Capacitor element

Abstract

A capacitor element 1 comprises a capacitor part 10 including: an anode plate 11 having a porous part 11B on at least one main surface of a core part 11A; a dielectric layer 12 provided on at least a part of a surface of the porous part 11B; a cathode layer 13 provided on at least a part of a surface of the dielectric layer 12; and a collector foil 14 provided on at least a part of a surface of the cathode layer 13 and electrically connected to the cathode layer 13. An interface resistance reduction layer 15 is provided on at least a part of a surface of the collector foil 14 on the cathode layer 13 side.

Description

Capacitor element

[0001] The present invention relates to a capacitor element.

[0002] Patent Document 1 discloses a solid electrolytic capacitor including: a foil-shaped anode having a porous portion on at least one surface thereof and through-holes formed at predetermined positions; a dielectric coating formed in the porous portion of the anode; an insulating layer having an opening formed in the dielectric coating; a solid electrolyte layer formed on the dielectric coating at the opening of the insulating layer; a cathode formed on at least a part of the solid electrolyte layer and disposed approximately parallel to the anode; an electrode formed on the insulating layer; and through-hole electrodes that penetrate the insulating layer and the anode to electrically connect the electrode to the anode and / or penetrate the insulating layer and the cathode to electrically connect the electrode to the cathode, wherein at least one of the through-hole electrodes has an elongated hole shape.

[0003] Furthermore, Patent Document 1 discloses a substrate with a built-in solid electrolytic capacitor, which has a second insulating layer formed on the insulating layer of at least one of the solid electrolytic capacitors, a wiring pattern formed on the second insulating layer, and vias that electrically connect the wiring pattern to the electrodes of the solid electrolytic capacitor.

[0004] Japanese Patent Application Laid-Open No. 2007-281111

[0005] Patent Document 1 describes that the cathode can be formed by, for example, printing a carbon paste, a silver paste, a nickel paste, or the like, vapor deposition of a metal, or lamination of a metal foil.

[0006] However, when metal foil is used as the material for the cathode that constitutes the capacitor built into the substrate, it is difficult to make the structural design and resistance design viable without measures such as matching the thermal design with the material of the anode and wiring that form the base.

[0007] The present invention has been made to solve the above problems, and has an object to provide a capacitor element that can reduce the resistance of the interface extending from the capacitor section to the outside.

[0008] The capacitor element of the present invention comprises a capacitor part including an anode plate having a porous part on at least one main surface of a core part, a dielectric layer provided on at least a part of the surface of the porous part, a cathode layer provided on at least a part of the surface of the dielectric layer, and a current collector foil provided on at least a part of the surface of the cathode layer and electrically connected to the cathode layer, wherein an interfacial resistance reducing layer is provided on at least a part of the surface of the current collector foil facing the cathode layer.

[0009] According to the present invention, it is possible to provide a capacitor element that can reduce the resistance of the interface extending from the capacitor section to the outside.

[0010] FIG. 1 is a cross-sectional view schematically showing an example of a capacitor element of the present invention. FIG. 2 is an enlarged view of a portion indicated by II in the capacitor element shown in FIG. 1. FIG. 3 is an example of an enlarged view of a portion indicated by III in the capacitor element shown in FIG. 1. FIG. 4 is a plan view taken along line IV-IV of the capacitor element shown in FIG. 1. FIG. 5 is a cross-sectional view schematically showing an example of a step of preparing an anode plate. FIG. 6 is a cross-sectional view schematically showing an example of a step of forming a first insulating portion. FIG. 7 is a cross-sectional view schematically showing an example of a step of forming a through-hole. FIG. 8 is a cross-sectional view schematically showing an example of a step of forming a second insulating portion. FIG. 9 is a cross-sectional view schematically showing an example of a step of forming a cathode layer. FIG. 10 is a cross-sectional view schematically showing an example of a step of forming an insulating adhesive layer. FIG. 11 is a cross-sectional view schematically showing an example of a step of stacking current collecting foils. FIG. 12 is a cross-sectional view schematically showing an example of a step of separating a portion of a current collecting foil. FIG. 13 is a cross-sectional view schematically showing an example of a step of forming a sealing layer. Fig. 14 is a cross-sectional view schematically showing an example of a process for forming a first through hole and a second through hole, Fig. 15 is a cross-sectional view schematically showing an example of a process for performing an electroless plating treatment, and Fig. 16 is a cross-sectional view schematically showing an example of a process for forming a through conductor and a wiring layer.

[0011] The capacitor element of the present invention will be described below. Note that the present invention is not limited to the following embodiments and may be modified as appropriate within the scope of the present invention. Furthermore, a combination of multiple individual preferred configurations described in the following embodiments also constitutes the present invention.

[0012] In this specification, terms indicating the relationship between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms indicating the shapes of elements are not expressions that only express a strict meaning, but are expressions that mean that a range of substantial equivalence, for example, a difference of about a few percent, is also included. Furthermore, in this specification, "equivalent" or "constant" is not an expression that means only completely equivalent or constant, but is an expression that means that a range of substantial equivalence or constant, for example, a difference of about a few percent, is included.

[0013] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, and other scales may differ from those of the actual product. In the drawings, the same or equivalent parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0014] Fig. 1 is a cross-sectional view schematically showing an example of a capacitor element of the present invention, and Fig. 2 is an enlarged view of a portion indicated by II in the capacitor element shown in Fig. 1.

[0015] 1 includes a capacitor section 10. As shown in FIG. 1, the capacitor element 1 may further include a sealing layer 20 provided so as to cover at least one main surface of the capacitor section 10.

[0016] In the example shown in FIG. 1, one capacitor section 10 is disposed inside the sealing layer 20 .

[0017] The number of capacitor sections 10 arranged inside sealing layer 20 is not particularly limited, and may be one or more.

[0018] The sealing layer 20 may be composed of only one layer or two or more layers. When the sealing layer 20 is composed of two or more layers, the materials constituting the respective layers may be the same or different.

[0019] 1, the sealing layer 20 is preferably provided on both principal surfaces that face each other in the thickness direction (Z direction in FIG. 1) of the capacitor section 10. The sealing layer 20 protects the capacitor section 10.

[0020] The sealing layer 20 is formed so as to seal the capacitor portion 10 by, for example, a method of thermocompressing an insulating resin sheet, or a method of applying an insulating resin paste and then thermally curing it.

[0021] The capacitor unit 10 includes an anode plate 11 having a porous portion 11B on at least one main surface of a core portion 11A, a dielectric layer 12 (see FIG. 2 ) provided on at least a portion of the surface of the porous portion 11B, a cathode layer 13 provided on at least a portion of the surface of the dielectric layer 12, and a current collector foil 14 provided on at least a portion of the surface of the cathode layer 13 and electrically connected to the cathode layer 13. In this way, the capacitor unit 10 constitutes an electrolytic capacitor. In the example shown in FIG. 1 , the anode plate 11 has the porous portion 11B on both main surfaces of the core portion 11A, but the porous portion 11B may be provided on only one main surface of the core portion 11A.

[0022] As shown in Figure 1, the capacitor section 10 is divided into an effective region RG1 in which the anode plate 11 and the cathode layer 13 face each other in the thickness direction (Z direction) via the dielectric layer 12, and a non-effective region RG2 other than the effective region RG1.

[0023] 1 , the inside of the porous portion 11B in the non-effective region RG2 is filled with a first insulating portion 31. Furthermore, an insulating adhesive layer 35 is provided between the current collecting foil 14 and the first insulating portion 31.

[0024] The cathode layer 13 includes, for example, a solid electrolyte layer provided on the surface of the dielectric layer 12. In this case, it is preferable that a current collecting foil 14 is provided on at least a part of the surface of the solid electrolyte layer that constitutes the cathode layer 13.

[0025] The current collector foil 14 preferably contains a metal. For example, the current collector foil 14 may be a metal foil or a metallized film in which a metal layer is provided on the surface of a film.

[0026] Examples of metals constituting the current collector foil 14 include copper, aluminum, silver, titanium, nickel, and alloys containing at least one of these metals. Among these, the metal constituting the current collector foil 14 is preferably copper or aluminum.

[0027] The thickness of the current collector foil 14 is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0028] 1 , the current collecting foil 14 preferably extends from the effective region RG1 to a part of the non-effective region RG2 of the capacitor portion 10. In other words, the current collecting foil 14 preferably extends from the surface of the cathode layer 13 to the outside of the cathode layer 13.

[0029] FIG. 3 is an example of an enlarged view of a portion indicated by III in the capacitor element shown in FIG.

[0030] 3 , an interfacial resistance reducing layer 15 is provided on at least a portion of the surface of the current collector foil 14 on the cathode layer 13 side. Here, the interfacial resistance reducing layer 15 is a layer that has a lower interfacial resistance with the cathode layer 13 than the current collector foil 14. In other words, the interfacial resistance of the interfacial resistance reducing layer 15 with the cathode layer 13 is lower than the interfacial resistance of the current collector foil 14 with the cathode layer 13.

[0031] For example, when current collector foil 14 is made of a metal such as copper or aluminum, an insulating natural oxide film easily forms on the surface of either metal. Therefore, if current collector foil 14 is used as a cathode for drawing current from capacitor unit 10, the resistance of the entire cathode will be very high, and the capacitor function will not be realized. Therefore, by providing interface resistance-reducing layer 15 on the surface of current collector foil 14 on the cathode layer 13 side, it is possible to reduce the resistance of the interface leading from capacitor unit 10 to the outside.

[0032] When the current collector foil 14 extends from the effective region RG1 to a part of the non-effective region RG2, the interfacial resistance reducing layer 15 is preferably also provided on the surface of the current collector foil 14 in the non-effective region RG2 facing the cathode layer 13. Alternatively, the interfacial resistance reducing layer 15 may be provided on the entire surface of the current collector foil 14 facing the cathode layer 13.

[0033] The interface resistance reducing layer 15 can be formed on the surface of the current collecting foil 14 by a method such as vapor deposition, sputtering, or paste coating.

[0034] The interfacial resistance reduction layer 15 preferably contains carbon, or may contain silver or silver oxide.

[0035] For example, it is preferable that the current collector foil 14 contains copper or aluminum and the interfacial resistance reducing layer 15 contains carbon. Alternatively, the current collector foil 14 may contain silver and the interfacial resistance reducing layer 15 may contain silver oxide.

[0036] The amount of oxygen present on the surface of the interfacial resistance reducing layer 15 facing the current collector foil 14 is preferably greater than the amount of oxygen present on the surface of the interfacial resistance reducing layer 15 facing the cathode layer 13 .

[0037] The amount of oxygen present on the surface of the interfacial resistance reducing layer 15 means the amount of oxygen (O) present on the outermost surface (depth 0 nm) when a surface analysis is performed by X-ray photoelectron spectroscopy (XPS).

[0038] 3 , a protective layer 16 may be provided between the current collector foil 14 and the interfacial resistance reducing layer 15. In this case, the protective layer 16 may be provided in an area of ​​the surface of the current collector foil 14 where the interfacial resistance reducing layer 15 is not provided. In other words, a part of the protective layer 16 may be exposed. Note that the protective layer 16 does not have to be provided between the current collector foil 14 and the interfacial resistance reducing layer 15.

[0039] The protective layer 16 may be, for example, a layer containing an oxide of the metal that constitutes the current collector foil 14. In this case, the protective layer 16 may be a natural oxide coating of the metal that constitutes the current collector foil 14. Alternatively, the protective layer 16 may be a layer other than an oxide that is formed on the surface of the current collector foil 14.

[0040] The surface roughness of current collector foil 14 on the cathode layer 13 side is preferably greater than the surface roughness on the opposite side to cathode layer 13. Increasing the surface roughness of current collector foil 14 on the cathode layer 13 side is advantageous for drawing out the resistance, while reducing the surface roughness of current collector foil 14 on the sealing layer 20 side provides excellent adhesion to sealing layer 20.

[0041] Of the surfaces of the current collector foil 14, the surface opposite the cathode layer 13 does not necessarily need to be provided with the interfacial resistance reducing layer 15, but may be provided with the interfacial resistance reducing layer 15. In this case, a protective layer 16 may be provided between the current collector foil 14 and the interfacial resistance reducing layer 15 on the surface opposite the cathode layer 13.

[0042] FIG. 4 is a plan view of the capacitor element shown in FIG. 1 taken along line IV-IV.

[0043] As shown in Figures 1 and 4, the capacitor element 1 may further include a cathode through conductor 41 that is arranged to penetrate the capacitor section 10 in the thickness direction (Z direction) in the non-effective region RG2 and is electrically connected to the collector foil 14.

[0044] 1 and 4 , in the non-effective region RG2, the inside of the through hole that penetrates the first insulating portion 31 and the anode plate 11 in the thickness direction is filled with the second insulating portion 32. An insulating adhesive layer 35 is provided between the current collecting foil 14 and the second insulating portion 32.

[0045] The cathode through conductor 41 is provided so as to penetrate the second insulating portion 32 in the thickness direction. As shown in Figures 1 and 4, the wall surface of the anode plate 11 exposed in the through hole penetrating the first insulating portion 31 and the anode plate 11 in the thickness direction is preferably insulated from the cathode through conductor 41 by the second insulating portion 32. On the other hand, the cathode through conductor 41 is preferably electrically connected to the wall surface of the current collecting foil 14.

[0046] As shown in FIGS. 1 and 4, the capacitor element 1 may further include an anode through conductor 42 that is provided in the non-effective region RG2 so as to penetrate the capacitor portion 10 in the thickness direction and is electrically connected to the anode plate 11.

[0047] The anode penetrating conductor 42 is provided so as to penetrate the first insulating portion 31 in the thickness direction. As shown in Figures 1 and 4, the anode penetrating conductor 42 is preferably electrically connected to the wall surface of the anode plate 11.

[0048] 1 , fragments of the current collecting foil 14 electrically insulated from the cathode layer 13 may be present on the surface of the first insulating part 31 where the anode penetrating conductor 42 is provided. Note that the current collecting foil 14 electrically insulated from the cathode layer 13 does not necessarily have to be present on the surface of the first insulating part 31 where the anode penetrating conductor 42 is provided.

[0049] The planar shape of the cathode through-conductor 41 (e.g., the cross-sectional shape perpendicular to the thickness direction of the anode plate 11) is not particularly limited and may be, for example, a circular shape. Similarly, the planar shape of the anode through-conductor 42 is not particularly limited and may be, for example, a circular shape. The planar shape of the cathode through-conductor 41 may be the same as or different from the planar shape of the anode through-conductor 42.

[0050] The number of cathode through conductors 41 is not particularly limited and may be one or two or more. Similarly, the number of anode through conductors 42 is not particularly limited and may be one or two or more. The number of cathode through conductors 41 may be the same as the number of anode through conductors 42, may be less than the number of anode through conductors 42, or may be more than the number of anode through conductors 42.

[0051] The diameter of the cathode through conductor 41 may be equal to the diameter of the anode through conductor 42 , may be smaller than the diameter of the anode through conductor 42 , or may be larger than the diameter of the anode through conductor 42 .

[0052] In this specification, the diameter of a through conductor means the diameter when the planar shape is circular, and means the equivalent circle diameter when the planar shape is other than circular.

[0053] The diameter of the cathode through conductor 41 may be constant or may vary in the thickness direction. Similarly, the diameter of the anode through conductor 42 may be constant or may vary in the thickness direction.

[0054] When viewed in the thickness direction of the anode plate 11, the cathode through conductor 41 is preferably provided around the entire periphery of the through hole as shown in FIG.

[0055] A first resin filling portion 51 filled with a resin material may be provided inside the cathode through conductor 41. In this case, the first resin filling portion 51 is provided in the space surrounded by the cathode through conductor 41 inside the through hole. When the space inside the through hole is eliminated by providing the first resin filling portion 51, the occurrence of delamination of the cathode through conductor 41 is suppressed. Note that the first resin filling portion 51 may be a conductor or an insulator.

[0056] 4, the anode through conductor 42 is preferably provided around the entire periphery of the through hole when viewed from the thickness direction of the anode plate 11. The material constituting the anode through conductor 42 may be the same as or different from the material constituting the cathode through conductor 41.

[0057] The anode through conductor 42 may be electrically connected to the wall surface of the anode plate 11 via the anode connection layer 45. In this case, the anode connection layer 45 functions as a barrier layer for the anode plate 11, more specifically, as a barrier layer for the core portion 11A and the porous portion 11B. When the anode connection layer 45 functions as a barrier layer for the anode plate 11, dissolution of the anode plate 11 that occurs during chemical treatment for forming a wiring layer (described later) is suppressed, and therefore penetration of the chemical solution into the capacitor portion 10 is suppressed, which tends to improve reliability.

[0058] The anode connection layer 45 preferably includes a metal layer containing nickel as a main component, which reduces damage to the metal (e.g., aluminum) constituting the anode plate 11, and therefore the barrier properties of the anode connection layer 45 against the anode plate 11 are likely to be improved.

[0059] For example, the wall surface of the anode plate 11 made of aluminum or an aluminum alloy may be subjected to a zincate treatment, followed by electroless nickel plating to form the anode connecting layer 45. The anode connecting layer 45 may include, in order from the anode plate 11, a metal layer mainly composed of zinc and a metal layer mainly composed of nickel.

[0060] The dimensions of the anode connection layer 45 in the thickness direction (Z direction) of the anode plate 11 may be equal to the dimensions of the anode plate 11 in the thickness direction, may be smaller than the dimensions of the anode plate 11 in the thickness direction, or may be larger than the dimensions of the anode plate 11 in the thickness direction.

[0061] The anode through conductor 42 may be connected directly to the wall surface of the anode plate 11 without the anode connection layer 45 therebetween.

[0062] A second resin filling portion 52 filled with a resin material may be provided inside the anode through conductor 42. In this case, the second resin filling portion 52 is provided in the space surrounded by the anode through conductor 42 inside the through hole. When the space inside the through hole is eliminated by providing the second resin filling portion 52, the occurrence of delamination of the anode through conductor 42 is suppressed. Note that the second resin filling portion 52 may be a conductor or an insulator.

[0063] Although not shown, the capacitor element 1 may further include a through conductor that is arranged to penetrate the capacitor section 10 in the thickness direction (Z direction) in the non-effective region RG2 and is not electrically connected to the anode plate 11 and the collecting foil 14.

[0064] 1, a first wiring layer 61 and a second wiring layer 62 are provided on the surface of the sealing layer 20. In FIG. 1, the first wiring layer 61 and the second wiring layer 62 are provided on both the upper and lower sides of the capacitor element 1, but they may be provided on only one side.

[0065] The first wiring layer 61 is electrically connected to the cathode through conductor 41. In the example shown in FIG. 1 , the first wiring layer 61 is electrically connected to the cathode layer 13 via the cathode through conductor 41 and the current collecting foil 14.

[0066] The second wiring layer 62 is electrically connected to the anode through conductor 42. In the example shown in FIG.

[0067] The capacitor element 1 shown in FIG. 1 is fabricated, for example, by the following method.

[0068] FIG. 5 is a cross-sectional view schematically showing an example of a step of preparing an anode plate.

[0069] In the step shown in FIG. 5, an anode plate 11 made of a valve metal is prepared.

[0070] For example, an anode plate 11 having a core portion 11A and porous portions 11B provided on both main surfaces thereof is anodized to form a dielectric layer (see FIG. 2) on the surface of the porous portions 11B.

[0071] Alternatively, a chemically formed foil may be prepared as the anode plate 11 having a dielectric layer (see FIG. 2) provided on the surface of the porous portion 11B.

[0072] FIG. 6 is a cross-sectional view schematically illustrating an example of a step of forming the first insulating portion.

[0073] 6, an insulating resin such as polyimide resin is applied to the upper surface of the porous portion 11B in a position that will become the ineffective region (see FIG. 1), and the insulating resin is allowed to penetrate into the porous portion 11B, thereby forming a first insulating portion 31 inside the porous portion 11B.

[0074] FIG. 7 is a cross-sectional view schematically showing an example of a step of forming a through hole.

[0075] In the step shown in FIG. 7, a through hole 70 is formed in the portion where the cathode through conductor 41 is to be formed by performing processing such as drilling or laser processing.

[0076] FIG. 8 is a cross-sectional view schematically illustrating an example of a step of forming the second insulating portion.

[0077] 8, an insulating material such as an insulating resin is filled into the through-hole 70 (see FIG. 7) by printing such as screen printing, thereby forming the second insulating portion 32 inside the through-hole 70.

[0078] FIG. 9 is a cross-sectional view schematically showing an example of a process for forming a cathode layer.

[0079] 9, the cathode layer 13 is formed in the region where the first insulating portion 31 is not formed. For example, a solid electrolyte layer is formed as the cathode layer 13.

[0080] FIG. 10 is a cross-sectional view schematically showing an example of a step of forming an insulating adhesive layer.

[0081] 10, an insulating adhesive layer 35 is formed in the region where the cathode layer 13 is not formed. As the insulating adhesive layer 35, for example, a B-stage adhesive is used.

[0082] FIG. 11 is a cross-sectional view that schematically shows an example of a process for laminating current collecting foils.

[0083] In the step shown in FIG. 11, the current collector foil 14 is laminated on the surfaces of the cathode layer 13 and the insulating adhesive layer 35 .

[0084] Although not shown, an interface resistance reducing layer (see FIG. 3) is provided on at least a portion of the surface of the current collector foil 14 on the side of the cathode layer 13. A protective layer (see FIG. 3) may be provided between the current collector foil 14 and the interface resistance reducing layer.

[0085] FIG. 12 is a cross-sectional view that schematically shows an example of a step of separating a part of the current collector foil.

[0086] 12 , the portion of the current collector foil 14 that will be electrically connected to the anode penetrating conductor 42 to be formed later is separated from the portion of the current collector foil 14 that will be electrically connected to the cathode penetrating conductor 41. Note that the portion of the current collector foil 14 that will be electrically connected to the anode penetrating conductor 42 to be formed later may be completely removed.

[0087] In this way, the capacitor section 10 is obtained.

[0088] FIG. 13 is a cross-sectional view schematically illustrating an example of a step of forming a sealing layer.

[0089] 13, an insulating resin sheet such as Ajinomoto Build-up Film (ABF) is laminated on the surface of capacitor section 10. After lamination, the laminate is placed in a mold, vacuum degassed, and then thermocompressed and cured. This forms sealing layer 20.

[0090] FIG. 14 is a cross-sectional view schematically illustrating an example of a step of forming the first through hole and the second through hole.

[0091] In the process shown in Figure 14, by performing processing such as drilling and laser processing, a first through hole 71 is formed in the area where the cathode through conductor 41 is to be formed, and a second through hole 72 is formed in the area where the anode through conductor 42 is to be formed.

[0092] At this time, by forming a first through hole 71 having a smaller diameter than the through hole 70 (see FIG. 7 ), a state is created in which the second insulating portion 32 is present between the through hole 70 and the first through hole 71. The current collecting foil 14 is exposed at the wall surface of the first through hole 71. Specifically, the current collecting foil 14 electrically connected to the cathode layer 13 is exposed at the wall surface of the first through hole 71. Meanwhile, the anode plate 11 is exposed at the wall surface of the second through hole 72. As shown in FIG. 14 , the current collecting foil 14 electrically insulated from the cathode layer 13 may be exposed at the wall surface of the second through hole 72.

[0093] FIG. 15 is a cross-sectional view schematically showing an example of a process for performing electroless plating.

[0094] 15 , the first through-hole 71 is subjected to electroless plating such as electroless copper plating. On the other hand, the second through-hole 72 is subjected to, for example, zincate treatment, followed by nickel plating and electroless copper plating. As shown in FIG. 15 , an anode connection layer 45 may be formed on the surface of the anode plate 11 exposed at the wall surface of the second through-hole 72.

[0095] FIG. 16 is a cross-sectional view schematically showing an example of a process for forming a through conductor and a wiring layer.

[0096] 16, an electrolytic plating process such as electrolytic copper plating is performed, whereby a cathode through conductor 41 is formed on the inner wall surface of the first through hole 71 (see FIG. 15), and an anode through conductor 42 is formed on the inner wall surface of the second through hole 72 (see FIG. 15).

[0097] Thereafter, a first resin filling portion 51 is formed by filling an insulating material such as insulating resin into a first through hole 71 (see Figure 15) in which a cathode penetrating conductor 41 is formed, and a second resin filling portion 52 is formed by filling an insulating material such as insulating resin into a second through hole 72 (see Figure 15) in which an anode penetrating conductor 42 is formed.

[0098] Furthermore, a plating layer is formed by performing an electrolytic plating process such as electrolytic copper plating on the surface of the sealing layer 20. Subsequently, the plating layer is etched so as to separate the cathode portion and the anode portion, thereby forming the first wiring layer 61 and the second wiring layer 62.

[0099] Through the above steps, the capacitor element 1 shown in FIG. 1 is obtained.

[0100] The detailed configuration of the capacitor element 1 will be described below.

[0101] Examples of the planar shape of the capacitor section 10 when viewed from the thickness direction include a rectangle (square or oblong), a quadrangle other than a rectangle, a polygon such as a triangle, a pentagon, or a hexagon, a circle, an ellipse, a combination of these, etc. The planar shape of the capacitor section 10 may also be an L-shape, a C-shape, a stepped shape, etc.

[0102] The anode plate 11 is preferably made of a valve metal that exhibits so-called valve action. Examples of the valve metal include simple metals such as aluminum, tantalum, niobium, titanium, and zirconium, and alloys containing at least one of these metals. Among these, aluminum or an aluminum alloy is preferred.

[0103] The shape of the anode plate 11 is preferably a flat plate, and more preferably a foil. Thus, in this specification, the term "plate-like" includes "foil-like".

[0104] The anode plate 11 may have the porous portion 11B on at least one main surface of the core portion 11A. That is, the anode plate 11 may have the porous portion 11B on only one main surface of the core portion 11A, or may have the porous portion 11B on both main surfaces of the core portion 11A. The porous portion 11B is preferably a porous layer formed on the surface of the core portion 11A, and more preferably an etched layer.

[0105] The thickness of the anode plate 11 before etching is preferably 60 μm or more and 200 μm or less. The thickness of the unetched core portion 11A after etching is preferably 15 μm or more and 70 μm or less. The thickness of the porous portion 11B is designed according to the required withstand voltage and electrostatic capacitance, but the combined thickness of the porous portions 11B on both sides of the core portion 11A is preferably 10 μm or more and 180 μm or less.

[0106] The pore diameter of the porous portion 11B is preferably 10 nm or more and 600 nm or less. The pore diameter of the porous portion 11B refers to the median diameter D50 measured with a mercury porosimeter. The pore diameter of the porous portion 11B can be controlled, for example, by adjusting various etching conditions.

[0107] The dielectric layer 12 provided on the surface of the porous portion 11B is porous, reflecting the surface condition of the porous portion 11B, and has a finely uneven surface shape. The dielectric layer 12 is preferably made of an oxide film of the valve metal. For example, when aluminum foil is used as the anode plate 11, the dielectric layer 12 made of an oxide film can be formed by anodizing the surface of the aluminum foil in an aqueous solution containing ammonium adipate or the like (also called chemical conversion treatment).

[0108] The thickness of the dielectric layer 12 is designed according to the required withstand voltage and capacitance, but is preferably 10 nm or more and 100 nm or less.

[0109] When the cathode layer 13 includes a solid electrolyte layer, examples of materials constituting the solid electrolyte layer include conductive polymers such as polypyrroles, polythiophenes, and polyanilines. Among these, polythiophenes are preferred, and poly(3,4-ethylenedioxythiophene), also known as PEDOT, is particularly preferred. The conductive polymer may also contain a dopant such as polystyrene sulfonate (PSS). The solid electrolyte layer preferably includes an inner layer that fills the pores (recesses) of the dielectric layer 12 and an outer layer that covers the dielectric layer 12.

[0110] The thickness of the solid electrolyte layer from the surface of the porous portion 11B is preferably 2 μm or more and 20 μm or less.

[0111] The solid electrolyte layer is 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 layer 12 and drying it.

[0112] The solid electrolyte layer can be formed in a predetermined region by applying the above-mentioned treatment liquid or dispersion liquid to the surface of the dielectric layer 12 by a method such as sponge transfer, screen printing, dispenser application, or inkjet printing.

[0113] The sealing layer 20 is made of an insulating material. In this case, the sealing layer 20 preferably contains an insulating resin.

[0114] Examples of the insulating resin contained in the sealing layer 20 include epoxy resin and phenol resin.

[0115] Preferably, the sealing layer 20 further contains a filler.

[0116] Examples of the filler contained in the sealing layer 20 include inorganic fillers such as silica particles and alumina particles.

[0117] Between the capacitor section 10 and the sealing layer 20, for example, a stress relaxation layer, a moisture-proof film, or the like may be provided.

[0118] The first insulating portion 31 is made of an insulating material. In this case, the first insulating portion 31 preferably contains an insulating resin.

[0119] Examples of insulating resins contained in the first insulating portion 31 include polyphenylsulfone resin, polyethersulfone resin, cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.), polyimide resin, polyamideimide resin, epoxy resin, and derivatives or precursors thereof.

[0120] The first insulating portion 31 may be made of the same resin as the sealing layer 20. Unlike the sealing layer 20, if the first insulating portion 31 contains an inorganic filler, this may adversely affect the effective capacitive portion of the capacitor portion 10. Therefore, the first insulating portion 31 is preferably made of a resin alone.

[0121] The first insulating portion 31 can be formed in a predetermined area by applying a mask material, such as a composition containing an insulating resin, to the surface of the porous portion 11B by a method such as sponge transfer, screen printing, dispenser application, or inkjet printing.

[0122] The first insulating portion 31 may be formed on the porous portion 11B either before or after the dielectric layer 12 is formed.

[0123] The second insulating portion 32 is made of an insulating material. In this case, the second insulating portion 32 preferably contains an insulating resin.

[0124] The insulating resin contained in the second insulating portion 32 may be the same resin as the insulating resin contained in the first insulating portion 31 , or may be the same resin as the insulating resin contained in the sealing layer 20 .

[0125] The second insulating portion 32 may further contain an inorganic filler such as silica particles or alumina particles.

[0126] The insulating adhesive layer 35 is made of an insulating material, and in this case, the insulating adhesive layer 35 preferably contains an insulating resin.

[0127] The insulating adhesive layer 35 may be made of, for example, a B-stage adhesive.

[0128] Examples of the constituent material of the first wiring layer 61 include metal materials containing low-resistance metals such as silver, gold, copper, etc. In this case, the first wiring layer 61 is formed by, for example, plating the surface of the cathode through conductor 41.

[0129] In order to improve the adhesion between the first wiring layer 61 and other members, in this case, the adhesion between the first wiring layer 61 and the cathode through conductor 41, a mixed material of at least one conductive filler selected from the group consisting of silver filler, copper filler, nickel filler, and carbon filler and a resin may be used as the constituent material of the first wiring layer 61.

[0130] Examples of the constituent material of the second wiring layer 62 include metal materials containing low-resistance metals such as silver, gold, copper, etc. In this case, the second wiring layer 62 is formed by, for example, plating the surface of the anode through conductor 42.

[0131] In order to improve the adhesion between the second wiring layer 62 and other members, in this case, the adhesion between the second wiring layer 62 and the anode penetrating conductor 42, a mixed material of at least one conductive filler selected from the group consisting of silver filler, copper filler, nickel filler, and carbon filler and a resin may be used as the constituent material of the second wiring layer 62.

[0132] The constituent materials of the first wiring layer 61 and the second wiring layer 62 are preferably the same at least in terms of type, but may be different from each other.

[0133] When multiple capacitor sections 10 are arranged inside the sealing layer 20, each of the capacitor sections 10 may be provided with a first wiring layer 61 electrically connected to the cathode layer 13 and a second wiring layer 62 electrically connected to the anode plate 11, or at least one of the first wiring layer 61 and the second wiring layer 62 may be provided in common among the multiple capacitor sections 10.

[0134] The capacitor element of the present invention is not limited to the above-described embodiment, and various applications and modifications can be made within the scope of the present invention with respect to the configuration of the capacitor element, the manufacturing conditions of the capacitor element, and the like.

[0135] The capacitor element of the present invention can be suitably used as a constituent material of a composite electronic component. Such a composite electronic component includes, for example, the capacitor element of the present invention, external electrodes provided on the outer side of the sealing layer of the capacitor element and electrically connected to the anode plate and cathode layer of the capacitor element, and an electronic component connected to the external electrodes.

[0136] In a composite electronic component, the electronic component connected to the external electrode may be a passive element or an active element. Both the passive element and the active element may be connected to the external electrode, or either the passive element or the active element may be connected to the external electrode. Also, a composite of a passive element and an active element may be connected to the external electrode.

[0137] Examples of passive elements include inductors, etc. Examples of active elements include memories, GPUs (Graphical Processing Units), CPUs (Central Processing Units), MPUs (Micro Processing Units), and PMICs (Power Management ICs).

[0138] The capacitor element of the present invention has a sheet-like shape as a whole. Therefore, in a composite electronic component, the capacitor element can be treated like a mounting substrate, and electronic components can be mounted on the capacitor element. Furthermore, by making the electronic components mounted on the capacitor element sheet-like, it is also possible to connect the capacitor element and the electronic components in the thickness direction via through-hole conductors that penetrate each electronic component in the thickness direction. As a result, active elements and passive elements can be configured like a single module.

[0139] For example, a switching regulator can be formed by electrically connecting the capacitor element of the present invention between a voltage regulator including a semiconductor active element and a load to which the converted DC voltage is supplied.

[0140] In a composite electronic component, a circuit layer may be formed on either side of a capacitor matrix sheet on which a plurality of capacitor elements of the present invention are laid out, and the circuit layer may be connected to a passive element or an active element.

[0141] Alternatively, the capacitor element of the present invention may be placed in a cavity provided in a substrate, embedded in resin, and then a circuit layer may be formed on the resin. Another electronic component (a passive element or an active element) may be mounted in another cavity of the same substrate.

[0142] Alternatively, the capacitor element of the present invention may be mounted on a smooth carrier such as a wafer or glass, an outer layer made of resin may be formed, a circuit layer may be formed, and then the capacitor element may be connected to a passive or active element.

[0143] The present specification discloses the following:

[0144] <1> A capacitor element comprising: an anode plate having a porous portion on at least one main surface of a core portion; a dielectric layer provided on at least a portion of a surface of the porous portion; a cathode layer provided on at least a portion of the surface of the dielectric layer; and a current collector foil provided on at least a portion of a surface of the cathode layer and electrically connected to the cathode layer, wherein an interfacial resistance reducing layer is provided on at least a portion of a surface of the current collector foil facing the cathode layer.

[0145] <2> The capacitor element according to <1>, wherein the capacitor section is divided into an effective area in which the anode plate and the cathode layer face each other in a thickness direction via the dielectric layer, and an ineffective area other than the effective area, and the current collecting foil extends from the effective area to a part of the ineffective area.

[0146] <3> The capacitor element according to <2>, wherein the interfacial resistance reducing layer is also provided on the surface of the current collector foil on the cathode layer side in the ineffective region.

[0147] <4> The capacitor element according to <3>, wherein the interfacial resistance reducing layer is provided on the entire surface of the current collector foil on the cathode layer side.

[0148] <5> The capacitor element according to any one of <1> to <4>, wherein the interfacial resistance reducing layer contains carbon.

[0149] <6> The capacitor element according to any one of <1> to <5>, wherein the amount of oxygen present on the surface of the interfacial resistance reducing layer facing the current collecting foil is greater than the amount of oxygen present on the surface of the interfacial resistance reducing layer facing the cathode layer.

[0150] <7> The capacitor element according to any one of <1> to <6>, wherein a protective layer is provided between the current collecting foil and the interfacial resistance reducing layer.

[0151] <8> The capacitor element according to any one of <1> to <7>, wherein the surface roughness of the current collector foil on the cathode layer side is greater than the surface roughness of the current collector foil on the opposite side to the cathode layer.

[0152] <9> The capacitor element according to any one of <1> to <8>, wherein the current collecting foil contains a metal.

[0153] <10> The capacitor element according to any one of <2> to <4>, further comprising a cathode through conductor provided in the non-effective region so as to penetrate the capacitor portion in a thickness direction and electrically connected to the current collecting foil.

[0154] <11> The capacitor element according to any one of <2> to <4> and <10>, further comprising an anode through conductor provided in the non-effective region so as to penetrate the capacitor portion in a thickness direction and electrically connected to the anode plate.

[0155] <12> The capacitor element according to any one of <1> to <11>, wherein the cathode layer includes a solid electrolyte layer provided on a surface of the dielectric layer, and the current collecting foil is provided on at least a part of a surface of the solid electrolyte layer.

[0156] <13> The capacitor element according to any one of <1> to <12>, further comprising a sealing layer provided so as to cover at least one main surface of the capacitor section.

[0157] REFERENCE SIGNS LIST 1 capacitor element 10 capacitor portion 11 anode plate 11A core portion 11B porous portion 12 dielectric layer 13 cathode layer 14 current collecting foil 15 interface resistance reducing layer 16 protective layer 20 sealing layer 31 first insulating portion 32 second insulating portion 35 insulating adhesive layer 41 cathode through conductor 42 anode through conductor 45 anode connecting layer 51 first resin filled portion 52 second resin filled portion 61 first wiring layer 62 second wiring layer 70 through hole 71 first through hole 72 second through hole RG1 effective region RG2 non-effective region

Claims

1. A capacitor element comprising a capacitor part including an anode plate having a porous part on at least one main surface of a core part, a dielectric layer provided on at least a part of the surface of the porous part, a cathode layer provided on at least a part of the surface of the dielectric layer, and a current collecting foil provided on at least a part of the surface of the cathode layer and electrically connected to the cathode layer, wherein an interfacial resistance reducing layer is provided on at least a part of the surface of the current collecting foil facing the cathode layer.

2. A capacitor element as described in claim 1, wherein the capacitor section is divided into an effective area where the anode plate and the cathode layer face each other in the thickness direction via the dielectric layer, and an ineffective area other than the effective area, and the current collecting foil extends from the effective area to a part of the ineffective area.

3. The capacitor element according to claim 2, wherein the interface resistance reducing layer is also provided on the surface of the current collecting foil on the cathode layer side in the ineffective region.

4. The capacitor element according to claim 3, wherein the interface resistance reducing layer is provided on the entire surface of the current collecting foil on the cathode layer side.

5. The capacitor element according to any one of claims 1 to 4, wherein the interfacial resistance reducing layer contains carbon.

6. A capacitor element according to any one of claims 1 to 5, wherein the amount of oxygen present on the surface of the interfacial resistance reducing layer facing the current collecting foil is greater than the amount of oxygen present on the surface of the interfacial resistance reducing layer facing the cathode layer.

7. The capacitor element according to any one of claims 1 to 6, wherein a protective layer is provided between the current collecting foil and the interfacial resistance reducing layer.

8. A capacitor element according to any one of claims 1 to 7, wherein the surface roughness of the collector foil on the cathode layer side is greater than the surface roughness of the collector foil on the opposite side to the cathode layer.

9. The capacitor element according to any one of claims 1 to 8, wherein the current collecting foil contains a metal.

10. The capacitor element according to any one of claims 2 to 4, further comprising a cathode through conductor provided in the ineffective region so as to penetrate the capacitor section in the thickness direction and electrically connected to the current collecting foil.

11. The capacitor element according to any one of claims 2 to 4 and 10, further comprising an anode through conductor provided in the non-effective region so as to penetrate the capacitor section in the thickness direction and electrically connected to the anode plate.

12. A capacitor element according to any one of claims 1 to 11, wherein the cathode layer includes a solid electrolyte layer provided on the surface of the dielectric layer, and the current collecting foil is provided on at least a portion of the surface of the solid electrolyte layer.

13. The capacitor element according to any one of claims 1 to 12, further comprising a sealing layer provided so as to cover at least one of the main surfaces of the capacitor section.

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