JP2012072033A - Method for manufacturing dielectric slurry and method for manufacturing laminated ceramic electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a dielectric slurry suited for producing a thin dielectric layer, and a laminated ceramic electronic part having a small dielectric loss, a high dielectric constant and a long life.SOLUTION: The method for manufacturing the dielectric slurry comprises: a step of mixing and dispersing a pre-dispersion treatment solution containing at least a dielectric powder and a solvent by carrying out a pre-dispersion treatment; and a step of mixing and dispersing the treated solution after the pre-dispersion treatment by carrying out a post-dispersion treatment. Here, the pre-dispersion treatment is a two-step dispersion treatment comprising a first pre-treatment and a second pre-treatment, wherein the first pre-treatment is carried out in a high-speed shear disperser and the second pre-treatment is carried out in a high-pressure homogenizer disperser or an ultrasonic disperser, and the post-dispersion treatment comprises a treatment carried out in a bead mill disperser using beads ≤0.1 mm in diameter. The rate of change of the BET specific surface area (β) of the dielectric powder after the pre-dispersion treatment to the BET specific surface area (α) of the dielectric powder before the pre-dispersion treatment falls within 0.7-3.5%, and the rate of change of the BET specific surface area (γ) of the dielectric powder after the post-dispersion treatment to the BET specific surface area (α) of the dielectric powder before the pre-dispersion treatment is ≤15%.

Description

  The present invention relates to a dielectric slurry manufacturing method and a multilayer ceramic electronic component manufacturing method.

  A multilayer ceramic capacitor as an example of a multilayer ceramic electronic component is incorporated in various electronic devices such as a mobile phone and a personal computer, and the demand thereof is increasing year by year. Furthermore, with the progress of miniaturization and weight reduction of electronic devices such as mobile phones and personal computers, there is a strong demand for miniaturization. For this reason, thinning and multilayering of dielectric green sheet layers are required. .

  In order to reduce the thickness of the dielectric layer, it is necessary to improve the dispersion of the dielectric. For example, in Patent Document 1 below, a dielectric is obtained by incorporating a mediumless high-pressure homogenizer as a disperser in the dielectric dispersion process. Dielectric coatings with a high degree of dispersion are produced.

  However, thinning and multilayering of dielectric green sheets are approaching the limit, and dielectrics are required to have characteristics such as finer particles of 0.15 μm or less and increased dielectric constant. It is very difficult to make dielectrics fine particles and improve the dielectric constant. In some cases, secondary aggregates of dielectrics become stronger or the dielectrics themselves are softer. It has become impossible to cope with this method.

  For example, the technique shown in Patent Document 1 discloses a dispersion method of a combination of a high-pressure homogenizer and a bead mill. In Patent Document 1, a 0.3 μm dielectric is mixed with other materials using a ball mill before processing a high-pressure homogenizer. However, in this dispersion method, when a dielectric material having a high dielectric constant is mixed with fine particles of 0.15 μm or less by a ball mill, coarse particles of several tens of μm may remain even though BET rises. is there.

  Conversely, if small beads with a diameter of 0.1 μm or less are used to suppress BET changes, coarse particles may remain even after dispersion, or if the bead separation mechanism of the disperser is a screen, the worst is aggregated particles on the screen. In the case of a disperser where bead separation is not a screen, the beads must be dispersed by increasing the bead diameter or circumferential speed in order to break up the coarse particles. It will cause a rise in BET and lead to increased contamination.

JP 2003-146664 A

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a dielectric slurry manufacturing method capable of providing a dielectric slurry suitable for thinning a dielectric layer, and a dielectric loss is small and high. To provide a multilayer ceramic electronic component having a dielectric constant and a long life.

  As a result of intensive studies on dielectric slurry suitable for thinning the dielectric layer, the present inventors have introduced medialess dispersion treatment in two stages in the pre-process of slurrying a dielectric powder of 0.15 μm or less. As a result, a balance between an increase in the BET specific surface area and the remaining coarse particles can be achieved, and a dielectric slurry for a thin film with less damage to the dielectric particles can be obtained by subsequent bead mill dispersion with beads having a diameter of 0.1 mm or less. The inventors have found that it can be manufactured and have completed the present invention.

That is, the method for producing a dielectric slurry according to the present invention includes:
A method for producing a dielectric slurry by mixing and dispersing at least a dielectric powder and a solvent,
A step of mixing and dispersing a dispersion pretreatment solution containing at least the dielectric powder and a solvent by a preliminary dispersion treatment;
And a step of mixing and dispersing the treated solution subjected to the preliminary dispersion treatment by post-dispersion treatment,
The preliminary distributed processing is a two-stage distributed processing of a first preprocessing and a second preprocessing that is performed after the first preprocessing and is different from the first preprocessing,
The first pretreatment is a dispersion treatment by a high-speed shear disperser;
The second pretreatment is a dispersion treatment using a high-pressure homogenizer disperser or an ultrasonic disperser,
The post-dispersion treatment includes a dispersion treatment by a bead mill disperser using beads having a bead diameter of 0.1 mm or less,
Change rate of BET specific surface area (β) of dielectric powder contained in solution after preliminary dispersion treatment relative to initial BET specific surface area (α) of dielectric powder contained in solution before preliminary dispersion treatment (100 × (β− The preliminary dispersion treatment is performed so that α) / α) is 0.7 to 3.5%,
Change rate of BET specific surface area (γ) of dielectric powder contained in solution after post-dispersion treatment relative to initial BET specific surface area (α) of dielectric powder contained in solution before preliminary dispersion treatment (100 × (γ− The post-dispersion processing is performed so that α) / α) is 15% or less.

  In the method for producing a dielectric slurry according to the present invention, a high-speed shearing treatment and a high-pressure homogenizer treatment or an ultrasonic treatment are combined to solve secondary agglomeration while suppressing damage to the dielectric powder, and thereafter the diameter 0 is performed. Dispersion with small diameter beads of 1 mm or less prevents coarse particles from remaining even when dispersed, enabling low damage dispersion and realizing a dielectric slurry that originally retains the characteristics of dielectric powder. .

  In the present invention, the change rate (100 × (β−α) / α) of the BET specific surface area of the dielectric powder before and after the preliminary dispersion treatment is 0.7 to 3.5%. When in this range, the dielectric is not damaged, the secondary aggregation is solved, and the dispersion efficiency by the small-diameter beads having a diameter of 0.1 mm or less is improved. In the dielectric slurry obtained by the method of the present invention, the dielectric powder having a fine and uniform particle diameter is uniformly dispersed.

  In the present invention, the change rate (100 × (γ−α) / α) of the BET specific surface area of the dielectric powder contained in the solution after the post-dispersion treatment is 15% or less. Even if the change rate of the BET specific surface area in the post-dispersion treatment is within a predetermined range, a highly dispersed slurry can be obtained, and a multilayer ceramic electronic component having a low dielectric loss, a high dielectric constant and a long life can be produced.

  The post-dispersion process may further include a medialess dispersion process performed after the dispersion process by the bead mill disperser. In the medialess dispersion treatment, a binder resin solution may be added. A dielectric slurry having a uniform particle size can be obtained with little damage to the dielectric powder.

A method for producing a multilayer ceramic electronic component according to the present invention includes:
Using the dielectric slurry obtained by the above-described dielectric slurry manufacturing method, forming a green sheet;
Forming an internal electrode pattern on the green sheet;
A step of forming a laminate by laminating a plurality of the green sheets on which the internal electrode pattern layer is formed;
Firing the laminate.

FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. 2A and 2B are schematic cross-sectional views showing the manufacturing process of the multilayer ceramic capacitor shown in FIG. FIG. 3 is a flowchart showing a manufacturing process of the dielectric slurry for thin film used in the process of manufacturing the multilayer ceramic capacitor according to one embodiment of the present invention. FIG. 4 is a conceptual diagram of a rotor stator type dispersing machine. FIG. 5 is a conceptual diagram of a homogenizer disperser. FIG. 6 is a conceptual diagram of an ultrasonic disperser.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
Structure of multilayer ceramic capacitor First, the overall structure of the multilayer ceramic capacitor manufactured using the ceramic slurry according to the present invention will be described.

  As shown in FIG. 1, the multilayer ceramic capacitor 2 according to this embodiment includes a capacitor body 4, a first terminal electrode 6, and a second terminal electrode 8. The capacitor body 4 includes dielectric layers 10 and internal electrode layers 12, and the internal electrode layers 12 are alternately stacked between the dielectric layers 10. One internal electrode layer 12 that is alternately stacked is electrically connected to the inside of the first terminal electrode 6 formed at one end 4 a of the capacitor body 4. The other internal electrode layer 12 that is alternately stacked is electrically connected to the inside of the second terminal electrode 8 formed at the other end 4 b of the capacitor body 4.

  In the capacitor body 4, an exterior dielectric layer 14 that does not have an internal electrode layer is formed at both ends in the stacking direction of the laminate of the dielectric layer 10 and the internal electrode layer 12.

  The shape and size of the multilayer ceramic capacitor 2 may be appropriately determined according to the purpose and application. When the multilayer ceramic capacitor 2 has a rectangular parallelepiped shape, the length (0.4 to 5.6 [mm]) × width (0.2 to 5.0 [mm]) × thickness (0.1 to 1.9) is usually used. [Mm]).

  The thickness of each dielectric layer 10 is not particularly limited, but is about 0.15 to 5.0 [μm], but is 1.0 μm or less in the present embodiment. The number of laminated dielectric layers 10 is not particularly limited, but is preferably 20 to 1000.

  The thickness of each internal electrode layer 12 is preferably about 0.15 to 5.0 [μm], more preferably about 0.25 to 0.5 [μm]. The thickness of the internal electrode layer 12 is more desirably thin as long as the electrode is not interrupted. The internal electrode layer 12 may be composed of a single layer, or may be composed of a plurality of layers having two or more different compositions.

Although the material of the 1st terminal electrode 6 and the 2nd terminal electrode 8 is not specifically limited, Usually, copper, copper alloy, nickel, nickel alloy, etc. are used. Although the thickness of the 1st terminal electrode 6 and the 2nd terminal electrode 8 is not specifically limited, It is about 10-50 [micrometer] normally.
Dielectric layer composition

Dielectric layer 10 contains, for example, the following main components and subcomponents.
It is preferable to use barium titanate as the dielectric powder as the main component. Further, a dielectric material containing at least one of Ca, Sr, Zr and Sn [eg (Ba, Zr) TiO ₃ ] may be used as a main component.

  Examples of the first subcomponent include rare earth element oxides of at least one of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Is done.

  An example of the second subcomponent is MgO. Note that at least one oxide selected from CaO, SrO, and BaO may be used as the third subcomponent.

Examples of the fourth subcomponent include SiO ₂ -based sintering aids. Examples of the fifth subcomponent include at least one oxide selected from V ₂ O ₅ , MoO ₃ and WO ₃ . Examples of the fifth subcomponent include at least one oxide selected from MnO and Cr ₂ O ₃ . For example, Al ₂ O ₃ may be used as the other subcomponent.
Manufacturing method of multilayer ceramic capacitor

Next, an example of a method for manufacturing the multilayer ceramic capacitor 2 according to the present embodiment will be described.
Green sheet manufacturing method

  In order to produce a green sheet that will constitute the dielectric layer 10 shown in FIG. 1, a coating material for a green sheet (dielectric slurry) is prepared.

  First, a dielectric slurry is obtained by dispersing and mixing a main component dielectric powder and subcomponent powders and a binder resin solution by a method described later.

  As the dielectric powder and each subcomponent powder, the above-mentioned oxides, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above-described oxides and composite oxides by firing, for example, carbonates , Oxalates, nitrates, hydroxides, organometallic compounds, and the like may be selected as appropriate and used as a mixture.

  The binder resin is not particularly limited, and may be appropriately selected from ordinary various binders such as polyvinyl butyral, acrylic, and ethyl cellulose. Also, the organic solvent to be used is not particularly limited, and alcohol solvents such as methanol, ethanol, propanol, methyl ethyl ketone, terpineol, butyl carbitol, acetone, toluene, etc., depending on the method used, such as printing method and sheet method. What is necessary is just to select suitably from various organic solvents.

  The dielectric slurry may be a solvent-based paint or a water-based paint. When the dielectric slurry is used as a water-based paint, it may be mixed with a dielectric raw material in which a water-soluble binder, a dispersant or the like is dissolved in water. The water-soluble binder is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, or the like may be used.

  There is no particular limitation on the content of the binder resin in the dielectric slurry. Usually, the binder resin may be about 10 to 20 [wt%], and the solvent may be about 50 to 400 [wt%]. The paste may contain additives selected from various dispersants, plasticizers, antistatic agents, viscosity modifiers, and the like as necessary. The total content of these is preferably 10% by weight or less.

  As shown in FIG. 2A, the dielectric slurry is formed into a sheet shape on a support film 20 such as PET to form an interior green sheet 10a. The interior green sheet 10a is a portion that becomes the dielectric layer 10 shown in FIG. 1 after firing.

  The method for forming the green sheet is not limited as long as a desired thickness can be applied. However, since the green sheet is a means for producing a thin film green sheet, an application method suitable for a thin film (1 μm or less) is preferable.

The green sheet is dried after coating, but drying is also preferably performed by a drying method suitable for the thin film, and a combination of atmosphere drying, AFD, far infrared rays, and the like is used. In particular, the first half of the drying furnace is preferably a method that can cope with gentle drying.
Formation method of internal electrode layer

  The formation method of the internal electrode layer 12 is not particularly limited as long as the layer can be formed uniformly. For example, a thick film formation method such as a screen printing method or a gravure printing method using an internal electrode layer paste, an offset printing, Or thin film methods, such as vapor deposition and sputtering, are mentioned. In this embodiment, a screen printing method is used.

  The internal electrode layer paste used in the present embodiment contains a conductive powder, a solvent, a dispersant, a plasticizer, an organic vehicle, an additive powder, and the like. The internal electrode layer paste is formed by pasting these components.

  The conductive powder is not particularly limited, but a base metal can be used because the constituent material of the dielectric layer 10 has resistance to reduction. As the base metal used as the conductive material, Ni or Ni alloy is preferable.

  The solvent is not particularly limited, and terpineol, butyl carbitol, kerosene, acetone, isobornyl acetate and the like can be used.

  Although it does not specifically limit as a dispersing agent, A maleic acid type dispersing agent, a polyethyleneglycol type dispersing agent, and / or an allyl ether copolymer dispersing agent are illustrated.

  As the plasticizer, phthalic acid ester, adipic acid, phosphoric acid ester, glycols and the like can be used.

  The binder is not particularly limited, and ethyl cellulose, acrylic resin, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene, or a copolymer thereof can be used.

  In the internal electrode layer paste, an additive powder having the same composition as the ceramic powder contained in the green sheet may be contained as a co-material. The common material has an effect of suppressing the sintering of the conductive powder in the firing process.

  In order to make the dielectric thin, it is necessary to make the internal electrode layer also thin. For this purpose, it is necessary to make the particle size of the original conductive material powder fine and to make the particle size distribution sharp. For the dispersion of the conductive material powder, the same dispersion treatment as that of the dielectric powder may be performed, or a wet classification treatment may be combined. Or you may perform a dry-classification process in the stage of electroconductive powder.

  In order to improve the dispersion of the internal electrode paste, it is also necessary to firmly disperse the paint. In particular, when fine particle Ni is used, it is necessary to first wet the Ni powder, the dispersant, the resin, and the solvent firmly in a high solid content state as a kneading step, and reduce the distance between the dispersant, the resin, and the Ni particles. . By this high solid content treatment, even a fine particle can have a low viscosity and a highly stable coating with time.

Examples of the apparatus for performing high solid content treatment include three rolls, two rolls, a pressure kneader, and a continuous kneader. Furthermore, it is preferable to treat this paint with a high-pressure homogenizer. Thereby, it can be set as the coating material suitable for thin film application | coating. The high-pressure homogenizer used at this time can be a liquid-liquid collision type, a wall surface collision type, a stirring type or an ultrasonic disperser. However, since electrode paste is generally highly viscous, an apparatus suitable for high viscosity is preferred.
Formation of capacitor body

  First, as shown in FIG. 2B, the internal electrode layer paste is printed on the interior green sheet 10a to prepare the interior green sheet 10a on which the internal electrode paste layer 12a is formed. The internal electrode paste layer 12a is a portion that becomes the internal electrode layer 12 shown in FIG. 1 after firing.

  Further, an exterior green sheet (not shown) in which the internal electrode paste layer 12a is not formed is also prepared. The exterior green sheet is a portion that becomes the exterior dielectric layer 14 shown in FIG. 1 after firing.

  The exterior green sheet can be formed of the same dielectric slurry as the interior green sheet 10a, but may be formed of a different dielectric slurry. The exterior green sheet is preferably formed in a thicker film than the interior green sheet 10a. This is to reduce the number of man-hours for laminating exterior green sheets. The interior green sheet 10a is preferably as thin as possible in order to improve the capacitance.

  First, a predetermined number of exterior green sheets are laminated, then a large number of interior green sheets 10a on which internal electrode paste layers 12a are formed, and a predetermined number of exterior green sheets are further laminated. Is cut into a predetermined shape to obtain a green chip.

  There are various lamination methods. In particular, there are a peeling type that peels off first from the peeled PET and a pressure-bonding type that peels after first bonding the layers, and each has merits and demerits. Therefore, a laminated type that easily satisfies the required characteristics of the product may be selected. The peel thermocompression bonding method is considered preferable in terms of productivity and thin film compatibility. The peeling thermocompression bonding method is a method in which a green sheet supplied by a roll is first peeled and then aligned and laminated while applying heat. First, since it peels, if the speed can be increased by devising peeling, the tact of the entire stack can be shortened, resulting in a highly productive laminator. In addition, by devising the sheet and peeled PET, it is possible to peel even a thin film.

  Next, the green chip obtained by cutting the laminate is subjected to binder removal processing, firing processing, and annealing processing. These conditions are general conditions.

The capacitor body 4 is obtained through the binder removal treatment, firing and annealing as described above. The capacitor element body 4 is subjected to end polishing by barrel polishing, sand blasting, or the like, and the external terminal paste is printed or transferred and baked to form the first terminal electrode 6 and the second terminal electrode 8. And a coating layer is formed by plating etc. on the surface of the 1st terminal electrode 6 and the 2nd terminal electrode 8 as needed. In this way, the multilayer ceramic capacitor 2 is manufactured. The multilayer ceramic capacitor 2 is mounted on a printed circuit board by soldering or the like, and is used for various electronic devices.
Method for manufacturing dielectric slurry

  Next, a method for producing a dielectric slurry for forming the interior green sheet 10a shown in FIG.

  As shown in FIG. 3, first, dielectric powder is prepared in step S1. The dielectric powder production method (solid phase method, hydrothermal synthesis method, sol-gel method, alkoxide method) does not matter, but the degree of aggregation of the dielectric powder varies depending on the production method, and pretreatment (preliminary) in the following steps S2 and S3 Distributed processing) conditions are slightly different.

  A pretreatment method (preliminary dispersion treatment) adapted to different cohesion levels is required depending on the dielectric powder production method, and this pretreatment improves dispersibility in the subsequent bead mill process (step S4). In step S2 or step S3, if it is vigorously dispersed by a bead mill or the like, the dielectric powder is damaged, and even if a fine dielectric powder with a high dielectric constant is used, a product (lamination) It is not a ceramic capacitor. Therefore, the point is how to break up the agglomerates without damaging them. In particular, in the case of fine particles of 0.15 μm or less, the cohesive force is strong because of the fine particles, and the behavior is clearly different from particles of 0.2 μm or more.

  Further, as a method usually performed as a means for improving the dielectric constant of the dielectric, the heat treatment temperature of the dielectric is increased or an additional heat treatment step is performed. However, the treatment also causes aggregation. Therefore, a special procedure is required to solve the strong secondary agglomerated powder.

  In this embodiment, the dielectric powder is first mixed with a high-speed stirrer (high-speed shearing disperser) with a peripheral speed of 20 m / s or higher in order to wet the solvent and the dispersant firmly. Examples of the high-speed shear disperser include a dissolver type, a rotor stator type, a colloid mill type, and a thin film swirl type, but a rotor stator type disperser (first pretreatment disperser) is preferably used. On the other hand, the dissolver type has insufficient shearing force, and the colloid mill type has a narrow gap between the rotor and the stator, which is a few hundredths of a millimeter, so the powder may be crushed or the slurry temperature will rise above the boiling point of the solvent. Or a lot of contamination. Similarly, in the thin film swirl type, since the slurry is likely to become high temperature, when using this disperser, any device needs to be devised.

  For example, as shown in FIG. 4, the rotor stator type disperser is a device for passing a treatment liquid through a gap between a rotor 30 that rotates together with a rotating shaft and a stator 32 that does not rotate, and performs dispersion mixing. In the present embodiment, an apparatus that can be used at a peripheral speed of 20 m / s or higher is particularly preferable.

  The particle size of this mixed solution is measured every time, and when the particle size distribution, particularly the distribution of coarse particles of 10 μm or more, does not change, a part of the paste is processed by the second pretreatment disperser. As the second pretreatment disperser, a medialess disperser such as a high pressure homogenizer or an ultrasonic disperser is used.

  As a high-pressure homogenizer, for example, as shown in FIG. 5, there is no collision with a collision type apparatus that performs a dispersion process by passing a treatment liquid through a predetermined flow path and causing the treatment unit (generator) to collide with the collision unit 34. There is a straight-through through-type generator type device (not shown). If the processing unit (generator) is a collision type, it is preferable because it requires less processing time, but the equipment becomes expensive. When using a penetrating generator that causes turbulent flow by changing the front and rear passage diameter without colliding, processing time is required, but there is no clogging of coarse particles, high cleaning performance, and suitable for pretreatment .

  As the ultrasonic disperser, for example, the apparatus shown in FIG. 6 is used, and the amplitude of the oscillator is effective for dispersibility, and is preferably 30 μm or more, more preferably 40 μm or more. However, it should be noted that if the amplitude of the ultrasonic vibration exceeds 45 μm, the vibrator 36 itself becomes chipped and becomes contaminated in the dispersion.

  Thereafter, in step S4 shown in FIG. 3, dispersion by a bead mill as post-dispersion processing is performed. As the bead mill, a disperser that can use Φ0.1 mm or less of zirconia beads is preferable. Any mill can be used as long as beads of φ0.1 mm or less can be used, but it is necessary to select carefully depending on the viscosity range of the slurry used and the amount of contamination generated. Dispersion using small diameter beads in this mill eliminates damage.

  The peripheral speed of the bead mill is preferably 10 m / s or less, more preferably 8 m / s or less (5 m / s or more). It is preferable to make the bead diameter as small as possible and disperse while keeping the peripheral speed as low as possible. However, if the peripheral speed is 5 m / s or less, a centrifugal type bead mill is not suitable because there is a high risk of bead outflow, and the dielectric powder is weak but requires insufficient shear to dissolve large agglomerates. is there.

  Using the small diameter beads of Φ0.1 mm or less, the dielectric is dispersed to a target particle size, and then a binder resin, a plasticizer, an antistatic agent, etc. are added to form a dielectric slurry (step S6). At this time, these materials may be mixed and dispersed by a bead mill, or may be mixed by a high-speed shearing device.

  Further, after this bead mill dispersion, further medialess dispersion (step S5) may be performed to obtain a dielectric slurry (step S6). Examples of the medialess disperser include a high-pressure homogenizer, and the processing conditions are preferably a pressure of 40 MPa to 250 MPa and a pass count of 3 to 10 passes.

In the present embodiment, the first BET change in the BET specific surface area (β) of the dielectric powder contained in the solution after the second pretreatment relative to the BET specific surface area (α) of the dielectric powder contained in the solution before the first pretreatment. Treatment used for the first pretreatment and the second pretreatment so that the rate (100 × (β−α) / α) is 0.7 to 3.5%, preferably 1.0 to 3.0%. A combination of devices and various conditions are selected. The BET specific surface area (α) of the dielectric powder contained in the solution before the first pretreatment varies depending on the type of dielectric powder and the synthesis method, but is preferably 7 to 15 m ² / g, more preferably 8 ˜13 m ² / g.

  In the present embodiment, the second BET change rate (100 × (γ−α) of the BET specific surface area (γ) of the dielectric powder contained in the solution after the post-dispersion treatment with respect to the initial BET specific surface area (α) of the dielectric powder. ) / Α) is determined to be 15% or less, preferably 12.5%, and the conditions of the bead mill in step S4 and the medialess dispersion condition in step S5 are determined. Note that it is not always necessary to perform medialess dispersion after the dispersion treatment by the bead mill. In the present invention, the “post-dispersion process” includes at least a bead mill process. After that, when medialess dispersion is performed, the medialess dispersion is also included in the post-dispersion process, and is finally performed after the dispersion process by the bead mill. All processes up to a slurry are included.

  As described above, in the method for manufacturing a dielectric slurry according to the present embodiment and the method for manufacturing a multilayer ceramic capacitor using the dielectric slurry, the medium is divided into two stages in the pre-process of the slurrying process of dielectric powder of 0.15 μm or less. By introducing the less dispersion treatment, the increase in BET specific surface area and the remaining coarse particles are balanced, and the subsequent bead mill dispersion with beads having a diameter of 0.1 mm or less causes little damage to the dielectric particles and the thin film A dielectric slurry suitable for the above can be produced.

  In the present embodiment, the first BET change rate (100 × (β−α) / α) of the BET specific surface area of the dielectric powder before and after the preliminary dispersion treatment (first pretreatment + second pretreatment) is 0.7 to 3.5%. In such a range, there is little damage to the dielectric and secondary aggregation, and the dispersion efficiency by the small-diameter beads having a diameter of 0.1 mm or less performed thereafter is improved. In the dielectric slurry obtained by the method of the present embodiment, dielectric powder having a fine and uniform particle diameter is uniformly dispersed.

  In the present embodiment, the second BET change rate (100 × (γ−α) / α) is 15% or less. By setting the rate of change of the BET specific surface area in all dispersion treatments within a predetermined range, it is possible to manufacture a multilayer ceramic electronic component having a low dielectric loss, a high dielectric constant and a long life.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, the manufacturing method according to the present invention can be used not only for manufacturing multilayer ceramic capacitors but also for manufacturing other multilayer ceramic electronic components such as inductors and varistors.

Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.
Example 1

(Ba _1-x Ca _x ) (Ti _1-y Zr _y ) O ₃ (BCTZ) produced by the solid phase method was treated at a calcining temperature of 900 ° C., the SEM diameter (D50) was 100 nm, and the initial BET ratio A dielectric powder having a surface area (α) of 8.5 m ² / g (average value of n = 5) and a dielectric constant of 6000 was prepared.

  Next, 75 parts by weight of a solvent composed of ethanol / propanol / xylene and 3 parts by weight of a dispersant composed of polycarboxylic acid were put into a rotor stator type disperser (2-axis high-speed despar mill manufactured by Asada Tekko), While stirring the rotor stator at a peripheral speed of 10 m / sec, 100 parts by weight of dielectric powder and a small amount of additive were added. After the peripheral speed was increased to 40 m / sec, a treatment (first pretreatment) was performed for 60 minutes. Thereafter, as a second pretreatment, this treatment solution was subjected to a 5-pass (5p) treatment at a pressure of 100 MPa with a high-pressure homogenizer (Nanomizer manufactured by Yoshida Kikai Kogyo Co., Ltd.).

Next, this processing solution was put into a bead mill apparatus (“Picomill” manufactured by Asada Tekko Co., Ltd.) filled with 80% Φ0.05 mm zirconia (ZrO ₂ ) beads, and the residence time was 6 m / sec with a screen mesh of 15 μm. Was subjected to dispersion treatment (bead mill dispersion) so as to be 15 minutes (first post-dispersion treatment).

  Thereafter, the treatment liquid was put into a rotor-stator type disperser, and polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd.) dissolved in 15% with respect to 100 parts by weight of the dielectric powder while stirring the rotor stator at a peripheral speed of 10 m / sec. , BH-3) and 10 parts by weight of DOP with respect to 100 parts by weight of resin as plasticizer were added. Further, 150 parts by weight of a solvent composed of ethanol / propanol / methyl ethyl ketone / xylene was added, and the peripheral speed was increased to 30 m / sec, followed by 60 minutes of treatment (second post-dispersion treatment). Thereafter, this treatment liquid was subjected to a 5-pass (5p) treatment at a pressure of 100 MPa with a high-pressure homogenizer (third post-dispersion treatment), and then passed through a 0.5 μm filter and a 0.3 μm filter for 5 passes, followed by a filtration treatment. A dielectric paint (finished paint) was obtained.

Part of 10 cc of the treatment liquid before and after the dispersion treatment was put in a crucible and dried in an oven at 130 ° C. for 3 hours. When the BET specific surface area was measured with a BET specific surface area measuring machine (Macsorb HM1208) for the dry powder obtained from this treatment liquid, the BET specific surface area (β) after the second pretreatment was 8.67 m ² / g, The finished coating had a BET specific surface area (γ) of 9.13 m ² / g (average value of n = 5).

From these values, the first BET change rate before and after the preprocessing (first preprocessing + second preprocessing) is 2.1%, and the BET before and after the total distributed processing (first preprocessing to third postdistributed processing). It was confirmed that the second BET change rate of the specific surface area was 7.5%. Further, 50 cc of H ₂ O was added to 0.1 cc of the paint after the pretreatment to dilute, and the D100 was measured with a laser diffraction type particle size distribution analyzer (MT3300 manufactured by Nikkiso Co., Ltd.), which was 1.06 μm. The results are shown in Table 1.

  Furthermore, a green sheet having a thickness of 0.9 μm was formed using a treatment liquid (finished paint) after post-dispersion treatment and after filtration. Further, an electrode having a thickness of 0.3 μm was screen-printed on the surface of the green sheet to obtain a sheet unit. This unit was put on a peeling thermocompression laminating machine, and a green sheet without electrodes was laminated to 20 μm, then 350 layers of this unit were laminated, and a sheet without electrodes was further laminated to 20 μm. .

This laminated unit was cut according to the electrode size, and after firing, firing was performed at two firing temperatures of 1140 ° C. and 1210 ° C., respectively. An external electrode was attached and cut to 0603 size to obtain a ceramic capacitor. With respect to 100 produced multilayer ceramic capacitors, the capacitance and tan δ were measured using an impedance analyzer (HP-4284A, manufactured by Hewlett-Packard Company). ε was calculated from this capacitance, interlayer thickness, and electrode area. Further, the lifetime (average lifetime: MTTF) of the 20 capacitors was measured by applying a voltage of 75 V between the layers at 200 ° C. The lifetime was determined by Weibull analysis. The characteristics relating to tan δ, ε, and lifetime are expressed as relative values when the value of Example 1 is 100%. These results are shown in Table 1.
In the present embodiment, the BET specific surface area is obtained by a method in which a gas (N ₂ gas) is adsorbed on the powder, thereby obtaining the specific surface area of the powder. Specifically, the BET specific surface area measurement described above is performed. It was determined by machine.
Example 2 and Comparative Example 1

  Evaluation was performed in the same manner as in Example 1 except that the peripheral speed of the homogenizer treatment in the pretreatment 1 was changed as shown in Table 1. The results are shown in Table 1. As shown in Table 1, in Example 2, the same result as in Example 1 was obtained. That is, in Example 2, the first BET change rate is in the range of 0.7 to 3.5%, the second BET change rate is 15% or less, and tan δ, ε, and lifetime are both as in Example 1. It was confirmed that there was no inferiority.

On the other hand, in Comparative Example 1, clogging occurred in the bead mill treatment, and a finished paint could not be obtained.
Example 3

BaTiO ₂ (BT) produced by a hydrothermal synthesis method is treated at a calcining temperature of 300 ° C., the SEM diameter is 120 nm, and the initial BET specific surface area (α) is 7.6 m ² / g (average value of n = 5). Evaluation was performed in the same manner as in Example 1 except that dielectric powder having a dielectric constant of 2000 was used and the thickness of the green sheet was 0.4 μm. The results are shown in Table 1. As shown in Table 1, the same results as in Example 1 were obtained. That is, the first BET change rate is within a range of 0.7 to 3.5%, the second BET change rate is 15% or less, and it is confirmed that tan δ, ε, and lifetime are comparable to those of Example 1. It was done.
Examples 4-a and 4-b

In Example 4-a, the calcined dielectric powder used in Example 3 was again heat treated at 500 ° C. (additional heat treatment), the SEM diameter (D50) was 120 nm, and the initial BET specific surface area (α) was 7. Evaluation was performed in the same manner as in Example 3 except that a dielectric powder having a dielectric constant of 6m ² / g (n = 5) and a dielectric constant of 2850 was used, and the thickness of the green sheet was changed to 0.5 μm. It was. Furthermore, Example 4-b evaluated by changing the frequency | count of the pre-processing condition 2 from 5 passes to 10 passes using BT powder similar to Example 4-a. The results are shown in Table 1. As shown in Table 1, the same results as in Example 3 were obtained. That is, the first BET change rate is in the range of 0.7 to 3.5%, the second BET change rate is 15% or less, and it is confirmed that tan δ, ε, and lifetime are comparable to Example 3. It was done. However, in Example 4-a, ε and lifetime were improved as compared with Example 3. Furthermore, in Example 4-b, it was confirmed that the aggregated powder generated by the heat treatment can be solved by increasing the pretreatment conditions, which leads to improvement in characteristics.
Comparative Example 2

The dielectric powder used in Example 3 was used, and instead of the rotor-stator-type disperser, as a first pretreatment, a dispersion treatment was performed with a dissolver (“TK Homomixer” manufactured by Primix), and the thickness of the green sheet was further increased. The evaluation was performed in the same manner as in Example 3 except that the thickness was 0.4 μm. The results are shown in Table 1. As shown in Table 1, in Comparative Example 2, clogging occurred in the second pretreatment, the subsequent treatment could not be performed, and a finished paint could not be obtained.
Comparative Example 3

Using the dielectric powder used in Example 3 and using a bead mill apparatus filled with zirconia (ZrO ₂ ) beads having a diameter of 10 mm as the first pretreatment instead of the rotor-stator-type disperser, the peripheral speed was 12 m / sec. Evaluation was performed in the same manner as in Example 3 except that the dispersion treatment was performed and the thickness of the green sheet was 0.4 μm. The results are shown in Table 1. As shown in Table 1, in Comparative Example 3, the first BET change rate is 12%, and the second BET change rate is also high, 17.5%. As compared with Example 3, tan δ is deteriorated and life characteristics are reduced. Was confirmed.
Comparative Example 4

Instead of the rotor stator type disperser, a bead mill device filled with Φ10 mm zirconia (ZrO ₂ ) beads was used as the first pretreatment, and the conditions of the high-pressure homogenizer used in the second pretreatment were 140 MPa and 5 passes. Were evaluated in the same manner as in Example 1. As shown in Table 1, in Comparative Example 4, the first BET change rate was 17.8%, and the second BET change rate was also high, 23.8%, and tan δ was deteriorated and life characteristics were lowered as compared with Example 1. Confirmed to do.

Examples 5 to 7 and Comparative Example 5

  Evaluation was performed in the same manner as in Example 1 except that the conditions of the homogenizer treatment in the second pretreatment were changed as shown in Table 2. The results are shown in Table 2. As shown in Table 2, in Examples 5-7, the same results as in Example 1 were obtained. That is, in Examples 5 to 7, the first BET change rate is in the range of 0.7 to 3.5%, the second BET change rate is 15% or less, and both tan δ, ε, and life are examples. Results similar to 1 were obtained.

On the other hand, in Comparative Example 5, since the first BET change rate was less than 0.7%, clogging occurred in the bead mill treatment, and a finished paint could not be obtained.
Examples 8 to 10 and Comparative Examples 6 to 8

  Evaluation was performed in the same manner as in Example 1 except that the conditions of the bead mill treatment were changed as shown in Table 3. The results are shown in Table 3. As shown in Table 3, in Examples 8 to 10, the same results as in Example 1 were obtained. That is, in Examples 8 to 10, the first BET change rate is in the range of 0.7 to 3.5%, the second BET change rate is 15% or less, and tan δ, ε, and lifetime are all in Example 1. Similar results were obtained.

On the other hand, in Comparative Examples 6 to 8, the second BET change rate exceeded 15%, and it was confirmed that all the characteristics of tan δ, ε, and lifetime were deteriorated as compared with Example 1.
Examples 11-14 and Comparative Examples 9, 10

  As the second pretreatment, an ultrasonic disperser (UW-600T manufactured by Nippon Seiki Co., Ltd.) is used instead of the high-pressure homogenizer, and the processing conditions of the ultrasonic disperser include the amplitude of ultrasonic vibration and the residence time of the processing liquid. The evaluation was performed in the same manner as in Example 1 except that the values were changed as shown in Table 4. Furthermore, as an evaluation different from that in Example 1, 10 cc of ethanol was added to 0.1 cc of the treatment liquid after the bead mill treatment, and the treatment was performed for 5 minutes with a 150 W ultrasonic disperser. Developed and dried on the eel, the outermost part was observed at 10 magnifications of 10,000 fields with JEOL JSM-6700F, and 1 μm or larger particles (number of coarse particles) were counted. These results are shown in Table 4.

  As shown in Table 4, in Examples 12 to 14, it was confirmed that the same result as in Example 1 was obtained even when an ultrasonic disperser was used as the second pretreatment instead of the homogenizer. . That is, the first BET change rate was in the range of 0.7 to 3.5%, the second BET change rate was 15% or less, and the same results as in Example 1 were obtained for tan δ, ε, and lifetime. . Moreover, in Examples 12-14, compared with the comparative examples 9 and 10 whose 1st BET change rate is less than 0.7%, the number of coarse particles was also few and it has confirmed that the lifetime was improving.

2 ... Multilayer ceramic capacitor 4 ... Capacitor body 6, 8 ... Terminal electrode 10 ... Dielectric layer 12 ... Internal electrode layer 10a ... Green sheet
12a ... Internal electrode paste layer

Claims (3)

A method for producing a dielectric slurry by mixing and dispersing at least a dielectric powder and a solvent,
A step of mixing and dispersing a dispersion pretreatment solution containing at least the dielectric powder and a solvent by a preliminary dispersion treatment;
And a step of mixing and dispersing the treated solution subjected to the preliminary dispersion treatment by post-dispersion treatment,
The preliminary distributed processing is a two-stage distributed processing of a first preprocessing and a second preprocessing that is performed after the first preprocessing and is different from the first preprocessing,
The first pretreatment is a dispersion treatment by a high-speed shear disperser;
The second pretreatment is a dispersion treatment using a high-pressure homogenizer disperser or an ultrasonic disperser,
The post-dispersion treatment includes a dispersion treatment by a bead mill disperser using beads having a bead diameter of 0.1 mm or less,
Change rate of BET specific surface area (β) of dielectric powder contained in solution after preliminary dispersion treatment relative to initial BET specific surface area (α) of dielectric powder contained in solution before preliminary dispersion treatment (100 × (β− The preliminary dispersion treatment is performed so that α) / α) is 0.7 to 3.5%,
Change rate of BET specific surface area (γ) of dielectric powder contained in solution after post-dispersion treatment relative to initial BET specific surface area (α) of dielectric powder contained in solution before preliminary dispersion treatment (100 × (γ− A dielectric slurry manufacturing method in which the post-dispersion treatment is performed so that α) / α) is 15% or less.   The method for producing a dielectric slurry according to claim 1, wherein the post-dispersion treatment further includes a medialess dispersion treatment performed after the dispersion treatment by the bead mill disperser. A step of forming a green sheet using the dielectric slurry obtained by the dielectric slurry manufacturing method according to claim 1,
Forming an internal electrode pattern on the green sheet;
A step of forming a laminate by laminating a plurality of the green sheets on which the internal electrode pattern layer is formed;
And a step of firing the multilayer body.

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