JP7632657B2 - Solid electrolytic capacitor and method for manufacturing the same - Google Patents

Description

The present invention relates to a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor.

Patent Document 1 discloses a solid electrolytic capacitor element that has a masking portion (mask layer) for insulating the anode and cathode portions and preventing the solid electrolyte from creeping up, and in which the thickness of the solid electrolyte layer at the periphery of the valve action metal porous substrate is greater than the thickness of the solid electrolyte layer at the center of the valve action metal porous substrate.

WO 01/75917

In solid electrolytic capacitor elements, the solid electrolyte layer tends to become thin near the mask layer and is also easily subjected to stress, which causes the conductive layer on the solid electrolyte layer to come into contact with the dielectric layer in this vicinity, making it easy for leakage current to occur due to tunneling current. This can result in a deterioration in voltage resistance and reflow resistance. Note that reflow resistance refers to the resistance of the finished solid electrolytic capacitor to stress during reflow.

In contrast, as described in Patent Document 1, it is expected that a thicker solid electrolyte layer around the periphery of the substrate will lead to a reduction in leakage current.

However, Patent Document 1 does not provide any specific explanation as to how to provide a conductive layer such as a conductive paste on the solid electrolyte layer. For example, if a conductive layer is formed so as to fill the depression in the center of the solid electrolyte layer, the entire solid electrolytic capacitor element will become thicker, and since there is no space for the conductive adhesive that connects the solid electrolytic capacitor elements to each other, the volumetric efficiency of the assembled solid electrolytic capacitor will deteriorate.

The present invention has been made to solve the above problems, and aims to provide a thin solid electrolytic capacitor. Furthermore, the present invention aims to provide a manufacturing method for a solid electrolytic capacitor that can realize a thin solid electrolytic capacitor.

The solid electrolytic capacitor of the present invention is a solid electrolytic capacitor comprising a laminate in which a plurality of solid electrolytic capacitor elements are laminated via a conductive adhesive, each of the solid electrolytic capacitor elements comprising an anode made of a valve action metal substrate and having a tip end surface and a base end surface, a dielectric layer provided on at least one of the main surfaces of the anode excluding at least the base end surface, a mask layer made of an insulating material and provided on the dielectric layer along the base end surface, and a cathode provided on the dielectric layer on the tip end surface side of the mask layer, the cathode having a solid electrolyte layer provided on the dielectric layer, a conductive layer provided on the solid electrolyte layer, and a convex portion along the mask layer, the thickness of the cathode in the remainder excluding the convex portion does not exceed the maximum thickness of the cathode in the convex portion, and the conductive adhesive is provided in the area sandwiched between the remainders of the cathodes of adjacent solid electrolytic capacitor elements.

The method for manufacturing a solid electrolytic capacitor element of the present invention includes a first step of immersing the anode having the mask layer formed on the dielectric layer in a treatment liquid containing a solid electrolyte from the tip surface side until it contacts the mask layer, a second step of pulling the anode out of the treatment liquid and drying the treatment liquid, a third step of immersing the anode from the tip surface side after drying the treatment liquid in a conductive paste, and a fourth step of pulling the anode out of the conductive paste and drying the conductive paste, and in at least one of the second step and the fourth step, the anode is dried in a state upside down from when it was immersed.

According to the present invention, a thin solid electrolytic capacitor can be provided. Furthermore, according to the present invention, a manufacturing method of a solid electrolytic capacitor that can realize a thin solid electrolytic capacitor can be provided.

FIG. 1 is a perspective view illustrating an example of a solid electrolytic capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line ZZ of the solid electrolytic capacitor shown in FIG. FIG. 3 is a plan view illustrating an example of a solid electrolytic capacitor element included in the solid electrolytic capacitor illustrated in FIG. FIG. 4 is a cross-sectional view taken along line XX of the solid electrolytic capacitor element shown in FIG. FIG. 5 is a cross-sectional view taken along line YY of the solid electrolytic capacitor element shown in FIG. FIG. 6 is an enlarged cross-sectional view of the base end portion of the solid electrolytic capacitor element shown in FIG. FIG. 7 is an enlarged cross-sectional view of the mask layer portion of the solid electrolytic capacitor element shown in FIG. FIG. 8 is a cross-sectional view illustrating an example of a solid electrolytic capacitor according to another embodiment of the present invention. FIG. 9 is a plan view illustrating an example of a solid electrolytic capacitor element included in the solid electrolytic capacitor shown in FIG. FIG. 10 is a cross-sectional view taken along line XX of the solid electrolytic capacitor element shown in FIG. FIG. 11 is a cross-sectional view taken along line YY of the solid electrolytic capacitor element shown in FIG. FIG. 12 is a schematic diagram showing an example of a step of immersing the anode on which the mask layer has been formed in a treatment liquid or conductive paste containing a solid electrolyte. FIG. 13 is a schematic diagram showing an example of a process of pulling the anode out of the treatment liquid and drying the treatment liquid or the conductive paste. FIG. 14 is a plan view that illustrates an example of a solid electrolytic capacitor element after the solid electrolyte layer or the conductive layer is formed through the drying step illustrated in FIG. FIG. 15 is a schematic diagram showing an example of a step of preparing a valve metal substrate on which a mask layer is formed. FIG. 16 is a schematic diagram showing an example of a process for forming a solid electrolyte layer or a cathode layer.

The solid electrolytic capacitor and the method for producing 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 modified and applied as appropriate 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.

Furthermore, each of the embodiments shown below is merely an example, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Repetition of descriptions of matters common to multiple embodiments will be omitted, and only the differences will be described.

[Solid electrolytic capacitor]
Fig. 1 is a perspective view showing an example of a solid electrolytic capacitor according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along line ZZ of the solid electrolytic capacitor shown in Fig. 1.

1 and 2, the length direction of the solid electrolytic capacitor 100 and the outer casing 110 is indicated by L, the width direction by W, and the height direction by T. Here, the length direction L, the width direction W, and the height direction T are perpendicular to each other.

1 and 2, the solid electrolytic capacitor 100 has a substantially rectangular parallelepiped outer shape. The solid electrolytic capacitor 100 comprises a laminate in which multiple solid electrolytic capacitor elements 1 are stacked with conductive adhesive 140 interposed therebetween. The solid electrolytic capacitor 100 further comprises an outer casing 110, a first external electrode 120, a second external electrode 130, and multiple solid electrolytic capacitor elements 1.

The exterior body 110 encapsulates multiple solid electrolytic capacitor elements 1. In other words, multiple solid electrolytic capacitor elements 1 are embedded in the exterior body 110.

The exterior body 110 has a generally rectangular parallelepiped shape. The exterior body 110 has a first main surface 110a and a second main surface 110b that face each other in the height direction T, a first side surface 110c and a second side surface 110d that face each other in the width direction W, and a first end surface 110e and a second end surface 110f that face each other in the length direction L.

As described above, the exterior body 110 has a substantially rectangular parallelepiped outer shape, but it is preferable that the corners and ridges are rounded. The corners are the parts where three faces of the exterior body 110 intersect, and the ridges are the parts where two faces of the exterior body 110 intersect.

The exterior body 110 is made, for example, of sealing resin.

The sealing resin contains at least resin, and preferably contains resin and filler.

Preferred resins include epoxy resins, phenolic resins, polyimide resins, silicone resins, polyamide resins, liquid crystal polymers, etc.

Silica particles, alumina particles, etc. are preferably used as fillers.

As a sealing resin, a material containing solid epoxy resin, phenolic resin and silica particles is preferably used.

When a solid sealing resin is used, a resin mold such as a compression mold or a transfer mold is preferably used, and a compression mold is more preferably used. When a liquid sealing resin is used, a molding method such as a dispensing method or a printing method is preferably used. In particular, it is preferable to form the exterior body 110 by sealing the periphery of the solid electrolytic capacitor element 1 with the sealing resin by compression molding.

The exterior body 110 may be composed of a substrate and a sealing resin provided on the substrate. The substrate is, for example, an insulating resin substrate such as a glass epoxy substrate. In this case, the bottom surface of the substrate constitutes the second main surface 110b of the exterior body 110. The thickness of the substrate is, for example, 100 μm.

The multiple solid electrolytic capacitor elements 1 are stacked in the height direction T via a conductive adhesive 140. The extension direction of each of the multiple solid electrolytic capacitor elements 1 is approximately parallel to the first main surface 110a and the second main surface 110b of the outer casing 110. The solid electrolytic capacitor elements 1 are bonded to each other via the conductive adhesive 140.

The conductive adhesive 140 contains, for example, metal particles such as gold, silver, copper, platinum, or the like, and resin, but here, silver is used as the metal particles and acrylic resin is used as the resin.
Other examples of the resin contained in the conductive adhesive 140 include urethane resin, epoxy resin, polyimide resin, and phenol resin.

Each solid electrolytic capacitor element 1 includes an anode 10 made of a valve metal substrate 11, a dielectric layer 20, a mask layer 30, and a cathode 40, and the cathode 40 includes a solid electrolyte layer 50 and a conductive layer 60. The structure of each solid electrolytic capacitor element 1 will be described later.

The first external electrode 120 is provided on the first end surface 110e of the exterior body 110. In FIG. 1, the first external electrode 120 is provided from the first end surface 110e of the exterior body 110 to each of the first main surface 110a, the second main surface 110b, the first side surface 110c, and the second side surface 110d. The first external electrode 120 is electrically connected to the conductive layer 60 of the cathode 40 of the solid electrolytic capacitor element 1 exposed from the exterior body 110 at the first end surface 110e. The first external electrode 120 may be directly or indirectly connected to the conductive layer 60 at the first end surface 110e of the exterior body 110.

The second external electrode 130 is provided on the second end surface 110f of the exterior body 110. In FIG. 1, the second external electrode 130 is provided from the second end surface 110f of the exterior body 110 to each of the first main surface 110a, the second main surface 110b, the first side surface 110c, and the second side surface 110d. The second external electrode 130 is electrically connected to the anode 10 (valve metal base 11) of the solid electrolytic capacitor element 1 exposed from the exterior body 110 at the second end surface 110f. The second external electrode 130 may be directly or indirectly connected to the anode 10 (valve metal base 11) at the second end surface 110f of the exterior body 110.

It is preferable that the first external electrode 120 and the second external electrode 130 are each 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 dispensing method, a spray coating method, a brush coating method, a drop casting method, an electrostatic coating method, a plating method, and a sputtering method.

The first external electrode 120 preferably has a resin electrode layer containing a conductive component and a resin component. When the first external electrode 120 contains a resin component, the adhesion between the first external electrode 120 and the sealing resin of the outer casing 110 is improved, thereby improving reliability.

The second external electrode 130 preferably has a resin electrode layer containing a conductive component and a resin component. When the second external electrode 130 contains a resin component, the adhesion between the second external electrode 130 and the sealing resin of the outer casing 110 is improved, thereby improving reliability.

It is preferable that the conductive component contains as its main component a metal such as silver, copper, nickel, or tin, or an alloy containing at least one of these metals.

It is preferable that the resin component contains epoxy resin, phenolic resin, etc. as the main component.

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 them, 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 first external electrode 120 and the second external electrode 130 are more likely to be flat than when the resin electrode layer is formed by applying a conductive paste by a dip coating method. That is, the thickness of the first external electrode 120 and the second external electrode 130 is more likely to be uniform.

When the first external electrode 120 has a resin electrode layer, the first external electrode 120 and the cathode conductor layer both contain resin components, thereby improving adhesion between the first external electrode 120 and the cathode conductor layer, thereby improving reliability.

At least one of the first external electrode 120 and the second external electrode 130 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, it is preferable that, for example, a copper plating layer, a nickel plating layer, and a tin plating layer are provided in this order (or with the exception of some plating layers).

At least one of the first external electrode 120 and the second external electrode 130 may have both a resin electrode layer and a plating layer. For example, the second external electrode 130 may have a resin electrode layer connected to the anode 10 (valve metal base 11) and an outer plating layer provided on the surface of the resin electrode layer. The second external electrode 130 may also have an inner plating layer connected to the anode 10 (valve metal base 11), a resin electrode layer provided to cover the inner plating layer, and an outer plating layer provided on the surface of the resin electrode layer.

[Solid electrolytic capacitor element]
Next, each solid electrolytic capacitor element 1 will be described in detail.
In this specification, when describing the configurations present on each of the main surfaces 10c and 10d of the anode 10, when they are to be described separately, the same reference numbers will be appended with "a" or "b" to distinguish them, and when they are to be described without distinction, the "a" and "b" will be omitted and only the same reference numbers will be appended.

Figure 3 is a plan view showing a schematic example of a solid electrolytic capacitor element provided in the solid electrolytic capacitor shown in Figure 1. Figure 4 is a cross-sectional view taken along line X-X of the solid electrolytic capacitor element shown in Figure 3. Figure 5 is a cross-sectional view taken along line Y-Y of the solid electrolytic capacitor element shown in Figure 3. Figure 6 is an enlarged cross-sectional view of the base end portion of the solid electrolytic capacitor element shown in Figure 4.

The solid electrolytic capacitor element 1 shown in Figures 3, 4, 5 and 6 comprises an anode 10 made of a valve metal substrate 11 and having a tip end surface 10a and a base end surface 10b, a dielectric layer 20 provided on the surface of the anode 10 except for the base end surface 10b, a mask layer 30 made of an insulating material and provided on the dielectric layer 20 along the base end surface 10b, and a cathode 40 provided on the dielectric layer 20 on the tip end surface 10a side of the mask layer 30, and the cathode 40 has a solid electrolyte layer 50 provided on the dielectric layer 20 and a conductive layer 60 provided on the solid electrolyte layer 50.

Then, on the side of one main surface 10c of the anode 10, the cathode 40 has a convex portion 41a along the mask layer 30, and the thickness of the cathode 40 (the solid electrolyte layer 50 and the conductive layer 60) in a remaining portion 42a excluding the convex portion 41a does not exceed a maximum thickness t1 (see FIG. 6 ) of the cathode 40 (the solid electrolyte layer 50 and the conductive layer 60) at the convex portion 41a.
Similarly, on the other main surface 10d side of the anode 10, the cathode 40 has a convex portion 41b along the mask layer 30, and the thickness of the cathode 40 (the solid electrolyte layer 50 and the conductive layer 60) in the remaining portion 42b excluding the convex portion 41b does not exceed the maximum thickness t2 (see FIG. 6 ) of the cathode 40 (the solid electrolyte layer 50 and the conductive layer 60) at the convex portion 41b.
This makes it possible to secure space for placing conductive adhesive 140 on the remaining portions 42a and 42b adjacent to the convex portions 41a and 41b, and also makes it possible to reduce the thickness of the solid electrolytic capacitor elements 1 in the remaining portions 42a and 42b, thereby improving the volumetric efficiency of the solid electrolytic capacitor 100 in which the solid electrolytic capacitor elements 1 are stacked, and making it possible to realize a thin solid electrolytic capacitor 100.
Furthermore, the protrusions 41a and 41b can prevent the conductive adhesive 140 from flowing to the mask layer 30 side and coming into contact with the dielectric layer 20, thereby preventing leakage current.

Thus, in solid electrolytic capacitor 100, conductive adhesive 140 is provided in a region sandwiched between remaining portions 42 of cathodes 40 of adjacent solid electrolytic capacitor elements 1 as shown in FIG.
In order to more effectively prevent leakage current, it is preferable that the conductive adhesive 140 does not cover the thickest portions 43 of the cathodes 40 of adjacent solid electrolytic capacitor elements 1, and it is preferable that the conductive adhesive 140 is not provided over the entire area sandwiched between the convex portions 41 of the cathodes 40 of adjacent solid electrolytic capacitor elements 1.

In this specification, the term "protruding portion" includes the protruding portion on the surface and the base portion overlapping the protruding portion.
Moreover, "the thickness of the cathode in the remainder" refers to the maximum thickness of the remainder of the cathode.

Furthermore, since the thickness of the solid electrolytic capacitor element 1 in the remaining portions 42a and 42b does not exceed the thickness Tmax of the solid electrolytic capacitor element 1 at the thickest portions 43a and 43b of the convex portions 41a and 41b, the overall thickness of the solid electrolytic capacitor element 1 can be similarly more effectively reduced.
The thickest parts 43a and 43b are the parts where the thickness of the protrusions 41a and 41b is the greatest, respectively.

Furthermore, the cathode 40 has, on the one main surface 10c side of the anode 10, an outer peripheral portion 45a including the protrusion 41a, and a central portion 46a surrounded by the outer peripheral portion 45a, and the thickness of the cathode 40 at the outer peripheral portion 45a is greater than the thickness of the cathode 40 at the central portion 46a (see FIGS. 3 to 5).
Similarly, the cathode 40 has, on the other main surface 10d side of the anode 10, an outer peripheral portion 45b including a convex portion 41b, and a central portion 46b surrounded by the outer peripheral portion 45b, and the thickness of the cathode 40 at the outer peripheral portion 45b is greater than the thickness of the cathode 40 at the central portion 46b.
A conductive adhesive 140 is then applied over the central portions 46a, 46b.
This makes it possible to prevent the conductive adhesive 140 from spilling out from above the cathode 40 .

Each component of the solid electrolytic capacitor element 1 is described in detail below.

The anode 10 is a thin film (foil) of a quadrangular shape in plan view composed of a valve metal substrate 11, and is preferably rectangular (strip-like) in plan view having a pair of long sides and a pair of short sides. The tip end surface 10a and the base end surface 10b are end surfaces located on a pair of sides (preferably a pair of short sides) of the anode 10, and the base end surface 10b is an exposed end surface that is not covered by the dielectric layer 20 and is exposed at one end surface of the solid electrolytic capacitor and connected to an external electrode described later. The anode 10 has a tip end surface 10a, a base end surface 10b, main surfaces 10c and 10d, and side surfaces 10e and 10f.

In this specification, "planar view" means viewed from the normal direction of the main surface of the anode (valve metal substrate).

Figure 7 is an enlarged cross-sectional view of the mask layer portion of the solid electrolytic capacitor element shown in Figure 4.

As shown in FIG. 7, each main surface of the valve metal substrate 11 (anode 10) has a plurality of recesses. Therefore, each main surface of the valve metal substrate 11 is porous. This increases the surface area of the valve metal substrate 11. Note that the present invention is not limited to the case where both main surfaces of the valve metal substrate 11 are porous, and only one of the main surfaces of the valve metal substrate 11 may be porous.

The valve metal substrate 11 is composed of a valve metal, such as a metal element such as aluminum, tantalum, niobium, titanium, zirconium, or an alloy containing these metals. An oxide film can be formed on the surface of the valve metal.

The valve metal base 11 need only be composed 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.

Here, the dielectric layer 20 is provided on the surface of the anode 10 except for the base end surface 10b. That is, the dielectric layer 20 is provided on the tip surface 10a, the main surfaces 10c and 10d, and the side surfaces 10e and 10f of the anode 10, but is not provided on the base end surface 10b of the anode 10.
However, it is sufficient that the dielectric layer 20 is provided on at least one of the main surfaces 10c and 10d of the anode 10, excluding at least the base end surface 10b.

The dielectric layer 20 is preferably composed of an oxide film provided on the surface of the valve metal substrate 11. For example, the dielectric layer 20 is composed of an oxide of aluminum. The oxide of aluminum is formed by anodizing the surface of the valve metal substrate 11, as described below.

The mask layer 30 is a linear (strand-like) insulating member provided on the dielectric layer 20 along the base end surface 10b of the anode 10, preferably along the short side of the anode 10, and separates the anode 10 from the cathode 40 to ensure insulation between them. The mask layer 30 divides the anode 10 into an area on the base end surface 10b side and an area on the tip end surface 10a side. Here, the mask layer 30 is disposed at a predetermined distance from the base end surface 10b, but may be disposed up to the edge of the base end surface 10b. The mask layer 30 is provided on the main surfaces 10c and 10d and the side surfaces 10e and 10f of the anode 10 via the dielectric layer 20, but it is sufficient that the mask layer 30 is provided on at least one of the main surfaces 10c and 10d of the anode 10 (however, the main surface on which the dielectric layer 20 is provided).

As shown in Fig. 7, the mask layer 30 is preferably provided so as to fill a plurality of pores (recesses) in the valve metal substrate 11. However, it is sufficient that the mask layer 30 covers a portion of the outer surface of the dielectric layer 20, and there may be pores (recesses) in the valve metal substrate 11 that are not filled by the mask layer 30.

The mask layer 30 is made of an insulating material. The mask layer 30 is formed by applying 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.

The masking material can be applied by, for example, screen printing, roller transfer, dispenser, inkjet printing, etc.

The cathode 40 has a solid electrolyte layer 50 provided on the dielectric layer 20 and a conductive layer 60 provided on the solid electrolyte layer 50. The cathode 40 is provided on the dielectric layer 20 on the tip surface 10a side of the mask layer 30. That is, the cathode 40 is provided on the dielectric layer 20 in the region on the tip surface 10a side of the anode 10 partitioned by the mask layer 30.

The cathode 40 has, on one main surface 10c side of the anode 10, a convex portion 41a along the mask layer 30 and a remaining portion 42a excluding the convex portion 41a, and, on the other main surface 10d side of the anode 10, a convex portion 41b along the mask layer 30 and a remaining portion 42b excluding the convex portion 41b.

The protrusions 41 are thick film portions in which the cathode 40 is partially thickened, and are formed linearly (in a band shape) parallel to the mask layer 30. That is, the protrusions 41 are linear protruding stripes.
Here, as shown in FIG. 6, the convex portion 41 has an arc-shaped surface when viewed in cross section in a direction perpendicular to the mask layer 30, but may have a trapezoidal or triangular surface.

4, when viewed in cross section in a direction perpendicular to the mask layer 30, the cathode 40 has a shape that is approximately linearly symmetrical with respect to the anode 10. That is, the protruding portions 41a and 41b have approximately the same shape, the remaining portions 42a and 42b have approximately the same shape, and the thickest portions 43a and 43b are located at approximately the same location on the anode 10.

On the main surface 10c side of the anode 10, the thickness of the cathode 40 in the remainder 42a does not exceed the maximum thickness t1 of the cathode 40 in the protruding portion 41a, and on the main surface 10d side of the anode 10, the thickness of the cathode 40 in the remainder 42b does not exceed the maximum thickness t2 of the cathode 40 in the protruding portion 41b. That is, the thickness of the cathode 40 in the remainder 42a is smaller than or approximately the same as the maximum thickness t1 of the cathode 40 in the protruding portion 41a, and the thickness of the cathode 40 in the remainder 42b is smaller than or approximately the same as the maximum thickness t2 of the cathode 40 in the protruding portion 41b.

More specifically, the difference between the maximum thickness t1 of the cathode 40 at the convex portion 41 a and the thickness of the cathode 40 at the remaining portion 42 a, particularly the central portion 46 a, is, for example, preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, and even more preferably 15 μm or more and 40 μm or less.
The same applies to the difference between the maximum thickness t2 of the cathode 40 in the protruding portion 41b and the thickness of the cathode 40 in the remaining portion 42b, particularly in the central portion 46b.
The "thickness of the cathode" refers to the thickness in the normal direction of one of the main surfaces of the anode.

In addition, the cathode 40 has, on one main surface 10c side of the anode 10, an outer peripheral portion 45a including a protrusion 41a and a central portion 46a surrounded by the outer peripheral portion 45a, and, on the other main surface 10d side of the anode 10, an outer peripheral portion 45b including a protrusion 41b and a central portion 46b surrounded by the outer peripheral portion 45b.

Each of the outer peripheral portions 45a, 45b includes a convex portion 41a, 41b along the mask layer 30, and a U-shaped portion 47a, 47b that is a substantially U-shaped portion along the tip surface 10a and the side surfaces 10e, 10f of the anode 10. The thickness of the convex portion 41a, 41b may be substantially the same as the thickness of the U-shaped portion 47a, 47b, respectively, or may be greater than the thickness of the U-shaped portion 47a, 47b. Each of the U-shaped portions 47a, 47b has a cross-sectional shape similar to that of the convex portion 41a, 41b, respectively, and has an arc-shaped surface when viewed in a cross section perpendicular to the extension direction, but may also have a trapezoidal or triangular surface.

The base end 44 of the cathode 40 is located on the outer main surface of the mask layer 30 (the main surface opposite to the anode 10). The cathode 40 may be provided so as to cover a part of the outer main surface of the mask layer 30 as shown in FIG. 6, or may be provided so as to cover the entire outer main surface of the mask layer 30. The cathode 40 may also be arranged in contact with the mask layer 30 so as not to cover the entire outer main surface of the mask layer 30.

The solid electrolyte layer 50 is provided on the dielectric layer 20. As shown in Fig. 7, the solid electrolyte layer 50 is preferably provided so as to fill a plurality of pores (recesses) of the valve metal substrate 11. However, it is sufficient that a portion of the outer surface of the dielectric layer 20 is covered with the solid electrolyte layer 50, and there may be pores (recesses) of the valve metal substrate 11 that are not filled with the solid electrolyte layer 50.

The solid electrolyte layer 50 is provided on the dielectric layer 20 on the tip surface 10a side of the mask layer 30. That is, the solid electrolyte layer 50 is provided on the dielectric layer 20 in the area on the tip surface 10a side of the anode 10 partitioned by the mask layer 30.

The solid electrolyte layer 50 has a thickness that gradually decreases from near the tip surface 10a of the anode 10 toward the mask layer 30 on each of the main surfaces 10c, 10d of the anode 10.

Materials constituting the solid electrolyte layer 50 include, for example, conductive polymers such as polypyrroles, polythiophenes, and polyanilines. Of 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).

The solid electrolyte layer 50 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 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.

It is preferable to form an outer layer that covers the entire dielectric layer 20 after forming an inner layer that fills the pores (recesses) of the valve metal substrate 11. The inner layer can be formed by, for example, a dipping method, sponge transfer, screen printing, a dispenser, inkjet printing, etc. Similarly, the outer layer can be formed by, for example, a dipping method, sponge transfer, screen printing, a dispenser, inkjet printing, etc.

The conductive layer 60 is provided on the solid electrolyte layer 50.

The conductive layer 60 is thicker at the outer periphery than at the central portion on each of the main surfaces 10c, 10d of the anode 10, thereby forming the convex portion 41, remaining portion 42, outer periphery portion 45, central portion 46, etc., on the cathode 40 as described above.

The conductive layer 60 includes, for example, a carbon layer or a cathode conductor layer. The conductive layer 60 may also be a composite layer in which a cathode conductor layer is provided on the outer surface of a carbon layer, or a mixed layer including carbon and a cathode conductor layer material.

The carbon layer is formed, for example, by applying a carbon paste containing carbon particles and resin to the surface of the solid electrolyte layer 50 and drying it.

Carbon paste can be applied by, for example, immersion method, sponge transfer, screen printing, spray application, dispenser, inkjet printing, etc.

The cathode conductor layer is formed, for example, by applying a conductive paste containing metal particles such as gold, silver, copper, platinum, etc. and a resin to the surface of the solid electrolyte layer or the carbon layer and drying it. The cathode conductor layer is preferably a silver layer.

The conductive paste can be applied by, for example, dipping, sponge transfer, screen printing, spray application, dispenser, inkjet printing, etc.

The thickness of the solid electrolytic capacitor element 1 in the remaining portions 42a and 42b does not exceed the thickness Tmax of the solid electrolytic capacitor element 1 in the thickest portions 43a and 43b. That is, the thickness of the solid electrolytic capacitor element 1 in the remaining portions 42a and 42b is smaller than or approximately the same as the thickness Tmax of the solid electrolytic capacitor element 1 in the thickest portions 43a and 43b. In addition, when the convex portions 41a and 41b are present on both main surfaces of the anode 10, the thickness Tmax of the solid electrolytic capacitor element 1 in the thickest portions 43a and 43b may be the distance between two planes parallel to the anode 10 and passing through the vertices of the thickest portions 43a and 43b.

Figure 8 is a cross-sectional view showing a schematic example of a solid electrolytic capacitor according to another embodiment of the present invention.

In the solid electrolytic capacitor 200 shown in Figure 8, instead of multiple solid electrolytic capacitor elements 1, multiple solid electrolytic capacitor elements 2 are stacked in the height direction T via conductive adhesive 140.

Each solid electrolytic capacitor element 2, like the solid electrolytic capacitor element 1, comprises an anode 10 composed of a valve metal substrate 11, a dielectric layer 20, a mask layer 30, and a cathode 40, and the cathode 40 has a solid electrolyte layer 50 and a conductive layer 60.

Figure 9 is a plan view showing a schematic example of a solid electrolytic capacitor element provided in the solid electrolytic capacitor shown in Figure 8. Figure 10 is a cross-sectional view taken along line X-X of the solid electrolytic capacitor element shown in Figure 9. Figure 11 is a cross-sectional view taken along line Y-Y of the solid electrolytic capacitor element shown in Figure 9.

In the solid electrolytic capacitor element 2 shown in Figures 9, 10, and 11, the solid electrolyte layer 50 has, on one main surface 10c side of the anode 10, an outer peripheral portion 55a including a protrusion 51a along the mask layer 30, and a central portion 56a surrounded by the outer peripheral portion 55a, and the thickness of the solid electrolyte layer 50 at the outer peripheral portion 55a is greater than the thickness of the solid electrolyte layer 50 at the central portion 56a.
Similarly, the solid electrolyte layer 50 has, on the other main surface 10d side of the anode 10, an outer peripheral portion 55b including a protrusion 51b along the mask layer 30, and a central portion 56b surrounded by the outer peripheral portion 55b, and the thickness of the solid electrolyte layer 50 at the outer peripheral portion 55b is greater than the thickness of the solid electrolyte layer 50 at the central portion 56b.
This makes it possible to increase the thickness of solid electrolyte layer 50 near mask layer 30 and at the end of anode 10, where solid electrolyte layer 50 is likely to become thin and is also likely to be subjected to stress, thereby making it possible to reduce leakage current near mask layer 30 and at the end of anode 10. In addition, it is possible to prevent the conductive adhesive from protruding from above cathode 40.

On the other hand, the conductive layer 60 on the solid electrolyte layer 50 has an approximately constant thickness.

As a result, the cathode 40 has a convex portion 41, a remaining portion 42, an outer peripheral portion 45, a central portion 46, etc., formed as described above.

Each outer peripheral portion 55a, 55b of the solid electrolyte layer 50 includes a protruding portion 51a, 51b along the mask layer 30 and a U-shaped portion 57a, 57b that is approximately U-shaped along the tip surface 10a and side surfaces 10e, 10f of the anode 10.
The thickness of the protrusions 51a, 51b may be substantially the same as the thickness of the U-shaped portions 57a, 57b, respectively, or may be greater than the thickness of the U-shaped portions 57a, 57b.

[Method of manufacturing solid electrolytic capacitor]
The solid electrolytic capacitors 100 and 200 can be manufactured by the following method. First, a method for manufacturing the solid electrolytic capacitor elements 1 and 2 will be described.

Figure 12 is a schematic diagram showing an example of a process for immersing an anode on which a mask layer has been formed in a treatment liquid or conductive paste containing a solid electrolyte. Figure 13 is a schematic diagram showing an example of a process for pulling the anode out of the treatment liquid and drying the treatment liquid or conductive paste. Figure 14 is a plan view showing an example of a solid electrolytic capacitor element after a solid electrolyte layer or conductive layer has been formed through the drying process shown in Figure 13.

12, first, the anode 10 having the mask layer 30 formed on the dielectric layer 20 is immersed in a treatment liquid 70 containing a solid electrolyte from the front end surface 10a side until it comes into contact with the mask layer 30 (first step). The treatment liquid 70 is supplied to a treatment tank 75.
Next, the anode 10 is pulled out of the treatment liquid 70, and the treatment liquid 70 is dried (second step).
12, the anode 10 from which the treatment liquid 70 has been dried is immersed in a conductive paste 71 from the tip surface side until it comes into contact with, for example, the mask layer 30 (third step). Note that, although the conductive paste 71 is supplied to a treatment tank 75 in FIG. 12, it is actually supplied to a treatment tank separate from the treatment liquid 70.
Thereafter, the anode 10 is lifted from the conductive paste 71, and the conductive paste 71 is dried (fourth step).
In at least one of the second and fourth steps, the anode 10 is dried in a state in which it is turned upside down from when it was immersed, as shown in Fig. 13. That is, the anode 10 is dried with the tip end surface 10a of the anode 10 facing up and the base end surface 10b of the anode 10 facing down.
Thereby, as shown in FIG. 14 , a cathode 40 having a convex portion 41 can be formed along the mask layer 30, and the thickness of the cathode 40 at the remaining portion 42 can be made not to exceed the maximum thickness of the cathode at the convex portion 41.

More specifically, as shown in Fig. 13, the coffee ring effect of the treatment liquid 70 or conductive paste 71 causes the solid electrolyte layer 50 and/or conductive layer 60 to be formed such that only the outer peripheral portion 45 is thick, as shown in Fig. 14. This coffee ring effect is due to the properties of the treatment liquid 70 or conductive paste 71, such as the viscosity, surface tension, and contact angle. This makes it possible to make the thickness of the outer peripheral portion 45 of the cathode 40 greater than the thickness of the central portion 46 of the cathode 40, as shown in Fig. 14.

In the fourth step, the anode 10 may be dried in a state in which it is inverted from when it was immersed. That is, in the drying step for forming the conductive layer 60, the anode 10 may be dried in an inverted state. This makes it possible to make the thickness of the peripheral portion of the conductive layer 60 greater than the thickness of the central portion of the conductive layer 60, as shown in FIG.

The third step and the fourth step may be alternately performed multiple times in this order. In this case, it is preferable to dry the anode 10 in a state in which it is inverted upside down from when it was immersed in at least one of the multiple fourth steps, and it is more preferable to dry the anode 10 in a state in which it is inverted upside down from when it was immersed in each of the multiple fourth steps.
This embodiment is suitable when the conductive layer 60 includes a carbon layer and a cathode conductor layer, as described above. That is, the conductive paste into which the anode 10 is immersed in the third step is a concept that includes a carbon paste.

In addition, the conductive pastes into which the anode 10 is immersed in the third step multiple times are usually different types of conductive paste, but may be the same type of conductive paste.

In the second step, the anode 10 may be dried in a state in which it is inverted from when it was immersed. That is, in the drying step for forming the solid electrolyte layer 50, the anode 10 may be dried in an inverted state. This makes it possible to make the thickness of the outer peripheral portion 55 of the solid electrolyte layer 50 greater than the thickness of the central portion 56 of the solid electrolyte layer 50, as shown in FIG. 10.

The first step and the second step may be alternately performed multiple times in this order. In this case, it is preferable to dry the anode 10 in a state in which it is inverted upside down from when it was immersed in at least one of the multiple second steps, and it is more preferable to dry the anode 10 in a state in which it is inverted upside down from when it was immersed in each of the multiple second steps.
This embodiment is suitable for the case where the inner and outer layers of the solid electrolyte layer 50 are formed separately, as described above.

In addition, the treatment liquid in which the anode 10 is immersed in the first step multiple times may be the same type of treatment liquid or different types of treatment liquid.

Specifically, for example, in the second step (drying step for forming the solid electrolyte layer 50), the anode 10 may be dried in the same orientation as when it was immersed, while in the fourth step (drying step for forming the conductive layer 60), the anode 10 may be dried in a state in which it is upside down compared to when it was immersed. This makes it possible to form a solid electrolytic capacitor element 1 in which the solid electrolyte layer 50 is bulging only near the tip surface 10a of the anode 10, as shown in FIG.

In addition, for example, in the second step (drying step for forming the solid electrolyte layer 50), the anode 10 may be dried in a state in which it is inverted from when it was immersed, and in the fourth step (drying step for forming the conductive layer 60), the anode 10 may be dried in a state in which it is inverted from when it was immersed. This makes it possible to form a solid electrolytic capacitor element 2 in which the solid electrolyte layer 50 is bulging near the tip surface 10a of the anode 10 and near the mask layer 30, as shown in FIG.

The manufacturing method of solid electrolytic capacitor elements 1 and 2 is described in more detail below. In the following example, a method of simultaneously manufacturing multiple solid electrolytic capacitor elements using a large valve metal substrate is described.

Figure 15 is a schematic diagram showing an example of a process for preparing a valve metal substrate having a mask layer formed thereon.

As shown in Figure 15, a valve metal substrate 11A having a dielectric layer 20 on its surface is prepared. The valve metal substrate 11A includes a plurality of element portions 12 and a support portion 13. Each element portion 12 is rectangular and protrudes from the support portion 13. A mask layer 30 is formed on the dielectric layer 20 of each element portion 12.

First, a valve metal substrate 11A having a porous portion on its surface is cut by laser processing, punching processing, or the like, to form a shape including a plurality of element portions 12 and support portions 13.

Next, a mask layer 30 is formed on both main surfaces and both side surfaces of the element portion 12 along the short sides of each element portion 12.

Thereafter, an oxide film that becomes the dielectric layer 20 is formed on the surface of the valve metal base 11A by anodizing the valve metal base 11A. At this time, an oxide film is also formed on the side of the element portion 12 that has been cut by laser processing, punching, or the like. A chemical foil on which an oxide of the valve metal has already been formed may be used as the valve metal base 11A. In this case, an oxide film is also formed on the side of the cut element portion 12 by anodizing the valve metal base 11A after cutting.

Figure 16 is a schematic diagram showing an example of a process for forming a solid electrolyte layer or a cathode layer.

A solid electrolyte layer 50 (see FIG. 7, etc.) is formed on the dielectric layer 20 of the element portion 12. As shown in FIG. 16, it is preferable to apply a treatment liquid containing a solid electrolyte to the valve metal substrate 11A by a dipping method. FIG. 16 shows a state in which a treatment liquid 70 containing a solid electrolyte, a conductive paste 71, or a carbon paste 72 is supplied to a treatment tank 75.

As the treatment liquid 70 containing a solid electrolyte, for example, a dispersion liquid of a conductive polymer is used. A conductive polymer film can be formed by applying the conductive polymer dispersion liquid to the outer surface of the dielectric layer 20 and drying it. Alternatively, a liquid containing a polymerizable monomer, for example, 3,4-ethylenedioxythiophene and an oxidizing agent, may be used as the treatment liquid 70 containing a solid electrolyte. A conductive polymer film can be formed by applying the polymerizable monomer containing liquid to the outer surface of the dielectric layer 20 and chemically polymerizing it. This conductive polymer film becomes the solid electrolyte layer 50.

16, the valve metal substrate 11A is immersed in the treatment liquid 70, so that the treatment liquid 70 permeates the porous portion of the valve metal substrate 11A. After a predetermined period of immersion, the valve metal substrate 11A is pulled out of the treatment liquid 70 and dried at a predetermined temperature for a predetermined period of time. The solid electrolyte layer 50 is formed by repeating the immersion in the treatment liquid 70, pulling out, and drying a predetermined number of times. At this time, in at least one drying cycle, for example in all drying cycles, the treatment liquid 70 may be dried in a state in which the valve metal substrate 11A is inverted from when it was immersed, i.e., with the element portion 12 on top and the support portion 13 on the bottom.

For example, the valve metal substrate 11A is immersed in a first dispersion liquid containing a conductive polymer, then pulled out, and then dried in a state in which the valve metal substrate 11A is inverted from when it was immersed, to form a first solid electrolyte layer. The immersion in the first dispersion liquid, pulling out, and drying may be performed multiple times.

After forming the first solid electrolyte layer, a primer layer may be formed by immersing the valve metal substrate 11A in a solution containing a primer compound, lifting it out and drying it.

The valve metal substrate 11A is then immersed in a second dispersion liquid containing a conductive polymer and pulled out, and then the valve metal substrate 11A is dried in an inverted state compared to when it was immersed, thereby forming a second solid electrolyte layer.

The solid electrolyte layer formed by the above method includes a first solid electrolyte layer provided on a dielectric layer and a second solid electrolyte layer provided on the first solid electrolyte layer.

The valve metal substrate 11A is washed with pure water to remove excess primer compound. After washing, a drying process is performed. In this manner, a solid electrolyte layer 50 is formed in a specified area.

After the solid electrolyte layer 50 is formed, the valve metal substrate 11A is immersed in the carbon paste 72, pulled up, and dried to form a carbon layer in a predetermined area, as shown in Fig. 16. At this time, the carbon paste 72 may be dried in a state in which the valve metal substrate 11A is inverted from when it was immersed, i.e., with the element portion 12 on top and the support portion 13 on the bottom.

After the carbon layer is formed, the valve metal substrate 11A is immersed in a conductive paste 71 containing metal particles such as silver paste, pulled up, and dried to form a cathode conductor layer in a predetermined region, as shown in Fig. 16. At this time, the conductive paste 71 may be dried in a state in which the valve metal substrate 11A is inverted from when it was immersed, i.e., with the element portion 12 on top and the support portion 13 on the bottom.

Then, the valve metal substrate 11A is cut to separate the element portion 12 to form a strip-shaped anode 10.

Through the above steps, solid electrolytic capacitor elements 1 and 2 are obtained.

Next, we will explain the manufacturing method of the solid electrolytic capacitors 100 and 200.

First, multiple solid electrolytic capacitor elements 1 and 2 are stacked. At this time, the conductive layers 60 of adjacent solid electrolytic capacitor elements 1 and 2 are connected to each other using a conductive adhesive.

Next, the multiple solid electrolytic capacitor elements 1 and 2 are molded using an insulating resin such as epoxy resin. Specifically, the multiple solid electrolytic capacitor elements 1 and 2 are mounted on an upper mold by a molding method, and the upper and lower molds are clamped together in a state in which the insulating resin such as epoxy resin is heated and melted in the cavity of the lower mold, and the insulating resin is solidified to form the exterior body 110.

Next, the solid electrolytic capacitor elements 1, 2 and the exterior body 110 are cut so that the base ends of the solid electrolytic capacitor elements 1, 2 are severed and the tip ends of the solid electrolytic capacitor elements 1, 2 are exposed. Specifically, the solid electrolytic capacitor elements 1, 2 and the exterior body 110 are cut by press-cutting, dicing or laser cutting. This process forms a chip. In addition, the base end surface 10b of the anode 10 is exposed on the cut surface on the base end side of the solid electrolytic capacitor elements 1, 2, and the cathode 40 (conductive layer 60) is exposed on the cut surface on the tip end side of the solid electrolytic capacitor elements 1, 2.

Next, it is preferable to barrel polish the chips. Specifically, the chips are enclosed together with an abrasive in a small box called a barrel, and the chips are polished by rotating the barrel. This makes the corners and edges of the chips round.

Next, a first external electrode 120 and a second external electrode 130 are formed on both ends of the chip. For example, a Cu plating layer is formed on both ends of the chip by electrolytic plating. Next, a Ni plating layer is formed on the Cu plating layer by electrolytic plating. After that, a Sn plating layer is formed on the Ni plating layer by electrolytic plating.

Through the above-mentioned processes, solid electrolytic capacitors 100, 200 are manufactured.

In the above embodiment, the cathode 40 has been described as having an outer peripheral portion 45 and a central portion 46, but the cathode 40 may have a first convex portion (convex streak portion) along the mask layer 30, a second convex portion (convex streak portion) along the tip surface 10a of the anode 10, and a flat portion excluding the first and second convex portions, and the thickness of the first and second convex portions may be greater than the thickness of the flat portion.

The following are examples that more specifically disclose the solid electrolytic capacitor and the method for manufacturing the solid electrolytic capacitor of the present invention. Note that the present invention is not limited to these examples.

Example 1
An aluminum foil having an etching layer on its surface was prepared as an anode (valve metal substrate), and anodized by immersing it in an aqueous solution of ammonium adipate to form a dielectric layer on the surface of the aluminum foil.

Next, a composition consisting of soluble polyimide siloxane and epoxy resin was roller-transferred onto the anode on which the dielectric layer was formed, thereby forming a mask layer on both main surfaces and both side surfaces of the anode via the dielectric layer.

Next, the element was immersed in a mixture of iron (III) paratoluenesulfonate, 3,4-ethylenedioxythiophene, and 1-butanol up to just below the mask layer, then pulled out and dried in the same direction as the immersion, forming a solid electrolyte layer on the dielectric layer. As shown in Figure 4, the thickness of the solid electrolyte layer gradually decreased from near the tip surface of the anode toward the mask layer on each main surface side of the anode. The thickness of the obtained element just below the mask layer, i.e., the thickness of the portion adjacent to the tip side of the anode relative to the mask layer, was 125 μm, the thickness of the lower end of the obtained element, i.e., the thickness on the tip side of the anode, was 190 μm, and the thickness of the central portion of the obtained element was 140 μm.

Furthermore, the element was immersed in carbon paste up to just below the mask layer, and after being pulled up, it was dried in a state in which it was turned upside down from the direction of immersion to form a carbon layer. Then, the element was immersed in silver paste in the same manner as the carbon layer to form a silver layer as a cathode conductor layer, thereby forming a conductive layer, and a solid electrolytic capacitor element was obtained. That is, the element pulled up from the silver paste was dried in a state in which it was turned upside down from the direction of immersion in the silver paste to form a silver layer. As shown in FIG. 4, the cathode including the carbon layer and the silver layer had an outer peripheral portion including a convex portion along the mask layer and a central portion surrounded by the outer peripheral portion and thinner than the outer peripheral portion on both main surfaces of the anode. The maximum thickness of the cathode at the convex portion of the outer peripheral portion was 45 μm, the thickness of the cathode at the tip side portion of the outer peripheral portion was 40 μm, and the thickness of the cathode at the central portion was 25 μm. The thickness of the obtained solid electrolytic capacitor element directly below the mask layer, i.e., the thickness at the thickest part of the convex portion of the cathode, was 210 μm, and the thickness excluding the conductive layer (carbon layer and silver layer) directly below the mask layer was 125 μm. The thickness of the lower end of the obtained solid electrolytic capacitor element, i.e., the thickness on the tip side of the anode, was 200 μm, and the thickness excluding the conductive layer (carbon layer and silver layer) at the lower end was 160 μm. The thickness of the central portion of the obtained solid electrolytic capacitor element was 170 μm, and the thickness excluding the conductive layer (carbon layer and silver layer) in the central portion was 140 μm.

The four obtained solid electrolytic capacitor elements were laminated using a conductive adhesive to obtain a laminate. The conductive adhesive was applied to the center portion of the cathode of the solid electrolytic capacitor element. The laminate was then sealed using epoxy resin and cut into pieces using a dicer. Next, a silver paste containing a resin component was screen printed on the cathode and anode end faces of the cut outer casing (sealing body) to form external electrodes on the cathode and anode, thereby obtaining a finished solid electrolytic capacitor. The thickness in the height direction of the obtained finished solid electrolytic capacitor was 1240 μm.

Example 2
A finished solid electrolytic capacitor was obtained in the same manner as in Example 1, except that the solid electrolyte layer was dried in a state in which it was upside down from the state in which it was immersed in the mixed liquid.
The solid electrolyte layer had, on both main surfaces of the anode, an outer peripheral portion including a protrusion along the mask layer, and a central portion surrounded by the outer peripheral portion and thinner than the outer peripheral portion, as shown in Fig. 10. The thickness of the obtained element directly below the mask layer, i.e., the thickness at the thickest portion of the protrusion of the solid electrolyte layer, was 160 µm, the thickness of the lower end portion of the obtained element, i.e., the thickness on the tip side of the anode, was 140 µm, and the thickness of the central portion of the obtained element was 130 µm.
Furthermore, after forming the cathode, the thickness of the obtained solid electrolytic capacitor element directly below the mask layer (the thickness at the thickest part of the protruding part of the solid electrolyte layer) was 200 μm, the thickness of the lower end part of the obtained solid electrolytic capacitor element (the thickness on the tip side of the anode) was 180 μm, and the thickness of the central part of the obtained solid electrolytic capacitor element was 150 μm. The thickness of the obtained finished solid electrolytic capacitor in the height direction was 1200 μm.

(Comparative Example 1)
In Example 1, a finished solid electrolytic capacitor was obtained in the same manner, except that the cathode (carbon paste and silver paste) was dried in a state in which it was immersed in the mixed liquid upside down. The cathode including the carbon layer and the silver layer had a gradually decreasing thickness from the vicinity of the tip surface of the anode toward the outer periphery. After the formation of the solid electrolyte layer and before the formation of the cathode, the thickness of the obtained element immediately below the mask layer, i.e., the thickness of the portion adjacent to the tip side of the anode with respect to the mask layer, was 125 μm, the thickness of the lower end of the obtained element, i.e., the thickness on the tip side of the anode, was 180 μm, and the thickness of the central portion of the obtained element was 140 μm. In addition, after the formation of the cathode, the thickness of the obtained solid electrolytic capacitor element immediately below the mask layer was 135 μm, the thickness of the lower end of the obtained solid electrolytic capacitor element (thickness on the tip side of the anode) was 220 μm, and the thickness of the central portion of the obtained solid electrolytic capacitor element was 160 μm. The thickness of the obtained solid electrolytic capacitor in the height direction was 1310 μm.

In Examples 1 and 2, the thickness of the finished product is the sum of the thickness of the four elements, the thickness of the epoxy resin (400 μm), and the thickness of the external electrodes (20 μm).
In contrast, in Comparative Example 1, the thickness of the finished product is the sum of the thickness of the four elements, the thickness of the conductive adhesive (30 μm), the thickness of the epoxy resin (400 μm), and the thickness of the external electrodes (20 μm).
In Examples 1 and 2, there is no need to consider the thickness of the conductive adhesive, whereas in Comparative Example 1, the thickness of the conductive adhesive is 30 μm. This is because in Examples 1 and 2, there is space to place the conductive adhesive in the center part of the cathode of the solid electrolytic capacitor element, so there is no need to consider the thickness of the conductive adhesive itself, whereas in Comparative Example 1, there is no space to place the conductive adhesive in the center part of the cathode of the solid electrolytic capacitor element, so the thickness of the conductive adhesive itself must be considered.

The solid electrolytic capacitors obtained in Examples 1 and 2 and Comparative Example 1 were evaluated for the thickness in the height direction of the finished product, the withstand voltage, and short circuits after the reflow test. The results are shown in Table 1 below.

In Examples 1 and 2, the outer periphery of the cathode of the solid electrolytic capacitor element is thick, so that the laminate can be laminated without increasing in thickness when using a conductive adhesive, and the thickness of the finished product can be reduced. In Example 2, the solid electrolyte layer is thicker just below the mask layer and in the outer periphery, which are susceptible to stress and electric field, so that the occurrence of short circuits during reflow is further suppressed and the withstand voltage is further improved compared to Example 1.

1, 2 Solid electrolytic capacitor element 10 Anode 10a Tip surface 10b Base end surface 10c, 10d Main surface 10e, 10f Side surface 11, 11A Valve metal base 12 Element portion 13 Support portion 20 Dielectric layer 30 Mask layer 40 Cathode 41a, 41b, 41 Convex portion 42a, 42b, 42 remaining portion 43a, 43b, 43 thickest portion 44 base end 45a, 45b, 45 outer peripheral portion 46a, 46b, 46 center portion 47a, 47b, 47 U-shaped portion 50 solid electrolyte layer 51a, 51b, 51 convex portion 55a, 55b, 55 outer peripheral portion 56a, 56b, 56 center part 57a, 57b, 57 U-shaped portion 60 Conductive layer 70 Treatment liquid 71 Conductive paste 72 Carbon paste 75 Treatment tank 100, 200 Solid electrolytic capacitor 110 Exterior body 110a First main surface 110b Second main surface 110c First side surface 110d Second side surface 110e First end surface 110f Second end surface 120 First external electrode 130 Second external electrode 140 Conductive adhesive t1, t2 Maximum thickness of cathode at convex portion Tmax Thickness of solid electrolytic capacitor element at thickest portion

Claims (7)

A solid electrolytic capacitor comprising a laminate in which a plurality of solid electrolytic capacitor elements are laminated with a conductive adhesive therebetween,
The solid electrolytic capacitor elements each include an anode made of a valve metal substrate and having a leading end surface and a base end surface;
a dielectric layer provided on at least one of the main surfaces of the anode, excluding at least the base end surface;
a mask layer formed of an insulating material and disposed on the dielectric layer along the base end surface;
a cathode provided on the dielectric layer on the tip surface side of the mask layer,
the cathode has a solid electrolyte layer provided on the dielectric layer, a conductive layer provided on the solid electrolyte layer, and a convex portion along the mask layer,
a thickness of the cathode in a remaining portion excluding the protruding portion does not exceed a maximum thickness of the cathode in the protruding portion,
The conductive adhesive is provided in a region sandwiched between the remnants of the cathode of adjacent solid electrolytic capacitor elements. the cathode has an outer circumferential portion including the protrusion and a central portion surrounded by the outer circumferential portion,
the thickness of the cathode at the outer circumferential portion is greater than the thickness of the cathode at the central portion;
The solid electrolytic capacitor of claim 1 , wherein the conductive adhesive is provided on the central portion. 3. A method for producing the solid electrolytic capacitor according to claim 1, comprising the steps of:
a first step of immersing the anode having the mask layer formed on the dielectric layer in a treatment liquid containing a solid electrolyte from the front end surface side until the front end surface contacts the mask layer;
a second step of removing the anode from the treatment solution and drying the treatment solution;
a third step of immersing the anode from which the treatment liquid has been dried into a conductive paste from the tip surface side;
a fourth step of lifting the anode from the conductive paste and drying the conductive paste;
In at least one of the second step and the fourth step, the anode is dried in a state in which it is turned upside down from when it was immersed. The method for manufacturing a solid electrolytic capacitor according to claim 3, wherein in the fourth step, the anode is dried in a state in which it is inverted from when it was immersed. The third step and the fourth step are alternately performed in this order multiple times,
The method for producing a solid electrolytic capacitor according to claim 4 , wherein in at least one of the fourth step performed a plurality of times, the anode is dried in a state in which it is turned upside down from when it was immersed. 4. The method for producing a solid electrolytic capacitor according to claim 3 , wherein in the second step, the anode is dried in a state in which it is turned upside down from when it was immersed. The first step and the second step are alternately performed in this order multiple times,
The method for producing a solid electrolytic capacitor according to claim 6 , wherein in at least one of the second steps, the anode is dried in a state in which it is turned upside down from when it was immersed.

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