JP2005194628A - Metal chip for producing metal powder for capacitor, production method therefor, and method of producing metal powder for capacitor using the chip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulverized material for producing fine metal powder, with little impurities, of niobium, tantalum or an alloy containing either metal as a main component. <P>SOLUTION: The metal chip for a pulverized material of embrittled niobium, tantalum or alloy containing either metal as a main component is composed of one metal selected from niobium, tantalum and alloy containing either metal as a main component, and has such a shape that the barrel is formed cylindrical and the diameter of the cylindrical part is 0.03 to 5 mm. The production method uses the metal chip. The method of producing metal powder for a capacitor uses the metal chip. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pulverized material (metal chip) for producing metal powder for capacitors. More specifically, it is a pulverized material for producing metal powder of niobium, tantalum or an alloy mainly composed of any one of these metals for capacitors, and does not affect the performance of the metal powder to be produced. The present invention relates to a metal chip made of a metal material basically the same as powder, a method for manufacturing the metal chip, and a method for manufacturing metal powder for a capacitor using the metal chip.

  A metal powder of niobium, tantalum or an alloy mainly containing any one of these metals is used as an anode material for electrolytic capacitors. As a method for producing the metal powder, a method in which a compound containing niobium element or tantalum element is reduced (US Pat. No. 4,141,720; Patent Document 1) and niobium, tantalum or one of these metals as a main component is used. There is a method in which the metal of the alloy is hydrogenated and then pulverized and further dehydrogenated (UK Patent No. 1219748; Patent Document 2, US Pat. No. 4,084,965; Patent Document 3). The former method requires a multi-step process for removing impurities because the impurities generated from the compound and reducing agent affect the performance of the capacitor, but it is difficult to remove with fine metal powder, for example sodium Impurities such as potassium and potassium, which have a great influence on the capacitor performance, usually have a defect that several tens of mass ppm remain.

  On the other hand, recent electrolytic capacitors are required to have a small size and large capacity, and finer metal powders are required. In the latter pulverization method, impurities such as sodium and potassium do not enter, so there is a movement to produce fine metal powder by the latter method.

US Pat. No. 4,141,720 British Patent No. 1219748 U.S. Pat. No. 4,084,965

  However, the latter method has a problem that impurities derived from the pulverized material used at the time of pulverization and that it is difficult to produce a fine metal powder by the pulverization method.

  As a result of diligent study, the inventors of the present invention do not affect the performance of niobium, tantalum for capacitors, or metal powders of alloys based on any one of these metals as a pulverizing material used in the pulverization method. In particular, the inventors have found that the above-mentioned problem can be solved by using a metal chip having a specific shape made of a metal material of the same quality as the pulverized material, and has completed the present invention.

That is, this invention relates to the metal powder produced using the following metal chips, the manufacturing method of a metal chip, and this metal chip.
1. Embrittlement characterized in that the body is made of one metal selected from niobium, tantalum having a cylindrical shape and a diameter of 0.03 to 5 mm, or an alloy containing any one of these metals as a main component. Metal chips for pulverized materials of niobium, tantalum or alloys mainly composed of any of these metals.
2. 2. The metal tip according to 1 above, wherein the length of the cylindrical portion is 0.03 to 5 mm.
3. 3. The metal tip according to either 1 or 2, wherein a part thereof is nitrided.
4). Niobium, tantalum or niobium, tantalum, or any one of these, characterized in that a thin wire made from one kind of metal selected from niobium, tantalum or an alloy containing any one of these metals as a main component is embrittled and then cut or folded A method for producing a metal tip for a pulverized material of an ingot made of an alloy containing as a main component a metal.
5). Niobium by using the metal tip according to any one of 1 to 3 as a pulverizing material, embrittlement and pulverization of niobium, tantalum, an alloy mainly containing any of these metals, or a mixture of these metals, A method for producing a metal powder for a capacitor, characterized in that the metal powder of an alloy containing tantalum or any one of these metals as a main component or a mixed powder of these metals is prepared and then debrittled.
6). 6. The method for producing metal powder for capacitors as described in 5 above, wherein a metal chip made of the same material as the metal powder to be produced is used.
7). 6. The method for producing metal powder for capacitors as described in 5 above, wherein the metal powder to be produced is niobium or an alloy containing niobium as a main component, and a tantalum chip is used as the metal chip.
8). After using a plurality of types of metal tips whose diameters (and lengths) are in a range of 0.03 to 5 mm in stages, the ingot hydride is first pulverized with a metal tip having a large cylinder diameter, The ingot hydride is pulverized sequentially using metal tips having a smaller cylindrical portion diameter, and metal powder having a diameter of 1/100 to 1/150 of the cylindrical portion diameter of the last used metal tip is prepared, and then dehydrogenated. 5. A method for producing metal powder for capacitors as described in 5.
9. 4. A niobium powder, a tantalum powder, or a metal powder of an alloy containing any one of these metals as a main component, or a mixture of these metal powders.

  The present invention is a pulverizing material that does not affect the performance of the metal powder of niobium, tantalum for capacitors or an alloy containing any one of these metals as a main component, and has a specific shape basically made of a homogeneous metal material. The present invention provides a metal chip, a method for producing the metal chip, and a method for producing metal powder for a capacitor using the metal chip. According to the metal chip of the present invention, a fine metal powder with few impurities can be produced, and a capacitor with good performance can be produced from the metal powder.

  One form of the metal powder of the present invention, the metal chip manufacturing method, and the metal powder produced using the metal chip will be described.

  The metal tip of the present invention is one kind of metal selected from niobium, tantalum, or an alloy containing any one of these metals as a main component, the body is cylindrical, and the diameter of the cylinder is 0.03 to It has a 5mm shape. Further, the length of the metal tip can be arbitrarily prepared except for extremely short ones, but 0.03 to 5 mm is preferably used for the production of metal powder described later.

  In the present invention, a part of the metal tip may be used after being subjected to at least one treatment selected from carbonization, phosphation, boronation, nitridation, sulfidation, and oxidation. These elements combined with the metal chip do not deteriorate the performance of the capacitor when the metal chip is produced as a pulverized material and the final capacitor is manufactured from the metal powder. It is a preferable element because it may improve the leakage current performance. In order to combine these elements with a part of the metal tip, it is obtained by reacting a compound or a simple substance containing these elements with a metal tip precursor in any step before producing the metal tip or metal tip. be able to. The concentration of the compound or simple substance, the reaction temperature, time, pressure, the abundance of elements in the metal tip, etc. can be managed by preliminary experiments.

  As an example, in order to nitride a part of the metal tip, for example, a method of nitriding the metal tip in a nitrogen gas atmosphere can be mentioned. In this case, the amount of nitrogen can be any numerical value between 20 and 150,000 mass ppm. As the nitriding method, any one of liquid nitriding, ion nitriding, gas nitriding, etc., or a combination thereof can be used. Gas nitriding treatment in a nitrogen gas atmosphere is preferable because the apparatus is simple and easy to operate.

  For example, a gas nitriding method using a nitrogen gas atmosphere is achieved by leaving the metal chip in a nitrogen atmosphere. The nitriding atmosphere temperature is 2000 ° C. or less and the standing time is several hours or less, so that a metal tip having a desired nitriding amount can be obtained. It is also possible to shorten the processing time by processing at a high temperature. The nitridation amount of the metal chip can be managed under the condition that the nitriding temperature and nitriding time of the object to be nitrided are confirmed by a preliminary experiment or the like.

  As an example of the method for manufacturing the metal tip described above, a method of cutting a metal thin wire made of the same material as the metal tip perpendicularly or obliquely to the longitudinal direction can be mentioned. By defining the diameter and cutting length of the fine metal wire, a metal tip having a desired diameter and length can be produced. The thin metal wire is cut, forged, rolled, stretched, annealed, polished, etc. from one metal ingot, metal rod or metal piece selected from, for example, niobium, tantalum or an alloy based on any one of these metals After performing at least one of the steps, various roller dies or / and hole dies are used. By the method described above, a metal fine wire having a diameter of 0.1 mm or more can be produced. A fine metal wire having a wire diameter of less than 0.1 mm can be obtained by electrolytically oxidizing a fine wire of 0.1 mm or more and then polishing an oxide film formed on the surface. The cross section of the produced metal thin wire is usually a perfect circle, but depending on the production method, there may be an oval shape or a shape in which a concave or convex part exists in a part of the circle, for example. . A metal tip made of a fine metal wire having a cross section deviating from such a perfect circle is also within the scope of the present invention.

  If a part or all of the fine metal wires are made brittle, the fine metal wires can be cut with a load instead of being cut with a blade when producing a metal tip. As the embrittlement method, nitriding or hydrogenation is preferable. When cutting a thin metal wire that has not been embrittled with a blade, there is a case where a loose burr appears in the cutting direction in which the blade of the cut surface of the manufactured metal tip hits. If such a metal tip is used, the surface of the container used when producing the metal powder may be damaged. On the other hand, in the case of cutting by weight cutting, there are few burrs on the cut surface. For nitriding a part or all of the thin metal wire, the above-described method of nitriding a part of the metal tip can be used. Examples of the method for hydrogenating part or all of the fine metal wires include a method of leaving the fine metal wires in a hydrogen stream or in hydrogen at a temperature of several hundred to 1000 ° C. After producing a metal chip from a thin metal wire partially or wholly hydrogenated, it is possible to dehydrogenate at a temperature of several hundred to 1000 ° C., for example, by leaving the metal chip in a reduced pressure or vacuum.

  An example of a method for producing a metal powder of niobium, tantalum, or an alloy mainly containing any one of these metals or a mixed powder of these metals using the metal tip of the present invention will be described.

  After embrittlement of a metal ingot to be produced, a metal chip is put into a small piece of metal that has been crushed to an appropriate size, and is stirred and ground in water. Examples of the embrittlement method include hydrogenation, nitridation, oxidation, and carbonization, but hydrogenation is preferable. When a metal tip having the same diameter and the same length is used, the average particle size of the pulverized metal powder is crushed to about 1/100 to 1/150 of the diameter of the used metal tip. can do. For example, when a metal chip having a diameter of 5 mm in a cylindrical portion is first introduced into a small metal piece as a pulverized material, metal powder having an average particle diameter of approximately 33 to 50 μm is obtained. Furthermore, when a metal chip having a diameter of 0.1 mm in the cylindrical portion is added as a pulverized material to a metal powder having such an average particle diameter, a metal powder having an average particle diameter of approximately 0.6 to 1 μm is obtained. Subsequently, when a metal tip having a diameter of 0.03 mm in the cylindrical portion is added as a pulverized material to the metal powder having the average particle diameter, a metal powder having an average particle diameter of approximately 0.2 to 0.3 μm is obtained. When metal chips having different cylindrical part diameters are mixed and used as a pulverized material, metal powder having a wide particle size distribution tends to be produced.

  The type of metal tip to be used is determined by preliminary experiments in consideration of the type and size of the metal piece, the type of pulverizer, the pulverization time, the number of times of pulverization, and the desired particle size distribution of the metal powder.

  When the metal powder having an average particle diameter of approximately 0.2 to 0.3 μm is niobium powder, the metal powder is granulated to an appropriate size and sintered at 1250 to 1280 ° C. to produce a sintered body. (Product of capacity C and formation voltage V) is 250,000 to 400,000 μF · V / g, and when the metal powder is tantalum, if sintered at 1280 to 1330 ° C. to produce a sintered body, 130,000 to 20 It becomes 10,000 μF · V / g, and it can be seen that it is the desired fine metal powder.

  When niobium powder is produced, niobium chips are used, and when tantalum powder is produced, tantalum chips are used to theoretically eliminate impurities derived from the pulverized material. Capacitors made from niobium powder, alloy powder containing niobium as the main component, or a mixture of niobium powder and alloy powder containing niobium as the main component, show no deterioration in performance even when tantalum is present as an impurity. A tantalum chip may be used as a pulverizing material. Furthermore, niobium oxide powder can be made finer by using the metal tip of the present invention. Capacitors made from niobium oxide powder do not deteriorate in performance even when niobium or tantalum is present as an impurity, and therefore niobium chips or tantalum chips may be used as a pulverizing material.

  In the present invention, a conventionally known method can be employed to hydrogenate a metal ingot. For example, the metal ingot can be hydrogenated in an arbitrary range from a low concentration to a limit concentration by appropriately selecting a time for leaving the metal ingot at a temperature of several hundred to 1000 ° C. in a hydrogen stream. In the present invention, it is preferable to hydrogenate to the limit concentration of each metal because subsequent pulverization can be performed satisfactorily. Further, in order to crush the hydrogenated ingot described above into metal pieces, it is preferable to use, for example, a hammer mill capable of producing small pieces having a size of several mm.

  As a specific method for adding metal chips to the above-described metal pieces crushed to an appropriate size or metal powder having a certain average particle size and stirring and pulverizing in water, for example, a stirring vessel provided with stirring blades Put metal pieces or metal powder and metal chips and water into a small piece by crushing into metal pieces or metal powder by stirring at high speed and separating any metal chip residues that are present without being crushed. A method to obtain metal powder with an average particle size, by putting metal pieces or metal powder and metal chips and water into a tube, circulating at high speed and pulverizing, and if present, separating metal chip residues Examples thereof include a method for obtaining metal powder having an average particle diameter. In the latter method, a reservoir is provided in the middle of the tube, and if a circuit is designed in which the pulverized material once accumulates in the reservoir and then sucked from the reservoir toward the tube, crushing the reservoir Conveniently, the end point of grinding can be controlled by analyzing the particle size of the product. The average particle size and particle size distribution of the metal powder produced by pulverization can be adjusted by classification operation. By the classification operation, for example, the average particle size can be reduced to about 1/30.

Next, for debrisification, dehydrogenation may be performed in the same manner as in the case of the metal tip described above, or dehydrogenation may be performed in the next granulation or sintering step.
The metal powder produced as described above is a primary particle. When the metal powder is molded to produce a compact, the metal powder is granulated at least once to increase the fluidity of the metal powder. It may be used as the next particle. Granulation may be performed after mixing metal powders having different average particle diameters.

  As a granulation method, for example, primary particles are kneaded with a material selected from at least one of water, an organic solvent, an organic binder, and an inorganic binder, and then heated, and further agglomerated, if remaining, binder removal, washing, and drying. The method obtained by the process of mentioning can be mentioned. As the binder, conventionally known binders such as acrylic polymers and metal oxides (for example, magnesium oxide) can be used.

  The metal powder or part of the granulated particles may be used after being subjected to at least one treatment selected from carbonization, phosphation, boronation, nitridation, sulfidation, and oxidation. These treatments can be performed by the same method as that for the metal tip described above.

  The metal powder or granulated particles produced as described above are used as an anode of a capacitor after being formed into an appropriate shape and sintered to form a sintered body. It is also possible to connect a lead wire or a lead foil at the time of molding or after sintering to form an anode lead of a capacitor. Metal powder or granulated particles can be dispersed in water or an organic solvent to form a slurry, which is directly attached to a metal foil and then sintered to form a capacitor anode body.

Hereinafter, specific examples of the present invention will be described in more detail, but the present invention is not limited to the following examples.
In the following examples, the average particle size of the metal powder is measured using a particle size distribution measuring device manufactured by Coulter, Inc., and the capacity of the granulated powder is measured using an LCR meter manufactured by Hewlett-Packard Company. Measurements were made at a frequency of 120 Hz at room temperature.

Example 1:
(1) Production of niobium chip A niobium ingot was cut and a rectangular parallelepiped niobium rod having a cross section of 30 × 20 mm and a length of 300 mm was taken out. The niobium rod was subjected to forging, annealing, and rolling steps to obtain a substantially circular niobium rod having a cross section of 10 mmφ. Furthermore, each of the niobium wires having a circular cross-section and a diameter of 5 mm, 1 mm, 0.3 mm, and 0.12 mm was prepared by sequentially drawing with a round die. Next, a niobium wire having a diameter of 0.12 mm prepared in the same manner is put in a 1% phosphoric acid aqueous solution, and the niobium wire is used as an anode, and a tantalum plate provided in the aqueous solution is used as a cathode to perform anodization at 70 V to form an oxide film on the surface of the niobium wire. Formed. A series of operations for polishing the oxide film and part of the niobium metal portion to reduce the diameter of the niobium wire was repeated a plurality of times to obtain niobium wires having a diameter of 0.07 mm and 0.03 mm. Of the niobium wires produced as described above, the niobium wires having diameters of 0.3 mm, 0.12 mm, 0.07 mm, and 0.03 mm are placed in a vacuum furnace in which the electrode heating element is molybdenum, and the nitrogen gas is passed at 400 ° C. A part was nitrided. Of the various niobium wires produced as described above, niobium wires having a diameter of 5 mm and 1 mm were cut with a commercially available automatic cutter so that the lengths of the cylindrical portions were 5 mm and 1 mm, respectively, thereby obtaining niobium chips. Niobium wires with diameters of 0.3 mm, 0.12 mm, 0.07 mm, and 0.03 mm are each 0.3 mm long using a cutting tool with a niobium guide, diamond cutter, and stepping motor as a niobium wire extrusion mechanism. 0.12 mm, 0.07 mm and 0.03 mm niobium chips were obtained.

(2) Preparation of niobium powder 150 kg of niobium ingot was placed in a vacuum furnace, and after removing the air and flowing hydrogen gas, it was first left at 800 ° C for 18 hours and then at 450 ° C for 18 hours. After removing the gas residue, introduce nitrogen gas containing 10 volume ppm of oxygen at room temperature and let stand for 30 minutes, remove the nitrogen gas, and in turn, nitrogen gas containing 100 volume ppm of oxygen and 0.1% oxygen Nitrogen gas, nitrogen gas containing 1% oxygen, and nitrogen gas containing 3% oxygen were introduced, and the introduction and removal operations were repeated. Finally, air is introduced (hereinafter, the process of introducing nitrogen gas containing oxygen and the process of introducing air is abbreviated as “gradual oxidation process”). A hydrogenated niobium ingot having an amount to niobium molar ratio of 1.2: 1 was prepared. Next, the niobium hydride ingot was crushed with a hammer mill to obtain niobium pieces having an average particle diameter of 8 mm. Next, after adding 3 parts of the 5 mm diameter niobium chip described above to 10 parts of the niobium piece by volume, water was added so that the solid matter was buried, and the 70 mm diameter niobium tube and the reservoir and the reservoir were added to the tube. It was circulated at high speed through a crushing machine having a returning pump and a stirring blade for transfer provided in the pipe. The pulverized product was collected from the liquid reservoir, and after removing the niobium chips, the average particle size was measured to control the pulverization process. When the average particle size reached 37 μm, the pulverization was finished, the niobium chips were removed and vacuum dried, and after the gradual oxidation process, the first niobium powder was obtained. In addition, the niobium chip with a diameter of 1 mm is similarly used for the first niobium powder, and the niobium powder with a diameter of 0.3 mm, 0.12 mm, 0.07 mm, and 0.03 mm is sequentially used in order to finally obtain the sixth niobium powder. It was. The average particle diameters of the second, third, fourth, fifth and sixth niobium powders were 8 μm, 2.5 μm, 1 μm, 0.53 μm and 0.28 μm, respectively. Niobium powder with an average particle size of 0.53 μm and 0.28 μm was dispersed in a solvent in which ethylene glycol and water were mixed at a mass ratio of 2: 1, then left under reduced pressure at 400 ° C. for 5 hours and then under vacuum at 800 ° C. for 4 hours. The mixture was allowed to stand, returned to room temperature, extracted after the gradual oxidation step, and each granulated powder that also served as a dehydrogenation step was obtained. 0.09 g of each granulated powder was taken and formed into a size of 4.4 × 3.5 × 1.7 mm together with a 0.3 mm niobium wire and vacuum sintered at 1280 ° C. for 30 minutes to obtain a sintered body. Next, the sintered body was placed in a 0.1% phosphoric acid aqueous solution, formed at 80 ° C. for 8 hours at 20 V to form an oxide film on the surface, washed and dried with water, and the capacity was measured in 40% sulfuric acid separately prepared. The results were 690 μF and 1210 μF, respectively, and the CV values (unit μF · V / g) of niobium powder were 153000 and 269000, respectively.

Example 2:
(1) Production of tantalum chip Example 1 except that in Example 1, a commercially available tantalum rod having a diameter of 10 mm and a length of 100 mm was used instead of the niobium ingot, and a thin wire was produced by drawing in the round die and subsequent steps. In the same manner as in Example 1, a tantalum chip having the same dimensions as Example 1 was obtained.

(2) Preparation of tantalum powder 1st to 6th tantalum powder in the same manner as in Example 1 except that 10 kg of a commercially available tantalum rod having a diameter of 20 mm and a length of 100 mm was used instead of 150 kg of niobium ingot. Got. The average particle size of each powder was 32 μm, 7.4 μm, 2.2 μm, 0.95 μm, 0.49 μm, and 0.26 μm, respectively. Tantalum powder having an average particle size of 0.49 μm and 0.26 μm was granulated in the same manner as in Example 1 to obtain each granulated powder. 0.15 g of each granulated powder was taken and formed into a size of 4.4 × 3.5 × 1.8 mm together with a 0.3 mm tantalum wire and vacuum sintered at 1310 ° C. for 30 minutes to obtain a sintered body. Next, the sintered body was put in a 0.1% phosphoric acid aqueous solution, formed at 80 ° C. for 8 hours at 20 V, formed an oxide film on the surface, washed and dried with water, and the capacity was measured in 40% sulfuric acid prepared separately. The results were 800 μF and 1140 μF, respectively, and the CV values of the tantalum powder were 107000 and 152000, respectively.

Claims (9)

  Embrittlement characterized in that the body is made of one metal selected from niobium, tantalum having a cylindrical shape and a diameter of 0.03 to 5 mm, or an alloy containing any one of these metals as a main component. Metal chips for pulverized materials of niobium, tantalum or alloys mainly composed of any of these metals.   The metal tip according to claim 1, wherein the length of the cylindrical portion is 0.03 to 5 mm.   3. The metal tip according to claim 1, wherein a part thereof is nitrided.   Niobium, tantalum or niobium, tantalum, or any one of these, characterized in that a thin wire made from one kind of metal selected from niobium, tantalum or an alloy containing any one of these metals as a main component is embrittled and then cut or folded A method for producing a metal tip for a pulverized material of an ingot made of an alloy containing as a main component a metal.   Niobium by embrittlement and pulverization of niobium, tantalum, an alloy containing any one of these metals as a main component, or a mixture of these metals, using the metal tip according to claim 1 as a pulverizing material. A method for producing a metal powder for a capacitor, characterized in that, after producing a metal powder of an alloy containing tantalum or any one of these metals as a main component or a mixed powder of these metals, it is debrittled.   6. The method for producing metal powder for capacitors according to claim 5, wherein a metal chip made of the same material as the metal powder to be produced is used.   6. The method of manufacturing metal powder for capacitors according to claim 5, wherein the metal powder to be manufactured is niobium or an alloy containing niobium as a main component, and a tantalum chip is used as the metal chip.   After using a plurality of types of metal tips whose diameters (and lengths) are in a range of 0.03 to 5 mm in stages, the ingot hydride is first pulverized with a metal tip having a large cylinder diameter, The ingot hydride is pulverized sequentially using metal chips having a smaller diameter of the cylindrical part, and metal powder having a diameter of 1/100 to 1/150 of the cylindrical part diameter of the last used metal chip is prepared and then dehydrogenated. Item 6. A method for producing metal powder for capacitors according to Item 5.   A niobium powder, a tantalum powder produced using the metal tip according to any one of claims 1 to 3, or a metal powder of an alloy mainly containing any one of these metals, or a mixture of these metal powders.