Lead terminal, production method therefor, and solid electrolytic capacitor

Abstract

Provided is a lead terminal having an external terminal part of which at least a part is exposed from an exterior body including a resin and an insulating filler and an internal terminal part which is embedded in the exterior body, wherein: at least one of the external terminal part and the internal terminal part has a plastic deformation surface in which recesses recessed in a plurality of curved surfaces are formed in a random arrangement; and the external terminal part and the internal terminal part include a base material composed of the same metal and a plating layer formed on a surface corresponding to at least a dimple or the recesses in the base material.

Description

Lead terminal, manufacturing method thereof, and solid electrolytic capacitor

[0001] The present disclosure relates to a lead terminal, a method for manufacturing the same, and a solid electrolytic capacitor.

[0002] Lead terminals are used in a variety of electronic components, electrochemical devices, and the like. In lead terminals with internal and external terminals, the internal terminal is embedded in an exterior body, while the external terminal is exposed from the exterior body. There is a need to improve the adhesion between the internal terminal and the exterior body. For example, a capacitor element, which is a key component of a solid electrolytic capacitor, includes an anode, a dielectric layer, and a cathode. The characteristics of a capacitor element deteriorate when exposed to oxygen and moisture. The solid electrolyte layer, in particular, is significantly affected by oxygen and moisture. If the adhesion between the internal terminal and the exterior body is insufficient, oxygen and moisture can penetrate through various pathways, degrading the electrolyte layer, even if the capacitor element is covered with an exterior body.

[0003] Patent Document 1 discloses a solid electrolytic capacitor in which an anodized film formed on a plate or foil made of valve metal is used as the dielectric, a dielectric polymer layer and a dielectric layer are sequentially formed on predetermined portions of this dielectric to form a capacitor element, a lead frame serving as a lead-out terminal is connected to the valve metal portion and the conductor layer portion of this capacitor element, and the capacitor element and a portion of the lead frame are further sheathed with a molding resin, in which a solder alloy layer or a tin metal layer with a copper metal layer as an underlayer is formed on the surface of the lead frame other than the portion that comes into contact with the molding resin, and only a copper metal layer is formed on the portion of the lead frame that comes into contact with the molding resin, and the surface of the copper metal layer is roughened.

[0004] Patent Document 2 proposes a capacitor lead terminal comprising an aluminum wire having a round bar portion and a flat portion and a metal wire welded to the round bar portion of the aluminum wire, characterized in that internal compressive stress is imparted to at least the surface layer of the boundary between the round bar portion and the flat portion of the aluminum wire. Patent Document 2 also proposes imparting internal compressive stress by performing a shot peening treatment to at least the boundary between the round bar portion and the flat portion of the aluminum wire.

[0005] Japanese Patent Laid-Open No. 5-21290 Japanese Patent Laid-Open No. 2013-143556

[0006] In various devices (e.g., electronic components and electrochemical elements), there is a demand for improving the reliability (e.g., performance stability) of the devices by improving the adhesion between the internal terminal portion of the lead terminal and the exterior body.

[0007] One aspect of the present disclosure relates to a lead terminal having an external terminal portion at least partially exposed from an outer casing containing a resin and an insulating filler, and an internal terminal portion embedded in the outer casing, wherein at least one of the external terminal portion and the internal terminal portion has a plastically deformed surface on which a plurality of curved recesses are formed in a random arrangement, and the external terminal portion and the internal terminal portion include a base material made of the same metal and a plating layer formed on a surface of the base material corresponding to at least the recesses.

[0008] Another aspect of the present disclosure relates to a solid electrolytic capacitor including: a capacitor element including an anode portion and a cathode portion; an anode lead frame electrically connected to the anode portion; a cathode lead frame electrically connected to the cathode portion via a conductive adhesive layer containing conductive particles; and the exterior housing, wherein at least one of the anode lead frame and the cathode lead frame is the lead terminal described above.

[0009] Yet another aspect of the present disclosure relates to a method for manufacturing a lead terminal having an outer casing, the method comprising the steps of: preparing a metal frame; forming a plastically deformed surface on at least a portion of the metal frame to obtain a lead terminal; and integrally molding the lead terminal and an outer casing, wherein the lead terminal includes a base material made of the same metal and a plating layer formed on at least a portion of a surface of the base material, and the step of forming the plastically deformed surface includes forming a plurality of curved recesses by shot peening, and leaving the plating layer on at least the surface of the base material corresponding to the recesses.

[0010] Yet another aspect of the present disclosure relates to a method for manufacturing a solid electrolytic capacitor, further comprising a step of attaching the lead terminal to a capacitor element, and the step of integrally molding the lead terminal and the outer casing is a step of integrally molding the capacitor element, the lead terminal, and the outer casing.

[0011] According to the present disclosure, it is possible to provide a lead terminal having excellent adhesion between an internal terminal portion and an outer casing, and the use of such a lead terminal can improve the reliability (e.g., performance stability) of various devices.

[0012] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0013] 1 is a cross-sectional view schematically showing a solid electrolytic capacitor according to Embodiment 1. FIG. 2 is a cross-sectional view schematically showing an example of a recess in a plastic deformation surface of a lead terminal according to the present embodiment.

[0014] The following describes examples of embodiments of a lead terminal according to the present disclosure and a solid electrolytic capacitor using the same, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits for specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit.

[0015] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0016] The term "solid electrolytic capacitor" may be read as "electrolytic capacitor", and the term "capacitor" may be read as "capacitor".

[0017] (Lead terminal) The lead terminal according to the present disclosure has an external terminal portion at least a portion of which is exposed from an exterior body containing a resin and an insulating filler, and an internal terminal portion embedded in the exterior body. The internal terminal portion is a portion that is not visible from the outside of the exterior body. The external terminal portion is a portion that is visible from the outside of the exterior body. For example, if the lead terminal has a plate-shaped portion and one surface of the plate-shaped portion is in contact with the exterior body, but the remaining surface is visible from the outside of the exterior body, then such plate-shaped portion is the external terminal portion.

[0018] Lead terminals are used in a variety of devices equipped with exterior housings, including electronic components, electrochemical elements, etc. Examples of electrochemical elements include solid electrolytic capacitors.

[0019] The lead terminal forms a conductive path that electrically connects the inside and outside of the exterior package. The internal terminal portion can be connected to a part of an element portion that forms a key part of a device sealed inside the exterior package. The external terminal portion serves to electrically connect such a device to a circuit member. Circuit members include substrates, electronic components, etc. The lead terminal may be used to connect a first device to a second device.

[0020] At least one of the external terminal and the internal terminal has a plastically deformed surface on which a plurality of curved recesses or dimples are formed in a random arrangement. That is, the recesses are formed by plastic deformation. The plastically deformed surface may have work hardening and compressive residual stress due to plastic deformation.

[0021] A random arrangement refers to an arrangement that does not have a clear regularity, and an arrangement that has some regularity but is disordered overall is included in the category of random arrangement. For example, an arrangement that has partial regularity or microscopic regularity but is disordered overall is a type of random arrangement. Furthermore, an arrangement that has a degree of regularity formed by natural principles is not excluded from the category of random arrangement. On the other hand, a matrix-like arrangement or an arrangement with a pattern is excluded from the category of random arrangement.

[0022] The plastically deformed surface has a large surface area and an anchoring effect, resulting in excellent adhesion to exterior bodies, adhesives, etc. The plastically deformed surface improves adhesion at least between the internal terminal portion and the exterior body, thereby improving the reliability of the device (e.g., performance stability). The plastically deformed surface also provides excellent wettability between the external terminal portion and a bonding material such as solder. This improves the connection strength between the device and the circuit member on which it is mounted, for example.

[0023] Among devices, the performance stability of solid electrolytic capacitors is easily affected by the adhesion between the internal terminals and the exterior body. Oxygen, moisture, and the like in the air easily reach the capacitor element sealed in the exterior body through the interface between the internal terminals and the exterior body. When the lead terminal of this embodiment is used, the anchoring action of the recesses or dimples formed on the plastically deformed surface improves the adhesion between the internal terminals and the exterior body, significantly suppressing deterioration of the capacitor element (particularly the solid electrolyte layer) due to the intrusion of oxygen and the like. In addition, the intrusion path of oxygen and the like via the interface between the plastically deformed surface and the exterior body is lengthened, making it more difficult for oxygen and the like to reach the capacitor element. As a result, a highly reliable solid electrolytic capacitor can be obtained.

[0024] The external terminal and the internal terminal include a substrate made of the same metal and a plating layer formed on the surface of the substrate. The plating layer is formed on a surface of the substrate that corresponds to at least the recesses or dimples. The plating layer may also be formed on a surface of the substrate that does not correspond to the recesses or dimples. The plating layer preferably covers at least the entire surface of the substrate other than the cut surface, or, for example, 90% or more. Similarly, the plastic deformation surface may be provided on at least the entire surface of the substrate other than the cut surface, or, for example, 90% or more.

[0025] The substrate is typically a single metal member, with a portion of the metal member being the external terminal portion and the remaining portion being the internal terminal portion. The materials of the external terminal portion and the internal terminal portion are identical and continuous. In other words, the external terminal portion and the internal terminal portion are not connected via a joint such as a weld. The recesses or dimples on the plastically deformed surface can be formed by simultaneous plastic deformation of the substrate and the plating layer. Due to the plastic deformation, at least a portion of the plating layer remains covering the curved surface of the recesses or dimples.

[0026] The shape of the lead terminal is not particularly limited, but typically has a plate-like portion. At least one of the external terminal portion and the internal terminal portion may have a plate-like portion, and such plate-like portion may have a plastically deformable surface. One or both of the external terminal portion and the internal terminal portion may have two or more plate-like portions and one or more bends or folds connecting the plate-like portions. All of the two or more plate-like portions may have plastically deformable surfaces.

[0027] The plastically deformed surface may be formed, for example, by impacting a curved object against the surface of the lead terminal to be plastically deformed, thereby plastically deforming the surface. The plastically deformed surface may also be a shot-peened surface. Shot-peening refers to a process in which countless spheres are impacted at high speed on a metal surface. Depending on the shape of the spheres, the curved surface of the recesses or dimples can be controlled to be spherical or oblate spheroidal. Shot-peening results in little peeling of the plating layer formed on the surface of the substrate, and the plating layer remains, for example, over 90% or 95% or more of the plastically deformed surface.

[0028] Generally, a plating layer is formed to improve the solderability of the external terminal portion of the lead terminal. When many of the external terminal portions are plastically deformed surfaces with a plating layer, the wettability of the external terminal portions with solder is improved, further improving the solderability. This significantly improves the connection strength between the device and the circuit member on which it is mounted.

[0029] Forming a plating layer only on the external terminals complicates the manufacturing process, so a plating layer is typically formed on the internal terminals as well. If much of the plating layer on the internal terminals were removed, the surface of the lead terminal would be oxidized, potentially increasing electrical resistance. The presence or absence of a plating layer has a significant effect on the portion of the lead terminal that connects to the capacitor element via a conductive adhesive layer, such as silver paste. When much of the internal terminals are plastically deformed surfaces with a plating layer, device degradation is suppressed. For example, when the device is a solid electrolytic capacitor, degradation of the capacitor element (e.g., an increase in ESR) can be suppressed.

[0030] The plating layer may be formed of a metal (including an alloy) such as nickel, gold, palladium, tin, or copper. The plating layer may include a nickel layer, a gold layer, a palladium layer, a tin layer, or a copper layer. For example, multiple plating layers may be formed on the substrate in the following order: a nickel layer, a gold layer, and a palladium layer. The plating layer may be formed by a known plating method.

[0031] The substrate may be formed of a metal (including alloys) including copper, nickel, iron, etc. Examples of alloys include iron-nickel alloys, stainless steel, etc.

[0032] (Solid Electrolytic Capacitor) Examples of the configuration and components of the solid electrolytic capacitor according to the present disclosure are further described below, but the configuration and components of the solid electrolytic capacitor are not limited to the following examples.

[0033] The solid electrolytic capacitor includes a capacitor element including an anode portion and a cathode portion, an anode lead frame electrically connected to the anode portion, a cathode lead frame electrically connected to the cathode portion via a conductive adhesive layer containing conductive particles, and an outer casing, the outer casing including a resin and an insulating filler, and at least one of the anode lead frame and the cathode lead frame is the lead terminal.

[0034] (Capacitor Element) The capacitor element is not particularly limited, but generally includes a dielectric layer interposed between an anode portion and a cathode portion. The anode portion may be composed of an anode body, or may include an anode body and an anode wire. The anode body may be a porous sintered body, or may be a metal foil with a porous surface. The dielectric layer is formed on the surface of the anode body. The cathode portion includes a solid electrolyte layer and a cathode layer. The solid electrolyte layer is disposed between the dielectric layer and the cathode layer. These components are not particularly limited, and components used in known solid electrolytic capacitors may be applied. Examples of these components are described below.

[0035] (Anode Body) The anode body may be formed by sintering particles of the material. Examples of the material particles include particles of a valve metal, particles of an alloy containing a valve metal, and particles of a compound containing a valve metal. These particles may be used alone or in combination of two or more types. A foil of a metal having valve action may be used as the anode body. Examples of valve metals include titanium (Ti), tantalum (Ta), niobium (Nb), aluminum (Al), etc. A preferred example of an anode body that is a sintered body is a tantalum sintered body. A preferred example of an anode body that is a metal foil is aluminum foil.

[0036] The dielectric layer formed on the surface of the anode body is not particularly limited, and may be formed by a known method. For example, the dielectric layer may be formed by anodizing the surface of the anode body.

[0037] (Anode Wire) A metal wire can be used as the anode wire. Examples of materials for the metal wire include the valve metals mentioned above, copper, aluminum alloys, etc. A portion of the anode wire is embedded in the anode body, and the remaining portion protrudes from the anode body.

[0038] (Solid Electrolyte Layer) The solid electrolyte layer is not particularly limited, and a solid electrolyte layer used in a known solid electrolytic capacitor may be applied. The solid electrolyte layer is disposed so as to cover at least a portion of the dielectric layer. The solid electrolyte layer may be formed using a manganese compound or a conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and derivatives thereof. These may be used alone or in combination. The conductive polymer may also be a copolymer of two or more monomers. Note that a derivative of a conductive polymer refers to a polymer having a conductive polymer as its basic skeleton. For example, an example of a polythiophene derivative is poly(3,4-ethylenedioxythiophene).

[0039] A dopant is added to the conductive polymer. The dopant can be selected depending on the conductive polymer, and known dopants (e.g., polymer dopants) may be used. Examples of dopants include naphthalenesulfonic acid, p-toluenesulfonic acid, polystyrenesulfonic acid, and salts thereof. An example of a solid electrolyte layer is formed using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonic acid (PSS).

[0040] The solid electrolyte layer containing the conductive polymer may be formed by polymerizing a raw material monomer on the dielectric layer, or by depositing a liquid containing the conductive polymer (and optionally a dopant) on the dielectric layer and then drying it.

[0041] (Cathode Layer) The cathode layer is a conductive layer and is disposed so as to cover at least a portion of the solid electrolyte layer. The cathode layer includes a conductive cathode extraction layer. The cathode layer may include another conductive layer (e.g., a carbon layer) disposed between the solid electrolyte layer and the cathode extraction layer. For example, the cathode layer may include a carbon layer formed on the electrolyte layer and a cathode extraction layer formed on the carbon layer. The cathode extraction layer may be formed from a metal paste (e.g., silver paste) containing conductive particles (e.g., metal particles) and a resin, or may be formed from a known silver paste. The carbon layer is a layer containing carbon and may be formed from a conductive carbon material such as graphite and a resin.

[0042] (Anode Lead Frame and Cathode Lead Frame) As described above, the lead frame (at least one of the anode lead frame and the cathode lead frame) is a lead terminal having an external terminal portion at least a part of which is exposed from an outer casing containing a resin and an insulating filler, and an internal terminal portion embedded in the outer casing. At least one of the external terminal portion and the internal terminal portion has a plastically deformable surface on which a plurality of curved recesses or dimples are formed in a random arrangement.

[0043] The external terminal portion and the internal terminal portion each include a substrate made of the same metal and a plating layer formed on the surface of the substrate. The substrate is made of a metal (copper, copper alloy, etc.). The thickness of the substrate is not particularly limited and may be in the range of 25 μm to 200 μm (e.g., in the range of 25 μm to 100 μm).

[0044] The plating layer is formed on the surface of the substrate at least corresponding to the recesses or dimples. The plating layer is formed of a metal (including alloys) such as nickel, gold, palladium, tin, copper, etc. The thickness of the plating layer (total thickness in the case of a multi-layer structure) may be, for example, 1 μm to 20 μm.

[0045] The anode lead frame is electrically connected to the anode portion. The anode lead frame includes a first internal terminal portion embedded in the exterior housing and a first external terminal portion at least a portion of which is exposed from the exterior housing. The first internal terminal portion and the anode portion may be connected by welding or the like. At least a portion of the external terminal portion functions as a connection terminal portion with the circuit member and is soldered or the like.

[0046] The cathode lead frame is electrically connected to the cathode portion. The cathode lead frame includes a second internal terminal portion embedded in the exterior housing and a second external terminal portion at least a portion of which is exposed from the exterior housing. The second internal terminal portion and the cathode portion may be connected by a conductive adhesive layer. At least a portion of the second external terminal portion functions as a connection terminal portion with a circuit member and is soldered or the like.

[0047] (Exterior Body) The exterior body is arranged around the capacitor element so that the capacitor element is not exposed on the surface of the solid electrolytic capacitor. The exterior body is integrally formed with the anode lead frame, the cathode lead frame, and the capacitor element. The exterior body is arranged to cover the first internal terminal portion of the anode lead frame and the second internal terminal portion of the cathode lead frame. The exterior body includes a resin (insulating resin) and an insulating filler.

[0048] The outer casing can be formed from a resin composition containing a resin and an insulating filler (e.g., an inorganic filler). The resin composition may contain, in addition to the resin and the insulating filler, a curing agent, a polymerization initiator, a catalyst, etc. Examples of the resin include insulating thermosetting resins and insulating thermoplastic resins. Specifically, examples of the resin include epoxy resin, phenolic resin, urea resin, polyimide, polyamideimide, polyurethane, diallyl phthalate, unsaturated polyester, polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), etc.

[0049] Examples of insulating fillers include insulating particles and insulating fibers, with particles being preferred. Examples of insulating materials constituting the insulating filler include insulating compounds (oxides, etc.) such as silica and alumina, glass, and mineral materials (talc, mica, clay, etc.). The insulating filler contained in the outer casing may be one type or two or more types.

[0050] There are no particular limitations on the content of the insulating filler in the outer casing, and it may be in the range of 30% by mass to 95% by mass (for example, in the range of 50% by mass to 90% by mass).

[0051] When at least the anode lead frame is a lead terminal having a plastically deformed surface, the surface of the internal terminal portion may have a plastically deformed surface in which the average diameter of the opening of the recess or dimple is D1. In this case, the average diameter D1 and the average particle diameter P1 of the insulating filler (insulating particles) may satisfy the relationship 0 < P1 / D1 < 1. This makes it easier for the insulating filler to enter the recess with the average diameter D1. The presence of the insulating filler with low thermal expansion in the recess with the average diameter D1 can prevent the adhesion between the lead frame and the exterior body from decreasing due to temperature changes. As a result, deterioration of the solid electrolyte layer due to the intrusion of oxygen, etc. can be significantly prevented.

[0052] The ratio P1 / D1 of the average particle diameter P1 to the average diameter D1 may be greater than 0, 0.1 or greater, 0.3 or greater, or 0.5 or greater. The ratio P1 / D1 may be less than 1, 0.9 or less, or 0.8 or less. From the viewpoint of effectively suppressing the intrusion of oxygen and the like, it is preferable that the average diameter D1 and the average particle diameter P1 satisfy 0.5≦P1 / D1≦0.8.

[0053] The average diameter D1 may be 0.1 μm or more, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more, or may be 300 μm or less, 250 μm or less, 200 μm or less, 100 μm or less, or 50 μm or less. The average diameter D1 may be in the range of 0.1 μm to 300 μm (e.g., 5 μm to 100 μm, 10 μm to 100 μm, or 10 μm to 50 μm).

[0054] (Conductive Adhesive Layer) The conductive adhesive layer connects the second internal terminal portion of the cathode lead frame and the cathode portion. The conductive adhesive layer contains conductive particles. Examples of the conductive particles include metal particles (e.g., silver particles). The conductive adhesive layer can be formed using a metal paste (e.g., silver paste) containing metal particles and a resin.

[0055] When at least the cathode lead frame is a lead terminal having a plastically deformed surface, the surface of the internal terminal portion may have a recess or dimple opening with an average diameter D2 and a plastically deformed surface in contact with the conductive adhesive layer. In this case, the average diameter D2 and the average particle diameter P2 of the conductive particles may satisfy 1.2≦D2 / P2. This configuration allows the conductive particles to easily enter the recess with the average diameter D2. As a result, the resistance between the second internal terminal portion and the cathode portion can be reduced. Furthermore, the presence of conductive particles with low thermal expansion in the recess with the average diameter D2 can prevent a decrease in adhesion between the lead frame and the conductive adhesive layer due to temperature changes. As a result, deterioration of the electrolyte layer due to the intrusion of oxygen, etc., and an increase in internal resistance can be significantly suppressed.

[0056] The ratio D2 / P2 of the average diameter D2 to the average particle diameter P2 may be less than 1.2, but is preferably 1.2 or more, and may be 2 or more. The ratio D2 / P2 may be 20 or less, or 15 or less.

[0057] The average diameter D2 may be 5 μm or more, 10 μm or more, or 20 μm or more, or may be 500 μm or less, 400 μm or less, 300 μm or less, or 100 μm or less. The average diameter D2 may be in the range of 5 μm to 500 μm (e.g., in the range of 5 μm to 100 μm).

[0058] Of the surfaces of the internal terminal portion, the plastically deformed surface that comes into contact with the exterior body may have recesses or dimples whose openings have an average diameter of the above-mentioned D1.

[0059] The diameter of the opening of each recess can be expressed as the equivalent circle diameter. The equivalent circle diameter can be determined by the following method. First, the opening of the recess is photographed from above. Next, the area of ​​the opening is obtained by image processing the obtained image. Next, the equivalent circle diameter is calculated from the obtained area. The average diameter D1 is determined by calculating the diameter (equivalent circle diameter) of the opening for each of 20 arbitrarily selected recesses and arithmetically averaging the obtained diameters. The average diameter D2 can also be determined by the same method as the average diameter D1.

[0060] The average particle size P1 is the median diameter (D50) at which the cumulative volume reaches 50% in a volume-based particle size distribution. The median diameter is determined using a laser diffraction / scattering particle size distribution analyzer. The average particle size P2 is also the median diameter (D50) and is determined in the same manner as the average particle size P1.

[0061] In the solid electrolytic capacitor of this embodiment, instead of the average diameter D1, the average diameter Dmin(1) of the shortest diameter of the openings of the recesses or dimples on the plastically deformed surface of the internal terminal portion of the anode lead frame and the average particle diameter P1 may satisfy a predetermined relationship. Specifically, the ratio P1 / Dmin(1) may satisfy the above relationship satisfied by the ratio P1 / D1.

[0062] In the solid electrolytic capacitor of this embodiment, the average diameter Dmin(2) of the shortest diameter of the openings of the recesses or dimples on the plastically deformed surface of the internal terminal portion of the cathode lead frame may satisfy a predetermined relationship instead of the average diameter D2. Specifically, the ratio Dmin(2) / P2 may satisfy the above-mentioned relationship satisfied by the ratio D2 / P2.

[0063] The shortest diameter of the opening of a recess is the shortest diameter among the diameters passing through the center of gravity of the opening of the recess. The shortest diameter can be determined as follows. First, images of the openings of the recesses are obtained by photographing multiple recesses from above. The center of gravity and the shortest diameter of the opening can be obtained by image analysis of the image. The average shortest diameter of the openings is obtained by determining the shortest diameter for each of 20 openings randomly selected from the image and then arithmetically averaging the 20 shortest diameters thus determined.

[0064] From another perspective, the present disclosure provides another solid electrolytic capacitor. In this other solid electrolytic capacitor, there is no limitation as to whether the ratio P1 / D1 satisfies the above-described relationship, but the ratio P1 / Dmin(1) satisfies the above-described relationship that the ratio P1 / D1 satisfies. In this other solid electrolytic capacitor, the ratio Dmin(2) / P2 may satisfy the above-described relationship that the ratio D2 / P2 satisfies. Except for these relationships, the other solid electrolytic capacitor is similar to the solid electrolytic capacitor according to this embodiment, and therefore, a redundant description will be omitted.

[0065] (Method for Manufacturing Lead Terminal) An example of a method for manufacturing a lead terminal will be described below. However, a lead terminal may be manufactured by a method other than that described below. The manufacturing method in the following example includes (i) a step of preparing a metal frame, and (ii) a step of forming a plastic deformation surface on at least a portion of the metal frame to obtain a lead terminal. The method for manufacturing a lead terminal may further include a step of integrally molding the lead terminal and an outer casing. Such a manufacturing method may constitute part of a method for manufacturing a solid electrolytic capacitor. The method for manufacturing a solid electrolytic capacitor may include a step of attaching a metal frame to a capacitor element, and a step of integrally molding the metal frame and the outer casing. In this case, the step of integrally molding the lead terminal and the outer casing may be a step of integrally molding the capacitor element, the metal frame, and the outer casing.

[0066] However, the lead terminal includes a substrate made of the same metal and a plating layer formed on at least a portion of the substrate surface. The plating layer may cover the entire surface or a portion (e.g., 90% or more) of the substrate surface. Alternatively, the plating layer may cover at least the entire surface or a portion (e.g., 90% or more) of the substrate surface excluding the cut surface.

[0067] The lead terminals function as external and internal terminals. Such metal frames are formed, for example, by cutting them out of a metal sheet. In this case, the external and internal terminals are a single metal member made of the same metal, with a portion of the metal member being the external terminal and the remaining portion being the internal terminal. In other words, the materials of the external and internal terminals are the same and continuous with each other.

[0068] The metal frame can be obtained, for example, by cutting a substrate from a metal sheet, which is the raw material for the substrate, and then forming a plating layer on at least a portion of the surface of the substrate (usually 90% or more of the surface or the entire surface). Alternatively, the metal frame can be obtained, for example, by forming a plating layer on at least a portion of the surface of the metal sheet, which is the raw material for the substrate (usually 90% or more of the surface or the entire surface), and then cutting the metal frame from the metal sheet with the plating layer. In the latter case, the plating layer is substantially absent on the cut surface of the substrate.

[0069] The shape of the lead terminal is not particularly limited, but typically has a plate-like portion derived from a metal sheet, for example, both the external terminal portion and the internal terminal portion have two or more plate-like portions and one or more bent portions or folds.

[0070] In the step (ii) of forming a plastically deformed surface, the plastically deformed surface may be formed on at least one of the external terminal portion and the internal terminal portion by shot peening.

[0071] Shot peening can form a plastically deformed surface with multiple curved recesses or dimples without substantially removing the plating layer. In other words, most of the plating layer can be left on the surface of the substrate corresponding to the recesses or dimples. Shot peening involves impacting the surface of a metal frame with tiny spheres (projectiles or shot), which simultaneously press and plastically deform the substrate and plating layer. As a result, curved recesses or dimples are formed. The plating layer typically remains formed on at least the surface of the substrate corresponding to the recesses or dimples, as well as on surfaces of the substrate that do not correspond to the recesses or dimples. In other words, the plating layer exists so as to cover the curved surfaces of the recesses or dimples on the surface of the substrate. Impacting the surface of the metal frame with tiny spheres results in the formation of countless such recesses or dimples in a random arrangement on the surface of the metal frame.

[0072] Although the case where a metal frame is first cut out and then a plastic deformation surface is formed on at least one of the external terminal portion and the internal terminal portion has been described above, a metal sheet having a plated layer may be used instead of the metal frame. In this case, the plastic deformation surface is first formed on the metal sheet having the plated layer, and then the lead terminals are cut out from the metal sheet having both the plastic deformation surface and the plated layer.

[0073] The material of the shot material (shot) is not particularly limited, but examples include iron-based, non-ferrous, glass-based, ceramic-based, and resin-based materials. The particle size of the spheres may be selected according to the particle size (e.g., average diameters D1 and D2) of the desired recesses or dimples. The metal contained in the plating layer of the lead terminal may also be used as the material of the shot material.

[0074] The plurality of recesses or dimples may be randomly and uniformly formed over the entire plastically deformed surface. In other words, the plastically deformed surface can be defined as a region on the surface of the lead terminal where the plurality of recesses or dimples are randomly and uniformly formed.

[0075] The ratio (Sc / Sa) of the area Sc of the openings of the recesses or dimples to the apparent area Sa of the plastically deformed surface may be 5% or more, 10% or more, 20% or more, or 30% or more, or may be 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50%, 40% or less, 30% or less, or 20% or less. The apparent area of ​​the surface is the area of ​​the plastically deformed surface when it is assumed to be a flat surface without recesses or dimples, and can be calculated from the outer shape of the internal terminal portion or the external terminal portion.

[0076] The plastic deformation surface may be provided on the entire or a portion (e.g., 90% or more) of the surface of the lead terminal. Alternatively, the plastic deformation surface may be provided on at least the entire or a portion (e.g., 90% or more) of the surface of the internal terminal portion. Alternatively, the plastic deformation surface may be provided on at least the entire or a portion (e.g., 90% or more) of the surface of the external terminal portion. Two or more plastic deformation surfaces having different average diameters D1 (or Dmin(1)), D2 (or Dmin(2)), Sc / Sa, etc. may be formed on one lead terminal.

[0077] Examples of solid electrolytic capacitors according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the solid electrolytic capacitors of the examples described below. The solid electrolytic capacitors of the examples described below can be modified based on the above description. The matters described below may also be applied to the above embodiments. In the embodiments described below, components that are not essential for the solid electrolytic capacitor according to the present disclosure may be omitted.

[0078] (Embodiment 1) A cross-sectional view of a solid electrolytic capacitor 100 (hereinafter referred to as "electrolytic capacitor 100") according to Embodiment 1 is shown in Figure 1. In Embodiment 1, an example in which an anode part includes an anode body and an anode wire will be described. Note that in Figure 1, the plating layer present on the surface of the lead terminal is omitted for clarity.

[0079] The electrolytic capacitor 100 includes a capacitor element 110, a lead terminal 200, a conductive adhesive layer 130, and an outer casing 140. The lead terminal 200 includes an anode lead frame 210 and a cathode lead frame 220.

[0080] 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 body 113 and an anode wire 112. The anode body 113 is a porous sintered body in the shape of a rectangular parallelepiped, and has a dielectric layer 114 formed on its surface.

[0081] A portion of the anode wire 112 protrudes from one end face of the anode body 113 toward the front surface 100f of the electrolytic capacitor 100. The other portion of the anode wire 112 is embedded in the anode body 113. The anode wire 112 extends along the longitudinal direction LD of the anode body 113. The cathode portion 115 includes a solid electrolyte layer 116 disposed so as to cover at least a portion of the dielectric layer 114, and a cathode layer 117 formed so as to cover at least a portion of the solid electrolyte layer 116.

[0082] The anode lead frame 210 includes a first internal terminal 211 embedded in the exterior housing 140 and an external terminal 212 exposed from the exterior housing 140. The external terminal 212 functions as an anode-side connection terminal (first connection electrode) 212a. The surface on which the anode-side connection terminal 212a is located may be referred to as the bottom surface 100b of the electrolytic capacitor 100. The surface opposite the bottom surface 100b may be referred to as the top surface 100t of the electrolytic capacitor 100. The surface opposite the front surface 100f may be referred to as the rear surface 100r of the electrolytic capacitor 100.

[0083] The cathode lead frame 220 includes a second internal terminal 221 embedded in the exterior housing 140 and a second external terminal 222 exposed from the exterior housing 140. The second external terminal 222 functions as a cathode-side connection terminal (second connection electrode) 222a. Hereinafter, the first internal terminal 211 and the second internal terminal 221 may be collectively referred to as internal terminal 201, and the first external terminal 212 and the second external terminal 222 may be collectively referred to as external terminal 202. The lead terminal 200 includes the internal terminal 201 and the external terminal 202.

[0084] The overall shape and arrangement of lead terminal 200 and the connection positions of lead terminal 200 with anode portion 111 and cathode portion 115 are not limited to the example shown in Fig. 1. For example, cathode lead frame 220 may be connected to cathode portion 115 at a portion other than the top surface 100t side (e.g., a portion on the bottom surface 100b side or a portion on the rear surface 100r side).

[0085] The internal terminal 201 has a first surface 201a that contacts the exterior body 140. Furthermore, the internal terminal 201 has a second surface 201b that is a surface of the second internal terminal 221 and that contacts the conductive adhesive layer 130. The second surface 201b is electrically connected to the cathode 115 (more specifically, the cathode layer 117) by the conductive adhesive layer 130. On the other hand, the external terminal 202 (i.e., the first connection electrode 212a and the second connection electrode 222a) has a third surface 202a that is exposed from the exterior body 140.

[0086] A plurality of recesses or dimples are formed in a random arrangement on the surfaces of the internal terminal portion and the external terminal portion of the solid electrolytic capacitor according to this embodiment. In embodiment 1, an example will be described in which a plurality of recesses 201c are formed entirely on each of the first surface 201a, the second surface 201b, and the third surface 202a. The recesses 201c are formed on both the first surface 201a and the third surface 202a of the anode lead frame 210, and on the first surface 201a, the second surface 201b, and the third surface 202a of the cathode lead frame 220.

[0087] An example of the arrangement of recesses 201c on the plastically deformed surface of a lead terminal is shown in cross section in Figure 2. In the example shown in Figure 2, the multiple recesses 201c are depicted as being arranged with a certain regularity, but in reality they are random. Also, in the example shown in Figure 2, the arrangement of recesses 201c on one surface of the internal terminal portion 201 or the external terminal portion 202 is depicted as being similar to the arrangement of recesses 201c on the other surface, but they may be different, usually at least in detail. In Figure 2, the cross-sectional shape of the recesses 201c is schematically shown as spherical, but the cross-sectional shape of the recesses 201c may be curved in various shapes.

[0088] As shown in FIG. 2 , the lead terminal 200 (anode lead frame 210 and cathode lead frame 220) includes a substrate 200a and a plating layer 200b formed on both sides of the substrate 200a. The plating layer 200b is formed on the entire surface of the lead terminal. That is, the plating layer 200b is present in the recesses 201c, and the plating layer 200b is also present on the surfaces between the multiple recesses 201c. In other words, the substrate 200a is not actually exposed at the bottom of the recesses 201c. In FIG. 2 , the diameter of the opening of the recess 201c is indicated by Op.

[0089] As described above, forming such recesses 201c in the internal terminal 201 or the external terminal 202 can suppress deterioration of the capacitor element 110 (e.g., an increase in ESR). As a result, the reliability of the electrolytic capacitor 100 can be improved. Furthermore, forming recesses 201c on the surface of the second internal terminal 221 of the cathode lead frame 220 that contacts the conductive adhesive layer 130 can reduce the resistance between the conductive adhesive layer 130 and the cathode lead frame 220. As a result, the characteristics of the electrolytic capacitor 100 can be improved. Furthermore, forming recesses 201c on the surfaces of the external terminals (first connection electrode 212a and second connection electrode 222a) improves wettability with a bonding material such as solder. As a result, the connection strength between the solid electrolytic capacitor and the circuit component on which it is mounted is improved.

[0090] The present disclosure can be used for lead terminals, methods for manufacturing the same, and various devices including lead terminals (for example, solid electrolytic capacitors).

[0091] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0092] 100: Solid electrolytic capacitor 110: Capacitor element 111: Anode portion 113: Anode body 114: Dielectric layer 115: Cathode portion 116: Solid electrolyte layer 140: Exterior body 200: Lead terminal 200a: Base material 200b: Plating layer 201: Internal terminal portion 201a: First surface 201b: Second surface 201c: Recess 202: External terminal portion 202a: Third surface 210: Anode lead frame 211: First internal terminal portion 212: First external terminal portion 212a: First connecting electrode 220: Cathode lead frame 221: Second internal terminal portion 222: Second external terminal portion 222a: Second connecting electrode Op: Diameter of opening

Claims

1. A lead terminal having an external terminal portion at least a part of which is exposed from an outer casing containing a resin and an insulating filler, and an internal terminal portion embedded in the outer casing, At least one of the external terminal portion and the internal terminal portion has a plastic deformation surface on which a plurality of curved recesses are formed in a random arrangement, The external terminal portion and the internal terminal portion include a base material made of the same metal and a plating layer formed on at least the surface of the base material corresponding to the recess.

2. 2. The lead terminal according to claim 1, wherein at least one of the external terminal portion and the internal terminal portion has a plate-like portion, and the plate-like portion has the plastic deformation surface.

3. The lead terminal according to claim 1 , wherein the plastically deformed surface is a shot-peened surface.

4. 4. The lead terminal according to claim 1, wherein the recess has a spherical or oblate spheroidal shape.

5. 4. The lead terminal according to claim 1, wherein the plating layer is present on more than 90% of the plastically deformed surface.

6. a capacitor element including an anode portion and a cathode portion; an anode lead frame electrically connected to the anode portion; a cathode lead frame electrically connected to the cathode portion via a conductive adhesive layer containing conductive particles; The exterior body; Including, A solid electrolytic capacitor, wherein at least one of the anode lead frame and the cathode lead frame is the lead terminal according to any one of claims 1 to 3.

7. At least the anode lead frame is the lead terminal according to claim 5, a surface of the internal terminal portion of the anode lead frame has the plastic deformation surface in which the average diameter of the opening of the recess is D1; 7. The solid electrolytic capacitor according to claim 6, wherein the average diameter D1 and the average particle diameter P1 of the insulating filler satisfy the relationship 0<P1 / D1<1.

8. 8. The solid electrolytic capacitor according to claim 7, wherein the average diameter D1 and the average particle size P1 satisfy 0.5≦P1 / D1≦0.

8.

9. 8. The solid electrolytic capacitor according to claim 7, wherein the average diameter D1 is in the range of 10 μm to 100 μm.

10. At least the cathode lead frame is the lead terminal according to claim 5, a surface of the internal terminal portion of the cathode lead frame has the recess with an average diameter of D2 at the opening thereof and has the plastic deformation surface in contact with the conductive adhesive layer; 7. The solid electrolytic capacitor according to claim 6, wherein the average diameter D2 and the average particle diameter P2 of the conductive particles satisfy 1.2≦D2 / P2.

11. 11. The solid electrolytic capacitor according to claim 10, wherein the average diameter D2 is in the range of 5 μm to 500 μm.

12. providing a metal frame; forming a plastic deformation surface on at least a portion of the metal frame to obtain a lead terminal; a step of integrally molding the lead terminal and the outer casing; and the lead terminal includes a base material made of the same metal and a plating layer formed on at least a part of a surface of the base material; The method for manufacturing a lead terminal having an outer casing includes forming a plurality of curved recesses by shot peening, and leaving the plating layer on at least the surfaces of the base material that correspond to the recesses.

13. a method for manufacturing a lead terminal having the outer casing according to claim 12; The method further includes a step of attaching the lead terminal to a capacitor element, a step of integrally molding the lead terminals and the outer casing; a step of integrally molding the capacitor element, the lead terminals, and the outer casing;