KR20170055642A - A silver coating method for copper powder used circuit printing and adhesive conductive paste - Google Patents

Abstract

The present invention relates to a silver (Ag) coating method for copper powder applicable to circuit printing and conductive adhesive paste, more specifically, to silver powder coated with silver using sodium potassium tartrate and ascorbic acid, To a silver coating method of copper powder having conductivity.
That is, the present invention relates to a method for preparing a solution 1 by dissolving silver salt and ammonia water in a first step;
A second step of dissolving a surface active agent and a reducing agent in distilled water to prepare solution 2;
A third step of removing foreign substances from the surface of the copper powder and surface activation by adding copper powder to the solution 2;
A fourth step of depositing the solution 1 in the solution 2 to precipitate silver on the surface of copper to coat silver;
And a fifth step of washing the silver-coated copper powder of the fourth step with distilled water and then vacuum drying the silver-coated copper powder. The silver coating method of the present invention is applicable to circuit printing and conductive adhesive pastes .

Description

Technical Field [0001] The present invention relates to a silver coating method for copper powder which is applicable to circuit printing and paste for conductive adhesive,

The present invention relates to a silver (Ag) coating method for copper powder applicable to circuit printing and conductive adhesive paste, more specifically, to silver powder coated with silver using sodium potassium tartrate and ascorbic acid, To a silver coating method of copper powder having conductivity.

As electronic devices have become more compact and thinner, electronic components have become thinner and electronic wiring lines become finer, and the diversity of electronic devices has widened and increased the application of thin film switches with high productivity. In addition, the consumption amount of the conductive paste for thin film sheet circuit printing is also increasing.

Conventionally, a metal powder such as copper has been used as an electric conduction filler of a conductive paste. However, high-purity silver (Ag) powder, which is an expensive conductive powder, has a disadvantage of high electrical conductivity but high manufacturing cost.

In view of this, in Korean Patent No. 1236245, which is disclosed as a prior art, 'metal powder for electroconductive paste and electroconductive paste', instead of silver powder, which is an expensive conductive powder, copper powder is formed into a plate shape so as to have electrical conductivity However, the copper powder according to the prior art has a disadvantage in that the density is similar to that of the (Ag) powder but the electrical conductivity is low.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a silver coating method of copper powder which has similar physical properties (density, electrical conductivity) as silver powder and can reduce the cost of conductive paste.

The present invention relates to a method for preparing a solution 1 comprising silver salt and an aqueous ammonia solution, A second step of dissolving a surface active agent and a reducing agent in distilled water to prepare solution 2; A third step of removing foreign substances from the surface of the copper powder and surface activation by adding copper powder to the solution 2; A fourth step of depositing the solution 1 in the solution 2 to precipitate silver on the surface of copper to coat silver; And a fifth step of washing the silver-coated copper powder of the fourth step with distilled water and then vacuum-drying the silver-coated copper powder. The silver coating method of the present invention is applicable to circuit printing and conductive adhesive paste.

The silver salt of the first step is any one or a mixture of two or more selected from silver chloride (AgCl), silver nitrate (AgNO ₃ ), silver sulfate (Ag ₂ SO ₄ ) and silver phosphate (Ag ₃ PO ₄ ) dissolved in water .

Surface active agent in the second step to remove the oxide film and the foreign matter of copper powder surface and to activate the surface of the ion is reduced to copper surface to occur well coating, and ammonium chloride (NH ₄ Cl), ammonium sulfate (NH ₄ SO ₄ ) and ammonium carbonate ((NH ₄ ) ₂ CO ₃ ).

The reducing agent in the second step is any one or a mixture of two or more selected from potassium sodium tartrate (KNaC ₄ H ₄ O ₆ ) and ascorbic acid (C ₆ H ₈ O ₆ ).

The silver-coated copper powder according to the present invention has the effect of providing a conductive paste which is inexpensive and has excellent quality by imparting dispersibility, adhesion, storage stability and excellent electrical conductivity of the paste for circuit printing and conductive adhesive.

1 is a scanning electron microscope (SEM) image of silver coated copper powder prepared according to Example 1 of the present invention.
2 shows X-ray diffraction results of the silver-coated copper powder prepared in Example 1 of the present invention.
3 is a scanning electron microscope (SEM) image of the silver-coated copper powder prepared in Example 2 of the present invention.
4 shows X-ray diffraction results of the silver-coated copper powder prepared in Example 2 of the present invention.
5 is a scanning electron microscope (SEM) image of the silver-coated copper powder prepared in Example 3 of the present invention.
6 shows X-ray diffraction results of the silver-coated copper powder prepared in Example 3 of the present invention.
7 is a scanning electron microscope (SEM) image of the silver-coated copper powder prepared in Example 4 of the present invention.
8 shows X-ray diffraction results of the silver-coated copper powder prepared in Example 4 of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The silver coating method of the copper powder according to the present invention is characterized in that silver is coated on the copper powder using potassium sodium tartrate and ascorbic acid to have conductivity similar to silver powder.

The silver coating method of a copper powder according to the present invention comprises: a first step of dissolving a silver salt and an aqueous ammonia in distilled water to prepare a solution 1 in which silver halide compound is formed; A second step of dissolving a surface active agent and a reducing agent in distilled water to prepare solution 2; A third step of removing foreign substances from the surface of the copper powder and surface activation by adding copper powder to the solution 2; A fourth step of depositing the solution 1 in the solution 2 to precipitate silver on the surface of copper to coat silver; And a fifth step of washing the silver coated copper powder of the fourth step with distilled water and then vacuum drying the silver coated copper powder.

The silver salt of the first step provides silver to be coated on the surface of the copper powder, and silver chloride (AgCl), silver nitrate (AgNO ₃ ), silver sulfate (Ag ₂ SO ₄ ) and silver phosphate (Ag ₃ PO ₄ ), Or a mixture of two or more thereof.

The ammonia water in the first step reacts with silver ions to form silver halide compounds as shown below, and the amount of ammonia water is 1 g to 2 g per 1 g of silver nitrate.

2AgNO ₃ + 2NH ₄ OH = Ag ₂ O + 2NH ₄ NO ₃ + H ₂ O

Ag ₂ O + 4NH ₄ OH = ₂ g (NH ₃ ) ₂ OH + 3H ₂ O

_{Ag (NH 3) 2 OH +} NH 4 NO 3 _{= Ag (NH 3) 2 NO} 3 + NH ₄ OH

Surface active agent in the second step to remove the oxide film and the foreign matter of copper powder surface and to activate the surface of the ion is reduced to copper surface to occur well coating, and ammonium chloride (NH ₄ Cl), ammonium sulfate (NH ₄ SO ₄₎ and ammonium carbonate _{((NH 4) 2 CO 3} ) it is a mixture of at least any one or more selected from the group consisting of.

The amount of the surface active agent in the second step is 0.01 to 0.1 g based on 1 g of the copper powder.

The reducing agent in the second step is a mixture of potassium sodium tartrate (KNaC ₄ H ₄ O ₆ ) and ascorbic acid (C ₆ H ₈ O ₆ ).

The amount of the reducing agent in the second step is 0.01 g to 0.5 g per 1 g of the copper powder.

The reaction between the copper surface and the surface active agent in the third step is as follows.

Cu ₂ O + 2 NH ₄ OH + (NH ₄ ) ₂ SO _{4 = (Cu (NH 3) 2} ) 2 SO 4 + 3H ₂ O

CuO + 2NH ₄ OH + (NH ₄ ) ₂ SO _{4 = (Cu (NH 3) 4} ) SO 4 + 3H 2 O

Cu (OH) ₂ + 2NH ₄ OH + (NH ₄ ) ₂ SO _{4 = (Cu (NH 3) 4} ) SO 4 + 4H 2 O

In the fourth step, silver is reduced and coated on the copper surface according to the following chemical formula.

_{Cu + 2 (Ag (NH 3} ) 2) NO 3 _{= (Cu (NH 3) 4} ) (NO 3) 2 + 2Ag

^{_{2Ag (NH 3) 2 + +}} 2OH - = Ag 2 O + 4NH 3 + H ₂ O

3Ag ₂ O + C ₄ H ₄ O ₆ ^{2 -} + 2OH ^- = 6Ag + 2C ₂ O ₄ ^{2 -} + 3H ₂ O

2Ag ⁺ + C ₆ H ₈ O ₆ + 2 OH ^- = 2 A + C ₆ H ₆ O ₆ + 2H ₂ O

The temperature of the solution in the fourth step is 10 ° C to 35 ° C, and the drying temperature in the fifth step is 50 ° C or less.

Hereinafter, the present invention will be described in detail with reference to examples.

30 g of silver nitrate and 60 g of ammonia water (28%) were placed in a beaker containing 500 ml of distilled water and dissolved and mixed to prepare solution 1. 30 g of sodium potassium tartrate, 5 g of ascorbic acid, and 15 g of ammonium sulfate were dissolved and mixed in a beaker containing 700 ml of distilled water to prepare solution 2. 300 g of a copper powder having a particle size of 5 mu m of the powder was placed in the solution 2 and stirred at 400 rpm for 10 minutes. After 10 minutes of stirring, Solution 1 was added to Solution 2 while stirring, and the solution was coated for 10 minutes. After the coated solution was sufficiently washed with water, the precipitate was put in a drier and dried at 25 캜 under vacuum for 24 hours.

The procedure of Example 1 was repeated except that ascorbic acid was removed from the reducing agent in Example 1.

The procedure of Example 1 was repeated except that the amount of silver nitrate was changed to 15 g in Example 1.

The procedure of Example 1 was repeated except that the amount of silver nitrate was changed to 60 g in Example 1.

The content of silver coated in Examples 1, 2, 3 and 4 is as follows.

As shown in the above table, it can be seen that the silver used in the coating is completely reduced without loss.

As can be seen from FIGS. 2, 4, 6 and 8, silver and copper are detected on the analysis results.

Also, as shown in FIGS. 1, 3, 5 and 7, it can be seen that the silver powders prepared according to Examples 1, 3 and 4 are evenly coated with silver on the surface of copper, but only potassium sodium tartrate as a reducing agent It can be seen that the powder produced by the method 2 has pores on its surface and the particles are not uniformly distributed over the entire surface and are not evenly coated.

While the present invention has been described with reference to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims (10)

A first step of dissolving silver salt and ammonia water to prepare solution 1;
A second step of dissolving a surface active agent and a reducing agent in distilled water to prepare solution 2;
A third step of removing foreign substances from the surface of the copper powder and surface activation by adding copper powder to the solution 2;
A fourth step of depositing the solution 1 in the solution 2 to precipitate silver on the surface of copper to coat silver;
And a fifth step of washing the silver-coated copper powder of the fourth step with distilled water and then vacuum-drying the silver-coated copper powder. The method for silver coating of copper powder applicable to circuit printing and conductive adhesive paste according to claim 1,
The method according to claim 1,
The silver salt of the first step is any one or a mixture of two or more selected from silver chloride (AgCl), silver nitrate (AgNO ₃ ), silver sulfate (Ag ₂ SO ₄ ) and silver phosphate (Ag ₃ PO ₄ ) dissolved in water A silver coating method of copper powder applicable to circuit printing and paste for conductive adhesives.
The method according to claim 1,
Wherein the amount of the aqueous ammonia in the first step is 1 g to 2 g per gram of silver nitrate.
The method according to claim 1,
Wherein the surface active agent in the second step is any one or a mixture of two or more selected from ammonium chloride (NH ₄ Cl), ammonium sulfate (NH ₄ SO ₄ ) and ammonium carbonate ((NH ₄ ) ₂ CO ₃ ) A silver coating method of copper powder applicable to circuit printing and paste for conductive adhesive.
The method according to claim 1,
Wherein the amount of the surface active agent in the second step is 0.01 to 0.1 g based on 1 g of the copper powder, which is applicable to the paste for circuit printing and conductive adhesive.
The method according to claim 1,
Wherein the reducing agent in the second step is a mixture of potassium sodium tartrate (KNaC ₄ H ₄ O ₆ ) and ascorbic acid (C ₆ H ₈ O ₆ ). The copper powder applicable to circuit printing and conductive adhesive pastes Coating method.
The method according to claim 1,
Wherein the amount of each of the reducing agents in the second step is 0.01 g to 0.5 g per 1 g of the copper powder, which is applicable to pastes for circuit printing and conductive adhesive.
The method according to claim 1,
Wherein the temperature of the solution in the fourth step is 10 ° C to 35 ° C. The silver coating method of copper powder applicable to paste for circuit printing and conductive adhesive.
The method according to claim 1,
Wherein the drying temperature in the fifth step is 50 DEG C or less. ≪ RTI ID = 0.0 > 8. < / RTI >
A copper powder applicable to a circuit printing and conductive adhesive paste produced by a coating method according to any one of claims 1 to 9.

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