KR101078183B1 - Method of producing slurries to make green sheet having uniform thickness - Google Patents

Abstract

The present invention is to use a release dispersant suitable for each of the ceramic powders used to form a mixture that ensures optimum dispersibility and then to mix to prepare a slurry having the optimum dispersion properties to produce a green sheet of uniform thickness It relates to a slurry blending method for producing a green sheet of uniform thickness.

The slurry for producing a green sheet having a uniform thickness according to the present invention comprises the steps of preparing a plurality of containers; Injecting an organic solvent into each of the plurality of containers; Adding and mixing a dispersant to the organic solvent, respectively; Adding a powder to the organic solvent to which the dispersing agent is added, and mixing and pulverizing them to produce a plurality of first mixtures; And mixing the plurality of first mixtures to produce a second mixture, wherein the dispersing agent is determined depending on the type of powder to be added to each of the plurality of containers.

Dispersant, binder, plasticizer, ceramic slurry, green sheet

Description

Slurry blending method for manufacturing green sheet of uniform thickness {METHOD OF PRODUCING SLURRIES TO MAKE GREEN SHEET HAVING UNIFORM THICKNESS}

The present invention relates to a slurry blending method for producing a green sheet having a uniform thickness, and more particularly, by using a release dispersant suitable for each of the ceramic powders to be used to form a mixture that ensures optimum dispersibility, and then mixes the optimum The present invention relates to a slurry blending method for producing a green sheet having a uniform thickness to prepare a slurry having a dispersing property to produce a green sheet having a uniform thickness.

Recently, due to the trend of miniaturization, light weight, and complex multifunctionality, the demand for stacking and complexing passive component elements is increasing, and various dielectric constant materials have been researched and developed to satisfy such demands. come.

Capacitors are the main components in electronic equipment. Among them, multilayer ceramic capacitors use high-k dielectric ceramics in a multilayer structure as a dielectric between electrodes, and have good temperature and frequency characteristics and can be manufactured in small size. It is widely used as a component.

In order to stack and composite various dielectric materials, such multilayer capacitors are manufactured by forming the materials in a thin plate shape, forming various patterns thereon, applying electrode materials, and then stacking, integrating and sintering them.

 The thin plate-like ceramic substrate used at this time is commonly referred to as green sheet or green tape. The composition of the green sheet is largely divided into organic and inorganic. The inorganic material includes a ceramic powder, the organic material includes a binder, a dispersant and a plasticizer, and a green sheet composed of a ceramic powder, which is an inorganic material that ultimately exhibits the characteristics of an electronic component through a process such as drying, can be obtained.

It is a slurry to make a green sheet, and the composition of the slurry is prepared by adding an organic solvent to a ceramic powder, which is an inorganic material, and a binder, a dispersant, and a plasticizer, which is an organic material.

The ceramic powder may be a single or a mixture of several kinds of raw materials, the characteristics of the ceramic powder is determined by the average particle size, particle size distribution, the surface area of the particles, etc., in particular the particle surface area is the most important characteristics of the slurry composition. That is, the larger the surface area of the ceramic powder particles, the greater the amount of binder to be added.

The binder is the main component that influences the properties of the green sheet. Excess binder increases the viscosity of the slurry too much, reduces the density of the green sheet (Green Body, Density, GBD), and when the amount of binder is too small, Can't combine

Dispersants are used to evenly disperse the ceramic powder particles throughout the sludge composition to lower the viscosity and increase the mixing, and to improve the release properties between the transport film and the green sheet when working with a doctor blade or the like.

Plasticizers change the properties of the binder and are added to make the hardness of the binder softer to increase the flexibility and workability of the green sheet.

The organic solvent may be selected in consideration of whether it is possible to form a homogeneous mixture with the binder and the temperature at which the organic solvent may be volatilized without modification of the binder in the drying process for manufacturing the green sheet.

The doctor blade method, which is a method used to prepare a thin plate-shaped green sheet from a slurry, is a slurry obtained by mixing ceramic powder with an aqueous or non-aqueous solvent and a binder, a plasticizer, a dispersant, an antifoaming agent, a surfactant, and the like in an appropriate ratio. After the production, the method of forming a certain thickness on a moving blade or a moving conveying film, called tape casting, continuous tape casting, knife casting, etc., various ceramics manufacturing field This is the method used by.

Conventionally, the ratio of the slurry composition was changed and combined according to the green sheet of the thickness to obtain. In order to obtain a high density green sheet, the slurry composition should be blended to contain the smallest amount of organic material and the maximum ceramic powder. The polymer dispersant which is most used in the conventional slurry manufacturing method is very diverse. In addition, in the case of the low temperature co-fired slurry composition, the slurry composition is generally a mixture of alumina and glass powder or other various powders, and the dispersion that occurs when the same organic solvent is encountered due to different chemical properties such as the surface state and specific surface area of each powder. Due to the different characteristics of the castle, it has been difficult to produce a green sheet having a uniform thickness.

The present invention has been made to solve the above problems, an object of the present invention is to produce a green sheet having an improved uniformity and density by using a dispersant suitable for each powder in the slurry composition blending process for producing an ultra-thin green sheet. will be.

An object of the present invention is to simplify the green sheet manufacturing process by preparing a slurry composition for low temperature co-firing using a release dispersant.

The slurry for producing a green sheet having a uniform thickness according to the present invention comprises the steps of preparing a plurality of containers; Injecting an organic solvent into each of the plurality of containers; Adding and mixing a dispersant to the organic solvent, respectively; Adding a powder to the organic solvent to which the dispersing agent is added, and mixing and pulverizing them to produce a plurality of first mixtures; And mixing the plurality of first mixtures to produce a second mixture, wherein the dispersing agent is determined depending on the type of powder to be added to each of the plurality of containers.

Adding and mixing a first dispersant to the first organic solvent; Administering a first ceramic powder to the first organic solvent mixed with a first dispersant to mix and grind to form a first mixture; Adding and mixing a second dispersant to the second organic solvent; Administering a second ceramic powder to the second organic solvent mixed with a second dispersant to mix and grind to form a second mixture; And a second mixing step of mixing the first mixture and the second mixture and then administering a binder and a plasticizer to mix the mixture.

The present invention can produce an ultra-thin green sheet of 100 μm or less using the slurry composition prepared by optimizing the dispersibility of each powder and then mixing them.

The present invention can produce a super uniform green sheet having a thickness uniformity of less than 2% using a slurry composition prepared by optimizing the dispersibility of each powder and then mixing them.

The present invention can produce a green sheet having a density of 60% or more of the powder density using the slurry composition prepared by optimizing the dispersibility of each powder and then mixing the powders.

Hereinafter, the ultra-uniform thickness characteristic of the green sheet produced using the slurry blended using the dispersant of the present invention will be described.

The present invention eliminates the possibility that some of the binder may not dissolve during mixing with the organic solvent by using a binder in a form that is sufficiently mixed with the ceramic powder in a small amount and dissolved in a solvent. That is, when mixing and milling using a binder in powder form, it is possible to prevent non-uniform mixing of the slurry which may occur due to insufficient amount of organic solvent, lack of milling media, lack of mixing time, and the like. The binder solvent may be selected in consideration of the viscosity characteristics of the slurry and suitability in a drying process in manufacturing the green sheet, but in the present invention, toluene may be used as the binder solvent.

The slurry for producing a green sheet according to the present invention is produced in the following order.

First, two or more organic solvents are mixed into a plurality of containers, and then a dispersant is added thereto, followed by mixing. In this case, the added dispersant is selected and used as a type that can optimize the dispersibility of the ceramic powder to be added in the next step. Next, the ceramic powder is administered to each container to be mixed, and the primary mixture is produced through a milling process such as ball milling in order to reduce the particle size of the raw powder. A plurality of mixtures thus prepared are mixed at a time to form a secondary mixture, and then the copolymer acrylic polymer and the plasticizer, which are binders present in the liquid phase in the toluene solution, are administered to the secondary mixture and mixed to increase the dispersion effect of the ceramic raw material as much as possible. Prepare a slurry.

As the organic solvent, it is preferable to use a solution which can form a homogeneous mixture with the binder in a solution phase, and which can volatilize at a low temperature during the drying process for manufacturing the green sheet to prevent decomposition of the binder. Consider using ethanol. In addition, in order to suppress the volatility of the binder solution to obtain a homogeneous green sheet, and to lower the viscosity of the slurry, it is preferable to add cyclo nucleic acid as an organic solvent.

The slurry produced through this process is subjected to degassing and stabilization process for a certain time to remove bubbles in the aggregated mass, and then formed into a desired thickness by using a tape caster equipment, and then burned out and calcined. By removing the green sheet is produced. In the tape casting process, which is a green sheet manufacturing process, a green sheet having an optimized thickness may be manufactured by setting the casting speed and temperature in consideration of the viscosity of the slurry supplied and the characteristics of the solvent used in the slurry.

Method for analyzing the dispersion characteristics of the slurry produced according to the present invention is as follows.

First, when the powder is administered to the organic solvent mixture of two or more organic solvents without using a dispersant, the dispersion characteristics of the powder present in the prepared slurry are analyzed.

Next, according to the present invention, a combination ratio of a dispersant, a powder, and an organic solvent mixture may be derived when the powder is optimally dispersed using various dispersants, and a slurry composition may be prepared using such a combination ratio to obtain a super uniform thickness. Green sheet having a can be produced.

The organic solvent mixture which has optimized dispersibility by utilizing a release dispersant will be described in more detail. For the low cost process, ethanol and toluene were used as organic solvents, and an optimized dispersed organic solvent mixture was derived to evaluate the dispersibility of the organic solvent mixture using a zeta potentiometer. Since the higher the zeta potential value, the better the dispersibility of the organic solvent mixture, the combination ratio may be derived when the combination of the alumina powder and the glass powder ensures optimum dispersibility, respectively. According to the resulting combination ratio, a mixture of alumina powder and glass powder having excellent dispersibility, respectively, is mixed again, and then a binder and a plasticizer are added to prepare a green sheet.

Thickness uniformity is evaluated comparatively about the green sheet produced using the dispersing agent and the green sheet produced using the slurry manufactured without using a dispersing agent as mentioned above.

Table 1 shows the dispersants and their properties that can be used to prepare the slurry.

product name polarity Ionization Molecular Weight Solid content (%) BYK115 Nonpolar Cation that 52 BYK161 Nonpolar Cation The 38 BYK182 High polarity Cation medium 51 BYK111 High polarity Negative ion that over 90 BYK180 High polarity neutrality that 79 BYK140 High polarity Cation The 52 KD-1 Polarity Cation - 100

1 is a graph showing zeta potential values measured after dispersing alumina powder and glass powder in an organic solvent mixture according to the present invention.

It can be seen from the graph of FIG. 1 that the KD-1 dispersant ensures excellent dispersibility in the case of alumina powder, and the BYK140 dispersant secures excellent dispersibility in the case of glass powder. It can be seen that the dispersibility is very poor when each powder is mixed with the organic solvent mixture without using a dispersant.

Table 2 is a table quantifying the results of FIG. 1 showing zeta potential values measured after dispersing alumina powder and glass powder in an organic solvent mixture according to the present invention.

mixture Zeta potential measurement (mV) Alumina -0.7 Glass 2.86 Alumina + BYK111 23.42 Yuri + BYK111 14.32 Alumina + KD-1 34.55 Glass + KD-1 0.82 Alumina + BYK182 2.7 Yuri + BYK182 23.3 Alumina + BYK140 30 Yuri + BYK140 49.6

Table 2 shows that the zeta potential is 34.55 when the KD-1 dispersant is used for the alumina powder, and the zeta potential is 49.6 when the BYK140 dispersant is used for the glass powder.

The low temperature cofired composition is a mixture of glass powder and alumina powder. In Table 3, a mixture of the glass powder and the alumina powder is specified as a powder.

Slurry type mixture Zeta potential measurement (mV) A powder -13.42 ~ 2.2 Powder + BYK111 14.08 Powder + KD-1 4.32 Powder + BYK182 1.44 Powder + BYK115 8.79 Powder + BYK180 0.63 Powder + BYK161 0.70 B Powder + BYK140 21.59 C Powder + KD1, BYK140 28.66

In the case of A, the zeta potential value when the dispersant was not added to the mixture of the glass powder and the alumina powder was -13.42 to 2.2 mV, and in the case of B, the dispersant BYK140 was added to the mixture of the glass powder and the alumina powder. Zeta potential value is 21.59, and in case of C, the alumina powder and the dispersant KD-1 were optimized and dispersed in the organic solvent according to the results obtained in Table 2, and the glass powder and the dispersant BYK140 were dispersed and optimized in the organic solvent. After the two mixtures were mixed again to prepare a low temperature co-fired slurry composition to measure the zeta potential value.

Based on the results of Table 3, the dispersibility of the mixture prepared by using a dispersant that optimizes the dispersibility of the glass powder and the alumina powder, respectively, is higher than the dispersibility when the glass powder and the alumina powder are mixed and then dispersed using a dispersant. You can see that it is better.

Slurry type A B C Green Sheet Thickness (㎛) 50 50 50 Thickness deviation (㎛) ± 3.1 ± 1.9 ± 0.5

Table 4 shows the green sheet thicknesses and thickness deviations prepared for the slurry compositions A, B, and C shown in Table 3. That is, the thickness and thickness variation of the green sheet produced using the slurry A composed of the mixture of the glass powder and the alumina powder without the dispersant added are 50 µm and ± 3.1 µm, respectively, and the mixture of the glass powder and the alumina powder (i.e., The thickness and thickness deviation of the green sheet produced using slurry B composed of low temperature co-firing type) were 50 µm and ± 1.9 µm, respectively. Finally, the thickness and thickness variation of the green sheet fabricated using Slurry C, which is composed by optimizing the dispersibility of the glass powder and the alumina powder and mixing them, are 50 µm and ± 0.5 µm, respectively. It can be seen that the thickness variation is superior to the produced green sheet.

The above description is merely illustrative of the technical details of the present invention, and those skilled in the art to which the present invention pertains may various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

1 is a graph showing zeta potential values measured after dispersing alumina powder and glass powder in an organic solvent mixture according to the present invention.

Claims (7)

Preparing a plurality of containers; Injecting an organic solvent into each of the plurality of containers; Adding and mixing a dispersant to the organic solvent, respectively; Adding a ceramic powder to the organic solvent to which the dispersing agent is added, and mixing and pulverizing them to produce a plurality of first mixtures; And Mixing the plurality of first mixtures to produce a second mixture, The dispersant is determined in accordance with the type of ceramic powder added to each of the plurality of containers, characterized in that Slurry compounding method for producing a green sheet of uniform thickness. The method of claim 1, And administering a mixture of the binder and the plasticizer to the second mixture.  Slurry compounding method for producing a green sheet of uniform thickness. The method of claim 1, The first and second organic solvents are composed of ethanol and cyclo nucleic acid Slurry compounding method for producing a green sheet of uniform thickness. 3. The method of claim 2, The binder is dissolved in a toluene solution Slurry compounding method for producing a green sheet of uniform thickness. delete delete delete

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