KR20120042076A - Method of manufacturing ultra fine metal powder and ultra fine metal powder manufactured thereby - Google Patents

Abstract

PURPOSE: Fine metal powder and a manufacturing method thereof are provided to manufacture an electrode layer with high packing density and connecting characteristics from the fine metal powder having a uniform shape. CONSTITUTION: A method for manufacturing fine metal powder comprises the steps of: preparing a master mold formed with a pattern(S10), spreading a polymer material on the pattern to form a sacrificial layer(S11), forming a metal layer on the sacrificial layer(S12), and removing the sacrificial layer and separating the metal layer from the master mold using solvent to form the fine metal powder(S13).

Description

Method of manufacturing ultra fine metal powder and ultra fine metal powder manufactured thereby

The present invention relates to a fine metal powder and a method of manufacturing the same, and more particularly to a fine metal powder used for an electrode for MLCC, etc., and a method for producing a fine metal powder that can be easily produced.

As the functions of electronic products are diversified and the spread of portable electronic devices increases, the parts constituting these electronic devices are also becoming more functional and bulky. As an example, multilayer ceramic capacitors (MLCCs), which are one of the main components in electronic products, have been actively developed in the direction of miniaturization, thinning, and large capacity.

In order to increase the capacity of a chip product having a predetermined thickness, it is necessary to increase the dielectric constant of the dielectric ceramic material or to increase the number of layers in the same chip product by implementing a thin thickness of the dielectric and electrode layers on the same material.

To this end, in the case of a ceramic green sheet (Ceramic green sheet) has been recently developed to a region of 1㎛ or less, accordingly, the demand for thinning the electrode layer is also intensified.

Thus, in order to form a thin electrode layer, the electrode powder for forming the electrode layer should be formed of fine powder. In the conventional case, a physical method of mechanically grinding to form a fine metal powder was mainly used, but this physical method has a limitation in forming a fine powder.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a fine metal powder which can easily prepare a fine metal powder used for an electrode for MLCC and the like, and a fine metal powder thereby.

In the method of manufacturing a fine metal powder according to the present invention, preparing a master mold having a pattern is formed, applying a polymer material on the pattern to form a sacrificial layer, forming a metal layer on the sacrificial layer, and removing the sacrificial layer. And separating the metal layer from the master mold to form individualized fine metal powder.

In an embodiment of the present invention, the separating may be a step of removing the sacrificial layer by using a solvent in which the sacrificial layer is dissolved.

In an embodiment of the present invention, the separating may be a step of removing the sacrificial layer by applying ultrasonic waves to the sacrificial layer submerged in a solvent.

In an embodiment of the present invention, the polymer material may be ethylcellulose, polyvinyl butyral (PVB), or polyvinyl alcohol (PVA).

In an embodiment of the present invention, the forming of the sacrificial layer may include preparing a polymer solution in which the polymer material is dissolved and applying a polymer solution on the sacrificial layer.

In an embodiment of the present invention, the polymer material is ethylcellulose, and the polymer solution may have a molecular weight of 40,000 to 200,000.

In an embodiment of the present invention, the polymer material is polyvinyl butyral (PVB), and the polymer solution may have a molecular weight of 200,000 to 400,000.

In an embodiment of the present invention, the applying process may be a process applied by a spray coating method, a transfer coating method, or a contact coating method.

In an embodiment of the present invention, the forming of the metal layer may be a step of forming the metal layer through sputtering, electroplating, thermal deposition, or electron beam deposition.

In an embodiment of the present invention, the sacrificial layer may be formed to a thickness of 0.1 ~ 2㎛.

In an embodiment of the present invention, the sacrificial layer may be formed to a thickness of 1 to 20% of the diameter of the fine metal powder.

In an embodiment of the present invention, the fine metal powder may have a width / thickness ratio of 10 to 200.

In an embodiment of the present invention, the fine metal powder may be nickel (Ni) powder.

In an embodiment of the present invention, the pattern may be formed in the form of a lattice in which protrusions and grooves are alternately arranged.

In addition, the fine metal powder according to an embodiment of the present invention can be prepared by any one of the above-described method for producing a fine metal powder.

The fine metal powder according to the present invention is formed into a flat flake shape having a uniform size distribution. Therefore, when the conductive paste or the electromagnetic shielding material is manufactured by using the fine metal powder according to the present invention, since the fine metal powder has a uniform shape, the packing density and the electrode connection are very high before and after heat treatment such as a firing process. An electrode film can be formed. Thus, the problem of deterioration of the connectivity of the electrode due to high temperature shrinkage can be minimized while forming the electrode of the MLCC thinner.

In addition, the method for producing a fine metal powder according to an embodiment of the present invention is to form a fine metal powder using a pattern, it is possible to freely control and form the shape of the fine metal powder, it is easy to form a special metal powder I can make it.

In addition, according to an embodiment of the present invention, even when a very thin thickness of the fine metal powder is made, the fine metal powder is easily separated from the master mold by the sacrificial layer. Therefore, it is possible to easily separate without damaging the pattern of the master mold or fine metal powder.

In addition, in the related art, in order to obtain powder particles having a shape other than spherical shape, the powder particles may be obtained only through a mechanical processing method. This problem causes a problem that the powders aggregate or form aggregates.

However, in the method for preparing micrometal powder according to the present invention, the size or shape of the powder particles is uniformly formed, and the powder is extracted in a dispersed form in a solvent, thereby minimizing the above problems.

1 is a perspective view schematically showing a fine metal powder according to an embodiment of the present invention.
Figure 2 is a photograph of the fine metal powder according to an embodiment of the present invention.
Figures 3a to 3d is a view showing a process for producing a fine metal powder according to an embodiment of the present invention.
Figure 4a is a photograph taken a plane of the pattern formed on the master mold according to this embodiment.
Figure 4b is a photograph taken along the line A-A 'of the master mold shown in Figure 4a.
5 is a photograph of a state in which a sacrificial layer is formed on a pattern of a master mold according to the present embodiment.
6 is a flow chart showing a method for producing a fine metal powder according to the present invention.

Prior to the detailed description of the present invention, the terms or words used in the present specification and claims should not be construed as limited to ordinary or preliminary meaning, and the inventor may designate his own invention in the best way It should be construed in accordance with the technical idea of the present invention based on the principle that it can be appropriately defined as a concept of a term to describe it. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that like elements are denoted by like reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may blur the gist of the present invention will be omitted. For the same reason, some of the elements in the accompanying drawings are exaggerated, omitted, or schematically shown, and the size of each element does not entirely reflect the actual size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view schematically showing a fine metal powder according to an embodiment of the present invention, Figure 2 is a photograph of the fine metal powder according to an embodiment of the present invention.

1 and 2, the fine metal powder 32 according to the present embodiment is characterized in that the particles are formed in the form of thin flakes. In the drawings, although the fine metal powder 32 is all formed in the form of square flakes, the present invention is not limited thereto, and the fine metal powder 32 may be formed in the form of flakes as long as necessary. It can be formed as.

In the present embodiment, the width (or diameter) / thickness ratio of the fine metal powder 32 is characterized in that 10 to 200.

In addition, the fine metal powder 32 according to the present embodiment may be nickel (Ni) powder used to form an electrode of a multilayer ceramic capacitor (MLCC).

As such, when the fine metal powder 32 is formed in the form of flakes, the size or thickness of the fine metal powder 32 can be uniformly formed, and the fine metal powder 32 agglomerates or forms an aggregate as in the prior art. I can solve the problem. This will be described in more detail in the method of manufacturing the fine metal powder 32 to be described later.

Next, a method for producing a fine metal powder according to the present invention will be described in detail through examples. The structure of the above-mentioned electrode powder will also become clearer from the following description of the method for producing the fine metal powder.

Figure 3a to 3d is a view showing a process for producing a fine metal powder according to an embodiment of the present invention, Figure 6 is a flow chart showing a method for producing a fine metal powder according to the present invention.

Referring to FIG. 3A together with reference to FIG. 6, the method of manufacturing micrometal powder 32 according to an embodiment of the present invention includes preparing a master mold (not shown) in which the pattern 12 is formed (S10). Begins.

The master mold according to the present embodiment may be formed in the shape of a cylindrical drum, and the pattern 12 may be formed along its outer circumferential surface.

In the case of this embodiment, the case where the pattern 12 is formed in the base film 10 attached along the cylindrical drum outer peripheral surface is taken as an example. In this case, the base film 10 may be polyethylene terephthalate (PET), polycarbonate (PC, polycarbonate), polypropylene (PP, polypropylene), or the like, but is not limited thereto.

As a method of forming the pattern 12 on the master mold (ie, the base film), various methods may be used. For example, optical lithography (Photolithography) technology using a photosensitive resin may be used based on the shape or dimension of the pattern 12, and nanoimprint lithography (NIL) using an ultraviolet curable resin or a thermosetting resin. Nano imprint Lithography) can also be used.

In addition, the pattern 12 according to the present exemplary embodiment may be formed by applying a gravure printing technique or by using a chemical etching method. In addition, it is also possible to form the pattern 12 on the master mold by machining directly.

FIG. 4A is a photograph of a plane of the pattern 12 formed in the master mold according to the present embodiment, and FIG. 4B is a photograph taken along line AA ′ of the master mold shown in FIG. 4A. Referring to this together, the pattern 12 of the master mold according to the present exemplary embodiment is formed in a lattice shape, and is configured such that protrusions and grooves are alternately arranged.

As the pattern 12 is formed, the square metal fine powder 32 may be formed by using both the top surface of the protrusion and the bottom surface of the groove. In addition, due to the shape of the pattern 12, the master mold according to the present embodiment may form the fine metal powder 32 by utilizing the entire area without wasting space.

Subsequently, as illustrated in FIG. 3B, a step S11 of forming a sacrificial layer 20 on the pattern 12 formed in the master mold is performed.

5 is a photograph of a state in which a sacrificial layer is formed on a pattern of a master mold according to the present embodiment.

Referring to this together, the sacrificial layer 20 serves to help the micrometallic powder 32 to be easily separated from the master mold while maintaining the shape when the micrometallic powder 32 is separated from the master mold. To this end, the method for producing a fine metal powder according to the present embodiment is characterized by using a material having a property of being easily dissolved in a specific solvent as the sacrificial layer 20.

For example, the sacrificial layer 20 according to the present embodiment may be formed of a polymer material. In addition, the sacrificial layer 20 is formed of a material that does not react with the fine metal powder 32.

More specifically, for example, ethyl cellulose may be used in the sacrificial layer 20 according to the present embodiment. In the case of ethyl cellulose, it is easily decomposed in many solvents such as ethanol, alcohol such as IPA (Iso Propyl Alcohol), ketones such as acetone, and methyl ethyl ketone (MEK).

In addition, the sacrificial layer 20 may be formed, or a water-soluble resin such as polyvinyl alcohol (PVA) may be used.

However, the present invention is not limited thereto, and may be variously used as long as it is a polymer material that is easily decomposed in a solvent and does not react with the fine metal powder 32. For example, polyvinyl butyral (PVB), polystyrene (PS), acrylic resin, or the like may be used, and various kinds of phenolic resins such as Novolac resin may also be used.

The sacrificial layer 20 may be formed by applying a solution (50, hereinafter, a polymer solution) in which a polymer material is dissolved using a solvent on the pattern 12 of the master mold. Here, the solvent may be a material that can easily dissolve the polymer material without modifying the pattern 12 formed on the base film 10.

In addition, as a coating method of the polymer solution, corresponding coating methods may be used according to the physical properties of the polymer solution, the shape and characteristics of the pattern 12, and the like. In particular, in order to uniformly form the sacrificial layer 20 on the pattern 12, it is necessary to select a polymer solution and design an appropriate coating process.

For example, when the viscosity of the polymer solution is relatively low and the pattern 12 of the master mold is formed in a fine size, a spray coating method may be used as the coating method. In this case, experimentally deriving optimized values for variables such as the size, pressure and air pressure of the spray nozzle together with the drying characteristics of the polymer solution, and if used, the sacrificial layer (with a more uniform thickness on the pattern 12) 20) can be formed.

However, the method of applying the polymer solution according to the present embodiment is not limited to a spray coating method, and a transfer method using a micro-gravure process, a bar coater, a roller, or the like. Various coating methods, such as the contact coating method used, can be used.

On the other hand, in the present embodiment, the case of manufacturing the Ni powder from the fine metal powder 32 is taken as an example. In this case, if the size (ie diameter) of the Ni powder is 10 μm or less, the optimal sacrificial layer 20 thickness is 0.1 to 2 μm. When calculating this as the size and ratio of the fine metal powder 32, the thickness of the sacrificial layer 20 is suitably formed to be 1 to 20% of the size (diameter) of the fine metal powder 32.

In addition, the molecular weight of the polymer material used as the sacrificial layer 20 affects the viscosity characteristics when preparing the polymer solution. Therefore, in the polymer solution according to the present embodiment, it is preferable that the polymer solution has a molecular weight of about 40,000 to 200,000 for ethyl cellulose, and the polymer solution has a molecular weight of about 200,000 to 400,000 for PVB. However, the present invention is not limited thereto, and the concentration of the polymer solution may be determined at an appropriate level in consideration of the coating method or the thickness of the sacrificial layer 20.

On the other hand, it is important that the sacrificial layer 20 according to the present embodiment is formed to an appropriate thickness on the pattern 12, it is suitable to be formed thicker than the thickness of the metal layer 30 to be formed later. When the sacrificial layer 20 is too thin (for example, 0.1 μm or less), it is difficult for the solvent to penetrate into the sacrificial layer 20 when the metal layer 30 is peeled off, and a large amount of time and energy may be consumed to separate the metal layer 30. Can be. On the contrary, when the sacrificial layer 20 is formed too thick (2 μm or more), a problem may occur in that the shape of the fine metal powder 32 is not uniformly formed.

Subsequently, as shown in FIG. 3C, a step S12 of forming the metal layer 30 on the sacrificial layer 20 is performed.

As described above, the present embodiment exemplifies a case in which nickel (Ni) powder is manufactured from the fine metal powder 32. Therefore, a nickel (Ni) layer is formed as the metal layer 30 on the sacrificial layer 20.

The metal layer 30 may be formed by various deposition methods, and for example, an electroforming process may be used. In more detail, in the step S12 of forming the metal layer 30 according to the present embodiment, a thin metal seed layer is formed on the sacrificial layer 20 by a sputtering method or the like, and then the metal seed layer is formed. Based on the electroplating process may be performed to form a metal layer 30 having a desired thickness on the metal seed layer.

Such electroplating is mainly used when the thickness of the finally formed metal layer 30 is several tens of micrometers or more. Therefore, it can be used to form metal flakes of a thicker size than the fine metal powder 32, or to form a plating layer.

On the other hand, in the case of forming the metal layer 30 with a thin thickness of several tens of nm to several μm, such as the fine metal powder 32, thermal evaporation, e-beam evaporation, sputtering, or the like. Physical vapor deposition method can be used. By these deposition methods, the metal layer 30 according to the present embodiment may be formed to a thickness of 10 nm to 100 nm. However, it is not limited thereto.

Subsequently, as shown in FIG. 3D, a step S13 of separating the metal layer 30 from the master mold is performed.

The metal layer 30 according to the present embodiment is separated from the master mold by a method of removing the sacrificial layer 20 interposed between the master mold and the metal layer 30.

To this end, in the method of manufacturing the fine metal powder 32 according to the present embodiment, the sacrificial layer 20 and the metal mold 30 have a specific solvent in which the sacrificial layer 20 is easily dissolved in a master mold (hereinafter, referred to as a metal structure). The sacrificial layer 20 is removed by immersing in (50, hereinafter, a polymer decomposition solvent).

For example, when ethyl cellulose is used as the polymer material, ethyl cellulose exhibits excellent solubility in ethanol, toluene, or a mixed solvent thereof. Therefore, when the metal structure is immersed in the polymer decomposition solvent 50, the sacrificial layer 20 formed of ethyl cellulose is easily dissolved by the polymer decomposition solvent 50 described above, so that the metal layer 30 is separated from the metal structure. As shown in FIG. 1, the micrometal powder 32 is formed as individualized particles.

Here, the method of manufacturing the fine metal powder according to the present embodiment may use ultrasonic waves for smooth separation of the metal layer 30. That is, the ultrasonic wave may be applied to the metal structure immersed in the polymer decomposition solvent 50 in which the sacrificial layer 20 is dissolved to accelerate dissolution of the sacrificial layer 20.

Such ultrasonic treatment may be unnecessary depending on the shape or size of the pattern 12. However, when ultrasonic waves are used together, the polymer decomposition solvent 50 can more easily penetrate into the sacrificial layer 20, and thus, the sacrificial layer ( 20) speeds up dissolution. Therefore, there is an advantage that the separation process of the metal layer is performed in a relatively short time.

Such ultrasonic waves may be applied by an ultrasonic vibrator (not shown) provided separately. However, in addition to the polymer decomposition solvent 50 and the metal structure can be used if the ultrasonic wave can be applied to the vessel in which a variety of devices can be used.

In addition, it is also possible to additionally use a magnet to easily extract the fine metal powder 32 separated from the metal structure.

The fine metal powder 32 according to the embodiment of the present invention manufactured by the above method may be utilized in various ways.

For example, the conductive paste may be prepared by mixing the fine metal powder 32, the resin binder, and the organic solvent according to the present embodiment. In this case, as the resin binder, an alkyd resin or ethyl cellulose, which is an organic compound which is easily lost during the firing process, may be used. The organic solvent may be applied to a green sheet by giving a suitable viscosity to the paste, and then easily dried. Terpineol, butylcarbitol acetate, kerosene, and the like, which are volatilized organic compounds, may be used.

The conductive paste according to the present embodiment manufactured as described above may be used to form an electrode (eg, nickel (Ni) electrode) in manufacturing an electronic device (eg, MLCC).

As described above, the fine metal powder according to the embodiment of the present invention may be a nickel (Ni) electrode powder for MLCC, it is formed in a flat flake shape having a uniform size distribution. Therefore, when the conductive paste or the electromagnetic shielding material is manufactured by using the fine metal powder according to the present invention, since the fine metal powder has a uniform shape, the packing density and the electrode connection are very high before and after heat treatment such as a firing process. An electrode film can be formed. As a result, a problem of deterioration in connectivity due to high temperature shrinkage can be minimized while forming a thinner electrode of MLCC.

In addition, the method for producing a fine metal powder according to an embodiment of the present invention is to form a fine metal powder using a pattern, it is possible to freely control and form the shape of the fine metal powder, it is easy to form a special metal powder I can make it.

In addition, according to an embodiment of the present invention, even when a very thin thickness of the fine metal powder is made, the fine metal powder is easily separated from the master mold by the sacrificial layer. Therefore, it is possible to easily separate without damaging the pattern of the master mold or fine metal powder.

In addition, in the related art, in order to obtain powder particles having a shape other than spherical shape, the powder particles may be obtained only through a mechanical processing method. This problem causes a problem that the powders aggregate or form aggregates.

However, in the method for preparing micrometal powder according to the present invention, the size or shape of the powder particles is uniformly formed, and the powder is extracted in a dispersed form in a solvent, thereby minimizing the above problems.

On the other hand, the method of producing a fine metal powder and the fine metal powder according to the present invention described above is not limited to the above-described embodiment, various applications are possible. For example, in the above-described embodiment, a case in which a pattern is formed in a lattice shape has been described as an example, but the present invention is not limited thereto, and the pattern is formed in various shapes as necessary, such as a circle, a triangle, or a rectangular parallelepiped shape. Fine metal powder can be prepared.

In addition, in the above-described embodiment, the case of manufacturing the electrode powder has been described as an example, but the present invention is not limited thereto, and may be easily applied to all cases of preparing metal in the form of flakes.

10: base film 12: pattern
20: sacrificial layer
30: metal layer 32: fine metal powder
50: polymer decomposition solvent

Claims (15)

Preparing a master mold having a pattern formed thereon;
Forming a sacrificial layer by applying a polymer material on the pattern;
Forming a metal layer on the sacrificial layer; And
Removing the sacrificial layer and separating the metal layer from the master mold to form individualized fine metal powders;
Micrometal powder production method comprising a. The method of claim 1, wherein the separating step,
Method for producing a fine metal powder, characterized in that for removing the sacrificial layer using a solvent in which the sacrificial layer is dissolved. The method of claim 2, wherein the separating step,
And removing the sacrificial layer by applying an ultrasonic wave to the sacrificial layer immersed in the solvent. The method of claim 1, wherein the polymer material,
Ethyl cellulose (ethylcellulose), polyvinyl butyral (PVB, polyvinyl butyral), or polyvinyl alcohol (PVA. The method of claim 1, wherein forming the sacrificial layer,
Preparing a polymer solution in which the polymer material is dissolved; And
Applying the polymer solution on the sacrificial layer;
Method for producing a fine metal powder comprising a. The method of claim 5,
The polymer material is ethyl cellulose (ethylcellulose), the polymer solution is a method of producing a fine metal powder, characterized in that the molecular weight of 40,000 ~ 200,000. The method of claim 5,
The polymer material is polyvinyl butyral (PVB), and the polymer solution has a molecular weight of 200,000 to 400,000. The method of claim 5, wherein the applying process,
A method of producing a fine metal powder, characterized in that the process is applied by a spray coating method, a transfer method coating method, or a contact coating method. The method of claim 1, wherein the forming of the metal layer comprises:
Forming the metal layer by sputtering, electroplating, thermal evaporation, or electron beam evaporation method, characterized in that the fine metal powder manufacturing method. The method of claim 1, wherein the sacrificial layer,
Method for producing a fine metal powder, characterized in that formed to a thickness of 0.1 ~ 2㎛. The method of claim 1, wherein the sacrificial layer,
Method for producing a fine metal powder, characterized in that formed in a thickness of 1 to 20% size with respect to the diameter of the fine metal powder. The method of claim 1, wherein the fine metal powder,
Method for producing a fine metal powder, characterized in that the width / thickness ratio of 10 to 200. The method of claim 1, wherein the fine metal powder,
Method for producing a fine metal powder, characterized in that the nickel (Ni) powder. The method of claim 1, wherein the pattern is,
Method for producing a fine metal powder, characterized in that formed in a lattice form alternately arranged projections and grooves. The fine metal powder produced by the method for producing the fine metal powder according to claim 1.

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