Solid electrolytic capacitor

Abstract

This solid electrolytic capacitor comprises: a sheet laminate formed by alternately laminating a plurality of flat membrane-like negative electrode foils and a plurality of flat membrane-like capacitor elements, each in which a dielectric layer and a solid electrolytic layer are sequentially formed on the surface of a flat membrane-like positive electrode foil having a porous part at a prescribed depth from the surface; first metal parts formed at an end of the solid electrolytic layer and at an end of the positive electrode foil in the sheet laminate; and an insulating resin for sealing the sheet laminate. The first metal parts have a first pore diameter larger than a second pore diameter of the porous part of the positive electrode foil.

Description

solid electrolytic capacitor

[0001] The present invention relates to a solid electrolytic capacitor having a laminate in which a plurality of capacitor elements and a plurality of cathode electrodes are alternately stacked.

[0002] Patent Document 1 describes a method for manufacturing a solid electrolytic capacitor and a solid electrolytic capacitor. The solid electrolytic capacitor described in Patent Document 1 includes a plurality of flat-film capacitor elements and a plurality of metal foils (cathodes). The flat-film capacitor elements include a foil-shaped valve metal substrate, a porous portion of the valve metal substrate and a dielectric layer formed on the surface thereof, and a solid electrolyte layer formed on the surface of the dielectric layer.

[0003] More specifically, the capacitor element of Patent Document 1 has the following configuration: The porous portion of the capacitor element is impregnated with an insulating resin (masking agent). Furthermore, an insulating adhesive is formed in a frame shape within this insulating resin. A solid electrolyte layer is formed within the frame of the insulating adhesive. Flat film-like capacitor elements and metal foils are alternately stacked to form an element stack. Furthermore, external electrodes in this solid electrolytic capacitor are formed on the ends of the element stack using conductive paste and Ni / Sn plating.

[0004] Japanese Patent Application Laid-Open No. 2019-79866

[0005] The solid electrolytic capacitor in Patent Document 1 has a certain degree of airtightness. That is, during MSL reflow, moisture that has penetrated the inside may evaporate, causing a sudden increase in internal pressure. This may cause cracks to form inside the solid electrolytic capacitor and reach the edge of the element stack. If these cracks occur during the manufacturing process, the Ni / Sn plating may penetrate into the cracks, causing LC defects in terms of long-term reliability.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a solid electrolytic capacitor that can suppress the occurrence of cracks and achieve high reliability.

[0007] The present invention provides a solid electrolytic capacitor comprising: a sheet laminate formed by alternately stacking a plurality of flat-film capacitor elements, each of which has a flat-film anode electrode foil having a porous portion extending to a predetermined depth from the surface, a dielectric layer, and a solid electrolyte layer, and a plurality of flat-film cathode electrode foils; a first metal portion formed on an end of the anode electrode foil and an end of the solid electrolyte layer in the sheet laminate; and an insulating resin sealing the sheet laminate. The first pore diameter of the first metal portion is larger than the second pore diameter of the porous portion of the anode electrode foil.

[0008] With this configuration, even if gas is generated due to evaporation of moisture contained inside the solid electrolytic capacitor, the gas can be easily released to the first metal part. In other words, an increase in the internal pressure of the solid electrolytic capacitor can be suppressed, and the occurrence of cracks inside the solid electrolytic capacitor can be suppressed.

[0009] According to the present invention, it is possible to provide a solid electrolytic capacitor that can suppress the occurrence of cracks and achieve high reliability.

[0010] FIG. 1 is a side cross-sectional view showing the configuration of a solid electrolytic capacitor according to a first embodiment. FIG. 2(A) is a side cross-sectional view showing the configuration of a set of capacitor elements and cathode electrodes before singulation. FIG. 2(B) is a side cross-sectional view showing the configuration of a capacitor element and cathode electrode set after singulation. FIG. 3(A) and FIG. 3(B) are side cross-sectional views showing the general configuration of a solid electrolytic capacitor. FIG. 4 is a perspective view showing the general appearance of the solid electrolytic capacitor. FIG. 5 is a diagram showing a schematic view of the flow of gas generated in the solid electrolytic capacitor. FIG. 6 is a flowchart showing an example of a general flow of a method for manufacturing a solid electrolytic capacitor according to this embodiment. FIG. 7 is a flowchart showing an example of a capacitor element sheet forming process. FIG. 8(A) is an external perspective view showing the shape of an anode electrode of a capacitor element before singulation. FIG. 8(B) is an external perspective view showing the shape of a capacitor element before singulation. FIG. 9 is an external view of a multi-component capacitor element. FIG. 10 is an external perspective view showing the shape of a cathode electrode before singulation. FIG. 11 is a flowchart showing an example of a process for forming a sheet laminate. FIGS. 12(A) and 12(B) are external perspective views showing a state in which a dam has been formed on a capacitor element sheet. FIGS. 13(A) and 13(B) are external perspective views showing a state in which a second dam and a first adhesive have been formed on a capacitor element sheet. FIGS. 14(A) and 14(B) are exploded perspective views showing a state in which capacitor element sheets and cathode electrode sheets are laminated. FIG. 15(A) is an exploded perspective view showing a laminated state of capacitor element sheets and cathode electrode sheets in a multi-layered state, and FIG. 15(B) is an external perspective view showing a laminated state of capacitor element sheets and cathode electrode sheets in a multi-layered state. FIG. 16 is a flowchart showing an example of a process for forming a first metal portion and a second metal portion. FIG. 17 is a side cross-sectional view showing the general configuration of a solid electrolytic capacitor according to a second embodiment. FIG. 18 is a side cross-sectional view showing the general configuration of a solid electrolytic capacitor according to a third embodiment. FIG. 19 is a side cross-sectional view showing the general configuration of a solid electrolytic capacitor according to a fourth embodiment.

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

[0012] (Explanation of Schematic Configuration of Solid Electrolytic Capacitor 1) First, the structure of a solid electrolytic capacitor according to an embodiment of the present invention will be described. FIG. 1 is a side cross-sectional view showing the configuration of a solid electrolytic capacitor according to a first embodiment. Note that in FIG. 1, only the insulating resin and external electrodes are hatched to make the drawing easier to see. FIG. 2(A) is a side cross-sectional view showing the configuration of a set of capacitor elements and cathode electrodes before singulation. FIG. 2(B) is a side cross-sectional view showing the configuration of a capacitor element and cathode electrode set after singulation. FIG. 2(C) is a side cross-sectional view showing the configuration of a set of capacitor elements and cathode electrodes after singulation.

[0013] As shown in FIGS. 1 , 2(A), 2(B), and 2(C), the solid electrolytic capacitor 1 includes a capacitor element laminate 100, an insulating resin 50, metal films 61 and 62, and external terminal electrodes 71 and 72. The capacitor element laminate 100 includes a plurality of flat-film capacitor elements 10 and a plurality of flat-film cathode electrodes 20. While FIG. 1 shows four flat-film capacitor elements 10 and four cathode electrodes, the number of such elements is not limited to four. The cathode electrodes 20 correspond to the "cathode electrode foil" of the present invention. Furthermore, the metal films 61 and 62 correspond to the "first metal portion" of the present invention, and the external terminal electrode 71 corresponds to the "second metal portion" of the present invention. The metal film 61 serves as a current collecting electrode on the anode side of the solid electrolytic capacitor 1, and the metal film 62 serves as a current collecting electrode on the cathode side of the solid electrolytic capacitor 1.

[0014] 1, solid electrolytic capacitor 1 has first main surface 101 and second main surface 102. First main surface 101 and second main surface 102 face each other. Second main surface 102 is the mounting surface of solid electrolytic capacitor 1.

[0015] As shown in FIG. 2B, the capacitor element 10 includes a flat film-like anode electrode 11, a dielectric layer 12, and a CP layer (solid electrolyte layer) 13.

[0016] Although detailed structural illustrations are omitted in Figures 2(A), 2(B), and 2(C), the anode 11 has numerous pores. In other words, the anode 11 is porous (porous body (porous portion)). The thickness ratio of the porous portion on one side of the anode 11 to the core metal portion and the porous portion on the other side is approximately 1:1:1. The dielectric layer 12 covers the outer surface of the anode 11. Because detailed structural illustrations of the anode 11 are omitted in Figures 2(A), 2(B), and 2(C), the dielectric layer 12 is schematically illustrated as covering the macroscopic surface of the anode 11. In reality, the dielectric layer 12 covers not only the macroscopic surface of the anode 11 but also the surfaces of the numerous pores in the anode 11. The anode 11 corresponds to the "anode electrode foil" in this invention.

[0017] The CP layer 13 covers the surface of the dielectric layer 12. The CP layer 13 is formed inside a frame-shaped first dam 14. The first dam 14 is insulating. The first dam 14 limits the area in which the CP layer 13 is formed. In the first embodiment, as described in the manufacturing method described below, the first dam 14 is formed in a frame shape, and then the CP layer 13 is formed inside the first dam 14. However, depending on the manufacturing method of the capacitor element 10, for example, when the capacitor element 10 is produced in an individualized state from the beginning, the first dam 14 does not have to be formed in a frame shape. That is, the first dam 14 may be formed on one side, or on two sides having a corner. Furthermore, the first dam 14 may be formed on two opposing sides in a planar view.

[0018] The CP layer 13 has a laminated structure of an inner layer CP (inner layer solid electrolyte layer) 131 and an outer layer CP (outer layer solid electrolyte layer) 132. The inner layer CP 131 is formed on the surface of the dielectric layer 12, and the outer layer CP 132 is formed on the surface of the inner layer CP 131.

[0019] The plurality of capacitor elements 10 and the plurality of cathode electrodes 20 are alternately stacked so that their flat film surfaces are parallel to each other and overlap each other in a plan view.

[0020] A second dam 30 and a first adhesive 40 are disposed between adjacent capacitor elements 10 and cathode electrodes 20. The second dam 30 has insulating and adhesive properties. The first adhesive 40 has electrical conductivity.

[0021] The second dam 30 is formed in a frame shape along the outer periphery of the surface of the capacitor element 10 where the CP layer 13 and the cathode electrode 20 face each other. As shown in Fig. 2B, the second dam 30 is formed so as to overlap the first dam 14. The second dam 30 is made of an insulating material such as an insulating resin.

[0022] The first adhesive 40 is disposed inside the frame defined by the second dam 30. The first adhesive 40 bonds the adjacent capacitor elements 10 and cathode electrodes 20 together.

[0023] In this stacked state, the first ends 10E1 of the plurality of capacitor elements 10 are at the same position in side view. Similarly, the second ends 10E2 of the plurality of capacitor elements 10 are at the same position in side view. Furthermore, the first ends 20E1 of the plurality of cathode electrodes 20 are at the same position in side view. Similarly, the second ends 20E2 of the plurality of cathode electrodes 20 are at the same position in side view. However, the "same position" includes unintentional variations during processing, and also includes cases where the positions are not strictly the same.

[0024] The first ends 10E1 of the plurality of capacitor elements 10 and the second ends 20E2 of the plurality of cathode electrodes 20 are arranged on the first end side of the capacitor element stack 100. The first ends 10E1 of the plurality of capacitor elements 10 protrude outward beyond the second ends 20E2 of the plurality of cathode electrodes 20.

[0025] The second ends 10E2 of the plurality of capacitor elements 10 and the first ends 20E1 of the plurality of cathode electrodes 20 are arranged on the second end side of the capacitor element stack 100. The first ends 20E1 of the plurality of cathode electrodes 20 protrude outward beyond the second ends 10E2 of the plurality of capacitor elements 10.

[0026] With this structure, the capacitor element laminate 100 is realized.

[0027] The above-described configuration has been described as an example of a configuration including the first adhesive 40. However, the CP layer 13 may be formed thicker, or a CP layer (solid electrolyte layer) containing a binder may be formed instead of the first adhesive 40. Even when the first adhesive 40 is omitted in this way, a structure in which the capacitor element 10 and the cathode electrode 20 are bonded together can be achieved.

[0028] The capacitor element stack 100 is sealed with insulating resin 50. More specifically, the insulating resin 50 covers the capacitor element stack 100 except for first ends 10E1 of the plurality of capacitor elements 10 (first ends 10E1 of the anode electrodes 11) and first ends 20E1 of the plurality of cathode electrodes 20.

[0029] The metal film 61 covers the first end 10E1 of the anode electrode 11 and the outer surface of the insulating resin 50 on the first end 10E1 side. That is, the metal film 61 serves as an anode-side current collecting electrode connected to the first ends 10E1 of the anode electrodes 11 of the multiple capacitor elements 10. Furthermore, the external terminal electrode 71 is formed to abut against the metal film 61.

[0030] Similarly, the metal film 62 covers the first end 20E1 of the cathode electrode 20 and the outer surface of the insulating resin 50 on the first end 20E1 side. That is, the metal film 62 serves as a cathode-side current collecting electrode connected to the first ends 20E1 of the cathode electrodes 20 of the multiple capacitor elements 10. Furthermore, the external terminal electrode 72 is formed so as to abut against the metal film 62.

[0031] The solid electrolytic capacitor 1 is realized by the above configuration.

[0032] (Detailed Structure of External Electrodes) Next, the detailed structures of the metal films 61, 62 and the external terminal electrodes 71, 72 will be described using FIGS. 3A, 3B, 4, and 5. FIG. 3A is a diagram showing an overview in which the metal film 61 is formed on the first end 10E1 side of the anode electrode 11 and the metal film 62 is formed on the first end 20E1 side of the cathode electrode 20. FIG. 3B is a diagram showing an overview in which the external terminal electrodes 71 and 72 are formed on the structure of FIG. 3A. FIG. 4 is an external perspective view showing an overview in which the external terminal electrodes 71, 72 are formed on the capacitor element laminate 100. For ease of understanding, the structures in FIGS. 3A, 3B, and 4 are enlarged and exaggerated.

[0033] 3A, the metal film 61 is formed by spraying metal onto the first end 10E1 of the anode electrode 11 and the outer surface of the insulating resin 50 on the first end 10E1 side. Similarly, the metal film 62 is formed by spraying metal onto the first end 20E1 of the cathode electrode 20 and the outer surface of the insulating resin 50 on the first end 20E1 side.

[0034] 3B and 4, the external terminal electrode 71 is formed so as to abut against the metal film 61. At this time, the external terminal electrode 71 covers a part of the mounting surface side (the second main surface 102 side of the capacitor element laminate 100) of the metal film 61. The external terminal electrode 71 has an opening on the surface side facing the mounting surface of the metal film 61. In other words, the external terminal electrode 71 is formed so as to have an opening 751 on the first main surface 101 side.

[0035] 3B and 4 , the external terminal electrode 72 is formed so as to abut against the metal film 62. In this case, the external terminal electrode 72 covers a part of the mounting surface side of the metal film 62 (the second main surface 102 side of the capacitor element laminate 100). The external terminal electrode 72 has an opening on the surface side facing the mounting surface of the metal film 62. In other words, the external terminal electrode 72 is formed so as to have an opening 752 on the first main surface 101 side.

[0036] Here, a detailed configuration of the metal films 61, 62 will be described. The first pore diameter D1 of the metal films 61, 62 is preferably larger than the second pore diameter D2 of the porous portion of the anode electrode 11. In this case, the first pore diameter D1 is the average pore diameter of the metal films 61, 62, and the second pore diameter D2 is the average pore diameter of the anode electrode 11.

[0037] The relationship between the first pore diameter D1 and the second pore diameter D2 is governed by the law of conservation of mass. In other words, the law (continuity equation) that the mass flow rate of the introduced fluid is always constant at any cross section is governed. That is, the gas generated at the anode electrode 11 is discharged from the anode electrode 11 in the direction of the metal films 61 and 62.

[0038] More specifically, because the first pore diameter D1 of the metal films 61, 62 is larger than the second pore diameter D2 of the anode electrode 11, gas generated in the anode electrode 11 easily flows from the anode electrode 11 toward the metal films 61, 62 (see FIG. 5 ). As described above, the external terminal electrode 71 is formed to have the opening 751 on the first main surface 101 side, and therefore the gas flows in the direction of the opening 751. Similarly, the external terminal electrode 72 is formed to have the opening 752 on the first main surface 101 side. Therefore, the gas flows in the direction of the opening 752.

[0039] With this configuration, for example, gas generated at anode electrode 11 during MSL reflow is released to the outside without remaining inside solid electrolytic capacitor 1. In other words, peeling and cracks caused by gas generated inside solid electrolytic capacitor 1 are suppressed.

[0040] Moreover, this relationship can be easily realized by forming the metal film 61 by thermal spraying.

[0041] (Method of Manufacturing Solid Electrolytic Capacitor 1) The solid electrolytic capacitor 1 having the above-described configuration is manufactured, for example, as follows: Fig. 6 is a flowchart showing an example of a schematic flow of the method of manufacturing the solid electrolytic capacitor according to this embodiment.

[0042] A capacitor element sheet is formed (FIG. 6: S11). A plurality of capacitor elements 10, each forming a different solid electrolytic capacitor 1, are formed in an array on the capacitor element sheet.

[0043] Next, the capacitor element sheet and the cathode electrode sheet are laminated with the second dam 30 and the first adhesive 40 sandwiched therebetween to form a sheet laminate ( FIG. 6 : S12). Note that the cathode electrode sheet is formed with an array of a plurality of cathode electrodes 20, each of which forms a different solid electrolytic capacitor 1. This forms a structure in which a plurality of capacitor element laminates 100 are arranged in a plane. In other words, the sheet laminate is a structure in which a plurality of capacitor element laminates 100 are arranged in a plane.

[0044] Next, the sheet stack is sealed with insulating resin 50 (FIG. 6: S13). As will be described in detail later, at this time, through holes that penetrate from the top surface to the bottom surface of the sheet stack are provided in the sheet stack, and resin sealing is performed by compression molding.

[0045] The process up to this sealing with insulating resin 50 is carried out in a multi-state (state in which a plurality of what will become solid electrolytic capacitors 1 are arranged) before the solid electrolytic capacitor 1 is divided into individual pieces.

[0046] Next, the sheet laminate sealed with insulating resin 50 is cut into individual pieces ( S14 in FIG. 6 ). Specifically, cutting is performed along cutting lines E11, E12, S11, and S12 shown in FIG. 12(B) (described later). This results in multiple solid electrolytic capacitors 1 (referred to as "solid electrolytic capacitor 1 bodies") without external electrodes. The solid electrolytic capacitor 1 bodies are then secondary sealed with insulating resin 50. More specifically, the side surfaces of the solid electrolytic capacitor 1 bodies (surfaces cut along cutting lines S11 and S12 (top, bottom, and side surfaces other than the end surfaces where the anode electrodes 11 and cathode electrodes 20 are exposed)) are covered with the secondary sealing of insulating resin 50. This allows the anode electrodes 11 and cathode electrodes 20 that are unnecessarily exposed during singulation to be covered with insulating resin 50.

[0047] Next, external electrodes consisting of metal films 61, 62 and external terminal electrodes 71, 72 are formed on the end faces of the element body of solid electrolytic capacitor 1 (FIG. 6: S15).

[0048] Next, each step will be described in more detail.

[0049] (Capacitor element sheet forming process) Fig. 7 is a flowchart showing an example of a capacitor element sheet forming process. Fig. 8(A) is an external perspective view showing the shape of the anode electrode of the capacitor element before singulation, and Fig. 8(B) is an external perspective view showing the shape of the capacitor element before singulation. Fig. 9 is an external view in a multi-state.

[0050] The anode 11 is subjected to chemical conversion treatment to form the dielectric layer 12 (FIG. 7: S111). At this time, numerous holes are formed in the surface of the anode 11 by etching, and the area near the surface of the anode 11 is porous. The dielectric layer 12 covers the surface of the anode 11, including the inner surfaces of the holes.

[0051] Next, anode through holes are formed in the anode electrode 11 ( FIG. 7 : S112). More specifically, as shown in FIG. 8A , a plurality of cylindrical anode through holes 19C and groove-shaped anode through holes 19L are formed in the anode electrode 11. The cylindrical anode through holes 19C and the groove-shaped anode through holes 19L are alternately arranged along the direction in which the portions that will become the anode electrodes 11 are arranged. The cylindrical anode through holes 19C are formed at positions that will realize first ends 10E1 of the anode electrodes 11. The groove-shaped anode through holes 19L are formed at positions that straddle the portions that will become adjacent anode electrodes 11 and at positions that will realize second ends 10E2 of adjacent anode electrodes 11.

[0052] Next, a CP layer (solid electrolyte layer) 13 is formed on the surface of the dielectric layer 12 (FIG. 7: S113). More specifically, as shown in FIG. 8B, a first dam 14 having a frame-shaped opening is formed. Then, the CP layer 13 (a laminated structure of an inner layer CP 131 and an outer layer CP 132) is formed within the opening of the first dam 14.

[0053] As shown in FIG. 9, this structure is implemented in a multi-state in which a plurality of capacitor elements 10 (a structure consisting of an anode electrode 11, a dielectric layer 12, a CP layer 13, and a first dam 14) are arranged two-dimensionally.

[0054] (Cathode Electrode Sheet Forming Process) FIG. 10 is an external perspective view showing the shape of the cathode electrode before being divided into individual pieces.

[0055] 10 , the cathode electrode 20 has a plurality of cylindrical cathode through holes 29C and groove-shaped cathode through holes 29L formed therein. The cylindrical cathode through holes 29C and the groove-shaped cathode through holes 29L are alternately arranged along the direction in which the portions that will become the cathode electrodes 20 are arranged. The cylindrical cathode through holes 29C are formed at positions that will realize first ends 20E1 of the cathode electrodes 20. The groove-shaped cathode through holes 29L are formed at positions that straddle the portions that will become adjacent cathode electrodes 20 and at positions that will realize second ends 20E2 of adjacent cathode electrodes 20.

[0056] (Sheet Laminate Forming Process) FIG. 11 is a flowchart showing an example of a sheet laminate forming process. FIG. 12 is an external perspective view showing a state in which a second dam has been formed on a capacitor element sheet, with FIG. 12(A) showing a multi-layer structure and FIG. 12(B) showing a portion of a single capacitor element. FIG. 13 is an external perspective view showing a state in which a second dam and a first adhesive have been formed on a capacitor element sheet, with FIG. 13(A) showing a multi-layer structure and FIG. 13(B) showing a portion of a single capacitor element. FIGS. 14(A) and 14(B) are exploded perspective views showing a state in which capacitor element sheets and cathode electrode sheets are laminated. FIGS. 14(A) and 14(B) show the portion corresponding to one solid electrolytic capacitor. FIG. 15(A) is an exploded perspective view showing a laminated state of capacitor element sheets and cathode electrode sheets in a multi-layer structure, and FIG. 15(B) is an external perspective view showing a laminated state of capacitor element sheets and cathode electrode sheets in a multi-layer structure.

[0057] The second dam 30 is formed on the capacitor element sheet (FIG. 11: S121). More specifically, as shown in FIGS. 12A and 12B, the second dam 30 having a frame-shaped opening is formed.

[0058] Next, as shown in FIGS. 13A and 13B, the first adhesive 40 is placed in the opening of the second dam 30 (FIG. 11: S122).

[0059] Next, as shown in Figures 14(A), 14(B), 15(A), and 15(B), capacitor element sheets and cathode electrode sheets are alternately stacked (Figure 11: S123). More specifically, the capacitor element sheets and cathode electrode sheets are stacked so as to satisfy the following conditions:

[0060] When viewed in the stacking direction, the multiple cylindrical anode through holes 19C in the capacitor element sheet overlap with the groove-shaped cathode through holes 29L in the cathode electrode sheet. When viewed in the stacking direction, the groove-shaped anode through holes 19L in the capacitor element sheet overlap with the multiple cylindrical cathode through holes 29C in the cathode electrode sheet. When viewed in the stacking direction, the groove-shaped anode through holes 19L in the capacitor element sheet overlap with the groove-shaped cathode through holes 29L in the cathode electrode sheet. A plurality of these through holes are formed in accordance with the number of capacitor elements arranged in the sheet laminate. Therefore, the sheet laminate is formed with a plurality of through holes that penetrate from the top surface to the bottom surface of the sheet laminate.

[0061] Next, the sheet laminate is heated and pressurized ( FIG. 11 : S124). This bonds the capacitor element sheet and the cathode electrode sheet together with the first adhesive 40, forming a sheet laminate. As described above, in the case of a structure in which the first adhesive 40 is omitted, step S122 can be omitted.

[0062] (Process for forming metal film and external terminal electrode) The process for forming the metal films 61 and 62 and the external terminal electrodes 71 and 72 will be described with reference to Figures 3(A), 3(B) and 16. Figure 16 is a flowchart showing an example of the process for forming the metal film and the external terminal electrodes.

[0063] 3A, metal spraying is performed on the first end 10E1 of the anode electrode 11 and the outer surface of the insulating resin 50 on the first end 10E1 side. Similarly, metal spraying is performed on the first end 20E1 of the cathode electrode 20 in the capacitor element laminate 100 and the outer surface of the insulating resin 50 on the first end 20E1 side (FIG. 16: S131). As a result, a metal film 61 is formed on the first end 10E1. Similarly, a metal film 62 is formed on the first end 20E1.

[0064] 3(B) shows an example of forming external terminal electrodes 71, 72 directly on the metal films 61, 62 by, for example, sputtering. Specifically, the external terminal electrode 71 is formed so as to cover the metal film 61. Similarly, the external terminal electrode 72 is formed so as to cover the metal film 62. In this case, the external terminal electrode 71 is formed so as to have an opening 751 facing the first main surface 101. Furthermore, the external terminal electrode 72 is formed so as to have an opening 752 facing the first main surface 101.

[0065] By using such a solid electrolytic capacitor 1, gas generated within the solid electrolytic capacitor 1 during, for example, MSL reflow is released to the outside without remaining within the solid electrolytic capacitor 1. This prevents peeling and cracks caused by the gas generated within the solid electrolytic capacitor 1. In other words, a highly reliable solid electrolytic capacitor 1 can be realized.

[0066] In the above-described configuration, the metal films 61, 62 are formed by thermal spraying. However, the metal films 61, 62 may be formed by a method other than thermal spraying as long as the first pore diameter D1 is larger than the second pore diameter D2.

[0067] In the above-described configuration, the metal film 62 and the external terminal electrode 72 are formed. However, in the present invention, it is sufficient that the solid electrolytic capacitor 1 is configured to include at least the metal film 61 and the external terminal electrode 71 connected to the anode electrode 11, and that gas generated within the solid electrolytic capacitor 1 is released to the outside from the external electrode on the anode side. In other words, instead of the metal film 62 and the external terminal electrode 72, a cathode side external electrode may be formed by a conventional method.

[0068] In the above-described configuration, the external terminal electrodes 71, 72 are shaped to cover the entire side surface (the first end 10E1 side of the anode electrode 11 and the first end 20E1 side of the cathode electrode 20) of the solid electrolytic capacitor 1. However, the external terminal electrodes 71, 72 may have any shape as long as they expose a portion of the metal films 61, 62 so that gas generated within the solid electrolytic capacitor 1 can be released to the outside. However, the term "shape that covers the entire surface" includes unintended variations that may occur during processing, and strictly speaking, also includes a shape that does not cover the entire surface.

[0069] That is, in the above-described configuration, an example has been shown in which the opening 751 of the external terminal electrode 71 and the opening 752 of the external terminal electrode 72 are formed on the first main surface 101 side. However, the openings 751 and 752 are not limited to being formed on the first main surface 101 side, and their positions are not limited as long as they do not cause problems in mounting. For example, the openings 751 and 752 may be located anywhere except in an area where they are covered with solder or a conductive adhesive during mounting and would prevent gas generated within the solid electrolytic capacitor 1 from being released to the outside. Furthermore, the openings 751 and 752 only need to have a size, shape, and number that allow gas to be released.

[0070] Second Embodiment Next, a solid electrolytic capacitor according to a second embodiment will be described with reference to the drawings. Fig. 17 is a side cross-sectional view showing the general configuration of the solid electrolytic capacitor according to the second embodiment.

[0071] 17 , the solid electrolytic capacitor 1A according to the second embodiment differs from the solid electrolytic capacitor 1 according to the first embodiment in that it includes a conductive resin layer. The other configuration of the solid electrolytic capacitor 1A is the same as that of the solid electrolytic capacitor 1, and a description of similar parts will be omitted.

[0072] 17 shows an example in which external terminal electrodes 71, 72 are formed on metal films 61, 62 using a conductive adhesive. Specifically, the metal film 61 is formed by spraying metal onto the first end 10E1 of the anode electrode 11 and the outer surface of the insulating resin 50 on the first end 10E1 side. A conductive resin layer 81 is formed to cover the surface of the metal film 61 facing the first end 10E1 (outer surface side). Furthermore, the external terminal electrode 71 is formed to cover the conductive resin layer 81.

[0073] Similarly, a metal film 62 is formed by metal spraying on the first end 20E1 of the cathode electrode 20 and the outer surface of the insulating resin 50 on the first end 20E1 side. A conductive resin layer 82 is formed to cover the surface (outer surface) of this metal film 62 facing the first end 20E1. Furthermore, an external terminal electrode 72 is formed to cover the conductive resin layer 82.

[0074] In the second embodiment, a structure in which the metal film 62 and the external terminal electrode 72 are formed is shown. However, any structure may be used as long as the solid electrolytic capacitor 1 includes at least the metal film 61 and the external terminal electrode 71 connected to the anode electrode 11, and the gas generated in the solid electrolytic capacitor 1 is released to the outside from the external electrode on the anode side. In other words, instead of the metal film 62 and the external terminal electrode 72, a cathode side external electrode may be formed by a conventional method.

[0075] By forming them in this manner, the adhesive strength between the metal film 61 and the external terminal electrode 71 is increased. Similarly, the adhesive strength between the metal film 62 and the external terminal electrode 72 is increased.

[0076] That is, electrical conductivity can be ensured by ensuring the contact area between the metal film 61 and the external terminal electrode 71 and the contact area between the metal film 62 and the external terminal electrode 72. Furthermore, the conductive resin layers 81 and 82 can suppress peeling due to differences in linear expansion coefficients between the conductive resin layer 81, the metal film 61, and the external terminal electrode 71, and between the conductive resin layer 82, the metal film 62, and the external terminal electrode 72.

[0077] Similarly, electrical conductivity can be ensured by ensuring the area where the metal film 62 and the external terminal electrode 72 come into contact with each other. Furthermore, the conductive resin layer 82 can suppress peeling between the metal film 62 and the external terminal electrode 72 due to the difference in linear expansion coefficient between them.

[0078] Even when using such a solid electrolytic capacitor 1A, gas generated at the anode electrode 11 during MSL reflow, for example, is released to the outside without remaining inside the solid electrolytic capacitor 1A. This prevents peeling and cracking caused by gas generated within the solid electrolytic capacitor 1A. Furthermore, it is possible to ensure electrical conductivity between the metal film 61, the conductive resin layer 81, and the external terminal electrode 71, and between the metal film 62, the conductive resin layer 82, and the external terminal electrode 72. In other words, a highly reliable solid electrolytic capacitor 1A can be realized.

[0079] Third Embodiment A solid electrolytic capacitor according to a third embodiment will now be described with reference to the drawings. Fig. 18 is a side cross-sectional view showing the general configuration of the solid electrolytic capacitor according to the third embodiment.

[0080] 18, the solid electrolytic capacitor 1B according to the third embodiment differs from the solid electrolytic capacitor 1 according to the first embodiment in that it includes a non-conductive resin layer. The other configuration of the solid electrolytic capacitor 1B is the same as that of the solid electrolytic capacitor 1, and a description of similar parts will be omitted.

[0081] 18 , a metal film 61 is formed by metal spraying on the first end 10E1 of the anode electrode 11 and the outer surface of the insulating resin 50 on the first end 10E1 side. A non-conductive resin layer 91 is formed to cover the surface of this metal film 61 facing the first end 10E1 (outer surface side). At this time, a portion of the surface of the metal film 61 is not covered by the non-conductive resin layer 91. Furthermore, an external terminal electrode 71 is formed to cover the non-conductive resin layer 91. The shape of the non-conductive resin layer 91 is not important as long as the metal film 61 and the external terminal electrode 71 can be used as an anode electrode.

[0082] Similarly, a metal film 62 is formed by metal spraying on the first end 20E1 of the cathode electrode 20 and the outer surface of the insulating resin 50 on the first end 20E1 side. A non-conductive resin layer 92 is formed to cover the surface of this metal film 62 facing the first end 20E1 (outer surface side). At this time, a portion of the surface of the metal film 62 is not covered by the non-conductive resin layer 92. Furthermore, an external terminal electrode 72 is formed to cover the non-conductive resin layer 92. The shape of the non-conductive resin layer 92 is not important as long as the metal film 62 and the external terminal electrode 72 can be used as a cathode electrode.

[0083] By forming them in this manner, the adhesive strength between the metal film 61 and the external terminal electrode 71 is increased. Similarly, the adhesive strength between the metal film 62 and the external terminal electrode 72 is increased.

[0084] In other words, by providing the non-conductive resin layers 91, 92, peeling due to differences in the linear expansion coefficients between the conductive resin layer 81, the metal film 61, and the external terminal electrode 71, and between the conductive resin layer 82, the metal film 62, and the external terminal electrode 72, can be suppressed.

[0085] Even when such a solid electrolytic capacitor 1B is used, gas generated at the anode electrode 11 during MSL reflow, for example, is released to the outside without remaining inside the solid electrolytic capacitor 1B. This prevents peeling and cracking caused by gas generated inside the solid electrolytic capacitor 1B. In other words, a highly reliable solid electrolytic capacitor 1B can be realized. Furthermore, by using a non-conductive resin, it can be formed more inexpensively than the conductive resin used in the second embodiment.

[0086] Fourth Embodiment A solid electrolytic capacitor according to a fourth embodiment will now be described with reference to the drawings. Fig. 19 is a side cross-sectional view showing the general configuration of the solid electrolytic capacitor according to the fourth embodiment.

[0087] 19 , the solid electrolytic capacitor 1C according to the fourth embodiment differs from the solid electrolytic capacitor 1A according to the second embodiment in the configuration of the conductive resin layer. The other configuration of the solid electrolytic capacitor 1C is the same as that of the solid electrolytic capacitor 1A, and a description of similar parts will be omitted.

[0088] 19 , the conductive resin layer 81 permeates the metal film 61. More specifically, the conductive resin layer 81 permeates to a thickness (T61 / 2) that is half the thickness T61 of the metal film 61. However, the half thickness includes unintentional variations during processing, and strictly speaking, it also includes the case where the conductive resin layer 81 is not half the thickness T61 of the metal film 61.

[0089] From the perspective of long-term use, there is a risk that oxygen or water vapor from the outside may penetrate into the metal film 61, causing deterioration inside the solid electrolytic capacitor 1C. However, the conductive resin layer 81 penetrates into the metal film 61 to a certain thickness (in the above example, about half the thickness of the metal film 61), thereby preventing the penetration of oxygen and water vapor.

[0090] That is, the above-described configuration allows gas to be released to the outside of the solid electrolytic capacitor 1C, while preventing oxygen and water vapor from entering the solid electrolytic capacitor 1C from the outside.

[0091] In the fourth embodiment, the configuration of the conductive resin layers 81 and 82 is shown. However, similar effects can be obtained even if the non-conductive resin layers 91 and 92 are used as in the third embodiment.

[0092] (Explanation of an example of specific materials, etc., of each component of the solid electrolytic capacitor 1) (Capacitor element 10) The capacitor element 10 is realized, for example, using the following materials and with the following thicknesses.

[0093] The anode 11 is made of a metal such as aluminum, tantalum, niobium, titanium, zirconium, or magnesium, or an alloy containing any of these metals. The anode 11 is preferably made of aluminum or an aluminum alloy. The anode 11 may be made of any valve metal that exhibits a so-called valve action.

[0094] The anode 11 is preferably flat, and the thickness of the core (the center portion not reached by the pores of the porous body) of the anode 11 is preferably 5 μm or more and 100 μm or less. The thickness (thickness of one side) of the porous portion (the portion where the pores of the porous body are formed) is preferably 5 μm or more and 200 μm or less.

[0095] The dielectric layer 12 is preferably made of an oxide film of the anode electrode 11. For example, when an aluminum foil is used for the anode electrode 11, the dielectric layer 12 is formed by oxidizing the aluminum foil in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts or ammonium salts. The thickness of the dielectric layer 12 is preferably 1 nm or more and 100 nm or less.

[0096] The inner layer CP131 may be a PEDOT:PSS layer realized by, for example, a conductive polymer having a skeleton of pyrroles, thiophenes, anilines, or the like, or a conductive polymer having a skeleton of thiophenes, such as PEDOT [poly(3,4-ethylenedioxythiophene)], and composited with polystyrene sulfonic acid (PSS) as a dopant. The inner layer CP131 may be formed, for example, by a method of forming a polymer film of poly(3,4-ethylenedioxythiophene) or the like on the surface of the dielectric layer 12 using a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene, or by a method of applying a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric portion and drying it.

[0097] The thickness of the outer layer CP 132 is preferably 2 μm or more and 20 μm or less. The material of the outer layer CP 132 is the same as the material of the inner layer CP 131.

[0098] The first adhesive 40 may be a mixture of insulating resin such as epoxy resin or phenolic resin and conductive particles such as carbon or silver.

[0099] The cathode electrode 20 is made of, for example, aluminum, titanium, copper, silver, etc. The thickness of the cathode electrode 20 is, for example, thinner than or approximately the same as the thickness of the anode electrode 11. The thickness of the cathode electrode 20 is preferably as thin as possible, about 5 μm to 50 μm, and preferably about 30 μm.

[0100] The insulating resin 50 may contain a filler. Examples of suitable resins include epoxy resin, phenol resin, polyimide resin, silicone resin, polyamide resin, and liquid crystal polymer. Examples of suitable fillers include insulating oxide particles such as silica particles, alumina particles, titania particles, and zirconia particles. The maximum diameter of the filler is preferably 30 μm or more and 40 μm or less. For example, a material containing silica particles in a solid epoxy resin and a phenol resin is more preferable.

[0101] The metal films 61, 62 are preferably formed from a metal that can be thermally sprayed. By using thermal spraying, the first pore diameter D1 of the metal films 61, 62 can be easily made larger than the second pore diameter D2 of the porous portion of the anode electrode 11. This is thought to be because, when the metal film 61 is formed by thermal spraying, relatively large metal particles in a molten or semi-molten state reach the first end 10E1 of the anode electrode 11 and the outer surface of the insulating resin 50 on the first end 10E1 side, and these large metal particles cool and solidify, easily forming pores. The same is true for the metal film 62.

[0102] It is preferable to use, for example, Au, Cu, or alloy 42 for the external terminal electrodes 71, 72. Note that the external terminal electrodes 71, 72 may be made of any material as long as the surfaces of the external terminal electrodes 71, 72 have high solder wettability.

[0103] The conductive resin layers 81 and 82 are made of a thermosetting resin having electrical conductivity, such as a phenolic resin.

[0104] The non-conductive resin layers 91 and 92 are made of a non-conductive thermosetting resin, such as an epoxy resin.

[0105] D1...first pore diameter D2...second pore diameter E11...cutting line S11...cutting line T61...thickness of metal film 1, 1A, 1B, 1C...solid electrolytic capacitor 10...capacitor element 10E1...first end 10E2...second end 11...anode electrode 12...dielectric layer 13...CP layer 131...inner layer CP 132...outer layer CP 14...first dam 19C...anode through-hole 19L...anode through-hole 20...cathode electrode 20E1...first end 20E2...second end 29C...cathode through-hole 29L...cathode through-hole 30...second dam 40...first adhesive 50...insulating resin 61, 62...metal film 71, 72...external terminal electrodes 81, 82...conductive resin layer 91, 92... Non-conductive resin layers 100... Capacitor element laminate 101... First main surface 102... Second main surface 751, 752... Openings

Claims

1. A solid electrolytic capacitor comprising: a sheet laminate formed by alternately laminating a plurality of flat film capacitor elements, each of which has a flat film anode electrode foil having a porous portion at a predetermined depth from the surface, and a plurality of flat film cathode electrode foils, each of which has a dielectric layer and a solid electrolyte layer formed on the surface of the flat film anode electrode foil; first metal portions formed on ends of the anode electrode foil and the solid electrolyte layer in the sheet laminate; and an insulating resin sealing the sheet laminate, wherein a first pore diameter of the first metal portion is larger than a second pore diameter of the porous portion of the anode electrode foil.

2. The solid electrolytic capacitor according to claim 1, further comprising a second metal portion covering a portion of the first metal portion.

3. The solid electrolytic capacitor according to claim 2, wherein the first metal portion and the second metal portion are joined by a conductive resin.

4. The solid electrolytic capacitor according to claim 3, wherein the conductive resin penetrates the first metal portion to a depth of approximately half the thickness of the first metal portion.

5. The solid electrolytic capacitor according to claim 2, further comprising a non-conductive resin that is in partial contact with the first metal portion and the second metal portion.

6. The solid electrolytic capacitor according to claim 5, wherein the non-conductive resin penetrates the first metal portion to a depth of approximately half the thickness of the first metal portion.