KR20180115373A - Method of dielectric ceramic composition for mlcc - Google Patents

Abstract

The present invention relates to a method of a dielectric ceramic composition for MLCC. According to the present invention, the method of a dielectric ceramic composition comprises: a first step of mixing and dispersing an additive instead of a sintering adjuvant while being contained in the dielectric ceramic composition at first; a second step of inputting BaTiO_3 into the dispersed mixture to be mixed, dispersed, and then, calcined; and a third step of mixing and dispersing an additional additive (sintering adjuvant) in the calcined mixture.

Description

METHOD OF DIELECTRIC CERAMIC COMPOSITION FOR MLCC BACKGROUND OF THE INVENTION [0001]

The present invention relates to a method for producing a dielectric composition for MLCC having high capacity and high reliability.

Multilayer ceramic capacitors (MLCCs) are widely used for components such as computers, mobile phones, and various communication devices because they have small volume, good reliability, good withstand voltage characteristics, and easy mounting.

The MLCC includes a plurality of ceramic dielectric sheets, internal electrodes interposed between the plurality of ceramic dielectric sheets, and external electrodes electrically connected to the internal electrodes.

Recently, as the climate environment becomes increasingly severe, MLCCs are required to have reliability (i.e. Insulation Resistance (IR) characteristics) in harsh environments (high temperature, high humidity, high pressure and high ESD) There is a continuing demand for miniaturization of electronic components according to the complexity. Accordingly, MLCCs are required to have higher capacity and higher reliability at a certain volume.

The most important thing in manufacturing such a high-capacity, high-reliability MLCC is realization of a thin dielectric layer. The dielectric capacity of the dielectric increases as the thickness of the dielectric layer becomes thinner and as the number of stacks of dielectric layers increases. As the thickness of the dielectric layer becomes thinner, more dielectric layers can be stacked at a constant volume, to be.

Recently, the demand for high-reliability high-capacity MLCC having a thickness of 2 탆 or less, thickness of 0.5 탆 or less, stacking number of 300 layers or more, and 1000 layers or more has been recently increased.

In order to make the dielectric layer thin, it is very important to miniaturize and uniformize the particle size of the BaTiO ₃ powder, which is a dielectric powder mainly used. In order to obtain such a fine BaTiO ₃ powder, a hydrothermal synthesis method is mainly used.

On the other hand, BaTiO ₃ powder having a dielectric structure with a dielectric property capable of being produced by hydrothermal synthesis has a grain size of 100 nm or more and a cubic crystal structure BaTiO ₃ is synthesized.

The cubic BaTiO ₃ having a thickness of 100 nm or less can be converted into a crystal structure having a dielectric property through heat treatment, but the fine grain size is not maintained in the heat treatment process, and thus the crystal grain size is increased.

In addition, an important part for thinning the dielectric layer will be a uniform dispersion of various additives in the dielectric layer mixed with BaTiO ₃ . In general, the dielectric layer includes various additives for the purpose of improving reliability, improving reduction resistance, suppressing grain growth, and lowering sintering temperature, together with dielectric powder BaTiO _{3. The} final dielectric layer is formed by uniformly mixing these various additives with the dielectric powder Dispersed to prepare a green sheet, and then sintered. If uniform dispersion of the additive and the dielectric powder is not achieved in the production of such a dielectric layer, thinning becomes difficult.

Korean Patent Publication No. 2006-0020196

An object of the present invention is to provide a method for producing a dielectric composition for MLCC capable of forming a thin and highly reliable dielectric layer.

(A) an A component composed of one or two or more metal oxides selected from Ho, Yb, Gd, Dy, Sm and Y; and an A component selected from W, Mo and V A component C composed of one or more metal oxides selected from the group consisting of Mn, Cr and Co, and one or more elements selected from Mg, Ca and Ba Mixing and dispersing a component D of a carbonate to prepare an additive slurry; (b) mixing and calcining BaTiO ₃ powder into the additive slurry; And (c) mixing and dispersing an E component composed of one or more oxides selected from Si, Li, Al and B into the calcined powder, wherein (a) and (c) in the BaTiO ₃ based on 100 moles of the component a is 0.5 to 2.0 mol, and the B component is 0.2% to 0.8 mole, the component C is 0.1 to 0.5 mole, the component D is 0.2 and 0.8 molar, the component E Wherein the BaTiO ₃ powder has a cubic crystal structure prepared by hydrothermal synthesis and has a particle size (D50) of 20 to 80 nm. The present invention also provides a method for producing a dielectric composition for a multilayer ceramic capacitor.

According to the present invention, it is possible to obtain a dielectric composition of a core-shell structure (core is BaTiO ₃ and shell is made of various additives) essential for high reliability and thinning.

In addition, a small cubic BaTiO ₃ Enables the uniformization and fineness of the particle size of the final dielectric composition, thereby enabling high reliability and high-capacity MLCC production.

Hereinafter, a method according to a preferred embodiment of the present invention will be described in detail, but the present invention is not limited to the following embodiments. Accordingly, it is obvious that those skilled in the art can variously change the present invention without departing from the technical idea of the present invention.

The method for preparing the dielectric composition according to the present invention comprises a first step of first mixing and dispersing the additive which is contained in the dielectric composition and is not a sintering aid, and the BaTiO ₃ is added to the thus dispersed mixture, And a third step of mixing and dispersing an additional additive (sintering aid) to the calcined mixture.

Wherein the dielectric composition comprises a _{BaTiO 3, A, B, C} , D and E materials.

Of these, A is preferably one or more metal oxides selected from the group consisting of Ho, Yb, Gd, Dy, Sm and Y, and the content thereof is preferably 0.5 to 2.0 moles per 100 moles of BaTiO ₃ .

The B is preferably at least one metal oxide selected from the group consisting of W, Mo and V, and its content is preferably 0.2 to 0.8 mol based on 100 mol of BaTiO ₃ .

The C is preferably at least one metal oxide selected from the group consisting of Mn, Cr and Co, and the content thereof is preferably 0.1 to 0.5 mol based on 100 mol of BaTiO ₃ .

The above D is preferably at least one carbonate selected from the group consisting of Mg, Ca and Ba, and its content is preferably 0.2 to 0.8 mol, based on 100 mol of BaTiO ₃ .

The E is preferably at least one oxide selected from the group consisting of Si, Li, Al and B, and its content is preferably 0.2 to 1.0 mole based on 100 moles of BaTiO ₃ .

In addition, the average particle size of the oxides and carbonate constituting A, B, C, D and E is coated on the surface of the BaTiO ₃ particles through the manufacturing process to form a shell to finally form a core-shell structure powder 10 nm or less is preferable.

BaTiO ₃ used in the second step of the present invention is prepared by hydrothermal synthesis and has a cubic crystal structure on the crystal structure. When the particle size (D50) is less than 20 nm, it is difficult to produce BaTiO ₃ meeting the stoichiometric ratio. Since it is difficult to form a fine dielectric layer, it is preferably 20 to 80 nm, and more preferably, the particle size (D50) may be 30 to 60 nm.

BaTiO ₃ having a cubic crystal structure is converted to BaTiO ₃ in a tetragonal structure with a dielectric property through a calcination process. If the calcination temperature is less than 600 ° C, it is difficult to form a stable core-shell structure between the additive and BaTiO _3. If the calcination temperature is higher than 900 ° C, 600 ° C to 900 ° C is preferable because excessive grain growth occurs after calcination.

When the particle size of the mixed powder after calcination is less than 100 nm, the tetragonal crystal structure does not completely appear and it is difficult to exhibit sufficient dielectric characteristics. When the particle size exceeds 200 nm, it is difficult to form a fine dielectric layer.

Further, in the present invention, the sintering aid added for the purpose of lowering the sintering temperature is mixed and dispersed after completion of mixing and calcination of BaTiO ₃ with other additives, thereby preventing the excessive growth of BaTiO _{3 in} the calcination.

[Example]

The step of preparing the dielectric composition according to a preferred embodiment of the present invention comprises a first step of preparing an additive dispersion slurry, two calcination steps of mixing the prepared additive dispersion slurry and BaTiO3 powder and transforming the crystal structure of BaTiO3, And a third step of mixing the calcined powder with the sintering aid. The specific process is as follows.

Stage 1  (Preparation step of additive dispersed slurry)

One or more metal oxides selected from the group consisting of Ho, Yb, Gd, Dy, Sm and Y having an average particle size of 10 nm or less and one or two or more species selected from the group consisting of W, Mo and V A metal oxide and at least one metal oxide selected from the group consisting of Mn, Cr and Co and at least one carbonate selected from the group consisting of Mg, Ca and Ba, 100: 0.2 to 0.8, 100: 0.1 to 0.5, and 100: 0.2 to 0.8, respectively, at a molar ratio relative to the BaTiO ₃ powder to be added in the process.

At this time, in the dispersing step, deionized water or alcohol is used as a solvent, and the mixture is uniformly mixed and dispersed with a bead mill using a zirconia ball having a diameter of 0.1 mm to prepare an additive dispersed slurry.

Step 2  ( BaTiO ₃  Powder mixing, dispersion, drying and calcination  step)

In the above additive dispersion slurry, BaTiO ₃ Powder was added and dispersed using a bead mill using 0.1 mm zirconia balls.

At this time, BaTiO ₃ The powder has a cubic crystal structure of 20 to 80 nm in particle size prepared by hydrothermal synthesis.

The dispersed BaTiO ₃ The slurry containing the powder was sprayed and dried in a droplet form using a spray drier, and the additive powders having a particle size of 10 nm or less were dispersed in BaTiO ₃ So as to be evenly dispersed with the particles.

Subsequently, calcination is performed at 600 ° C for 2 hours using a box furnace or a tunnel furnace, and BaTiO ₃ having a cubic crystal structure is converted into a tetragonal crystal structure.

Step 3  ( Sintering aid  Mixing step)

One or more oxides selected from the group consisting of Si, Li, Al, and B were weighed so as to have a molar ratio of 100: 0.2 to 1.0 based on the amount of the BaTiO ₃ powder added to the calcined powder, A dielectric composition is obtained.

Here, the mixing and dispersion are performed by using a bead mill using a zirconia ball having a diameter of 0.1 mm and drying using a final spray drier to obtain a dielectric composition in which the sintering aid is evenly dispersed.

Tables 1 to 3 below show specific examples of MLCC characteristics according to the composition, process conditions, and dielectric layer thickness of the dielectric composition prepared by the above method. In the table below, HALT (h) stands for Highly Accelerated Life Test, and the value of each component is based on mol. The accelerated life test was carried out by applying a DC voltage of 20 KV / mm at 150 ° C.

The samples used in the accelerated life test were made as follows.

The dielectric composition prepared according to the method described above is mixed with a binder, a solvent or the like in accordance with the ratio and dispersed to prepare a paste to form a thin film. A nickel or nickel alloy electrode is printed on the surface by screen printing and laminated. After the CIP (Cool Isostatic Press) was performed, the cut specimens were annealed at 300 ° C to remove the binder, and then sintered in a reducing atmosphere using a tunnel or a tube furnace to prepare standard specimens for measurement of dielectric properties .

No. MgCO ₃ CaCO ₃ Mn ₃ O ₄ Cr ₂ O ₃ SiO ₂ Al ₂ O ₃ Dy ₂ O ₃ Y ₂ O ₃ V ₂ O ₅ Calcination temperature
(° C) 1-step dispersion solvent Medium thickness
(탆) HALT (h) One 0.3 0.4 0.3 0 0.6 0 0.5 0 0.4 800 Alcohol 0.8 21 2 0.3 0.4 0.3 0 0.6 0 1.0 0 0.4 800 Alcohol 0.8 27 3 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 800 Alcohol 0.8 29 4 0.3 0.4 0.3 0 0.6 0 2.0 0 0.4 800 Alcohol 0.8 27 5 0.3 0.4 0.3 0 0.6 0 2.5 0 0.4 800 Alcohol 0.8 20 6 0.3 0.4 0.3 0 0.6 0 0.5 0 0.4 800 Deionized water 0.8 20 7 0.3 0.4 0.3 0 0.6 0 1.0 0 0.4 800 Deionized water 0.8 28 8 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 800 Deionized water 0.8 30 9 0.3 0.4 0.3 0 0.6 0 2.0 0 0.4 800 Deionized water 0.8 26 10 0.3 0.4 0.3 0 0.6 0 2.5 0 0.4 800 Deionized water 0.8 19 11 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 600 Deionized water 0.8 18 12 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 700 Deionized water 0.8 21 13 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 750 Deionized water 0.8 26 14 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 800 Deionized water 0.8 25 15 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 850 Deionized water 0.8 27 16 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 870 Deionized water 0.8 23 17 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 900 Deionized water 0.8 18 18 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 700 Deionized water 1.2 21 19 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 720 Deionized water 1.2 23 20 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 750 Deionized water 1.2 27

No. MgCO ₃ CaCO ₃ Mn ₃ O ₄ Cr ₂ O ₃ SiO ₂ Al ₂ O ₃ Dy ₂ O ₃ Y ₂ O ₃ V ₂ O ₅ calcination
Temperature
(° C) 1-step dispersion solvent Medium thickness
(탆) HALT (h) 21 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 800 Deionized water 1.2 26 22 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 850 Deionized water 1.2 28 23 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 870 Deionized water 1.2 25 24 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 900 Deionized water 1.2 20 25 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 700 Deionized water 1.5 22 26 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 720 Deionized water 1.5 24 27 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 750 Deionized water 1.5 27 28 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 800 Deionized water 1.5 28 29 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 850 Deionized water 1.5 27 30 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 870 Deionized water 1.5 26 31 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 900 Deionized water 1.5 23 32 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 750 Alcohol 1.2 26 33 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 800 Alcohol 1.2 27 34 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 850 Alcohol 1.2 24 35 0.3 0.4 0.3 0 0.6 0 1.5    0 0.4 750 Alcohol 1.5 27 36 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 800 Alcohol 1.5 29 37 0.3 0.4 0.3 0 0.6 0 1.5 0 0.4 850 Alcohol 1.5 26 38 0.3 0.4 0.3 0 0.6 0 0 0.5 0.4 800 Alcohol 1.2 20 39 0.3 0.4 0.3 0 0.6 0 0 1.0 0.4 800 Alcohol 1.2 25 40 0.3 0.4 0.3 0 0.6 0 0 1.5 0.4 800 Alcohol 1.2 25

No. MgCO ₃ CaCO ₃ Mn ₃ O ₄ Cr ₂ O ₃ SiO ₂ Al ₂ O ₃ Dy ₂ O ₃ Y ₂ O ₃ V ₂ O ₅ Calcination temperature (캜) 1-step dispersion solvent Medium thickness
(탆) HALT (h) 41 0.3 0.4 0.3 0 0.6 0 0 2.0 0.4 800 Alcohol 1.2 26 42 0.3 0.4 0.3 0 0.6 0 0 2.5 0.4 800 Alcohol 1.2 22 43 0.3 0.4 0.3 0 0.6 0 0 1.0 0.4 800 Deionized water 1.2 24 44 0.3 0.4 0.3 0 0.6 0 0 1.5 0.4 800 Deionized water 1.2 26 45 0.5 0.4 0.3 0 0.6 0.3 1.0 0.5 0.4 750 Deionized water 0.8 26 46 0.5 0.4 0.3 0 0.6 0.3 0.5 1.0 0.4 750 Deionized water 0.8 21 47 0.5 0.4 0.3 0 0.6 0.3 0 1.5 0.4 750 Deionized water 0.8 17 48 0.5 0.4 0.3 0 0.2 0.3 1.5 0 0.4 800 Deionized water 1.2 18 49 0.5 0.4 0.3 0 0.4 0.3 1.5 0 0.4 800 Deionized water 1.2 23 50 0.5 0.4 0.3 0 0.8 0.3 1.5 0 0.4 800 Deionized water 1.2 21 51 0.5 0.4 0.2 0.1 0.5 0 0 1.5 0.4 850 Deionized water 1.5 26 52 0.5 0.4 0.1 0.2 0.5 0 0 1.5 0.4 850 Deionized water 1.5 24 53 0.2 0.2 0 0.3 0 0.6 1.5 0 0.3 800 Deionized water 1.2 20 54 0.4 0.2 0 0.3 0 0.6 1.5 0 0.3 800 Deionized water 1.2 25 55 0.6 0.2 0 0.3 0 0.6 1.5 0 0.3 800 Deionized water 1.2 24 56 0.8 0.2 0 0.3 0 0.6 1.5 0 0.3 800 Deionized water 1.2 21 57 0 0.4 0 0.3 0 0.6 1.5 0 0.3 800 Deionized water 1.2 23 58 0 0.8 0 0.3 0 0.6 1.5 0 0.3 800 Deionized water 1.2 19 59 0.4 0.3 0.3 0 0.5 0 0 1.5 0.3 800 Deionized water 1.2 25 60 0.4 0.3 0.3 0 0.5 0 0 1.5 0.6 800 Deionized water 1.2 24

As can be seen from Tables 1 to 3, when MLCCs are manufactured using the dielectric composition according to the present invention, high reliability can be ensured even when a dielectric layer is formed with a very small thickness.

Claims (4)

(a) a B component composed of one or more metal oxides selected from Ho, Yb, Gd, Dy, Sm and Y and one or more metal oxides selected from W, Mo and V, Component and a component C composed of one or more kinds of metal oxides selected from Mn, Cr and Co and a component D composed of one or more kinds of carbonates selected from Mg, Ca and Ba are mixed and dispersed Preparing an additive slurry;
(b) mixing and calcining BaTiO ₃ powder into the additive slurry; And
(c) mixing and dispersing the calcined powder with an E component composed of one or more oxides selected from Si, Li, Al and B,
Wherein (a) and (c) in step, the BaTiO ₃ based on 100 moles of the component A is 0.5 to 2.0 mol, and the B component is 0.2% to 0.8 mole, the component C is 0.1 to 0.5 mole, the component D Is 0.2 to 0.8 mol and the E component is mixed in a ratio of 0.2 to 1.0 mol,
Wherein the BaTiO ₃ powder has a cubic crystal structure prepared by hydrothermal synthesis and has a particle size (D50) of 20 to 80 nm. The method according to claim 1,
The dispersion of step (a) uses deionized water or alcohol as the solvent. The method of producing a dielectric composition for a multilayer ceramic capacitor, 3. The method according to claim 1 or 2,
Wherein the calcination in the step (b) is performed at 600 to 900 占 폚. 3. The method according to claim 1 or 2,
Wherein the average particle size of the mixed powder after the completion of the step (b) is 100 to 200 nm.