Solid electrolytic capacitor and method for manufacturing the same

Abstract

To provide a solid electrolytic capacitor with a structure allowing low profile.SOLUTION: A solid electrolytic capacitor 100 comprises a laminate 140 obtained by stacking a plurality of capacitor elements 1. The capacitor 1 comprises: a valve action metal substrate 10 that has at least one main face on which a dielectric layer 20 is stacked; a separator 30 that is provided on the dielectric layer 20 and separates the valve action metal substrate 10 into an anode part 31 and a cathode part 32; a solid electrolyte layer 40 that is provided on the dielectric layer 20 of the cathode part 32; a carbon layer 50 that is provided on the solid electrolyte layer 40; and an adhesive Ag layer 60 and a cathode Ag layer 70 that are provided on the carbon layer 50. The adhesive Ag layer 60 is arranged between the capacitor elements 1 on a side closer to the anode part 31 than the cathode Ag layer 70. The cathode Ag layer 70 is arranged on a side closer to the cathode part 32 than the adhesive Ag layer 60. The adhesive Ag layer 60 and the cathode Ag layer 70 are different in composition.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor. [Background technology]

[0002] Patent Document 1 discloses a solid electrolytic capacitor. The solid electrolytic capacitor described in Patent Document 1 includes an element stack in which multiple capacitor elements are stacked. In each capacitor element, a cathode extraction layer covering at least a portion of the solid electrolyte layer includes a carbon layer and a conductive paste layer. The capacitor elements are connected in parallel by a conductive adhesive layer interposed between the cathode portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 142972 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration described in Patent Document 1, a conductive paste layer is provided on the entire surface of a carbon layer in each capacitor element, and a conductive adhesive layer is provided on a part of the conductive paste layer. Therefore, in the area where the capacitor elements are connected in the thickness direction, the layers are stacked in the following order: carbon layer / conductive paste layer / conductive adhesive layer / conductive adhesive layer / conductive paste layer / carbon layer. The conductive paste layer and the conductive adhesive layer are both conductive resin layers containing metal.

[0005] In the configuration described in Patent Document 1, four conductive resin layers exist between the carbon layers of two adjacent capacitor elements. However, since the conductive resin layer between the carbon layers of two adjacent capacitor elements is a layer that bonds the capacitor elements together, it is considered that one layer between the capacitor elements is sufficient from the standpoint of bonding between the capacitor elements. For this reason, the configuration of the solid electrolytic capacitor described in Patent Document 1 can be said to be unnecessarily thick due to the presence of many layers between the capacitor elements, and there is a problem in that it should be made even thinner.

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a solid electrolytic capacitor having a structure that allows for a low height. [Means for solving the problem]

[0007] The solid electrolytic capacitor of the present invention is a solid electrolytic capacitor comprising a laminate in which a plurality of capacitor elements are stacked, each of the capacitor elements comprising: a valve action metal base having a dielectric layer on at least one main surface; a separator provided on the dielectric layer to separate the valve action metal base into an anode portion and a cathode portion; a solid electrolyte layer provided on the dielectric layer in the cathode portion; a carbon layer provided on the solid electrolyte layer; and an adhesive Ag layer and a cathode Ag layer, both of which are provided on the carbon layer, wherein the adhesive Ag layer is disposed between the capacitor elements on the anode portion side of the cathode Ag layer, and the cathode Ag layer is disposed on the cathode portion side of the adhesive Ag layer, and the adhesive Ag layer and the cathode Ag layer have different compositions.

[0008] The method for producing a solid electrolytic capacitor of the present invention includes the steps of: preparing a valve metal substrate having a dielectric layer on at least one main surface thereof, a separator and a solid electrolyte layer provided on the dielectric layer, and further providing a carbon layer on the solid electrolyte layer; applying a cathode Ag layer composition to a part of the cathode portion side of the valve metal substrate having the carbon layer provided thereon to form a cathode Ag layer on the carbon layer; and applying an adhesive Ag layer composition to the valve metal substrate having the carbon layer provided on the anode portion side of the part where the cathode Ag layer is formed to form an adhesive Ag layer on the carbon layer, thereby producing a capacitor element; and bonding a plurality of the capacitor elements together via the adhesive Ag layer to obtain a laminate. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a solid electrolytic capacitor having a structure that allows for a low height. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of a capacitor element. [Figure 2] FIG. 2 is a perspective view schematically illustrating an example of a solid electrolytic capacitor. [Figure 3] FIG. 3 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 2 taken along line AA. [Figure 4] FIG. 4 is an enlarged view of the area where the adhesive Ag layer and the cathode Ag layer are in contact (the area indicated by area C in FIG. 3). [Figure 5] FIG. 5 is a cross-sectional view schematically showing another example of a capacitor element. [Figure 6] FIG. 6 is a perspective view schematically showing another example of a solid electrolytic capacitor. [Figure 7] FIG. 7 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 6 taken along line BB. [Figure 8] FIG. 8 is a schematic diagram showing an example of a step of preparing a valve metal substrate on which a separator, a solid electrolyte layer, and a carbon layer are formed. [Figure 9] FIG. 9 is a schematic diagram showing an example of a process for forming a cathode Ag layer. [Figure 10] FIG. 10 is a schematic diagram showing an example of a process for forming an adhesive Ag layer. DETAILED DESCRIPTION OF THE INVENTION

[0011] The solid electrolytic capacitor and the method for manufacturing the solid electrolytic capacitor of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual desirable configurations described below.

[0012] [Solid electrolytic capacitor] The solid electrolytic capacitor of the present invention is a solid electrolytic capacitor comprising a laminate in which a plurality of capacitor elements are stacked, each of the capacitor elements comprising: a valve action metal base having a dielectric layer on at least one main surface; a separator provided on the dielectric layer to separate the valve action metal base into an anode portion and a cathode portion; a solid electrolyte layer provided on the dielectric layer in the cathode portion; a carbon layer provided on the solid electrolyte layer; and an adhesive Ag layer and a cathode Ag layer, both of which are provided on the carbon layer, wherein the adhesive Ag layer is disposed between the capacitor elements on the anode portion side of the cathode Ag layer, and the cathode Ag layer is disposed on the cathode portion side of the adhesive Ag layer, and the adhesive Ag layer and the cathode Ag layer have different compositions.

[0013] The solid electrolytic capacitor of the present invention includes at least two types of Ag layers, which are conductive layers containing Ag: an adhesive Ag layer and a cathode Ag layer. Hereinafter, when simply referring to the Ag layer, the adhesive Ag layer and the cathode Ag layer are collectively referred to without distinction.

[0014] FIG. 1 is a cross-sectional view schematically showing an example of a capacitor element. FIG. 2 is a perspective view schematically showing an example of a solid electrolytic capacitor, and FIG. 3 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 2 taken along line AA.

[0015] The solid electrolytic capacitor of the present invention comprises a laminate in which a plurality of capacitor elements are stacked. First, the capacitor elements that make up the solid electrolytic capacitor of the present invention will be described. The capacitor element 1 shown in FIG. 1 includes a valve metal substrate 10 having a dielectric layer 20 on its surface, a separator 30 provided on the dielectric layer 20, a solid electrolyte layer 40 provided on the dielectric layer 20, a carbon layer 50 provided on the solid electrolyte layer 40, and an adhesive Ag layer 60 and a cathode Ag layer 70 provided on the carbon layer 50.

[0016] As shown in FIG. 1, a separation portion 30 having a predetermined width is provided on the periphery of the dielectric layer 20. The separation portions 30 are provided on both main surfaces and both side surfaces of the valve metal substrate 10 along the short sides of the valve metal substrate 10. The separation portions 30 separate the valve metal substrate 10 into an anode portion 31 and a cathode portion 32. In FIG. 1 , the region to the right of the separation portion 30 where the solid electrolyte layer 40, the carbon layer 50, and the Ag layer (the adhesive Ag layer 60 or the cathode Ag layer 70) are not formed is the anode portion 31, and the region to the left of the separation portion 30 where the solid electrolyte layer 40, the carbon layer 50, and the Ag layer (the adhesive Ag layer 60 or the cathode Ag layer 70) are formed is the cathode portion 32.

[0017] The solid electrolyte layer 40 is provided on the dielectric layer 20 of the cathode section 32. The solid electrolyte layer 40 may be provided so as to cover a portion of the outer surface of the separation section 30, or so as not to overlap the separation section 30 with its tip on the separation section 30 side, or so as to cover the entire outer surface of the separation section 30.

[0018] The shape of the valve metal substrate 10 as viewed from the normal direction of the main surface of the valve metal substrate 10, i.e., the shape of the valve metal substrate 10 as viewed in plan from the thickness direction, is quadrangular, and preferably rectangular having long and short sides. The main surface of the valve metal substrate 10 is preferably porous. By making the main surface of the valve metal substrate 10 porous, the surface area of ​​the valve metal substrate 10 is increased. Note that the valve metal substrate 10 is not limited to a case where both the front and back surfaces are porous, and only one of the front and back surfaces of the valve metal substrate 10 may be porous.

[0019] The valve metal substrate 10 is made of a valve metal such as an elemental metal such as aluminum, tantalum, niobium, titanium, or zirconium, or an alloy containing these metals. An oxide film can be formed on the surface of the valve metal.

[0020] The valve metal substrate 10 may be formed of a core and a porous portion provided on at least one of the main surfaces of the core, and may be formed from a metal foil having an etched surface, a metal foil having a porous sintered powder body formed on the surface, or the like.

[0021] The dielectric layer 20 is provided on at least one main surface of the valve metal substrate 10. The dielectric layer 20 is preferably formed of an oxide film provided on the surface of the valve metal. For example, the dielectric layer 20 is formed of an aluminum oxide. The aluminum oxide is formed by anodizing the surface of the valve metal substrate 10, as described below.

[0022] The separator 30 is provided on the dielectric layer 20 and is formed by applying a resin solution called a mask material, such as a composition containing an insulating resin. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, etc.), a composition consisting of soluble polyimidesiloxane and epoxy resin, polyimide resin, polyamideimide resin, and derivatives or precursors thereof. Instead of applying the above-described mask material, the separation portion 30 may be formed by coining. Coining involves pressing a portion of the porous portion provided on the main surface of the valve metal substrate 10 to crush the porous portion, thereby suppressing capillary action in the porous portion and allowing the pressed portion to function as the separation portion. Alternatively, the separation portion 30 may be formed by, for example, applying a resin tape. When using a resin tape, the resin tape may be removed after the manufacturing process requiring the separation portion 30 is completed. Alternatively, the resin tape may be left in place. In this case, the resin tape preferably has insulating properties as well as heat and cold resistance sufficient to withstand the temperatures experienced by the solid electrolytic capacitor. Furthermore, the separation portion 30 may be formed by combining the above-described methods.

[0023] The mask material can be applied by, for example, screen printing, roller transfer, dispenser, inkjet printing, or the like.

[0024] The solid electrolyte layer 40 is disposed on the dielectric layer 20 . Examples of materials that can be used to form the solid electrolyte layer 40 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 polymers may also contain dopants such as polystyrene sulfonate (PSS).

[0025] The solid electrolyte layer 40 is formed, for example, by a method of forming a polymerized film of a conductive polymer such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer 20 using a liquid containing a polymerizable monomer such as 3,4-ethylenedioxythiophene, or by a method of applying a dispersion liquid of a conductive polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric layer 20 and drying it.

[0026] A carbon layer 50 is provided on the solid electrolyte layer 40 . The carbon layer 50 is formed, for example, by applying a carbon paste to the surface of the solid electrolyte layer 40 and drying it.

[0027] The carbon paste can be applied by, for example, a dipping method, sponge transfer, screen printing, spray application, a dispenser, inkjet printing, or the like.

[0028] On the carbon layer 50, an adhesive Ag layer 60 and a cathode Ag layer 70 are provided. In the embodiment shown in FIG. 1, the carbon layer 50 is exposed in a region closer to the anode part 31 than the region where the adhesive Ag layer 60 is formed. If the carbon layer is exposed in this region, the electrical connection between the solid electrolyte layer 40 and the adhesive Ag layer 60 is improved via the carbon layer 50, and the ESR can be reduced.

[0029] The adhesive Ag layer and the cathode Ag layer will be described below. Both the adhesive Ag layer and the cathode Ag layer are conductive layers containing Ag, but their compositions are different. The difference in composition between the adhesive Ag layer and the cathode Ag layer can be identified by observing a boundary in the Ag layer on the carbon layer when observing the cross section of the capacitor element under an electron microscope. It can also be identified by the difference in element concentrations across the boundary when performing elemental analysis using SEM-EDX. Typically, the adhesive Ag layer has a high concentration of carbon (C) due to the large amount of binder, while the cathode Ag layer has a low concentration of carbon (C) due to the small amount of binder.

[0030] The adhesive Ag layer is disposed between the capacitor elements on the anode side of the cathode Ag layer, and serves to bond adjacent capacitor elements together. In order to bond adjacent capacitor elements together, it is preferable that the amount of binder contained in the adhesive Ag layer be greater than the amount of binder contained in the cathode Ag layer. The amount of binder contained in the adhesive Ag layer and the cathode Ag layer can be measured by determining the relative magnitude relationship of the amount of carbon in the adhesive Ag layer and the cathode Ag layer, regarding the amount of carbon (C) as the amount of binder in elemental analysis by SEM-EDX.

[0031] The cathode Ag layer is disposed closer to the cathode part than the adhesive Ag layer, plays a role in leading out the cathode part from the carbon layer, and is electrically connected to the cathode external electrode. In order to reduce the ESR (equivalent series resistance) of a solid electrolytic capacitor, it is preferable that the Ag layer has high conductivity (low specific resistance), and therefore it is preferable that the amount of binder contained in the cathode Ag layer is less than the amount of binder contained in the adhesive Ag layer.

[0032] In addition, from the viewpoint of reducing the ESR of the solid electrolytic capacitor, it is preferable that the resistivity of the cathode Ag layer be lower than the resistivity of the adhesive Ag layer. The resistivity of the adhesive Ag layer and the cathode Ag layer can be defined as a value measured by a four-terminal method using a milliohmmeter or the like on measurement samples each formed into a sheet from the adhesive Ag layer composition and the cathode Ag layer composition.

[0033] Both the adhesive Ag layer and the cathode Ag layer contain Ag, but may contain conductive particles other than Ag. Furthermore, the Ag particles contained in the adhesive Ag layer and the cathode Ag layer may have different particle sizes or shapes. For example, the Ag particles contained in the adhesive Ag layer may be spherical, and the Ag particles contained in the cathode Ag layer may be flat.

[0034] The thickness of the adhesive Ag layer and the thickness of the cathode Ag layer in the capacitor element may be the same or different. As shown in Figure 1, the thickness of the adhesive Ag layer may be greater than the thickness of the cathode Ag layer. The thickness of the adhesive Ag layer in the capacitor element is preferably, for example, 5 μm or more and 50 μm or less. The thickness of the cathode Ag layer in the capacitor element is preferably, for example, 3 μm or more and 30 μm or less.

[0035] A solid electrolytic capacitor of the present invention including the capacitor element described above will now be described. The solid electrolytic capacitor 100 shown in Figures 2 and 3 has a laminate in which multiple capacitor elements are stacked and sealed with a sealing material to form a sealed body 110, and is equipped with an anode-side lead frame 120 connected to the anode portions of the capacitor elements and a cathode-side lead frame 130 connected to the cathode portions of the capacitor elements.

[0036] As shown in FIG. 3, in solid electrolytic capacitor 100, adhesive Ag layers 60 are arranged between multiple capacitor elements 1 to bond the capacitor elements 1 together, forming a laminate 140 in which multiple capacitor elements 1 are stacked. The anode parts 31 of the capacitor elements 1 are gathered together by the anode side lead frame 120 and are drawn out to the outside of the sealing body 110 . The cathode parts 32 of the capacitor elements 1 are gathered together by the cathode side lead frame 130 and are drawn out to the outside of the sealing body 110 .

[0037] FIG. 4 is an enlarged view of the area where the adhesive Ag layer and the cathode Ag layer are in contact (the area indicated by area C in FIG. 3). The adhesive Ag layer 60 and the cathode Ag layer 70 are in contact with each other and have a boundary therebetween. The cathode Ag layer and the adhesive Ag layer may overlap in the thickness direction on the cathode part side of the adhesive Ag layer.

[0038] The thickness of the cathode Ag layer in a solid electrolytic capacitor is defined as the thickness of the cathode Ag layer provided on the carbon layer of each capacitor element, as indicated by the double-headed arrow t1 in Figure 4, and is preferably 3 μm or more and 30 μm or less. The thickness of the adhesive Ag layer in a solid electrolytic capacitor is defined as the thickness of the adhesive Ag layer at the contact point between the adhesive Ag layer and the cathode Ag layer. This thickness is indicated by the double-headed arrow t2 in Figure 4, and is preferably 5 μm or more and 50 μm or less. The thickness of the adhesive Ag layer is defined between capacitor elements where no lead frame is present between the capacitor elements. The thickness of the adhesive Ag layer is preferably thicker than the thickness of the cathode Ag layer. The thickness of the cathode Ag layer is measured as the thickness of the cathode Ag layer per capacitor element, and the thickness of the adhesive Ag layer is measured as the thickness of the adhesive Ag layer for two capacitor elements. The thickness of the adhesive Ag layer per capacitor element is also preferably thicker than the thickness of the cathode Ag layer. That is, it is preferable that "thickness of adhesive Ag layer in solid electrolytic capacitor×½>thickness of cathode Ag layer in solid electrolytic capacitor".

[0039] In the solid electrolytic capacitor of the present invention, the cathode Ag layer is not disposed on the anode side of the Ag layer on the carbon layer, and the capacitor elements are bonded together only by the adhesive Ag layer. This reduces the number of layers between the capacitor elements, resulting in a solid electrolytic capacitor with a structure that allows for a low profile. Furthermore, the amount of the cathode Ag layer is reduced, which allows for cost reduction. The area of ​​the region where the Ag layer is formed on the carbon layer affects the ESR; if the area of ​​this region is small, the ESR tends to be large. However, because the cathode Ag layer is formed in the cathode-side region on the carbon layer, the area of ​​the region where the Ag layer is formed on the carbon layer is the same as that of conventional solid electrolytic capacitors, and an increase in ESR is prevented. The cathode Ag layer and adhesive Ag layer have different compositions, but it is preferable to use an Ag layer with low resistivity as the cathode Ag layer. The more the cathode Ag layer is applied, the smaller the ESR becomes. However, depending on the material of the solid electrolyte layer, the effect on ESR is small even if the area of ​​the applied cathode Ag layer is small. In such cases, the technology of the present invention, in which the cathode Ag layer is not provided over the entire surface of the carbon layer, but rather there is a region on the carbon layer where only the adhesive Ag layer is provided, is particularly effective.

[0040] FIG. 5 is a cross-sectional view schematically showing another example of a capacitor element. In the capacitor element 2 shown in FIG. 5, the adhesive Ag layer 60 provided on the carbon layer 50 extends onto the separator 30. When a capacitor element of this type is used, the solid electrolyte layer 40 and the carbon layer 50 are formed up to the end of the separator 30, so the area of ​​the cathode portion is increased and the ESR of the solid electrolytic capacitor can be reduced. A solid electrolytic capacitor can be manufactured using such a capacitor element.

[0041] FIG. 6 is a perspective view schematically showing another example of a solid electrolytic capacitor, and FIG. 7 is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 6 taken along line BB. 6 has a substantially rectangular parallelepiped shape. The solid electrolytic capacitor 200 includes a sealing body 210, an anode external electrode 220, and a cathode external electrode 230. As shown in FIG. 7, adhesive Ag layers 60 are disposed between a plurality of capacitor elements 1 to bond the capacitor elements 1 together, forming a laminate 240 in which a plurality of capacitor elements 1 are stacked.

[0042] The anode external electrode 220 is provided on the first end surface 210e of the sealing body 210. In FIG. 6, the anode external electrode 220 is provided from the first end surface 210e of the sealing body 210 to each of the first main surface 210a, the second main surface 210b, the first side surface 210c, and the second side surface 210d. The anode external electrode 220 is electrically connected to the valve metal base 10 of the capacitor element 1 exposed from the sealing body 210. The anode external electrode 220 may be directly or indirectly connected to the valve metal base 10 at the first end surface 210e of the sealing body 210.

[0043] The cathode external electrode 230 is provided on the second end surface 210f of the sealing body 210. In FIG. 6, the cathode external electrode 230 is provided from the second end surface 210f of the sealing body 210 to each of the first main surface 210a, the second main surface 210b, the first side surface 210c, and the second side surface 210d. The cathode external electrode 230 is electrically connected to the cathode Ag layer 70 of the capacitor element 1 exposed from the sealing body 210. The cathode external electrode 230 may be directly or indirectly connected to the cathode Ag layer 70 at the second end surface 210f of the sealing body 210.

[0044] The anode external electrode 220 and the cathode external electrode 230 are each preferably formed by at least one method selected from the group consisting of a dip coating method, a screen printing method, a transfer method, an inkjet printing method, a dispense method, a spray coating method, a brush coating method, a drop casting method, an electrostatic coating method, a plating method, and a sputtering method.

[0045] The anode external electrode 220 preferably has a resin electrode layer containing a conductive component and a resin component. When the anode external electrode 220 contains a resin component, the adhesion between the anode external electrode 220 and the sealing resin of the sealing body 210 is improved, thereby improving reliability.

[0046] The cathode external electrode 230 preferably has a resin electrode layer containing a conductive component and a resin component. When the cathode external electrode 230 contains a resin component, the adhesion between the cathode external electrode 230 and the sealing resin of the sealing body 210 is improved, thereby improving reliability.

[0047] The conductive component preferably contains, as a main component, a metal such as silver, copper, nickel, or tin, or an alloy containing at least one of these metals.

[0048] The resin component preferably contains an epoxy resin, a phenolic resin, or the like as a main component.

[0049] The resin electrode layer is formed by, for example, a dip coating method, a screen printing method, a transfer method, an inkjet printing method, a dispensing method, a spray coating method, a brush coating method, a drop casting method, an electrostatic coating method, or the like. Among these, the resin electrode layer is preferably a printed resin electrode layer formed by applying a conductive paste by a screen printing method. When the resin electrode layer is formed by applying a conductive paste by a screen printing method, the anode external electrode 220 and the cathode external electrode 230 are more likely to be flat than when the resin electrode layer is formed by applying a conductive paste by a dip coating method. In other words, the thickness of the anode external electrode 220 and the cathode external electrode 230 is more likely to be uniform.

[0050] At least one of the anode external electrode 220 and the cathode external electrode 230 may have a so-called plating layer formed by a plating method. Examples of the plating layer include a zinc-silver-nickel layer, a silver-nickel layer, a nickel layer, a zinc-nickel-gold layer, a nickel-gold layer, a zinc-nickel-copper layer, and a nickel-copper layer. On these plating layers, for example, a copper plating layer, a nickel plating layer, and a tin plating layer are preferably provided in this order (or with some of the plating layers removed).

[0051] At least one of the anode external electrode 220 and the cathode external electrode 230 may have both a resin electrode layer and a plating layer. For example, the anode external electrode 220 may have a resin electrode layer connected to the valve metal substrate 10 and an outer plating layer provided on the surface of the resin electrode layer. Alternatively, the anode external electrode 220 may have an inner plating layer connected to the valve metal substrate 10, a resin electrode layer provided so as to cover the inner plating layer, and an outer plating layer provided on the surface of the resin electrode layer.

[0052] In the solid electrolytic capacitor shown in Figure 7, the cathode Ag layer is not placed on the anode side of the Ag layer on the carbon layer, and the capacitor elements are bonded together only by the adhesive Ag layer. This reduces the number of layers between the capacitor elements, resulting in a solid electrolytic capacitor with a structure that allows for a low profile.

[0053] [Solid electrolytic capacitor manufacturing method] The method for producing a solid electrolytic capacitor of the present invention includes the steps of: preparing a valve metal substrate having a dielectric layer on at least one main surface thereof, a separator and a solid electrolyte layer provided on the dielectric layer, and further providing a carbon layer on the solid electrolyte layer; applying a cathode Ag layer composition to a part of the cathode portion side of the valve metal substrate having the carbon layer provided thereon to form a cathode Ag layer on the carbon layer; and applying an adhesive Ag layer composition to the valve metal substrate having the carbon layer provided on the anode portion side of the part where the cathode Ag layer is formed to form an adhesive Ag layer on the carbon layer, thereby producing a capacitor element; and bonding a plurality of the capacitor elements together via the adhesive Ag layer to obtain a laminate.

[0054] First, the process for producing the capacitor element will be described. In the following example, a method for simultaneously manufacturing a plurality of capacitor elements using a large valve metal substrate will be described.

[0055] FIG. 8 is a schematic diagram showing an example of a step of preparing a valve metal substrate on which a separator, a solid electrolyte layer, and a carbon layer are formed.

[0056] 8 includes a plurality of element portions 11 and a support portion 12. Each element portion 11 has a rectangular shape and protrudes from the support portion 12. In addition, an isolation portion 30 is formed on the dielectric layer of each element portion 11. The solid electrolyte layer and the carbon layer are formed in a region closer to the cathode part of the element part 11 (lower side in FIG. 8) than the separator 30. The solid electrolyte layer and the carbon layer can be formed by a conventionally known method. FIG. 8 shows the carbon layer 50 formed in a region closer to the tip end of the element section 11 than the separation section 30.

[0057] FIG. 9 is a schematic diagram showing an example of a process for forming a cathode Ag layer. FIG. 9 shows a step of immersing the cathode portion side of the element portion 11 of the valve metal substrate 10A in a composition 310 for a cathode Ag layer. Approximately half the length of the element portion 11 is immersed in the composition for cathode Ag layer 310, whereby the composition for cathode Ag layer 310 is adhered to a part of the carbon layer 50 on the cathode portion side of the valve acting metal substrate 10A, and then the composition is pulled up and dried, thereby providing the cathode Ag layer 70. The composition for the cathode Ag layer is a paste containing Ag particles, a binder, a solvent, and the like. The thickness of the cathode Ag layer formed in this step is preferably 3 μm or more and 30 μm or less.

[0058] FIG. 10 is a schematic diagram showing an example of a process for forming an adhesive Ag layer. FIG. 10 shows a step of applying, by a dispenser 330, a composition 320 for an adhesive Ag layer onto the carbon layer 50 on the anode side of the portion where the cathode Ag layer 70 is formed. The dispenser 330 is moved from the end of the anode part side of the portion where the cathode Ag layer 70 is formed as the starting point, and is moved from there toward the anode part side (the right side in FIG. 10 ), thereby making it possible to form the adhesive Ag layer 60 in a portion where the cathode Ag layer 70 is not formed. It is also possible to prevent the cathode Ag layer 70 and the adhesive Ag layer 60 from overlapping in the thickness direction.

[0059] Although Figure 10 shows only one valve action metal substrate, the adhesive Ag layer composition may be applied to multiple valve action metal substrates connected by supports in the strip shape shown in Figure 8, or the adhesive Ag layer composition may be applied after the valve action metal substrate is cut into individual pieces. After the composition for an adhesive Ag layer is formed on one main surface of the valve metal substrate, the valve metal substrate is turned over and the composition for an adhesive Ag layer is formed on the other main surface of the valve metal substrate.

[0060] In the method for manufacturing a solid electrolytic capacitor of the present invention, Ag layers are formed in two separate steps in different regions on a carbon layer, thereby producing a capacitor element in which a cathode Ag layer is provided on the cathode side and an adhesive Ag layer is provided on the anode side. A solid electrolytic capacitor can then be manufactured by further performing a step of bonding a plurality of capacitor elements together via an adhesive Ag layer to obtain a laminate.

[0061] After obtaining the laminate, a sealing body can be produced using a sealing material, and external electrodes can be formed. When producing a solid electrolytic capacitor having a lead frame as shown in Figures 2 and 3, the capacitor elements can be laminated with the lead frame sandwiched between them when producing the laminate.

[0062] In the method for producing a solid electrolytic capacitor of the present invention, the composition for the cathode Ag layer and the composition for the adhesive Ag layer preferably have different compositions. The binder concentration in the composition for the adhesive Ag layer is preferably higher than the binder concentration in the composition for the cathode Ag layer. The Ag concentration in the composition for the cathode Ag layer is preferably higher than the Ag concentration in the composition for the adhesive Ag layer.

[0063] The binder concentration in the composition for a cathode Ag layer is preferably 3% by weight or more and 15% by weight or less, and the Ag concentration in the composition for a cathode Ag layer is preferably 40% by weight or more and 90% by weight or less.

[0064] The binder concentration in the composition for the adhesive Ag layer is preferably 10% by weight or more and 40% by weight or less, and the Ag concentration in the composition for the adhesive Ag layer is preferably 60% by weight or more and 90% by weight or less.

[0065] Furthermore, it is preferable that the resistivity of the composition for the cathode Ag layer is lower than the resistivity of the composition for the adhesive Ag layer. The resistivity of the cathode Ag layer composition and the adhesive Ag layer composition can be defined as a value measured by a four-terminal method using a milliohmmeter or the like on measurement samples each formed into a sheet from the cathode Ag layer composition and the adhesive Ag layer composition. The resistivity of the cathode Ag layer composition is 1×10 -5 Ω cm or more, 1×10 -4 It is preferable that the resistivity of the adhesive Ag layer composition is 1×10 -4 Ω cm or more, 1×10 -3 It is preferable that the resistivity is Ω·cm or less.

[0066] The viscosities of the cathode Ag layer composition and the adhesive Ag layer composition are not particularly limited. From the viewpoint of facilitating the formation of a cathode Ag layer by immersion, the viscosity of the cathode Ag layer composition is preferably 50 mPa s or more and 5000 mPa s or less. In addition, from the viewpoint of facilitating the formation of an adhesive Ag layer using a dispenser, the viscosity of the composition for an adhesive Ag layer is preferably 3000 mPa·s or more and 30000 mPa·s or less.

[0067] The present specification discloses the following:

[0068] The present disclosure (1) is a solid electrolytic capacitor including a laminate in which a plurality of capacitor elements are stacked, the capacitor elements including: a valve action metal substrate having a dielectric layer on at least one main surface; a separator provided on the dielectric layer to separate the valve action metal substrate into an anode portion and a cathode portion; a solid electrolyte layer provided on the dielectric layer in the cathode portion; a carbon layer provided on the solid electrolyte layer; and an adhesive Ag layer and a cathode Ag layer, both of which are provided on the carbon layer, wherein the adhesive Ag layer is disposed between the capacitor elements on the anode portion side of the cathode Ag layer, and the cathode Ag layer is disposed on the cathode portion side of the adhesive Ag layer, and the adhesive Ag layer and the cathode Ag layer have different compositions.

[0069] The present disclosure (2) is the solid electrolytic capacitor according to the present disclosure (1), wherein the amount of binder contained in the adhesive Ag layer is greater than the amount of binder contained in the cathode Ag layer.

[0070] The present disclosure (3) is the solid electrolytic capacitor according to the present disclosure (1) or (2), in which the cathode Ag layer has a lower resistivity than the adhesive Ag layer.

[0071] The present disclosure (4) is the solid electrolytic capacitor according to any one of the present disclosures (1) to (3), in which the carbon layer is exposed in a region closer to the anode part than the region where the adhesive Ag layer is formed.

[0072] The present disclosure (5) is the solid electrolytic capacitor according to any one of the present disclosures (1) to (3), wherein the adhesive Ag layer provided on the carbon layer extends onto the separating portion.

[0073] The present disclosure (6) is a method for producing a solid electrolytic capacitor, comprising the steps of: preparing a valve action metal substrate having a dielectric layer on at least one main surface thereof, a separator and a solid electrolyte layer provided on the dielectric layer, and further providing a carbon layer on the solid electrolyte layer; applying a cathode Ag layer composition to a part of the cathode portion side of the valve action metal substrate provided with the carbon layer to form a cathode Ag layer on the carbon layer; and applying an adhesive Ag layer composition to the valve action metal substrate provided with the carbon layer on the anode portion side of the part where the cathode Ag layer is formed to form an adhesive Ag layer on the carbon layer to form a capacitor element; and bonding a plurality of the capacitor elements together via the adhesive Ag layer to obtain a laminate.

[0074] The present disclosure (7) is the method for producing a solid electrolytic capacitor according to the present disclosure (6), wherein in the step of forming the cathode Ag layer on the carbon layer, a part of the valve metal base provided with the carbon layer, including an end portion on the cathode side, is immersed in the composition for cathode Ag layer.

[0075] The present disclosure (8) is the method for producing a solid electrolytic capacitor according to the present disclosure (6) or (7), wherein in the step of forming the adhesive Ag layer on the carbon layer, the adhesive Ag layer composition is applied by a dispenser onto the carbon layer on the anode side of the portion where the cathode Ag layer is formed.

[0076] The present disclosure (9) is the method for producing a solid electrolytic capacitor according to any one of the present disclosures (6) to (8), wherein the composition for the cathode Ag layer and the composition for the adhesive Ag layer have different compositions. [Explanation of symbols]

[0077] 1, 2 Capacitor element 10, 10A Valve action metal substrate 11 Element section 12 Support part 20 dielectric layer 30 Separation part 31 Anode part 32 Cathode 40 Solid electrolyte layer 50 carbon layers 60 Adhesive Ag layer 70 Cathode Ag layer 100, 200 solid electrolytic capacitor 110, 210 Sealing body 120 Anode side lead frame 130 Cathode side lead frame 140, 240 laminate 210a First principal surface 210b 2nd principal surface 210c 1st side 210d 2nd side 210e 1st end face 210f 2nd end face 220 Anode external electrode 230 Cathode external electrode 310 Composition for cathode Ag layer 320 Composition for adhesive Ag layer 330 Dispenser

Claims

1. A solid electrolytic capacitor including a laminate in which a plurality of capacitor elements are stacked, The capacitor element includes a valve metal substrate having a dielectric layer on at least one of its main surfaces; a separator provided on the dielectric layer and separating the valve metal substrate into an anode portion and a cathode portion; a solid electrolyte layer provided on the dielectric layer of the cathode portion; a carbon layer provided on the solid electrolyte layer; an adhesive Ag layer and a cathode Ag layer, both of which are provided on the carbon layer; the adhesive Ag layer is disposed between the capacitor elements on the anode portion side of the cathode Ag layer, the cathode Ag layer is disposed closer to the cathode portion than the adhesive Ag layer, The adhesive Ag layer and the cathode Ag layer have different compositions.

2. 2. The solid electrolytic capacitor according to claim 1, wherein the amount of binder contained in the adhesive Ag layer is greater than the amount of binder contained in the cathode Ag layer.

3. 3. The solid electrolytic capacitor according to claim 1, wherein the cathode Ag layer has a resistivity lower than that of the adhesive Ag layer.

4. 3. The solid electrolytic capacitor according to claim 1, wherein the carbon layer is exposed in a region closer to the anode portion than the region where the adhesive Ag layer is formed.

5. 3. The solid electrolytic capacitor according to claim 1, wherein the adhesive Ag layer provided on the carbon layer extends onto the separating portion.

6. a step of preparing a valve metal substrate having a dielectric layer on at least one main surface thereof, a separator and a solid electrolyte layer provided on the dielectric layer, and a carbon layer provided on the solid electrolyte layer; a step of applying a cathode Ag layer composition to a part of the cathode portion side of the valve metal substrate having the carbon layer provided thereon to form a cathode Ag layer on the carbon layer; and a step of applying an adhesive Ag layer composition to a part of the valve metal substrate having the carbon layer provided thereon that is closer to the anode portion than the part where the cathode Ag layer is formed to form an adhesive Ag layer on the carbon layer, thereby forming a capacitor element; and a step of bonding a plurality of the capacitor elements together via the adhesive Ag layer to obtain a laminate.

7. 7. The method for manufacturing a solid electrolytic capacitor according to claim 6, wherein in the step of forming the cathode Ag layer on the carbon layer, a part of the valve acting metal base, including an end portion on a cathode portion side, on which the carbon layer is provided, is immersed in the composition for cathode Ag layer.

8. 8. The method for manufacturing a solid electrolytic capacitor according to claim 6, wherein in the step of forming the adhesive Ag layer on the carbon layer, the adhesive Ag layer composition is applied with a dispenser onto the carbon layer on the anode portion side of the portion where the cathode Ag layer is formed.

9. The method for producing a solid electrolytic capacitor according to claim 6 or 7, wherein the composition for the cathode Ag layer and the composition for the adhesive Ag layer have different compositions.

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