Electrolytic capacitor element

Abstract

This electrolyte capacitor element 1 comprises: an anode 10 which is composed of a valve action metal substrate 11 and has a front end surface 10a and a base end surface 10b; a dielectric layer 20 which is provided on at least one main surface 10c, 10d of the anode except at least the base end surface 10b; a mask layer 30 which is composed of an insulation material and is provided on the dielectric layer 20 along the base end surface 10b; and a cathode 40 which is provided on the dielectric layer 20 in the front end surface 10a rather than the mask layer 30, wherein the cathode 40 includes a solid electrolyte layer 50 provided on the dielectric layer 20 and a conductive layer 60 provided on the solid electrolyte layer 50, wherein the solid electrolyte layer 50 includes a first layer 51 that is provided on the dielectric layer 20 and includes a first conductive polymer, and a second layer 52 that is provided on the first layer 51 and includes a second conductive polymer and particles of which the average particle diameter is 0.1 μm to 10 μm, wherein the particles are partially arranged within a surface of the second layer 52.

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor element. [Background technology]

[0002] Patent Document 1 discloses an electrolytic capacitor in which a first conductive polymer layer is provided on the surface of an anode body made of a strip-shaped metal foil so as to be thicker at the ends in the width direction of the anode body than at the center in the width direction of the anode body in order to suppress deterioration of electrical characteristics such as an increase in equivalent series resistance (ESR) and leakage current, and describes that the first conductive polymer layer is formed using a liquid composition made of a dispersion liquid containing conductive solid particles.

[0003] Patent Document 2 discloses an electrolytic capacitor in which, in order to reduce leakage current, silica particles are attached to a dielectric layer that covers the surface of an anode body within the pores of the anode body, and the silica particles are covered with a solid electrolyte layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-191178 [Patent Document 2] International Publication No. 2020 / 111093 Summary of the Invention [Problem to be solved by the invention]

[0005] In electrolytic capacitor elements, stress is generally concentrated at the edges of the anode (such as corners and ridges), which can easily cause short circuits during reflow. However, with conventional methods, it is difficult to form a solid electrolyte layer on the edges, which tends to make them thin, making it difficult to prevent short circuits at the edges.

[0006] Patent Document 1 states that the first conductive polymer layer can repair defects in the dielectric film, which are often present on the end face of the anode body, but there is room for improvement in that the effect is not sufficient for electrolytic capacitors that have corners. Furthermore, the first conductive polymer layer formed using the liquid composition is a layer formed by the conductive polymers being entangled or bonded to each other on the surface of the anode body (see paragraph

[0036] ). In the examples, the first conductive polymer layer is observed to be in the form of a smooth layer and white mycelium (see Figure 13), and it is recognized that the conductive polymer does not exist as particles in the finished electrolytic capacitor.

[0007] In Patent Document 2, silica particles, which are an insulator, are in contact with the surface of the dielectric, and the solid electrolyte layer cannot be in contact with the surface of the dielectric at that location, resulting in a decrease in capacity. In addition, these silica particles do not affect the thickness of the solid electrolyte layer on the edge portion of the anode, so there is room for improvement in that short circuits caused by thinning the solid electrolyte layer cannot be suppressed.

[0008] The present invention has been made to solve the above problems, and has an object to provide an electrolytic capacitor element that can suppress short circuits while suppressing an increase in equivalent series resistance. [Means for solving the problem]

[0009] In a first aspect, the electrolytic capacitor element of the present invention comprises: 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 main surface of the anode excluding at least the base end surface; a mask layer made of an insulating material 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, wherein the cathode has a solid electrolyte layer provided on the dielectric layer and a conductive layer provided on the solid electrolyte layer, and the solid electrolyte layer comprises: a first layer provided on the dielectric layer and containing a first conductive polymer; and a second layer provided on the first layer and containing a second conductive polymer and particles having an average particle size of 0.1 μm or more and 10 μm or less, the particles being partially distributed within the plane of the second layer.

[0010] In a second aspect, the electrolytic capacitor element of the present invention comprises: 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 main surface of the anode excluding at least the base end surface; a mask layer made of an insulating material provided on the dielectric layer along the base end surface; and a cathode provided on the dielectric layer on a side closer to the tip end surface than the mask layer, wherein the cathode has a solid electrolyte layer provided on the dielectric layer and a conductive layer provided on the solid electrolyte layer, and the solid electrolyte layer comprises: a first layer provided on the dielectric layer and containing a first conductive polymer; and a second layer provided on the first layer and containing a second conductive polymer and particles having an average particle size of 0.1 μm or more and 10 μm or less, the particles being present in greater numbers in the plane of the second layer as they approach the outer periphery of the second layer. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an electrolytic capacitor element that can suppress an increase in equivalent series resistance and also suppress short circuits. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a plan view schematically illustrating an example of an electrolytic capacitor element according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the electrolytic capacitor element shown in FIG. 1 taken along line XX. [Figure 3] FIG. 3 is a perspective view of the electrolytic capacitor element shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA of the electrolytic capacitor element shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line BB of the electrolytic capacitor element shown in FIG. [Figure 6] FIG. 6 is a perspective view schematically showing another example of the electrolytic capacitor element according to the first embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view taken along line CC of the electrolytic capacitor element shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line DD of the electrolytic capacitor element shown in FIG. [Figure 9] FIG. 9 is a perspective view schematically showing still another example of the electrolytic capacitor element according to the first embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view taken along line EE of the electrolytic capacitor element shown in FIG. [Figure 11] FIG. 11 is a cross-sectional view taken along line FF of the electrolytic capacitor element shown in FIG. [Figure 12] FIG. 12 is a perspective view schematically showing still another example of the electrolytic capacitor element according to the first embodiment of the present invention. [Figure 13] FIG. 13 is a cross-sectional view taken along line GG of the electrolytic capacitor element shown in FIG. [Figure 14] FIG. 14 is a cross-sectional view taken along line HH of the electrolytic capacitor element shown in FIG. [Figure 15] FIG. 15 is an enlarged cross-sectional view of the mask layer portion of the electrolytic capacitor element shown in FIG. [Figure 16] FIG. 16 is an enlarged cross-sectional view of the particle region of the electrolytic capacitor element shown in FIG. [Figure 17] FIG. 17 is a schematic diagram showing an example of a step of preparing a valve metal substrate on which a mask layer is formed. [Figure 18] FIG. 18 is a schematic diagram showing an example of a process for forming the first and second solid electrolyte layers. [Figure 19] FIG. 19 is a schematic diagram showing an example of a step of arranging particles. [Figure 20] FIG. 20 is a perspective view schematically illustrating an example of an electrolytic capacitor element according to Embodiment 2 of the present invention. [Figure 21] FIG. 21 is a cross-sectional view taken along line JJ of the electrolytic capacitor element shown in FIG. [Figure 22] FIG. 22 is a cross-sectional view taken along line KK of the electrolytic capacitor element shown in FIG. [Figure 23] FIG. 23 is an enlarged cross-sectional view of the particle region of the electrolytic capacitor element shown in FIG. [Figure 24] FIG. 24 is a schematic diagram showing an example of a step of immersing a valve metal substrate on which a mask layer has been formed into a particle dispersion liquid. [Figure 25] FIG. 25 is a schematic diagram showing an example of a process of pulling up a valve metal substrate from a particle dispersion and drying the particle dispersion. [Figure 26] FIG. 26 is a schematic diagram showing an example of a step of immersing a valve metal substrate on which a mask layer has been formed in a first layer forming treatment liquid containing particles. [Figure 27] FIG. 27 is a schematic diagram showing an example of a process of pulling up a valve metal substrate from a particle-containing first layer-forming treatment liquid and drying the treatment liquid. [Figure 28] FIG. 28 is a perspective view that schematically illustrates an example of an electrolytic capacitor that includes an electrolytic capacitor element according to an embodiment of the present invention. [Figure 29] FIG. 29 is a cross-sectional view taken along line ZZ of the electrolytic capacitor shown in FIG. [Figure 30] FIG. 30 is a plan view schematically showing an example of an electrolytic capacitor element according to a comparative embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The electrolytic capacitor element of the present invention will now be described. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual desirable configurations described below.

[0014] Furthermore, the embodiments described below are merely examples, 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 differences will be described.

[0015] (Embodiment 1) [Electrolytic capacitor element] Fig. 1 is a plan view schematically illustrating an example of an electrolytic capacitor element according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line XX of the electrolytic capacitor element shown in Fig. 1. Note that in Fig. 1, a solid electrolyte layer 50 covered with a conductive layer 60 is indicated by a dashed line. Furthermore, in Figs. 1 and 2, the solid electrolyte layer 50 is shown without distinguishing between a first layer 51 and a second layer 52.

[0016] The electrolytic capacitor element 1 shown in FIGS. 1 and 2 is a solid electrolytic capacitor element, and includes: 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 provided on the dielectric layer 20 along the base end surface 10b; and a cathode 40 provided on the dielectric layer 20 closer to the tip end surface 10a than the mask layer 30. 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.

[0017] Fig. 3 is a perspective view of the electrolytic capacitor element shown in Fig. 1. Fig. 4 is a cross-sectional view of the electrolytic capacitor element shown in Fig. 3 taken along line AA. Fig. 5 is a cross-sectional view of the electrolytic capacitor element shown in Fig. 3 taken along line BB. Note that Figs. 3, 4, and 5 show the state before the conductive layer 60 of the cathode 40 is formed, and the particle region 53R where the particles 53 exist is hatched. Also, Fig. 3 does not show the dielectric layer 20, and also shows a see-through state of the members inside the second layer 52 of the solid electrolyte layer 50.

[0018] As shown in Figures 3, 4, and 5, solid electrolyte layer 50 is provided on dielectric layer 20 and includes a first layer 51 containing a first conductive polymer, and a second layer 52 provided on first layer 51 and containing a second conductive polymer and particles 53 having an average particle diameter of 0.1 μm or more and 10 μm or less, and particles 53 are partially arranged within the plane of second layer 52. This makes it possible to prevent short circuits while suppressing an increase in the equivalent series resistance of the electrolytic capacitor element 1. The reason (action) for obtaining this effect is thought to be as follows. That is, it is believed that the inclusion of particles 53 having the above average particle diameter in the second layer 52 disperses stress during reflow and improves the mechanical strength of the second layer 52. Furthermore, in the electrolytic capacitor element 1, the particles 53 are partially arranged within the plane of the second layer 52, allowing the particles 53 to be selectively arranged in locations where stress is likely to concentrate and short circuits are likely to occur during reflow (e.g., corners of the anode 10). Furthermore, the presence of the particles 53 facilitates film formation, allowing the thickness of the solid electrolyte layer 50 to be increased in locations where short circuits are likely to occur (e.g., corners of the anode 10). As a result, the occurrence of short circuits is suppressed. Meanwhile, the particles 53 may increase the equivalent series resistance due to insulation resistance. However, in the electrolytic capacitor element 1, the particles 53 are partially arranged within the plane of the second layer 52 and are present only in a limited area within the solid electrolyte layer 50, preventing an increase in the equivalent series resistance of the entire electrolytic capacitor element 1. From the above, it is believed that short circuits can be suppressed while suppressing an increase in the equivalent series resistance of the entire electrolytic capacitor element 1.

[0019] From the viewpoint of preventing short circuits alone, it may be possible to arrange particles 53 over the entire surface of second layer 52, but in that case, the conductivity of the entire solid electrolyte layer 50 may decrease, possibly leading to an increase in the equivalent series resistance of electrolytic capacitor element 1.

[0020] In this specification, the term "conductive polymer" includes a main chain and a dopant.

[0021] 4 and 5, the particles 53 may be unevenly distributed on the first layer 51 side in the thickness direction of the second layer 52. That is, the particles 53 may be attached to the outer surface of the first layer 51, and the particles 53 may be covered with the second layer 52. This allows the particles 53 to be easily arranged by a dipping method or the like, as described below.

[0022] The average particle diameter of particles 53 is preferably larger than the average pore diameter of anode 10 (the average pore diameter of the porous portion described below). This makes it possible to more effectively increase the thickness of solid electrolyte layer 50 at locations where short circuits are likely to occur (for example, corners of anode 10). Furthermore, since particles 53 can be prevented from penetrating the pores of anode 10 and coming into contact with the surface of dielectric layer 20, a decrease in capacity can be prevented.

[0023] More specifically, the average particle size of the particles 53 is 0.1 μm or more and 10 μm or less, preferably 0.2 μm or more and 8 μm or less, and more preferably 0.3 μm or more and 5 μm or less.

[0024] Here, the "average particle diameter of particles" refers to the median diameter obtained from the results of determining the particle size distribution (distribution of maximum diameters) of particles within a specified area by image analysis in an SEM photograph image of the cross section of the second layer containing particles, for example.

[0025] The average pore size of the anode 10 is not particularly limited, but is preferably 10 nm or more and 500 nm or less, more preferably 20 nm or more and 300 nm or less, and even more preferably 30 nm or more and 100 nm or less.

[0026] Here, the "average pore diameter of the anode" is defined as, for example, the mode diameter (peak value) in the distribution of widths (maximum widths) of recessed portions when the SEM photograph image of the anode surface is binarized, since the portions exposed on the surface and the recessed portions (pore diameters) have different colors.

[0027] Particles 53 may be (1) made of a conductive polymer, (2) made of an insulator, or (3) made of a composite of a conductive polymer and an insulating particle. In the cases of (1) and (3), the particles 53 are conductive particles, so it is possible to suppress an increase in equivalent series resistance due to the particles 53. In these cases, the conductive polymer constituting the particles 53 may be the same as or different from the first conductive polymer, i.e., may have a different main chain or dopant. The same applies to whether the conductive polymer constituting the particles 53 is the same as or similar to the second conductive polymer. In the cases of (2) and (3), examples of the insulating material constituting the particles 53 include silica, alumina, and titanium oxide. In the case of (3), the particles 53 may have a core-shell structure in which insulating particles are coated with a conductive polymer layer.

[0028] 3, 4, and 5, the anode 10 has six faces: a tip face 10a, a base face 10b, a pair of main faces 10c and 10d, and a pair of side faces 10e and 10f, and also has corners where three of these six faces intersect and ridges where two of these six faces intersect, and particles 53 (particle regions 53R) are present at each corner 10g of the tip face 10a. Since short circuits are generally likely to occur at the corners of an anode, this configuration can more effectively prevent short circuits.

[0029] Fig. 6 is a perspective view schematically illustrating another example of the electrolytic capacitor element according to the first embodiment of the present invention. Fig. 7 is a cross-sectional view taken along line CC of the electrolytic capacitor element shown in Fig. 6. Fig. 8 is a cross-sectional view taken along line DD of the electrolytic capacitor element shown in Fig. 6. Note that Figs. 6, 7, and 8 show the state before the conductive layer 60 of the cathode 40 is formed, and the particle region 53R where the particles 53 exist is hatched. Fig. 6 does not illustrate the dielectric layer 20, and also shows a see-through state of the members inside the second layer 52 of the solid electrolyte layer 50.

[0030] As shown in Figures 6, 7, and 8, particles 53 (particle region 53R) may be further present on the tip surface 10a and on each ridge portion 10h formed by the tip surface 10a. Since short circuits are generally likely to occur at the ridge portions of the anode, this can more effectively prevent short circuits. Furthermore, it is easier to arrange particles 53 (particle region 53R) in the case shown in Figure 6 than in the case shown in Figure 3.

[0031] In this specification, a corner is a portion where three faces intersect, and a ridge is a portion where two faces intersect. Also, a corner formed by a certain face means a corner where three faces including that face intersect, and a ridge by a certain face means a ridge where two faces including that face intersect.

[0032] Fig. 9 is a perspective view schematically illustrating yet another example of the electrolytic capacitor element according to the first embodiment of the present invention. Fig. 10 is a cross-sectional view taken along line EE of the electrolytic capacitor element shown in Fig. 9. Fig. 11 is a cross-sectional view taken along line FF of the electrolytic capacitor element shown in Fig. 9. Note that Figs. 9, 10, and 11 illustrate the state before the conductive layer 60 of the cathode 40 is formed, and the particle region 53R where the particles 53 exist is hatched. Furthermore, Fig. 9 omits the illustration of the dielectric layer 20 and shows a see-through state of the members located inside the second layer 52 of the solid electrolyte layer 50.

[0033] 9, 10, and 11, particles 53 (particle regions 53R) may be further present on each of the side surfaces 10e, 10f and on each of the ridges 10j formed by the side surfaces 10e, 10f, thereby making it possible to particularly effectively suppress short circuits.

[0034] Fig. 12 is a perspective view schematically illustrating yet another example of the electrolytic capacitor element according to the first embodiment of the present invention. Fig. 13 is a cross-sectional view taken along line GG of the electrolytic capacitor element shown in Fig. 12. Fig. 14 is a cross-sectional view taken along line HH of the electrolytic capacitor element shown in Fig. 12. Note that Figs. 12, 13, and 14 illustrate the cathode 40 in a state prior to the formation of the conductive layer 60, and the particle region 53R where the particles 53 exist is hatched. Fig. 12 does not illustrate the dielectric layer 20, and also illustrates a see-through state of the members located inside the second layer 52 of the solid electrolyte layer 50.

[0035] 12, 13, and 14, particles 53 (particle region 53R) may be present along the mask layer 30. The solid electrolyte layer becomes thin in areas along the mask layer, which may result in short circuits. However, by having particles 53 (particle region 53R) present along the mask layer 30, short circuits in areas along the mask layer 30 can be effectively suppressed.

[0036] Furthermore, although not shown, a second layer may be formed that has both the particles 53 (particle region 53R) shown in Figure 3, Figure 6 or Figure 9 and the particles 53 (particle region 53R) shown in Figure 12. That is, for example, by combining the particles 53 (particle region 53R) shown in Figures 6 and 12, the particles 53 (particle region 53R) may be present at each corner 10g defined by the tip surface 10a, the tip surface 10a, and each ridge line 10h defined by the tip surface 10a, and may also be present along the mask layer 30.

[0037] Each component of the electrolytic capacitor element 1 will be described in detail below.

[0038] The anode 10 is a thin film (foil) made of a valve metal substrate 11 and has a quadrangular shape in plan view, preferably a rectangular shape (strip shape) having a pair of long sides and a pair of short sides in plan view. 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 not covered with the dielectric layer 20, exposed at one end surface of the electrolytic capacitor and connected to an external electrode (described later). The anode 10 has the tip end surface 10a, the base end surface 10b, main surfaces 10c and 10d, and side surfaces 10e and 10f.

[0039] In this specification, the term "plan view" means a view from the normal direction of the main surface of the anode (valve metal substrate).

[0040] FIG. 15 is an enlarged cross-sectional view of the mask layer portion of the electrolytic capacitor element shown in FIG.

[0041] As shown in Fig. 15, a plurality of pores (recesses) are provided on each main surface of the valve metal substrate 11 (anode 10). 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 both main surfaces of the valve metal substrate 11 are not limited to being porous, and only one of the main surfaces of the valve metal substrate 11 may be porous.

[0042] The valve metal substrate 11 is made of a valve metal such as an elemental metal such as aluminum, tantalum, niobium, titanium, or zirconium, or an alloy containing these metals. An oxide film can be formed on the surface of the valve metal.

[0043] The valve metal substrate 11 may be any substrate as long as it is 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 with an etched surface, a metal foil with a porous sintered powder body formed on the surface, or the like.

[0044] 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 end 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.

[0045] The dielectric layer 20 is preferably made of an oxide film provided on the surface of the valve metal substrate 11. For example, the dielectric layer 20 is made of aluminum oxide. The aluminum oxide is formed by anodizing the surface of the valve metal substrate 11, as will be described later.

[0046] The mask layer 30 is a linear (stripe-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. The mask layer 30 separates the anode 10 from the cathode 40, ensuring insulation between them. The mask layer 30 partitions the anode 10 into a region on the base end surface 10b side and a region 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 it may be disposed up to the edge of the base end surface 10b. The mask layer 30 is provided on the principal surfaces 10c and 10d and the side surfaces 10e and 10f of the anode 10 via the dielectric layer 20. However, like the dielectric layer 20, the mask layer 30 may be provided on at least one of the principal surfaces 10c and 10d of the anode 10 (the principal surface on which the dielectric layer 20 is provided).

[0047] 15, the mask layer 30 is preferably provided so as to fill a plurality of pores (recesses) in the valve metal base 11. However, it is sufficient that the mask layer 30 covers a part of the outer surface of the dielectric layer 20, and there may be pores (recesses) in the valve metal base 11 that are not filled with the mask layer 30.

[0048] 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-perfluoroalkyl vinyl ether copolymer, etc.), a composition of soluble polyimide siloxane and epoxy resin, polyimide resin, polyamide-imide resin, and derivatives or precursors thereof.

[0049] The mask material can be applied by, for example, screen printing, roller transfer, dispenser, inkjet printing, or the like.

[0050] 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 front end surface 10a side of the mask layer 30. That is, the cathode 40 is provided on the dielectric layer 20 in a region on the front end surface 10a side of the anode 10 that is partitioned by the mask layer 30.

[0051] The solid electrolyte layer 50 is provided on the dielectric layer 20. As shown in Fig. 15, the solid electrolyte layer 50 is preferably provided so as to fill a plurality of pores (recesses) in the valve metal substrate 11. However, it is sufficient that the solid electrolyte layer 50 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 with the solid electrolyte layer 50.

[0052] The solid electrolyte layer 50 is provided on the dielectric layer 20 on the front end surface 10a side of the mask layer 30. That is, the solid electrolyte layer 50 is provided on the dielectric layer 20 in the region on the front end surface 10a side of the anode 10 partitioned by the mask layer 30.

[0053] As described above, the solid electrolyte layer 50 includes a first layer 51 provided on the dielectric layer 20 and including a first conductive polymer, and a second layer 52 provided on the first layer 51 and including a second conductive polymer and particles 53 having an average particle size of 0.1 μm or more and 10 μm or less. The particles 53 are arranged only in a partial region, not in the entire area, in the plane of the second layer 52. That is, the particles 53 are unevenly distributed in the in-plane direction of the second layer 52, not in the thickness direction. On the other hand, the first layer 51 and the second layer 52 are disposed over the entire surface of the solid electrolyte layer 50. Therefore, both the first layer 51 and the second layer 52 are disposed within the surface of the solid electrolyte layer 50, and the second layer 52 covers the first layer 51.

[0054] FIG. 16 is an enlarged cross-sectional view of the particle region of the electrolytic capacitor element shown in FIG.

[0055] As shown in Fig. 16, the first layer 51 is formed in the pores of the valve metal substrate 11 and on the surface of the valve metal substrate 11. The particles 53 are disposed on the first layer 51 and are substantially not present in the pores. The second layer 52 covers the first layer 51 together with the particles 53, and the particles 53 are present in a state of being embedded (taken in) in the second layer 52 and are directly covered by the second layer 52 (second conductive polymer). The particles 53 are unevenly distributed on the first layer 51 side in the thickness direction of the second layer 52. The particles 53 may include particles 53 a having a particle diameter smaller than the pore diameter of the valve metal substrate 11 .

[0056] The thickness of first layer 51 is not particularly limited and may be, for example, approximately the same as the thickness of the inner layer of a general solid electrolyte layer. Specifically, the maximum thickness of first layer 51 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.2 μm or more and 5 μm or less, and even more preferably 0.3 μm or more and 3 μm or less.

[0057] The thickness of the second layer 52 is also not particularly limited and may be, for example, approximately the same as the thickness of the outer layer of a general solid electrolyte layer. Specifically, the maximum thickness of the second layer 52 is preferably 2 μm or more and 50 μm or less, more preferably 3 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less. The total thickness of the first layer 51 and the second layer 52, ie, the thickness of the solid electrolyte layer 50, is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 25 μm or less.

[0058] The locations where the particles 53 are arranged can be set as appropriate, but as described above, the following are preferred: (1) a configuration in which the particles 53 are present at each corner 10g of the anode 10 (see Figure 3, etc.); (2) a configuration in which the particles 53 are further present on the tip surface 10a of the anode 10 and each ridge portion 10h formed by the tip surface 10a (see Figure 6, etc.); (3) a configuration in which the particles 53 are further present on each side surface 10e, 10f of the anode 10 and each ridge portion 10j formed by the side surfaces 10e, 10f (see Figure 9, etc.); or (4) a configuration in which the particles 53 are present along the mask layer 30 (see Figure 12, etc.).

[0059] In the case of (1), the particles 53 (particle region 53R) may be present at at least one of the four corners 10g of the tip surface 10a, but it is preferable that the particles 53 are present at each of the four corners 10g. 3 shows a case where particle regions 53R are provided independently at two corners 10g formed by the same side surface 10e or 10f (corners 10g aligned vertically in FIG. 3), but particle regions 53R may be provided integrally at these two corners 10g. That is, the four ridges 10h formed by the tip surface 10a include two ridges 10ha formed by the side surface 10e or 10f and the tip surface 10a, but particles 53 (particle regions 53R) may also be present at the ridges 10ha.

[0060] In the case of (2), the particles 53 (particle region 53R) may be present on at least one of the four ridges 10h formed by the tip surface 10a, but are preferably present on each of the four ridges 10h. Thus, the particles 53 (particle region 53R) are preferably present in the tip portion of the anode 10 (a portion that includes the tip surface 10a as a part), and are preferably present from the tip surface 10a to each of the main surface 10c, the main surface 10d, the side surface 10e, and the side surface 10f.

[0061] In the case of (3), the particles 53 (particle region 53R) may be present on at least one of the two side surfaces 10e and 10f, but preferably on each of the two side surfaces 10e and 10f. Also, the particles 53 (particle region 53R) may be present on at least one of the four ridges 10j formed by the side surfaces 10e and 10f, but preferably on each of the four ridges 10j. In this case, the particles 53 (particle region 53R) do not necessarily have to be present on the tip surface 10a and on each ridge line 10h formed by the tip surface 10a.

[0062] In the case of (4), the particles 53 (particle region 53R) may be present along the mask layer 30 on at least one of the main surfaces 10c and 10d and the side surfaces 10e and 10f of the anode 10, but it is preferable that the particles 53 be present along the mask layer 30 on each of these surfaces. In this case, it is preferable that there is no gap between the particle region 53R and the mask layer 30, and the particle region 53R is preferably arranged alongside the mask layer 30 while being in contact with the mask layer 30. Furthermore, although gaps may occur between the first layer 51 and the mask layer 30 when only the first layer 51 is present, it is preferable that the particle region 53R fills the gaps between the first layer 51 and the mask layer 30.

[0063] The shape of the particles 53 is not particularly limited, and examples thereof include spherical, ellipsoidal, and irregular shapes.

[0064] In either case, the shape of the particle region 53R is not particularly limited, and examples include a shape in which the peripheral contour line is composed of multiple straight lines that are perpendicular to each other, as shown in Figure 3, a shape in which at least two of the straight lines of the peripheral contour line intersect diagonally, and a shape in which at least one of the straight lines of the peripheral contour line is curved.

[0065] Examples of materials that can be used to form the solid electrolyte layer 50 include conductive polymers having a main chain, such as polypyrrole, polythiophene, and polyaniline. Among these, polythiophene is preferred, and poly(3,4-ethylenedioxythiophene), also known as PEDOT, is particularly preferred. The conductive polymers contain a dopant, such as polystyrene sulfonate (PSS).

[0066] 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 a method of applying a dispersion of a conductive polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric layer 20 and drying it. In particular, the method of forming a polymerized film of a conductive polymer using a liquid containing a polymerizable monomer is more likely to result in a thinner solid electrolyte layer 50 on the corners 10g and ridges 10h and 10j of the anode 10 and on the edge of the mask layer 30 than a method using a dispersion of a conductive polymer, thereby more effectively suppressing short circuits. That is, the first layer 51 and the second layer 52 are preferably formed, for example, by a method of forming a polymerized film of a conductive polymer such as poly(3,4-ethylenedioxythiophene) on the dielectric layer 20 using a liquid containing a polymerizable monomer such as 3,4-ethylenedioxythiophene. In this way, the first conductive polymer contained in the first layer 51 and the second conductive polymer contained in the second layer 52 may be the same conductive polymer (having the same main chain and dopant), or may be different conductive polymers (having different main chains or dopants at least in one direction).

[0067] The first layer 51 is preferably formed as 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, or the like.

[0068] The second layer 52 is preferably formed as an outer layer that covers the entire dielectric layer 20. The outer layer can be formed by, for example, a dipping method, sponge transfer, screen printing, a dispenser, inkjet printing, or the like.

[0069] For example, after forming the first layer 51, a dispersion of the particles 53 is applied to a predetermined region on the first layer 51, dried, and then the second layer 52 is formed, whereby the particles 53 are disposed in the second layer 52. As a method for applying the particles 53, inkjet printing is suitable in the above cases (1), (3), and (4), and a dipping method is suitable in the above case (2).

[0070] The conductive layer 60 is provided on the solid electrolyte layer 50. The conductive layer 60 covers substantially the entire area of ​​the solid electrolyte layer 50 and is in contact with the mask layer 30. The conductive layer 60 may be disposed up to just before the mask layer 30. The conductive layer 60 has a substantially constant thickness.

[0071] 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 containing carbon and a cathode conductor layer material.

[0072] 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.

[0073] The carbon paste can be applied by, for example, a dipping method, sponge transfer, screen printing, spray application, a dispenser, inkjet printing, or the like.

[0074] The cathode conductor layer is formed, for example, by a method of applying a conductive paste containing metal particles such as gold, silver, copper, or platinum and a resin to the surface of the solid electrolyte layer or the carbon layer and drying the paste. The cathode conductor layer is preferably a silver layer.

[0075] The conductive paste can be applied by, for example, a dipping method, sponge transfer, screen printing, spray application, a dispenser, inkjet printing, or the like.

[0076] [Method of manufacturing electrolytic capacitor elements] The following describes a method for manufacturing the electrolytic capacitor element 1. In the following example, a method for simultaneously manufacturing a plurality of electrolytic capacitor elements using a large valve metal substrate will be described.

[0077] FIG. 17 is a schematic diagram showing an example of a step of preparing a valve metal substrate on which a mask layer is formed.

[0078] As shown in Fig. 17, a valve metal base 11A having a dielectric layer 20 on its surface is prepared. The valve metal base 11A includes a plurality of element portions 12 and a support portion 13. Each element portion 12 has a rectangular shape and protrudes from the support portion 13. A mask layer 30 is formed on the dielectric layer 20 of each element portion 12.

[0079] First, the valve metal substrate 11A having a porous portion on the surface is cut by laser processing, punching, or the like, to form a shape including a plurality of element portions 12 and support portions 13.

[0080] Next, a mask layer 30 is formed on both main surfaces and both side surfaces of each element portion 12 along the short sides of each element portion 12 .

[0081] Thereafter, the valve metal substrate 11A is anodized to form an oxide film that will become the dielectric layer 20 on the surface of the valve metal substrate 11A. At this time, an oxide film is also formed on the side surfaces of the element portions 12 that have been cut by laser processing, punching, or the like. Note that a chemically formed foil on which an oxide of the valve metal has already been formed may also be used as the valve metal substrate 11A. In this case, an oxide film is also formed on the side surfaces of the cut element portions 12 by anodizing the valve metal substrate 11A after cutting.

[0082] FIG. 18 is a schematic diagram showing an example of a process for forming the first and second solid electrolyte layers.

[0083] A first layer 51 (see FIG. 3, etc.) of the solid electrolyte layer 50 is formed on the dielectric layer 20 of the element section 12. As shown in FIG. 18, the treatment liquid for forming the first layer 51 is preferably applied to the valve metal base 11A by a dipping method. FIG. 18 shows a state in which a treatment liquid 70 for forming the first layer 51 or a treatment liquid 71 for forming the second layer is supplied to a treatment tank 75.

[0084] The treatment liquid 70 for forming the first layer 51 may be, for example, a liquid containing a polymerizable monomer, such as 3,4-ethylenedioxythiophene, and an oxidant, such as iron(III) paratoluenesulfonate. The liquid containing the polymerizable monomer may be applied to the outer surface of the dielectric layer 20, and a film containing the first conductive polymer may be formed by chemical polymerization. Alternatively, the treatment liquid 70 for forming the first layer 51 may be a dispersion liquid of the first conductive polymer. The dispersion liquid of the first conductive polymer may be applied to the outer surface of the dielectric layer 20 and dried to form a conductive polymer film. This conductive polymer film becomes the first layer 51 of the solid electrolyte layer 50.

[0085] 18, the valve metal substrate 11A is immersed in the treatment liquid 70, whereby the treatment liquid 70 is impregnated into the porous portion of the valve metal substrate 11A. After immersion for a predetermined time, the valve metal substrate 11A is removed from the treatment liquid 70 and dried at a predetermined temperature for a predetermined time. The process of immersion in the treatment liquid 70, removal, and drying may be repeated a predetermined number of times. As a result, the first layer 51 of the solid electrolyte layer 50 is formed.

[0086] For example, the valve metal substrate 11A is immersed in a liquid containing a polymerizable monomer (which may be a first dispersion liquid containing a first conductive polymer), pulled out, and then dried to form the first layer 51 as an inner layer (a portion provided on the dielectric layer 20 and filling the pores of the valve metal substrate 11) of the solid electrolyte layer 50. The immersion in the liquid containing a polymerizable monomer, the pulling out, and the drying may be performed multiple times.

[0087] After forming the first layer 51, 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. When the primer layer is formed, the valve metal substrate 11A is washed with pure water to remove excess primer compound. After washing, a drying process is performed.

[0088] FIG. 19 is a schematic diagram showing an example of a step of arranging particles.

[0089] After forming the first layer 51 of the solid electrolyte layer 50, particles 53 (see FIG. 6, etc.) are arranged in a predetermined region on the first layer 51. For example, as shown in FIG. 19, a dispersion of particles 53 is applied to the first layer 51 by a dipping method. FIG. 19 shows a state in which a dispersion 72 of particles 53 is supplied to a treatment tank 76. Note that the dispersion 72 of particles 53 may contain additives other than the particles 53 to improve or stabilize the dispersibility.

[0090] The solvent for the dispersion liquid 72 of the particles 53 is not particularly limited, and examples thereof include water, ethanol, and 2-propanol.

[0091] The concentration of particles 53 in dispersion 72 of particles 53 is preferably 1% by weight or more and 50% by weight or less, more preferably 5% by weight or more and 40% by weight or less, and even more preferably 10% by weight or more and 30% by weight or less.

[0092] As shown in Fig. 19, by immersing the tip of the valve metal substrate 11A in the dispersion liquid 72, the dispersion liquid 72 adheres to the outer surface of the first layer 51. After immersion for a predetermined time, the valve metal substrate 11A is pulled out of the dispersion liquid 72 and dried at a predetermined temperature for a predetermined time. The process of immersion in the dispersion liquid 72, pulling out, and drying may be repeated a predetermined number of times. As a result, the particles 53 are arranged in the particle region 53R as shown in Fig. 6.

[0093] Alternatively, the particles 53 may be arranged in a predetermined region by ejecting the dispersion 72 of the particles 53 onto the outer surface of the first layer 51 by spray coating or inkjet printing. This allows the particles 53 to be arranged in the particle region 53R as shown in FIGS. 3, 9, and 12.

[0094] After the particles 53 are arranged, the second layer 52 (see FIG. 3, etc.) of the solid electrolyte layer 50 is formed on the first layer 51 and the particles 53. For example, as shown in FIG. 18, it is preferable to apply a treatment liquid 71 for forming the second layer 52 to the first layer 51 and the particles 53 by a dipping method. The presence of the particles 53 makes it easier for the treatment liquid to remain there, so the film thickness of the second layer 52 in the particle region 53R can be increased.

[0095] The treatment liquid 71 for forming the second layer 52 may be, for example, a liquid containing a polymerizable monomer, such as 3,4-ethylenedioxythiophene, and an oxidant, such as iron(III) paratoluenesulfonate. The liquid containing the polymerizable monomer may be applied to the first layer 51 and the outer surfaces of the particles 53, and a film containing the second conductive polymer may be formed by chemical polymerization. Alternatively, the treatment liquid 71 for forming the second layer 52 may be a dispersion liquid of the second conductive polymer. The dispersion liquid of the second conductive polymer may be applied to the first layer 51 and the outer surfaces of the particles 53, and then dried to form a conductive polymer film. This conductive polymer film becomes the second layer 52 of the solid electrolyte layer 50.

[0096] 18, by immersing the valve metal substrate 11A in the treatment liquid 71, the treatment liquid 71 adheres to the first layer 51 and the outer surfaces of the particles 53. After immersion for a predetermined time, the valve metal substrate 11A is removed from the treatment liquid 71 and dried at a predetermined temperature for a predetermined time. The process of immersion in the treatment liquid 71, removal, and drying may be repeated a predetermined number of times. As a result, the second layer 52 of the solid electrolyte layer 50 is formed.

[0097] For example, the valve metal substrate 11A is immersed in a liquid containing a polymerizable monomer (which may be a dispersion liquid containing a second conductive polymer), pulled out, and then dried to form the second layer 52 as the outer layer (the portion connected to the inner layer and covering the entire dielectric layer 20) of the solid electrolyte layer 50. The immersion in the liquid containing a polymerizable monomer, the pulling out, and the drying may be performed multiple times.

[0098] As a result of the above, the first layer 51 and the second layer 52 of the solid electrolyte layer 50 are formed in predetermined regions, and the particles 53 are partially arranged within the surface of the second layer 52.

[0099] After the solid electrolyte layer 50 is formed, the valve metal substrate 11A is immersed in the carbon paste, pulled out, and dried to form a carbon layer in a predetermined region.

[0100] After the carbon layer is formed, the valve metal substrate 11A is immersed in a conductive paste containing metal particles such as silver paste, and then pulled out and dried to form a cathode conductor layer in a predetermined region.

[0101] Then, the valve metal substrate 11A is cut to separate the element portion 12, and the strip-shaped anode 10 is formed, with the cut surface serving as the base end surface 10b.

[0102] Through the above steps, the electrolytic capacitor element 1 is obtained.

[0103] (Embodiment 2) [Electrolytic capacitor element] Fig. 20 is a perspective view schematically illustrating an example of an electrolytic capacitor element according to Embodiment 2 of the present invention. Fig. 21 is a cross-sectional view taken along line JJ of the electrolytic capacitor element shown in Fig. 20. Fig. 22 is a cross-sectional view taken along line KK of the electrolytic capacitor element shown in Fig. 20. Note that Figs. 20, 21, and 22 show the state before the conductive layer 60 of the cathode 40 is formed, and the particle region 53R where the particles 53 exist is hatched. Furthermore, Fig. 20 does not illustrate the dielectric layer 20, and also shows a see-through state of the members inside the second layer 52 of the solid electrolyte layer 50.

[0104] 20, 21, and 22, the solid electrolyte layer 50 is provided on the dielectric layer 20 and has a first layer 51 containing a first conductive polymer, and a second layer 52 provided on the first layer 51 and containing a second conductive polymer and particles 53 having an average particle size of 0.1 μm or more and 10 μm or less, as in the first embodiment. However, unlike the first embodiment, the particles 53 are present in greater numbers within the plane of the second layer 52, the closer they are to the periphery of the second layer 52. This makes it possible to prevent short circuits while suppressing an increase in the equivalent series resistance of the electrolytic capacitor element 2. The reason (action) for obtaining this effect is thought to be as follows. That is, it is believed that the inclusion of particles 53 having the above average particle diameter in the second layer 52 disperses stress during reflow and improves the mechanical strength of the second layer 52. In the electrolytic capacitor element 2, the particles 53 are present in greater numbers closer to the outer periphery of the second layer 52 within the plane of the second layer 52. This allows the particles 53 to be preferentially placed in locations where stress tends to concentrate and short circuits are likely to occur during reflow (such as corners of the anode 10). Furthermore, the presence of particles 53 facilitates film formation, allowing the thickness of the solid electrolyte layer 50 to be increased in locations where short circuits are likely to occur (such as corners of the anode 10). As a result, the occurrence of short circuits is suppressed. On the other hand, the particles 53 may increase the equivalent series resistance due to insulation resistance. However, in the electrolytic capacitor element 2, the particles 53 are present in greater numbers closer to the periphery of the second layer 52 within the plane of the second layer 52 and are present in fewer numbers closer to the center of the second layer 52, thereby preventing an increase in the equivalent series resistance of the entire electrolytic capacitor element 2. From the above, it is believed that it is possible to prevent short circuits while suppressing an increase in the equivalent series resistance of the entire electrolytic capacitor element 2.

[0105] Here, "the particles are present in greater numbers closer to the periphery of the second layer within the plane of the second layer" means the following case: In SEM photographs of two orthogonal cross sections (for example, two cross sections that are parallel to two intersecting sides (for example, the long and short sides) of the anode 10 and pass through the center 52c of the second layer 52) as shown in Figures 21 and 22, the number of particles per unit area is measured at five points, including both end portions, the center, and an intermediate portion between them, and the number decreases in the order of one end portion, one intermediate portion, and the center, and increases in the order of the center, the other intermediate portion, and the other end portion.

[0106] Furthermore, on each main surface 10c, 10d side of the anode 10, the particles 53 are present in greater numbers (greater number per unit area) the closer they are to the tip surface 10a and each side surface 10e, 10f of the anode 10 and the mask layer 30 from the center 52c of the second layer 52 (the center of the main surface of the second layer 52). The particles 53 may be present at the center 52c of the second layer 52 and its vicinity, or may not be substantially present at the center 52c of the second layer 52 and its vicinity.

[0107] FIG. 23 is an enlarged cross-sectional view of the particle region of the electrolytic capacitor element shown in FIG.

[0108] In this embodiment, as shown in FIG. 16, the particles 53 are disposed on the first layer 51 and are not substantially present in the pores of the valve metal substrate 11. The particles 53 may be directly covered by the second layer 52 (second conductive polymer), or may be covered by a coating layer made of the first conductive polymer and then indirectly covered by the second layer 52 (second conductive polymer) as shown in FIG. 23. In either case, the particles 53 are embedded (incorporated) in the second layer 52 and covered by the second layer 52 (second conductive polymer). However, from the viewpoint of device characteristics, the state shown in FIG. 16 is preferable. The particles 53 are unevenly distributed toward the first layer 51 in the thickness direction of the second layer 52. That is, the particles 53 may be attached to the outer surface of the first layer 51, and the second layer 52 may cover them. In the case shown in FIG. 23, some of the particles 53 a having a particle diameter smaller than the pore diameter of the valve metal substrate 11 may enter the pores of the valve metal substrate 11 .

[0109] The particles 53 are arranged in the second layer 52, for example, by forming the first layer 51, applying a dispersion of the particles 53 to a predetermined area on the first layer 51, drying it, and then forming the second layer 52.

[0110] [Method of manufacturing electrolytic capacitor elements] The following describes a method for manufacturing the electrolytic capacitor element 2. The electrolytic capacitor element 2 can be manufactured in the same manner as in the first embodiment, except that the process for forming the solid electrolyte layer 50 is different.

[0111] Fig. 24 is a schematic diagram showing an example of a process of immersing a valve action metal substrate on which a mask layer has been formed into a particle dispersion liquid, and Fig. 25 is a schematic diagram showing an example of a process of pulling the valve action metal substrate out of the particle dispersion liquid and drying the particle dispersion liquid.

[0112] In this embodiment, after forming the first layer 51 of the solid electrolyte layer 50 in the same manner as in the first embodiment, the valve action metal substrate 11A is immersed in a dispersion 72 of particles 53 until it comes into contact with the mask layer 30, as shown in Fig. 24. The dispersion 72 is supplied to a treatment tank 76.

[0113] Next, the valve metal substrate 11A is pulled out of the dispersion liquid 72, and the dispersion liquid 72 is dried. In this drying step, as shown in FIG. 25, the valve metal substrate 11A is dried in a state in which it is turned upside down from when it was immersed. That is, it is dried with the element portion 12 on top and the support portion 13 on the bottom. As a result, due to the coffee ring effect, the particles 53 are arranged on the first layer 51 so that the closer to the periphery of the first layer 51, the more numerous they are.

[0114] In this method, the solvent of the dispersion liquid 72 is not particularly limited, and examples thereof include water, ethanol, and 2-propanol.

[0115] Furthermore, in this method, the concentration of particles 53 in the dispersion liquid 72 is preferably 1% by weight or more and 50% by weight or less, more preferably 5% by weight or more and 40% by weight or less, and even more preferably 10% by weight or more and 30% by weight or less.

[0116] Thereafter, the second layer 52 of the solid electrolyte layer 50 is formed in the same manner as in the first embodiment, thereby forming the solid electrolyte layer 50 in the state shown in FIG.

[0117] Fig. 26 is a schematic diagram showing an example of a process of immersing a valve metal substrate on which a mask layer has been formed in a particle-containing first layer-forming treatment liquid, and Fig. 27 is a schematic diagram showing an example of a process of pulling the valve metal substrate out of the particle-containing first layer-forming treatment liquid and drying the treatment liquid.

[0118] 26 , the valve metal substrate 11A having the mask layer 30 formed on the dielectric layer 20 may be immersed in a treatment liquid 73 having particles 53 dispersed therein for forming the first layer 51 until the valve metal substrate 11A comes into contact with the mask layer 30. The treatment liquid 73 is supplied to a treatment tank 76.

[0119] Subsequently, the anode 10 may be removed from the treatment solution 73, and the treatment solution 73 may be dried. In this drying process, as shown in FIG. 27, the valve metal substrate 11A is dried in a state in which it is inverted from when it was immersed. That is, the valve metal substrate 11A is dried with the element portion 12 facing up and the support portion 13 facing down. As a result, the first layer 51 is formed, and due to the coffee ring effect, the particles 53 are arranged on the valve metal substrate 11A so that the particles 53 are more numerous near the outer periphery of the support portion 13. As shown in FIG. 23, the pores of the valve metal substrate 11 are filled with the first conductive polymer constituting the first layer 51, and the surfaces of the particles 53 are coated with the first conductive polymer. Note that the particles 53 are present on the first layer 51, except for particles 53a whose particle diameter is smaller than the pore diameter of the valve metal substrate 11.

[0120] According to this method, the formation of the first layer 51 and the arrangement of the particles 53 can be carried out simultaneously, and therefore, the productivity is excellent.

[0121] In this method, the solvent of the treatment liquid 73 is not particularly limited, and examples thereof include 1-butanol, 2-butanol, and ethanol.

[0122] Furthermore, in this method, the concentration of particles 53 in the treatment liquid 73 is preferably 0.1% by weight or more and 20% by weight or less, more preferably 0.3% by weight or more and 10% by weight or less, and even more preferably 0.5% by weight or more and 5% by weight or less.

[0123] Thereafter, the second layer 52 of the solid electrolyte layer 50 is formed in the same manner as in the first embodiment, thereby forming the solid electrolyte layer 50 in the state shown in FIG.

[0124] [Electrolytic capacitor] An example of an electrolytic capacitor including the electrolytic capacitor element of the present invention will be described below. The electrolytic capacitor element of the present invention may be included in an electrolytic capacitor having a different configuration. For example, a lead frame may be used as an external electrode. The electrolytic capacitor may also include an electrolytic capacitor element other than the electrolytic capacitor element of the present invention (i.e., an electrolytic capacitor element having a structure different from that of the electrolytic capacitor element of the present invention).

[0125] Fig. 28 is a perspective view schematically illustrating an example of an electrolytic capacitor including an electrolytic capacitor element according to an embodiment of the present invention, and Fig. 29 is a cross-sectional view taken along line ZZ of the electrolytic capacitor shown in Fig. 28.

[0126] 28 and 29, the length direction of electrolytic capacitor 100 and package 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.

[0127] 28 and 29, the electrolytic capacitor 100 has a substantially rectangular parallelepiped outer shape. The electrolytic capacitor 100 is a solid electrolytic capacitor and includes an outer casing 110, a first external electrode 120, a second external electrode 130, and a plurality of electrolytic capacitor elements 1. Note that electrolytic capacitor 100 may include at least one electrolytic capacitor element 2 instead of at least one electrolytic capacitor element 1, but the following description will be given of a case where only electrolytic capacitor element 1 is included as the electrolytic capacitor element.

[0128] The exterior body 110 seals a plurality of electrolytic capacitor elements 1. That is, a plurality of electrolytic capacitor elements 1 are embedded in the exterior body 110. However, the exterior body 110 may seal a single electrolytic capacitor element 1. That is, a single electrolytic capacitor element 1 may be embedded inside the exterior body 110.

[0129] The exterior body 110 has a substantially rectangular parallelepiped outer 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.

[0130] As described above, exterior body 110 has a substantially rectangular parallelepiped outer shape, but it is preferable that the corners and ridges are rounded.

[0131] The exterior body 110 is made of, for example, a sealing resin.

[0132] The sealing resin contains at least a resin, and preferably contains a resin and a filler.

[0133] As the resin, epoxy resin, phenol resin, polyimide resin, silicone resin, polyamide resin, liquid crystal polymer, etc. are preferably used.

[0134] As the filler, silica particles, alumina particles, etc. are preferably used.

[0135] As the sealing resin, a material containing a solid epoxy resin, a phenolic resin, and silica particles is preferably used.

[0136] When a solid sealing resin is used, resin molding such as compression molding or transfer molding is preferably used, with compression molding being more preferred. When a liquid sealing resin is used, molding methods such as dispensing or printing are preferably used. Among these, compression molding is preferred to seal the periphery of the electrolytic capacitor element 1 with the sealing resin to form the exterior body 110.

[0137] 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 forms the second main surface 110b of the exterior body 110. The thickness of the substrate is, for example, 100 μm.

[0138] The multiple electrolytic capacitor elements 1 are stacked in the height direction T via a conductive adhesive 140. The extending direction of each of the multiple electrolytic capacitor elements 1 is approximately parallel to the first main surface 110a and the second main surface 110b of the exterior body 110. The electrolytic capacitor elements 1 are bonded to each other via the conductive adhesive 140.

[0139] The conductive adhesive 140 contains, for example, metal particles such as gold, silver, copper, platinum, etc., 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.

[0140] The first external electrode 120 is provided on the first end surface 110e of the exterior package 110. In FIG. 28 , the first external electrode 120 is provided from the first end surface 110e of the exterior package 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 electrolytic capacitor element 1 that is exposed from the exterior package 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 package 110.

[0141] The second external electrode 130 is provided on the second end surface 110f of the package 110. In FIG. 28, the second external electrode 130 is provided from the second end surface 110f of the package 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 substrate 11) of the electrolytic capacitor element 1 exposed from the package 110 at the second end surface 110f. The second external electrode 130 may be directly or indirectly connected to the anode 10 (valve metal substrate 11) at the second end surface 110f of the package 110.

[0142] 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.

[0143] 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 exterior body 110 is improved, thereby improving reliability.

[0144] 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 exterior body 110 is improved, thereby improving reliability.

[0145] The conductive component preferably contains, as a main component, a metal such as silver, copper, nickel, or tin, or an alloy containing at least one of these metals.

[0146] The resin component preferably contains an epoxy resin, a phenolic resin, or the like as a main component.

[0147] The resin electrode layer is formed by, for example, a dip coating method, a screen printing method, a transfer method, an inkjet printing method, a dispensing method, a spray coating method, a brush coating method, a drop casting method, an electrostatic coating method, or the like. Among these, the resin electrode layer is preferably a printed resin electrode layer formed by applying a conductive paste by a screen printing method. When the resin electrode layer is formed by applying a conductive paste by a screen printing method, the 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.

[0148] When the first external electrode 120 has a resin electrode layer, the first external electrode 120 and the cathode conductor layer both contain a resin component, which increases the adhesion between the first external electrode 120 and the cathode conductor layer, thereby improving reliability.

[0149] 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 to provide, in this order (or with some of the plating layers removed), a copper plating layer, a nickel plating layer, and a tin plating layer, for example.

[0150] 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 substrate 11) and an outer plating layer provided on the surface of the resin electrode layer. Alternatively, the second external electrode 130 may have an inner plating layer connected to the anode 10 (valve metal substrate 11), a resin electrode layer provided so as to cover the inner plating layer, and an outer plating layer provided on the surface of the resin electrode layer.

[0151] In the above embodiment, the first layer 51 is disposed over the entire surface of the solid electrolyte layer 50. However, the first layer 51 may be disposed partially over the surface of the solid electrolyte layer 50. That is, the first layer 51 may be selectively disposed only in an area of ​​the surface of the solid electrolyte layer 50 where the second layer 52 is not disposed. In this case, inkjet printing is a suitable method for forming the first layer 51.

[0152] Furthermore, in the above embodiment, the electrolytic capacitor element 1 is described as a solid electrolytic capacitor using a conductive polymer as the electrolyte material, but the electrolytic capacitor element of the present invention may also be a so-called hybrid electrolytic capacitor element that uses an electrolytic solution in addition to a solid electrolyte such as a conductive polymer as the electrolyte material.

[0153] In the above embodiment, the electrolytic capacitor element 1 is used in a chip-type electrolytic capacitor 100, but the electrolytic capacitor element of the present invention may be used by being embedded in a package substrate included in a semiconductor device. Here, an example of the semiconductor device is a semiconductor composite device in which a voltage regulator (voltage control device) and a load are mounted on a package substrate.

[0154] (Comparative form) FIG. 30 is a plan view schematically showing an example of an electrolytic capacitor element according to a comparative embodiment of the present invention.

[0155] 30, in the electrolytic capacitor element according to the comparative example, the solid electrolyte layer 50X does not contain particles, and the solid electrolyte layer 50X tends to be thin on the edge portions 10Xa (e.g., corners and ridges) of the anode 10X where stress tends to concentrate, which makes it easy for short circuits to occur during reflow. [Example]

[0156] EXAMPLES Hereinafter, examples will be given that more specifically disclose the electrolytic capacitor element of the present invention, but the present invention is not limited to these examples.

[0157] Example 1 An aluminum foil with an etching layer on its surface was prepared as an anode (valve metal substrate), and a dielectric layer was formed on the surface of the aluminum foil by anodizing it by immersing it in an ammonium adipate aqueous solution. The average pore diameter of this anode (valve metal substrate) was measured by mercury intrusion porosimetry and was found to be 100 nm.

[0158] Next, a composition consisting of a soluble polyimidesiloxane and an epoxy resin was roller-transferred onto the aluminum foil on the surface of which a dielectric layer was formed, thereby forming mask layers on both main surfaces and both side surfaces of the foil via the dielectric layer.

[0159] Next, the aluminum foil 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. This chemically polymerized 3,4-ethylenedioxythiophene on the dielectric layer, forming the first layer of the solid electrolyte layer on the dielectric layer.

[0160] Next, only the tip (bottom end) of the aluminum foil was immersed in an aqueous slurry containing silica particles with a median diameter of 0.5 μm in the volume-based cumulative particle size distribution measured by dynamic light scattering (hereinafter referred to as the median diameter (D50) by dynamic light scattering), and then pulled out and dried in the same direction as the immersion, thereby partially distributing the silica particles on the first layer (see Figure 6).

[0161] Next, the aluminum foil was immersed in a mixture of iron(III) paratoluenesulfonate, 3,4-ethylenedioxythiophene, and 1-butanol up to just below the mask layer, then removed and dried. This chemically polymerized 3,4-ethylenedioxythiophene on the first layer, forming a second solid electrolyte layer that covered the first layer and the silica particles.

[0162] Next, a carbon layer and a silver layer were formed in this order to obtain an electrolytic capacitor element.

[0163] Four of the resulting electrolytic capacitor elements were stacked using a conductive adhesive to obtain a laminate. The laminate was then sealed using epoxy resin and diced using a dicer. A silver paste containing a resin component was then screen-printed onto the cathode and anode end faces of the sealed body to form external electrodes on the cathode and anode, yielding a finished electrolytic capacitor.

[0164] In addition, SEM images of the resulting electrolytic capacitor were taken, and the average particle size of the particles and the average pore size of the anode were measured by the above-mentioned method. As a result, the average particle size of the particles was 0.55 μm, and the average pore size of the anode was 0.12 μm.

[0165] Example 2 A finished electrolytic capacitor was obtained in the same manner as in Example 1, except that the solid electrolyte layer was formed as follows.

[0166] Specifically, an aluminum foil with a dielectric layer formed on its surface was immersed up to just below the mask layer in a mixture of iron(III) paratoluenesulfonate, 3,4-ethylenedioxythiophene, 1-butanol, and silica particles with a median diameter (D50) of 0.5 μm as determined by dynamic light scattering. The aluminum foil was then pulled out and dried upside down from the direction of immersion. This chemically polymerized 3,4-ethylenedioxythiophene on the dielectric layer, forming the first layer of a solid electrolyte layer on the dielectric layer, and the coffee ring phenomenon caused silica particles to be concentrated at the mask edge, tip (bottom end), and side of the aluminum foil.

[0167] Next, the aluminum foil was immersed in a mixture of iron(III) paratoluenesulfonate, 3,4-ethylenedioxythiophene, and 1-butanol up to just below the mask layer, then removed and dried. This chemically polymerized 3,4-ethylenedioxythiophene on the first layer, forming a second solid electrolyte layer that covered the first layer and the silica particles.

[0168] In addition, an SEM photograph of the resulting finished electrolytic capacitor was taken, and the average particle size of the particles was measured by the method described above, and the result was that the average particle size of the particles was 0.55 μm. The average pore size of the anode was the same as in Example 1.

[0169] Example 3 A finished electrolytic capacitor was obtained in the same manner as in Example 1, except that the solid electrolyte layer was formed as follows.

[0170] Specifically, an aluminum foil with a dielectric layer formed on its surface was immersed in a mixed solution of iron(III) paratoluenesulfonate, 3,4-ethylenedioxythiophene, and 1-butanol up to just below the mask layer, then pulled out and dried. This chemically polymerized 3,4-ethylenedioxythiophene on the dielectric layer, forming a first layer of a solid electrolyte layer on the dielectric layer.

[0171] Next, an aqueous dispersion slurry containing 3,4-polyethylenedioxythiophene·polystyrenesulfonate particles with a median diameter (D50) of 1 μm as determined by dynamic light scattering was selectively spray-coated only on each corner of the tip surface (bottom end) of the aluminum foil, and then dried, thereby partially disposing the 3,4-polyethylenedioxythiophene·polystyrenesulfonate particles on the first layer (see Figure 3).

[0172] Next, the aluminum foil was immersed in a mixture of iron(III) paratoluenesulfonate, 3,4-ethylenedioxythiophene, and 1-butanol up to just below the mask layer, then removed and dried. This chemically polymerized 3,4-ethylenedioxythiophene on the first layer, forming a second layer of solid electrolyte covering the first layer and the 3,4-polyethylenedioxythiophene-polystyrenesulfonic acid particles.

[0173] In addition, an SEM photograph of the resulting finished electrolytic capacitor was taken, and the average particle size of the particles was measured by the method described above, and the result was that the average particle size of the particles was 0.97 μm. The average pore size of the anode was the same as in Example 1.

[0174] Example 4 A completed electrolytic capacitor was obtained in the same manner as in Example 3, except that an aqueous dispersion slurry containing silica particles coated with 3,4-polyethylenedioxythiophene-polystyrenesulfonic acid, which had a median diameter (D50) of 1 μm as measured by dynamic light scattering, was used instead of an aqueous dispersion slurry containing 3,4-polyethylenedioxythiophene-polystyrenesulfonic acid particles, which had a median diameter (D50) of 1 μm as measured by dynamic light scattering.

[0175] In addition, an SEM photograph of the resulting finished electrolytic capacitor was taken, and the average particle size of the particles was measured by the method described above, and the result was that the average particle size of the particles was 1.01 μm. The average pore size of the anode was the same as in Example 1.

[0176] (Comparative Example 1) A finished electrolytic capacitor was obtained in the same manner as in Example 1, except that silica particles were not disposed. The average pore size of the anode was the same as in Example 1.

[0177] (Comparative Example 2) A completed electrolytic capacitor was obtained in the same manner as in Example 1, except that the entire area below the aluminum foil mask layer was immersed in an aqueous dispersion slurry containing silica particles with a median diameter (D50) of 0.5 μm as determined by dynamic light scattering. In other words, the aqueous dispersion slurry was dried without turning the substrate upside down from the immersion direction. In this comparative example, the coffee ring phenomenon did not occur, and the particles were uniformly distributed on the first layer of the solid electrolyte layer. Therefore, after the second layer of the solid electrolyte layer was formed, the particles were uniformly distributed within the surface of the second layer.

[0178] In addition, an SEM photograph of the resulting finished electrolytic capacitor was taken, and the average particle size of the particles was measured by the method described above, and the result was that the average particle size of the particles was 0.55 μm. The average pore size of the anode was the same as in Example 1.

[0179] The equivalent series resistance (ESR) of the finished product and the incidence of short circuits during reflow were evaluated for the electrolytic capacitors obtained in Examples 1 to 4 and Comparative Examples 1 and 2. The results are shown in Table 1 below. The ESR indicates a relative value to the ESR of the electrolytic capacitor obtained in Comparative Example 1.

[0180] [Table 1]

[0181] In Example 1, since particles were present at the tip (including each corner) of the aluminum foil, the second layer (outer layer) of the solid electrolyte layer was formed thick, and the particles also increased the mechanical strength of the corners of the aluminum foil, so the occurrence of short circuits during reflow was suppressed compared to Comparative Example 1. Furthermore, since the area in which the silica particles were arranged was smaller than in Comparative Example 2, the increase in ESR due to the insulation resistance of the silica particles was also suppressed. In Example 2, the formation of the first layer (inner layer) of the solid electrolyte layer and the arrangement of the particles could be performed at the same time, improving productivity. In Examples 3 and 4, the use of conductive particles enabled the suppression of the increase in ESR. [Explanation of symbols]

[0182] 1, 2 Electrolytic capacitor element 10, 10X anode 10a Tip surface 10b Proximal surface 10c, 10d main surface 10e, 10f side 10g corner 10h, 10ha, 10j ridgeline area 10Xa Edge 11, 11A Valve metal substrate 12 Element section 13 Support part 20 dielectric layer 30 mask layers 40 cathode 50, 50X solid electrolyte layer 51 1st layer 52 2nd layer 52c center 53 particles 53a particle 53R particle area 60 Conductive layer 70, 71, 73 Processing liquid 72 Particle dispersion 75, 76 Treatment tank 100 Solid electrolytic capacitor 110 Exterior body 110a 1st main surface 110b 2nd principal surface 110c 1st side 110d 2nd side 110e 1st end face 110f 2nd end face 120 1st external electrode 130 2nd external electrode 140 Conductive adhesive

Claims

1. an anode constructed from a valve metal substrate and having a distal end surface and a proximal end surface; a dielectric layer provided on at least one main surface 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; a cathode provided on the dielectric layer on the front end surface side of the mask layer, the cathode has a solid electrolyte layer provided on the dielectric layer and a conductive layer provided on the solid electrolyte layer, the solid electrolyte layer includes: a first layer provided on the dielectric layer and including a first conductive polymer; and a second layer provided on the first layer and including a second conductive polymer and particles having an average particle size of 0.1 μm or more and 10 μm or less; The particles are partially disposed within the plane of the second layer.

2. the anode has six surfaces, including the tip surface, the base surface, a pair of main surfaces, and a pair of side surfaces, and has a corner portion where three of the six surfaces intersect, and a ridge portion where two of the six surfaces intersect, The electrolytic capacitor element according to claim 1 , wherein the particles are present at corners defined by the tip surfaces.

3. The electrolytic capacitor element according to claim 2 , wherein the particles are further present on the tip surfaces and on ridges formed by the tip surfaces.

4. 4. The electrolytic capacitor element according to claim 2, wherein the particles are further present on each of the side surfaces and on a ridge portion formed by each of the side surfaces.

5. 3. The electrolytic capacitor element according to claim 1, wherein the particles are present along the mask layer.

6. an anode constructed from a valve metal substrate and having a distal end surface and a proximal end surface; a dielectric layer provided on at least one main surface 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; a cathode provided on the dielectric layer on the front end surface side of the mask layer, the cathode has a solid electrolyte layer provided on the dielectric layer and a conductive layer provided on the solid electrolyte layer, the solid electrolyte layer includes: a first layer provided on the dielectric layer and including a first conductive polymer; and a second layer provided on the first layer and including a second conductive polymer and particles having an average particle size of 0.1 μm or more and 10 μm or less; An electrolytic capacitor element, wherein the particles are present in greater numbers within the plane of the second layer as they approach the periphery of the second layer.

7. The electrolytic capacitor element according to claim 1 , wherein the particles have an average particle size larger than an average pore size of the anode.

8. The electrolytic capacitor element according to claim 1 , wherein the particles are unevenly distributed on the first layer side in the thickness direction of the second layer.

9. 10. The electrolytic capacitor element according to claim 1, wherein the particles are made of a conductive polymer.

10. 10. The electrolytic capacitor element according to claim 1, wherein the particles are made of an insulating material.

11. 7. The electrolytic capacitor element according to claim 1, wherein the particles are composed of a composite of a conductive polymer and insulating particles.

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