JP2011174144A - Fine powder of copper and method for producing the same - Google Patents

Abstract

A copper fine powder having an average particle size of 1.0 to 3.0 μm and a sharp particle size distribution and a method for producing the same are provided.
A cumulative volume percent diameter _{D 50} measured by a laser diffraction method is 1.0 to 3.0 m, and a copper fine powder which is _{D 90} ≧ 1.6 × _{D 50.} The copper fine powder is prepared by adding a cuprous oxide to an aqueous medium containing a natural resin or polysaccharide, or a derivative thereof to prepare a slurry, and adding an acid aqueous solution to the slurry to perform a disproportionation reaction. can get.
[Selection] Figure 1

Description

  The present invention relates to a copper fine powder suitably used for, for example, a conductive paste or filler and a method for producing the same.

Conventionally, conductive paste containing fine copper powder has been used to form circuit board wiring and through-hole conductors. Also, various materials are known in which conductivity is imparted by adding copper fine powder to a matrix, such as an electromagnetic shielding material.
As such copper fine powder, a technique is disclosed in which cuprous oxide is reduced with a hydrazine-based reducing agent to obtain a copper powder having a particle size of approximately 0.2 to 1.0 μm (Patent Document 1).
Further, a technique for obtaining copper powder having an average particle size of 0.2 to 100 μm by an atomizing method is disclosed (Patent Document 2).
On the other hand, a technique has been disclosed in which dendritic electrolytic copper powder is pulverized and densified using a jet mill to obtain spherical copper fine powder having an average particle size of 1 to 6 μm (Patent Document 3).

JP 2008-50661 (Claim 1, 0011) JP 2008-95169 A JP 2008-13837 A

However, when the particle size of the copper fine powder is less than 1.0 μm, it becomes difficult to handle the powder, the surface area with respect to the volume of the powder increases, and the surface of the powder is easily oxidized.
In addition, as described in Patent Document 2, since atomized powder has a wide particle size distribution, classification (particularly classification on the larger particle diameter side) is necessary to obtain copper fine powder having a desired particle size range. As a result, the yield of the final product is reduced and the cost is increased. Recently, products having an average particle size of 5 μm or less have been produced by the high-pressure water atomization method, but the improvement of product yield deterioration due to classification is not sufficient, which is economically disadvantageous. In particular, those having an average particle size of 3 μm or less have high milling yield and are high-grade products.
Moreover, in the case of the technique described in Patent Document 3, it is necessary to install a jet mill, and the manufacturing apparatus becomes complicated.

  That is, the present invention has been made to solve the above problems, and aims to provide a copper fine powder having an average particle size of 1.0 to 3.0 μm and a sharp particle size distribution and a method for producing the same. To do.

As a result of various studies, the present inventors have obtained a disproportionation reaction by adding an acid aqueous solution to cuprous oxide, thereby obtaining a copper fine powder having an average particle size of 1.0 to 3.0 μm without classification. I found out.
That copper fine powder of the present invention, the accumulated volume percentage diameter _{D 50} measured by a laser diffraction method is 1.0 to 3.0 m, and a copper fine powder which is _{D 90} ≧ 1.6 × _{D 50.}

  The copper fine powder is prepared by adding cuprous oxide to an aqueous medium containing a natural resin or polysaccharide, or a derivative thereof to prepare a slurry, and adding an acid aqueous solution to the slurry to perform a disproportionation reaction. It is preferable that it is obtained.

  The copper fine powder production method of the present invention is prepared by adding a cuprous oxide to an aqueous medium containing an additive of a natural resin, polysaccharide or derivative thereof to prepare a slurry, and adding an aqueous acid solution to the slurry. Perform the leveling reaction.

  According to the present invention, copper fine powder having an average particle size of 1.0 to 3.0 μm and a sharp particle size distribution can be obtained.

It is a schematic diagram which shows the particle size distribution of the copper fine powder which concerns on embodiment of this invention. It is a schematic diagram which shows the particle size distribution obtained by classifying the coarse powder side of atomized powder.

Hereinafter, the copper fine powder which concerns on embodiment of this invention, and its manufacturing method are demonstrated.
The copper fine powder according to the embodiment of the present invention has an integrated volume percentage diameter D ₅₀ measured by a laser diffraction method of 1.0 to 3.0 μm and D ₉₀ ≧ 1.6 × D ₅₀ .
The laser diffraction method irradiates particles dispersed in a dispersion medium with laser light and measures the scattering according to the size (volume, equivalent optical diameter) of the particles. Measuring. As a laser diffraction type measuring device, for example, a laser diffraction type particle size measuring device (model number SALD-2100) manufactured by Shimadzu Corporation can be used. As the dispersion medium, for example, pure water can be used.
Here, the cumulative volume percentage diameter is the particle diameter D at which the cumulative volume of the particles becomes a predetermined percentage, and the subscript D indicates the percentage value. For example, D ₅₀ is the particle size when the number smaller than a certain particle size (total volume of particles) occupies 50% of the total powder. As described above, in the laser diffraction method, the particle size ( Since the scattering according to the volume and the optical equivalent diameter) is measured, the integrated volume percentage diameter is obtained. D ₉₀ is the particle diameter when the number smaller than a certain particle diameter occupies 90% of the total powder.

_{D 50} of the copper fine powder according to an embodiment of the present invention is 1.0 to 3.0 m. If D ₅₀ is less than 1.0 .mu.m, with the handling of the powder becomes difficult, surface area is increased relative to the volume of the powder, comprising surface powder is easily oxidized. If D ₅₀ exceeds 3.0 [mu] m, defects such as gaps occur between the particles occurs when used as a conductive paste or the like becomes grainy.
Further, the copper fine powder satisfy the relation of _{D 90} ≧ 1.6 × _{D 50.} FIG. 1 schematically shows the particle size distribution of copper fine powder according to an embodiment of the present invention. This copper fine powder is, for example, by changing the concentration of the natural resin and polysaccharide mixed with cuprous oxide and the reaction start temperature by the method described later, without classifying D ₅₀ in the range of 1.0 to 3.0 μm. Can be controlled. Therefore, as shown in FIG. 1, when the frequency (number of particles) of copper fine powder is plotted against the particle diameter, a curve G ₀ close to a normal distribution is obtained. Then, the copper fine powder is distributed with a spread to the extent that satisfy the relation of D ₉₀ ≧ 1.6 × D _50.
Incidentally, in copper fine powder of the present invention, D ₅₀ may contain a powder of less than 1.0 .mu.m. D ₅₀ is less than 1.0μm _{powders, D 50} enters the space of the particles of 1.0 to 3.0 m, no problem in use because it increases the packing density. However, when D ₅₀ is too increased proportions of components below 1.0 .mu.m, with the handling of the powder becomes difficult, surface area is increased relative to the volume of the powder, the surface of the powder is likely to be oxidized and the D ₅₀ It is necessary to make the content ratio of components less than 1.0 μm 30% or less.

On the other hand, Fig.2 (a) shows typically the state which classified the coarse powder side of the conventional atomized powder. FIG. 2B schematically shows the particle size distribution after the coarse powder side is excessively classified and removed in FIG. It can be seen that particles having a diameter larger than D ₅₀ are reduced by excessive classification, and a portion larger than D _{50 of} curve G falls rapidly, and D ₉₀ <1.6 × D ₅₀ is satisfied.
As described above, the copper fine powder according to the embodiment of the present invention is a powder in which D ₅₀ is controlled to 1.0 to 3.0 μm without excessive classification. For example, the copper fine powder is conductive in various particle size ranges. It is expected to be used in a wide range of applications such as making pastes.

As described below, the copper fine powder according to the embodiment of the present invention is prepared by adding cuprous oxide to an aqueous medium containing a natural resin or polysaccharide, or a derivative thereof, and preparing a slurry. It can be produced by adding an aqueous solution to carry out a disproportionation reaction. Thus, a copper fine powder having a predetermined particle diameter can be obtained by a chemical reaction by a chemical reaction, and a classification device or the like is not required, the production is easy, the yield is high, and the production cost can be reduced. As a method for controlling the D ₅₀ of the copper fine powder to 1.0 to 3.0 μm, the addition amount of natural resin or polysaccharide, or a derivative thereof, the blending ratio of these and cuprous oxide, or the acid aqueous solution to the slurry Controlling the addition start temperature of (for example, sulfuric acid) can be mentioned.
Here, by mixing cuprous oxide and sulfuric acid and performing a disproportionation reaction, copper fine powder and copper sulfate can be obtained. However, as the reaction is conventionally performed at a low temperature, particle growth after nucleation of copper powder occurs. It is known that copper powder can be reduced and copper powder can be refined. However, as described above, the reaction between the cuprous oxide slurry and the acid solution (sulfuric acid) leads to dilution of sulfuric acid with water in the cuprous oxide slurry, and the heat of dilution of sulfuric acid is generated. For this reason, since temperature control after the start of the reaction is difficult, the liquid temperature of the cuprous oxide slurry before the disproportionation reaction is regarded as “(sulfuric acid) addition start temperature = reaction start temperature”. (The liquid temperature of the cuprous oxide slurry and sulfuric acid before the disproportionation reaction is adjusted to the same temperature, and then the reaction (addition of sulfuric acid) is started).
Although the disproportionation reaction proceeds without using natural resins, polysaccharides, or derivatives thereof, it is difficult to obtain copper powder having a particle size distribution with an average particle size of 3.0 μm or less.

Examples of natural resins include gum arabic (powder), pine resin (rosin), gelatin and glue. Examples of polysaccharides include glycogen, starch, cellulose, dextrin, gum arabic, and casein.
Natural resin or polysaccharide derivatives are those obtained by modifying natural resins or polysaccharides by oxidation, esterification or the like, and include carboxymethyl cellulose.
By changing the blending ratio of these natural resins or polysaccharides or their derivatives and cuprous oxide, the particle size of the copper fine powder can be adjusted. For cuprous oxide, it is possible to proportion such these natural resins the more, to reduce the D ₅₀ of the copper fine powder. To adjust the _{D 50} of the copper fine powder to 1.0 to 3.0 m, it is preferable blending ratio of such natural resin is 0~1.143g / L in the slurry.

And these natural resins or polysaccharides, or derivatives thereof can be put into an aqueous medium such as pure water, and cuprous oxide can be added to prepare a slurry. The concentration of cuprous oxide in the slurry is not particularly limited, but is suitably 500 g / L or less, and can usually be 300 g / L or less (for example, 143 g / L). However, when the slurry concentration of cuprous oxide is extremely low, the reaction becomes difficult to proceed.
Next, when an aqueous acid solution is added to the slurry to perform a disproportionation reaction, fine copper powder is generated in the slurry. The reaction formula for the disproportionation reaction is as follows.
Cu ₂ 0 + H ₂ SO ₄ → Cu + CuSO ₄ + H ₂ O
In this reaction formula, hydrogen ions attack the oxygen of cuprous oxide.
Cu ₂ 0 + 2H ⁺ → 2Cu ⁺ + H ₂ O
The liberated monovalent cation Cu ⁺ is unstable and easily disproportionated in an aqueous solution.
2Cu ⁺ → ^Cu ↓ ⁺ Cu ²⁺
Then, the divalent cation Cu ²⁺ and sulfate ion SO ₄ ²⁻ react to produce copper sulfate CuSO ₄ .
Cu ²⁺ + SO ₄ ²⁻ → CuSO ₄

The concentration of the acid aqueous solution can be, for example, 1% by mass (0.375N) to 65% by mass (18N). Examples of the acid aqueous solution include aqueous solutions of sulfuric acid, nitric acid, phosphoric acid, and acetic acid. Specific examples of the acid aqueous solution include dilute sulfuric acid (concentration: 38 mass%: 9N).
The above disproportionation reaction can be carried out at a reaction temperature of about room temperature to 50 ° C. by adding an aqueous acid solution for a period of 5 seconds to 180 minutes. A higher reaction temperature, it is possible to increase the D ₅₀ of the copper fine powder.

The slurry containing the copper fine powder obtained in the disproportionation reaction is subjected to solid-liquid separation and appropriately washed with water. At this time, it is preferable to obtain a copper powder by subjecting the copper fine powder after solid-liquid separation and water washing to reduction treatment with an alkaline solution, and further repeating solid-liquid separation and water washing. The reasons for performing the reduction treatment are (1) reducing unreacted cuprous oxide to copper, (2) removing the surface oxide of the produced copper fine powder, and smoothing the acid treatment and rust prevention treatment in the subsequent steps. To do. By performing the reduction treatment, reduction of residual cuprous oxide and improvement of the rust prevention treatment effect are achieved.
Moreover, it is preferable to perform an acidification treatment with an acid in the course of repeating the above-described solid-liquid separation and water washing. The reason for acidifying with acid is that (1) water washing on the acid side is effective for cleaning effect and solid-liquid separation, and (2) BTA (benzotriazole) used in the rust inhibitor is on the acid side. It works effectively. Thus, after the final water washing treatment, it is preferable to filter the obtained copper fine powder and further vacuum-dry it because the surface oxidation of the copper fine powder can be effectively prevented.

Example 1
In 7 L of pure water, 4.0 g of gum arabic (manufactured by Junsei Chemical Co., Ltd., genuine first grade gum arabic (powder) (acacia (powder)) is dissolved, and 1000 g of cuprous oxide is added and suspended while stirring. A slurry was prepared and held at room temperature, the cuprous oxide concentration in the slurry was about 143 g / L, and the gum arabic concentration in the slurry was about 0.57 g / L.
Next, 1000 cc of dilute sulfuric acid (concentration 38 mass%: 9 N, molar ratio (acid aqueous solution / slurry): 1.5) kept at room temperature was slowly added to the slurry over 16 minutes to carry out a disproportionation reaction. The reaction was completed in about 10 minutes after the addition of dilute sulfuric acid. The produced copper fine powder was washed, further coated with a predetermined rust preventive oil on the surface, subjected to a rust preventive treatment, and further dried to obtain 420 g of copper fine powder.

(Example 2)
420 g of copper fine powder was obtained in the same manner as in Example 1 except that the amount of gum arabic added to pure water was changed to 1.6 g (the gum arabic concentration in the slurry was about 0.23 g / L).

(Example 3)
420 g of copper fine powder was obtained in the same manner as in Example 1 except that the amount of gum arabic added to pure water was changed to 1.2 g (the gum arabic concentration in the slurry was about 0.17 g / L).

Example 4
420 g of copper fine powder was obtained in the same manner as in Example 1 except that the amount of gum arabic added to pure water was changed to 0.8 g (the gum arabic concentration in the slurry was about 0.11 g / L).

(Example 5)
420 g of copper fine powder was obtained in the same manner as in Example 1 except that the amount of gum arabic added to the pure water was changed to 0.4 g (the gum arabic concentration in the slurry was about 0.06 g / L).

(Example 6)
The amount of gum arabic added to the pure water was changed to 8.0 g (the gum arabic concentration in the slurry was about 1.14 g / L), and the temperature of the slurry and dilute sulfuric acid (that is, the reaction start temperature) was changed to 50 ° C. Except for this, 420 g of copper fine powder was obtained in the same manner as in Example 1.

(Example 7)
The amount of gum arabic added to the pure water was changed to 0.8 g (the gum arabic concentration in the slurry was about 0.11 g / L), and the temperature of the slurry and dilute sulfuric acid (that is, the reaction start temperature) was changed to 50 ° C. Except for this, 420 g of copper fine powder was obtained in the same manner as in Example 1.

(Comparative Example 1)
420 g of copper fine powder was obtained in the same manner as in Example 1 except that the amount of gum arabic added to pure water was changed to 8.0 g (the concentration of gum arabic in the slurry was about 1.14 g / L).

(Comparative Example 2)
420 g of copper fine powder was obtained in the same manner as in Example 1 except that gum arabic was not added to pure water.

(Comparative Example 3)
420 g of copper fine powder was obtained in the same manner as in Example 1 except that the gum arabic was not added to pure water and the temperature of the diluted sulfuric acid (that is, the reaction temperature) was changed to 50 ° C.

(Comparative Example 4)
The powder production conditions of the water atomizer were as follows: molten copper temperature 1400 ° C., orifice diameter φ4 mm, atomized water film water pressure 80 MPa, water volume 80 liters / min. (Excerpt from cited document 2)

(Comparative Example 5)
The powder production conditions of the water atomizer were as follows: molten copper temperature 1400 ° C., orifice diameter φ4 mm, atomized water film water pressure 80 MPa, water volume 80 liters / min. (Excerpt from cited document 2)
The copper fine powder obtained above was collected using an air classifier or a wet classifier to obtain a powder having a particle size distribution of D50 = 3 μm. The yield was 39%.

(Comparative Example 6)
The powder production conditions of the water atomizer were as follows: molten copper temperature 1400 ° C., orifice diameter φ4 mm, atomized water film water pressure 80 MPa, water volume 80 liters / min. (Excerpt from cited document 2)
The copper fine powder obtained above was collected using an air classifier or a wet classifier to obtain a powder having a particle size distribution of D50 = 2 μm. The yield was 19%.

The following evaluation was performed about the copper fine powder of each Example and the comparative example.
<Particle size of copper fine powder>
Using a laser diffraction particle size distribution measuring device (manufactured by Shimadzu Corporation, model number: SALD-2100), the particle size distribution of the copper fine powders of each of the examples and comparative examples was measured. D ₅₀ and D ₉₀ calculated from the particle size distribution are shown in Table 1.
To measure the particle size distribution, a fine suspension (about 0.1 g) of copper fine powder was added to a 10 cc beaker with a spatula, and pure water (dispersion medium) was further added to prepare a suspension. This suspension was put into a dispersion tank of a measuring apparatus, and measurement was first performed without ultrasonic irradiation. Next, ultrasonic waves were applied, measurement was performed every minute, and measurement was performed for up to 10 minutes. The measured value at 10 minutes after ultrasonic irradiation was adopted.
The obtained results are shown in Table 1. The relative ratio of gum arabic in Table 1 is the ratio of the gum arabic in the slurry of Comparative Example 1 (1.143 g / L).

As is clear from Table 1, in Examples 1 to 7 in which copper fine powder was produced by a disproportionation reaction between cuprous oxide and an aqueous acid solution, D ₅₀ was 1.0 to 3.0 μm, and D ₉₀ A powder with a particle size distribution of ≧ 1.6 × D ₅₀ was obtained. Incidentally, when comparing the D ₅₀ of Examples 1 to 5, lowering the addition ratio of gum arabic, it can be seen that an increase in particle diameter.
Also, the D ₅₀ results of Examples 5 and 6, by increasing the reaction initiation temperature to 50 ° C., it can be seen that it is possible further increase the particle size.

On the other hand, when Examples 1 to 5 and Comparative Example 1 in which the reaction temperature (sulfuric acid addition temperature) is all room temperature are compared, Submicron powder is obtained on the contrary in Comparative Example 1 having a higher Arabic gum concentration, The result was out of D ₅₀ = 1 to 3 μm. This indicates that the reaction temperature (sulfuric acid addition temperature) influences the particle size of the copper fine powder in addition to the gum arabic concentration in the slurry.
In Comparative Examples 2 and 3 where no gum arabic was added to the slurry, the D ₅₀ exceeded 3 μm and the particle size increased.
In Comparative Example 4 to obtain a copper fine powder using atomization method, the particle diameter was increased D ₅₀ exceeds the 3 [mu] m.
In Comparative Examples 5 and 6 in which the copper fine powder of Comparative Example 4 was further excessively classified, D ₅₀ was 3.0 μm by classification, but the yields were each reduced to less than 50%.

Claims (3)

Copper fine powder accumulated volume percentage diameter _{D 50} measured by a laser diffraction method is 1.0 to 3.0 m, and a _{D 90} ≧ 1.6 × _{D 50.}   The copper fine powder is prepared by adding cuprous oxide to an aqueous medium containing a natural resin or polysaccharide, or a derivative thereof to prepare a slurry, and adding an acid aqueous solution to the slurry to perform a disproportionation reaction. The copper fine powder according to claim 1, which is obtained.   3. A cuprous oxide is added to an aqueous medium containing an additive of a natural resin, a polysaccharide or a derivative thereof to prepare a slurry, and an acid aqueous solution is added to the slurry to perform a disproportionation reaction. The manufacturing method of the copper fine powder of description.

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