Solid electrolytic capacitor

A solid electrolytic capacitor that includes a capacitor element laminate, a first external electrode, and a second external electrode. The capacitor element laminate includes capacitor elements, cathode lead-out layers, and a sealing body. At least one capacitor element includes an anode foil, dielectric layers, and cathode layers. The first external electrode is connected to the anode foil exposed at the first end surface of the capacitor element laminate. The second external electrode is connected to the cathode lead-out layers exposed at the second end surface of the capacitor element laminate. A first cathode lead-out layer and a second cathode lead-out layer are both conductive paste layers, and uniformly extend from where the first cathode lead-out layer and the second cathode lead-out layer are disposed on the cathode layers to the second external electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application No. 2019-054614, filed Mar. 22, 2019, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a solid electrolytic capacitor.

BACKGROUND OF THE INVENTION

Patent Literature 1 (WO 2018/074408) discloses a solid electrolytic capacitor including a stack of multiple units each including a valve-action metal substrate having a porous layer on a surface, a dielectric layer on a surface of the porous layer, and a solid electrolyte layer on the dielectric layer, wherein a conductor layer is disposed between the units, at least one conductor layer includes metal foil, the units and the conductor layers are enclosed in an exterior resin, an end surface on an anode side of the valve-action metal substrate is directly connected to an anode external electrode on a surface of the exterior resin at one end surface of the solid electrolytic capacitor, and the metal foil is directly connected to a cathode external electrode on a surface of the exterior resin at the other end surface of the solid electrolytic capacitor.

SUMMARY OF INVENTION

The solid electrolytic capacitor disclosed in Patent Literature 1 uses metal foil as the cathode lead-out layers. The metal foil does not have a capacitor function, so that the effective volume of the capacity as a whole is small. Also, the production of the solid electrolytic capacitor disclosed in Patent Literature 1 requires processing metal foil, which tends to complicate the production process.

The present invention is made to solve the above problems, and aims to provide a highly reliable solid electrolytic capacitor having a structure with low resistance, which can be produced at low cost.

The solid electrolytic capacitor of the present invention includes a capacitor element laminate, a first external electrode at a first end surface of the capacitor element laminate, and a second external electrode at a second end surface of the capacitor element laminate. The capacitor element laminate includes capacitor elements, cathode lead-out layers, and a sealing body enclosing the capacitor elements and the cathode lead-out layers. At least one of the capacitor elements includes an anode foil made of a valve-action metal, dielectric layers on opposed surfaces of the anode foil, and cathode layers including a solid electrolyte layer on surfaces of each of the dielectric layers. The cathode layers are connected to respective cathode lead-out layers. The first external electrode is connected to the anode foil exposed at the first end surface of the capacitor element laminate. The second external electrode is connected to the respective cathode lead-out layers exposed at the second end surface of the capacitor element laminate. The respective cathode lead-out layers include a first cathode lead-out layer on an upper surface of the capacitor element and a second cathode lead-out layer on a lower surface of the capacitor element. The first cathode lead-out layer and the second cathode lead-out layer are both conductive paste layers, and uniformly extend from where the first cathode lead-out layer and the second cathode lead-out layer are disposed on the cathode layers to the second external electrode. The first cathode lead-out layer and the second cathode lead-out layer exposed at the second end surface of the capacitor element laminate are insulated from the anode foil.

The present invention provides a highly reliable solid electrolytic capacitor having a structure with low resistance, which can be produced at low cost.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The solid electrolytic capacitor of the present invention is described below.

The present invention is not limited to the following preferred embodiments, and may be suitably modified without departing from the gist of the present invention. Combinations of two or more preferred features described in the following preferred features are also within the scope of the present invention.

In the solid electrolytic capacitor of the present invention, the cathode lead-out layers include a first cathode lead-out layer on an upper surface of the capacitor element and a second cathode lead-out layer on a lower surface of the capacitor element; the first cathode lead-out layer and the second cathode lead-out layer are both conductive paste layers, and uniformly extend to the second external electrode; and the first cathode lead-out layer and the second cathode lead-out layer exposed at the second end surface of the capacitor element laminate are insulated from the anode foil.

In the solid electrolytic capacitor of the present invention, since the cathode lead-out layers are conductive paste layers, use of metal foil as the cathode lead-out layers is no longer required. Thus, the solid electrolytic capacitor can be produced at low cost. Since the metal foil is not required, there are fewer interfaces between different materials of a conductive path leading to the second external electrode. Thus, the resulting structure has low resistance.

Further, since the first cathode lead-out layer is disposed on the upper surface of the capacitor element and the second cathode lead-out layer is disposed on the lower surface of the capacitor element, influence of environmental exposure can be blocked. Thus, the solid electrolytic capacitor has higher reliability.

The following embodiments are examples, and features of different embodiments can be partially exchanged or combined with each other. In the second embodiment and subsequent embodiments, a description of features common to the first embodiment is omitted, and only different points are described. In particular, similar effects by similar features are not mentioned in each embodiment.

First Embodiment

In the solid electrolytic capacitor according to the first embodiment of the present invention, metal foil exposed at the second end surface of the capacitor element laminate is disposed in a space where the capacitor element is not present between the first cathode lead-out layer and the second cathode lead-out layer. The metal foil is a portion separated from the anode foil by a slit, and is completely insulated from the anode foil.

In the solid electrolytic capacitor according to the first embodiment of the present invention, the metal foil separated from the anode foil is used directly as a support portion of the cathode lead-out layers. Thus, there is no difference in the linear expansion coefficient, and structural strain or cracking that may occur when the solid electrolytic capacitor is heated can be prevented or reduced.

FIG. 1is a schematic perspective view of an example of a solid electrolytic capacitor according to a first embodiment of the present invention.

A solid electrolytic capacitor1shown inFIG. 1includes a capacitor element laminate100, a first external electrode141, and a second external electrode142.

InFIG. 1, the length direction of the solid electrolytic capacitor1or the capacitor element laminate100is indicated by L, the width direction thereof is indicated by W, and the thickness direction thereof is indicated by T. Here, the length direction L, the width direction W, and the thickness direction T are perpendicular to each other. A plane along the length direction L and the thickness direction T of the solid electrolytic capacitor1or the capacitor element laminate100is referred to as an LT plane; a plane along the length direction L and the width direction W thereof is referred to as an LW plane; and a plane along the width direction W and the thickness direction T thereof is referred to as a WT plane.

The outer shape of the capacitor element laminate100is a rectangular parallelepiped. The capacitor element laminate100includes a first end surface E1and a second end surface E2opposite to each other in the length direction L, a first lateral surface S1and a second lateral surface S2opposite to each other in the width direction W, and a first main surface M1and a second main surface M2opposite to each other in the thickness direction T. The first end surface E1and the second end surface E2are WT planes, the first lateral surface S1and the second lateral surface S2are LT planes, and the first main surface M1and the second main surface M2are LW planes. In the present embodiment, the second main surface M2is a bottom of the capacitor element laminate100, and is a side that defines a mounting surface of the solid electrolytic capacitor1.

In the capacitor element laminate100, corners and edges may be rounded. The corner is a portion where three surfaces of the capacitor element laminate100meet, and the edge is a portion where two surfaces of the capacitor element laminate100meet.

The first external electrode141is provided at the first end surface E1of the capacitor element laminate100. In the present embodiment, the first external electrode141extends to a portion of the first main surface M1, a portion of the second main surface M2, a portion of the first lateral surface S1, and a portion of the second lateral surface S2of the capacitor element laminate100. The first external electrode141may not extend to a portion of the first main surface M1of the capacitor element laminate100. For example, the first external electrode141provided at the first end surface E1may extend to a portion of the second main surface M2.

The second external electrode142is provided at the second end surface E2of the capacitor element laminate100. In the present embodiment, the second external electrode142extends to a portion of the first main surface M1, a portion of the second main surface M2, a portion of the first lateral surface S1, and a portion of the second lateral surface S2of the capacitor element laminate100. The second external electrode142may not extend to a portion of the first main surface M1of the capacitor element laminate100. For example, the second external electrode142provided at the second end surface E2may extend to a portion of the second main surface M2.

FIG. 2is a cross-sectional view taken along the line II-II of the solid electrolytic capacitor shown inFIG. 1.FIG. 2is an LT cross-sectional view of the solid electrolytic capacitor1.FIG. 3is an exploded perspective view of a capacitor element laminate defining the solid electrolytic capacitor shown inFIG. 1.

As shown inFIG. 2andFIG. 3, the capacitor element laminate100includes capacitor elements110, cathode lead-out layers120, and a sealing body130. InFIG. 2andFIG. 3, the capacitor elements110and the cathode lead-out layers120are stacked in the thickness direction T. The sealing body130encloses the capacitor elements110and the cathode lead-out layers120.

Each capacitor element110includes an anode foil11, a dielectric layer12, and a cathode layer13. The cathode layers13of the capacitor element110are connected to the respective cathode lead-out layers120.

The anode foil11includes a core portion and a porous portion on a surface of the core portion. The anode foil11includes the dielectric layer12on a surface of the porous portion. Preferably, the anode foil11includes a porous portion on both surfaces of the core portion.

The anode foil11is made of a valve-action metal that functions as a valve. Examples of the valve-action metal include elemental metals such as aluminum, tantalum, niobium, titanium, zirconium, and alloys containing at least one of these metals. Of these, aluminum and an aluminum alloy are preferred.

The porous portion of the anode foil11may be an etched layer formed on a surface of the anode foil11, or a porous layer printed and sintered on the surface of the anode foil11. When the valve-action metal is aluminum or an aluminum alloy, an etched layer can be formed on the surface by etching with hydrochloric acid or the like.

The thickness of the anode foil11before etching is preferably 60 μm to 200 μm. The thickness of the non-etched core portion after etching is preferably 15 μm to 70 μm. The thickness of the porous portion is designed according to the withstand voltage and capacitance required. Yet, the total thickness of the porous portions on both sides of the core portion is preferably 10 μm to 180 μm.

The dielectric layer12is provided on the surface of the porous portion of the anode foil11. The dielectric layer12is formed along the surface of the porous portion, and thus includes pores (recesses).

The dielectric layer12is preferably made of an oxide film of the valve-action metal. For example, when an aluminum foil is used as the anode foil11, the surface of the aluminum foil is anodized (chemically treated) in an aqueous solution containing ammonium adipate or the like, whereby the dielectric layer12made of an oxide film can be formed.

The thickness of the dielectric layer12is designed according to the withstand voltage and capacitance required, but it is preferably 10 nm to 100 nm.

The cathode layer13is provided on the surface of the dielectric layer12. The cathode layer13includes a solid electrolyte layer13aon the surface of the dielectric layer12. Preferably, the cathode layer13further includes a carbon layer13bon a surface of the solid electrolyte layer13a.

Examples of materials of the solid electrolyte layer13ainclude conductive polymers such as polypyrroles, polythiophenes, and polyanilines. Of these, polythiophenes are preferred, and poly(3,4-ethylenedioxythiophene) (PEDOT) is particularly preferred. Examples of the conductive polymers may also include dopants such as poly(styrene sulfonate) (PSS).

The solid electrolyte layer13ais formed by, for example, a method in which a treatment solution containing a monomer such as 3,4-ethylenedioxythiophene is used to form a polymerized film of poly(3,4-ethylenedioxythiophene) or the like on the surface of the dielectric layer12, or a method in which a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) is applied to the surface of the dielectric layer12and drying the dispersion. Preferably, the solid electrolyte layer13ais formed by first forming an inner layer filling the pores (recesses) in the dielectric layer12and then forming an external layer covering the dielectric layer12.

The solid electrolyte layer13acan be formed in a predetermined region by applying the treatment solution or dispersion to the dielectric layer12by, for example, sponge transfer, screen printing, inkjet printing, or using a dispenser. The thickness of the solid electrolyte layer13ais preferably 2 μm to 20 μm.

The carbon layer13bis provided to electrically and mechanically interconnect the solid electrolyte layer13aand the cathode lead-out layer120.

The carbon layer13bcan be formed in a predetermined region by applying a carbon paste to the solid electrolyte layer13aby, for example, sponge transfer, screen printing, inkjet printing, or using a dispenser. Preferably, the cathode lead-out layers120in the subsequent step are stacked while the carbon layer13bis viscous before drying. The thickness of the carbon layer13bis preferably 2 μm to 20 μm.

The cathode lead-out layers120include a first cathode lead-out layer21on an upper surface of the capacitor element110, and a second cathode lead-out layer22on a lower surface of the capacitor element110. The first cathode lead-out layer21and the second cathode lead-out layer22are separately disposed in one capacitor element110, and are not connected to each other. At an outermost surface in the thickness direction T (i.e., an outermost surface parallel to the LW plane), the first cathode lead-out layer21or the second cathode lead-out layer22faces the sealing body130.

The first cathode lead-out layer21and the second cathode lead-out layer22are both conductive paste layers.

Each conductive paste layer can be formed in a predetermined region by applying a conductive paste to the cathode layer13by, for example, sponge transfer, screen printing, inkjet printing, or using a dispenser. The conductive paste is preferably one mainly containing silver, copper, or nickel. In the case of screen printing, a conductive paste layer having a thickness of 2 μm to 20 μm can be made.

Herein, the conductive paste layers encompass not only layers formed by curing or drying a conductive paste but also layers formed by sintering a conductive paste. Thus, the conductive paste layers also encompass, for example, an electrode layer formed from a metal nanoparticle paste such as a silver nanoparticle paste.

The first cathode lead-out layer21and the second cathode lead-out layer22both uniformly extend from where the first cathode lead-out layer21and the second cathode lead-out layer22are disposed on the cathode layers13to the second external electrode142. The first cathode lead-out layer21and the second cathode lead-out layer22exposed at the second end surface E2of the capacitor element laminate100are insulated from the anode foil11.

In the first embodiment of the present invention, a metal foil51exposed at the second end surface E2of the capacitor element laminate100is provided in a space where the capacitor elements110is not present between the first cathode lead-out layer21and the second cathode lead-out layer22.

The metal foil51is a portion separated from the anode foil11by a slit SL described later (seeFIG. 7), and is completely insulated from the anode foil11. The metal foil51is electrically insulated from the anode foil11, but these are originally the same layer. Thus, the metal foil51includes the dielectric layer12on the surface.

Preferably, an insulating portion52filling the slit SL is provided between the metal foil51and the anode foil11. An insulating material of the insulating portion52includes at least a resin, preferably a resin and a filler. Examples of the resin include epoxy resins and phenol resins. Examples of the filler include silica particles, alumina particles, and metal particles.

The width of the insulating portion52(the length indicated by W52inFIG. 2) is, for example, 30 μm to 150 μm.

In an example shown inFIG. 2, insulating layers60are provided between the first cathode lead-out layer21and the metal foil51and between the second cathode lead-out layer22and the metal foil51. The insulating layers60are also provided between the capacitor elements110. Each insulating layer60may include a single layer or multiple layers. For example, each insulating layer60includes a mask layer61described later (seeFIG. 8) and an insulating adhesive layer62on a surface of the mask layer61(seeFIG. 12). The insulating layers60may not be provided at the portions described above, or resin molded bodies instead of the insulating layers60may be provided at the portions described above.

The mask layer61is formed by, for example, applying a masking material made of an insulating material such as an insulating resin to the surface of the anode foil11and solidifying or curing the masking material by heat or the like. The masking material is preferably applied by, for example, screen printing, inkjet printing, or using a dispenser.

Examples of the insulating material of the masking material include insulating resins such as polyphenylsulfone resin, polyethersulfone resin, cyanate ester resin, fluorine resins (e.g., tetrafluoroethylene and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), compositions containing a soluble polyimide siloxane and an epoxy resin, polyimide resin, polyamideimide resin, and derivatives or precursors thereof.

The insulating adhesive layer62is formed by, for example, applying an insulating material such as an insulating resin to the mask layer61and solidifying or curing the masking material by heat or the like. The insulating material is preferably applied by, for example, screen printing, inkjet printing, or using a dispenser.

Components and the viscosity of the insulating adhesive layer62may be the same as those of the mask layer61, but are preferably different from those of the mask layer61.

In the first embodiment of the present invention, the insulating portion52may extend to at least one of an upper surface or a lower surface of the anode foil11. In this case, another insulating layer may be provided between the anode foil11and the insulating portion52extending to the upper surface or the lower surface of the anode foil11.

Similarly, the insulating portion52may extend to at least one of an upper surface or a lower surface of the metal foil51. In this case, another insulating layer may be provided between the metal foil51and the insulating portion52extending to the upper surface or the lower surface of the metal foil51.

An insulating layer is provided between the anode foil and the cathode lead-out layer (conductive paste layer) or between the metal foil and the cathode lead-out layer, whereby the difference in the linear expansion coefficient between the cathode lead-out layer and the anode foil or the metal foil can be adjusted.

FIG. 4is a schematic cross-sectional view of an example of another insulating portion.

In an example shown inFIG. 4, the insulating portion52extends to the upper surface and the lower surface of the anode foil11. The mask layer61as another insulating layer is provided between the anode foil11and the insulating portion52extending to the upper surface and the lower surface of the anode foil11. Similarly, the insulating portion52extends to the upper surface and the lower surface of the metal foil51. The mask layer61is provided between the metal foil51and the insulating portion52extending to the upper surface and the lower surface of the metal foil51.

The capacitor elements110and the cathode lead-out layers120are enclosed in the sealing body130. In examples shown inFIG. 2andFIG. 3, the sealing body130includes a resin molded body31and a support board32.

An insulating material of the resin molded body31includes at least a resin, preferably a resin and a filler. Examples of the resin include epoxy resins and phenol resins. Examples of the filler include silica particles, alumina particles, and metal particles.

The resin molded body31can be formed by a method that uses a resin mold such as a compression mold or a transfer mold. For example, a compression mold is used to enclose a stack of the capacitor elements110and the cathode lead-out layers120.

The support board32is provided on the bottom to integrate the stack of the capacitor elements110and the cathode lead-out layers120. The support board32is preferably a glass epoxy board. The sealing body130may not include the support board32. In such a case, the sealing body130may include a resin molded body also on the bottom.

The first external electrode141is connected to the anode foil11exposed at the first end surface E1of the capacitor element laminate100.

The second external electrode142is connected to the cathode lead-out layers120exposed at the second end surface E2of the capacitor element laminate100.

The first external electrode141and the second external electrode142can be formed by, for example, plating, sputtering, immersion coating, or printing. In the case of plating, a plating layer may be, for example, a Zn·Ag·Ni layer, a Ag·Ni layer, a Ni layer, a Zn·Ni·Au layer, a Ni·Au layer, a Zn·Ni·Cu layer, or a Ni·Cu layer. Preferably, additional plating layers including a Cu plating layer, a Ni plating layer, and a Sn plating layer in the stated order (or without one or some of these layers) are formed on the above plating layers.

Second Embodiment

In a solid electrolytic capacitor according to the second embodiment of the present invention, an insulating layer fills a space where the capacitor element is not present between the first cathode lead-out layer and the second cathode lead-out layer.

In the solid electrolytic capacitor according to the second embodiment of the present invention, the insulating layer and the resin molded body may be formed of different insulating materials, or may be formed of the same insulating material.

When the insulating layer and the resin molded body are made of different insulating materials, the insulating layer can be imparted with a function that improves reliability (e.g., low moisture permeability or stress relaxing ability) by appropriately selecting an insulating material to make the insulating layer.

In contrast, when the insulating layer and the resin molded body are made of the same insulating material, there is no difference in the linear expansion coefficient between the insulating layer and the resin molded body because the insulating material is the same, and structural strain or cracking that may occur when the solid electrolytic capacitor is heated can be prevented or reduced.

FIG. 5is a schematic cross-sectional view of an example of a solid electrolytic capacitor according to a second embodiment of the present invention.

A solid electrolytic capacitor2shown inFIG. 5includes a capacitor element laminate100A, the first external electrode141, and the second external electrode142. The structures of the first external electrode141and the second external electrode142are as described in the first embodiment.

The capacitor element laminate100A includes the capacitor elements110, the cathode lead-out layers120, and the sealing body130. The structures of each capacitor element110, each cathode lead-out layer120, and the sealing body130are as described for the first embodiment.

In the second embodiment of the present invention, an insulating layer53fills a space where the capacitor elements110is not present between the first cathode lead-out layer21and the second cathode lead-out layer22.

An insulating material of the insulating layer53includes at least a resin, preferably a resin and a filler. Examples of the resin include epoxy resins and phenol resins. Examples of the filler include silica particles, alumina particles, and metal particles.

In the second embodiment of the present invention, the insulating layer53and the resin molded body31may be formed of different insulating materials, or may be formed of the same insulating material.

In an example shown inFIG. 5, other insulating layers60are provided between the first cathode lead-out layer21and the insulating layer53. The insulating layers60are also provided between the capacitor elements110. Each insulating layer60may include a single layer or multiple layers. For example, each insulating layer60includes the mask layer61and the insulating adhesive layer62on the surface of the mask layer61. The insulating layers60may not be provided.

In the second embodiment of the present invention, the insulating layer53may extend to at least one of the upper surface or the lower surface of the anode foil11. In this case, another insulating layer may be provided between the anode foil11and the insulating portion53extending to the upper surface or the lower surface of the anode foil11.

Method of Producing Solid Electrolytic Capacitor

The following describes an example of a method of producing the solid electrolytic capacitor of the present invention. Each step of the method is described. In the following example, a method of simultaneously producing multiple solid electrolytic capacitors by using a large electrode sheet is described.

(A) Preparing Electrode Sheet

In step (A), an electrode sheet including a dielectric layer on a surface is prepared.

FIG. 6is a schematic perspective view of an example of the electrode sheet.

An electrode sheet10shown inFIG. 6is made of the anode foil11including the dielectric layer12on a surface.

The electrode sheet10is preferably produced as follows.

First, the anode foil11including a core portion and a porous portion on a surface of the core portion is prepared, and the dielectric layer12is formed on a surface of the porous portion.

In order to improve the production efficiency, a chemically treated foil that has been subjected to chemical treatment may be used as the anode foil11having the dielectric layer12on the surface.

(B) Forming Slits in Electrode Sheet

In step (B), slits are formed in the electrode sheet to separate a metal foil that defines cathode exposed portions from the anode foil.

FIG. 7is a schematic perspective view of an example of the electrode sheet including the slits.

FIG. 7shows multiple capacitor element regions R10in the electrode sheet10. The capacitor element regions R10are regions divided by first end portions E11and second end portions E12which are opposite to each other in the length direction L, and first lateral portions S11and second lateral portions S12which are opposite to each other in the width direction W. Each capacitor element region R10shares the first end portion E11or the second end portion E12with its adjacent capacitor element region R10in the length direction L. Each capacitor element region R10shares the first lateral portion S11or the second lateral portion S12with its adjacent capacitor element region R10in the width direction W.

As shown inFIG. 7, the slit SL is formed in each capacitor element region R10of the electrode sheet10. The slits SL are formed near the second end portions E12and are parallel to the second end portions E12. The width of each slit SL (dimension in the L direction) is, for example, 30 μm to 150 μm. The length of each slit SL (dimension in the W direction) is smaller than its dimension in the W direction of the capacitor element region R10.

(C) Forming Mask Layer

In step (C), a mask layer is formed to cover the end portions and lateral portions of each capacitor element region in the electrode sheet. Step (C) is an optional step.

FIG. 8is a schematic perspective view of an example of the electrode sheet including a mask layer.

In the electrode sheet10shown inFIG. 8, the first end portion E11, the second end portion E12, the first lateral portion S11, and the second lateral portion S12of each capacitor element region R10are covered with the mask layer61. InFIG. 8, some portions of the second end portion E12, the first lateral portion S11, and the second lateral portion S12are not covered with the mask layer61, but the mask layer61may be formed on these portions. The mask layer61may be formed on inner walls of the slits SL.

In step (D), insulating portions are formed by filling the slits with an insulating material.

FIG. 9is a schematic perspective view of an example of the electrode sheet including the insulating portions.

InFIG. 9, the insulating portions52filling the slits SL are formed. The insulating portions52may be formed not only in the slits SL but may also be formed to extend on at least one of an upper surface or a lower surface of the electrode sheet10. In this case, the insulating portions52may be connected to each other on the upper surface or the lower surface of the electrode sheet10.

In step (E), a cathode layer is formed on a surface of each dielectric layer of the electrode sheet. In step (E), preferably, a solid electrolyte layer is first formed on the surface of each dielectric layer of the electrode sheet, and a carbon layer is then formed on a surface of each solid electrolyte layer.

FIG. 10is a schematic perspective view of an example of the electrode sheet including the solid electrolyte layers.

InFIG. 10, each solid electrolyte layer13ais formed in the region surrounded by the mask layer61.

FIG. 11is a schematic perspective view of an example of the electrode sheet including the carbon layers.

InFIG. 11, the carbon layer13bis formed on a surface of each solid electrolyte layer13a. The solid electrolyte layer13aand the carbon layer13btogether form the cathode layer13(seeFIG. 2).

(F) Forming Insulating Adhesive Layers

In step (F), an insulating adhesive layer is formed. In the case where step (C) is performed, an insulating adhesive layer is formed on a surface of the mask layer. In the case where step (C) is not performed, an insulating adhesive layer is formed to cover the end portions and lateral portions of each capacitor element region in the electrode sheet. Step (F) is an optional step.

FIG. 12is a schematic perspective view of an example of the electrode sheet including the insulating adhesive layers.

InFIG. 12, the insulating adhesive layer62is formed on the surface of each mask layer61. The mask layer61and the insulating adhesive layer62together form the insulating layer60(seeFIG. 2).

The order of step (C), step (D), step (E), and step (F) is not limited.

The total thickness of the mask layer61and the insulating adhesive layer62may be the same as the thickness of the cathode layer13, but is preferably greater than the thickness of the cathode layer13.

In step (G), the cathode lead-out layers are formed by using a conductive paste. Specifically, the first cathode lead-out layer is formed on a surface of the cathode layer on the upper surface of the anode foil, and the second cathode lead-out layer is formed on a surface of the cathode layer on the lower surface of the anode foil.

FIG. 13is a schematic perspective view of an example of the electrode sheet including cathode lead-out layers.

InFIG. 13, on the upper surface of the anode foil11, each first cathode lead-out layer21is formed to bridge the carbon layers13bacross the second end portion E12of each capacitor element region R10. Although not shown, similarly on the lower surface of the anode foil11, each second cathode lead-out layer22is formed to bridge the carbon layers13bacross the second end portion E12of each capacitor element region R10. The cathode lead-out layers120(seeFIG. 2) are thus formed.

(H) Stacking Electrode Sheets and Enclosing

In step (H), the electrode sheets including the cathode lead-out layers are stacked to produce an electrode sheet laminate which is then enclosed, whereby a multilayer block body is produced.

When stacking the electrode sheets, preferably, another electrode sheet is provided on one electrode sheet while the cathode lead-out layer is viscous and wet. In other words, preferably, the electrode sheets are stacked together after the cathode lead-out layers are formed by using a conductive paste, prior to drying the conductive paste.

When stacking the electrode sheets, the electrode sheets may be stacked on a support board such as a glass epoxy board.

The electrode sheet laminate can be enclosed by using the resin mold such as a compression mold described above.

A sealing material of the resin mold includes at least a resin, preferably a resin and a filler. Examples of the resin include epoxy resins and phenol resins. Examples of the filler include silica particles, alumina particles, and metal particles.

FIG. 14is a schematic perspective view of an example of the multilayer block body.

In a multilayer block body200shown inFIG. 14, the multiple electrode sheets10stacked on a support board132are covered with a sealing material131.

(I) Cutting Multilayer Block Body to Produce Multiple Capacitor Element Laminates

In step (I), the multilayer block body is cut to produce multiple capacitor element laminates.

The following describes an example of a method of producing multiple capacitor element laminates.

First, a multilayer block body is cut along a first lateral portion and a second lateral portion of each capacitor element region. The multilayer block body can be cut by, for example, dicing with a dicer.

FIG. 15is a schematic perspective view of an example of the multilayer block body after cutting.

InFIG. 15, the multilayer block body200shown inFIG. 14is cut along the first lateral portion and the second lateral portion of each capacitor element region to produce a multilayer block body210including gaps G along the first lateral portion and the second lateral portion.

Next, gaps in the multilayer block body are filled with a sealing material. The gaps can be filled with a sealing material by using the resin mold such as a compression mold described above. The sealing material can be, for example, a sealing material used to produce the multilayer block body.

FIG. 16is a schematic perspective view of an example of the multilayer block body in which gaps are filled with a sealing material.

InFIG. 16, gaps G in the multilayer block body210shown inFIG. 15are filled with a sealing material133, whereby a multilayer block body220is produced.

Subsequently, the multilayer block body220is cut along the first end portion and the second end portion of each capacitor element region, and is also cut along the first lateral portion and the second lateral portion of each capacitor element region. Thereby, the individual capacitor element laminate100shown inFIG. 3can be obtained. The multilayer block body220is cut by, for example, dicing with a dicer, cutting using a cutting blade, laser cutting, or scribing.

FIG. 17is a schematic perspective view of an example of the capacitor element laminate cut into individual pieces.

InFIG. 17, the multilayer block body220shown inFIG. 16is cut to produce multiple capacitor element laminates100.

The multilayer block body220is cut at a portion between the slits SL during cutting along the second end portion of each capacitor element region, whereby the capacitor element laminate100shown inFIG. 2can be produced. The multilayer block body220may be cut on the slits SL, whereby the capacitor element laminate100A shown inFIG. 5can be produced.

(J) Forming External Electrodes

A first external electrode is formed at a first end surface of the capacitor element laminate, and a second external electrode is formed at a second end surface of the capacitor element laminate. A solid electrolytic capacitor is thus produced.

The solid electrolytic capacitor of the present invention is not limited to the above embodiments, and various modifications and changes can be made to the structure of the solid electrolytic capacitor, production conditions, and the like within the scope of the present invention.

The methods of producing the multilayer block body, cutting the multilayer block body, and forming the external electrodes to produce the solid electrolytic capacitor of the present invention are not limited. Any methods other than those described above may be used.

REFERENCE SIGNS LIST