JP2012206888A - Methods for producing ceramic slurry, green sheet and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing ceramic slurry, which suppresses the generation of an undissolved solid of a resin and effectively disperses a ceramic powder, in the ceramic slurry, and which gives a green sheet excellent in sheet properties (smoothness and sheet strength), and to provide a method for producing a green sheet, using a ceramic slurry obtained by the producing method, and to provide a method for producing an electronic component, using the green sheet.SOLUTION: The method for producing ceramic slurry includes: a first dispersion step of dispersing a first liquid to be treated containing at least a binder resin and a first solvent but not substantially containing a ceramic powder by a dispersion treatment with a swirling flow; a second dispersion step of dispersing a second liquid to be treated containing at least a ceramic powder and a second solvent; and a third dispersion step in which a first dispersion solution obtained in the first dispersion step and a second dispersion solution obtained in the second dispersion step are mixed and the mixed solution is dispersed by a dispersion treatment with medium-type dispersion or by a dispersion treatment with a swirling flow.

Description

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

  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 type of multilayer electronic component, as the number of layers increases and the layers become thinner, the green sheets forming the dielectric layers are also made thinner. When the green sheet becomes thinner, sheet strength decreases, sheet attack occurs, scratches on the green sheet due to contact with the printing device, etc. become prominent, resulting in frequent occurrence of characteristic defects such as short-circuit defects in the finally obtained multilayer ceramic capacitor. To do.

  For this reason, as the thickness of the green sheet is reduced, a technique for producing a green sheet that has excellent sheet strength and does not generate a sheet attack is indispensable for the production of multilayer ceramic capacitors.

  In Patent Document 1, a binder liquid is produced by uniformly dissolving a binder in a solvent, and then a plasticizer is added to and mixed with the binder liquid to produce a binder plasticizer mixed solution. Thereafter, the binder plasticizer is produced. A method for producing a ceramic slurry for a green sheet has been proposed by mixing the mixed solution and the ceramic slurry.

  However, along with the thinning of the green sheet, if the process of dissolving the binder resin in the solvent is a stirring / mixing process using a stirrer, problems such as the generation of undissolved resin in the final ceramic slurry It has been found by the present inventors.

  In particular, it is conceivable to use a binder resin with a high degree of polymerization as one measure for securing the sheet strength when thinning the green sheet. Was remarkable. As a result, the obtained green sheet may have adverse effects such as a decrease in sheet strength.

JP-A-8-26832

  The present invention was made in view of such a situation, and even when the green sheet is thinned, a method for producing a ceramic slurry capable of obtaining a green sheet having no sheet attack and having excellent sheet strength, It is another object of the present invention to provide a method for manufacturing a green sheet and a method for manufacturing an electronic component with few short-circuit defects.

In order to solve the above problems, a method for producing a ceramic slurry according to the present invention comprises:
A first dispersion treatment step of dispersing a first liquid to be treated which contains at least a binder resin and a first solvent and substantially does not contain ceramic powder;
A second dispersion treatment step of dispersing a second liquid to be treated containing at least a ceramic powder and a second solvent;
A manufacturing method comprising a third dispersion step of mixing and dispersing the first dispersion solution obtained in the first dispersion step and the second dispersion solution obtained in the second dispersion step. And
The first dispersion process is a dispersion process using a swirl flow;
The binder resin is a butyral resin having a polymerization degree of 1700 to 3000.

  In the method for producing a ceramic slurry according to the present invention, first, a first dispersion treatment using a swirling flow is performed on a resin solution (first liquid to be treated) that does not contain ceramic powder. The first dispersion solution in which the resin is sufficiently dissolved in the first dispersion treatment step is then mixed with the second dispersion solution containing the ceramic powder and subjected to dispersion treatment again. It has been confirmed by experiments of the present inventors that a ceramic slurry having excellent dispersibility can be obtained by applying such a treatment even when a binder resin having a high degree of polymerization is used. In addition, when the first dispersion treatment (dispersion treatment using a swirl flow) is not performed, or when the first dispersion treatment is performed by another dispersion method, such an excellent ceramic slurry cannot be obtained. Was confirmed.

  In the ceramic slurry according to the present invention, even when a binder resin having a high degree of polymerization is used, the resin undissolved material is small and the dispersibility as a ceramic slurry is excellent. Therefore, even when a thin green sheet is formed, it is possible to obtain a green sheet that has excellent sheet strength and the like and can suppress the occurrence of sheet attack. As a result, the short-circuit defect rate of the finally obtained multilayer electronic component is reduced.

  Preferably, the second distributed processing is distributed processing by medium type distribution.

  Preferably, the third dispersion process is a dispersion process using a swirl flow.

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 the manufacturing method of the green sheet which has the process of apply | coating the ceramic slurry obtained by the said manufacturing method, and drying.

  Preferably, the thickness of the dried green sheet is 1 μm or less, more preferably 0.5 μm or less. When the film thickness of each green sheet is large, even when a binder resin with a high degree of polymerization is used, the influence of the resin undissolved material and dispersibility in the ceramic slurry is small, and the short-circuit defect rate is also small. However, as the film thickness of the green sheet decreases, the influence of the characteristics of the ceramic slurry (such as the dispersibility of the binder resin and the ceramic powder) increases. However, according to the present invention, even when a thin green sheet is formed with a ceramic slurry using a binder resin with a high degree of polymerization, a green sheet having excellent sheet strength and the like and capable of suppressing the occurrence of sheet attack is obtained. be able to.

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

  According to the present invention, even when a binder resin having a high degree of polymerization is used in the ceramic slurry, the resin undissolved component can be reduced and the ceramic powder contained in the ceramic slurry can be effectively dispersed. Moreover, according to the present invention, a green sheet that is thinned by a ceramic slurry using a binder resin with a high degree of polymerization can be formed, and a green sheet that is excellent in sheet strength and the like and that can suppress the occurrence of sheet attack is obtained. be able to. As a result, it is possible to reduce short-circuit defects in laminated electronic components (particularly ceramic capacitors).

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. 3A is a schematic front view of a disperser used in the first dispersion step in the method for producing a ceramic slurry according to one embodiment of the present invention. Moreover, FIG.3 (b) is the schematic front view to which the dispersion | distribution part in Fig.3 (a) was expanded. FIG. 4A is a schematic front view of a disperser according to high pressure dispersion. FIG. 4B is a schematic front view of the stirrer. 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. FIG. 7 is a graph showing the difference in effect between the example of the present invention and the comparative example when the thickness of the green sheet is 1 μm. FIG. 8 is a graph showing the effect of the embodiment of the present invention. FIG. 9 is a graph showing an effect when the first dispersion process is not performed by the swirl flow dispersion according to the comparative example 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 (0.4 to 5.6 mm, preferably 0.4 to 3.2 mm) × horizontal (0.2 to 5.0 mm, preferably 0.2 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.

Method for Producing Green Sheet First, a ceramic slurry (green sheet coating material) is prepared in order to produce 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 steps shown in FIGS.

  First, a ceramic slurry is obtained by dispersing and mixing ceramic powder, a binder resin, a solvent, and if necessary, a plasticizer, a dispersant, an antistatic agent, and the like. In addition, the manufacturing method (process shown in FIG. 2) of a ceramic slurry is mentioned later.

  The ceramic powder is not particularly limited, and can be appropriately selected from various compounds that become composite oxides or oxides, such as carbonates, nitrates, hydroxides, organometallic compounds, and the like, and can be used as a mixture. The ceramic powder is usually used as a powder having an average particle size of 0.3 μm or less, preferably 0.2 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 ceramic powder is contained in an amount of 10 to 60 parts by weight, preferably 15 to 45 parts by weight, based on 100 parts by weight of the ceramic slurry.

  As the binder resin, a butyral resin having a polymerization degree of 1700 to 3000 and preferably 1700 to 2600 is used. If the degree of polymerization is too large, the resin cannot be sufficiently dissolved by the first dispersion treatment, and the sheet strength tends to decrease when a green sheet is formed due to the generation of undissolved resin. On the other hand, if the degree of polymerization is too small, wrinkles (sheet attack) due to printing tend to occur when the internal electrode layer is printed on the formed green sheet.

  The binder resin is preferably 10 to 50 parts by weight, more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the ceramic powder.

  Although it does not specifically limit as a solvent, According to the method to utilize, the alcohol solvent represented by methanol, ethanol, propanol, etc., the ketone solvent represented by acetone, methyl ethyl ketone (MEK), toluene, xylene, Aromatic solvents such as ethylbenzene, ester solvents such as methyl acetate, ethyl acetate, and butyl acetate, hexane, industrial gasoline, aliphatic solvents such as mineral spirits, and terpineol And various organic solvents such as butyl carbitol may be appropriately selected.

  The solvent is preferably 50 to 80 parts by weight, more preferably 60 to 70 parts by weight with respect to 100 parts by weight of the ceramic slurry.

  The ceramic slurry may contain additives selected from various dispersants, plasticizers, dielectrics, glass frit, insulators, and the like as necessary. However, the total content of these additives is preferably 10 parts by weight or less with respect to 100 parts by weight of the ceramic slurry.

  Examples of the plasticizer include, but are not limited to, phthalic acid esters such as dioctyl phthalate (DOP) and benzylbutyl phthalate, aliphatic dibasic acid esters, phosphoric acid esters, and glycols. The plasticizer preferably has a content of 10 to 50 parts by weight with respect to 100 parts by weight of the binder resin.

  Further, the dispersant is not particularly limited, and examples thereof include a maleic acid dispersant, a polyethylene glycol dispersant and / or an allyl ether copolymer dispersant.

  As shown in FIG. 5a, the ceramic slurry is formed into a sheet shape on a support film 20 such as PET to form a green sheet 10a. The 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 method for producing the ceramic slurry is a means for producing a thin film green sheet, it is an application method suitable for a thin film (1 μm or less). Is preferred.

  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.

Method for producing a ceramic slurry Next, a method of manufacturing the ceramic slurry to form a green sheet 10a shown in Figure 5a.

(First distributed processing step)
As shown in FIG. 2, first, in step S1, a first liquid to be treated containing at least a binder resin and a first solvent and substantially free of ceramic powder is prepared. In addition, the first liquid to be treated may contain a plasticizer, a dispersant, an antistatic agent, and the like.

  The weight ratio of the binder resin is preferably 1 to 15 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the first liquid to be treated. Thereby, the binder resin can be sufficiently dissolved in the solvent by the first dispersion treatment, and a uniform first dispersion treatment liquid can be obtained.

  The content of the binder resin contained in the first liquid to be treated is preferably 80 parts by weight or more, more preferably 90 parts by weight or more, with respect to 100 parts by weight of the binder resin finally contained in the ceramic slurry. It is. Thus, the first dispersion treatment can effectively prevent the generation of the resin undissolved material as the ceramic slurry, and the first dispersion solution in which the binder resin is uniformly dispersed can be obtained.

  It does not specifically limit as a 1st solvent, For example, organic solvents, such as an alcohol solvent, a ketone solvent, an ester solvent, an aromatic solvent, an aliphatic solvent, are used. Although these organic solvents can be used alone, in the present embodiment, a mixed solvent of an alcohol solvent and an aromatic solvent is preferably used as the first solvent. Thereby, it can melt | dissolve enough and a uniform 1st dispersion | distribution processing liquid is obtained.

  The weight ratio of the first solvent is preferably 75 to 90 parts by weight, more preferably 80 to 90 parts by weight with respect to 100 parts by weight of the first liquid to be treated. Thereby, the binder resin can be sufficiently dissolved in the solvent by the first dispersion treatment, and a uniform first dispersion treatment liquid can be obtained.

  As shown in FIG. 2, as step S2, the first liquid to be treated may be mixed and stirred in advance by a stirrer or the like prior to the first dispersion processing step (S3). As the stirrer, for example, a stirrer 41 having rotating blades 42 as shown in FIG. 4B can be used, for example. In the present embodiment, the agitation process is a process in which the treatment liquid is gently mixed as compared with the dispersion process, and is distinguished from the dispersion process.

  Next, as shown in FIG. 3, as step S3, a first dispersion treatment is performed on the first liquid to be treated to obtain a first dispersion solution.

  In general, dispersion processing includes medium type dispersion (not shown) using an agitator mill such as a ball mill, a bead mill, or a sand mill, high-pressure dispersion using a disperser as shown in FIG. Such as swirling flow dispersion by a disperser as shown in FIG.

  However, in step S3, when the first dispersion process is a dispersion process using a medium-type disperser, the binder resin is not sufficiently dissolved in the solvent, and an undissolved resin is generated. In rally, the sheet strength tends to decrease.

  Further, in step S3, when the first dispersion process is a dispersion process by high-pressure dispersion, the binder resin is damaged, and when the internal electrode layer is printed on the green sheet in which the ceramic slurry is formed, printing is performed. Wrinkles (sheet attack) tend to occur.

  Therefore, in the first dispersion process performed in step S3, it is important how to dissolve the binder resin uniformly without damaging the binder resin. Therefore, in the present embodiment, the first dispersion process is performed by a dispersion process using a swirling flow. By performing the first liquid to be treated by a dispersion process using a swirl flow, the resin undissolved material is not generated, and the occurrence of sheet attack is prevented in the green sheet obtained by sheeting the finally obtained ceramic slurry. The sheet strength and the like are also improved.

  The dispersion process using the swirling flow is performed using, for example, a disperser 50 illustrated in FIG. 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 15000 (1 / sec) or more, more preferably 25000 to 100,000 (1 / sec). By setting the shear rate of the swirling flow within the above range, the dispersibility is improved and the sheet strength is improved.

Note that the shear rate of the swirling flow is defined by the following equation (1).
Shear rate (1 / s) = peripheral speed (m / s) / t (mm) (1)
In the equation (2), t is the width t of the gap 58 in the disperser shown in FIG.

  When the disperser shown in FIG. 3A is used, the width t of the gap 58 is preferably 0.1 to 5.0 m, more preferably 0.1 to 2.0 mm, and the peripheral speed is preferably 10 to 10 mm. 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.

  In the dispersers shown in FIGS. 3A and 3B, the gap 58 between the stirring tank 51 and the rotary blade 53 serves as a dispersive part, and a shearing force due to the swirling flow acts on the fluid.

In the present invention, the residence time is defined by the following equation (2).
Residence time = V2 / V1 x T (2)

In the above formula (2),
V1: Volume of the dispersion part (cm ³ ) in the disperser,
V2: the effective volume (cm ³ ) of the treatment tank in the disperser,
T: Actual distributed processing time (minutes).

  The residence time in the dispersion part is preferably 0.3 minutes or more, more preferably 0.3 to 1 minute. Dispersion of the binder resin is insufficient, and if it is too long, the improvement in dispersibility is slight and the production efficiency is deteriorated.

(Second distributed processing step)
As shown in FIG. 2, first, in step S4, a second liquid to be treated containing at least a ceramic powder and a second solvent is prepared. In addition, the second liquid to be treated may include a plasticizer, a dispersant, a binder resin, a part of the first dispersion liquid, and the like.

  The weight ratio of the ceramic powder is 30 to 70 parts by weight, more preferably 40 to 65 parts by weight with respect to 100 parts by weight of the second liquid to be treated. Thereby, the 2nd dispersion solution with favorable dispersibility can be obtained.

  It does not specifically limit as a 2nd solvent, For example, organic solvents, such as an alcohol solvent, a ketone solvent, an ester solvent, an aromatic solvent, an aliphatic solvent, are used. In the present embodiment, the second solvent preferably contains an alcohol solvent and an aromatic solvent, and the total mass of the alcohol solvent and the aromatic solvent is 100 parts by weight. 10 to 20 parts by weight are included.

  The weight ratio of the second solvent is preferably 30 to 70 parts by weight, more preferably 40 to 65 parts by weight with respect to 100 parts by weight of the second liquid to be treated. Thereby, the 2nd dispersion solution with favorable dispersibility can be obtained.

  The weight ratio of the plasticizer is preferably 0 to 3 parts by weight, and the weight ratio of the dispersant is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the second liquid to be treated.

  The second liquid to be treated may contain a binder resin. The binder resin is not particularly limited, and may be the same as or different from the binder resin contained in the first liquid to be treated. Further, the second liquid to be treated may contain a binder resin by adding a part of the first dispersion treatment liquid. Dispersion stability is improved by mixing a small amount of the binder resin in the second liquid to be treated.

  The weight ratio of the binder resin contained in the second liquid to be treated is preferably 0 to 20 parts by weight with respect to 100 parts by weight of the ceramic powder. The content of the binder resin contained in the second liquid to be treated is preferably 20% by weight or less of the binder resin finally contained in the ceramic slurry.

  Moreover, when adding binder resin by adding a part of 1st dispersion processing liquid, the addition ratio of a 1st dispersion processing liquid is preferably 0-20 with respect to 100 weight part of 2nd to-be-processed liquids. Parts by weight. Further, the content of the first dispersion treatment liquid contained in the second treatment liquid is preferably 20% by weight or less of the first dispersion treatment liquid finally contained in the ceramic slurry.

In step S4, a second dispersion treatment is performed on the second liquid to be treated to obtain a second dispersion solution.
The second dispersion process is not particularly limited, but is a dispersion process by medium-type dispersion, a dispersion process by swirl flow, or a dispersion process by high-pressure dispersion, and preferably a dispersion process by medium-type dispersion.

  Examples of the medium type dispersion in the second dispersion treatment step include dispersion by a dispersing machine such as a ball mill, a bead mill, a sand mill, an attritor, and a paint shaker (basket mill).

  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 3.0 mm. As a result, the ceramic powder can be refined without damaging the ceramic powder, the media and the slurry can be easily separated, and a second dispersion solution having excellent dispersibility can be obtained.

  Dispersion treatment by medium type dispersion is particularly suitable for the second dispersion treatment step because coarse particles such as secondary particles of ceramic powder can be efficiently crushed compared to other dispersion treatments.

  The dispersion by the swirl flow in the second dispersion step can be performed in the same range as the condition of the swirl flow dispersion in the first dispersion step. However, it is not necessary to perform the same setting as in the first dispersion step, and the setting can be appropriately selected within the range of preferable conditions for the swirling flow dispersion.

  For example, as shown in FIG. 4A, an apparatus for performing high-pressure dispersion in the second dispersion treatment step causes a treatment liquid to pass through a predetermined flow path and collide with the collision unit 40 by a treatment unit (generator). There are collision-type devices that perform distributed processing, and through-type generator-type devices (not shown) that do not collide and have only a straight pipe.

  The treatment unit is preferably a collision type because it requires less processing time, but the equipment becomes expensive. When a penetrating generator that does not collide is used, processing time is required, but there is no clogging of coarse particles, high cleaning property, and it is suitable for the second dispersion processing step.

  When the disperser shown in FIG. 4A is used, the pressure when the treatment liquid is caused to collide from the treatment unit to the collision unit 40 is preferably 50 to 200 MPa. If the pressure is too high, the crystallinity of the ceramic powder tends to be reduced.

  The particle size of the main component powder after the second dispersion step is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.3 μm. Thereby, the ceramic slurry excellent in the dispersibility can be obtained, without reducing the crystallinity of ceramic powder. Furthermore, when the obtained ceramic slurry is formed into a sheet, a green sheet excellent in smoothness can be obtained.

(Third distributed processing step)
Next, as step S6, a predetermined amount of the first dispersion solution obtained in the first dispersion treatment step (S3) is added to the second dispersion solution obtained in the second dispersion treatment step (S5). The distributed processing is performed by the distributed processing of No.

  In this embodiment, as shown in FIG. 2, a predetermined amount of the first dispersion solution is added to the second dispersion solution after the second dispersion step, and the third dispersion treatment is performed, thereby generating undissolved resin. And the ceramic powder can be dispersed in one particle unit.

  In step S6, the amount of the first dispersion solution added to the second dispersion solution is determined according to the intended use of the ceramic slurry. In this embodiment, the total amount of the second dispersion solution is 100 parts by weight. On the other hand, the addition ratio of the first dispersion solution is preferably 30 to 200 parts by weight.

  A filtering step may be provided after step S3 for the first dispersion before being added to the second dispersion in step S6. By filtering the first dispersion solution, it is possible to remove even a slightly generated resin undissolved material, so that the sheet characteristics can be further improved.

  In the third 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 third dispersion process is not particularly limited, and is a dispersion process by medium type dispersion, a dispersion process by swirl flow, or a dispersion process by high pressure dispersion. Preferably, in this embodiment, by swirl flow or medium type dispersion. Dispersion processing, more preferably dispersion processing by swirling flow.

  The dispersion by the swirl flow in the third dispersion step can be performed in the same range as the condition of the swirl flow dispersion in the first dispersion step. However, it is not necessary to perform the same setting as in the first dispersion step, and the setting can be selected as appropriate within the range of preferable conditions for the dispersion processing by the swirl flow.

  The medium type dispersion in the third dispersion step can be performed in the same range as the conditions of the medium type dispersion process in the second dispersion step. However, it is not necessary to perform the same setting as in the second dispersion step, and the setting can be appropriately selected within the range of preferable conditions for the medium-type dispersion processing. In particular, the processing time is preferably set longer than that in the second dispersion step. Preferably, it is 5 to 15 hours.

  The high pressure dispersion in the third dispersion step can be performed in the same range as the high pressure dispersion conditions in the second dispersion step. However, it is not necessary to perform the same setting as in the first dispersion step, and the setting can be appropriately selected within the range of preferable conditions for the dispersion treatment by high-pressure dispersion.

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.

  In the embodiment according to the present invention, the thickness of each dielectric layer 10 is preferably 1 μm or less, more preferably 0.5 μm or less. As described above, according to the method for manufacturing a green sheet according to the embodiment of the present invention, even when a binder resin having a high degree of polymerization is used, the binder resin can be uniformly dispersed in the ceramic slurry. In addition, the interlayer thickness can be reduced (thinned), and 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.

  In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change variously. 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, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

Sample 1
(First distributed processing step)
First, the 1st process liquid was prepared. The 1st to-be-processed liquid was produced as follows. That is, a binder resin and a first solvent were mixed, and a plasticizer or the like was further added as necessary. The first liquid to be treated does not contain ceramic powder.

  As the binder resin, a polyvinyl butyral resin having a polymerization degree of 1450 was used, and the addition amount was 6 parts by weight with respect to 100 parts by weight of the first liquid to be treated.

  Moreover, the solvent which consists of ethanol / 1-propanol / xylene was used as a 1st solvent, and the addition amount was 92 weight part with respect to 100 weight part of 1st to-be-processed liquids. The content ratios of various solvents were 45% by weight of ethanol, 45% by weight of 1-propanol, and 10% by weight of xylene in the first solvent.

  Further, dioctyl phthalate (DOP) was used as the plasticizer, and the amount added was 2 parts by weight with respect to 100 parts by weight of the first liquid to be treated.

  Next, a first dispersion treatment was performed on the first liquid to be treated by a swirling flow to obtain a first dispersion solution.

  As conditions for the dispersion treatment by the swirl flow, using the apparatus shown in FIG. 3A, the peripheral speed is 50 m / s, the clearance is 2 mm, the shear rate is 25000 (1 / s), and the residence time in the dispersion part is 0.25. Set to be minutes. The same applies to the dispersion processing using the swirling flow.

(Second distributed processing step)
Next, the 2nd to-be-processed liquid was prepared. The second liquid to be treated was produced as follows. That is, the ceramic powder and the second solvent were mixed, and a binder resin, a dispersant, a first liquid to be treated, and the like were added as necessary.

As the ceramic powder, BaTiO ₃ , MgCO ₃ , MnCO ₃ , (Ba, Ca) SiO ₃ and a rare earth compound having an average particle diameter of 0.1 μm are used, and the addition amount is based on 100 parts by weight of the second treated liquid. , 50 parts by weight.

  Moreover, the solvent which consists of ethanol / 1-propanol / xylene was used as a 2nd solvent, and the addition amount was 40 weight part with respect to 100 weight part of 2nd dispersion solutions. The content ratio of various solvents was 40% by weight of ethanol, 40% by weight of propanol, and 20% by weight of xylene in the second solvent.

  Moreover, as a dispersing agent, the anionic dispersing agent was used, and the addition amount was 2 weight part with respect to 100 weight part of ceramic powder.

  The second solution to be treated may contain a part of the binder resin or the first dispersion solution as necessary, but the sample 1 does not contain any of them.

  Next, the second dispersion treatment was performed on the second liquid to be treated by the medium-type dispersion treatment to obtain a second dispersion solution.

  The conditions for the medium-type dispersion treatment were set such that the media diameter was 2 mm, the rotation speed was 45 rpm, and the treatment time was 3 hours.

(Third distributed processing step)
Next, a ceramic slurry was prepared. The ceramic slurry was produced as follows. That is, the first dispersion solution obtained in the first dispersion treatment step was added to and mixed with the second dispersion solution obtained in the second dispersion treatment step, and the third dispersion treatment was performed by swirling flow.

  The amount of the first dispersion solution added was 150 parts by weight with respect to 100 parts by weight of the second dispersion treatment solution.

  The third dispersion process was a dispersion process using a swirling flow. The conditions for the dispersion treatment by the swirling flow were set such that the peripheral speed was 50 m / s, the clearance was 2 mm, the shear rate was 25000 / s, and the residence time in the dispersion part was 0.50 minutes.

  Through the above steps, a ceramic slurry (green sheet coating material) was obtained.

(Green sheet formation)
The produced ceramic slurry was applied onto a PET film with a doctor blade so that the thickness of the dried green sheet was 1.0 μm, thereby forming a green sheet 10a. Next, the green sheet 10a formed on the PET film was continuously fed into a drying furnace, and the solvent contained in the green sheet 10a was dried. The drying temperature was 75 ° C. and the drying time was 1 minute.
(Preparation of internal electrode layer paste)
Next, 0.2 μm Ni particles, dihydroterpineol, ethyl cellulose resin, and DOP were kneaded with three rolls and slurried to obtain an internal electrode layer paste.

(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. The internal electrode layer paste was applied on this and dried, and then 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, this laminate was cut to a predetermined size to obtain a ceramic green chip. Next, the ceramic green chip was heated to remove the binder. Next, the ceramic green chip was fired at 1000 ° C. to 1400 ° C. to obtain a sintered body. Next, in order to re-oxidize the dielectric layer in the sintered body, the sintered body was heated. A terminal electrode was formed on the reoxidized fired body to obtain a multilayer ceramic capacitor.

  The size of the obtained multilayer ceramic capacitor is 1.6 mm × 0.8 mm × 0.8 mm, the number of dielectric layers sandwiched between internal electrode layers is 100, and the thickness of the dielectric layer per layer The (interlayer thickness) was 0.80 to 0.85 μm, and the thickness of the internal electrode layer was 0.70 to 0.75 μm.

Samples 2-7
In Samples 2-7, the multilayer ceramic capacitors of Samples 2-7 were prepared under the same conditions as Sample 1, except that the polymerization degree of the binder resin contained in the first liquid to be treated was changed as shown in Table 1. did.

Samples 8-14
Samples 8 to 14 are the same as Samples 1 to 7 except that the first treatment liquid similar to Samples 1 to 7 is added to the second dispersion solution without being subjected to the first dispersion treatment. Under the conditions, multilayer ceramic capacitors of Samples 8 to 14 were produced.

  (Evaluation)

(Sheet strength)
In the manufacturing process of the multilayer ceramic capacitors obtained in Samples 1 to 14, the sheet strength at the green sheet stage was evaluated. In the measurement, the green sheet is pulled up vertically using the load cell 65 of the tensile testing machine 64 shown in FIG. 6, and when the green sheet breaks, the stress applied to the load cell 65 is measured, and the maximum stress in the measurement sample is 100. The relative value in the case of the above was taken as the sheet strength. The green sheet as a reference sample at this time was a strip shape having a width of 10 mm, a length of 40 mm, and a thickness of 1 μm, the interval between the upper and lower jigs was 10 mm, and the extension speed of the jig was 8 mm / sec.
The results are shown in Table 1. In this embodiment, the sheet strength is preferably 80% or more, more preferably 90% or more.

(Seat attack rate)
Moreover, in the manufacturing process of the multilayer ceramic capacitors obtained in Samples 1 to 14, the sheet attack occurrence rate when the internal electrode layer paste was printed on the green sheet was evaluated. In order to evaluate the presence or absence of sheet attack, the number of wrinkles in the printed pattern was measured. Specifically, using an actual microscope, 100 patterns of 1.6 mm × 0.8 mm were observed with oblique light (angle of 10 degrees), and the number of wrinkles was counted visually. In this example, the case where the sheet attack occurrence rate was 10% or less was considered good. More preferably, it is 0%.

(Short defective rate)
Moreover, the short defect characteristic was evaluated as characteristic evaluation of the multilayer ceramic capacitor obtained in Samples 1-14. The short-circuit defect rate was measured for 100 samples of multilayer ceramic capacitors. In the measurement, an insulation resistance meter (E2377A multimeter manufactured by HEWLETT PACKARD) was used. In the measurement, the resistance value of each sample was measured, and a sample having a resistance value of 10 kΩ or less was determined as a short-circuit defective sample. The ratio of the sample that caused the short defect to the total measurement sample was defined as the short defect rate. The results are shown in Table 1. In this embodiment, a preferable value of the short-circuit defect rate is determined for each thickness of the green sheet. When the thickness is 2.0 μm, the short-circuit defect rate is preferably 8% or less, more preferably 3% or less. When the thickness is 1.0 μm, the short-circuit defect rate is preferably 10% or less, more preferably 5% or less. When the thickness is 0.5 μm, the short-circuit defect rate is preferably 20% or less, more preferably 10% or less.

  As shown in Table 1, the samples 2 to 6 in which the first dispersion treatment by the swirl flow dispersion treatment was performed on the first liquid to be treated containing the butyral resin having a polymerization degree in a predetermined range are sufficient. Sheet strength was obtained, and the occurrence rate of sheet attack was also within a preferable range. In addition, the short defect rate also shows good results.

  On the other hand, even when the dispersion treatment by the swirling flow is performed as the first dispersion treatment, in the sample 1 in which the degree of polymerization of the butyral resin is smaller than the predetermined range, the occurrence rate of the sheet attack becomes high, and as a result As a result, the short defect rate is higher than those of Samples 2-6. Further, in the sample 7 in which the degree of polymerization of the butyral resin is larger than the predetermined range, the dispersibility of the binder resin can be sufficiently improved even when the dispersion treatment by the swirling flow is performed as the first dispersion treatment. In addition, the short defect rate is higher than those of Samples 2-6.

  In Samples 8 to 14 where the first dispersion treatment is not subjected to the dispersion treatment using the swirling flow, either the sheet strength or the sheet attack occurrence rate is not within a preferable range, and the degree of polymerization of the resin is increased. As a result, the sheet strength decreased, and short-circuit defects occurred frequently.

  FIG. 7 shows the relationship between the degree of polymerization of the butyral resin shown in Table 1 and the short-circuit defect rate. As shown in FIG. 7, in samples 2 to 6 according to the example, even though the degree of polymerization of the butyral resin increases, the short-circuit defect rate does not increase, whereas in samples 8 to 14 according to the comparative example, As the degree of polymerization of the butyral resin increases, the short-circuit defect rate increases. In this invention, it has confirmed that it was effective when the polymerization degree of a butyral resin exists in a predetermined range.

Samples 1a-14a
In Samples 1a to 14a, the ceramic slurry prepared in Samples 1 to 14 was applied onto a PET film with a doctor blade so that the thickness after drying was 2.0 μm, and the green sheet 10a was formed. Under the same conditions as Samples 1 to 14, multilayer ceramic capacitors of Samples 1a to 14a were produced. In the obtained multilayer ceramic capacitor, the thickness of each dielectric layer (interlayer thickness) was 1.65 to 1.75 μm, and the thickness of the internal electrode layer was 0.80 to 0.85 μm.

Samples 1b-14b
In Samples 1b to 14b, the ceramic slurry prepared in Samples 1 to 14 was applied on a PET film with a doctor blade so that the thickness after drying was 0.5 μm, and the green sheet 10a was formed. Under the same conditions as Samples 1 to 14, multilayer ceramic capacitors of Samples 1b to 14b were produced. In the obtained multilayer ceramic capacitor, the thickness of each dielectric layer (interlayer thickness) was 0.43 to 0.45 μm, and the thickness of the internal electrode layer was 0.50 to 0.55 μm.

  8 and 9 show the relationship between the degree of polymerization of the butyral resin shown in Tables 1 and 2 and the short-circuit defect rate. As shown in FIG. 8, in samples 2 to 6, 2a to 6a, and 2b to 6b according to Examples, when the degree of polymerization of the butyral resin is within a predetermined range, the thickness of the green sheet is 2 μm, It was confirmed that the short-circuit defect rate can be reduced even when the thickness is reduced to 1 μm and 0.5 μm.

  On the other hand, as shown in FIG. 9, in the samples 8 to 14, 8a to 14a, and 8b to 14b according to the comparative examples, as the degree of polymerization of the butyral resin increases, the short defect rate increases, When the thickness was 0.5 μm, it was confirmed that the entire sample was short-circuited.

Samples 31-39
In the first, second and third dispersion treatments, a multilayer ceramic capacitor is obtained in the same manner as the sample 4b except that any one of dispersion by swirl flow, medium dispersion, and high pressure dispersion is combined as shown in Table 3. Samples 31 to 39 were prepared and subjected to the same evaluation. The results are shown in Table 3.

  The conditions for the dispersion treatment by high-pressure dispersion were set so that a pressure was 100 MPa using a high-pressure homogenizer (hereinafter, the same apparatus was used for dispersion treatment by high-pressure dispersion).

  Further, the conditions of the medium type dispersion as the first and third dispersion processes were set such that the media diameter was 2 mm, the rotation speed was 45 rpm, and the treatment time was 10 hours.

  Moreover, the conditions of the swirling flow dispersion as the second and third dispersion processes were both set to the same conditions as the first dispersion process.

  As shown in Table 3, in the samples 30 and 31 subjected to the dispersion process other than the swirl flow dispersion as the first dispersion process, the characteristics of either the sheet strength or the sheet attack occurrence rate are not within a preferable range. The short defect rate is also higher than that of the sample 4b.

  On the other hand, in the samples 32 to 39 subjected to the swirl flow dispersion process as the first dispersion process, even if the second and third dispersion processes are changed, any of the sheet strength and the occurrence rate of the sheet attack is detected. These characteristics are also within the preferable range, and the short-circuit defect rate is similar to that of the sample 4b.

Samples 40-44, 41b, 42b, and 44b
In the samples 40 and 41, the multilayer ceramic capacitor samples 40 and 41 were made in the same manner as the sample 4 except that the shear rate was changed by changing the peripheral speed as shown in Table 4 in the first dispersion treatment by the swirling flow. A similar evaluation was made. In the sample 42, the multilayer ceramic capacitor sample 42 was prepared in the same manner as the sample 4 except that the shear rate was changed by changing the peripheral speed and clearance as shown in Table 4 in the first dispersion treatment by the swirling flow. A similar evaluation was made. In Samples 43 and 44, multilayer ceramic capacitor samples 43 and 44 were produced in the same manner as Sample 4 except that the residence time in the dispersion portion was changed as shown in Table 4 in the first dispersion treatment by swirling flow. Similar evaluations were made. The results are shown in Table 4.

  In 41b and 42b, in the first dispersion process by the swirling flow, the shear rate is changed by changing the peripheral speed and clearance as shown in Table 4, and in 44b, in the first dispersion process by the swirling flow, in Table 1 Thus, except that the residence time in the dispersion part was changed, multilayer ceramic capacitor samples 41b, 42b, and 44b were produced in the same manner as the sample 4b, and the same evaluation was performed. The results are shown in Table 4.

  As shown in Table 4, in the first dispersion treatment by the swirl flow, even when the shear rate and the residence time in the dispersion portion were changed, both the characteristics of the sheet strength and the occurrence rate of the sheet attack were within a preferable range. . In addition, the short defect rate also shows good results.

Samples 50 and 51
Sample 50 is the same as Sample 4 except that 10% by weight of the binder resin that will eventually be included in the ceramic slurry is included in the second liquid to be subjected to the second dispersion treatment. Similarly, multilayer ceramic capacitors were produced and evaluated in the same manner. Moreover, in the sample 51, 10% by weight of the first dispersion solution to be finally contained in the ceramic slurry was included in the second treatment liquid, and the second dispersion treatment was performed. Except for the above, a multilayer ceramic capacitor was produced in the same manner as Sample 4, and the same evaluation was performed. The results are shown in Table 5.

  As shown in Table 5, even in the sample 50 containing the binder resin as the second liquid to be treated, both the sheet strength and the sheet attack occurrence rate were within the preferable range. In addition, the short defect rate also shows good results.

  Further, even in the sample 51 containing a part of the first dispersion as the second liquid to be treated, both the sheet strength and the occurrence rate of the sheet attack were within a preferable range. In addition, the short defect rate also shows good results.

  Therefore, in the present invention, a part of the binder resin that is finally contained in the ceramic slurry or a part of the first dispersion obtained in the first dispersion treatment is used as the second treatment target. Even when it was included in the liquid, it was confirmed that there was no problem as long as it was a predetermined amount or less.

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 40 ... Collision part 41 ... Stirrer 42 ... Rotating blade 50 ... Disperser 51 ... Stirring tank 52 ... Shaft 53 ... Rotating blade 57 ... Arm 58 ... Gap 64 ... Tensile tester 65 ... Load cell 66 ... Measured object (green sheet)

Claims (6)

A first dispersion treatment step of dispersing a first liquid to be treated which contains at least a binder resin and a first solvent and substantially does not contain ceramic powder;
A second dispersion treatment step of dispersing a second liquid to be treated containing at least a ceramic powder and a second solvent;
A manufacturing method comprising a third dispersion step of mixing and dispersing the first dispersion solution obtained in the first dispersion step and the second dispersion solution obtained in the second dispersion step. And
The first dispersion process is a dispersion process using a swirl flow;
The method for producing a ceramic slurry, wherein the binder resin is a butyral resin having a degree of polymerization of 1700 to 3000.   2. The method for producing a ceramic slurry according to claim 1, wherein the second dispersion treatment is a dispersion treatment by a medium type dispersion.   The method for producing a ceramic slurry according to claim 1 or 2, wherein the third dispersion treatment is a dispersion treatment using a swirling flow.   The manufacturing method of the green sheet which has the process of apply | coating the ceramic slurry obtained by the manufacturing method in any one of Claims 1-3, and drying.   The method for producing a green sheet according to claim 4, wherein the green sheet after drying has a thickness of 1.0 μm or less. A step of laminating a green sheet obtained by the manufacturing method according to claim 4 or 5 and an internal electrode pattern layer to obtain a green chip;
And a step of firing the green chip.

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