Solid electrolytic capacitor

Abstract

A solid electrolytic capacitor includes: an element stack, an anode terminal, a cathode terminal, and an outer member covering the element stack, the anode terminal, and the cathode terminal in a state where a part of each of the anode terminal and the cathode terminal is exposed. The element stack has a plurality of capacitor elements stacked with each other, and a conductive material interposed between adjacent two capacitor elements among the plurality of capacitor elements. Each of the plurality of capacitor elements includes an anode portion and a cathode portion, and the conductive material is disposed on the cathode portion. The anode terminal is connected to the anode portion. The cathode terminal is connected to the cathode portion via a conductive paste. In addition, the cathode terminal has an opposing surface opposing a front end of the element stack with a gap therebetween, and a seal material is filled in at least a part of the gap.

Description

Technical Field

[0001] This invention relates to solid electrolytic capacitors. Background Technology

[0002] Previously, solid electrolytic capacitors were known to have multiple capacitor elements, each with a cathode portion, cathode terminals connected to the cathode portions via a conductive paste, and an outer casing covering them (e.g., Patent Document 1). In Patent Document 1, by connecting the cathode portions of the multiple capacitor elements with a conductive film, the ESR (Equivalent Series Resistance) of the solid electrolytic capacitor was reduced.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-091444 Summary of the Invention

[0006] One aspect of the present invention relates to a solid electrolytic capacitor. This solid electrolytic capacitor includes: an element stack, an anode terminal, a cathode terminal, and an outer casing covering the element stack, the anode terminal, and the cathode terminal with portions of each of the anode and cathode terminals exposed. The element stack has a plurality of capacitor elements stacked on top of each other, and a conductive material between adjacent capacitor elements. Each of the plurality of capacitor elements includes an anode portion and a cathode portion, and the conductive material is disposed on the cathode portion. The anode terminal is connected to the anode portion. The cathode terminal is connected to the cathode portion via a conductive paste. Furthermore, the cathode terminal has a facing surface that faces the front end of the element stack across a gap, and at least a portion of the gap is filled with a sealing material.

[0007] According to the present invention, a solid electrolytic capacitor with high airtightness can be obtained. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view showing the structure of the solid electrolytic capacitor of the present invention.

[0009] Figure 2 This is a cross-sectional view showing the configuration of the capacitor element of the present invention.

[0010] Figure 3 This is a cross-sectional view showing another configuration of the solid electrolytic capacitor of the present invention.

[0011] Figure 4 This is a cross-sectional view showing another configuration of the solid electrolytic capacitor of the present invention. Detailed Implementation

[0012] Before describing the embodiments, the problems in the prior art are briefly illustrated below. Solid electrolytic capacitors, in order to avoid the degradation of the characteristics of multiple capacitor elements, require a structure with excellent hermeticity. However, in the past, there has been insufficient research into improving the hermeticity of the structure of solid electrolytic capacitors. Under these circumstances, the present invention provides a solid electrolytic capacitor with high hermeticity.

[0013] Embodiments of the solid electrolytic capacitor of the present invention will be described below by way of example. However, the present invention is not limited to the examples described below. In the following description, specific values ​​and materials are illustrated, but other values ​​and materials may be applied as long as the effects of the present invention can be obtained.

[0014] (Solid electrolytic capacitor)

[0015] The solid electrolytic capacitor of the present invention comprises an element stack, an anode terminal, a cathode terminal, and an external component. These components will be described below.

[0016] (Component stack-up)

[0017] The component stack comprises multiple capacitor elements stacked on top of each other, and conductive material. Each capacitor element includes an anode and a cathode. The anodes of the multiple capacitor elements overlap and are electrically connected to each other. The multiple anodes can be joined together, for example, by welding.

[0018] A conductive material is placed between the cathode portions of two adjacent capacitor elements within a plurality of capacitor elements. The conductive material can electrically connect and integrate the cathode portions of multiple overlapping capacitor elements. The conductive material can be, for example, a paste containing metal or a film containing metal.

[0019] (Anode terminal)

[0020] The anode terminal is connected to the anode portion of the capacitor element. The anode terminal may be made of, for example, copper or a copper alloy. The anode terminal is formed, for example, by punching a metal foil into a metal frame of a predetermined shape and then bending the metal frame.

[0021] (Cathode terminal)

[0022] The cathode terminal is connected to the cathode portion of the capacitor element via a conductive paste. The cathode terminal may be made of, for example, copper or a copper alloy. The cathode terminal has a facing surface S1 that opposes the front end of the element stack across a gap G. At least a portion of the gap G is filled with a sealing material.

[0023] (Sealing material)

[0024] The sealing material contains resin as an essential component and filler as an optional component. Ceramic particles, such as inorganic oxides, are preferably used as fillers. The sealing material is less permeable to air than conductive materials and conductive pastes. By filling at least a portion of the gap G with sealing material, at least a portion of the conductive material and conductive paste are covered by the sealing material, thus making it difficult for external air to reach the capacitor element. Furthermore, air moves along the interface where the cathode terminal separates from the outer casing. Such separation occurs, for example, when the circuit components of a solid electrolytic capacitor are heated by reflow soldering or similar processes, causing moisture present inside or around the capacitor element to vaporize and the outer casing to expand in volume. On the other hand, when the gap G is filled with sealing material, air is prevented from reaching the capacitor element if separation between the cathode terminal and the sealing material does not occur. Even if separation between the cathode terminal and the sealing material occurs, by adding the interface between the cathode terminal and the sealing material along the path of air to the capacitor element, the path of air from the outside to the capacitor element is lengthened. Through these measures, the airtightness of the solid electrolytic capacitor can be improved.

[0025] The sealing material may contain a curing catalyst at a concentration of 1% by mass or less. The curing catalyst may include both phosphorus-based and nitrogen-based catalysts. The concentration of nitrogen-based catalyst may be less than that of phosphorus-based catalyst. Alternatively, the material may contain only a phosphorus-based catalyst. The curing catalyst may be latent.

[0026] By incorporating a curing catalyst into the sealing material, the viscosity of the sealing material can be maintained at a low level for a certain period of time during molding, thereby improving the adhesion between the cathode terminal and the sealing material and suppressing delamination. This further enhances the hermeticity of solid electrolytic capacitors.

[0027] In this specification, "front end of the element stack" refers to the cathode-side end of the element stack. Specifically, the element stack has two ends: an anode-side end and a cathode-side end. When referred to as "front end" in this specification, it refers to the latter.

[0028] (External components)

[0029] The outer casing covers the element stack, anode terminals, and cathode terminals with portions of both terminals exposed. The outer casing can be made of resin material or may contain filler. Ceramic particles, such as inorganic oxides, are preferably used as filler for the outer casing. For example, the composition of the outer casing can be the same as that of the sealing material filling the aforementioned gaps.

[0030] A portion of the outer casing can constitute a sealing material. In this case, it is preferable that the outer casing and the sealing material are integrally formed from the same molding material. As the molding material, a thermosetting resin composition comprising resin components and fillers is preferred. The resin components comprise a main agent and a curing agent. By integrally forming the outer casing and the sealing material, the solid electrolytic capacitor of the present invention can be easily manufactured, and its manufacturing cost can be suppressed. It should be noted that when the outer casing and the sealing material are integrally formed in the finished solid electrolytic capacitor, even if the constituent materials of the outer casing and the sealing material are different, the sealing material is also part of the outer casing.

[0031] A portion of the external component may not constitute a sealing material. In other words, the sealing material may also be separately constituted from the external component. Therefore, the material of the sealing material filling the gap can be appropriately selected.

[0032] Hereinafter, the gap G between the cathode terminal and the front end of the element stack is divided into (a) the gap between the capacitor element closest to the connection point of the cathode terminal and the element stack (hereinafter also referred to as the connection-side capacitor element) and the cathode terminal (hereinafter also referred to as gap A), and (b) the gap between all capacitor elements other than the connection-side capacitor element and the cathode terminal (hereinafter also referred to as gap B).

[0033] The conductive paste may not be present in the gaps (gap B) between the capacitor elements and the opposing surfaces S1 of the cathode terminals, except for the capacitor elements on the connection side. The conductive paste has lower strength than the sealing material and allows air to permeate more easily. Therefore, it is desirable that the gap B is free of conductive paste and filled with sealing material. This increases the bonding distance between the cathode terminal and the resin material, making it less likely for air to reach the capacitor elements from the outside, thus further improving the airtightness of the solid electrolytic capacitor. It should be noted that when the gap B is free of conductive paste and filled with sealing material, a small void V may form between the sealing material and the conductive paste. Such a void V can form in the gap A where the conductive paste can penetrate. However, since the void V is small enough, it will not significantly affect the airtightness of the solid electrolytic capacitor. In the cross-section of the gap G in the direction D2 opposite to the opposing surface S1 at the front end of the element stack, the area of ​​the void V can be, for example, 16000 μm². 2 the following.

[0034] The size of the gap G between the front end of the element stack and the opposing surface S1 in the opposing direction D2 is preferably 40 μm or more. Furthermore, the size of the gap G is more preferably 60 μm or more. By ensuring that the gap G is 40 μm or more, the strength of the sealing material is maintained, and cracks are less likely to form, thus ensuring the airtightness of the solid electrolytic capacitor.

[0035] The conductive material can remain in contact with the opposing surface S1 of the cathode terminal in the gap B between all capacitor elements except the capacitor element on the connection side. The conductive material is less strong than the sealing material and allows air to pass through easily. If the conductive material were in contact with the cathode terminal in the gap B, air could sometimes reach the capacitor element via the conductive material. Therefore, it is desirable that the conductive material not contact the opposing surface S1 of the cathode terminal in the gap B.

[0036] The sealing material only needs to fill the gap B between all capacitor elements except the connecting capacitor element and the opposing surface S1 of the cathode terminal, or it can fill at least a portion of the gap A. In this case, it is desirable that the sealing material in the gap B extends continuously in the stacking direction D1 of the multiple capacitor elements. This significantly reduces the contact between the conductive material and the opposing surface S1 of the cathode terminal in the gap B. It is desirable that the sealing material continuously fills the gap B along the opposing surface S1 in a manner that contacts the opposing surface S1. This results in a sufficiently long engagement distance between the cathode terminal and the external component, thereby further improving the hermeticity of the solid electrolytic capacitor.

[0037] It should be noted that conductive paste may also be present in the gap A between the capacitor element on the connection side and the opposing surface S1 of the cathode terminal. In this case, it is preferable that the entire portion of the gap G where there is no conductive paste is filled with sealing material. However, it is also possible for a small gap V to be formed between the sealing material and the conductive paste, and even in this case, it is defined as the entire portion of the gap G where there is no conductive paste being filled with sealing material.

[0038] The opposing surface S1 of the cathode terminal can be inclined relative to the stacking direction D1, with the gap G increasing as it moves upward from the connection point between the cathode terminal and the element stack. The angle between the opposing surface S1 of the cathode terminal and the stacking direction D1 of the multiple capacitor elements can be greater than 0° and less than 30°. If the angle between the opposing surface S1 of the cathode terminal and the stacking direction D1 is greater than 30°, the volume occupied by the cathode terminal in the solid electrolytic capacitor increases. Therefore, without changing the overall size of the solid electrolytic capacitor, the element stack (each capacitor element) must be made smaller, resulting in a smaller capacitance of the solid electrolytic capacitor, which is therefore not preferable.

[0039] By tilting the opposing surface S1 of the cathode terminal relative to the stacking direction D1 of the multiple capacitor elements, contact between the front end of the element stack and the opposing surface S1 of the cathode terminal can be prevented when the capacitor elements are stacked from the connection portion of the cathode terminal. This ensures a gap is formed between the front end of the element stack and the cathode terminal, thus further improving the hermeticity of the solid electrolytic capacitor. Additionally, it improves the filling ability of the sealing material into the gap G.

[0040] In any of the above embodiments, the capacitor element closest to the connection point of the cathode terminal and the element stack is preferably the capacitor element furthest from the cathode terminal exposed from the outer casing. This maximizes the air path from the exposed portion to the capacitor element, further improving the airtightness of the solid electrolytic capacitor.

[0041] Sealing material can be filled throughout gap G (i.e., both gap A and gap B). This further extends the air path from the cathode terminal exposed on the outer component to the capacitor element, thereby further improving the airtightness of the solid electrolytic capacitor.

[0042] When the sealing material contains filler, the size of the gap G between the front end of the element stack and the opposing surface S1 in the opposing direction D2 can be larger than the maximum size of the filler. Sufficient filler readily enters the gap G, improving the strength of the sealing material present in the gap G. Therefore, cracking of the sealing material is less likely to occur in the opposing direction D2, and air bypass pathways are less likely to form. Furthermore, the shrinkage rate of the sealing material with filler entering the gap G is reduced, suppressing the peeling of the sealing material from the cathode terminal. Therefore, the hermeticity of the solid electrolytic capacitor can be further improved. It is desirable for the filler to fill the entire gap B. That is, when drawing a straight line along the aforementioned opposing direction D2, it is desirable that a straight line cannot be drawn without crossing the particles of the filler.

[0043] Here, "maximum size of the filler" refers to the particle size of the largest particle among the filler particles contained in the sealing material. For example, when the particle size of the filler contained in the sealing material is in the range of 5 μm or more and 60 μm or less, the maximum size of the filler is 60 μm. The maximum size of the filler is obtained as the maximum value of the diameter of an equivalent circle, which is formed by taking a cross-section of the sealing material and selecting any 100 particles, such that the equivalent circle has an area equal to their area. The maximum size of the filler can be, for example, less than 100 μm or less than 60 μm.

[0044] The size of the gap G in the opposing direction D2 can be larger than 1.5 times the maximum size of the filler. For example, when the maximum size of the filler is 60 μm, the size of the gap G can be greater than 90 μm. This makes it easier for the filler to enter the gap G, further improving the hermeticity of the solid electrolytic capacitor. It should be noted that the size of the gap G in the opposing direction D2 is measured at the center height of the opposing surface S1 of the cathode terminal in the aforementioned stacking direction D1, using the connection point between the cathode terminal and the element stack as a reference. From the viewpoint of miniaturizing solid electrolytic capacitors, it is desirable that the upper limit of the size of the gap G in the opposing direction D2 be set to, for example, one-tenth of the length of the capacitor element in the opposing direction D2.

[0045] Sealing materials can be cured products of compositions comprising a base agent and a curing agent. Both the base agent and the curing agent are contained in the resin component. For example, thermosetting resin compositions are suitable as sealing materials or molding materials for exterior components. Epoxy resins are representative examples of base agents in thermosetting resin compositions. Polyamines, phenolic resins, and acid anhydrides are representative examples of curing agents in thermosetting resin compositions.

[0046] The main agent may contain a first component having a biphenyl backbone. Examples of the first component include biphenyl-type epoxy resins and biphenyl aralkyl-type epoxy resins. Among these, biphenyl aralkyl-type epoxy resins are preferred. The first component contributes to the low viscosity of the molding material forming the sealing material or outer component, and has low water absorption or hygroscopicity, low molding shrinkage, and excellent adhesion to metal. That is, moisture is less likely to remain inside or around the capacitor element, the volume expansion of the outer component during reflow soldering is easily suppressed, and peeling between the cathode terminal and the sealing material is inherently less likely to occur.

[0047] Biphenyl aralkyl type epoxy resins have a biphenyl backbone and multiple glycidyl ether groups within their molecules. Biphenyl aralkyl type epoxy resins can be phenol-biphenylene resins formed by replacing phenolic hydroxyl groups with glycidyl ether groups.

[0048] The main component of the sealing material can further include a second component in addition to the first component. The second component can be an epoxy resin without a biphenyl backbone. Therefore, the second component can impart properties to the sealing material and molding material that cannot be achieved by the first component alone. Thus, the balance of properties of the sealing material and molding material can be arbitrarily controlled. As the second component, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, hydrogenated bisphenol A type epoxy resin, phenolic resin, cresol resin, alicyclic aliphatic epoxy resin, dicyclopentadiene type epoxy resin, etc., can be used. These can be used alone or in combination of two or more.

[0049] The proportion of the first component in the main agent can be greater than 50% by mass. For example, in a thermosetting resin composition where the first component is a biphenyl aralkyl type epoxy resin, the proportion of the biphenyl aralkyl type epoxy resin in all epoxy resins (i.e., the total of the first and second components) is greater than the total proportion of all epoxy resins other than the biphenyl type epoxy resin (i.e., the second component). As a result, the advantages brought by the first component are amplified, the adhesion strength between the opposing surface S1 and the sealing material is further improved, and the airtightness of the solid electrolytic capacitor can be further enhanced.

[0050] The molding shrinkage rate of the sealing material can be less than 0.5%. Here, the molding shrinkage rate of the sealing material is determined according to JISK 6911. As a result, it is easy to reduce the stress generated at the interface between the opposing surface S1 and the sealing material, and the hermeticity of the solid electrolytic capacitor can be further improved.

[0051] When the sealing material contains filler, the filler content in the sealing material can be 80% by mass or more and 92% by mass or less. This allows for a good balance of the resin's various properties, such as low viscosity, low water absorption, low stress, and high adhesion. Ceramic particles are preferred as fillers, and inorganic oxides and inorganic nitrides are preferred as ceramic particles. Inorganic oxides such as silicon dioxide, alumina, titanium dioxide, magnesium oxide, and zinc oxide can be used, but are not limited to these. Inorganic nitrides such as boron nitride, silicon nitride, and aluminum nitride can be used, but are not limited to these.

[0052] Hereinafter, an example of the solid electrolytic capacitor of the present invention will be specifically described with reference to the accompanying drawings. The above-described constituent elements can be applied to the constituent elements of the solid electrolytic capacitor of the example described below. The constituent elements of the solid electrolytic capacitor of the example described below can be modified based on the above description. Furthermore, the matters described below can also be applied to the above-described embodiments. In the constituent elements of the solid electrolytic capacitor of the example described below, non-essential constituent elements of the solid electrolytic capacitor of the present invention can be omitted. It should be noted that the figures shown below are schematic and do not accurately reflect the actual shape and number of components.

[0053] like Figure 1 As shown, the solid electrolytic capacitor 10 includes an element stack 20, an anode terminal 60, a cathode terminal 70, and an external component 80.

[0054] (Component stack-up)

[0055] The component stack 20 is a stack of multiple (five in this example) capacitor elements 30. The multiple capacitor elements 30 are... Figure 1 Stacking occurs in the top-bottom direction (stacking direction D1). For example... Figure 2 As shown, each capacitor element 30 has an anode body 31, a dielectric layer 32, a solid electrolyte layer 33, and a cathode layer 34.

[0056] Anode 31 is a foil formed of aluminum valve-acting metal, a portion of which ( Figure 1 or Figure 2 The right side portion of the capacitor element 30 becomes the anode portion 38. The anode portions 38 of each capacitor element 30 are joined together.

[0057] The dielectric layer 32 is formed on the side separated from the anode portion 38 by the insulating layer 37 through vapor phase methods such as anodic oxidation and vapor deposition (i.e., on the side where the dielectric layer 37 is separated from the anode portion 38). Figure 2 Alumina is formed on the surface of the anode 31, which is located further to the left of the insulating layer 37.

[0058] It should be noted that the valve-acting metal in this embodiment is aluminum, but it can also be tantalum, niobium, titanium, or other valve-acting metals. The anode body 31 is a foil of the valve-acting metal, but it can also be a porous sintered body formed from valve-acting metal powder.

[0059] A solid electrolyte layer 33 is formed on the surface of the dielectric layer 32. The solid electrolyte layer 33 contains a conductive polymer. If necessary, the solid electrolyte layer 33 may further contain dopants, additives, etc.

[0060] As conductive polymers, known conductive polymers used in solid electrolytic capacitors, such as π-conjugated conductive polymers, can be used. Examples of conductive polymers include those with a basic backbone of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylidene, polyphenylene oxide, and polythiophene vinylidene. Among these, polymers with a basic backbone of polypyrrole, polythiophene, or polyaniline are preferred. The aforementioned polymers also include homopolymers, copolymers of two or more monomers, and their derivatives (substitutes with substituents, etc.). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). Conductive polymers can be used alone or in combination of two or more.

[0061] As a dopant, at least one selected from anionic and polyanionic dopants may be used. Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonic acid ions, and carboxylic acid ions, but there are no particular limitations. Examples of dopants that generate sulfonic acid ions include benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. Examples of polyanionic dopants include polymeric polysulfonic acids and polymeric polycarboxylic acids. Examples of polymeric polysulfonic acids include polyvinylsulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid sulfonic acid, and polymethacrylic acid sulfonic acid. Examples of polymeric polycarboxylic acids include polyacrylic acid and polymethacrylic acid. Polyanionic dopants also include polyester sulfonic acid and phenol sulfonic acid phenolic resins. However, polyanionic dopants are not limited to these.

[0062] As needed, the solid electrolyte layer 33 may further comprise known additives and known conductive materials other than conductive polymers. Examples of such conductive materials include at least one selected from conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0063] The cathode layer 34 is composed of a carbon layer 35 formed on the surface of the solid electrolyte layer 33 and a conductive layer 36 formed on the surface of the carbon layer 35. The conductive layer 36 may be composed of a silver paste. As the silver paste, for example, a composition containing silver particles and a resin component (adhesive resin) may be used. As the resin component, thermoplastic resins may also be used, but thermosetting resins such as imide resins and epoxy resins are preferred.

[0064] A portion of each capacitor element 30 (in) Figure 1 or Figure 2 The portion further to the left of the insulating layer 37 becomes the cathode portion 39. The cathode portion 39 includes all the constituent elements from the anode body 31 to the cathode layer 34.

[0065] like Figure 1 As shown, the element stack 20 further includes a conductive material 40 disposed on the cathode portion 39 and between adjacent capacitor elements 30. The conductive material 40 is, for example, composed of a silver paste. The conductive material 40 is disposed between adjacent cathode portions 39 within the plurality of cathode portions 39 and is electrically connected to them. As the silver paste constituting the conductive material 40, a composition comprising, for example, silver particles and a resin component (adhesive resin) may also be used. The composition of the silver paste constituting the conductive material 40 may be the same as or different from the silver paste constituting the conductive layer 36.

[0066] (Anode terminal)

[0067] Anode terminal 60 and Figure 1 The anode portion 38 of the lowest capacitor element 30 is connected. Thus, the anode terminal 60 is electrically connected to the anode portions 38 of the plurality of capacitor elements 30. The anode terminal 60 is made of, for example, copper, iron, a copper alloy, or an iron alloy. Regarding the anode terminal 60, a portion including the connection to the anode portion 38 is covered by the outer casing 80, while the remaining portion is exposed from the outer casing 80.

[0068] (Cathode terminal)

[0069] The cathode terminal 70 is connected to, for example, a conductive paste 50 formed of silver paste and... Figure 1 The cathode portion 39 of the lowest capacitor element 30 is connected. Thus, the cathode terminal 70 is electrically connected to the cathode portions 39 of the plurality of capacitor elements 30. As the silver paste constituting the conductive paste 50, a composition containing, for example, silver particles and a resin component (adhesive resin) may be used. The composition of the silver paste constituting the conductive paste 50 may be the same as or different from the silver paste constituting the conductive layer 36 or the conductive material 40. The cathode terminal 70 is, for example, made of copper, iron, a copper alloy, or an iron alloy. Regarding the cathode terminal 70, a portion including the connection portion to the cathode portion 39 is covered by the outer casing 80, while the remaining portion is exposed from the outer casing 80.

[0070] The cathode terminal 70 has a facing surface S1 that faces the front end 20a of the element stack 20 across a gap G. The facing direction D2 between the front end 20a of the element stack 20 and the facing surface S1 is... Figure 1 The size of the gap G in the left-right direction is, for example, about 100 μm, as long as it is larger than the maximum size of the filler described later.

[0071] It should be noted that, in Figure 1 In the configuration, the opposing surface S1 of the cathode terminal 70 is arranged such that the gap G between the front end 20a of the element stack 20 and the opposing surface S1 is approximately constant along the stacking direction D1 of the plurality of capacitor elements, but if... Figure 3 As shown, the opposing surface S1 of the cathode terminal 70 can also be inclined relative to the stacking direction D1, such that the gap G increases as it moves upward from the connection point of the cathode terminal 70 with the element stack 20. In this case, the angle between the opposing surface S1 of the cathode terminal 70 and the stacking direction D1 of the plurality of capacitor elements can be 0° or more and 30° or less.

[0072] (External components)

[0073] The outer casing 80 covers the element laminate 20, the anode terminal 60, and the cathode terminal 70 with portions of each exposed. The outer casing 80 is a cured product of a thermosetting resin composition comprising a base agent and a curing agent. The base agent comprises a first component having a biphenyl backbone (in this example, a biphenyl aralkyl type epoxy resin). The molding shrinkage of the outer casing 80 is preferably 0.5% or less.

[0074] The external component 80 preferably contains filler in a proportion of 80% to 92% by mass or more. The maximum size of the filler is, for example, about 60 μm, but it can also be smaller or larger.

[0075] Part of the external components 80 ( Figure 1 The portion indicated by reference numeral 81 in the accompanying drawings fills the gap G between the front end 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70. Preferably, a portion of the outer component 80 is filled as a sealing material within the entire gap G. This example illustrates how a portion of the outer component 80 can serve as a sealing material.

[0076] like Figure 4 As shown, the conductive paste 50 may not contact the opposing surface S1 of the cathode terminal 70. In this case, a portion of the outer component 80 is also filled as a sealing material in the area between the opposing surface S1 and the conductive paste 50.

[0077] It should be noted that at least a portion of the gap G needs to be filled with a portion of the outer component 80. For example, it can be filled with a portion of the outer component 80, except for... Figure 1 Between all capacitor elements 30 except the lowest capacitor element 30 (connecting side capacitor element) and the opposing surface S1 of the cathode terminal 70, a portion of the outer component 80 is filled in the gap G.

[0078] In the area of ​​gap G where a portion of the outer component 80 is filled, there is no conductive paste 50. In the same area of ​​gap G, the conductive material 40 does not contact the opposing surface S1 of the cathode terminal 70.

[0079] The outer component 80 is formed integrally with the sealing material 81, for example, by introducing the molding material into a mold in which the component stack 20 is disposed using a transfer molding method, but the method of forming the outer component 80 is not limited to this.

[0080] <Example>

[0081] for Figure 4 The solid electrolytic capacitor of this embodiment (in which six capacitor elements are stacked) is configured as shown in Table 1 below. Solid electrolytic capacitors for each embodiment and comparative example were fabricated by varying the gap G between the front end 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70. For these solid electrolytic capacitors, the rate of change of ESR (ΔESR) before and after a reliability test was measured to evaluate their hermeticity. For the solid electrolytic capacitors of each embodiment and comparative example, after measuring the initial ESR, a reliability test was conducted at 125°C for 3000 hours, and the ESR after the reliability test was measured. The rate of change of ESR, ΔESR, is obtained using the following formula.

[0082] ΔESR (%) = ((ESR after reliability testing) - (initial ESR)) / (initial ESR) × 100

[0083] The evaluation results for the examples and comparative examples are shown in Table 1. Here, the airtightness is evaluated based on the magnitude of the AESR, where "◎" indicates very good, "○" indicates good, "△" indicates acceptable, and "×" indicates poor.

[0084] [Table 1]

[0085] Gap G (μm) ΔESR (%) airtightness Example 1 19 2968 Δ Example 2 28 632 Δ Example 3 40 289 ○ Example 4 50 125 ○ Example 5 60 68 ◎ Example 6 72 47 ◎ Comparative Example 1 0 17917 ×

[0086] As shown in Table 1, in Examples 1 to 6, where a gap G is provided between the front end 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70, and a sealing material is filled therein, the ΔESR is suppressed to less than 1 / 6 compared to Comparative Example 1, where the gap G is 0 μm (meaning the front end 20a of the element stack 20 is in contact with the opposing surface S1 of the cathode terminal 70). This is believed to be due to the improved hermeticity of the solid electrolytic capacitor, thereby suppressing the degradation of the capacitor element caused by external air. In particular, in Examples 3 to 6, where the gap G is 40 μm or more, the ΔESR is suppressed to less than 1 / 60 compared to Comparative Example 1 because the hermeticity of the solid electrolytic capacitor is even higher. Furthermore, in Examples 5 to 6, where the gap G is 60 μm or more, the ΔESR is suppressed to less than 1 / 260 compared to Comparative Example 1 because the hermeticity of the solid electrolytic capacitor is further improved.

[0087] Industrial availability

[0088] This invention can be applied to solid electrolytic capacitors.

[0089] Explanation of reference numerals in the attached figures

[0090] 10: Solid electrolytic capacitors

[0091] 20: Component stack

[0092] 20a: Front end of the component stack

[0093] 30: Capacitor Components

[0094] 31: Anode

[0095] 32: Dielectric layer

[0096] 33: Solid electrolyte layer

[0097] 34: Cathode layer

[0098] 35: Carbon layer

[0099] 36: Conductor layer

[0100] 37: Insulating layer

[0101] 38: Anode section

[0102] 39: Cathode section

[0103] 40: Conductive materials

[0104] 50: Conductive paste

[0105] 60: Anode terminal

[0106] 70: Cathode terminal

[0107] S1: Opposite surface

[0108] 80: External components

[0109] 81: Part of the external components (sealing material)

[0110] G: Gap

Claims

1. A solid electrolytic capacitor, comprising: A component stack having a plurality of capacitor elements stacked on top of each other and each including an anode portion and a cathode portion, and a conductive material disposed on the cathode portion and between two adjacent capacitor elements within the plurality of capacitor elements; Anode terminal, which is connected to the anode portion; A cathode terminal is connected to the cathode portion via a conductive paste; as well as An external component covers the element stack, the anode terminal, and the cathode terminal with a portion of each of the anode terminal and the cathode terminal exposed. The plurality of capacitor elements includes a connection-side capacitor element closest to the connection portion of the cathode terminal and the element stack. The cathode terminal has a facing surface that is spaced apart from the front end of the element stack. The gap includes the area between the connecting-side capacitor element and the opposing surface of the cathode terminal, and the area between at least one of the plurality of capacitor elements (excluding the connecting-side capacitor element) and the opposing surface of the cathode terminal. At least a portion of the gap is filled with sealing material. The sealing material fills the area between the opposing surfaces of at least one of the plurality of capacitor elements (excluding the connecting side capacitor element) and the cathode terminal within the gap. The sealing material includes filler. The size of the gap between the front end of the element stack and the opposing surface in the opposite direction is greater than 1.5 times the maximum size of the filler.

2. The solid electrolytic capacitor according to claim 1, wherein, The sealing material is part of the external component.

3. The solid electrolytic capacitor according to claim 1, wherein, The conductive paste is not present in the region between the opposing surfaces of all capacitor elements (excluding the connecting side capacitor element) and the cathode terminal within the gap.

4. The solid electrolytic capacitor according to claim 1, wherein, In the region between the opposing surface of the cathode terminal and all capacitor elements except the connecting side capacitor element within the gap, the conductive material does not contact the opposing surface.

5. The solid electrolytic capacitor according to claim 1, wherein, The external component has an upper surface and a lower surface in the stacking direction of the plurality of capacitor elements, wherein the lower surface is closer to the connection-side capacitor element than the upper surface. The cathode terminal is located closer to the upper surface than the lower surface at the point where it protrudes from the outer component.

6. The solid electrolytic capacitor according to claim 1, wherein, The sealing material is filled in such a way that it extends continuously in the stacking direction of the plurality of capacitor elements.

7. The solid electrolytic capacitor according to claim 1, wherein, The sealing material is filled into the entire gap.

8. The solid electrolytic capacitor according to claim 1, wherein, The size of the gap is 40 μm or more.

9. The solid electrolytic capacitor according to any one of claims 1 to 8, wherein, The opposing surface of the cathode terminal is inclined relative to the stacking direction in such a way that the size of the gap between the opposing surface of the cathode terminal and the front end of the element stack increases from the connection portion of the cathode terminal and the element stack along the stacking direction of the plurality of capacitor elements.

10. The solid electrolytic capacitor according to any one of claims 1 to 8, wherein, The sealing material is a cured product of a composition comprising a main agent and a curing agent. The main agent contains a first component having a biphenyl skeleton.

11. The solid electrolytic capacitor according to claim 10, wherein, The first component is a biphenyl aryl epoxy resin.

12. The solid electrolytic capacitor according to claim 10, wherein, The main agent also includes a second component in addition to the first component.

13. The solid electrolytic capacitor according to claim 12, wherein, The proportion of the first component in the main agent is greater than 50% by mass.

14. The solid electrolytic capacitor according to any one of claims 1 to 8, wherein, The forming shrinkage rate of the sealing material is less than 0.5%.

15. The solid electrolytic capacitor according to any one of claims 1 to 8, wherein, The filler content in the sealing material is 80% or more by mass and 92% or less by mass.

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