Solid electrolytic capacitors

Abstract

To provide a solid electrolytic capacitor that can suppress performance degradation even if cracks occur in the dielectric. [Solution] A solid electrolytic capacitor 1 containing a solid electrolyte comprises a first electrode 10, a second electrode 20, a dielectric 30 located between the first electrode 10 and the second electrode 20, and a humidity control agent 40, wherein the humidity control agent 40 contains crosslinked polymer particles containing polyacrylic acid.

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolytic capacitor. [Background Art]

[0002] A solid electrolytic capacitor using a solid electrolyte is known (for example, Patent Document 1). The solid electrolytic capacitor includes an anode, a cathode, a dielectric disposed between the anode and the cathode, and the solid electrolyte. For example, a conductive polymer is used as the solid electrolyte. In this case, the conductive polymer is used as a part of the cathode so as to be in contact with the dielectric, for example.

[0003] The solid electrolytic capacitor having such a configuration can achieve low ESR (Equivalent Series Resistance) and high capacitance density due to the high electrical conductivity of the conductive polymer. [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2001-196277 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] However, in conventional solid electrolytic capacitors, cracks may occur in the dielectric, leading to degradation in the performance of the solid electrolytic capacitor.

[0006] The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide a solid electrolytic capacitor that can suppress performance degradation even when cracks occur in the dielectric. [Means for Solving the Problem]

[0007] To achieve the above objective, one embodiment of a solid electrolytic capacitor according to the present disclosure is a solid electrolytic capacitor comprising a solid electrolyte, a first electrode, a second electrode, a dielectric located between the first electrode and the second electrode, and a humidity control agent, wherein the humidity control agent comprises crosslinked polymer particles containing polyacrylic acid. [Effects of the Invention]

[0008] According to this disclosure, it is possible to realize a solid electrolytic capacitor that can suppress performance degradation even if cracks occur in the dielectric. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an external perspective view of a solid electrolytic capacitor according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view of a solid electrolytic capacitor according to Embodiment 1. [Figure 3] Figure 3 is an enlarged cross-sectional view of a solid electrolytic capacitor according to Embodiment 1. [Figure 4] Figure 4 shows the moisture absorption and release properties of Sunfresh ST-500D, a water-absorbing polymer. [Figure 5] Figure 5 illustrates the situation when a crack occurs in the dielectric of a comparative example solid electrolytic capacitor. [Figure 6] Figure 6 is a diagram illustrating the state of a solid electrolytic capacitor according to Embodiment 1 when a crack occurs in the dielectric material. [Figure 7] Figure 7 is a partial cross-sectional perspective view of a solid electrolytic capacitor according to Embodiment 2. [Figure 8] Figure 8 is an external perspective view of a solid electrolytic capacitor according to Embodiment 3. [Figure 9] Figure 9 is a partial cross-sectional view showing a part of a solid electrolytic capacitor according to Embodiment 3. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the following embodiments are examples and are not intended to limit this disclosure. Accordingly, any components in the following embodiments that are not described in the independent claims representing the highest-level concepts of this disclosure will be described as optional components.

[0011] Please note that each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, the scale and other aspects may not necessarily be consistent across all figures. In addition, the same reference numerals are used for substantially identical components in each figure, and redundant explanations are omitted or simplified. Furthermore, in this specification, the terms "up" and "down" do not necessarily refer to the upward (vertically upward) and downward (vertically downward) directions in absolute spatial perception.

[0012] (Embodiment 1) First, the configuration of the solid electrolytic capacitor 1 according to Embodiment 1 will be described using Figures 1 to 3. Figure 1 is an external perspective view of the solid electrolytic capacitor 1 according to Embodiment 1. Figure 2 is a cross-sectional view of the solid electrolytic capacitor 1 according to Embodiment 1 along the line II-II in Figure 1. Figure 3 is an enlarged cross-sectional view of the solid electrolytic capacitor 1 according to Embodiment 1. Figure 3 shows a cross-sectional view of region III enclosed by the dashed line in Figure 2.

[0013] As shown in Figure 1, the solid electrolytic capacitor 1 according to this embodiment is a chip-type SMD (Surface Mount Device) electronic component. Specifically, the solid electrolytic capacitor 1 according to this embodiment is a molded type electronic component in which the capacitor element 2 is molded by an outer resin layer 5.

[0014] As shown in Figure 2, the solid electrolytic capacitor 1 includes a capacitor element 2, a first extraction electrode 3 and a second extraction electrode 4 electrically connected to the capacitor element 2, and an exterior resin layer 5 covering the capacitor element 2, the first extraction electrode 3 and the second extraction electrode 4.

[0015] The first extraction electrode 3 is an anode terminal connected to the first electrode 10 (anode) of the capacitor element 2. The first extraction electrode 3 and the first electrode 10 can be joined by resistance welding, laser welding or the like.

[0016] The second extraction electrode 4 is a cathode terminal connected to the second electrode 20 (cathode) of the capacitor element 2. The second extraction electrode 4 and the second electrode 20 are joined via a conductive layer 6 such as a conductive adhesive.

[0017] The first extraction electrode 3 and the second extraction electrode 4 are lead terminals led out from the capacitor element 2 to the outside of the exterior resin layer 5. In the present embodiment, the first extraction electrode 3 and the second extraction electrode 4 are lead frames bent into a predetermined shape. The first extraction electrode 3 and the second extraction electrode 4 are made of, for example, a metal material such as copper or aluminum, or an alloy thereof.

[0018] The exterior resin layer 5 covers the entire capacitor element 2. That is, the exterior resin layer 5 seals the capacitor element 2. The exterior resin layer 5 is an exterior member constituting an outer member of the solid electrolytic capacitor 1. In the present embodiment, the outer shape of the exterior resin layer 5 is a substantially rectangular parallelepiped. Therefore, the outer shape of the solid electrolytic capacitor 1 is also a substantially rectangular parallelepiped.

[0019] The exterior resin layer 5 covers a part of the first extraction electrode 3 and a part of the second extraction electrode 4. That is, a part of the first extraction electrode 3 and a part of the second extraction electrode 4 are exposed to the outside of the exterior resin layer 5.

[0020] The outer resin layer 5 is composed of a curable resin composition or a thermoplastic resin. As the curable resin, a resin that hardens or polymerizes with heat or light can be used. For example, as the curable resin, epoxy resin, phenolic resin, polyimide resin, polyamide-imide resin, or unsaturated polyester can be used. On the other hand, as the thermoplastic resin, polyphenylene sulfide (PPS) or polybutylene terephthalate (PBT) can be used. The outer resin layer 5 can be formed using molding techniques such as injection molding, insert molding, or compression molding.

[0021] Next, the specific structure of the capacitor element 2 in the solid electrolytic capacitor 1 will be described. The capacitor element 2 (capacitor element) comprises a first electrode 10, a second electrode 20, and a dielectric 30.

[0022] The first electrode 10 and the second electrode 20 constitute a pair of electrodes in the capacitor element 2. The first electrode 10 and the second electrode 20 face each other across the dielectric 30. In this embodiment, the first electrode 10 is the anode, and the second electrode 20 is the cathode.

[0023] The first electrode 10 is a metal electrode made of a metallic material. The first electrode 10 is made of valve metal (valve acting metal) or an alloy thereof. For example, the first electrode 10 is made of aluminum, tantalum, niobium, titanium, or an alloy thereof. In this embodiment, the first electrode 10 is an aluminum electrode with aluminum as the main component. In other words, the solid electrolytic capacitor 1 is an aluminum electrolytic capacitor.

[0024] In this embodiment, the first electrode 10 is a porous body. Specifically, the surface layer of the first electrode 10 has a porous structure. That is, the surface layer of the first electrode 10 has a fine uneven surface. The porous structure of the first electrode 10 can be formed by etching the metal body that constitutes the first electrode 10 or by sintering metal powder to produce the first electrode 10. The size of the holes (pores) in the porous structure of the first electrode 10 is, for example, 10 nm to 500 nm.

[0025] The first electrode 10 is a single-layer metal electrode consisting of one metal layer, but is not limited to this. For example, the first electrode 10 may be a laminated structure in which a metal layer and a conductive layer are laminated. In this case, the conductive layer may be a metal layer.

[0026] As shown in Figure 2, the second electrode 20 is provided on the side of the dielectric 30 opposite to the side of the first electrode 10. Specifically, the second electrode 20 is provided on the top, bottom, and side surfaces of the dielectric 30 so as to cover it. The second electrode 20 may also be separated into two parts, upper and lower.

[0027] The second electrode 20 is in contact with the dielectric 30. In this embodiment, the second electrode 20 has a solid electrolyte layer 21 and a conductive layer 22, and the solid electrolyte layer 21 is in contact with the dielectric 30.

[0028] The solid electrolyte layer 21 is located between the dielectric 30 and the conductive layer 22. Specifically, the solid electrolyte layer 21 is provided on the top, bottom, and side surfaces of the dielectric 30 so as to cover the dielectric 30. The solid electrolyte layer 21 is composed of a solid electrolyte. In this embodiment, the solid electrolyte layer 21 is composed of a conductive polymer. In other words, a conductive polymer is used as the solid electrolyte. Examples of conductive polymers include polypyrrole (PPy), polyaniline (PANI), polythiophene (PT), polyethylenedioxythiophene (PEDOT), poly-3-methylthiophene (P3MT), poly-3-hexylthiophene (P3HT), polyphenylene vinylene (PPV), polyfluorene (PFO), polyparaphenylene (PPP), or polythienylene vinylene (PTV). Thus, the second electrode 20 is composed of a material containing a conductive polymer. Therefore, the solid electrolytic capacitor 1 is a solid polymer capacitor.

[0029] The conductive layer 22 functions as a cathode extraction layer. The conductive layer 22 is provided on the top, bottom, and side surfaces of the solid electrolyte layer 21 so as to cover the solid electrolyte layer 21. In this embodiment, the conductive layer 22 has a first conductive layer 22a and a second conductive layer 22b laminated on the first conductive layer 22a. In other words, the conductive layer 22 has a laminated structure of the first conductive layer 22a and the second conductive layer 22b. The first conductive layer 22a and the second conductive layer 22b are in contact.

[0030] The first conductive layer 22a is located closer to the dielectric 30 (on the first electrode 10 side) than the second conductive layer 22b. In other words, the first conductive layer 22a is located between the second conductive layer 22b and the dielectric 30. On the other hand, the second conductive layer 22b is located closer to the outer resin layer 5 than the first conductive layer 22a. The second conductive layer 22b is in contact with the outer resin layer 5.

[0031] The first conductive layer 22a and the second conductive layer 22b are composed of conductive materials. In this embodiment, the first conductive layer 22a and the second conductive layer 22b are metal layers composed of metallic materials. Examples of metallic materials that constitute the first conductive layer 22a and the second conductive layer 22b include silver, nickel, copper, aluminum, tantalum, molybdenum, carbon (including graphite), or alloys thereof. The first conductive layer 22a and the second conductive layer 22b are composed of different metallic materials. In this embodiment, the first conductive layer 22a is a carbon paste layer composed of carbon paste, and the second conductive layer 22b is a silver paste layer composed of silver paste.

[0032] The dielectric 30 is the part of the capacitor element 2 that stores charge. The dielectric 30 is located between the first electrode 10 and the second electrode 20. The dielectric 30 is in contact with each of the first electrode 10 and the second electrode 20.

[0033] In this embodiment, the dielectric 30 is provided on the upper, lower, and side surfaces of the first electrode 10 so as to cover the first electrode 10. The dielectric 30 may also be separated into two parts, upper and lower.

[0034] The dielectric 30 is a thin dielectric layer (dielectric film). In this embodiment, the dielectric 30 is an oxide of the metal constituting the first electrode 10. Specifically, the dielectric 30, being a thin film, is an oxide film of the metal constituting the first electrode 10. More specifically, the dielectric 30 is an oxide film formed by anodizing the valve metal constituting the first electrode 10, and is formed over the entire surface of the first electrode 10. For example, if the first electrode 10 is made of aluminum, the dielectric 30 is an aluminum oxide film (Al2O3 film). Also, if the first electrode 10 is made of tantalum, the dielectric 30 is a tantalum oxide film (Ta2O5 film). In this embodiment, since the first electrode 10 is made of aluminum, the dielectric 30 is an aluminum oxide film. Specifically, the dielectric 30 is formed on the surface of the first electrode 10, which has a porous structure. Therefore, the dielectric 30 is an oxide film formed along the uneven shape of the porous structure, resulting in an uneven shape. In other words, the interface between the first electrode 10 and the dielectric 30 has an uneven shape that follows the uneven shape (pores) of the first electrode 10.

[0035] The dielectric 30 may be formed by methods other than anodic oxidation. For example, the dielectric 30 may be formed by atomic layer deposition (ALD). In this case, the dielectric 30 does not have to be an oxide of the metal constituting the first electrode 10. For example, an oxide film of a metal with a high dielectric constant, such as zirconia, may be formed as the dielectric 30 by ALD.

[0036] The capacitor element 2 configured in this way includes a humidity control agent 40, as shown in Figure 3. The humidity control agent 40 contains crosslinked polymer particles containing polyacrylic acid. Crosslinked polymer particles containing polyacrylic acid are an example of a superabsorbent polymer (SAP). Superabsorbent polymers are hygroscopic materials and have both moisture-releasing and moisture-absorbing functions. In other words, superabsorbent polymers have moisture absorption and release properties, such as releasing moisture into the surroundings or absorbing moisture from the surroundings. When the temperature rises, the moisture inside the superabsorbent polymer is more easily vaporized, promoting moisture release.

[0037] In particular, cross-linked polymer particles containing polyacrylic acid have a cross-linked structure within their molecules and possess high moisture absorption and release capabilities. In other words, cross-linked polymer particles containing polyacrylic acid have excellent moisture absorption capabilities that efficiently absorb moisture from the air and suppress the rise in ambient humidity, as well as excellent moisture release capabilities that release moisture and prevent the surrounding area from drying out.

[0038] Furthermore, cross-linked polymer particles containing polyacrylic acid can maintain their humidity control effect longer than common humidity control agents such as silica gel or charcoal. In addition, cross-linked polymer particles containing polyacrylic acid can absorb a large amount of moisture with a small amount and have a high moisture absorption capacity (water retention). Note that while humidity control agent 40 contains a polymer containing polyacrylic acid, it may also be the cross-linked polymer particles containing polyacrylic acid themselves.

[0039] As cross-linked polymer particles containing polyacrylic acid, for example, the superabsorbent polymers manufactured by Sanyo Chemical Industries, Ltd., as shown in Table 1 below, can be used.

[0040] [Table 1]

[0041] The superabsorbent polymers listed in Table 1 are all white powders with sodium polyacrylate as the main component. Furthermore, the superabsorbent polymers listed in Table 1 are partially sodium salt crosslinked polymers of acrylic acid and contain numerous carboxyl groups.

[0042] Both "Sunfresh ST-250" and "Sunfresh ST-500D" have a central particle size (D50) of 380 μm, but their water absorption capacity differs. The water absorption capacity of "Sunfresh ST-250" is 600 g / g, while that of "Sunfresh ST-500D" is 400 g / g. In Table 1, the water absorption capacity represents the amount of water absorbed relative to deionized water, indicating the amount of deionized water that 1 g of superabsorbent polymer can absorb. The water absorption capacity Q [g / g] is expressed by the formula Q = (Ws - Wd) / Wd, where Ws [g] is the weight of the superabsorbent polymer after water absorption and Wd [g] is the initial weight of the dried superabsorbent polymer.

[0043] "Sunfresh ST-500MPSA" has a smaller particle size than "Sunfresh ST-250" and "Sunfresh ST-500D". Specifically, the central particle size (D50) of "Sunfresh ST-500MPSA" is 30 μm. Also, the water absorption capacity of "Sunfresh ST-500MPSA" is the same as that of "Sunfresh ST-250", at 600 g / g.

[0044] Figure 4 shows an example of the moisture absorption and release properties of crosslinked polymer particles containing polyacrylic acid. Figure 4 shows the moisture absorption and release properties of "Sunfresh ST-500D" in Table 1. As shown in Figure 4, "Sunfresh ST-500D" repeatedly absorbs moisture and releases moisture over time. Crosslinked polymer particles containing polyacrylic acid will have the moisture absorption and release properties shown in Figure 4.

[0045] The humidity control agent 40, composed of cross-linked polymer particles containing polyacrylic acid, can be placed at any location on the capacitor element 2. As shown in Figure 3, in this embodiment, the humidity control agent 40 is placed on the second electrode 20. Specifically, the humidity control agent 40 is placed within the conductive layer 22 of the second electrode 20. More specifically, the humidity control agent 40, which is a cross-linked polymer particle, is dispersed in the first conductive layer 22a, which is a silver paste layer, and the second conductive layer 22b, which is a carbon paste layer.

[0046] In this case, by mixing the humidity control agent 40, which is a crosslinked particle, with silver paste and applying it, a first conductive layer 22a, which is a silver paste layer with multiple crosslinked particles dispersed inside, can be produced. Similarly, by mixing the humidity control agent 40, which is a crosslinked particle, with carbon paste and applying it, a second conductive layer 22b, which is a carbon paste layer with multiple crosslinked particles dispersed inside, can be produced.

[0047] Furthermore, the humidity control agent 40, which is composed of cross-linked polymer particles containing polyacrylic acid, is placed in the capacitor element 2 while bearing moisture. In other words, the humidity control agent 40, which has been pre-impregnated with moisture, is placed inside the capacitor element 2. Specifically, as described above, the humidity control agent 40 (cross-linked polymer particles containing polyacrylic acid) that bears moisture is dispersed in the conductive layer 22 of the second electrode 20.

[0048] Next, the effects of the solid electrolytic capacitor 1 according to this embodiment will be explained in comparison with the comparative example solid electrolytic capacitor 1X using Figures 5 and 6. Figure 5 is a diagram illustrating the state when a crack 30a occurs in the dielectric 30 of the comparative example solid electrolytic capacitor 1X. Figure 6 is a diagram illustrating the state when a crack 30a occurs in the dielectric 30 of the solid electrolytic capacitor 1 according to Embodiment 1. Note that Figures 5 and 6 correspond to the cross-sectional view in Figure 3.

[0049] The comparative example solid electrolytic capacitor 1X lacks the humidity control agent 40 compared to the solid electrolytic capacitor 1 according to Embodiment 1. Otherwise, the comparative example solid electrolytic capacitor 1X and the solid electrolytic capacitor 1 according to Embodiment 1 have the same configuration.

[0050] As shown in Figure 5(a), in the comparative example solid electrolytic capacitor 1X, air gap cracks 30a may occur inside the dielectric 30 of the capacitor element 2X due to stress caused by the voltage applied to the solid electrolytic capacitor 1X, mechanical shock (mechanical stress, vibration, etc.), or thermal shock (temperature change, etc.). When air gap cracks 30a occur in the dielectric 30, the first electrode 10 and the second electrode 20 that sandwich the dielectric 30 may short-circuit. The heat generated when this short-circuit occurs can insulate a part of the solid electrolyte layer 21 (specifically, the conductive polymer) in contact with the dielectric 30, as shown in Figure 5(b), and this insulator 50 may fill the air gap cracks 30a that have occurred in the dielectric 30. As a result, the capacitance of the capacitor element 2X in the solid electrolytic capacitor 1X decreases, or the ESR of the capacitor element 2X increases due to the cutting of π electrons in the conductive polymer constituting the solid electrolyte layer 21, thus degrading the performance of the solid electrolytic capacitor 1X.

[0051] In contrast, the solid electrolytic capacitor 1 in this embodiment includes a humidity control agent 40 containing crosslinked polymer particles that contain polyacrylic acid. Specifically, as shown in Figure 6(a), the humidity control agent 40 is placed within the conductive layer 22 of the second electrode 20 in the capacitor element 2. Furthermore, moisture is pre-supported in the humidity control agent 40, and the humidity control agent 40, which is composed of crosslinked polymer particles that contain polyacrylic acid, contains moisture.

[0052] As a result, as shown in Figure 6(a), when an air gap crack 30a occurs inside the dielectric 30 of the capacitor element 2 due to stress caused by the voltage applied to the solid electrolytic capacitor 1, mechanical shock, or thermal shock, the dielectric 30 self-repairs due to the moisture contained in the humidity control agent 40 and the crack 30a disappears. Specifically, when the first electrode 10 is made of aluminum and the dielectric 30 is made of aluminum oxide (Al2O3), the moisture contained in the humidity control agent 40 and the aluminum constituting the first electrode 10 react chemically according to the following equation (Equation 1) to produce aluminum oxide.

[0053] Al+H2O→Al2O3+H2...(Formula 1)

[0054] As a result, as shown in Figure 6(b), the generated aluminum oxide fills the cracks 30a in the air gap. In other words, the aluminum oxide generated by the moisture contained in the humidity control agent 40 becomes part of the dielectric 30 composed of aluminum oxide and fills the air gap.

[0055] Thus, in the solid electrolytic capacitor 1 of this embodiment, even if a crack 30a occurs in the dielectric 30, it self-repairs and the crack 30a disappears. In this case, for the solid electrolytic capacitor 1 equipped with a moisture-bearing humidity control agent 40, it is preferable that the humidity in the void portion inside the solid electrolytic capacitor 1 be maintained at 30% to 80%. This suppresses the occurrence of a hydration reaction due to too much moisture (humidity) inside the solid electrolytic capacitor 1, thereby ensuring the self-repair function of the dielectric 30 by the humidity control agent 40. Furthermore, from the viewpoint of ensuring the self-repair function, it is more preferable that the humidity in the void portion inside the solid electrolytic capacitor 1 be maintained at 40% to 60%.

[0056] As described above, the solid electrolytic capacitor 1 in this embodiment allows the dielectric 30 to self-repair even if a crack 30a occurs in the dielectric 30. This prevents a decrease in the capacitance of the capacitor element 2 or an increase in the ESR of the capacitor element 2 due to the formation of an insulator 50 in the crack 30a of the dielectric 30. Therefore, a solid electrolytic capacitor 1 can be realized that can suppress a decrease in performance even if a crack 30a occurs in the dielectric 30.

[0057] Furthermore, in this embodiment, the crosslinked polymer particles containing polyacrylic acid preferably have a portion of the polyacrylic acid neutralized, so that the crosslinked particles (humidity control agent 40) have the structure of an alkali metal salt of acrylic acid. This improves the moisture absorption and release functions of the crosslinked particles, thereby improving the functionality of the humidity control agent 40. In this case, it is preferable that the proportion of neutralized acrylic acid groups to the total acrylic acid groups be between 20% and 90%. This further improves the moisture absorption function of the crosslinked particles.

[0058] Furthermore, the crosslinking agent in the crosslinked particles preferably has ether bonds. This makes them less susceptible to hydrolysis compared to ester-based crosslinking agents, resulting in chemically stable crosslinked particles with high moisture absorption capabilities. In addition, crosslinked particles that do not deteriorate easily even after repeated moisture absorption and release cycles can be obtained.

[0059] Furthermore, the cross-linked particles constituting the humidity control agent 40 are preferably micro-cross-linked particles with a low cross-linking density. A low cross-linking density increases the degree of freedom of the polymer chains, making it easier for moisture to penetrate into the interior, thus improving the moisture absorption function of the cross-linked particles. Moreover, a low cross-linking density results in a faster moisture absorption rate, allowing for the absorption of a large amount of moisture in a short time.

[0060] The crosslinking density can be adjusted by changing the amount of bifunctional or more crosslinkable compounds during the production of crosslinked particles. The crosslinking density can be expressed by the following equation (2).

[0061] Crosslinking density (mol%) = 100 × number of moles of polymerizable functional groups of the crosslinkable compound with two or more functions / (number of moles of acrylic acid + number of moles of polymerizable functional groups of the crosslinkable compound with two or more functions) ... (Equation 2)

[0062] For example, the crosslinked particles are preferably micro-crosslinked particles with a crosslinking density of 0.01 mol% to 10 mol%, and even better, micro-crosslinked particles with a crosslinking density of 0.05 mol% to 5 mol%. If the crosslinking density of the crosslinked particles exceeds 10 mol%, the water absorption function of the crosslinked particles of the polymer containing polyacrylic acid decreases significantly. On the other hand, if the crosslinking density of the crosslinked particles is less than 0.01 mol%, the mechanical strength of the polymer in the crosslinked particles of the polymer containing polyacrylic acid weakens, making it difficult to handle as a humidity control agent 40.

[0063] Furthermore, the volume-average particle diameter of the cross-linked particles in the humidity control agent 40 is preferably between 10 μm and 500 μm, and even more preferably between 30 μm and 400 μm. By making the volume-average particle diameter of the cross-linked particles 10 μm or more, the surface area of ​​the cross-linked particles can be increased, thereby improving the moisture absorption and moisture release functions of the cross-linked particles. If the volume-average particle diameter of the cross-linked particles is less than 10 μm, the moisture absorption and moisture release functions of the cross-linked particles may be significantly reduced. On the other hand, if the volume-average particle diameter of the cross-linked particles exceeds 500 μm, the moisture absorption rate of the cross-linked particles may be significantly reduced. In this specification, "volume-average particle diameter" means the particle diameter at which the cumulative volume calculated from the smallest diameter side in the particle diameter distribution measured by laser diffraction becomes 50%.

[0064] In this embodiment, the humidity control agent 40 was placed in both the first conductive layer 22a, which is a silver paste layer, and the second conductive layer 22b, which is a carbon paste layer, but this is not limited to this. The humidity control agent 40 may be placed in only one of the first conductive layer 22a and the second conductive layer 22b. In other words, the humidity control agent 40 only needs to be placed in at least one of the first conductive layer 22a and the second conductive layer 22b.

[0065] Furthermore, in this embodiment, the humidity control agent 40 was placed in the conductive layer 22 of the second electrode 20, but it is not limited to this. In other words, the humidity control agent 40 may be placed in a part of the second electrode 20 other than the conductive layer 22. For example, the humidity control agent 40 may be placed in the solid electrolyte layer 21 of the second electrode 20. Also, the humidity control agent 40 may be placed at any part of the capacitor element 2 other than the second electrode 20, or at any part of the solid electrolytic capacitor 1 other than the capacitor element 2. For example, the humidity control agent 40 may be placed in the outer resin layer 5. However, it is preferable that the humidity control agent 40 be placed in a layer close to the dielectric 30, and in particular, in a layer in contact with the dielectric 30. This allows the dielectric 30 to efficiently self-repair due to the moisture contained in the humidity control agent 40.

[0066] (Embodiment 2) Next, the solid electrolytic capacitor 1A according to Embodiment 2 will be described with reference to Figure 7. Figure 7 is a partial cross-sectional perspective view of the solid electrolytic capacitor 1A according to Embodiment 2.

[0067] In the first embodiment described above, the solid electrolytic capacitor 1A was a chip-type electronic component in which the capacitor element 2 was molded by an outer resin layer 5. However, as shown in Figure 7, the solid electrolytic capacitor 1A according to this embodiment is a metal case-type electronic component in which the capacitor element 2A is housed in a metal case 7.

[0068] In this embodiment, the capacitor element 2A is constructed by winding a first electrode 10A, which is made of metal foil on which an oxide film as a dielectric 30 is formed as a dielectric on its surface by anodizing, with a separator 60 interposed between the two electrodes. Aluminum foil can be used as the metal foil constituting the first electrode 10A and the second electrode 20A. In this case, the dielectric 30 formed by anodizing the first electrode 10A becomes aluminum oxide.

[0069] The metal case 7 is an exterior component that covers the capacitor element 2A. For example, the metal case 7 is a bottomed cylindrical shape. The metal case 7 is, for example, an aluminum case made of aluminum.

[0070] The separator 60 is placed between the dielectric 30 and the second electrode 20A. The separator 60 is a paper separator. In this case, the separator 60 can be made of cellulose fiber paper or synthetic fiber paper, etc. The separator 60 has a porous structure. In this embodiment, the solid electrolyte layer 21 (not shown) is impregnated into the separator 60.

[0071] Furthermore, although not shown in the figures, in this embodiment as well, a humidity control agent 40 is placed on the capacitor element 2A. For example, the humidity control agent 40 is supported on the separator 60. Similar to Embodiment 1 above, the humidity control agent 40 contains crosslinked polymer particles containing polyacrylic acid and is supported on the separator 60 in a state containing moisture.

[0072] As described above, the solid electrolytic capacitor 1A in this embodiment, similar to Embodiment 1, comprises a first electrode 10A, a second electrode 20A, a dielectric 30 located between the first electrode 10A and the second electrode 20A, and a humidity control agent 40 containing crosslinked polymer particles containing polyacrylic acid.

[0073] With this configuration, similar to Embodiment 1 described above, even if an air gap crack occurs inside the dielectric 30 of the capacitor element 2A, the moisture contained in the humidity control agent 40 causes the dielectric 30 to self-repair and the crack disappears. This makes it possible to suppress a decrease in the capacitance of the capacitor element 2A or an increase in the ESR of the capacitor element 2A due to cracks in the dielectric 30. Therefore, it is possible to realize a solid electrolytic capacitor 1A that can suppress a decrease in performance even if cracks occur in the dielectric 30.

[0074] (Embodiment 3) Next, the solid electrolytic capacitor 1B according to Embodiment 3 will be described with reference to Figures 8 and 9. Figure 8 is an external perspective view of the solid electrolytic capacitor 1B according to Embodiment 3. Figure 9 is a partial cross-sectional view showing a part of the solid electrolytic capacitor 1B according to Embodiment 3.

[0075] As shown in Figure 8, the solid electrolytic capacitor 1B is a thin, sheet-like solid electrolytic capacitor, having an upper surface (top surface) called a first surface 1a and a lower surface (bottom surface) called a second surface 1b. The second surface 1b is the surface opposite the first surface 1a. Specifically, the first surface 1a and the second surface 1b are parallel.

[0076] As shown in Figure 9, the solid electrolytic capacitor 1B, similar to embodiments 1 and 2 described above, has a capacitor element 2B composed of at least a first electrode 10, a second electrode 20B, and a dielectric 30. Specifically, the solid electrolytic capacitor 1B comprises a first electrode 10, a second electrode 20B, a dielectric 30, a first extraction electrode 3B, a second extraction electrode 4B, and an insulating resin layer 5B. Note that the first extraction electrode 3B and the second extraction electrode 4B are not shown in Figure 8. The solid electrolytic capacitor 1B may have one capacitor element 2B or may have multiple capacitor elements 2B.

[0077] The second electrode 20B in the capacitor element 2B has a solid electrolyte layer 21 and a conductive layer 22B laminated on the solid electrolyte layer 21, similar to Embodiment 1 described above. However, in this embodiment, the conductive layer 22B is a single layer. The conductive layer 22B is, for example, a metal layer made of a metallic material. In this case, examples of metallic materials constituting the conductive layer 22B include silver, nickel, copper, aluminum, tantalum, molybdenum, carbon (including graphite), or alloys thereof.

[0078] In this embodiment, the capacitor element 2B has two second electrodes 20B. One of the two second electrodes 20B is an upper second electrode located above the first electrode 10 and the dielectric 30, and the other of the two second electrodes 20B is a lower second electrode located below the first electrode 10 and the dielectric 30. Therefore, the first electrode 10 and the dielectric 30 are located between the upper second electrode and the lower second electrode. The second electrode 20B may be integrated by connecting the upper second electrode and the lower second electrode, as in the second electrode 20 in Embodiment 1.

[0079] Furthermore, in this embodiment, the dielectric 30 is provided separately on the upper and lower surfaces of the first electrode 10. Therefore, the capacitor element 2B has two dielectrics 30. One of the two dielectrics 30 is the upper dielectric formed on the upper surface of the first electrode 10, and the other of the two dielectrics 30 is the lower dielectric formed on the lower surface of the first electrode 10. Therefore, the first electrode 10 is located between the upper dielectric and the lower dielectric. Note that, as in the dielectric 30 of Embodiment 1, the upper dielectric and the lower dielectric may be connected and integrated.

[0080] The insulating resin layer 5B encapsulates the first electrode 10, the second electrode 20B, and the dielectric 30. In other words, the insulating resin layer 5B encapsulates the capacitor element 2B, which is composed of the first electrode 10, the second electrode 20B, and the dielectric 30. Specifically, the capacitor element 2B is embedded in the insulating resin layer 5B.

[0081] In this embodiment, the insulating resin layer 5B is a thin insulating resin substrate. The thickness of the insulating resin layer 5B is constant overall, but is not limited to this. The insulating resin layer 5B also serves as the base substrate for the solid electrolytic capacitor 1B. Therefore, the solid electrolytic capacitor 1B is a sheet-shaped capacitor-embedded substrate having a structure in which the capacitor element 2B is embedded in an insulating resin layer 5B made of a thin insulating resin substrate. The sheet-shaped capacitor-embedded substrate can be used as a circuit board or an electronic substrate, etc.

[0082] The surface of the insulating resin layer 5B is the element surface of the solid electrolytic capacitor 1B. Specifically, the upper surface, which is one side of the insulating resin layer 5B, is the first surface 1a of the solid electrolytic capacitor 1B, and the lower surface, which is the other side of the insulating resin layer 5B, is the second surface 1b of the solid electrolytic capacitor 1B.

[0083] The insulating resin layer 5B is composed of an insulating resin material. The insulating resin material constituting the insulating resin layer 5B is appropriately selected considering properties such as high-frequency characteristics, low dielectric properties, and heat resistance. Examples of insulating resin materials that can be used to constitute the insulating resin layer 5B include epoxy resins such as FR-4, polyimide resins, fluororesins such as PTFE, or acrylic resins.

[0084] The first extraction electrode 3B is connected to the first electrode 10 of the capacitor element 2B, similar to Embodiment 1 described above. However, in this embodiment, the first extraction electrode 3B is connected to the first electrode 10 via a first through-via 5Ba that penetrates the insulating resin layer 5B. Specifically, the first extraction electrode 3B has a through-port that penetrates the insulating resin layer 5B and is connected to the first electrode 10. In this embodiment, the first extraction electrode 3B is exposed on both the upper and lower surfaces of the insulating resin layer 5B. Therefore, the first extraction electrode 3B not only penetrates the insulating resin layer 5B, but also penetrates the first electrode 10 and the dielectric 30.

[0085] The second extraction electrode 4B is connected to the second electrode 20B of the capacitor element 2B, similar to Embodiment 1 described above. However, in this embodiment, the second extraction electrode 4B is connected to the second electrode 20B via a second through-via 5Bb that penetrates the insulating resin layer 5B. Specifically, the second extraction electrode 4B has a through-port that penetrates the insulating resin layer 5B and is connected to the second electrode 20B. In this embodiment, the second extraction electrode 4B has an upper second extraction electrode provided on the upper surface side of the insulating resin layer 5B and a lower second extraction electrode provided on the lower surface side of the insulating resin layer 5B.

[0086] In this embodiment, the first extraction electrode 3B and the second extraction electrode 4B are embedded in the insulating resin layer 5B. In this case, the first extraction electrode 3B and the second extraction electrode 4B can be formed by embedding them in the first through-via 5Ba and the second through-via 5Bb by, for example, electroless plating, a plating resist method, or a filling plating method. The first through-via 5Ba and the second through-via 5Bb can be formed in the insulating resin layer 5B by, for example, laser light or a drill. The first extraction electrode 3B and the second extraction electrode 4B embedded in the first through-via 5Ba and the second through-via 5Bb can be made of, for example, a metallic material such as copper or aluminum, or an alloy thereof.

[0087] Furthermore, although not shown in the figures, in this embodiment as well, a humidity control agent 40 is placed on the capacitor element 2B. For example, the humidity control agent 40 is supported on the second electrode 20B. In this case, the humidity control agent 40 can be placed on either one or both of the solid electrolyte layer 21 and the conductive layer 22B of the second electrode 20B. The humidity control agent 40, as in Embodiment 1 described above, contains crosslinked polymer particles containing polyacrylic acid and is supported on the second electrode 20B in a state containing moisture.

[0088] As described above, the solid electrolytic capacitor 1B in this embodiment, similar to Embodiment 1, comprises a first electrode 10, a second electrode 20B, a dielectric 30 located between the first electrode 10 and the second electrode 20B, and a humidity control agent 40 containing crosslinked polymer particles containing polyacrylic acid.

[0089] With this configuration, similar to Embodiment 1 described above, even if an air gap crack occurs inside the dielectric 30 of the capacitor element 2B, the moisture contained in the humidity control agent 40 causes the dielectric 30 to self-repair and the crack disappears. This makes it possible to suppress a decrease in the capacitance of the capacitor element 2B or an increase in the ESR of the capacitor element 2B due to cracks in the dielectric 30. Therefore, it is possible to realize a solid electrolytic capacitor 1B that can suppress a decrease in performance even if cracks occur in the dielectric 30.

[0090] In this embodiment, the humidity control agent 40 was placed on the second electrode 20B, but this is not limited to that. In other words, it may be placed at any location on the capacitor element 2B other than the second electrode 20B, or at any location on the solid electrolytic capacitor 1B other than the capacitor element 2B. For example, the humidity control agent 40 may be placed on the insulating resin layer 5B.

[0091] (modified version) The solid electrolytic capacitors related to this disclosure have been described above based on Embodiments 1 to 3, but this disclosure is not limited to Embodiments 1 to 3.

[0092] For example, the sheet-shaped solid electrolytic capacitor 1B in the above embodiment 3 is a double-sided extraction type, with the first extraction electrode 3B and the second extraction electrode 4B provided on both sides of the first surface 1a and the second surface 1b of the solid electrolytic capacitor 1B, but it is not limited to this. Specifically, the solid electrolytic capacitor 1B may be a single-sided extraction type. In other words, the first extraction electrode 3B and the second extraction electrode 4B may be provided on only one of the first surface 1a and the second surface 1b of the solid electrolytic capacitor 1B. In this case, the second electrode 20B and the dielectric 30 may also be formed only on one side of the first electrode 10.

[0093] Furthermore, in the above embodiment 3, the first extraction electrode 3B and the second extraction electrode 4B constitute a pair of extraction electrodes on one side, but this is not limited to this. For example, the first extraction electrode 3B and the second extraction electrode 4B may constitute a pair of extraction electrodes on both sides. In this case, for example, with respect to a capacitor element in which the first electrode 10 is provided on the surface facing the first surface 1a of the dielectric 30 and the second electrode 20B is provided on the surface facing the second surface 1b of the dielectric 30, a structure in which the first extraction electrode 3B is provided on the surface facing the first surface 1a and the second extraction electrode 4B is provided on the surface facing the second surface 1b can be considered.

[0094] Furthermore, this disclosure also includes forms obtained by applying various modifications to the above embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of this disclosure. In addition, this disclosure also includes any combination of two or more claims from the multiple claims described in the claims at the time of filing this application, provided that they are not technically contradictory. For example, if the cited claims described in the claims at the time of filing this application are made into a multi-claim or multi-multi-claim so as to refer to all of the higher-level claims without technically contradictory, then all combinations of claims included in that multi-claim or multi-multi-claim are also included in this disclosure. [Industrial applicability]

[0095] The technology disclosed herein is useful as a solid electrolytic capacitor. [Explanation of Symbols]

[0096] 1, 1A, 1B Solid electrolytic capacitors 1a 1st page 1b 2nd side 2, 2A, 2B Capacitor Elements 3, 3B First extraction electrode 4, 4B Second extraction electrode 5. Exterior resin layer 5B Insulating resin layer 5Ba First Through Via 5Bb Second Through Via 6. Conductive layer 7 Metal case 10, 10A 1st electrode 20, 20A, 20B 2nd electrode 21 Solid electrolyte layer 22, 22B conductive layer 22a First conductive layer 22b Second conductive layer 30 Dielectrics 30a Crack 40 Humidity control agents 50 Insulator 60 Separators

Claims

1. A solid electrolytic capacitor containing a solid electrolyte, First electrode and The second electrode and A dielectric material located between the first and second electrodes, Equipped with a humidity control agent, The humidity control agent includes cross-linked polymer particles containing polyacrylic acid. Solid electrolytic capacitor.

2. The volume-average particle diameter of the cross-linked particles is 10 μm or more and 500 μm or less. The solid electrolytic capacitor according to claim 1.

3. The volume-average particle diameter of the cross-linked particles is 30 μm or more and 400 μm or less. The solid electrolytic capacitor according to claim 1.

4. A portion of the polyacrylic acid is neutralized, and the crosslinked particles have the structure of an alkali metal salt of acrylic acid. The solid electrolytic capacitor according to claim 1.

5. The proportion of neutralized acrylic acid groups to the total acrylic acid groups is between 20% and 90%. The solid electrolytic capacitor according to claim 4.

6. The crosslinking agent of the aforementioned crosslinked particles has an ether bond. The solid electrolytic capacitor according to claim 1.

7. The aforementioned crosslinked particles have a crosslinking density of 0.01 mol% or more and 10 mol% or less. The solid electrolytic capacitor according to claim 1.

8. The second electrode has a solid electrolyte layer composed of the solid electrolyte, The solid electrolyte is composed of a conductive polymer, The solid electrolyte layer is in contact with the dielectric. The solid electrolytic capacitor according to claim 1.

9. The second electrode has a conductive layer comprising at least one of a silver paste layer and a carbon paste layer. The solid electrolyte layer is located between the dielectric and the conductive layer. The humidity control agent is disposed within the conductive layer. The solid electrolytic capacitor according to claim 8.

10. The system includes a separator disposed between the dielectric and the second electrode, The separator is impregnated with the solid electrolyte. The humidity control agent is placed in the separator. The solid electrolytic capacitor according to claim 1.

11. The first electrode is made of aluminum or tantalum. A solid electrolytic capacitor according to any one of claims 1 to 10.

12. The dielectric is an oxide of the metal constituting the first electrode. The solid electrolytic capacitor according to claim 11.

13. The humidity in the void portion within the solid electrolytic capacitor is 30% to 80%. A solid electrolytic capacitor according to any one of claims 1 to 10.

14. A capacitor element is composed of at least the first electrode, the second electrode, and the dielectric, moreover, The insulating resin layer in which the capacitor element is embedded, A first extraction electrode connected to the first electrode via a first through-via penetrating the insulating resin layer, The device comprises a second extraction electrode connected to the second electrode via a second through-via penetrating the insulating resin layer, A solid electrolytic capacitor according to any one of claims 1 to 10.

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