KR101078253B1 - Preparation of Ag coated Cu powder by electroless plating method - Google Patents

Abstract

The present invention relates to a method for forming a silver coating layer of copper powder using an electroless plating method,

a) preparing a first solution by adding hydroquinone to copper powder and a reducing agent in which the oxide layer is removed from distilled water, and preparing a second solution by mixing an aqueous solution of silver nitrate and an aqueous ammonia solution;

b) The concentration of hydroquinone is 0.06 to 0.18 M (mol / L), the concentration of silver nitrate is 0.11 to 0.19 M (mol / L), and the concentration of aqueous ammonia is 1.1 to 1.7 M (mol / L). Reacting the first solution and the second solution by mixing the second solution;

c) drying the copper powder having the silver coating layer formed after mixing and reacting the first solution and the second solution;

It relates to a method for forming a silver coating layer of copper powder comprising a.

Electroless plating method, reducing agent, hydroquinone, silver coating, copper powder, reaction temperature

Description

Silver coating layer formation method of copper powder {Preparation of Ag coated Cu powder by electroless plating method}

The present invention relates to a method for forming a silver coating layer of copper powder. Specifically, the present invention relates to a method of forming a uniform silver coating layer on the surface of copper powder by an electroless plating method using a reduction reaction of a silver sphere solution.

Gold (Au), silver (Ag), copper (Cu) and nickel (Ni) are metal materials with excellent thermal and electrical properties. Among them, gold and silver (Ag) have excellent electrical properties but are expensive. Disadvantages, copper and nickel also have excellent electrical properties, while weak to oxidation. In order to overcome the shortcomings of gold, silver, copper and nickel, researches to develop powders having core-shell structure and excellent thermal and electrical properties of copper and silver have been actively conducted in the electronics industry. It's going on.

Generally, powder coating methods include electroplating, electroless plating, and gas phase reaction, but methods such as electroplating and gas phase reaction are difficult in industrialization because of poor efficiency. On the other hand, the electroless plating method has a more dense and uniform thickness of the coating layer compared to other coating methods, enables efficient coating without generating free metal, and can be applied to various substrates such as plastics or organic materials as well as conductors. have. In addition, in the industrial aspect, since the manufacturing cost is low and mass production is possible, many researches are actively underway.

Meanwhile, Korean Patent Publication No. 2007-0104802 discloses a first solution by mixing a silver nitrate solution with an aqueous ammonia solution and dissolving a dispersant to form a first solution. After adding and mixing the metal powder and the reducing agent, the acidity (pH) is adjusted to 7 to 10 to prepare a second solution, and mixing the first solution and the second solution of the metal powder with a silver coating layer comprising the step of mixing. It provides a manufacturing method. In this document, ascorbic acid, rochelle salt, hydrazine, formaldehyde, formalin or mixtures thereof are preferably used as reducing agents. Although the copper powder in which the silver coating layer was formed according to the Example described was manufactured, it was not satisfactory because the nonuniform silver coating layer was formed in the particle size and particle shape of the copper powder as a whole.

Among the comparative examples described in the literature, there was an example of using hydroquinone as a reducing agent, but when using hydroquinone as a reducing agent, a coating layer was not formed on the surface of the base metal powder, and the base metal powders were entangled with each other. It is stated that it can.

The present invention is to solve the problems of the prior art as described above, according to the disclosed technology, when using a hydroquinone (hydroquinone) as a reducing agent to form a coating layer on the surface of the base metal powder, it is possible to form a silver coating layer of copper powder Ascorbic acid, rochelle salt, hydrazine described in the literature by adjusting the addition amount of copper powder, reaction temperature and molar concentration of coating solution when using hydroquinone as a reducing agent in the process Compared to the use of a reducing agent consisting of formaldehyde, formalin, or a mixture thereof, forming a copper powder having a uniform silver coating layer and forming a silver coating layer of copper powder having excellent thermal and electrical properties having a uniform particle size. To provide a way.

In order to achieve the above object, in the present invention, a silver nitrate aqueous solution was used as a raw material to form a silver coating layer of copper powder, and a new reducing system was developed using hydroquinone as a reducing agent. Specifically, the present invention,

a) preparing a first solution by adding hydroquinone to copper powder and a reducing agent in which the oxide layer is removed from distilled water, and preparing a second solution by mixing an aqueous solution of silver nitrate and an aqueous ammonia solution;

b) The concentration of hydroquinone is 0.06 to 0.18 M (mol / L), the concentration of silver nitrate is 0.11 to 0.19 M (mol / L), and the concentration of aqueous ammonia is 1.1 to 1.7 M (mol / L). Reacting the first solution and the second solution by mixing the second solution;

c) drying the copper powder having the silver coating layer formed after mixing and reacting the first solution and the second solution;

It provides a method for forming a silver coating layer of copper powder comprising a.

Hereinafter, the present invention will be described in more detail.

The present invention uses an electroless plating method to form a silver coating layer on the surface of the copper powder to suppress the oxidation of copper and to enable the production of powders having both excellent thermal and electrical properties of copper and silver as well as high price of silver powder. The present invention also relates to a method for forming a silver coating layer of copper powder having a silver coating layer having a core shell structure.

Copper and silver are metal materials with excellent thermal and electrical properties. However, silver has the disadvantage of being expensive and copper has a disadvantage of being vulnerable to oxidation. In order to overcome the disadvantages of copper and silver, coating silver on the surface of the particles of copper powder inhibits the oxidation of copper and enables the production of powders having both excellent thermal and electrical properties of copper and silver, and also solves the high price problem of silver powder. It becomes possible. The copper powder formed with the silver coating layer thus prepared may be used as an electromagnetic shielding powder.

The particle size of the copper powder is preferably in the range of 5 to 40 μm, more preferably 10 to 30 μm.

In the present invention, the method for forming a silver coating layer of copper powder,

a) preparing a first solution by adding hydroquinone to copper powder and a reducing agent in which the oxide layer is removed from distilled water, and preparing a second solution by mixing an aqueous solution of silver nitrate and an aqueous ammonia solution;

b) The concentration of hydroquinone is 0.06 to 0.18 M (mol / L), the concentration of silver nitrate is 0.11 to 0.19 M (mol / L), and the concentration of aqueous ammonia is 1.1 to 1.7 M (mol / L). Reacting the first solution and the second solution by mixing the second solution;

c) drying the copper powder having the silver coating layer formed after mixing and reacting the first solution and the second solution;

It includes.

First, a first solution is prepared by adding hydroquinone as a copper powder and a reducing agent in which an oxide layer is removed from distilled water.

The copper powder of step a) is preferably used to remove the oxide layer by the acidic solution, and enables the formation of a silver coating layer by activating the surface of the copper powder by removing the oxide layer of the copper powder.

The acidic solution used in step a) may be preferably a nitric acid solution or a sulfuric acid solution, of which sulfuric acid solution may be most preferably used for removing the oxide layer of the copper powder. The acidic solution is preferably to use a strong acid solution that does not contain water, it is difficult to remove the oxide layer on the entire surface of the copper powder when water.

In the step a), the reducing agent used in the preparation of the first solution affects the reactivity and the reaction rate, and thus plays an important role in determining the particle shape and particle size of the copper powder finally formed with the silver coating layer. Hydroquinone may be preferably used as the reducing agent.

The amount of copper powder added in step a) is preferably added in an amount of 10 to 20% by weight based on the total weight of distilled water, more preferably 12 to 16% by weight of copper powder. When the amount of the copper powder added is less than 10% by weight, silver that is not adsorbed on the surface of the particles of the copper powder is precipitated in excess, and when the amount of the copper powder exceeds 20% by weight, the thickness of the silver coating layer decreases, thereby reducing thermal and electrical properties. There is.

In the preparation of the second solution of step a), the mixing of the silver nitrate solution and the aqueous ammonia solution is intended to form a silver complex ion having a high affinity in the aqueous solution so that the dispersion of the silver occurs well and uniform coating occurs well.

The aqueous ammonia solution used in the preparation of the second solution of step a) is used as a surface active agent of the copper powder, to enhance the activity of the copper surface, to remove impurities remaining on the copper surface, and to disperse the copper powder well. Get up.

In step b), the concentration of hydroquinone is 0.06 to 0.18 M (mol / L), the concentration of silver nitrate is 0.11 to 0.19 M (mol / L), and the concentration of aqueous ammonia is 1.1 to 1.7 M ( mol / L) to react the first solution and the second solution by mixing.

The concentration of hydroquinone in the mixed solution of the first solution and the second solution of step b) is preferably 0.06 to 0.18 M (mol / L), more preferably 0.1 to 0.15 M (mol / L). desirable. When the concentration of the hydroquinone is lower than 0.06 M (mol / L), the reducing power of the hydroquinone is reduced, and when the concentration of the hydroquinone is higher than 0.18 M (mol / L), the particle size of the manufactured copper powder is reduced. There is a problem in forming a silver coating layer on the copper powder.

In the step b), the concentration of the silver nitrate solution in the mixed solution of the first solution and the second solution is preferably 0.11 to 0.19 M (mol / L), more preferably 0.14 to 0.16 M (mol / L). When the concentration of the silver nitrate solution was lower than 0.11 M (mol / L), the silver coating layer was not sufficiently formed. When the concentration of the silver nitrate was higher than 0.19 M (mol / L), the copper with the silver coating layer prepared due to excessive precipitation of silver was formed. There is a problem that the coating layer on the surface of the particles of the powder is formed thick.

In step b), the concentration of the aqueous ammonia solution in the mixed solution of the first solution and the second solution is preferably 1.1 to 1.7 M (mol / L), more preferably 1.3 to 1.5 M (mol / L). When the concentration of the aqueous ammonia is lower than 1.1 M (mol / L), the silver is not adsorbed on the surface of the particles of the copper powder, when higher than 1.7 M (mol / L) copper powder with a silver coating layer prepared There is a problem that the roughness of the particle surface is increased.

The reaction temperature of the step of reacting the first solution and the second solution of step b) by mixing is preferably 1 to 10 ℃, more preferably 3 to 6 ℃. When the reaction temperature is lower than 1 ° C, the silver coating layer is unevenly generated on the surface of the copper powder. If the reaction temperature is higher than 10 ° C, the roughness of the surface of the copper powder having the silver coating layer prepared is increased.

In the method of forming a silver coating layer of the copper powder, when the aqueous solution of ammonia is added to the silver nitrate aqueous solution according to Formula 1, the solution gradually changes from yellow to dark brown. When the reaction of Formula 2 and Formula 3 is performed again, the color of the solution changes to transparent. When the solution converted by Chemical Formula 3 is added to an acidic solution containing copper powder, the reaction occurs spontaneously as the standard oxidation / reduction potential difference (ΔE ⁰ ) has a positive value as in Chemical Formula 4, Ag ⁺ having a high standard reduction potential is precipitated as Ag ⁰ .

Formula 5 is a precipitation reaction of silver by a reducing agent, and Ag (NH ₃ ) ₂ ⁺ complex ions produced by ammonia water are precipitated as silver as crystals grow by hydroquinone, a reducing agent. When this reaction is successful, a uniform silver coating layer is formed on the surface of the copper powder.

In the present invention, the method of forming a silver coating layer of copper powder forms a silver coating layer on the surface of the copper powder to suppress oxidation of the copper powder, thereby making it possible to manufacture a copper powder having a silver coating layer having both excellent thermal and electrical properties of copper and silver. In addition, a copper powder having a uniform silver coating layer may be prepared.

When explaining this invention based on an Example and a comparative example as follows, this invention is not limited by an Example and a comparative example.

In order to analyze the cross-section of the copper powder with a silver coating layer prepared according to Examples 1 and 2 and Comparative Examples 1 to 12 of the present invention, JEOL's model name JSM-5410 scanning electron microscope (SEM, scanning electron) microscopy) was used, and was analyzed using an energy dispersive x-ray spectrometer (EDX) of HORIBA's model name EX-250 for quantitative analysis of the copper powder having the silver coating layer.

Example 1

In order to remove the oxide layer of copper powder, a copper powder having a particle size of 25 μm was added to the sulfuric acid solution, followed by stirring for 20 minutes to wash. The first solution was prepared by adding hydroquinone as a reducing agent for reducing silver nitrate. The second solution was prepared by mixing a silver nitrate solution with an aqueous ammonia solution, and the hydroquinone concentration was 0.1 M (mol / L), the silver nitrate solution was 0.15 M (mol / L), and the ammonia solution was 1.4. The first solution and the second solution were mixed and reacted while stirring for 20 minutes at a reaction temperature of 4 ° C. such that M (mol / L). After completion of the reaction, the copper powder formed with the silver coating layer was collected, washed several times with distilled water and ethanol, and dried at 60 ° C. for 24 hours to prepare a copper powder having a silver coating layer.

[Example 2]

 It carried out similarly to Example 1 except the addition amount of the said copper powder is 16 weight%.

Comparative Example 1

 The same procedure as in Example 1 was carried out except that the concentration of hydroquinone in the mixed solution of the first solution and the second solution was 0.01 M (mol / L).

Comparative Example 2

 Except that the concentration of hydroquinone (hydroquinone) in the mixed solution of the first solution and the second solution was 0.05 M (mol / L) was carried out in the same manner as in Example 1.

Comparative Example 3

 The same procedure as in Example 1 was performed except that the concentration of hydroquinone in the mixed solution of the first solution and the second solution was 0.20 M (mol / L).

[Comparative Example 4]

In the mixed solution of the first solution and the second solution was carried out in the same manner as in Example 1 except that the concentration of the silver nitrate solution is 0.25 M (mol / L).

[Comparative Example 5]

 The same process as in Example 1 was carried out except that the concentration of the aqueous ammonia solution in the mixed solution of the first solution and the second solution was 1.0 M (mol / L).

[Comparative Example 6]

 The same process as in Example 1 was carried out except that the concentration of the aqueous ammonia solution in the mixed solution of the first solution and the second solution was 1.8 M (mol / L).

Comparative Example 7

 The same process as in Example 1 was carried out except that the concentration of the aqueous ammonia solution in the mixed solution of the first solution and the second solution was 2.2 M (mol / L).

Comparative Example 8

The reaction was carried out in the same manner as in Example 1 except that the reaction temperature of the step of reacting the first solution and the second solution by mixing was room temperature.

[Comparative Example 9]

 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature of the step of reacting the first solution and the second solution by mixing was 50 ° C.

[Comparative Example 10]

 The reaction was carried out in the same manner as in Example 1, except that the reaction temperature of the step of reacting the first solution and the second solution by mixing was 80 ° C.

Comparative Example 11

It carried out similarly to Example 1 except the addition amount of the said copper powder is 4 weight%.

[Comparative Example 12]

 It carried out similarly to Example 1 except the addition amount of the said copper powder is 8 weight%.

Table 1 shows each composition and reaction conditions added in Examples 1 and 2 and Comparative Examples 1 to 12.

1 is a scanning electron microscope (SEM) photograph of the copper powder prepared according to Example 1 and Comparative Examples 1 to 3, Figure 1 (a) is Comparative Example 1, Figure 1 (b) is Comparative Example 2 FIG. 1 (c) shows Example 1 and FIG. 1 (d) shows a copper powder having a silver coating layer prepared according to Comparative Example 3. FIG.

1 (a) and 1 (b) show that some of the unreacted substances such as AgO and AgO ₂ were detected due to the reduced reducing power of hydroquinone, and FIG. 1 (d) shows the particle size of FIG. 1. It confirmed that it became small compared with (a)-FIG. 1 (c). On the other hand, in Figure 1 (c) it was confirmed that the copper powder formed with a silver coating layer having excellent dispersibility and the same particle size of the copper powder, it was confirmed that the silver coating layer is uniformly formed on the surface of the copper powder.

2 is a scanning electron microscope (SEM) photograph of the copper powder prepared according to Example 1 and Comparative Example 4, Figure 2 (a) is Example 1 and Figure 2 (b) is prepared according to Comparative Example 4 It shows the copper powder in which the silver coating layer was formed.

Comparative Example 4 was carried out in the same manner as in Example 1 except that the concentration of the silver nitrate aqueous solution in the mixed solution of the first solution and the second solution is 0.25 M (mol / L), copper prepared in Comparative Example 4 The powder was excessively precipitated silver through Figure 2 (b) was confirmed that the coating layer was formed on the surface of the copper powder thick, while the copper powder prepared in Example 1 is on the surface of the copper powder through Figure 2 (a) It was confirmed that the silver coating layer was formed uniformly.

3 is a scanning electron microscope (SEM) image of the copper powder prepared according to Example 1 and Comparative Examples 5 to 7, Figure 3 (a) is Comparative Example 5, Figure 3 (b) is Example 1 3 (c) shows a comparative example 6 and FIG. 3 (d) shows a copper powder having a silver coating layer prepared according to Comparative Example 7. FIG.

Figure 3 (a) was confirmed that the silver was not absorbed on the surface of the copper powder particles, Figure 3 (c) and Figure 3 (d) is a roughness of the silver coating layer and the copper powder surface formed non-uniformly on the surface of the copper powder particles Was confirmed to rise. On the other hand, Figure 3 (b) it was confirmed that the most silver is adsorbed on the surface of the particles of the copper powder to form a uniform silver coating layer.

More specifically, FIG. 4 is an energy dispersive X-ray spectrometer (EDX) measurement result of copper powder prepared according to Example 1 and Comparative Examples 5 to 7, and FIG. 4 (a) is Comparative Example 5, FIG. 4 (b) is Example 1, FIG. 4 (c) is Comparative Example 6, and FIG. 4 (d) is an energy dispersive X-ray spectrometer (EDX) measurement result of a copper powder having a silver coating layer prepared according to Comparative Example 7. to be. In FIG. 4A, the copper powder peak inside the particles can be confirmed, but the silver peak on the surface of the particles was analyzed in a small amount. 4 (c) and 4 (d), it was confirmed that the non-uniform silver coating layer grew excessively on the surface of the particles of copper powder, resulting in thick silver peaks on the surface of the particles. On the other hand, in Figure 4 (b) it was confirmed that a uniform silver coating layer was formed on the surface of the copper powder particles.

5 is a scanning electron microscope (SEM) image of the copper powder prepared according to Example 1 and Comparative Examples 8 to 10, Figure 5 (a) is Example 1, Figure 5 (b) is Comparative Example 8 5 (c) shows a comparative example 9 and FIG. 5 (d) shows a copper powder having a silver coating layer prepared according to Comparative Example 10.

5 (a) to 5 (d), in the reaction of mixing the first solution and the second solution, the amount of silver precipitated increases as the reaction temperature increases, and the silver coating layer on the surface of the copper powder particles The roughening was confirmed. In FIG. 5 (b), a small amount of silver that was relatively uniform but was not adsorbed onto the copper powder was detected. In FIG. 5 (c), it was confirmed that the silver coating layer on the surface of the copper powder particles was formed unevenly. Also in FIG. 5 (d), as the temperature was increased, the precipitation reaction was accelerated to confirm that the silver coating layer was unevenly formed. On the other hand, in Figure 5 (a) it was confirmed that a uniform silver coating layer was formed on the surface of the copper powder particles.

6 is a scanning electron microscope (SEM) photograph of the copper powder prepared according to Examples 1 and 2, Comparative Examples 11 and 12, and FIG. 6 (a) is Comparative Example 11 and FIG. 6 (b). Comparative Example 12, Figure 6 (c) is Example 1, Figure 5 (d) shows a copper powder formed with a silver coating layer prepared according to Example 2.

6 (a) to 6 (d), the addition amount of copper powder in the mixed solution of the first solution and the second solution is 4% by weight. In 6 (b), a relatively large proportion of silver nitrate was coated on the surface of the copper powder particles due to the aqueous solution, and the remaining silver was precipitated in the solution. On the other hand, in Figure 6 (c) of the addition amount of the copper powder and Figure 6 (d) of the addition amount of the copper powder was found that the coating layer was uniformly formed on the surface of the copper powder particles.

1 is a scanning electron microscope (SEM) image of a copper powder formed with a silver coating layer prepared according to the present invention, Figure 1 (a) is Comparative Example 1, Figure 1 (b) is Comparative Example 2, Figure 1 (c) Example 1, Figure 1 (d) is a scanning electron microscope (SEM) photograph of the copper powder is formed silver coating layer prepared according to Comparative Example 3.

FIG. 2 is a scanning electron microscope (SEM) photograph of a copper powder having a silver coating layer prepared according to the present invention. FIG. 2 (a) is Example 1 and FIG. 2 (b) is a silver coating layer prepared according to Comparative Example 4. It is a scanning electron microscope (SEM) photograph of this formed copper powder.

3 is a scanning electron microscope (SEM) photograph of a copper powder having a silver coating layer prepared according to the present invention. FIG. 3 (a) is Comparative Example 5 and FIG. 3 (b) is Example 1 and FIG. 3 (c). Figure 6 (d), Figure 3 (d) is a scanning electron microscope (SEM) photograph of the copper powder is formed silver coating layer prepared according to Comparative Example 7.

FIG. 4 is an energy dispersive X-ray spectrometer (EDX) measurement result of a copper powder having a silver coating layer prepared according to the present invention. FIG. 4 (a) is Comparative Example 5 and FIG. 4 (c) is a comparative example 6, Figure 4 (d) is an energy dispersive X-ray spectroscopy (EDX) measurement results of the copper powder with a silver coating layer prepared according to Comparative Example 7.

FIG. 5 is a scanning electron microscope (SEM) photograph of a copper powder having a silver coating layer prepared according to the present invention. FIG. 5 (a) is Example 1, and FIG. 5 (b) is Comparative Example 8 and FIG. 5 (c). 5 is a scanning electron microscope (SEM) photograph of a copper powder having a silver coating layer prepared according to Comparative Example 10. FIG.

FIG. 6 is a scanning electron microscope (SEM) photograph of a copper powder having a silver coating layer prepared according to the present invention. FIG. 6 (a) is Comparative Example 11 and FIG. 6 (b) is Comparative Example 12 and FIG. 6 (c). 6 is a scanning electron microscope (SEM) photograph of a copper powder having a silver coating layer prepared according to Example 2. FIG.

Claims (8)

a) a first solution is prepared by adding a copper powder from which an oxide layer is removed by an acidic solution with a base metal powder and a reducing agent into distilled water and a hydroquinone as a reducing agent; step; b) The concentration of hydroquinone is 0.1 to 0.15 M (mol / L), the concentration of silver nitrate is 0.14 to 0.16 M (mol / L), and the concentration of ammonia is 1.3 to 1.5 M (mol / L). Reacting the first solution and the second solution by mixing the second solution; c) drying the copper powder having the silver coating layer formed after mixing and reacting the first solution and the second solution; Silver coating layer forming method of the copper powder comprising a. delete The method of claim 1, The copper powder addition amount of step a) is a method for forming a silver coating layer of copper powder, characterized in that added to 10 to 20% by weight based on the total weight of distilled water. The method of claim 3, Particle size of the copper powder is a method for forming a silver coating layer of copper powder in the range of 5 to 40㎛. The method of claim 1, The reaction temperature of the step of reacting by mixing the first solution and the second solution of step b) is a method of forming a silver coating layer of copper powder in the range of 1 to 10 ℃. delete delete delete

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