Solid electrolytic capacitors

Abstract

This solid electrolytic capacitor comprises: an element stack; an anode terminal; a cathode terminal; and an exterior member coating the element stack, the anode terminal, and the cathode terminal in such a way that a part of each of the anode terminal and the cathode terminal is exposed. The element stack comprises a plurality of capacitor elements stacked on each other, and an electrically conductive material interposed between two capacitor elements adjacent to each other among the plurality of capacitor elements. Each of the plurality of capacitor elements includes an anode portion and a cathode portion, and the electrically 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 an electrically conductive paste. Further, the cathode terminal has an opposing surface opposing a tip-end of the element stack via a gap, the gap being at least partially filled with sealing material.

Description

Technical Field

[0001] The present disclosure relates to a solid electrolytic capacitor.

Background Art

[0002] Conventionally, a solid electrolytic capacitor including a plurality of capacitor elements each having a cathode portion, a cathode terminal connected to the cathode portion via a conductive paste, and an exterior member covering them is known (for example, Patent Document 1). In Patent Document 1, by connecting the cathode portions of the plurality of capacitor elements with a conductive film, reduction of the ESR (Equivalent Series Resistance) of the solid electrolytic capacitor is achieved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] One aspect of the present disclosure relates to a solid electrolytic capacitor. The solid electrolytic capacitor includes an element laminate, an anode terminal, a cathode terminal, and an exterior member that covers the element laminate, 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 laminate has a plurality of capacitor elements laminated on each other and a conductive material interposed between two adjacent capacitor elements in 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. Further, the cathode terminal has a facing surface facing the tip of the element laminate with a gap therebetween, and at least a part of the gap is filled with a sealing material.

[0005] According to this disclosure, a highly airtight solid electrolytic capacitor can be obtained. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a cross-sectional view showing the configuration of a solid electrolytic capacitor according to this disclosure. [Figure 2] Figure 2 is a cross-sectional view showing the configuration of the capacitor element according to this disclosure. [Figure 3] Figure 3 is a cross-sectional view showing another configuration of the solid electrolytic capacitor according to this disclosure. [Figure 4] Figure 4 is a cross-sectional view showing yet another configuration of the solid electrolytic capacitor according to this disclosure. [Modes for carrying out the invention]

[0007] Prior to describing the embodiments, the problems in the prior art are briefly outlined below. Solid electrolytic capacitors are desirable to have a structure with excellent airtightness in order to avoid degradation of the characteristics of multiple capacitor elements. However, conventional efforts to improve the airtightness of solid electrolytic capacitor structures have not been sufficiently considered. In this context, this disclosure provides a solid electrolytic capacitor with high airtightness.

[0008] Embodiments of solid electrolytic capacitors relating to this disclosure will be described below with examples. However, this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are achieved.

[0009] (Solid electrolytic capacitor) The solid electrolytic capacitor according to this disclosure comprises a laminated element, an anode terminal, a cathode terminal, and an outer casing. These will be described below.

[0010] (Laminated element) The element stack comprises a plurality of capacitor elements stacked on top of each other and a conductive material. Each of the plurality of capacitor elements includes an anode portion and a cathode portion. The anode portions of the plurality of capacitor elements are stacked and electrically connected to each other. The plurality of anode portions may be joined to each other, for example, by welding.

[0011] The conductive material is interposed between the cathode portions of two adjacent capacitor elements within a plurality of capacitor elements. The conductive material may electrically connect and integrate the cathode portions of the stacked plurality of capacitor elements. The conductive material may be, for example, a paste containing metal or a film containing metal.

[0012] (Anode terminal) 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 out a metal foil to form a metal frame of a predetermined shape and then bending the metal frame.

[0013] (Cathode terminal) 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 an opposing surface S1 that faces the tip of the element stack with a gap G in between. At least a portion of the gap G is filled with a sealing material.

[0014] (Sealing material) The encapsulant contains a resin material as an essential component and a filler as an optional component. Ceramic particles such as inorganic oxides are preferably used as the filler. The encapsulant also contains a conductive material and a conductive base. ToyoIt is also difficult for air to permeate. Because at least a portion of the gap G is filled with a sealing material, at least a portion of the conductive material and conductive paste is covered with the sealing material, making it difficult for outside air to reach the capacitor element. In addition, air moves along the interface where the cathode terminal and the outer casing material have separated. Such separation occurs, for example, when a circuit component equipped with a solid electrolytic capacitor is heated by reflow or other means, causing moisture present inside or around the capacitor element to vaporize and the volume of the outer casing material to expand. On the other hand, if the gap G is filled with a sealing material, and no separation occurs between the cathode terminal and the sealing material, the reach of air to the capacitor element is inhibited. Even if separation occurs between the cathode terminal and the sealing material, the interface between the cathode terminal and the sealing material is added to the path of air to reach the capacitor element, lengthening the path of air from the outside to the capacitor element. As a result, the airtightness of the solid electrolytic capacitor can be improved.

[0015] The encapsulant may contain a curing catalyst in a content of 1% by mass or less. The curing catalyst may include two types: a phosphorus-based curing catalyst and a nitrogen-based curing catalyst. The content of the nitrogen-based curing catalyst may be less than that of the phosphorus-based curing catalyst. The encapsulant may also contain only one type of curing catalyst, a phosphorus-based curing catalyst. The curing catalyst may have latent properties.

[0016] By including a curing catalyst in the sealing material, the viscosity of the sealing material during molding can be maintained at a low level for a certain period of time, improving the adhesion between the cathode terminal and the sealing material and suppressing delamination. This further enhances the airtightness of the solid electrolytic capacitor.

[0017] In this specification, "tip of the element stack" means the cathode end of the element stack. Specifically, an element stack has two ends, an anode end and a cathode end, but in this specification, "tip" refers to the latter.

[0018] (Exterior components) The exterior member covers the element laminate, 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 exterior member may be made of a resin material and may contain a filler. As the filler of the exterior member, ceramic particles such as inorganic oxides are preferably used. For example, the composition of the exterior member may be the same as the composition of the sealing material filled in the gap.

[0019] A part of the exterior member may constitute the sealing material. In this case, it is preferable that the exterior member and the sealing material are integrally formed of the same molding material. As the molding material, a thermosetting resin composition containing a resin component and a filler is preferably used. The resin component includes a main agent and a curing agent. By integrally forming the exterior member and the sealing material, the solid electrolytic capacitor of the present disclosure can be easily manufactured and its manufacturing cost can be suppressed. In the case where the exterior member and the sealing material are integrated in the finished product of the solid electrolytic capacitor, even if the constituent materials of the exterior member and the sealing material are different, it is considered that the sealing material is a part of the exterior member.

[0020] A part of the exterior member does not have to constitute the sealing material. In other words, the sealing material may be configured separately from the exterior member. Thereby, it becomes possible to appropriately select the material of the sealing material filled in the gap.

[0021] Hereinafter, the gap G between the cathode terminal and the tip of the element laminate is (a) cathode terminal Element laminate body and is divided into the gap (hereinafter also referred to as gap A) between the capacitor element closest to the connection point (hereinafter also referred to as the connection-side capacitor element) and the cathode terminal, and (b) the gap (hereinafter also referred to as gap B) between all the capacitor elements excluding the connection-side capacitor element and the cathode terminal.

[0022] The conductive paste does not necessarily need to be present in the gap (gap B) between all capacitor elements except the connected capacitor element and the opposing surface S1 of the cathode terminal. The conductive paste is less strong and more permeable to air than the sealant. Therefore, it is desirable that the gap B is not filled with conductive paste and is instead filled with sealant. This increases the bonding distance between the cathode terminal and the resin material, making it more difficult for air to reach the capacitor elements from the outside, and further improving the airtightness of the solid electrolytic capacitor. However, if the gap B is not filled with conductive paste and is instead filled with sealant, a small gap V may be formed between the sealant and the conductive paste. Such a gap V may be formed in gap A into which the conductive paste can penetrate. However, since the gap V is sufficiently small, it does not significantly affect the airtightness of the solid electrolytic capacitor. In the cross-section of the gap G in the direction D2 between the leading edge of the element stack and the opposing surface S1, the area of ​​the gap V is, for example, 16,000 μm². 2 The following is also acceptable.

[0023] The dimension of the gap G in the opposing direction D2 between the leading edge of the element stack and the opposing surface S1 is preferably 40 μm or more. More preferably, the dimension of the gap G is 60 μm or more. By having a gap G of 40 μm or more, the strength of the sealing material is maintained and crack formation is made less likely, thus ensuring the airtightness of the solid electrolytic capacitor.

[0024] The conductive material does not need to be in contact with the opposing surface S1 of the cathode terminal in the gap B between all capacitor elements except the connecting capacitor element and the opposing surface S1 of the cathode terminal. The conductive material has lower strength than the sealing material and is more permeable to air. If the conductive material and the cathode terminal are in contact in the gap B, air may reach the capacitor element through the conductive material. Therefore, it is desirable that the conductive material and the opposing surface S1 of the cathode terminal are not in contact in the gap B.

[0025] The sealing material only needs to be filled in the gap B between at least all capacitor elements except the connecting capacitor element and the opposing surface S1 of the cathode terminal, but it may also be filled in at least a portion of the gap A. In this case, it is desirable that the sealing material be filled in gap B so as to extend continuously in the stacking direction D1 of the multiple capacitor elements. This highly suppresses contact between the conductive material and the opposing surface S1 of the cathode terminal in gap B. It is also desirable that the sealing material be filled in gap B continuously along the opposing surface S1 so as to contact the opposing surface S1. This makes the bonding distance between the cathode terminal and the outer casing sufficiently long, further improving the airtightness of the solid electrolytic capacitor.

[0026] Furthermore, the conductive paste may also be present in the gap A between the connecting capacitor element and the opposing surface S1 of the cathode terminal. In this case, it is preferable that the sealing material fills the entire portion of the gap G where the conductive paste is not present. However, a small air gap V may be formed between the sealing material and the conductive paste, and even in such a case, it is defined as the sealing material filling the entire portion of the gap G where the conductive paste is not present.

[0027] The opposing surface S1 of the cathode terminal may be inclined with respect to the stacking direction D1 such that the gap G increases upward from the connection point of the cathode terminal with the element stack. The angle between the opposing surface S1 of the cathode terminal and the stacking direction D1 of the multiple capacitor elements may be between 0° and 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 within the solid electrolytic capacitor increases. Therefore, if the overall size of the solid electrolytic capacitor is not changed, the element stack (each capacitor element) must be made smaller, which is undesirable because it reduces the capacitance of the solid electrolytic capacitor.

[0028] Because the opposing surface S1 of the cathode terminal is inclined with respect to the stacking direction D1 of the multiple capacitor elements, it is possible to prevent the leading edge of the element stack from contacting the opposing surface S1 of the cathode terminal when stacking the capacitor elements from the connection point of the cathode terminal. As a result, a gap is always formed between the leading edge of the element stack and the cathode terminal, further improving the airtightness of the solid electrolytic capacitor. In addition, it is possible to improve the filling of the gap G by the sealing material.

[0029] In any of the above cases, cathode terminal Element stacking body and The capacitor element closest to the connection point is preferably the capacitor element furthest from the point where the cathode terminal is exposed from the outer casing. This allows for the longest possible air path from the exposed point to the capacitor element, further enhancing the airtightness of the solid electrolytic capacitor.

[0030] The entire gap G (i.e., both gap A and gap B) may be filled with a sealing material. This further lengthens the air path from where the cathode terminal is exposed from the outer casing to the capacitor element, thereby further improving the airtightness of the solid electrolytic capacitor.

[0031] When the encapsulant contains filler, the dimension of the gap G in the opposing direction D2 between the leading edge of the element stack and the opposing surface S1 may be larger than the maximum size of the filler. This allows a sufficient amount of filler to easily enter the gap G, increasing the strength of the encapsulant present in the gap G. Therefore, cracks in the encapsulant are less likely to occur in the opposing direction D2, and air bypass passages are less likely to form. In addition, the shrinkage rate of the encapsulant with filler in the gap G is reduced, suppressing delamination between the encapsulant and the cathode terminal. Therefore, the airtightness of the solid electrolytic capacitor can be further improved. It is desirable that the filler fills the entire gap B. In other words, when drawing a straight line along the opposing direction D2, it is desirable that the straight line cannot be drawn without crossing the filler particles.

[0032] Here, "maximum filler size" refers to the particle size of the largest filler particle contained in the sealant. For example, if the particle size of the filler contained in the sealant is in the range of 5 μm to 60 μm, the maximum filler size is 60 μm. The maximum filler size can be determined by photographing a cross-section of the sealant, selecting 100 arbitrary particles, and finding the maximum diameter of an equivalent circle having the same area as those particles. The maximum filler size may be, for example, 100 μm or less, or 60 μm or less.

[0033] The dimension of the gap G in the opposing direction D2 may be greater than 1.5 times the maximum size of the filler. For example, if the maximum size of the filler is 60 μm, the dimension of the gap G may be greater than 90 μm. This makes it easier for the filler to penetrate the gap G, further improving the airtightness of the solid electrolytic capacitor. The dimension of the gap G in the opposing direction D2 can be measured at the height of the center of the opposing surface S1 of the cathode terminal in the stacking direction D1, with reference to the connection point of the cathode terminal with the element stack. From the viewpoint of miniaturizing the solid electrolytic capacitor, it is desirable to set the upper limit of the dimension of the gap G in the opposing direction D2 to, for example, one-tenth of the length of the capacitor element in the opposing direction D2.

[0034] The sealing material may be a cured product of a composition containing a main component and a curing agent. Both the main component and the curing agent are contained in the resin component. For example, thermosetting resin compositions are suitable as molding materials for sealing materials or exterior components. A typical example of the main component of a thermosetting resin composition is epoxy resin. Typical examples of curing agents for a thermosetting resin composition include polyamines, phenolic resins, and acid anhydrides.

[0035] The main component may contain a first component having a biphenyl skeleton. 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 lowering the viscosity of the molding material that forms the encapsulant or outer casing, and also has low water absorption or hygroscopicity, a small molding shrinkage rate, and excellent adhesion to metal. In other words, moisture is less likely to accumulate inside or around the capacitor element, volume expansion of the outer casing during reflow is easily suppressed, and delamination between the cathode terminal and the encapsulant is inherently less likely to occur.

[0036] Biphenyl aralkyl epoxy resins have a biphenyl skeleton and multiple glycidyl ether groups within their molecules. Biphenyl aralkyl epoxy resins may also be phenol biphenylene resins in which phenolic hydroxyl groups are substituted with glycidyl ether groups.

[0037] The main component of the encapsulant may further contain a second component in addition to the first component. The second component may be an epoxy resin that does not have a biphenyl skeleton. This allows the second component to impart physical properties of the encapsulant or molding material that cannot be achieved with the first component alone. Thus, the balance of physical properties of the encapsulant or 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, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic aliphatic epoxy resin, dicyclopentadiene type epoxy resin, etc. These may be used individually or in combination of two or more types.

[0038] The proportion of the first component in the main component may be greater than 50% by mass. For example, in a thermosetting resin composition in which the first component is a biphenyl aralkyl type epoxy resin, the proportion of the biphenyl aralkyl type epoxy resin in the total epoxy resin (i.e., the sum 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). This increases the benefits of the first component, further enhances the adhesion strength between the opposing surface S1 and the encapsulant, and further improves the airtightness of the solid electrolytic capacitor.

[0039] The molding shrinkage rate of the sealing material may be 0.5% or less. Here, the molding shrinkage rate of the sealing material is measured according to JIS K 6911. This makes it easier to reduce the stress generated at the interface between the opposing surface S1 and the sealing material, and further improves the airtightness of the solid electrolytic capacitor.

[0040] When the encapsulant contains a filler, the filler content in the encapsulant may be 80% by mass or more and 92% by mass or less. This allows for a good balance of resin properties such as low viscosity, low water absorption, low stress, and high adhesion. Ceramic particles are preferred as the filler, and inorganic oxides and inorganic nitrides are preferred as ceramic particles. As inorganic oxides, silica, alumina, titania, magnesium oxide, zinc oxide, etc., may be used, but are not limited to these. As inorganic nitrides, boron nitride, silicon nitride, aluminum nitride, etc., may be used, but are not limited to these.

[0041] Hereinafter, an example of a solid electrolytic capacitor according to this disclosure will be specifically described with reference to the drawings. The components of the example solid electrolytic capacitor described below can be the components described above. The components of the example solid electrolytic capacitor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiments. Among the components of the example solid electrolytic capacitor described below, components that are not essential to the solid electrolytic capacitor according to this disclosure may be omitted. Note that the figures shown below are schematic and do not accurately reflect the actual shape and number of components.

[0042] As shown in Figure 1, the solid electrolytic capacitor 10 comprises an element stack 20, an anode terminal 60, a cathode terminal 70, and an outer casing member 80.

[0043] (Laminated element) The element stack 20 is a stack of multiple (five in this example) capacitor elements 30. The multiple capacitor elements 30 are stacked in the vertical direction (stack direction D1) as shown in Figure 1. Each capacitor element 30 has an anode 31, a dielectric layer 32, a solid electrolyte layer 33, and a cathode layer 34, as shown in Figure 2.

[0044] The anode body 31 is a foil made of aluminum valve metal, and a portion of it (the right-hand portion in Figure 1 or Figure 2) is the anode portion 38. The anode portions 38 of each capacitor element 30 are joined to each other.

[0045] The dielectric layer 32 is made of aluminum oxide formed on the surface of the anode body 31 on the side separated from the anode portion 38 by the insulator layer 37 (i.e., to the left of the insulator layer 37 in Figure 2) by a vapor phase method such as anodizing or vapor deposition.

[0046] In this embodiment, the valve metal is aluminum, but it may be tantalum, niobium, titanium, or other valve metals. The anode 31 is a foil of the valve metal, but it may be a porous sintered body made of powder of the valve metal.

[0047] The solid electrolyte layer 33 is formed on the surface of the dielectric layer 32. The solid electrolyte layer 33 contains a conductive polymer. The solid electrolyte layer 33 may also contain dopants, additives, etc., as needed.

[0048] As conductive polymers, known ones used in solid electrolytic capacitors, such as π-conjugated conductive polymers, can be used. Examples of conductive polymers include polymers with polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene as the basic skeleton. Of these, polymers with polypyrrole, polythiophene, or polyaniline as the basic skeleton are preferred. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (such as substituted products having substituents). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). Conductive polymers may be used individually or in combination of two or more.

[0049] As the dopant, at least one selected from the group consisting of anions and polyanions is used. Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions, but are not particularly limited. Examples of dopants that generate sulfonate ions include benzenesulfonic acid, p-toluenesulfonic acid, and naphthalenesulfonic acid. Examples of polyanions include high molecular weight polysulfonic acid and high molecular weight polycarboxylic acid. Examples of high molecular weight polysulfonic acid include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylic sulfonic acid, and polymethacrylatesulfonic acid. Examples of high molecular weight polycarboxylic acid include polyacrylic acid and polymethacrylate. Polyanions also include polyestersulfonic acid and phenolsulfonic acid novolac resins. However, polyanions are not limited to these.

[0050] The solid electrolyte layer 33 may optionally further contain known additives and known conductive materials other than conductive polymers. Examples of such conductive materials include at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.

[0051] 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 silver paste. As the silver paste, for example, a composition containing silver particles and a resin component (binder resin) can be used. As the resin component, a thermoplastic resin can be used, but it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.

[0052] A portion of each capacitor element 30 (the portion to the left of the insulating layer 37 in Figure 1 or Figure 2) forms a cathode portion 39. The cathode portion 39 includes all components from the anode body 31 to the cathode layer 34.

[0053] As shown in Figure 1, the element stack 20 is arranged on the cathode portion 39 and further comprises a conductive material 40 interposed between two adjacent capacitor elements within the plurality of capacitor elements 30. The conductive material 40 is composed of, for example, silver paste. The conductive material 40 is interposed between two adjacent cathode portions 39 within the plurality of cathode portions 39 and electrically connects them to each other. The silver paste constituting the conductive material 40 can be, for example, a composition containing silver particles and a resin component (binder resin). 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.

[0054] (Anode terminal) The anode terminal 60 is connected to the anode portion 38 of the lowermost capacitor element 30 in Figure 1. This electrically connects the anode terminal 60 to the anode portions 38 of multiple capacitor elements 30. The anode terminal 60 is made of, for example, copper, iron, a copper alloy, or an iron alloy. A portion of the anode terminal 60, including the connection point to the anode portion 38, is covered by the exterior member 80, while the remaining portion is exposed from the exterior member 80.

[0055] (Cathode terminal) The cathode terminal 70 is connected to the cathode portion 39 of the lowermost capacitor element 30 in Figure 1 via a conductive paste 50, for example, made of silver paste. This electrically connects the cathode terminal 70 to the cathode portions 39 of multiple capacitor elements 30. The silver paste constituting the conductive paste 50 can be, for example, a composition containing silver particles and a resin component (binder resin). 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 made of, for example, copper, iron, a copper alloy, or an iron alloy. A portion of the cathode terminal 70, including the connection portion with the cathode portion 39, is covered by an exterior member 80, while the remainder is exposed from the exterior member 80.

[0056] The cathode terminal 70 has an opposing surface S1 that faces the tip 20a of the element stack 20 with a gap G between them. The dimension of the gap G in the opposing direction D2 (left-right direction in Figure 1) between the tip 20a of the element stack 20 and the opposing surface S1 is, for example, about 100 μm, but it is sufficient if it is larger than the maximum size of the filler, which will be described later.

[0057] In Figure 1, the opposing surface S1 of the cathode terminal 70 is positioned such that the gap G between the tip 20a of the element stack 20 and the opposing surface S1 is approximately constant along the stacking direction D1 of the multiple capacitor elements. However, as shown in Figure 3, the opposing surface S1 of the cathode terminal 70 may be tilted with respect to the stacking direction D1 such that the gap G increases upward from the connection point between the cathode terminal 70 and the element stack 20. In that case, the angle between the opposing surface S1 of the cathode terminal 70 and the stacking direction D1 of the multiple capacitor elements may be between 0° and 30°.

[0058] (Exterior components) The exterior member 80 covers the element laminate 20, the anode terminal 60, and the cathode terminal 70, with a portion of each of the anode terminal 60 and cathode terminal 70 exposed. The exterior member 80 is a cured product of a thermosetting resin composition containing a main agent and a curing agent. The main agent contains a first component having a biphenyl skeleton (in this example, a biphenyl aralkyl type epoxy resin). The molding shrinkage rate of the exterior member 80 is preferably 0.5% or less.

[0059] The exterior component 80 preferably contains filler in a content ratio of 80% by mass or more and 92% by mass or less. The maximum size of the filler is, for example, about 60 μm, but it may be smaller or larger than this.

[0060] A portion of the exterior member 80 (indicated by reference numeral 81 in Figure 1) is filled into the gap G between the tip 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70. It is preferable that a portion of the exterior member 80 fills the entire gap G as a sealing material. This example is an example where a portion of the exterior member 80 serves as a sealing material.

[0061] As shown in Figure 4, the conductive paste 50 does not need to be in contact with the opposing surface S1 of the cathode terminal 70. In that case, a portion of the outer casing member 80 is also filled as a sealing material in the area between the opposing surface S1 and the conductive paste 50.

[0062] Furthermore, it is sufficient that at least a portion of the gap G is filled with a portion of the exterior member 80. For example, in Figure 1, a portion of the exterior member 80 may be filled in the gap G between all capacitor elements 30 except the lowest capacitor element 30 (connecting capacitor element) and the opposing surface S1 of the cathode terminal 70.

[0063] In the region of gap G where a portion of the exterior member 80 is filled, there is no conductive paste 50. In this region of gap G, the conductive material 40 is not in contact with the opposing surface S1 of the cathode terminal 70.

[0064] The exterior member 80 is formed integrally with the sealing material 81 by, for example, introducing a molding material into a mold in which the element stack 20 is placed using a transfer molding method, but the method of forming the exterior member 80 is not limited to this.

[0065] <Examples> For the solid electrolytic capacitor configuration of this embodiment shown in Figure 4 (where six capacitor elements are stacked), solid electrolytic capacitors of each example and comparative example were created by changing the gap G between the tip 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70, as shown in Table 1 below. For these solid electrolytic capacitors, the airtightness was evaluated by measuring the rate of change of ESR (ΔESR) before and after the reliability test. For each solid electrolytic capacitor of the example and comparative example, the initial ESR was measured, and then a reliability test was performed by holding it in a 125°C atmosphere for 3000 hours, and the ESR after the reliability test was measured. ΔESR, which represents the rate of change of ESR, was calculated using the following formula. ΔESR(%) = ((ESR after reliability testing) - (initial ESR)) / (initial ESR) × 100 Table 1 shows the evaluation results for the examples and comparative examples. Here, airtightness is evaluated by the magnitude of ΔESR, with "◎" indicating very good, "〇" indicating good, "△" indicating acceptable, and "×" indicating poor.

[0066] [Table 1]

[0067] As shown in Table 1, in Examples 1 to 6, where a gap G was provided between the tip 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70, and a sealing material was filled, the ΔESR was reduced to 1 / 6 or less compared to Comparative Example 1, where the gap G was 0 μm (meaning that the tip 20a of the element stack 20 and the opposing surface S1 of the cathode terminal 70 were in contact). This is thought to be because the airtightness of the solid electrolytic capacitor was improved, thereby suppressing deterioration of the capacitor element due to the outside air. In particular, in Examples 3 to 6, where the gap G was 40 μm or more, the airtightness of the solid electrolytic capacitor was further improved, which is thought to have reduced the ΔESR to 1 / 60 or less compared to Comparative Example 1. Furthermore, in Examples 5 to 6, where the gap G was 60 μm or more, the airtightness of the solid electrolytic capacitor was further improved, which is thought to have reduced the ΔESR to 1 / 260 or less compared to Comparative Example 1. [Industrial applicability]

[0068] This disclosure can be used in solid electrolytic capacitors. [Explanation of Symbols]

[0069] 10: Solid electrolytic capacitors 20: Elemental laminate 20a: Tip of the element stack 30: Capacitor element 31: Anode 32: Dielectric layer 33: Solid electrolyte layer 34: Cathode layer 35: Carbon layer 36: Conductive layer 37: Insulator layer 38: Anode section 39: Cathode part 40: Conductive materials 50: Conductive paste 60:Anode terminal 70: Cathode terminal S1: Opposing surface 80: Exterior components 81: Part of the exterior components (sealant) G: Gap

Claims

1. A laminate of elements comprising a plurality of capacitor elements stacked on top of each other, each including an anode portion and a cathode portion, and a conductive material disposed on the cathode portion and interposed between two adjacent capacitor elements within the plurality of capacitor elements, A positive terminal connected to the aforementioned positive electrode section, A cathode terminal connected to the cathode portion via a conductive paste, The element stack, the anode terminal, and the cathode terminal are covered by an exterior member that covers them in such a way that a portion of each of the anode terminal and the cathode terminal is exposed. The cathode terminal has an opposing surface that faces the tip of the element stack with a gap in between, A sealing material is filled into at least a portion of the aforementioned gap. The plurality of capacitor elements include the connection-side capacitor element closest to the connection point of the cathode terminal with the element stack, The conductive material does not come into contact with the opposing surface in the region between the gap, all capacitor elements other than the connecting capacitor element among the plurality of capacitor elements, and the opposing surface of the cathode terminal. The sealing material includes a filler, The dimension of the gap between the tip of the element stack and the opposing surface in the opposing direction is 40 μm or more, and is larger than the maximum size of the filler. The upper limit of the dimension of the gap is one-tenth of the length of the capacitor element in the opposing direction. A solid electrolytic capacitor in which the entire gap is filled with the sealing material, and the filler is filled in the gap such that when a straight line is drawn along the opposing direction, it is not possible to draw a straight line without crossing the particles of the filler.

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

3. The solid electrolytic capacitor according to claim 1 or 2, wherein the sealing material is filled so as to extend continuously in the stacking direction of the plurality of capacitor elements.

4. The solid electrolytic capacitor according to any one of claims 1 to 3, wherein the dimension of the gap is greater than 1.5 times the maximum size of the filler.

5. The solid electrolytic capacitor according to any one of claims 1 to 4, wherein the opposing surface of the cathode terminal is inclined with respect to the stacking direction such that the dimension of the gap between the opposing surface of the cathode terminal and the tip of the element stack increases along the stacking direction of the plurality of capacitor elements from the connection point of the cathode terminal with the element stack.

6. The sealing material is a cured product of a composition containing a main component and a curing agent. The solid electrolytic capacitor according to any one of claims 1 to 5, wherein the main component comprises a first component having a biphenyl skeleton.

7. The solid electrolytic capacitor according to claim 6, wherein the first component is a biphenyl aralkyl type epoxy resin.

8. The solid electrolytic capacitor according to claim 6 or 7, wherein the main component further comprises a second component other than the first component.

9. The solid electrolytic capacitor according to claim 8, wherein the proportion of the first component in the main component is greater than 50% by mass.

10. The solid electrolytic capacitor according to any one of claims 1 to 9, wherein the molding shrinkage rate of the sealing material is 0.5% or less.

11. The solid electrolytic capacitor according to any one of claims 1 to 10, wherein the content ratio of the filler in the sealing material is 80% by mass or more and 92% by mass or less.

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