JP2011084433A - Methods for producing ceramic slurry, green sheet and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing ceramic slurry in which ceramic powder included in the ceramic slurry can be dispersed effectively while excellently keeping crystallinity of the ceramic powder and which can allow a green sheet obtained therefrom to have smooth surface and excellent sheet strength, to provide a method for producing the green sheet by using the ceramic slurry obtained by this producing method and to provide a method for producing electronic components by using the green sheet. <P>SOLUTION: The method for producing ceramic slurry comprises: a step of preparing ceramic slurry including ceramic powder and a solvent; a first dispersion step of dispersing the prepared ceramic slurry in a media disperser; a step of adding a post-addition resin to the ceramic slurry dispersed at the first dispersion step; and a second dispersion step of dispersing the resin-added ceramic slurry by a whirling flow. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a ceramic slurry, a method for producing a green sheet produced using the ceramic slurry obtained by the production method, and a method for producing an electronic component produced using the green sheet.

  In recent years, downsizing and higher performance of multilayer electronic components such as multilayer ceramic capacitors have been promoted due to miniaturization of electronic devices. Here, in order to reduce the size and increase the performance of the multilayer electronic component, it is necessary to increase the number of layers and reduce the thickness.

  In a multilayer ceramic capacitor, which is a kind of multilayer electronic component, as the number of layers increases and the layers become thinner, the green sheet forming the dielectric layer also becomes thinner, and the thickness has shifted to 2 μm or less. When the green sheet becomes thinner, the surface roughness of the sheet cannot be ignored with respect to the thickness. Since the unevenness portion of the surface roughness causes variation in the dielectric thickness after firing, the thinned portion has high electric field strength, causing short circuit failure and breakdown voltage failure.

  On the other hand, the convex portion causes local electric field concentration, and similarly causes short circuit failure and breakdown voltage failure. Therefore, as the green sheet becomes thinner, a technique for producing a green sheet having a smooth surface and a uniform thickness is indispensable for manufacturing a multilayer ceramic capacitor. In order to smooth the surface of the thinned green sheet and make the thickness uniform, the average particle size of the ceramic powder in the green sheet must be made finer and the dispersibility of each particle in the green sheet can be increased. It is essential.

  Here, as a manufacturing method of a green sheet, it is usually obtained by applying a ceramic slurry and drying. The ceramic slurry is a dispersion of ceramic powder, solvent, resin, and the like. As a dispersion method, for example, a medium-type dispersion method using an agitator mill such as a ball mill, a bead mill, or a sand mill, or a high-pressure dispersion method such as a high-pressure jet mill is used.

  In general, the dispersion process is roughly divided into two stages. The dispersion treatment in the first stage is mainly for the purpose of crushing and dispersing the ceramic powder. The dispersion process at the second stage is mainly for mixing with the resin.

  Conventionally, in the second stage dispersion treatment, a method using a medium type dispersing machine such as a ball mill or a bead mill, or a dispersion treatment using a homogenizer or a high-pressure jet mill has been employed (Patent Document 1).

  However, when the medium type disperser is used, the damage to the ceramic powder increases, and the crystallinity of the ceramic powder, particularly the main component powder such as calcium titanate, strontium titanate and / or barium titanate decreases, There is a risk that reliability may be lowered and dispersibility of the ceramic powder may be insufficient.

  On the other hand, in the case of performing dispersion treatment using a homogenizer or a high-pressure jet mill, although there is a merit of improving dispersibility, the molecular weight of the resin is lowered and the sheet strength when formed into a sheet may be lowered.

JP 2005-193235 A

  The present invention has been made in view of such a situation, and an object thereof is to effectively disperse while maintaining good crystallinity of the ceramic powder contained in the ceramic slurry, and to have a smooth surface and a sheet. Manufacturing method of ceramic slurry capable of obtaining green sheet having good strength, manufacturing method of green sheet manufactured using ceramic slurry obtained by the manufacturing method, and manufacturing method of electronic component using the green sheet Is to provide.

In order to solve the above problems, a method for producing a ceramic slurry according to the present invention comprises:
Preparing a ceramic slurry containing a ceramic powder and a solvent;
A first dispersion step of dispersing the ceramic slurry with a medium-type disperser;
Adding a post-addition resin to the ceramic slurry after the first dispersion step;
And a second dispersion step of dispersing the ceramic slurry by a swirl flow.

  Preferably, the pre-added resin is added to the ceramic slurry before the first dispersion step.

  Preferably, the pre-added resin is 0% by weight or more and 20% by weight or less with respect to the resin finally contained in the ceramic slurry.

  Preferably, the shear rate of the swirling flow in the second dispersion step is 15,000 to 100,000 (1 / sec).

  Preferably, the medium type disperser is either a ball mill or a bead mill.

Moreover, in order to solve the said subject, the manufacturing method of the green sheet which concerns on this invention is the following.
It is a manufacturing method of the green sheet which has the process of apply | coating said ceramic slurry and drying.

  Preferably, the dried green sheet has a thickness of 1.5 μm or less.

Furthermore, in order to solve the above problems, a method for manufacturing an electronic component according to the present invention includes:
The green sheet;
An internal electrode pattern layer;
To obtain a green chip by stacking,
And a step of firing the green chip.

  ADVANTAGE OF THE INVENTION According to this invention, it can disperse | distribute effectively, maintaining the crystallinity of the ceramic powder contained in a ceramic slurry favorable. Moreover, according to the present invention, a green sheet having a smooth surface and good sheet strength can be obtained.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a process diagram showing a method for producing a ceramic slurry according to an embodiment of the present invention. FIG. 3 is a schematic front view of a disperser used in the second dispersion step in the method for producing a ceramic slurry according to an embodiment of the present invention. FIG. 4 is a schematic perspective view of a disperser used in the second dispersion step in the method for producing a ceramic slurry according to an embodiment of the present invention. FIG. 5A is a process schematic diagram showing a manufacturing process of the multilayer ceramic capacitor shown in FIG. FIG. 5b is a process schematic diagram showing a continuation process of FIG. 5a. FIG. 5c is a process schematic diagram showing a continuation process of FIG. 5b. FIG. 6 is an explanatory diagram of a green sheet evaluation method according to an embodiment of the present invention.

  The electronic component manufactured by the manufacturing method according to the embodiment of the present invention is not particularly limited, and examples thereof include a multilayer ceramic capacitor, a multilayer chip varistor, and a multilayer thermistor. In this embodiment, a multilayer ceramic capacitor is illustrated.

Overall Configuration of Multilayer Ceramic Capacitor As shown in FIG. 1, a multilayer ceramic capacitor 2 according to an embodiment of the present invention includes a capacitor element body 4 having a configuration in which dielectric layers 10 and internal electrode layers 12 are alternately stacked. Have. A pair of external electrodes 6 and 8 are formed on both side ends of the capacitor element body 4 so as to be electrically connected to the internal electrode layers 12 arranged alternately in the capacitor element body 4.

  The internal electrode layers 12 are laminated so that the side end faces are alternately exposed on the surfaces of the opposite end portions of the capacitor element body 4. The pair of external electrodes 6 and 8 are formed at both ends of the capacitor element body 4 and are connected to the exposed end surfaces of the alternately arranged internal electrode layers 12 to constitute a capacitor circuit.

  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, it is usually vertical (0.6 to 5.6 mm, preferably 0.6 to 3.2 mm) × horizontal (0.3 to 5.0 mm, preferably 0.3 to 1.6 mm) × thickness (0.1 to 1.9 mm, preferably 0.3 to 1.6 mm).

  The capacitor element body is manufactured, for example, by simultaneously firing a green chip composed of a green sheet and a predetermined pattern of internal electrode pattern layers. Below, an example of the manufacturing method of the multilayer ceramic capacitor 2 which concerns on this embodiment is demonstrated.

Ceramic Slurry First, a ceramic slurry (green sheet coating material) is prepared in order to manufacture a green sheet that will form the dielectric layer 10 shown in FIG. 1 after firing. The dielectric layer 10 of FIG. 1 is manufactured by the process shown in FIG.

  The ceramic slurry contains at least a ceramic powder, a solvent, and a resin. In addition, a plasticizer, a dispersant, a charging aid, and the like may be included.

  First, ceramic powder is prepared. The ceramic powder includes a main component powder and a subcomponent powder.

  The main component powder of the ceramic powder is not particularly limited, and is composed of a dielectric material such as calcium titanate, strontium titanate and / or barium titanate.

  The particle size of the main component powder is generally larger than the particle size of the subcomponent powder, for example, 0.01 to 0.5 μm or less, preferably about 0.4 μm or less. In order to form a very thin green sheet, it is desirable to use a powder finer than the thickness of the green sheet.

  The subcomponent powder includes, for example, at least one of an alkaline earth metal, a transition metal, a rare earth element, and a glass composition. Alkaline earth metals, transition metals, rare earth elements are not limited to powders in the form of elements alone, but also various oxides and complex oxides such as carbonates, nitrates, hydroxides, organometallic compounds And may be contained in the subcomponent powder. Such subcomponent powder is generally contained in the ceramic slurry in a small proportion of, for example, 1 to 6 parts by mass with respect to 100 parts by mass of the main component powder. In addition, as subcomponent powder, after subcomponent powder is previously mixed with a ball mill etc., the dried powder is calcined at 500 to 1000 ° C., and then the calcined product is coarsely pulverized. .

  Examples of the solvent include, but are not limited to, glycols, alcohols, ketones, esters, and / or aromatic solvents.

  Examples of glycols include ethyl carbitol, butanediol, 2-butoxyethanol and the like. Examples of the alcohol include methanol, ethanol, propanol, butanol and the like. Examples of ketones include acetone, methyl ethyl ketone (MEK), diacetone alcohol, and the like. Furthermore, examples of the esters include methyl acetate and ethyl.

  Furthermore, examples of the aromatic solvent include toluene, xylene, benzyl acetate and the like.

  The resin is preferably dissolved in an organic solvent in advance to prepare a resin solution. The resin is not particularly limited, and an acrylic resin, a polyvinyl butyral resin, a polyvinyl acetal resin, an ethyl cellulose resin, or the like is used. In this embodiment, the polyvinyl butyral resin or the polyvinyl acetal resin is used in order to reduce the thickness of the sheet. Is used.

  The organic solvent used for the resin solution is not particularly limited, and for example, organic solvents such as alcohol, butyl carbitol, acetone, and toluene are used. In the present embodiment, the organic solvent preferably includes an alcohol solvent and an aromatic solvent, and the total mass of the alcohol solvent and the aromatic solvent is 100 parts by mass. More than 20 parts by mass.

  Examples of alcohol solvents include methanol, ethanol, propanol, butanol and the like. Examples of the aromatic solvent include toluene, xylene, benzyl acetate and the like.

  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, dioctyl phthalate is preferably used, but is not particularly limited in the present invention, and is appropriately selected according to the type of resin. The charging aid is not particularly limited, but is preferably an imidazoline-based charge remover.

First Dispersion Step In the present embodiment, as the first dispersion step, at least ceramic powder and a solvent are dispersed by a medium type disperser to obtain a first slurry. At this time, it is preferable to disperse the resin (pre-added resin).

  The amount of the pre-added resin is preferably 0% by weight or more and 20% by weight or less with respect to the resin finally contained in the ceramic slurry. Dispersion stability is improved by mixing a small amount of pre-added resin. On the other hand, when the amount of the pre-added resin is too large, the viscosity of the slurry increases, so that it becomes difficult to disintegrate and the smoothness tends to be insufficient when formed into a sheet.

  The pre-added resin is preferably dissolved in an organic solvent in advance to prepare a pre-added resin solution.

  A secondary component pulverized slurry prepared by pre-pulverizing and mixing secondary component powder, solvent, and dispersing agent with a ball mill or the like is prepared in advance, and main component powder, solvent, pre-added resin, plasticizer, and other additives are prepared there. It is good also as what is disperse | distributed by the disperser mentioned later and is made into 1st slurry.

  In addition, when the pre-added resin solution is added before the first dispersion step, it is preferable to add the main component powder and other components to the pre-added resin solution. The pre-added resin having a high polymerization degree is difficult to dissolve in the solvent, and the dispersibility of the ceramic slurry tends to be deteriorated by a normal method. For this reason, the dispersibility of the ceramic slurry can be improved by dissolving the pre-added resin in the organic solvent and then adding the main component powder and other components to the organic solution. Can be suppressed.

  The weight ratio of the ceramic powder to the entire first slurry is 30 to 70% by weight, more preferably 30 to 60% by weight. When the weight ratio of the ceramic powder is too small, the dispersion efficiency is deteriorated, and when it is too large, the particles tend to aggregate.

  The weight ratio of the pre-added resin is 0 to 6% by weight, more preferably 0 to 2% by weight, based on the entire first slurry. When the weight ratio of the resin is too large, dispersion tends to be difficult to proceed.

  The weight ratio of the solvent is 30 to 70% by weight, more preferably 40 to 65% by weight with respect to the entire first slurry. If the weight ratio of the solvent is too small, the particles tend to aggregate, and if it is too large, the dispersion efficiency tends to deteriorate.

  The particle size of the main component powder after the first dispersion step is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.3 μm. When the particle size of the main component powder is large, the dispersibility of the ceramic slurry is lowered, and the smoothness of the green sheet is lowered. On the other hand, when the particle size of the main component powder is small, the crystallinity of the ceramic powder tends to decrease.

  Examples of the medium type disperser include a ball mill, a bead mill, a sand mill, an attritor, and a paint shaker (basket mill). A bead mill is preferable.

  The conditions for dispersion are not particularly limited. For example, when using a bead mill, the dispersion time is 5 to 60 minutes, more preferably 10 to 40 minutes. The peripheral speed of the apparatus is preferably 3 to 20 m / s, more preferably 5 to 15 m / s. If the peripheral speed is too low, the dispersibility tends to decrease. On the other hand, if the peripheral speed is too high, the crystallinity of the ceramic powder tends to decrease, or the sheet strength tends to decrease due to destruction of the pre-added resin.

  The medium used for dispersion is 30 to 90% by volume of the capacity of the apparatus, and the diameter of the medium is preferably 0.01 to 2.0 mm, more preferably 0.03 to 0.3 mm. If the media diameter is too large, damage to the ceramic powder will increase, or it will be difficult to make the ceramic powder fine. If the media diameter is too small, it will be difficult to separate the media and slurry. Dispersion efficiency may be degraded.

Addition of Post-Addition Resin In the present invention, a second slurry containing a resin (post-addition resin) is added to the first slurry obtained by the first dispersion step to obtain an overall slurry.

  Further, the weight ratio of the post-added resin with respect to the entire slurry obtained by adding the second slurry to the first slurry is more than 0 wt% and not more than 20 wt%.

  The weight ratio of the solvent contained in the whole slurry is 50 to 80% by weight, more preferably 60 to 70% by weight with respect to the whole slurry. If the weight ratio of the solvent is too small, the viscosity tends to increase or the particles tend to aggregate, and if it is too large, the viscosity tends to be low and sheet formation tends to be difficult.

  Moreover, you may make a 2nd slurry contain a dispersing agent and / or a plasticizer.

  The post-added resin is preferably dissolved in an organic solvent in advance to form a post-added resin solution.

  If a large amount of the pre-added resin is mixed in the slurry in the first dispersion step, the structure of the pre-added resin is destroyed by the media, and the molecular weight of the resin is reduced. As a result, there is a problem that the strength of the molded sheet is lowered. On the other hand, as in the present invention, by dividing the resin into the ceramic slurry before the first dispersion step and after the first dispersion step, it is possible to reduce the destruction of the resin due to the media of the media-type disperser. The strength of the sheet can be prevented from lowering.

Second Dispersion Step Next, after the first dispersion step, the entire slurry to which a predetermined amount of post-added resin has been added is dispersed by a swirling flow.

  In the present embodiment according to the present invention, as shown in FIG. 2, shearing stress is applied to the aggregated powder in the ceramic slurry by subjecting the ceramic slurry after the first dispersion step to a dispersion treatment by a swirling flow. As a result, the aggregation is loosened, and the ceramic powder can be dispersed in one particle unit. This stress is applied using only the ceramic slurry and does not use media such as beads, so there is no concern about contamination.

  The weight ratio of the ceramic powder to the entire slurry is determined according to the intended use of the ceramic slurry.

  In the second dispersion step, the dispersibility and dispersion stability of each component in the entire slurry are promoted. In the present embodiment, the dispersion treatment is performed until the glossiness of the obtained slurry is maximized.

  The dispersion by the swirling flow in the second dispersion step is performed using, for example, the disperser 50 shown in FIGS. 3 and 4. The disperser 50 includes a cylindrical stirring tank 51, a shaft 52 concentric with the stirring tank 51, and a cylindrical rotary blade 53. The shaft 52 and the rotary blade 53 are connected by an arm 57, and a gap 58 having a width t is provided between the stirring tank and the rotary blade. Thereby, a swirling flow is generated in a donut-shaped gap 58 having a width t as the rotary blade 53 rotates.

  The shear rate of the swirling flow is preferably 15,000 to 100,000 (1 / sec), more preferably 10,000 to 100,000 (1 / sec), and particularly preferably 20,000 to 50,000 (1 / sec). If the shear rate of the swirling flow is too low, the dispersibility tends to decrease. On the other hand, if the shear rate of the swirling flow is too high, the crystallinity of the ceramic powder is lowered, or the sheet strength tends to be lowered due to the destruction of the resin.

  3 and 4, the width t of the gap 58 is preferably 0.1 to 5.0 mm, more preferably 0.1 to 2.0 mm, and the peripheral speed is preferably 10 to 100 m. / S, more preferably 30 to 100 m / s. The shape of the disperser is preferably a rotary type and is based on shearing by a swirling flow. By adopting this structure, it is not necessary to apply pressure from the outside in order to generate a shearing force, and therefore it is possible to prevent excessive dispersion due to a pressure difference generated for the generation of the shearing force.

  Further, the disperser 50 has a supply pipe 54 and a discharge pipe 55. In the case of continuous dispersion, the ceramic slurry can be continuously taken in and out by these pipes, but in the case of batch dispersion, You may provide a cover in the lower part of a discharge pipe.

  The rotary blade 53 may have a structure having a plurality of small holes 56 or a structure in which grooves are processed. The arm 57 may also have a structure having a small hole or the like.

Formation of Green Sheet 10a The ceramic slurry produced through the steps shown in FIG. 2 is formed on the surface of a support sheet 20 made of, for example, a PET film, as shown in FIG. The green paste 10a is formed by applying the paste for use. The green sheet 10a becomes the dielectric layer 10 shown in FIG. 1 after firing.

Formation of Internal Electrode Layer 12a The internal electrode layer 12 in FIG. 1 is obtained by firing the internal electrode pattern layer 12a shown in FIG. 5b. The conductive material contained in the internal electrode pattern layer 12a in the present invention is not particularly limited, but a base metal can be used because the constituent material of the dielectric layer 10 has reduction resistance. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more elements selected from Mn, Cr, Co and Al, and the Ni content in the alloy is preferably 95% by weight or more.

  The internal electrode pattern layer 12a is obtained by forming the internal electrode layer paste into a predetermined pattern. The internal electrode layer paste is obtained by kneading a conductive powder, a solvent, a dispersant, a plasticizer, a binder, an additive powder, and the like with a ball mill or the like to form a slurry.

  Next, as shown in FIG. 5b, an internal electrode layer paste is applied to the surface of the green sheet 10a formed on the support sheet 20 in a predetermined pattern to form the internal electrode pattern layer 12a. The internal electrode pattern layer 12a becomes the internal electrode layer 12 shown in FIG. 1 after firing.

  The method for forming the internal electrode pattern layer 12a in FIG. 5b is not particularly limited as long as the layer can be formed uniformly. For example, a thick film forming method such as a screen printing method or a gravure printing method using an electrode layer paste, Or thin film methods, such as vapor deposition and sputtering, are illustrated.

  As shown in FIG. 5 c, the green sheet 10 a on which the internal electrode pattern layer 12 a is formed is peeled off from the support sheet 20 and sequentially laminated to form a laminate 24. This green sheet is a portion that becomes the dielectric layer 10 shown in FIG. 1, and is alternately laminated together with the electrode film that becomes the internal electrode layer 12, and then cut into a laminated chip, which is subjected to binder removal processing and firing processing. Thus, the capacitor element body 4 is obtained.

Formation of External Electrode The capacitor element body 4 thus obtained is subjected to end face polishing by sandblasting or the like, and external electrode paste 6 is baked to form external electrodes 6 and 8. The conductive material contained in the external electrodes 6 and 8 is not particularly limited, but in the present invention, inexpensive Ni, Cu, and alloys thereof can be used.

  Then, if necessary, a pad layer is formed on the external electrodes 6 and 8 by plating or the like. The external electrode paste may be prepared in the same manner as the above internal electrode pattern layer paste.

  The thickness of each dielectric layer 10 is generally 0.5 to 5.0 μm, but in the embodiment according to the present invention, the thickness is preferably reduced to 1.5 μm or less. As described above, according to the method for manufacturing a green sheet according to the embodiment of the present invention, since the surface roughness of the sheet is reduced to a very small value compared to the interlayer thickness, the interlayer thickness is reduced (thinned). In addition, electronic components such as multilayer ceramic capacitors can be made multilayered and miniaturized.

  The multilayer ceramic capacitor manufactured by the method according to the present invention is mounted on a printed circuit board by soldering or the like, and is used for various electronic devices.

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

  In addition, examples of the multilayer ceramic component manufactured using the ceramic slurry according to the present invention are not limited to multilayer ceramic capacitors, but include inductors and varistors.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the present invention is not limited to a multilayer ceramic capacitor, and any electronic component having a dielectric layer may be used.

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

Sample 1
(Method for producing ceramic slurry)
BaTiO ₃ powder (BT-02 / Sakai Chemical Industry Co., Ltd.) was used as a starting material for the ceramic powder which is the main component powder. (Ba _0.6 Ca _0.4 ) SiO ₃ : 1.48 parts by mass, Y ₂ O ₃ : 1.01 parts by mass, MgCO ₃ : 0.72% by mass with respect to 100 parts by mass of this BaTiO ₃ powder. cr ₂ O _3: 0.13% by mass, and _V 2 _O 5: to be 0.045 mass% were prepared subcomponent powder.

  First, only the auxiliary component powder was mixed with a ball mill to form a slurry. That is, subcomponent powder (total amount 8.8 g), ethanol: n-propanol: xylene solvent 15 g of 42.5: 42.5: 15, and dispersing agent (0.1 g) were mixed with a ball mill. Pre-grinding was performed for 20 hours to obtain an auxiliary component ground slurry.

(First dispersion step)
Next, with respect to BaTiO ₃ : 260.0 g, subcomponent pulverized slurry 24 g, ethanol 123 g, n-propanol 123 g, xylene 56 g, diethylene glycol monoethyl ether (DGME) 136 g, mineral spirit 15 g, dispersant 1.4 g, DOP 6 g of (dioctyl phthalate), 0.8 g of an imidazoline charging aid, and 3.3 g of a polyvinyl butyral resin solution (pre-added resin solution) were dispersed by a ball mill.

  As the polyvinyl butyral resin solution, BH6 (polybutyral resin / PVB) 15% lacquer (Sekisui Chemical BH6 dissolved in ethanol / n-propanol = 1: 1) was used.

The capacity of the ball mill used in the first dispersion step was 1 L, the media had a diameter of 2 mm, and 33% by volume was added to the ball mill. Here, the peripheral speed of the ball mill apparatus was 3 m / s, and the dispersion time was 20 minutes. In this example, in the first dispersion step, the dispersion was performed until the BaTiO ₃ powder became 0.2 μm or less.

(Addition of post-added resin)
Next, 29.7 g of a polyvinyl butyral resin solution (post-added resin solution) having the same composition as the polyvinyl butyral resin solution added before the first dispersing step was added to the first slurry after the first dispersing step to obtain an overall slurry.

(Second dispersion step)
Next, as a second dispersion step, the entire slurry was dispersed by a swirling flow. The second dispersion step was performed by a disperser 50 shown in FIGS. The shear rate of the swirling flow was 50000 (1 / sec), the peripheral speed was 100 m / s, and the dispersion time was 3 minutes. The capacity of the container was 0.25 L, and the width t of the gap 58 was 2.0 mm. In the second dispersion step, the obtained slurry was dispersed until the time when the glossiness was maximized when it was made into a sheet.

  A ceramic slurry (green sheet coating material) was obtained through the above steps.

(Green sheet formation)
The produced ceramic slurry was applied to a PET film with a thickness of 2.0 μm with a doctor blade and dried to produce a green sheet. The coating speed was 50 m / min, and the drying conditions were a temperature in the drying furnace of 80 ° C. and a drying time of 2 minutes.

(Evaluation of green sheet)
The glossiness, crystallinity and sheet strength of the green sheet were evaluated.

(Glossiness (smoothness))
Glossiness was measured on a glass surface with a refractive index of 1.567 using a gloss meter (Nippon Denshoku VG2000) with a reflectance of 10% at an incident angle of 60 ° as a glossiness of 100% (FIG. 6A). )). In this example, 60% or more was considered good. The results are shown in Table 1.

(Sheet strength)
The green sheet is gripped with the jig shown in FIG. 6B, the load cell 65 of the tensile testing machine 64 is pulled up vertically, the stress applied to the load cell 65 when the green sheet breaks is measured, and the maximum in the measurement sample is measured. The relative value when the stress was 100 was taken as the sheet strength. The green sheet as a sample at this time was formed in a strip shape having a width of 10 mm, a length of 40 mm, and a thickness of 1 μm, an interval between the upper and lower jigs of 10 mm, and an extension speed of the jig of 8 mm / sec. The results are shown in Table 1.

(X-ray diffraction)
X-ray diffraction analysis of the barium titanate powder in the obtained ceramic slurry was performed, and the K factor determined by the following formula was determined. The larger the K factor, the higher the crystallinity. In this example, 4.0 or more was considered good. The (200) peak is a tetragonal-derived main peak, and the (002) peak is a tetragonal-derived main peak. “Minimum value of (002) peak and (200) peak” tends to increase as chipping increases. The results are shown in Table 1.

(Preparation of internal electrode layer paste)
Next, 44.6 parts by weight of Ni particles, 52 parts by weight of terpineol, 3 parts by weight of ethyl cellulose, and 0.4 parts by weight of benzotriazole are kneaded with three rolls to form a slurry for an internal electrode layer paste. Obtained.

(Production of multilayer ceramic capacitor)
A multilayer ceramic capacitor 1 shown in FIG. 1 was produced using the pastes prepared above as follows.

  First, a green sheet was formed on a PET film using the obtained dielectric layer paste. After the internal electrode layer paste was printed thereon, the sheet was peeled from the PET film. Subsequently, these green sheets and protective green sheets (not printed with the internal electrode layer paste) were laminated and pressure-bonded to obtain a laminate.

  Next, the laminate was cut into a size of 1.6 mm × 0.8 mm × 0.8 mm to obtain a green chip. Thereafter, the green chip was solidified and dried and polished.

(Green chip firing process)
The green chip 42 after barrel polishing was washed with water and dried. The dried green chip was subjected to binder removal processing, firing and annealing under the following conditions to obtain a capacitor element body 4.
Debinder processing conditions Temperature rising rate: 32.5 ° C / hour,
Holding temperature: 260 ° C.
Temperature holding time: 8 hours,
Atmosphere: in the air.
Firing conditions Temperature rising rate: 200 ° C./hour,
Holding temperature: 1260-1280 ° C
Temperature holding time: 2 hours,
Cooling rate: 200 ° C./hour,
Atmospheric gas: humidified N ₂ + H ₂ mixed gas (oxygen partial pressure: 10 ⁻⁷ Pa).
Annealing conditions Temperature rising rate: 200 ° C./hour,
Holding temperature: 1050 ° C.
Temperature holding time: 2 hours,
Cooling rate: 200 ° C./hour,
Atmospheric gas: humidified N ₂ gas (oxygen partial pressure: 1.01 Pa).

  Note that a wetter with a water temperature of 20 ° C. was used for humidifying the atmospheric gas during firing and annealing.

(Formation of external electrodes)
The capacitor element body 4 thus obtained was subjected to end surface polishing by sandblasting or the like, and Cu was applied as an external electrode to form external electrodes 6 and 8.

  The size of the obtained capacitor sample is 1.6 mm × 0.8 mm × 0.8 mm, the number of dielectric layers sandwiched between internal electrode layers is 300, and the thickness of the dielectric layer per layer ( The interlayer thickness was 1.2 μm, and the thickness of the internal electrode layer was 1.2 μm.

Samples 2-17, 21-37
A green sheet and a capacitor sample were prepared in the same manner as Sample 1 except that the first dispersion step and the second dispersion step were performed by the methods shown in Tables 1 and 2, and the crystallinity of the ceramic powder in the ceramic slurry, the green sheet Were measured for glossiness and sheet strength (Samples 2-17, 21-37). The results are shown in Tables 1 and 2. It should be noted that the glossiness reaches a maximum value after a certain dispersion time has elapsed, and then does not increase any more. Based on this, it is considered that the second dispersion step is completed when the glossiness reaches the maximum.

  In addition, “high pressure dispersion” in the table means high pressure dispersion treatment, and was performed by the following method.

(High pressure dispersion treatment)
In the high-pressure dispersion treatment, the dispersion treatment was performed under the pressure conditions shown in Tables 1 and 2 using a high-pressure dispersion apparatus (Ultimizer HJP-25005 manufactured by Sugino Machine).

Samples 41-44
A green sheet and a capacitor sample were prepared in the same manner as in Sample 1 except that the first dispersion step and the second dispersion step were performed by the method shown in Table 3 and the sheet thickness was as shown in Samples 41 to 44. The crystallinity of the ceramic powder in the rally, the glossiness of the green sheet, and the sheet strength were measured (Samples 41 to 44). Samples 41 to 44 and Samples 1 and 12 were measured for the short-circuit defect rate of the capacitor samples by the method described below. The results are shown in Table 3.

(Measurement of short defect rate)
The short-circuit defect rate was measured by preparing 50 capacitor samples and examining the number of short-circuit defects. Specifically, using an insulation resistance meter (E2377A multimeter manufactured by HEWLETT PACKARD), the resistance value is measured. A sample having a resistance value of 10 kΩ or less is defined as a short defect sample. The ratio of samples was defined as the short defect rate. In this example, the case where the short-circuit defect rate was 10% or less was considered good.

(Samples 1, 2, 5-9a, 10-17, 21-27)
Samples 1, 2, 5 to 9a, 10 to 17, and 21 to 27 are samples in which the first dispersion step is performed by a medium type disperser, and the second dispersion step is performed by dispersion by a swirling flow. It turns out that it becomes favorable and crystallinity is also favorable.

(Samples 2, 28)
From samples 2 and 28, when the resin is added after the first dispersion step (sample 2), the glossiness and sheet strength are better than when the resin is not added after the first dispersion step (sample 28). It can be seen that the crystallinity is also good.

(Samples 2, 29)
From samples 2 and 29, when the resin is added before the first dispersion step (sample 2), the glossiness, sheet strength, and crystallinity are higher than when the resin is not added before the first dispersion step (sample 29). It turns out that is good.

(Samples 2, 36, 37)
When the resin added before the first dispersion step is smaller than the resin added after the first dispersion step (sample 2) from Samples 2, 36 and 37, the resin added before the first dispersion step is the first. Compared with the case where the amount of resin added after the dispersion step is larger (sample 37), or the case where the amount of resin added before the first dispersion step is the same as that added after the first dispersion step (sample 36) It can be seen that the sheet strength and crystallinity are good.

(Samples 29 to 35)
From samples 29 to 35, when the resin added before the first dispersion step is 0% or more and 20% or less of the weight of the resin finally added (samples 29 to 34), otherwise (sample 35) ), The glossiness, sheet strength and crystallinity are better.

(Samples 3-9b)
From samples 3 to 9b, when the shear rate of the swirling flow in the second dispersion step is 15000 (1 / sec) to 100,000 (1 / sec) (samples 5 to 9a), the other cases (samples 3, 4, It can be seen that the gloss, sheet strength and crystallinity are good compared to 9b).

(Samples 1, 12, 41 to 44)
From Samples 1, 12, 41 to 44, when the first dispersion step is dispersion by a ball mill and the second dispersion step is dispersion by a swirl flow (Samples 41, 42, 1), the first dispersion step and the second dispersion Compared with the case where the processes are both ball mill dispersions (samples 43, 44 and 12), the gloss, crystallinity and sheet strength are good even when the sheet thickness is reduced, and the short-circuit defect rate of the capacitor sample is also high. It turns out that it becomes a favorable thing. From this, the effectiveness of the present invention in the case where the sheet thickness is 1.5 μm or less became clear.

2 ... Multilayer ceramic capacitor 4 ... Capacitor element body 6, 8 ... External electrode 10 ... Dielectric layer 10a ... Inner green sheet 11a ... Outer green sheet 12 ... Internal electrode layer 12a ... Internal electrode pattern layer 20 ... Support sheet 24 ... Laminate DESCRIPTION OF SYMBOLS 50 ... Dispersing machine 51 ... Stirrer tank 52 ... Shaft 53 ... Rotary blade 54 ... Supply pipe 55 ... Discharge pipe 56 ... Small hole 57 ... Arm 58 ... Gap 61 ... Light receiver 62 ... Light source 63 ... Measurement object (green sheet)
64 ... Tensile tester 65 ... Load cell 66 ... Measurement object (green sheet)

Claims (8)

Preparing a ceramic slurry containing a ceramic powder and a solvent;
A first dispersion step of dispersing the ceramic slurry with a medium-type disperser;
Adding a post-addition resin to the ceramic slurry after the first dispersion step;
And a second dispersion step of dispersing the ceramic slurry by swirling flow.   The method for producing a ceramic slurry according to claim 1, wherein a pre-added resin is added to the ceramic slurry before the first dispersion step.   The method for producing a ceramic slurry according to claim 1, wherein the pre-added resin is 0% by weight or more and 20% by weight or less with respect to a resin that the ceramic slurry finally contains.   The method for producing a ceramic slurry according to any one of claims 1 to 3, wherein the shear rate of the swirling flow in the second dispersion step is 15000 to 100,000 (1 / sec).   The method for producing a ceramic slurry according to any one of claims 1 to 4, wherein the medium type disperser is either a ball mill or a bead mill.   The manufacturing method of the green sheet which has the process of apply | coating the ceramic slurry in any one of Claims 1-5, and drying.   The method for producing a green sheet according to claim 6, wherein the green sheet after drying has a thickness of 1.5 μm or less. A green sheet according to claim 6 or 7,
An internal electrode pattern layer;
To obtain a green chip by stacking,
And a step of firing the green chip.

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