CN1526028B - Niobium powder, niobium sintered body, and capacitor using the sintered body - Google Patents

Abstract

The present invention provides: (1) the niobium powder for the capacitor has the tap density of 0.5-2.5 g/ml, the average particle size of 10-1000 microns, the angle of repose of 10-60 degrees and the BET specific surface area of 0.5-40 m²A/g and a plurality of pore size peaks in the pore size distribution, and a method for preparing the same; (2) a niobium sintered body obtained by sintering the above niobium powderThe porous ceramic material has a plurality of pore size peaks within a range of 0.01 to 500 micrometers, and preferably two peaks having the highest relative intensities among the plurality of pore size peaks are within a range of 0.2 to 0.7 micrometers and within a range of 0.7 to 3 micrometers, respectively, and a method for manufacturing the same; a capacitor using the sintered body and a method for manufacturing the same; and (4) an electronic circuit and an electronic device using the above capacitor.

Description

Niobium powder, niobium sintered body, and capacitor using the sintered body

Cross References to Related Applications

This application is an application under 35 U.S.C. Section 111(a), which requires a filing under 35 U.S.C. 111(b) on May 21, 2001, pursuant to 35 U.S.C. The benefit of the filing dates of U.S. Provisional Application Nos. 60/291,925 filed and 60/331,200 filed November 9, 2001.

technical field

The present invention relates to niobium powder and its sintered body, which can stably produce capacitors having large capacitance per unit mass, good leakage current characteristics and excellent moisture resistance, and also relates to capacitors and niobium powder using niobium powder and sintered body, Sintered bodies and methods of manufacturing capacitors.

Background technique

Capacitors used in electronic instruments such as portable phones and personal computers are required to have small size and large capacitance. Among these capacitors, tantalum capacitors are preferred because of their high capacitance and performance relative to their size.

In addition, in recent years, electronic devices are required to operate at low voltage and high frequency with low noise, and for solid electrolytic capacitors, low equivalent parallel resistance (ESR) is also required. In such tantalum capacitors, a sintered body of tantalum powder is generally used as the anode part. This powder is shaped and then sintered to integrate the powder and make an electrode called a sintered body. The inside of the sintered body is composed of powder particles that are electrically and mechanically connected to each other to form a three-dimensional complex structure. On the surface of the sintered body including the surface of the internal pores, a dielectric film layer is formed and impregnated with a material as a counter electrode, thereby preparing a capacitor. As long as the dielectric thin film layer is uniformly bonded to the inner or outer surface of the sintered body, the capacitance of the manufactured capacitor is microscopically mainly determined by the contact state of the counter electrode material with the dielectric thin film layer.

In order to increase the capacitance of a tantalum capacitor, it is necessary to improve the quality of a sintered body or use a sintered body whose surface area is increased by crushing tantalum powder.

The method of improving the quality of the sintered body necessarily involves the expansion of the shape of the capacitor, which cannot meet the requirements of miniaturization. On the other hand, in the method of crushing tantalum powder to increase the specific surface area, the pore size of the tantalum sintered body is reduced or the pores closed in the sintering stage are increased, and as a result, the impregnation of the cathode reagent in the subsequent step becomes difficult.

For example, assuming that when using phosphoric acid aqueous solution as the counter electrode material, the contact state of the solution and the dielectric film layer is complete, and the capacitance apparent ratio (also referred to as the cathode reagent impregnation ratio) at this moment is 100%, In the case of using a counter electrode material having a high viscosity, especially a solid electrode material, a capacitance apparent ratio of 100% can hardly be obtained. In particular, when the average particle size of the tantalum powder is small or the sintered body produced from the tantalum powder has a large shape, the difficulty increases and in extreme cases, the apparent capacitance ratio is not even 50%. With such a low capacitance apparent ratio, it is impossible to manufacture capacitors with sufficiently high moisture resistance.

In the case where the tantalum powder from which the tantalum sintered body is produced has a small pore size, it basically leads to a small pore size of the tantalum sintered body and a low apparent ratio of capacitance. Therefore, there arises a problem that the ESR cannot be lowered.

As one of measures to solve these problems, a capacitor using a sintered body produced using a dielectric material having a dielectric constant greater than that of tantalum and giving a high apparent ratio of capacitance as one electrode can be considered.

As such an electrode material that can be supplied industrially, niobium is known to have a higher dielectric constant than tantalum and to have a large storage capacity.

JP-A-55-157226 (the term "JP-A" used here means "Unexamined Published Japanese Patent Application") discloses a sintered device for producing capacitors, in which, agglomerated The rectification effect of the metal powder is press-formed and then sintered, the formed and sintered green body is cut into fine pieces, the wire part is joined to it, and these are sintered again. However, details of the fabrication method and properties of the niobium capacitor are not described in this patent publication.

US Patent 4,084,965 discloses a capacitor using a sintered body of niobium powder having an average particle size of 5.1 microns obtained by hydrogenating and pulverizing niobium ingots. However, the disclosed capacitors have large leakage current (hereinafter sometimes simply referred to as "LC") values and have little practical use.

JP-A-10-242004 (WO 98/38660) discloses a technique of partially niobium nitride powder and thus improving the LC value.

The tap density of niobium powder for capacitors is an important factor in the niobium powder forming operation. The tap density of conventional niobium powder is 2.5 g/ml or more, specifically about 4 g/ml, which is insufficient for forming.

That is, if such niobium powder is formed and sintered to prepare a sintered body, the niobium powder flows poorly from the hopper of the forming machine into the metal mold, and it is difficult to weigh a constant amount of niobium powder and make it flow into the metal mold. As a result, it causes problems such as insufficient shape stability of shaped products, insufficient strength of shaped products and sintered bodies, and often produces capacitors with inferior LC. If special forming equipment that can also handle poor fluidity is used, the forming cost increases excessively, and this is not practical.

Thus, conventionally known niobium powders for capacitors have problems in that the powders are not fully suitable for continuous molding and the productivity of capacitors is low.

disclosure of invention

The object of the present invention is to provide a capacitor with large capacitance per unit mass, low leakage current and high moisture resistance; a sintered body that can be used as an electrode material of the capacitor and can obtain a high apparent ratio of capacitance; The material of the sintered body is preferably niobium powder that exhibits good fluidity in forming operations, promotes continuous forming, and enables stable production of capacitors; and methods of manufacturing the capacitor, the sintered body, and the niobium powder.

As a result of extensive research to solve the above-mentioned problems, the present inventors have found that a high apparent ratio of capacitance can be obtained when niobium powder having a specific pore size distribution, preferably a plurality of pore size peaks in the pore size distribution, is used for capacitor electrodes, And it is possible to produce capacitors with small leakage current and good wettability. The present inventors have also found that niobium powder preferably having a tap density of 0.5-2.5 g/ml, more preferably an average particle size of 10-1,000 micrometers, exhibits good fluidity, is capable of continuous molding and is used as a material for the above-mentioned sintered body. The material is preferable, and when the niobium powder is used, a capacitor with a small leakage current can be stably produced. The present inventors have found that, more preferably, a capacitor using as an electrode a niobium sintered body produced from niobium powder having a wide range of pore size distribution and a plurality of pore size peaks of 0.5 μm or more can simultaneously obtain a high apparent ratio of capacitance and low ESR. Based on these inventions, the present invention has been accomplished.

More specifically, the present invention relates to the following niobium powder, niobium sintered body, and capacitor using the same, and to a method for manufacturing the niobium powder, niobium sintered body, and capacitor.

(1) A niobium powder for capacitors, having a tap density of 0.5 to 2.5 g/ml.

(2) The niobium powder as described in 1 above, wherein the average particle size is 10 to 1,000 micrometers.

(3) The niobium powder according to the above 1 or 2, wherein the angle of repose is 10° to 60°.

(4) The niobium powder according to any one of 1 to 3 above, wherein the BET specific surface area is 0.5 to 40 m ² /g.

(5) The niobium powder as described in any one of 1 to 4 above, which has a pore size distribution with a pore size peak in the range of 0.01 to 500 μm.

(6) The niobium powder as described in 5 above, wherein the pore size distribution has a plurality of pore size peaks.

(7) The niobium powder as described in the above 5 or 6, wherein any one of the peak pore diameters is in the range of 0.5 to 100 micrometers.

(8) The niobium powder as described in any one of 1 to 7 above, wherein the content of at least one element selected from the group consisting of nitrogen, carbon, boron and sulfur is 200,000 mass ppm or less.

(9) A sintered body using the niobium powder as described in any one of 1 to 8 above.

(10) The sintered body as described in 9 above, which has a pore size distribution with a pore size peak of 0.01 to 500 μm.

(11) A niobium sintered body for capacitor electrodes, wherein the pore size distribution of the niobium sintered body has a plurality of pore size peaks.

(12) The niobium sintered body as described in 11 above, wherein the pore size distribution has two pore size peaks.

(13) The niobium sintered body as described in the above 11 or 12, wherein, among the plurality of pore diameter peaks, peaks of two peaks having the highest relative intensities exist in the range of 0.2 to 0.7 microns and the range of 0.7 to 3 microns, respectively Inside.

(14) The niobium sintered body as described in any one of the above-mentioned 11 to 13, wherein, among the plurality of pore diameter peaks, the peak having the highest relative intensity is present at a lower position than the peak having the next highest relative intensity. side of the larger diameter.

(15) The niobium sintered body as described in any one of 9 to 14 above, wherein the volume of the sintered body is 10 mm ³ or more including the volume of pores.

(16) The niobium sintered body as described in any one of 9 to 15 above, wherein the specific surface area of the sintered body is 0.2 to 7 m ² /g.

(17) The niobium sintered body as described in any one of 9 to 16 above, wherein a part of the sintered body is nitrided.

(18) The niobium sintered body as described in any one of 12 to 17 above, wherein the sintered body is a sintered body obtained from a niobium shaped body that produces a niobium sintered body at 1300°C. A sintered body with an hourly CV value of 40,000 to 200,000 μFV/g.

(19) A capacitor comprising an electrode using the niobium sintered body as described in any one of 9 to 18 above, a counter electrode and a dielectric material interposed therebetween.

(20) The capacitor as described in 19 above, wherein the dielectric material mainly contains niobium oxide.

(21) The capacitor as described in 19 above, wherein the counter electrode is at least one material selected from an electrolytic solution, an organic semiconductor, and an inorganic semiconductor.

(22) The capacitor as described in 21 above, wherein the counter electrode is an organic semiconductor, and the organic semiconductor is selected from organic semiconductors containing benzopyrroline tetramer and chloranil, mainly containing tetrathiotetracene. At least one material of an organic semiconductor, an organic semiconductor mainly containing tetracyanoquinodimethane, and a conductive polymer.

(23) The capacitor as described in 22 above, wherein the conductive polymer is at least one member selected from the group consisting of polypyrrole, polythiophene, polyaniline and substituted derivatives thereof.

(24) The capacitor as described in 22 above, wherein the conductive polymer is a conductive polymer obtained by doping a dopant into a polymer containing a repeating unit represented by the following formula (1) or (2) :

(wherein R ¹ to R ⁴ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl, alkoxy or alkyl ester group containing 1 to 10 carbon atoms, a halogen atom, nitro, cyano, primary, secondary or tertiary amino, CF ₃ groups, phenyl and substituted phenyl monovalent groups; each pair of R ¹ and R ² , R ³ and R ⁴ can be in any positions combined to form a divalent chain for at least one ^3- , ^{4- ,} 5-, ^6- or 7-membered saturated or unsaturated Hydrocarbon ring structure; the cyclic bonded chain can contain carbonyl, ether, ester, amide, thioether, sulfinyl, sulfonyl or imino at any position; X represents an oxygen atom, sulfur atom or nitrogen atom; ^R5 only when X exists only when it is a nitrogen atom, and independently represents a hydrogen atom or a linear or branched, saturated or unsaturated alkyl group containing 1 to 10 carbon atoms).

(25) The capacitor as described in 24 above, wherein the conductive polymer is a conductive polymer containing a repeating unit represented by the following formula (3):

(Wherein, R ⁶ and R ⁷ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl group containing 1 to 6 carbon atoms, or a substituent, used to form At least one 5-, 6- or 7-membered saturated hydrocarbon ring structure obtained by an alkyl group containing two oxygen atoms; and the ring structure includes a vinylidene bond that may be substituted, a phenylene structure that may be substituted structure).

(26) The capacitor as described in 22 above, wherein the conductive polymer is a conductive polymer obtained by doping a dopant into poly(3,4-ethylenedioxythiophene).

(27) The capacitor as described in 19 above, wherein the counter electrode is made of a material at least partially having a layered structure.

(28) The capacitor as described in 19 above, wherein the material of the counter electrode contains an organic sulfonate anion as a dopant.

(29) A method for producing the niobium powder described in any one of 1 to 8 above, which includes activation treatment of niobium or a niobium compound.

(30) The method for producing niobium powder as described in 29 above, wherein the activation treatment of niobium or a niobium compound is performed by at least one step selected from a sintering step and a crushing step.

(31) The method for producing niobium powder as described in 29 or 30 above, wherein the activation treatment of niobium or a niobium compound is performed using a mixture of niobium or a niobium compound and an activator.

(32) The method for producing niobium powder as described in any one of 29 to 31 above, wherein the average particle size of the niobium or niobium compound processed by the activation treatment is 0.01 to 10 micrometers.

(33) The method for producing niobium powder as described in any one of 29 to 32 above, wherein the niobium or niobium compound contains at least one element selected from nitrogen, carbon, boron and sulfur in an amount of 200,000 ppm or less.

(34) The method for producing niobium powder as described in any one of 29 to 33 above, wherein the niobium compound is at least one selected from the group consisting of niobium hydride, niobium alloy and niobium hydride alloy.

(35) The method for producing niobium powder as described in 34 above, wherein the component other than niobium contained in the niobium alloy or niobium hydrogenated alloy is at least one element selected from elements having an atomic number of 88 or less , but excluding hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine, niobium, helium, neon, argon, krypton, xenon and radon.

(36) The method for producing niobium powder as described in 31 above, wherein the mixture containing niobium or a niobium compound and an activator is obtained by mixing these components using a solvent.

(37) The method for producing niobium powder as described in 36 above, wherein the solvent is at least one solvent selected from the group consisting of water, alcohol, ether, cellosolve, ketone, aliphatic hydrocarbon, aromatic hydrocarbon, and halogenated hydrocarbon .

(38) The method for producing niobium powder as described in 31 above, wherein the activator is used in an amount of 1 to 40% by mass based on the total amount of niobium or niobium compounds.

(39) The method for producing niobium powder as described in 31 or 38 above, wherein the average particle size of the activator is 0.01 to 500 micrometers.

(40) The method for producing niobium powder as described in any one of 31, 38 and 39 above, wherein the activator has a plurality of particle size peaks.

(41) The method for producing niobium powder as described in any one of 31, 38-40 above, wherein the activator is a substance that is removed in gaseous form at a temperature of 2,000°C or below.

(42) The method for producing niobium powder as described in the above 41, wherein the activator is selected from naphthalene, anthracene, quinone, camphor, polyacrylic acid, polyacrylate, polyacrylamide, polymethacrylic acid, polymethyl At least one of acrylate, polymethacrylamide, polyvinyl alcohol, NH ₄ Cl, ZnO, WO ₂ , SnO ₂ and MnO ₃ .

(43) The method for producing niobium powder as described in any one of 31, 38-40 above, wherein the activator is selected from water-soluble substances, organic solvent-soluble substances, acid solution-soluble substances, alkali solution-soluble substances, Substances that form complexes and become substances soluble in water, organic solvents, acid solutions or alkaline solutions, substances that become soluble in water, organic solvents, acid solutions or alkaline solutions at a temperature of 2000°C or less at least one of the substances.

(44) The method for producing niobium powder as described in the above 43, wherein the activator is selected from metals and carbonic acid, sulfuric acid, sulfurous acid, halogen, perhalogenic acid, hypohalous acid, nitric acid, nitrous acid, phosphoric acid, acetic acid , a compound of oxalic acid or boric acid, a metal, at least one of a metal hydroxide and a metal oxide.

(45) The method for producing niobium powder as described in the above 43, wherein the activator is selected from lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium, radium, scandium, yttrium , cerium, neodymium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, silver, gold, zinc, cadmium, boron , aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, arsenic, antimony, bismuth, selenium, tellurium, polonium and their compounds.

(46) The method for producing niobium powder as described in any one of 29 to 40 and 43 to 45 above, wherein the activation treatment is deactivation by heating and/or under reduced pressure before or during the sintering step. agent treatment.

(47) The method for producing niobium powder as described in any one of 29 to 40 and 43 to 45 above, wherein the activation treatment is performed by making a solvent and Treatment of sintered or crushed product contacts to remove activator components.

(48) The method for producing niobium powder as described in 47 above, wherein the solvent is at least one selected from water, an organic solvent, an acid solution, an alkali solution, and a solution containing a ligand forming a soluble complex. kind.

(49) The method for producing niobium powder as described in 48 above, wherein the acid solution is at least one solution selected from nitric acid, sulfuric acid, hydrofluoric acid and hydrochloric acid.

(50) The method for producing niobium powder as described in 48 above, wherein the alkaline solution contains at least one component selected from the group consisting of alkali metal hydroxides and ammonia.

(51) The method for producing niobium powder as described in 48 above, wherein the ligand is at least one selected from ammonia, glycine and ethylenediaminetetraacetic acid.

(52) The method for producing niobium powder as described in 48 above, wherein the organic solvent is methyl isobutyl ketone.

(53) A method for producing nitrogen-containing niobium powder, which comprises treating the niobium powder described in any one of 1 to 7 above with at least one method selected from liquid nitriding, ion nitriding, and gas nitriding .

(54) A method for producing carbon-containing niobium powder, which comprises treating the niobium powder described in any one of 1 to 7 above with at least one method selected from solid-phase carbonization and liquid-phase carbonization.

(55) A method for producing boron-containing niobium powder, which comprises treating the niobium powder described in any one of the above 1 to 7 with at least one method selected from gas-phase boronization and solid-phase boronization,

(56) A method for producing sulfur-containing niobium powder, which comprises treating the niobium powder described in any one of 1 to 7 above with at least one method selected from gas phase vulcanization, ion vulcanization and solid phase vulcanization.

(57) A niobium powder obtained by the production method described in any one of 29 to 56 above.

(58) A method for producing a niobium sintered body using the niobium powder described in any one of 1 to 8 and 57 above.

(59) A method of producing a capacitor comprising an electrode using a niobium sintered body, a dielectric material formed on the surface of the sintered body, and a counter electrode provided on the dielectric material, wherein the niobium sintered body is formed by Obtained by sintering the niobium powder described in any one of 1-8 and 57 above.

(60) The method for producing a capacitor as described in 59 above, wherein the dielectric material is formed by electrolytic oxidation.

(61) A method of producing a capacitor comprising an electrode using a niobium sintered body, a dielectric material formed on a surface of the sintered body, and a counter electrode provided on the dielectric material, wherein the The niobium sintered body is the niobium sintered body described in any one of 9 to 18 above.

(62) An electronic circuit using the capacitor described in any one of 19 to 28 above.

(63) An electronic device using the capacitor described in any one of 19 to 28 above.

Brief description of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an enlarged view schematically illustrating a niobium powder of the present invention having two or more pore size peaks.

Fig. 2 is a schematic diagram of the pore size distribution of niobium powder measured by mercury intrusion porosimetry.

Modes of Carrying Out the Invention

A capacitor having good leakage current characteristics and excellent moisture resistance, a niobium sintered body capable of imparting these properties and giving a high apparent ratio of capacitance, and a niobium sintered body which is preferable as the material of the sintered body and has good fluidity and can be continuously formed are described below Niobium powder, and methods for producing the capacitor, niobium sintered body, and niobium powder.

In the present invention, capacitor niobium powder (sometimes simply referred to as "niobium powder") having a tap density of 0.5 to 2.5 g/ml is used as the niobium powder satisfying the above performance of capacitors and improving productivity in capacitor production.

The niobium powder for capacitors used herein refers to niobium powder that mainly contains niobium and can be used as a material for producing capacitors. The niobium powder may contain, for example, components capable of forming an alloy with niobium, ie components other than niobium, such as nitrogen and/or oxygen.

A capacitor can be produced by forming and sintering niobium powder for capacitors using the following method to obtain a niobium sintered body for capacitors (sometimes simply referred to as a niobium sintered body), and then forming a dielectric layer and a counter electrode layer thereon.

The niobium powder for capacitors is added to a solution obtained by dissolving a binder described later in an organic solvent such as toluene or methanol and mixing well using a shaking mixer or a V-type mixer. Then, the organic solvent is distilled off under reduced pressure using a drier such as a cone drier to prepare a binder-containing niobium mixed powder. This mixed powder is loaded into the hopper of the automatic forming machine, weighed and the niobium powder flows through the feeding tube from the hopper to the metal mold of the metal forming machine, so that it automatically falls into the metal mold and is formed together with the wire . After removing the binder, the shaped product is sintered at 500 to 2,000° C. under reduced pressure to produce a niobium sintered body.

The niobium sintered body is formed by electrochemical treatment, for example, in an electrolyte solution of phosphoric acid and adipic acid with a concentration of 0.1% by mass, at 30-90°C and a voltage of 20-60V, for 1-30 hours, to form mainly Dielectric layer of niobium oxide. Solid electrolyte layers such as manganese dioxide, lead dioxide and conductive polymer and graphite layers and silver paste layers are formed on the dielectric layer. After a cathode lead was attached thereto by brazing, it was sealed with resin to prepare a solid electrolytic capacitor.

At the time of molding, without mixed powder with suitable fluidity or angle of repose, the powder cannot flow smoothly from the hopper into the metal mold, and molding cannot be performed stably. In particular, since the mixed powder is conveyed from a hopper using a method such as vibration, etc., the excessively large or small tap density or average particle size of the mixed powder results in large dispersion of the quality of the shaped product or the strength or shape of the sintered body, and in some In some cases, chipping or cracking is caused, resulting in a poor leakage current value. Therefore, the tap density, average particle size, fluidity and angle of repose of the mixed powder are important factors to produce a good sintered body and a good capacitor.

These physical properties of the mixed powder rarely change before and after mixing with the binder, but are determined by the physical properties of the niobium powder for capacitors used. Important therefore are the tap density, average particle size, flowability and angle of repose of the niobium powder used. The fluidity and angle of repose of niobium powder are mainly affected by the tap density or the average particle size, therefore, the tap density and the average particle size become important factors.

In the present invention, the tap density is preferably 0.5-2.5 g/ml, more preferably 0.8-1.9 g/ml, in order to increase the productivity and strength of the sintered body, improve fluidity or angle of repose, and thereby reduce leakage current. The average particle size of the niobium powder of the present invention is preferably 10 to 1,000 microns, more preferably 50 to 200 microns.

In order to allow the niobium powder to freely fall from the hopper into the metal mold of the forming machine, the angle of repose of the niobium powder of the present invention is preferably 10°-60°, more preferably 10°-50°.

By sequentially performing at least one sintering step and a crushing step, a powder containing niobium powder or niobium compound powder (hereinafter referred to as "raw niobium powder") and an activator (also referred to as "pore-forming material", and hereinafter sometimes referred to as "additive" ) mixture (hereinafter referred to as "raw material mixture") can produce niobium powder with the above physical properties.

During the production of niobium powder according to the invention from the raw material mixture, the activator is removed in a sintering step or a crushing step. The removal of the activator is also carried out independently of said sintering or crushing step.

Depending on the chemical nature of the activator, various methods for removing the activator may be optionally used. One method or a combination of these methods can be used which can easily remove the activator.

Examples of a method of removing the activator include a method of evaporating, sublimating, or thermally decomposing the activator and removing it as a gas, and a method of removing the activator by dissolving it in a solvent.

In the case of removal of the activator in gaseous form, it may be carried out in the sintering step, or a step of removing the activator under heating and/or reduced pressure may be provided prior to sintering.

In the case of removing the activator by dissolving the raw material mixture in a solvent after sintering or during or after the crushing process, a solvent described below is brought into contact with the sintered product or the crushed product to dissolve and remove the activator.

The step of nitriding, boriding, carbonizing or sulfurizing a portion of the niobium powder may be provided at any stage in the process of producing the niobium powder of the present invention from the raw material mixture.

The method for producing the niobium powder of the present invention is described in detail below.

The raw niobium powder may be at least one powder selected from niobium, niobium hydride, niobium alloy and niobium hydride alloy. A portion of the powder can be nitrided, sulfurized, carburized or borated. "Alloy" as used in the present invention includes solid solutions with other alloying components.

The average particle size of the raw niobium powder is preferably 0.01-10 microns, more preferably 0.02-5 microns, even more preferably 0.05-2 microns.

Examples of the method of obtaining niobium used as a raw material niobium powder include a method of hydrogenating, crushing and dehydrogenating niobium ingot, niobium pellets or niobium powder, a method of reducing potassium fluoroniobate with sodium etc. and crushing the reduced product, using hydrogen, carbon, A method of reducing niobium oxide by at least one of magnesium and aluminum and crushing the reduced product, and a method of reducing niobium halide with hydrogen.

Examples of methods of obtaining niobium hydride used as a raw material niobium powder include methods of hydrogenating and crushing niobium ingots, niobium particles, or niobium powder.

Examples of a method of obtaining a niobium hydrogenated alloy used as a raw material niobium powder include a method of crushing a niobium alloy ingot, a niobium alloy particle, or a hydride of niobium alloy powder. Examples of a method of obtaining a niobium alloy used as a raw material niobium powder include a method of dehydrogenating the niobium hydride alloy obtained as above.

As an alloy component other than niobium, a niobium alloy or a niobium hydride alloy containing at least one element selected from elements having an atomic number of 88 or less, excluding hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine, niobium, Helium, Neon, Argon, Krypton, Xenon, and Radon.

An activator is a substance which may be removed at any step in the production of the niobium powder of the present invention from the raw material mixture. In the niobium powder of the present invention, pores are usually formed in the portion where the activator is removed.

The particle size of the activator affects the pore size of the niobium powder of the present invention, the pore size of the niobium powder affects the pore size of the niobium sintered body, and the pore size of the niobium sintered body affects the capacitance of the capacitor and the impregnation ability of the cathode agent in the capacitor production step.

The impregnation ability of the cathodic agent has a great influence in the production of capacitors with high capacity and low ESR. When producing a sintered body by forming niobium powder under reduced pressure, the pore diameter of the niobium sintered body is naturally smaller than that of the niobium powder. Since it is difficult to impregnate a cathode agent into a niobium sintered body produced from niobium powder having a small pore size, the average pore size of the niobium powder is preferably 0.5 micron or more, more preferably 1 micron or more.

The average pore size of the niobium powder is preferably 0.01-500 microns, more preferably 0.03-300 microns, and even more preferably 0.1-200 microns. In order to have a pore diameter within this range, the average particle size of the activator is preferably 0.01-500 microns, more preferably 0.03-300 microns, even more preferably 0.1-200 microns.

The average pore size of the niobium powder is most preferably 0.5-100 microns, and the average particle size of the activator is most preferably 0.5-100 microns.

Using a small particle size activator can reduce the void diameter, and using a large particle size activator can increase the pore size.

By adjusting the particle size distribution of the activator, the pore size distribution can be adjusted.

In order to obtain a capacitor having a sufficiently large capacitance without problems involved in catholyte impregnation ability, it is preferable to appropriately provide pores small enough in the niobium sintered body in accordance with the physical properties of the catholyte to produce a desired capacitance, and appropriately provide pores large enough To ensure satisfactory impregnation of cathodic agent.

In order to adjust the pore size distribution of niobium powder or niobium sintered body, for example, by using an activator (powder) having a particle size distribution of two or more peaks, niobium powder can be made to have a pore size distribution of two or more peaks. By sintering this niobium powder, a niobium sintered body of equal pore size having two or more peaks in the pore size distribution can be obtained. In this case, the peak pore size preferably exists in the range of 0.01-500 microns, more preferably 0.03-300 microns, further preferably 0.1-200 microns, particularly preferably 0.1-30 microns, most preferably 0.2-3 microns.

The niobium powder from which the above niobium sintered body is produced has two or more peaks in the particle size distribution. Any one of the two or more peaks is preferably 0.5 micron or greater. For example, in order to produce a niobium sintered body having two peaks of 0.7 and 3 microns in the particle size distribution, the two peaks of the niobium powder can be adjusted to about 1.5 and about 2.5 microns. In order to obtain niobium powder with a small pore size of 1.5 microns and a large pore size of 25 microns, it is necessary to use activators with average pore sizes of 1.5 microns and 25 microns, respectively. In general, when small-diameter pores and large-diameter pores exist in niobium powder, the large-diameter pores become smaller during press-forming. Therefore, the large-diameter peak is preferably 20 micrometers or more. It is also preferred that 30% by volume or more of the total pore volume has a pore size of 20 microns or greater, more preferably 40% by volume or more.

The above embodiments are described in detail below based on the drawings. Fig. 1 is an enlarged view schematically illustrating niobium powder of the present invention. The niobium powder in Fig. 1 is a granulated powder comprising a raw powder with a specific pore size formed by an activator. Pores (A) and (B) were formed using activators with average diameters of about 1.5 microns and about 25 microns, respectively. In this way, the original powders can be efficiently coagulated with each other. Fig. 2 is a schematic diagram of the pore size distribution of niobium powder measured by mercury intrusion porosimetry. Peak (A) corresponds to pores (A) formed by activators having an average diameter of about 1.5 microns, and peak (B) corresponds to pores (B) formed by activators having an average diameter of about 25 microns. Peak (B) is higher than peak (A), and 44% of the total pore volume has a pore size of 20 microns or larger.

For example, by mixing two or more activators having different peaks in the particle size distribution, an activator having two or more peaks in the particle size distribution can be obtained.

Examples of the substance as the activator include a substance that becomes a gas at or below the sintering temperature and a substance that is soluble in a solvent at least after sintering.

Examples of substances that become gas at or below the sintering temperature include substances that become gas by evaporation, sublimation, or thermal decomposition. Inexpensive substances that can easily become gas without leaving residues even at low temperatures are preferred. Examples thereof include aromatic compounds such as naphthalene, anthracene and quinone, camphor, NH ₄ Cl, ZnO, WO ₂ , SnO ₂ , MnO ₃ , and organic polymers.

Examples of organic polymers include polyacrylic acid, polyacrylate, polyacrylamide, polymethacrylic acid, polymethacrylate, polymethacrylamide, and polyvinyl alcohol.

Substances soluble at least after sintering are substances in which the residue of the activator or its thermal decomposition products are soluble in the solvent. A substance that can be easily dissolved in a solvent described below after sintering or during or after crushing is particularly preferable. Such substances can be selected from many substances depending on the combination of solvents.

Examples thereof include compounds of metals with carbonic acid, sulfuric acid, sulfurous acid, halogens, perhalogenous acids, hypohalous acids, nitric acid, nitrous acid, phosphoric acid, acetic acid, oxalic acid or boric acid, metal oxides, metal hydroxides and metals.

Among them, compounds having large solubility in solvents described below such as acids, alkalis or ammonium salt solutions are preferable. Examples include compounds containing lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium, radium, scandium, yttrium, cerium, neodymium, erbium, titanium, zirconium, hafnium, vanadium, niobium, Tantalum, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, silver, gold, zinc, cadmium, aluminum, gallium, indium, thallium, germanium, tin, lead, antimony, Compounds of at least one of bismuth, selenium, tellurium, polonium, boron, silicon and arsenic. Among them, metal salts are preferable, and examples such as barium oxide, manganese (II) nitrate and calcium carbonate are more preferable.

These activators may be used alone or in combination of two or more kinds thereof.

In order to effectively form a specific pore size, a substance existing in a solid form at a sintering temperature is preferable as an activator material. The reason is that the activator in the solid state at the sintering temperature hinders the excessive agglomeration of the original niobium powder, so that the niobium powder can fuse with each other only at the contact point. If the activator is present in liquid or gaseous form at the sintering temperature, it will do little to hinder this agglomeration and may form smaller pores than desired. Thus, the pore size becomes more stable with activators containing higher melting point species such as barium oxide, calcium carbonate, aluminum oxide, and magnesium oxide than with activators containing low melting point species such as aluminum metal, magnesium metal, magnesium hydride, and calcium metal .

If a small amount of activator is added, the tap density and angle of repose become larger, while if a large amount is added, the tap density becomes smaller and the closed pores increase during the sintering stage. In order to obtain an angle of repose of 60° or less and a tap density of 0.5 to 2.5 g/ml without the problem of closed pores in the sintering stage, the amount of activator added is generally 1 to 40% by mass or less (unless otherwise specified , mass % is hereinafter referred to as %), preferably 5 to 25%, more preferably 10 to 20%, based on raw material niobium, but this can vary according to the average particle size of the activator.

The raw material mixture can be obtained by mixing the activator and the niobium raw material each in powder form without using a solvent or by mixing the activator and the niobium raw material using a suitable solvent and drying the mixture.

Examples of usable solvents include water, alcohols, ethers, cellosolves, ketones, aliphatic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons.

Mixing can be performed using a mixer. As for the mixer, usual equipment such as a shaker mixer, a V-type mixer and a Nauter mixer can be used without any problem. The temperature at the time of mixing is limited by the boiling point and freezing point of the solvent, but is generally -50 to 120°C, preferably -50 to 50°C, more preferably -10 to 30°C. The time taken for mixing is not particularly limited as long as it is 10 minutes or more, however, mixing is preferably performed in an oxygen-free atmosphere using an inert gas such as nitrogen or argon for 1 to 6 hours.

In case a solvent is used, the resulting mixture is dried at below 80°C, preferably below 50°C, using a conical drier or a compartment drier. If the mixture is dried at a temperature of 80° C. or higher, the oxygen contained in the niobium or niobium hydride powder disadvantageously increases.

In the case where the activator becomes a gas at or below the sintering temperature, the activator can be removed at the time of sintering, but by setting conditions such as temperature, pressure, and time as conditions that promote removal according to the chemical properties of the activator, it can be independently The step of outgassing and removing the activator prior to sintering is provided. In this case, the activator is evaporated at 100-800° C. under reduced pressure within several hours.

In the case of using niobium hydride or a niobium hydride alloy as the raw material niobium, dehydrogenation can be achieved by performing the above steps regardless of the kind of the activator.

The sintering step is performed at 500 to 2,000°C, preferably 800 to 1,500°C, more preferably 1,000 to 1300°C, under reduced pressure or in a reducing atmosphere such as argon. After the sintering is completed, the sintered product is preferably cooled until the niobium temperature (sometimes simply referred to as "product temperature") becomes 30°C or lower, and an inert gas containing 0.01 to 10% by volume, preferably 0.1 to 1% by volume of oxygen is gradually added Such as nitrogen or argon, so that the temperature of the product does not exceed 30° C., and after standing for 8 hours or more, the sintered product is taken out to obtain a sintered mass.

In the crushing step, the sintered agglomerate is crushed to a suitable particle size using a crusher such as a roller granulator.

Where the activator is soluble in a solvent at least after the sintering step, a suitable solvent is brought into contact with the sintered agglomerate or the crushed powder after sintering and before, during or after crushing or at a plurality of these steps, whereby the The activator is dissolved and removed. The activator component is preferably dissolved and removed from the crushed powder after crushing due to ease of removal.

The solvent used here is a solvent in which the activator to be dissolved has a sufficiently high solubility. Solvents that are cheap and leave little residue are preferred. For example, in the case of water-soluble activators, water can be used; in the case of organic solvent-soluble activators, organic solvents such as methyl isobutyl ketone, ethanol or dimethylsulfoxide (DMSO) can be used; In the case of activators, acid solutions such as nitric acid, sulfuric acid, phosphoric acid, boric acid, carbonic acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid or organic acids can be used; Alkaline solutions such as alkali metal hydroxides, alkaline earth metal hydroxides, or ammonia; in the case of activators that form soluble complexes, amine solutions such as ammonia or ethylenediamine that become complex ligands, Amino acids such as glycine, polyphosphoric acids such as sodium tripolyphosphate, crown ethers, thiosulfates such as sodium thiosulfate, or chelating agents such as ethylenediaminetetraacetic acid.

Ammonium salt solutions such as ammonium chloride, ammonium nitrate and ammonium sulfate, cation exchange resins and anion exchange resins can also be suitably used. Preference is given to dissolution and removal of the activator at lower temperatures. If the activator is dissolved and removed at high temperature, the surface of niobium is oxidized because niobium has a high affinity for oxygen. Therefore, the temperature for dissolution and removal is preferably 50°C or lower, more preferably -10°C to 40°C, further preferably 0°C to 30°C. For the reasons above, it is preferable to choose a method that generates little heat during dissolution and removal. For example, when using metal oxides or metals as activators, dissolution and removal with acids generally produces high neutralization heats. Therefore, it is preferable to select a method that generates little heat, such as dissolving in water and an organic solvent, forming a soluble complex by using a solvent of ammonium nitrate salt and ethylenediamine tetraacetate and dissolving in an ion-exchange resin containing in solvent.

Specific examples of combinations of activators and solvents include barium oxide and water, calcium oxalate and hydrochloric acid, aluminum oxide and sodium hydroxide aqueous solution, hafnium oxide and methyl isobutyl ketone, and magnesium carbonate and tetrasodium edetate aqueous solution.

After dissolving and removing the activator, wash and dry the residue well. For example, in the case of removing barium oxide with water, the residue is sufficiently washed with an ion exchange solution until the conductivity of the washing solution decreases to 5 μS/cm or less. Subsequently, the product is dried under reduced pressure at a product temperature of 50°C or lower. Here, the amount of residual activator or solvent component is generally 100 ppm or less, but this varies with washing conditions.

In order to improve the LC value, the thus obtained niobium powder, sintered agglomerate and niobium raw material powder may be subjected to nitriding, boriding, carbonizing or sulfurizing of a part of the niobium powder, or a plurality of these treatments.

The niobium powder of the present invention may contain the obtained niobium nitride, niobium boride, niobium carbide or niobium sulfide or a plurality of these substances. The total amount of each element of nitrogen, boron, carbon and sulfur varies depending on the shape of the niobium powder, but it is 0 to 200,000 ppm, preferably 50 to 100,000 ppm, more preferably 200 to 20,000 ppm. If the total content exceeds 200,000 ppm, the capacity characteristics of the produced capacitor deteriorate and are not suitable for capacitors.

The nitriding of the niobium powder may be performed by any one of liquid phase nitriding, ion nitriding, and gas phase nitriding, or a combination thereof. Among them, vapor phase nitriding in a nitrogen atmosphere is preferable because of its simple equipment and easy operation. For example, vapor phase nitriding in a nitrogen atmosphere can be achieved by allowing the above niobium powder to stand in a nitrogen atmosphere. With a nitriding atmosphere temperature of 2,000° C. or less and a standing time of 100 hours or less, niobium powder having a target nitriding amount can be obtained. Processing at higher temperatures can shorten processing times.

The boronization of niobium powder can be gas phase boronization or solid phase boronization. For example, niobium powder can be boridated by allowing it to stand with a boron source such as boron particles or a boron halide such as boron trifluoride at a temperature of 2,000° C. or less under reduced pressure for 1 minute to 100 hours.

Carbonization of niobium powder may be any of gas phase carbonization, solid phase carbonization and liquid phase carbonization. For example, niobium powder can be carbonized under reduced pressure by allowing it to stand at a temperature of 2,000° C. or below for 1 minute to 100 hours together with a carbon source such as a carbon material or a carbon-containing organic material (eg, methane).

The vulcanization of niobium powder can be any of gas phase vulcanization, ion vulcanization and solid phase vulcanization. For example, vapor phase vulcanization in a sulfur atmosphere can be achieved by allowing niobium powder to stand in a sulfur atmosphere. With a sulfidation atmosphere temperature of 2,000° C. or less and a rest time of 100 hours or less, niobium powder having a targeted amount of sulfidation can be obtained. Processing times can be shortened by processing at higher temperatures.

The BET specific surface area of the niobium powder of the present invention thus obtained is usually 0.5-40 m ² /g, preferably 0.7-10 ^{m 2} /g, more preferably 0.9-2 m ² /g.

The niobium powder of the present invention can be a mixture of different niobium powders with different tap density, particle size, angle of repose, BET specific surface area, pore size distribution and treatment by nitriding, boriding, carbonizing or vulcanizing.

The sintered body of the present invention that can be used as a capacitor electrode is preferably produced by, for example, sintering the above-mentioned niobium powder of the present invention. For example, niobium powder is press-formed into a predetermined shape, and then heated at 500°C to 2,000°C, preferably 800°C to 1,500°C, more preferably 1,000°C to 1300°C, at 10 ⁻⁵ to 10 ² Pa for 1 minute to 10 minutes. Hour.

The pore size distribution of the sintered body obtained from the niobium powder of the present invention usually has a pore size peak in the range of 0.01 to 500 microns.

By adjusting the applied pressure during forming to a specific pressure value, the sintered body can have a larger peak number of pore diameters than niobium powder. The value of the applied pressure varies with the pressure forming conditions such as the physical properties of niobium powder, the shape of the formed product, and the forming machine, but it is within the range from the pressure capable of press forming to the pressure at which the pores of the sintered body are not closed. The preferred pressure value is determined through preliminary experiments according to conditions such as the physical properties of the niobium powder to be formed so that it has multiple pore diameter peaks. For example, the value of the applied pressure can be controlled by controlling the load of the forming machine applied to the shaped article.

The pore size distribution of the sintered body preferably has at least two pore size peaks in order to contain pores small enough to obtain the desired capacitance and pores large enough to obtain satisfactory impregnation of the catholyte depending on the physical properties of the catholyte. From such a sintered body having a plurality of peaks in the pore size distribution, a capacitor having excellent impregnation ability against electrodes and a high apparent ratio of capacitance can be produced.

When among the multiple pore size distribution peaks, there are two peaks with the highest relative intensity in the range of 0.2 to 0.7 microns and in the range of 0.7 to 3 microns, preferably in the range of 0.2 to 0.7 microns and 0.9 to 3 microns respectively At peak, capacitors produced from this sintered body can have good moisture resistance. Among the plurality of pore size distribution peaks, the peak having the highest relative intensity preferably exists on the larger diameter side than the peak of the next highest relative intensity because the capacitor can have more excellent moisture resistance.

The specific surface area of the sintered body thus produced is generally 0.2 to 7 m ² /g.

In general, the larger the shape of the sintered body, the more difficult it is to impregnate the electrode. For example, in the case where the sintered body has a size of 10 mm ³ or more, the sintered body of the present invention having a plurality of peaks in the pore size distribution can be used particularly effectively.

The sintered body of the present invention may be partially nitrided. As for the nitriding method, the above-mentioned method and reaction conditions for niobium powder can be used. It is also possible to pre-nitridize a part of the nitrogen powder for producing a sintered body and nitriding a part of the sintered body produced from this niobium powder.

Such a sintered body usually contains 500 to 70,000 mass ppm of oxygen because there are naturally oxidized oxygen contained in the niobium powder before sintering and oxygen added by natural oxidation after sintering. In the sintered body of the present invention, the content of elements other than niobium, alloy-forming elements, oxygen, and nitrogen is usually 400 mass ppm or less.

As an example, when the sintered body of the present invention is sintered at 1300° C., the CV value (the product of the electrochemical forming voltage at 80° C. in a 0.1% by mass phosphoric acid solution for 120 minutes and the electric capacity at 120 Hz) is 4,000 ~200,000 μFV/g.

The production of the capacitor device is described below.

For example, preparing a wire containing a rectifying metal such as niobium or tantalum and having an appropriate shape and length is integrally formed during press molding of niobium powder so that a part of the wire is inserted into the inside of the shaped product, so that the wire can be used as The lead-out wire of the sintered body. Alternatively, niobium powder is formed and sintered without using a lead wire, and then, a separately prepared lead wire is connected thereto by welding or the like.

Using this sintered body as an electrode, a capacitor can be produced by interposing a dielectric material between the electrode and a counter electrode. For example, a capacitor is produced by using a niobium sintered body as an electrode, forming a dielectric material on the surface of the sintered body (including the inner surface of pores), and providing a counter electrode on the dielectric material.

The dielectric material used for the capacitor is preferably a dielectric material mainly containing niobium oxide, more preferably a dielectric material mainly containing niobium pentoxide. For example, a dielectric material mainly containing niobium pentoxide can be obtained by electrolytic oxidation of a niobium sintered body as an electrode. For the electrolytic oxidation of the niobium electrodes in the electrolyte, aqueous solutions of protic acids, such as 0.1% aqueous phosphoric acid, sulfuric acid, 1% acetic acid or adipic acid, are generally used. In the case where the niobium oxide dielectric material is thus obtained by electrochemically forming a niobium electrode in an electrolytic solution, the capacitor of the present invention is an electrolytic capacitor and the niobium electrode is used as an anode.

In the capacitor of the present invention, the counter electrode of the niobium sintered body is not particularly limited, for example, at least one material (compound) selected from electrolytic solutions, organic semiconductors and inorganic semiconductors known in the art of aluminum electrolytic capacitors can be used .

Specific examples of the electrolytic solution include a dimethylformamide-ethylene glycol mixed solution in which 5% by mass of isobutyltripropylammonium tetrafluoroborate is dissolved and an isocarbonate solution in which 7% by mass of tetraethylammonium tetrafluoroborate is dissolved. Propyl ester-ethylene glycol mixed solution.

Specific examples of organic semiconductors include organic semiconductors containing phenylpyrroline tetramer and chloranil, organic semiconductors mainly containing tetrathiotetracene, organic semiconductors mainly containing tetracyanoquinodimethane, and organic semiconductors containing Conductive polymers of repeating units represented by (1) or (2):

Wherein, R ¹ to R ⁴ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl group, an alkoxy group or an alkyl ester group, a halogen atom, Monovalent groups of nitro, cyano, primary, secondary or tertiary amino groups, _CF3 groups, phenyl and substituted phenyl groups; each pair of ^R1 and ^R2 , ^R3 and ^R4 can be combined at any position Forming a bivalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon ring together with carbon atoms substituted by ^R1 and ^R2 or by ^R3 and ^R4 Structure; the ring-bound chain can contain carbonyl, ether, ester, amide, thioether, sulfinyl, sulfonyl or imino at any position; X represents an oxygen atom, a sulfur atom or a nitrogen atom; R ⁵ can only be used when X is nitrogen atoms, and independently represent a hydrogen atom or a linear or branched, saturated or unsaturated alkyl group containing 1 to 10 carbon atoms.

In the present invention, R ¹ to R ⁴ in formula (1) or (2) each independently preferably represent a hydrogen atom or a linear or branched, saturated or unsaturated alkane containing 1 to 6 carbon atoms. group or alkoxy group, and each pair of R ¹ and R ² , R ³ and R ⁴ may combine to form a ring.

In the present invention, the conductive polymer containing a repeating unit represented by formula (1) is preferably a conductive polymer containing a structural unit represented by the following formula (3) as a repeating unit:

Wherein, R ⁶ and R ⁷ each independently represent a hydrogen atom, a linear or branched saturated or unsaturated alkyl group containing 1 to 6 carbon atoms, or a substituent, which is used to form At least one 5-, 6- or 7-membered saturated hydrocarbon ring structure obtained by an alkyl group containing two oxygen atoms; and the ring structure includes a vinylene bond that may be substituted, a phenylene structure that may be substituted structure.

A conductive polymer having such a chemical structure is doped with a dopant, and for the dopant, known dopants can be used without limitation.

Specific examples of the inorganic semiconductor include inorganic semiconductors mainly containing lead dioxide or manganese dioxide, and inorganic semiconductors containing triiron tetroxide. These semiconductors may be used alone, or two or more kinds thereof may be used in combination.

Examples of polymers containing repeating units represented by formula (1) or (2) include polyaniline, polyphenylene ether, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole, and substituted derivatives thereof and copolymers. Among them, polypyrrole, polythiophene and substituted derivatives thereof (such as poly(3,4-ethylenedioxythiophene)) are preferable.

When the conductivity of the organic or inorganic semiconductor used is 10 ⁻² S/cm˜10 ³ S/cm, the produced capacitor can have a smaller impedance value and can increase high-frequency capacitance.

For example, electrical conductivity can be produced by polymerizing polymerizable compounds such as aniline, thiophene, furan, pyrrole, methylpyrrole, or their substituted derivatives under the action of an oxidizing agent that satisfactorily performs a two-electron oxidation of dehydrogenation. polymer. Examples of the polymerization reaction of the polymerizable compound (monomer) include gas phase polymerization and solution polymerization. A conductive polymer layer is formed on the surface of the niobium sintered body of the niobium sintered body with the dielectric material thereon. In the case where the conductive polymer is an organic solvent-soluble polymer capable of solution coating, a method of coating the polymer on the surface of the sintered body to form a conductive polymer layer is used.

A preferable example of a production method using solution polymerization is one in which a niobium sintered body on which a dielectric layer has been formed is immersed in a solution (solution 1) containing an oxidizing agent, and then the sintered body is dipped in a solution containing a monomer and Dopant solution (Solution 2) to conduct polymerization to form a conductive polymer layer on the surface of the sintered body. It is also possible to immerse the sintered body in the solution 1 after immersing it in the solution 2 . The solution 2 used in the above method may be a monomer solution not containing a dopant. In the case of using a dopant, the dopant may be present together with the solution containing the oxidizing agent.

The operation of performing these polymerization steps from the sintered body with the dielectric material thereon is repeated one or more times, preferably 3 to 20 times, so that a dense and layered conductive polymer layer can be easily formed.

In the manufacturing method of the capacitor of the present invention, any oxidizing agent may be used as long as it does not adversely affect the performance of the capacitor and the reducing agent of the oxidizing agent can become a dopant and improve the conductivity of the conductive polymer. Industrially inexpensive compounds that are easy to handle at the time of production are preferred.

Specific examples of oxidizing agents include Fe(III)-based compounds such as _FeCl3 , _FeClO4 , and Fe (organic acid anion) salts; anhydrous aluminum chloride/cuprous chloride; alkali metal persulfates; ammonium persulfate; peroxides manganese such as potassium permanganate; quinines such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone and tetracyano halogens such as iodine and bromine; peracids; sulfonic acids such as sulfuric acid, oleum, sulfur trioxide, chlorosulfonic acid, fluorosulfonic acid, and sulfamic acid; ozone; and many of these oxidizing agents mixture.

Examples of basic compounds of organic acid anions forming the above-mentioned Fe (organic acid anion) salt include organic sulfonic acids, organic carboxylic acids, organic phosphoric acids, and organic boric acids. Specific examples of organic sulfonic acids include benzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, α-sulfonaphthalene, β-sulfonaphthalene, naphthalene disulfonic acid, and alkylnaphthalenesulfonic acid (alkyl Examples include butyl, triisopropyl and di-tert-butyl).

Specific examples of organic carboxylic acids include acetic acid, propionic acid, benzoic acid and oxalic acid. In addition, polymer electrolyte anions such as polyacrylic acid, polymethacrylic acid, polystyrenesulfonic acid, polyvinylsulfonic acid, poly-α-methylsulfonic acid, polyvinylsulfuric acid, and polyethylenesulfonic acid can also be used in the present invention. Sulfonic acid and polyphosphoric acid. These organic sulfuric acids and organic carboxylic acids are merely examples, and the present invention is not limited to these. Examples of counter cations of the above-mentioned anions include alkali metal ions such as H ⁺ , Na ⁺ and K ⁺ , and ammonium ions substituted by hydrogen atoms, tetramethyl, tetraethyl, tetrabutyl or tetraphenyl, however, the present invention Not limited to these. Among these oxidizing agents, trivalent Fe-based compounds, cuprous chloride, alkali metal persulfates, ammonium persulfate or quinones are preferably contained.

For the anion having a dopant capability (anion other than the reducing agent anion of the oxidizing agent) that may exist together as needed in the production of the polymer composition of the conductive polymer, an anion containing an oxidizing agent generated from the above-mentioned oxidizing agent ( oxidizing agent) as an electrolyte anion or other electrolyte anion as a counter anion. Specific examples thereof include protic acid anions, including halide anions of Group 5B elements such as PF ₆ ⁻ , SbF ₆ ⁻ and AsF ₆ ⁻ ; halide anions of Group 3B elements such as BF ₄ ⁻ ; halide anions such as I ⁻ (I ₃ ⁻ ), Br ^- and Cl ^- ; perhalogenate ions such as ClO ₄ ^- ; Lewis acid anions such as AlCl ₄ ^- , FeCl ₄ ^- and SnCl ₅ ^- ; inorganic acid anions such as NO ₃ ^- and SO ₄ ^2- ; sulfonic acid anions Such as p-toluenesulfonic acid, naphthalenesulfonic acid and alkyl-substituted naphthalenesulfonic acid containing 1 to 5 carbon atoms (hereinafter referred to as "Cl-5"); organic sulfonate anions such as CF ₃ SO ₃ ^- and CH ₃ SO ₃ ^- ; and carboxylate anions such as CH ₃ COO ^- and C ₆ H ₅ COO ^- .

Other examples include polymer electrolyte anions such as polyacrylic acid, polymethacrylic acid, polystyrenesulfonic acid, polyvinylsulfonic acid, polyvinylsulfuric acid, poly-α-methylsulfonic acid, polyvinylsulfonic acid, and polyphosphoric acid. However, the present invention is not limited to these. Among these anions, high-molecular or low-molecular organic sulfonic acid compounds or polyphosphoric acid compounds are preferable. Preferably, an aromatic sulfonic acid compound (for example, sodium dodecylbenzenesulfonate, sodium naphthalenesulfonate) is used as the anion-donating compound.

Among organic sulfonate anions, more effective dopants are sulfoquinone compounds containing one or more sulfoanion groups (—SO ₃ —) in the molecule and having a quinone structure, and anthracenesulfonate anions.

醌、5，6-

醌、6，12-

醌、苊醌、二氢苊醌、莰醌、2，3-莰二酮、9，10-菲醌和2，7-芘醌。Examples of the basic skeleton of the sulfoquinone anion of the above-mentioned sulfoquinone compound include p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthracene Quinone, 1,4-anthraquinone, 1,2-anthraquinone, 1,4-

quinone, 5,6-

quinone, 6,12-

quinone, acenaphthoquinone, dihydroacenaphthenequinone, camphorquinone, 2,3-camphenedione, 9,10-phenanthrenequinone and 2,7-pyrenequinone.

Where the counter electrode is solid, a conductive layer may be provided thereon in order to obtain good electrical contact with external leads (eg lead frame) if required.

The conductive layer can be formed, for example, by curing a conductive paste, plating, metallization, or forming a heat-resistant conductive resin film. Preferable examples of the conductive paste include silver paste, copper paste, aluminum paste, carbon paste, and nickel paste; these may be used alone or in combination of two or more thereof. Where two or more pastes are used, these pastes may be mixed or may be superimposed on each other in separate layers. Examples of electroplating include nickel plating, copper plating, silver plating, and aluminum plating. Examples of vapor deposited metals include aluminum, nickel, copper and silver.

More specifically, for example, a carbon paste and a silver paste are sequentially laminated on the second electrode, and these are molded with a material such as epoxy resin, thereby producing a capacitor. The capacitor may have niobium or tantalum leads which are sintered and formed integrally with the niobium sintered body or subsequently welded.

The capacitor of the present invention thus prepared is cased using, for example, a resin mold, a resin case, a metal case, impregnation of resin, or laminated films, and then used as a capacitor product for various purposes.

In the case where the counter electrode is a liquid, for example, the prepared capacitor comprising the above two electrodes and a dielectric material is housed in a case electrically connected to the counter electrode to complete the capacitor. In this case, the electrode side of the niobium sintered body is led to the outside through the above-mentioned niobium or tantalum lead wire while being insulated from the case with insulating rubber or the like.

By producing a sintered body for a capacitor using the niobium powder produced according to the embodiment of the present invention described above and producing a capacitor from the sintered body, a capacitor having a small leakage current and good reliability can be obtained.

Compared with traditional tantalum capacitors, the capacitor of the present invention has larger volume capacitance, so more miniaturized capacitor products can be obtained.

The inventive capacitor having such properties can be applied, for example, as a bypass capacitor or coupling capacitor commonly used in analog circuits and digital circuits, and can also be used in conventional tantalum capacitors.

In general, such capacitors are commonly used in electronic circuits, and when the capacitor of the present invention is used, restrictions on the arrangement of electronic parts or the discharge of heat are reduced, and therefore, an electronic circuit with high reliability can be arranged in a larger area than conventional electronic circuits. within the tighter spaces required by the circuit.

In addition, when the capacitor of the present invention is used, electronic instruments such as computers, computer peripherals such as PC cards, mobile devices such as portable phones, Household equipment, equipment installed in vehicles, artificial satellites and communication equipment.

Best Mode for Carrying Out the Invention

The present invention is described in detail below with reference to Examples and Comparative Examples, however, the present invention is not limited to these examples.

In each example, the tap density, angle of repose, particle size and pore size of the niobium powder and the capacitance, leakage current, apparent ratio of capacitance, moisture resistance and ESR value of the capacitor were determined by the following methods.

(1) Determination of tap density

The tap density is measured according to the method of using a tap device and a measuring instrument in the apparent specific gravity measurement method of industrial sodium carbonate stipulated in JIS (Japanese Industrial Standard 2000 Edition) K1201-1.

(2) Determination of angle of repose

The angle of repose is measured using a fluidity measuring instrument and a sample amount specified in JIS (Japanese Industrial Standards 2000 edition) Z2504. More specifically, the niobium monoxide powder was dropped toward the horizontal plane from a hopper with a lower height of 6 cm relative to the horizontal plane, and the angle of the slope from the apex of the formed cone to the horizontal plane relative to the horizontal plane was defined as the angle of repose.

(3) Determination of particle size

The particle size distribution was measured by a laser diffraction scattering method using an apparatus manufactured by Microtrack (HRA 9320-X100). The particle size value (D ₅₀ ; microns) corresponding to 50% by volume in cumulative volume % is assigned as the mean particle size.

(4) Determination of pore size

The pore size distribution was measured by mercury porosimetry using Poresizer 9320 manufactured by Micromeritics.

In the present invention, the maximum value is determined by the rate of change of the press-fitted amount and by defining the pore diameter shown by the maximum value as the peak value, the maximum value is taken as the size of the relative intensity of the peak to which the peak value belongs.

(5) Determination of capacitance of capacitor

At room temperature, an LCR measuring device manufactured by Hewlett-Packard was connected between the terminals of the prepared sheet, and the measured value at 120 Hz was used as the capacitance of the capacitor processed into the sheet.

(6) Determination of capacitor leakage current

The current value measured after applying a DC voltage of 6.3 V between the terminals of the produced sheet at room temperature for 1 minute was taken as the leakage current value of the processed sheet capacitor.

(7) The apparent ratio of the capacitance of the capacitor

Assuming that the capacitance measured in 30% sulfuric acid was 100% when the sintered body was electrochemically formed in a 0.1% phosphoric acid solution at 80°C and 20V for 1,000 minutes, the apparent capacitance ratio was used as the capacitance after production of the capacitor. The ratio of capacity is expressed.

(8) Humidity resistance value of capacitor

The humidity resistance value is indicated by the number of produced capacitors whose capacitance after standing at 60° C. and 95% relative humidity for 500 hours is less than 110% or less than 120% of the initial value. The more the number less than 110%, the better the moisture resistance value.

(9) Determination of the ESR value of the capacitor

At room temperature, an LCR measuring device manufactured by Hewlett-Packard was connected between the terminals of the produced sheet, and the ESR measurement value at 100 kHz, 1.5 VDC, and 0.5 Vrms was used as the ESR of the capacitor.

Example 1

Put 5,000 grams of potassium fluoroniobate fully vacuum-dried at 80°C and sodium whose molar mass is 10 times that of potassium fluoroniobate into a nickel crucible, and make it undergo a reduction reaction at 1,000°C for 20 hours under an argon atmosphere . After the reaction was complete, the reduced product was cooled, washed successively with water, 95% sulfuric acid, and then water, dried in vacuum and pulverized for 40 hours using an alumina jar ball mill containing silica alumina balls. The pulverized product was immersed and stirred in a 3:2 (by mass) mixed solution of 50% nitric acid and 10% aqueous hydrogen peroxide solution. Then, the pulverized product was sufficiently washed with water until the pH value reached 7 to remove impurities, and then vacuum-dried. The average particle size of the raw niobium powder was 1.2 microns.

In a niobium tank, 500 g of this raw niobium powder was placed and 50 g of polybutylmethacrylate and 1 liter of toluene were added thereto. Additionally, zirconia balls were added and the contents were mixed for 1 hour using a shaking mixer. After removing the zirconia balls, the mixture was placed in a conical dryer and dried under vacuum at 1×10 ² Pa and 80°C.

Subsequently, the niobium powder was heated at 1×10 ^-2 Pa at 250-400°C for 12 hours to decompose and remove polybutylmethacrylate, and then heated at 1,150°C under a reduced pressure of 4×10 ^-3 Pa Sinter for 2 hours. The niobium powder sintered agglomerate was cooled until the product temperature was reduced to 30° C. or lower, and then crushed using a roller granulator to obtain crushed niobium powder with an average particle size of 100 μm.

This crushed niobium powder was subjected to nitriding treatment at 300° C. for 2 hours by blowing nitrogen gas under pressure to obtain about 450 g of niobium powder. The nitrogen content is 0.22%.

The physical properties of this niobium powder such as tap density, average particle size, angle of repose, BET specific surface area and peak pore diameter are shown in Table 1.

The thus-obtained niobium powder (about 0.1 g) was charged into the hopper of a tantalum device automatic forming machine (TAP-2R, manufactured by Seiken), and automatically formed together with a niobium wire of 0.3 mmφ to manufacture a size of about 0.3 cm× A shaped product of 0.18 cm x 0.45 cm. Appearance and scatter in shaped product quality are shown in Table 1.

The shaped product was left to stand at 1,250° C. for 30 minutes in a vacuum of 4×10 ⁻³ Pa to obtain a sintered body. 100 pieces of this sintered body were prepared, and each was electrochemically formed using a 0.1% phosphoric acid aqueous solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface.

Subsequently, the operation of immersing the sintered body in a 60% manganese nitrate aqueous solution and then heating it at 220° C. for 30 minutes was repeated to form a manganese dioxide layer as a counter electrode layer on the oxide dielectric film. On this counter electrode layer, a carbon layer and a silver paste layer are laminated in this order. After mounting a lead frame thereon, the device as a whole is molded with epoxy resin to manufacture a chip capacitor. Table 1 shows the capacitance apparent ratio of the capacitors and the average capacitance and average leakage current (hereinafter abbreviated as "LC") of chip capacitors (n=100 pieces). The LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.

Example 2

In a reactor made of SUS 304, 1,000 g of niobium ingots were placed, and hydrogen gas was continuously flowed into it at 400°C for 10 hours. After cooling, the hydrogenated niobium ingots were placed in a SUS 304 jar containing zirconia balls and pulverized for 10 hours. Then, the hydride was made into a 20% by volume slurry with water, loaded into a nail crusher together with zirconia balls and wet pulverized at a temperature of 40° C. or lower for 7 hours to obtain pulverized niobium hydride slurry . The average particle size of this starting niobium hydride powder was 0.9 microns.

In the SUS can making, this slurry (98% slurry concentration) was charged and 200 g of barium oxide having an average particle size of 1 µm was added thereto. Additionally, zirconia balls were added and the contents were mixed for 1 hour using a shaker mixer. After removing the zirconia balls, the mixture was placed in a niobium barrel and vacuum-dried at 1×10 ² Pa and 50°C.

Subsequently, the resulting mixture was heated at 400°C for 4 hours at 1×10 ^-2 Pa to dehydrogenate the niobium hydride, and then sintered at 1,100°C for 2 hours under a reduced pressure of 4×10 ^-3 Pa. The obtained barium oxide-mixed niobium sintered agglomerate was cooled until the product temperature dropped to 30° C. or lower, and then crushed using a roll granulator to obtain barium oxide-mixed niobium crushed powder with an average particle size of 95 μm.

500 g of the barium oxide-mixed niobium crushed powder and 1,000 g of ion-exchanged water were charged into a polytetrafluoroethylene container and cooled to 15° C. or lower. Separately, an aqueous solution obtained by mixing 600 g of 60% nitric acid, 150 g of 30% hydrogen peroxide, and 750 g of ion-exchanged water and cooling to 15° C. or lower was prepared. Then, 500 g of the aqueous solution was added dropwise to the aqueous solution in which the crushed niobium powder of barium oxide had been suspended and mixed with stirring, taking care not to allow the water temperature to exceed 20°C. After the dropwise addition was complete, the solution was stirred continuously for an additional hour, allowed to stand for 30 minutes, and then decanted. 2,000 g of ion-exchanged water was added thereto, and the resulting solution was stirred for 30 minutes, left to stand for 30 minutes, and then decanted. This operation was repeated 5 times. Then, the crushed niobium powder was charged into a column made of Teflon, and washed with water for 4 hours while flowing deionized water. At this time, the electric conductivity of the washing water was 0.9 μS/cm.

After the water washing was completed, the crushed niobium powder was dried at 50°C under reduced pressure, and subjected to nitriding treatment at 300°C for 3 hours by passing nitrogen under pressure, as a result, about 350 g of niobium powder was obtained. The nitrogen content is 0.28%.

The physical properties of this niobium powder such as tap density, average particle size, angle of repose, BET specific surface area and peak pore diameter are shown in Table 1.

The thus-obtained niobium powder (about 0.1 g) was charged into the hopper of a tantalum device automatic forming machine (TAP-2R, manufactured by Seiken), and automatically formed together with a niobium wire of 0.3 mmφ to manufacture a size of about 0.3 cm× A shaped product of 0.18 cm x 0.45 cm. Appearance and scatter in shaped product quality are shown in Table 1.

The shaped product was left to stand at 1,250° C. for 30 minutes in a vacuum of 4×10 ⁻³ Pa to obtain a sintered body. 100 pieces of this sintered body were prepared, and each was electrochemically formed using a 0.1% phosphoric acid aqueous solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface.

Subsequently, the operation of contacting the oxide dielectric film with an equal volume mixed solution of 10% ammonium persulfate aqueous solution and 0.5% anthraquinone sulfonic acid solution, and then contacting with pyrrole vapor was repeated at least 5 times, so that the oxide dielectric film containing Counter electrode of polypyrrole.

On this counter electrode layer, a carbon layer and a silver paste layer are laminated in this order. After mounting a lead frame thereon, the device as a whole is molded with epoxy resin to manufacture a chip capacitor. Table 1 shows the capacitance apparent ratio of the capacitors and the average capacitance and average LC value of the chip capacitors (n=100 pieces). The LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.

Embodiment 3-10

Produce niobium powder, its shaped product, sintered body and capacitor with the method identical with embodiment 1, but change the add-on of average grain size and polymethyl butyl methacrylate, or produce with the method identical with embodiment 2, but The average particle size and the amount of barium oxide added were varied. The physical properties and appearance of the niobium powder and the dispersibility of the quality of the shaped product, as well as the capacitance and LC of the capacitor are shown in Table 1.

Examples 11-22

Produce the niobium powder, shaped product and sintered body of embodiment 11～14 and 16～18 with the method identical with embodiment 1, produce the niobium powder, shaped product of embodiment 15 and 19～22 with the method identical with embodiment 2 and sintered bodies, but in each case the activators listed in Table 1 were used instead of polybutylmethacrylate or barium oxide. The physical properties and appearance of the niobium powder and the dispersibility of the quality of the shaped product, as well as the capacitance and LC of the capacitor are shown in Table 1.

These shaped articles were then left to stand at 1,250°C for 30 minutes under a reduced pressure of 4×10 ^-3 Pa to obtain a sintered body. 100 pieces of each sintered body were prepared, and electrochemically formed at a voltage of 20 V for 200 minutes using a 0.1% phosphoric acid aqueous solution to form an oxide dielectric film on the surface.

Subsequently, each sintered body on which the oxide dielectric thin film had been formed was immersed in an aqueous solution (solution 1) containing 25% by mass of ammonium persulfate, pulled out, dried at 80° C. for 30 minutes, and dipped in an aqueous solution containing 18% by mass of ammonium persulfate. 3,4-Ethylenedioxythiophene-containing isopropanol solution (solution 2), pulled out, and left to stand in the air at 60° C. for 10 minutes to carry out oxidative polymerization. This sintered body was dipped again in solution 1, and then treated in the same manner as above. The operation from immersion in Solution 1 to oxidative polymerization was repeated 8 times. Then, the sintered body was washed with warm water at 50° C. for 10 minutes, and dried at 100° C. for 30 minutes, thereby forming a counter electrode containing conductive poly(3,4-ethylenedioxythiophene).

On this counter electrode, a carbon layer and a silver paste layer are laminated in this order. After mounting a lead frame thereon, the device as a whole is molded with epoxy resin to manufacture a chip capacitor. Table 1 shows the capacitance apparent ratio of the capacitors, the average capacitance and the average LC value of the chip capacitors (n=100 pieces). The LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.

Examples 23-25

Produce niobium powder, sintered body and capacitor with the method identical with embodiment 2, but as raw material, use niobium-tin alloy powder in embodiment 23, use niobium hydride-rhenium alloy powder in embodiment 24, in embodiment 25 Niobium hydride-yttrium-boron alloy powder is used in The physical properties, capacity and LC of the capacitors are shown in Table 1.

Comparative example 1-3

2,000 g of potassium fluoroniobate fully vacuum-dried at 80° C. and sodium 10 times the molar amount of potassium fluoroniobate were charged into a nickel crucible, and subjected to a reduction reaction at 1,000° C. for 20 hours under an argon atmosphere. After the reaction was complete, the reduced product was cooled, washed with water in sequence, washed with 95% sulfuric acid, then washed with water, dried in vacuum and pulverized using an alumina jar ball mill containing silica-alumina balls, varying the pulverization time. The pulverized product was immersed and stirred in a 3:2 (by mass) mixed solution of 50% nitric acid and 10% aqueous hydrogen peroxide solution. Then, each pulverized product was sufficiently washed with water until the pH value reached 7 to remove impurities, and then vacuum-dried. The produced niobium powder has an average particle size of 1.3 microns to 10 microns.

Subsequently, 50 g of the obtained niobium powder was placed in a reactor made of SUS304, and nitrogen gas was continuously flowed thereinto at 300° C. for 2 to 4 hours to obtain niobium nitride.

The physical properties of each niobium powder such as tap density, average particle size, angle of repose, BET specific surface area and peak pore diameter are shown in Table 1.

The thus-obtained niobium powder (about 0.1 g) was charged into a hopper of a tantalum device automatic forming machine (TAP-2R, manufactured by Seiken), and attempted to be automatically formed together with a niobium wire of 0.3 mmφ. The results obtained are shown in Table 1.

Comparative Examples 4-9

Using the same method as in Example 2 but changing the amount of barium oxide with an average particle size of 1 micron, niobium powder with a tap density of 0.2-0.4 g/ml or 2.6-3.3 g/ml was obtained. Its physical properties are shown in Table 1.

The thus-obtained niobium powder (about 0.1 g) was charged into the hopper of a tantalum device automatic forming machine (TAP-2R, manufactured by Seiken), and automatically formed together with a niobium wire of 0.3 mmφ to manufacture a size of about 0.3 cm× A shaped product of 0.18 cm x 0.45 cm. Appearance and scatter in shaped product quality are shown in Table 1.

These shaped articles were left to stand at 1,250° C. for 30 minutes in a vacuum of 4×10 ⁻³ Pa to obtain a sintered body. 100 pieces of each sintered body were prepared, and electrochemically formed at a voltage of 20 V for 200 minutes using a 0.1% phosphoric acid aqueous solution to form an oxide dielectric film on the surface.

Subsequently, the operation of bringing the oxide dielectric film into contact with an equal-volume mixed solution of 10% ammonium persulfate aqueous solution and 0.5% anthraquinonesulfonic acid solution and then contacting pyrrole vapor was repeated at least 5 times, so that the oxide dielectric film containing Counter electrode of polypyrrole.

On this counter electrode, a carbon layer and a silver paste layer are laminated in this order. After mounting a lead frame thereon, the device as a whole is molded with epoxy resin to manufacture a chip capacitor. Table 1 shows the capacitance apparent ratio of the capacitors, the average capacitance and the average LC value of the chip capacitors (n=100 pieces). The LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.

Examples 26-31

The hydride of the niobium ingot was crushed and dehydrogenated to obtain primary particles with an average particle size of 0.8 microns. The obtained primary particles were sintered and pulverized to obtain niobium granulated powder. Then, 0.1 g of the granulated powder was packed in a metal mold (4.0 mm × 3.5 mm × 1.8 mm) together with a separately prepared niobium wire with a length of 10 mm and a thickness of 0.3 mm, and an automatic tantalum device forming machine (TAP- 2R, manufactured by Seiken) to which the loads shown in Table 2 were applied to produce shaped articles. Each shaped product was then sintered at 1300° C. for 30 minutes to obtain a target sintered body. By controlling the load applied by the forming machine, sintered bodies having the pore size distribution shown in Table 2 were produced. The size, specific surface area, and CV value of the sintered body of Example 26 were 24.7 mm ³ , 1.1 m ² /g, and 85,000 μFV/g, respectively. In other examples, each value is within ±2% of Example 26.

Examples 32-34

A sintered body was obtained in the same manner as in Examples 26 to 28, but changing the average particle size to 0.5 µm by classifying the primary particles. The size, specific surface area, and CV value of the sintered body of Example 32 were 24.9 mm ³ , 1.5 m ² /g, and 125,000 μFV/g, respectively. In other examples, each value is within ±1% of Example 32. The pore size distribution of each sintered body produced is shown in Table 2.

Example 35

A sintered body was obtained in the same manner as in Example 31, but niobium powder obtained in the same manner as in Example 4 was used instead of the granulated powder. The size, specific surface area, and CV value of the sintered body of Example 35 were 24.8 mm ³ , 1.2 m ² /g, and 78,000 μFV/g, respectively. The pore size distribution of the produced sintered body is shown in Table 2.

Comparative Examples 10-12

A sintered body was produced in the same manner as in Examples 26 to 28, but instead of the niobium granulated powder used in Examples 26 to 28, niobium powder prepared by reducing niobium chloride with magnesium by heat treatment at 1,100°C was used. The size, specific surface area, and CV value of the sintered body of Comparative Example 10 were 24.3 mm ³ , 0.8 m ² /g, and 84,000 μFV/g, respectively. In other comparative examples, each value was within ±2% of Comparative Example 10. The pore size distribution of each sintered body produced is shown in Table 2.

Example 36

60 various sintered bodies produced by the same method as in Example 21 and Examples 26 to 35, each electrochemically formed in 0.1% phosphoric acid aqueous solution at 80°C and 20V for 1,000 minutes, so as to form oxidation on the surface of the sintered body. Dielectric thin films. These electrochemically formed sintered bodies were grouped, and each group consisted of 30 sintered bodies. The 30 sintered bodies in each group were impregnated with the two cathodic agents A and B shown in Table 3. Carbon paste and silver paste were layered sequentially thereon, and the device was molded with epoxy resin to prepare a chip capacitor. Table 4 shows the capacitance apparent ratio and moisture resistance value of each of the manufactured capacitors.

Comparative Example 13

Sixty various sintered bodies produced by the same method as Comparative Examples 9-12 were each electrochemically formed in 0.1% phosphoric acid aqueous solution at 80°C and 20V for 1,000 minutes to form an oxide dielectric film on the surface of the sintered bodies. These electrochemically formed sintered bodies were grouped, and each group consisted of 30 sintered bodies. Thirty sintered bodies in each group were impregnated with cathodic agent A shown in Table 3. Carbon paste and silver paste were layered sequentially thereon, and the device was molded with epoxy resin to prepare a chip capacitor. Table 4 shows the capacitance apparent ratio and moisture resistance value of each of the manufactured capacitors.

Example 37

The raw niobium hydride powder was pulverized by the same method as in Example 2 to obtain a slurry. The hydrogenating agent powder had an average particle size of 0.6 microns. After the slurry was centrifuged, the supernatant was removed by decantation. Anhydrous acetone was added thereto so that the slurry had a concentration of 40% by mass and was well suspended. After the resulting solution was centrifuged, the supernatant was removed by decantation. Anhydrous acetone was added thereto so that the slurry had a concentration of 60% by mass and was well suspended. This slurry was packed in a SUS tank, and barium oxide having an average particle size of 1.4 micrometers and 23 micrometers was added thereto at 15% by mass and 10% by mass of the mass of niobium, respectively. Additionally, zirconia balls were added and the contents were mixed using a shaker mixer for 1 hour. After removing the zirconia balls, the mixture was placed in a niobium barrel and vacuum dried at 1×10 ² Pa and 50°C.

Barium oxide-mixed niobium sintered agglomerates and niobium crushed powder were obtained in the same manner as in Example 2.

500 g of the barium oxide-mixed niobium crushed powder were added to 1,000 g of ion-exchanged water cooled to 15°C or lower while stirring, taking care not to make the water temperature exceed 20°C. After the addition was complete, the solution was stirred continuously for an additional hour, allowed to stand for 30 minutes, and then decanted. 2,000 g of ion-exchanged water was added thereto, and the resulting solution was stirred for 30 minutes, left to stand for 30 minutes, and then decanted. This operation was repeated 5 times. Then, the crushed niobium powder was charged into a column made of Teflon, and washed with water for 4 hours while flowing deionized water. At this time, the electric conductivity of the washing water was 0.5 μS/cm.

After the water washing was completed, the crushed niobium powder was dried at 50° C. under reduced pressure and subjected to nitriding treatment at 300° C. for 3 hours by nitrogen under pressure, and as a result, about 350 g of niobium powder was obtained. The nitrogen content is 0.30%.

The physical properties of this niobium powder such as tap density, average particle size, angle of repose, BET specific surface area and peak pore diameter are shown in Table 5.

Shaped articles were produced in the same manner as in Example 2. The appearance and mass dispersibility of the shaped articles are shown in Table 5.

Then, a dielectric film was formed on the surface of the sintered body of the shaped article in the same manner as in Example 2. A counter electrode is then formed and a carbon layer and a silver paste layer are sequentially laminated thereon. After mounting a lead frame thereon, the device as a whole is molded with epoxy resin to prepare a chip capacitor. Table 5 shows the capacitance apparent ratio of the capacitors and the average capacitance and average LC value of the chip capacitors (n=100).

Examples 38-44

A crushed niobium powder mixed with an activator was obtained in the same manner as in Example 37 by changing the kind of activator added, the average pore size and the amount of the two niobium powders to be mixed. The solvent for dissolving the activator is selected from water, acid, alkali, solvent containing ion exchange resin, ammonium nitrate solvent and solution containing ethylenediamine tetraacetate. The activator was dissolved in the same manner as in Example 37 to obtain niobium powder. The physical properties of this niobium powder are shown in Table 5.

Shaped articles and sintered bodies were manufactured in the same manner as in Example 37 to prepare chip capacitors. Table 5 shows the appearance and mass dispersibility of the shaped articles and the capacitance and average LC value of the capacitors.

Examples 45-47

As raw materials, niobium-neodymium alloy powder was used in Example 45, niobium-tungsten alloy powder was used in Example 46, and niobium-tantalum alloy powder was used in Example 47, and obtained by the same method as in Example 37. Niobium alloy powder. The physical properties of the niobium alloy powder are shown in Table 5.

Shaped articles and sintered bodies were produced in the same manner as in Example 37 to produce chip capacitors. Table 5 shows the appearance and mass dispersibility of the shaped articles and the capacitance and average LC value of the capacitors.

Examples 48-58

Using the niobium powders obtained in Examples 37 to 47, a niobium sintered body was produced in the same manner as in Example 2. The pore size distribution of the sintered body is shown in Table 6.

Examples 59-69

100 of each of the sintered bodies obtained in Examples 48 to 58 were prepared, and electrochemically formed using a 0.1% by mass phosphoric acid aqueous solution at 20 V and 80° C. for 1,000 minutes to form an oxide dielectric film on the surface. These sintered bodies were impregnated with the cathodic agents shown in Table 3. A carbon layer and a silver paste layer were sequentially stacked thereon and the whole was molded with epoxy resin to prepare a chip capacitor. The capacitance apparent ratios and ESRs of the prepared capacitors are shown in Table 7.

Comparative Examples 14-17

100 of each of the sintered bodies obtained in Comparative Examples 9 to 12 were prepared, and electrochemically formed using a 0.1% by mass phosphoric acid aqueous solution at 20 V and 80° C. for 1,000 minutes to form an oxide dielectric film on the surface. These sintered bodies were impregnated with the cathodic agents shown in Table 3. A carbon layer and a silver paste layer were sequentially stacked thereon and the whole was molded with epoxy resin to prepare a chip capacitor. The capacitance apparent ratios and ESRs of the prepared capacitors are shown in Table 7.

Table 2

table 3 method cathodic agent Method of impregnating cathodic agent A Polypyrrole Repeated gas phase polymerization of the sintered body with ammonium persulfate and anthraquinone sulfonic acid attached thereto with pyrrole vapor B Mixture of lead dioxide and lead sulfate (lead dioxide: 98% by mass) Repeated immersion of the sintered body in a mixture of lead acetate and ammonium persulfate

Table 4

Table 6

Table 7 Examples and Comparative Examples The method of obtaining the sintered body capacitance apparent ratio capacitance ESRΩ Example 59 Example 48 98 592 0.024 Example 60 Example 49 97 587 0.023 Example 61 Example 50 93 557 0.022 Example 62 Example 51 93 556 0.022 Example 63 Example 52 98 58 5 0.023 Example 64 Example 53 98 58 9 0.023 Example 65 Example 54 97 58 1 0.024 Example 66 Example 55 98 590 0.022 Example 67 Example 56 98 592 0.024 Example 68 Example 57 98 587 0.023 Example 69 Example 58 98 587 0.025

Comparative Example 14 Comparative Example 9 twenty two 64 0.158 Comparative Example 15 Comparative Example 10 71 305 0.083 Comparative Example 16 Comparative Example 11 73 314 0.081 Comparative Example 17 Comparative Example 12 68 291 0.090

Industrial Applicability

The niobium powder of the present invention having a tap density of 0.5 to 2.5 g/ml, an average particle size of 10 to 1000 microns, an angle of repose of 10 to 60° and a BET specific surface area of 0.5 to 40 m ² /g is excellent in fluidity and Can be formed continuously. The niobium sintered body obtained by sintering the niobium powder and having a pore size peak in the range of 0.01 to 500 microns and preferably having multiple pore size peaks in the pore size distribution is used for capacitor electrodes, which can obtain a high capacitance apparent ratio and can produce Capacitors with low leakage current and excellent moisture resistance.

Claims (20)

1. niobium sintered body that is used for electrode for capacitors, wherein, the pore size distribution of niobium sintered body has a plurality of apertures peak value, in the peak value of a plurality of apertures, has the peak value at two peaks of high relative intensity and is present in 0.2～0.7 micrometer range respectively and in 0.7～3 micrometer range.

2. the niobium sintered body described in the claim 1, wherein, described pore size distribution has two aperture peak values.

3. the niobium sintered body described in the claim 1 wherein, in the peak value of a plurality of apertures, has the peak value at the peak of high relative intensity and is present in than having time side of the peak value larger diameter at the peak of high relative intensity.

4. the niobium sintered body described in the claim 1, wherein, the volume of described sintered compact is 10mm ³Or bigger, comprise the volume of hole.

5. the niobium sintered body described in the claim 1, wherein, the specific surface area of described sintered compact is 0.2～7m ²/ g.

6. the niobium sintered body described in the claim 1, wherein, a part of sintered compact is by nitrogenize.

7. the niobium sintered body described in the claim 1, wherein, described sintered compact is the sintered compact that is obtained by a kind of niobium molding, described niobium molding produce a kind of when 1300 ℃ of sintering the CV value be the sintered compact of 40,000～200,000 μ FV/g.

8. electrical condenser comprises an electrode, a counter electrode and the intervenient dielectric materials of the niobium sintered body described in each that uses claim 1～7.

9. the electrical condenser described in the claim 8, wherein, described dielectric materials mainly comprises niobium oxides.

10. the electrical condenser described in the claim 8, wherein, counter electrode is at least a material that is selected from electrolyte solution, organic semiconductor and inorganic semiconductor.

11. the electrical condenser described in the claim 10, wherein, counter electrode is an organic semiconductor, and organic semiconductor be selected from the organic semiconductor that comprises benzopyrrole quinoline tetramer and chloranil, mainly comprise the organic semiconductor of four thio naphthacene, mainly comprise the organic semiconductor of four cyano quinone bismethane and at least a material of electric conductive polymer.

12. the electrical condenser described in the claim 11, wherein, electric conductive polymer is at least a composition that is selected from polypyrrole, Polythiophene, polyaniline and substitutive derivative thereof.

13. the electrical condenser described in the claim 11, wherein, electric conductive polymer is by mix the electric conductive polymer that doping agent obtains in the polymkeric substance of the repeating unit that contains following formula (1) or (2) expression:

Wherein, R ¹～R ⁴Expression independently of one another is selected from hydrogen atom, contains saturated or unsaturated alkyl, alkoxyl group or alkyl ester group group, halogen atom, nitro, cyano group, primary, the second month in a season or uncle's amino, the CF of the straight or branched of 1～10 carbon atom ₃The univalent perssad of the phenyl of group, phenyl and replacement; Each is to R ¹And R ², R ³And R ⁴Can be at an arbitrary position in conjunction with forming the divalence chain, be used for by R ¹And R ²Or by R ³And R ⁴The carbon atom that replaces forms at least one 3-, 4-, the saturated or unsaturated hydrocarbons ring structure of 5-, 6-or 7-unit together; Optional carbonyl, ether, ester, acid amides, thioether, sulfinyl, alkylsulfonyl or the imino-of containing at an arbitrary position of ring-type bonded chain; X represents Sauerstoffatom, sulphur atom or nitrogen-atoms; R ⁵Only when X is nitrogen-atoms, just exist, and represent hydrogen atom independently or contain straight or branched, the saturated or unsaturated alkyl of 1～10 carbon atom.

14. the electrical condenser described in the claim 13, wherein, electric conductive polymer is the electric conductive polymer that contains by the repeating unit of following formula (3) expression:

Wherein, R ⁶And R ⁷Represent hydrogen atom independently of one another, contain the saturated or unsaturated alkyl of the straight or branched of 1～6 carbon atom, perhaps a substituting group is used to form at least one 5-, the 6-that contain two Sauerstoffatoms or the 7-unit stable hydrocarbon ring structure that are obtained by the alkyl that mutually combines at an arbitrary position; And ring texture comprises having the structure of can substituted vinylidene key, can substituted phenylene structure.

15. the electrical condenser described in the claim 11, wherein, electric conductive polymer is by mix the electric conductive polymer that doping agent obtains in poly-(3,4-ethylidene dioxy thiophene).

16. the electrical condenser described in the claim 8, wherein, counter electrode is made by the material that has laminate structure to small part.

17. the electrical condenser described in the claim 8, wherein, the material of counter electrode contains organic sulfonic acid root negatively charged ion as doping agent.

18. method of producing electrical condenser, described electrical condenser comprises an electrode that uses niobium sintered body, the dielectric materials that forms and provides on described dielectric materials on described sintered compact surface a counter electrode, wherein, described niobium sintered body is at the niobium sintered body described in each of claim 1～7.

19. electronic circuit that uses the electrical condenser described in each of claim 8～17.

20. electronic machine that uses the electrical condenser described in each of claim 8～17.