KR101676131B1 - Method for manufacturing metal composite - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a metal composite, and more particularly, to a method of manufacturing a core-shell structure metal composite by coating a different metal on the surface of the metal powder.

Description

[0001] METHOD FOR MANUFACTURING METAL COMPOSITE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a metal composite, and more particularly, to a method of manufacturing a core-shell structure metal composite by coating a different metal on the surface of the metal powder.

The paste using metal powder is the most widely used technique in printed circuit boards. It can be applied to electronic packaging processes, solar cells, mobile electronic devices, etc. because it can be used for coating, painting and ink by diluting metal paste in organic solvents. In addition, it is utilized as a material for shielding electromagnetic waves generated from electronic devices.

At present, the conductive metal powder contained in the paste is mainly silver, copper, aluminum and nickel.

Among them, copper or nickel silver has the next highest conductivity, and since it has a large electromagnetic wave absorption loss and reflection loss value, it has been applied variously with silver.

However, metals with high oxidation resistance such as copper or nickel are exposed to air for a long period of time, resulting in oxidation on the surface, which leads to conductivity or malfunction.

On the other hand, silver is highly utilizable as a conductive metal powder because of its high conductivity, but silver is relatively expensive, which is disadvantageous in terms of cost.

For this purpose, in order to increase the competitiveness of the conductive metal powder, there is a continuing need for the development of a metal powder, which has a cost similar to that of using a silver powder with a lowered cost of the metal powder.

Under such technical background, the present inventors have found that the use of a composite of a core-shell structure in which the surface of a nickel powder is coated with silver as a means for keeping the electrical properties of the conductive metal powder at an allowable level, .

However, in the case of copper or nickel having a high oxidation resistance, it is confirmed that there is a problem that an oxide film is formed on the surface of air in the air, and the silver coating layer does not grow properly on the oxide film of the metal.

That is, since the oxide film formed on the surface of the oxidation-resistant metal lowers the adhesion with the noble metal coating layer such as silver, it is difficult to form a uniform coating layer when the noble metal is coated on the surface of the oxidation-resistant metal powder.

Accordingly, it is an object of the present invention to provide a method for producing a core-shell structure metal composite by uniformly coating a different metal such as a noble metal on the surface of the metal powder.

According to an aspect of the present invention, there is provided a method for producing a metal composite by forming a second metal coating layer on a surface of a first metal powder, comprising the steps of: a) preparing a first reaction solution containing a first metal powder and a reducing agent ; b) preparing a second reaction solution comprising a second metal precursor and a first metal oxide film remover; And c) reacting the first reaction solution and the second reaction solution to remove a first metal oxide film existing on the surface of the first metal powder and forming a second metal coating layer on the surface of the first metal powder May be provided.

Here, the first metal powder may be at least one metal selected from copper, nickel, tin, zinc, aluminum and iron.

Here, the reducing agent may be at least one reducing sugar selected from glucose, fructose, maltose and lactose.

The reducing agent may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, (s) selected from the group consisting of suberic acid, azelaic acid, sebacic acid, citric acid, isocitric acid, aconitic acid, At least one adjuvant selected from propane-1,2,3-tricarboxylic acid, trimesic acid, meleic acid and tartaric acid.

Here, the reducing agent is glucose and may further include citric acid as an auxiliary agent.

Here, the mass ratio of the glucose to the citric acid may be in the range of 1:10 to 20: 1.

Here, the second metal precursor may be at least one selected from silver salts, platinum salts and gold salts.

Here, the first metal oxide film remover may be ethylene diamine (EDA).

Here, the molar ratio of the second metal precursor to the first metal oxide film remover in the second reaction solution may be in the range of 1: 100 or more and less than 1: 200.

In this case, the second metal coating layer is first formed on the surface of the first metal powder through the step c), and further reacted with the third reaction solution containing the second metal precursor and the complexing agent And d) forming a second metal coating layer in a second step.

Here, the complexing agent may be at least one selected from ethylenediaminetetraacetic acid (EDTA), thiosulfate, ammonia, cyanide, sulphite, and thiourea.

Here, the molar ratio of the second metal precursor to the complexing agent in the third reaction solution may be in the range of 1:10 to 1:30.

The method may further include a step of pre-treating the first metal powder with an acidic or basic solution before the step a).

According to the present invention, since the oxide film formed on the surface of the metal particles is removed and the noble metal is coated, the adhesion between the metal particles and the dissimilar metal can be improved, and the core-shell structure metal having a uniform dissimilar metal coating layer Complex can be produced.

FIG. 1A is an SEM image of a metal complex prepared by reacting a second reaction solution containing EDTA-ammonia with a first reaction solution. FIG. 1B is a cross-sectional view of a metal complex prepared by reacting a second reaction solution containing EDA with a first reaction solution SEM photograph of a metal complex.
2 shows ICP analysis results of a metal complex prepared by reacting a metal complex prepared by reacting a second reaction solution containing EDTA-ammonia with a first reaction solution, a second reaction solution containing EDA, and a first reaction solution .
FIG. 3 is a graph showing the results of reaction between a second reaction solution containing EDTA-ammonia and a first reaction solution, reacting the remaining reaction solution with a second reaction solution containing EDA and the first reaction solution, The results of the analysis are shown.
4 is a SEM photograph of the metal complex according to the change of the molar ratio of the precursor and EDA in the second reaction solution.

Certain terms are hereby defined for convenience in order to facilitate a better understanding of the present invention. Unless otherwise defined herein, scientific and technical terms used in the present invention shall have the meanings commonly understood by one of ordinary skill in the art. Also, unless the context clearly indicates otherwise, the singular form of the term also includes plural forms thereof, and plural forms of the term should be understood as including its singular form.

Terms including ordinals such as first, second, etc. may be used to describe various elements, but the elements are not limited by such terms. These terms are used only to distinguish one component from another.

Hereinafter, various aspects of the present invention will be described in detail.

A method for producing a metal complex according to the present invention comprises the steps of: a) preparing a first reaction solution containing a first metal powder and a reducing agent; b) preparing a second reaction solution comprising a second metal precursor and a first metal oxide film remover; And c) reacting the first reaction solution and the second reaction solution to remove a first metal oxide film existing on the surface of the first metal powder and forming a second metal coating layer on the surface of the first metal powder .

At this time, the removal of the first metal oxide film and the formation of the second metal coating layer occur simultaneously, and it is preferable that the removal rate of the first metal oxide film is faster than the regeneration rate of the first metal oxide film.

The first metal powder to form the core of the metal composite may be copper, nickel, tin, zinc, aluminum, iron, or the like as a metal powder having an oxide film on its surface, that is, an oxidation resistant metal powder.

At least one metal powder selected from copper, nickel, tin, zinc, aluminum and iron may be used alone as the first metal powder or at least two metal powders selected from copper, nickel, tin, zinc, Metal alloy powder may be used.

In addition, the first metal powder may be used after being pre-treated with an acid such as hydrochloric acid, sulfuric acid, nitric acid or the like or a basic solution such as sodium hydroxide, magnesium hydroxide or the like for surface modification or the like.

The reducing agent in the first reaction liquid may contain a second metal ion (e.g., a silver ion, a platinum ion and / or a metal ion) present in a precursor (e.g., a silver salt, a platinum salt and / Gold ion) is induced to form a second metal coating layer on the surface of the first metal powder forming the core of the metal composite.

That is, a second metal coating layer is formed on the surface of the first metal powder to produce a metal composite having a core-shell structure.

Here, the reducing agent used for inducing the reduction reaction of the second metal ion for forming the second metal coating layer is preferably at least one reducing sugar selected from glucose, fructose, maltose and lactose.

The reducing agent may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, And salts thereof. The compounds of the present invention include, but are not limited to, suberic acid, azelaic acid, sebacic acid, citric acid, isocitric acid, aconitic acid, May be used in combination with at least one adjuvant selected from propane-1,2,3-tricarboxylic acid, trimesic acid, meleic acid and tartaric acid. .

Preferably, in the present invention, glucose may be used as a reducing agent, and citric acid may be used as an auxiliary agent.

At this time, citric acid may be contained in the mixture in citrate form.

Since the first metal oxide film removing agent to be described later is generally a basic substance, it is particularly preferable to use a mixture of glucose and citric acid to maintain an appropriate reducing power under a basic pH atmosphere formed by the first metal oxide film removing agent.

The citric acid or citric acid salt together with the glucose acts as a reducing agent for the second metal precursor and can also serve as a dispersing agent for the first metal powder.

For example, when ascorbic acid having a high reduction rate is used as a reducing agent conventionally used for reducing metal ions (here, the second metal precursor), the reducing power of ascorbic acid to the second metal ion is excessively strong Thereby inducing the self-nucleating reaction of the second metal ion in the reaction solution. Accordingly, it is difficult for the second metal coating layer to be uniformly formed on the surface of the first metal powder.

Accordingly, in order to remove the oxide film formed on the surface of the first metal powder and form a uniform second metal coating layer on the surface of the first metal powder by using the first metal oxide film remover as in the present invention, It is preferable to use a mixture of glucose and citric acid as a reducing agent capable of maintaining an appropriate level of reducing power under the pH atmosphere formed by the above-mentioned method.

Also, preferably, the mass ratio of glucose to citric acid in the mixture is in the range of 1:10 to 20: 1. That is, when the mass ratio of glucose to citric acid is excessively low, it is difficult to form a uniform second metal coating layer on the surface of the first metal powder because the second metal precursor is not sufficiently reduced.

On the other hand, when the mass ratio of glucose to citric acid is excessively high, that is, when the content of citric acid is excessively low, it is difficult to maintain a proper reducing power in a pH atmosphere formed by the first metal oxide film remover, It is difficult to form a uniform second metal coating layer.

The first metal oxide film remover in the second reaction liquid serves primarily to remove the oxide film formed on the surface of the first metal powder and secondarily reduces the reduction potential of the second metal ion in the second reaction liquid, It suppresses the self-nucleation reaction of ions.

At this time, it is preferable that the first metal oxide film removing agent is ethylene diamine (EDA).

Here, EDA can act as a complexing agent for forming a complex with the second metal ion, but EDA (ethylenediaminetetraacetic acid), thiosulfate, ammonia, Cyanide, sulphite, or thiourea. The term " cyanide "

As has been confirmed in the examples to be described later, the removal effect of the oxide film formed on the surface of the first metal powder by the commonly used complexing agent is considerably lower than that of EDA and falls within the category of the first metal oxide film removing agent defined herein It is difficult to see.

The molar ratio of the second metal precursor to the first metal oxide film remover in the second reaction liquid is preferably in the range of 1: 100 or more and less than 1: 200. The molar ratio of the second metal precursor to the first metal oxide film remover in the second reaction liquid is related to the degree of formation of the second metal coating layer on the surface of the first metal powder.

That is, since the removal rate of the oxide film formed on the surface of the first metal powder increases as the molar ratio of the first metal oxide film remover to the second metal precursor increases, the second metal precursor is reduced on the surface of the first metal powder, The area for forming the two-metal coating layer gradually increases.

Also, as the molar ratio of the first metal oxide film remover to the second metal precursor increases, the removal rate of the oxide film formed on the surface of the first metal powder increases.

However, if the molar ratio of the second metal precursor to the first metal oxide film remover is less than 1: 100, the oxide film formed on the surface of the first metal powder is difficult to remove sufficiently, It is difficult to form a uniform second metal coating layer on the surface of the first metal powder because it is slower than the regeneration speed of the second metal precursor and the reduction rate of the second metal precursor.

In other words, as the molar ratio of the first metal oxide film remover to the second metal precursor increases, the non-uniform silver crystal growth rate and the regeneration rate of the oxide film formed on the surface of the first metal powder, It is possible to more uniformly form the second metal coating layer on the surface of the first metal powder because the removal rate of the oxide film formed on the surface of the powder is relatively faster.

On the other hand, when the molar ratio of the second metal precursor to the first metal oxide film remover is more than 1: 200, not only the removal of the oxide film formed on the surface of the first metal powder, but also the melting of the first metal powder itself, Perforations may occur between the powder and the second metal coating layer.

The perforation between the first metal powder corresponding to the core of the metal composite body having the core-shell structure and the second metal coating layer corresponding to the shell results in a failure of the prepared metal complex, and further, Can be reduced.

Therefore, the first metal oxide film removing agent used in the present invention primarily serves to remove the oxide film formed on the surface of the first metal powder, and secondly, by reducing the reduction potential of the second metal ion in the second reaction solution, It is preferable that the oxide film formed on the surface of the first metal powder is removed in a molar ratio of 1: 100 or more and less than 1: 200 in relation to the second metal precursor in the second reaction solution, And is defined as a material that induces a uniform second metal coating layer on the surface of the metal powder.

In addition, in the method of manufacturing a metal complex according to the present invention, the first reaction solution and the second reaction solution are reacted in step c) to form a second metal coating layer on the surface of the first metal powder, And a second reaction liquid containing a complexing agent to form a second metal coating layer.

Here, crystal growth of the second metal coating layer formed on the surface of the first metal powder is additionally performed. Thus, the second metal coating layer can be more uniformly formed on the surface of the first metal powder.

Here, the complexing agent in the third reaction solution is at least one selected from ethylenediaminetetraacetic acid (EDTA), thiosulfate, ammonia, cyanide, sulphite, and thiourea , Which is distinguished from EDA, which is the first metal oxide film remover in the second reaction solution.

As described above, the complexing agent in the third reaction solution forms a complex of the second metal ion-complexing agent through coordination bonding with the second metal ion in the second reaction liquid, thereby lowering the reducing potential of the second metal ion , Thereby inhibiting the self-nucleating reaction of the second metal ion.

In this case, the molar ratio of the second metal precursor to the complexing agent in the third reaction solution is preferably in the range of 1:10 to 1:30.

When the molar ratio of the complexing agent to the second metal precursor is less than the above range, the second metal is unevenly coated on the surface of the first metal powder because the reduction potential of the second metal ion at the beginning of the reaction becomes too large, The surface of the first metal powder may be exposed or the second metal coating layer may not be formed uniformly because the second metal is further grown on the non-uniform coating layer in the step.

On the other hand, if it exceeds the above range, the reduction reaction of the second metal ion by the complexing agent is excessively suppressed, and secondary formation of the second metal coating layer is difficult to be smoothly performed.

In order to produce the metal complex according to the present invention, the same process as that of using the third reaction liquid may be repeatedly performed.

As described above, the metal complex according to the present invention firstly removes the oxide film formed on the surface of the first metal powder and reduces the second metal precursor to form a second metal coating layer on the surface of the first metal powder.

In addition, it is possible to manufacture a metal composite in which a second metal coating layer is formed on the surface of the first metal powder by forming a second metal coating layer on the surface of the first metal powder having the second metal coating layer formed thereon .

That is, the step of forming the second metal coating layer primarily includes removing the oxide film formed on the surface of the first metal powder to increase the surface area of the first metal powder that can be reduced by the second metal precursor, The second metal coating layer may be formed on the surface of the first metal powder without removing the oxide film formed on the surface of the first metal powder, 2 is a coating step for improving the uniformity of the second metal coating layer through additional growth of the metal coating layer.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto.

Example

(1) Pretreatment of the first metal powder and preparation of the first reaction solution

3 g of nickel powder was added to a mixture of distilled water of 14.5 g of 35% HCl and 42.86 ml of water, and the mixture was reacted for 1 hour while stirring vigorously. After centrifugation, the solution was discarded, and distilled water was added thereto, followed by centrifugation three times. The above-mentioned nickel particles were dispersed in 45 ml of water, and 5 g of glucose and 5 g of citric acid were added.

(2) Preparation of second reaction solution and third reaction solution

The second reaction solution was prepared by adding 30.96 ml of EDA and 0.525 g of silver nitrate to 14.04 ml of water. To the 20.23 ml of water, the third reaction solution was prepared by adding 24.77 ml of EDTA and 1.05 g of silver nitrate to water.

(3) Formation of second metal coating layer (primary)

45 ml of the second reaction solution was added to the first reaction solution at a rate of 20 to 100 ml per hour using a solution injecting apparatus at 500 rpm to form a silver coating layer on the surface of the nickel powder. After the injection was completed, additional reaction was allowed for 5 minutes.

(4) Formation of second metal coating layer (secondary) and obtaining metal complex

After addition of 5 g of glucose and 5 g of citric acid, 45 ml of the third reaction solution was added at a rate of 20 to 100 ml per hour using a solution injecting apparatus at 500 rpm to form a silver coating layer on the surface of the nickel powder . The reaction was carried out for 90 minutes.

After the reduction reaction was completed, the reaction product was centrifuged at 3000 rpm in a centrifuge, and after the solution was discarded, distilled water was added and centrifugation was repeated three times, followed by particle washing and drying to obtain a core- Metal complex.

Comparative Example  One

A metal complex of a core-shell structure was obtained in the same manner as in Example except that EDTA-ammonia was used instead of EDA in the second reaction solution of the above Example.

Comparative Example  2

The molar ratio of silver nitrate to EDA in the second reaction solution in the above example was set to 1:50. In the other procedures, a metal complex of a core-shell structure was obtained in the same manner as in Example.

Comparative Example  3

The molar ratio of silver nitrate to EDA in the second reaction solution of the above Example was set to 1:75, and a metal complex of a core-shell structure was obtained in the same manner as in the other procedures.

Comparative Example  4

The molar ratio of silver nitrate to EDA in the second reaction solution of the above Example was set to 1: 200, and a metal complex of a core-shell structure was obtained in the same procedure as the other procedures

Metal complex SEM  Photo analysis results

FIG. 1A is an SEM image of a metal complex prepared by reacting a second reaction solution containing EDTA-ammonia and a first reaction solution according to Comparative Example 1, FIG. 1B is a SEM image of a second reaction solution containing EDA and a first reaction SEM photographs of the metal complexes prepared by reacting the metal complexes.

Referring to the SEM image of FIG. 1A, it can be seen that the crystal growth of silver is non-uniform on the surface of the nickel powder. This is a result of silver coating in a state in which the oxide film formed on the surface of nickel, which is an oxidation-resistant metal, is not sufficiently removed. On the other hand, referring to the SEM image of FIG. 1B, it can be seen that the silver is formed tightly and uniformly tightly on the surface of the nickel powder.

4A is an SEM photograph of nickel before the silver coating layer is formed, and B and C are SEM images of the metal complex when the molar ratio of silver nitrate and EDA is 1:50 and 1:75, respectively, according to Comparative Example 2 and Comparative Example 3 SEM picture.

B and C, it can be seen that as the molar ratio of EDA to silver nitrate increases, silver crystals gradually grow on the surface of the nickel powder, but it is insufficient to form a uniform silver coating layer. That is, since the nickel oxide film formed on the surface of the nickel powder is not sufficiently removed, it is almost impossible to form a uniform silver coating layer.

On the other hand, referring to D and E in which the molar ratios of silver nitrate and EDA are 1: 100 and 1: 150 according to an embodiment of the present invention, silver crystals grow more uniformly on the surface of nickel powder than B and C, As shown in Fig.

As the molar ratio of EDA to silver nitrate increases, the removal rate of the nickel oxide film formed on the surface of the first metal powder increases, so that silver nitrate is reduced on the surface of the nickel powder and the area for forming the silver coating layer gradually increases.

That is, as the molar ratio of EDA to silver nitrate increases, the rate of removal of the nickel oxide film formed on the surface of the nickel powder is relatively faster than the irregular silver crystal growth rate and the regeneration rate of the nickel oxide film. It is possible to form more uniformly.

If the molar ratio of EDA to silver nitrate is excessively large, the removal rate of the nickel oxide film formed on the surface of the nickel powder is excessively fast do.

Therefore, it is possible to cause not only the nickel oxide film formed on the surface of the nickel powder but also the nickel powder itself to be melted, thereby confirming that the nickel powder and the silver coating layer are perforated.

ICP  Analysis

FIG. 2 is a graph showing the results of a reaction between a metal complex prepared by reacting a second reaction solution containing EDTA-ammonia and a first reaction solution according to Comparative Example 1 and a second reaction solution containing EDA and a first reaction solution, FIG. 3 is a graph showing the results of ICP analysis of a metal complex prepared by reacting a second reaction solution containing EDTA-ammonia with a first reaction solution according to a comparative example, And the ICP analysis result of the remaining reaction solution after reacting the second reaction solution containing the first reaction solution with the first reaction solution.

Referring to FIG. 2, the content of nickel in the metal composite prepared according to Comparative Example 1 is higher than that of the metal composite prepared according to the embodiment. This is because, in the case of the metal composite produced according to the embodiment, it is expected that the removal of the nickel oxide film formed on the surface of the nickel powder by EDA is performed more than in the comparative example.

Also, referring to FIG. 3, it can be seen that the content of molten nickel (Ni) in the remaining reaction liquid is higher in the case of Example 1 than in Comparative Example 1. It can be confirmed that EDTA-ammonia can also melt nickel similarly to EDA in that both the example and the comparative example 1 contain molten nickel in the remaining reaction solution.

However, the degree of melting of nickel is negligible compared to that of EDA. This is due to the difference in removal rate of EDTA-ammonia and EDTA from the nickel oxide film, and the removal rate of EDTA-ammonia nickel oxide film is higher than that of nickel oxide film It can be expected to be slow.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention as set forth in the appended claims. The present invention can be variously modified and changed by those skilled in the art, and it is also within the scope of the present invention.

Claims (13)

A method for producing a metal composite by forming a second metal coating layer on a surface of a first metal powder,
a) preparing a first reaction solution comprising a first metal powder and a reducing agent;
b) preparing a second reaction solution comprising a second metal precursor and a first metal oxide film remover; And
c) reacting the first reaction solution and the second reaction solution to remove a first metal oxide film existing on the surface of the first metal powder, and forming a second metal coating layer on the surface of the first metal powder;
/ RTI >
here,
Wherein the first metal oxide film removing agent is ethylene diamine (EDA)
METHOD FOR PRODUCING METAL COMPLEX
The method according to claim 1,
Wherein the first metal powder is at least one metal selected from copper, nickel, tin, zinc, aluminum and iron.
The method according to claim 1,
Wherein the reducing agent is at least one reducing sugar selected from glucose, fructose, maltose and lactose.
The method of claim 3,
The reducing agent may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, acid, azelaic acid, sebacic acid, citric acid, isocitric acid, aconitic acid, propane-1,2,3-tricarboxylic acid further comprising at least one adjuvant selected from propane-1,2,3-tricarboxylic acid, trimesic acid, meleic acid and tartaric acid. ≪ / RTI >
5. The method of claim 4,
Wherein the reducing agent is glucose and further comprises citric acid as an auxiliary agent.
6. The method of claim 5,
Wherein the mass ratio of glucose to citric acid is in the range of 1:10 to 20: 1.
The method according to claim 1,
Wherein the second metal precursor is at least one selected from silver salts, platinum salts and gold salts.
delete The method according to claim 1,
Wherein the molar ratio of the second metal precursor to the first metal oxide film remover in the second reaction solution is in the range of 1: 100 to less than 1: 200.
The method according to claim 1,
In the above manufacturing method,
Forming a second metal coating layer on the surface of the first metal powder through the step c)
Further comprising the step (d) of further forming a second metal coating layer by further reacting with a third reaction solution containing a second metal precursor and a complexing agent.
11. The method of claim 10,
Wherein the complexing agent is at least one selected from ethylenediaminetetraacetic acid (EDTA), thiosulfate, ammonia, cyanide, sulphite, and thiourea. ≪ / RTI >
11. The method of claim 10,
Wherein the molar ratio of the second metal precursor to the complexing agent in the third reaction solution is in the range of 1:10 to 1:30.
The method according to claim 1,
Further comprising the step of pre-treating the first metal powder with an acidic or basic solution before the step a).

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