Patent ID: 12227672

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described as follows with reference to the attached drawings. It is not intended to limit the techniques described herein to specific embodiments, and it should be understood to include various modifications, equivalents, and/or alternatives to the embodiments of the present disclosure. In connection with the description of the drawings, similar reference numerals may be used for similar components.

In the drawings, for clarity of description, parts irrelevant to the description may be omitted, and thicknesses of elements may be magnified to clearly represent layers and regions. Components having the same functions within a scope of the same idea may be described using the same reference numerals. In the present specification, expressions such as “having”, “may have”, “include” or “may include” may indicate a presence of corresponding features (e.g., components such as numerical values, functions, operations, components, or the like), and may not exclude a presence of additional features.

In the drawings, an X direction may be defined as a second direction, a Y direction may be defined as a third direction, and a Z direction may be defined as a first direction or a stacking direction.

Method for Manufacturing Conductive Paste

Hereinafter, a method for manufacturing a conductive paste according to an embodiment of the present disclosure will be described in detail with reference toFIGS.2to5.

Referring toFIG.2, a method for manufacturing a conductive paste according to an embodiment of the present disclosure includes: an operation of forming a first mixture110including a metal powder101, a dispersant102, and a hydrophobic solvent103(S1), an operation of forming a second mixture210including a hydrophilic binder201and a hydrophilic solvent202(S2), and an operation of forming a third mixture310by mixing the first and second mixtures110and210.

Hereinafter, each step of a manufacturing process of the conductive paste according to the present embodiment will be described in detail.

Referring toFIG.3, a first mixture110including a metal powder101, a dispersant102, and a hydrophobic solvent103may be formed (S1).

The metal powder101is sufficient as long as it has conductivity and is not particularly limited, but may be, for example, any one or more selected from a group consisting of Ni, Cu, Au, Ag, Pd, Pt, and alloys thereof.

As the dispersant102, for example, non-ionic surfactants, cationic surfactants, anionic surfactants, or the like, may be used, and these may be used alone or a mixture of two or more thereof may be used as the dispersant102.

As will be described later, the dispersant102included in the first mixture is adsorbed to an interface between the first mixture110and the second mixture210. In this case, a hydrophobic group of the dispersant102is adsorbed to a side of the first mixture110, and the hydrophilic group is adsorbed to a side of the second mixture210.

When the dispersant102is adsorbed to an interface between the first mixture110and the second mixture210, the third mixture310may be more stably maintained in a form of an oil-in-water emulsion.

The hydrophobic solvent103is sufficient as long as it exhibits hydrophobicity and is not particularly limited, for example, an organic solvent such as acetate-based solvents such as dihydroterpinyl acetate, isobornyl acetate, isobornyl propinate, isobornyl butyrate, isobornyl isobutylate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, or the like, terpene-based solvents such terpineol, dihydroterpineol, or the like; hydrocarbon-based, such as tridecane, nonane, cyclohexane, or the like, carboxylic acid-based, and ester-based solvents may be used.

However, the configuration of the first mixture110is not limited thereto, and for example, various additives such as ceramic materials may be further included.

Referring toFIG.3, the first mixture110is present in a form in which the metal powder101and the dispersant102are uniformly dispersed in the hydrophobic solvent103.

Next, a second mixture210including a hydrophilic binder201and a hydrophilic solvent202may be formed (S2).

A binder is an organic component contributing to improving bonding properties between the ceramic green sheet and particles included in the conductive paste. The hydrophilic binder201is sufficient as long as it exhibits hydrophilicity and is not particularly limited. For example, polyvinyl alcohol, cellulose, or a water-soluble acrylic resin may be used as the hydrophilic binder201.

The hydrophilic binder201does not affect the metal powder111in the particles of the first mixture110, and serves as a matrix in which the aggregate of the metal powder can be dispersed when the conductive paste is dried.

The hydrophilic solvent202is sufficient as long as it can dissolve the hydrophilic binder201and is not particularly limited. For example, water or dimethyl sulfoxide may be used as the hydrophilic solvent202.

Referring toFIG.3, the second mixture210is present in a form in which the hydrophilic binder201is dispersed in the hydrophilic solvent202.

Next, a third mixture310may be formed by mixing the first mixture110and the second mixture210(S3).

The method for manufacturing a conductive paste according to an embodiment of the present disclosure may further include an operation of stirring the third mixture310.

Referring toFIG.3, the stirred third mixture301may exist in an emulsion state. Emulsion means a substance in which particles of another liquid that are not soluble in the former liquid in one liquid are dispersed as colloidal particles or larger particles.

According to an embodiment of the present disclosure, a volume ratio of the first mixture110to the second mixture210may be 1 or less. When the volume ratio of the first mixture110to the second mixture210is 1 or less, the third mixture310may exist as an oil-in-water emulsion in which the first mixture110exhibits hydrophobicity is dispersed in a form of spherical particles in the second mixture210exhibits hydrophilicity.

Referring toFIG.3, a diameter of particles of the first mixture110dispersed in the second mixture210may be 0.1 to 100 μm. When the diameter of the particles of the first mixture110is 0.1 to 100 μm, the first mixture110may be dispersed in the second mixture210as particles of a certain size to form an emulsion having a uniform shape.

The conventional conductive paste was prepared by dispersing a metal powder and a binder in an organic solvent exhibiting hydrophobicity. In this case, when the conductive paste is printed on the ceramic green sheet to form an internal electrode, the organic solvent included in the conductive paste and the organic binder included in the ceramic green sheet have compatibility with each other, so that there was a problem in that the conductive paste melts or swells the pre-stacked ceramic green sheet.

As will be described later, when the conductive paste prepared according to an embodiment of the present disclosure is formed on the ceramic green sheet, a conductive paste in a state of the third mixture310is formed on the pre-stacked ceramic green sheet.

That is, although the second mixture210exhibiting hydrophilicity is present on the ceramic green sheet, they do not have compatibility with each other. In addition, since the first mixture110is present in a form of spherical particles dispersed in the second mixture210, the first mixture110is not present on the ceramic green sheet. Accordingly, the hydrophobic solvent103of the first mixture110does not swell or dissolve the organic binder in the stacked ceramic green sheet.

Even during the process of drying the conductive paste formed on the ceramic green sheet, the third mixture310may maintain a form of an emulsion due to a dispersant102in the first mixture110. As a result, only the hydrophobic solvent103and the hydrophilic solvent202are removed during the drying process, and the dried conductive paste has a form in which aggregates of metal powder are evenly and densely dispersed in a matrix formed of the hydrophilic binder201.

Accordingly, even when a plurality of ceramic green sheets having a conductive paste formed thereon are stacked in the manufacturing process of the multilayer ceramic capacitor, a sheet attack phenomenon may not occur with respect to the pre-stacked ceramic green sheets.

Referring toFIG.4, the dispersant102included in the first mixture is adsorbed to an interface between the first mixture110and the second mixture210. In this case, a hydrophobic group102aof the dispersant is adsorbed to a side of the first mixture, and a hydrophilic group102bis adsorbed to aside of the second mixture. When the dispersant is adsorbed to an interface of the first mixture110and the second mixture210, a shape of an oil-in-water emulsion can be more stably maintained.

A content of the dispersant102in the first mixture110may be preferably 0.01 wt % or more.

When the content of the dispersant102in the first mixture110is 0.01 wt % or more, the shape of the oil-in-water emulsion can be more stably maintained. That is, the shape of the oil-in-water emulsion is maintained even during a plurality of staking processes, thereby suppressing a sheet attack phenomenon on the pre-stacked ceramic green sheet.

EXPERIMENTAL EXAMPLE

A first mixture including 27.68 wt % of Ni powder, 0.5 wt % of conventional surfactant (ED116, an amine-based dispersant), and hexyl acetate as a solvent, and a second mixture including 5 wt % of polyvinyl alcohol as a binder and water as a solvent were formed.

The first mixture and the second mixture were mixed at a volume ratio of 1:5 to form a third mixture, and stirred to prepare an emulsion-type conductive paste.

After coating the prepared conductive paste on a PET film with a blade, hot air drying at 60° C. to evaporate all the solvents present in the first and second mixtures to form a dry coating film of the conductive paste, followed by being observed with an optical microscopy (OM), was undertaken.

Referring toFIG.5, all solvents of the first and second mixtures were removed. That is, the hydrophilic binder is present even after drying, and forms a dry hydrophilic coating film.

In addition, the dispersant remains even during the drying process to maintain an emulsion form. Therefore, it can be confirmed that the Ni powder exists in a form of spherical Ni aggregates evenly and densely dispersed in the hydrophilic binder.

Method for Manufacturing Multilayer Ceramic Capacitor

A conductive paste prepared according to an embodiment of the present disclosure may be used for manufacturing an internal electrode in a multilayer ceramic capacitor.

FIG.6is a perspective view of a multilayer ceramic capacitor400manufactured using a conductive paste according to an embodiment of the present disclosure, andFIG.7is a cross-sectional view taken along line A-A′ of the multilayer ceramic capacitor400ofFIG.6.

Referring toFIGS.6and7, the ceramic body410may include a plurality of dielectric layers411and first and second internal electrodes421and422formed on the dielectric layers411, and may be formed by stacking a plurality of dielectric layers411on which first and second internal electrodes421and422are formed. Also, the first and second internal electrodes421and422may be disposed to face each other with one dielectric layer411interposed therebetween. The first and second internal electrodes may be formed by a conductive paste prepared according to an embodiment of the present disclosure.

First and second external electrodes431and432are formed on an exterior of the ceramic body410to be electrically connected to the first and second internal electrodes421and422, respectively. Specifically, the first and second external electrodes431and432may be formed by applying a separate conductive paste to an outer surface of the ceramic body410to be electrically connected to the first and second electrodes421and422, respectively, and then sintering the same.

FIG.8is a process flow diagram of a process for manufacturing a multilayer ceramic capacitor400according to an embodiment of the present disclosure.

Referring toFIG.8, a method for manufacturing a multilayer ceramic capacitor includes: an operation of preparing a ceramic green sheet (P1), an operation of forming a conductive paste on the ceramic green sheet (P2), an operation forming a ceramic laminate by staking a ceramic green sheet on which the conductive paste is formed (P3), an operation of sintering the ceramic laminate (P4), and an operation of forming an external electrode on an exterior of the ceramic laminate. The conductive paste includes a first mixture including a metal powder, a dispersant, and a hydrophobic solvent, and a second mixture including a hydrophilic binder and a hydrophilic solvent, the conductive paste being an emulsion in which the first mixture is dispersed in the second mixture.

Hereinafter, each step of the process for manufacturing the multilayer ceramic capacitor according to the embodiment of the present disclosure will be described in detail.

First, a slurry formed including ceramic powder such as barium titanate (BaTiO3), an organic binder, and the like is applied to a carrier film and dried to prepare a ceramic green sheet (P1).

Next, a conductive paste is formed on the ceramic green sheet (P2). The conductive paste includes a first mixture including a metal powder, a dispersant, and a hydrophobic solvent, and a second mixture including a hydrophilic binder and a hydrophilic solvent, the conductive paste being an emulsion in which the first mixture is dispersed in the second mixture.

A method for forming a conductive paste is not particularly limited, and for example, a screen-printing method, a gravure printing method, or the like may be used.

Next, a ceramic green sheet on which the conductive paste is formed is stacked to form a ceramic laminate (P3), and an external electrode is formed on an exterior of the laminate (P4). The operation of forming the external electrode may be performed using a paste for external electrodes. The application of the paste for external electrodes may be performed by dipping the laminate into the paste for external electrodes, but is not limited thereto.

FIG.9illustrates that a conductive paste according to an embodiment of the present disclosure is formed on a pre-stacked ceramic green sheet111.

When the conductive paste according to an embodiment of the present disclosure is formed on the ceramic green sheet, the second mixture210′ exhibiting hydrophilicity is present on the ceramic green sheet111, although the second mixture210′ is present on the ceramic green sheet111, the second mixture210′ and an organic binder in the ceramic green sheet111, and the like, do not have compatibility with each other.

In addition, since the first mixture110‘ exists in a form of spherical particles dispersed in the second mixture210’, the first mixture110′ does not exist on the ceramic green sheet111. Accordingly, a hydrophobic solvent103‘of the first mixture110’ does not cause the organic binder in the stacked ceramic green sheet111to swell or be dissolved.

Even during a process of drying the conductive paste formed on the ceramic green sheet, the conductive paste may maintain a form of an emulsion due to a dispersant102′ in the first mixture110′.

As a result, only the hydrophobic solvent103′ and a hydrophilic solvent202′ are removed during the drying process, and the dried conductive paste has a form in which aggregates of the metal powder101′ are evenly and densely dispersed in a matrix made of the hydrophilic binder201′.

Accordingly, even when a plurality of ceramic green sheets on which conductive pastes are formed are stacked in a manufacturing process of a multilayer ceramic capacitor, a sheet attack phenomenon does not occur with respect to the pre-stacked ceramic green sheets.

As set forth above, according to an embodiment of the present disclosure, by providing a method for manufacturing a conductive paste and a method for manufacturing a multilayer ceramic capacitor according to an embodiment of the present disclosure, when an internal electrode pattern is formed on a ceramic green sheet, a sheet attack phenomenon may not occur, and deterioration of insulation of a dielectric layer of the resultantly-obtained multilayer ceramic capacitor may be prevented and a short-circuit defect rate may be reduced.

However, various and advantageous advantages and effects of the present invention are not limited to the above description, and will be more readily understood in the process of describing specific embodiments of the present invention.

While the embodiments have been illustrated and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope in the embodiment as defined by the appended claims.