WO2006062234A1

WO2006062234A1 - Method for manufacturing metal powder, method for manufacturing porous sintered body, metal powder, and capacitor

Info

Publication number: WO2006062234A1
Application number: PCT/JP2005/022774
Authority: WO
Inventors: Osamu Kubota; Hitoshi Iijima; Tomoo Izumi
Original assignee: Cabot Supermetals K.K.
Priority date: 2004-12-10
Filing date: 2005-12-12
Publication date: 2006-06-15

Abstract

Disclosed is a method for manufacturing a metal powder wherein when the metal powder is manufactured by causing a reaction between a metal salt and a reducing agent in a molten salt which fills a part of the space inside a reaction container, a nitrogen-containing gas heated to 600˚C or higher is introduced into the rest of the space inside the reaction container. A porous sintered body can be obtained by molding this metal powder and sintering it.

Description

Technical field of manufacturing metal powder and porous sintered body, metal powder, and capacitor

The present invention relates to a metal powder suitable for an anode electrode raw material for a high-capacity solid electrolytic capacitor, a method for producing a metal powder, and a method for producing a porous sintered body. The present invention also relates to a capacitor produced using the metal powder. This application claims priority based on Japanese Patent Application No. 2004-358199 filed on December 10, 2004 and US Provisional Application No. 60 / 635,470 filed on December 13, 2004, The contents are incorporated here.

Background art

In recent years, electronic integrated circuits are required to be driven at a lower voltage, have a higher frequency, and have lower noise, and there has been an increasing demand for low ESR and low ESL for solid electrolytic capacitors. Examples of the metal powder suitably used for the anode electrode of the solid electrolytic capacitor include niobium, tantalum, titanium, tungsten, and molybdenum. Among these, tantalum capacitors using tantalum are rapidly becoming popular as parts for mobile phones and personal computers because they are small, low ESR and high capacity. However, there is still a demand for higher capacity (higher CV value) and lower ESR of tantalum capacitors, and because of the high capacity of capacitors, fine tantalum powder with a large specific surface area is required. Development is ongoing.

[0003] In recent years, the driving voltage of electronic circuits has been declining, so the rated voltage of capacitors has also been declining. Along with this, the formation voltage for forming the dielectric oxide film also decreases. When the force formation voltage decreases, the thickness of the formed dielectric oxide film tends to decrease, so long-term reliability is low. There was a problem of becoming. As a countermeasure, a method of doping metal powder with nitrogen is known. For example, Japanese Patent Laid-Open No. 2001-223141 (Patent Document 1) discloses that in the production of a metal powder by reacting a metal salt with a reducing agent in a molten salt filled in a reactor, Discloses a method of blowing nitrogen-containing gas. However, in the method described in Patent Document 1, since nitrogen is uniformly nitrided to obtain nitrogen in a solid solution state, nitrogen is contained in the metal powder more than necessary (nitrogen content: 8000 to 10000 ppm). As a result, there was a problem that the metal powder became too hard and lost its utility.

Therefore, in Japanese Patent Application Laid-Open No. 2003-55702 (Patent Document 2), when a metal powder is produced by reacting a metal salt with a reducing agent in a molten salt filled in a part of the reactor, A method of introducing a nitrogen-containing gas into the remainder inside the reactor has been proposed. However, in the method described in Patent Document 2, since nitrogen cannot be sufficiently contained in the metal powder, the effect of nitrogen doping cannot be exhibited sufficiently.

Disclosure of the invention

Problems to be solved by the invention

[0004] The present invention has been made in view of the above circumstances, can increase the surface area without excessively containing nitrogen, and has long-term reliability when a metal powder is used in a solid electrolyte capacitor. Another object of the present invention is to provide a method for producing a metal powder and a porous sintered body that have high performance and can be increased in capacity. Another object of the present invention is to provide a metal powder that can be suitably used for an anode electrode of a capacitor, and a capacitor using the metal powder.

Means for solving the problem

In the method for producing metal powder of the present invention, when producing metal powder by reacting a metal salt with a reducing agent in a molten salt filled in a part of the inside of the reactor, A nitrogen-containing gas heated to 600 ° C or higher is introduced into the remainder.

In the method for producing metal powder of the present invention, it is preferable that the metal salt is niobium and Z or tantalum potassium fluoride salt, and the reducing agent is sodium.

In the method for producing a porous sintered body of the present invention, the metal powder obtained by the above-described method for producing metal powder is molded and sintered.

[0006] The metal powder of the present invention can be used for a capacitor containing or consisting of the powder of the present invention. For example, a part of the anode electrode of a capacitor using a conventional technique may be composed of the powder of the present invention. The metal powder of the present invention is a wet capacitor, It can also be used for misalignment of solid electrolyte capacitors.

[0007] The metal powder of the present invention may be a tantalum powder having the following characteristics! However, the composition range of the powder of the present invention is not limited to the following.

Purity:

The rest as tantalum (Ta)

The oxygen (O) content is about 5000 ppm from about 5000 ppm force, preferably about 20000 ppm from about 8000 ppm force to about 15000 ppm. More preferably, the oxygen content may be about 15000 ppm from about 1OOOOppm, and more preferably about 15000ppm from about 12000ppm.

The carbon (C) content is about lppm to 100 ppm, preferably about 50 ppm with about 10 ppm. More preferably, it may have a carbon content of about 20 ppm to about 30 ppm. The content of honey (N) is about 20000 ppm from about lOOppm strength, preferably about 5000 ppm from about lOOOOppm strength. More preferably, it may have a honey content of about 3000 ppm at about 4000 ppm, and more preferably about 3500 ppm at about 3000 ppm.

The hydrogen (H) content is about 1000 ppm from about lOppm strength, preferably about 750 ppm from about 300 ppm strength. More preferably, the hydrogen content may be from about 400 ppm to about 600 ppm! / ヽ The iron (Fe) content is from about 1 ppm to 50 ppm, preferably from about 5 ppm to about 20 ppm.

[0008] The nickel (Ni) content is from about 1 ppm to 150 ppm, preferably from about 5 ppm force to about ΙΟΟρ pm. More preferably, it may have a nickel content of about 25 ppm to 75 ppm. The chromium (Cr) content is about lppm force 100ppm, preferably about 5ppm to about 50ppm. More preferably, it may have a chromium content of about 5 ppm to 20 ppm! /.

The sodium (Na) content is from about 0.1 ppm to 50 ppm, preferably from about 0.5 ppm to about 5 ppm.

The Kazikum (K) content is about 100 ppm from about 0.1 ppm force, preferably about 50 ppm from 5 ppm force. More preferably, it may have a potassium content of about 30 ppm to about 50 ppm. The magnesium (Mg) content is about 1 ppm to about 50 ppm, preferably about 5 ppm to about 25 ppm. The soot (P) content is about 500 ppm from about 5 ppm force, preferably about 300 ρρm from about lOOppm force.

The fluorine (F) content is about 500 ppm from about 1 ppm force, preferably about 300 ρpm from about 25 ppm force. More preferably, the fluorine content may be about 50 ppm from about 300 ppm, and more preferably about 300 ppm from about 100 ppm from lOOppm.

[0009] The particle size of the powder can be about 1.30 μm or less as measured by the Fischer Sub Sheave Size (FS). The particle diameter is preferably adjusted to a predetermined range. For example, the particle size of the powder by FS may be about 0.45 μm force and about 1.30 μm. The particle size of the powder may be less than 0.45 μm, for example, from about 0.1 μm force to about 0.40 μm, or from about 0.20 μm force to about 0.40 μm. The Balta density of the powder may be 1.35 g / cc or less. For example, from about 0.80 g / cc to about 1.30 g / cc, from about 1. Og / cc to about 1.20 g / cc.

[0010] The particle size of the powder, which was represented by a mesh size, as a percentage of total (weight ^_0/0), has a particle size distribution, such as the following, I also! /,.

+ # 60 is about 0.0 to about 1%, preferably about 0.0 to about 0.5%, more preferably 0.0 or about 0.0%.

# 60 / # 170 is about 45% force is also about 70%, preferably about 55% force is also about 65%, more preferably about 60% to about 65%.

# 170 / # 325 is about 20% force is also about 50%, preferably about 25% force is also about 40%, more preferably about 30% force is also about 35%.

# 325 / # 400 is about 1.0% from about 1.0% force, preferably about 7.5% from about 2.5% force, more preferably about 6% also about 4% force.

The # 400 is about 0.1% force to about 2.0%, preferably about 0.5% force to about 1.5%.

[0011] When the above powder is processed into an anode electrode, the powder is compressed to a density of 4.5 g / cc, sintered at 1150 ° C for 10 minutes, and formed at a formation temperature of 60 ° C and a formation potential of 10V (volt). May be. In that case, the capacitance of the anode electrode can be set to CV value of 185000 μ FV / g force, 250000 μ FV / g, for example, 190000 μ FV / g force, 230000 V / g, or 200000 μ FV / g force. And 230000 μFV / g. The leakage current can be less than lOnA / zz FV or less, and the range can be about 2.5 to about 7 ηΑ / μ FV, or about 3.0 force to about 6 ηΑ / μ FV. As processing conditions of the anode electrode, sintering for 10 minutes at a sintering temperature of 1200 ° C. or 1250 ° C. and / or formation (for example, anodizing treatment) at a conversion potential of 16 V may be performed. Even under these conditions, the above-mentioned numerical value or range of electric capacity and / or leakage current can be obtained. Any electric capacity and leakage current within the above ranges can be used for the purpose of the present invention.

Hereinafter, in the description of the specification, the CV value is expressed as the product of the specific capacitance and the rated voltage in the same manner as described above, and the electric capacity is discussed using that value.

[0012] The pores of the tantalum powder of the present invention can have a monomorphic pore size distribution or a multinomial pore size distribution such as a binomial distribution in a state after sintering. The pores may have a central peak in the range of about 0.1 l ^ m force to 0.2 m, for example, 0.1 111 to 0.18 m. Further, the pore volume may be represented by V and the pore diameter may be represented by d, and the peak of the pore diameter may have a height of about 0.3 to about 0.5 dVZd (logd), for example, 0.4 dVZd (logd).

The tantalum powder of the present invention may have a specific surface area measured by the BET method of about 1.5 m ² / g to about 10 m ² / g. A more preferred specific surface area is from about 4 m ² / g to about 9 m ² / g, for example from about 4.5 m ² / g to about 8 m ² / g! /.

The invention's effect

[0014] According to the method for producing a metal powder and the method for producing a porous sintered body of the present invention, the surface area of the metal powder can be increased without excessively containing nitrogen. Therefore, the obtained metal powder or porous sintered body has high long-term reliability when used in a solid electrolyte capacitor, and has a high capacity, specifically, a CV value of 200,000 / z FVZg or more. Is possible.

Brief Description of Drawings

FIG. 1 is a diagram schematically showing a metal powder production apparatus used in an embodiment of the metal powder production method of the present invention.

FIG. 2 is a graph showing the relationship between CV value and nitrogen content.

FIG. 3A shows the density of a sintered body according to an embodiment of the present invention. It is a figure which shows the relationship of CV value.

FIG. 3B is a diagram showing the relationship between the formation potential and the CV value in one embodiment of the present invention. FIG. 4 is a scanning electron microscope image showing the state of powder in one embodiment of the present invention.

FIG. 5 is a scanning electron microscope image showing a state of a sintered body according to an embodiment of the present invention.

FIG. 6A is a graph showing a cumulative distribution of powder pore diameters according to an embodiment of the present invention.

FIG. 6B is a graph showing a frequency distribution of powder pore diameters according to an embodiment of the present invention. Explanation of symbols

[0016] 11 reactor, 11a Remaining inside reactor

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] (Method for producing metal powder)

An embodiment of the method for producing metal powder of the present invention will be described. FIG. 1 shows a manufacturing apparatus used in the metal powder manufacturing method of the present embodiment. This production apparatus 10 comprises a reactor 11, a gas introduction pipe 12 for introducing a nitrogen-containing gas into the reactor 11, and a gas discharge pipe 13 for discharging the nitrogen-containing gas from the reactor 11. A metal salt inlet 14 for introducing a metal salt into the reactor 11, a reducing agent inlet 15 for introducing a reducing agent into the reactor 11, and a stirring blade 16 for stirring the reactor 11. It is a thing. It is preferable that the reactor 11 in the production apparatus 10 has a clad material strength of nickel and inconel.

The gas introduction pipe 12 in the production apparatus 10 is provided so that the jet outlet 12a is positioned above the surface of the molten salt charged in the reactor 11, and the nitrogen-containing gas introduced into the reactor 11 is provided. The surface of the reaction melt containing the molten salt, the metal salt, and the reducing agent is brought into contact.

[0018] In the method for producing metal powder using the production apparatus 10, first, a part of the reactor 11 is filled with a diluted salt, and then the diluted salt in the reactor 11 is not filled. The nitrogen-containing gas heated from the gas introduction pipe 12 is introduced into the space portion (the remainder inside the reactor) 11a. The introduced nitrogen-containing gas is discharged from the gas discharge pipe 13 to the outside of the reactor 11, and the nitrogen-containing gas is circulated in the reactor 11. In this manner, the inside of the reactor 11 is kept in a heated nitrogen-containing gas atmosphere, and at the same time, the diluted salt is heated to 800 to 900 ° C. and melted. Thereafter, the metal salt is charged into the molten diluted salt (hereinafter referred to as “molten salt”) from the metal salt inlet 14, and then the reducing agent is reduced by an amount necessary for the reduction of the metal salt previously charged. It is introduced from the agent inlet 15.

Thereby, the reduction reaction represented by the following formula (1) is performed in the reactor 11. At this time, the reaction melt is gently stirred by operating the stirring blade 16.

K TaF + 5Na → 2KF + 5NaF + Ta-(1)

2 7

[0019] Next, when the reaction between the previously introduced metal salt and the reducing agent is almost completed, the metal salt and the reducing agent are sequentially added while continuing the flow of the nitrogen-containing gas. By repeating this operation, the metal salt of the raw material and the reducing agent are divided and reacted little by little to produce a metal powder.

The produced metal powder settles in the reaction melt because its specific gravity is larger than that of the molten salt. Since the sedimentation facilitates the recovery of the metal powder having a dilute salt strength, the rotation speed of the stirring blade 16 is preferably set to a level that does not hinder the sedimentation of the metal.

[0020] After completion of the above reduction reaction, the reaction melt is cooled, and the resulting agglomerates are washed repeatedly with water, a weakly acidic aqueous solution or the like, and the diluted powder is removed to recover the metal powder. At that time, if necessary, separation operations such as centrifugation and filtration may be combined, or the metal powder may be washed and purified with a solution in which hydrofluoric acid and hydrogen peroxide are dissolved. !

In this production method, potassium chloride (KC1), sodium chloride (NaCl), potassium fluoride (KF), and eutectic salts thereof can be used as a diluted salt.

[0022] As the nitrogen-containing gas, a gas containing molecular nitrogen (N), ammonia, urea, N

2 3 etc. gas.

The atmosphere inside the reactor 11 preferably has a nitrogen gas concentration of 50% by volume or more because nitrogen can be more easily contained in the metal powder. In order to achieve a nitrogen gas concentration of 50% by volume, pure nitrogen gas having a nitrogen concentration of about 100% is preferable among the nitrogen-containing gases. Further, a gas obtained by diluting pure nitrogen gas with argon gas or the like within a range where the nitrogen concentration is 50% or more may be used. If pure nitrogen gas or a gas diluted in the above range is used, the nitrogen gas concentration in the nitrogen-containing gas atmosphere in the reactor 11 is maintained at 50 volume% or more, and nitrogen is easily added to the metal powder immediately. Can be contained. The temperature of the nitrogen-containing gas is 600 ° C or higher, preferably 800 ° C or higher. Examples of the method for heating the nitrogen-containing gas include a method in which the gas introduction pipe 12 is heated by a heater, high-temperature heat exchange, high-frequency heating, or the like. Further, the gas introduction pipe 12 can be passed through the molten salt for heating.

[0023] The metal salt is preferably a niobium and potassium fluoride salt of z or tantalum when producing a metal powder consisting of any one of niobium, tantalum, and niobium tantalum alloys particularly suitable for capacitor applications. When these potassium fluoride salts are used, chain-like particles suitable for the production of a porous sintered body used as an anode electrode can be easily produced. Specific examples of potassium fluoride salts include K TaF, K NbF, and K NbF.

2 7 2 7 2 6

It is. Examples of metal salts other than potassium fluoride include salts such as niobium pentachloride, lower niobium chloride, tantalum pentachloride, and lower salts and tantalum, and halides such as iodide and bromide.

[0024] Examples of the reducing agent include alkali metals and alkaline earth metals such as sodium, magnesium and calcium, and hydrides thereof, that is, magnesium hydride and calcium hydride. Of these, sodium is preferred when potassium fluoride is used as the metal salt. When potassium fluoride is used as the metal salt and sodium is used as the reducing agent, fluorine in the potassium fluoride salt reacts with sodium to produce a fluoride of sodium. Since this sodium fluoride is water-soluble, it has the advantage that it can be easily removed in a later step.

[0025] In addition, in the method for producing the metal powder, the amount of the diluted salt is about 15 to 25 times the total mass of the metal salt and the reducing agent, and the metal salt It is preferable to set the number of additions of the reducing agent to 40 to 60 times in proportion to the dilution rate.

[0026] Further, in the method for producing the metal powder, boron oxide (B 2 O 3) is fluorinated in the molten salt.

twenty three

Boron compounds such as potassium potassium (KBF) may be added. Add boron compounds

Four

Thus, excessive refinement of the reduced metal powder can be suppressed. Here, the addition amount of boron is preferably 5 to: LOOppm with respect to the metal powder. If it is less than 5 ppm, the effect of suppressing the miniaturization is insufficient. On the other hand, if it exceeds lOOppm, the movement of boron oxide through the gas phase increases during sintering and may be deposited on the lead wire when used as a capacitor. Good It ’s not good.

[0027] The metal powder obtained by this production method contains nitrogen. The form of nitrogen in the metal powder is preferably a state in which nitrogen is solid-solved in the metal. When nitrogen forms a solid solution in the metal, the lattice constant of the metal crystal changes. Therefore, the solid solution of nitrogen in the metal can be confirmed by shifting the position of the X-ray diffraction peak. For example, when 3000 p pm of nitrogen is dissolved in tantalum, the distance between the (110) planes of metal tantalum is d = 0.23375 nm (= 2.3375 A) and d = 0.23400 nm (= 2.33400 A). 0. Increase by 1%. In contrast, when the form of nitrogen in the metal powder is a crystalline nitride composed of nitrogen and metal, the capacitance of the capacitor and the reliability of the dielectric oxide film may be reduced.

The amount of nitrogen W in the metal powder is determined by impulse melting heating of the sample in helium gas using a commercially available oxygen Z nitrogen analyzer (Horiba EMGA520) and the generated gas is quantified by TCD (thermal conductivity method). It can be obtained by the method to do.

[0028] In the metal powder production method described above, a nitrogen-containing gas heated to 600 ° C or higher is introduced into the remainder inside the reactor, and the heated nitrogen-containing gas is introduced into the surface of the reaction melt. By making contact with, the metal salt can easily contain nitrogen. As a result, when the metal salt is reduced, nitrogen adhering to the surface of the metal salt at the molecular level can suppress the coarsening of particles, so that the specific surface area can be increased.

In addition, it is estimated that the same effect as described above is exhibited when the nitrogen-containing gas is in a plasma state and the gas in that state is introduced into the remaining part of the reactor.

[0029] In the conventional method in which the nitrogen-containing gas introduction tube is immersed in the reaction melt and the nitrogen-containing gas is blown, the amount of contact between the metal salt and nitrogen is large, so the nitrogen content in the metal powder becomes excessive. On the other hand, in the manufacturing method of the present embodiment, the nitrogen-containing gas contacts the reaction melt only at the surface 17 of the reaction melt (see FIG. 1), so the amount of contact between the metal salt and nitrogen can be reduced. . Moreover, the metal powder that has been reduced and already added with nitrogen settles in the reaction melt and moves away from the surface 17, so that the metal and nitrogen come into contact again. Therefore, nitrogen can be introduced only into the metal immediately after reduction, and it is possible to prevent the nitrogen content from becoming excessive.

FIG. 2 shows the relationship between the nitrogen content in the metal powder and the CV value. As shown in this figure There is a correlation between the nitrogen content and the CV value, and the higher the nitrogen content, the greater the CV value. Since the CV value correlates positively with the specific surface area, this figure suggests that the specific surface area increases with increasing nitrogen content. In the conventional method in which a nitrogen-containing gas is blown into the molten salt, the amount of nitrogen contained in the metal powder greatly increases as the CV value (horizontal axis) increases. On the other hand, in the manufacturing method of the present embodiment, the amount of nitrogen contained in the powder slightly increases as the CV value (horizontal axis) increases, but the degree is smaller than that of the conventional method. . Therefore, in the blowing method, the amount of nitrogen contained in the metal powder tends to be excessive, whereas according to the method of this embodiment, the metal powder can contain only the necessary minimum amount of nitrogen. That is, in the production method of the present embodiment, the specific surface area of the metal powder without excessive nitrogen can be increased.

From the above, according to the manufacturing method of the present embodiment, the specific surface area S of the metal powder can be easily increased to 5.0 m ² Zg or more while containing the necessary minimum amount of nitrogen. If a metal powder having a specific surface area S of 5.0 m ² Zg is used, a capacitor having a higher capacity, specifically, a capacitor having a formation voltage of 10 V and a CV value of 200,000 μFVZg or more can be easily obtained.

[0032] When the metal salt and the reducing agent are added separately as in the production method of the present embodiment, rapid heat generation due to reaction heat can be suppressed as compared to the method of adding them in a lump. A metal powder having a fine and uniform particle size distribution can be obtained.

[0033] In the above-described embodiment, the metal salt and the reducing agent are separately added to the molten salt. However, the present invention is not limited to this embodiment. For example, the metal salt and the reducing agent are each added at a predetermined addition rate. It may be added continuously in degrees. Even when continuously added in this manner, a rapid temperature rise can be suppressed, and a metal powder having a fine and uniform particle size distribution can be obtained.

[0034] (Method for producing porous sintered body)

Next, an embodiment of a method for producing a porous sintered body of the present invention will be described.

In the method for producing a porous sintered body of the present embodiment, first, pretreatment such as thermal aggregation treatment, deoxygenation treatment, and slow oxidation stabilization treatment is performed on the metal powder obtained as described above. Here, the thermal agglomeration treatment is a treatment in which the metal powder is heated and agglomerated in a vacuum to convert the ultrafine particles present in the metal powder into secondary particles having a relatively large particle size. Secondary particles The porous sintered body obtained by molding and sintering the material has larger pores than the porous sintered body obtained from the ultrafine primary particles. Therefore, when used as an anode electrode, the electrolyte solution penetrates into the porous sintered body, so that the capacity can be increased. Moreover, impurities such as sodium and magnesium derived from the diluted salt contained in the metal powder can be removed by heating in vacuum.

As conditions for thermal aggregation, it is preferable to heat at 800 to 1200 ° C. for 0.5 to 1 hour by high frequency heating. As a specific example of high-frequency heating, a cooling dielectric coil is wound around a 20 mmφ reactor at a distance of 5 mm with a spacing of 5 mm, and the heating zone is set to 100 mm while keeping the inside of the reactor in a vacuum. Can be applied to the dielectric coil.

[0035] In the deoxygenation treatment, the cake-like powder obtained by thermal aggregation is crushed in the air or in an inert gas, and then a reducing agent such as magnesium is added, and in an inert gas atmosphere such as argon. This is a treatment in which oxygen in the metal powder reacts with the reducing agent by heating at a temperature between the melting point and the boiling point of the reducing agent for 1 to 3 hours.

The slow oxidation stabilization process is a process of introducing air into the argon gas during cooling after the deoxygenation process. After the gradual oxidation stabilization treatment, it is preferable to remove the substances derived from the reducing agent such as magnesium and magnesium oxide remaining in the powder by acid washing.

[0036] Next, after 3-5 mass% camphor (CHO) or the like as a binder is mixed with the metal powder that has been pretreated as described above, the mixture is press-molded to obtain a molded body.

10 16

Make it. Subsequently, a porous sintered body can be produced by calcinating the sintered body at a sintering temperature of 1000 to 1200 ° C. for about 0.3 to 1 hour and sintering. When this porous sintered body is used as an anode electrode, a lead wire is embedded in the metal powder before the metal powder is press-molded, and the lead wire is integrated and sintered. It is preferable to keep it.

[0037] Since the porous sintered body obtained in this way has a large specific surface area, it is formed at 60 ° C and 10V in accordance with EIAJR C 2361, and the anode electrode of the solid electrolytic capacitor When a solid electrolytic capacitor is manufactured, it is possible to achieve a high capacity with a CV value in terms of specific capacitance of 200,000 to 350,000 / z FVZg. EIAJ RC-2361 is JEOL It is defined as a test method for tantalum sintered elements for electrolytic capacitors by the Japan Machinery Manufacturers Association standard.

[0038] The obtained porous sintered body preferably has a density of 103 to 115% of the density of the molded body. If the density of the porous sintered body is less than 103% of the density of the molded body, the strength is insufficient and it is not practical. On the other hand, if it exceeds 115%, volume shrinkage due to sintering is too large, and it is difficult to control the dimensions of the sintered body. By setting the density of the porous sintered body to 103 to 115% of the density of the molded body, the porous sintered body is suitable for a solid electrolytic capacitor.

The porous sintered body preferably has a compressive strength of 3 to 20 times the compressive strength of the molded product. If the compressive strength of the porous sintered body is less than three times the compressive strength of the compact, the strength is insufficient, and abnormalities may occur when a solid electrolytic capacitor is used that is not practical. On the other hand, if it exceeds 20 times, the strength is too high and it is too hard, and the number of vacancies is reduced, so that the impregnation with manganese oxide is insufficient, and the production of the cathode body may be difficult.

Note that the porous sintered body of the present invention is not limited to the above-described embodiment, and for example, pretreatment may be omitted. However, in order to obtain a high-quality porous sintered body, it is preferable to perform the above pretreatment.

[0040] A solid electrolytic capacitor can be produced using the porous sintered body obtained by the production method described above. In the method for producing a solid electrolytic capacitor, first, the porous sintered body is subjected to a current of 40 to 80 mAZg in an electrolytic solution such as phosphoric acid and nitric acid having a temperature of 30 to 60 ° C. and a concentration of about 0.1% by mass. The pressure is increased to 10V at the density, and it is processed and oxidized for 1 to 3 hours. This chemically oxidized porous sintered body is used as an anode electrode for a solid electrolytic capacitor. That is, a solid electrolyte layer such as manganese dioxide, lead oxide or a conductive polymer, a graphite layer, and a silver paste layer are sequentially formed on this anode electrode by a known method, and a cathode terminal is further formed thereon. After connection by soldering or the like, a solid electrolytic capacitor can be obtained by forming a resin sheath.

[0041] Next, the metal powder as one embodiment of the present invention will be described. The metal powder as an embodiment of the present invention may have the following composition. However, the composition range of the powder of the present invention is not limited to the following.

purity: The rest as tantalum (Ta)

The oxygen (O) content is about 5000 ppm from about 5000 ppm force, preferably about 20000 ppm from about 8000 ppm force to about 15000 ppm. More preferably, it may have an oxygen content of about 15000 ppm, such as about 15,000 ppm, and more preferably about 15000 ppm.

The carbon (C) content is about lppm to 100 ppm, preferably about 50 ppm with about 10 ppm. More preferably, it may have an oxygen content of about 20 ppm to about 30 ppm! /.

The content of honey (N) is about 20000 ppm from about lOOppm strength, preferably about 5000 ppm from about lOOOOppm strength. More preferably, it may have a honey content of about 3000 ppm at about 4000 ppm, and more preferably about 3500 ppm at about 3000 ppm.

The hydrogen (H) content is about 1000 ppm from about lOppm strength, preferably about 750 ppm from about 300 ppm strength. More preferably, the hydrogen content may be from about 400 ppm to about 600 ppm! / ヽ The iron (Fe) content is from about 1 ppm to 50 ppm, preferably from about 5 ppm to about 20 ppm. The nickel (Ni) content is From about lppm to 150 ppm, preferably from about 5 ppm force to about ΙΟΟρ pm. More preferably, it may have a nickel content of about 25 ppm to 75 ppm! / ヽ. The chromium (Cr) content is about lppm force 100ppm, preferably about 5ppm to about 50ppm. More preferably, it may have a chromium content of about 5 ppm to 20 ppm! /.

The Kazikum (K) content is about 100 ppm from about 0.1 ppm force, preferably about 50 ppm from 5 ppm force. More preferably, it may have a potassium content of about 30 ppm to about 50 ppm. The magnesium (Mg) content is about 1 ppm to about 50 ppm, preferably about 5 ppm to about 25 ppm.

The soot (P) content is about 500 ppm from about 5 ppm force, preferably about 300 ρρm from about lOOppm force.

The fluorine (F) content is from about 1 ppm to about 500 ppm, preferably from about 25 ppm force to about 300 ppm. More preferably ί or about 50 ppm force, about 300 ppm, more preferably ί or about lOOppm force Even if the fluorine content is about 300ppm!

The impurity composition can be obtained by a microanalysis method such as inductively coupled plasma mass spectrometry (ICP mass spectrometry). If a powder having the above preferred composition range is used, a capacitor having a high capacity can be obtained. The preferred range is defined by the function of the capacitor and the economic efficiency at the time of powder production.

[0043] The particle size of the above powder can be about 1.30 m or less as measured by the Fisher sub-sieve size (FS). The particle size can be arbitrarily adjusted in the powder production process. In order to obtain a preferable particle size distribution, it is preferable to adjust the particle size within a predetermined range. For example, the particle size of the powder by FS may be 0.45 111 or 1.30 / z m. It may be 0.45 / z m or less, for example, about 0.1 μm force or 0.40 μm, or about 0.20 μm force or about 0.40 μm. The Balta density of the powder may be 1.35 g / cc or less. For example, from about 0.80 g / cc to about 1.30 g / cc, or from about 1. Og / cc to about 1.20 g / cc.

[0044] The particle size of the powder, which was represented by a mesh size, as a percentage of total (weight ^_0/0), has a particle size distribution, such as the following, I also! /,.

# 170 / # 325 is about 20% force is also about 50%, preferably about 25% force is about 40%, more preferably about 30% force is about 35%.

# 325 / # 400 is about 1.0% force about 10%, preferably about 2.5% force about 7.5%, more preferably about 4% force about 6%.

The # 400 is about 0.1% force to about 2.0%, preferably about 0.5% force to about 1.5%. Where + # 60 is the powder remaining on the # 60 (60 mesh) sieve, # 60 / # 170 is finer than # 60, and # 170/325, the powder remaining on the # 170 sieve 325/400 is the same), # 400 is a finer powder than # 400.

[0045] The tantalum powder having the above composition and particle size distribution can be produced using the method for producing a metal powder of the present invention. However, the above tantalum powder is applied to the above manufacturing method. Therefore, the tantalum powder having the above characteristics is not limited, and may be manufactured using other manufacturing methods.

[0046] When the above powder is processed into an anode electrode, sintering is performed at a molding temperature of 60 ° C, a density at compression of 4.5 g / cc, and 1150 ° C for 10 minutes, and then formed at a conversion potential of 10 V (volts). For example, anodization may be performed. In that case, the capacitance of the anode electrode in terms of CV is 185000 / z FV / g force 25 0000 μ FV / g, for example 190000 μ FV / g force 230000 μ FV / g, or 200000 μ FV / g The power is 230000 FV / g. Also, the leakage current can be less than ΙΟηΑ / FV or less, and the range can be about 2.5 to about 7ηΑ / μFV, or about 3.0η to about 6ηΑ / μFV.

As processing conditions for the anode electrode, sintering for 10 minutes at a sintering temperature of 1200 ° C or 1250 ° C and / or formation at a conversion potential of 16V may be performed. Even under these conditions, the electric capacity and / or leakage current in the above-mentioned numerical value or range can be obtained. Any electric capacity and leakage current within the above ranges can be used for the purpose of the present invention.

[0047] The pores of the tantalum powder of the present invention can have a monomorphic pore size distribution or a multinomial pore size distribution such as a binomial distribution in a state after sintering. The pores may have a central peak in the range of about 0.1 l ^ m force to 0.2 m, for example, 0.1 111 to 0.18 m. Further, the pore volume may be represented by V and the pore diameter may be represented by d, and the peak of the pore diameter may have a height of about 0.3 to about 0.5 dVZd (logd), for example, 0.4 dVZd (logd).

Example

[0048] [Example 1] (Production of metal powder)

Using the production apparatus 10 shown in FIG. 1, tantalum powder was produced by the following procedure. First, 15 kg each of potassium fluoride and potassium chloride as dilution salts were charged into a 50 L reactor 11. Next, nitrogen gas heated to 900 ° C (purity 99.999%) is introduced at a flow rate of 3 LZ from the gas introduction pipe 12 to the upper part of the diluted salt in the reactor 11 (the remainder inside the reactor). The inside of the reactor 11 was kept in a nitrogen atmosphere by discharging from the discharge pipe 13. At the same time, Nozomi The salt was heated to 850 ° C to form molten salt. Next, 37.5 g of potassium tantalum fluoride is added to the reactor 11 from the metal salt inlet 14 to each time, and after 1 minute, 10.8 g of dissolved sodium is added from the reducing agent inlet 15 to 3 Reacted for 1 minute. This operation was repeated 40 times to carry out a reduction reaction. During this operation, the inside of the reactor 11 was maintained in a nitrogen atmosphere and stirred with the stirring blade 16 (stirring blade rotation speed: 150 rpm). After completion of the reduction reaction, the mixture was cooled, and the resulting agglomerates were crushed and washed with a weakly acidic aqueous solution to obtain tantalum powder. Further, purification was performed with a cleaning solution containing hydrofluoric acid and hydrogen peroxide.

[0049] Next, to the obtained tantalum powder (dried product) lOOg, after adding about lOOppm of phosphoric acid with respect to tantalum, water is added until the whole is uniformly wet while giving vibration, to form a nodule. Preaggregation was performed. At this time, the amount of water to be a baby boom was approximately 25 ml. Next, the nodule was dried and then heated in a vacuum heating furnace at 1150 ° C. for 1 hour to cause thermal aggregation. The thermally agglomerated nodules were first roughly crushed with a ceramic roll crusher and further pulverized to a particle size of 250 m or less with a pin mill in an argon atmosphere. The pulverized material lOOg was mixed with 3 g of magnesium chip and kept at 800 ° C. for 2 hours in a heating furnace in an argon atmosphere to react oxygen and magnesium in tantalum for deoxygenation. And in the subsequent cooling process

ヽ, removed from the furnace. The extracted powder was washed with aqueous nitric acid, and magnesium and magnesium oxide were washed and removed.

[0050] (Production of porous sintered body)

Then, the tantalum powder 0. 15 mg, added camphor 2 mass ^_0/0 as a binder, were mixed, 3mm diameter was press molded to form a compact density 4. 5gZcm ^3. The compact was then heated in a vacuum sintering furnace at 1150 ° C for 20 minutes to produce a porous sintered body.

(Chemical conversion oxidation conditions)

The obtained porous sintered body was subjected to chemical oxidation (anodic oxidation) in a 10 mass% phosphoric acid aqueous solution at a chemical conversion voltage of 10 V, a temperature of 60 ° C., and a holding time of 120 minutes to form a dielectric oxide film.

(Wet method electrical characteristics measurement)

A porous sintered body with a dielectric oxide film formed in 30.5% by volume sulfuric acid aqueous solution Then, the capacitance (expressed by CV value) was measured at a bias voltage of 1.5 V and a frequency of 120 Hz. The results are shown in Table 1.

(BET surface area measurement)

Nitrogen gas was adsorbed on tantalum powder, and the monomolecular layer adsorption amount was obtained using the BET equation, and the monomolecular layer adsorption amount force BET surface area was obtained.

(Element determination method)

In accordance with JIS H 1699: 1999, the amounts of nitrogen, oxygen, sodium, and lithium in tantalum powder were measured.

[0051] [Example 2]

A tantalum powder was obtained in the same manner as in Example 1 except that the nitrogen gas was heated to 600 ° C. And, after the porous sintered body was produced and chemically oxidized in the same manner as in Example 1, the wet method was applied. Electrical characteristics were measured. The results are shown in Table 1.

[0052] [Example 3]

A tantalum powder was obtained in the same manner as in Example 1 except that the nodule of tantalum powder was dried and then heated in a vacuum heating furnace and thermally aggregated instead of being heated and aggregated at 1000 ° C. for 5 minutes.

Then, in the same manner as in Example 1, after producing a porous sintered body and chemical conversion oxidation, electrical characteristics were measured by a wet method. The results are shown in Table 1.

[0053] [Example 4]

In the reduction reaction of Example 1, 85 g of potassium tantalum fluoride was added each time, and after 1 minute, 25 g of dissolved sodium was added and reacted for 5 minutes, except that this operation was repeated 30 times. Produced tantalum powder in the same manner as in Example 2. Then, in the same manner as in Example 1, after producing a porous sintered body and chemical conversion oxidation, electrical characteristics were measured by a wet method. The results are shown in Table 1.

[0054] [Comparative Example 1]

A tantalum powder was obtained in the same manner as in Example 4 except that the nitrogen gas was not heated. Then, in the same manner as in Example 1, after the porous sintered body was produced and subjected to chemical oxidation, the wet method was used. The electrical characteristics were measured. The results are shown in Table 1.

[0055] [Comparative Example 2]

A tantalum powder was obtained in the same manner as in Example 1 except that the nitrogen gas was not heated. Then, the porous sintered body was manufactured and subjected to chemical oxidation in the same manner as in Example 1, and then the electrical characteristics were measured by the wet method. The results are shown in Table 1.

[0056] [Table 1]

[0057] In Examples 1 to 4 in which the metal salt was reduced while introducing nitrogen gas heated to 600 ° C or higher into the remainder inside the reactor, the CV of the porous sintered body obtained with a large surface area was obtained. All of the high values were those with a CV value of 200,000 μFVZg or more.

On the other hand, in Comparative Examples 1 and 2, which did not heat nitrogen gas, nitrogen could not be sufficiently contained in the metal powder, and the surface area could not be increased.

The CV value was lower than the porous sintered body obtained in ~ 4.

[0058] [Examples 5 and 6]

Next, two types of tantalum powders produced as examples of the metal powder of the present invention

Contrast its characteristics.

(Adjustment of metal powder)

As examples of the metal powder of the present invention, the same production method as in Example 1 was used to prepare two types of tantalum powders, Example 5 and Example 6. The results of trace element analysis are shown in Table 2. Example 5 is a force in which the purity of the tantalum powder is within the above-mentioned preferable range. Example 6 is also within the scope of the present application.

Table 2 shows the particle diameters of the powders of Examples 5 and 6 and the Balta density, which were determined using the Fisher sub-sieve size (FS). In addition, the particle size distribution of the powder expressed in mesh size Are shown in Table 2. Trace element analysis was performed by ICP mass spectrometry. Fischer sub-sheve size was measured by ASTM B330-02 and by Balta density measurement by ISZ2504.

[0059] (Production of porous sintered body)

Next, using this tantalum powder, compacts each having a diameter of 3 mm and a density of 4.5 gZcm ³ were produced. The molded body was then subjected to a vacuum sintering furnace for Example 5 at 1150 ° C for 10 minutes, and 1200 ° C for 10 minutes, for Example 6, 1200 ° C for 10 minutes in a vacuum heating furnace. The porous sintered body was manufactured by heating for a minute.

(Chemical conversion oxidation conditions)

The obtained porous sintered body was subjected to chemical oxidation (anodic oxidation) in a 0.1% by volume phosphoric acid aqueous solution at a chemical conversion voltage of 10 V, a temperature of 60 ° C, a holding time of 120 minutes, and a current density of 90 mA / g. A body acid film was formed.

(Wet method electrical characteristics measurement)

With respect to the porous sintered body on which the dielectric oxide film was formed, the electric capacity (expressed by CV value) was measured under the same conditions as in Example 1. In addition, leakage current (LC value) was measured in a phosphoric acid aqueous solution at a temperature of 25 ° C and a voltage of 7 V for 3 minutes. These results are shown in Table 2.

In addition, for the powders of Examples 5 and 6 sintered at a sintering temperature of 1200 ° C, the CV values were measured for those formed at the conversion potential of 8V and 15V under the above-mentioned formation conditions. The results are plotted in FIG. 3B.

(Measurement of powder compressibility)

Table 2 also shows the loss angle tangent tan δ, the density Ds of the sintered body, and the density ratio Ds / GD of the sintered body and the press-formed body.

[0060] [Table 2] Example 5 Example 6 Sintering temperature 荚麵 5 Actual-Example 6

0 11380 8130 Π50Τ; CV 219100

C 26 34 LC Λ) 971.7

Composition N 3500 3960 LC (nA // i FV) 4,4

Analytical value H 413 296 tan 6 (%) 178

<ppm) Fe 8 10 Ds (g / cc) 4.50

Ni 60 17 1200 CV (/ i FV / g) 201580 183000

Cr 7 9 991.9 976.7

Na 2 2 LC (nA ^ FV) 4.9 5,3

K 36 23 tan έ (%) 181 HS

Mg 15 15 Ds (g / ec) 4,81 4.56

P 241 150 Ds / GD 1.07 1.01

Physical properties FS m) 0,37 0.47 FS: Particle size by Fisher sub-size

BD (g / cc) 1.20 1.40 BD; Bulk density

Particle distribution Size wt% wt% CV: CV value

+ # 60 0,0 0.0 LC: Leakage

64.0 72.6 tan 6: Tangent of loss angle

.J-

# 17 19.0: Density of sintered body

# 325 / # 400 4.8 6.2 Ds / GD: Sintered body density / Molded body density

-# 400 0.8 2,2

FIG. 3A is a plot of the results in Table 2 with the horizontal axis representing the density of the sintered body sintered at 1150 ° C. and 1200 ° C. and the vertical axis representing the CV value.

FIG. 3B shows CV values when the powders of Example 5 and Example 6 were formed at conversion potentials of 8V, 10V, and 15V. From the figure, Example 5 having a preferred composition range shows that the formation potential is

It can be seen that the electric capacity is high around 10V!

FIG. 4 is a scanning electron microscope image (SEM image) showing the powder structure of Examples 5 and 6.

Fig. 5 shows the sintered compacts obtained by compressing the powders of Examples 5 and 6 at a compression density of 4.5 and sintering at 1200 ° C.

SEM image.

6A and 6B are diagrams showing the pore size distribution of the sintered powder for Examples 5 and 6, FIG. 6A is a cumulative distribution, and FIG. 6B is a frequency distribution. .

[0063] Regarding the numerical values described above, for the purposes of the present invention, the numerical ranges shown in the above description and figures may be within 20%, within 10%, or within 5%.

Industrial applicability

[0064] According to the method for producing a metal powder of the present invention, a metal powder such as tantalum or niobium having a low nitrogen concentration, a fine particle and a large specific surface area can be produced. Sintering the metal powder of the present invention to produce a porous sintered body, which is used as an anode electrode of a capacitor Therefore, it is possible to manufacture a solid electrolyte capacitor having a high capacity in addition to high long-term reliability.

Claims

The scope of the claims

[1] A method for producing metal powder, comprising:

When producing metal powder by reacting a metal salt with a reducing agent in a molten salt filled in a part of the reactor,

A method for producing metal powder in which a nitrogen-containing gas heated to 600 ° C or higher is introduced into the remainder of the reactor.

2. The method for producing metal powder according to claim 1, wherein the metal salt is at least one of a potassium fluoride salt of niobium and a potassium fluoride salt of tantalum, and the reducing agent is sodium.

[3] A method for producing a porous sintered body, which is a method for producing a porous sintered body, wherein the metal powder obtained by the method for producing a metal powder according to claim 1 or 2 is molded and sintered. .

[4] Tantalum powder,

About 5000ppm to 20000ppm oxygen,

About lppm to about lOOppm of carbon,

From about lOOppm to about 20000ppm nitrogen,

About lOppm force is about lOOOppm hydrogen,

About lppm power is also about 50ppm iron,

About lppm force nickel of about 150ppm,

About lppm power is also about lOOppm chromium,

¾0. Lppm force ¾50ppm N

About 0.1 lppm strength and about 10 ppm Kazikum,

About lppm to about 50ppm magnesium,

About 5 ppm force and about 500 ppm phosphorus,

About lppm force also contains about 500ppm fluorine,

With the remaining tantalum,

The particle size due to the Fischer sub-sieve size is about 1.30 μm or less,

The nozzle density is about 1.35 g / cc or less,

The particle size distribution force expressed in mesh size is expressed as a percentage by weight with respect to the whole. # 60 / # 170 force about 45% force about 70%,

# 170 / # 325 20% force 50%

# 325 / # 400 force S about 1.0% force ^) about 10%,

# 400 force S 0. 1 ^_0/0 Power et al. 2.0%

Tantalum powder.

[5] The tantalum powder according to claim 4, wherein the pore size distribution of the pores is a singlet distribution.

6. The tantalum powder according to claim 4, wherein the specific surface area by BET method is about 1.5 m ² / g to about 10 m ² / g.

[7] The tantalum powder according to claim 4, wherein the pore diameter showing the peak strength in the pore size distribution is about 0.

Tantalum powder in the range of 1 μm to about 0.2 μm.

[8] The tantalum powder according to claim 7, wherein the peak height of the pore diameter is about 0.3 to about 0.5 dV / d (logd) where V is the volume of the pore and d is the pore diameter. Tantalum powder.

[9] The tantalum powder according to claim 4, wherein the pore diameter distribution is a multinomial distribution.

[10] A tantalum powder of claim 4 wherein the density during compression 4.5 ₈ / «11 ^3, the sintering temperature 1150. C, sintering in 10 minutes, forming temperature 60 ° C, forming anode electrode at conversion potential 10V, electric capacity force SCV value about 185000 μFV / g force about 250000 μFV / g, leakage current force Tantalum powder with less than 10ηΑ / μ FV.

[11] The tantalum powder according to claim 4,

About 8000ppm force is also 15000ppm oxygen,

About lOppm power is also about 50ppm carbon,

About lOOOppm to about 5000ppm nitrogen,

About 300 ppm power is about 750 ppm hydrogen,

About 5ppm force is also about 20ppm iron,

About 5ppm to about lOOppm nickel,

About 5ppm strength is also about 50ppm chromium,

About 0.5ppm strength is also about 5ppm sodium About 5ppm potassium is also about 50ppm potassium,

About 5 ppm force, about 25 ppm magnesium,

About lOOppm power is also about 300ppm phosphorus,

About 25 ppm force also contains about 300 ppm fluorine,

With the remaining tantalum,

The particle size according to the Fischer sub-sheave size is about 0.10 μm to about 0.40 μm, the norm density is about 0.80 g / cc force, 1.30 g / cc,

The particle size distribution force expressed in mesh size is expressed as a percentage by weight with respect to the whole.

# 60 / # 170 force about 55% force about 65%,

# 170 / # 325 force S approximately 25% force ^) approximately 40%,

# 325 / # 400 force S about 2.5% force ^) about 7.5%,

# 400 force S 0. 5 ^_0/0 Power et al. 1.5%

Tantalum powder.

[12] The tantalum powder according to claim 4,

About 12000ppm force is also about 15000ppm oxygen,

About 20ppm force is also about 30ppm carbon,

About 3000ppm force is also about 3500ppm nitrogen,

About 400 ppm to about 600 ppm hydrogen,

About 5ppm force is also about 20ppm iron,

About 25 ppm force and about 75 ppm nickel,

About 5 ppm force and about 20 ppm chromium,

About 0.5ppm strength is also about 5ppm sodium,

About 30ppm strength is also about 50ppm potassium,

About 5 ppm force, about 25 ppm magnesium,

About lOOppm power is also about 300ppm phosphorus,

About lOOppm force also contains about 300ppm fluorine,

With the remaining tantalum, The particle size is about 0.20 μm to about 0.40 μm, and the density of the Nork density is about 1. Og / cc to 1.20 g / cc.

The particle size distribution force expressed in mesh size.

# 60 / # 170 force S approximately 60% force approximately 65%,

# 170 / # 325 About 30% force About 35% force

# 325 / # 400 force 4% force 6%,

# 400 force S 0. 5 ^_0/0 Power et al. 1.5%

Tantalum powder.

Tantalum powder, compressed density 4.5g / cm ³ , sintering temperature 1150 ° C, sintering at 10 minutes, formation temperature 60 ° C, formation potential 10V into anode electrode, electric capacity is CV A tantalum powder with a value of about 185,000 μFV / g force, about 250000 μFV / g, and a leakage current force of less than 10ηΑ / μFV.