KR100193381B1 - Ceramic Slurry for Green Sheet - Google Patents

Abstract

The present invention relates to a ceramic slurry for green sheets, and more particularly, to a ceramic slurry, an anionic polymer electrolyte dispersant, an acrylic copolymer binder, a polyalcohol plasticizer and an aqueous-non-aqueous dispersion solvent, In addition to improving the environmental friendliness by minimizing the content and increasing the water content, it also reduces the manufacturing cost and increases the industrial use value.In particular, it contains the anionic binder component together with the anionic polyelectrolyte dispersant, which is flexible in the green sheet. The present invention relates to a ceramic slurry for green sheet that gives a large amount.

Description

Ceramic Slurry for Green Sheet

The present invention relates to a ceramic slurry for green sheets, and more particularly, to a ceramic slurry, an anionic polymer electrolyte dispersant, an acrylic copolymer binder, a polyalcohol plasticizer and an aqueous-non-aqueous dispersion solvent, In addition to improving the environmental friendliness by minimizing the content and increasing the water content, it also reduces the manufacturing cost and increases the industrial use value.In particular, it contains the anionic binder component together with the anionic polyelectrolyte dispersant, which is flexible in the green sheet. The present invention relates to a ceramic slurry for green sheet that gives a large amount.

Generally, a ceramic green sheat is manufactured by molding a ceramic slurry composed of ceramic powder, organic additives, and a dispersion solvent into a thin film or plate. Today, such ceramic green sheets are widely used for miniaturization and high functionality of electronic components used in the electronic communication industry such as computers and mobile communication. In addition, according to the type of ceramic powder used, it is used for various purposes such as ceramic package, laminated circuit board, laminated capacity, laminated chip parts, and the like. In particular, in the case of multilayer chip parts, various operating frequency ranges from hundreds of KHz to several GHz are formed around NiZn-based ferrites with low high frequency loss, and electronic devices such as inductors, LC filters, and EMI suppression elements Is being used. Sheet lamination and screen printing are used for chipping electronic components for surface mounting.

In general, ceramic green sheets are manufactured using an organic solvent-based binder (referred to as an organic binder). For example, a binder such as butyral resin and vinyl resin was dissolved in an organic solvent in which trichloroethylene, toluene, methyl ethyl ketone, alcohol and the like were properly combined, and then mixed with ceramic powder for a long time to prepare a slurry. Then, after removing the bubbles in the slurry using a blade having a predetermined interval formed on a carrier film on a sheet, and dried by heating to prepare a ceramic green sheet. However, when manufacturing a ceramic green sheet using an organic solvent-based binder, the toxicity and flammability of the organic solvent are pointed out as the biggest problems, and environmental regulations such as VOC (volatile organic compounds) regulation and ISO 14000 activation are intensified. As a result, the use of organic solvent slurries is becoming increasingly difficult. In addition, when the wet-treated ceramic raw material proceeds to a process using an organic solvent, it must be re-dispersed in the organic solvent after undergoing a complete drying process, there is a problem that the manufacturing cost according to the drying process increases.

In order to solve the problem of manufacturing a ceramic green sheet using the conventional organic solvent-based binder has been studied to manufacture a water-soluble binder. As a result, known methods for producing water-soluble binders such as polyacrylic acid (US Pat. No. 4,329,271), modified cellulose (European Patent No. 408,906, 1990), and ethylene-acrylic acid copolymer (US Pat. No. 5,086,093) are known. The manufacturing method of the ceramic green sheet used was actively developed.

Although the problems arising during the preparation of the organic solvent slurry have been somewhat solved by the use of the water-soluble binder, the following problems are still pointed out in the aqueous slurry.

In preparing an aqueous slurry, the kind of binder is greatly limited because it is not easy to select a binder applicable to water. In addition, since the solvent used in the preparation of the aqueous slurry is water, the drying rate is slowed due to high latent heat of evaporation of water, thereby causing a defect in the green sheet. In addition, since the dispersion of ceramic particles is greatly influenced by the pH of the slurry in the process of preparing the aqueous slurry, it is difficult to maintain a stable dispersion state.

As an improvement of the method for manufacturing a ceramic green sheet using the water-soluble binder as described above, a slurry of an aqueous-non-aqueous solvent is prepared by using an organic solvent that is relatively toxic to a water-soluble polymer and can be mixed with some water. A method of improving the flow characteristics of the slurry and the physical properties of the ceramic green sheet has been proposed by utilizing the advantages of the organic solvent and the aqueous system.

In the method of preparing a slurry of an aqueous-non-aqueous solvent using a water-soluble binder, since an organic solvent is partially replaced with water, there is little effect on the human body. And easy handling. In addition, since water is inexpensive and easily purchased, the manufacturing cost is also very low compared to the organic solvent-based method, so the industrial use value is very high.

Meanwhile, US Pat. No. 4,353,958 prepares a slurry of an aqueous-non-aqueous solvent using a polyurethane resin compatible with water as a binder, and prepares a green sheet using the same. In addition, Japanese Laid-Open Patent Publication No. 60-33251 discloses an alumina slurry by mixing water and methanol in an alumina powder using a water-soluble acrylic acid polymer binder, to prepare an alumina green sheet. At this time, glycerin was used as a plasticizer, and polyoxyethylene nonyl phenol ether which is a nonionic surfactant was used as a dispersing agent. As a result of sintering the alumina green sheet thus obtained and the sheet obtained by the conventional organic solvent method at 1800 ° C., the result was higher in quality than the organic solvent method, and the productivity was obtained with the same productivity as in the case of using the organic solvent. Doing. However, although the flexibility of the green sheet, which is the most important physical property of the ceramic green sheet, is pointed out as a problem, the Japanese patent does not mention the flexibility of the green sheet for processing. And when evaluating the characteristics of the prepared alumina substrate, it is evaluated by firing, which proves that the alumina green sheet of the Japanese patent does not need a sophisticated processing process or does not have the flexibility of the green sheet.

On the other hand, in the manufacture of stacked chip inductors, the flexibility of the green sheet is inevitable due to the nature of the process, as well as the cutting process of the ferrite green sheet, as well as the precision processing to drill small holes of the correct size to prevent short circuits and the lamination operation. Is required.

In the manufacture of such a flexible ceramic green sheet, if a method of reducing the content of the organic solvent and increasing the content of water is developed, it would be highly desirable in terms of economy and environment.

The present inventors have endeavored to produce a ceramic slurry having excellent physical properties, such as providing flexibility to the green sheet while relatively reducing the content of the organic solvent in water. As a result, ceramic powder is used as a raw material, and the glass transition temperature (T _g ) is contained in the binder as an acrylic copolymer, which gives flexibility to the binder itself, and adds a plasticizer which is mutually soluble with the binder. Enhance the flexibility of the sheet to improve the processability of cutting and punching the green sheet.Although water is mainly used as a solvent, aliphatic alcohols, which are relatively less toxic, are appropriately mixed to increase the water content in the dispersed aqueous solution to increase environmental friendliness. The purpose of the present invention is to provide a ceramic slurry for a green sheet which reduces the manufacturing cost by omitting the drying step after the pulverization treatment.

The present invention is a ceramic slurry containing a ceramic powder, a binder, a plasticizer, a dispersant, and an aqueous-non-aqueous dispersion solvent, 100 parts by weight of ceramic powder, 0.1 to 2.0 parts by weight of anionic polyelectrolyte having a molecular weight of 2,000 to 50,000, molecular weight 10,000 It is characterized by a ceramic slurry for producing green sheets containing 1.5 to 15 parts by weight of acrylic copolymer of 30 to 300,000, 0.4 to 4.0 parts by weight of polyalcohol having a molecular weight of 200 to 100,000, and 40 to 80 parts by weight of aqueous-non-aqueous dispersion solvent. do.

Referring to the present invention in more detail as follows.

The ceramic slurry of the present invention contains an anionic polyelectrolyte having high dispersibility with ceramic powder, contains a binder and a plasticizer that can be mixed with water and give flexibility to the green sheet, and a small amount of aliphatic alcohol in water. It contains the dispersion solvent contained.

In addition, the ceramic powder used as a raw material in the present invention is a known material, for example, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), silica alumina oxide, zirconia (ZrO ₂ ), barium titanate (BaTiO ₃ ), ferrite, or a ceramic material compatible with water may be applied, and any of them can be used to achieve the effects of the present invention.

The following describes the manufacturing process of the ferrite powder in the ceramic powder used as a raw material in the present invention.

The content ratio of each metal oxide constituting the ferrite powder is determined in consideration of electromagnetic characteristics, preferably 48 mol% Fe ₂ O ₃ , 7 mol% NiO, 13 mol% CuO and ZnO 32 mol% [Ref. Korean Journal of Magnetics, (6), 937-46 (1995); Korean Journal of Magnetics, (6), 928-35 (1995). The ferrite material contains a dispersant to prepare a slurry having a concentration of 60 to 85% by weight, pulverize it to about 1 μm or less, and calcinate at about 700 ° C. for about 3 hours to obtain a ferrite powder having magnetic properties. At this time, when the concentration of the slurry is less than 60% by weight, the processing capacity per batch is lowered. When the concentration of the slurry is higher than 85% by weight, the viscosity of the slurry is increased to reduce the grinding efficiency and handling of the raw pulverized product. Do it.

In order to use the ferrite powder prepared above as a raw material of the ceramic slurry for green sheet, a wet grinding process must be performed as a pretreatment operation of the ferrite powder. When preparing an organic solvent-based slurry for tape molding, after fully drying the wet ferrite powder, an organic solvent and an additive required for slurry preparation are added and dried, and then the ferrite particles aggregated in the drying process are dried. Milling process must be added for redispersion. However, the present invention has a linkage of a process for producing a tape moldable slurry without a drying process by directly adding a binder and a plasticizer that can be mixed with a water-based ferrite powder, thereby lowering the manufacturing cost of the product. .

Next will be described in more detail the manufacturing process of the ceramic slurry for producing a green sheet according to the present invention.

Ceramic powder is wet milled together with anionic polyelectrolyte and ion-exchanged water using stainless balls having a high specific gravity as a grinding medium to prepare a high concentration slurry having a ceramic powder concentration of about 60 to 85 wt%. In the present invention, stainless balls are used as the dispersion medium, but other balls such as alumina balls, zirconia balls, and the like may be used in consideration of trace impurities added during ball milling. At this time, if the concentration of the ceramic powder contained in the prepared slurry is less than 60% by weight, the solid content is small, so that the amount of the solvent to be dried during the manufacture of the green sheet is excessive. it's difficult.

The dissociation state of the dispersant and the surface charge of the ceramic powder may vary according to the slurry pH change during the grinding process. Therefore, the dispersant selection is very important because the dispersibility and viscosity of the slurry as well as the slurry concentration and grinding efficiency are greatly influenced. It is important.

Therefore, in the present invention, an anionic polyelectrolyte having a molecular weight of 2,000 to 50,000 is used in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the ceramic powder. It has a high dissociation degree even under strong alkali conditions, thereby increasing the dispersibility of the ceramic powder, and having an anion of the same kind as the binder used, making it easy to form a high concentration slurry. As the anionic polyelectrolyte, an ammonium polyacrylic acid salt, a polyacrylic acid amine salt, or the like is used. When the molecular weight thereof is less than 2,000, the dispersing effect is lowered. If the amount of the anionic polymer electrolyte is less than 0.1 part by weight based on 100 parts by weight of the ceramic powder, the above-described dispersion effect may not be obtained. When the amount of the anionic polymer electrolyte is used in excess of 2.0 parts by weight, the dispersibility may be lowered.

Without the process of drying the high concentration slurry containing the ceramic powder and the anionic polymer electrolyte, a binder, a plasticizer and a dispersion solvent are immediately added to prepare the ceramic slurry for the green sheet of the present invention.

As the binder, an acrylic copolymer having a molecular weight of 10,000 to 300,000 is used because the glass transition temperature is much lower than room temperature to help disperse the ceramic powder and add flexibility to the green sheet. It is preferable that the acrylic copolymer has a glass transition temperature (T _g ) in the range of -30 to 100 ° C and an acid value in the range of KOH 20 to 200 mg / g. Even if the T _g of the acrylic copolymer used is less than -30 ° C, the flexibility expectation of the binder is constant, and if it exceeds 100 ° C, it is difficult to expect the flexibility of the binder. If the acid value is less than 20 mg / g KOH, the affinity with water as a solvent is lowered, and if the acid value exceeds 200 mg / g, the affinity with an organic solvent is lowered. And, the acrylic copolymer is 1.5 to 15 parts by weight based on 100 parts by weight of the ceramic powder, the mechanical strength of the green sheet is sharply lowered if the amount is less than 1.5 parts by weight, the viscosity is sharply increased if it exceeds 15 parts by weight The preparation of the slurry becomes impossible.

In addition, the mutual solubility of the plasticizer and the binder also plays an important role in the production of uniform mixing and green sheet of good quality. As a result of the solubility test according to the change of the binder / plasticizer ratio, the solubility between the binder and the plasticizer was good when the ratio of the acrylic copolymer / polyalcohol was maintained in the weight ratio range of 3 to 7/1. As the plasticizer, polyalcohols include polyethylene glycol, polypropylene glycol, and the like, and in order to increase the flexibility of the green sheet, it is preferable to use a molecular weight of 200 to 100,000, and 0.4 to 4.0 parts by weight based on 100 parts by weight of ceramic powder. do.

In addition, the present invention selects an aqueous-non-aqueous solvent as a dispersion solvent to adopt the advantages of each of the aqueous and non-aqueous. Conventionally, ceramic slurries have been prepared in an aqueous-non-aqueous solvent. However, in the present invention, a non-aqueous solvent that significantly increases the amount of water and also contains a small amount within a range in which physical properties required for the ceramic sheet is not degraded. Use low-toxic aliphatic alcohol. As such aliphatic alcohols, alcohols having 3 to 10 carbon atoms are used, and isopropyl alcohol, 2-n-butoxyethanol or a mixture thereof is preferably used. In the mixing ratio of water and aliphatic alcohol contained as a dispersion solvent, it is preferable to maintain the water / aliphatic alcohol in the range of about 0.7 to 5.0 / 1 by weight in terms of physical properties and environmental friendliness of the green sheet. In addition, the aqueous-non-aqueous dispersion solvent contains 40 to 80 parts by weight with respect to 100 parts by weight of the ceramic powder. When the content of the dispersion solvent is less than 40 parts by weight, the viscosity rises rapidly, making it difficult to prepare a slurry. When the concentration of the slurry is too low, it may be difficult to prepare the sheet.

The ceramic slurry of the present invention prepared by the above manufacturing process is tape-formed to produce a flexible green sheet. The circuit printing, lamination, and circuit connection between layers by screen printing method are repeated thereon, and after firing, an electrode is formed to manufacture a chip inductor.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

In addition, in the following examples, the ferrite powder prepared in Preparation Example is used as a raw material, but in addition to the ferrite powder, any ceramic powder generally compatible with water may be applied.

Preparation Example: Preparation of Ferrite Powder

Fe ₂ O ₃ , NiO, CuO and ZnO from Aldrich (USA) were dried at 120 ° C. for 5 hours. Fe ₂ O _3, NiO, CuO, and considering a purity such that ZnO ratio of 48 mol% of each content, and 7 mol%, 13 mol% and 32 mol% of the _{Fe 2 O 3 267.9 g, NiO} 18.6 g, CuO 36.2 g and ZnO 90.2 g was quantified. 7.2 g of an ammonium polyacrylic acid salt [manufactured by Novko Korea, molecular weight: about 15,000, 40 wt% solution,-(-CH ₂ -CHCOONH _3- ) _n- ] was quantified as a dispersant.

A ball mill (a pot of polyethylene, 9.23 cm in diameter and 1 l in volume) is charged with 170.8 g of the raw material, dispersant, and ion exchanged water prepared above, with a slurry concentration of 70% by weight and a total slurry volume of about 250 cc. The grinding media were filled with about 1/2 L of an apparent volume of about 8 mm of stainless balls. Ball milling was carried out at about 80 rpm for about 18 hours.

The particle size analysis (Mastersizer χ, MALVERN, UK) and the nitrogen adsorption method of the pulverized mixed raw materials showed that the average particle diameter was about 0.54 µm and the specific surface area was 8.83 m 2 / g.

The mixed, ground and dried mixed raw materials were sieved to 250 μm or less as described above, and calcined at 700 ° C. for 3 hours in a furnace to obtain a single-phase NiCuZn ferrite powder. The calcined powder was 1 μm or less in size. The particles existed in the form of aggregated secondary particles. This was used as NiCuZn ferrite powder in the next step.

Example 1:

602 g of NiCuZn ferrite powder prepared in Preparation Example, 124.5 g of ion-exchanged water, and 10.5 g of ammonium polyacrylate salt (40% by weight) were added to a ball mill, and then 81% by weight of the high-concentration slurry was ground for 60 hours in the same manner as in the above milling. Ball milling. Then, 297.5 g of NiCuZn ferrite slurry was collected (including 240.8 g of NiCuZn ferrite powder, 52.5 g of ion-exchanged water, and 4.2 g of a dispersant in a 40 wt% solution).

In the aqueous NiCuZn ferrite slurry collected above, a ferrite slurry was added by adding a binder that can be mixed into the aqueous system, adding water and an aliphatic alcohol solvent at the same time, and then adding a plasticizer to the ball mill for 18 hours. Was prepared.

At this time, 51.2 g of an acrylic copolymer binder having an acid value of KOH 54.5 mg / g, a glass transition temperature of -15 ° C., and a molecular weight of 60,000 (AK103B, Korea, 50 wt% resin) was added. The acrylic copolymer binder of Aekyung Co., Ltd. contains 25.6 g of a mixed organic solvent of isopropyl alcohol / 2-n-butoxyethanol (40/60 weight ratio).

As a plasticizer, 8.3 g of polyethylene glycol (Wakosa, Japan) having a molecular weight of 1000 was prepared in an 80% by weight aqueous solution. At this time, the total of the mixed organic solvent and the ion-exchanged water added to prepare the slurry for tape molding by adjusting the viscosity of the slurry was 52.3 g.

Mixed organic solvents are isopropyl alcohol (C ₃ H ₇ OH, primary reagent, Heyman, UK) and 2-n-butoxyethanol (CH ₃ (CH ₂ ) ₃ OCH ₂ CH ₂ OH, primary reagent, Showa company , Japan) in a weight ratio of 40:60. In Example 1, 52.3 g of the mixed organic solvent was added.

In the composition ratio of the slurry, the total amount of the organic matter (dispersant, binder, plasticizer) was 14.07 parts by weight, and the total amount of the mixed solvent of water and the organic solvent was 55.87 parts by weight based on 100 parts by weight of the NiCuZn ferrite powder. The concentration of was 58.84 wt%. Accordingly, the total amount of the organic material including the binder in the completely dried ferrite sheet represented 14.07 parts by weight based on 100 parts by weight of the ferrite powder. As a result, the weight ratio of water / organic solvent contained in the NiCuZn ferrite slurry was 0.73 / 1.

And the green sheet was manufactured using the ferrite slurry obtained above using a doctor blade (Tsugawa Corporation, DB-150 type, Japan). More specifically, by adjusting the outlet of the slurry to 300 ㎛ to flow out the slurry on a thin polymer film at a rate of 50 cm / min, and dried within 15 minutes at about 45 ℃ to prepare a NiCuZn ferrite green sheet of about 100 ㎛ thickness It was.

Example 2

The ferrite slurry was prepared in the same manner as in Example 1 using the NiCuZn ferrite powder prepared in Preparation Example, and 17.3 g of ion-exchanged water and 35.0 g of mixed organic solvent were added to adjust the viscosity of the slurry. As a result, the manufactured ferrite slurry had a weight ratio of water / organic solvent of 1.22 / 1. The manufacturing method of the green sheet was also the same as in Example 1.

Example 3

The ferrite slurry was prepared in the same manner as in Example 1 using NiCuZn ferrite powder prepared in Preparation Example, and 35.0 g of ion-exchanged water and 17.3 g of mixed organic solvent were added to adjust the viscosity of the slurry. As a result, the manufactured ferrite slurry had a weight ratio of water / organic solvent of 2.14 / 1. The manufacturing method of the green sheet was also the same as in Example 1.

Example 4

Ferrite slurry was prepared in the same manner as in Example 1 using NiCuZn ferrite powder prepared in Preparation Example, and 42.9 g of ion-exchanged water and 9.4 g of mixed organic solvent were added to adjust the viscosity of the slurry. As a result, the manufactured ferrite slurry had a weight ratio of water / organic solvent of 2.84 / 1. The manufacturing method of the green sheet was also the same as in Example 1.

Example 5

Ferrite slurry was prepared in the same manner as in Example 1 using NiCuZn ferrite powder prepared in Preparation Example, and 52.3 g of ion-exchanged water was added to adjust the viscosity of the slurry. As a result, the manufactured ferrite slurry had a weight ratio of water / organic solvent of 4.26 / 1. The manufacturing method of the green sheet was also the same as in Example 1.

Comparative Example 1

In order to compare the physical properties of the water-based green sheet using another water-soluble resin binder, a ferrite slurry was prepared in the same manner as in Example 1, using the NiCuZn ferrite powder prepared in Preparation Example, and for adjusting the viscosity of the slurry 65.8 g of exchange water were added. As the binder, acrylic water-soluble resin (AS-1100, 30 wt% solution, Dong-A Synthetic Co., Japan) was used.

In the composition ratio of the slurry, the total amount of organic matter (dispersant, binder, plasticizer) was 14.07 parts by weight, the total amount of the dispersion solvent was 69.2 parts by weight, and the concentration of the ferrite slurry was 58.84 weight based on 100 parts by weight of NiCuZn ferrite powder. It was%. Therefore, the total amount of the organic material including the binder in the completely dried ferrite sheet was 14.07 parts by mass based on 100 parts by weight of ferrite powder, and was the same as in Example 1. The manufacturing method of the green sheet was the same as in Example 1.

Comparative Example 2

In order to compare the physical properties of the green sheet using the organic solvent binder, the slurry for tape molding was prepared as follows.

602 g of NiCuZn ferrite powder, 124.5 g of ion-exchanged water, and 10.5 g of ammonium polyacrylate salt (40% by weight) prepared in the preparation example were added to a ball mill, and the high concentration slurry of 81% by weight was bowled for 60 hours. After drying and coarsely pulverizing at 120 ° C. for 20 hours, 301.4 g of NiCuZn ferrite powder was degreased at 400 ° C. for 3 hours to remove the dispersant, and polyvinyl butyral resin as a binder (polymerization degree: 700, Wacosa, Japan). ) 32 g), 10.4 g of dibutyl phthalate (wakosa, Japan) as a plasticizer, and 218 g of a mixed organic solvent (cyclohexane: 52% by weight, ethanol: 20% by weight, toluene: 28% by weight) Into the mixture and mixed for 18 hours to prepare an organic solvent NiCuZn ferrite slurry.

In the composition ratio of the slurry, the total amount of organic matter (dispersant, binder, plasticizer) was 14.07 parts by weight, the total amount of the dispersion solvent was 74.14 parts by weight, and the concentration of the ferrite slurry was 53.13 weight based on 100 parts by weight of NiCuZn ferrite powder. It was%. Therefore, the total amount of the organic material including the binder in the completely dried ferrite sheet was 14.07 parts by mass based on 100 parts by weight of ferrite powder, and was the same as in Example 1. The manufacturing method of the green sheet was the same as in Example 1.

Experimental Example 1

The green sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 2 measured viscosity and mechanical properties in the following manner.

Viscosity Measurement

Viscosity of the slurry ball-milled at 20 ± 0.1 ° C using a cone and plate viscometer (DV-II ⁺ , USA) and Cp42 and Cp52 measuring instruments (0.5, 5, 50 rpm) ) Was measured according to the change. In this case, the slurry concentrations of the Examples and Comparative Examples and the amount of the added organic matter are shown in Table 1 below.

-Measurement of mechanical properties-

The mechanical properties of the green sheet were measured using Instron (Daekyung Tech & Tester Co., Ltd., Korea) to measure the fracture elongation stress (necessary force until fracture occurs when tensile), elongation and elasticity (force required to cause deformation of the unit). The temperature was 25 ± 3 ° C., the humidity was 60 ± 10%, and the tensile speed of the specimen was 10 mm / min. In this case, in Examples 1 to 5 and Comparative Examples 1 to 2, the addition amount of the organic substance contributing to the properties of the ferrite green sheet in the completely dry state was 14.07 parts by weight based on 100 parts by weight of the ferrite powder.

The physical property measurement results of the green sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 2 below.

a) Comparative Example 1 uses only water as a dispersion solvent

b) Comparative Example 2 uses a mixed organic solvent consisting of cyclohexane, ethanol and toluene as a dispersion solvent

c) the amount of the dispersion solvent contained per 100 parts by weight of the ferrite slurry

d) the amount of each organic substance per 100 parts by weight of ferrite powder

According to the results of Table 1 and Table 2, the concentration of ferrite in the slurry of Examples 1 to 5 was 58.84% by weight, and the concentration of ferrite in the slurry of Comparative Examples 1 to 2 was about 53 to 55% by weight. It can be seen that the viscosity of the slurry is generally low despite the high state. In addition, Examples 1 to 5 show a tendency that the viscosity of the slurry decreases as the water content of the dispersion solvent increases, which enables the production of a high concentration slurry as the water content increases, and the green sheet is prepared using the high concentration slurry. In the case of manufacturing, the content of solids increases, so that the shrinkage rate is significantly reduced, so the defective rate is also reduced.

In addition, the green sheet prepared in Examples 1 to 5 according to the present invention exhibits a fracture extension stress of about 2 to 4 megapascals, an elongation of about 2 to 4%, and an elasticity of about 80 to 160 megapascals. On the other hand, the green sheet (Comparative Example 1) manufactured by water showed fracture elongation stress of about 7 megapascals, elongation of about 0.9%, and elastic modulus of about 800 megapascals. Elongational stress was about 19 megapascals, elongation was about 7%, and elasticity was about 290 megapascals.

The water-based non-aqueous green sheet according to the present invention maintains almost the same level of fracture elongation as compared to the green sheet of Comparative Example 1 (aqueous), but the elongation is about 2 to 4 times higher and the elasticity is about 5 to 10 times higher. The low level of ceramic green sheet has proved to be excellent in flexibility. In addition, compared to the green sheet of Comparative Example 2 (organic solvent system), the fracture elongation stress and the elongation rate are maintained at a slightly lower level, but the elastic modulus is superior to that of Comparative Example 2, so it can be seen that it is much more flexible.

Experimental Example 2

The following experiments were conducted to investigate the flexibility and processability of water-based non-aqueous ceramic green sheets.

The silver paste was screen printed so that a circuit of 0.5 or 1 turns was formed on one layer of the NiCuZn ceramic green sheet manufactured by using the ferrite slurry of the present invention prepared in Examples 2 and 5. After laminating the ceramic sheet 10 times while forming a circuit of 5.5 wheels while connecting the circuits between the layers, firing at 875 to 925 ° C. for 2 hours using a box furnace (NEY 6-525, USA) in air And attached to the electrode to prepare a multilayer ferrite chip inductor (MLFC) of 3216 size (3.2 × 1.6mm). The temperature increase rate was raised to 3 ℃ / min to degreasing organic matter and maintained at 400 ℃ for 3 hours, and after degreasing, firing was continuously carried out to raise the temperature to 10 ℃ / min and maintained at a predetermined temperature for about a time, Cool down to 200 ° C. at 20 ° C./min. The weight reduction rate of MLFC produced by firing at 880 ° C. to 950 ° C. for 2 hours was almost constant at about 12.1 to 12.6% by mass, and the bowel shrinkage was in the range of 16 to 17%. This is due to the mixed organic material in the manufacture of the green sheet, the organic material distributed in the ceramic sheet showed a nearly uniform distribution, and showed a nearly uniform shrinkage during firing.

On the other hand, the electromagnetic characteristics of the 3216 size MLFC produced by firing at 900 ° C for 2 hours were measured in the range of 0.1 to 40 MHz using an Impedance / Gain-Phase Analyzer (Hewlett packard, HP4194A, USA). Miracles could be obtained. Therefore, the manufacturing method of the ceramic green sheet using the aqueous binder and the aqueous-non-aqueous solvent has been shown to be excellent in flexibility and processability to enable the manufacture of stacked chip inductors.

As described above, the ceramic green sheet prepared in the present invention exhibits slightly lower physical properties compared to the conventional organic solvent green sheet, but has significantly superior organic solvent sheet content while significantly reducing the content of the organic solvent. It may be preferable in terms of environmental friendliness and economics.

In addition, the green sheet manufactured using the ceramic slurry of the present invention exhibited adequate flexibility not only for cutting, but also for precision processing and laminating operations of small holes of the correct size.

Claims (8)

A ceramic slurry containing a ceramic powder, a binder, a plasticizer, a dispersant, and an aqueous-non-aqueous dispersion solvent, comprising 100 parts by weight of ceramic powder, 0.1 to 2 parts by weight of anionic polyelectrolyte having a molecular weight of 2,000 to 50,000, and a molecular weight of 10,000 to 300,000. A ceramic slurry for producing a green sheet, comprising 1.5 to 15 parts by weight of an acrylic copolymer, 0.4 to 4.0 parts by weight of a polyalcohol having a molecular weight of 200 to 100,000, and 40 to 80 parts by weight of an aqueous-non-aqueous dispersion solvent. The powder of claim 1, wherein the ceramic powder is selected from alumina (Al ₂ O ₃ ), silica (SiO ₂ ), silica alumina-based oxide, zirconia (ZrO ₂ ), barium titanate (BaTiO ₃ ), and ferrite. Ceramic slurry for producing a green sheet, characterized in that. The ceramic slurry of claim 1, wherein the acrylic copolymer has a glass transition temperature of −30 to 100 ° C. and an acid value of KOH 20 to 200 mg / g. The ceramic slurry of claim 1, wherein the anionic polyelectrolyte is an ammonium polyacrylate or polyamine amine salt. The ceramic slurry of claim 1, wherein the polyalcohol is polyethylene glycol or polypropylene glycol. The ceramic slurry for producing a green sheet according to claim 1, wherein the anionic polyelectrolyte / polyalcohol is contained in a range of 3 to 7/1 by weight. The ceramic slurry of claim 1, wherein the aqueous solvent-non-aqueous dispersion solvent is a mixture of water and aliphatic alcohol in a weight ratio of 0.7 to 5.0 / 1. 8. The ceramic slurry of claim 7, wherein the aliphatic alcohol is isopropyl alcohol, 2-n-butoxyethanol or a mixed solvent thereof.