KR101738494B1

KR101738494B1 - Silver coating method of copper powder

Info

Publication number: KR101738494B1
Application number: KR1020150090291A
Authority: KR
Inventors: 홍성철; 박상혁
Original assignee: 호서대학교 산학협력단; (주)엡실론
Priority date: 2015-06-25
Filing date: 2015-06-25
Publication date: 2017-05-22
Also published as: KR20170000998A

Abstract

The present invention relates to a silver coating method of copper powder for electromagnetic shielding and a silver-coated powder produced thereby, and more particularly, to a silver coating method for preventing electromagnetic interference It is possible to omit the sensing process and simplify the silver coating process of the entire copper powder and to uniformly coat the silver with a thin film to reduce the use of expensive silver and to improve the electromagnetic shielding reliability And a silver-coated powder prepared by the method.

Description

[0001] The present invention relates to a silver coating method of copper powder for shielding electromagnetic waves,

Technological advances in the field of electronic communications are taking place at a very rapid pace, and it is no exaggeration to say that electronic devices are used in almost every part of everyday life. In recent years, due to heightened interest in the environment and health, electromagnetic interference generated from various kinds of electronic devices, which are particularly used on a daily basis, has become a serious problem. These electromagnetic disturbances have been known to cause malfunctions of other devices as well as serious problems to the human body.

In order to block electromagnetic waves generated in such electronic devices and wireless communication devices, metal powders or composite powders generally having excellent conductivity have been used as materials for electromagnetic interference or shielding electromagnetic waves by mixing with polymer resins. In particular, Good gold and silver are known to be used. However, these materials are burdened with the cost increase of materials because they are very expensive. Therefore, studies on effective materials capable of lowering the cost while exhibiting the shielding effect of electromagnetic waves have been continuously conducted.

In recent years, silver coated copper powder or whisker powder coated with silver on the surface of copper or whisker, which is an inexpensive material, has been developed and is expanding its market.

However, when silver coating is applied to conventional copper powder or whisker powder, it is necessary to add degreasing, etching, and a sensing process to improve the adhesion between the powder and the expensive silver, .

Korean Registered Patent No. 10-1307238 (Registered on May 3, 2013)

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to eliminate the degreasing, etching, and sensing process for improving the adhesion of the conventional copper powder by pre- A silver coating method of copper powder for shielding electromagnetic waves which can simplify the silver coating process of the silver coating and can reduce the manufacturing cost, and a silver coating powder produced thereby.

Another object of the present invention is to provide a silver coating method of a copper powder for shielding electromagnetic waves and a silver coating powder produced by the method, which can uniformize the silver plating layer for corrosion resistance while improving the adhesion with silver, .

It is still another object of the present invention to provide a silver powder for electro-magnetic shielding which is capable of silver coating through reduction of potassium silicate (Potsssium Silver Cyanide) by simply pretreating copper powder with PEI without degreasing and cleaning of copper powder And a silver coating powder prepared thereby.

It is still another object of the present invention to provide a silver coating method of copper powder for shielding electromagnetic waves which can reduce the production cost by simplifying the process, reducing silver consumption, and maintaining electromagnetic wave shielding reliability by forming a uniform plating layer, Silver coating powder.

According to another aspect of the present invention, there is provided a silver coating method of a copper powder for shielding electromagnetic waves, comprising: preparing a copper powder; Pre-treating the prepared copper powder with polyethylenimine (PEI); And applying the PEI pretreated copper powder to a plating solution containing a silver compound to perform silver coating.

Here, the copper powder may be in the form of dendrite, spherical, dendrimer, needle, and flake.

It is preferable that the diameter of the spherical copper powder and the length of the dendritic copper powder are respectively 5 to 40 탆.

The silver compound is preferably potassium cyanide (KAgCN ₂ ).

In the preparation of the copper powder, the copper powder is put into pure water and stirred for a predetermined time with a stirrer. In the PEI preprocessing step, the PEI is added to the stirred copper powder and stirred for a certain period of time .

Further, it is preferable that the plating solution containing the silver compound further comprises a stabilizer.

The stabilizer is preferably at least one of 1,2,3-benzotriazole (benzotriazole), polystyrenesulfonate, naphthalenesulfonate, ligninsulfonate, and polyacrylate.

In addition, the amount of silver to be coated is preferably 5 to 15% by weight based on the total weight of the copper powder.

Further, the color of the silver-coated copper powder is preferably pink.

There is provided a silver coated copper powder for electromagnetic shielding which is produced by the silver coating method of copper powder for shielding electromagnetic waves as described above.

According to the silver coating method of copper powder for electromagnetic wave shielding according to the present invention and the silver coating powder produced by the method of the present invention as described above, it is possible to perform the degreasing, etching, So that the silver coating process of the entire copper powder can be simplified.

In addition, copper powder can be coated efficiently and economically, and even if copper powder has various forms such as dendrite type, spherical type, dendrimer type, needle type, and flake type, the characteristics of the PEI preprocessing process So that the reliability of the electromagnetic wave shielding performance can be enhanced while maintaining surface conductivity.

It is possible to obtain more uniformity by using the basic hydrogen bonding force possessed by PEI, and to obtain economical gain and reliability of physical properties by plating (coating) silver with a thin film.

1 is a scanning electron microscope (SEM) photograph of a silver coated copper powder for electromagnetic wave shielding produced according to Example 1 of the present invention.
2 is a scanning electron microscope (SEM) photograph of silver coated copper powder for electromagnetic wave shielding produced according to Example 2 of the present invention.
3 is a scanning electron microscope (SEM) photograph of silver coated copper powder for electromagnetic wave shielding produced according to Example 3 of the present invention.
4 is a scanning electron microscope (SEM) photograph of a silver coated copper powder for electromagnetic shielding according to a comparative example of the present invention.
5 is a graph showing the results of electromagnetic wave shielding measurement using the silver-coated copper powder of Example 3 of the present invention.

The present invention may be embodied in many other forms without departing from its spirit or essential characteristics. Accordingly, the embodiments of the present invention are to be considered in all respects as merely illustrative and not restrictive.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises", "having", "having", and the like are intended to specify the presence of stated features, integers, steps, operations, components, Steps, operations, elements, components, or combinations of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

The silver coating method of copper powder for shielding electromagnetic waves according to the present invention comprises: a step of pretreating copper powder with PEI; Forming a dispersion in which copper powder is dispersed; And a step of depositing a dispersion in which the copper powder is dispersed in a plating solution containing a silver compound to perform silver coating.

In the PEI (polyethylenimine) preprocessing step of the copper powder, a copper powder is first prepared as a core material.

The form of the copper powder may be a dendrite type, a spherical type, a dendrimer type, an acicular type, a flake type, or the like. Particularly, in the case of a dendritic type, that is, a copper powder taking a tissue form of a resin, it is more effective by the pretreatment of PEI (polyethylenimine) of the copper powder which is a feature of the present invention.

When the copper powder has a spherical shape, its diameter is preferably in the range of 5 to 40 μm, and when the copper powder is a dendrimer type, the length is preferably in the range of 5 to 40 μm.

If the diameter or the length of the copper powder exceeds the above range, there is a problem that the surface is rough and desired physical properties can not be obtained when the copper powder is made into a paste, a sheet or a coating agent. When the diameter is less than the above range, the particles are too small to cause agglomeration, and a lot of time and effort are required for the washing and filtration process, thereby causing problems in the profitability.

The polyethylenimine (PEI) is a kind of synthetic polymer having an amino group in the chain. It has the advantage of improving the adhesion to silver after pretreatment through hydrogen bonding and uniformly coating silver with a thin film.

In the PEI pretreatment, the prepared copper powder is added to a predetermined amount of pure water and agitated for a certain period of time. Then, a predetermined amount of PEI is added, and the mixture is stirred for a predetermined period of time to be pre-treated.

Therefore, it is possible to omit the degreasing, etching, and sensing steps for improving the conventional adhesiveness through the pre-treatment of the copper powder with the PEI, thereby simplifying the silver coating process of the entire copper powder.

In the dispersion forming step in which the copper powder is dispersed, the PEI pretreated copper powder can be stably dispersed by the dispersing agent to form a dispersion in which the copper powder is dispersed.

That is, the copper powder is added to a solution containing a dispersant, and the mixture is stirred using an agitator or the like to form a dispersion in which the copper powder is dispersed. In the present invention, it is possible to uniformly coat silver on the surface of the copper powder by preventing the fine copper powder from aggregating during the reduction precipitation of silver by forming the dispersion.

Since the copper powder is very fine particles, it is very important to form such a PEI preprocessing and dispersion solution for uniform coating, since the silver coating may be coagulated when the silver coating is performed without the PEI preprocessing and dispersion step .

The dispersing agent that can be used for forming the dispersion is preferably at least one dispersing agent selected from the group consisting of polystyrene sulfonate, naphthalene sulfonate, lignin sulfonate, polyacrylate and polycarboxylic acid, but is not limited thereto.

Here, the dispersion forming step may be omitted as an optional step.

In the step of silver coating the dispersion containing the copper powder in a plating solution containing a silver compound, the dispersion of the copper powder or the PEI-treated copper powder formed as described above is first applied to a plating solution containing a silver compound, And then mixed into the plating solution.

The silver compound (plating solution) that can be used in the present invention is preferably potassium cyanide (KAgCN ₂ ) and / or sodium cyanide (NaCN) solution (reducing agent) , And it is most preferable to add less than 10% by weight in terms of economy.

Here, the potassium silver cyanide used as the silver compound has an advantage that the silver plating process is easier than the silver nitrate.

The complex is added to activate silver before it is coated on the surface of the copper powder. In the present invention, it is preferable to use ammonia water as a complexing agent, but the present invention is not limited thereto. The above complex is not essential for the present invention.

The stabilizer used in the present invention is for stably coating silver on the copper powder and for helping dispersion and uniform coating of the fine powder. The stabilizer may be at least one selected from the group consisting of aromatic compounds such as 1,2,3-benzotriazole (benzotriazole), polystyrene sulfonate, naphthalene sulfonate, lignin sulfonate and polyacrylate , But is not limited to aromatic stabilizers in the present invention. It is preferable that the stabilizer is added in an amount of 10 to 100 g / L, and it is most preferable to add 39.6 g / L in view of stable and uniform coating of silver and dispersion of fine powder.

The silver complex thus formed is reduced and precipitated on the surface of the powder by a reducing agent to form a coating. The reducing agent is most preferably sodium cyanide, but hydrazine monohydrate, formaline, glucose, ascorbic acid it is preferable to use any one selected from the group consisting of ascorbic acid, sugar alcohol, and borohydride.

The reducing agent is optional in the present invention and is not essential.

On the other hand, after the reducing agent is added, the silver powder is washed, treated with fatty acid, and then dried at about 60 to 80 ° C for 1 to 2 hours to complete the silver coating of the copper powder for electromagnetic shielding according to the present invention.

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

However, the following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

Example 1

300 g of copper powder having a diameter of 10 탆 was added to 3 L of pure water and stirred at 400 rpm for 5 minutes with a stirrer. Thereafter, 1 g of PEI was added to the stirred copper powder and stirred for 5 minutes. A plating solution prepared by mixing 277.78 g of Potsssium Silver Cyanide (KAgCN ₂ ), 555.56 g of sodium cyanide (NaCN) and 12 g of stabilizer 1,2,3-Benzotriazole in 300 ml of pure water was added thereto And reacted for 10 minutes.

After plating, the substrate was washed, treated with fatty acid, and dried at 70 ° C for 1 hour and 30 minutes.

Example 2

300 g of copper powder having a diameter of 10 탆 was added to 3 L of pure water and stirred at 400 rpm for 5 minutes with a stirrer. Thereafter, 3 g of PEI was added to the stirred copper powder and stirred for 5 minutes. A plating solution prepared by mixing 277.78 g of Potsssium Silver Cyanide (KAgCN ₂ ), 555.56 g of sodium cyanide (NaCN) and 12 g of stabilizer 1,2,3-Benzotriazole in 300 ml of pure water was added thereto And reacted for 10 minutes.

Example 3

300 g of copper powder having a diameter of 10 탆 was added to 3 L of pure water and stirred at 400 rpm for 5 minutes with a stirrer. Thereafter, 5 g of PEI was added to the stirred copper powder and stirred for 5 minutes. A plating solution prepared by mixing 277.78 g of Potsssium Silver Cyanide (KAgCN ₂ ), 555.56 g of sodium cyanide (NaCN) and 12 g of stabilizer 1,2,3-Benzotriazole in 300 ml of pure water was added thereto And reacted for 10 minutes.

Comparative Example

300g of copper powder of 10um was stirred in a degreasing solution (APC, International Corporation) for 10 minutes, and then reacted in an etching solution (RT200, Hojin Plateck) for 10 minutes and washed with pure water. The washed powder was poured into 3 L of pure water and stirred at 400 rpm for 5 minutes. A plating solution prepared by mixing 277.78 g of Potsssium Silver Cyanide (KAgCN ₂ ), 555.56 g of sodium cyanide (NaCN) and 12 g of stabilizer 1,2,3-Benzotriazole in 300 ml of pure water was added thereto And reacted for 10 minutes.

Test examples 1 to 4: Characteristic test of silver coated copper powder

The resistance values of the silver-coated copper powders prepared in Examples 1 to 3 and Comparative Examples were measured. The surface characteristics were observed by a scanning electron microscope and the results are shown in Table 1 below.

characteristic Test Example 1 Test Example 2 Test Example 3 Test Example 4 Powder color Pink Light pink Pink Ivory Resistance (m? / Cm) 0.35 0.264 0.24 0.45

As shown in Table 1, the silver-coated copper powder prepared by the silver coating method of the copper powder for shielding electromagnetic waves according to the present invention is surrounded by silver (refer to FIG. 1 to FIG. 3) The resistance value was also low.

That is, as in Examples 2 and 3 of Table 1, it was found that when the amount of PEI added is 3 g or more, it has a low resistance value, and that the amount of PEI is at least 3 g or more.

On the other hand, in the test examples, the color of the coated copper powder is indicated as pink rather than silver because the silver plating amount is reduced to less than 10% by weight with respect to the copper powder, and the color of the copper powder used as the core is projected as it is. That is, it was confirmed that the silver powder was thinly and uniformly coated as the content of silver decreased, and the color of the copper powder appeared pink.

In particular, in the case of the silver coated copper powder prepared in Example 3, as shown in FIG. 3, the surface of the silver powder was very well surrounded by a relatively large amount of 5 g of PEI, and the resistance value was the lowest at 0.24? / Cm.

That is, as shown in FIG. 3, in the case of Example 3, it was found that the top end portion of the dendrite was sharply and uniformly coated with silver as the best performance.

Further, as shown in FIG. 3, it was found that each dendritic particle was dispersed without scattering, and aggregation was smaller than in the other examples and comparative examples.

The results of electromagnetic wave shielding measurement using the silver-coated copper powder of Example 3 are shown in FIG. As shown in FIG. 5, it can be seen that excellent shielding measurement results of 35 dB or less are exhibited in all the electromagnetic waves (Hz).

On the other hand, in the comparative example in which the PEI according to the present invention was put into the degreasing and etching process, the resistance value was not different from that of the other examples, and the resistance value was higher than those of Test Examples 2 and 3.

Accordingly, it was confirmed that when the PEI pretreatment by the PEI according to the present invention was applied, the silver coated copper powder had excellent surface characteristics and a low resistance value and thus had excellent electromagnetic wave shielding efficiency.

The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims

Preparing a copper powder;
Pre-treating the prepared copper powder with polyethylenimine (PEI);
Dispersing the PEI pretreated copper powder with a dispersant to form a dispersion in which copper powder is dispersed;
And a silver coating step of depositing the dispersion in which the copper powder is dispersed in a plating solution containing a silver compound, a complexing agent and a stabilizer to perform silver coating,
Wherein the dispersing agent is at least one of polystyrene sulfonate, naphthalene sulfonate, lignin sulfonate, polyacrylate, and polycarboxylic acid,
The complexing agent uses ammonia water,
Wherein the stabilizer is at least one selected from the group consisting of 1,2,3-Benzotriazole (benzotriazole), polystyrenesulfonate, naphthalenesulfonate, ligninsulfonate, and polyacrylate. Way.

The method according to claim 1,
Wherein the shape of the copper powder is one of a dendrite type, a spherical type, a dendrimer type, an acicular type, and a flake type.

The method according to claim 2,
Wherein the diameter of the spherical copper powder and the length of the dendritic copper powder are respectively 5 to 40 占 퐉.

The method according to claim 1,
Wherein the silver compound is potassium silver cyanide (KAgCN ₂ ).

The method according to claim 1,
In preparing the copper powder, the copper powder is poured into pure water and agitated with a stirrer for a certain period of time,
Wherein the PEI pretreatment step comprises charging the stirred copper powder with the PEI, and stirring the copper powder for a predetermined period of time.

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The method according to claim 1,
Wherein the amount of silver to be coated is 5 to 15% by weight based on the total weight of the copper powder.

The method according to claim 1,
Wherein the silver coated copper powder is pink in color.

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