KR101510369B1 - Process for producing copper powder and copper powder - Google Patents

Abstract

A copper powder having a narrow particle size distribution width and suppressing the content of impurities, and a copper powder obtained by the method, which have high conductivity and high homogeneity. In order to accomplish this object, a hydrazine reducing agent is added to a slurry of the same salt compound obtained by adding an alkali solution to a copper salt aqueous solution to prepare a slurry of hydrous copper halide, Wherein the hydrazine-based reducing agent is added to the slurry obtained by slurrying the washed copper oxide slurry again so that the molar ratio of phosphorus to phosphorus becomes P / Cu = 0.0001 to 0.003 until the final reduction reaction is completed, A phosphorus compound is added to the reaction slurry, and the like.

Description

PROCESS FOR PRODUCING COPPER POWDER AND COPPER POWDER [0002]

The present invention relates to a process for producing copper powder by a wet process, and more particularly to a process for producing copper powder by a two-stage reduction process using a copper salt aqueous solution as a starting solution, And to a copper powder to be obtained.

Copper powder has been widely used as a raw material for copper paste or copper ink. For example, the copper paste is formed by appropriately blending a resin component into copper powder composed of minute particles having a particle diameter of several micrometers, and is applied to circuit formation of a printed wiring board using a screen printing method, various electric contact parts, etc., (Solidified) so as to exhibit conductivity as a conductor film.

Along with the miniaturization of printed wiring boards and the like, the copper powder has been required more and more in the market in terms of conductivity, reliability, etc. of a circuit formed by the copper paste. For example, in the case of the fine wiring, slight fluctuations related to the electrical characteristics may affect the product, and therefore, the electrical stability of the conductive filler is required to be high. In addition, in order to finely line the fine wiring, a conductive filler that is fine is required. However, since the copper powder has a higher surface energy and is more likely to coagulate as it becomes fine, the particle size distribution becomes wider and it is difficult to obtain fine and uniform copper powder. Therefore, copper powder of a fine and uniform size is required.

Further, at the time of forming a conductor, carbonaceous gas is generated at a high-temperature sintering due to the carbon component contained in the copper powder particles, and the conductor becomes uneven, thereby obstructing formation of a stable conductor. Specifically, when copper powder containing a large amount of carbon in the inside of the powder particles is used for the material of the copper paste, carbon dioxide gas is generated inside the sintered film formed at the time of high-temperature firing. This carbon dioxide gas tends to cause cracks on the surface of the sintered film or internal defects of the conductor. As described above, copper powder containing carbon and other impurities fluctuates in electric characteristics such as resistance value and the like. For this reason, there is a demand for a copper powder having a high purity with a minimum of impurities.

As an example of a method for producing copper powder, Patent Document 1 discloses a flake copper powder controlled to have a good particle diameter by a wet reduction method. Patent Document 2 discloses a copper paste composition for external electrodes using copper powder having a phosphorus content of 0.01 to 0.10 mass% and an oxygen content of 0.30 mass% or less. Patent Document 2 discloses a spherical copper powder used for a copper paste composition for external electrodes having an average particle diameter of 1 to 4 탆 and an organic vehicle is used for obtaining an appropriate viscosity and application property for the external electrode copper paste composition . On the other hand, it is described that the method of producing copper powder disclosed in Patent Document 2 is not particularly limited such as wet reduction method and dry method, and is preferably obtained by water atomization.

Patent Document 1: Japanese Patent Application Laid-Open No. 2005-314755 Patent Document 2: Japanese Patent Application Laid-Open No. 2005-222737 Patent Document 3: Japanese Patent Application Laid-Open No. 2005-314755 Patent Document 4: Japanese Patent No. 3570591

With respect to the demand for copper powder which is fine, homogeneous and low-impurity, the copper powder produced by the spraying method can produce copper powder having a low carbon content and excellent in dispersibility, but since it contains coarse particles It is not suitable for fine wiring and the like, and tends to contain other impurities. Further, if the classification is strengthened in order to eliminate coarse particles, there is a problem that the manufacturing cost is increased due to prolonged production or deterioration of the yield.

On the other hand, in the copper powder by the wet reduction method of the related art, the primary particles themselves tend to be fine and homogeneous, but in view of reactivity, organic-based reducing agents are often used (see, for example, Patent Document 3). As a result, the amount of organic adsorbed in the copper powder increases, so that the content of carbon tends to increase.

In addition, in the case of the wet reduction method using an inorganic reducing agent (for example, Patent Document 4), the above problem on the carbon content is solved, but aggregation tends to occur, and the particle size of the obtained copper powder is broad .

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a copper powder having a very narrow particle size distribution and a small content of impurities and having high conductivity and high homogeneity, and a copper powder capable of obtaining such copper powder with high product yield And a method for producing the same.

The inventors of the present invention have conducted extensive research and have obtained copper powder for achieving the above-mentioned problems by employing the following copper powder production method using a wet reduction method.

Method for producing copper powder: A method for producing copper powder according to the present invention is characterized in that a hydrazine-based reducing agent is added to a slurry of the same salt compound obtained by adding an alkali solution to an aqueous solution of the same salt to prepare a hydrous slurry, And a hydrazine reducing agent is added to the re-slurried cleaned hydrous copper slurry, wherein the molar ratio of phosphorus to copper is in the range of from 0.0001 to 0.15% until the final reduction reaction is completed, 0.003, based on the total weight of the reaction slurry.

Further, in the copper powder production method according to the present invention, it is preferable that the copper concentration of the above-mentioned equivalent salt compound slurry is 1 mol / L to 3 mol / L.

In the method for producing copper powder according to the present invention, it is preferable that the alkali solution is an aqueous ammonia solution.

In the method for producing copper powder according to the present invention, it is preferable to add a hydrazine reducing agent to the above-mentioned equivalent salt compound slurry and adjust the pH to 3.5 to 6.0 when the reduction reaction is carried out.

In the method for producing copper powder according to the present invention, it is preferable that a hydrazine-based reducing agent is added to the above-mentioned equivalent salt compound slurry and pH adjustment is carried out with an aqueous ammonia solution at the time of performing the reduction reaction.

In the method for producing a copper powder according to the present invention, it is preferable to adjust the pH of the slurry prior to addition of the hydrazine reducing agent to 4.1 to 6.0 in the cleaning slurry.

Copper powder according to the present invention: The copper powder according to the present invention is a copper powder obtained by the copper powder production method, and has a volume cumulative average particle diameter D ₅₀ of 0.1 μm to 5.0 μm according to a laser diffraction scattering type particle size distribution measurement method , A standard deviation SD of particle size distribution measured by a laser diffraction scattering particle size distribution measurement method, and a value of SD / D ₅₀ expressed by using the volume cumulative average particle diameter D ₅₀ of 0.2 to 0.5.

The copper powder according to the present invention preferably has a carbon content of less than 0.01 mass% after heat treatment at 400 占 폚 for 30 minutes in an atmospheric environment.

The copper powder manufacturing method according to the present invention can produce a copper powder having a very narrow particle size distribution while minimizing the inclusion of impurities. The copper powder according to the present invention is obtained by the above production method.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the relationship between the amount of phosphorus compound added and the particle size distribution width in the process for producing copper powder according to the present invention. Fig.
Fig. 2 is a particle size standard distribution diagram of copper powder obtained in Example 1. Fig.
3 is an SEM photograph of the copper powder obtained in Example 1. Fig.
4 is a particle size standard distribution diagram of copper powder obtained in Example 2. Fig.
5 is an SEM photograph of copper powder obtained in Example 2. Fig.
6 is a particle size standard distribution chart of copper powder obtained in Comparative Example 2. Fig.
7 is a particle size standard distribution chart of copper powder obtained in Comparative Example 3. Fig.
8 is an SEM photograph of copper powder obtained in Comparative Example 3. Fig.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing copper powder according to the present invention and a preferred embodiment of the powder will be described.

Process for Producing Copper Powder: First, the outline of the process as a premise of the process for producing copper powder according to the present invention will be described. First, an alkaline solution is added to the aqueous solution of the same salt to obtain a slurry of the same salt. A hydrazine reducing agent is added to the slurry of the same salt compound to obtain a slurry of hydrous copper oxide (first reduction treatment). Subsequently, the copper oxide slurry is washed with water and re-slurried to obtain a slurry for cleaning copper oxide, and a hydrazine-based reducing agent is added to the washed copper oxide slurry again (second reducing treatment) to reduce and precipitate the copper powder, .

In the method for producing copper powder according to the present invention, a phosphorus compound is added to the reaction slurry in a molar ratio of P / Cu = 0.0001 to 0.003 until the completion of the final reduction reaction in the step . That is, in the above method, by adding a very small amount of phosphorus component to the copper, it is possible to suppress coagulation in the growth process of the precipitated particles, and to produce copper powder of high quality with a narrow particle size distribution width and low impurity . Hereinafter, a method for producing the copper powder will be described in detail.

First, an alkali solution is added to an aqueous solution of the same salt to react with the same salt to produce a corresponding salt salt, which is obtained as a salt salt of the same salt. For example, an alkali solution is slowly added to an aqueous solution of the same salt over a period of 30 minutes, and then the mixture is allowed to stand for 30 minutes to be aged, thereby reacting with the same salt to obtain a divalent copper compound.

Here, the aqueous solution of the same salt is obtained by partially dissolving water with a water-soluble copper salt. Examples of the water-soluble copper salt include copper sulfate, nitrate copper, copper acetate, and copper chloride, among which copper sulfate and nitrate are preferable. Examples of the alkali solution include an aqueous ammonia solution, potassium hydroxide, sodium hydroxide and the like. Particularly, the use of an aqueous ammonia solution is preferable in that impurities are excluded and copper powder of high purity can be obtained.

The copper concentration of the slurry of the same salt is preferably 1 mol / L to 3 mol / L. If the copper concentration of the slurry of the same salt is less than 1 mol / L, the effect of improving the production efficiency can not be obtained as compared with the conventional one. On the other hand, if the copper concentration of the same salt compound slurry exceeds 3 mol / L, coagulation tends to occur, and it is difficult to control the particle size distribution, so that the production stability can not be expected. More preferably, the copper concentration of the flame-retardant compound slurry is 1.5 to 2.5 mol / L.

The amount of the alkali solution required to obtain the neutralized product as the neutralized product is taken into account and the relationship with the pH in subsequent steps is taken into consideration. For example, when an aqueous ammonia solution is used as the alkali solution, the amount of the aqueous ammonia solution added is 1.0 mol to 3.8 mol of the ammonia component with respect to 1 mol of copper. If the ammonia component is out of this range, it becomes difficult to control the pH to a proper range in the subsequent reduction process.

In the method for producing copper powder according to the present invention, it is preferable to adjust the liquid amount so that the copper concentration of the same salt compound slurry is relatively high. In the conventional wet reduction method, when the copper concentration of the copper salt compound slurry prior to reduction is increased, aggregation of precipitated particles tends to occur, and copper powder having a narrow particle size distribution width can not be efficiently produced. However, in the method for producing copper powder according to the present invention, by adjusting the pH fluctuation range and the mixing conditions of the materials to be used in various manners, the copper concentration of the same salt slurry before the reduction reaction falls within the above- A narrow copper powder can be obtained.

Next, a hydrazine-based reducing agent is added to the above-mentioned equivalent salt compound slurry to obtain a hydrous slurry (first reduction). In the method for producing copper powder according to the present invention, the addition amount of the hydrazine reducing agent is adjusted to such an extent that the same salt compound is reduced to copper oxyhydroxide to obtain a copper oxyhydroxide slurry. That is, the first reducing treatment is used to produce a slurry of hydrous copper, stabilizes the reaction during the subsequent second reducing treatment, and uniformizes the particles to be subjected to reduction precipitation.

When the hydrazine-based reducing agent is used in the first reduction treatment, the possibility of the reducing agent component remaining on the surface of the hydrogel particles is low, and thus it is difficult to become a contaminant.

As the hydrazine-based reducing agent, hydrazine hydrate, hydrazine sulfate, anhydrous hydrazine and the like can be considered, but hydrazine hydrate is most preferable. These hydrazine-based reducing agents can be used singly or in combination. The hydrazine-based reducing agent is preferably used for the reaction in a solution state in order to quickly diffuse into the solution of the reaction system to obtain a homogeneous reaction.

The addition amount of the hydrazine reducing agent is preferably 0.3 mol to 0.5 mol relative to 1 mol of copper in the slurry of the same salt. When the addition amount of the hydrazine reducing agent is less than 0.3 mol with respect to 1 mol of copper, the unreacted coin salt compound remains in a large amount, which is not preferable. On the other hand, if the addition amount of the hydrazine reducing agent is more than 0.5 mol relative to 1 mol of copper, the reduction reaction can not be stopped in the step of suboxidation.

On the other hand, a hydrazine reducing agent is added to the slurry of the same salt compound to adjust the pH to 3.5 to 6.0 when the reduction reaction is carried out. If the solution pH is out of the above range, the deviation of particle diameters of the obtained copper oxyhydroxide particles becomes large, and the particle size distribution width of copper powder particles as a final product is widened.

In the first reduction treatment from the slurry of the same salt compound as the hydrous slurry, it is preferable to carry out a reduction treatment while adding a hydrazine reducing agent and controlling the pH fluctuation using an ammonia aqueous solution as a pH adjuster. The use of an ammonia aqueous solution as the pH adjuster is considered as follows. Considering that neutralization is carried out using ammonia as an alkali solution at the time of producing the slurried salt of the same salt, the use of the same materials is avoided as far as possible So as to exclude residual impurities as much as possible. As a result, purity control of the obtained copper powder is facilitated.

In the first reduction treatment described above, the hydrazine reducing agent is added continuously at a ratio of 0.3 mol to 0.5 mol and an aqueous ammonia solution (as ammonia) at a ratio of 0.2 mol to 0.4 mol at the end of the addition to 1 mol of copper in the same salt salt slurry . The pH of the reaction slurry added in this manner may be adjusted so that the difference between the starting point pH at the start of addition of the reducing agent and the pH adjuster and the end point pH at the end of the addition is 3.0 or less.

Herein, the hydrous slurry refers to a slurry containing copper oxide, and may contain components other than hydrolysis. This also applies to the cleaning slurry which will be described later.

When the pH of the obtained hydrous copper slurry is in the range of 3.5 to 6.0, the pH fluctuation of the reaction slurry can be suppressed within a preferable range in the subsequent steps. As a result, the grain size of the obtained copper powder can be made uniform. If the copper oxyhydroxide slurry is made more alkaline than pH 6.0, the copper component in the copper oxyhydroxide slurry does not stop in the copper oxyhydroxide, but forms a metal and agglomerates. On the other hand, when the copper oxyhydroxide slurry is made to the acidic side rather than the pH 3.5, the reduction of the suboxide is insufficient and the production efficiency is lowered.

The temperature of the reaction slurry during the first reduction treatment is preferably in the range of 40 占 폚 to 60 占 폚. At a temperature lower than 40 ° C, the reduction reaction rate is too slow to satisfy industrial productivity. On the other hand, if the temperature of the reaction slurry exceeds 60 캜, the reduction rate becomes too fast and a non-uniform reduction reaction occurs, so that powder characteristics of the obtained copper powder are deteriorated.

Subsequently, the slurry of hydrous copper oxide is washed with water and re-slurried to obtain a cleaning slurry. First, the agar slurry is allowed to settle to precipitate the agar agar particles. After the sedimentation of the granules of hydrous ascorbic acid, the supernatant liquid is removed and water is added to the granitic particles, and the resuspended particles are re-slurried to prepare a cleaning granular slurry. When the pH of the cleaning slurry is 4.1 to 6.0, the pH fluctuation in subsequent steps can be suppressed to a desirable range, and the particle size of the obtained copper powder can be made uniform with high precision.

There is no particular limitation on the cleaning method of copper oxide particles, and a known cleaning method can be employed. However, it is preferable to employ the following repulp cleaning to control the cleaning level to the pH value of the hydrous copper slurry during cleaning. The repulp cleaning is carried out a plurality of times by sedimenting the ascorbic acid, discarding the supernatant, and adding the washing water. It is preferable that the repulp cleaning be repeatedly carried out until the pH of the cleaned hydrous slurry to which the washing water is added is a constant pH value in the range of 4.1 to 6.0. If the pH of the cleaning slurry is on the acid side than 4.1, the reduction efficiency is poor. On the other hand, if the pH of the cleaning slurry is higher than 6.0 on the alkaline side, then there is a large variation in reaction when the reducing agent is added to obtain copper powder and poor dispersibility.

More preferably, the cleaning hydrogel slurry is washed until a certain pH in the range of pH 4.3 to 4.7 is reached. By setting the pH of the cleaning slurry to within this range, the process stability is the most excellent.

A hydrazine-based reducing agent is added to the thus-prepared washed hydrous slurry to reduce and precipitate the copper powder (second reduction treatment). Then, the precipitated particles are filtered, washed and dried to obtain a copper powder. It is preferable that the amount of the hydrazine reducing agent to be added is added at a ratio of 0.3 mol to 1.5 mol relative to 1 mol of copper contained in the cleaning copper oxide slurry at the end of the addition. The hydrazine type reducing agent to be added to the slurry of the same salt compound and the hydrazine type reducing agent to be added to the washing acid hydrolyzate slurry are added together in a ratio of 0.6 to 2.0 mol based on 1 mol of copper.

It is preferable to adjust the pH of the slurry immediately before the reduction reaction by the addition of the hydrazine reducing agent to the range of 4.1 to 6.0. If the pH during the reduction reaction is more acidic than 4.1, the coarse particles increase and the dispersibility deteriorates. On the other hand, when the pH at the reduction reaction is on the alkaline side than 6.0, the amount of the reducing agent increases and the number of the fine precipitated particles becomes excessively large.

On the other hand, in the same manner as in the case of adding the hydrazine-based reducing agent to the slurry of the same salt compound (the first reducing treatment), the copper concentration of the washing acid hydrolyzate slurry before the addition of the hydrazine reducing agent (second reducing treatment) is changed from 1 mol / L to 3 mol / L, copper powder having a narrow particle size distribution width can be obtained. On the other hand, the more preferable copper concentration is 1.5 mol / L to 2.5 mol / L.

The temperature of the hydrazine-based reducing agent to be added is preferably maintained at a constant temperature in the range of 40 ° C to 60 ° C. If the temperature of the hydrazine-based reducing agent is lower than 40 ° C, the reduction reaction becomes dull and the industrially desirable productivity is not satisfied. On the other hand, if the temperature of the hydrazine-based reducing agent is higher than 60 ° C, the reduction reaction becomes too fast and the particle size tends to become uneven.

Since the reducing agent used in the first reducing treatment and the second reducing treatment is a homogeneous hydrazine reducing agent, the reducing ability of the hydrazine as a reducing agent is suitable for obtaining a copper powder having good powder characteristics. In addition to this, it is possible to reduce the different kinds of components used for reduction of the copper powder as much as possible, and to suppress the incorporation of impurities into the particle surface of the copper powder.

On the other hand, while the reaction slurry in the stage where the second reducing treatment is finished, particles are collided with each other in a slurry which is centrifugally flowing at a high speed by using a fluid milling method (fine roll mill) or a laminar flow mixing method (TK FILMICS etc.) It is also preferable to carry out a disintegration treatment for disintegrating the particles to bring them closer to the primary particles and at the same time smoothing the surface of the particles, thereby further improving the particle dispersibility.

Addition of phosphorus compound: The method of producing copper powder according to the present invention is characterized in that in the above-mentioned production method, a compound having phosphorus and copper molar ratio of P / Cu = 0.0001 to 0.003 is added until the final reduction reaction is completed, . ≪ / RTI > By adding the phosphorus compound, the phosphorus compound acts as a steric hindrance to prevent coagulation and growth of the precipitated particles, and it is possible to achieve monodispersion. As a result, the particle size distribution of the obtained copper powder can be remarkably narrowed.

Phosphorus compounds are added in very small amounts, with the molar ratio of phosphorus in the reaction slurry being P / Cu = 0.0001 to 0.003. In order to obtain a high-purity copper powder by suppressing the impurity content, it is necessary to minimize the amount and kind of the additive material in the production process. However, since atomization tends to cause aggregation, it is effective to add a phosphorus compound in order to obtain a copper powder having a fine particle size and a very narrow particle size distribution width. The inventors of the present invention have studied to minimize the addition amount of the phosphorus compound and found that it is most effective to add the phosphorus compound at the above ratio.

Here, FIG. 1 shows the correlation between the addition ratio of the phosphorus compound and the particle size distribution width. In the graph of Fig. 1, P / Cu representing the addition ratio of the phosphorus compound was taken on the axis of abscissa, and the cumulative mean particle diameter D ₅₀ and the laser diffraction scattering particle size distribution measurement method And the SD / D ₅₀ value, which is expressed by using the standard deviation SD of the particle size distribution measured by the standard deviation SD.

Here, the standard deviation SD is an index showing the deviation of total grain diameter data obtained by the laser diffraction scattering type grain size distribution measurement method. The larger the value is, the larger the deviation is. The degree of the particle size distribution width is represented by SD / D ₅₀ , which is the ratio of the standard deviation SD to the volume cumulative average particle diameter D ₅₀ . The larger the value, the larger the particle size distribution width.

1, in the case of phosphorus added (P / Cu = 0), in the case of the phosphorus addition amount of less than P / Cu = 0.0001, the value of SD / D ₅₀ is more than 0.55, The effect of monodispersion by the above-mentioned method can not be sufficiently obtained. On the other hand, when the phosphorus addition ratio is set to P / Cu = 0.0001 or more, the value of SD / D ₅₀ remarkably decreases. Further, even when phosphorus in an amount exceeding P / Cu = 0.003, which is the upper limit of the present invention, is added, there is no change in the value of SD / D ₅₀ . Originally, the object of the present invention is to obtain a high-purity copper powder in which the content of impurities is suppressed, so that the amount of phosphorus to be added is minimized. Therefore, the upper limit of the addition amount of phosphorus is set to P / Cu = 0.003.

The addition time of the phosphorus compound may be determined by adding a hydrazine reducing agent to the cleansing copper oxide slurry and adding the phosphorus compound at any stage until the reduction reaction is completed. Particularly, since the cleaning slurry is added after the cleaning slurry, the amount of the phosphorus compound can be suppressed to a small amount, which is preferable in terms of suppressing the impurity content.

The phosphorus compound is preferably a water-soluble compound in order to efficiently disperse the phosphorus component in the reaction slurry. As the water-soluble phosphorus compound, any of sodium phosphate, phosphoric acid and ammonium hypophosphite is preferably used. Particularly, when ammonium hypophosphite is used, it is suitable for precipitation of fine particles having a uniform particle diameter.

The copper powder thus obtained is converted into a copper powder by a general process such as filtration, washing and drying. The copper powder is preferably subjected to an organic surface treatment in order to improve oxidation resistance. As the surface treatment agent, it is preferable to include any of fatty acids or amines if necessary, and specifically, fatty acids such as oleic acid and stearic acid, and amines such as octadecylamine and oleylamine are preferable. In addition, even in the dried copper powder state, if necessary, the granulation treatment, the hybridizer, and the turbo classifier can be used to perform collision treatment of the particles, Can be improved.

Copper powder according to the present invention: The copper powder according to the present invention is copper powder obtained by the above copper powder production method. The volume cumulative average particle diameter D ₅₀ measured by the laser diffraction scattering particle size distribution measurement method is 0.1 탆 to 5.0 탆, and the SD / D ₅₀ value indicating the width of the particle size distribution width is 0.2 to 0.5. In other words, by using the copper powder production method, it is possible to manufacture copper powder having a D ₅₀ = 0.1 μm to 5.0 μm size in a state that the particle size distribution width of the SD / D ₅₀ value is 0.2 to 0.5.

In the copper powder according to the present invention, if D ₅₀ is less than 0.1 탆, coagulation accompanying atomization occurs. On the other hand, if the addition amount of the phosphorus compound is increased in order to suppress aggregation, the object of the present invention can not be achieved that the amount of impurities is low enough not to cause defective conduction in the fine wiring formation circuit. On the other hand, when the D ₅₀ is higher than 5.0 탆, it is not suitable for formation of fine wiring. On the other hand, a more preferable average particle diameter D ₅₀ is 0.5 to 3.5 탆.

The copper powder according to the present invention generally has a grain size in the range of fine grains having a D ₅₀ of 0.1 탆 to 5.0 탆 and a grain size distribution width of SD / D ₅₀ = 0.2 to 0.5, It is a sharp copper powder. As described above, SD / D ₅₀ represents the degree of particle size distribution width of copper powder. When the value of SD / D ₅₀ is in the range of 0.2 to 0.5, the aggregation is small. When the value of SD / D ₅₀ is more than 0.5, the deviation of the particles is large, which is not suitable for forming the fine wiring.

The copper powder according to the present invention has a carbon content of less than 0.01 mass% after heat treatment at 400 占 폚 for 30 minutes in an atmospheric environment, and has a very low carbon content. Here, the copper powder according to the present invention is subjected to an organic surface treatment for preventing oxidation, but this surface treatment agent disappears from the surface of the copper powder at a temperature of about 200 to 300 캜. Therefore, the copper powder after firing at 400 ° C for 30 minutes is in a state where the surface treating agent is removed, and the carbon content of the copper powder measured in this state is estimated by estimating the carbon content of the copper powder under the temperature at which the conductor film is formed by firing You can. On the other hand, the carbon content of the copper powder in the present specification was measured using a carbon analyzer (EMIA-320V manufactured by Horiba Ltd.).

When the copper powder according to the present invention is used for copper paste or the like, the surface treatment agent disappears before the sintering start temperature of the conductor surface at the time of firing the copper paste, and after the sintered film is formed on the surface of the copper body, It is possible to prevent the occurrence of cracks on the surface of the conductor and to form a conductor of high quality.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. The present invention is not limited to the following examples. On the other hand, the manufacturing conditions of the copper powders of the following examples and comparative example 2 are shown in Table 1 for easy comparison.

   Note) Reducing agent: hydrazine monohydrate

       pH adjuster: aqueous ammonia solution of 25 wt%

Example  One

First, 6.5 L of pure water was added to 6,000 g of copper sulfate, and the mixture was stirred. Thereafter, water was further added to adjust the concentration of the copper sulfate solution (equivalent salt solution) to 9 L while maintaining the solution temperature at 50 캜. To the aqueous solution of copper sulfate was added 2537 ml of an aqueous ammonia solution (concentration 25 wt%) over 30 minutes to neutralize the solution to obtain a slurry of the same salt compound. Then, the same salt compound slurry was allowed to stand for 30 minutes and aged. Up to this point, the liquid temperature of the slurry of the same salt was maintained at 50 캜, but after aging, the liquid temperature was adjusted to 45 캜.

Next, water was added to adjust the amount of the solution so that the copper concentration of the slurry of the same salt was 2.0 mol / L. 450 g of hydrazine monohydrate (hydrazine type reducing agent) and 591 ml of an aqueous ammonia solution (concentration 25% by weight) as a pH adjusting agent were continuously added thereto over a period of 30 minutes, (First reduction treatment). Then, in order to complete the reduction reaction, stirring was continued for another 30 minutes.

Thereafter, purified water was added to the hydrous slurry for the repulp cleaning, and the amount of the solution was adjusted to 18 L, and the solution was allowed to settle to precipitate the hydrous copper oxide particles. The pH of the supernatant liquid after discarding was 14 L until the pH reached 4.7. Then, 8 L of pure warm water was added to adjust the total liquid volume to 12 L, while maintaining the liquid temperature at 45 캜 while adjusting the copper concentration to 2.Omol / L, thereby obtaining a cleaned hydrous slurry.

To the cleaned hydrous copper slurry after adjusting the copper concentration, 3.02 g of ammonium hypophosphite was added and stirred for 5 minutes (phosphorus compound addition step).

Again, water was added to adjust the amount of the solution so that the copper concentration of the washed copper oxide slurry became 2.Omol / L. 1200 g of hydrazine monohydrate (hydrazine-based reducing agent) was added to the cleaning slurry of copper nitrate over 30 minutes. Subsequently, the mixture was further stirred for 15 minutes to complete the reduction reaction, and the copper powder was subjected to reduction precipitation (second reduction treatment).

The precipitated copper particles were collected by filtration. After washing, the copper powder was placed in 5 L of a methanol solution in which 1.5 g of octadecylamine had been dissolved to carry out an organic surface treatment. After separation by filtration, the copper powder was heat-dried at 70 DEG C for 5 hours and then subjected to a crushing treatment To obtain copper powder.

D ₁₀ , D ₅₀ , D ₉₀ , BET specific surface area, tap filling density, and carbon content were measured for the copper powder obtained in Example 1. The specific surface area D _BET was calculated based on the BET specific surface area of the obtained copper powder. The carbon content after the organic powder-treated copper powder obtained in Example 1 was calcined at 400 占 폚 for 30 minutes in an air atmosphere was measured. The results are shown in Table 2. Fig. 2 shows a particle size standard distribution chart, and Fig. 3 shows a scanning electron microscope (SEM) photograph. Each measurement method will be described below.

Volume cumulative average particle size D ₅₀ according to laser diffraction scattering particle size distribution measurement method: 0.1 g of copper powder was mixed with 0.1% aqueous solution of SN DIS DISC 5468 (manufactured by SAN NOPCO) and ultrasonic homogenizer (US- 300T) for 5 minutes and then measured at a flow rate of 50 cm3 / min using a laser diffraction scattering particle size distribution analyzer Micro Trac HRA 9320-X100 (manufactured by Leeds + Northrup). The particle diameters at the volume cumulative 50% were D ₅₀ , and the particle diameters D ₁₀ and D ₉₀ of the volume cumulative 10% and 90% were measured in the same manner.

Tap filling density (TD): Measured using Powder Tester PT-E (Hosokawa Micron Co., Ltd.).

Specific surface area: 2.OOg of the sample was degassed at 75 占 폚 for 10 minutes, and then measured by the BET one-point method using Monosorb (manufactured by Quanta Crrome). The specific surface area D _BET is calculated by the formula D _BET = 6 / (8.92 × SSA (2)) using the specific surface area SSA measured by the BET one point method and the true specific gravity 8.92 assuming the obtained copper powder as a true sphere ).

Carbon content: The carbon content after holding at 400 占 폚 for 30 minutes was measured using a carbon analyzer (EMIA-320V manufactured by Horiba Ltd.).

Example  2

Example 2 is different from Example 1 in the addition timing of the phosphorus compound.

That is, instead of adding ammonium hypophosphite to the slurry for cleaning copper oxide, 11.06 g of trisodium phosphate dodecahydrate was added as a phosphorus compound while maintaining the liquid temperature of the aqueous solution of copper sulfate at 50 占 폚, ≪ / RTI >

The same data as in Example 1 was measured and calculated for the copper powder obtained in Example 2. The results are shown in Table 2. Fig. 4 shows a volume-based particle size distribution chart, and Fig. 5 shows a scanning electron microscope (SEM) photograph.

Comparative Example

[Comparative Example 1]

Comparative Example 1 is an example in which an organic reducing agent is used in the production of copper powder by a wet reduction method.

First, 400 g of copper sulfate pentahydrate is added to 3 L of pure water at 60 캜, and a solution of a copper salt aqueous solution containing divalent copper ions is prepared. Then, pure water was added to the aqueous solution of the same salt maintained at a temperature of 60 占 폚 to make the copper concentration 2 mol / L.

Then, 460 ml of a 25% sodium hydroxide aqueous solution was added in this order while maintaining the liquid temperature of the aqueous solution of the same salt at 60 캜 to obtain a slurry of the same salt compound.

Subsequently, 100 g of hydrazine monohydrate was added over 30 minutes while maintaining the liquid temperature of the slurry of the same salt as 50 占 폚. The mixture was further stirred for 60 minutes to completely conduct the reduction reaction, and the copper powder was reduced and precipitated.

The copper powder thus obtained was collected by filtration. Then, the copper powder was put into 5 L of a methanol solution in which 1.5 g of octadecylamine had been dissolved to carry out an organic surface treatment, stirred for 30 minutes, and dried by heating at 80 DEG C for 5 hours to obtain a powder. The same data as in Example 1 was measured for the powder characteristics of the obtained copper powder. As a result, the particle size distribution was sharp, but the carbon content after baking at 400 DEG C for 30 minutes was 0.07 wt%.

[Comparative Example 2]

Comparative Example 2 is an example in which no phosphorus compound is added during the production of the copper powder by the wet reduction method. That is, copper powder was obtained in the same manner as in Example 1 except that no phosphorus compound was added at all. The same data as in Example 1 was measured and calculated for the powder characteristics of the obtained copper powder. The results are shown in Table 2. 6 shows a volume-based particle size distribution chart of the copper powder obtained in Comparative Example 2. Fig.

[Comparative Example 3]

Comparative Example 3 is an example in which the concentration of the copper-containing solution is adjusted to the same concentration as that of the same salt-containing slurry of Example 1 using the method disclosed in Patent Document 4. First, 395 g of copper sulfate pentahydrate and 0.05 L of pure water were mixed, and 40 g of sodium pyrophosphate was added to prepare a copper-containing solution. Subsequently, 500 g of concentrated ammonia water (concentration: 28%) was added to the copper-containing solution and mixed to prepare a copper ion complex ion solution. Pure water was added to the copper ammonium ion complex solution to adjust the total liquid volume to 0.79 L and the same concentration as in Example 1. 200 g of hydrazine hydrate as a reducing agent was added and stirred at a temperature of 30 캜 to the monoammonium complex ion solution, and the temperature was raised to 80 캜 for 2 hours to allow the reaction to proceed sufficiently. Thereafter, copper powder obtained as metal copper was recovered from the solution and washed.

On the other hand, as described above, in Comparative Example 3, sodium pyrophosphate, which is a phosphorus compound, is added during the production of the copper-containing solution, and then the reduction reaction is performed. The same data as in Example 1 was measured and calculated for the powder characteristics of the obtained copper powder. The results are shown in Table 2. The volume-based particle size distribution of copper powder obtained in Comparative Example 3 is shown in Fig. 7, and a scanning electron microscope (SEM) photograph is shown in Fig.

* The carbon content is the carbon content of the powder after firing at 400 ° C for 30 minutes

Hereinafter, copper powder obtained in Examples and copper powder obtained in Comparative Examples are prepared.

First of all, according to the embodiment, the particle size reference distribution chart of Fig. 2 shows a sharp distribution because the particle size distribution width is narrowed with a particle diameter of 1 mu m as the frequency peak. This is also seen from the fact that the values of SD / D ₅₀ and D ₉₀ / D ₁₀ are low. The tap filling density (TD) showed a low value. In addition, the yield was as high as 96%. The carbon content after baking at 400 占 폚 for 30 minutes in an atmospheric atmosphere was not less than 0.01 wt% since it did not reach the lower limit of 0.01 wt% that can be detected by the measuring apparatus.

Next, the carbon contents of Examples 1 and 2 and Comparative Example 1 are less than 0.01 wt%, whereas the carbon content of Comparative Example 1 is 0.07 wt%. The copper powder of Comparative Example 1 using the organic reducing agent exhibits a value greatly exceeding the carbon content of the copper powder according to the present invention. The copper powder having such a carbon content level is a fine particle which is a problem of the present invention, And it is difficult to improve the conductivity.

Subsequently, in comparison with Example 2 and Comparative Example 2, the average particle diameter and the carbon content are equivalent. However, SD / D ₅₀ and D ₉₀ / D ₁₀ are remarkably low in the examples, and SD / D ₅₀ shows a remarkable difference of about 30%. It is clear that the particle size distribution width of the examples is narrow.

In the copper powder obtained in Comparative Example 3, a scanning electron microscope (SEM) photograph of the copper powder shown in Fig. 8 shows that a lot of aggregation occurred. In addition, the average diameter of the primary particles obtained by the image analysis of a scanning electron micrograph shown in Figure 8 is but 2㎛ degree and agglomeration violently, as a result, D ₅₀ = 34.68㎛ degree. Further, although the SD / D ₅₀ is low, as described above, the size of the agglomerated particles is much larger than that of the examples, and therefore it is difficult to say that the particle size distribution as the fine-grained copper powder is shown. Therefore, a large amount of coarse particles are contained, which is unsuitable for forming a fine wiring. In addition, it can be seen that the yield is also lower than that in Examples. That is, it was difficult to produce a fine-particle copper powder having a sharp particle size distribution with a high yield by the method of Comparative Example 3.

The copper powder manufacturing method according to the present invention can make the particles homogenized and produce a copper powder having less impurities than the conventional product. When the obtained copper powder is used as a conductor forming material by a screen printing method, it is possible to prevent defective formation of fine wirings and to form a conductor with excellent electrical stability. Therefore, the copper powder according to the present invention is suitable for forming a fine wiring.

Claims (9)

A hydrazine reducing agent is added to a slurry of the same salt compound obtained by adding an alkaline solution to an aqueous solution of copper salt to prepare a slurry for hydrothermal activity. The hydrous slurry of the hydrothermal slurry is washed with water, and a re-slurried cleansing slurry (Copper powder) to which a hydrazine reducing agent is added,
The washing is carried out by standing the hydrous copper slurry and precipitating the hydrous copper hydroxides, then removing the supernatant, and adding water to wash the hydrous copper hydroxides,
Wherein a phosphorus compound is added to the reaction slurry so that phosphorus and copper molar ratio become P / Cu = 0.0001 to 0.003 at any stage until the final reduction reaction is completed. The method according to claim 1,
Wherein the copper concentration of said flame-resistant compound slurry is from 1 mol / L to 3 mol / L. 3. The method according to claim 1 or 2,
Wherein the alkali solution is an aqueous ammonia solution. 3. The method according to claim 1 or 2,
Wherein a hydrazine reducing agent is added to the slurry of the same salt to adjust the pH to 3.5 to 6.0 when the reduction reaction is carried out. 5. The method of claim 4,
Wherein a hydrazine reducing agent is added to the slurry of the same salt to effect a reduction reaction with an aqueous ammonia solution. 3. The method according to claim 1 or 2,
Wherein the pH of the slurry before adding the hydrazine reducing agent to the cleansing copper oxide slurry is adjusted to 4.1 to 6.0. A copper powder obtained by the copper powder production method according to any one of claims 1 to 3,
A volume cumulative average particle diameter D ₅₀ determined by a laser diffraction scattering type particle size distribution measurement method is 0.1 탆 to 5.0 탆,
Wherein the value of SD / D ₅₀ expressed by using the standard deviation SD of the particle size distribution measured by the laser diffraction scattering particle size distribution measurement method and the volume cumulative average particle diameter D ₅₀ is 0.2 to 0.5. 8. The method of claim 7,
Copper powder having a carbon content of less than 0.01% by mass after heat treatment at 400 占 폚 for 30 minutes in an air atmosphere. The method according to claim 1,
Wherein the reaction slurry is a cleaned hydrous copper slurry.

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