Solid electrolytic capacitor and method for manufacturing the solid electrolytic capacitor

Abstract

This solid electrolytic capacitor (10) comprises a plurality of capacitor elements (20) and a plurality of negative electrode films (30). The plurality of capacitor elements (20) each comprise a positive electrode (21), a dielectric layer (210), and an inner layer CP (22) and an outer layer CP (23). The negative electrode films 30 each include an insulating base material (31) and a plurality of conductive fillers (32). The plurality of capacitor elements (20) and the plurality of negative electrode films (30) are alternately stacked in a state in which the outer layer CP (23) and the negative electrode films (30) are in contact with each other. A region, in which the outer layer CP (23) and the negative electrode films (30) are in contact with each other, has a portion in which a solid electrolytic layer and the negative electrode are both present.

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor having a structure in which a capacitor element, in which a dielectric layer and a solid electrolyte layer are formed on a valve metal body, and a cathode film are laminated together. [Background technology]

[0002] The solid electrolytic capacitor of Patent Document 1 includes an element stack consisting of first layers that function as capacitors and second layers that function as cathodes. The first layers are made of valve metal elements with a dielectric layer formed on their surfaces, and a solid electrolyte layer provided on the dielectric layer. The second layer is made of metal foil.

[0003] A carbon paste layer is formed between the first and second layers, i.e., between the solid electrolyte layer and the metal foil, electrically connecting and physically bonding the solid electrolyte layer and the metal foil together through the carbon paste layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-079866 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration of Patent Document 1, corrosion of the cathode made of metal foil may occur due to the intrusion of moisture from the outside, etc. Furthermore, in the configuration of Patent Document 1, due to the difference in the linear expansion coefficient between the metal foil and the solid electrolyte layer, there is a possibility that peeling and insulation may occur due to expansion and contraction stress caused by thermal history between the metal foil and the solid electrolyte layer.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a solid electrolytic capacitor that suppresses corrosion of the cathode and internal insulation peeling. [Means for solving the problem]

[0007] The solid electrolytic capacitor of the present invention includes a plurality of capacitor elements and a plurality of cathodes. Each of the plurality of capacitor elements includes a film-like valve metal element, a dielectric layer, and a solid electrolyte layer. The cathode includes a second resin base material and a second conductive material. The plurality of capacitor elements and the plurality of cathodes are alternately stacked with the solid electrolyte layer and the cathode in contact with each other. The region where the solid electrolyte layer and the cathode contact each other has a portion where the solid electrolyte layer and the cathode are mixed.

[0008] In this configuration, the solid electrolyte layer and the cathode are primarily made of the same type of resin, and the solid electrolyte layer and the cathode are mixed at their contact point. This increases the contact area between the solid electrolyte layer and the cathode, improving the adhesive strength between them. Furthermore, the occurrence of a clear interface due to differences in physical properties is suppressed, and peeling is suppressed. Furthermore, because the cathode is not a metal foil, corrosion is suppressed. [Effects of the Invention]

[0009] According to this invention, corrosion of the cathode and internal insulation peeling can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of the appearance of a solid electrolytic capacitor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side cross-sectional view showing the configuration of the solid electrolytic capacitor according to the embodiment of the present invention. [Figure 3] FIG. 3(A) is a plan view of the capacitor element, and FIG. 3(B) is a side cross-sectional view of the capacitor element. [Figure 4] FIG. 4 is a cross-sectional view showing the configuration of the cathode film. [Figure 5] FIG. 5 is an enlarged cross-sectional view of the contact portion between the outer layer CP and the cathode film. [Figure 6] FIG. 6 is a flowchart showing an example of a schematic flow of the method for manufacturing the solid electrolytic capacitor according to this embodiment. [Figure 7]FIG. 7(A) is an external perspective view of a capacitor element sheet, and FIG. 7(B) is an external perspective view of a cathode sheet. [Figure 8] FIG. 8 is an external perspective view of a laminate (sheet-type capacitor laminate) of a capacitor element sheet and a cathode sheet. DETAILED DESCRIPTION OF THE INVENTION

[0011] A solid electrolytic capacitor and a method for manufacturing the solid electrolytic capacitor according to an embodiment of the present invention will be described with reference to the drawings.

[0012] (Explanation of the configuration of solid electrolytic capacitor 10) Fig. 1 is an external perspective view of a solid electrolytic capacitor according to an embodiment of the present invention. Fig. 2 is a side cross-sectional view showing the configuration of a solid electrolytic capacitor according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along a plane perpendicular to the top, bottom, and end faces of the body of the solid electrolytic capacitor. Note that in Fig. 2, to clearly illustrate the configuration, the dimensions in each direction are appropriately emphasized, and the dimensions in the height direction (z-axis direction in the drawing) are particularly emphasized (exaggerated).

[0013] As shown in FIGS. 1 and 2, solid electrolytic capacitor 10 includes element body 11, resin electrode 71, resin electrode 72, external electrode 81, and external electrode .

[0014] The element body 11 has 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 element body 11 includes a plurality of capacitor elements 20, a plurality of cathode films 30, an insulating resin 50, and an insulator layer 500.

[0015] (Capacitor element 20) Fig. 3(A) is a plan view of the capacitor element, and Fig. 3(B) is a side cross-sectional view of the capacitor element, Fig. 3(B) is a cross-sectional view taken along a plane perpendicular to the flat film surface and end surface of the capacitor element.

[0016] 3(A) and 3(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 form a solid electrolyte layer SEL.

[0017] The anode electrode 21 is in the form of a flat membrane and has end surfaces 211, 212, flat membrane surfaces 213, and flat membrane surfaces 214. Although detailed structural illustration is omitted in FIG. 3, the anode electrode 21 has a large number of holes recessed from the flat membrane surfaces 213, 214. In other words, portions of the anode electrode 21 with a predetermined thickness near the flat membrane surfaces 213, 214 are porous. The thickness ratio of the porous body and core metal portion on one side of the anode electrode 21 to the porous body on the other side is approximately 1:1:1. The dielectric layer 210 covers the outer surface of the anode electrode 21. Because detailed structural illustration of the anode electrode 21 is omitted in FIG. 3, the dielectric layer 210 is schematically illustrated as covering the macroscopic surface (flat membrane surfaces 213, 214) of the anode electrode 21. However, in reality, the dielectric layer 210 covers not only the macroscopic surface (flat membrane surfaces 213 and 214) of the anode electrode 21, but also the inner surfaces of the numerous pores of the anode electrode 21.

[0018] The anode electrode 21 is made of, for example, a metal such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, or silicon, or an alloy containing these metals. The anode electrode 21 is preferably made of aluminum or an aluminum alloy. The anode electrode 21 may be any valve metal that exhibits a so-called valve action.

[0019] The inner layer CP22 covers the surface of the dielectric layer 210. The inner layer CP22 is made of a conductive polymer and fills the fine recesses in the porous portion.

[0020] 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 so as to cover the entire dielectric layer 210 after the inner layer CP22 is formed to fill the fine recesses in the porous portion. The outer layer CP23 is made of the same material as the inner layer CP22. The outer layer CP23 may be made of a material (including a composition) different from that of the inner layer CP22 as long as it contains a resin material.

[0021] The insulator layer 500 is formed near the end faces 211 and 212 of the flat membrane surfaces 213 and 214 of the anode electrode 21. The insulator layer 500 is a frame body that restricts the formation areas of the inner layer CP22 and the outer layer CP23. As a result, for example, the inner layer CP22 and the outer layer CP23 do not reach the end face 211 of the anode electrode 21.

[0022] With this configuration, the anode electrode 21 and the solid electrolyte layer (a laminate of the inner layer CP22 and the outer layer CP23) face each other with the dielectric layer 210 sandwiched between them, and the capacitor element 20 functions as a capacitor having a predetermined capacitance.

[0023] (Cathode film 30) Fig. 4 is a cross-sectional view showing the configuration of a cathode film. As shown in Fig. 4, a cathode film 30 includes an insulating substrate 31 and a plurality of conductive fillers 32. The insulating substrate 31 is a film having a predetermined thickness and contains a resin material. The conductive fillers 32 are metal particles. Note that the conductive fillers 32 are not limited to metal, but are preferably metal.

[0024] With this configuration, the cathode film 30 has electrical conductivity while the main body has insulating properties. Furthermore, since the cathode film 30 is not a metal foil, corrosion due to moisture and the like is suppressed.

[0025] The insulating substrate 31 of the cathode film 30 may be either thermosetting or thermoplastic, each of which has its own advantages, which will be described later.

[0026] (Layer structure of multiple capacitor elements 20 and multiple cathode films 30) The plurality of capacitor elements 20 and the plurality of cathode films 30 are arranged so that their respective flat film surfaces are approximately parallel to the top and bottom surfaces of the element body 11. The plurality of capacitor elements 20 and the plurality of cathode films 30 are alternately stacked in a direction perpendicular to the top and bottom surfaces (the height direction of the element body 11 (z-axis direction in the figure)). Note that, although the number of the plurality of capacitor elements 20 is three and the number of the plurality of cathode films 30 is four in FIG. 2, this is not a limitation.

[0027] At this time, the capacitor element 20 and the cathode film 30 adjacent to each other in the stacking direction are in contact with each other. 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.

[0028] (Configuration of element 11) This laminate of a plurality of capacitor elements 20 and a plurality of cathode films 30 is covered with insulating resin 50. In this way, element body 11 is formed.

[0029] End faces 211 of the plurality of capacitor elements 20 are exposed to the outside of element body 11 from end face 111 of element body 11. End faces 311 of the plurality of cathode films 30 are exposed to the outside of element body 11 from end face 112 of element body 11.

[0030] (Terminal conductor configuration) The resin electrode 71 abuts against and covers the end face 111 of the element body 11. In this way, the resin electrode 71 is connected to the end faces 211 of the plurality of capacitor elements 20. The external electrode 81 has 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 form a first terminal conductor.

[0031] The resin electrode 72 abuts against and covers the end face 112 of the element body 11. In this way, the resin electrode 72 is connected to the end faces 311 of the multiple cathode films 30. The external electrode 82 has 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 form a second terminal conductor.

[0032] The solid electrolytic capacitor 10 is realized by the above configuration.

[0033] (Connection structure between solid electrolyte layer and cathode film 30) In the above configuration, the contact portion between the outer layer CP23 and the cathode film 30 has the following structure: Fig. 5 is an enlarged cross-sectional view of the contact portion between the outer layer CP and the cathode film.

[0034] 5, in a region 323 where the outer layer CP23 and the cathode film 30 contact each other, the outer layer CP23 and the cathode film 30 are mixed together. Here, "mixed together" means that the ratio of the resin portion originating from the outer layer CP23 to the resin portion originating from the cathode film 30 in the stacking direction of the outer layer CP23 and the cathode film 30 (the z-axis direction in FIG. 5) is not uniform in a plane perpendicular to the stacking direction (a two-dimensional region determined by the x-axis and y-axis directions in FIG. 5), and the portions originating from the outer layer CP23 and the portions originating from the cathode film 30 are intricately mixed together. In other words, a resin solid solution region is formed.

[0035] When the resin material constituting the outer layer CP23 is the same as the resin material constituting the cathode film 30, a clear boundary line is not visible, as shown by the solid line in Figure 5, but the outer layer CP23 and the cathode film 30 are essentially mixed together.

[0036] This configuration increases the contact area and improves the adhesive strength between the outer layer CP23 and the cathode film 30. Furthermore, the outer layer CP23 and the cathode film 30 are prevented from having a clear interface due to differences in physical properties, and interfacial peeling between the outer layer CP23 and the cathode film 30 is suppressed.

[0037] This can suppress corrosion of the cathode and prevent separation and insulation between the cathode and the solid electrolyte layer in the solid electrolytic capacitor 10. It is preferable that the resin material of the outer layer CP23 and the resin material of the cathode film 30 are exactly the same, but they may have similar compositions as long as they achieve the above-mentioned effects.

[0038] Furthermore, the plurality of cathode films 30 are connected to a resin electrode 72. In this configuration, both the cathode films 30 and the resin electrode 72 contain a resin material (resin component), which reduces the difference in physical properties between the cathode films 30 and the resin electrode 72 and prevents separation and insulation between the cathode films 30 and the resin electrode 72.

[0039] (Method of manufacturing solid electrolytic capacitor 10) The solid electrolytic capacitor 10 having the above-described configuration is manufactured, for example, as follows. Fig. 6 is a flowchart showing an example of a schematic flow of a method for manufacturing a solid electrolytic capacitor according to this embodiment. Fig. 7(A) is an external perspective view of a capacitor element sheet, and Fig. 7(B) is an external perspective view of a cathode sheet. Fig. 8 is an external perspective view of a laminate (sheet-type capacitor laminate) of a capacitor element sheet and a cathode sheet.

[0040] A capacitor element sheet 20M is formed (S11). As shown in Fig. 7(A), the capacitor element sheet 20M is a sheet on which a plurality of capacitor elements 20 are two-dimensionally arranged. The specific configuration of the plurality of capacitor elements 20 is as described above, and includes the anode electrode 21, the dielectric layer 210, the inner layer CP22, and the outer layer CP23, and the insulator layer 500 is formed for the inner layer CP22 and the outer layer CP23.

[0041] A cathode sheet 30M is formed (S12). As shown in Fig. 7(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 and the arrangement pitch of the plurality of capacitor elements 20 are the same.

[0042] The plurality of capacitor element sheets 20M and the plurality of cathode sheets 30M are stacked in order and thermocompression bonded (S13). More specifically, the plurality of capacitor element sheets 20M and the plurality of cathode sheets 30M are stacked such that the outer surfaces 230 of the plurality of outer layers CP23 of the capacitor element sheets 20M adjacent in the stacking direction face and abut against the cathode film 30 of the cathode sheet 30M. This forms a sheet-type capacitor laminate.

[0043] Then, the sheet-type capacitor laminate is heated and pressurized, which deforms a portion at a predetermined depth from the contact surface between the outer layer CP23 and the cathode film 30, resulting in a state in which the portion originating from the outer layer CP23 and the portion originating from the cathode film 30 are intertwined and mixed (resin solid solution region: see FIG. 5).

[0044] The sheet-type capacitor laminate is cut along cutting lines CL1 and CL2 as shown in Fig. 8 to separate the laminate (S14). At this time, since the cathode sheet 30M (cathode film 30) is made of a resin as the base material, burrs generated on the cut surface can be suppressed. This makes it possible to suppress undesired short circuits and the like.

[0045] The singulated capacitor laminate is coated with insulating resin 50 (S15). At this time, the insulating resin 50 is heated and pressurized. This solidifies the insulating resin 50, and the element body 11 of the solid electrolytic capacitor 10 is formed. At this time, by appropriately adjusting the temperature during thermocompression bonding of the insulating resin 50, the thermocompression bonding of the insulating resin 50 can be used to appropriately adjust the state in which the portion originating from the outer layer CP23 and the portion originating from the cathode film 30 are intricately mixed together.

[0046] Terminal conductors are formed on end faces 111 and 112 of element body 11 (S16). More specifically, a resin electrode 71 is formed on end face 111 of element body 11, and electrode films 811 and 812 are formed on the surface of resin electrode 71. A resin electrode 72 is formed on end face 112 of element body 11, and electrode films 821 and 822 are formed on the surface of resin electrode 72.

[0047] By using the manufacturing method described above, 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 can be manufactured easily and more reliably, with strong adhesive strength between the outer layer CP23 and the cathode film 30, and with reduced insulation due to peeling.

[0048] (Physical properties of the cathode film 30) (When the insulating base material 31 is a thermosetting resin and the content of the conductive filler 32 is low) Since the insulating base material 31 has high fluidity before heating, the resin solid solution region becomes large (in the thickness direction), and the adhesive strength between the outer layer CP23 and the cathode film 30 becomes high.

[0049] Furthermore, since the insulating base material 31 is a thermosetting resin, the shape of the cathode film 30 is highly maintainable when the insulating base material 31 is heated and compressed and then cooled, i.e., after the resin is dissolved in a solid solution. This improves the stability of the adhesion between the cathode film 30 and the outer layer CP23, and improves the long-term reliability of the solid electrolytic capacitor 10.

[0050] (When the insulating base material 31 is a thermosetting resin and the content of the conductive filler 32 is high) Because the insulating base material 31 is a thermosetting resin, the shape of the cathode film 30 is highly maintainable when it is cooled after heat-pressure bonding, i.e., after the resin is solid-dissolved. This improves the stability of adhesion between the cathode film 30 and the outer layer CP23, and improves the long-term reliability of the solid electrolytic capacitor 10.

[0051] Furthermore, since the content of the conductive filler 32 is high, the cathode film 30 has high strength and can be firmly bonded even in a small resin solid solution region.

[0052] The specific numerical value indicating whether the content of the conductive filler 32 is low or high can be set appropriately from the viewpoint of the fluidity and strength of the cathode film 30. As an example, from the viewpoint of improving fluidity, a conductive filler 32 content of 30 volume % or less is defined as a low conductive filler 32 content, and from the viewpoint of improving strength, a conductive filler 32 content of 70 volume % or more is defined as a high conductive filler 32 content. Note that these are merely examples, and can be appropriately adjusted depending on, for example, the physical properties and thickness of the insulating base material 31, and can be appropriately set depending on the degree of influence of the conductive filler 32 content on the fluidity or strength of the cathode film 30.

[0053] (When the insulating substrate 31 is made of thermoplastic resin) Since the insulating base material 31 has high fluidity when heated, the resin solid solution region becomes large (in the thickness direction), and the adhesive strength between the outer layer CP23 and the cathode film 30 increases. In addition, no additional processing is required on the material side for heat melting. [Explanation of symbols]

[0054] 10: Solid electrolytic capacitor 11: Base body 20: Capacitor element 20M: Capacitor element sheet 21: Anode electrode 22: Inner layer CP 23: Outer layer CP 30: Cathode film 30M: Cathode sheet 31: Insulating substrate 32: Conductive filler 50: Insulating resin 71, 72: Resin electrodes 81, 82: External electrode 111, 112: End face 210: Dielectric layer 211, 212: End face 213, 214: Flat membrane surface 230: Exterior 311: End face 323: Area 500: Insulator layer 811, 812, 821, 822: Electrode films

Claims

1. a plurality of capacitor elements each including a film-like valve metal element, a dielectric layer, and a solid electrolyte layer; a plurality of cathodes; Equipped with the cathode includes a second resin base material and a second conductive material, the plurality of capacitor elements and the plurality of cathodes are alternately stacked in a state in which the solid electrolyte layer and the cathode are in contact with each other, a region where the solid electrolyte layer and the cathode are in contact with each other includes a portion where the solid electrolyte layer and the cathode are mixed; Solid electrolytic capacitor.

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

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

4. a capacitor laminate in which the plurality of capacitor elements and the plurality of cathodes are laminated; an insulating resin that insulates and seals the capacitor laminate, exposing the valve metal elements at one end surface and the cathodes at the other end surface; a first terminal conductor formed on the one end surface and connected to the plurality of valve metal elements; a second terminal conductor formed on the other end surface and connected to the cathode; Equipped with the second terminal conductor includes a resin electrode in contact with the other end surface; 4. The solid electrolytic capacitor according to claim 1.

5. forming a capacitor element sheet in which capacitor elements each including a film-like valve metal element, a dielectric layer, and a solid electrolyte layer are arranged; forming a cathode sheet on which a plurality of cathodes are arranged; laminating the capacitor element sheet and the cathode sheet; a step of heat-pressing the laminated capacitor element sheet and the cathode sheet together; The method for manufacturing a solid electrolytic capacitor includes the steps of:

6. The cathode sheet includes a resin substrate made of a thermosetting resin. The method for manufacturing the solid electrolytic capacitor according to claim 5 .

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

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