KR100586945B1 - Ceramic Slurry for Green Sheet Having Low Density - Google Patents

Abstract

A ceramic slurry for low density ceramic green sheets containing a nonpolar solvent. A ceramic slurry for producing a green sheet comprising a ceramic powder, a dispersant, a dispersion solvent, and a binder, wherein the ceramic slurry for producing a low density green sheet comprises a nonpolar solvent in a ceramic powder: nonpolar solvent = 100: 2-17 weight ratio. Is provided. The green sheet made of the ceramic slurry has a low density, and the delamination and the warpage of the electrode part, which are conventionally produced when manufacturing a high laminated product using the same, are improved. The porosity in the green sheet is improved so that the structural shape such as the step is also improved. The air that can be trapped in the sheet can be easily discharged during vacuum packaging, thereby preventing the defects generated after the chip is manufactured. In the binder removal process, it contains a sufficient path for the removal of organic matter, which is advantageous and can reduce the amount of residual coal.

Non-polar solvent, low density green sheet, low binder soluble polar solvent

Description

Ceramic Slurry for Green Sheet Having Low Density             

1 is a schematic diagram showing a change in shrinkage rate with drying of a ceramic slurry,

2 is a process schematic diagram showing the mixing procedure of the ceramic slurry according to the present invention;

Figure 3 is a graph showing the density of the green sheet prepared from the ceramic slurry of Example 2.

The present invention relates to a ceramic slurry for low density ceramic green sheets, and more particularly, to a ceramic slurry for low density ceramic green sheets containing a nonpolar solvent.

The ceramic slurry (paste) for manufacturing a green sheet is mix | blended based on ceramic powder, a dispersing agent, a dispersion solvent, a binder, and a plasticizer.

The density of the green sheet made of such a ceramic slurry depends on the type of dispersant, dispersion solvent, and binder.

The laminated component manufactured using the ceramic green sheet is manufactured to print internal electrodes on the component to realize desired electrical component characteristics. However, as the number of stacks increases due to the higher internal electrode thickness compared to the green sheet thickness, delamination due to poor bonding between sheets occurs even after the lamination and crimping processes. Problems occur.

Accordingly, an object of the present invention is to provide a ceramic slurry for low density green sheet.

Still another object of the present invention is to provide a ceramic slurry for producing a low density green sheet having excellent electrical characteristics as well as no delamination and cracking.

According to the invention,

In the ceramic slurry for producing a green sheet comprising a ceramic powder, a dispersant, a dispersion solvent and a binder,

There is provided a ceramic slurry for producing a low density green sheet, wherein the nonpolar solvent is contained in a ceramic powder: nonpolar solvent = 100: 2-17 weight ratio.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In general, the ceramic slurry used to manufacture the green sheet includes an additive such as ceramic powder, a dispersant, a dispersion solvent, a binder, a plasticizer, and an antistatic agent.

In the present invention, during the green sheet manufacturing process using the ceramic slurry (paste) by adding a non-polar solvent to the ceramic slurry generally prepared as described above, the dispersion solvent and the non-polar solvent is gradually evaporated sequentially. Accordingly, shrinkage of the green sheet is reduced, and the distance between ceramic powders is kept far from each other, thereby making it possible to manufacture green sheets of low density.

Furthermore, in the present invention, the density of the green sheet manufactured from the ceramic paste is increased by using the nonpolar solvent as well as the polar solvent having a low binder solubility in the binder rather than the dispersion solvent when the ceramic paste is prepared. To be further reduced.

BaTiO 3 is generally used as a ceramic powder in the manufacture of the ceramic paste used to manufacture the green sheet.

Phosphate ester etc. are generally used as a dispersing agent.

The dispersion solvent is mainly used as a main solvent for dispersing the ceramic powder in the manufacture of the ceramic paste, and a mixed solvent of a nonpolar solvent such as toluene and benzene and an alcoholic polar solvent is mainly used. The dispersion solvent is used as a dispersion medium, and should also be capable of dissolving a polymer binder which is a ceramic binder.

As the polymer binder, polyvinylbutyral (PVB) and acrylic polymers are generally used.

Phthalates are generally used as plasticizers.

The ceramic slurry is thinly coated on the surface of the support film using a doctor blade method or a coater using a die and dried to produce a desired ceramic green sheet. The green sheet manufactured as described above is greatly contracted as the dispersion solvent evaporates upon drying, and thus, the gap between ceramic powders becomes closer and denser.

Therefore, in the present invention, a separate nonpolar solvent is added to the ceramic slurry in order to alleviate the shrinkage caused by the evaporation of the dispersion solvent and to control the ceramic powder to exist far from each other on the dried green sheet.

As the nonpolar solvent, a solvent having a lower volatility than a dispersion solvent is used. In other words, if the difference in relative volatility between the dispersion solvent and the added nonpolar solvent is large, the density of the green sheet is further lowered.

FIG. 1 illustrates the difference in tendency of shrinkage during drying of a conventional ceramic slurry containing no nonpolar solvent (line A) and a ceramic slurry containing nonpolar solvent of the present invention (line B).

In FIG. 1, step (a) is an initial drying step, in which the dispersion solvent starts to dry and thus the binder starts to shrink.

Step (b) is a drying intermediate step, whereby the dispersion solvent begins to dry rapidly, and the shrinkage of the binder becomes active, and the conventional ceramic slurry containing no nonpolar solvent shrinks more than the ceramic slurry containing the nonpolar solvent of the present invention. . In step (b), the non-polar solvent, which is less volatile than the dispersing solvent, is still dried in small amounts and is present on the green sheet so that the ceramic powder is located far away. The dispersion solvent is completely dried in step (b).

Step (c) is a drying finishing step, in which the shrinkage of the binder is stopped by the completion of the drying of the dispersion solvent in step (b), the nonpolar solvent is gradually dried, and after the nonpolar solvent is dried, the place occupied by the nonpolar solvent is void By remaining in the green sheet, a low density green sheet is obtained.

Any hydrocarbon solvent may be used as the nonpolar solvent, and preferably a solvent selected from the group consisting of n-paraffins, iso-paraffins, alkenes, cycloparaffins, cycloalkenes and aromatic hydrocarbon solvents having a boiling point of 100 to 400 ° C Can be used. The nonpolar solvents are available separately as hydrocarbon solvent petrochemicals, either separately or in any state mixture thereof. Since the boiling point of the solvent used as a dispersion solvent is usually less than 100 ℃, a solvent having a boiling point of more than 100 ℃ higher than this is used. Moreover, when the boiling point of a nonpolar solvent exceeds 400 degreeC, defects generate | occur | produce, such as brittle of the produced green sheet.

The nonpolar solvent may be added in a ceramic powder: nonpolar solvent = 100: 2-17 weight ratio. If the content of the nonpolar solvent is less than the lower limit, a sufficient density reduction effect of the green sheet cannot be obtained, and if it exceeds the upper limit, the porosity in the green sheet becomes large, and the green sheet becomes weak and brittle, and furthermore, It is not dried and causes a defect such as short.

Furthermore, the nonpolar solvent is added last in the blending of the ceramic slurry. That is, the ceramic powder and the dispersant are first mixed in the dispersion solvent in the dispersion facility, and then the binder is mixed to prepare a ceramic slurry. Generally, plasticizers can be blended into the binder. The nonpolar solvent is finally added to the ceramic slurry blended up to the binder. The blending procedure of the ceramic slurry according to the present invention is shown in FIG. 2.

The order of compounding of the above components is also important, since the nonpolar solvent degrades the dispersibility of the ceramic powder. That is, dispersibility of ceramic powder is inferior when a nonpolar solvent is added first. In addition, since the non-polar solvent has little solubility in the polymer binder, it is not preferable to mix the non-polar solvent with the dispersion solvent in advance to prepare the slurry.

Furthermore, as a dispersion solvent used in the manufacture of the ceramic slurry, a conventional dispersion solvent is used in combination with a polar solvent (hereinafter, referred to as a 'low binder soluble polar solvent') having a low binder solubility or a solubility in a binder rather than a dispersion solvent. As a result, it is possible to produce a green sheet having a lower density. The low binder soluble polar solvent refers to a solvent having a binder and dispersable due to its affinity, but having a lower affinity and solubility for the binder than the solvent.

The solubility index for the binder is somewhat different among the alcohol-based solvents used as the dispersion solvent. In general, as the carbon number increases, the solubility index is lowered, and as the solubility index is lowered, the affinity and solubility for the binder used, for example, PVB, is reduced.

In a solvent having such a low solubility index, even when the binder is dissolved, the binder is not structurally completely dissolved in the dispersion solvent. As such, by using a solvent having a low solubility index for the binder together with a conventional dispersion solvent, a green sheet having a lower density can be produced.

That is, by using a low binder soluble polar solvent having a low carbon solubility in the binder together with a conventional dispersion solvent, the dissolution time of the resin binder to the dispersion solvent is increased, and the loosening of the resin binder is slightly reduced. When the green sheet is dried, the distance between ceramic powders becomes farther. Accordingly, the porosity inside the green sheet is increased to produce a low density green sheet.

The low binder soluble polar solvent may be added at 10-50% by weight of the total dispersion solvent weight. If it is less than 10% by weight, the effect of reducing the density of the green sheet according to the use of a polar binder polar solvent is insignificant, and if it exceeds 50% by weight, the viscosity of the ceramic slurry becomes too high and dispersibility is not preferable.

These low binder soluble polar solvents also act as dispersing solvents due to their bindering properties and, therefore, can be used initially at the time of powder dispersion, i.e., with the dispersing solvent.

As the low binder soluble polar solvent, C3-C7 polar alcohol may be used. The C3-C7 polar alcohol may be used as a two-component mixed solvent which is a mixture with a nonpolar dispersion solvent or as a three-component mixed solvent which is a mixture of a mixed solvent of a polar alcohol having a carbon number of 2 or less and a nonpolar dispersion solvent.

In the ceramic slurry of the present invention, the type and amount of each component used in the manufacture of the ceramic slurry, and a general manufacturing method are generally known in the art, and these may be appropriately selected and used as necessary. This does not limit the present invention.

By using the ceramic slurry of this invention, a low density green sheet can be manufactured. The prepared low density green sheet has an increase in the decay rate at the time of lamination to increase the adhesion between the sheets, it is possible to prevent the air trap (air trap) during the vacuum packaging with a high porosity of the sheet.

In addition, a sufficient path required for organic matter removal during the debinder process may be formed to reduce the amount of residual coal. Furthermore, structural problems such as step difference in stacking, which occur additionally as chip components are increased in capacity and stacked, can be solved.

The ceramic slurry of the present invention can be utilized in any field requiring the manufacture of ceramic green sheets, such as low density MLCC, chip resistor, chip inductor, LTCC, chip antenna.

Hereinafter, the present invention will be described in detail through examples. However, the following Examples do not limit the present invention.

Example 1

To the azeotropic dispersion solvent of toluene and ethanol, BaTiO3 powder having an average particle diameter of 400 μm and phosphate ester dispersant diluted at 50% by weight were added and stirred, followed by adding and blending a PVB binder and a di-octyl phthalate (DOP) plasticizer. To prepare a ceramic slurry.

 PVB binder resin 7% by weight (7 parts by weight of binder resin per 100 parts by weight of BaTiO3) relative to the weight of BaTiO3 powder, DOP plasticizer was 35% by weight of the binder resin weight, phosphate ester dispersant was formulated to 0.15% by weight relative to the weight of BaTiO3 powder. The dispersion solvent was used in a weight ratio of 10 times the weight of the binder.

The ceramic slurry was dispersed in a Beads Mill and milled for 12 hours. Then, decane and dodecane, respectively, were added to the ceramic slurry in an amount of 10 parts by weight per 100 parts by weight of BaTiO 3 powder as a nonpolar solvent and mixed with a mixer for 1 hour. After that, a sheet having a thickness of about 13 μm was manufactured using an AEM molding machine using an experimental doctor blade. The drying temperature of the molding machine was set to 75 ^° C.

The sheet is cut and peeled off using a 17 cm x 7 cm jig and the sheet is folded in eight layers.

Folded by measuring the thickness, converting the sheet thickness, and then measuring the total weight of the sheet to calculate the total density of the ceramic slurry without a non-polar solvent, the ceramic slurry with decane and the ceramic slurry with dodecane added The density of the sheet was measured.

The density of the green sheet prepared without adding the nonpolar solvent was 3.54 g / cc, and the density of the green sheet prepared by adding the decane as the nonpolar solvent was 2.48 g / cc, and the density of the green sheet prepared with the addition of the dodecane was 2.44 g / cc.

Example 2

BaTiO3 powder having an average particle diameter of 400 μm and a phosphate ester dispersant diluted to 50% by weight were added to the dispersion solvent, followed by stirring, followed by adding a PVB binder and a DOP plasticizer to the ceramic slurry using a ball mill. Was prepared.

PVB binder resin 8% by weight (8 parts by weight of binder resin per 100 parts by weight of BaTiO3), DOP plasticizer 30% by weight of the binder resin, 0.15% by weight of the phosphate ester dispersant was added to the BaTiO3 powder. The dispersion solvent was used in a weight ratio of 10 times the weight of the binder.

As the dispersion solvent, (1) ethanol and toluene azeotropic solvent and (2) butanol, ethanol and toluene tricomponent solvent (mixing ratio = 3: 4: 3 weight ratio) were used, respectively.

Each of the ceramic slurries prepared above was used to form a sheet having a thickness of 11.3 μm and a sheet having a thickness of 5.6 μm, respectively.

Sheets with a thickness of 11.3 μm were prepared directly using a film-free Paloma molding machine (with two drying zones and dried at a temperature profile of 80 ^o C-90 ^o C) and a thickness of 5.6 The sheets of um were molded in a die molding machine capable of thin film molding.

The thickness and density of the prepared sheets were calculated in the same manner as in Example 1, and the results are shown graphically in FIG. 3.

As can be seen in Figure 3, for the sheet thickness of 11.3um, the density was 3.6g / cc when using a mixed solvent of ethanol and toluene, the density of 3.51g / cc when using a mixed solvent of toluene, ethanol and butanol Was reduced.

In the case of the sheet having a thickness of 5.6 um, the density was 3.375 g / cc when the mixed solvent of ethanol and toluene was used, and the density was 3.2881 g / cc when the mixed solvent of toluene, ethanol and toluene was used.

As such, when a solvent having a low solubility in a binder is used together, the sheet density is lower than that in the case where only a mixed solvent of toluene and ethanol is used.

As in Example 1, the green sheet made of the ceramic slurry to which the nonpolar solvent was added showed a lower density than the green sheet made of the ceramic slurry to which the nonpolar solvent was not added. As in Example 2, greensheets made from ceramic slurries with low binder soluble polar solvents exhibited lower densities than greensheets made from slurries without low binder soluble polar solvents.

Therefore, when manufacturing the ceramic slurry, it can be seen that the density of the green sheet made of a ceramic slurry using both a non-polar solvent and a low binder soluble polar solvent is further reduced.

The green sheet made of a ceramic slurry containing a non-polar solvent has a low density, and the delamination and the warpage of the electrode part, which are conventionally produced when manufacturing a high laminated product using the same, are improved. Porosity in the green sheet is improved, and structural shapes such as steps are also improved. Furthermore, by easily discharging air that may be trapped in the sheet during vacuum packaging, defects generated after chip manufacturing are prevented. Moreover, the process includes a sufficient path for the removal of organics in the debinder process, which is advantageous and can reduce the amount of residual coal.

Claims (5)

In the ceramic slurry for producing a green sheet comprising a ceramic powder, a dispersant, a dispersion solvent and a binder, A ceramic slurry for producing a low density green sheet, comprising a nonpolar solvent in a ceramic powder: nonpolar solvent = 100: 2-17 weight ratio. The ceramic slurry for producing a low density green sheet according to claim 1, wherein a ceramic powder and a dispersant are added and blended to the dispersion solvent, and then a binder is added followed by addition of a nonpolar solvent. The ceramic slurry of claim 1 or 2, wherein the nonpolar solvent is less volatile than a dispersion solvent. The ceramic of claim 3, wherein the nonpolar solvent is selected from the group consisting of n-paraffins, iso-paraffins, alkenes, cycloparaffins, cycloalkenes and aromatic solvents having a boiling point of 100 to 400 ° C. Slurry. The ceramic slurry of claim 1 or 2, wherein the dispersion solvent comprises C3-C7 polar alcohol in an amount of 10-50% by weight of the total weight of the dispersion solvent.

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