Solid electrolytic capacitor and method for manufacturing the same

Abstract

A disclosed solid electrolytic capacitor 10 comprises: at least one capacitor element 11; an anode lead terminal 12; a cathode lead terminal 13; and a cladding resin 21 that covers 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 that is exposed from the cladding resin 21; and a covered portion 17 that is covered by the cladding resin 21. The covered portion 17 has a surface region including: a first oxide film 18; and a second oxide film 19 that is more brittle than the first oxide film 18. The surface region includes: 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 in 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 a solid electrolytic capacitor. [Background technology]

[0002] Conventionally, solid electrolytic capacitors that use a solid as an electrolyte have been known (for example, 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 exterior resin that covers these, with a portion of each lead terminal exposed from the exterior resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-134360 Summary of the Invention [Problem to be solved by the invention]

[0004] When outside air enters a solid electrolytic capacitor and reaches the capacitor element, a chemical reaction may occur, causing deterioration of the capacitor element. To suppress such deterioration over time, solid electrolytic capacitors are required to have high airtightness. In this situation, one of the objectives of the present disclosure is to improve the airtightness of solid electrolytic capacitors. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a solid electrolytic capacitor comprising: 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 exterior resin covering the capacitor element, the anode lead terminal, and the cathode lead terminal so that a portion of each of the anode lead terminal and the cathode lead terminal is exposed, wherein 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 covered portion having a surface region including a first oxide film and a second oxide film that is more brittle than the first oxide film, the surface region having 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.

[0006] Another aspect of the present disclosure relates to a method for manufacturing a solid electrolytic capacitor, the method comprising: 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 portion to be exposed from an exterior resin and a portion to be coated by the exterior resin, the portion to be coated having a first oxide film formed thereon; a third step of mounting the capacitor element on the lead frame via a conductive paste; a fourth step of heating the capacitor element and the lead frame to solidify the conductive paste and form a second oxide film on the portion to be coated, the second oxide film being more brittle than the first oxide film; a fifth step of forming, on the portion to be coated, a first surface region where the first oxide film and the second oxide film are formed and a second surface region where the first oxide film is formed and where the amount of the second oxide film per unit area is smaller than that of the first surface region; and a sixth step of coating the capacitor element and the portion to be coated with the exterior resin. [Effects of the Invention]

[0007] According to the present disclosure, the airtightness of the solid electrolytic capacitor can be improved.

[0008] 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 application, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a solid electrolytic capacitor according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view showing a main part of the solid electrolytic capacitor. [Figure 3] 1A and 1B are cross-sectional views showing changes in a main part during a manufacturing method of a solid electrolytic capacitor, in which (a) shows a state in which a first oxide film has been formed, (b) shows a state in which a first and second oxide film have been formed, and (c) shows a state in which at least a portion of the second oxide film has been removed. DETAILED DESCRIPTION OF THE INVENTION

[0010] Examples of embodiments of a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor according to the present disclosure are described below. However, the present disclosure is not limited to the examples described below. While specific numerical values ​​and materials may be exemplified in the following description, other numerical values ​​and materials may be used as long as the effects of the present disclosure are achieved. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be interpreted as "numerical value A or greater 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. When multiple materials are exemplified, one of the materials can be selected and used alone, or two or more can be used in combination. The present disclosure also encompasses combinations of two or more claims arbitrarily selected from the appended claims. In other words, any of the materials can be combined as long as no technical contradiction arises. Note that "solid electrolytic capacitor" can be interpreted as "electrolytic capacitor," and "capacitor" can be interpreted as "capacitor."

[0011] (Solid electrolytic capacitor) A solid electrolytic capacitor according to the present disclosure includes at least one capacitor element, an anode lead terminal, a cathode lead terminal, and an exterior resin.

[0012] 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 them from each other. The insulating portion may be formed of, for example, insulating tape or insulating resin. Only one capacitor element may be provided, or multiple capacitor elements may be provided. In the latter case, the multiple capacitor elements may be stacked on top of each other.

[0013] The anode section may be configured to include a portion of an anode body (a portion on one side of the insulating section) made of a valve metal contained in the capacitor element. The cathode section may be configured of a solid electrolyte layer and a cathode layer formed in this order on the surface of a cathode-forming section, which is the remaining portion of the anode body (a portion on the other side of the insulating section). A dielectric layer is provided between the anode body and the solid electrolyte layer. The cathode section does not necessarily have to include a cathode layer.

[0014] 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.

[0015] The dielectric layer is formed on the surface of at least the cathode-forming portion, which is the remaining portion of the anode body. The dielectric layer may be made of an oxide (e.g., aluminum oxide) formed on the surface of the anode body by a liquid phase method such as anodic oxidation or a gas phase method such as vapor deposition or atomic layer deposition.

[0016] The solid electrolyte layer is formed on the surface of the dielectric layer. The solid electrolyte layer may include a conductive polymer. The solid electrolyte layer may further include a dopant, if necessary.

[0017] The conductive polymer may be a known one used in solid electrolytic capacitors, such as a π-conjugated conductive polymer. Examples of conductive polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. Among these, polymers with a basic skeleton of polypyrrole, polythiophene, or polyaniline are preferred. The above polymers include homopolymers, copolymers of two or more monomers, and derivatives thereof (e.g., substituted products having substituents). For example, polythiophenes include poly(3,4-ethylenedioxythiophene). The conductive polymers may be used alone or in combination of two or more.

[0018] The dopant may be at least one selected from the group consisting of low molecular weight anions and polyanions. Examples of low molecular weight anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Examples of dopants that generate sulfonate ions include benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. Examples of polyanions include polymeric polysulfonic acids and polymeric polycarboxylic acids. Examples of polymeric polysulfonic acids include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylicsulfonic acid, and polymethacrylicsulfonic acid. Examples of polymeric polycarboxylic acids include polyacrylic acid and polymethacrylic acid. Examples of polyanions include polyestersulfonic acid and phenolsulfonic acid novolac resin. However, the polyanions are not limited to these.

[0019] The solid electrolyte layer may further contain, as necessary, known additives and known conductive materials other than conductive polymers, such as at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0020] 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. For example, the silver paste may be a composition containing silver particles and a resin component (binder resin). Although a thermoplastic resin may be used as the resin component, it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.

[0021] The anode lead terminal is electrically connected to the anode portion of the capacitor element. The anode lead terminal may be connected to the anode portion by, for example, laser welding or resistance welding. The constituent material of the anode lead terminal is not particularly limited, but may be, for example, copper or a copper alloy.

[0022] The cathode lead terminal is electrically connected to the cathode portion of the capacitor element. The cathode lead terminal may be connected to the cathode portion via, for example, a conductive paste (e.g., silver paste). The constituent material of the cathode lead terminal is not particularly limited, but may be, for example, copper or a copper alloy.

[0023] The exterior resin covers the capacitor element, the anode lead terminal, and the cathode lead terminal so that each of the anode lead terminal and the cathode lead terminal is partially exposed. The exterior resin may be made of an insulating resin material and may contain a filler as needed. For example, a thermosetting resin containing an epoxy resin as a main component may be used as the insulating resin material.

[0024] 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 exposed portion may constitute an external terminal of the solid electrolytic capacitor. The covered portion has a surface region including a first surface region and a second surface region. The first surface region has a first oxide film and a second oxide film that is more brittle than the first oxide film (in other words, more brittle than the first oxide film). In the first surface region, the first oxide film may be formed on the base material, and the second oxide film may be formed on the first oxide film. In the second surface region, the first oxide film is formed and the amount of the second oxide film per unit area is smaller than in the first surface region. In the second surface region, the first oxide film may be formed on the base material. The first oxide film in the first surface region and the first oxide film in the second surface region may be continuous with each other. The amount of the second oxide film per unit area in 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 in the first surface region.

[0025] The first oxide film may be an oxide film (a natural oxide film) that is inevitably present on the base material of each lead terminal. The second oxide film may be an oxide film that grows or forms more rapidly than the first oxide film during the manufacturing process (particularly the heat treatment process) of the solid electrolytic capacitor. The oxygen content ratio of the first oxide film to the metal elements may be lower than the oxygen content ratio of the second oxide film to the metal elements. The natural oxide film (the first oxide film) and the second oxide film can be easily distinguished by cross-sectional SEM observation, etc. The second oxide film is more brittle than the first oxide film and is easily removed by any removal method, such as thermal treatment, non-thermal treatment, mechanical treatment, or chemical treatment. For example, if 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, the second oxide film can be considered to be more brittle than the first oxide film. The laser used to evaluate brittleness may be, for example, a UV laser with a peak wavelength of 355 nm and a maximum output of 2 W or more (40 kHz). For example, the MD-U1000C manufactured by Keyence Corporation may be used as such a laser. The scanning speed of the laser irradiation may be, for example, 250 mm / s.

[0026] The present inventors discovered that the second oxide film present on the surface of each lead terminal is a factor that reduces the airtightness of the solid electrolytic capacitor. Specifically, the second oxide film, which is more brittle than the first oxide film, crumbles relatively easily even when in close contact with the exterior resin covering each lead terminal. Where the second oxide film crumbles, tiny gaps form between each lead terminal and the exterior resin, creating paths for outside air to penetrate. In contrast, as described above, each lead terminal of the solid electrolytic capacitor disclosed herein has a second surface region with a small amount of second oxide film per unit area. Because the second surface region does not contain a large amount of the easily crumbling second oxide film, the lead terminal maintains close contact with the exterior resin, making it difficult for outside air to penetrate. This improves the airtightness of the solid electrolytic capacitor.

[0027] In each of the anode lead terminal and the cathode lead terminal, the second surface region may be provided at least near the exposed portion of the coating. The vicinity of the exposed portion of the coating can also be said to be near the base of each lead terminal. Such a region corresponds to an entrance for outside air to enter the solid electrolytic capacitor, and providing at least the second surface region therein can effectively prevent outside air from entering.

[0028] In each of the anode lead terminal and the cathode lead terminal, the second surface region may be provided on both main surfaces. This configuration can suppress the formation of an outside air intrusion path over a wider area than when the second surface region is provided on only one of the main surfaces. The second surface region may also be provided on a side surface connecting the two main surfaces.

[0029] (Solid Electrolytic Capacitor Manufacturing Method) The method for manufacturing a solid electrolytic capacitor according to the present disclosure includes a first step, a second step, a third step, a fourth step, a fifth step, and a sixth step.

[0030] 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 multiple capacitor elements may be prepared.

[0031] In the second step, a lead frame is prepared, which has a portion to be exposed from the exterior resin and a portion to be coated with the exterior resin, and a first oxide film formed on the portion to be coated. The constituent material of the lead frame is not particularly limited, but may be, for example, copper or a copper alloy. The first oxide film may be an oxide film that is naturally present on the base material of the lead frame. The first oxide film may also be formed on the portion to be exposed.

[0032] In the third step, the capacitor element is mounted on a lead frame via a conductive paste (for example, silver paste), which may be applied to the cathode portion of the capacitor element.

[0033] In the fourth step, the capacitor element and the lead frame are heated to solidify the conductive paste and form a second oxide film on the portion to be coated, the second oxide film being more brittle than the first oxide film (in other words, more brittle than the first oxide film). 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.

[0034] In the fifth step, a first surface region, in which a first oxide film and a second oxide film are formed, and a second surface region, in which the first oxide film is formed and in which the amount of the second oxide film per unit area is smaller than that of the first surface region, are formed on the portion to be coated. The first surface region may be a surface region that maintains the surface state formed in the fourth step. The second surface region may 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 method for removing the second oxide film is not particularly limited, and any removal method using thermal treatment, non-thermal treatment, mechanical treatment, chemical treatment, or the like can be used. Note that, prior to the fifth step, it is preferable to join the anode portion of the capacitor element and the lead frame to each other, for example, by welding.

[0035] In the sixth step, the capacitor element and the portion to be covered are covered with an exterior resin.

[0036] In the solid electrolytic capacitor manufactured by the manufacturing method including the above-mentioned steps 1 to 6, each lead terminal formed by processing the lead frame has a second surface region in a portion corresponding to the portion to be covered (i.e., the above-mentioned covering portion), which makes it difficult for a path for outside air to enter, thereby improving the airtightness of the solid electrolytic capacitor.

[0037] In the fifth step, the second surface region may be formed by irradiating the portion to be coated with a laser. The laser irradiation may remove at least a portion of the second oxide film on a portion of the surface of the portion to be coated. The surface region from which at least a portion of the second oxide film has been removed constitutes the second surface region. The removal may be performed by scanning the laser over the region from which the second oxide film is to be removed.

[0038] In the fifth step, a second surface region may be formed at least near the to-be-exposed portion of the to-be-covered portion. The vicinity of the to-be-exposed portion of the to-be-covered portion can be considered to be near the base of each lead terminal in the finished solid electrolytic capacitor. Such a region corresponds to an entrance for external air to enter the solid electrolytic capacitor, and providing at least the second surface region therein can effectively prevent external air from entering. In the laser-irradiated region, a linear laser irradiation mark is formed as a result of removing the second oxide film. The appearance of the laser irradiation mark differs from that of the non-irradiated region. Therefore, in the present disclosure, the feature that "the coating portion has a first oxide film and a second oxide film that is more brittle than the first oxide film, and has 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" may be rephrased as "the coating portion has a linear laser irradiation mark near the base of the exposed portion of at least one lead terminal."

[0039] In the fifth step, second surface regions may be formed on both main surfaces of the portion to be covered. This configuration can prevent the formation of an outside air intrusion path over a wider area in the completed solid electrolytic capacitor than when the second surface region is formed on only one main surface. The second surface region may also be formed on the side surface connecting the two main surfaces.

[0040] As described above, according to the present disclosure, by providing each lead terminal with a second surface region where the brittle second oxide film is not present in large amounts, the airtightness of the solid electrolytic capacitor can be improved.

[0041] An example of a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor according to the present disclosure will be described in detail below with reference to the drawings. The components and steps described above can be applied to the components and steps of the example solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor described below. The components and steps of the example solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Among the components and steps of the example solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor described below, components and steps that are not essential to the solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0042] (Solid electrolytic capacitor) The solid electrolytic capacitor 10 of this embodiment is a so-called gull-wing type (where each lead terminal extends from the side surface along the underside of the exterior resin), but is not limited to this. For example, the solid electrolytic capacitor 10 may be a so-called bottom electrode type (where each lead terminal is exposed from the underside of the exterior resin). Furthermore, while the solid electrolytic capacitor 10 of this embodiment has each capacitor element facing the same direction, this is not limiting, and some capacitor elements may face in opposite directions to the remaining capacitor elements. In the latter case, the currents flowing through some capacitor elements and the remaining capacitor elements face in opposite directions, and the magnetic fields of the two currents cancel each other out, thereby reducing the ESL of the solid electrolytic capacitor 10.

[0043] As shown in FIG. 1, solid electrolytic capacitor 10 includes a plurality of (five in this example) capacitor elements 11, an anode lead terminal 12, a cathode lead terminal 13, and an exterior resin 21.

[0044] A plurality of capacitor elements 11 are stacked on top of one another. Each capacitor element 11 has an anode portion 11a and a cathode portion 11b. An insulating portion 11c is provided between anode portion 11a and cathode portion 11b to electrically insulate them from each other.

[0045] The anode portions 11a adjacent to each other in the stacking direction are connected to each other by welding (for example, laser welding or resistance welding). The cathode portions 11b adjacent to each other in the stacking direction are connected to each other by a conductive material 14. The conductive material 14 is made of, for example, silver paste.

[0046] 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). In this embodiment, the anode lead terminal 12 is made of a copper alloy, but is not limited to this. The shape of the anode lead terminal 12 is not limited to that shown in the drawing and can be designed as desired.

[0047] Cathode lead terminal 13 is electrically connected to cathode portion 11b of capacitor element 11. Cathode lead terminal 13 is connected to cathode portion 11b via conductive paste 15. Conductive paste 15 is made of, for example, silver paste. In this embodiment, cathode lead terminal 13 is made of a copper alloy, but is not limited to this. The shape of cathode lead terminal 13 is not limited to that shown in the drawing and can be designed as desired.

[0048] Exterior resin 21 covers a plurality of capacitor elements 11, anode lead terminals 12, and cathode lead terminals 13 so as to expose a portion (exposed portion 16 described below) of each of anode lead terminals 12 and cathode lead terminals 13. Exterior resin 21 is made of an insulating resin material.

[0049] Each of anode lead terminal 12 and cathode lead terminal 13 has exposed portion 16 exposed from exterior resin 21 and covered portion 17 covered with exterior resin 21. Exposed portion 16 constitutes an external terminal of solid electrolytic capacitor 10.

[0050] 2, coating 17 has a surface region including first surface region 17a and second surface region 17b. For convenience, both anode lead terminal 12 and cathode lead terminal 13 are shown in the same orientation in FIG.

[0051] The first surface region 17a is formed with a first oxide film 18 and a second oxide film 19 that is more brittle than the first oxide film 18. The second surface region 17b is formed with the first oxide film 18 and has a smaller amount of the second oxide film 19 per unit area than the first surface region 17a. For example, the amount of the second oxide film 19 per unit area in the second surface region 17b may be 5% or less of the amount of the second oxide film 19 per unit area in the first surface region 17a.

[0052] 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 vicinity of the exposed portion 16 of the covering portion 17. The dimension 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, for example, 100 μm or more. Furthermore, 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.

[0053] (Solid Electrolytic Capacitor Manufacturing Method) Next, a method for manufacturing the above-described solid electrolytic capacitor 10 will be described with reference to Figure 3 as needed. For convenience, in Figure 3, 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 facing the same direction. In Figure 3, the exterior resin 21 of the finished product is indicated by a two-dot chain line.

[0054] 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.

[0055] In the first step, a plurality of capacitor elements 11 each having an anode portion 11a and a cathode portion 11b are prepared.

[0056] In the second step, lead frames 30a, 30b are prepared, each having a to-be-exposed portion 31 and a to-be-coated portion 32, with a first oxide film 18 formed on the to-be-coated portion 32 (FIG. 3(a)). The to-be-exposed portion 31 is the portion to be exposed from the exterior resin 21, and corresponds to the exposed portion 16 of the completed solid electrolytic capacitor 10. The to-be-coated portion 32 is the portion to be coated with the exterior resin 21, and corresponds to the coated portion 17 of the completed solid electrolytic capacitor 10.

[0057] In the third step, a plurality of capacitor elements 11 are placed on lead frames 30a and 30b via conductive paste 15. The conductive paste 15 is applied to the cathode portions 11b of the capacitor elements 11. Also, in the third step, the plurality of capacitor elements 11 are stacked one on another with conductive material 14 interposed therebetween.

[0058] In the fourth step, the plurality of capacitor elements 11 and the lead frames 30a, 30b are heated to solidify the conductive paste 15 and the conductive material 14, and a second oxide film 19, which is more brittle than the first oxide film 18, is formed on the portion to be coated 32 (Figure 3(b)).

[0059] In the fifth step, a first surface region 17a and a second surface region 17b are formed on the portion to be coated 32. The first surface region 17a is a surface region on which a first oxide film 18 and a second oxide film 19 are formed. The second surface region 17b is a surface region on which the first oxide film 18 is formed and on which the amount of the second oxide film 19 per unit area is smaller than that of the first surface region 17a (FIG. 3(c)).

[0060] In the fifth step, the second surface region 17b is formed by irradiating the to-be-coated portion 32 with a laser. In addition, in the fifth step, the second surface region 17b is formed at least in the vicinity of the to-be-exposed portion 31 in the to-be-coated portion 32. Furthermore, in the fifth step, the second surface region 17b is formed on both main surfaces of the to-be-coated portion 32. For example, the laser may be irradiated in a line along the boundary between the to-be-coated portion 32 and the to-be-exposed portion 31. The number of times of laser irradiation (or scanning) may be within a range of, for example, 1 to 3 times, and it is preferable to irradiate only once. The laser may be a CW laser or a pulsed laser. The dimension of the second surface region 17b formed on the to-be-coated portion 32 side from the boundary between the to-be-exposed portion 31 and the to-be-coated portion 32 may be approximately the same as the laser beam diameter, and may be, for example, 100 μm or more.

[0061] In a sixth step, the capacitor elements 11 and the portions to be coated 32 are coated with the exterior resin 21. After that, a bending step is performed in which the lead frames 30a, 30b are bent along the outer surface of the exterior resin 21, and the solid electrolytic capacitor 10 is completed. [Example]

[0062] The solid electrolytic capacitors 10 of the following examples and comparative examples were subjected to a gross leak test to evaluate their airtightness. The gross leak test was conducted in accordance with the U.S. military standard MIL-STD-883. For each example and comparative example, 100 samples were used.

[0063] Example A gull-wing type solid electrolytic capacitor 10 was evaluated. During the manufacturing process of the solid electrolytic capacitor 10, the second surface region 17b was formed by irradiating the to-be-coated portion 32 with a laser before coating with the exterior resin 21. A UV laser (MD-U1000C manufactured by Keyence Corporation) was used, and the scanning speed of the laser irradiation was 250 mm / s. Therefore, the first surface region 17a and the second surface region 17b were formed in the coating portion 17 of the completed solid electrolytic capacitor 10. The amount of pressure reduction in the gross leak test was 100 on average (a dimensionless reference value).

[0064] Comparative Example A gull-wing type solid electrolytic capacitor was evaluated. It was fabricated using the same process as solid electrolytic capacitor 10 of the example, except that laser irradiation was not performed on portion to be coated 32. The amount of reduced pressure in the gross leak test was 1712 (dimensionless) on average.

[0065] As described above, the amount of pressure reduction in the solid electrolytic capacitor 10 of the example was much smaller than that in the solid electrolytic capacitor of the comparative example. Here, in the gross leak test, the smaller the amount of pressure reduction, the higher the airtightness. Therefore, it can be said that the example is superior.

[0066] 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. [Industrial Applicability]

[0067] The present disclosure can be used for a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor. [Explanation of symbols]

[0068] 10: Solid electrolytic capacitor 11: Capacitor element 11a: Anode section 11b: Cathode part 11c: Insulation part 12: Anode lead terminal 13: Cathode lead terminal 14: Conductive materials 15: Conductive paste 16:Exposed part 17: Covering part 17a: 1st surface area 17b: 2nd surface area 18: First oxide film 19: Second oxide film 21: Exterior resin 30a, 30b: lead frame 31: Exposed area 32: Part to be covered

Claims

1. 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; an exterior resin that covers the capacitor element, the anode lead terminal, and the cathode lead terminal so that a portion of each of the anode lead terminal and the cathode lead terminal is exposed, each of the anode lead terminal and the cathode lead terminal has an exposed portion exposed from the exterior resin and a covered portion covered with the exterior resin; the coating portion has a surface region including a first oxide film and a second oxide film that is more brittle than the first oxide film, The solid electrolytic capacitor has 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. 2. The solid electrolytic capacitor according to claim 1, wherein the second surface region is provided at least near the exposed portion of the coating in each of the anode lead terminal and the cathode lead terminal.

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

4. a first step of providing at least one capacitor element having an anode portion and a cathode portion; a second step of preparing a lead frame having a portion to be exposed from an exterior resin and a portion to be coated with the exterior resin, the portion to be coated having a first oxide film formed thereon; a third step of mounting the capacitor element on the lead frame via a conductive paste; a fourth step of heating the capacitor element and the lead frame to solidify the conductive paste and form a second oxide film, which is more brittle than the first oxide film, on the portion to be coated; a fifth step of forming, on the portion to be coated, a first surface region on which the first oxide film and the second oxide film are formed, and a second surface region on which the first oxide film is formed and on which the amount of the second oxide film per unit area is smaller than that of the first surface region; a sixth step of coating the capacitor element and the portion to be coated with the exterior resin; A method for manufacturing a solid electrolytic capacitor, comprising:

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

6. 6. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein in the fifth step, the second surface region is formed at least in the vicinity of the to-be-exposed portion of the to-be-covered portion.

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

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