JP4371323B2 - Niobium powder, niobium sintered body, and capacitor using niobium sintered body - Google Patents

Description

  The present invention relates to niobium powder and a sintered body that can stably produce a capacitor having a large capacity per unit mass and good leakage current characteristics and moisture resistance, a capacitor using these, and a method for producing the same.

  Capacitors used in electronic devices such as mobile phones and personal computers are desired to be small and have a large capacity. Among such capacitors, a tantalum capacitor is preferred because it has a large capacity for its size and good performance. Furthermore, recent electronic devices are required to operate at a low voltage, operate at a high frequency, and reduce noise, and a solid electrolytic capacitor is also required to have a lower ESR (equivalent series resistance).

  Generally, a tantalum powder sintered body is used as an anode body of a tantalum capacitor. By sintering this powder after molding, it is integrated into an electrode called a sintered body. The inside of the sintered body has a three-dimensional complicated shape in which the powder is electrically and mechanically connected. A dielectric film layer is formed on the surface including the surface of the internal void of the sintered body, and then a capacitor is formed by impregnating a material to be a counter electrode. The capacitance of the produced capacitor greatly depends on the contact state between the counter electrode material and the dielectric coating layer as long as the dielectric coating layer is uniformly attached to the surface outside the sintered body.

  In order to increase the capacity of these tantalum capacitors, it is necessary to increase the mass of the sintered body or use a sintered body having a surface area increased by pulverizing tantalum powder. In the method of increasing the mass of the sintered body, the shape of the capacitor inevitably increases and does not satisfy the demand for downsizing. On the other hand, in the method of increasing the specific surface area by pulverizing the tantalum powder, the pore diameter of the tantalum sintered body is reduced, and the number of closed pores is increased in the sintering stage, making it difficult to impregnate the cathode agent in the subsequent process . For example, when a phosphoric acid aqueous solution is used as the counter electrode material, the contact state with the dielectric coating layer is perfect, and the capacity appearance rate (also referred to as the cathode agent impregnation rate) at that time is 100%. When using a material, particularly a solid electrode material, it was difficult to set the capacity appearance rate to 100%. In particular, when the average particle size of the tantalum powder is small or the shape of the sintered body made from the tantalum powder is large, the difficulty increases, and in an extreme case, the capacity appearance rate is less than 50%. There was also. In addition, in the case of such a low capacity appearance rate, the moisture resistance of the produced capacitor could not be obtained sufficiently. In addition, when the pore diameter of the tantalum powder for producing the tantalum sintered body is small, the pore diameter of the sintered body is inevitably small and the capacity appearance rate is low. As a result, there arises a problem that ESR cannot be lowered.

  As one of the means to solve these drawbacks, a capacitor using an electrode material capable of obtaining a dielectric having a dielectric constant larger than that of tantalum and producing a sintered body having a high capacity appearance rate can be considered. It is done.

  As such an electrode material that can be supplied industrially, niobium having a larger dielectric constant and a larger reserve than tantalum is known.

  Japanese Patent Application Laid-Open No. 55-157226 (Patent Document 1) discloses that niobium fine powder having a particle size of 2.0 μm or less is pressed from an agglomerated powder and sintered, and the molded sintered body is finely cut. And the manufacturing method of the sintered element for capacitors which joins a lead part to this and sinters again is indicated. However, the publication does not give details on the characteristics of the capacitor.

  US Pat. No. 4,084,965 discloses a capacitor in which a niobium ingot is hydrogenated and pulverized to obtain niobium powder having an average particle diameter of 5.1 μm, which is sintered. However, the disclosed capacitor has a large leakage current (hereinafter sometimes abbreviated as LC) value, and is not practical.

  Japanese Patent Laid-Open No. 10-224004 (Patent Document 2) discloses that the LC value is improved by nitriding a part of niobium powder.

  The tapping density of the niobium powder for capacitors is an important factor in forming the niobium powder. For the conventional ones, the tapping density is larger than 2.5 g / ml and about 4 g / ml. It wasn't enough for that.

  That is, when forming a sintered body by forming and sintering such niobium powder, the flow of niobium powder from the molding machine hopper to the mold is poor, and a certain amount of niobium powder is always measured and put into the mold. It was difficult. For this reason, there is a drawback that the shape of the molded body is not always sufficiently stabilized, the strength of the molded body and the sintered body is insufficient, and as a result, a capacitor having a poor LC is frequently produced. In addition, if a special molding apparatus that can handle powder with poor flowability is used, the molding cost becomes too high and it is not practical.

  For these reasons, the conventionally known niobium powder for capacitors is not sufficiently adaptable to continuous molding, and there is a problem that the productivity of capacitors is low.

JP-A-55-157226 US Patent No. 4,084,965

  The object of the present invention is preferably a capacitor having a large capacity per unit mass and a small leakage current value and a capacitor having high moisture resistance, a sintered body that can be obtained as an electrode material and has a high capacity appearance rate, and this sintered body material. An object of the present invention is to provide a niobium powder that has good flowability in operation during molding, is easy to be continuously formed, and that enables stable production of capacitors, and a method for manufacturing the same.

  The present inventors diligently studied the aforementioned problems. As a result, when a niobium sintered body having a specific pore distribution, preferably a niobium sintered body having a pore distribution having a plurality of pore diameter peak tops, is used for a capacitor electrode, a high capacity appearance rate can be obtained. They found that capacitors with low leakage current and good moisture resistance can be produced. Furthermore, niobium powder having a tapping density of 0.5 to 2.5 g / ml, more preferably an average particle size of 10 to 1000 μm, has good flowability and can be continuously formed. It has been found that a capacitor having a low leakage current value can be stably produced by using this niobium powder. These were found and the present invention was completed. More preferably, a niobium sintered body prepared by using niobium powder having a wide pore distribution and a plurality of peak diameter peak tops, all of which have a pore diameter peak top of 0.5 μm or more, is used as a capacitor electrode. We found that low ESR can be achieved with a high capacity appearance rate.

（式中、Ｒ¹〜Ｒ⁴はそれぞれ独立して水素原子、炭素数１乃至１０の直鎖上もしくは分岐状の飽和もしくは不飽和のアルキル基、アルコキシ基あるいはアルキルエステル基、またはハロゲン原子、ニトロ基、シアノ基、１級、２級もしくは３級アミノ基、ＣＦ₃基、フェニル基及び置換フェニル基からなる群から選ばれる一価基を表わす。Ｒ¹とＲ²及びＲ³とＲ⁴の炭化水素鎖は互いに任意の位置で結合して、かかる基により置換を受けている炭素原子と共に少なくとも１つ以上の３〜７員環の飽和または不飽和炭化水素の環状構造を形成する二価鎖を形成してもよい。前記環状結合鎖には、カルボニル、エーテル、エステル、アミド、スルフィド、スルフィニル、スルホニル、イミノの結合を任意の位置に含んでもよい。Ｘは酸素、硫黄又は窒素原子を表し、Ｒ⁵はＸが窒素原子の時のみ存在して、独立して水素又は炭素数１乃至１０の直鎖上もしくは分岐状の飽和もしくは不飽和のアルキル基を表す。）で示される繰り返し単位を含む重合体に、ドーパントをドープした導電性高分子である前記１２に記載のコンデンサ。
１５．導電性高分子が、下記一般式（３）

（式中、Ｒ⁶及びＲ⁷は、各々独立して水素原子、炭素数１乃至６の直鎖状もしくは分岐状の飽和もしくは不飽和のアルキル基、または該アルキル基が互いに任意の位置で結合して、２つの酸素元素を含む少なくとも１つ以上の５〜７員環の飽和炭化水素の環状構造を形成する置換基を表わす。また、前記環状構造には置換されていてもよいビニレン結合を有するもの、置換されていてもよいフェニレン構造のものが含まれる。）で示される繰り返し単位を含む導電性高分子である前記１４に記載のコンデンサ。
１６．導電性高分子が、ポリ（３，４−エチレンジオキシチオフェン）にドーパントをドープした導電性高分子である前記１２に記載のコンデンサ。
１７．対電極が、層状構造を少なくとも一部に有する材料からなる前記９に記載のコンデンサ。
１８．対電極が、有機スルホン酸アニオンをドーパントとして含んだ材料である前記９に記載のコンデンサ。
１９．ニオブ焼結体を一方の電極とし、その焼結体表面上に形成された誘電体と、前記誘電体上に設けられた対電極を含むコンデンサの製造方法であって、ニオブ焼結体が、前記１乃至８のいずれか１項に記載のニオブ焼結体であることを特徴とするコンデンサの製造方法。
２０．前記９乃至１８のいずれか１項に記載のコンデンサを使用した電子回路。
２１．前記９乃至１８のいずれか１項に記載のコンデンサを使用した電子機器。 That is, the present invention relates to the following niobium powder, a niobium sintered body, a capacitor using the niobium powder, and a manufacturing method thereof.
1. A niobium sintered body for a capacitor electrode, wherein the pore distribution of the niobium sintered body has a plurality of pore diameter peak tops.
2. 2. The niobium sintered body according to 1 above, wherein the pore distribution comprises two pore diameter peak tops.
3. 2. The niobium firing according to 1 or 2 above, wherein the peak tops of the two peaks having the highest relative intensity among the plurality of pore diameter peak tops are in the ranges of 0.2 to 0.7 μm and 0.7 to 3 μm, respectively. Union.
4). 4. The niobium according to any one of 1 to 3, wherein a peak top of a peak having the highest relative intensity among a plurality of pore diameter peak tops is located on a larger diameter side than a peak top of a peak having the next highest relative intensity. Sintered body.
5. 5. The niobium sintered body according to 1 to 4, wherein the sintered body has a volume of 10 mm ³ or more including a pore void volume.
6). 6. The niobium sintered body according to 1 to 5, wherein the sintered body has a specific surface area of 0.2 to 7 m ² / g.
7). 7. The niobium sintered body according to 1 to 6, wherein a part of the sintered body is nitrided.
8). 8. The sintered body according to any one of 2 to 7, which is a sintered body obtained from a niobium molded body that gives a sintered body having a CV value of 40000 to 200000 μFV / g when sintered at 1300 ° C. Niobium sintered body.
9. 9. A capacitor comprising the niobium sintered body according to any one of 1 to 8 as one electrode and a dielectric interposed between the counter electrode.
10. 10. The capacitor as described in 9 above, wherein the main component of the dielectric is niobium oxide.
11. 10. The capacitor according to 9, wherein the counter electrode is at least one material selected from the group consisting of an electrolytic solution, an organic semiconductor, and an inorganic semiconductor.
12 The counter electrode is an organic semiconductor, and the organic semiconductor is an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, and an organic semiconductor composed mainly of tetracyanoquinodimethane. 12. The capacitor as described in 11 above, which is at least one material selected from the group consisting of conductive polymers.
13. 13. The capacitor according to 12 above, wherein the conductive polymer is at least one selected from polypyrrole, polythiophene, polyaniline, and substituted derivatives thereof.
14 The conductive polymer is represented by the following general formula (1) or general formula (2).

(Wherein R ^{1 to} R ⁴ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group, alkoxy group or alkyl ester group having 1 to 10 carbon atoms, a halogen atom, a nitro group, A monovalent group selected from the group consisting of a group, a cyano group, a primary, secondary or tertiary amino group, a CF ₃ group, a phenyl group and a substituted phenyl group, R ¹ and R ² and R ³ and R ⁴ The hydrocarbon chain is bonded to each other at any position to form a cyclic structure of at least one 3 to 7-membered saturated or unsaturated hydrocarbon with the carbon atom substituted by such group The cyclic bond chain may contain a bond of carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl, imino at any position, X is oxygen, sulfur or Represents a nitrogen atom, R ⁵ is present X only when the nitrogen atom, represented by independently. Representing the linear on or branched alkyl group, saturated or unsaturated hydrogen or 1 to 10 carbon atoms) 13. The capacitor as described in 12 above, which is a conductive polymer in which a polymer containing a repeating unit is doped with a dopant.
15. The conductive polymer is represented by the following general formula (3)

(In the formula, R ⁶ and R ⁷ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl groups are bonded to each other at an arbitrary position. And represents a substituent that forms a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon containing two oxygen elements, and the cyclic structure has an optionally substituted vinylene bond. 15. The capacitor as described in 14 above, which is a conductive polymer containing a repeating unit represented by formula (1):
16. 13. The capacitor as described in 12 above, wherein the conductive polymer is a conductive polymer obtained by doping poly (3,4-ethylenedioxythiophene) with a dopant.
17. 10. The capacitor according to 9 above, wherein the counter electrode is made of a material having at least a part of a layered structure.
18. 10. The capacitor according to 9 above, wherein the counter electrode is a material containing an organic sulfonate anion as a dopant.
19. A niobium sintered body as one electrode, a dielectric formed on the surface of the sintered body, and a capacitor manufacturing method including a counter electrode provided on the dielectric, the niobium sintered body, A method for manufacturing a capacitor, which is the niobium sintered body according to any one of 1 to 8 above.
20. 19. An electronic circuit using the capacitor according to any one of 9 to 18 above.
21. 19. An electronic device using the capacitor according to any one of 9 to 18.

Niobium powder for capacitors of the present invention having a tapping density of 0.5 to 2.5 g / ml, an average particle size of 10 to 1000 μm, an angle of repose of 10 to 60 degrees, and a BET specific surface area of 0.5 to 40 m ² / g Has good flowability, can be continuously formed, has a pore diameter peak top in the range of 0.01 μm to 500 μm obtained by sintering the niobium powder, and preferably has a plurality of pores. By using the niobium sintered body of the present invention having a pore distribution with a diameter peak top as a capacitor electrode, a high capacity appearance rate is obtained, a leakage current is low, and a capacitor with good moisture resistance can be produced.

  Hereinafter, a capacitor having good leakage current characteristics and moisture resistance, a niobium sintered body that draws out the characteristics and obtains a high capacity appearance rate, niobium powder that has good flowability and can be continuously formed as a sintered body material, and These manufacturing methods will be described.

  In the present invention, as niobium powder that satisfies the characteristics of the capacitor and improves the productivity of capacitor production, niobium powder for capacitors having a tapping density of 0.5 to 2.5 g / ml (simply abbreviated as niobium powder). May be used). Here, the niobium for a capacitor means niobium as a main component and can be a material for producing a capacitor. This may include components other than niobium such as, for example, components that can be alloyed with niobium, nitrogen, and / or oxygen.

  The ob powder is formed and sintered for the capacitor by the following method to obtain a sintered body for the capacitor (sometimes abbreviated simply as a niobium sintered body), and a dielectric layer and a counter electrode are formed thereon. , You can get a capacitor.

  Niobium powder for a capacitor is put into a solution in which a binder (described later) is dissolved in an organic solvent such as toluene or methanol, and this is sufficiently mixed using a shaker, a V-type mixer or the like. Then, using a dryer such as a conical dryer, the organic solvent is distilled off under reduced pressure to produce a niobium blended powder containing a binder. This mixed powder is put into an automatic molding machine hopper. Niobium blended powder is weighed while flowing naturally through the introduction pipe from the hopper to the molding machine mold, and molded together with the lead wire. After the binder is removed under reduced pressure, the compact is sintered at 500 ° C. to 2000 ° C. to produce a niobium sintered body. For example, the niobium sintered body is subjected to chemical conversion treatment for 1 to 30 hours by raising the pressure to 20 to 60 V in an electrolytic solution such as phosphoric acid and adipic acid having a temperature of 30 to 90 ° C. and a concentration of about 0.1% by mass. Create a dielectric layer mainly composed of niobium. A solid electrolyte layer such as manganese dioxide, lead dioxide, or conductive polymer is formed on the dielectric layer, and then a graphite layer and a silver paste layer are formed. Next, a cathode terminal is connected thereto by soldering or the like, and then sealed with resin to produce a solid electrolytic capacitor.

  For this reason, in the mixed powder which does not have moderate flowability and angle of repose, it cannot flow stably from a hopper to a metal mold, and cannot be formed stably. Especially because it is transported from the hopper using a method such as vibration, even if the tapping density and average particle size of the blended powder are too large or too small, the mass of the molded body, the strength of the sintered body and the variation in shape will increase. Chipping and cracking may occur, resulting in a poor leakage current value. As described above, the tapping density, the flat particle diameter, the flowability and the angle of repose of the blended powder are important factors in producing a good sintered body and capacitor.

  Such physical properties of the blended powder hardly change before and after blending with the binder, and the physical properties of the blended powder are determined by the physical properties of the used capacitor niobium powder. Therefore, the tapping density, average particle diameter, flowability, angle of repose, etc. of the niobium powder used are important. Since the flowability and angle of repose of niobium powder are greatly affected by the tapping density and the average particle diameter, the tapping density and the average particle diameter are important factors.

  In order to obtain the effect of improving the productivity and the strength of the sintered body accompanying the improvement of the flowability and the angle of repose, and the accompanying reduction of the leakage current value, in the present invention, the tapping density is 0.5 to 2.5 g / ml is preferred, and 0.8 to 1.9 g / ml is particularly preferred. Moreover, 10-1000 micrometers is preferable and, as for the average particle diameter of the niobium powder of this invention, 50-200 micrometers is especially preferable.

  In order for the niobium powder to fall naturally from the molding machine hopper to the mold, the repose angle of the niobium powder of the present invention is preferably 10 to 60 degrees, more preferably 10 to 50 degrees.

  Niobium powder having the above physical properties is also referred to as niobium powder or niobium compound powder (hereinafter referred to as “raw niobium powder”) and an activator (“pore forming agent”. And the like (hereinafter referred to as “raw material mixture”) as a raw material, and can be produced through at least a sintering step and a pulverizing step. The activator is removed in any step of the sintering step or the crushing step for producing the niobium powder of the present invention from the raw material mixture. The removal of the activator may be performed independently of the sintering step and the crushing step.

  As a method for removing the activator, various methods can be arbitrarily adopted depending on the chemical properties of the activator, and any one or more methods that can easily remove the activator may be used in combination. Examples of the method for removing the activator include a method for removing the activator by evaporating, sublimating or thermally decomposing it into a gas, and a method for removing the activator by dissolving it in a solvent.

  When removing the activator as a gas, it may be performed in a sintering step, or a step of removing the activator by heating and / or decompression before sintering may be provided. When the activator is dissolved and removed in a solvent, the activator is dissolved and removed by bringing the solvent, which will be described later, into contact with the sintered product or its crushed material after sintering, during or after crushing the raw material mixture. .

  Further, in any of the steps of producing the niobium powder of the present invention from the raw material mixture, a step of nitriding, boriding, carbonizing, or sulfiding a part of the niobium powder may be provided.

  Hereinafter, the manufacturing method of the niobium powder of the present invention will be described in detail. As the raw material niobium powder, at least one kind of powder selected from niobium, niobium hydride, niobium alloy, and niobium hydride alloy can be used. Some of these may be nitrided, sulfided, carbonized, or borated. The alloy used in the present invention includes a solid solution with the other alloy component. The average particle diameter of the raw material niobium powder is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm, and particularly preferably 0.05 to 2 μm.

  The method of obtaining niobium as raw material niobium powder is, for example, a method of hydrogenating niobium ingot, niobium pellets, niobium powder, etc., pulverizing and dehydrogenating, a method of reducing potassium fluorinated niobate with sodium etc. Examples thereof include a method of reducing niobium oxide using at least one of hydrogen, carbon, magnesium, aluminum and the like, pulverizing the reduced product, or a method of reducing niobium halide with hydrogen.

  Examples of the method for obtaining niobium hydride to be a raw material niobium powder include a method in which niobium ingot, niobium pellets, niobium powder and the like are hydrogenated and pulverized.

  Moreover, the method of obtaining the niobium hydride alloy used as raw material niobium powder can be obtained by a method of pulverizing these hydrides such as niobium alloy ingot, niobium alloy pellets, or niobium alloy powder. As a method for obtaining a niobium alloy as raw material niobium powder, there is a method of dehydrogenating this niobium hydride alloy.

  The niobium alloy, the niobium hydride alloy, as an alloy component other than niobium, from the group consisting of elements having an atomic number of 88 or less, hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine, niobium, helium, neon, It contains at least one element selected from the group excluding krypton, argon, xenon, and radon.

  An activator is a substance that can be removed in any step of producing the niobium powder of the present invention from a raw material mixture. Usually, in the niobium powder of the present invention, the portion from which the activator is removed forms pores.

  The particle size of the activator affects the pore diameter of the niobium powder of the present invention, the pore diameter of the niobium powder affects the pore diameter of the niobium sintered body, and the pore diameter of the sintered body indicates the capacitance of the capacitor. And the impregnation property of the cathode agent in the capacitor manufacturing process.

  The impregnation property of the cathodic agent has a great influence on the production of a capacitor having a high capacity and a low ESR. Since the niobium sintered body is prepared by press-molding niobium powder, the pore diameter of the sintered body is necessarily smaller than the pore diameter of niobium powder. Considering the difficulty of impregnation of the cathode material into the sintered body prepared from the powder having a small pore diameter peak, the niobium powder has an average pore diameter of 0.5 μm or more, particularly 1 μm or more. It is desirable.

  The average diameter of these pores is preferably 0.01 to 500 μm, more preferably 0.03 to 300 μm, and particularly preferably 0.1 to 200 μm. Therefore, the average particle diameter of the activator is preferably 0.01 to 500 μm, more preferably 0.03 to 300 μm, and particularly preferably 0.1 to 200 μm.

  The most preferable niobium powder has a pore diameter of 0.5 μm to 100 μm as an average diameter, and the most preferable average particle diameter of the activator for producing the pore diameter is 0.5 μm to 100 μm. In order to reduce these pore diameters, an activator having a small particle size may be used, and in order to increase the pore diameter, an activator having a large particle size may be used.

  Further, the pore diameter distribution can be adjusted by adjusting the particle size distribution of the activator. In order to obtain a capacitor having a sufficient capacity without the problem of impregnation of the cathodic agent, the niobium sintered body is small enough to obtain a desired capacity, and large enough to be sufficiently impregnated with the cathodic agent. It is preferable that the pores are appropriately provided in accordance with the physical properties of the cathode agent.

  In order to adjust the pore diameter distribution of the niobium powder or the niobium sintered body, for example, an activator (powder) having a particle size distribution having two or more peak tops is used, and the niobium powder has two or more peak tops. A pore diameter distribution can be provided. By sintering the niobium powder, a niobium sintered body having a pore size distribution having two or more peak tops having the same pore diameter can be obtained. In this case, the pore diameter peak top is preferably in the range of 0.01 to 500 μm, more preferably 0.03 to 300 μm, further preferably 0.1 to 200 μm, and particularly preferably 0.1 to 30 μm. 0.2 to 3 μm is most preferable.

  The niobium powder that gives such a niobium sintered body has two or more pore diameter peak tops. The niobium powder preferably has two or more pore diameter peak tops of 0.5 μm or more. For example, when creating a niobium sintered body having two pore diameter peak tops at 0.7 μm and 3 μm, the two pore diameter peak tops of niobium powder are adjusted to, for example, about 1.5 μm and about 25 μm. Just do it.

  The average particle size of the activator that gives such a small pore diameter of about 1.5 μm is about 1.5 μm, and the average particle size of the activator that gives a large pore diameter of about 25 μm is about 25 μm. Usually, when a small pore diameter and a large pore diameter are present in niobium powder, the large pore diameter is crushed and becomes smaller during pressure molding. Therefore, it is desirable that the large pore diameter peak top be 20 μm or more. Even when there are three pore diameter peak tops, the large pore diameter peak top is desirably 20 μm or more. Further, it is desirable that 30% by volume or more of the total pore volume has a pore diameter of 20 μm or more, and particularly preferably 40% by volume or more.

  Further, the above example will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the state of the niobium powder of the present invention. The niobium powder of the present invention is a granulated powder having specific pores in which the primary powder is formed by an activator. The pore A is a pore formed by an activator having an average particle size of about 1.5 μm, and the pore B is a pore formed by an activator having an average particle size of about 25 μm. Thus, it is possible to agglomerate primary powders efficiently. FIG. 2 is a schematic view when the pore distribution of the niobium powder of the present invention is measured by a mercury intrusion method. Peak A is the peak of pore A formed by an activator of about 1.5 μm, and peak B is the peak of pore B formed by an activator of about 25 μm. The height of the peak B is higher than that of the peak A, and the total pore volume 44% is a pore diameter of 20 μm or more.

  An activator having two or more peak tops in the particle size distribution can be obtained, for example, by mixing two or more activators having different peak tops in the particle size distribution.

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

Examples of the substance that becomes a gas below the sintering temperature include a substance that becomes a gas by evaporation, sublimation, or thermal decomposition, and an inexpensive substance that easily becomes a gas without leaving a residue even at a low temperature is preferable. Examples of such substances 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 the organic polymer include polyacrylic acid, polyacrylic acid ester, polyacrylamide, polymethacrylic acid, polymethacrylic acid ester, polymethacrylamide, and polyvinyl alcohol.

  The substance that is soluble at least after sintering is a substance in which the activator or the residue of its thermal decomposition product is soluble in the solvent, and the solvent described later after sintering, during crushing, or after crushing Substances that readily dissolve in water are particularly preferred, but can be selected from many substances in combination with solvents.

  Examples of such materials include compounds of metal and carbonic acid, sulfuric acid, sulfurous acid, halogen, perhalogenic acid, hypohalous acid, nitric acid, nitrous acid, phosphoric acid, acetic acid, oxalic acid, or boric acid, metal oxides, metals A hydroxide and a metal are mentioned. Preferably, it is a compound having high solubility in a solvent such as acid, alkali, ammonium salt solution, for example, lithium, sodium, potassium, rubidium, cesium, and 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, bismuth, selenium, tellurium, polonium, boron, silicon, and arsenic Compounds containing at least one selected from the like. Of these, metal salts are preferable, and barium oxide, manganese (II) nitrate, calcium carbonate, and the like are more preferable. These activators may be used alone or in combination of two or more without any problem.

  Considering efficient formation of specific pores, a substance that exists as a solid at the sintering temperature is preferred. This is because, at the sintering temperature, the activator is present as a solid, thereby blocking the aggregation of the niobium primary powder more than necessary and causing the fusion of niobium only at the contact points of niobium. When present in a liquid or gas at the sintering temperature, the blocking effect is small, and pores smaller than the desired pores may be formed. Therefore, a higher melting point, for example, barium oxide, calcium carbonate, aluminum oxide, magnesium oxide, etc., than when a low melting point material such as aluminum metal, magnesium metal, magnesium hydride, calcium metal or the like is used as an activator. The pore diameter is more stable when used as an activator.

  If the addition amount of the activator is small, the tapping density and the angle of repose become large, and if it is large, the tapping density becomes small and the number of closed holes in the sintering stage increases. In order to obtain a tapping density of 0.5 to 2.5 g / ml at an angle of repose of 60 degrees or less without the problem of closed pores in the sintering stage, it varies depending on the average particle diameter of the activator. 1% by mass to 40% by mass with respect to the raw material niobium (hereinafter, unless otherwise specified, mass% is simply abbreviated as%), preferably 5% or more and 25% or less, more preferably 10% or more and 20% or less. It is.

  The raw material mixture may be a mixture of the above-described activator and the above-mentioned niobium raw material without solvent, or a mixture obtained by mixing both using a suitable solvent and drying.

  Examples of the solvent that can be used include water, alcohols, ethers, cellosolves, ketones, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and the like. A mixer can also be used for mixing. As the mixer, ordinary apparatuses such as a shake mixer, a V-type mixer, and a Nauta mixer can be used without any problem. Although the temperature in mixing is limited by the boiling point and freezing point of the solvent, it is generally -50 ° C to 120 ° C, preferably -50 ° C to 50 ° C, more preferably -10 ° C to 30 ° C. The time required for mixing is not particularly limited as long as it is 10 minutes or longer, but it is usually 1 to 6 hours, and it is desirable to carry out in an oxygen-free atmosphere using an inert gas such as nitrogen or argon.

  When a solvent is used, the obtained mixture is dried at a temperature of less than 80 ° C., preferably less than 50 ° C., using a conical dryer or a shelf dryer. Drying at a temperature of 80 ° C. or higher is not preferable because the amount of oxygen in niobium or niobium hydride fine powder increases.

  When the activator becomes a gas below the sintering temperature, it is possible to remove the activator during sintering, but sintering under conditions such as temperature, pressure, time, etc. that are easy to remove in accordance with the chemical properties of the activator. A step of removing the activator in the form of gas may be independently provided. In this case, for example, the activator is distilled off at 100 ° C. to 800 ° C. under reduced pressure for several hours.

  When niobium hydride or a niobium hydride alloy is used as the raw material niobium, dehydrogenation can be performed by performing this step regardless of the type of the activator.

  The sintering step is performed at 500 ° C. to 2000 ° C., preferably 800 ° C. to 1500 ° C., more preferably 1000 ° C. to 1300 ° C. under reduced pressure or a reducing atmosphere such as argon. Preferably, after the sintering is completed, the niobium is cooled until the temperature of the niobium (also abbreviated as the product temperature) is 30 ° C. or less, and is 0.01 vol% to 10 vol%, preferably 0.1 vol% to 1 vol% An inert gas such as nitrogen or argon containing oxygen is gradually added so that the product temperature does not exceed 30 ° C., and is left for 8 hours or longer to obtain a sintered ingot. In the crushing step, the sintered ingot is crushed to an appropriate particle size using a crusher such as a roll granulator.

  If the activator is soluble in the solvent at least after the sintering step, an appropriate solvent is sintered or crushed powder after sintering, before crushing, during crushing, after crushing, or in these multiple steps The activator component is dissolved and removed. From the viewpoint of easy removal, it is preferable to dissolve and remove from the crushed powder after pulverization.

  As a solvent used here, it is a solvent from which the solubility of the activator which should be melt | dissolved is obtained sufficiently, Preferably, what is cheap and cannot remain easily is good. For example, if the activator is water-soluble, use water. If the activator is soluble in organic solvents, use an organic solvent such as methyl isobutyl ketone, ethanol, or dimethylsulfoalkylside (DMSO). If it is acid-soluble, use nitric acid, sulfuric acid, phosphorus. If an acid solution such as acid, boric acid, carbonic acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, or organic acid is used and is alkali-soluble, alkali metal hydroxide, alkaline earth metal water If an alkaline solution such as oxide or ammonia is used to form a soluble complex, the ligand is ammonia, amines such as ethylenediamine, amino acids such as glycine, polyphosphoric acids such as sodium tripolyphosphate, crown ethers A solution of a thiosulfate such as sodium thiosulfate or a chelating agent such as ethylenediaminetetraacetic acid may be used.

  Also, ammonium salt solutions such as ammonium chloride, ammonium nitrate, and ammonium sulfate, cation exchange resins, and anion exchange resins can be suitably used. It is desirable that the temperature at which the activator is removed by dissolution is low. Since niobium has a high affinity with oxygen, the surface of niobium is oxidized when the temperature for dissolution and removal is high. Therefore, 50 degrees C or less is preferable. It is preferable to dissolve and remove at −10 ° C. to 40 ° C., particularly preferably at 0 ° C. to 30 ° C. For the above reasons, it is preferable to select a method that generates less heat when dissolved and removed. For example, when a metal oxide or metal is used as the activator, the method of dissolving and removing with an acid generates heat of neutralization. Therefore, for example, select a method that hardly generates heat, such as a method of dissolving in water or an organic solvent, a method of forming a soluble complex using an aqueous ammonium nitrate salt solution or ethylenediaminetetraacetic acid, or a method of dissolving in a solution containing an ion exchange resin. You can also

  More specifically, the combination of the activator and the solvent is, for example, barium oxide and water, calcium oxalate and hydrochloric acid, aluminum oxide and sodium hydroxide aqueous solution, hafnium oxide and methyl isobutyl ketone, magnesium carbonate and ethylenediaminetetraacetic acid tetrasodium salt aqueous solution Etc.

  After dissolving and removing the activator, it is thoroughly washed and dried. For example, when barium oxide is removed with water, it is sufficiently washed with ion exchange water until the electric conductivity of the washing water becomes 5 μS / cm or less. Next, it is dried at a product temperature of 50 ° C. or lower under reduced pressure. The amount of the activator and solvent component remaining here is usually 100 ppm or less, although it depends on the washing conditions.

  In order to further improve the LC value in the niobium powder thus obtained, the sintered ingot, or the niobium raw material powder, a part of the niobium powder is nitrided, borated, carbonized, sulfided, or a plurality of these Processing may be performed.

  The obtained niobium nitride, niobium boride, niobium carbide, niobium sulfide, or a plurality of these may be contained in the niobium powder of the present invention. The total content of each element of nitrogen, boron, carbon, and sulfur varies depending on the shape of the niobium powder, but is 0 ppm to 200,000 ppm, preferably 50 ppm to 100,000 ppm, and more preferably 200 ppm to 20 ppm. 1,000 ppm. If it exceeds 200,000 ppm, the capacity characteristics deteriorate and it is not suitable as a capacitor.

The niobium powder nitriding method can be performed by any one of liquid nitriding, ion nitriding, gas nitriding, or a combination thereof. Gas nitriding in a nitrogen gas atmosphere is preferable because the apparatus is simple and easy to operate. For example, the gas nitriding method using a nitrogen gas atmosphere is achieved by leaving the niobium powder in a nitrogen atmosphere. The temperature of the nitriding atmosphere is 2000 ° C. or less and the standing time is 100 hours or less, so that a niobium powder having a desired nitriding amount can be obtained. Further, the processing time can be shortened by processing at a higher temperature.

  The method for boring niobium powder may be either gas boriding or solid phase boriding. For example, niobium powder may be allowed to stand at 2000 ° C. or less for 1 minute to 100 hours under reduced pressure together with a boron source of boron halide such as boron pellets or trifluoroboron.

  Niobium powder may be carbonized by gas carbonization, solid phase carbonization, or liquid carbonization. For example, niobium powder may be allowed to stand at 2000 ° C. or lower for 1 minute to 100 hours under reduced pressure together with a carbon source such as a carbon material or an organic substance having carbon such as methane.

  Niobium powder may be sulfurized by any of gas sulfiding, ionic sulfiding, and solid phase sulfiding. For example, the method of gas sulfiding in a sulfur gas atmosphere is achieved by leaving the niobium powder in a sulfur atmosphere. The temperature of the sulfiding atmosphere is 2000 ° C. or less and the standing time is 100 hours or less, so that niobium powder having the desired amount of sulfiding can be obtained. Further, the processing time can be shortened by processing at a higher temperature.

The BET specific surface area of the niobium powder of the present invention obtained as described above is usually 0.5 to 40 m ² / g, preferably 0.7 to 10 m ² / g, more preferably 0.9 to ² m ² / g. g.

  The niobium powder of the present invention may be used by mixing niobium powders each having different tapping density, particle size, angle of repose, BET specific surface area, pore size distribution, nitriding, boriding, carbonization, and sulfidation.

The sintered body of the present invention that can be used for the capacitor electrode is preferably produced, for example, by sintering the niobium powder of the present invention described above. For example, after press-molding niobium powder into a predetermined shape, 10 ^-5 to 10 ² Pa for 1 minute to 10 hours, 500 ° C to 2000 ° C, preferably 800 ° C to 1500 ° C, more preferably 1000 ° C to 1300 ° C. The sintered body can be obtained by heating in the range of.

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

  Further, by adjusting the pressure during molding to a specific pressure value, the sintered body can have more pore diameter peak tops than the number of pore diameter peak tops of the niobium powder. This pressure value varies depending on the physical properties of the niobium powder, the shape of the molded body, or the pressure molding conditions of the molding machine, etc., but a pressure that does not close the pores of the sintered body beyond the pressure at which pressure molding is possible. Within the following range. A preferable pressurization value can be determined according to the physical properties of the niobium powder to be molded so as to have a plurality of pore diameter peak tops by a preliminary experiment. In addition, a pressurization value can be adjusted by adjusting the load applied to the molded object of a molding machine, for example.

  The pore size distribution of the sintered body includes at least two pores so that the pores are small enough to obtain a desired capacity and the pores are large enough to be sufficiently impregnated with the cathode agent in accordance with the physical properties of the cathode agent. It is preferable to have a pore diameter peak top. Thus, a sintered body having a pore diameter distribution having a plurality of peak tops can provide a capacitor with good counter electrode impregnation and a high capacity appearance rate.

  The peak tops of the two peaks having the highest relative intensity among the plurality of pore diameter peak tops are 0.2 to 0.7 μm and 0.7 to 3 μm, respectively, preferably 0.2 to 0 respectively. When the thickness is 0.7 μm and 0.9 to 3 μm, the moisture resistance of the capacitor produced from this sintered body is preferable. Furthermore, if the peak top of the peak with the highest relative intensity among the plurality of pore diameter peak tops is on the larger diameter side than the peak top of the peak with the next highest relative intensity, the capacitor has better moisture resistance. Therefore, it is particularly preferable.

The specific surface area of the sintered body produced in this manner will generally 0.2m ² / g~7m ² / g. Usually, the larger the shape of the sintered body, the more difficult the impregnation of the counter electrode. For example, when the size of the sintered body is 10 mm ³ or more, the sintered body having a pore diameter distribution having a plurality of peak tops according to the present invention can be used particularly effectively.

  The sintered body of the present invention may be partially nitrided. As the nitriding method, the method and reaction conditions applied to the niobium powder described above can be adopted. It is also possible to nitride a part of the niobium powder for producing the sintered body and further nitride a part of the sintered body produced from this powder.

  Such a sintered body usually contains 500 to 70000 mass ppm of oxygen. This is because there is natural oxidized oxygen contained in the niobium powder before sintering and oxygen added by natural oxidation after sintering. The content of elements other than niobium, alloy forming elements, oxygen, and nitrogen in the sintered body of the present invention 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 conversion voltage value in the case of 120 ° C. differentiation at 80 ° C. in a 0.1 mass% phosphoric acid aqueous solution and the capacity at 120 Hz) Product) is 40000-200000 μFV / g.

  Next, manufacturing of the capacitor element will be described. For example, a lead wire made of a valve metal such as niobium or tantalum and having an appropriate shape and length is prepared, and a part of the lead wire is inserted into the molded body when the niobium powder is pressure-molded as described above. The lead wire is assembled and designed so that it becomes the lead for drawing out the sintered body, or the lead wire prepared separately is formed and sintered without the lead wire and connected by welding or the like Design as follows.

  A capacitor can be manufactured from the above-mentioned sintered body as one electrode and a dielectric interposed between the counter electrode. For example, a niobium sintered body is used as one electrode, a dielectric is formed on the surface of the sintered body (including the surface in the pores), and a counter electrode is provided on the dielectric to constitute a capacitor.

  Here, the dielectric of the capacitor is preferably a dielectric mainly composed of niobium oxide, more preferably a dielectric mainly composed of niobium pentoxide. A dielectric body mainly composed of niobium pentoxide can be obtained, for example, by electrolytic oxidation of a niobium sintered body that is one of the electrodes. Electrolytic oxidation of the niobium electrode in the electrolytic solution is usually performed using a protonic acid aqueous solution, for example, a 0.1% phosphoric acid aqueous solution, a sulfuric acid aqueous solution, a 1% acetic acid aqueous solution, an adipic acid aqueous solution, or the like. Thus, when a niobium electrode is formed in an electrolytic solution to obtain a niobium oxide dielectric, the capacitor of the present invention becomes an electrolytic capacitor and the niobium electrode becomes an anode.

  In the capacitor of the present invention, the counter electrode (counter electrode) of the niobium sintered body is not particularly limited. For example, at least one selected from an electrolyte, an organic semiconductor, and an inorganic semiconductor known in the aluminum electrolytic capacitor industry. These materials (compounds) can be used.

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

  Specific examples of the organic semiconductor include an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, an organic semiconductor composed mainly of tetracyanoquinodimethane, or the following general formula (1 ) Or a conductive polymer containing a repeating unit represented by the general formula (2).

In the formula, each of R ^{1 to} R ⁴ independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a branched or saturated alkyl group, an alkoxy group or an alkyl ester group, a halogen atom, or a nitro group. , A monovalent group selected from the group consisting of a cyano group, a primary, secondary or tertiary amino group, a CF ₃ group, a phenyl group and a substituted phenyl group. The hydrocarbon chains of R ¹ and R ² and R ³ and R ⁴ are bonded to each other at any position, and at least one or more 3- to 7-membered saturated or unsaturated groups with carbon atoms substituted by such groups. You may form the bivalent chain | strand which forms the cyclic structure of a saturated hydrocarbon. The cyclic bond chain may contain a bond of carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl, or imino at any position. X represents an oxygen, sulfur or nitrogen atom, R ⁵ is present only when X is a nitrogen atom, and is independently hydrogen or a linear or branched saturated or unsaturated alkyl group having 1 to 10 carbon atoms. Represents.

Furthermore, in the present invention, R ^{1 to} R ⁴ in the general formula (1) or general formula (2) are preferably each independently a hydrogen atom, a linear or branched saturated group having 1 to 6 carbon atoms. Alternatively, it represents an unsaturated alkyl group or alkoxy group, and R ¹ and R ² and R ³ and R ⁴ may be bonded to each other to form a ring.

  Furthermore, in the present invention, the conductive polymer containing a repeating unit represented by the general formula (1) is preferably a conductive polymer containing a structural unit represented by the following general formula (3) as a repeating unit. Can be mentioned.

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

  A conductive polymer having such a chemical structure is doped with a dopant. A well-known dopant can be used for a dopant without a restriction | limiting.

  Specific examples of the inorganic semiconductor include an inorganic semiconductor mainly composed of lead dioxide or manganese dioxide, and an inorganic semiconductor composed of iron trioxide. Such semiconductors may be used alone or in combination of two or more.

  Examples of the polymer containing the repeating unit represented by the general formula (1) or (2) include polyaniline, polyoxyphenylene, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole, and substituted derivatives thereof. And copolymers. Of these, polypyrrole, polythiophene, and substituted derivatives thereof (for example, poly (3,4-ethylenedioxythiophene)) are preferable.

When the organic semiconductor and the inorganic semiconductor having a conductivity in the range of 10 ⁻² S / cm to 10 ³ S / cm are used, the impedance value of the manufactured capacitor is further reduced, and the capacitance at high frequency is further increased. Can do.

  As the method for producing the conductive polymer layer, for example, aniline, thiophene, furan, pyrrole, methylpyrrole or a polymerizable compound of these substituted derivatives may be oxidized enough to cause an oxidation reaction of dehydrogenative two-electron oxidation. A method of polymerizing by the action of the agent is employed. The polymerization reaction from the polymerizable compound (monomer) includes, for example, vapor phase polymerization of a monomer, solution polymerization, and the like, and is formed on the surface of a niobium sintered body having a dielectric. In the case where the conductive polymer is an organic solvent-soluble polymer that can be applied by solution, a method in which the conductive polymer is formed by applying to the surface is employed.

  As one of preferred production methods by solution polymerization, a niobium sintered body having a dielectric layer formed is immersed in a solution containing an oxidizing agent (solution 1), and then immersed in a solution containing a monomer and a dopant (solution 2). And a method of polymerizing and forming a conductive polymer layer on the surface. Further, the sintered body may be immersed in the solution 1 after being immersed in the solution 2. Moreover, in the said solution 2, you may use for the said method as a monomer solution which does not contain a dopant. Moreover, when using a dopant, you may use it making it coexist in the solution containing an oxidizing agent.

  A dense and layered conductive polymer layer can be easily formed by repeating such a polymerization process operation once or more, preferably 3 to 20 times, with respect to the niobium sintered body having a dielectric. .

  In the method for manufacturing a capacitor of the present invention, the oxidant may be any oxidant that does not adversely affect the performance of the capacitor and can be used to improve the electric power of the conductive polymer by using the reduced form of the oxidant as a dopant. Industrially inexpensive compounds that are easy to handle in production are preferred.

Specific examples of such an oxidizing agent include FeCl (III) compounds such as FeCl ₃ , FeClO ₄ , Fe (organic acid anion) salt, anhydrous aluminum chloride / cuprous chloride, alkali metal peroxide. Sulfates, ammonium persulfates, peroxides, manganese such as potassium permanganate, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone Quinones such as tetracyano-1,4-benzoquinone, halogens such as iodine and bromine, sulfonic acids such as peracid, sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid and amidosulfuric acid, ozone and the like A combination of these plural oxidizing agents can be mentioned.

  Among these, examples of the basic compound of the organic acid anion that forms the Fe (organic acid anion) salt include organic sulfonic acid or organic carboxylic acid, organic phosphoric acid, and organic boric acid. Specific examples of the organic sulfonic acid include benzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, α-sulfo-naphthalene, β-sulfo-naphthalene, naphthalene disulfonic acid, alkylnaphthalenesulfonic acid (alkyl group). As butyl, triisopropyl, di-t-butyl, etc.).

On the other hand, specific examples of the organic carboxylic acid include acetic acid, propionic acid, benzoic acid, oxalic acid and the like. Furthermore, in the present invention, polyelectrolyte anions such as polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl sulfonic acid, polyvinyl sulfate poly-α-methyl sulfonic acid, polyethylene sulfonic acid, and polyphosphoric acid are also used. In addition, the example of these organic sulfonic acid or organic carboxylic acid is a mere illustration, and is not limited to these. Examples of the counter cation of the anion include alkali metal ions such as H ⁺ , Na ⁺ and K ⁺ , or ammonium ions substituted with a hydrogen atom, a tetramethyl group, a tetraethyl group, a tetrabutyl group, a tetraphenyl group, or the like. However, it is not limited to these. Of the above oxidizing agents, particularly preferred are oxidizing agents containing trivalent Fe compounds, or cuprous chloride, alkali persulfates, ammonium persulfates, and quinones.

An anion (anion other than the reductant anion of the oxidant) having a dopant ability to coexist as necessary in the method for producing a polymer composition of a conductive polymer is an oxidant anion (oxidation) produced from the oxidant described above. It is possible to use an electrolyte anion having a reductant of the agent) as a counter ion or another electrolyte anion. Specifically, for example, a halide anion of a group 5B element such as PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻ , a halide anion of a group 3B element such as BF ₄ ⁻ , I ⁻ (I ₃ ⁻ ), Br ⁻ , Halogen anions such as Cl ⁻ , perhalogenate anions such as ClO ₄ ⁻ , Lewis acid anions such as AlCl ₄ ⁻ , FeCl ₄ ⁻ and SnCl ₅ ⁻ , or inorganic acid anions such as NO ₃ ⁻ and SO ₄ ²⁻ Or sulfonate anions such as p-toluenesulfonic acid, naphthalenesulfonic acid, alkyl-substituted naphthalenesulfonic acid having 1 to 5 carbon atoms (abbreviated as C1-5), CF ₃ SO ₃ ⁻ , CH ₃ SO ₃ ⁻ Mention may be made of organic acid sulfonate anions or protonic acid anions such as carboxylic acid anions such as CH ₃ COO ⁻ and C ₆ H ₅ COO ⁻ .

  Similarly, anions of polymer electrolytes such as polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl sulfonic acid, polyvinyl sulfuric acid, poly-α-methyl sulfonic acid, polyethylene sulfonic acid, and polyphosphoric acid can be exemplified. However, it is not limited to these. However, preferably, anions of high molecular weight and low molecular weight organic sulfonic acid compounds or polyphosphoric acid compounds are used, and desirably aromatic sulfonic acid compounds (sodium dodecylbenzene sulfonate, sodium naphthalene sulfonate, etc.) are used. Used as an anion-providing compound.

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

  As the basic skeleton of the sulfoquinone anion of the sulfoquinone compound, p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthraquinone, 1,4-anthraquinone, 1,2-anthraquinone, 1,4-chrysenequinone, 5,6-chrysenequinone, 6,12-chrysenequinone, acenaphthoquinone, acenaphthenequinone, camphorquinone, 2,3-bornanedione, 9,10-phenanthrenequinone, 2,7- Examples include pyrenequinone.

  When the counter electrode (counter electrode) is solid, a conductor layer may be provided thereon in order to improve electrical contact with an external lead (for example, a lead frame) used as desired.

  The conductor layer can be formed by, for example, solidifying a conductive paste, plating, metal deposition, a heat-resistant conductive resin film, or the like. As the conductive paste, a silver paste, a copper paste, an aluminum paste, a carbon paste, a nickel paste, and the like are preferable, but these may be used alone or in combination of two or more. When using 2 or more types, they may be mixed or overlapped as separate layers. After applying the conductive paste, it is left in the air or heated to solidify. Examples of plating include nickel plating, copper plating, silver plating, and aluminum plating. Further, examples of the deposited metal include aluminum, nickel, copper, and silver.

  Specifically, for example, a carbon paste and a silver paste are sequentially laminated on the second electrode and sealed with a material such as an epoxy resin to constitute a capacitor. The capacitor may have a niobium or tantalum lead that is sintered integrally with the niobium sintered body or is later welded.

  The capacitor of the present invention having the above-described configuration can be made into a capacitor product for various uses by, for example, a resin mold, a resin case, a metallic outer case, resin dipping, and a laminate film.

  Further, when the counter electrode is liquid, the capacitor composed of the two electrodes and the dielectric is housed in, for example, a can electrically connected to the counter electrode to form a capacitor. In this case, the electrode side of the niobium sintered body is designed so as to be insulated from the can by insulating rubber or the like while being led out through the niobium or tantalum lead described above.

  As described above, by manufacturing a sintered body for a capacitor using the niobium powder manufactured according to the embodiment of the present invention described above, and manufacturing a capacitor from the sintered body, a capacitor having a small leakage current value and a good reliability. Can be obtained.

  In addition, the capacitor of the present invention has a larger capacitance than the conventional tantalum capacitor, and a smaller capacitor product can be obtained.

  The capacitor of the present invention having such characteristics can be applied to, for example, a use as a bypass capacitor and a coupling capacitor frequently used in an analog circuit and a digital circuit, and a use of a conventional tantalum capacitor.

  In general, such a capacitor is frequently used in an electronic circuit. Therefore, if the capacitor of the present invention is used, restrictions on the arrangement of electronic components and exhaust heat are alleviated, and a highly reliable electronic circuit is accommodated in a narrower space than before. be able to.

  Furthermore, if the capacitor of the present invention is used, electronic devices that are smaller and more reliable than conventional devices, for example, computer peripheral devices such as computers and PC cards, mobile devices such as mobile phones, home appliances, in-vehicle devices, artificial satellites, communication Equipment etc. can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these examples.

  In each example, the tapping density, repose angle, particle diameter and pore diameter of the niobium powder, capacitor capacity, leakage current value, capacity appearance rate, moisture resistance value and ESR value were measured by the following methods.

(1) Tapping density measurement The tapping density was measured according to the method using a tapping device and the measuring instrument among the apparent specific gravity measuring methods for industrial sodium carbonate specified in JIS (Japanese Industrial Standard 2000) K1201-1. .

(2) Angle of repose measurement The angle of repose uses niobium powder falling on the horizontal plane from the height of 6cm below the hopper with respect to the horizontal plane using the flowability measuring instrument and sample amount specified in JIS (Japanese Industrial Standard 2000) Z2504. The angle of repose of the slope with respect to the horizontal plane from the top of the generated cone was defined as the angle of repose.

(3) Particle size measurement The particle size distribution was measured by a laser diffraction scattering method using an apparatus manufactured by Microtrack (HRA 9320-X100). The average particle diameter was defined as a particle size value (D ₅₀ ; μm) corresponding to the cumulative volume% of 50 volume%.

(4) Pore diameter measurement The pore distribution was measured by a mercury intrusion method using a Poresia 9320 manufactured by Micro Merits. In the present invention, the maximum value is obtained from the rate of change of the press-fit amount, the pore diameter indicated by the maximum value is set as the peak top, and the maximum value is set as the relative intensity of the peak to which the peak top belongs.

(5) Capacitor capacity measurement At room temperature, an LCR measuring instrument manufactured by Hewlett-Packard Co. was connected between the terminals of the manufactured chip, and the measured capacitance value at 120 Hz was taken as the capacity of the chip-processed capacitor.

(6) Measurement of Leakage Current of Capacitor The current value measured after continuously applying a DC voltage of 6.3 V for 1 minute between the terminals of the manufactured chip at room temperature was taken as the leakage current value of the capacitor processed into the chip.

(7) Capacitor appearance rate Capacitor formation with a sintered body formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. and 20 V for 1000 minutes, with the capacity measured in 30% sulfuric acid as 100% It was expressed as a ratio to the later capacity.

(8) Moisture resistance value of the capacitor The capacity when the produced capacitor was allowed to stand at 60 ° C. and 95% RH for 500 hours was expressed as the number of less than 110% and less than 120% of the initial value. It was judged that the moisture resistance value was better as the number was less than 110%.

(9) ESR measurement of capacitor At room temperature, an LCR measuring instrument manufactured by Hewlett-Packard Co. was connected between terminals of the manufactured chip, and 100 kHz, 1.5 VDC, 0.5 Vrms. The ESR measured value was taken as the ESR of the chip processed capacitor.

Example 1: In 5000 g of potassium fluoride niobate sufficiently vacuum-dried at 80 ° C in a nickel crucible, 10 times the molar amount of sodium fluoride niobate was charged and reduced at 1000 ° C for 20 hours in an argon atmosphere. Reaction was performed. After the reaction, the reaction mixture was cooled, and the reduced product was washed with water, then washed with 95% sulfuric acid and water in that order, and then vacuum dried. Furthermore, after grind | pulverizing for 40 hours using the ball mill of the alumina pot containing a silica alumina ball | bowl, the ground material was immersed and stirred in the 3: 2 (mass ratio) liquid mixture of 50% nitric acid and 10% hydrogen peroxide solution. Thereafter, the product was sufficiently washed with water until the pH reached 7, to remove impurities, and vacuum dried. The average particle diameter of the raw material niobium powder was 1.2 μm.
500 g of this raw material niobium powder was put in a pot made of niobium, and 50 g of polymethylmethacrylic acid butyl ester having an average particle diameter of 1 μm and 1 liter of toluene were added. Further, zirconia balls were added and mixed for 1 hour with a shaking mixer. The mixture from which the zirconia balls were removed was placed in a conical dryer and vacuum dried under the conditions of 1 × 10 ² Pa and 80 ° C.
Subsequently, this niobium powder was heated at 1 × 10 ⁻² Pa at 250 to 400 ° C. for 12 hours to decompose and remove polymethyl methacrylate but also at 1150 ° C. under reduced pressure of 4 × 10 ⁻³ Pa. Sintered for 2 hours. After cooling to a product temperature of 30 ° C. or lower, the niobium sintered mass was crushed with a roll granulator to obtain a niobium crushed powder having an average particle size of 100 μm.
The niobium pulverized powder was subjected to nitriding treatment at 300 ° C. for 2 hours by flowing nitrogen under pressure to obtain about 450 g of niobium powder. The nitrogen content was 0.22%.
Table 1 shows the physical properties of the niobium powder such as tapping density, average particle diameter, angle of repose, BET specific surface area, and pore diameter peak top.
The niobium powder (about 0.1 g) thus obtained is placed in a tantalum element automatic molding machine (TAP-2R manufactured by Seken Co., Ltd.) hopper and automatically molded with a 0.3 mmφ niobium wire. A molded body was prepared so as to have a size of 0.3 cm × 0.18 cm × 0.45 cm. Table 1 shows the appearance and mass variations of the molded body.
Next, these compacts were allowed to stand at 1250 ° C. for 30 minutes under a vacuum of 4 × 10 ⁻³ Pa to obtain sintered bodies. 100 sintered bodies were prepared, and subjected to electrolytic conversion for 200 minutes using a 0.1% phosphoric acid aqueous solution at a voltage of 20 V to form a dielectric oxide film on the surface.
Subsequently, after being immersed in a 60% aqueous manganese nitrate solution, heating at 220 ° C. for 30 minutes was repeated to form a manganese dioxide layer as a counter electrode layer on the dielectric oxide film. Subsequently, a carbon layer and a silver paste layer were sequentially laminated thereon. Next, after the lead frame was mounted, the whole was sealed with an epoxy resin to produce a chip capacitor. Table 1 shows the capacitance appearance rate of this capacitor, and the average (n = 100) of the capacitance and leakage current value (hereinafter abbreviated as “LC”) of this chip capacitor. The LC value is a value when 6.3 V is applied for 1 minute at room temperature.

Example 2 1000 g of niobium ingot was placed in a reaction vessel made of SUS304, and hydrogen was continuously introduced at 400 ° C. for 10 hours. After cooling, the hydrogenated niobium lump was placed in a SUS pot containing zirconia balls and ground for 10 hours. Next, a 20% by volume slurry of this hydride with water and zirconia balls were placed in a spike mill, and wet pulverized at 40 ° C. or lower for 7 hours to obtain a pulverized niobium hydride slurry. The average particle diameter of the raw material niobium hydride powder was 0.9 μm.
This slurry (slurry concentration 98%) was put in a SUS pot, and 200 g of barium oxide having an average particle diameter of 1 μm was added. Further, zirconia balls were added and mixed for 1 hour with a shaking mixer. The mixture from which the zirconia balls were removed was placed in a niobium bat and dried under conditions of 1 × 10 ² Pa and 50 ° C.
Subsequently, the obtained mixture was heated at 1 × 10 ⁻² Pa at 400 ° C. for 4 hours to dehydrogenate niobium hydride, and this mixture was further reduced at 1100 ° C. for 2 hours at 4 × 10 ⁻³ Pa under reduced pressure. Sintered. After cooling the product temperature to 30 ° C. or lower, the sintered niobium ingot mixed with barium oxide was crushed with a roll granulator to obtain a crushed niobium powder mixed with barium oxide having an average particle size of 95 μm.
500 g of niobium pulverized powder mixed with barium oxide and 1000 g of ion-exchanged water were placed in a polytetrafluoroethylene container and cooled to 15 ° C. or lower. Separately, an aqueous solution prepared by mixing 600 g of 60% nitric acid, 150 g of 30% hydrogen peroxide, and 750 g of ion-exchanged water cooled to 15 ° C. or lower is prepared, and the water temperature exceeds 20 ° C. while stirring 500 g of this aqueous solution. It was dripped in the niobium pulverized powder suspension aqueous solution mixed with barium oxide. After completion of the dropping, stirring was further continued for 1 hour, the mixture was allowed to stand for 30 minutes, and then decanted. After adding 2000 g of ion-exchanged water and stirring for 30 minutes, the mixture was allowed to stand for 30 minutes and then decanted. This operation was repeated 5 times. Further, the niobium pulverized powder was placed in a polytetrafluoroethylene column and washed with water for 4 hours while flowing ion exchange water. The electrical conductivity of the washing water at this time was 0.9 μS / cm.
The niobium crushed powder that had been washed with water was dried at 50 ° C. under reduced pressure, and further, nitrogen was passed under pressure, and nitriding was performed at 300 ° C. for 3 hours to obtain about 350 g of niobium powder. The nitrogen content was 0.28%.
Table 1 shows physical properties of the niobium powder such as tapping density, average particle diameter, angle of repose, BET specific surface area, and average pore diameter.
The niobium powder (about 0.1 g) thus obtained is placed in a tantalum element automatic molding machine (TAP-2R manufactured by Seken Co., Ltd.) hopper and automatically molded with a 0.3 mmφ niobium wire. A molded body was produced so as to be 0.3 cm × 0.18 cm × 0.45 cm. Table 1 shows the appearance and mass variations of the molded body.
Next, these compacts were allowed to stand at 1250 ° C. for 30 minutes under a reduced pressure of 4 × 10 ⁻³ Pa to obtain sintered bodies. 100 sintered bodies were prepared, and subjected to electrolytic conversion for 200 minutes using a 0.1% phosphoric acid aqueous solution at a voltage of 20 V to form a dielectric oxide film on the surface.
Subsequently, an equivalent mixture of 10% aqueous solution of ammonium persulfate and 0.5% aqueous solution of anthraquinone sulfonic acid was brought into contact with the dielectric oxide film, and then contacted with pyrrole vapor was performed at least 5 times to make polypyrrole. The counter electrode (counter electrode) consisting of was formed.
Subsequently, a carbon layer and a silver paste layer were sequentially laminated thereon. Next, after the lead frame was mounted, the whole was sealed with an epoxy resin to produce a chip capacitor. Table 1 shows the capacity appearance rate of this capacitor and the average (n = 100) of the capacitance and LC value of this chip type capacitor. The LC value is a value when 6.3 V is applied for 1 minute at room temperature.

Examples 3 to 10: Using the same method as in Example 1, the average particle size and addition amount of polymethylmethacrylic acid butyl ester, and using the same method as in Example 2, the average particle size and addition amount of barium oxide. The niobium powder, its molded body, sintered body, and capacitor were produced by changing each of them. Table 1 shows the physical properties of these niobium powders, the appearance of the molded body, the variation in mass, the capacitance of the capacitors, and the LC.

Examples 11 to 22: Examples 11 to 14 and 16 to 18 use the same method as in Example 1, Examples 15 and 19 to 22 use the same method as in Example 2, and polymethyl butyl methacrylate, respectively. Niobium powder, a molded body, and a sintered body were prepared using the activator shown in Table 1 instead of ester or barium oxide. Table 1 shows the physical properties of the niobium powder, the appearance of the molded body, and the mass variation.
Next, these compacts were allowed to stand at 1250 ° C. for 30 minutes under a reduced pressure of 4 × 10 ⁻³ Pa to obtain sintered bodies. 100 sintered bodies were prepared, and subjected to electrolytic conversion for 200 minutes using a 0.1% phosphoric acid aqueous solution at a voltage of 20 V to form a dielectric oxide film on the surface.
Subsequently, after being immersed in an aqueous solution (solution 1) containing 25% by mass of ammonium persulfate, it is pulled up, dried at 80 ° C. for 30 minutes, and then a sintered body on which a dielectric is formed is obtained by massing 3,4-ethylenedioxythiophene by 18%. After being dipped in an isopropanol solution containing 2% (solution 2), it was pulled up and left in an atmosphere at 60 ° C. for 10 minutes to carry out oxidative polymerization. This was again immersed in solution 1 and further treated in the same manner as described above. The operation from immersion in solution 1 to oxidative polymerization was repeated 8 times, followed by washing with warm water at 50 ° C. for 10 minutes, and drying at 100 ° C. for 30 minutes, whereby conductive poly (3, A counter electrode (counter electrode) composed of 4-ethylenedioxythiophene) was formed.
Subsequently, a carbon layer and a silver paste layer were sequentially laminated thereon. Next, after the lead frame was mounted, the whole was sealed with an epoxy resin to produce a chip capacitor. Table 1 shows the capacity appearance rate of this capacitor and the average (n = 100) of the capacitance and LC value of this chip type capacitor. The LC value is a value when 6.3 V is applied for 1 minute at room temperature.

Examples 23 to 25: Using the same method as in Example 2, the starting materials were Nio Boots alloy powder in Example 23, Niobium hydride-rhenium alloy powder in Example 24, and Niobium yttrium hydride in Example 25. Niobium powder, a sintered body, and a capacitor were prepared using each of boron alloy powders. The physical properties, capacity, and LC are shown in Table 1.

Comparative Examples 1 to 3: In a nickel crucible, sodium fluorinated niobate was thoroughly vacuum-dried at 80 ° C., and sodium was added in an amount 10 times the amount of potassium fluoride niobate, and 1000 ° C. in an argon atmosphere for 20 hours. A reduction reaction was performed. After the reaction, the reaction mixture was cooled, and the reduced product was washed with water, then washed with 95% sulfuric acid and water in that order, and then vacuum dried. Further, the pulverized product was pulverized by changing the pulverization time using a ball mill of an alumina pot containing silica alumina balls, and the pulverized product was immersed and stirred in a 3: 2 (mass ratio) mixed solution of 50% nitric acid and 10% hydrogen peroxide. . Thereafter, the product was sufficiently washed with water until the pH reached 7, to remove impurities, and vacuum dried. The average particle diameter of the produced niobium powder was 1.3 to 10 μm.
50 g of each niobium powder thus obtained was placed in a reaction vessel made of SUS304, and nitrogen was continuously introduced at 300 ° C. for 2 to 4 hours to obtain niobium nitride.
Table 1 shows physical properties of the niobium powder such as tapping density, average particle diameter, angle of repose, BET specific surface area, and average pore diameter.
The niobium powder (about 0.1 g) thus obtained was placed in a tantalum element automatic molding machine (TAP-2R manufactured by Seken Co., Ltd.) hopper, and automatic molding was attempted with a 0.3 mmφ niobium wire. The results are shown in Table 1.

Comparative Examples 4 to 9: The amount of barium oxide having an average particle diameter of 1 μm was changed, and the tapping density was changed to 0.2 to 0.4 g / ml and 2.6 to 3.3 in the same manner as in Example 2. 3 g / ml of niobium powder was obtained. The physical properties of this product are shown in Table 1.
The niobium powder (about 0.1 g) thus obtained is placed in a tantalum element automatic molding machine (TAP-2R manufactured by Seken Co., Ltd.) hopper and automatically molded with a 0.3 mmφ niobium wire. A molded body was produced so as to be 0.3 cm × 0.18 cm × 0.45 cm. Table 1 shows the appearance and mass variations of the molded body.
Next, these compacts were allowed to stand at 1250 ° C. for 30 minutes under a vacuum of 4 × 10 ⁻³ Pa to obtain sintered bodies. 100 sintered bodies were prepared, and subjected to electrolytic conversion for 200 minutes using a 0.1% phosphoric acid aqueous solution at a voltage of 20 V to form a dielectric oxide film on the surface.
Subsequently, an equivalent mixture of 10% aqueous solution of ammonium persulfate and 0.5% aqueous solution of anthraquinone sulfonic acid was brought into contact with the dielectric oxide film, and then the contact with pyrrole vapor was performed at least 5 times to make polypyrrole. The counter electrode (counter electrode) consisting of was formed.
Subsequently, a carbon layer and a silver paste layer were sequentially laminated thereon. Next, after the lead frame was mounted, the whole was sealed with an epoxy resin to produce a chip capacitor. Table 1 shows the capacity appearance rate of this capacitor and the average (n = 100) of the capacitance and LC value of this chip type capacitor. The LC value is a value when 6.3 V is applied for 1 minute at room temperature.

Examples 26 to 31: Primary particles having an average particle diameter of 0.8 μm were obtained by pulverizing and dehydrogenating a hydride of niobium ingot. The primary particles were fired and pulverized to obtain a granulated powder of niobium. 0.1 g of this granulated powder is prepared separately and placed in a mold (4.0 mm × 3.5 mm × 1.8 mm) together with a niobium wire having a length of 10 mm and a thickness of 0.3 mm, and a tantalum element automatic molding machine Weight was applied as shown in Table 2 with TAP-2R (Seken Co., Ltd.) to produce a molded body. Subsequently, it sintered at 1300 degreeC for 30 minutes, and the target sintered compact was obtained. By adjusting the weight of the molding machine, sintered bodies having a pore diameter distribution as shown in Table 2 were prepared. The size, specific surface area, and CV value of the sintered body of Example 26 are 24.7 mm ³ , 1.1 m ² / g, and 85000 μFV / g, respectively. It was within 2%.

Examples 32-34: Sintered bodies were obtained in the same manner as in Examples 26-28, except that the primary particles were classified to make the average particle size of the primary particles 0.5 μm. 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 125000 μFV / g, respectively. It was within 1%. The pore diameter distribution of the produced sintered body is shown in Table 2.

Example 35: A niobium powder obtained in the same manner as in Example 4 was used instead of the granulated powder, and a sintered body was obtained in the same manner as in Example 31. 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 78000 μFV / g, respectively. The pore diameter distribution of the produced sintered body is shown in Table 2.

Comparative Examples 10-12: Implemented except that niobium powder obtained by reducing niobium chloride with magnesium instead of the niobium granulated powder used in Examples 26-28 was heat treated at 1100 ° C. Sintered bodies were produced in the same manner as in Examples 26 to 28. The size, specific surface area, and CV value of the produced sintered body of Comparative Example 10 were 24.3 mm ³ , 0.8 m ² / g, and 84000 μFV / g, respectively. Within 10 ± 2%. The pore diameter distribution of the produced sintered body is shown in Table 2.

Example 36: The method of producing sintered bodies in Example 21 and Examples 26 to 35 was used to produce 60 similar sintered bodies each, and each sintered body was 80 in 0.1% phosphoric acid aqueous solution. Chemical conversion was carried out at 20 ° C. for 1000 minutes, and a dielectric oxide film layer was formed on the surface of the sintered body. Next, the formed sintered body is divided into 30 parts each, and each set of 30 sintered bodies is impregnated with two kinds of cathode agents A and B shown in Table 3, and then carbon paste, silver paste Were sequentially laminated and sealed with an epoxy resin to produce a chip-type capacitor. Table 4 shows the capacity appearance rate and the moisture resistance value of the manufactured capacitors.

Comparative Example 13: In the method in which the sintered bodies were prepared in Comparative Examples 9 to 12, 60 similar sintered bodies were each prepared, and each sintered body was 80 ° C. for 1000 minutes in a 0.1% phosphoric acid aqueous solution. , 20 V, and a dielectric oxide film layer was formed on the surface of the sintered body. Next, each of the formed sintered bodies is divided into 30 pieces, and each set of 30 sintered bodies is impregnated with the cathode agent of A shown in Table 3, and then a carbon paste and a silver paste are sequentially laminated, A chip capacitor was fabricated by sealing with an epoxy resin. Table 4 shows the capacity appearance rate and the moisture resistance value of the manufactured capacitors.

Example 37 A ground slurry of niobium hydride powder was obtained in the same manner as in Example 2. The average particle diameter of the niobium hydride powder was 0.6 μm. The slurry was spun down and decanted to remove the supernatant. Anhydrous acetone was added to a slurry concentration of 40% by mass and suspended well, followed by centrifugal sedimentation, and the supernatant was removed. This operation was repeated three times. Anhydrous acetone was added to a slurry concentration of 60% by mass and suspended well. This slurry was put in a SUS pot, and 15 mass% and 10 mass% of barium oxide having an average particle diameter of 1.4 μm and 23 μm were added to niobium, respectively. Further, zirconia balls were added and mixed for 1 hour with a shaking mixer. The mixture from which the zirconia balls were removed was placed in a niobium bat and dried under conditions of 1 × 10 ² Pa and 50 ° C. A niobium sintered lump mixed with barium oxide and a niobium pulverized powder were obtained in the same manner as in Example 2.
500 g of niobium pulverized powder mixed with barium oxide was added to 1000 g of ion-exchanged water cooled to 15 ° C. or lower while stirring so that the water temperature did not exceed 20 ° C. After completion of the addition, stirring was further continued for 1 hour, and the mixture was allowed to stand for 30 minutes and then decanted. After adding 2000 g of ion-exchanged water and stirring for 30 minutes, the mixture was allowed to stand for 30 minutes and decanted. This operation was repeated 5 times, and the niobium pulverized powder was placed in a polytetrafluoroethylene column and washed with water for 4 hours while flowing ion exchange water. The electrical conductivity of the washing water at this time was 0.5 μS / cm.
The niobium crushed powder that had been washed with water was dried at 50 ° C. under reduced pressure, and further, nitrogen was passed under pressure, and nitriding was performed at 300 ° C. for 3 hours to obtain about 350 g of niobium powder. The nitrogen content was 0.30%. Table 5 shows the physical properties of the niobium powder such as tapping density, average particle diameter, angle of repose, BET specific surface area, and average pore diameter. A molded body was prepared in the same manner as in Example 2. Table 5 shows variations in appearance and mass of the molded body.
Further, after a dielectric film was formed by the same operation as in Example 2, an electrode was formed and a carbon layer and a silver paste layer were laminated. Next, after the lead frame was mounted, the whole was sealed with an epoxy resin to produce a chip capacitor. Table 5 shows the capacity appearance rate of this capacitor, and the average (n = 100) of the capacity and LC value of this chip capacitor.

Examples 38 to 44: In the same manner as in Example 37, the type of activator to be added, the two types of average particle sizes to be mixed, and the amount added were changed to obtain niobium crushed powder mixed with an activator. The solvent for eluting the activator is selected from water, acid, alkali, a solution containing an ion exchange resin, an ammonium nitrate solution, and a solution containing ethylenediaminetetraacetic acid, and the activator is eluted in the same manner as in Example 37. Niobium powder was obtained. The physical properties are shown in Table 5. Further, a molded body and a sintered body were prepared by the same method as in Example 37, and a chip capacitor was prepared. Table 5 shows the appearance, mass variation, capacitor capacity, and LC average of the molded body.

Examples 45 to 47: Using the same method as in Example 37, as starting materials, Example 45 uses niobium-neodymium alloy powder, Example 46 uses niobium-tungsten alloy powder, and Example 47 uses niobium-tantalum alloy powder. In each case, a niobium alloy powder was obtained. The physical properties are shown in Table 5. Further, a molded body and a sintered body were prepared by the same method as in Example 37, and a chip capacitor was prepared. Table 5 shows the appearance, mass variation, capacitor capacity, and LC average of the molded body.

Examples 48 to 58: Niobium sintered bodies were prepared in the same manner as in Example 2 using the niobium powder prepared in Examples 37 to 47. Table 6 shows the pore diameter distribution of the sintered body.

Examples 59 to 69: 100 niobium sintered bodies produced in Examples 48 to 58 were produced, and each sintered body was formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 1000 minutes at 20 V. A dielectric oxide film layer was formed on the surface of the sintered body. Next, the formed sintered body was impregnated with the cathode agent A shown in Table 3, and then a carbon paste and a silver paste were laminated in order and sealed with an epoxy resin to produce a chip type capacitor. Table 7 shows the capacity appearance rate and ESR of the manufactured capacitor.

Comparative Examples 14 to 17: 100 niobium sintered bodies prepared in Comparative Examples 9 to 12 were prepared, and each sintered body was formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 1000 minutes at 20 V, and then sintered. A dielectric oxide film layer was formed on the bonded surface. Next, the formed sintered body was impregnated with the cathode agent A shown in Table 3, and then a carbon paste and a silver paste were laminated in order and sealed with an epoxy resin to produce a chip type capacitor. Table 7 shows the capacity appearance rate and ESR of the manufactured capacitor.

It is sectional drawing which shows the mode of the niobium powder of this invention typically. It is the schematic at the time of measuring the pore distribution of the niobium powder of this invention by the mercury intrusion method.

Explanation of symbols

1 Pore A
2 Pore B

Claims (21)

  A niobium sintered body for a capacitor electrode, wherein the pore distribution of the niobium sintered body has a plurality of pore diameter peak tops.   The niobium sintered body according to claim 1, wherein the pore distribution is composed of two pore diameter peak tops.   The niobium according to claim 1 or 2, wherein the peak tops of the two peaks having the highest relative intensity among the plurality of pore diameter peak tops are in the range of 0.2 to 0.7 µm and 0.7 to 3 µm, respectively. Sintered body.   4. The peak top of the peak having the highest relative intensity among the plurality of pore diameter peak tops is located on the larger diameter side than the peak top of the peak having the next highest relative intensity. 5. Niobium sintered body. The niobium sintered body according to any one of claims 1 to 4, wherein the sintered body has a volume of 10 mm ³ or more including a pore void volume. The niobium sintered body according to claim 1, wherein the sintered body has a specific surface area of 0.2 to 7 m ² / g.   The niobium sintered body according to any one of claims 1 to 6, wherein a part of the sintered body is nitrided.   The sintered body obtained from a niobium compact that gives a sintered body having a CV value of 40,000 to 200,000 μFV / g when sintered at 1300 ° C. The niobium sintered body described.   A capacitor comprising the niobium sintered body according to any one of claims 1 to 8 as one electrode and a dielectric interposed between the counter electrode.   The capacitor according to claim 9, wherein a main component of the dielectric is niobium oxide.   The capacitor according to claim 9, wherein the counter electrode is at least one material selected from the group consisting of an electrolytic solution, an organic semiconductor, and an inorganic semiconductor.   The counter electrode is an organic semiconductor, and the organic semiconductor is an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, and an organic semiconductor composed mainly of tetracyanoquinodimethane. The capacitor according to claim 11, wherein the capacitor is at least one material selected from the group consisting of conductive polymers.   The capacitor according to claim 12, wherein the conductive polymer is at least one selected from polypyrrole, polythiophene, polyaniline, and substituted derivatives thereof. The conductive polymer is represented by the following general formula (1) or general formula (2).

(Wherein R ^{1 to} R ⁴ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group, alkoxy group or alkyl ester group having 1 to 10 carbon atoms, a halogen atom, a nitro group, A monovalent group selected from the group consisting of a group, a cyano group, a primary, secondary or tertiary amino group, a CF ₃ group, a phenyl group and a substituted phenyl group, R ¹ and R ² and R ³ and R ⁴ The hydrocarbon chain is bonded to each other at any position to form a cyclic structure of at least one 3 to 7-membered saturated or unsaturated hydrocarbon with the carbon atom substituted by such group The cyclic bond chain may contain a bond of carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl, imino at any position, X is oxygen, sulfur or Represents a nitrogen atom, R ⁵ is present X only when the nitrogen atom, represented by independently. Representing the linear on or branched alkyl group, saturated or unsaturated hydrogen or 1 to 10 carbon atoms) The capacitor according to claim 12, which is a conductive polymer in which a polymer including a repeating unit is doped with a dopant. The conductive polymer is represented by the following general formula (3)

(In the formula, R ⁶ and R ⁷ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl groups are bonded to each other at an arbitrary position. And represents a substituent that forms a cyclic structure of at least one or more 5- to 7-membered saturated hydrocarbon containing two oxygen elements, and the cyclic structure has an optionally substituted vinylene bond. The capacitor according to claim 14, wherein the capacitor is a conductive polymer including a repeating unit represented by the formula (1):   The capacitor according to claim 12, wherein the conductive polymer is a conductive polymer obtained by doping poly (3,4-ethylenedioxythiophene) with a dopant.   The capacitor according to claim 9, wherein the counter electrode is made of a material having at least a part of a layered structure.   The capacitor according to claim 9, wherein the counter electrode is a material containing an organic sulfonate anion as a dopant.   A niobium sintered body as one electrode, a dielectric formed on the surface of the sintered body, and a capacitor manufacturing method including a counter electrode provided on the dielectric, the niobium sintered body, A method for manufacturing a capacitor, which is the niobium sintered body according to any one of claims 1 to 8.   An electronic circuit using the capacitor according to any one of claims 9 to 18.   The electronic device using the capacitor | condenser of any one of Claim 9 thru | or 18.

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