JP2002343687A - Niobium for capacitor, and capacitor using niobium sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor, having a niobium as its raw material whose withstanding voltage characteristic, is improved, and to provide the niobium used a the raw material for the capacitor. SOLUTION: A process for reducing the chromium content of a niobium for capacitors is inserted into the manufacturing process of the niobium for capacitors, and the niobium for capacitors, whose chromium content is not larger that 50 mass ppm, is obtained. By using the sintered body of this niobium for capacitors as one-side electrode, a capacitor is formed out of the other-side electrode and a dielectric, interposed between both the electrodes so as to obtain the capacitor having improved withstanding-voltage characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to niobium (niobium powder, niobium granules, and sintered bodies thereof) capable of producing a capacitor having a good withstand voltage characteristic and a large capacity per unit volume, and the niobium. The present invention relates to a capacitor using a sintered body.

[0002]

2. Description of the Related Art Capacitors used in electronic devices such as mobile phones and personal computers are desired to be small in size and large in capacity. Among conventional capacitors, tantalum capacitors are preferably used because of their large capacity for their size and good performance. A sintered body of tantalum powder is generally used as an anode body of the tantalum capacitor. In order to increase the capacity of the tantalum capacitor, it is necessary to increase the weight of the sintered body, or to use a sintered body in which the surface area is increased by making finer tantalum powder.

In the former method of increasing the weight of a sintered body,
The shape of the capacitor is inevitably increased and does not satisfy the demand for miniaturization. On the other hand, in the latter method of increasing the surface area by refining the tantalum powder, the pore diameter of the tantalum sintered body is reduced, and the number of closed pores is increased in the sintering step, so that impregnation of the cathode agent in the subsequent process becomes difficult. . As one of the researches to solve these drawbacks, a sintered powder capacitor using a material having a higher dielectric constant than tantalum has been considered. Niobium is a material having such a high dielectric constant.

[0004] Niobium is similar to tantalum, but its properties as a material for capacitors differ greatly. For example, in tantalum, oxygen is 10,000 mass ppm as an impurity.
The leakage current characteristic is greatly degraded when Nb is also present. However, in the case of niobium, such a phenomenon does not occur, and the degradation of the leakage current characteristic is small even with an oxygen content of tens of thousands ppm.

However, the withstand voltage characteristics of capacitors made from niobium are inferior to those made from tantalum.

Prior literature on the relationship between the amount of impurity elements contained in niobium powder and the performance of capacitors is disclosed in International Publication W.
WO 00/49633 and International Publication WO 00/5
No. 6486. In the former, the content of specific impurity elements such as iron, nickel, and cobalt is controlled to 100 mass ppm or less, and in the latter, the carbon content is 40 ppm.
It is disclosed that when the content of iron, nickel and chromium is about 5 ppm to about 200 ppm, the capacitor performance such as the specific leakage current value of the capacitor is improved. However, none of the documents discloses a relationship between the chromium content and the withstand voltage characteristics of the capacitor.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a capacitor having improved withstand voltage characteristics using niobium as a raw material, and niobium as a raw material thereof.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that impurities (B, C, F, Na, M) generally contained in niobium as a raw material.
g, Ca, Fe, Ni, Zn, W, Cr, etc.)
In particular, there is a correlation between the chromium content and the withstand voltage of the capacitor, and the chromium content is low (particularly 50 mass ppm).
It has been found that a capacitor using niobium has a remarkable improvement in withstand voltage. This is considered to be due to the fact that the deterioration around the impurity element which is partially present in the dielectric layer of the capacitor when a voltage is applied becomes particularly remarkable around the chromium element. However, normally available niobium raw materials have a high chromium content, and the above properties cannot be obtained if used as is. Therefore, a method for producing niobium having a small chromium content as a raw material for a capacitor having a small with good withstand voltage characteristic was found, and the present invention was completed.

The present invention relates to the following niobium for a capacitor, the powder, a granulated product thereof, a sintered body thereof, a capacitor using the sintered body, and a method of manufacturing the same.
That is, the present invention provides: (1) Niobium for a capacitor mainly containing niobium, wherein the chromium content is 50 mass ppm or less. (2) The niobium for a capacitor according to the above (1), wherein the chromium content is 40 mass ppm or less. (3) The preceding item 2 in which the chromium content is 5 mass ppm or less.
4. Niobium for a capacitor according to 4. (4) The preceding item 3, wherein the chromium content is 3 mass ppm or less.
4. Niobium for a capacitor according to 4. (5) The niobium for a capacitor according to any one of the above items 1 to 4, wherein the niobium for a capacitor mainly containing niobium contains a niobium nitride. (6) The niobium for a capacitor according to any one of the above items 1 to 4, wherein the niobium for a capacitor mainly containing niobium contains a niobium carbide. (7) The niobium for a capacitor according to any one of the above items 1 to 4, wherein the niobium for a capacitor mainly containing niobium contains a niobium boride. (8) The niobium for a capacitor as described in any one of the above items 1 to 7, wherein the niobium for a capacitor containing niobium as a main component is a powder having an average particle diameter of 0.1 μm to 3 μm. (9) The niobium for a capacitor according to any one of (1) to (7) above, wherein the niobium for a capacitor containing niobium as a main component is a granulated product and has an average particle diameter of 10 μm to 300 μm. (10) Niobium for a capacitor mainly containing niobium is
A niobium sintered body having a BET specific surface area of 0.5 m
^The niobium for a capacitor according to any one of Items 1 to 7, wherein the niobium is ² / g to 7 m ² / g.

(11) In a capacitor composed of a niobium sintered body mainly containing niobium as one electrode, the other electrode and a dielectric material interposed between the two electrodes, the sintered body is A capacitor which is a sintered body of niobium for a capacitor according to any one of the above items 1 to 10. (12) The capacitor according to the above item 11, wherein the main component of the dielectric constituting the capacitor is niobium oxide. (13) The capacitor according to the above (11) or (12), wherein the other electrode is at least one selected from the group consisting of an electrolytic solution, an organic semiconductor, and an inorganic semiconductor. (14) The organic semiconductor is an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, an organic semiconductor composed mainly of tetracyanoquinodimethane, and the following general formula (1) Or (2)

Embedded image (In the formulas (1) and (2), R _{1 to} R ₄ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 10 carbon atoms, an alkoxy group or an alkyl ester group. , Halogen atom, nitro group,
Cyano group, primary, secondary or tertiary amino group, CF
Represents a monovalent group selected from the group consisting of _three groups, a phenyl group and a substituted phenyl group. The hydrocarbon chains of R ₁ and R ₂ and R ₃ and R ₄ may be linked to each other at any position to form at least one 3
A divalent chain forming a cyclic structure of a saturated or unsaturated hydrocarbon of a 7-membered ring may be formed. The cyclic bonding chain, carbonyl, ether, ester, amide, sulfide,
A sulfinyl, sulfonyl, or imino bond may be included at any position. X represents an oxygen, sulfur or nitrogen atom,
R ₅ is present X only when the nitrogen atom, independently represent hydrogen or straight-chain or branched, saturated or unsaturated alkyl group having 1 to 10 carbon atoms. 14. The capacitor according to item 13, wherein the capacitor is at least one organic semiconductor selected from the group consisting of organic semiconductors mainly composed of a conductive polymer obtained by doping a polymer containing two or more repeating units represented by the formula (1) with a dopant. (15) The conductive polymer is represented by the following general formula (3)

Embedded image (Wherein, R ₆ and R ₇ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl groups are bonded to each other at an arbitrary position. A substituent forming at least one or more 5- to 7-membered saturated hydrocarbon cyclic structure containing two oxygen elements, wherein the cyclic structure has an optionally substituted vinylene bond 15. The capacitor according to item 14, which is a conductive polymer containing a repeating unit represented by the following formula: (16) The capacitor according to the above item 13, wherein the organic semiconductor is at least one selected from polypyrrole, polythiophene, polyaniline, and substituted derivatives thereof. (17) The organic or inorganic semiconductor has a conductivity of 10 ⁻² S · c
m ^-1 ~10 ³ S · cm ^- preceding paragraph 13 is of the ^first range
A capacitor according to claim 1.

(18) A method for manufacturing niobium for a capacitor, comprising a step of reducing the chromium content of a substance containing niobium as a main component in the manufacturing process. (19) The step of reducing the chromium content includes the step of contacting a liquid containing at least one selected from the group consisting of hydrofluoric acid, nitric acid, sulfuric acid, and hydrochloric acid with a substance mainly containing niobium. 16. A method for producing niobium for a capacitor according to the above item 15. (20) The method for producing niobium for a capacitor according to the above (18) or (19), wherein the substance containing niobium as a main component contains niobium nitride. (21) The method for producing niobium for a capacitor according to the above (18) or (19), wherein the substance containing niobium as a main component contains niobium carbide. (22) The method for producing niobium for a capacitor according to the above (18) or (19), wherein the substance containing niobium as a main component is a substance containing niobium boride. (23) The method for producing niobium for a capacitor according to any one of the aforementioned items 18 to 22, wherein the substance containing niobium as a main component is a powder. (24) The method for producing niobium for a capacitor according to the above (23), wherein the powder has an average particle diameter of 0.1 μm to 3 μm. (25) The substance described in the above item 1, wherein the substance containing niobium as a main component is a granulated substance, and the average particle diameter thereof is 10 μm to 300 μm.
23. The method for producing niobium for a capacitor according to any one of 8 to 22. (26) a substance composed mainly of niobium, a sintered body, a manufacturing method of a niobium capacitor according to item 18 that has a BET specific surface area of 0.5m ² / g~7m ² / g. (27) A method for producing a niobium granulated product for a capacitor, comprising the step of granulating the niobium for a capacitor described in item 8 above. (28) A method for manufacturing a niobium sintered body for a capacitor, comprising sintering the niobium for a capacitor according to the above item 9 in a method for manufacturing a niobium sintered body for a capacitor. (29) Niobium for a capacitor obtained by the method according to any one of the above items 18 to 28.

(30) In a method of manufacturing a capacitor composed of one electrode containing niobium as a main component, the other electrode, and a dielectric material interposed between the two electrodes, a niobium is formed during the manufacturing process. A process for reducing the chromium content in an electrode whose main component is chromium. (31) A method for manufacturing a capacitor comprising a niobium sintered body containing niobium as a main component as one electrode, and the other electrode and a dielectric material interposed between the two electrodes, wherein A method for manufacturing a capacitor, comprising at least the method according to claim 1 as a manufacturing step. (32) The preceding item 12 in which niobium oxide is formed by electrolytic oxidation
3. The method for manufacturing a capacitor according to claim 1. (33) A capacitor obtained by the manufacturing method according to the above (30) or (31).

(34) An electronic circuit using the capacitor described in any one of the above items 11 to 17 and 33. (35) An electronic device using the capacitor according to any one of the above items 11 to 17 and 33.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A niobium for a capacitor according to the present invention will be described below based on an example of an embodiment. The niobium for a capacitor of the present invention contains niobium as a main component and can be a material for manufacturing a capacitor. This embodiment includes a powder, a granulated product, or a sintered body.

As a raw material of niobium for a capacitor, for example, reduction of niobium halide with hydrogen, magnesium, sodium, etc., sodium reduction of potassium niobium fluoride, molten salt of potassium niobium fluoride on a nickel cathode (NaCl + KCl 2) Powder of niobium obtained by such means as electrolysis and hydrogenation and pulverization of a metal niobium ingot can be used. It is fully conceivable that the niobium powder obtained by these methods contains impurities from the environment such as a niobium raw material, a reducing agent, and equipment used.

Chromium in niobium can also be mixed as an impurity through such a route. Chromium content in niobium powder,
50 mass ppm or less, preferably 40 mass ppm or less, more preferably 5 mass ppm or less, particularly preferably 3 mass pp in the niobium granulated product and / or the niobium sintered body.
m or less, the niobium powder of the present invention, niobium granules,
And / or a niobium sintered body can be obtained.

As a method for obtaining niobium having a low chromium content, a method using a special niobium production apparatus which takes into consideration a raw material having a sufficiently low chromium content and a small amount of chromium, or a method in which niobium is mixed during the niobium production process. There is a method of incorporating a step of removing chromium. In any method, the chromium content is not more than 50 mass ppm, preferably 4 mass ppm.
Any method can be applied to the present invention without particular limitation as long as the method can reduce the amount to 0 mass ppm or less, more preferably 5 mass ppm or less, and particularly preferably 3 mass ppm or less.

For example, among the above-mentioned niobium raw materials and reducing agents, a method of using a higher purity and suppressing the chromium contamination by using a chromium-free equipment is used. Examples of the method include a method in which an acid and an alkali containing at least one of nitric acid, sulfuric acid, and hydrochloric acid, or a method in which the acid, the alkali, and the aqueous hydrogen peroxide solution are sequentially used or used in common for washing.

Preferably, the latter method uses an acid and hydrogen peroxide. This method can be applied to niobium having a fixed composition (niobium containing niobium nitride or the like described later) or niobium having a fixed form (powder, granulated material, and sintered body) as niobium for a capacitor. . In other words, since this method can be used in a relatively later step during the manufacturing process of niobium for a capacitor, in many steps before that, it is not always necessary to use a raw material or an apparatus that pays special attention to chromium contamination. .

The average particle size of the niobium powder of the present invention is preferably 3 μm or less in order to increase the specific surface area of the powder. This is because the capacitance of the capacitor made of the niobium powder is proportional to its specific surface area. Therefore, in order to increase the capacitor capacity, it is effective to increase the surface area, that is, to reduce the average particle size. However, if the particle size is too small, it becomes difficult to impregnate the cathode agent in a later step. In consideration of these, the average particle size of the niobium powder is preferably 0.1 to 3 μm. The average particle size of the niobium granules is preferably from 10 to 300 μm.

The niobium granules of the present invention are obtained, for example, by granulating the above-mentioned niobium powder to an appropriate size. As the granulation method, a conventionally known method can be employed. For example, powder 5
After leaving in a high-temperature vacuum of 00 ° C to 2000 ° C, wet or dry crushing, mixing with a suitable binder such as acrylic resin or polyvinyl alcohol and powder, crushing, acrylic resin, camphor, phosphoric acid Or a method of mixing with an appropriate compound such as boric acid, leaving the mixture to stand under a high-temperature vacuum, and then performing wet or dry pulverization. The particle size of the niobium granulated product can be arbitrarily changed depending on the degree of granulation and crushing, but usually, an average particle size of 10 μm to 300 μm is used. Classification after granulation and crushing may be used. Further, after granulation, a suitable amount of powder before granulation may be mixed and used (in the present invention, a granulated product obtained by mixing ungranulated powder is also referred to as “granulated product”), or Alternatively, niobium granules having a plurality of average particle sizes may be mixed and used in an appropriate amount. The specific surface area of the thus niobium granulated product prepared by, although it can be arbitrarily changed, is used as a normal 0.5m ² / g~7m ² / g.

Further, in order to further improve the leakage current characteristics, the niobium powder of the present invention may have a part of niobium bonded to at least one of nitrogen, carbon and boron. It may contain any of niobium nitride, niobium carbide and dioboboride, which are compounds of nitrogen, carbon and boron, or a combination of two or three of these. The sum of the bonding amounts, that is, the sum of the contents of nitrogen, carbon, and boron varies depending on the shape of the niobium powder, but is 50 to 200 for powder having an average particle size of about 0.1 to 3 μm.
000 ppm by mass, preferably 300 to 20,000 ppm by mass. If it is less than 50 ppm by mass, the leakage current characteristics are not sufficiently improved, and if it exceeds 200,000 ppm by mass, the capacity characteristics are deteriorated.

The nitriding method for forming niobium nitride may be carried out by any of a liquid nitrogen method, an ion nitriding method, a gas nitriding method and the like, or a combination thereof. A gas nitriding treatment in a nitrogen gas atmosphere is preferable because it is simpler and easier.
The gas nitriding method in a nitrogen gas atmosphere is performed by leaving niobium powder in a nitrogen atmosphere. The nitriding atmosphere temperature is 2000 ° C. or less, and the leaving time is within several hours, so that the desired amount of nitrogen can be obtained. The higher the temperature, the shorter the nitriding time. As described above, the amount of nitriding can be controlled by controlling the nitriding temperature and the nitriding time.

The carbonization method for forming niobium carbide may be any of gas carbonization, solid phase carbonization, and liquid carbonization, or a combination thereof. For example, niobium powder is mixed with a carbon material and an organic substance containing carbon such as methane under reduced pressure for 200 hours.
It is carried out by leaving at 0 ° C. or lower for several minutes to several tens of hours.

A boride method for forming dioborides is also provided.
Either gas boriding or solid-phase boriding may be used. For example, niobium powder is mixed with boron pellets and boron halide such as trifluoroboron as a boron source under reduced pressure for 200 hours.
It is carried out by leaving at 0 ° C. or lower for several minutes to several tens of hours.

The niobium sintered body for a capacitor of the present invention can be manufactured by sintering the above-mentioned niobium powder or granulated material. An example of the manufacturing method is shown below, but the present invention is not limited to this example.

[0027] For example, after the pressure molding niobium powder into a predetermined shape, 10 ^-4 to 10 ² Pa under reduced pressure or in an inert gas such as Ar, for several minutes to several hours, at 500 to 2000 ° C. Obtained by heating.

In addition, niobium or tan having an appropriate shape and length
Prepare a lead wire made of valve metal such as
During the pressure molding of the niobium powder, one of the lead wires
Part is integrally molded so that it is inserted into the molded body,
The lead wire will be the lead of the sintered body
It can be designed as follows. Made in this way
The specific surface area of the niobium sintered body of the present invention can be arbitrarily changed.
But usually 0.5m ^Two/ G or more 7m^Two/ G or less
Is used.

A capacitor can be manufactured from the thus produced sintered body as one electrode and a dielectric interposed between the other electrodes. A dielectric made of niobium oxide may be used as a dielectric of the capacitor. For example, a dielectric made of niobium oxide can be obtained by forming a niobium sintered body as one electrode in an electrolytic solution. In order to form a niobium electrode in an electrolytic solution, an aqueous solution of a protonic acid, for example, 0. This is performed using a 1% by mass aqueous solution of phosphoric acid or sulfuric acid. When a niobium electrode is formed in an electrolytic solution to obtain a dielectric composed of niobium oxide, the capacitor of the present invention becomes an electrolytic capacitor, and the niobium side becomes an anode.

On the other hand, the other electrode in the capacitor of the present invention is not particularly limited. For example, at least one compound selected from an electrolytic solution, an organic semiconductor, and an inorganic semiconductor known in the aluminum electrolytic capacitor industry.

Specific examples of the electrolytic solution include a mixed solution of dimethylformamide and ethylene glycol in which 5% by mass of isobutyltripropylammonium tetrafluoroborate electrolyte is dissolved, and propylene carbonate in which 7% by mass of tetraethylammonium tetrafluoroborate is dissolved. Examples include a mixed solution of ethylene glycol.

When an organic semiconductor and an inorganic semiconductor having a conductivity of 10 ⁻² S · cm ⁻¹ to 10 ³ S · cm ⁻¹ are used, the impedance value of the manufactured capacitor can be further reduced. preferable. Specific examples of the organic semiconductor having such characteristics include an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, and an organic semiconductor composed mainly of tetracyanoquinodimethane. And an organic semiconductor containing, as a main component, a conductive polymer obtained by doping a polymer containing a repeating unit represented by the following general formula (1) or (2) with a dopant.

[0033]

Embedded image

In the formula, R _{1 to} R ₄ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl group, alkoxy group or alkyl ester group having 1 to 10 carbon atoms, or a halogen atom Nitro group, cyano group, primary, secondary or tertiary amino group, CF ₃ group, phenyl group and substituted phenyl group. The hydrocarbon chains of R ₁ and R ₂ and R ₃ and R ₄ may be bonded to each other at any position to form a saturated or unsaturated at least one or more 3- to 7-membered ring together with the carbon atom substituted by such a group. A divalent chain forming a cyclic structure of a saturated hydrocarbon may be formed. The cyclic bond may include a carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl, or imino bond at any position. X represents an oxygen, sulfur or nitrogen atom, R ₅ is present only when X is a nitrogen atom, and is independently hydrogen or a linear or branched saturated or unsaturated alkyl group having 1 to 10 carbon atoms. Represents

Further, in the present invention, the above general formula
R of the general formula (2) or (1)₁~ R_FourIs preferably
Each independently represents a hydrogen atom, a linear chain having 1 to 6 carbon atoms.
Or branched saturated or unsaturated alkyl group or alkyl group
A oxy group;₁And R_TwoAnd R _ThreeAnd R_FourAre connected to each other
It may be annular.

Further, in the present invention, the conductive polymer containing a repeating unit represented by the general formula (2) is
Preferably, a conductive polymer containing a structural unit represented by the following general formula (3) as a repeating unit is exemplified.

[0037]

Embedded image

In the formula, R ₆ and R ₇ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl groups are at any positions relative to each other. Represents a substituent which forms a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon containing two oxygen elements. The cyclic structure includes those having a vinylene bond which may be substituted, and those having a phenylene structure which may be substituted.

The conductive polymer having such a chemical structure is charged because it has polaron or bipolaron in the molecule, and is doped with a dopant.
Known dopants can be used without limitation as the dopant.

Specific examples of the inorganic semiconductor include an inorganic semiconductor containing lead dioxide or manganese dioxide as a main component and an inorganic semiconductor made of triiron tetroxide. Such a semiconductor may be used alone or in combination of two or more.

When the other electrode is solid, a conductor layer may be provided thereon to improve electrical contact with an external lead (for example, a lead frame).

The conductor layer can be formed by, for example, solidifying a conductive paste, plating, metal deposition, forming a heat-resistant conductive resin film, or the like. As the conductive paste, a silver paste, a copper paste, an aluminum paste, a carbon paste, a nickel paste, and the like are preferable, but one or more of these may be used. When two or more kinds are used, they may be mixed or may be stacked as separate layers. After applying the conductive paste, it is left in the air or solidified by heating or the like. Examples of the plating include nickel plating, copper plating, silver plating, and aluminum plating. Examples of the metal to be deposited include aluminum, nickel, copper, and silver.

Specifically, for example, a capacitor is formed by sequentially laminating a carbon paste and a silver paste on the other electrode and sealing with a material such as epoxy resin. The capacitor may have niobium or tantalum leads which are integrally molded with the niobium sintered body or later welded.

When the other electrode is a liquid, the capacitor formed by the electrodes and the dielectric is housed in, for example, a can electrically connected to the other electrode to form a capacitor. In this case, the electrode side of the niobium sintered body is designed so as to be led out to the outside through the niobium or tantalum lead and to be insulated from the can by insulating rubber or the like.

The capacitor of the present invention having the above-described structure can be made into a capacitor product for various uses by, for example, a resin mold, a resin case, a metal outer case, resin dipping, and a laminate film. Further, when the capacitor of the present invention is used, the same withstand voltage,
A smaller capacitor product can be obtained as compared with a conventional capacitor having the same capacity.

Since capacitors are frequently used in electronic circuits such as cellular phones and computers, the use of the capacitor of the present invention allows the electronic circuit to be housed in a smaller space than before. Further, by using the capacitor of the present invention, an electronic device smaller than before can be obtained.

[0047]

The present invention will be described below in more detail with reference to examples and comparative examples. In each case, the nitrogen content of the niobium powder was determined using a nitrogen / oxygen analyzer manufactured by LECO. The Cr content was measured by IPC-MS.

The withstand voltage value of each of the manufactured capacitors was determined by subtracting 1 from the voltage applied to each of the 30 capacitors in each test example.
When the voltage was sequentially increased by V, the voltage value was such that the number of short-circuited capacitors exceeded five.

Examples 1 to 7, Comparative Example Niobium powder (average particle size: 3 μm) obtained by introducing hydrogen gas into a niobium ingot and wet-crushing was pulverized in a jet mill without dehydrogenation in a nitrogen atmosphere. did. Without taking out to the outside, it was first left at 400 ° C. under reduced pressure for dehydrogenation, and then left at 850 ° C. to be crushed to produce niobium powder. Subsequently, by flowing nitrogen gas at 300 ° C. for 20 minutes, 100 g of partially (about 1600 ppm by mass) niobium powder was obtained.

10 g of niobium powder at this stage was used as a comparative example, and the remaining 90 g was placed in a 3: 2 mixed solution of nitric acid and hydrogen peroxide solution, and stirred at room temperature. Approximately 10 every hour
Each g was extracted and washed with pure water. Wash water pH
Was thoroughly washed with water until the value became 7, and then 10 g of each of the powders of Examples 1 to 7 was obtained by vacuum drying. Table 1 shows the average particle size and the Cr content of each of the two obesium powders.

[0051]

[Table 1]

Next, 1.8 mm ×
Thirty molded articles having a size of 3.5 mm × 4.5 mm were produced. At this time, a niobium wire having a diameter of 0.3 mm was molded together to obtain a lead. These at 1250 ℃ 7 × 10 ^-3
Sintering was performed under a vacuum of Pa to obtain a sintered body. 0.1% for each sintered body
After forming a dielectric layer made of niobium oxide by forming a dielectric layer made of niobium oxide at 80 ° C. and 12 V in a phosphoric acid aqueous solution, polypyrrole (ammonium persulfate as an oxidizing agent, sodium anthraquinone sulfonate as a dopant, and The reaction between pyrrole and oxidant was repeated)
Was filled in the pores inside the sintered body. Further, a carbon paste and a silver paste were sequentially laminated, mounted on a lead frame, and sealed with an epoxy resin to produce a capacitor.

The specific surface areas of the sintered bodies of the respective examples were all 1 m ² /
g. Table 2 shows the capacity, withstand voltage and the number of capacitors that were short-circuited when the withstand voltage was applied.
It was shown to.

[0054]

[Table 2]

From the results of Examples 1 to 6, Cr in the niobium powder was
It can be seen that depending on the content, the withstand voltage characteristics of the capacitor made from the niobium powder become better.

[0056]

When the niobium for a capacitor of the present invention is used for a capacitor, a capacitor having good withstand voltage characteristics can be obtained.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Isao Kawabe 1-1-1, Onodai, Midori-ku, Chiba-shi, Chiba Pref.

Claims (35)

[Claims] 1. A niobium for a capacitor comprising niobium as a main component, wherein the chromium content is 50 mass ppm or less. 2. The niobium for a capacitor according to claim 1, wherein the chromium content is 40 mass ppm or less. 3. The niobium for a capacitor according to claim 2, wherein the chromium content is 5 mass ppm or less. 4. The niobium for a capacitor according to claim 3, wherein the chromium content is 3 mass ppm or less. 5. The niobium for a capacitor according to claim 1, wherein the niobium for a capacitor containing niobium as a main component contains a niobium nitride. 6. The niobium for a capacitor according to claim 1, wherein the niobium for a capacitor containing niobium as a main component contains a niobium carbide. 7. The niobium for a capacitor containing niobium as a main component contains niobium boride.
9. Niobium for a capacitor according to the item. 8. The niobium for a capacitor containing niobium as a main component is a powder having an average particle size of 0.1 μm to 3 μm.
8. The niobium for a capacitor according to any one of items 7 to 7. 9. Niobium for a capacitor containing niobium as a main component is a granulated product having an average particle size of 10 μm to 300 μm.
The niobium for a capacitor according to any one of claims 1 to 7, wherein the thickness is μm. 10. Niobium capacitors consisting primarily of niobium, a niobium sintered body, the BET specific surface area any one of claims 1 to 7 is 0.5m ² / g~7m ² / g 2. Niobium for a capacitor according to item 1. 11. A capacitor comprising a niobium sintered body mainly composed of niobium as one electrode, and the other electrode and a dielectric material interposed between the two electrodes. Item 11. A capacitor which is a sintered body of niobium for a capacitor according to any one of items 1 to 10. 12. The capacitor according to claim 11, wherein a main component of the dielectric constituting the capacitor is niobium oxide. 13. The capacitor according to claim 11, wherein the other electrode is at least one selected from the group consisting of an electrolytic solution, an organic semiconductor, and an inorganic semiconductor. 14. An organic semiconductor comprising a benzopyrroline tetramer and chloranil, an organic semiconductor containing tetrathiotetracene as a main component, an organic semiconductor containing tetracyanoquinodimethane as a main component, and a compound represented by the following general formula: 1) or (2) (In the formulas (1) and (2), R _{1 to} R ₄ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 10 carbon atoms, an alkoxy group or an alkyl ester group. , Halogen atom, nitro group,
Cyano group, primary, secondary or tertiary amino group, CF
Represents a monovalent group selected from the group consisting of _three groups, a phenyl group and a substituted phenyl group. The hydrocarbon chains of R ₁ and R ₂ and R ₃ and R ₄ may be linked to each other at any position to form at least one 3
A divalent chain forming a cyclic structure of a saturated or unsaturated hydrocarbon of a 7-membered ring may be formed. The cyclic bonding chain, carbonyl, ether, ester, amide, sulfide,
A sulfinyl, sulfonyl, or imino bond may be included at any position. X represents an oxygen, sulfur or nitrogen atom,
R ₅ is present X only when the nitrogen atom, independently represent hydrogen or straight-chain or branched, saturated or unsaturated alkyl group having 1 to 10 carbon atoms. 14. The capacitor according to claim 13, wherein the capacitor is at least one organic semiconductor selected from the group consisting of organic semiconductors containing a conductive polymer obtained by doping a dopant into a polymer containing two or more repeating units represented by the formula (1). 15. The conductive polymer according to the following general formula (3): (In the formula, R ₆ and R ₇ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl groups are bonded to each other at an arbitrary position. A substituent which forms a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon containing two oxygen elements, wherein the cyclic structure has an optionally substituted vinylene bond And a phenylene structure which may be substituted.) The capacitor according to claim 14, which is a conductive polymer containing a repeating unit represented by the following formula: 16. The capacitor according to claim 13, wherein the organic semiconductor is at least one selected from polypyrrole, polythiophene, polyaniline, and substituted derivatives thereof. 17. An organic or inorganic semiconductor having an electric conductivity of 10 ^-2.
14. The capacitor according to claim 13, which is in a range of S · cm ⁻¹ to 10 ³ S · cm ⁻¹ . 18. A method for producing niobium for a capacitor, the method comprising the step of reducing the chromium content of a substance containing niobium as a main component in the production process. 19. The step of reducing the chromium content includes contacting a liquid containing at least one selected from the group consisting of hydrofluoric acid, nitric acid, sulfuric acid, and hydrochloric acid with a niobium-based substance. The method for producing niobium for a capacitor according to claim 15, which is a step. 20. The method for manufacturing niobium for a capacitor according to claim 18, wherein the substance containing niobium as a main component includes niobium nitride. 21. The method for manufacturing niobium for a capacitor according to claim 18, wherein the substance containing niobium as a main component contains niobium carbide. 22. The method for producing niobium for a capacitor according to claim 18, wherein the substance containing niobium as a main component is a substance containing niobium boride. 23. The method for manufacturing niobium for a capacitor according to claim 18, wherein the substance containing niobium as a main component is a powder. 24. An average particle size of the powder is 0.1 μm to 3 μm.
The method for producing niobium for a capacitor according to claim 23, wherein 25. The method for producing a niobium for a capacitor according to claim 18, wherein the substance containing niobium as a main component is a granulated substance, and has an average particle size of 10 μm to 300 μm. . 26. substance mainly composed of niobium, a sintered body, the BET specific surface area of 0.5m ² / g~7m ² /
19. The method for producing niobium for a capacitor according to claim 18, wherein g is g. 27. A method for producing a niobium granule for a capacitor, comprising the step of granulating the niobium for a capacitor according to claim 8. 28. A method for producing a niobium sintered body for a capacitor, comprising sintering the niobium for a capacitor according to claim 9. 29. Niobium for a capacitor obtained by the method according to claim 18. Description: 30. A method for manufacturing a capacitor comprising one electrode containing niobium as a main component, the other electrode, and a dielectric material interposed between the two electrodes, wherein niobium is added during the manufacturing process. A method for manufacturing a capacitor, comprising a step of reducing a chromium content in an electrode as a main component. 31. A method of manufacturing a capacitor comprising a niobium sintered body mainly containing niobium as one electrode, and the other electrode and a dielectric material interposed between the two electrodes. 29. A method for manufacturing a capacitor, comprising the method according to at least one of the items 30 to 28 as a manufacturing step. 32. The method according to claim 12, wherein niobium oxide is formed by electrolytic oxidation. 33. A capacitor obtained by the method according to claim 30. 34. An electronic circuit using the capacitor according to any one of claims 11 to 17 and 33. 35. Electronic equipment using the capacitor according to any one of claims 11 to 17 and 33.