Solid electrolytic capacitor and method for manufacturing solid electrolytic capacitor

Abstract

The disclosed solid electrolytic capacitor (10) is provided with at least one capacitor element (11), an anode lead terminal (12), a cathode lead terminal (13), and an exterior resin (21) covering the capacitor element (11), the anode lead terminal (12), and the cathode lead terminal (13). The anode lead terminal (12) and the cathode lead terminal (13) each have an exposed portion (16) exposed from the exterior resin (21) and a covering portion (17) covered by the exterior resin (21). The coating portion (17) has a surface region including a first oxide coating film (18) and a second oxide coating film (19) having a higher brittleness than the first oxide coating film (18). The surface region has a first surface region (17a) and a second surface region (17b) in which the amount of the second oxide film (19) per unit area is smaller than that of the first surface region (17a). As a result, the airtightness of the solid electrolytic capacitor can be improved.

Description

Technical Field

[0001] The present disclosure relates to a solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor. Background Art

[0002] Conventionally, solid electrolytic capacitors using solid electrolytes are known (eg, Patent Document 1). The solid electrolytic capacitor of Patent Document 1 includes a capacitor element, an anode lead terminal, a cathode lead terminal, and an outer resin covering these components, and each lead terminal is partially exposed from the outer resin.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-134360 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] If external air enters the interior of a solid electrolytic capacitor and reaches the capacitor element, a chemical reaction may occur and the capacitor element may deteriorate. In order to suppress such time-dependent degradation, solid electrolytic capacitors are required to have higher airtightness. Under such circumstances, one of the purposes of the present disclosure is to improve the airtightness of solid electrolytic capacitors.

[0008] Solutions for solving problems

[0009] A technical solution disclosed in the present invention relates to a solid electrolytic capacitor. The solid electrolytic capacitor comprises: at least one capacitor element having an anode portion and a cathode portion; an anode lead terminal electrically connected to the anode portion; a cathode lead terminal electrically connected to the cathode portion; and an outer resin covering the capacitor element, the anode lead terminal and the cathode lead terminal in a manner that a portion of each of the anode lead terminal and the cathode lead terminal is exposed, the anode lead terminal and the cathode lead terminal respectively having an exposed portion exposed from the outer resin and a covered portion covered by the outer resin, the covered portion having a surface region including a first oxide film and a second oxide film having a greater brittleness than the first oxide film, the surface region having a first surface region and a second surface region having a smaller amount of the second oxide film per unit area than the first surface region.

[0010] Another technical solution of the present disclosure relates to a method for manufacturing a solid electrolytic capacitor. The manufacturing method comprises: a first step of preparing at least one capacitor element having an anode portion and a cathode portion; a second step of preparing a lead frame having a predetermined exposed portion exposed from an exterior resin and a predetermined covered portion covered by the exterior resin, wherein a first oxide coating is formed on the predetermined covered portion; a third step of placing the capacitor element on the lead frame via a conductive paste; a fourth step of heating the capacitor element and the lead frame to cure the conductive paste and form a second oxide coating having a greater brittleness than the first oxide coating on the predetermined covered portion; a fifth step of forming a first surface region and a second surface region on the predetermined covered portion, wherein the first surface region has the first oxide coating and the second oxide coating, wherein the second surface region has the first oxide coating and the amount of the second oxide coating per unit area is less than that of the first surface region; and a sixth step of covering the capacitor element and the predetermined covered portion with the exterior resin.

[0011] Effects of the Invention

[0012] According to the present disclosure, the airtightness of a solid electrolytic capacitor can be improved.

[0013] The novel features of the present invention are described in the appended claims, but the present invention, both in structure and content, together with other objects and features of the present invention, will be better understood through the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view schematically showing an example of the solid electrolytic capacitor of the present disclosure.

[0015] Figure 2 It is a cross-sectional view showing the main parts of the solid electrolytic capacitor.

[0016] Figure 3 is a cross-sectional view showing changes in the main parts of the method for manufacturing a solid electrolytic capacitor, Figure 3 (a) shows a state where the first oxide film is formed, Figure 3 (b) shows a state where the first oxide film and the second oxide film are formed. Figure 3 (c) shows a state where at least a portion of the second oxide film is removed. DETAILED DESCRIPTION

[0017] Hereinafter, the embodiments of the solid electrolytic capacitor and the method for manufacturing the solid electrolytic capacitor disclosed in the present invention are illustrated. However, the present disclosure is not limited to the examples described below. In the following description, specific values ​​and materials are sometimes illustrated, but other values ​​and materials may also be applied as long as the effect of the present invention can be obtained. In this specification, the description of "value A to value B" includes value A and value B, which can be replaced by "value A or more and value B or less". In the following description, when the lower limit and upper limit of the numerical value related to a specific physical property, condition, etc. are illustrated, as long as the lower limit is not above the upper limit, any one of the illustrated lower limits and any one of the illustrated upper limits can be arbitrarily combined. In the case of exemplifying multiple materials, one can be selected from them and used alone, or two or more can be used in combination. In addition, the present disclosure includes a combination of matters recorded in two or more claims arbitrarily selected from the multiple claims recorded in the attached claims. In other words, as long as no technical contradiction occurs, matters recorded in two or more claims arbitrarily selected from the multiple claims recorded in the attached claims can be combined. In addition, "solid electrolytic capacitor" can be replaced by "electrolytic capacitor" and "capacitor" can be replaced by "capacitor".

[0018] (Solid Electrolytic Capacitors)

[0019] The solid electrolytic capacitor disclosed herein includes at least one capacitor element, an anode lead terminal, a cathode lead terminal, and an exterior resin.

[0020] At least one capacitor element has an anode portion and a cathode portion. An insulating portion may be provided between the anode portion and the cathode portion to electrically insulate the two. The insulating portion may be composed of, for example, an insulating tape or an insulating resin. There may be only one capacitor element or multiple capacitor elements. In the latter case, multiple capacitor elements may be stacked on top of each other.

[0021] The anode portion may be configured to include a portion of the anode body formed of a valve metal possessed by the capacitor element (a portion on one side based on the insulating portion). The cathode portion may be configured to include a solid electrolyte layer and a cathode layer sequentially formed on the surface of the cathode forming portion which is the remaining portion of the anode body (a portion on the other side based on the insulating portion). A dielectric layer is provided between the anode body and the solid electrolyte layer. In addition, the cathode portion may not include a cathode layer.

[0022] Examples of the valve metal constituting the anode body include aluminum, tantalum, niobium, titanium, etc. The anode body may be a foil of the valve metal or a sintered body of valve metal particles.

[0023] The dielectric layer is formed at least on the surface of the cathode forming portion which is the remainder of the anode body. The dielectric layer may be formed of an oxide (eg, aluminum oxide) formed on the surface of the anode body by a liquid phase method such as anodic oxidation, vapor deposition, or a gas phase method such as atomic layer deposition.

[0024] The solid electrolyte layer is formed on the surface of the dielectric layer. The solid electrolyte layer may contain a conductive polymer. The solid electrolyte layer may further contain a dopant as required.

[0025] As the conductive polymer, known conductive polymers used for solid electrolytic capacitors can be used, for example, π-conjugated conductive polymers can be used. As conductive polymers, for example, polymers with polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polybenzone and polythiophene vinylene as basic skeletons can be cited. Among them, polymers with polypyrrole, polythiophene, or polyaniline as basic skeletons are preferred. The above-mentioned polymers also include homopolymers, copolymers of two or more monomers and their derivatives (substitutes with substituents, etc.). For example, polythiophene includes poly(3,4-ethylenedioxythiophene) and the like. Conductive polymers can be used alone or in combination of two or more.

[0026] As a dopant, for example, at least one selected from the group consisting of low molecular anions and polyanions can be used. As low molecular anions, for example, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, carboxylate ions, etc. can be cited, and there is no particular restriction. As a dopant that generates sulfonate ions, for example, benzenesulfonic acid, p-toluenesulfonic acid and naphthalenesulfonic acid can be cited. As a polyanion, for example, polymer-type polysulfonic acids and polymer-type polycarboxylic acids can be cited. As polymer-type polysulfonic acids, polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryloyl sulfonic acid and polymethacryloyl sulfonic acid can be cited. As polymer-type polycarboxylic acids, polyacrylic acid, polymethacrylic acid, etc. can be cited. Polyanions also include polyester sulfonic acid and phenolsulfonic acid phenolic resins. However, polyanions are not limited to this.

[0027] The solid electrolyte layer may further contain known additives and known conductive materials other than the conductive polymer as required. Such conductive materials include, for example, at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0028] The cathode layer may be composed of a carbon layer formed on the surface of the solid electrolyte layer and a conductor layer formed on the surface of the carbon layer. The conductor layer may be composed of a silver paste. As the silver paste, for example, a composition comprising silver particles and a resin component (binder resin) can be used. As the resin component, although a thermoplastic resin can also be used, a thermosetting resin such as an imide resin or an epoxy resin is preferably used.

[0029] The anode lead terminal is electrically connected to the anode portion of the capacitor element. The anode lead terminal can be connected to the anode portion by, for example, laser welding or resistance welding. The material of the anode lead terminal is not particularly limited, and can be, for example, copper or a copper alloy.

[0030] The cathode lead terminal is electrically connected to the cathode portion of the capacitor element. The cathode lead terminal can be connected to the cathode portion via, for example, a conductive paste (eg, silver paste). The constituent material of the cathode lead terminal is not particularly limited, and can be, for example, copper or a copper alloy.

[0031] The outer coating resin covers the capacitor element, the anode lead terminal, and the cathode lead terminal in a manner that a portion of each of the anode lead terminal and the cathode lead terminal is exposed. The outer coating resin can be composed of an insulating resin material and can also contain fillers as needed. For example, the insulating resin material can use a thermosetting resin with epoxy resin as the main component.

[0032] The anode lead terminal and the cathode lead terminal respectively have an exposed portion exposed from the outer resin and a coated portion coated by the outer resin. The exposed portion can constitute an external terminal of the solid electrolytic capacitor. The coated portion has a surface region including a first surface region and a second surface region. The first surface region is formed with a first oxide film and a second oxide film having a brittleness greater than that of the first oxide film (in other words, brittler than the first oxide film). In the first surface region, a first oxide film can be formed on a base material, and a second oxide film can be formed on the first oxide film. The first oxide film is formed on the second surface region, and the amount of the second oxide film per unit area is less than that of the first surface region. In the second surface region, a first oxide film can be formed on the base material. The first oxide film of the first surface region and the first oxide film of the second surface region can be continuous with each other. The amount of the second oxide film per unit area of ​​the second surface region may be 20% or less, 10% or less, 5% or less, or 1% or less of the amount of the second oxide film per unit area of ​​the first surface region.

[0033] The first oxide film may be an oxide film (natural oxide film) that is necessarily present on the base material of each lead terminal. The second oxide film may be an oxide film that grows or is formed more rapidly than the first oxide film in the manufacturing process (particularly the heat treatment process) of the solid electrolytic capacitor. The content ratio of the oxygen element in the first oxide film to the metal element may be lower than the content ratio of the oxygen element in the second oxide film to the metal element. The natural oxide film (first oxide film) and the second oxide film can be easily distinguished by cross-sectional SEM observation, etc. In addition, the brittleness of the second oxide film is greater than that of the first oxide film, and it is easy to remove by any removal method such as heat treatment, non-heat treatment, mechanical treatment or chemical treatment. For example, when the amount of the second oxide film removed by irradiating the second oxide film with a laser is greater than the amount of the first oxide film removed by irradiating the first oxide film with a laser, it can be regarded that the brittleness of the second oxide film is greater than that of the first oxide film. The laser used to evaluate the brittleness can be, for example, a UV laser with a peak wavelength of 355 nm and a maximum output of 2 W or more (40 kHz). As such a laser, for example, MD-U1000C manufactured by Keyence Corporation can be used. In addition, the scanning speed of the laser irradiation can be, for example, 250 mm / s.

[0034] The inventors of the present application have found that the second oxide film present on the surface of each lead terminal is the main reason for the decrease in the airtightness of the solid electrolytic capacitor. That is, the second oxide film, which is more brittle than the first oxide film, is relatively easy to break even if it is in close contact with the outer resin covering each lead terminal. At the location where the second oxide film breaks, a tiny gap is generated between each lead terminal and the outer resin, and the gap forms an entry path for external gas. In contrast, as described above, each lead terminal of the solid electrolytic capacitor disclosed in the present invention has a second surface area with a small amount of the second oxide film per unit area. In the second surface area, since there are not many second oxide films that are easy to break, the close contact state between each lead terminal and the outer resin can be maintained, and it is not easy to form an entry path for external gas. Therefore, the airtightness of the solid electrolytic capacitor can be improved.

[0035] Alternatively, in each of the anode lead terminal and the cathode lead terminal, the second surface region is at least provided in a portion of the covering portion located near the exposed portion. The portion of the covering portion located near the exposed portion can also be referred to as a portion located near the root portion of each lead terminal in appearance. Such a region is equivalent to an entrance of an entry path for external air to enter the solid electrolytic capacitor, and by providing at least the second surface region here, the entry of external air can be effectively suppressed.

[0036] Alternatively, the second surface region may be provided on two main surfaces in the anode lead terminal and the cathode lead terminal. According to this structure, compared with the case where the second surface region is provided on only one main surface, the formation of a path for the entry of external gas can be suppressed in a wider range. The second surface region may also be provided on the side surface connecting the two main surfaces.

[0037] (Method for manufacturing solid electrolytic capacitor)

[0038] The method for manufacturing a solid electrolytic capacitor disclosed herein includes a first step, a second step, a third step, a fourth step, a fifth step, and a sixth step.

[0039] In the first step, at least one capacitor element having an anode portion and a cathode portion is prepared. Only one capacitor element may be prepared, or a plurality of capacitor elements may be prepared.

[0040] In the second step, a lead frame is prepared, which has an exposure portion exposed from the exterior resin and a covering portion covered by the exterior resin, and a first oxide film is formed on the covering portion. The constituent material of the lead frame is not particularly limited, and for example, it can be copper or a copper alloy. The first oxide film can be an oxide film that is necessarily present on the base material of the lead frame. The first oxide film can also be formed on the exposure portion.

[0041] In the third step, the capacitor element is placed on the lead frame via a conductive paste (eg, silver paste). The conductive paste may be applied to the cathode portion of the capacitor element.

[0042] In the fourth step, the capacitor element and the lead frame are heated to cure the conductive paste and form a second oxide film having greater brittleness than the first oxide film (in other words, brittler than the first oxide film) on the intended coating portion. The content ratio of oxygen element to metal element in the second oxide film may be higher than the content ratio of oxygen element to metal element in the first oxide film.

[0043] In the fifth step, a first surface region and a second surface region are formed in the coating predetermined portion, the first surface region is formed with a first oxide film and a second oxide film, the second surface region is formed with a first oxide film and the amount of the second oxide film per unit area is less than that of the first surface region. The first surface region can be a surface region that maintains the surface state formed in the fourth step. The second surface region can be a surface region formed by removing at least a portion of the second oxide film from the surface state formed in the fourth step. The removal method of the second oxide film is not particularly limited, and any removal method utilizing heat treatment, non-heat treatment, mechanical treatment or chemical treatment can be adopted. In addition, it is preferred that the anode portion of the capacitor element and the lead frame are joined to each other, for example, by welding, before the fifth step.

[0044] In the sixth step, the capacitor element and the portion to be covered are covered with an exterior resin.

[0045] In the solid electrolytic capacitor manufactured by the manufacturing method having the first to sixth steps, each lead terminal formed by processing the lead frame has a second surface area at a portion corresponding to the intended covering portion (i.e., the covering portion). Therefore, it is difficult to form a path for the entry of external air, and the airtightness of the solid electrolytic capacitor can be improved.

[0046] Alternatively, in the fifth step, the second surface region is formed by irradiating the intended coating portion with laser light. By irradiating the laser light, at least a portion of the second oxide coating can be removed from a portion of the surface of the intended coating portion. The surface region from which at least a portion of the second oxide coating is removed constitutes the second surface region. The removal can be performed by laser scanning the region from which the second oxide coating is to be removed.

[0047] Alternatively, in the fifth step, a second surface region is formed at least in a portion of the coating predetermined portion located near the exposure predetermined portion. The portion of the coating predetermined portion located near the exposure predetermined portion can also be said to be a portion located near the root of each lead terminal in the appearance of the completed solid electrolytic capacitor. Such a region is equivalent to the entrance of the entry path for external gas to enter the solid electrolytic capacitor, and by providing the second surface region at least here, the entry of external gas can be effectively suppressed. In the area irradiated with the laser, the second oxide film is removed, and as a result, a linear laser irradiation mark is formed. The appearance of the laser irradiation mark is different from the appearance of the area not irradiated with the laser. Therefore, in the present disclosure, "the coating portion has a first oxide film and a second oxide film with a greater brittleness than the first oxide film, and has a first surface region and a second surface region with a smaller amount of the second oxide film per unit area than the first surface region." Such a feature can be replaced by "the coating portion has a linear laser irradiation mark near the root of the exposed portion of at least one lead terminal." Such a feature.

[0048] Alternatively, in the fifth step, the second surface region is formed on the two main surfaces of the covering predetermined portion. According to this structure, compared with the case where the second surface region is formed only on one main surface, the formation of the external air inlet path can be suppressed in a larger range in the completed solid electrolytic capacitor. The second surface region can also be formed on the side surface connecting the two main surfaces.

[0049] As described above, according to the present disclosure, by providing each lead terminal with the second surface region where there are not many brittle second oxide films, the airtightness of the solid electrolytic capacitor can be improved.

[0050] Hereinafter, an example of a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor disclosed in the present invention will be specifically described with reference to the accompanying drawings. The constituent elements and processes of the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor described in the following example can apply the above-mentioned constituent elements and processes. The constituent elements and processes of the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor described in the following example can be changed based on the above-mentioned description. In addition, the matters described below can also be applied to the above-mentioned embodiment. The constituent elements and processes of the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor described in the following example that are not necessary for the solid electrolytic capacitor and the method for manufacturing a solid electrolytic capacitor disclosed in the present invention can also be omitted. In addition, the figures shown below are schematic and do not accurately reflect the shape and number of actual components.

[0051] (Solid Electrolytic Capacitors)

[0052] The solid electrolytic capacitor 10 of the present embodiment is a so-called gull wing type (a type in which each lead terminal extends from the side of the outer resin along the lower surface) solid electrolytic capacitor, but is not limited to this. For example, the solid electrolytic capacitor 10 may also be a so-called lower surface electrode type (a type in which each lead terminal is exposed from the lower surface of the outer resin) solid electrolytic capacitor. In addition, in the solid electrolytic capacitor 10 of the present embodiment, each capacitor element is oriented in the same direction, but is not limited to this, and it is also possible that a part of the capacitor elements and the remaining capacitor elements are oriented in opposite directions. In the latter case, the current flowing in a part of the capacitor elements and the current flowing in the remaining capacitor elements are oriented in opposite directions to each other, and the magnetic fields of the two currents cancel each other out, thereby reducing the ESL of the solid electrolytic capacitor 10.

[0053] like Figure 1 As shown, solid electrolytic capacitor 10 includes a plurality of (five in this example) capacitor elements 11 , anode lead terminal 12 , cathode lead terminal 13 , and exterior resin 21 .

[0054] A plurality of capacitor elements 11 are stacked one on another. Each capacitor element 11 has an anode portion 11a and a cathode portion 11b. An insulating portion 11c is provided between the anode portion 11a and the cathode portion 11b to electrically insulate the anode portion 11a and the cathode portion 11b.

[0055] Anode portions 11a adjacent to each other in the stacking direction are connected to each other by welding (eg, laser welding or resistance welding). Cathode portions 11b adjacent to each other in the stacking direction are connected to each other by conductive material 14. Conductive material 14 is made of, for example, silver paste.

[0056] The anode lead terminal 12 is electrically connected to the anode portion 11a of the capacitor element 11. The anode lead terminal 12 is connected to the anode portion 11a by welding (for example, laser welding or resistance welding). The anode lead terminal 12 of this embodiment is made of a copper alloy, but is not limited thereto. In addition, the shape of the anode lead terminal 12 is not limited to the shape shown in the figure, and can be designed arbitrarily.

[0057] The cathode lead terminal 13 is electrically connected to the cathode portion 11b of the capacitor element 11. The cathode lead terminal 13 is connected to the cathode portion 11b via a conductive paste 15. The conductive paste 15 is made of, for example, a silver paste. The cathode lead terminal 13 of this embodiment is made of a copper alloy, but is not limited thereto. In addition, the shape of the cathode lead terminal 13 is not limited to the shape shown in the figure, and can be designed arbitrarily.

[0058] External resin 21 covers a plurality of capacitor elements 11, anode lead terminal 12, and cathode lead terminal 13 so that a portion (exposed portion 16 described later) of each of anode lead terminal 12 and cathode lead terminal 13 is exposed. External resin 21 is made of an insulating resin material.

[0059] Anode lead terminal 12 and cathode lead terminal 13 each have exposed portion 16 exposed from exterior resin 21 and covered portion 17 covered by exterior resin 21. Exposed portion 16 constitutes an external terminal of solid electrolytic capacitor 10.

[0060] like Figure 2 As shown in FIG. 1 , the covering portion 17 has a surface region including a first surface region 17a and a second surface region 17b. Figure 2 In FIG. 1 , for convenience, both the anode lead terminal 12 and the cathode lead terminal 13 are shown in the same orientation.

[0061] The first surface region 17a is formed with a first oxide film 18 and a second oxide film 19 having greater brittleness than the first oxide film 18. The second surface region 17b is formed with the first oxide film 18, and the amount of the second oxide film 19 per unit area is less than that of the first surface region 17a. For example, the amount of the second oxide film 19 per unit area of ​​the second surface region 17b may be less than 5% of the amount of the second oxide film 19 per unit area of ​​the first surface region 17a.

[0062] In each of the anode lead terminal 12 and the cathode lead terminal 13, the second surface region 17b is provided at least in the portion of the covering portion 17 located near the exposed portion 16. The size of the second surface region 17b formed on the covering portion 17 side from the boundary between the exposed portion 16 and the covering portion 17 is preferably 100 μm or more, for example. In addition, in each of the anode lead terminal 12 and the cathode lead terminal 13, the second surface region 17b is provided on both main surfaces.

[0063] (Method for manufacturing solid electrolytic capacitor)

[0064] Next, refer to Figure 3 A method for manufacturing the above-mentioned solid electrolytic capacitor 10 will be described. Figure 3 In the figure, for convenience, the lead frame 30a corresponding to the anode lead terminal 12 and the lead frame 30b corresponding to the cathode lead terminal 13 are shown in the same direction. Figure 3 In FIG. 1 , the finished exterior resin 21 is indicated by a two-dot chain line.

[0065] The method for manufacturing a solid electrolytic capacitor includes a first step, a second step, a third step, a fourth step, a fifth step, and a sixth step.

[0066] In the first step, a plurality of capacitor elements 11 each having anode portion 11 a and cathode portion 11 b are prepared.

[0067] In the second step, lead frames 30a and 30b are prepared. The lead frames 30a and 30b have an exposed portion 31 and a covered portion 32. The first oxide film 18 ( Figure 3 (a)). The exposed portion 31 is a portion exposed from the exterior resin 21, and corresponds to the exposed portion 16 of the completed solid electrolytic capacitor 10. The covered portion 32 is a portion covered by the exterior resin 21, and corresponds to the covered portion 17 of the completed solid electrolytic capacitor 10.

[0068] In the third step, a plurality of capacitor elements 11 are placed on lead frames 30a and 30b via conductive paste 15. Conductive paste 15 is applied to cathode portion 11b of capacitor element 11. In the third step, a plurality of capacitor elements 11 are stacked on top of each other via conductive material 14.

[0069] In the fourth step, the plurality of capacitor elements 11 and lead frames 30a, 30b are heated to cure the conductive paste 15 and the conductive material 14 and to form the second oxide film 19 ( 18 ) having greater brittleness than the first oxide film 18 on the intended coating portion 32. Figure 3 (b)).

[0070] In the fifth step, the first surface region 17a and the second surface region 17b are formed on the coating planned portion 32. The first surface region 17a is a surface region where the first oxide film 18 and the second oxide film 19 are formed. The second surface region 17b is a surface region where the first oxide film 18 is formed and the amount of the second oxide film 19 per unit area is less than that of the first surface region 17a ( Figure 3 (c)).

[0071] In the fifth step, the second surface region 17b is formed by irradiating the intended covering portion 32 with a laser. In addition, in the fifth step, the second surface region 17b is formed at least on a portion of the intended covering portion 32 located near the intended exposure portion 31. And, in the fifth step, the second surface region 17b is formed on the two main surfaces of the intended covering portion 32. The laser can be irradiated linearly along the boundary between the intended covering portion 32 and the intended exposure portion 31, for example. The number of irradiations (or scans) of the laser can be, for example, in the range of 1 to 3 times, preferably 1 time. The laser can be a CW laser or a pulsed laser. The size of the second surface region 17b formed on the side of the intended covering portion 32 from the boundary between the intended exposure portion 31 and the intended covering portion 32 can be the same as the beam diameter of the laser, for example, it can be more than 100μm.

[0072] In the sixth step, the plurality of capacitor elements 11 and the intended covering portion 32 are covered with the exterior resin 21. After that, the lead frames 30a and 30b are bent along the outer surface of the exterior resin 21, and the solid electrolytic capacitor 10 is completed.

[0073] Example

[0074] The solid electrolytic capacitors 10 of the following examples and comparative examples were evaluated for airtightness by performing a total leakage test. The total leakage test was performed in accordance with the U.S. military standard MIL-STD-883. The number of samples for each of the examples and comparative examples was 100.

[0075] 《Implementation Examples》

[0076] The gull-wing type solid electrolytic capacitor 10 was evaluated. In the manufacturing process of the solid electrolytic capacitor 10, before being coated with the outer resin 21, the second surface area 17b is formed by laser irradiation of the coating predetermined portion 32. Here, a UV laser (MD-U1000C manufactured by KEYENCE Corporation) is used, and the scanning speed of the laser irradiation is set to 250 mm / s. Therefore, the first surface area 17a and the second surface area 17b are formed in the coating portion 17 of the completed solid electrolytic capacitor 10. The decompression amount in the total leakage test is calculated as an average value of 100 (dimensionless reference value).

[0077] 《Comparative Example》

[0078] The gull-wing type solid electrolytic capacitor was evaluated and produced by the same process as the solid electrolytic capacitor 10 of the example except that the laser irradiation was not performed on the coating target portion 32. The decompression amount in the total leakage test was 1712 (dimensionless) as an average value.

[0079] As described above, the decompression amount of the solid electrolytic capacitor 10 of the embodiment is much smaller than that of the solid electrolytic capacitor of the comparative example. Here, in the total leakage test, the smaller the decompression amount, the higher the airtightness. Therefore, it can be said that the superiority of the embodiment is demonstrated.

[0080] The present invention has been described by the present preferred embodiments, but such disclosure should not be construed in a limiting sense. Various modifications and changes will undoubtedly be apparent to those skilled in the art in the art to which the present invention belongs by reading the above disclosure. Therefore, the appended claims should be interpreted as including all modifications and changes without departing from the true spirit and scope of the present invention.

[0081] Industrial Applicability

[0082] The present disclosure can be utilized for a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor.

[0083] Description of Reference Numerals

[0084] 10. Solid electrolytic capacitor; 11. Capacitor element; 11a. Anode portion; 11b. Cathode portion; 11c. Insulating portion; 12. Anode lead terminal; 13. Cathode lead terminal; 14. Conductive material; 15. Conductive paste; 16. Exposed portion; 17. Coated portion; 17a. First surface region; 17b. Second surface region; 18. First oxide coating; 19. Second oxide coating; 21. External resin; 30a, 30b. Lead frame; 31. Predetermined exposed portion; 32. Predetermined coated portion.

Claims

1. A solid electrolytic capacitor, in, The solid electrolytic capacitor has: at least one capacitor element having an anode portion and a cathode portion; an anode lead terminal electrically connected to the anode portion; a cathode lead terminal electrically connected to the cathode portion; as well as an outer resin covering the capacitor element, the anode lead terminal, and the cathode lead terminal in a manner that a portion of each of the anode lead terminal and the cathode lead terminal is exposed, The anode lead terminal and the cathode lead terminal each have an exposed portion exposed from the exterior resin and a covered portion covered by the exterior resin. The coating portion has a surface region including a first oxide film and a second oxide film having greater brittleness than the first oxide film. The surface region includes a first surface region and a second surface region in which the amount of the second oxide film per unit area is smaller than that of the first surface region.

2. The solid electrolytic capacitor according to claim 1, in, In each of the anode lead terminal and the cathode lead terminal, the second surface region is provided at least in a portion of the covering portion located near the exposed portion.

3. The solid electrolytic capacitor according to claim 1 or 2, in, In the anode lead terminal and the cathode lead terminal, the second surface region is provided on both main surfaces.

4. A method for manufacturing a solid electrolytic capacitor, in, The manufacturing method has the following features: In a first step, at least one capacitor element having an anode portion and a cathode portion is prepared; In a second step, a lead frame is prepared, the lead frame having a predetermined exposed portion exposed from an exterior resin and a predetermined covered portion covered by the exterior resin, wherein a first oxide coating is formed on the predetermined covered portion; A third step is to place the capacitor element on the lead frame via a conductive paste; A fourth step of heating the capacitor element and the lead frame to cure the conductive paste and form a second oxide film having greater brittleness than the first oxide film on the intended coating portion; A fifth step of forming a first surface region and a second surface region on the intended coating portion, wherein the first surface region is formed with the first oxide film and the second oxide film, and the second surface region is formed with the first oxide film and the amount of the second oxide film per unit area is less than that of the first surface region; as well as In a sixth step, the capacitor element and the portion to be covered are covered with the exterior resin.

5. The method for manufacturing a solid electrolytic capacitor according to claim 4, in, In the fifth step, the second surface region is formed by irradiating the portion to be covered with laser light.

6. The method for manufacturing a solid electrolytic capacitor according to claim 4 or 5, in, In the fifth step, the second surface region is formed at least in a portion of the planned covering portion that is located near the planned exposure portion.

7. The method for manufacturing a solid electrolytic capacitor according to claim 4 or 5, in, In the fifth step, the second surface region is formed on both main surfaces of the portion to be covered.

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