Solid electrolytic capacitor

Abstract

To provide a solid electrolytic capacitor having high heat resistance.SOLUTION: The solid electrolytic capacitor 100 includes at least one capacitor element 110 including an anode part 111 and a cathode part 112, an anode lead terminal 120, a cathode lead terminal 130, and an exterior body 140 covering the capacitor element, wherein the anode lead terminal and the cathode lead terminal each have a main surface and a side surface, At least a part of a main surface of the exposed portion is covered with the low-melting-point material, and a first side surface region of a side surface of the embedded portion is not covered with the low-melting-point material, the first side surface region being more than 0. 36mm away from a boundary between the embedded portion and the exposed portion, the embedded portion including an embedded portion 120A and an exposed portion 130A that are embedded in the package body, the exposed portion including an exposed portion 120B and an exposed portion 130B that are exposed from the package body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to solid electrolytic capacitors. [Background technology]

[0002] Solid electrolytic capacitors are installed in a variety of electronic devices. A solid electrolytic capacitor typically includes an anode lead terminal and a cathode lead terminal electrically connected to a capacitor element, and an exterior body that covers the capacitor element.

[0003] Patent Document 1 discloses a chip-type solid electrolytic capacitor having a solid electrolytic capacitor element comprising an anode body made of a valve metal from which an anode lead is drawn, an oxide film formed on the surface of the anode body, a solid electrolyte layer formed on the oxide film, and a cathode lead layer made of a graphite layer and a silver paste layer formed on the solid electrolyte layer, wherein a plate-shaped lead frame terminal is connected to the cathode lead layer with a conductive adhesive, and wherein a first plating layer serving as a base is formed on the entire surface of both sides of the lead frame terminal, and a second plating layer made of a precious metal is formed only on the surface of the first plating layer that comes into contact with the conductive adhesive (see Figure 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-67876 Summary of the Invention

[0005] a cathode lead terminal having a cathode connecting surface electrically connected to the cathode portion; and an exterior housing covering the capacitor element, wherein the anode lead terminal and the cathode lead terminal each have a main surface having the anode connecting surface and the cathode connecting surface, and a side surface intersecting the main surface, and each include an embedded portion embedded in the exterior housing and an exposed portion exposed from the exterior housing, wherein in at least one lead terminal selected from the anode lead terminal and the cathode lead terminal, at least a portion of the main surface of the exposed portion is covered with a low-melting point material, and in the side surface of the embedded portion, at least a first side surface region that is more than 0.36 mm away from a boundary between the embedded portion and the exposed portion is not covered with the low-melting point material.

[0006] It should be noted that a comprehensive or specific aspect of the present disclosure may be realized as a solid electrolytic capacitor, a device and system including the solid electrolytic capacitor, a method using the solid electrolytic capacitor, or any combination thereof.

[0007] According to the present disclosure, a solid electrolytic capacitor with high heat resistance can be realized. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating the configuration of an example of a solid electrolytic capacitor according to the present disclosure. [Figure 2] FIG. 2 is a perspective view schematically showing the structure of a main part of the solid electrolytic capacitor shown in FIG. [Figure 3] 3A and 3B are a plan view and a side view, respectively, schematically showing the cathode lead terminal of the main part of the solid electrolytic capacitor shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view schematically illustrating the configuration of another example of a solid electrolytic capacitor according to the present disclosure. [Figure 5] FIG. 5 is a cross-sectional view schematically illustrating the configuration of yet another example of a solid electrolytic capacitor according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Before describing the embodiments, the problems in the prior art will be briefly described below.

[0010] Patent Document 1 proposes the above-mentioned chip-type solid electrolytic capacitor in which a tin plating layer is formed on the first plating layer only on at least a portion of the area of ​​the lead frame on which the second plating layer is formed where the second plating layer is not formed (see FIG. 2). Patent Document 1 also proposes the above-mentioned chip-type solid electrolytic capacitor in which a tin plating layer is formed on the first plating layer on at least a portion of the backside of the lead frame on which the second plating layer is formed (see FIG. 3).

[0011] However, as shown in Figures 2 and 3 of Patent Document 1, if a low-melting-point material such as a tin-plated layer is present in the area of ​​the lead frames 24, 34 that contacts the exterior resin 2, when the solid electrolytic capacitor is heated to a high temperature (for example, when mounted on a substrate), the low-melting-point material may melt, move, and segregate, causing voids between the lead frames 24, 34 and the exterior resin 2. As a result, the inside of the solid electrolytic capacitor becomes more likely to communicate with the external environment, making the solid electrolytic capacitor more susceptible to deterioration.

[0012] In view of the above problems, the present disclosure makes it possible to realize a solid electrolytic capacitor with high heat resistance.

[0013] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained. Note that components other than those characteristic of the present disclosure may be those of known solid electrolytic capacitors. In this specification, when a "range between numerical value A and numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0014] A solid electrolytic capacitor according to one embodiment of the present disclosure includes at least one capacitor element including an anode portion and a cathode portion, an anode lead terminal having an anode connection surface electrically connected to the anode portion, a cathode lead terminal having a cathode connection surface electrically connected to the cathode portion, and an exterior body covering the capacitor element.

[0015] The anode lead terminal and the cathode lead terminal each have a main surface having an anode connecting surface and a cathode connecting surface, and a side surface intersecting the main surface, and also include an embedded portion embedded in the outer casing and an exposed portion exposed from the outer casing.

[0016] The main surface is divided into a front and a back (here, main surface A and the opposite main surface B). The side surface is a surface that extends along the outline of the lead terminal when viewed from the normal direction of the main surface, and is a linear surface having a very small area with a width corresponding to the thickness of the lead terminal. However, here, we focus on the side surface that extends across the embedded portion and the exposed portion. Such a side surface is also divided into one side and the other (here, side surface A and the opposite side surface B).

[0017] That is, typically, there are two first side surface regions and two second side surface regions, and two first main surface regions and two second main surface regions, as described below. In this embodiment, the following conditions A, B, and other conditions are intended to be satisfied in each of the first side surface regions and first main surface regions. Also, the conditions to be satisfied by the second side surface regions and second main surface regions, as described below, are intended to be satisfied in each of the second side surface regions and second main surface regions.

[0018] At least one lead terminal selected from an anode lead terminal and a cathode lead terminal (hereinafter also referred to as "lead terminal A") has at least a portion of the main surface of the exposed portion covered with a low-melting-point material.

[0019] On the other hand, the embedded portion of the lead terminal A satisfies the following condition A.

[0020] <Condition A> At least a first side surface region of the side surface of the embedded portion of the lead terminal A, which is more than 0.36 mm away from the boundary between the embedded portion and the exposed portion, is not covered with the low-melting-point material. The first side surface region is a region whose distance from the boundary along the extending portion of the lead terminal A is greater than 0.36 mm.

[0021] Furthermore, it is desirable that the lead terminal A further satisfies the following condition B.

[0022] <Condition B> At least a first main surface region of the main surface of the embedded portion of the lead terminal A that is more than 0.15 mm away from the boundary between the embedded portion and the exposed portion is not covered with the low-melting-point material. The first main surface region is a region that is a distance from the boundary along the extending portion of the lead terminal A that is greater than 0.15 mm.

[0023] Here, the distance from the boundary along the extension of lead terminal A can be measured by observing a cross section parallel to the extension direction of lead terminal A of the solid electrolytic capacitor. In such a cross section, the distance that defines the first side surface region is determined by the length of the center line of the side surface of lead terminal A. The distance that defines the first main surface region is determined by the length of the line drawn by the main surface of lead terminal A. Hereinafter, each distance from the boundary will be interpreted in the same manner.

[0024] In addition, "not covered with a low-melting point material" means not only that it is not covered with the same material as the low-melting point material (hereinafter also referred to as "low-melting point material A") that covers at least a portion of the main surface of the exposed portion, but also that it is not covered with a low-melting point material other than low-melting point material A.

[0025] The side surface of the embedded portion can be conceptually divided into a first side surface region and a second side surface region, which is the remaining portion other than the first side surface region. The first side surface region is a region that is more than 0.36 mm away from the boundary between the embedded portion and the exposed portion. The second side surface region is a region that is 0.36 mm or less away from the boundary between the embedded portion and the exposed portion. The first side surface region and the second side surface region are continuous.

[0026] When condition A is satisfied, the low-melting-point material is allowed to cover the second side surface region of the side surface of the embedded portion with the low-melting-point material, but it is desirable that the region that can be covered with the low-melting-point material be limited to a region of the second side surface region that is 0.25 mm or less away from the boundary between the embedded portion and the exposed portion, it is more desirable that 90% or more of the area of ​​the second side surface region is not covered with the low-melting-point material, and it is even more desirable that the second side surface region is not covered with the low-melting-point material at all.

[0027] If the first side region of the embedded portion is covered with a low-melting-point material, when the solid electrolytic capacitor is heated to a high temperature (e.g., when mounted on a substrate), the low-melting-point material melts and moves vertically downward along the side of the embedded portion, segregating, which can create a gap between the embedded portion and the exterior case. In contrast, if at least the first side region of the side of the embedded portion is not covered with a low-melting-point material, a gap is less likely to form between the embedded portion and the exterior case. Even if a gap does form, the distance from the boundary between the embedded portion and the exposed portion is limited to 0.36 mm or less. This reduces communication between the interior of the solid electrolytic capacitor and the external environment, thereby suppressing degradation of the solid electrolytic capacitor. For example, this can suppress degradation of the conductive polymer contained in the solid electrolyte layer, thereby suppressing a decrease in capacitance. It can also suppress an increase in ESR.

[0028] The main surface of the embedded portion can be conceptually divided into a first main surface region and a second main surface region, which is the remaining portion other than the first main surface region. The first main surface region is located more than 0.15 mm away from the boundary between the embedded portion and the exposed portion. The second principal surface region is a region that is 0.15 mm or less away from the boundary between the buried portion and the exposed portion. The first principal surface region and the second principal surface region are continuous.

[0029] When condition B is satisfied, the second principal surface region of the principal surface of the embedded portion is permitted to be covered with the low-melting point material. However, the region that can be covered with the low-melting point material is desirably limited to a region of the second principal surface region that is 0.1 mm or less or 0.05 mm or less away from the boundary between the embedded portion and the exposed portion, it is more desirable that 90% or more of the area of ​​the second principal surface region is not covered with the low-melting point material, and it is even more desirable that the second principal surface region is not covered at all with the low-melting point material.

[0030] If the first main surface region of the main surface of the embedded portion is covered with a low-melting-point material, when the solid electrolytic capacitor is heated to a high temperature (e.g., when mounted on a substrate), the low-melting-point material may melt and some of the fluidized low-melting-point material may segregate toward the exposed portion of the embedded portion. As a result, a gap may form between the embedded portion and the exterior case. In contrast, if at least the first main surface region of the main surface of the embedded portion is not covered with a low-melting-point material, a gap is less likely to form between the embedded portion and the exterior case. Furthermore, even if a gap does form, the distance from the boundary between the embedded portion and the exposed portion is limited to a range of 0.15 mm or less. This makes it less likely for the interior of the solid electrolytic capacitor to communicate with the external environment, thereby suppressing degradation of the solid electrolytic capacitor.

[0031] Gravity tends to promote the movement and segregation of the molten low-melting-point material on the sides of the embedded portion. Therefore, lead terminal A must satisfy at least condition A. In other words, even if lead terminal A satisfies only condition A, a corresponding improvement in heat resistance can be expected. However, it is desirable for lead terminal A to satisfy both conditions A and B.

[0032] Furthermore, if at least a portion of the main surface of the exposed portion of at least one of the anode lead terminal and the cathode lead terminal is covered with a low-melting point material and condition A (preferably conditions A and B) is satisfied, a corresponding improvement in heat resistance can be expected. However, from the perspective of significantly improving heat resistance, it is desirable that at least a portion of the main surface of the exposed portion of both the anode lead terminal and the cathode lead terminal is covered with a low-melting point material and condition A (preferably conditions A and B) is satisfied.

[0033] In a solid electrolytic capacitor, the distance between the external environment and the cathode part is usually shorter than the distance between the external environment and the anode part. Therefore, when at least a portion of the main surface of the exposed part of the cathode lead terminal is covered with a low-melting-point material, it is desirable for the cathode lead terminal to satisfy condition A (preferably both conditions A and B) in order to more reliably achieve improved heat resistance.

[0034] Furthermore, in the lead terminal A, the side surfaces of the exposed portion do not have to be covered with the low-melting-point material. By designing the lead terminal in this manner, it is possible to more reliably and easily realize a configuration in which the first side surface region and the second side surface region are not covered with the low-melting-point material.

[0035] Hereinafter, the condition that the side surface of the exposed portion is not covered with a low-melting point material is defined as condition C. At least one of the anode lead terminal and the cathode lead terminal may satisfy condition C, but from the viewpoint of more reliably realizing improved heat resistance, it is desirable that at least the cathode lead terminal satisfy condition C, and both the anode lead terminal and the cathode lead terminal may satisfy condition C.

[0036] The main surface of the exposed portion is divided into main surface A, which is connected to a connection electrode of a component such as a circuit board, and main surface B, which is on the opposite side. At least a part of the area of ​​main surface A needs to be covered with the low-melting-point material. Main surface B does not need to be covered with the low-melting-point material at all, but at least a part of the area of ​​main surface B may be covered with the low-melting-point material.

[0037] The method for attaching the low melting point material to the metal foil is not particularly limited, but liquid phase methods such as electrolytic plating and electroless plating, and gas phase methods such as vapor deposition can be used.

[0038] (Lead terminal) The lead terminal is also called a lead frame. The anode lead terminal and the cathode lead terminal may have any shape as long as they each have a main surface and a side surface intersecting the main surface. The anode lead terminal and the cathode lead terminal are formed, for example, by cutting a starting material (generally a metal foil) into a predetermined shape. When the starting material is a metal foil, the main surfaces originate from both the front and back surfaces of the metal foil, and the side surfaces are formed by cutting the metal foil into the predetermined shape.

[0039] The anode connection surface is provided on at least a main surface of the anode lead terminal. The cathode connection surface is provided on at least a main surface of the cathode lead terminal. The anode connection surface is electrically connected to the anode portion by means of physical contact, bonding or joining with a conductive adhesive or solder, welding, or the like. The cathode connection surface may be electrically connected to the cathode portion by means of physical contact, a conductive adhesive, welding, or the like. Physical contact includes contact that involves deformation of the lead terminal due to pressure, such as by crimping. The conductive adhesive is, for example, a mixture of resin and conductive particles. The resin may be a curable resin. The conductive particles may be carbon particles, metal particles, or the like.

[0040] A portion of the anode lead terminal closer to the anode portion is embedded in the exterior housing together with the anode portion, and a portion of the cathode lead terminal closer to the cathode portion is embedded in the exterior housing together with the cathode portion. The remaining portions of the anode lead terminal and the cathode lead terminal extend outside the exterior housing. Thus, the anode lead terminal and the cathode lead terminal each include an embedded portion embedded in the exterior housing and an exposed portion exposed from the exterior housing. The exposed portions of the anode lead terminal and the cathode lead terminal each function as external electrodes for connecting the solid electrolytic capacitor to a connection electrode of a component such as a circuit board.

[0041] The starting material for the lead terminal (and the material of the lead terminal after it has been formed into a lead terminal) is not particularly limited as long as it is electrochemically and chemically stable and conductive, but metal foil is generally used. The thickness of the lead terminal (the distance between the main surfaces of the metal foil) is, for example, 25 μm to 200 μm, or 25 μm to 100 μm, from the viewpoint of reducing the height.

[0042] A lead terminal that satisfies the above condition C can be obtained by, for example, adhering a low-melting-point material to a starting material for the lead terminal (generally a metal foil) while shielding the embedded portion with a shielding material such as masking tape, and then cutting the starting material into a predetermined shape. In other words, a lead terminal that satisfies condition C can be obtained by a method in which a low-melting-point material is adhered to a starting material for the lead terminal (generally a metal foil), and then forming the side surfaces of the embedded portion and the exposed portion.

[0043] At least one of the main surfaces of the anode lead terminal and the cathode lead terminal may be roughened, thereby improving adhesion between the lead terminal and the exterior body and further reducing communication between the inside of the solid electrolytic capacitor and the external environment.

[0044] The roughened main surface (rough surface) may be provided on at least a portion of the main surface of the embedded portion of at least one of the anode lead terminal and the cathode lead terminal. The ratio of the rough surface to the total area of ​​the main surface of the embedded portion may be, for example, 50% or more, 80% or more, or 90% or more. The rough surface may be formed across the embedded portion and the exposed portion so as to be formed on at least a portion of the main surface of the exposed portion.

[0045] The roughening may be performed by, for example, sandblasting, roughening plating, roughening etching, etc. The sandblasting method is preferred because it allows quick processing and is excellent in cost performance. The roughening plating method is preferred because it is low cost. The roughening etching method is preferred because it can remove unevenness. The roughening plating method and the roughening etching method are advantageous in that they leave no beads (projection material) behind, unlike the sandblasting method.

[0046] The developed interface area ratio (Sdr) of the roughened main surface (rough surface) may be, for example, 0.4 or more. Here, the developed interface area ratio is a parameter measured in accordance with ISO 25178. By setting Sdr to 0.4 or more, the adhesion between the lead terminal and the exterior body is further improved, making it even more difficult for the inside of the solid electrolytic capacitor to communicate with the external environment.

[0047] Although there is no particular upper limit to the developed interface area ratio, keeping the developed interface area ratio at or below a certain value facilitates the production of lead terminals. The developed interface area ratio of the rough surface may be 10.0 or less, 6.0 or less, 4.0 or less, 2.0 or less, 1.0 or less, or 0.6 or less. The developed interface area ratio may be in the range of 0.4 to 10.0, 0.4 to 6.0, 0.4 to 4.0, 0.4 to 2.0, 0.4 to 1.0, or 0.4 to 0.6.

[0048] In sandblasting, for example, by reducing the particle size of the particles (shot material) (for example, by increasing the grit size), it is possible to increase the developed surface area ratio of the rough surface to 0.4 or more. Also, by increasing the number of sandblasting shots, it is possible to increase the developed interface area ratio of the sandblasted rough surface. There are no particular limitations on the particles (shot material) used in sandblasting, and alumina particles or garnet particles may also be used.

[0049] When the roughened surface is formed by a roughening plating method, Sdr can be increased to 0.4 or more by increasing the surface area, for example, by forming needle-like or particulate plating. For example, the proportion of needle-like or particulate plating may be increased.

[0050] When the roughened surface is formed by roughening etching, for example, the difference between the etching rate of the grain boundaries and the etching rate of the crystal grains (the grain boundaries have a higher etching rate) can be utilized to form a roughened shape, thereby increasing the surface area and, as a result, making it possible to achieve an Sdr of 0.4 or more. For example, the ratio of crystal grain boundaries to crystal grains in the metal can be changed by selecting the metal that constitutes the starting material of the lead terminal, or the difference in etching rate can be changed by changing the etching conditions.

[0051] (low melting point material) The low-melting-point material broadly encompasses materials that melt when heated (e.g., when mounted on a substrate) when the solid electrolytic capacitor is incorporated as a component into a device. The melting point of the low-melting-point material may be, for example, 180°C to 240°C. The low-melting-point material covering at least a portion of the main surface of the exposed portion melts when connecting a connection electrode of a component such as a circuit board to the exposed portion (external electrode), thereby contributing to the connection between the two.

[0052] The low-melting-point material may include tin (Sn) or solder. In this case, at least a portion of the exposed portion is bonded to a connecting electrode as an external electrode via tin or solder. Bonding via such a metal material is strong.

[0053] Examples of solder include materials specified in JIS Z 3282-1999. Specific examples include lead-containing solders such as Sn-Pb, Pb-Sn, Sn-Pb-Sb, Sn-Pb-Bi, Sn-Pb-Cd, Sn-Pb-Cu, Sn-Pb-Ag, Pb-Ag, and Pb-Ag-Sn; and lead-free solders such as Sn-Sb, Sn-Bi, Sn-Cu, Sn-Cu-Ag, Sn-In, Sn-In-Ag-Bi, Sn-Ag, Sn-Ag-Cu, Sn-Ag-Bi-Cu, Sn-Zn, and Sn-Bi-Zn.

[0054] The low-melting-point material is applied to at least the exposed portion of the lead terminal as a layer or film having a thickness of, for example, 5 μm to 20 μm. When the low-melting-point material is Sn or solder, for example, a plating layer of the low-melting-point material having the above thickness may be formed on at least the exposed portion of the lead terminal. The thickness of the low-melting-point material on the main surface of the exposed portion may be calculated as the average value of measurements taken at any five points, for example.

[0055] (exterior body) The exterior casing seals the capacitor element, the embedded portion of the anode lead terminal, and the embedded portion of the cathode lead terminal so that the capacitor element is not exposed to the outside. The exterior casing also insulates the anode lead terminal from the cathode lead terminal. The exterior casing may be made of a known material and configuration used in solid electrolytic capacitors. The exterior casing may be formed using, for example, an insulating thermosetting resin composition. The thermosetting resin composition includes a thermosetting resin and may also include additives. The additive may also include an inorganic filler. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethanes, polyimides, and unsaturated polyesters. The thermosetting resin composition is formed by a molding method such as transfer molding so as to seal the capacitor element, the embedded portion of the anode lead terminal, and the embedded portion of the cathode lead terminal.

[0056] (Capacitor element) The capacitor element has an anode portion and a cathode portion. A dielectric layer is interposed between the anode portion and the cathode portion. The anode portion includes an anode body. The cathode portion is provided so as to cover the dielectric layer formed on at least a portion of the surface of the anode body.

[0057] The anode body includes a metal foil containing a valve metal or a porous sintered body containing a valve metal. The anode body including the metal foil is, for example, sheet-shaped or flat. The surface of the metal foil is usually roughened. The anode body including the porous sintered body is, but is not particularly limited to, generally rectangular or prismatic. The anode body including the porous sintered body may have an anode wire embedded in the porous sintered body. The anode wire is used for connection to an anode lead terminal. The thickness of the anode body including the metal foil is, but is not particularly limited to, for example, 15 μm or more and 300 μm or less. The thickness of the anode body including the porous sintered body is, but is not particularly limited to, for example, 15 μm or more and 5 mm or less.

[0058] Valve metals include aluminum, tantalum, titanium, niobium, etc. The anode body may contain one or more valve metals.

[0059] (dielectric layer) The dielectric layer is formed, for example, by anodizing the surface of the anode body using a chemical conversion treatment or the like. Therefore, the dielectric layer may contain an oxide of a valve metal. For example, when aluminum is used as the valve metal, the dielectric layer may contain Al2O3. However, the dielectric layer is not particularly limited and may be made of any material that functions as a dielectric.

[0060] (cathode) The cathode section includes, for example, a solid electrolyte layer covering at least a portion of the dielectric layer and a cathode extraction layer covering at least a portion of the solid electrolyte layer. The solid electrolyte layer can be formed of, for example, a manganese compound, a conductive polymer, or the like.

[0061] Examples of conductive polymers that can be used include polypyrrole, polyaniline, polythiophene, polyacetylene, and derivatives thereof. A solid electrolyte layer containing a conductive polymer can be formed, for example, by chemical polymerization and / or electrolytic polymerization of raw material monomers on a dielectric layer. Alternatively, the conductive layer can be formed by applying a solution in which the conductive polymer is dissolved or a dispersion in which the conductive polymer is dispersed to the dielectric layer.

[0062] The cathode extraction layer is formed so as to cover at least a portion of the solid electrolyte layer. The cathode extraction layer has, for example, a carbon layer and a metal paste layer (e.g., a silver paste layer) formed on the surface of the carbon layer. The carbon layer is made of a composition containing a conductive carbon material such as graphite. The metal paste layer is made of a composition containing silver particles and a binder resin. However, the configuration of the cathode extraction layer is not particularly limited as long as it has a current collecting function.

[0063] An example of a solid electrolytic capacitor 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 example electrolytic capacitor described below. Furthermore, the components of the example 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. Furthermore, in the embodiment described below, components that are not essential for the electrolytic capacitor of the present disclosure may be omitted.

[0064] The embedded portion of the cathode lead terminal may have a guide portion that rises from the cathode connecting surface and regulates the position of the capacitor element. For example, at least one guide portion may be provided on each end of the cathode connecting surface in a direction perpendicular to the direction from the anode lead terminal to the cathode lead terminal.

[0065] When the solid electrolytic capacitor has a plurality of stacked capacitor elements, the embedded portion of at least one of the anode lead terminal and the cathode lead terminal may have an element mounting portion adjacent to one of the outermost capacitor elements. In this case, the guide portion may be provided so as to rise only on one of the principal surface A and principal surface B of the embedded portion, on which the capacitor element is mounted.

[0066] 1 is a cross-sectional view schematically illustrating the configuration of an example of a solid electrolytic capacitor 100 according to the present disclosure. The solid electrolytic capacitor 100 includes at least one capacitor element 110 including an anode portion 111 and a cathode portion 112, an anode lead terminal 120 having an anode connection surface 121A electrically connected to the anode portion 111, a cathode lead terminal 130 having a cathode connection surface electrically connected to the cathode portion 112, and an exterior body 140 that covers the capacitor element 110. The cathode lead terminal 130 has an element mounting portion 131A adjacent to one of the outermost capacitor elements.

[0067] The solid electrolytic capacitor 100 has a plurality of stacked capacitor elements 110. The anode section 111 has an anode body including a metal foil with a roughened surface, and the metal foil includes a valve metal. Thus, the anode section 111 is in the form of a sheet or a flat plate.

[0068] The anode lead terminal 120 and the cathode lead terminal 130 each have a main surface having an anode connecting surface 121A and a cathode connecting surface, and a side surface intersecting the main surface. The anode lead terminal 120 includes an embedded portion 120A embedded in the exterior body 140 and an exposed portion 120B exposed from the exterior body 140. The cathode lead terminal 130 includes an embedded portion 130A embedded in the exterior body 140 and an exposed portion 130B exposed from the exterior body 140. The anode lead terminal 120 and the cathode lead terminal 130 are both extended to the outside from the side surfaces of the solid electrolytic capacitor.

[0069] The main surface of the exposed portion of at least one of the anode lead terminal (120) and the cathode lead terminal (130) is covered with a low-melting-point material.

[0070] Embedded portion 130A of cathode lead terminal 130 has element mounting portion 131A adjacent to one of the outermost capacitor elements 110. At least a portion of element mounting portion 131A is a cathode connecting surface. Element mounting portion 131A has guide portion 132A that rises from the cathode connecting surface and regulates the position of capacitor element 110.

[0071] Anode connection surface 121A of embedded portion 120A of anode lead terminal 120 is connected to anode portion 111 by, for example, welding. Cathode connection surface (element mounting portion 131A) of embedded portion 130A of cathode lead terminal 130 is connected to cathode portion 112 via, for example, a conductive adhesive.

[0072] One guide portion 132A is provided on each end of the cathode connecting surface in a direction perpendicular to the direction from the anode lead terminal 120 toward the cathode lead terminal 130. The guide portion 132A is provided so as to rise only on one main surface side on which the capacitor element 110 is mounted.

[0073] Fig. 2 is a perspective view schematically showing the structure of a main part of solid electrolytic capacitor 100 shown in Fig. 1. Fig. 3 is a plan view (A) and a side view (B) schematically showing cathode lead terminal 130, a main part of solid electrolytic capacitor 100 shown in Fig. 2. In Fig. 2, embedded portion 130A of cathode lead terminal 130 embedded in exterior body 140 is indicated by a dashed line.

[0074] The side surface of the embedded portion 130A of the cathode lead terminal 130 is divided into a first side surface region 133A that is more than 0.36 mm away from the boundary 130C between the embedded portion 130A and the exposed portion 130B, and a second side surface region 134A that is 0.36 mm or less away from the boundary 130C.

[0075] The main surface of the buried portion 130A of the cathode lead terminal 130 is divided into a first main surface region 135A that is more than 0.15 mm away from a boundary 130C between the buried portion 130A and the exposed portion 130B, and a second main surface region 136A that is 0.15 mm or less away from the boundary 130C.

[0076] It is sufficient if the first side surface region 133A is not covered with the low melting point material, but it is preferable that neither the first side surface region 133A nor the first main surface region 135A is covered with the low melting point material.

[0077] Although it is acceptable for both the second side surface region 134A and the second main surface region 136A to be covered with a low-melting point material, from the standpoint of reliably improving the heat resistance of the solid electrolytic capacitor, it is desirable that at least one of the second side surface region 134A and the second main surface region 136A is not covered with a low-melting point material, and it is more desirable that both the second side surface region 134A and the second main surface region 136A are not covered with a low-melting point material.

[0078] Although the side surface 137B of the exposed portion 130B of the cathode lead terminal 130 may be covered with a low-melting-point material, it is preferable that the side surface 137B is not covered with a low-melting-point material, which can further reliably improve the heat resistance of the solid electrolytic capacitor.

[0079] It is sufficient that at least the region of main surface 138B of exposed portion 130B of cathode lead terminal 130 that is connected to a connection electrode of a component such as a circuit board is covered with a low-melting-point material. From the viewpoints of easy mounting on a board and strong bonding with the connection electrode, it is desirable that 90% or more (e.g., 100%) of main surface 138B be covered with a low-melting-point material.

[0080] When the solid electrolytic capacitor has a plurality of stacked capacitor elements, the embedded portion of at least one of the anode lead terminal and the cathode lead terminal has a sandwiched portion interposed between two adjacent first and second elements selected from the plurality of capacitor elements. In this case, the guide portions may be provided so as to rise up on both the main surface A side and the main surface B side of the embedded portion.

[0081] FIG. 4 is a cross-sectional view schematically illustrating the configuration of another solid electrolytic capacitor 100A according to the present disclosure. The solid electrolytic capacitor 100A has a capacitor element 110 similar to that of the solid electrolytic capacitor 100. However, the structures of the anode lead terminal 120 and the cathode lead terminal 130 differ from those of the solid electrolytic capacitor 100. The anode connection surface 121A of the embedded portion 120A of the anode lead terminal 120 is electrically connected to the anode portion 111 through physical contact. In this case, the anode portions 111 of multiple capacitor elements are stacked and sandwiched between parts of the embedded portion 120A of the anode lead terminal 120 and crimped to the anode connection surface 121A. The anode lead terminal 120 and the cathode lead terminal 130 are both extended from the bottom surface (the lower side in FIG. 4) of the solid electrolytic capacitor.

[0082] 5 is a cross-sectional view schematically illustrating the configuration of yet another solid electrolytic capacitor 100B according to the present disclosure. The solid electrolytic capacitor 100B has a capacitor element 110 similar to that of the solid electrolytic capacitor 100. However, the structures of the anode lead terminal 120 and the cathode lead terminal 130 differ from those of the solid electrolytic capacitor 100. The embedded portion 120A of the anode lead terminal 120 has a sandwiched portion 121A interposed between two adjacent elements, a first element 110A and a second element 110B, selected from a plurality of capacitor elements. The embedded portion 130A of the cathode lead terminal 130 has a sandwiched portion 131A interposed between the first element 110A and the second element 110B.

[0083] At least a part of held portion 121A is an anode connection surface. The anode connection surface (held portion 121A) is connected to anode portion 111 by, for example, welding. At least a part of held portion 131A is a cathode connection surface. The cathode connection surface (held portion 131A) is connected to cathode portion 112 by, for example, a conductive adhesive.

[0084] Two guide portions 132A are provided on each end of the cathode connecting surface in a direction perpendicular to the direction from the anode lead terminal 120 toward the cathode lead terminal 130. The guide portions 132A are provided so as to rise on both the main surface sides (main surface A side and main surface B side) on which the capacitor element 110 is mounted.

[0085] [Example] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0086] Examples 1 and 2 and Comparative Examples 1 and 2 A solid electrolytic capacitor having a laminate in which six capacitor elements were stacked was fabricated in the following manner.

[0087] (1) Fabrication of capacitor elements An aluminum foil (thickness: 100 μm) was prepared as a substrate, and the surface of the aluminum foil was etched to obtain an anode body with a porous portion (thickness: 35 μm on one main surface of the aluminum foil and 35 μm on the other main surface). The anode body was immersed in a 0.3% by mass phosphoric acid solution (liquid temperature: 70°C) and a DC voltage of 10 V was applied for 20 minutes to form a dielectric layer containing aluminum oxide (Al2O3) on the surface of the anode body.

[0088] The anode body was divided into an anode portion, a cathode forming portion, and a separation portion between them, and part of the separation portion was compressed by press working to form a thin portion (thickness 35 μm). An insulating resist tape (separation member) was attached to the thin portion.

[0089] The anode body on which the dielectric layer was formed was immersed in a liquid composition containing a conductive material to form a precoat layer.

[0090] A polymerization solution containing pyrrole (monomer of conductive polymer), naphthalenesulfonic acid (dopant), and water was prepared. The anode body with the dielectric layer and precoat layer formed thereon was immersed in the polymerization solution, and electrolytic polymerization was carried out at an applied voltage of 3 V to form a solid electrolyte layer.

[0091] A dispersion of graphite particles dispersed in water was applied to the solid electrolyte layer and then dried to form a carbon layer on the surface of the solid electrolyte layer. Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer, and then heated to harden the binder resin, forming a metal paste layer (silver paste layer, thickness 15 μm). In this way, a cathode extraction layer composed of a carbon layer and a metal paste layer was formed, and a capacitor element was obtained.

[0092] The six obtained capacitor elements were stacked with conductive paste interposed therebetween, and the anode portions were joined together by laser welding to obtain a laminate.

[0093] (2) Anode lead terminal and cathode lead terminal Copper foil (thickness: 100 μm) was prepared for forming the anode and cathode lead terminals. The copper foil was then processed into a lead frame of a predetermined shape. Here, the processed copper foil before being separated into individual lead terminals is referred to as the lead frame. The lead frame is an assembly of anode and cathode lead terminals of multiple solid electrolytic capacitors. A laminate was mounted in the embedded portion of the cathode lead terminal, and an element mounting portion was formed adjacent to one of the outermost capacitor elements.

[0094] The portions of the lead frame that would become the embedded anode and cathode lead terminals were shielded with masking tape. A low-melting-point Sn plating layer (10 μm thick) was then formed on the exposed portions. The portions that would become the embedded anode lead terminals were carefully masked, not only on the main surface but also on the side surfaces, to prevent the Sn plating from penetrating into the second side region. The portions that would become the embedded cathode lead terminals were masked in a standard manner, without careful masking on the side surfaces. The distances (Cd1, Cd2) from the boundary between the embedded and exposed portions of the cathode lead terminal to the embedded portion (Cd1, Cd2) are shown in Table 1. Next, the portions that would become the embedded anode and cathode lead terminals were roughened using sandblasting. The exposed portions of the anode and cathode lead terminals were not roughened. The developed interface area ratio (Sdr) of the roughened surface, measured in accordance with ISO 25178, was 0.4.

[0095] In each table, the symbols represent the following. Note that each distance was measured by observing the cross section of the solid electrolytic capacitor with an electron microscope. In each table, negative values ​​for Cd1, Cd2, Ad1, and Ad2 indicate that the Sn did not reach the boundary between the buried and exposed portions, and the distance from the boundary to the Sn covering the exposed portion.

[0096] Cd1: The penetration distance of Sn from the boundary between the buried and exposed parts on the main surface of the buried part of the cathode lead terminal

[0097] Cd2: The penetration distance of Sn from the boundary between the buried and exposed parts on the side of the buried part of the cathode lead terminal

[0098] Ad1: The penetration distance of Sn from the boundary between the buried part and the exposed part on the main surface of the buried part of the anode lead terminal

[0099] Ad2: The penetration distance of Sn from the boundary between the buried and exposed parts on the side of the buried part of the anode lead terminal

[0100] Sdr: developed interface area ratio

[0101] Rhm: Airtightness defect rate

[0102] Resr:ESR defective rate

[0103] (3) Assembly of solid electrolytic capacitors The laminate of capacitor elements was connected to the element mounting portion where the cathode lead terminal was embedded. At this time, a conductive paste was interposed between the cathode portion of one of the capacitor elements arranged on the outermost side of the laminate and the cathode connection surface of the element mounting portion. Meanwhile, an anode lead terminal was connected to the anode portion of the laminate of capacitor elements.

[0104] Next, the capacitor element, the embedded portion of the anode lead terminal, and the embedded portion of the cathode lead terminal were sealed by transfer molding. In this way, 100 units each of solid electrolytic capacitors A1, A2, B1, and B2 (rated voltage 2.5 V) of the type generally shown in Figure 1 were produced.

[0105] [evaluation] (1) Airtightness defect rate Solid electrolytic capacitors A1, A2, B1, and B2 are IPC / JEDEC J-STD-0 The capacitors were heated under the same temperature conditions as in the reflow process in accordance with 20D (maximum temperature 260°C for 30 seconds). The airtightness was then evaluated using a gross leak test. Capacitors whose pressure change was greater than the specified value were deemed to have poor airtightness, and the failure rate (%) was calculated. The results are shown in Table 1.

[0106] (2)ESR defective rate The initial ESR values ​​X0 (mΩ) of solid electrolytic capacitors A1, A2, B1, and B2 at a frequency of 100 kHz were measured using a four-terminal LCR meter at 20°C. Next, the rated voltage was applied to the solid electrolytic capacitors at 125°C for 1,000 hours (reliability test). The ESR values ​​(X1) (mΩ) were then measured using the same method as above. If X1 was more than twice X0, the capacitor was deemed defective, and the failure rate (%) was calculated. The results are shown in Table 1.

[0107] [Table 1]

[0108] Examples 3 to 5 The portions where the cathode lead terminals would be embedded were carefully masked on both the main surface and the side surfaces, with Cd1 and Cd2 set as shown in Table 2. In addition, for solid electrolytic capacitor A5 of Example 5, the conditions for the sandblasting method were changed so that the developed area ratio Sdr of the lead terminals was set to 0.6. Except for the above, solid electrolytic capacitors A3 to A5 were fabricated and evaluated in the same manner as in Example 1. Results The results are shown in Table 2.

[0109] [Table 2]

[0110] Examples 6 to 8 In the production of the lead frame, before processing the copper foil into a lead frame of a predetermined shape, the portions that would become the embedded portions of the anode lead terminal and the cathode lead terminal were shielded with masking tape, and then a Sn plating layer was formed on the exposed portions. The copper foil was then processed into a lead frame of a predetermined shape. The side surfaces of the portions that would become the embedded portions of the anode lead terminal and the cathode lead terminal were not covered with Sn at all, since these were cut surfaces formed after the Sn plating layer was formed on the copper foil. Except for the above, solid electrolytic capacitors A6 to A8 were produced and evaluated in the same manner as in Examples 3 to 5. The results are shown in Table 3.

[0111] [Table 3]

[0112] Examples 9 and 10 and Comparative Examples 3 to 5 In Comparative Examples 3 and 4, the portion where the cathode lead terminal was to be embedded was masked in a normal manner without strict masking of the side surfaces, and Cd1 and Cd2 were changed as shown in Table 4.

[0113] In Examples 9 and 10 and Comparative Example 5, the portion where the cathode lead terminal was to be embedded was strictly masked not only on the main surface but also on the side surface, and Cd1 and Cd2 were changed as shown in Table 4.

[0114] Except for the above, solid electrolytic capacitors A9, A10, and B3 to B5 were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0115] [Table 4]

[0116] Example 11 and Comparative Example 6 Cd1 and Cd2 were changed as shown in Table 5. In addition, the solid electrolytic capacitor of Comparative Example 7 In Example B7, the conditions of the sandblasting method were changed to set the developed area ratio Sdr of the lead terminal to 0.3. Except for the above, solid electrolytic capacitors A11 and B6 were fabricated and evaluated in the same manner as in Example 6. The results are shown in Table 5.

[0117] [Table 5]

[0118] Examples 12 and 13 and Comparative Examples 7 and 8 Contrary to Examples 1 and 2 and Comparative Examples 1 and 2, the portion of the cathode lead terminal to be embedded was carefully masked not only on the main surface but also on the side surfaces to prevent Sn plating from penetrating into the second side surface region. On the other hand, the portion of the anode lead terminal to be embedded was masked normally, without carefully masking the side surfaces. Except for the above, solid electrolytic capacitors A12, A13, B7, and B8 were fabricated and evaluated in the same manner as in Examples 1 and 2 and Comparative Examples 1 and 2. The results are shown in Table 6.

[0119] [Table 6]

[0120] Examples 14 to 16 The area where the anode lead terminal would be embedded was carefully masked on both the main surface and the side surface, with Ad1 and Ad2 as shown in Table 7. Furthermore, for solid electrolytic capacitor A16 of Example 16, the sandblasting conditions were changed to set the lead terminal developed area ratio Sdr to 0.6. Except for the above, solid electrolytic capacitors A14 to A16 were fabricated and evaluated in the same manner as in Example A12. The results are shown in Table 7.

[0121] [Table 7]

[0122] Examples 17 to 19 In the lead frame production, before processing the copper foil into a lead frame of a predetermined shape, the portions that would become the embedded portions of the anode lead terminal and the cathode lead terminal were shielded with masking tape, and then a Sn plating layer was formed on the exposed portions, and then the copper foil was processed into a lead frame of a predetermined shape. Except for the above, solid electrolytic capacitors A17 to A19 were produced and evaluated in the same manner as in Examples 14 to 16. The results are shown in Table 8.

[0123] [Table 8]

[0124] Examples 20 and 21 and Comparative Examples 9 to 10 In Comparative Examples 9 and 10, the portion where the anode lead terminal was to be embedded was masked in a normal manner without strict masking of the side surfaces, and Ad1 and Ad2 were changed as shown in Table 9.

[0125] In Examples 20 and 21, the portion where the anode lead terminal was to be embedded was strictly masked not only on the main surface but also on the side surface, and Ad1 and Ad2 were changed as shown in Table 9.

[0126] Except for the above, solid electrolytic capacitors A20, 21, B9, and B10 were fabricated and evaluated in the same manner as in Example 11. The results are shown in Table 9.

[0127] [Table 9]

[0128] Example 22 and Comparative Example 11 Ad1 and Ad2 were changed as shown in Table 10. For solid electrolytic capacitor B11 of Comparative Example 11, the sandblasting conditions were changed to set the lead terminal developed area ratio Sdr to 0.3. Other than the above, solid electrolytic capacitors A22 and B11 were fabricated and evaluated in the same manner as in Example 17. The results are shown in Table 10.

[0129] [Table 10] [Industrial Applicability]

[0130] The solid electrolytic capacitor according to the present disclosure has high heat resistance, and even when exposed to high temperatures, the inside of the solid electrolytic capacitor is less likely to be in communication with the external environment, and deterioration of the solid electrolyte layer is suppressed, so that the solid electrolytic capacitor can be used in a variety of applications where heat resistance is required. [Explanation of symbols]

[0131] 100, 100A, 100B solid electrolytic capacitors 110 Capacitor element 110A 1st element 110B Second element 111 Anode part 112 cathode part 120 Anode lead terminal 120A Anode lead terminal buried part 120B Exposed part of anode lead terminal 121A Anode connection surface or clamped part of buried part of anode lead terminal 130 Cathode lead terminal 130A Cathode lead terminal buried part 130B Exposed part of cathode lead terminal 130C Cathode lead terminal boundary 131A The clamped part of the element mounting part or the buried part of the cathode lead terminal 132A Guide part 133A First side area of ​​the buried portion of the cathode lead terminal 134A Second side area of ​​the buried portion of the cathode lead terminal 135A First main surface area of ​​the buried portion of the cathode lead terminal 136A Second main surface area of ​​the buried portion of the cathode lead terminal 137B Side of exposed part of cathode lead terminal 138B Main surface of exposed part of cathode lead terminal 140 Exterior body

Claims

1. at least one capacitor element including an anode portion and a cathode portion; an anode lead terminal having an anode connection surface electrically connected to the anode portion; a cathode lead terminal having a cathode connection surface electrically connected to the cathode portion; an exterior body that covers the capacitor element, the anode lead terminal and the cathode lead terminal each have a main surface having the anode connecting surface and the cathode connecting surface, and a side surface intersecting the main surface, and each include an embedded portion embedded in the exterior body and an exposed portion exposed from the exterior body, In at least one lead terminal selected from the anode lead terminal and the cathode lead terminal, at least a portion of the main surface of the exposed portion is covered with a low-melting point material; and A solid electrolytic capacitor, wherein at least a first side region of the side surface of the embedded portion that is more than 0.36 mm away from the boundary between the embedded portion and the exposed portion is not covered with the low melting point material.

2. 2. The solid electrolytic capacitor according to claim 1, wherein at least a first main surface region of the main surface of the embedded portion that is more than 0.15 mm away from a boundary between the embedded portion and the exposed portion is not covered with the low melting point material.

3. 3. The solid electrolytic capacitor according to claim 1, wherein the side surface of the exposed portion of the at least one lead terminal is not covered with the low-melting-point material.

4. 4. The solid electrolytic capacitor according to claim 1, wherein the main surface of the at least one lead terminal is roughened.

5. 5. The solid electrolytic capacitor according to claim 4, wherein the developed interface area ratio of the roughened main surface is 0.4 or more.

6. 6. The solid electrolytic capacitor according to claim 1, wherein the low-melting-point material has a melting point of 180°C to 240°C.

7. 7. The solid electrolytic capacitor according to claim 6, wherein the low melting point material is tin or solder.

8. 8. The solid electrolytic capacitor according to claim 1, wherein the embedded portion of the cathode lead terminal has a guide portion that rises from the cathode connection surface and regulates the position of the capacitor element.

9. a plurality of the capacitor elements stacked one on top of the other; At least one of the anode lead terminal and the cathode lead terminal, The solid electrolytic capacitor according to any one of claims 1 to 8, wherein the embedded portion has a sandwiched portion interposed between two adjacent first and second elements selected from the plurality of capacitor elements.

10. a plurality of the capacitor elements stacked one on top of the other; 9. The solid electrolytic capacitor according to claim 1, wherein the embedded portion of the cathode lead terminal has an element mounting portion adjacent to one of the outermost capacitor elements.

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