Solid electrolytic capacitor and method for manufacturing solid electrolytic capacitor

Abstract

A solid electrolytic capacitor (10) is provided with a plurality of capacitor elements (20) and a plurality of cathode films (30). Each of the plurality of capacitor elements (20) is provided with an anode electrode (21), a dielectric layer (210), an inner layer CP (22), and an outer layer CP (23). The cathode film (30) includes an insulating base material (31) and a plurality of conductive fillers (32). The plurality of capacitor elements (20) and the plurality of cathode films (30) are alternately laminated in a state in which the outer layer CPs (23) are in contact with the cathode films (30). A region where the outer layer CP (23) is in contact with the cathode film (30) has a portion where the solid electrolyte layer and the cathode are mixed.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor having a structure in which a capacitor element and a cathode film are stacked, wherein the capacitor element is obtained by forming a dielectric layer and a solid electrolyte layer on a valve metal body. Background Art

[0002] The solid electrolytic capacitor of Patent Document 1 comprises a stacked element body in which a first layer that functions as a capacitor and a second layer that functions as a cathode are stacked. The first layer comprises a valve metal body having a dielectric layer formed on the surface and a solid electrolyte layer provided on the dielectric layer. The second layer comprises a metal foil.

[0003] A carbon paste layer is formed between the first layer and the second layer, that is, between the solid electrolyte layer and the metal foil. The solid electrolyte layer and the metal foil are electrically connected and physically bonded via the carbon paste layer.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-079866 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, in the structure of Patent Document 1, corrosion of the cathode including the metal foil may occur due to the intrusion of moisture from the outside, etc. In addition, in the structure of Patent Document 1, due to the difference in linear expansion coefficient between the metal foil and the solid electrolyte layer, the expansion and contraction stress caused by the thermal history between the metal foil and the solid electrolyte layer may cause insulation peeling.

[0009] Therefore, an object of the present invention is to provide a solid electrolytic capacitor that suppresses cathode corrosion and internal insulation separation.

[0010] Means for solving problems

[0011] The solid electrolytic capacitor of the present invention comprises a plurality of capacitor elements and a plurality of cathodes. The plurality of capacitor elements respectively comprise a film-shaped valve-acting metal body, a dielectric layer and a solid electrolyte layer. The cathode comprises a second resin substrate and a second conductive material. The plurality of capacitor elements and the plurality of cathodes are alternately stacked in a state where the solid electrolyte layer is in contact with the cathode. The region where the solid electrolyte layer is in contact with the cathode has a portion where the solid electrolyte layer and the cathode are mixed.

[0012] In this structure, the solid electrolyte layer and the cathode are mainly composed of the same type of resin, and the solid electrolyte layer and the cathode are mixed in their contact portion. Therefore, the contact area between the solid electrolyte layer and the cathode becomes larger, and the bonding strength between the solid electrolyte layer and the cathode is improved. In addition, the interface is suppressed due to the difference in physical properties, and peeling is suppressed. In addition, since the cathode is not a metal foil, corrosion is suppressed.

[0013] Effects of the Invention

[0014] According to the present invention, corrosion of the cathode and internal insulation separation can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a perspective view of the appearance of a solid electrolytic capacitor according to an embodiment of the present invention.

[0016] Figure 2 It is a side cross-sectional view showing the structure of a solid electrolytic capacitor according to an embodiment of the present invention.

[0017] Figure 3 (A) is a top view of the capacitor element. Figure 3 (B) is a side cross-sectional view of the capacitor element.

[0018] Figure 4 is a cross-sectional view showing the structure of a cathode film.

[0019] Figure 5 It is an enlarged cross-sectional view of the contact portion between the outer layer CP and the cathode film.

[0020] Figure 6 This is a flowchart showing an example of a schematic flow of a method for manufacturing a solid electrolytic capacitor according to the present embodiment.

[0021] Figure 7 (A) is a three-dimensional diagram of the appearance of the capacitor element sheet. Figure 7 (B) is a three-dimensional diagram of the appearance of the cathode plate.

[0022] Figure 8 This is a perspective view of the appearance of a laminate of capacitor element sheets and cathode sheets (chip capacitor laminate). DETAILED DESCRIPTION

[0023] A solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor according to embodiments of the present invention will be described with reference to the drawings.

[0024] (Description of Structure of Solid Electrolytic Capacitor 10)

[0025] Figure 1 It is a perspective view of the appearance of a solid electrolytic capacitor according to an embodiment of the present invention. Figure 2 It is a side cross-sectional view showing the structure of a solid electrolytic capacitor according to an embodiment of the present invention. Figure 2 is a cross-sectional view of a solid electrolytic capacitor taken along a plane perpendicular to the top, bottom, and end faces of the body. Figure 2 In order to describe the structure in an easily understandable manner, the dimensions in various directions are appropriately emphasized, and in particular, the dimension in the height direction (z-axis direction in the drawing) is emphasized (exaggerated).

[0026] like Figure 1 , Figure 2 As shown, the solid electrolytic capacitor 10 includes a base body 11 , a resin electrode 71 , a resin electrode 72 , an external electrode 81 , and an external electrode 82 .

[0027] The green body 11 is in a rectangular parallelepiped shape and has a top surface, a bottom surface, an end surface 111 , an end surface 112 , and two side surfaces. The green body 11 includes a plurality of capacitor elements 20 , a plurality of cathode films 30 , an insulating resin 50 , and an insulating layer 500 .

[0028] (Capacitor element 20)

[0029] Figure 3 (A) is a top view of the capacitor element. Figure 3 (B) is a side cross-sectional view of the capacitor element. Figure 3 (B) is a cross-sectional view of a surface perpendicular to the flat film surface and the end surface of the capacitor element.

[0030] like Figure 3 (A) Figure 3 As shown in (B), the capacitor element 20 includes an anode electrode 21, an inner layer CP22, and an outer layer CP23. The inner layer CP22 and the outer layer CP23 constitute a solid electrolyte layer SEL.

[0031] The anode electrode 21 is in the form of a flat film, and has an end face 211, an end face 212, a flat film surface 213, and a flat film surface 214. Figure 3 Although the detailed structure is omitted in the figure, the anode electrode 21 has many holes recessed from the flat membrane surfaces 213 and 214. In other words, the portion of the anode electrode 21 with a predetermined thickness near the flat membrane surfaces 213 and 214 is a porous body in a porous state. The thickness ratio of the porous body on one side of the anode electrode 21, the core bone portion, and the porous body on the other side is about 1:1:1. The dielectric layer 210 covers the outer surface of the anode electrode 21. Figure 3 In the figure, the detailed structure of the anode electrode 21 is omitted, and therefore the dielectric layer 210 is schematically illustrated as covering the macroscopic surface (flat film surface 213, 214) of the anode electrode 21. However, in reality, the dielectric layer 210 covers not only the macroscopic surface (flat film surface 213, 214) of the anode electrode 21, but also the inner surfaces of many holes of the anode electrode 21.

[0032] Anode electrode 21 includes, for example, a single metal such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, silicon, or an alloy containing these metals. Anode electrode 21 is preferably aluminum or an aluminum alloy. Anode electrode 21 may be a valve-acting metal body that exhibits a so-called valve action.

[0033] The inner layer CP22 covers the surface of the dielectric layer 210. The inner layer CP22 includes a conductive polymer and fills the fine recesses of the porous portion.

[0034] The outer layer CP23 covers the surface of the inner layer CP22. In other words, for example, the outer layer CP23 is a layer formed to cover the entire dielectric layer 210 after the inner layer CP22 that fills the fine recessed portion of the porous portion is formed. The outer layer CP23 includes the same material as the inner layer CP22. The outer layer CP23 may include a resin material, or may be a material different from that of the inner layer CP22 (including composition).

[0035] The insulator layer 500 is formed near the end faces 211 and 212 on the flat film surfaces 213 and 214 of the anode electrode 21. The insulator layer 500 is a frame that limits the formation area of ​​the inner layer CP22 and the outer layer CP23. Thus, for example, the inner layer CP22 and the outer layer CP23 do not reach the end face 211 in the anode electrode 21.

[0036] With such a structure, the anode electrode 21 and the solid electrolyte layer (a laminate of the inner layer CP22 and the outer layer CP23 ) face each other via the dielectric layer 210 , and the capacitor element 20 functions as a capacitor having a predetermined electrostatic capacitance.

[0037] (Cathode film 30)

[0038] Figure 4 is a cross-sectional view showing the structure of the cathode film. Figure 4 As shown, the cathode film 30 includes an insulating substrate 31 and a plurality of conductive fillers 32. The insulating substrate 31 is a film of a predetermined thickness and is made of a resin material. The conductive fillers 32 are metal particles. The conductive fillers 32 are not limited to metals, but are preferably metals.

[0039] By having such a structure, the cathode film 30 has electrical conductivity while having insulation in its main body. In addition, since the cathode film 30 is not a metal foil, corrosion due to moisture or the like can be suppressed.

[0040] The insulating base material 31 of the cathode film 30 may be thermosetting or thermoplastic, and each has its own advantages. The advantages will be described below.

[0041] (Laminate Structure of Multiple Capacitor Elements 20 and Multiple Cathode Films 30)

[0042] The plurality of capacitor elements 20 and the plurality of cathode films 30 are arranged so that their respective flat film surfaces are substantially parallel to the top and bottom surfaces of the blank 11. The plurality of capacitor elements 20 and the plurality of cathode films 30 are alternately stacked in a direction orthogonal to the top and bottom surfaces (the height direction of the blank 11 (the z-axis direction in the figure)). Figure 2 In the embodiment, the number of the plurality of capacitor elements 20 is 3, and the number of the plurality of cathode films 30 is 4, but the present invention is not limited thereto.

[0043] At this time, the capacitor elements 20 adjacent to each other in the stacking direction are in contact with the cathode film 30. More specifically, the flat film surface of the cathode film 30 is in contact with the outer surface 230 of the outer layer CP23 of the capacitor element 20.

[0044] (Structure of green body 11)

[0045] The stacked body of the plurality of capacitor elements 20 and the plurality of cathode films 30 is covered with insulating resin 50. Thus, green body 11 is formed.

[0046] End faces 211 of the plurality of capacitor elements 20 are exposed from end faces 111 of the body 11 to the outside of the body 11. In addition, end faces 311 of the plurality of cathode films 30 are exposed from end faces 112 of the body 11 to the outside of the body 11.

[0047] (Construction of terminal conductor)

[0048] The resin electrode 71 contacts the end surface 111 of the green body 11 and covers the end surface 111. Thus, the resin electrode 71 is connected to the end surfaces 211 of the plurality of capacitor elements 20. The external electrode 81 is a laminated structure of an electrode film 811 and an electrode film 812. The electrode film 811 covers the outer surface of the resin electrode 71, and the electrode film 812 covers the outer surface of the electrode film 811. The resin electrode 71 and the external electrode 81 constitute a first terminal conductor.

[0049] The resin electrode 72 abuts against the end surface 112 of the body 11 and covers the end surface 112. Thus, the resin electrode 72 is connected to the end surfaces 311 of the plurality of cathode films 30. The external electrode 82 is a laminated structure of an electrode film 821 and an electrode film 822. The electrode film 821 covers the outer surface of the resin electrode 72, and the electrode film 822 covers the outer surface of the electrode film 821. The resin electrode 72 and the external electrode 82 constitute a second terminal conductor.

[0050] The solid electrolytic capacitor 10 is realized by the above-described structure.

[0051] (Connection Structure of Solid Electrolyte Layer and Cathode Film 30)

[0052] In the above structure, the contact portion between the outer layer CP23 and the cathode film 30 has the following structure. Figure 5 It is an enlarged cross-sectional view of the contact portion between the outer layer CP and the cathode film.

[0053] like Figure 5 As shown, in the area 323 where the outer layer CP23 contacts the cathode film 30, the outer layer CP23 and the cathode film 30 are mixed. The mixed existence here means that the stacking direction of the outer layer CP23 and the cathode film 30 ( Figure 5 The ratio of the resin portion based on the outer layer CP23 to the resin portion based on the cathode film 30 in the plane orthogonal to the stacking direction ( Figure 5 The outer layer CP23 is uneven in the two-dimensional region determined by the x-axis direction and the y-axis direction, and the portion based on the outer layer CP23 and the portion based on the cathode film 30 are mixed alternately. In other words, a resin solid solution region is formed.

[0054] In addition, when the resin material constituting the outer layer CP23 is the same as the resin material constituting the cathode film 30, no Figure 5 There is no obvious boundary line as shown by the solid line, but in fact, the outer layer CP23 and the cathode film 30 are mixed.

[0055] This structure increases the contact area between the outer layer CP23 and the cathode film 30, thereby improving the bonding strength. In addition, the interface between the outer layer CP23 and the cathode film 30 is suppressed from being significantly generated due to the difference in physical properties, thereby suppressing the interface peeling between the outer layer CP23 and the cathode film 30.

[0056] Thus, the solid electrolytic capacitor 10 can suppress the corrosion of the cathode and the stripping insulation between the cathode and the solid electrolyte layer. In addition, the resin material of the outer layer CP23 and the resin material of the cathode film 30 are preferably completely the same, but can also be similar in composition within the scope of the above-mentioned effects.

[0057] In addition, a plurality of cathode films 30 are connected to the resin electrode 72. In this structure, both the cathode film 30 and the resin electrode 72 include a resin material (resin component). Thus, the difference in physical properties between the cathode film 30 and the resin electrode 72 is reduced, and the delamination insulation between the cathode film 30 and the resin electrode 72 can be suppressed.

[0058] (Method of Manufacturing Solid Electrolytic Capacitor 10)

[0059] The solid electrolytic capacitor 10 having the above-described structure is manufactured, for example, as follows. Figure 6 This is a flowchart showing an example of a schematic flow of a method for manufacturing a solid electrolytic capacitor according to the present embodiment. Figure 7 (A) is a three-dimensional diagram of the appearance of the capacitor element sheet. Figure 7 (B) is a three-dimensional diagram of the appearance of the cathode plate. Figure 8This is a perspective view of the appearance of a laminate of capacitor element sheets and cathode sheets (chip capacitor laminate).

[0060] The capacitor element sheet 20M is formed (S11). Figure 7 As shown in (A), the capacitor element sheet 20M is a sheet in which a plurality of capacitor elements 20 are two-dimensionally arranged. The specific structure of the plurality of capacitor elements 20 is as described above, and includes an anode electrode 21, a dielectric layer 210, an inner layer CP22, and an outer layer CP23, and an insulating layer 500 for the inner layer CP22 and the outer layer CP23.

[0061] The cathode sheet 30M is formed (S12). Figure 7 As shown in (B), the cathode sheet 30M is a sheet in which a plurality of cathode films 30 are two-dimensionally arranged. The arrangement pitch of the plurality of cathode films 30 is the same as the arrangement pitch of the plurality of capacitor elements 20 .

[0062] Multiple capacitor element sheets 20M and multiple cathode sheets 30M are stacked in sequence and heat-pressed (S13). More specifically, multiple capacitor element sheets 20M and multiple cathode sheets 30M are stacked so that the outer surfaces 230 of multiple outer layers CP23 of adjacent capacitor element sheets 20M in the stacking direction are in contact with the cathode film 30 of the cathode sheet 30M. Thus, a sheet-type capacitor stack is formed.

[0063] Then, the chip capacitor laminate is heated and pressurized. By heating and pressurizing, the portion of the contact surface between the outer layer CP23 and the cathode film 30 is deformed to a predetermined depth, and becomes a state where the portion based on the outer layer CP23 and the portion based on the cathode film 30 are interlaced and mixed as described above (resin solid solution area: refer to Figure 5 ).

[0064] Along Figure 8 The chip capacitor laminate is cut into individual pieces along the cutting lines CL1 and CL2 as shown ( S14 ). At this time, the cathode sheet 30M (cathode film 30 ) is made of resin as a base material, so burrs generated on the cut surface can be suppressed. Thus, undesired short circuits can be suppressed.

[0065] The monolithic capacitor laminate is covered with an insulating resin 50 (S15). At this time, the insulating resin 50 is heated and pressurized. As a result, the insulating resin 50 is cured to form the green body 11 of the solid electrolytic capacitor 10. At this time, if the temperature during the heating and pressing of the insulating resin 50 is appropriately adjusted, the heating and pressing of the insulating resin 50 can be used to appropriately adjust the state of the above-mentioned staggered mixing of the portion based on the outer layer CP23 and the portion based on the cathode film 30.

[0066] Terminal conductors are formed on the end faces 111 and 112 of the body 11 ( S16 ). More specifically, the resin electrode 71 is formed on the end face 111 of the body 11, and the electrode films 811 and 812 are formed on the surface of the resin electrode 71 . The resin electrode 72 is formed on the end face 112 of the body 11, and the electrode films 821 and 822 are formed on the surface of the resin electrode 72 .

[0067] By using the above manufacturing method, the solid electrolytic capacitor 10 can be manufactured without using a conductive adhesive between the outer layer CP23 and the cathode film 30. Furthermore, the solid electrolytic capacitor 10 having strong bonding strength between the outer layer CP23 and the cathode film 30 and suppressing insulation separation can be manufactured easily and more reliably.

[0068] (Physical Properties of Cathode Film 30)

[0069] (Insulating base material 31 is thermosetting resin and the content of conductive filler 32 is low)

[0070] In the state before heating, the fluidity of the insulating base material 31 is high, so the resin solid solution region becomes larger (in the thickness direction), and the bonding strength between the outer layer CP23 and the cathode film 30 becomes higher.

[0071] In addition, since the insulating base material 31 is a thermosetting resin, the shape of the cathode film 30 is highly maintainable when cooled after heat and pressure bonding, that is, after the resin is solidified. As a result, the stability of the bonding between the cathode film 30 and the outer layer CP23 is increased, and the long-term reliability of the solid electrolytic capacitor 10 is increased.

[0072] (Insulating base material 31 is thermosetting resin and the content of conductive filler 32 is high)

[0073] Since the insulating base material 31 is a thermosetting resin, the shape of the cathode film 30 is highly maintainable when cooled after heat and pressure bonding, that is, after the resin is solidified. As a result, the stability of the bonding between the cathode film 30 and the outer layer CP23 is increased, and the long-term reliability of the solid electrolytic capacitor 10 is increased.

[0074] In addition, since the content of the conductive filler 32 is high, the strength of the cathode film 30 is high, and strong adhesion can be achieved even in a region where the resin is less solid-solubilized.

[0075] The specific numerical value indicating whether the content of the conductive filler 32 is low or high can be appropriately set from the viewpoint of the fluidity and strength of the cathode film 30. As an example, from the viewpoint of improving fluidity, a case where the content of the conductive filler 32 is 30% by volume or less is defined as a low content of the conductive filler 32, and from the viewpoint of improving strength, a case where the content of the conductive filler 32 is 70% by volume or more is defined as a high content of the conductive filler 32. In addition, these are examples, and for example, the content can be appropriately adjusted according to the physical properties and thickness of the insulating base material 31, and the content of the conductive filler 32 can be appropriately set according to the degree of influence on the fluidity or strength of the cathode film 30.

[0076] (When the insulating base material 31 is a thermoplastic resin)

[0077] Since the insulating base material 31 has high fluidity during heating, the resin solid solution region becomes larger (in the thickness direction), and the bonding strength between the outer layer CP23 and the cathode film 30 becomes higher. In addition, no additional processing on the material side is required for heating and melting.

[0078] Description of Reference Numerals

[0079] 10: Solid electrolytic capacitor;

[0080] 11: blank;

[0081] 20: Capacitor element;

[0082] 20M: capacitor element sheet;

[0083] 21: anode electrode;

[0084] 22: inner CP;

[0085] 23: Outer CP;

[0086] 30: cathode film;

[0087] 30M: cathode sheet;

[0088] 31: Insulating substrate;

[0089] 32: Conductive filler;

[0090] 50: Insulating resin;

[0091] 71, 72: resin electrodes;

[0092] 81, 82: external electrodes;

[0093] 111, 112: end face;

[0094] 210: dielectric layer;

[0095] 211, 212: end face;

[0096] 213, 214: flat membrane surface;

[0097] 230: outer surface;

[0098] 311: end face;

[0099] 323: Region;

[0100] 500: insulator layer;

[0101] 811, 812, 821, 822: electrode membrane.

Claims

1. A solid electrolytic capacitor comprising: a plurality of capacitor elements, each of which includes a film-shaped valve-acting metal body, a dielectric layer, and a solid electrolyte layer; and Multiple cathodes, The cathode includes a second resin substrate and a second conductive material, The plurality of capacitor elements and the plurality of cathodes are alternately stacked in a state where the solid electrolyte layer is in contact with the cathode. The region where the solid electrolyte layer is in contact with the cathode has a portion where the solid electrolyte layer and the cathode are mixed.

2. The solid electrolytic capacitor according to claim 1, wherein: The second resin base material is a thermosetting resin.

3. The solid electrolytic capacitor according to claim 1, wherein: The second resin substrate is a thermoplastic resin.

4. The solid electrolytic capacitor according to any one of claims 1 to 3, wherein: The solid electrolytic capacitor comprises: a capacitor stack in which the plurality of capacitor elements and the plurality of cathodes are stacked; An insulating resin that insulates and seals the capacitor stack so that the plurality of valve-acting metal bodies are exposed at one end face and the plurality of cathodes are exposed at another end face; A first terminal conductor formed on the one end surface and connected to the plurality of valve-acting metal bodies; and a second terminal conductor formed on the other end surface and connected to the cathode, The second terminal conductor includes a resin electrode in contact with the other end surface.

5. A method for manufacturing a solid electrolytic capacitor, comprising the following steps: forming a capacitor element sheet obtained by arranging capacitor elements including a film-shaped valve-acting metal body, a dielectric layer, and a solid electrolyte layer; forming a cathode sheet formed by arranging a plurality of cathodes; stacking the capacitor element sheet and the cathode sheet; and The stacked capacitor element sheets and the cathode sheet are heat-compressed.

6. The method for manufacturing a solid electrolytic capacitor according to claim 5, wherein: The cathode sheet includes a resin base material of a thermosetting resin.

7. The method for manufacturing a solid electrolytic capacitor according to claim 5, wherein: The cathode sheet includes a resin substrate of a thermoplastic resin.

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