KR20200049348A - Method for treating the surface of silver coated powder for electrically conductive paste - Google Patents

Abstract

A surface treatment method of silver coating powder for a conductive paste is disclosed. According to the present invention, the surface treatment method of a silver coating powder for a conductive paste comprises the steps of: (a) pretreating the powder; (b) silver coating the pretreated powder to form a silver coated powder; and (c) surface treating by introducing the silver coated powder into a self-assembled monolayer solution.

Description

METHOD FOR TREATING THE SURFACE OF SILVER COATED POWDER FOR ELECTRICALLY CONDUCTIVE PASTE}

The present application relates to a surface treatment method of a silver coating powder for conductive pastes.

Metal powder has been widely used as a raw material for conductive pastes in electronic materials. In addition, since the conductive paste is easy to handle, it has been widely used from experimental purposes to electronic industrial use. Particularly, the powder coated on the surface with a silver coating layer is used for circuit formation of a printed wiring board using a screen printing method, various electrical contacts, electromagnetic wave shielding materials, etc., and has been widely used as a material for securing conductivity. This is advantageous even economically because the silver coating powder is superior in oxidation stability and conductivity compared to a conventional metal powder, and is not expensive, unlike a noble metal powder made of only gold or silver. This is because it is also possible to impart conductivity to a non-conductive material by coating silver on glass or silica. Therefore, a low-resistance conductor can be manufactured at low cost by using the silver coating powder.

However, the existing silver coating powder was treated with an acid value solution such as oleic acid, stearic acid, or adipic acid, but in the case of silver coating powder treated with such a coating agent, electronic products During the process, the surface deterioration due to the acid value of the coating agent is promoted at a high temperature of 280 ℃, which is the condition of surface mount technology, and the silver coating coated on the metal powder falls or the metal powder inside the uncoated oxide is oxidized, resulting in an increase in resistance. Due to this problem, studies on the surface treatment method of the silver coating powder for improving the high temperature and heat resistance of the silver coating powder have been continuously conducted.

The background technology of the present application is disclosed in Korean Patent Publication No. 10-2015-0090032.

The present application is to solve the problems of the prior art described above, the surface treatment method of the silver coating powder for conductive pastes that can withstand the high temperature of 280 ℃, which is a condition of the surface-mounting technology, which is one of the process of electronic products, silver coating powder It is aimed at providing.

However, the technical problems to be achieved by the embodiments of the present application are not limited to the technical problems as described above, and other technical problems may exist.

As a technical means for achieving the above technical problem, the surface treatment method of the silver coating powder for conductive paste according to the first aspect of the present application comprises the steps of: (a) pre-treating the powder; (b) silver coating the pretreated powder to form a silver coated powder; And (c) silver coating the powder into a self-assembled monolayer solution to perform surface treatment.

In addition, the surface-treated silver coating powder according to the second aspect of the present application may be prepared by a surface treatment method of the silver coating powder for conductive paste according to the first aspect of the present application.

The above-described problem solving means are merely exemplary and should not be construed as limiting the present application. In addition to the exemplary embodiments described above, additional embodiments may exist in the drawings and detailed description of the invention.

According to the above-described problem solving means of the present application, surface treatment by a self-assembled monolayer solution may be performed on the silver-coated powder, so that high-temperature heat resistance is improved and the silver-coated powder is a surface mount technology (SMT) condition. In the high-temperature processing condition of 280 ° C, an increase in the resistance value can be suppressed.

1 is a schematic flowchart of a method for treating a surface of a silver coating powder for a conductive paste according to an embodiment of the present application.

Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present application pertains may easily practice. However, the present application may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly describe the present application in the drawings, parts irrelevant to the description are omitted, and like reference numerals are assigned to similar parts throughout the specification.

Throughout this specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. do.

Throughout the present specification, when a member is positioned on another member “on”, “on the top”, “top”, “bottom”, “bottom”, “bottom”, this means that one member is attached to another member. This includes cases where there is another member between the two members as well as when in contact.

Throughout the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless specifically stated to the contrary.

The present application relates to a surface treatment method of a silver coating powder for conductive pastes.

Hereinafter, a surface treatment method of a silver coating powder for a conductive paste according to an embodiment of the present application (hereinafter referred to as 'this surface treatment method') will be described.

1 is a schematic flowchart of a method for treating a surface of a silver coating powder for a conductive paste according to an embodiment of the present application.

Referring to FIG. 1, the surface treatment method includes a step of pre-processing the powder (S100).

The powder can include one or more of metals and non-metals. For example, the powder may include at least one of a metallic material such as nickel (Ni) and copper (Cu) and a non-metallic material such as glass and silica.

In addition, the step S100 may include a step of degreasing the powder and etching the degreased powder so that oil and oxides on the surface of the powder are removed and hydrophilicity is imparted to the surface of the powder. That is, each of degreasing the powder and etching the degreased powder may be referred to as a pre-treatment step for improving the adhesion of silver to the surface by removing oil and oxides on the surface of the core material to be coated. Particularly, by performing the etching, hydrophilicity is imparted to the surface of the material (powder), so that coating can be facilitated.

In addition, the step S100 may include a step of sensitizing the etched powder so that a metal salt having a reducing power is adsorbed on the powder surface. The sensitizing step is one of the pre-treatment processes for improving the adhesion between powder and silver, and it is possible to adsorb a metal salt having a reducing power on the powder surface, and it may be preferable to use tin chloride.

In addition, referring to Figure 1, the surface treatment method includes the step of forming a coated powder by silver coating the pretreated powder (S300). Here, the term "silver coating" is preferably understood as a concept encompassing both coating with silver and coating with a silver compound. Thus, herein, silver may refer to a silver or silver compound. Also, for reference, the silver compound may be silver nitrate (AgNO ₃ ).

Step S300 may be performed with one or more of a substitution coating and a reduction coating. The substitution coating may be a coating in a form in which a surface of a core material to be coated is partially melted to provide electrons to silver electrons to precipitate, that is, to change positions. In addition, the reduction coating may be a method of artificially giving electrons to silver electrons and depositing them by depositing a reducing agent when the core material cannot supply electrons. Step S300 may be performed with one or more of such substitution coating and reduction coating.

In addition, in step S300, the silver-coated powder may coat silver so that silver contains 3% to 80% of the weight of the powder. Accordingly, the silver-coated powder herein may include silver in an amount of 3% or more and 80% or less based on the weight of the powder.

In addition, the silver-coated powder (silver-coated powder) may include one or more of a ball type, a flake type, and a dendrite type.

In addition, the diameter (particle size) of the silver coated powder (silver coated powder) may be 1 nm or more and 1 mm or less.

In addition, referring to FIG. 1, the surface treatment method includes a step (S500) of introducing a silver-coated powder into a self-assembled monomolecular layer solution. For example, in step S500, a wet method may be used. Specifically, in step S500, a self-assembled monomolecular film may be formed on the surface of the silver-coated powder by reacting the silver-coated powder in a solution of the self-assembled monolayer for a predetermined time.

In addition, the self-assembled monolayer solution may be a solution in which an alkanthiol or a phosphonic acid system is dispersed. Alkanthiols or phosphonic acid-based solutions may be suitable because they react well with metals. Accordingly, the step S500 may be referred to as a method of preparing a self-assembled monomolecular layer solution in which a solution of an alkanthiol or a phosphonic acid system is dispersed in a solvent, and then surface-treating a silver-coated powder in the solution.

Specifically, the self-assembled monolayer solution may be one in which at least one of octadecylphosphonic acid and octanethiol is dispersed in an ethanol solution (see Table 1 and Table 3 to be described later). For reference, the self-assembled monolayer solution may preferably include octadecylphosphonic acid.

In addition, referring to FIG. 1, the present surface treatment method may include a step (S400) of processing the silver-coated powder between the steps S300 and S500.

Illustratively, the step S400 may include dissolving the coating agent in isopropyl alcohol (Isopropylalcohol), then adding the silver coated powder and stirring it, and filtering and drying the stirred silver coated powder. In addition, as an additive applicable as a coating agent in the step S400 may include oleic acid, stearic acid, adipic acid, and the like. However, oleic acid and stearic acid may be most preferable as the coating agent.

In addition, since the acid value of the coating agent may affect at a high temperature, in step S400, after dissolving the coating agent in isopropyl alcohol, silver coating powder may be added and an amide-based solution may be added and stirred to adjust the acid value. For example, in the past, the silver-coated powder was treated with an acid value solution, and the silver-coated powder treated with the coating agent accelerated surface deterioration at a high temperature of 280 ° C., which is a surface mount technology condition during the electronic product process due to the acid value of the coating agent. There was a problem in that the coated silver coating fell or the uncoated powder oxidized to increase the self-propelled value. On the other hand, according to the surface treatment method, since the amide-based solution is added to the coating agent treatment, the acid value of the coating agent is adjusted to prevent the above-described problems from occurring. For example, as the amide-based solution, oleamide may be preferable.

In summary, in step S400, after dissolving a coating agent containing at least one of oleic acid, stearic acid, and adipic acid in isopropylalcohol, add a silver-coated powder and add an amide-based solution to adjust the acid value. While stirring, the stirred silver coated powder can be filtered and dried.

In addition, in step S400, isopropyl alcohol may contain a coating agent in an amount of 0.1% or more and 1.0% or less based on the weight of the silver coated powder, and an amide-based solution in an amount of 0.01% or more and 0.2% or less.

In addition, in step S400, isopropyl alcohol, the oleic acid contained in the coating agent may be included in a greater proportion to the weight than oleamide (Oleamide) contained in the amide-based solution (see Table 2 to be described later). For example, isopropyl alcohol may contain oleic acid and oleamide in a ratio of 6: 1.

In addition, in step S400, the filtering of the stirred silver coated powder may be filtering using a mesh network (see Table 2 to be described later). According to the filtering using the mesh network, it is possible to secure higher heat resistance than vacuum filtering and filtering by centrifugation.

According to the foregoing, after the surface treatment method, after coating the silver-coated powder with a coating agent (step S400), a self-assembled monomolecular film technique (step S500) may be applied. Accordingly, the surface treatment method may have a form in which a self-assembled monomolecular film technique and a coating agent treatment technique are applied to the silver-coated powder in a complex manner.

Hereinafter, the effects of the present application will be specifically confirmed through Examples. However, the present application is not limited by the following examples.

[Example 1]

As performed by the steps of S100, S300 and S500 of the present surface treatment method, 10 g of silver coated powder (silver coated powder) having a particle size of 10 µm and a silver content of 10% is ethanol (Octanethiol) 10 g ethanol) The solution was added to a self-assembled monolayer solution dispersed in 10 mL, and left to stand for 12 hours or more and 18 hours or less, followed by surface treatment with a self-assembled monolayer film solution, filtered and dried, followed by octaneol self-assembled monolayer film treatment. A coating powder was prepared.

[Example 2]

A silver coating treated with a self-assembled monomolecular film in the same manner as in Example 1, except that octadecylphosphonic acid was used instead of octane thiol as performed by steps S100, S300, and S500 of the present surface treatment method. Powders were prepared. Specifically, 10 g of silver-coated powder having a particle size of 10 µm and a silver content of 10% was introduced into a self-assembled monolayer solution in which 10 g of octadecylphosphonic acid was dispersed in 10 mL of an ethanol solution, for more than 12 hours and 18 hours. By leaving as described below, the surface treatment with a self-assembled monolayer membrane solution, followed by filtering and drying, to prepare an octadecylphosphonic acid self-assembled monolayer membrane treated silver coating powder.

[Example 3]

As carried out by steps S100, S300 and 400 of the present surface treatment method, 10 g of silver coated powder having a particle size of 10 µm and a silver content of 10% is 0.045 g of oleic acid and 0.0075 g of oleamide (the ratio of oleic acid to oleamide) This is set to 6: 1) was put in a solution dissolved in 15 mL of isopropyl alcohol, stirred for 30 minutes at 100 rpm, filtered using a mesh net, and the filtered silver coating powder was washed with isopropyl alcohol and dried. To prepare a silver coating powder treated with an existing acid value solution.

[Example 4]

It is carried out by steps S100, S300 and S400 of the present surface treatment method, except that the addition amount of each of oleic acid and oleamide is set to 0.0075g, 0.45g (the ratio of oleic acid to oleamide is set to 1: 6). Silver powder was prepared in the same manner as in Example 3. Specifically, 10 g of silver-coated powder having a particle size of 10 µm and a silver content of 10% was added to 0.0075 g of oleic acid and 0.45 g of oleamide (the ratio of oleic acid to oleamide is set to 1: 6) in 15 mL of isopropyl alcohol. After putting it in the dissolved solution and stirring for 30 minutes at 100 rpm, it was filtered using a mesh net, and the filtered silver coating powder was washed with isopropyl alcohol and dried to prepare a silver coating powder treated with an existing acid value solution. .

[Example 5]

As it is carried out by steps S100, S300, S400 and S500 of the surface treatment method, a silver coating powder was prepared in the same manner as in Example 3, and then an octanethiol self-assembled monolayer was treated in the same manner as in Example 1. Specifically, 10 g of silver-coated powder having a particle size of 10 µm and a silver content of 10% was 0.045 g of oleic acid and 0.0075 g of oleamide (the ratio of oleic acid to oleamide was set to 6: 1) in 15 mL of isopropyl alcohol. It was put into the dissolved solution, stirred for 30 minutes at 100 rpm, filtered using a mesh net, and washed the filtered silver coating powder with isopropyl alcohol and dried to prepare a silver coating powder treated with an existing acid value solution. After that, 10 g of the prepared silver coating powder was introduced into a self-assembled monolayer solution in which 10 g of octanethiol was dispersed in 10 mL of an ethanol solution, and allowed to stand for 12 hours or more and 18 hours or less, thereby self-assembled monolayer film solution After the surface treatment, and filtered and dried, an octanethiol self-assembled monomolecular film-treated silver coating powder was prepared.

[Example 6]

A silver coating powder was prepared in the same manner as in Example 5, except that octadecylphosphonic acid was used instead of octanethiol as performed by steps S100, S300, S400, and S500 of the present surface treatment method. Specifically, 10 g of silver-coated powder having a particle size of 10 µm and a silver content of 10% was 0.045 g of oleic acid and 0.0075 g of oleamide (the ratio of oleic acid to oleamide was set to 6: 1) in 15 mL of isopropyl alcohol. It was put into the dissolved solution, stirred for 30 minutes at 100 rpm, filtered using a mesh net, and washed the filtered silver coating powder with isopropyl alcohol and dried to prepare a silver coating powder treated with an existing acid value solution. After that, 10 g of the prepared silver coating powder was introduced into a self-assembled monolayer solution in which 10 g of octadecylphosphonic acid was dispersed in 10 mL of an ethanol solution, and allowed to stand for 12 hours or more and 18 hours or less, resulting in a self-assembled monolayer film solution. After surface treatment, filtering and drying were performed to prepare an octaneol self-assembled monolayer-treated silver coating powder.

[Comparative Example 1]

To confirm the effect of improving the high temperature heat resistance according to the presence or absence of surface treatment, a silver coated powder was prepared, and then the surface was not treated.

[Comparative Example 2]

When filtering, a silver coating powder was prepared in the same manner as in Example 3, except that vacuum filtering was used.

[Comparative Example 3]

A silver coating powder was prepared in the same manner as in Example 3, except that centrifugation was used instead of filtering.

In addition, in order to confirm the high temperature heat resistance of the silver coating powders according to Examples 1 to 6 and Comparative Examples 1 to 3, the high temperature heat resistance was measured and the results are shown in a table.

For reference, high temperature heat resistance was measured by the following method.

Conductive pastes were prepared by mixing silver coating powder according to Examples 1 to 6 and Comparative Examples 1 to 3, an epoxy resin, and toluene for 2 minutes at 500 rpm for 2 minutes, and vacuum defoaming for 3 minutes, thereby preparing (made) conductive pastes. Was coated and dried at 100 ° C. for 2 minutes to prepare a conductive film, cut the produced conductive film into 7 cm in width and 1 cm in length, and then laminated and cured in a 5 cm test circuit coupon at 160 ° C. and 10 kgf pressure for 1 hour. After that, the initial line resistance value is measured, and the surface mount technology condition is simulated by heating three times at 250 ° C. and 7 minutes in a high-temperature oven to measure the line resistance value after the surface mount technology process to determine the rate of resistance change compared to the initial resistance value. The calculation confirmed the high temperature and heat resistance of each silver coating powder. When preparing the conductive paste, the AS-80 of Toagosei was used as the epoxy resin, and the toluene was 99.5% pure gold of Daejung Gold.

In addition, the following rate of resistance change is a value calculated using the following [Equation].

[expression]

[Table 1]

As shown in Table 1, the rate of change of resistance of the surface-treated silver coating powder (Example 1 and Example 2) using the self-assembled monomolecular film technique is higher than that of surface-treated silver coating powder (Comparative Example 1). Appears low. Through this, it can be confirmed that the surface-treated silver coating powder (Examples 1 and 2) using the self-assembled monomolecular film technology has better heat resistance at high temperatures than the surface-treated silver coating powder. In other words, referring to Table 1, the rate of change of resistance of the silver-coated powder surface-treated using a self-assembled monolayer solution containing at least one of octanethiol and octadecylphosphonic acid is the resistance of the silver-coated powder without surface treatment. It is confirmed that it appears much lower than the rate of change. In addition, when compared with Example 1 and Example 2, when using a self-assembled monolayer solution containing octadecylphosphonic acid than when using a self-assembled monolayer solution containing octane thiol (Example 1) (Example 2) It is confirmed that the resistance change rate appears to be lower than.

[Table 2]

Referring to Table 2, an example in which oleic acid was added more than oleamide (Example 3, more preferably oleic acid and ureamide was added at a ratio of 6: 1) is an example in which oleamide was added more than oleic acid ( It can be seen that the resistance change rate is lower than in Example 4). On the other hand, in contrast to Example 3, Comparative Example 2 and Comparative Example 3, the filtered example using the mesh network (Example 3) is more resistant than Comparative Example 2 using vacuum filtering or Comparative Example 3 using centrifugation. It can be seen that the rate of change is low. Accordingly, as in the solution in which the coating agent of step S400 of the present surface treatment method is dissolved, the solution contains oleic acid (coating agent) in a greater proportion than oleamide (added to adjust the acid value) (Example 3) It can be confirmed that this is preferable from the viewpoint of high temperature heat resistance. In addition, it can be seen that, as in step S400 of the surface treatment method, filtering using a mesh network is preferable in terms of securing high high temperature heat resistance.

[Table 3]

As shown in Table 3, according to the present surface treatment method, a combination of treating a silver coated powder with a coating agent and surface treating the silver coated powder with a self-assembled monolayer solution (Examples 5 and 6) The rate of change of resistance was lower than that of the silver-coated powder (Example 3), which treated the surface only with the coating agent. Accordingly, it can be confirmed that the heat resistance at high temperature is improved compared to the conventional method when applying the surface treatment method (using self-assembled monomolecular film technology). That is, this surface treatment method is more effective in terms of high temperature and heat resistance through the organic linkage of the steps S400 (the process of treating the silver coated powder with a coating agent) and the step S500 (the process of treating the silver coated powder with a self-assembled monolayer solution). It can be seen that it exhibits an improved effect.

In summary, this surface treatment method relates to a surface treatment method of a silver coating powder for a conductive paste in an electronic material. According to this surface treatment method, silver coating powder is improved by improving high temperature heat resistance through surface treatment of a silver coated powder. The effect of increasing the resistance value may be suppressed in a high-temperature processing condition of 280 ° C., which is a surface mount technology (SMT) condition.

In addition, the present application can provide a surface-treated silver coating powder prepared by the above-described surface treatment method. As described above, the silver coating powder provided by the present application has improved high-temperature heat resistance, so that an increase in resistance value can be suppressed at a high-temperature processing condition of 280 ° C., which is a surface mount technology (SMT) condition.

The above description of the present application is for illustrative purposes, and those skilled in the art to which the present application pertains will understand that it is possible to easily modify to other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present application is indicated by the claims below, rather than the detailed description, and it should be interpreted that all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof are included in the scope of the present application.

Claims (10)

In the surface treatment method of the silver coating powder for conductive paste,
(a) pre-treating the powder;
(b) silver coating the pretreated powder to form a silver coated powder; And
(c) surface treatment by introducing the silver-coated powder into a self-assembled monolayer solution, followed by surface treatment. According to claim 1,
The self-assembled monolayer solution is a solution in which alkanethiol or phosphonic acid is dispersed, the surface treatment method of the silver coating powder for conductive pastes. According to claim 1,
In step (c),
The self-assembled monolayer solution is a method of treating the surface of the silver coating powder for conductive pastes in which at least one of octadecylphosphonic acid and octanethiol is dispersed in an ethanol solution. According to claim 1,
Between step (b) and step (c),
(D) the surface treatment method of the silver coating powder for a conductive paste further comprising the step of coating the silver coated powder. The method of claim 4,
Step (d) is,
After dissolving a coating agent containing at least one of oleic acid, stearic acid, and adipic acid in isopropylalcohol, the silver coated powder is added and an amide-based solution is added to adjust the acid value, followed by stirring. Filtering and drying the coated powder, the surface treatment method of the silver coating powder for a conductive paste. The method of claim 5,
In step (d),
The isopropyl alcohol, containing the coating agent in an amount of 0.1% or more and 1.0% or less based on the weight of the silver-coated powder, and containing the amide-based solution in an amount of 0.01% or more and 0.2% or less. Surface treatment method. The method of claim 5,
In step (d),
The isopropyl alcohol, the oleic acid contained in the coating agent is contained in a greater proportion to the weight than the oleamide (Oleamide) contained in the amide-based solution, the surface treatment method of the silver coating powder for conductive paste. The method of claim 7,
In step (d),
The filtering of the stirred silver-coated powder is filtering using a mesh net, a method for surface treatment of the silver-coated powder for conductive pastes. According to claim 1,
Step (a) is,
Degreasing the powder and etching the degreased powder so that oil and oxides on the surface of the powder are removed and hydrophilicity is imparted to the surface of the powder; And
The method comprising the step of sensitizing the etched powder, so that a metal salt having a reducing power is adsorbed on the surface of the powder, the surface treatment method of the silver coating powder for a conductive paste. Surface-treated silver coating powder prepared by claim 1.

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