JP7247673B2 - Electrolytic capacitor anode manufacturing method, electrolytic capacitor manufacturing method, and electrolytic capacitor - Google Patents

Description

The present invention relates to a method for manufacturing an anode of an electrolytic capacitor, a method for manufacturing an electrolytic capacitor, and an electrolytic capacitor.

Electrolytic capacitors such as solid electrolytic capacitors are manufactured, for example, by anodizing an anode made of a valve action metal to form a dielectric film on the surface thereof, and then forming a cathode on the surface of the dielectric film. be. Aluminum, tantalum, niobium, titanium, zirconium and the like are used as valve metals.

In recent years, there has been a demand for higher capacity capacitors, and the use of titanium, which is an oxide with a high dielectric constant, as a valve action metal has been investigated. However, electrolytic capacitors using titanium as a valve action metal have a problem of large leakage current compared to electrolytic capacitors using aluminum, tantalum, or the like. Therefore, studies are being conducted to reduce the leakage current by adding other metals to titanium to form an alloy.

For example, Patent Document 1 discloses an electrolytic capacitor containing an anode body containing titanium, zirconium and a third element, a dielectric obtained by anodizing the anode body, and an electrolyte, wherein the third element is at least one selected from aluminum, gallium, tin, carbon, oxygen, or nitrogen, and the third element is contained in an amount of 0.1 atomic % or more and less than 10 atomic %. is disclosed.

In Patent Document 1, in order to produce an anode body, first, raw materials of titanium, zirconium, and a third element are weighed in a desired ratio, and then an alloy ingot is produced by a melting method, a sintering method, a mechanical alloy method, or the like. are doing. The produced alloy ingot is processed by a mechanical pulverization method such as a ball mill or a bead mill, or a molten metal pulverization method such as an atomization method, an impact method, or a granulation method. After pressure-molding the alloy powder obtained by the above treatment, the compact is heat-treated under high vacuum and high temperature to obtain an anode body made of a sintered alloy powder.

JP 2017-22281 A

Patent document 1 has the following description.
・Allotropic transformation temperature is low for alloys consisting only of titanium and zirconium. If anodizing is performed after heat treatment at a temperature above the transformation temperature, many film breaks occur in the formed oxide film, resulting in leakage current. known to be on the rise.
・When heat treatment is performed at a temperature higher than the transformation temperature, martensitic transformation occurs from the high-temperature β phase to the low-temperature α phase, and at this time the metal structure (grain boundaries) appears.
・Normally, impurity metal elements such as iron and nickel are concentrated at grain boundaries. Triggered by this concentrated impurity metal element, a large number of film breakages occur at the grain boundaries.

According to Patent Document 1, by adding a third element to titanium and zirconium, the α phase is stabilized, and martensitic transformation can be made difficult to occur even when heat treatment is performed at a temperature equal to or higher than the transformation temperature. . As a result, the growth of grain boundaries and the concentration of impurity metal elements in the grain boundaries are suppressed, the film breakage of the dielectric formed by the anodizing treatment is reduced, and the leakage current is improved.

Thus, in Patent Document 1, the leakage current is suppressed by adjusting the composition of the titanium alloy forming the anode of the electrolytic capacitor. However, there is still room for improvement in suppressing the leakage current of electrolytic capacitors. In particular, no study has been made so far on suppressing leakage current by processing titanium alloys in the stage of manufacturing the anodes of electrolytic capacitors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an anode of an electrolytic capacitor that can suppress leakage current. Another object of the present invention is to provide a method for manufacturing an electrolytic capacitor capable of suppressing leakage current, and an electrolytic capacitor.

The method for producing an anode of an electrolytic capacitor according to the present invention includes the steps of preparing and mixing titanium alloy single raw materials as starting raw materials, and heating the mixed starting raw materials to a temperature equal to or higher than the melting point of the starting raw materials and melting them. cooling the molten starting material to obtain an alloy ingot; subjecting the alloy ingot to hot forging; and forming the hot forged alloy ingot into a plate shape. , and a step of processing into powder or foil.

The method for manufacturing an electrolytic capacitor of the present invention comprises the steps of obtaining an anode of a predetermined shape by the method of manufacturing an anode of an electrolytic capacitor of the present invention, and anodizing the anode to form a dielectric film on the surface of the anode. and forming a cathode on the surface of the dielectric film.

An electrolytic capacitor of the present invention is an electrolytic capacitor comprising one or more electrolytic capacitor elements, wherein the electrolytic capacitor element is formed by an anode made of a titanium alloy and an anodization of the anode on the surface of the anode. and a cathode disposed on the surface of the dielectric film, wherein the titanium alloy has an average grain size of 100 μm or more and 300 μm or less and an average crystallite size of 50 μm or more and 200 μm or less. .

According to the present invention, leakage current of an electrolytic capacitor can be suppressed.

FIG. 1 is a phase diagram of a Ti—Zr binary alloy. FIG. 2 is a ternary phase diagram of a Ti—Zr—Al alloy at 800°C. FIG. 3 is a binary phase diagram at 0 to 1700° C. with a Ti ratio of 70 atom % in a Ti—Zr—Al alloy. FIG. 4 is an example of a temperature profile of temperature rise and temperature drop. FIG. 5 is a cross-sectional view schematically showing one example of the electrolytic capacitor of the present invention. FIG. 6A is a SEM observation (×100) of the surface of the same titanium alloy as in Example 7 acid-treated with hydrofluoric-nitric acid, and FIG. The cross section is observed by SEM (×200). FIG. 6C is a SEM observation (×100) of the surface of the same titanium alloy as in Comparative Example 1 acid-treated with hydrofluoric-nitric acid, and FIG. The cross section is observed by SEM (×200). FIG. 7 is a schematic diagram for explaining the grain size and crystallite size of a titanium alloy.

A method for manufacturing an anode of an electrolytic capacitor, a method for manufacturing an electrolytic capacitor, and an electrolytic capacitor according to the present invention will be described below.
However, the present invention is not limited to the following configurations, and can be appropriately modified and applied without changing the gist of the present invention. Combinations of two or more of the individual desirable configurations described below are also part of the present invention.

[Manufacturing method of anode for electrolytic capacitor]
The method for manufacturing an anode of an electrolytic capacitor of the present invention comprises the following steps (1) to (5).
(1) Step of preparing and mixing titanium alloy single raw materials as starting raw materials (2) Step of heating and melting the mixed starting raw materials to a temperature equal to or higher than the melting point of the starting raw materials (3) Step of melting the molten starting raw materials (4) Hot forging the alloy ingot (5) Processing the hot forged alloy ingot into a plate, powder or foil.

The present invention is characterized in that an alloy ingot (hereinafter also referred to as an ingot) is hot forged. By subjecting a titanium alloy to hot forging, which is processing of the β-phase region, the crystal grain size of the titanium alloy can be reduced and the alloy crystals can be densified. Therefore, by using such a titanium alloy as an anode and anodizing the anode to form a dielectric film on the surface thereof, the film quality of the dielectric film can be improved and the leakage current of the electrolytic capacitor can be suppressed. .

(1) Step of preparing and mixing single raw materials of titanium alloy as starting raw materials In step (1), single raw materials of titanium alloy as starting raw materials are weighed and mixed so as to have a predetermined composition ratio.

The titanium alloy is preferably a ternary alloy of Ti--Zr--Al. In this case, it is preferable that Ti be 70 atom % or more and 74 atom % or less, Zr be 18 atom % or more and 27 atom % or less, and Al be 3 atom % or more and 8 atom % or less.

It should be noted that unavoidable impurities such as C and N may be contained in the starting materials and in the manufacturing process described later.

Also, for example, in consideration of evaporation of Al during melting, Al may be weighed by increasing the composition ratio at the time of weighing (for example, +0.5 to 1 atom % of the target).

The solid solubility limit of Al in a ternary alloy of Ti--Zr--Al will be described below.

FIG. 1 is a phase diagram of a Ti—Zr binary alloy.
As shown in FIG. 1, it is known that Ti and Zr form a complete solid solution. FIG. 1 was created with reference to Metal Data Book, edited by The Japan Institute of Metals, 3rd Edition, Maruzen (1995).

FIG. 2 is a ternary phase diagram of a Ti—Zr—Al alloy at 800°C. FIG. 3 is a binary phase diagram at 0 to 1700° C. with a Ti ratio of 70 atom % in a Ti—Zr—Al alloy.
The state diagrams of FIGS. 2 and 3 were created using thermodynamic equilibrium calculation software and thermodynamic database "FactSage" manufactured by Computational Mechanics Research Center.

Table 1 shows the substances taken into account in the calculations. However, Table 1 also includes substances that do not appear in the phase diagram of the calculation results.

From point A in FIG. 3, it can be seen that the solid solubility limit of Al with a Ti ratio of 70 atom % (boundary between HCP and HCP+ALM) is 8 atom %. Therefore, by mixing Al in the alloy so that it is contained within 8 atom %, it becomes difficult for heterogeneous phases other than the alloy to be generated in the ingot after alloy production. Heterogeneous phases in the alloy are not preferable because they degrade electrical properties, which will be described later.

(2) Step of heating and melting the mixed starting materials to a temperature equal to or higher than the melting point of the starting materials (3) Step of cooling the melted starting materials to obtain an alloy ingot Steps (2) and (3) ), the mixed starting materials are charged into, for example, a water-cooled Cu crucible of a high-frequency melting furnace and mixed. After evacuating the furnace, Ar substitution is performed. After that, the temperature is raised and lowered according to a desired temperature profile.

As a method for dissolving the starting material, a high-frequency melting method is preferable, and a high-frequency induction levitation melting method is more preferable. Among the high-frequency melting methods, when the high-frequency induction levitation melting method is used, there is no contact between the starting material to be melted and the Cu crucible, so contamination and the like from the Cu crucible is suppressed.

FIG. 4 is an example of a temperature profile of temperature rise and temperature drop.
First, the temperature in the furnace is slowly raised from normal temperature (point A) to about 600° C. (point B) so that Al, which has a low specific gravity, does not come to the surface and evaporate during melting. Subsequently, the temperature is raised to 1750° C., which is higher than the melting point of the starting material, to melt the starting material (point C). The peak temperature is preferably 1650°C or higher and 1850°C or lower. Furthermore, the peak temperature of 1750° C. is continued for 15 minutes (point D). The time for which the peak temperature is maintained is preferably 10 minutes or more and 20 minutes or less.

Next, the temperature is lowered (vacuum cooling) while evacuating for Ar evacuation. First, the temperature is lowered from the peak temperature for about 5 minutes at a first cooling rate of 200°C/min (point E). Subsequently, the temperature is lowered at a second cooling rate of 100°C/min for about 5 minutes (point F). At this point, the temperature is below the melting point of the starting material. After that, the temperature is lowered at a third cooling rate of about 10°C/min until it reaches normal temperature (point G).

Then, the cooled material is removed from the water-cooled Cu crucible to obtain an alloy lump (ingot). As in the above temperature profile, the alloy ingot is rapidly cooled at a cooling rate of 100° C./min or more and 200° C./min or less until it reaches the melting point of the starting material or less. preferable in terms of Miniaturization and uniformity of alloy grain size lead to improvement of electrical properties and reduction of variation.

Also, when obtaining an alloy ingot, a so-called casting process may be performed in which the alloy ingot is poured into a cylindrical or prismatic mold from the point D and cooled.

(4) Step of hot forging the alloy ingot The alloy ingot tends to have different alloy grain sizes due to the temperature distribution between the central portion and the outer peripheral portion. That is, the alloy grain size is likely to be reduced in the outer peripheral portion, which is easily quenched, and the alloy grain size is likely to be coarsened in the central portion, which is difficult to be quenched. Therefore, the alloy ingot is further subjected to hot forging.

In step (4), for example, steps (4-1) to (4-5) are performed.
(4-1) After applying an anti-oxidation coating agent to the surface of the alloy ingot, the alloy ingot is uniformly reheated. The reheating temperature is preferably 900° C. or higher and 1200° C. or lower, which is the range of the BCC phase.
(4-2) The alloy ingot is subjected to free forging by a 10-ton press or the like, and gas remaining inside is removed by deformation of the alloy ingot.
(4-3) Mold into a round bar of a predetermined size (for example, Φ50 mm) by die forging.
(4-4) Obtain a rod-shaped alloy ingot by natural cooling. Instead of natural cooling, a temperature drop of 100° C./min or more and 200° C./min or less as indicated by points E and F in FIG. 4 may be used. Rapid cooling by quenching may also be used.
(4-5) Grind the surface of the round bar-shaped alloy ingot with a cylindrical grinder to remove the oxide film (black scale) on the surface.

(5) Processing the hot forged alloy ingot into plate, powder or foil The alloy ingot thus obtained is subjected to, for example, wire discharge, mechanical polishing and acid treatment. etc., it can be formed into a plate-like chip (for example, 5×15×0.5 mmt).
As for the powder form, hydrogenated alloy powder can be obtained by, for example, pulverizing an alloy ingot by a gas atomization method and then performing a hydrogenation treatment at 500° C. or higher and 650° C. or lower for 30 minutes in an H ₂ atmosphere.
As for the foil shape, for example, a rolled alloy foil having a thickness of 20 μm or more and 100 μm or less can be obtained by cutting an alloy ingot into a predetermined size and then hot-rolling it at 400° C. or more and 800° C. or less.

As described above, an anode having a predetermined shape is obtained.

[Manufacturing method of electrolytic capacitor]
The method for manufacturing an electrolytic capacitor of the present invention includes the following steps (6) and (7) in addition to the above steps (1) to (5).
(6) A step of anodizing the anode to form a dielectric film on the surface of the anode (7) A step of forming a cathode on the surface of the dielectric film

(6) A step of anodizing the anode to form a dielectric film on the surface of the anode. membrane) can be formed.

(7) Step of forming a cathode on the surface of the dielectric film For example, the dielectric film is coated with a first conductive polymer and dried, and a second conductive polymer is printed thereon and dried. Then, carbon paste and silver paste are printed and dried. As described above, a cathode can be formed on the surface of the dielectric film.

In the above example, a solid electrolyte such as a conductive polymer is used as the electrolyte, but a liquid electrolyte such as an electrolytic solution may also be used.

[Electrolytic capacitor]
The electrolytic capacitor of the present invention will be described below with reference to FIG.

FIG. 5 is a cross-sectional view schematically showing one example of the electrolytic capacitor of the present invention.
FIG. 5 schematically shows the structure of an electrolytic capacitor 1 in which a plurality of electrolytic capacitor elements 2 each having a plate-like chip formed in the size of the anode of the electrolytic capacitor are laminated.

The electrolytic capacitor 1 shown in FIG. a body 44; The electrolytic capacitor element 2 comprises an anode 10 made of a titanium alloy such as a Ti--Zr--Al alloy, a dielectric film 20 made of a chemical film obtained by anodizing the surface of the anode 10, and disposed on the surface of the dielectric film 20. and a cathode 30 to be applied. The cathode 30 includes, for example, from the dielectric film 20 side, a solid electrolyte layer made of a conductive polymer, a carbon layer, and a silver layer.

The electrolytic capacitor 1 shown in FIG. 5 includes a first electrolytic capacitor element laminate 41a and a second electrolytic capacitor element laminate 41b each having three electrolytic capacitor elements 2 laminated. The number of electrolytic capacitor elements is not particularly limited, and a single electrolytic capacitor element may be used.

The electrolytic capacitor elements 2 of the first electrolytic capacitor element laminate 41a and the second electrolytic capacitor element laminate 41b are electrically connected to the anode-side external electrode 42 via the anode 10, and are electrically connected via the cathode 30. is electrically connected to the cathode-side external electrode 43 at the bottom. In order to prevent a short circuit between the anode 10 and the cathode 30, an insulating mask 15 is formed on the exposed portion of the anode 10. As shown in FIG.

The anode-side external electrode 42 and the cathode-side external electrode 43 are made of, for example, a plate-like lead frame made of Cu, and are formed along the opposing side surfaces of the rectangular parallelepiped electrolytic capacitor 1 to form mounting surfaces. pulled out to the back. The anode-side external electrode 42 and the anode 10, and the cathode-side external electrode 43 and the cathode 30 are integrally joined by, for example, welding such as resistance welding, crimping, ultrasonic bonding, or conductive paste such as silver paste. The anode-side external electrode 42 and the cathode-side external electrode 43 may be formed with plating or conductive paste on the side surfaces.

The exterior body 44 is made of, for example, a sealing resin such as epoxy resin, and covers the entire electrolytic capacitor element 2 , part of the anode-side external electrode 42 , and part of the cathode-side external electrode 43 . Note that the exterior body 44 may be a resin case or a metal case other than the sealing resin.

The electrolytic capacitor of the present invention is characterized in that the titanium alloy forming the anode has an average grain size of 100 μm to 300 μm and an average crystallite size of 50 μm to 200 μm. This makes it possible to obtain an electrolytic capacitor with a large capacitance while suppressing leakage current.

In the electrolytic capacitor of the present invention, the titanium alloy forming the anode is preferably a ternary alloy of Ti--Zr--Al. In this case, the Al content is preferably 3 atom % or more and 8 atom % or less, more preferably 5 atom % or more and 8 atom % or less. By setting the Al content within the above range, the leakage current of the electrolytic capacitor can be suppressed, and the CV value can be reduced.

In the electrolytic capacitor of the present invention, the composition ratio of the titanium alloy is preferably 70 atom % or more and 74 atom % or less of Ti, 18 atom % or more and 27 atom % or less of Zr, 3 atom % or more and 8 atom % or less of Al, and 70 atom % of Ti. More preferably, the content is 74 atom % or more, Zr is 18 atom % or more and 27 atom % or less, and Al is 5 atom % or more and 8 atom % or less. By setting the composition ratio of the titanium alloy within the above range, the leakage current of the electrolytic capacitor can be suppressed and the CV value can be reduced.

The components and composition of the titanium alloy can be measured by subjecting the titanium alloy to be measured to X-ray photoelectron spectroscopy (XPS) or energy dispersive X-ray analysis (EDX).

The electrolytic capacitor of the present invention is not limited to a solid electrolytic capacitor. For example, an electrolytic capacitor provided with an anode and a cathode via a separator and filled with an electrolytic solution, or an electrolytic capacitor filled with an electrolytic solution and a solid electrolyte. There may be.

The following are examples that more specifically disclose the electrolytic capacitor of the present invention. It should be noted that the present invention is not limited only to these examples.

[Production of electrolytic capacitor]
Electrolytic capacitors of Examples 1 to 18 and Comparative Example 1 were produced by performing the following steps.

(1) A step of preparing and mixing titanium alloy single raw materials as starting raw materials. They were weighed and mixed so as to obtain a ratio (unit: atom %).
In Examples 1 to 18 and Comparative Example 1, Ti is weighed in the range of 70 atom % to 74 atom %, Zr is in the range of 18 atom % to 27 atom %, and Al is in the range of 3 atom % to 8 atom %. . The composition ratio shown in Table 2 is the composition ratio at the time of charging (when weighing) the starting materials, and the total of Ti, Zr and Al is 100 atm %.

(2) Step of heating and melting the mixed starting materials to a temperature equal to or higher than the melting point of the starting materials (3) Step of cooling the melted starting materials to obtain an alloy ingot High-frequency melting of the mixed starting materials It was charged and mixed in a water-cooled Cu crucible of a furnace (high-frequency induction levitation melting method). The total weight at this time is about 7 kg. After evacuating the furnace, Ar substitution was performed.

Thereafter, the temperature was raised and lowered according to the temperature profile shown in FIG. The cooled material was removed from the water-cooled Cu crucible to obtain an alloy ingot.

(4) Step of hot forging the alloy ingots The alloy ingots of Examples 1 to 18 were subjected to the following hot forging treatments (4-1) to (4-5).
(4-1) After coating the surface of the alloy ingot with an anti-oxidation coating agent, the alloy ingot is uniformly reheated at 1050° C. for 60 minutes.
(4-2) The alloy ingot is subjected to free forging by a 10t press, and the gas retained inside is removed by deformation of the alloy ingot.
(4-3) Form into a round bar of Φ50 mm by die forging.
(4-4) Obtain a rod-shaped alloy ingot by natural cooling.
(4-5) Grind the surface of the round bar-shaped alloy ingot with a cylindrical grinder to remove the oxide film (black scale) on the surface.

On the other hand, the alloy ingot of Comparative Example 1 was not subjected to the above hot forging treatment.

(5) Step of processing the alloy ingot into a plate A plate-like chip of 5×15×0.5 mmt was formed by performing wire discharge, mechanical polishing, and acid treatment.

(6) A step of anodizing the anode to form a dielectric film on the surface of the anode. A chemical film (dielectric film) was formed by performing the anodizing treatment for 1 hour.

(7) A step of forming a cathode on the surface of the dielectric film. Coat the first conductive polymer on the dielectric film with a jet dispenser and dry it. bottom. Then, carbon paste and silver paste were printed and dried. As described above, solid electrolytic capacitors were produced as the electrolytic capacitors of Examples 1 to 18 and Comparative Example 1.

[Electrical characteristics of electrolytic capacitors]
Table 3 shows the electrical characteristics of the electrolytic capacitors of Examples 1 to 18 and Comparative Example 1.
In Table 3, Cap is the capacitance at 120 Hz when an AC voltage of 0.5 V is applied to the electrolytic capacitor at a frequency of 100 Hz to 1 MHz. LC is the leakage current value when a voltage of 6.3 V is applied to the electrolytic capacitor for 3 minutes. CV is a value obtained by dividing the above LC value by Cap and 6.3 V (rated voltage).

As shown in Table 3, the electrolytic capacitors of Examples 1 to 18 that were subjected to hot forging were superior in Cap, LC and CV to the electrolytic capacitor of Comparative Example 1 that was not subjected to hot forging. It has excellent properties.

[Average grain size and average crystallite size of titanium alloy]
FIG. 6A is a SEM observation (×100) of the surface of the same titanium alloy as in Example 7 acid-treated with hydrofluoric-nitric acid, and FIG. The cross section is observed by SEM (×200).
On the other hand, FIG. 6C is a SEM observation (×100) of the surface of the same titanium alloy as in Comparative Example 1 acid-treated with hydrofluoric acid, and FIG. 6D is the same titanium alloy as in Comparative Example 1 subjected to ion milling. The cross section is observed by SEM (×200).

Similarly, a plurality of the same titanium alloys as those of Example 7 and Comparative Example 1 were observed with an SEM, grain sizes and crystallite sizes were measured by binarization, and average values were obtained.

FIG. 7 is a schematic diagram for explaining the grain size and crystallite size of a titanium alloy.
In FIG. 7, the grain size of the titanium alloy is indicated by D, and the crystallite size is indicated by d.

In Example 7, the particle size D and the crystallite size d of arbitrary five crystal grains were measured in the SEM observation of FIGS. 6A and 6B. Furthermore, SEM observations such as those shown in FIGS. 6A and 6B were also performed for another part of Example 7, and the particle size D and the crystallite size d of arbitrary five crystal particles were measured. An average value of the crystallite diameter d was obtained. Similarly for Comparative Example 1, the average values of the particle size D and the crystallite size d were determined.

Table 4 shows the average particle size and average crystallite size of each.

As shown in FIGS. 6A, 6B, 6C, 6D and Table 4, among titanium alloys of the same composition, the titanium alloy subjected to hot forging treatment is superior to the titanium alloy not subjected to hot forging treatment. It can be seen that the grain size and crystallite size are smaller than

As described above, by hot forging the titanium alloy, the grain size and crystallite size of the titanium alloy are refined.
Furthermore, it can be confirmed from the above electrical properties that the dielectric film obtained by anodizing the titanium alloy also has the effect of miniaturizing the titanium alloy.

1 electrolytic capacitor 2 electrolytic capacitor element 10 anode 15 insulating mask 20 dielectric film 30 cathode 41a first electrolytic capacitor element laminate 41b second electrolytic capacitor element laminate 42 anode side external electrode 43 cathode side external electrode 44 exterior body

Claims (6)

A step of preparing and mixing a single raw material of a titanium alloy as a starting raw material;
a step of heating and melting the mixed starting materials to a temperature equal to or higher than the melting point of the starting materials;
a step of cooling the molten starting material by lowering the temperature to obtain an alloy ingot;
a step of heating the alloy ingot to the β-phase region and subjecting it to hot forging by free forging and die forging ;
A method of manufacturing an anode for an electrolytic capacitor, comprising a step of processing the alloy lump subjected to the hot forging process into a plate shape, powder shape or foil shape. obtaining an anode of a predetermined shape by the method of manufacturing an anode for an electrolytic capacitor according to claim 1;
anodizing the anode to form a dielectric film on the surface of the anode;
and forming a cathode on the surface of the dielectric film. An electrolytic capacitor comprising one or more electrolytic capacitor elements,
The electrolytic capacitor element is
an anode made of a titanium alloy;
a dielectric film formed on the surface of the anode by anodizing the anode;
a cathode disposed on the surface of the dielectric film,
An electrolytic capacitor, wherein the titanium alloy has an average grain size of 100 µm or more and 300 µm or less, and an average crystallite size of 50 µm or more and 200 µm or less. The titanium alloy is a ternary alloy of Ti—Zr—Al,
4. The electrolytic capacitor according to claim 3, wherein the Al content is 3 atom % or more and 8 atom % or less. The titanium alloy is a ternary alloy of Ti—Zr—Al,
4. The electrolytic capacitor according to claim 3, wherein the Al content is 5 atom % or more and 8 atom % or less. The composition ratio of the titanium alloy according to any one of claims 3 to 5, wherein Ti is 70 atom% or more and 74 atom% or less, Zr is 18 atom% or more and 27 atom% or less, and Al is 3 atom% or more and 8 atom% or less. Electrolytic capacitor.

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