JP4360680B2 - Niobium powder for capacitors, sintered niobium and capacitors - Google Patents

Description

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

As electronic devices such as mobile phones and personal computers become smaller, faster, and lighter in weight, capacitors used in these electronic devices are required to be smaller and lighter, with larger capacities and lower ESR. ing.
Among such capacitors, a tantalum capacitor is preferred because it has a large capacity for its size and good performance.

In order to increase the capacity of the tantalum capacitor, it is necessary to increase the amount of powder used, or to use a sintered body having a surface area increased by making tantalum powder finer.
The method of increasing the amount of powder used does not satisfy the requirements for reduction in size and weight because the structure of the capacitor inevitably increases in size. In the method of increasing the surface area by refining the tantalum powder, the pore diameter of the tantalum sintered body is reduced, so that a high-capacity tantalum capacitor cannot be produced and the ESR cannot be lowered.

As a method for solving these drawbacks, a sintered capacitor using a powder material having a higher dielectric constant and lower density than tantalum is conceivable. Niobium is attracting attention as a material having such a high dielectric constant.
Niobium capacitors are manufactured in the same way as tantalum capacitors.

  As a niobium capacitor anode body, a niobium powder sintered body is generally used. For example, niobium powder is granulated by mixing fine niobium powder and a liquid binder, then molded by compression molding, and then the anode lead is implanted in this molded body at high temperature and high vacuum sintering. Thus, an electrode called a niobium anode sintered body is manufactured. The surface of this niobium anode sintered body is electrolytically oxidized (formed) to form a nonconductive insulating layer (niobium insulating oxide layer), and a counter electrode layer (cathode) such as manganese dioxide or conductive polymer is formed on the nonconductive insulating layer. Layer), carbon paste, silver paste, and the like are sequentially laminated on the counter electrode layer, and then sealed with a material such as an epoxy resin to manufacture a niobium capacitor.

Niobium capacitors are less stable than tantalum capacitors.
This is because an insulating oxide layer of tantalum produced by electrolytic oxidation is formed only of tantalum pentoxide and has extremely high stability. On the other hand, niobium forms an insulating oxide layer mainly composed of niobium pentoxide containing a stable semiconducting suboxide (for example, niobium dioxide, niobium monoxide, etc.), thus increasing the leakage current value. Inferior in electrical stability, such as a decrease in withstand voltage (ratio of conversion voltage / actuation voltage).

In addition, the increase in the thickness of tantalum pentoxide in chemical conversion is about 2 nm / V, whereas the increase in the thickness of niobium pentoxide in chemical conversion is as thick as about 3.7 nm / V. The insulating oxide layer mainly composed of niobium pentoxide is fragile and is vulnerable to thermal stimulation. In particular, when a conductive polymer is used for the counter electrode, an increase in leakage current during exterior sealing using a material such as an epoxy resin and an increase in leakage current during solder reflow during substrate mounting are significant problems. In recent years, there has been an increasing demand for lead-free solder, and an increase in solder reflow temperature has further increased the leakage current value of niobium capacitors. Thus, the use of niobium capacitors has been limited to fields where the operating voltage is low and leakage current does not affect due to the low withstand voltage.
There are various approaches to these problems.

  Patent Document 1 (Japanese Patent Laid-Open No. 10-242004) describes that the leakage current value of a niobium capacitor is improved by partially nitriding niobium powder.

  In Patent Document 2 (WO00 / 49633) and Patent Document 3 (WO01 / 6525), when Ni, Co, Si, Na, K, and Mg are specified elements and the total content is 350 ppm or less, niobium is used. It is described that the variation in the leakage current value of the capacitor can be improved.

  Patent Document 4 (WO00 / 15555) and Patent Document 5 (WO00 / 15556) disclose niobium oxide powder with reduced oxygen for capacitors in which niobium oxide is partially reduced in the presence of an oxygen getter metal. . Although the nature of the anode is disclosed, there is no example of making a capacitor.

  Patent Document 6 (WO02 / 15208) and Patent Document 7 (WO02 / 93596) describe that the leakage current value of a capacitor can be improved by adding other elements to niobium powder or niobium monoxide powder or alloying them. However, there is no description of withstand voltage and solder heat resistance.

  In Patent Document 8 (Japanese Patent Publication No. 2003-514378), the surface of niobium powder is coated with the elements Al, Si, Ti, Zr, Mo, W, Y, Ta, and the oxide niobium barrier layer is coated with Al, Si, It is described that Ti, Zr, Mo, W, Y, and Ta metals are included. Although the properties of the anode made from this niobium powder are described, there is no example of making a capacitor.

  In Patent Document 9 (WO01 / 26123), a compound having a silicon-oxygen bond, or a silicon-containing compound that generates a silicon-oxygen bond by a hydrolysis reaction, a condensation reaction, an oxidation reaction, a thermal reaction, or the like is provided on one surface of a niobium surface. The composition of the shape which covered the part or most was described. Although it is described that a compound having a silicon-oxygen bond is incorporated into the dielectric oxide film during the chemical conversion and the leakage current value and capacity deterioration of the niobium capacitor are improved, there is no description of withstand voltage and solder heat resistance. .

  In this way, various improvements have been attempted, but it is still not sufficient, and in particular, improvement in withstand voltage and improvement in solder heat resistance are required.

Japanese Patent Laid-Open No. 10-224004 International Publication No. 00/49633 Pamphlet International Publication No. 01/6525 Pamphlet International Publication No. 00/15555 pamphlet International Publication No. 00/15556 Pamphlet International Publication No. 02/15208 Pamphlet International Publication No. 02/93596 Pamphlet Special table 2003-514378 gazette International Publication No. 01/26123 Pamphlet

  The object of the present invention is not only high capacity, low leakage current, low ESR and tan δ characteristics, but also particularly niobium capacitors with good withstand voltage and solder heat resistance, and niobium powder for capacitors and niobium capable of producing such capacitors. It is providing the sintered compact and the manufacturing method thereof.

  By using a sintered body of niobium powder or a granulated powder thereof in which a mixed layer of silicon nitride and niobium is provided in the vicinity of the surface as a sintered body used for the capacitor anode, The present inventors have found that a capacitor having excellent leakage current characteristics, ESR characteristics, and tan δ characteristics, and particularly excellent withstand voltage characteristics and solder heat resistance can be obtained.

（式中、Ｒ¹〜Ｒ⁴はそれぞれ独立して水素原子、炭素数１〜１０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、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し、
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く、
前記環状の結合鎖は、その任意の位置にカルボニル、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、イミノの結合を含んでもよく、
Ｘは酸素、硫黄または窒素原子を表し、Ｒ⁵はＸが窒素原子の時のみ存在して、水素原子または炭素数１〜１０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４５に記載のコンデンサ。
４８．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１〜６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し、
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４７に記載のコンデンサ。
４９．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４８に記載のコンデンサ。
５０．対電極の材料が、層状構造を少なくとも一部に有する前記４１または４３に記載のコンデンサ。
５１．対電極の材料が、有機スルホン酸アニオンをドーパントとして含む前記４１または４３に記載のコンデンサ。
５２．前記４１〜５１のいずれかに記載のコンデンサを使用した電子回路。
５３．前記４１〜５１のいずれかに記載のコンデンサを使用した電子機器。 The present invention provides the following niobium powder for capacitors, granulated powder of niobium for capacitors, sintered niobium for capacitors, capacitors and methods for producing them.
1. A niobium powder for a capacitor having a niobium layer and a mixed layer of silicon nitride and niobium, wherein the mixed layer is present in the vicinity of the surface of the powder particles.
2. 2. The niobium powder for a capacitor as described in 1 above, wherein the mixed layer has a thickness of 8 to 2000 nm.
3. 2. The niobium powder for capacitors as described in 1 above, wherein the content of silicon nitride is 50 to 500,000 mass ppm.
4). 2. The niobium powder for capacitors as described in 1 above, wherein the silicon nitride is a compound represented by Si _α N _β (wherein α and β represent positive integers).
5. 5. The niobium powder for capacitors as described in 4 above, wherein the silicon nitride is at least one selected from SiN, Si ₂ N ₂ , Si ₂ N ₃ and Si ₃ N ₄ .
6). 2. The niobium powder for a capacitor as described in 1 above, wherein the niobium in the niobium layer and the mixed layer is at least one selected from pure niobium, a niobium compound, a niobium alloy, and a hydride thereof.
7). 7. The niobium powder for a capacitor as described in 6 above, wherein the niobium compound is at least one selected from niobium hydride, niobium nitride and niobium oxide.
8). 2. The niobium powder for capacitors as described in 1 above, wherein the average particle size is 0.05 to 5 μm.
9. ^{2. The} niobium powder for a capacitor as described in 1 above, wherein the specific surface area is 0.5 to 70 m ² / g.
10. A method for producing niobium powder for a capacitor, comprising: a step of etching niobium powder; a step of impregnating an etching hole with silicon nitride; and a step of sealing the etching hole.
11. 11. The method for producing niobium powder for capacitors as described in 10 above, wherein the niobium powder is a primary powder having an average particle size of 0.05 to 5 μm, an agglomerated powder thereof or a granulated powder thereof.
12 At least one element selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, selenium and tellurium after the etching step, before the impregnation step, after the impregnation step and before the sealing step, or after the sealing step 11. The method for producing a niobium powder for a capacitor as described in 10 above, which comprises a step of doping.
13. 11. The method for producing niobium powder for a capacitor as described in 10 above, wherein the etching hole sealing step is performed in the presence of niobium, niobium compound, niobium alloy and hydride thereof having an average particle diameter of 1 to 200 nm.
14 11. The method for producing niobium powder for a capacitor as described in 10 above, wherein the niobium powder is at least one selected from niobium, a niobium compound, a niobium alloy and a hydride thereof.
15. 15. The method for producing a niobium powder for a capacitor as described in 14 above, wherein the niobium compound is a niobium compound containing nitrogen and / or oxygen.
16. 11. The method for producing a niobium powder for a capacitor as described in 10 above, wherein the etching agent used in the etching step is an acid or an alkali.
17. 17. The method for producing niobium powder for capacitors as described in 16 above, wherein the etching agent is an acid solution containing hydrofluoric acid or fluoroacetic acid.
18. 17. The method for producing niobium powder for capacitors as described in 16 above, wherein the etching agent is an alkaline solution having a pH of 10 or more.
19. 11. The method for producing a niobium powder for a capacitor as described in 10 above, wherein the silicon nitride to be impregnated is a particle having an average particle diameter of 1 to 200 nm.
20. 11. The method for producing niobium powder for capacitors as described in 10 above, wherein ultrasonic irradiation is performed in the impregnation step.
21. A niobium granulated powder for a capacitor obtained by granulating the niobium powder for a capacitor according to any one of 1 to 9 above.
22. A niobium granulated powder for a capacitor, comprising a niobium layer, a mixed layer of silicon nitride and niobium, wherein the mixed layer is present in the vicinity of the outer surface and the inner surface of the hole.
23. The niobium granulated powder for capacitors as described in 22 above, wherein the mixed layer has a thickness of 8 to 2000 nm.
24. The niobium granulated powder for capacitors as described in 22 above, wherein the content of silicon nitride is 50 to 500,000 mass ppm.
25. 23. The niobium granulated powder for capacitors as described in 21 or 22 above, having an average particle diameter of 5 to 1000 μm.
26. Item 23. The niobium granulated powder for capacitors as described in 21 or 22 above, wherein the specific surface area is 0.5 to 40 m ² / g.
27. 23. The niobium granulated powder for capacitors as described in 21 or 22 above, wherein one or more pore diameter distribution peaks are present in the range of 0.01 to 500 μm.
28. 26. The niobium granulated powder for capacitors as described in 25 above, wherein at least one peak of pore diameter distribution is present at 0.1 to 0.9 μm and at least one peak at 0.9 to 3 μm.
29. A niobium sintered body for a capacitor obtained by sintering the niobium powder for a capacitor according to any one of 1 to 9 above.
30. 29. A niobium sintered body for a capacitor obtained by sintering the niobium granulated powder for a capacitor according to any one of 21 to 28.
31. A niobium sintered body for a capacitor, comprising a niobium layer, a mixed layer of silicon nitride and niobium, wherein the mixed layer is present in the vicinity of the outer surface and the inner surface of the hole.
32. 32. The niobium sintered body for a capacitor as described in 31 above, wherein the mixed layer has a thickness of 8 to 2000 nm.
33. 32. The niobium sintered body for capacitors as described in 31 above, wherein the content of silicon nitride is 50 to 500,000 mass ppm.
34. 32. The niobium sintered body for capacitors as described in any one of 29 to 31 above, wherein the porosity is 55% by volume or more.
35. 32. The niobium sintered body for capacitors as described in any one of 29 to 31 above, which has a specific surface area of 0.006 m ² / mm ³ or more.
36. 32. The niobium sintered body for capacitors as described in any one of 29 to 31 above, which has a specific surface area of 0.005 to 0.06 m ² / mm ³ .
37. 32. The niobium sintered body for capacitors as described in any one of 29 to 31 above, wherein one or more pore diameter distribution peaks exist within a range of 0.01 to 100 μm.
38. 38. The niobium sintered body for a capacitor as described in 37 above, wherein at least one peak of pore diameter distribution is present at less than 1.0 μm and at least one is present at 1.0 μm or more.
39. 32. The niobium sintered body for capacitors as described in any one of 29 to 31 above, wherein the volume of pores having a diameter of 1 μm or more is 13% by volume or more of the total pore volume.
40. 32. The niobium sintered body for capacitors as described in any one of 29 to 31 above, having a capacity of 40000 to 400000 μFV / g.
41. The capacitor | condenser comprised from the dielectric material which interposed the niobium sintered compact for capacitors | capacitors in any one of said 29-40 as one electrode, and was interposed between counter electrodes.
42. 42. The capacitor according to 41, wherein the dielectric is mainly composed of niobium oxide containing silicon nitride.
43. A capacitor composed of a sintered niobium for a capacitor as one electrode and a dielectric interposed between the counter electrode, wherein the dielectric is mainly composed of niobium oxide containing silicon nitride. Capacitor.
44. 44. The capacitor according to 41 or 43, wherein the counter electrode material is at least one material selected from the group consisting of an electrolytic solution, an organic semiconductor, and an inorganic semiconductor.
45. The organic semiconductor is selected from the group consisting of an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, an organic semiconductor composed mainly of tetracyanoquinodimethane, and a conductive polymer. 45. The capacitor as described in 44 above, which is at least one kind.
46. 46. The capacitor according to 45, wherein the conductive polymer is at least one selected from polypyrrole, polythiophene, polyaniline, and substituted derivatives thereof.
47. 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 alkyl group having 1 to 10 carbon atoms, an alkoxy group or an alkyl ester group, 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;
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. It may form a divalent chain that forms a cyclic structure of a saturated hydrocarbon,
The cyclic bond chain may include a bond of carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl, imino at any position thereof,
X represents an oxygen, sulfur or nitrogen atom, R ⁵ is present only when X is a nitrogen atom, and represents a hydrogen atom or a linear or branched saturated or unsaturated alkyl group having 1 to 10 carbon atoms. . )
46. The capacitor according to 45 above, which is a conductive polymer obtained by doping a polymer containing a repeating unit represented by
48. The conductive polymer is represented by the following general formula (3)

(Wherein R ⁶ and R ⁷ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl group is bonded to each other at an arbitrary position. And represents 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. )
48. The capacitor according to 47 above, which is a conductive polymer obtained by doping a polymer containing a repeating unit represented by
49. 49. The capacitor according to 48 above, wherein the conductive polymer is a conductive polymer obtained by doping a dopant into poly (3,4-ethylenedioxythiophene).
50. 44. The capacitor according to 41 or 43, wherein the counter electrode material has a layered structure at least in part.
51. 44. The capacitor according to 41 or 43, wherein the counter electrode material contains an organic sulfonate anion as a dopant.
52. The electronic circuit using the capacitor | condenser in any one of said 41-51.
53. The electronic device using the capacitor | condenser in any one of said 41-51.

[Niobium powder for capacitors]
By using the niobium powder for capacitors of the present invention, a niobium capacitor having particularly good withstand voltage and solder heat resistance can be obtained. Although the details of the reason are not clear, it is considered as follows.
The niobium powder for a capacitor according to the present invention is a mixture of silicon nitride and niobium from the vicinity of the surface of the powder particle to the center by TEM (transmission electron microscope) image and EPMA (electron beam microanalysis) of the powder particle cut surface. It is confirmed that it is formed of two layers, a layer made of niobium and a layer made of niobium at the center of the particle. Moreover, also about the granulated powder and sintered compact which were manufactured by the below-mentioned method, it is confirmed by the cut surface analysis that the 2 layer structure is hold | maintained.
FIG. 1 shows an example of a TEM photograph of the mixed layer portion present in the sintered body. 2 and 3 show the results of electron diffraction of the a and b portions in the figure. FIG. 4 shows a diffraction pattern derived from silicon nitride. From these comparisons, it was confirmed that the portion a in FIG. 1 was a mixed layer with the respective diffraction patterns of silicon nitride and niobium being recognized.

When the sintered body produced from the niobium powder for capacitors of the present invention is electrolytically oxidized, an insulating oxide layer is formed. It was confirmed that the silicon nitride was also present in the insulating oxide layer by analyzing the cut surface of this chemical (an electrolytically oxidized niobium sintered body). Therefore, it is considered that the niobium powder for capacitors of the present invention formed a novel insulating oxide layer having better withstand voltage and solder heat resistance than an insulating layer made of only niobium oxide. In particular, silicon nitride represented by the molecular formula Si ₃ N ₄ as silicon nitride gives good withstand voltage and solder heat resistance. This is considered to be due to the high ability of silicon nitride represented by the molecular formula Si ₃ N ₄ to form solid solutions with various oxides.

  In the niobium powder of the present invention, the thickness of the mixed layer of silicon nitride and niobium is important. This is because it is necessary for the insulating oxide layer of the chemical compound to contain silicon nitride that can improve withstand voltage and solder heat resistance. It is said that the insulating oxide layer formed by the conversion of niobium is formed with a thickness of about 26% outside from the original niobium metal interface and about 74% inside, and most of the insulating oxide layer is the original niobium layer. It is generated inside the metal interface (surface technology, page 447, volume 54, number 7, 2003). Therefore, it is desirable that the mixed layer of silicon nitride and niobium has a thickness equivalent to or greater than that of the insulating oxide layer formed inside. In general, the formation of a niobium solid electrolytic capacitor is carried out at 3V to 150V, preferably 5V to 100V, more preferably 10V to 80V, and most preferably 13V to 70V. As described above, the growth of the niobium insulating oxide film thickness is about 3.7 nm / chemical conversion V. In the 3V conversion, a niobium insulating oxide film having a thickness of about 11 nm is formed, and the inner thickness from the original niobium metal interface is formed. This will generate about 8 nm. Therefore, the thickness of the mixed layer of silicon nitride and niobium is preferably 8 nm or more. Furthermore, it preferably has a thickness of 13 nm or more, 27 nm or more, or 35 nm or more.

  The upper limit of the thickness of the mixed layer is theoretically the particle radius of the niobium powder, but if it is too thick, the capacity is reduced. Therefore, it is preferable to be about 4/5 of the niobium particle radius at the maximum. For example, niobium powder having an average particle size of 5 μm is about 2000 nm, if the average particle size is 3 μm, about 1200 nm, if the average particle size is 1 μm, about 400 nm, if the average particle size is 0.8 μm, about 320 nm, When the average particle size is 0.5 μm, about 200 nm, when the average particle size is 0.3 μm, about 120 nm, when the average particle size is 0.2 μm, about 80 nm, and when the average particle size is 0.1 μm, about If it is 40 nm and the average particle size is 0.05 μm, it is about 20 nm. Thus, if the average particle size is reduced, the conversion voltage at which a niobium insulating oxide film having the effect of withstand voltage and solder heat resistance can be formed becomes smaller. For example, if the average particle size is 1.0 μm, the conversion voltage for providing the effect of withstand voltage and solder heat resistance is up to 146 V, and if the average particle size is 0.5 μm, the average particle size is up to 73 V. If it is 0.3 μm, it is up to 44V.

  In the niobium powder of the present invention, the mixed layer of silicon nitride and niobium is a layer in which silicon nitride exists as fine particles dispersed in the niobium layer. The presence of a mixed layer of silicon nitride and niobium in the vicinity of the powder particle surface means a state in which silicon nitride (fine particles) are embedded and dispersed from the niobium powder particle surface to a certain depth. .

  The layer near the surface of the niobium powder of the present invention needs to be a mixed layer of silicon nitride and niobium. This is because silicon nitride is an insulator, and therefore, if there is a single layer of silicon nitride on the surface, formation cannot be performed sufficiently, and only an unstable niobium oxide oxide film can be formed.

The silicon nitride content can be determined by measuring the silicon content by ICP analysis and the nitrogen content by a nitrogen oxygen analyzer.
The content of silicon nitride varies depending on the particle diameter of the powder, the thickness of the mixed layer of silicon nitride and niobium, the surface area, and the like. An object of the present invention is to improve a withstand voltage and solder heat resistance by stabilizing a niobium insulating oxide film formed by chemical conversion on the surface of a niobium sintered body produced from niobium powder. It is necessary to contain a sufficient amount of silicon nitride per surface area.

According to the present invention, the powder having a specific surface area of 0.5 to 70 m ² / g, and silicon nitride is desirably contained by 50 mass ppm or more by powder analysis. If it is less than 50 ppm by mass, it is difficult to obtain the effect of withstand voltage and soldering heat resistance. On the other hand, if it exceeds 500,000 ppm by mass, the niobium content becomes low and the capacity decreases. Therefore, it is preferable that it is 50-500000 mass ppm, and 100-400000 mass ppm, 150-300000 mass ppm, and 200-200000 mass ppm are still more preferable.

The silicon nitride in the present invention can be suitably used as long as it is a compound composed of nitrogen and silicon represented by the following formula (4). These may be used alone or in combination of two or more.
Si _α N _β (4)
(In the formula, α and β represent positive integers.)
Specific examples of the compound represented by the formula (4) include SiN, Si ₂ N ₂ , Si ₂ N ₃ , Si ₃ N _{4 and the} like.
These compounds take the form of amorphous, amorphous, glassy, colloidal, solution, crystal and the like. When these compounds are granulated and used as relatively large particles, oxides such as magnesium oxide and yttrium oxide may be included as a granulation aid.

  In the niobium powder obtained according to the manufacturing method of the present invention described later, silicon nitride is enclosed in etching pits (holes) formed in niobium particles to form a mixed layer of silicon nitride and niobium. Accordingly, silicon nitride is preferably a particle of 1 to 200 nm, more preferably 1 to 100 nm and 1 to 50 nm, although it depends on the size and depth of the etching pit diameter. The shape of the particles is not particularly limited, such as a spherical shape, a flat shape, a columnar shape, or a flake shape, but is preferably a spherical shape because of its ease of introduction into the etching pits.

Other physical properties of the niobium powder of the present invention are preferably as follows.
Average particle size: 0.05-5 μm,
Bulk density: 0.2-3.5 g / ml,
Tapping density: 0.2-3.0 g / ml,
Specific surface area: 0.5 to 70 m ² / g.

[Manufacture of niobium powder for capacitors]
The niobium powder for a capacitor of the present invention can be produced by a method including a step of etching niobium powder, a step of impregnating silicon nitride into an etching pit, and a step of sealing the etching pit.

  The niobium for a capacitor used in the present invention has niobium as a main component and can be a material for producing a capacitor. This includes, in addition to pure niobium, for example, conductive (including semiconductor) niobium compounds including components that can be alloyed with niobium, nitrogen (50 to 50000 ppm), and / or oxygen (2000 to 200000 ppm). May be. Examples of the niobium compound containing nitrogen and / or oxygen include niobium mononitride, niobium monoxide and / or hexaniobium monoxide. Usually, these compounds take the form of amorphous, amorphous, glassy, colloidal, crystalline and the like. Further, hydrides of these pure niobium, niobium alloys, and niobium compounds may be used. Components other than niobium of the niobium alloy and niobium compound include hydrogen, beryllium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, zirconium, hafnium, vanadium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, Ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold, zinc, cadmium, mercury, boron, aluminum, gallium, indium, thallium, carbon, silicon, germanium, tin, lead, nitrogen, phosphorus, arsenic, antimony, Bismuth, oxygen, sulfur, selenium, tellurium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosym, holmium, erbium, thuri Arm, ytterbium, and at least one element selected from the group consisting of lutetium can be exemplified. Further, before the step of impregnating silicon nitride after etching the niobium powder in the present invention, or before the step of sealing the etching pit after impregnating the silicon nitride, or the above-mentioned etching pits. Before and after the sealing step, a step of doping at least one element selected from the group consisting of nitrogen, oxygen, boron, phosphorus, sulfur, selenium and tellurium may be provided. For nitrogen doping, for example, gas nitriding, ion nitriding, solid nitriding or the like is used, and among these, gas nitriding which can uniformly distribute nitrogen on the surface of niobium particles is preferable.

  As the niobium powder used for producing the niobium powder for a capacitor, a primary powder, an agglomerated powder, a granulated powder or the like having an average particle diameter of 0.05 to 5 μm can be preferably used. This niobium powder can be suitably used regardless of the shape such as spherical shape, rod shape, flat shape, and flake shape. In order to obtain a higher-capacity niobium sintered body for capacitors, it is desirable to use niobium powder having a small heat history and a large specific surface area. Therefore, it is particularly preferable to use a primary powder as the raw material niobium powder.

  Such niobium powder is a method for producing niobium powder, niobium compound powder, niobium alloy powder by pulverization described in U.S. Patent No. 4084965, JP-A-10-242004, JP-A-2002-25864, etc., Prepared by using known methods such as niobium powders by reduction of niobium oxides and niobium halides described in U.S. Pat. No. 17288941, U.S. Pat. No. 4,876,632, JP-A-2000-119710, etc. can do.

This raw material niobium powder is etched to form etching pits (pores). Etching is preferably a chemical etching method using an alkaline solution or an acidic solution. An alkaline solution or an acidic solution may be used in combination.
As the alkaline solution, an alkali metal solution, an alkaline earth metal solution, an amine solution, an ammonia solution, a quaternary ammonium salt solution, or the like can be used. You may mix and use these solutions. Examples of the medium include alcohols, ketones, ethers, cellosolves, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, DMSO (dimethyl sulfoxide), DMF (dimethylformamide), etc. An organic solvent or water can be used. You may mix and use these media. The alkali used for etching must be sufficiently removed. As a method for removal, vacuum distillation is simple and preferable. Therefore, an alkali agent having a vapor pressure at a relatively low temperature is preferable. Particularly preferred are ammonia solution, methylamine solution, dimethylamine solution and the like. The concentration of the alkaline substance in the alkaline solution varies depending on the particle size of niobium powder, reaction temperature, etc., but is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and 3 to 20% by mass. Further preferred.

  As the acidic solution, a hydrofluoric acid solution, a fluoroacetic acid solution, or the like can be used. In order to control the etching reaction, for example, a mixture with other acids such as nitric acid, sulfuric acid and hydrochloric acid may be used. As the medium, the same organic solvent and water as in the alkaline solution can be used, or they may be mixed and used. The concentration of hydrogen fluoride or fluoroacetic acid in the acidic solution is desirably 0.01 to 30% by mass, preferably 0.1 to 10% by mass, and more preferably 0.2 to 7% by mass.

  The etching reaction under alkaline conditions proceeds more slowly than acidic ones. Etching under alkaline conditions is desirably performed under more severe conditions. Accordingly, the pH is preferably 8 or more, more preferably 9 or more, and particularly preferably 10 or more.

  The etching reaction is usually performed in the range of 1 to 100 hours from the freezing point of the alkaline solution or acidic solution to 100 ° C. or less. When the reaction is fast, it is desirable to carry out at a lower temperature, but when it is too low, the reaction becomes extremely slow, so it is preferably carried out at −100 to 80 ° C., more preferably at −30 to 60 ° C., It is particularly preferable to carry out at −10 to 40 ° C.

  After completion of the etching reaction, the alkaline solution or acidic solution is sufficiently washed away with a solvent such as water. Then, niobium powder in which etching pits are formed on the powder surface is obtained by drying at 80 ° C. or lower under reduced pressure. The diameter of the etching pit is usually 5 to 200 nm, although it depends on the particle size of the raw niobium powder and the etching conditions.

  Subsequently, the etching pits of the niobium powder are impregnated with silicon nitride. In the presence of an inert gas, the silicon nitride powder having an average particle diameter of 1 to 200 nm and niobium powder having etching pits are sufficiently mixed using an apparatus such as a Nauter mixer or a V-type mixer. When a silicon nitride ball of 0.3 mm or more coexists, the mixing efficiency increases. The mixing is desirably performed for at least 5 minutes. Thereafter, ultrasonic waves are irradiated for 1 second to 10 hours to impregnate the etching pits with silicon nitride powder. The efficiency of impregnation is better when short-time irradiation and powder mixing are repeated than when ultrasonic waves are irradiated for a long time. Usually, it is desirable to perform ultrasonic irradiation for 10 seconds 3 times or more, preferably 10 times or more, and more preferably 20 times or more. The frequency of the ultrasonic waves is preferably 15 kHz or more, and particularly preferably 20 kHz or more. The output varies depending on the material, shape, size, amount of niobium powder, etc. of the container, but it is usually preferably 100 W or more. The temperature at which silicon nitride and niobium powder with etching pits are mixed and then subjected to ultrasonic irradiation is usually room temperature. When the temperature rises to 50 ° C. or higher, it is desirable to cool. Performing at 0 ° C. or lower is not particularly problematic, but requires equipment such as a refrigerator, which is economically undesirable.

  After ultrasonic irradiation, a mixture of niobium powder in which etching pits are impregnated with silicon nitride powder and excess silicon nitride is dispersed in a solvent such as water. Utilizing the specific gravity difference and the particle size difference between the niobium powder and silicon nitride, only the niobium powder is centrifuged and the supernatant containing excess silicon nitride is decanted. The temperature at this time is preferably 0 to 50 ° C. If it exceeds 50 ° C., the reaction between water and niobium tends to proceed, the oxygen concentration increases, and the sinterability during the production of the sintered body tends to be hindered. Although there is no problem in particular to make it 0 degrees C or less, facilities, such as a refrigerator, are needed and it is economically unpreferable. The obtained niobium powder may be further dispersed in a solvent such as water, centrifuged, and decanted. Solvents to be dispersed include alcohols, ketones, ethers, cellosolves, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, DMSO (dimethyl sulfoxide), DMF (dimethylformamide) An organic solvent such as water or water can be preferably used. A mixture of these solvents may be used.

  The wet niobium powder containing silicon nitride powder is well dispersed in the etching pits thus obtained in a solvent, and the niobium pot mill, bead mill, shaking mixer, V-type mixer and the like are combined with niobium beads. Add and mix vigorously. At this time, niobium powder containing silicon nitride powder is vigorously sandwiched between the niobium beads and the inner wall of the mill so that the surface of niobium is deformed to seal the etching pit, and the silicon nitride is fixed to the niobium powder. The temperature for vigorous mixing is preferably 0 to 50 ° C. If it exceeds 50 ° C., the reaction between water and niobium tends to proceed, the oxygen concentration increases, and the sinterability during the production of the sintered body tends to be hindered. Although there is no problem in particular to make it 0 degrees C or less, facilities, such as a refrigerator, are needed and it is economically unpreferable. The time required for this intense mixing is usually from 1 minute to 1000 hours. Furthermore, niobium compounds such as niobium, niobium monoxide, niobium monoxide, niobium dioxide, niobium pentoxide, niobium nitride, niobium mononitride, niobium alloys and these having an average particle size equivalent to the added silicon nitride When a hydride or the like is added, silicon nitride can be fixed to the niobium powder in a shorter time. The time required for mixing when these compounds are added is usually from 1 minute to 100 hours. Solvents to be dispersed include alcohols, ketones, ethers, cellosolves, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, DMSO (dimethyl sulfoxide), DMF (dimethylformamide) An organic solvent such as water or water can be preferably used. A mixture of these solvents may be used.

  The niobium powder of the present invention in which the etching pits are sealed and silicon nitride is encapsulated is dried at 80 ° C. or lower under reduced pressure as necessary after the niobium beads are separated.

  When hydride is used for the niobium powder added to seal the raw material niobium powder or silicon nitride, before the step of etching the niobium powder or before the step of impregnating the silicon nitride into the etching pits Alternatively, a dehydrogenation step can be provided before and after the step of sealing the etching pits. Dehydrogenation can be performed at 200 to 900 ° C. under reduced pressure.

[Niobium granulated powder]
The niobium granulated powder for capacitors of the present invention has a porous structure and is characterized in that a mixed layer of silicon nitride and niobium exists in the vicinity of the surface. Here, the vicinity of the surface includes both the outer surface and the inner surface of the pore.
As the niobium granulated powder, those having the following values are preferable.
Average particle size: 10 to 1000 μm
Bulk density: 0.4 to 2.3 g / ml
Tapping density: 0.5 to 2.5 g / ml
Angle of repose: 10 to 60 degrees Thickness of silicon nitride and niobium layer: 8 to 2000 nm
Silicon nitride content: 50 to 500,000 mass ppm
Pore diameter peak: 0.01 to 500 μm
Number of pore diameter peaks: 1 or more Specific surface area: 0.5 to 40 m ² / g
In particular, when two or more pore diameter peaks are present, it is preferable that at least one pore diameter peak exists at 0.1 to 0.9 μm and at least one pore diameter peak exists at 0.9 to 3 μm.

The niobium granulated powder for a capacitor of the present invention can be produced by granulating the above-mentioned niobium powder for a capacitor or a secondary agglomerated powder thereof. The granulated powder has better flowability than the niobium primary powder or its secondary agglomerated powder, and is excellent in handleability in producing a sintered body.
As a granulation method, thermal aggregation is generally performed by exposing to heat at a temperature of about 400 to about 1300 ° C. for 1 minute to 100 hours under reduced pressure. In particular, it is preferable to use a method for producing granulated powder using an activator described in WO02 / 093596 and WO02 / 092864. Porous niobium granulated powder for capacitors with adjusted pore diameter distribution can be easily obtained by this method, and the sintered body using this granulated powder is impregnated with the cathode agent when manufacturing capacitors. And the electrical characteristics of the capacitor are stabilized.

[Sintered body]
The niobium sintered body for capacitors of the present invention has a porous structure and is characterized in that a mixed layer of silicon nitride and niobium exists in the vicinity of the surface including the vicinity of the pore surface. Preferred physical property values are shown below.
Volume: 0.3-1000mm ³
Density: 2.5-4.0 g / ml
Porosity: 55% by volume or more Silicon nitride and niobium layer thickness: 8-2000 nm
Silicon nitride content: 50 to 500,000 mass ppm
Pore peak top: 0.01 to 100 μm
Number of pore peak tops: 1 or more Specific surface area: 0.005 to 0.06 m ² / mm ³
Capacity: 40000-400000 μFV / g
In particular, when there are a plurality of pore diameter peaks, it is preferable that at least one pore diameter peak is present at less than 1.0 μm and at least one pore diameter peak is present at 1 μm or more. Furthermore, the pore volume having a diameter of 1 μm or more is preferably 13% by volume or more of the total pore volume.

The niobium sintered body of the present invention is formed by using the above-described niobium powder or niobium granulated powder, and press-molding the raw material powder into a predetermined shape using an automatic molding machine together with a lead wire. For example, it can be produced by heating at 10 ⁻⁵ to 10 ² Pa for 1 minute to 10 hours, 500 to 2000 ° C., preferably 800 to 1500 ° C., more preferably 1000 to 1400 ° C.

  When the niobium granulated powder described above is used, the lead wire may be suitably used if it is niobium, a niobium compound, or a niobium alloy, but preferably has the same structure as the powder material. Therefore, it is preferable to use a niobium lead which is composed of a mixed layer of silicon nitride and niobium, and the mixed layer is present near the surface of the niobium lead. The reason for this is that when the sintered body is formed, a part of the lead wire is also formed, so that the insulating oxide film formed on the lead wire needs to be stabilized. The thickness of the mixed layer of silicon nitride and niobium and the content of silicon nitride are preferably about the same as the powder. The niobium sintered body of the present invention produced by using this method has good impregnation of the cathode agent when producing a capacitor, and the electrical characteristics of the capacitor are stabilized.

When manufacturing a sintered body having a relatively large size (10 mm ³ or more) with good impregnation properties, a mixing step of mixing niobium powder for capacitors, a pore forming agent and an organic binder to obtain a mixture, A molding process for obtaining a molded body by compression molding, a sintering process for obtaining a sintered body containing a pore forming agent by sintering the molded body, and a removing process for removing the pore forming agent contained in the sintered body A method of manufacturing a niobium sintered body electrode for a solid electrolytic capacitor (Japanese Patent Application No. 2003-123208) can be used. The niobium sintered body produced by this method has the above physical properties, and the specific surface area of the sintered body per volume calculated from the specific surface area per mass and the sintered body density is 0.01 m ² / mm ^3. It can also be set as above. The capacity of the sintered body of about 20 mm ³ can be 800 μF / piece or more, and further 1000 μF / piece or more. Also, the volume of the sintered body 50 mm ^3, 100 mm ³ and no significant reduction of the cathode agent impregnation ratio be increased, ESR can be a stable, voltage resistance and solder heat resistance good capacitor.

[Capacitor]
Next, the capacitor element will be described.
The above-described niobium sintered body can be used as one electrode, and a capacitor can be manufactured from 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, as the dielectric of the capacitor, a dielectric mainly composed of niobium oxide is preferable, and a dielectric mainly composed of niobium pentoxide is more preferable. In the present invention, physical properties are improved by including silicon nitride in these dielectric layers.
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 a niobium electrode in an 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. In particular, when an organic semiconductor is used, the effect on the solder heat resistance of the capacitor is great. This is presumably because inorganic semiconductors are small in changes to heat such as thermal expansion, but organic semiconductors are large.

  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, R ^{1 to} R ⁴ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, 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.

Further, in the present invention, R ^{1 to} R ⁴ in the general formula (1) or the general formula (2) are preferably each independently a hydrogen atom or 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. It is done.

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.

The conductive polymer containing 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, an inorganic semiconductor composed of triiron tetroxide, and the like. Such semiconductors may be used alone or in combination of two or more.

  Examples of the polymer containing a 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 to 10 ³ S / cm are used, the impedance value of the manufactured capacitor is further reduced, and the capacitance at high frequency can be further increased.

  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. Examples of the polymerization reaction from the polymerizable compound (monomer) include vapor phase polymerization, solution polymerization, and electrolytic polymerization of the monomer, which are formed on the surface of the 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 the reduced form of the oxidant can serve as a dopant to improve the conductivity of the conductive polymer. 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 15 element such as PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻ , a halide anion of a Group 13 element such as BF ₄ ⁻ , I ⁻ (I ₃ ⁻ ), Halogen anions such as Br ⁻ and Cl ⁻ , perhalogenate anions such as ClO ₄ ⁻ , Lewis acid anions such as AlCl ₄ ⁻ , FeCl ₄ ⁻ and SnCl ₅ ⁻ , or inorganic such as NO ₃ ⁻ and SO ₄ ²⁻ Acid anions, or sulfonate anions such as p-toluenesulfonic acid and naphthalenesulfonic acid, alkyl-substituted naphthalenesulfonic acid having 1 to 5 carbon atoms, organic sulfonate anions such as CF ₃ SO ₃ ⁻ and CH ₃ SO ₃ ^— , or Examples thereof include proton 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, or the like is 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 may be stacked as separate layers. After applying the conductive paste, it is left in the air or heated to solidify. Examples of the plating include nickel plating, copper plating, silver plating, and aluminum plating. Moreover, aluminum, nickel, copper, silver etc. are mentioned as a vapor deposition metal.

  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. This capacitor may have a niobium lead or a tantalum lead sintered together with the niobium sintered body or welded later.

  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.

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 content of silicon nitride, the thickness of the mixed layer of silicon nitride and niobium, the capacity of the capacitor, the voltage resistance, and the solder heat resistance were measured and evaluated by the following methods.

(1) Content of silicon nitride The amount of silicon is measured using an ICP analyzer (ICPS-2000) manufactured by Shimadzu Corporation, and the amount of nitrogen is measured using an oxygen nitrogen analyzer (EMGA-620W) manufactured by Horiba, Ltd. The total amount was taken as the amount of silicon nitride (when niobium containing silicon or nitrogen was used as the raw material, the amount obtained by subtracting silicon or nitrogen contained in the raw material was taken as the silicon nitride content).
Silicon nitride content = (Analytical amount of silicon−Amount of silicon contained in raw material) + (Analytical amount of nitrogen−Amount of nitrogen contained in raw material)

(2) Thickness of mixed layer of silicon nitride and niobium Nitriding is performed on the cut surface of the powder using a TEM measuring instrument (HF-2200) manufactured by Hitachi, Ltd. and an EPMA measuring instrument (JXA8900) manufactured by JEOL. The thickness of the mixed layer of silicon and niobium was measured.

(3) Capacitance of Capacitor At room temperature, an LCR measuring machine (4294A) manufactured by Agilent Technologies was connected between terminals of the manufactured chip capacitor, and the capacitance was measured at a bias of 1.5 V and 120 Hz.

(4) Capacitance resistance of the capacitor The current value measured after each voltage of DC voltage 1 to 20V was continuously applied for 1 minute at room temperature between the terminals of the chip-type capacitor produced with an electrolytic oxidation voltage of 20V. The leakage current value of the capacitor processed into a chip was used. The graph is plotted with the DC voltage applied on the horizontal axis and the leakage current value on the vertical axis, and the applied voltage at the inflection point of the leakage current value (if there are two or more inflection points, the voltage at the lowest inflection point) is used. Various capacitors were compared as the maximum possible voltage. The higher the voltage, the better the withstand voltage.

(5) Solder heat resistance The prepared capacitor is mounted on a 1.5 mm thick laminated substrate together with solder, and after passing through a reflow furnace three times, the leakage current value when LC voltage is applied (LC and Which may be abbreviated). The number of LC values of 0.05 CV or less (C represents the capacitance of the capacitor and V represents the applied voltage) was counted. It can be determined that the larger the number, the better the solder heat resistance. The reflow conditions were such that the maximum temperature reached 260 ° C. and a temperature of 230 ° C. or higher was maintained for 60 seconds. In the reflow furnace, the capacitor is heated three times, and a practical thermal history (for example, soldering of the component mounted on the surface of the substrate, soldering of the component mounted on the back surface, soldering of the retrofitted component) Evaluation for three thermal histories in the case of implementation is possible.
(6) Average particle diameter The particle size distribution was measured by a laser diffraction scattering method using an apparatus manufactured by Microtrack (HRA 9320-X100). The average particle size was defined as a particle size value (D ₅₀ ; μm) corresponding to 50% of the cumulative volume%.
(7) Bulk density
It was measured according to a method using a powder apparent density meter specified in JIS (Japanese Industrial Standard 2000 version) Z 2504 and a measuring instrument.
(8) Tapping density
JIS (Japanese Industrial Standard 2000 edition) K1201-1 industrial sodium carbonate apparent specific gravity measurement method was measured according to a tapping device method and measuring equipment.
(9) Repose angle
JIS (Japanese Industrial Standards 2000 version) Z 2504 is used to measure the flowability of the sample and the sample amount. Niobium powder is dropped onto the horizontal surface from the height of 6 cm below the hopper, and from the top of the resulting cone. The angle of the slope relative to the horizontal plane with respect to the horizontal plane was defined as the repose angle.
(10) pore diameter peak, pore volume of 1 μm or more
The pore distribution was measured by a mercury intrusion method using an AutoPoreIV Prosimeter 9505 manufactured by Micro Meritics. In the present invention, the maximum value is obtained from the rate of change of the press-fitting amount, and the pore diameter showing the maximum value is defined as the pore diameter peak. The pore volume of 1 μm or more was determined from the integrated volume having a pore diameter of 1 μm or more.
(11) Specific surface area
It is a value (m ² / g) measured using NOVA1200 of Quantachrome.
(12) Porosity Calculated from the volume of the sintered body and the true density of niobium.

  Moreover, the capacitors of Examples 44 to 58 and Comparative Examples 1 to 6 were manufactured by any one of the following manufacturing methods 1 to 4.

Capacitor manufacturing method 1:
100 niobium anode sintered bodies each having a dielectric oxide film formed on the surface thereof by electrolytic oxidation at a voltage of 20 V using a 0.1% phosphoric acid aqueous solution for 6 hours were prepared. Next, 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.

Capacitor manufacturing method 2:
100 niobium sintered bodies each having a dielectric oxide film formed on the surface were prepared by electrolytic oxidation for 6 hours at a voltage of 20 V using a 0.1% phosphoric acid aqueous solution. Next, after being immersed in a 1: 1 (volume ratio) mixed solution of 35% lead acetate aqueous solution and 35% ammonium persulfate aqueous solution, the reaction at 40 ° C. for 1 hour was repeated to form a counter electrode layer on the dielectric oxide film. A mixed layer of lead dioxide and lead sulfate 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.

Capacitor manufacturing method 3:
100 niobium sintered bodies each having a dielectric oxide film formed on the surface were prepared by electrolytic oxidation for 6 hours at a voltage of 20 V using a 0.1% phosphoric acid aqueous solution. Next, 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. 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.

Capacitor fabrication method 4:
100 niobium sintered bodies each having a dielectric oxide film formed on the surface were prepared by electrolytic oxidation for 6 hours at a voltage of 20 V using a 0.1% phosphoric acid aqueous solution. Next, the niobium sintered body was dipped in an aqueous solution (solution 1) containing 25% by mass of ammonium persulfate and then pulled up, dried at 80 ° C. for 30 minutes, and then a sintered body on which a dielectric was formed was obtained as 3, 4 -Oxidation polymerization was performed by immersing in an isopropanol solution (solution 2) containing 18% by mass of ethylenedioxythiophene and then pulling it up and leaving it in an atmosphere of 60 ° C for 10 minutes. 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.

Example 1 Production of Niobium Powder After hydrogenating a niobium ingot, 2000 g of niobium hydride powder having an average particle diameter of 0.5 μm obtained by pulverization was prepared. This hydrogen acid solution 20L containing 0.5% by mass hydrofluoric acid, 1.0% by mass nitric acid and 1.0% by mass hydrogen peroxide was stirred with the hydrogen so that the water temperature did not exceed 10 ° C. Niobium powder was added. Further, stirring was continued for 15 minutes so that the water temperature did not exceed 10 ° C. The pH was adjusted to 7 with an aqueous potassium hydroxide solution, and the powder was precipitated with a centrifuge. After removing the supernatant, 10 L of ion-exchanged water was used to suspend the powder, the powder was precipitated with a centrifuge, and then the method of removing the supernatant was repeated 10 times. Niobium hydride powder having etching pits was obtained by drying under reduced pressure at 50 ° C. under reduced pressure of 1 × 10 ² Pa.
In an argon atmosphere, 300 g of silicon nitride powder having an average particle diameter of 20 nm is added to 1000 g of niobium hydride powder in which etching pits are formed, mixed for 10 minutes with a mixer, and then subjected to 10 ultrasonic waves with a frequency of 20 kHz and 300 W. Irradiated for 2 seconds. Further, the method of mixing for 10 minutes at room temperature and ultrasonic irradiation for 10 seconds was repeated 20 times.
After suspending 1300 g of this mixture of niobium hydride powder and silicon nitride powder in 10 L of ion-exchanged water, the niobium hydride powder was precipitated with a centrifuge, and the supernatant containing excess silicon nitride powder was removed. This operation was repeated three times to obtain a wet body of niobium hydride powder containing silicon nitride powder in the etching pits.
100 g of niobium powder having an average particle diameter of 20 nm (oxygen content is about 13%) and niobium beads having an average particle diameter of 3 mm are placed in a solution obtained by suspending this wet body in 2000 ml of ion-exchanged water. Mixed for hours. At this time, when the internal temperature exceeded 50 ° C., the shaking mixer was stopped, and after sufficiently cooling, a method of restarting shaking was performed. After removing niobium beads from this suspension using a standard sieve having an opening of 1 mm, the powder was settled with a centrifuge and the supernatant was removed. Under reduced pressure of the resulting wet product of 1 × 10 ² Pa, after drying under vacuum under conditions of 50 ℃, 1 × 10 ² Pa or less under reduced pressure, and dehydrogenation under conditions of 450 ° C., near the powder particle surface A niobium powder having a mixed layer of silicon nitride and niobium was obtained.
The average particle diameter of this niobium powder was 0.5 μm, the silicon nitride content was 240 mass ppm, and the thickness of the mixed layer of silicon nitride and niobium was 54 nm.

Example 2 Production of Niobium Powder 2000 g of niobium agglomerated powder having an average particle diameter of 4 μm in which particles of about 0.5 μm were agglomerated by a method of reducing niobium oxide was prepared. Niobium powder was added to 20 L of 20 mass% aqueous ammonia solution while stirring. Furthermore, after stirring for 50 hours, the powder was precipitated with a centrifuge. After removing the supernatant, 10 L of ion-exchanged water was used to suspend the powder, the powder was precipitated with a centrifuge, and then the method of removing the supernatant was repeated 10 times. Niobium powder with etching pits was obtained by drying under reduced pressure at 50 ° C. under reduced pressure of 1 × 10 ² Pa.
In an argon atmosphere, 200 g of silicon nitride powder having an average particle diameter of 10 nm is added to 1000 g of niobium powder having etching pits, mixed with a mixer for 10 minutes, and then irradiated with ultrasonic waves having a frequency of 20 kHz and 300 W for 10 seconds. did. Further, the method of mixing for 10 minutes at room temperature and ultrasonic irradiation for 10 seconds was repeated 20 times.
After 1200 g of the mixture of niobium powder and silicon nitride powder was suspended in 10 L of ion-exchanged water, niobium powder was precipitated with a centrifuge, and the supernatant containing excess silicon nitride powder was removed. This operation was repeated three times to obtain a wet body of niobium powder containing silicon nitride powder in the etching pits.
Niobium beads having an average particle diameter of 5 mm were put into a solution obtained by suspending this wet body in 2000 ml of ion-exchanged water, and mixed for 10 hours with a shaking mixer. When the internal temperature exceeded 50 ° C., the shaking mixer was stopped, and after sufficiently cooling, a method of restarting shaking was performed. After removing niobium beads from this suspension using a standard sieve having an opening of 1 mm, the powder was settled with a centrifuge and the supernatant was removed. The obtained wet body was dried under reduced pressure under a reduced pressure of 1 × 10 ² Pa at 50 ° C. to obtain a niobium powder having a mixed layer of silicon nitride and niobium near the surface of the powder particles.
The average particle diameter of this niobium powder was 1 μm, the silicon nitride content was 130 mass ppm, and the thickness of the mixed layer of silicon nitride and niobium was 25 nm.

Examples 3 to 13: Production of niobium powder Examples 3, 5, 7 and 9 use the same method as in Example 1, and 0.2 to 1.5% by mass of hydrofluoric acid and 0. Etching was performed at −30 to 10 ° C. using a mixed acid aqueous solution of 4-3.0 mass% nitric acid and 0.4-3.0 mass% hydrogen peroxide. Etching is performed at 0 to 40 ° C. using a 10 to 20% trifluoroacetic acid solution obtained by dissolving trifluoroacetic acid in a water-ethanol solution as an etching solution. The silicon nitride having an average particle diameter of 10 to 50 nm is etched using a 15 to 20% by mass ammonia solution in which ammonia is dissolved in a water-ethanol solution as an etching solution. Using powder Niobium powder having a mixed layer of silicon nitride and niobium near the particle surface was obtained. The physical properties are shown in Table 1.

Example 14 Production of Niobium Powder The niobium powder obtained in Example 1 was heated at 360 ° C. for 2 hours in a nitrogen atmosphere to perform a nitriding reaction. The amount of nitriding of the obtained powder was 4000 ppm. Table 2 shows the physical properties of this powder.

Examples 15 to 20: Production of niobium powder Using the niobium species shown in Table 2, Examples 15 and 16 use the same method as in Example 1, and 0.2 to 1.5% by mass of fluorine as an etching solution. Etching was performed at −30 to 10 ° C. using a mixed acid aqueous solution of hydrofluoric acid, 0.4 to 3.0 mass% nitric acid, and 0.4 to 3.0 mass% hydrogen peroxide. Were etched at 0 to 40 ° C. using a 10 to 20% trifluoroacetic acid solution in which trifluoroacetic acid was dissolved in a water-ethanol solution as an etching solution using the same method as in Example 1. Examples 19 and 20 Is a method similar to Example 2, using a 15-20 mass% ammonia solution in which ammonia is dissolved in a water-ethanol solution as an etchant, etching at 20-60 ° C., and an average particle size of 10-50 nm. Niobium powder having a mixed layer of silicon nitride and niobium in the vicinity of the surface of the powder particles was obtained using silicon nitride containing The physical properties are also shown in Table 2.

Example 21: Production of granulated powder 1000 g of niobium powder having a mixed layer of silicon nitride and niobium in the vicinity of the powder particle surface obtained by the same method as in Example 1, 1000 ml of toluene, and average particle diameter as a pore forming material 150 g of barium oxide having an average particle size of 3 μm and 60 g of barium oxide having an average particle size of 3 μm were put in a niobium pot, and niobium beads having an average particle size of 5 mm were further added, followed by mixing with a shaking mixer for 1 hour. The mixture from which the niobium beads had been removed was placed in a niobium bat and dried under the conditions of 1 × 10 ² Pa and 50 ° C. Subsequently, the mixture was sintered at 1150 ° C. for 12 hours under a reduced pressure of 4 × 10 ⁻³ Pa. After cooling until the product temperature became 30 ° C. or less, argon containing 0.1% oxygen was gradually added so that the product temperature did not exceed 30 ° C., and a thin oxide film was formed on the niobium powder surface. . The obtained barium oxide mixed niobium sintered lump was pulverized with a roll granulator to obtain a barium oxide mixed niobium pulverized powder having an average particle size of 105 μm.
500 g of niobium pulverized powder mixed with barium oxide and 1000 g of ion-exchanged water were placed in a Teflon (registered trademark) 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 less 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 dropwise addition, the mixture was further stirred for 1 hour, 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 crushed powder was put in a Teflon (registered trademark) column and washed with water for 4 hours while flowing ion-exchanged water. The electrical conductivity of the washing water at this time was 0.9 μS / cm.
The niobium pulverized powder that had been washed with water was dried at 50 ° C. under reduced pressure to obtain niobium granulation having a mixed layer of silicon nitride and niobium in the vicinity of the surface. The niobium granulated powder had an average particle size of 125 μm, a silicon nitride content of 240 mass ppm, and a thickness of the mixed layer of silicon nitride and niobium was 65 nm. Table 3 shows the physical properties of this niobium granulated powder.

Examples 22 to 28: Production of granulated powder Example 4 (Example 22), Example 6 (Example 23), Example 8 (Example 24), Example 14 (Example 25), Example 16 (Example 26), Niobium primary powder obtained by the same method as in Example 18 (Example 27) and Example 20 (Example 28), and in the same manner as in Example 21, the pore forming material A niobium granulated powder having a mixed layer of silicon nitride and niobium in the vicinity of the surface was prepared using barium oxide, calcium oxide or magnesium oxide having an average particle diameter of 1 μm and / or 3 μm. Table 3 shows the physical properties of this niobium granulated powder.

Example 29: Production of sintered body 50 g of camphor was dissolved in 1000 ml of toluene at room temperature. In this solution, 840 g of niobium powder having a mixed layer of silicon nitride and niobium in the vicinity of the powder particle surface obtained by the same method as in Example 5, 80 g of barium oxide powder having an average particle diameter of 0.7 μm, and an average particle diameter of 2 μm 80 g of barium oxide was dispersed. Using 2 mm niobium beads, the mixture was mixed for 1 hour with a dynomill. This slurry was put into a Nauta mixer, dried under reduced pressure at 1 × 10 ² Pa and 80 ° C., and granulated to obtain a mixed granulated product of barium oxide, camphor and niobium having an average particle size of 120 μm. From this mixed granulated product, camphor was removed at 480 ° C. under a reduced pressure of 1 × 10 ² Pa or less to obtain 1000 g of a mixed granulated product of hard niobium and barium oxide having an average particle size of 120 μm.
Disperse a hard granulated mixture of niobium and barium oxide in a solution of 30 g of polyisobutyl methacrylate in 500 ml of toluene, and dry under reduced pressure at 1 × 10 ² Pa and 80 ° C. using a conical dryer. Produced a granulated product of 120 μm of niobium, barium oxide and polyisobutyl methacrylate.
This mixed granulated product is put into a hopper of a tantalum element automatic molding machine (manufactured by Seiko Co., Ltd., TAP-2R) and automatically molded with a 0.3 mmφ niobium wire, and the size is approximately 3.3 mm × 1.8 mm × 4. A molded body was prepared so as to be ³ mm (about 25 mm ³ ). The density of the molded body in terms of niobium was 2.8 g / ml (amount of niobium 72 mg).
Next, this molded body was heated at 1 × 10 ⁻² Pa at 250 to 400 ° C. for 3 hours to decompose and remove polyisobutyl methacrylate and left to stand at 1150 ° C. for 60 minutes under a reduced pressure of 4 × 10 ⁻³ Pa. After ligation, the product was cooled until the product temperature was 30 ° C. or lower. The process of gradually adding nitrogen gas containing 0.1% by volume of oxygen so that the product temperature does not exceed 30 ° C and removing under reduced pressure is repeated until the product temperature does not change, and then left for 8 hours or more. The niobium sintered body mixed with barium oxide was taken out.
1000 pieces of this niobium sintered body mixed with barium oxide and 1000 g of ion-exchanged water were put into a Teflon (registered trademark) 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 less, was prepared, and the water temperature exceeded 20 ° C. while stirring 500 g of this aqueous solution. The solution was dropped into a vessel containing a niobium sintered body mixed with barium oxide and ion-exchanged water so as to dissolve barium oxide. After completion of the dropwise addition, stirring was continued for another 2 hours, 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 sintered body was placed in a column made of Teflon (registered trademark), washed with water for 4 hours while flowing ion exchange water, and barium oxide was removed as a barium salt. The electrical conductivity of the washing water at this time was 0.9 μS / cm.
The niobium sintered body was dried under reduced pressure under conditions of 1 × 10 ² Pa and 50 ° C., and then cooled until the product temperature was 30 ° C. or lower. The process of gradually adding nitrogen gas containing 0.1% by volume of oxygen so that the product temperature does not exceed 30 ° C and removing under reduced pressure is repeated until the product temperature does not change, and then left for 8 hours or more. A niobium anode sintered body having a mixed layer of silicon nitride and niobium in the vicinity of the surface where the niobium lead wire was implanted was obtained. The volume of this anode sintered body was about 22 mm ³ , the sintered body density was 3.2 g / ml, the specific surface area was 0.0077 m ² / mm ³ , and the porosity was 63%. Further, the total volume of pores having pore diameter distribution peaks at 0.7 μm and 2 μm and having a diameter of 1 μm or more was 17% by volume of the total pore volume. The silicon nitride content was 1600 mass ppm, and the thickness of the mixed layer of silicon nitride and niobium was 118 nm.

Examples 30 to 32: Manufacture of sintered body Example 30 is the same as Example 15, Example 31 is Example 17, and Example 32 is a method similar to Example 19 in which silicon nitride is formed in the vicinity of the powder particle surface. Niobium powder with a mixed layer of niobium was obtained. Using this niobium powder, a niobium anode sintered body having a mixed layer of silicon nitride and niobium in the vicinity of the surface where the niobium lead wire was implanted was obtained in the same manner as in Example 29. Table 4 shows the physical properties of this sintered body.

Example 33: Production of sintered body A niobium granulated powder having a mixed layer of silicon nitride and niobium near the surface was obtained in the same manner as in Example 21. The niobium granulated powder is dispersed in a solution of 30 g of polyisobutyl methacrylate in 500 ml of toluene, dried under reduced pressure at 1 × 10 ² Pa and 80 ° C., and niobium having an average particle size of 125 μm and polyisobutyl methacrylate. A mixed granulated product was obtained. This mixed granulated product is put into a hopper of a tantalum element automatic molding machine (manufactured by Seiko Co., Ltd., TAP-2R) and automatically molded with a 0.3 mmφ niobium wire, and the size is approximately 3.3 mm × 1.8 mm × 4. A molded body was prepared so as to be ³ mm (about 25 mm ³ ). The density of the molded body in terms of niobium was 2.8 g / ml (amount of niobium 72 mg).
Next, this molded body was heated at 1 × 10 ⁻² Pa at 250 to 400 ° C. for 3 hours to decompose and remove polyisobutyl methacrylate and left to stand at 1250 ° C. for 30 minutes under a reduced pressure of 4 × 10 ⁻³ Pa. After ligation, the product was cooled until the product temperature was 30 ° C. or lower. The process of gradually adding nitrogen gas containing 0.1% by volume of oxygen so that the product temperature does not exceed 30 ° C and removing under reduced pressure is repeated until the product temperature does not change, and then left for 8 hours or more. A niobium anode sintered body having a mixed layer of silicon nitride and niobium in the vicinity of the surface was obtained.
This anode sintered body had a volume of about 22 mm ³ , a sintered body density of 3.2 g / ml, a specific surface area of 0.0059 m ² / mm ³ , and a porosity of 63%. Moreover, the pore diameter peak tops were found at 0.7 μm and 2.3 μm, and the pore volume of 1 μm or more was 12% by volume of the total pore volume. The silicon nitride content was 240 mass ppm, and the thickness of the mixed layer of silicon nitride and niobium was 65 nm.

Examples 34 to 40: Production of sintered body Example 34 is Example 22, Example 35 is Example 23, Example 36 is Example 24, Example 37 is Example 25, Example 38 In Example 26, Example 39 in Example 27, and Example 40 in the same manner as in Example 28, niobium granulated powder having a mixed layer of silicon nitride and niobium in the vicinity of the surface was obtained. Using this niobium granulated powder, a niobium anode sintered body having a mixed layer of silicon nitride and niobium was produced in the vicinity of the surface where the niobium lead wire was implanted in the same manner as in Example 33. Table 4 shows the physical properties of this sintered body.

Examples 41 to 43: Manufacture of sintered body In the same manner as in Example 29, automatic molding was performed together with a 0.3 mmφ niobium wire, and Example 41 has a size of approximately 2.6 mm × 1.4 mm × 3. 4 mm (about 12 mm ³ ), Example 42 has a size of about 4.3 mm × 2.3 mm × 5.6 mm (about 55 mm ³ ), and Example 43 has a size of about 5.5 mm × 3.0 mm × A 7.2 mm (about 119 mm ³ ) shaped body was obtained and then sintered to obtain a sintered body. The volume of the sintered body was about 11 mm ^{3 in} Example 41, about 48 mm ^{3 in} Example 42, and about 105 mm ³ in Example 43. Table 4 shows the physical properties of this sintered body.

Examples 44 to 58: Manufacture of capacitors 100 each of the same sintered bodies were produced by the method of producing sintered bodies in Examples 29 to 43. Each sintered body was formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body is impregnated with a cathode agent by any one of the capacitor production methods 1 to 4, and then a carbon paste and a silver paste are laminated in order, and sealed with an epoxy resin to form a chip capacitor. Was made. Table 5 shows the capacity, withstand voltage, and solder heat resistance of the produced capacitors.

Comparative Example 1 Capacitor Using Niobium Powder with Potassium Fluoride Niobate In a nickel crucible, 5000 g of potassium fluoride niobate sufficiently vacuum-dried at 80 ° C. was charged with 10 times the amount of sodium fluoride of potassium fluoride niobate. The reduction reaction was carried out at 1000 ° C. for 20 hours in an argon atmosphere. 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 niobium pot containing a niobium ball, 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 size of the obtained niobium powder was 0.5 μm.
After obtaining a granulated powder having an average particle size of 100 μm by the same method as in Example 21, a niobium sintered body having no mixed layer of silicon nitride and niobium was obtained by the same method as in Example 33.
100 sintered bodies were formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body was impregnated with a cathodic agent by the method of capacitor production method 4, 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 5 shows the capacity, withstand voltage, and solder heat resistance of the capacitor thus prepared.

Comparative Example 2: Capacitor using partially nitrided niobium powder 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 niobium pot containing niobium balls and ground for 10 hours. Next, a 20% by volume slurry of this hydride with water and niobium balls were placed in a spike mill, and wet pulverized at 40 ° C. or lower for 10 hours to obtain a pulverized niobium hydride slurry, followed by centrifugation. Thereafter, the supernatant was removed to obtain a wet body of niobium hydride powder. The wet body was dried under reduced pressure at 133 Pa and 50 ° C., and then heated at 1 × 10 ⁻² Pa and 400 ° C. for 4 hours to dehydrogenate niobium hydride to niobium and cooled to room temperature. Further, nitrogen was passed under pressure and nitriding was performed at 300 ° C. for 3 hours to obtain about 1000 g of partially nitrided niobium powder. The niobium hydride powder had an average particle size of 0.5 μm and a nitrogen content of 0.38% by mass.
This powder was made into a granulated powder having an average particle diameter of 110 μm in the same manner as in Example 21, and then a niobium sintered body having no mixed layer of silicon nitride and niobium was obtained in the same manner as in Example 33. Obtained.
100 sintered bodies were formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body was impregnated with a cathodic agent by the method of capacitor production method 4, 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 5 shows the capacity, withstand voltage, and solder heat resistance of the capacitor thus prepared.

Comparative Example 3: Capacitor using a partially nitrided niobium-silicon alloy 1000 g of a niobium-silicon alloy (atomic ratio Nb: Si = 94: 6) ingot was placed in a reaction vessel made of SUS304, and hydrogen was introduced at 400 ° C. for 10 hours. I kept doing it. After cooling, the hydrogenated niobium alloy lump was put into a niobium pot containing niobium balls and pulverized for 10 hours. Next, in a spike mill, the hydrogenated slurry of 20% by volume with water and niobium balls are placed, and wet pulverized at 40 ° C. or lower for 10 hours to obtain a pulverized niobium hydride-silicon alloy slurry. After centrifuging, the supernatant was removed to obtain a wet body of hydrogenated niobium-silicon alloy powder. The wet body was dried under reduced pressure at 133 Pa and 50 ° C., and then heated at 1 × 10 ⁻² Pa and 400 ° C. for 4 hours to dehydrogenate the niobium hydride-silicon alloy to a niobium-silicon alloy. After cooling, nitrogen was further circulated under pressure and nitriding was performed at 300 ° C. for 3 hours to obtain about 1000 g of partially nitrided niobium-silicon alloy powder. The raw material niobium hydride-silicon alloy powder had an average particle size of 0.5 μm and a nitrogen content of 0.35% by mass.
A niobium-silicon alloy having no mixed layer of silicon nitride and niobium was obtained in the same manner as in Example 33 after obtaining a granulated powder having an average particle size of 95 μm by the same method as in Example 21. A sintered body was obtained.
100 sintered bodies were formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body was impregnated with a cathodic agent by the method of capacitor production method 4, 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 5 shows the capacity, withstand voltage, and solder heat resistance of the capacitor thus prepared.

Comparative Example 4 Capacitor Using Niobium Monoxide Powder by Reduction 211 g of flaky niobium powder and 119 g of Nb ₂ O ₅ powder were mixed and placed on a tantalum tray. This tray was placed in a vacuum heat treatment furnace and heated to 1000 ° C. Hydrogen gas was put into the furnace and the pressure was adjusted to 2 × 10 ⁴ Pa. The temperature was further adjusted to 1250 ° C. and maintained for 30 minutes. After all the hydrogen gas was removed from the furnace, argon gas was placed in the furnace. The temperature was lowered to 1050 ° C., and while maintaining the temperature at 1050 ° C., argon gas was extracted from the furnace until the pressure reached 5 × 10 ⁻² Pa. At this temperature, argon gas was put into the furnace until it reached 9.3 × 10 ⁴ Pa, and the furnace was cooled to 60 ° C. Further, argon gas was added until 9.3 × 10 ⁴ Pa, and the air was filled until 101 kPa. After 4 minutes, the pressure was reduced to 1.3 Pa. After that, it was refilled with argon gas to 8.0 × 10 ⁴ Pa and subsequently with air to 101 kPa and maintained for 4 minutes. The container was depressurized to 1.3 Pa. Then, it refilled to 5.3x10 < ⁴ > Pa with argon gas, and it continued until it became 101 kPa with air. After 4 minutes, the container was depressurized to 1.3 Pa. Thereafter, the container was refilled with argon gas to 2.7 × 10 ⁴ Pa and subsequently with air to 101 kPa and maintained for 4 minutes. The container was depressurized to 1.3 Pa. The container was refilled to 101 kPa with air and maintained for 4 minutes. The container was depressurized to 1.3 Pa. The container was refilled to 101 kPa with argon gas and released to remove the sample. Niobium powder containing Nb and NbO was obtained through a 40-mesh sieve.
Using this niobium powder, a niobium sintered body having no mixed layer of silicon nitride and niobium was obtained in the same manner as in Example 33.
100 sintered bodies were formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body was impregnated with a cathodic agent by the method of capacitor production method 4, 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 5 shows the capacity, withstand voltage, and solder heat resistance of the capacitor thus prepared.

Comparative Example 5: Capacitor using niobium powder coated with SiO 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 niobium pot containing niobium balls and ground for 10 hours. Next, in a spike mill, a 20 vol% slurry of this hydride with water and niobium balls were added, and 10 g of amorphous SiO ₂ having an average particle diameter of 20 nm was added, and then 10 ° C. at 40 ° C. or lower. A wet slurry of niobium hydride was obtained by wet milling for a period of time, and after centrifugation, the supernatant was removed to obtain a wet body of niobium hydride powder. This wet body was dried under reduced pressure at 133 Pa and 50 ° C., then heated at 1 × 10 ⁻² Pa and 400 ° C. for 4 hours to dehydrogenate the niobium hydride powder to form niobium powder, cooled to room temperature, About 1000 g of niobium powder whose surface was covered with SiO ₂ was obtained. The niobium powder had an average particle size of 0.5 μm and a SiO ₂ content of 0.5% by mass.
This niobium powder was obtained in the same manner as in Example 21 to obtain a granulated powder having an average particle diameter of 80 μm, and then the same method as in Example 33 was used to obtain a SiO ₂ surface having no mixed layer of silicon nitride and niobium. A sintered niobium body was obtained.
100 sintered bodies were formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body was impregnated with a cathode agent by the method 4 for producing a capacitor, 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 5 shows the capacity, withstand voltage, and solder heat resistance of the capacitor thus prepared.

Comparative Example 6: Capacitor Using Niobium Powder Coated with Silica In the same manner as Comparative Example 5, the surface having an average particle diameter of 0.5 μm and an SiO ₂ content of 1.5% by mass was covered with SiO ₂ . Niobium powder was obtained.
To 1000 g of this niobium powder, 75 g of ground metal magnesium was sufficiently mixed and placed in a niobium tray. This tray was placed in a vacuum heat treatment furnace, and the inside of the furnace was replaced with argon gas. Argon was extracted so that the argon gas in the furnace was 8 × 10 ⁴ Pa. The temperature was raised at 8 ° C./min until the inside of the furnace reached 450 ° C. While maintaining the inside of the system at about 1 × 10 ⁵ Pa, the temperature was increased from 450 ° C. to 650 ° C. at 4 ° C./min, and this temperature was maintained for 2 hours. After cooling to room temperature, argon gas was added to 9.3 × 10 ⁴ Pa and the air was filled to 101 kPa. After 4 minutes, the pressure was reduced to 1.3 Pa. After that, it was refilled with argon gas to 8.0 × 10 ⁴ Pa and subsequently with air to 101 kPa and maintained for 4 minutes. The container was depressurized to 1.3 Pa. Then, it refilled to 5.3x10 < ⁴ > Pa with argon gas, and it continued until it became 101 kPa with air. After 4 minutes, the container was depressurized to 1.3 Pa. Thereafter, the container was refilled with argon gas to 2.7 × 10 ⁴ Pa and subsequently with air to 101 kPa and maintained for 4 minutes. The container was depressurized to 1.3 Pa. The container was refilled to 101 kPa with air and maintained for 4 minutes. The container was depressurized to 1.3 Pa. The container was refilled to 101 kPa with argon gas and then released to obtain niobium powder whose surface was covered with metal Si. The niobium powder had an average particle size of 0.5 μm and an Si content of 0.8% by mass.
This powder was obtained in the same manner as in Example 21 to obtain a granulated powder having an average particle size of 125 μm, and then the same method as in Example 33, and the surface without a mixed layer of silicon nitride and niobium was made of metal Si A sintered niobium body was obtained.
100 sintered bodies were formed in a 0.1% phosphoric acid aqueous solution at 80 ° C. for 600 minutes at 20 V to form a dielectric oxide film layer on the surface of the sintered body. Next, the formed sintered body was impregnated with a cathodic agent by the method of capacitor production method 4, 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 5 shows the capacity, withstand voltage, and solder heat resistance of the capacitor thus prepared.

FIGS. 5 and 6 show graphs drawn for evaluating the withstand voltage of the sintered body of Example 33 produced by the capacitor producing method 4 and the capacitor obtained in Comparative Example 6, respectively. It can be seen that the first inflection point of the leakage current of the capacitor according to Example 33 exists near 7V, and the capacitor of Comparative Example 6 exists near 4V. The closer this value is to the formation voltage (20 V in this example and the comparative example), the better the voltage resistance.

The capacitor of the present invention is a capacitor with high capacity, low ESR, excellent withstand voltage and solder heat resistance, and a small leakage current value and good long-term reliability. In particular, the effect of improving the withstand voltage and solder heat resistance when an organic semiconductor is used as the other electrode material is great.
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 conventional tantalum capacitor.
In general, since such a capacitor is frequently used in an electronic circuit, an electronic component in an integrated circuit having a particularly high number of clocks can be obtained by using the capacitor having high capacity, low ESR, withstand voltage, and good soldering heat resistance according to the present invention. The restrictions on the arrangement and exhaust heat are relaxed, and a highly reliable electronic circuit can be stored in a narrower space than before.
Furthermore, by using the capacitor of the present invention, electronic devices that are smaller and more reliable than conventional ones, for example, computer peripheral devices such as computers and PC cards, mobile devices such as mobile phones, home appliances, in-vehicle devices, artificial satellites, A communication device or the like can be obtained.

It is a TEM photograph of the mixed layer part which exists in a sintered compact. 2 is an electron diffraction image of a portion (mixed layer portion of silicon nitride and niobium) in FIG. 1. 2 is an electron beam diffraction image of a portion b (niobium layer portion) in FIG. 1. It is an electron beam diffraction image derived from silicon nitride. It is a graph which shows the voltage endurance of the capacitor using the sintered compact of Example 33. 7 is a graph showing the voltage resistance of a capacitor using the sintered body of Comparative Example 6.

Claims (53)

  A niobium powder for a capacitor having a niobium layer and a mixed layer of silicon nitride and niobium, wherein the mixed layer is present in the vicinity of the surface of the powder particles.   The niobium powder for a capacitor according to claim 1, wherein the mixed layer has a thickness of 8 to 2000 nm.   The niobium powder for a capacitor according to claim 1, wherein the content of silicon nitride is 50 to 500,000 mass ppm. The niobium powder for a capacitor according to claim 1, wherein the silicon nitride is a compound represented by Si _α N _β (wherein α and β represent positive integers). The niobium powder for a capacitor according to claim 4, wherein the silicon nitride is at least one selected from SiN, Si ₂ N ₂ , Si ₂ N ₃ and Si ₃ N ₄ .   The niobium powder for a capacitor according to claim 1, wherein the niobium in the niobium layer and the mixed layer is at least one selected from pure niobium, a niobium compound, a niobium alloy, and a hydride thereof.   The niobium powder for a capacitor according to claim 6, wherein the niobium compound is at least one selected from niobium hydride, niobium nitride, and niobium oxide.   The niobium powder for a capacitor according to claim 1, wherein the average particle size is 0.05 to 5 µm. The niobium powder for a capacitor according to claim 1, wherein the specific surface area is 0.5 to 70 m ² / g.   A method for producing niobium powder for a capacitor, comprising: a step of etching niobium powder; a step of impregnating an etching hole with silicon nitride; and a step of sealing the etching hole.   The method for producing a niobium powder for a capacitor according to claim 10, wherein the niobium powder is a primary powder having an average particle diameter of 0.05 to 5 μm, an agglomerated powder thereof or a granulated powder thereof.   At least one element selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, selenium and tellurium after the etching step, before the impregnation step, after the impregnation step and before the sealing step, or after the sealing step The manufacturing method of the niobium powder for capacitors of Claim 10 including the process of dope.   The method for producing niobium powder for a capacitor according to claim 10, wherein the step of sealing the etching hole is performed in the presence of niobium, niobium compound, niobium alloy and hydride thereof having an average particle diameter of 1 to 200 nm.   The method for producing niobium powder for a capacitor according to claim 10, wherein the niobium powder is at least one selected from niobium, a niobium compound, a niobium alloy, and a hydride thereof.   The method for producing niobium powder for a capacitor according to claim 14, wherein the niobium compound is a niobium compound containing nitrogen and / or oxygen.   The method for producing a niobium powder for a capacitor according to claim 10, wherein the etching agent used in the etching step is an acid or an alkali.   The method for producing a niobium powder for a capacitor according to claim 16, wherein the etching agent is an acid solution containing hydrofluoric acid or fluoroacetic acid.   The method for producing a niobium powder for a capacitor according to claim 16, wherein the etching agent is an alkaline solution having a pH of 10 or more.   The method for producing a niobium powder for a capacitor according to claim 10, wherein the silicon nitride to be impregnated is a particle having an average particle diameter of 1 to 200 nm.   The method for producing a niobium powder for a capacitor according to claim 10, wherein ultrasonic irradiation is performed in the impregnation step.   A niobium granulated powder for a capacitor obtained by granulating the niobium powder for a capacitor according to any one of claims 1 to 9.   A niobium granulated powder for a capacitor, comprising a niobium layer, a mixed layer of silicon nitride and niobium, wherein the mixed layer is present in the vicinity of the outer surface and the inner surface of the hole.   The niobium granulated powder for a capacitor according to claim 22, wherein the mixed layer has a thickness of 8 to 2000 nm.   The niobium granulated powder for a capacitor according to claim 22, wherein the content of silicon nitride is 50 to 500,000 mass ppm.   The niobium granulated powder for a capacitor according to claim 21 or 22, wherein the average particle diameter is 5 to 1000 µm. The niobium granulated powder for capacitors according to claim 21 or 22, wherein the specific surface area is 0.5 to 40 m ² / g.   23. The niobium granulated powder for a capacitor according to claim 21 or 22, wherein one or more pore diameter distribution peaks are present in a range of 0.01 to 500 [mu] m.   26. The niobium granulated powder for a capacitor according to claim 25, wherein at least one peak of the pore diameter distribution is present at 0.1 to 0.9 [mu] m and at least one peak at 0.9 to 3 [mu] m.   The niobium sintered compact for capacitors formed by sintering the niobium powder for capacitors according to any one of claims 1 to 9.   A niobium sintered body for a capacitor obtained by sintering the niobium granulated powder for a capacitor according to any one of claims 21 to 28.   A niobium sintered body for a capacitor, comprising a niobium layer, a mixed layer of silicon nitride and niobium, wherein the mixed layer is present in the vicinity of the outer surface and the inner surface of the hole.   32. The niobium sintered body for capacitors according to claim 31, wherein the mixed layer has a thickness of 8 to 2000 nm.   32. The niobium sintered body for a capacitor according to claim 31, wherein the content of silicon nitride is 50 to 500,000 mass ppm.   32. The niobium sintered body for a capacitor according to claim 29, wherein the porosity is 55% by volume or more. The niobium sintered body for a capacitor according to any one of claims 29 to 31, wherein the specific surface area is 0.006 m ² / mm ³ or more. 32. The niobium sintered body for a capacitor according to claim 29, wherein the specific surface area is 0.005 to 0.06 m < ² > / mm < ³ >.   32. The niobium sintered body for a capacitor according to any one of claims 29 to 31, wherein one or more peaks of the pore diameter distribution exist within a range of 0.01 to 100 [mu] m.   38. The niobium sintered body for a capacitor according to claim 37, wherein at least one peak of the pore diameter distribution is present at less than 1.0 μm and at least one is present at 1.0 μm or more.   32. The niobium sintered body for capacitors according to claim 29, wherein the volume of pores having a diameter of 1 [mu] m or more is 13% by volume or more of the total pore volume.   The niobium sintered body for a capacitor according to any one of claims 29 to 31, having a capacity of 40000 to 400000 µFV / g.   41. A capacitor comprising the niobium sintered body for a capacitor according to any one of claims 29 to 40 as one electrode, and a dielectric interposed between the counter electrode.   The capacitor according to claim 41, wherein the dielectric is mainly composed of niobium oxide containing silicon nitride. The capacitor according to claim 41 or 42, wherein the dielectric is an insulating oxide layer formed by forming a niobium sintered body for a capacitor at 3 to 150V . 44. The capacitor according to claim 41 , wherein the counter electrode material is at least one material selected from the group consisting of an electrolytic solution, an organic semiconductor, and an inorganic semiconductor.   The organic semiconductor is selected from the group consisting of an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, an organic semiconductor composed mainly of tetracyanoquinodimethane, and a conductive polymer. 45. The capacitor of claim 44, wherein the capacitor is at least one.   46. The capacitor according to claim 45, 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 alkyl group having 1 to 10 carbon atoms, an alkoxy group or an alkyl ester group, 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;
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. It may form a divalent chain that forms a cyclic structure of a saturated hydrocarbon,
The cyclic bond chain may include a bond of carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl, imino at any position thereof,
X represents an oxygen, sulfur or nitrogen atom, R ⁵ is present only when X is a nitrogen atom, and represents a hydrogen atom or a linear or branched saturated or unsaturated alkyl group having 1 to 10 carbon atoms. . )
46. The capacitor according to claim 45, which is a conductive polymer obtained by doping a polymer containing a repeating unit represented by the following formula: The conductive polymer is represented by the following general formula (3)

(Wherein R ⁶ and R ⁷ are each independently a hydrogen atom, a linear or branched saturated or unsaturated alkyl group having 1 to 6 carbon atoms, or the alkyl group is bonded to each other at an arbitrary position. And represents 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. )
48. The capacitor according to claim 47, which is a conductive polymer obtained by doping a polymer containing a repeating unit represented by formula (I) with a dopant.   The capacitor according to claim 48, wherein the conductive polymer is a conductive polymer in which a dopant is doped into poly (3,4-ethylenedioxythiophene). 50. The capacitor according to claim 41 , wherein the counter electrode material has a layered structure at least in part. The capacitor according to claim 41 , wherein the counter electrode material contains an organic sulfonate anion as a dopant.   The electronic circuit using the capacitor | condenser in any one of Claims 41-51.   The electronic device using the capacitor | condenser in any one of Claims 41-51.

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