Solid electrolytic capacitor and method for manufacturing solid electrolytic capacitor

Abstract

This solid electrolytic capacitor comprises a sheet laminate, a first resin, a second resin, and an external electrode. The sheet laminate is formed by alternately stacking a plurality of flat-film capacitor elements and a plurality of flat-film cathodic electrode foils. The first resin is disposed in an interlayer space between the plurality of flat-film capacitor elements and the plurality of flat-film cathodic electrode foils in the sheet laminate. The second resin encapsulates the sheet laminate. The external electrode is connected to the sheet laminate. Each of the flat-film capacitor elements further comprises a flat-film anodic electrode foil, a dielectric layer formed on the surface of the anodic electrode foil, a third resin formed on the surface of the dielectric layer, and a solid electrolyte layer formed in an area defined by the third resin. The first resin is in contact with the external electrode, the second resin, the flat-film capacitor elements, and the flat-film cathodic electrode foils.

Description

Solid electrolytic capacitor and method for manufacturing the same

[0001] The present invention relates to a solid electrolytic capacitor having a structure in which a laminate of a plurality of capacitor elements is molded with an insulating resin.

[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-shaped capacitor elements and a plurality of metal foils (cathodes). The flat film-shaped capacitor element includes a foil-shaped valve action metal substrate, a porous portion of the valve action metal substrate, a dielectric layer formed on the surface, and a solid electrolyte layer formed on the surface of the dielectric layer.

[0003] The flat film-shaped capacitor elements and the metal foils are alternately laminated, thereby forming an element laminate. The element laminate is sealed with an insulating resin.

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

[0005] In the solid electrolytic capacitor described in Patent Document 1, between the flat film-shaped capacitor element and the metal foil (hereinafter, interlayer), and the element laminate is sealed with an insulating resin. However, when the interlayer is sealed with an insulating resin, the inflow path of the insulating resin is very narrow, and there is a risk that the inflow path becomes long. As a result, it is impossible to allow sufficient insulating resin to flow into the interlayer, and a space (void) that is not sealed with the insulating resin is generated.

[0006] When such voids occur, there is a risk of causing the following problems.

[0007] (Problem 1) LC failure is likely to occur due to the intrusion of plating solution from the outside. (Problem 2) Long-term reliability deteriorates due to the intrusion of moisture from the outside. Therefore, an object of the present invention is to provide a solid electrolytic capacitor that suppresses LC failure and has high long-term reliability.

[0008] The solid electrolytic capacitor of this invention comprises a sheet laminate, a first resin, a second resin, and an external electrode. The sheet laminate is formed by alternately stacking a plurality of flat film capacitor elements and a plurality of flat film cathode electrode foils. The first resin is disposed between layers, which are the spaces between the plurality of flat film capacitor elements and the plurality of flat film cathode electrode foils in the sheet laminate. The second resin seals the sheet laminate. The external electrode is connected to the sheet laminate. The flat film capacitor element further comprises a flat film anode electrode foil, a dielectric layer formed on the surface of the anode electrode foil, a third resin formed on the surface of the dielectric layer, and a solid electrolyte layer formed within a region restricted by the third resin. The first resin is in contact with the external electrode, the second resin, the flat film capacitor element, and the flat film cathode electrode foil.

[0009] This solid electrolytic capacitor can seal areas prone to interlayer void formation with a first resin. This prevents the intrusion of plating solution from the outside of the solid electrolytic capacitor, thereby suppressing LC defects. Furthermore, it prevents the intrusion of moisture from the outside of the solid electrolytic capacitor, improving long-term reliability. Therefore, a highly reliable solid electrolytic capacitor can be realized.

[0010] The method for manufacturing a solid electrolytic capacitor according to this invention comprises the steps of forming a sheet laminate, forming a first resin, forming a second resin, and forming an external electrode. In the step of forming a sheet laminate, a sheet laminate is formed by alternately stacking a plurality of flat film capacitor elements and a plurality of flat film cathode electrode foils in the stacking direction. In the step of forming the first resin, a first resin is formed to be disposed between the layers, which are the spaces between the plurality of flat film capacitor elements and the plurality of flat film cathode electrode foils in the sheet laminate. In the step of forming the second resin, a second resin is formed to seal the sheet laminate. In the step of forming the external electrode, an external electrode is formed to be connected to the sheet laminate.

[0011] The flat film capacitor element comprises a flat film anode electrode foil, a dielectric layer formed on the surface of the anode electrode foil, a third resin formed on the surface of the dielectric layer, and a solid electrolyte layer formed within a region restricted by the third resin. The first resin is formed to be in contact with the external electrode, the second resin, the flat film capacitor element, and the flat film cathode electrode foil.

[0012] In this method for manufacturing solid electrolytic capacitors, areas prone to interlayer void formation can be sealed with a first resin. This means that the intrusion of plating solution from outside the solid electrolytic capacitor can be suppressed, thereby suppressing LC defects. Furthermore, since the intrusion of moisture from outside the solid electrolytic capacitor can be suppressed, long-term reliability is improved. Therefore, this method for manufacturing solid electrolytic capacitors makes it possible to realize highly reliable solid electrolytic capacitors.

[0013] This invention makes it possible to provide a solid electrolytic capacitor that suppresses LC defects and has high long-term reliability.

[0014] Figure 1 is a cross-sectional view showing the configuration of a solid electrolytic capacitor according to the first embodiment. Figure 2(A) is a cross-sectional view showing the configuration of a capacitor element and cathode electrode set before individualization, and Figure 2(B) is a cross-sectional view of the capacitor element. Figures 3(A) and 3(B) are diagrams showing the configuration of a capacitor element and cathode electrode set before individualization. Figures 4(A) and 4(B) are schematic diagrams showing the stacked state of a solid electrolytic capacitor. Figure 5 is a flowchart showing an example of the solid electrolytic capacitor formation process. Figure 6 is an external view of the capacitor element in a multi-layered state. Figure 7 is a flowchart showing an example of the capacitor element sheet formation process. Figures 8(A), 8(B), 8(C), and 8(D) are schematic diagrams showing the process of forming the capacitor element of a solid electrolytic capacitor according to the first embodiment. Figure 9 is an external view of the capacitor element sheet in a multi-layered state. Figure 10 is an external perspective view showing the shape of the cathode electrode before individualization. Figure 11 is an external view of the cathode electrode in a multi-layered state. Figure 12 is a flowchart showing an example of the sheet stacking process. Figure 13 is an exploded perspective view showing the state in which the capacitor element sheet and the cathode electrode sheet are stacked. Figure 14(A) is a cross-sectional view of a conventional configuration, and Figure 14(B) is a cross-sectional view of the first embodiment. Figure 15 is a cross-sectional view showing the configuration of the capacitor element and cathode electrode set before individualization according to the second embodiment.

[0015] [First Embodiment] A solid electrolytic capacitor according to the first embodiment of the present invention will be described with reference to the figures.

[0016] (General description of the configuration of the solid electrolytic capacitor 1) First, the structure of the solid electrolytic capacitor according to the embodiment of the present invention will be described. Figure 1 is a cross-sectional view showing the configuration of the solid electrolytic capacitor according to the first embodiment. Figures 2(A) and 2(B) are cross-sectional views showing the configuration of the capacitor element and cathode electrode set before individualization. Figures 3(A) and 3(B) are diagrams showing the configuration of the capacitor element and cathode electrode set before individualization. Figures 4(A) and 4(B) are schematic diagrams showing the stacked state of the solid electrolytic capacitor. Note that in Figures 3(A) and 3(B), some hatching has been omitted to make the diagrams easier to understand.

[0017] As shown in Figures 1, 2(A), and 2(B), the solid electrolytic capacitor 1 comprises a capacitor element laminate 100, an outer resin 50, resin bodies 150 and 250, an external electrode 61, and an external electrode 62. The capacitor element laminate 100 comprises a plurality of flat film capacitor elements 10 and a plurality of flat film cathode electrodes 20. Note that the number of flat film capacitor elements 10 and cathode electrodes 20 in the configuration shown in Figure 1 is not limited to this.

[0018] In Figure 1, the direction parallel to the top surface 101 and bottom surface 102 of the capacitor element stack 100 is defined as the X-axis direction. The direction parallel to the top surface 101 and bottom surface 102 of the capacitor element stack 100 and perpendicular to the X-axis direction is defined as the Y-axis direction. The Z-axis direction is the thickness direction of the solid electrolytic capacitor and is perpendicular to the XY plane. In the figures shown below, the magnitude in the Z-axis direction (thickness direction) is exaggerated.

[0019] The cross-sectional views in Figures 1, 2(A), and 2(B) are cross-sectional views of the capacitor element laminate 100 in Figure 1 taken along a plane (XZ plane) perpendicular to the top surface 101 and bottom surface 102. This flat film-shaped cathode electrode 20 corresponds to the "cathode electrode foil" in the present invention. The resin body 150 and resin body 250 correspond to the "first resin". Furthermore, the resin body 150 corresponds to the "first anode resin", and the resin body 250 corresponds to the "first cathode resin". In addition, the outer resin 50 corresponds to the "second resin" in the present invention.

[0020] As shown in Figure 2(B), the capacitor element 10 comprises a flat film anode electrode 11, a dielectric layer 12, a CP layer (solid electrolyte layer) 13, a CP dam 14, and a resin body 150. This flat film anode electrode 11 corresponds to the "anode electrode foil" in the present invention. The CP dam 14 corresponds to the "third resin" in the present invention.

[0021] Although detailed structural illustrations are omitted in Figures 2(A) and 2(B), the anode electrode 11 has numerous pores. In other words, the anode electrode 11 is porous. The ratio of the thickness of the porous portion on one side of the anode electrode 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 electrode 11. In Figures 2(A) and 2(B), detailed structural illustrations of the anode electrode 11 are omitted, so the dielectric layer 12 is schematically shown as covering the macroscopic surface of the anode electrode 11. In reality, the dielectric layer 12 covers not only the macroscopic surface of the anode electrode 11 but also the inner surfaces of the numerous pores in the anode electrode 11.

[0022] The CP layer 13 covers the surface of the dielectric layer 12. A frame-shaped CP dam 14 is formed around the outer periphery of the CP layer 13. The CP dam 14 is insulating. The CP dam 14 restricts the area where the CP layer 13 is formed.

[0023] The CP layer 13 has a laminated structure consisting of an inner CP (inner solid electrolyte layer) 131 and an outer CP (outer solid electrolyte layer) 132. The inner CP 131 is formed on the surface of the dielectric layer 12, and the outer CP 132 is formed on the surface of the inner CP 131.

[0024] As shown in Figures 2(A), 2(B), 3(A), and 3(B), the resin body 150 is formed to overlap the CP dam 14. More specifically, in the Z-axis direction, the resin body 150 is positioned to overlap the CP dam 14. The resin body 150 is insulating. Similarly, a resin body 250 is formed on the cathode electrode 20. More specifically, in the Z-axis direction, the resin body 250 is positioned to overlap the cathode electrode 20. The resin body 250 is insulating. A more detailed structure will be described later.

[0025] Multiple capacitor elements 10 and multiple cathode electrodes 20 are stacked alternately so that their respective flat surfaces are parallel and overlap when viewed from above. In this case, the outer layer CP132 of the capacitor elements and the cathode electrodes 20 are directly connected. In the structure shown in Figure 2(A), the outer layer CP132 of the capacitor elements 10 and the cathode electrodes 20 are bonded together so that they are in contact. As a result, adjacent capacitor elements 10 and cathode electrodes 20 are bonded together and electrically connected. By stacking the capacitor elements 10 and cathode electrodes 20 in this way without using adhesive, the thickness of the solid electrolytic capacitor 1 can be reduced. However, if the adhesive does not affect the thickness of the solid electrolytic capacitor 1, the capacitor elements 10 and cathode electrodes 20 may be bonded together using an adhesive. In this case, it is preferable that the adhesive contains carbon.

[0026] In this stacked state, the first ends 10E1 (see Figure 1) of the multiple capacitor elements 10 are in approximately the same position when viewed from the side. Similarly, the second ends 10E2 (see Figure 1) of the multiple capacitor elements 10 are in approximately the same position when viewed from the side. Furthermore, the first ends 20E1 (see Figure 1) of the multiple cathode electrodes 20 are in approximately the same position when viewed from the side. Similarly, the second ends 20E2 (see Figure 1) of the multiple cathode electrodes 20 are in approximately the same position when viewed from the side. Note that the first ends 10E1 of the multiple capacitor elements 10 correspond to the "first ends" in this invention.

[0027] The first ends 10E1 of the multiple capacitor elements 10 and the second ends 20E2 of the multiple cathode electrodes 20 are positioned close to the external electrode 61, which will be described later. The first ends 10E1 of the multiple capacitor elements 10 protrude outward more than the second ends 20E2 of the multiple cathode electrodes 20.

[0028] The second ends 10E2 of the multiple capacitor elements 10 and the first ends 20E1 of the multiple cathode electrodes 20 are positioned close to the external electrode 62, which will be described later. The first ends 20E1 of the multiple cathode electrodes 20 protrude outward from the second ends 10E2 of the multiple capacitor elements 10. The first ends 20E1 of the multiple cathode electrodes 20 correspond to the "second ends" in this invention.

[0029] This structure enables the realization of a capacitor element laminate 100 having a top surface 101 and a bottom surface 102 at both ends in the stacking direction of the multiple capacitor elements 10 and multiple cathode electrodes 20.

[0030] The capacitor element laminate 100 is sealed with an outer resin 50. The outer resin 50 has insulating properties.

[0031] The external electrode 61 covers the first end of the outer resin 50 (the first end 10E1 of the anode electrode 11 of the plurality of capacitor elements 10). The external electrode 61 is connected to the first end 10E1 of the anode electrode 11 of the plurality of capacitor elements 10. The external electrode 62 covers the second end of the outer resin 50 (the first end 20E1 of the cathode electrode 20). The external electrode 62 is connected to the first end 20E1 of the plurality of cathode electrodes 20.

[0032] (More detailed structure of resin body 150 and resin body 250) First, the structure of resin body 150 will be described. Resin body 150 is formed at a position close to the first end 10E1 of the capacitor element 10. As described above, resin body 150 is formed to overlap the CP dam 14 in the Z-axis direction. In the examples shown in Figures 2(A), 2(B), 3(A), and 3(B), resin body 150 is formed to abut the CP dam 14 and the second end 20E2 of the cathode electrode 20. Furthermore, it is preferable that the surface of resin body 150 opposite to the surface that abuts the second end 20E2 of the cathode electrode 20 in the X-axis direction is formed to be flush with the first end 10E1 of the multiple capacitor elements 10. It is preferable that resin body 150 is formed by arranging sheet-shaped resin or by pattern printing such as screen printing.

[0033] Furthermore, as shown in Figure 2(B), it is preferable that the thickness of the resin body 150 in the Z-axis direction is less than or equal to half the thickness of the cathode electrode 20 in the Z-axis direction. This configuration prevents the thickness of the solid electrolytic capacitor 1 from being unnecessarily increased.

[0034] As shown in Figure 4(A), when viewed from above from the first end 10E1 side of the multiple capacitor elements 10, the resin body 150 and the capacitor elements 10 are arranged alternately. Furthermore, the capacitor elements 10 and the resin body 150 are formed so that their respective surfaces are in contact. More specifically, the resin body 150 is configured to fill the space (hereinafter referred to as the first space) formed by the multiple capacitor elements 10, the cathode electrode 20 and the external electrode 61. Moreover, the configuration in which the resin body 150 is filled is not limited to a configuration in which the entire first space is filled with the resin body 150, but also includes a configuration in which a part of the first space is not filled with the resin body 150. With such a configuration, it is possible to suppress the intrusion of plating solution from the outside into the first end 10E1 side of the solid electrolytic capacitor 1, thereby suppressing LC defects. Furthermore, since it is possible to suppress the intrusion of moisture from the outside into the first end 10E1 side of the solid electrolytic capacitor 1, long-term reliability is improved.

[0035] Next, the structure of the resin body 250 will be described. The resin body 250 is formed at a position close to the first end 20E1 of the cathode electrode 20. As described above, the resin body 250 is formed to overlap the cathode electrode 20 in the Z-axis direction. In the examples shown in Figures 2(A), 2(B), 3(A), and 3(B), the resin body 250 is formed to abut the cathode electrode 20 and the second end 10E2 of the plurality of capacitor elements 10. Furthermore, it is preferable that the resin body 250 is formed such that the surface opposite to the surface that abuts the second end 10E2 of the plurality of capacitor elements 10 in the X-axis direction is flush with the first end 20E1 of the cathode electrode 20. It is preferable that the resin body 250 is formed by arranging sheet-shaped resin, similar to the resin body 150, or by pattern printing such as screen printing.

[0036] Furthermore, as shown in Figure 2(B), it is preferable that the thickness of the resin body 250 in the Z-axis direction is less than or equal to half the thickness of the capacitor element 10. This configuration prevents the thickness of the solid electrolytic capacitor 1 from being unnecessarily increased.

[0037] As shown in Figure 4(B), when viewed from above from the first end 20E1 side of the cathode electrode 20, the resin body 250 and the cathode electrode 20 are arranged alternately. Furthermore, the cathode electrode 20 and the resin body 250 are formed so that their respective surfaces are in contact. More specifically, the resin body 250 is configured to fill the space (hereinafter referred to as the second space) formed by the plurality of capacitor elements 10, the cathode electrode 20 and the external electrode 62. Moreover, the configuration in which the resin body 250 is filled is not limited to a configuration in which the resin body 250 fills the entire second space, but also includes a configuration in which a part of the second space is not filled with the resin body 250. With such a configuration, the intrusion of plating solution from the outside into the first end 20E1 side of the solid electrolytic capacitor 1 can be suppressed, thereby suppressing LC defects. Furthermore, since the intrusion of moisture from the outside into the first end 20E1 side of the cathode electrode 20 of the solid electrolytic capacitor 1 can be suppressed, long-term reliability is improved.

[0038] Furthermore, the Young's modulus of resin bodies 150 and 250 (hereinafter referred to as the first Young's modulus) is smaller than the Young's modulus of the outer resin 50 (hereinafter referred to as the second Young's modulus). This makes it possible for the resin bodies 150 and 250 to relieve stress even when the pressure increases during reflow. The difference between the first and second Young's modulus can be achieved, for example, by adjusting the amount of filler.

[0039] The solid electrolytic capacitor 1 is realized with the above configuration.

[0040] (Method for Manufacturing Solid Electrolytic Capacitor 1) The solid electrolytic capacitor 1 having the above configuration can be manufactured, for example, as follows. Figure 5 is a flowchart showing an example of a schematic flow of the method for manufacturing the solid electrolytic capacitor according to this embodiment. Figure 6 is an external perspective view showing the state in which the capacitor element sheet and the cathode electrode sheet are stacked.

[0041] A capacitor element sheet is formed (Figure 5: S11). The capacitor element sheet is formed with multiple capacitor elements 10 arranged in a sequence, each forming a different solid electrolytic capacitor 1 (see Figure 9, described later).

[0042] Next, as shown in FIG. 6, a capacitor element sheet and a cathode electrode sheet are laminated to form a sheet laminate 110 (FIG. 5: S12). Note that the cathode electrode sheet is formed in a state where a plurality of cathode electrodes 20 for forming respective different solid electrolytic capacitors 1 are arranged. As a result, a structure in which a plurality of capacitor element laminates 100 are two-dimensionally arranged in a plane is formed. In other words, the sheet laminate 110 is a structure in which a plurality of capacitor element laminates 100 are two-dimensionally arranged in a plane.

[0043] Next, the sheet laminate 110 is sealed with an exterior resin 50 (FIG. 5: S13). At this time, as shown in FIG. 13 to be described later, the sheet laminate is provided with through holes penetrating from the upper surface to the lower surface of the sheet laminate 110, and resin sealing is performed by compression molding. As a result, the through holes are filled with the exterior resin 50.

[0044] Up to the sealing with the exterior resin 50, the process is performed in a multi-state (a state in which a plurality of components that will become the solid electrolytic capacitors 1 are arranged) before the solid electrolytic capacitors 1 are separated into individual pieces.

[0045] Next, the sheet laminate 110 sealed with the exterior resin 50 is cut and separated into individual pieces (FIG. 5: S14). Specifically, cutting is performed along a cutting line shown in FIG. 8(D) to be described later. As a result, a plurality of solid electrolytic capacitors 1 (referred to as the bodies of the solid electrolytic capacitors 1) in a state where external electrodes are not formed are formed. In other words, the anode electrode 11 and the cathode electrode 20 are covered with the exterior resin 50, and individual pieces in which the anode electrode 11 and the cathode electrode 20 are not undesirably exposed to the outside are formed.

[0046] Next, external electrodes 61 and 62 are formed on the end faces of the bodies of the solid electrolytic capacitors 1 (FIG. 5: S15).

[0047] Next, each step will be described in more detail. (Process of forming the capacitor element sheet) FIG. 7 is a flowchart showing an example of the process of forming the capacitor element sheet. FIGS. 8(A), 8(B), 8(C), and 8(D) are schematic views showing the process of forming the capacitor element of the solid electrolytic capacitor according to the first embodiment. FIG. 9 is an external view of the capacitor element in the multi-state. Note that in FIGS. 8(A), 8(B), 8(C), and 8(D), a part of the capacitor element in the multi-state is shown.

[0048] As shown in FIG. 8(A), a chemical conversion treatment is performed on the anode electrode 11 to form the dielectric layer 12 (FIG. 7: S111). At this time, a large number of holes are formed on the surface of the anode electrode 11 by etching, and the vicinity of the surface of the anode electrode 11 is a porous body. The dielectric layer 12 covers the surface of the anode electrode 11 including the inner surfaces of the holes.

[0049] Next, a CP layer (solid electrolyte layer) 13 is formed on the surface of the dielectric layer 12 (FIG. 7: S112). More specifically, as shown in FIG. 8(B), a CP dam 14 having a frame-shaped opening is formed. Then, as shown in FIG. 8(C), a CP layer 13 (a laminated structure of an inner layer CP131 and an outer layer CP132) is formed in the opening of the CP dam 14.

[0050] Next, a resin body 150 is formed on the surface of the CP dam 14 (FIG. 7: S113). More specifically, as shown in FIG. 8(C), the resin body 150 is formed on the surface of the CP dam 14 parallel to the Y-axis direction.

[0051] Next, as shown in Figure 8(D), anode through-holes are formed in the anode electrode 11 (Figure 7: S114). More specifically, as shown in Figure 8(D), a plurality of cylindrical anode through-holes 19C and groove-shaped anode through-holes 19L are formed in the anode electrode 11. In this case, the plurality of cylindrical anode through-holes 19C and groove-shaped anode through-holes 19L penetrate not only the anode electrode 11 but also the CP dam 14 and the resin body 150. The plurality of cylindrical anode through-holes 19C and groove-shaped anode through-holes 19L are arranged alternately along the direction of the cutting line where the portions that will become the plurality of anode electrodes 11 are aligned. The plurality of cylindrical anode through-holes 19C are formed at positions that realize the first end 10E1 of the anode electrode 11. The groove-shaped anode through-hole 19L is formed at a position that straddles the portions that will become adjacent anode electrodes 11, and at a position that provides the second end 10E2 of adjacent anode electrodes 11.

[0052] In this process, the resin body 150 is removed when forming the anode through-hole 19L. As a result, the resin body 250 fits into the position where the anode through-hole 19L is formed, as shown in Figure 2(B). Therefore, an unnecessary increase in the thickness of the sheet laminate 110 is suppressed.

[0053] As shown in Figure 9, this structure is implemented in a multi-state configuration in which multiple capacitor elements 10 (structures consisting of an anode electrode 11, a dielectric layer 12, a CP layer 13, a CP dam 14, and a resin body 150) are arranged in two dimensions.

[0054] In the above configuration, the process involves forming the CP dam 14 in step S112, forming the resin body 150 in step S113, and then forming the anode through-hole in the anode electrode 11 in step S114. However, it is also possible to form the CP dam 14 and the resin body 150 after forming the anode through-hole in the anode electrode 11, without blocking the anode through-hole.

[0055] (Cathode electrode sheet formation process) Figure 10 is an external perspective view showing the shape of the cathode electrode before individualization. Figure 11 is an external perspective view showing the shape of the cathode electrode in a multi-layer state before individualization.

[0056] As shown in Figures 10 and 11, a resin body 250 is formed on the surface of the cathode electrode 20. The resin body 250 is formed on both sides of the surface of the cathode electrode 20. Multiple cylindrical cathode through holes 29C and groove-shaped cathode through holes 29L are formed in positions overlapping the resin body 250. The multiple cylindrical cathode through holes 29C and groove-shaped cathode through holes 29L are arranged alternately along the direction of the cutting line where the portions that will become the cathode electrode 20 are aligned. That is, the resin body 250 is arranged on the cathode electrode 20 in a non-continuous, island-like shape. The resin body 250 is formed, for example, by arranging a sheet-shaped resin or by pattern printing such as screen printing.

[0057] Multiple cylindrical through-holes 29C for the cathode are formed in positions that realize the first end 20E1 of the cathode electrode 20 and overlap the resin body 250. Groove-shaped through-holes 29L for the cathode are formed in positions that straddle the portions that will become adjacent cathode electrodes 20 and in positions that realize the second end 20E2 of adjacent cathode electrodes 20.

[0058] In this process, the resin body 250 is removed when forming the cathode through-hole 29L. As a result, the resin body 150 fits into the position where the cathode through-hole 29L is formed, as shown in Figure 2(B). Therefore, an unnecessary increase in the thickness of the sheet laminate 110 is suppressed.

[0059] (Formation process of sheet laminate) Figure 12 is a flowchart showing an example of the formation process of the first sheet laminate. Figure 13 is an exploded perspective view showing a structure in which capacitor element sheets and cathode electrodes are laminated.

[0060] As shown in Figure 12, capacitor element sheets and cathode electrode sheets are stacked alternately (Figure 12: S121). More specifically, the capacitor element sheets and cathode electrode sheets are stacked in such a way that the following conditions are met. By stacking the capacitor element sheets and cathode electrode sheets in this way, a sheet stack 110 is formed.

[0061] - When viewed in the stacking direction (Z-axis direction), the multiple cylindrical anode through-holes 19C in the capacitor element sheet and the groove-shaped cathode through-holes 29L in the cathode electrode sheet overlap (see Figure 13). - When viewed in the stacking direction (Z-axis direction), the groove-shaped anode through-holes 19L in the capacitor element sheet and the multiple cylindrical cathode through-holes 29C in the cathode electrode sheet overlap (see Figure 13). - When viewed in the stacking direction (Z-axis direction), the resin body 150 in which the multiple cylindrical anode through-holes 19C in the capacitor element sheet are formed overlaps with the groove-shaped cathode through-holes 29L in the cathode electrode sheet (see Figure 13). - When viewed in the stacking direction (Z-axis direction), the groove-shaped anode through-holes 19L in the capacitor element sheet and the resin body 250 in which the multiple cylindrical cathode through-holes 29C in the cathode electrode sheet are formed overlap (see Figure 13). Therefore, multiple through holes are formed in the sheet laminate 110, extending from the top surface to the bottom surface of the sheet laminate 110.

[0062] Next, the sheet laminate 110 is heated and pressurized (Figure 12: S122).

[0063] (Comparison with Conventional Configuration) Next, using Figures 14(A) and 14(B), we will compare the configuration of the solid electrolytic capacitor in the conventional configuration with that of the solid electrolytic capacitor 1 in the first embodiment. Figure 14(A) is a cross-sectional view in the XZ plane of the solid electrolytic capacitor in the conventional configuration. Figure 14(B) is a cross-sectional view in the XZ plane of the solid electrolytic capacitor 1 in the first embodiment. In Figure 14(B), the resin body 150 is used as an example, but the configuration of the resin body 250 is similar.

[0064] As shown in Figure 14(A), in the conventional configuration, a void occurs between the capacitor element and the cathode electrode. This is thought to be because the inflow path for the insulating resin forming the outer resin 50 is very narrow and long. In other words, it is not possible to inflow a sufficient amount of insulating resin between the layers, resulting in the creation of spaces (voids) that are not sealed with insulating resin. As a result of the formation of these voids, plating solutions and moisture from the outside can easily penetrate.

[0065] On the other hand, as shown in Figure 14(B), the resin body 150 is formed near the first end 10E1 of the capacitor element 10. The resin body 150 is formed to overlap the CP dam 14 in the Z-axis direction. With this configuration, when forming the sheet laminate 110, the space between the capacitor element 10 and the cathode electrode 20 is filled with the resin body 150. Therefore, the intrusion of plating solution from the outside can be suppressed. In other words, LC defects are suppressed. In addition, since the intrusion of moisture from the outside can be suppressed, the long-term reliability of the solid electrolytic capacitor 1 is improved. Therefore, a highly reliable solid electrolytic capacitor 1 can be realized.

[0066] As shown in Figures 2(A) and 4(A), the resin body 150 is formed to be substantially flush with the first end 10E1 of the capacitor element 10. However, the resin body 150 may also be formed along the end of the first end 10E1 of the capacitor element 10. In other words, it is preferable that the resin body 150 be formed in a part that is susceptible to the effects of plating solution and moisture. Even with such a configuration, the intrusion of plating solution and moisture from the outside can be suppressed.

[0067] Furthermore, the resin body 150 may be formed to overlap a portion of the end of the second end 20E2 of the cathode electrode 20. In other words, the resin body 150 may overlap the second end 20E2 of the cathode electrode 20 as long as it does not affect the thickness of the sheet laminate 110 (solid electrolytic capacitor 1).

[0068] In the above-described configuration, the resin body 150 is shown to be formed on both sides in the Z-axis direction of the capacitor element 10. However, the resin body 150 may be formed on only one side. In this case, it is preferable to form it so that its thickness is approximately twice that of the resin body 150 shown in the first embodiment.

[0069] Similarly, as shown in Figures 2(A) and 4(B), the resin body 250 is formed to be substantially flush with the first end 20E1 of the cathode electrode 20. However, it may also be formed along the outer circumference of the cathode electrode 20. Even with such a configuration, the intrusion of plating solution and moisture from the outside can be suppressed.

[0070] Furthermore, the resin body 250 may be formed to overlap a portion of the end of the second end 10E2 of the capacitor element 10. In other words, the resin body 250 may overlap the second end 10E2 of the capacitor element 10 as long as it does not affect the thickness of the sheet laminate 110 (solid electrolytic capacitor 1).

[0071] In the above-described configuration, the resin body 250 is shown to be formed on both sides in the Z-axis direction of the cathode electrode 20. However, the resin body 250 may be formed on only one side. In this case, it is preferable to form it so that its thickness is approximately twice that of the resin body 250 shown in the first embodiment.

[0072] It is preferable that the resin body 150 and the resin body 250 are made of the same component. This suppresses fracture of the interface between the resin body 150 and the resin body 250 due to external stress, etc., and improves the strength of the solid electrolytic capacitor 1. However, the resin body 150 and the resin body 250 may be made of different components as long as the strength of the solid electrolytic capacitor 1 is not impaired.

[0073] Furthermore, the first Young's modulus of the resin body 150 and the first Young's modulus of the resin body 250 may be the same or different. In other words, it is sufficient that the first Young's modulus of the resin body 150 and the first Young's modulus of the resin body 250 are smaller than the second Young's modulus of the outer resin 50.

[0074] [Second Embodiment] A solid electrolytic capacitor according to a second embodiment of the present invention will be described with reference to the figures.

[0075] Figure 15 is a schematic diagram of the capacitor element and cathode electrode according to the second embodiment. As shown in Figure 15, the capacitor element and cathode electrode according to the second embodiment differ from those according to the capacitor element and cathode electrode according to the first embodiment in the shape of the resin body 150A and the resin body 250A. Other components of the solid electrolytic capacitor according to the second embodiment are the same as those of the solid electrolytic capacitor according to the first embodiment, and the description of the similar parts will be omitted.

[0076] As shown in Figure 15, the resin body 150A has a stepped shape. More specifically, the resin body 150A has a stepped shape along the corner CR2 of the cathode electrode 20. In this way, the resin body 150A is formed to cover the corner CR2, making it possible to efficiently mask the cathode electrode 20. Therefore, the insulation of the corner CR2 of the cathode electrode 20 is further improved by the resin body 150A. The size of the resin body 150A does not need to be large enough to affect the capacitance of the solid electrolytic capacitor.

[0077] Similar to the resin body 150A, the resin body 250A has a stepped shape. More specifically, the resin body 250A has a stepped shape that follows the corner CR1 of the capacitor element 10. In this way, the resin body 250A is formed to cover the corner CR1, making it possible to efficiently mask the capacitor element 10. Therefore, the insulation of the corner CR1 of the capacitor element 10 is further improved by the resin body 250A. The size of the resin body 250A does not need to affect the capacitance of the solid electrolytic capacitor.

[0078] Even with this configuration, when viewed from above from the first end 10E1 side of the multiple capacitor elements 10, the resin body 150A and the capacitor elements 10 are arranged alternately. Furthermore, the capacitor elements 10 and the resin body 150A are formed so that their respective surfaces are in contact. In other words, the intrusion of external plating solution into a position close to the first end 10E1 of the solid electrolytic capacitor can be suppressed, thereby suppressing LC defects. Moreover, since the intrusion of external moisture into a position close to the first end 10E1 of the capacitor elements 10 of the solid electrolytic capacitor 1 can be suppressed, long-term reliability is improved.

[0079] Similarly, when viewed from above from the first end 20E1 side of the cathode electrode 20, the resin body 250A and the cathode electrode 20 are arranged alternately. Furthermore, the cathode electrode 20 and the resin body 250A are formed so that their respective surfaces are in contact. In other words, the intrusion of external plating solution into a position close to the first end 20E1 of the solid electrolytic capacitor can be suppressed, thereby suppressing LC defects. Moreover, since the intrusion of external moisture into a position close to the first end 20E1 of the cathode electrode 20 of the solid electrolytic capacitor 1 can be suppressed, long-term reliability is improved.

[0080] (Description of specific materials and other examples for each component of the solid electrolytic capacitor 1) (Capacitor element 10) The capacitor element 10 is realized using, for example, the following materials and thicknesses.

[0081] The anode electrode 11 is made of, for example, a single metal such as aluminum, tantalum, niobium, titanium, zirconium, or magnesium, or an alloy containing these metals. Preferably, the anode electrode 11 is aluminum or an aluminum alloy. The anode electrode 11 can be any valve-acting metal that exhibits so-called valve action.

[0082] The anode electrode 11 is preferably flat, and the thickness of the core portion of the anode electrode 11 (the central part not reached by the pores of the porous material) is preferably 5 μm or more and 100 μm or less. The thickness of the porous portion (the portion where the pores of the porous material are formed) (thickness on one side) is preferably 5 μm or more and 200 μm or less.

[0083] The dielectric layer 12 is preferably made of an oxide film of the anode electrode 11. For example, when aluminum foil is used for the anode electrode 11, the dielectric layer 12 is formed by oxidation in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts, ammonium salts, etc. The thickness of the dielectric layer 12 is preferably 1 nm or more and 100 nm or less.

[0084] The inner layer CP131 may be realized using, for example, a conductive polymer with a backbone of pyrroles, thiophenes, anilines, etc., or a conductive polymer with a backbone of thiophenes such as PEDOT [poly(3,4-ethylenedioxythiophene)], and may also be a PEDOT:PSS layer compounded with polystyrene sulfonic acid (PSS) as a dopant. The inner layer CP131 may be formed by, for example, using a processing solution containing a monomer such as 3,4-ethylenedioxythiophene to form a polymerized film of poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer 12, or by applying a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric part and drying it.

[0085] The thickness of the outer layer CP132 is preferably 2 μm or more and 20 μm or less. The material of the outer layer CP132 is the same as the material of the inner layer CP131.

[0086] The cathode electrode 20 is preferably made of aluminum or an aluminum alloy. The thickness of the cathode electrode 20 is, for example, about the same as the thickness of the anode electrode 11.

[0087] The exterior resin 50 (first resin and second resin) may contain fillers. Preferred resins include, for example, epoxy resins, phenolic resins, polyimide resins, silicone resins, polyamide resins, and liquid crystal polymers. Preferred fillers include, for example, insulating oxide particles such as silica particles, alumina particles, titania particles, and zirconia particles. The maximum diameter of the filler is preferably, for example, 30 μm or more and 40 μm or less. For example, a solid epoxy resin containing silica particles is more preferable.

[0088] This specification discloses the following:

[0089] <1> A solid electrolytic capacitor comprising: a sheet laminate formed by alternately stacking a plurality of flat film capacitor elements and a plurality of flat film cathode electrode foils in the stacking direction; a first resin disposed between layers which is the space between the plurality of flat film capacitor elements and the plurality of flat film cathode electrode foils in the sheet laminate; a second resin that seals the sheet laminate; and an external electrode connected to the sheet laminate, wherein the flat film capacitor element further comprises: a flat film anode electrode foil; a dielectric layer formed on the surface of the anode electrode foil; a third resin formed on the surface of the dielectric layer; and a solid electrolyte layer formed within a region restricted by the third resin, wherein the first resin is in contact with the external electrode, the second resin, the flat film capacitor elements, and the flat film cathode electrode foil.

[0090] <2> The solid electrolytic capacitor according to <1>, wherein the first Young's modulus of the first resin is smaller than the second Young's modulus of the second resin.

[0091] <3> The solid electrolytic capacitor according to <1> or <2>, wherein the flat film-shaped anode electrode foil has a first end connected to the external electrode, and the flat film-shaped cathode electrode foil has a second end connected to the external electrode, and the first resin comprises a first anode resin formed between the layers near the first end, and a first cathode resin formed between the layers near the second end.

[0092] <4> The solid electrolytic capacitor according to <3>, wherein the thickness of the first anode resin is half or less the thickness of the cathode electrode foil.

[0093] <5> The solid electrolytic capacitor according to <3>, wherein the thickness of the first cathode resin is half or less of the thickness of the capacitor element.

[0094] <6> A solid electrolytic capacitor according to any one of <1> to <5>, further comprising: an anode through-hole that penetrates the plurality of flat film capacitor elements in the thickness direction; and a cathode through-hole that penetrates the flat film cathode electrode foil in the thickness direction, wherein the first resin is formed adjacent to the anode through-hole and the cathode through-hole.

[0095] <7> The solid electrolytic capacitor according to any one of claims <3> to <5>, wherein when the sheet laminate is viewed from the side, the first anode resin and the anode electrode foil are arranged alternately near the first end.

[0096] <8> When the sheet laminate is viewed from the side, the first cathode resin and the cathode electrode foil at a position close to the second end are arranged alternately, the solid electrolytic capacitor according to any one of claims <3> to <5>.

[0097] <9> A method for manufacturing a solid electrolytic capacitor, comprising the steps of: forming a sheet laminate formed by alternately stacking a plurality of flat film capacitor elements and a plurality of flat film cathode electrode foils in the stacking direction; forming a first resin disposed between layers, which is the space between the plurality of flat film capacitor elements and the plurality of flat film cathode electrode foils in the sheet laminate; forming a second resin for sealing the sheet laminate; and forming an external electrode connected to the sheet laminate, wherein the flat film capacitor element comprises: a flat film anode electrode foil; a dielectric layer formed on the surface of the anode electrode foil; a third resin formed on the surface of the dielectric layer; and a solid electrolyte layer formed within a region restricted by the third resin, and the first resin is formed to be in contact with the external electrode, the second resin, the flat film capacitor element, and the flat film cathode electrode foil.

[0098] Inner layer CP...131 Outer layer CP...132 CR1, CR2...Corner 1...Solid electrolytic capacitor 10...Capacitor element 10E1, 20E1...First end 10E2, 20E2...Second end 11...Anode electrode 12...Dielectric layer 13...CP layer 14...Dam for CP 19C, 19L...Through-hole for anode 20...Cathode electrode 29C, 29L...Through-hole for cathode 50...Costal resin 61, 62...External electrodes 100...Capacitor element laminate 101...Top surface 102...Bottom surface 110...Sheet laminate 150, 150A, 250, 250A...Resin body

Claims

1. A solid electrolytic capacitor comprising: a sheet laminate formed by alternately stacking a plurality of flat film capacitor elements and a plurality of flat film cathode electrode foils in the stacking direction; a first resin disposed between layers, which is the space between the plurality of flat film capacitor elements and the plurality of flat film cathode electrode foils in the sheet laminate; a second resin that seals the sheet laminate; and an external electrode connected to the sheet laminate, wherein the flat film capacitor element further comprises: a flat film anode electrode foil; a dielectric layer formed on the surface of the anode electrode foil; a third resin formed on the surface of the dielectric layer; and a solid electrolyte layer formed within a region restricted by the third resin, wherein the first resin is in contact with the external electrode, the second resin, the flat film capacitor elements, and the flat film cathode electrode foil.

2. The solid electrolytic capacitor according to claim 1, wherein the first Young's modulus of the first resin is smaller than the second Young's modulus of the second resin.

3. The solid electrolytic capacitor according to claim 1 or 2, wherein the flat film-shaped anode electrode foil has a first end connected to the external electrode, and the flat film-shaped cathode electrode foil has a second end connected to the external electrode, and the first resin comprises a first anode resin formed between the layers near the first end, and a first cathode resin formed between the layers near the second end.

4. The solid electrolytic capacitor according to claim 3, wherein the thickness of the first anode resin is half or less the thickness of the cathode electrode foil.

5. The solid electrolytic capacitor according to claim 3, wherein the thickness of the first cathode resin is less than or equal to half the thickness of the capacitor element.

6. A solid electrolytic capacitor according to any one of claims 1 to 5, further comprising: an anode through-hole penetrating the plurality of flat film capacitor elements in the thickness direction; and a cathode through-hole penetrating the flat film cathode electrode foil in the thickness direction, wherein the first resin is formed adjacent to the anode through-hole and the cathode through-hole.

7. The solid electrolytic capacitor according to any one of claims 3 to 5, wherein, when the sheet laminate is viewed from the side, the first anode resin and the anode electrode foil are arranged alternately near the first end.

8. The solid electrolytic capacitor according to any one of claims 3 to 5, wherein, when the sheet laminate is viewed from the side, the first cathode resin and the cathode electrode foil near the second end are arranged alternately.

9. A method for manufacturing a solid electrolytic capacitor, comprising the steps of: forming a sheet laminate by alternately stacking a plurality of flat film capacitor elements and a plurality of flat film cathode electrode foils in the stacking direction; forming a first resin disposed between layers, which is the space between the plurality of flat film capacitor elements and the plurality of flat film cathode electrode foils in the sheet laminate; forming a second resin for sealing the sheet laminate; and forming an external electrode connected to the sheet laminate, wherein the flat film capacitor element comprises: a flat film anode electrode foil; a dielectric layer formed on the surface of the anode electrode foil; a third resin formed on the surface of the dielectric layer; and a solid electrolyte layer formed within a region restricted by the third resin, and the first resin is formed so as to be in contact with the external electrode, the second resin, the flat film capacitor element, and the flat film cathode electrode foil.

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