Solid electrolytic capacitor and method for manufacturing the same

Abstract

Realize a solid electrolytic capacitor with excellent thermal shock resistance. [Solution] A solid electrolytic capacitor (1) includes capacitor elements (2A-2C) each including an anode body (6) having a porous portion on its surface, a dielectric layer (7), and a cathode portion (8) covering at least a portion of the dielectric layer (7), an anode terminal (4), and a resin outer casing (3) that seals at least the capacitor elements. The anode body (6) has a cathode-forming portion and an anode thin portion adjacent to the cathode-forming portion. The dielectric layer (7) covers at least a portion of the surface of the porous portion in the cathode-forming portion. In the anode thin portion, the porous portion has been removed, or the thickness of the porous portion (7A) in the anode thin portion is thinner than the thickness of the porous portion in the cathode-forming portion. The anode body is connected to the anode terminal (4) at the anode thin portion.

Description

Technical Field

[0001] The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same.

Background Art

[0002] An electrolytic capacitor includes a capacitor element, an electrode terminal electrically connected to the capacitor element, and an exterior body that seals the capacitor element. A solid electrolyte layer is provided on the cathode portion of the capacitor element. The solid electrolyte layer contains a conductive polymer and is formed so as to cover at least a part of the roughened dielectric layer.

[0003] In Patent Document 1, in the formation of the solid electrolyte layer, a forbidden band is formed by compressing the roughened layer between the anode lead-out portion and the cathode portion by pressing, or by removing the roughened layer by cutting. The forbidden band suppresses the penetration of the conductive polymer to the anode lead-out portion side through the roughened layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the use of solid electrolytic capacitors has been expanding, and their use in high-temperature environments has also been promoted. However, considering use in high-temperature environments, conventional solid electrolytic capacitors have insufficient reliability against thermal shock.

Means for Solving the Problems

[0006] One aspect of the present invention relates to a solid electrolytic capacitor including: an anode body having a porous portion on its surface; a dielectric layer; a cathode portion covering at least a part of the dielectric layer; an anode terminal; and a resin exterior body that seals at least the solid electrolytic capacitor. The anode body has a cathode forming portion and an anode thin portion adjacent to the cathode forming portion. The dielectric layer covers at least a part of the surface of the porous portion in the cathode forming portion. In the anode thin portion, the porous portion is removed or the thickness of the porous portion in the anode thin portion is smaller than the thickness of the porous portion in the cathode forming portion. The anode body is connected to the anode terminal at the anode thin portion.

[0007] Another aspect of the present invention relates to a method for manufacturing a solid electrolytic capacitor, including: a first step of preparing an anode body having a porous portion on its surface; a second step of forming a dielectric layer on at least a part of the porous portion; a third step of partially compressing or removing the porous portion to provide an anode forming portion having a small thickness and a cathode forming portion having a larger thickness than the anode forming portion on the anode body; a fourth step of providing a cathode portion on at least a part of the dielectric layer in the cathode forming portion; and a fifth step of forming an anode thin portion including the remaining portion of the anode forming portion by cutting and removing a part of the anode forming portion to obtain a solid electrolytic capacitor element.

Advantages of the Invention

[0008] A solid electrolytic capacitor excellent in heat shock resistance can be realized.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] A solid electrolytic capacitor according to an embodiment of the present invention includes a capacitor element, an anode terminal, and at least a resin exterior body that seals the capacitor element. The capacitor element includes an anode body having a porous portion on the surface layer, a dielectric layer, and a cathode portion that covers at least a part of the dielectric layer. In the capacitor element, the anode body has a cathode forming portion and an anode thin portion adjacent to the cathode forming portion, and the dielectric layer covers at least a part of the surface of the porous portion in the cathode forming portion. Further, in the anode thin portion, the porous portion is removed and the non-porous core material portion is exposed, or the thickness of the porous portion in the anode thin portion is thinner than the thickness of the porous portion in the cathode forming portion. The anode body is connected to the anode terminal at the anode thin portion.

[0011] Here, the fact that the anode body is connected to the anode terminal at the anode thin portion means that the connection portion for electrically connecting the anode body to the anode terminal is formed in the anode thin portion. As a method of electrically connecting the anode thin portion and the anode terminal, in addition to the case where the anode thin portion is in direct contact with the anode terminal, as will be described later, the anode thin portions of a plurality of capacitor elements are overlapped to form an anode laminate, and the anode laminate is brought into contact with the anode terminal. The fact that the anode body is connected to the anode terminal at the anode thin portion includes both of these cases.

[0012] The anode body usually has an anode portion and a cathode forming portion. The dielectric layer can be formed so as to cover at least a part of the porous portion of the cathode forming portion. The cathode portion can be formed so as to cover at least a part of the dielectric layer. The cathode portion includes a solid electrolyte layer. The cathode portion includes, for example, a solid electrolyte layer that covers at least a part of the dielectric layer and a cathode lead-out layer that covers at least a part of the solid electrolyte layer.

[0013] The anode thin portion provided adjacent to the cathode forming portion has a role of preventing the solid electrolyte from penetrating to the anode side through the porous portion of the cathode forming portion in the formation process of the solid electrolyte layer. The anode thin portion has, for example, a compressed layer in which the porous portion is compressed.

[0014] In the conventional solid electrolytic capacitor, a thin anode portion is provided between the connection portion (anode lead portion) of the anode portion with the anode terminal and the cathode forming portion. In this case, it was found that the capacity of the solid electrolytic capacitor is easily reduced by repeatedly exposing it to high temperature and low temperature environments. When the cause of the capacity reduction was investigated, it was found that a crack was generated in the anode lead portion (especially near the boundary with the thin anode portion) and that stress was concentrated in this crack portion. It was found that fatigue failure of the anode lead portion originated from the crack due to thermal shock, and capacitance loss occurred. Note that the crack is easily formed during the press processing for forming the thin anode portion. Also, when the porous portion is removed by cutting, cracks are easily formed due to the load applied during processing. In either case, the crack is easily formed at the boundary between the processed area and the non-processed area of the anode body body.

[0015] Therefore, in the solid electrolytic capacitor of this embodiment, the region where the anode body is pressed is expanded to the region where the anode lead portion is formed. Then, a part of the region thinned by the press working is cut and removed, and the remaining portion is made into the thin anode portion. In this manner, an anode body is obtained in which the entire anode portion, including the anode lead portion, is the thin anode portion. In this case, of the region thinned by the press working, the region where cracks are likely to exist is included in the part of the anode foil that has been cut and removed, and there are almost no cracks on the anode lead portion side of the remaining thin anode portion. Therefore, by connecting the thin anode portion, in which cracks are greatly reduced, to the anode terminal, fatigue failure of the anode lead portion originating from the cracks is suppressed. This suppresses the decrease in capacity due to thermal shock, and provides reliability against thermal shock. This makes it possible to realize a highly reliable solid electrolytic capacitor.

[0016] The anode thin portion can be formed by compressing the porous portion of the anode body by press working. However, the anode thin portion may also be formed by removing at least a portion of the porous portion by cutting work, laser processing, or the like. Alternatively, the anode thin portion may be formed by removing the entire porous portion to expose the core portion.

[0017] When the capacitor element is encapsulated with a resin exterior, usually at least a part of the surface of the anode lead-out portion and at least a part of the anode terminal are covered with the resin exterior. At the contact portion between the resin exterior and the anode lead-out layer and the anode terminal, thermal stress is likely to occur due to the difference in the coefficient of thermal expansion from that of the resin exterior, and stress concentration due to thermal shock is likely to occur. Therefore, the problem of capacitance reduction due to thermal shock is likely to become apparent. However, in the solid electrolytic capacitor of the present embodiment, since there are almost no cracks in the anode thin portion, even when at least a part of the surface of the anode thin portion and at least a part of the anode terminal are covered with the resin exterior, the capacitance reduction due to thermal shock is suppressed.

[0018] Similarly, when the anode portion is bent or curved, the capacitor element is in a state where bending stress is constantly applied to the anode portion, so it is in an environment where it is easily subjected to stress concentration due to thermal shock, and the problem of capacitance reduction due to thermal shock is likely to become apparent. However, in the solid electrolytic capacitor of the present embodiment, since there are almost no cracks in the anode thin portion, even when the anode thin portion is bent or curved, the capacitance reduction due to thermal shock is suppressed.

[0019] The anode thin portion has a separation portion adjacent to the cathode formation portion and an anode lead-out portion separated from the cathode formation portion by the separation portion, and an insulating layer may be disposed on at least one main surface of the separation portion. The insulating layer is, for example, an insulating tape or the like. The insulating layer has a role of preventing the solid electrolyte from being formed on the anode portion in the formation process of the solid electrolyte layer. The insulating layer is usually formed on both sides of the separation portion, but at least one of the insulating layers formed on both sides may be removed after the solid electrolyte layer is formed.

[0020] When the insulating layer is not removed, the thickness of the insulating layer may be greater than the total thickness of the solid electrolyte layer and the cathode lead-out layer (the thickness of the cathode portion), or may be equal to or less than the thickness of the cathode portion. In order to clearly separate the anode lead-out portion and the cathode portion, it is preferable that the thickness of the insulating layer is greater than the thickness of the cathode portion.

[0021] A solid electrolytic capacitor can include a plurality of capacitor elements. In this case, an element laminate in which a plurality of capacitor elements are stacked can be formed. The element laminate includes, for example, an anode laminate portion in which anode thin portions of a plurality of capacitor elements are stacked, and a cathode laminate portion in which cathode portions of a plurality of capacitor elements are stacked. The anode laminate portion is electrically connected to an anode terminal, and the cathode laminate portion is electrically connected to a cathode terminal. The electrical connection between the anode laminate portion and the anode terminal may be made by joining the anode lead portions (anode thin portions) of the plurality of capacitors to each other by welding or caulking, etc., and bringing the joined portion into contact with the anode terminal, or by bundling the anode lead portions (anode thin portions) of the plurality of capacitors in the anode laminate portion at a certain interval and bringing the end faces of the respective anode lead portions into contact with the anode terminal. In any case, since no cathode portion is formed in the anode laminate portion, the thickness at the location where the anode laminate portion contacts the anode terminal is likely to be thinner than the thickness of the cathode laminate portion.

[0022] When the thickness of the anode laminate portion is different from the thickness of the cathode laminate portion, in at least any one of the plurality of capacitor elements constituting the element laminate, bending or curving of the anode portion cannot be avoided. In particular, in the capacitor element located in the uppermost layer or the lowermost layer of the element laminate, the anode portion is likely to be greatly bent or curved. As a result, as described above, it is likely to receive stress concentration due to thermal shock, and the problem of capacitance reduction due to thermal shock is likely to become apparent.

[0023] Furthermore, when an insulating layer exists in the separation portion, if the thickness of the insulating layer is large, the element laminate is likely to have a bulged shape in the separation portion. In particular, when the thickness of the insulating layer is larger than the total thickness of the solid electrolyte layer and the cathode lead layer, the bulge in the separation portion is significant. As a result, the degree of bending or curving of the anode portion becomes larger, and a larger bending stress is likely to be applied to the anode portion.

[0024] However, in the solid electrolytic capacitor of the present embodiment, as described above, even when the anode thin portion is bent or curved, a decrease in capacitance due to thermal shock is suppressed. The solid electrolytic capacitor of the present embodiment is particularly useful in a structure having an element laminate in which a plurality of capacitor elements are laminated.

[0025] From the viewpoint of reducing the degree of bending or curving of the anode portion and suppressing stress concentration due to thermal shock, it is preferable to remove at least one of the two insulating layers formed on both surfaces of the separation portion. Specifically, in the plurality of capacitor elements constituting the element laminate, the insulating layer may be disposed on only one of the first main surface and the second main surface of the separation portion. At this time, the plurality of capacitor elements may be laminated such that one first main surface of a pair of capacitor elements that are stacked on each other faces the second main surface of the other capacitor element with one layer of the insulating layer interposed therebetween. Note that, among the plurality of capacitor elements constituting the element laminate, a part may have insulating layers on both the first main surface and the second main surface.

[0026] FIG. 1 is a cross-sectional view schematically showing the structure of a solid electrolytic capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of a capacitor element used in the solid electrolytic capacitor.

[0027] In the illustrated example, the solid electrolytic capacitor 1 includes a plurality of capacitor elements 2A to 2C. The solid electrolytic capacitor 1 further includes an exterior body (specifically, a resin exterior body) 3 that seals the capacitor elements 2A to 2C, an anode terminal 4, and a cathode terminal 5. The exterior body 3 has a substantially rectangular parallelepiped outer shape, and the solid electrolytic capacitor 1 also has a substantially rectangular parallelepiped outer shape.

[0028] The capacitor elements 2A to 2C include an anode body 6, a dielectric layer 7, and a cathode portion 8 that covers the dielectric layer 7. The anode body 6 has a core material portion and a porous portion. The capacitor elements 2A to 2C are laminated via a conductive adhesive (not shown) interposed between the cathode portions to form an element laminate.

[0029] The anode body 6 has a portion (cathode formation portion) where the dielectric layer 7 is formed in the porous portion, and a portion (anode thin portion) adjacent to the cathode formation portion where the thickness of the porous portion is formed thinner than that of the cathode formation portion. In the illustrated example, the porous portion thinned by compressing the anode body 6 by pressing is shown as the compression layer 7A. The portion where the compression layer 7A is formed is the anode thin portion. The anode thin portion is divided into a separation portion adjacent to the cathode formation portion and an anode lead-out portion. In the anode lead-out portion, connection with the anode terminal 4 is made. An insulating layer 13 is formed in the separation portion so as to cover the surface of the anode body 6 in a band shape, and contact between the cathode portion 8 and the anode lead-out portion is restricted.

[0030] In the cathode formation portion, the cathode portion 8 includes a solid electrolyte layer 9 that covers at least a part of the dielectric layer 7, and a cathode lead-out layer 10 that covers the solid electrolyte layer 9. The cathode lead-out layer 10 is, for example, a carbon layer laminated with a conductive paste layer. In the illustrated example, the porous portion and the dielectric layer are not distinguished.

[0031] As shown in FIG. 2, the capacitor elements 2A to 2C are divided into three regions: an anode lead-out region A1, a separation region A2, and a cathode formation region A3, depending on the difference in the laminated structure. The anode body 6 The portion belonging to the anode lead-out region A1 of corresponds to the above-mentioned anode lead-out portion. Similarly, the portion belonging to the separation region A2 of the anode body 6 and the portion corresponding to the cathode formation region A3 of the anode body 6 respectively correspond to the above-mentioned separation portion and cathode formation portion.

[0032] In the anode lead-out region A1, the anode lead-out portions of the capacitor elements 2A to 2C are overlapped with each other, and the anode laminated portion of the element laminate is formed. An anode terminal 4 having an external terminal 4A bent and formed into a predetermined shape is electrically connected to the anode laminated portion. The external terminal 4A is a part of the anode terminal 4 and may be integral with the remaining portion of the anode terminal 4 or may be a separate member. On the other hand, in the cathode formation region A3, the cathode lead-out layers 10 of the capacitor elements 2A to 2C are overlapped with each other, and the cathode laminated portion of the element laminate is formed. A cathode terminal 5 is electrically connected to the cathode laminated portion via an adhesive layer 14 formed of a conductive adhesive. The outer surface of the cathode terminal 5 functions as an external terminal.

[0033] The element laminate is sealed by an exterior body 3, but at least a part of the external terminal 4A which is a part of the anode terminal 4 and a part of the cathode terminal 5 are exposed from the exterior body 3.

[0034] In the separation region A2, an insulating layer 13 is provided on one surface of the separation portion of the anode body 6 which is an anode thin portion. Since the separation portions are overlapped with each other with the insulating layer 13 interposed therebetween, and the anode lead-out portions are overlapped with each other for connection to the anode terminal 4, in the separation region A2, the separation portions of the capacitor element 2A located in the uppermost layer and the capacitor element 2C located in the lowermost layer are curved and bent at the connection portion with the anode lead-out portion. In particular, the degree of bending at the connection portion with the anode lead-out portion is large. Therefore, bending stress is applied to the anode lead-out portions of the capacitor element 2A and the capacitor element 2C, and when cracks are present, stress concentration due to thermal shock is received, and the anode lead-out portion is likely to undergo fatigue failure.

[0035] However, in the solid electrolytic capacitor 1, since both the anode lead-out portion and the separation portion of the anode body 6 are anode thin portions, there are almost no cracks in the anode lead-out portion and the separation portion in the first place. Therefore, even if thermal shock is applied, fatigue failure of the anode lead-out portion is unlikely to occur. As a result, the solid electrolytic capacitor 1 suppresses a decrease in capacitance due to thermal shock and has high reliability against thermal shock.

[0036] The configuration of the solid electrolytic capacitor will be described in more detail below. (Outer package 3) The outer package 3 seals the capacitor element. From the viewpoint of suppressing the intrusion of air into the capacitor element, it is desirable that a part of the anode terminal 4 and the cathode terminal 5 is sealed by the outer package 3. The resin outer package can be formed by sealing the capacitor element and a part of the anode terminal 4 and the cathode terminal 5 with a resin material.

[0037] The resin outer package preferably contains a cured product of a curable resin composition, and may also contain a thermoplastic resin or a composition containing the same. Examples of the resin material constituting the case include a thermoplastic resin or a composition containing the same.

[0038] The resin outer package can be formed using molding techniques such as injection molding, insert molding, and compression molding. For example, the resin outer package can be formed by filling a curable resin composition or a thermoplastic resin (composition) into a predetermined location so as to cover the capacitor element and one end portions of the anode terminal 4 and the cathode terminal 5 using a predetermined mold. When a laminate of a plurality of capacitor elements 2A to 2C is used, the resin outer package may be formed so as to cover the laminate and a part of the anode terminal 4 and the cathode terminal 5.

[0039] The curable resin composition may contain, in addition to the curable resin, a filler, a curing agent, a polymerization initiator, and / or a catalyst, etc. Examples of the curable resin include epoxy resin, phenol resin, urea resin, polyimide, polyamideimide, polyurethane, diallyl phthalate, unsaturated polyester, etc. The curable resin composition may contain a plurality of curable resins.

[0040] As the filler, for example, insulating particles (inorganic, organic) and / or fibers are preferable. Examples of the insulating material constituting the filler include insulating compounds (such as oxides) such as silica and alumina, glass, and mineral materials (such as talc, mica, and clay). The exterior resin layer may contain one kind of these fillers or may contain a combination of two or more kinds. The content of the filler in the exterior resin layer is, for example, 10 to 90% by mass.

[0041] As the thermoplastic resin, for example, polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), etc. can be used. The composition containing the thermoplastic resin may contain, in addition to the thermoplastic resin, the above-mentioned fillers, etc.

[0042] (Anode terminal 4, cathode terminal 5) One end of the anode terminal 4 and the cathode terminal 5 is electrically connected to the capacitor element, and the other end is drawn out to the outside of the exterior body 3. In the solid electrolytic capacitor 1, one end side of the anode terminal 4 and the cathode terminal 5 is covered by the exterior body 3 together with the capacitor elements 2A to 2C. As the anode terminal 4 and the cathode terminal 5, for example, what is called a lead frame may be used. Examples of the material of the anode terminal 4 and the cathode terminal 5 include metals such as copper or alloys thereof.

[0043] (Capacitor elements 2A to 2C) The capacitor elements 2A to 2C each include an anode body 6 constituting an anode portion, a dielectric layer 7, and a cathode portion 8 including a solid electrolyte layer 9. The cathode portion 8 only needs to include at least the solid electrolyte layer 9, but as shown in FIGS. 1 and 2, it is preferable to include the solid electrolyte layer 9 and a cathode lead-out layer 10 covering the solid electrolyte layer 9.

[0044] An electrolytic capacitor has at least one capacitor element. The electrolytic capacitor may have one capacitor element, or may have a plurality of capacitor elements 2A to 2C in the electrolytic capacitor 1 as in the example shown in FIG. 1. The number of capacitor elements included in the electrolytic capacitor may be determined according to the application.

[0045] (Anode body 6) The anode body 6 can include a valve metal, an alloy containing a valve metal, and a compound containing a valve metal, etc. These materials can be used alone or in combination of two or more. As the valve metal, for example, aluminum, tantalum, niobium, and titanium are preferably used. The porous part of the anode body 6 can be obtained, for example, by roughening the surface of a base material (such as a foil-shaped or plate-shaped base material) containing a valve metal by etching or the like.

[0046] The anode body 6 is thinned so as not to generate cracks as much as possible in the part other than the cathode forming part where the dielectric layer 7 is formed. This is done, for example, by performing a process of thinning the thickness of the porous part or removing the porous part to expose the core material part by pressing, cutting, or laser processing.

[0047] (Dielectric layer 7) The dielectric layer 7 is formed by anodizing the valve metal on the surface of the anode body 6 by a forming treatment or the like. The dielectric layer 7 only needs to be formed so as to cover at least a part of the anode body 6. The dielectric layer 7 is usually formed on the surface of the anode body 6. Since the dielectric layer 7 is formed on the porous surface of the anode body 6, it is formed along the inner wall surfaces of the holes and depressions (pits) on the surface of the anode body 6.

[0048] The dielectric layer 7 contains an oxide of the valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains Al2O3. Note that the dielectric layer 7 is not limited to this, and any material that functions as a dielectric may be used. When the surface of the anode body 6 is porous, the dielectric layer 7 is formed along the surface of the anode body 6 (including the inner wall surface of the pores).

[0049] (Cathode portion 8, Solid electrolyte layer 9) The solid electrolyte layer 9 constituting the cathode portion 8 contains a conductive polymer, and may further contain a dopant, an additive, etc. as required. As the conductive polymer, for example, polypyrrole, polythiophene, polyaniline, and their derivatives can be used. The solid electrolyte layer 9 can be formed, for example, by chemically polymerizing and / or electrolytically polymerizing a raw material monomer on the dielectric layer 7. Alternatively, it can be formed by bringing a solution in which a conductive polymer is dissolved or a dispersion in which a conductive polymer is dispersed into contact with the dielectric layer 7. The solid electrolyte layer 9 only needs to be formed so as to cover at least a part of the dielectric layer 7.

[0050] (Cathode lead-out layer 10) The cathode lead-out layer 10 constituting the cathode portion 8 can be formed, for example, by laminating a carbon layer and a conductive paste layer. The carbon layer only needs to have conductivity, and can be formed using a conductive carbon material such as graphite, for example. As the conductive paste layer, a composition containing metal particles and a binder resin (such as an epoxy resin) can be used, for example. The metal particles are, for example, silver particles. Note that the configuration of the cathode lead-out layer 10 is not limited to this, and any configuration having a current collecting function may be used. The cathode lead-out layer 10 is formed so as to cover at least a part of the solid electrolyte layer 9.

[0051] [Method for manufacturing a solid electrolytic capacitor] The above solid electrolytic capacitor can be manufactured by a manufacturing method including a step of preparing an anode body having a porous portion on the surface layer (first step), a step of forming a dielectric layer on at least a part of the porous portion (second step), a step of partially compressing or removing the porous portion to provide the anode body with a thin anode forming portion and a cathode forming portion having a greater thickness than the anode forming portion (third step), a step of providing a cathode portion on at least a part of the dielectric layer in the cathode forming portion (fourth step), and a step of forming a thin anode portion including the remaining portion of the anode forming portion by cutting and removing a part of the anode forming portion to obtain a capacitor element (fifth step). Hereinafter, each step will be described in more detail.

[0052] (First step) In this step, an anode body having a porous portion on the surface layer is prepared by a known method according to the type of the anode body 6. The anode body can be prepared, for example, by roughening the surface of a foil-shaped or plate-shaped base material containing a valve action metal. The roughening only needs to be able to form irregularities on the surface of the base material, and for example, it may be performed by etching (for example, electrolytic etching) the surface of the base material.

[0053] (Second step) Next, a dielectric layer is formed on at least a part of the porous portion. The dielectric layer is formed by anodizing the surface of the anode body. The anodization can be performed by a known method, for example, chemical conversion treatment, etc. The chemical conversion treatment can be performed, for example, by immersing the anode body in a chemical conversion solution to impregnate the anode body with the chemical conversion solution, and applying a voltage between the anode body as an anode and a cathode immersed in the chemical conversion solution. As the chemical conversion solution, for example, an aqueous phosphoric acid solution is preferably used. Note that the formation of the dielectric layer may be performed on the anode body in which the porous portion has not been thinned before performing the third step described later, or may be performed on the cathode forming portion after the third step.

[0054] (Third step) Next, the porous portion of the anode body is partially compressed or removed to provide a region with a small thickness in a part of the anode body, which serves as the anode forming portion. On the other hand, the remaining portion of the anode body that is not compressed or removed includes the region where the dielectric layer is to be formed in the third step (cathode forming portion). The compression of the porous portion can be performed by pressing the anode forming portion. Alternatively, the porous portion of the anode forming portion may be removed by cutting to reduce the thickness of the porous portion. At this time, cracks may be formed on the surface of the anode forming portion (especially at the boundary between the processed region and the unprocessed region) due to the load during processing.

[0055] (Step 4) Next, a cathode portion is provided on at least a part of the dielectric layer of the cathode forming portion. The cathode portion includes a solid electrolyte layer. In this step, for example, a solid electrolyte layer is formed so as to cover at least a part of the dielectric layer, and a cathode lead-out layer is formed so as to cover at least a part of the solid electrolyte layer.

[0056] When the solid electrolyte layer contains a conductive polymer, the solid electrolyte layer can be formed, for example, by attaching a treatment liquid containing the conductive polymer and then drying it. The treatment liquid may further contain other components such as a dopant. For the conductive polymer, for example, poly(3,4-ethylenedioxythiophene) (PEDOT) is used. For the dopant, for example, polystyrene sulfonic acid (PSS) is used. The treatment liquid is a dispersion or solution of the conductive polymer. Examples of the dispersion medium (solvent) include water, an organic solvent, or a mixture thereof. The solid electrolyte layer containing a conductive polymer may be formed, for example, by impregnating with monomers or oligomers and polymerizing them by chemical polymerization or electrolytic polymerization.

[0057] Subsequently, a cathode lead-out layer composed of a carbon layer and a conductive paste layer can be formed by sequentially applying a carbon paste and a conductive paste on at least a part of the surface of the formed solid electrolyte layer. The configuration of the cathode lead-out layer is not limited to this, and any configuration having a current collecting function may be used.

[0058] (Step 5) Next, a part of the thinned anode forming portion is cut and removed. As a result, in the anode forming portion, the portion where cracks are likely to be formed is removed. On the other hand, there are almost no cracks in the remaining anode thin portion of the anode forming portion. As a result, a capacitor element with almost no cracks in the anode lead portion can be obtained.

[0059] After that, if necessary, an element laminate in which a plurality of cathode portions are laminated may be formed using the capacitor element. The anode lead portion of the capacitor element or the element laminate is electrically connected to the anode terminal, and the cathode lead layer of the capacitor element or the element laminate is electrically connected to the cathode terminal. Further, the capacitor element or the element laminate is sealed by covering it with a resin exterior, and a solid electrolytic capacitor can be manufactured.

[0060] After the above-described third step (thinning of the anode forming portion) and before the above-described fourth step (cathode portion formation), a step of forming an insulating layer on both surfaces of the anode forming portion may be provided. The insulating layer is for preventing the solid electrolyte from being formed on the anode forming portion in the fourth step. The insulating layer is provided in a region of the anode forming portion close to the cathode forming portion. In this case, the region of the anode forming portion where the insulating layer is not formed becomes the anode lead portion. The anode lead portion is separated from the cathode portion by the insulating layer. After the above-described fourth step and before the above-described fifth step, the insulating layer formed on at least one surface of the anode forming portion may be removed. The insulating layer may be formed by applying a liquid insulating material containing an insulating resin to a predetermined position, or may be formed by attaching a tape-shaped insulating material (insulating tape) containing an insulating resin to a predetermined position. Among these, it is preferable that the insulating layer is formed by an insulating tape. This is because the formation of the insulating layer is easy, and after the formation of the solid electrolyte layer, the insulating tape disposed on at least one main surface can be easily removed by peeling.

[0061]

[0062] ​When forming an element laminate in which the cathode portions of a plurality of capacitor elements are laminated, one of the insulating layers formed on both surfaces of the anode forming portion may be removed, and the capacitor elements may be laminated without removing the other insulating layer. In forming the element laminate, the plurality of capacitor elements may be stacked such that the surface (first main surface) on which one of the insulating layers of a pair of capacitor elements that can be stacked on each other is formed and the surface (second main surface) from which the other insulating layer is removed face each other. As a result, for example, as shown in FIG. 1, one first main surface and the other second main surface of a pair of capacitor elements are configured to face each other with a single insulating layer therebetween.

[0063] [Examples] Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

[0064] 《Example 1》 A solid electrolytic capacitor 1 was fabricated and its characteristics were evaluated in the following manner. (1) Fabrication of capacitor element An aluminum foil (thickness: 100 μm) was prepared as a base material, and the entire surface of the aluminum foil was subjected to an etching treatment to obtain an anode body. The anode body was immersed in a phosphoric acid solution having a concentration of 0.3% by mass (liquid temperature: 70°C), and a DC voltage of 70 V was applied for 20 minutes to form a dielectric layer containing aluminum oxide (Al2O3) on a part of the surface of the anode body.

[0065] Subsequently, a predetermined region (anode forming portion) of the anode body was thinned by pressing. In the anode forming portion, insulating resistive tapes were attached to both surfaces at locations close to the dielectric layer.

[0066] Thereafter, the anode body on which the dielectric layer was formed was immersed in an aqueous dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS) (concentration: 2% by mass), and then dried to form a solid electrolyte layer.

[0067] A dispersion liquid in which carbon particles are 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 cure the binder resin, thereby forming a conductive paste layer. In this way, a cathode lead-out layer composed of a carbon layer and a conductive paste layer was formed. Furthermore, a part of the anode formation region was removed by cutting. In this way, a capacitor element was obtained.

[0068] (2) Assembly of solid electrolytic capacitor Six of the above capacitor elements were stacked with their cathode lead-out layers facing each other to form an element laminate. The anode lead-out portions of the six capacitor elements were connected to the anode terminal, and the lowermost cathode lead-out layer was connected to the cathode terminal via an adhesive layer. Furthermore, an exterior body was formed using a resin containing silica particles as a filler to seal the capacitor element. In this way, a solid electrolytic capacitor was manufactured.

[0069] <<Comparative Example 1>> In the production of the capacitor element, the region to be thinned by pressing was changed. The width of the pressing region was set narrow so that only the region where the insulating resistive tape is provided in the anode body is thinned. After the formation of the cathode lead-out layer, the anode body was cut at the portion that was not thinned to obtain a capacitor element.

[0070] Except for the above, a solid electrolytic capacitor was obtained in the same manner as in Example 1. In this case, the connection portion of the anode lead-out portion to the anode terminal is not thinned by pressing, and the boundary between the pressed portion and the non-pressed portion exists between the location where the insulating tape is provided and the anode lead-out portion.

[0071] The following evaluations were performed on the solid electrolytic capacitors of the examples and comparative examples manufactured above.

[0072] [Evaluation] The solid electrolytic capacitors of Example 1 and Comparative Example 1 were each placed in an environment of -55°C for 30 minutes, and then in an environment of 125°C for 30 minutes. This was regarded as one heat cycle, and the heat cycle of -55°C / 125°C was repeated 1500 times. After each heat cycle, the capacitance at 20°C was measured.

[0073] In the solid electrolytic capacitor of Comparative Example 1, the capacitance decreased discontinuously after 800 heat cycles, and capacitance loss was observed. On the other hand, in the solid electrolytic capacitor of Example 1, no capacitance loss was observed even after 1500 heat cycles.

[0074] The solid electrolytic capacitor after 1500 heat cycles was cut along a plane parallel to the stacking direction of the element laminate, and a photograph of the cross-sectional shape of the anode body at the anode lead-out portion was observed. As a result, in the solid electrolytic capacitor of Comparative Example 1, the anode lead-out portion was broken in some capacitor elements. On the other hand, in the solid electrolytic capacitor of Example 1, no breakage of the anode lead-out portion was observed. [Industrial Applicability]

[0075] Since the solid electrolytic capacitor according to the present invention is excellent in heat shock resistance, it can be used in various applications assumed to be used in a high-temperature environment. [Explanation of Reference Numerals]

[0076] 1: Solid electrolytic capacitor, 2A - 2C: Capacitor element, 3: Exterior body, 4: Anode terminal, 4A: External terminal of anode terminal, 5: Cathode terminal, 6: Anode body, 7: Dielectric layer, 7A: Compression layer, 8: Cathode portion, 9: Solid electrolyte layer, 10: Cathode lead-out layer, 13: Insulating layer, 14: Adhesive layer, A1: Anode lead-out region, A2: Separation region, A3: Cathode formation region

Claims

1. A capacitor element comprising an anode body having a porous portion on its surface, a dielectric layer, and a cathode portion covering at least a part of the dielectric layer; an anode terminal; and a resin exterior body that seals at least the capacitor element, wherein the anode body has an anode portion and a cathode formation portion, and the entire anode portion is an anode thin portion adjacent to the cathode formation portion; the dielectric layer covers at least a part of the surface of the porous portion in the cathode formation portion; the cathode portion covers at least a part of the surface of the porous portion in the cathode formation portion via the dielectric layer; in the anode thin portion, the porous portion is removed or the thickness of the porous portion in the anode thin portion is thinner than the thickness of the porous portion in the cathode formation portion; a solid electrolytic capacitor in which the anode body is connected to the anode terminal at the anode thin portion.

2. The anode thin portion has a separation portion adjacent to the cathode formation portion and an anode lead-out portion separated from the cathode formation portion by the separation portion; The solid electrolytic capacitor according to claim 1, wherein an insulating layer is disposed on at least one main surface of the separation portion.

3. A capacitor element comprising an anode body having a porous portion on its surface, a dielectric layer, and a cathode portion covering at least a part of the dielectric layer; an anode terminal; and a resin exterior body that seals at least the capacitor element, wherein the anode body has an anode portion and a cathode formation portion, and the entire anode portion is an anode thin portion adjacent to the cathode formation portion; the dielectric layer covers at least a part of the surface of the porous portion in the cathode formation portion; the cathode portion covers at least a part of the surface of the porous portion in the cathode formation portion via the dielectric layer; in the anode thin portion, the porous portion is removed or the thickness of the porous portion in the anode thin portion is thinner than the thickness of the porous portion in the cathode formation portion; the anode body is connected to the anode terminal at the anode thin portion; the anode thin portion has a separation portion adjacent to the cathode formation portion and an anode lead-out portion separated from the cathode formation portion by the separation portion; comprising an element laminate in which a plurality of the capacitor elements are laminated; in each of the plurality of capacitor elements, an insulating layer is disposed on either the first main surface or the second main surface of the separation portion. A solid electrolytic capacitor in which one of the first main surfaces of the pair of capacitor elements that are overlapped with each other and the second main surface of the other capacitor element are laminated so as to face each other with one layer of the insulating layer interposed therebetween.

4. The cathode portion includes a solid electrolyte layer that covers at least a part of the dielectric layer and a cathode lead-out layer that covers at least a part of the solid electrolyte layer. The solid electrolytic capacitor according to claim 2 or 3, wherein the thickness of the insulating layer is larger than the total thickness of the solid electrolyte layer and the cathode lead-out layer.

5. An element laminate including a plurality of the capacitor elements laminated. The element laminate includes an anode laminate portion in which the anode thin portions of the plurality of capacitor elements are laminated and a cathode laminate portion in which the cathode portions of the plurality of capacitor elements are laminated. The solid electrolytic capacitor according to any one of claims 1 to 4, wherein the thickness at the location where the anode terminal of the anode laminate portion contacts is thinner than the thickness of the cathode laminate portion.

6. A first step of preparing an anode body having a porous portion on the surface layer. A second step of forming a dielectric layer on at least a part of the porous portion. A third step of partially compressing or removing the porous portion to thin a part of the anode body, thereby providing an anode forming portion including the thinned portion and a cathode forming portion adjacent to the anode forming portion and not including the thinned portion on the anode body. A fourth step of providing a cathode portion on at least a part of the dielectric layer in the cathode forming portion. A fifth step of cutting and removing a part of the anode forming portion to form an anode thin portion by leaving only a part of the thinned portion in the anode forming portion, thereby obtaining a capacitor element. A sixth step of connecting the anode body of the capacitor element to an anode terminal at the anode thin portion. A method for manufacturing a solid electrolytic capacitor, further including a step of forming an element laminate in which a plurality of the cathode portions are laminated using a plurality of the capacitor elements after the fifth step.

7. A first step of preparing an anode body having a porous portion on the surface layer. A second step of forming a dielectric layer on at least a part of the porous portion. A third step of partially compressing or removing the porous portion to thin a part of the anode body, thereby providing an anode forming portion including the thinned portion and a cathode forming portion adjacent to the anode forming portion and not including the thinned portion on the anode body. In the cathode forming portion, a fourth step of providing a cathode portion on at least a part of the dielectric layer; A fifth step of forming a thin anode portion by cutting and removing a part of the anode forming portion so that only a part of the thinned portion of the anode forming portion remains, thereby obtaining a capacitor element; A sixth step of connecting the anode body of the capacitor element to the anode terminal at the thin anode portion, and After the third step and before the fourth step, a step of forming an insulating layer on both surfaces of the thinned portion of the anode forming portion; After the fourth step and before the fifth step, a step of removing the insulating layer formed on either one of the surfaces of the anode forming portion, the method for manufacturing a solid electrolytic capacitor further comprising the steps.

8. After the fifth step, a step of forming an element laminate in which a plurality of the cathode portions are laminated using a plurality of the capacitor elements is further provided, In the formation of the element laminate, the plurality of capacitor elements are overlapped such that one surface on which the insulating layer of a pair of the capacitor elements that can be overlapped with each other is formed faces the other surface on which the insulating layer is removed. The method for manufacturing a solid electrolytic capacitor according to Claim 7.

9. The insulating layer is an insulating tape, The step of removing the insulating layer is a step of peeling off the insulating tape adhered to the one surface of the anode forming portion. The method for manufacturing a solid electrolytic capacitor according to Claim 7 or 8.

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