectric layer of the end face (e), so the leakage current is likely to increase. In the solid electrolytic capacitor (S), since no cathode lead-out layer is formed on the end face (e), even if conductive particles with a smaller average particle size are used, the leakage current of the end face (e) will not increase. On the other hand, by using conductive particles with a smaller average particle size, the ESR can be reduced. In addition, the average particle size is the median particle size (D50) at which the cumulative volume reaches 50% in the volume-based particle size distribution. The average particle size (median particle size) is obtained using a laser diffraction / scattering particle size distribution measuring device.

[0061] (Outer package)

[0062] The exterior body is not particularly limited. The exterior body may be formed of an insulating resin material used for sealing the capacitor element.

[0063] An example of the solid electrolytic capacitor (S) according to the present embodiment will be described with reference to the accompanying drawings. The constituent elements of the example described below can be applied to the above-described constituent elements. The solid electrolytic capacitor of the example described below can be changed based on the above description. The matters described below can also be applied to the above-described embodiment.

[0064] (Embodiment 1)

[0065] Figure 1 It is a cross-sectional view schematically showing the solid electrolytic capacitor of Embodiment 1. Figure 1 The solid electrolytic capacitor 100 shown includes a capacitor element 110, an anode lead terminal 121, a cathode lead terminal 122, a conductive layer 123, and an exterior resin (exterior body) 130. The conductive layer 123 is formed of silver paste or the like.

[0066] The capacitor element 110 includes an anode portion 111, a dielectric layer 114, and a cathode portion 115. The anode portion 111 includes an anode wire 112 and an anode body 113. The anode body 113 is a porous sintered body. The anode body 113 has a rectangular parallelepiped shape. The anode body 113 has an end face 113e, a bottom face 113b, and four side faces 113s. The end face 113e is substantially quadrilateral.

[0067] The anode wire 112 has a round bar shape (a thin cylindrical shape). A part of the anode wire 112 is buried in the anode body 113, and the other part protrudes from the end face 113e of the anode body 113. The anode lead terminal 121 is connected to the anode wire 112. The anode lead terminal 121 is electrically connected to the anode body 113 via the anode wire 112.

[0068] The dielectric layer 114 is formed to cover a part of the surface of the anode wire 112 and the entire surface of the anode body 113. The cathode portion 115 includes a solid electrolyte layer 116, a carbon layer 117, and a silver particle layer 118. The carbon layer 117 and the silver particle layer 118 are the above-described carbon layer and silver particle layer. The cathode lead terminal 122 is connected to the silver particle layer 118 via the conductive layer 123. That is, the cathode lead terminal 122 is connected to the cathode portion 115 via the conductive layer 123. The carbon layer 117 and the silver particle layer 118 constitute a cathode lead-out layer.

[0069] Figure 2 A cross-sectional view schematically showing the capacitor element 110. As Figure 2As shown, the distance from the first surface 116a of the solid electrolyte layer 116 formed on the bottom surface 113b to the second surface 116b of the solid electrolyte layer 116 formed on the end surface 113e is defined as L. The first surface 116a is the surface of the solid electrolyte layer 116 on the bottom surface 113b. The second surface 116b is the surface of the solid electrolyte layer 116 on the end surface 113e. The carbon layer 117 is formed to cover most of the bottom surface 113b and the side surface 113s. The carbon layer 117 covers the region in the side surface 113s where the distance from the first surface 116a is X or less. The distance X between the end 117e of the carbon layer 117 and the first surface 116a and the distance L satisfy the above relationship.

[0070] The silver particle layer 118 is formed to cover most of the bottom surface 113b and the side surface 113s. The silver particle layer 118 covers the region in the side surface 113s where the distance from the first surface 116a is Y or less. The distance Y between the end 118e of the silver particle layer 118 and the first surface 116a and the distance L satisfy the above relationship. The carbon layer 117 and the silver particle layer 118 are not formed to cover the end surface 113e. In other words, the carbon layer 117 and the silver particle layer 118 are not formed above the end surface 113e.

[0071] Figure 3 An example of the end surface 113e is shown. In Figure 3 the diameter D of the anode wire 112 and the length W of the short side of the end surface 113e are shown. As described above, the diameter D and the length W can satisfy 0.5 ≤ D / W.

[0072] (Supplementary Note)

[0073] Based on the above description, the following technology is disclosed.

[0074] (Technology 1)

[0075] A solid electrolytic capacitor, wherein,

[0076] The solid electrolytic capacitor includes:

[0077] An anode body, which is a porous sintered body;

[0078] An anode wire, which protrudes from the end surface of the anode body;

[0079] A dielectric layer, which is formed on the surface of the anode body;

[0080] A solid electrolyte layer, which is formed on the dielectric layer;

[0081] A carbon layer, which is formed on the solid electrolyte layer; and

[0082] A silver particle layer, at least a part of which is formed on the carbon layer and contains silver particles,

[0083] The anode body has a bottom surface on the side opposite to the end surface and a side surface connecting the end surface and the bottom surface.

[0084] The solid electrolyte layer is formed to cover the entire bottom surface, the entire side surface, and at least a part of the end surface.

[0085] The carbon layer is formed to cover the entire bottom surface and a part of the side surface and does not cover the end surface.

[0086] The silver particle layer is formed to cover the entire bottom surface and a part of the side surface and does not cover the end surface.

[0087] When the distance from the first surface of the solid electrolyte layer formed on the bottom surface to the second surface of the solid electrolyte layer formed on the end surface is set to L,

[0088] The carbon layer is formed to cover the region in the side surface where the distance from the first surface is X (where 0.89 ≤ X / L < 1.00) or less.

[0089] The silver particle layer is formed to cover the region in the side surface where the distance from the first surface is Y (where 0.90 ≤ Y / L < 1.00) or less.

[0090] (Technology 2)

[0091] The solid electrolytic capacitor according to Technology 1, wherein,

[0092] The L and the X satisfy the relationship of 0.95 ≤ X / L < 1.00.

[0093] The L and the Y satisfy the relationship of 0.95 ≤ Y / L < 1.00.

[0094] (Technology 3)

[0095] The solid electrolytic capacitor according to Technology 1 or 2, wherein,

[0096] The entire silver particle layer is formed on the carbon layer.

[0097] (Technology 4)

[0098] The solid electrolytic capacitor according to any one of Technologies 1 to 3, wherein,

[0099] The diameter D of the anode wire and the length W of the short side of the end surface satisfy 0.5 ≤ D / W.

[0100] Example

[0101] The solid electrolytic capacitor (S) of the present disclosure will be described in more detail by way of examples.

[0102] (Experimental Example 1)

[0103] In Experimental Example 1, a plurality of solid electrolytic capacitors with different formation ranges of the carbon layer were fabricated and evaluated.

[0104] (Capacitor A1)

[0105] A capacitor A1 (solid electrolytic capacitor) having the same structure as that shown below was fabricated according to the following steps. First, a capacitor element was formed. A sintered body of tantalum particles was used as the anode body. A tantalum wire was used as the anode lead. The dielectric layer (tantalum oxide layer) was formed by oxidizing the surface of the tantalum sintered body (porous sintered body). The solid electrolyte layer was formed using a conductive polymer. Figure 1

[0106]

[0107]

[0108] Next, the anode lead terminal was connected to the anode wire by welding. In addition, the cathode lead terminal and the silver particle layer were connected using silver paste. Then, a part of the anode lead terminal, a part of the cathode lead terminal, and the capacitor element were covered with an outer resin. By doing so, capacitor A1 was fabricated.

[0109] (Other capacitors)

[0110] Capacitors A2 to A3 and capacitors C1 to C3 were fabricated in the same manner and under the same conditions as those for the fabrication of capacitor A1, except that the conditions for forming the carbon layer were changed. Specifically, the value of the above-mentioned X / L was changed to be the value shown in Table 1 to form the carbon layer. In addition, in capacitor C2, the carbon layer adhered to a part of the end face (e) of the sintered body. In capacitor C3, the entire end face (e) was covered with the carbon layer.

[0111] The equivalent series resistance (ESR) and leakage current of the fabricated solid electrolytic capacitors were measured. The formation conditions of the carbon layer and the evaluation results of the capacitors are shown in Table 1. The ESR and leakage current in Table 1 are relative values when the value of capacitor C1 is set to 1.0. The proportion of defective products in Table 1 represents the proportion of capacitors with a leakage current exceeding a predetermined value. Preferably, the ESR, leakage current, and proportion of defective products are low.

[0111] [Table 1]

[0112]

[0113] Capacitors A1 to A3 are the solid electrolytic capacitors (S) of the present disclosure. Capacitors C1 to C3 are comparative examples. As shown in Table 1, capacitors A1 to A3 have a lower ESR compared to capacitor C1. Also, capacitors A1 to A3 have a significantly smaller leakage current compared to capacitors C2 and C3.

[0114] (Experimental Example 2)

[0115] In Experimental Example 2, a plurality of solid electrolytic capacitors with different formation ranges of the silver particle layer were fabricated and evaluated.

[0116] (Capacitor B1)

[0117] Capacitor B1 was fabricated in the same manner and under the same conditions as capacitor A1 of Experimental Example 1, except for the different formation ranges of the carbon layer and the silver particle layer. In capacitor B1, the silver particle layer was formed such that the value of Y / L was 0.90. The silver particle layer was formed by dipping the sintered body having the carbon layer formed thereon into silver paste, then lifting it, and heating. The carbon layer was formed such that the value of X / L was 0.95 or more and less than 1.00.

[0118] (Other capacitors)

[0119] Capacitors B2 to B3 and capacitors C4 to C6 were fabricated in the same manner and under the same conditions as the fabrication of capacitor B1, except for changing the conditions for forming the silver particle layer. Specifically, the value of Y / L was changed to be the values shown in Table 2 to form the silver particle layer. Also, in capacitor C5, the silver particle layer adhered to a part of the end face (e) of the sintered body. In capacitor C6, the entire end face (e) was covered with the silver particle layer.

[0120] The equivalent series resistance (ESR) and leakage current of the fabricated solid electrolytic capacitors were measured. The formation conditions of the silver particle layer and the evaluation results of the capacitors are shown in Table 2. The ESR and leakage current in Table 2 are relative values when the value of capacitor C4 is set to 1.0. The proportion of defective products in Table 2 represents the proportion of capacitors with a leakage current exceeding a predetermined value.

[0121] [Table 2]

[0122]

[0123] Capacitors B1 to B3 are the solid electrolytic capacitors (S) of the present disclosure. Capacitors C4 to C6 are comparative examples. As shown in Table 2, capacitors B1 to B3 have a lower ESR compared to capacitor C4. Also, capacitors B1 to B3 have a significantly smaller leakage current compared to capacitors C5 and C6.

[0124] Industrial Applicability

[0125] The present disclosure can be used for solid electrolytic capacitors.

[0126] The present invention has been illustrated by the current preferred embodiments, but such a disclosure should not be construed in a limiting sense. Various modifications and changes will be obvious to those skilled in the art in the technical field to which the present invention pertains upon reading the above disclosure. Accordingly, the appended claims should be construed to cover all modifications and changes without departing from the true spirit and scope of the present invention.

[0127] Description of Reference Numerals

[0128] 100, solid electrolytic capacitor; 110, capacitor element; 111, anode portion; 112, anode lead; 113, anode body; 113b, bottom surface; 113e, end surface; 113s, side surface; 114, dielectric layer; 115, cathode portion; 116, solid electrolyte layer; 116a, first surface; 116b, second surface; 117, carbon layer; 118, silver particle layer.

Claims

1. A solid electrolytic capacitor, wherein, the solid electrolytic capacitor comprises: an anode body, which is a porous sintered body; an anode lead, which protrudes from an end face of the anode body; a dielectric layer, which is formed on a surface of the anode body; a solid electrolyte layer, which is formed on the dielectric layer; a carbon layer, which is formed on the solid electrolyte layer; and a silver particle layer, at least a part of which is formed on the carbon layer and contains silver particles, the anode body has a bottom surface on a side opposite to the end face and a side surface connecting the end face and the bottom surface, the solid electrolyte layer is formed to cover the whole of the bottom surface, the whole of the side surface, and at least a part of the end face, the carbon layer is formed to cover the whole of the bottom surface and a part of the side surface and does not cover the end face, the silver particle layer is formed to cover the whole of the bottom surface and a part of the side surface and does not cover the end face, when the distance from a first surface of the solid electrolyte layer formed on the bottom surface to a second surface of the solid electrolyte layer formed on the end face is set as L, the carbon layer is formed to cover a region in the side surface where the distance from the first surface is X or less, wherein 0.89 ≤ X / L < 1.00, the silver particle layer is formed to cover a region in the side surface where the distance from the first surface is Y or less, wherein 0.90 ≤ Y / L < 1.

00.

2. The solid electrolytic capacitor according to claim 1, wherein, the L and the X satisfy the relationship of 0.95 ≤ X / L < 1.00, the L and the Y satisfy the relationship of 0.95 ≤ Y / L < 1.

00.

3. The solid electrolytic capacitor according to claim 1 or 2, wherein, the whole of the silver particle layer is formed on the carbon layer.

4. The solid electrolytic capacitor according to claim 1 or 2, wherein, the diameter D of the anode lead and the length W of the short side of the end face satisfy 0.5 ≤ D / W.

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