TW202041466A - Paste for internal electrode and method for manufacturing laminated ceramic electronic part capable of preventing sintering during firing even though a coexisting material powder is added to prevent fracture - Google Patents

Abstract

The present invention relates to a paste for internal electrodes and a method for manufacturing laminated ceramic electronic parts. Provided is a paste for internal electrodes capable of preventing sintering during firing even though a coexisting material powder is added to prevent fracture. The paste for internal electrodes disclosed in the present invention includes: a conductive powder; a coexisting material powder composed of dielectric particles; and a dispersion medium. The dielectric particles are metal oxide particles having a perovskite structure represented by the general formula ABO3 (1). In addition, the A site in the above formula (1) includes at least Ba, and the B site includes at least Ti. In the paste for internal electrodes, a molar ratio (A/B) of the atom occupying the A site to the atom occupying the B site in formula (1) is 0.89 or more and 0.99 or less, and the average particle size of the coexisting material powder is 10 nm or more and 50 nm or less. Thus, although the coexisting material powder for preventing fracture is added, it can still prevent sintering during firing.

Description

Paste for internal electrodes and manufacturing method of laminated ceramic electronic parts

The present invention relates to a paste for internal electrodes. More specifically, the present invention relates to a paste for internal electrodes for forming internal electrode layers of multilayer ceramic electronic parts.

A multilayer ceramic capacitor (Multi-Layer Ceramic Capacitor: MLCC) has a structure in which a multi-layer laminate includes a dielectric layer containing a dielectric (ceramic material) and an internal electrode layer containing a conductive metal. This MLCC can be produced as follows: the surface of the dielectric green sheet as the precursor of the dielectric layer is provided with a paste for internal electrodes as the precursor of the internal electrode layer, and the dielectric green sheet is laminated in multiple layers It can be produced by co-firing.

Patent Document 1 and Patent Document 2 disclose technologies related to the dielectric layer of the MLCC. For example, Patent Document 1 discloses a dielectric powder in which a layer rich in Ti and solid-dissolved rare earth elements is formed on the outermost layer of a core particle formed of barium titanate (BaTiO ₃ ), and the surface is further made of Ba compound Covered. By using the dielectric powder, it is possible to prevent a short circuit in an MLCC with a thinned dielectric layer. In addition, Patent Document 2 discloses a method for producing barium titanate particles suitable for the dielectric layer of MLCC, which is a method of producing fine, uniform particle size, and rectangular parallelepiped barium titanate particles.

However, when the internal electrode paste and the dielectric green sheet are co-fired, depending on the behavior during firing (the firing start temperature, firing shrinkage, etc.), cracks may occur in the internal electrode layer. ) Etc. Therefore, in the manufacturing process of MLCC, a ceramic material of the same type as the dielectric material used in the dielectric layer is added to the internal electrode paste as a coexisting material powder, so that the behavior of the internal electrode paste is the same as that of the dielectric green sheet. The behavior proceeds approximately. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2013-163614 [Patent Document 2] Japanese Patent Application Publication No. 2017-202942

[The problem to be solved by the invention]

However, the internal electrode paste containing the coexisting material powder has a problem of deterioration in heat resistance. Specifically, in the internal electrode paste containing the coexisting material powder, excessive sintering (particle growth) occurs during firing, and various defects may occur in the internal electrode layer after formation. The present invention was made in order to solve the above-mentioned problems, and its object is to provide a paste for internal electrodes that can prevent sintering during firing even though coexisting material powder is added to prevent fracture. [Means to solve the problem]

In order to solve the above-mentioned problems, the inventors studied the cause of the deterioration of heat resistance in the internal electrode paste containing the coexisting material powder. As a result, it was found that the use of the ceramic material (barium titanate) used as the dielectric of the dielectric layer directly as the coexisting material powder of the internal electrode layer is the cause of the deterioration of heat resistance.

Specifically, barium titanate having a perovskite structure is generally used among the dielectrics used in the formation of the dielectric layer. In this barium titanate, barium (Ba) occupies the A site in the crystal structure, and titanium (Ti) occupies the B site. Moreover, as disclosed in Patent Document 1 and the like, in barium titanate used as a dielectric material, in order to improve the dielectric constant, the atoms occupying the A site (Ba) and the atoms occupying the B site (Ti) The molar ratio (A/B) is controlled to be approximately 1 (for example, 1.000 or more and 1.008 or less). On the other hand, among the coexisting material powders contained in the internal electrode layer, the A/B has not been specifically studied, and A/B is used to be equivalent to the dielectric layer side (ie, A/B=1 ) Of the dielectric particles. Regarding this point, the inventors of the present invention have repeatedly conducted various experiments and studies, and as a result, surprisingly found that as the A/B becomes higher, it becomes easier to produce sintering during firing. In addition, experiments and studies were further repeated, and as a result, it was found that if dielectric particles with an A/B of 0.99 or less are used as the coexisting material powder, the occurrence of sintering can be suppressed. Furthermore, the inventors of the present invention conducted repeated experiments and found that the average particle size of the coexisting material powder also has an effect on heat resistance. Based on these findings, the inventors found that by controlling the "A/B of the dielectric particles" and the "average particle size of the coexisting material powder" within an appropriate range, it is possible to appropriately prevent sintering during firing.

The internal electrode paste disclosed here is based on the above knowledge. The internal electrode paste is a conductive paste for forming an internal electrode layer of a laminated ceramic electronic component, and includes: conductive powder; coexisting material powder composed of dielectric particles; and a dispersion medium. The dielectric particles are metal oxide particles with a perovskite structure represented by the general formula ABO ₃ (1). It should be noted that the A site in the formula (1) includes at least Ba and the B site includes at least Ti. Furthermore, the internal electrode paste disclosed here is characterized in that the molar ratio (A/B) of the atom occupying the A site to the atom occupying the B site in formula (1) is 0.89 or more and 0.99 or less, and the coexisting material The average particle size of the powder is 10 nm or more and 50 nm or less. In this way, in the internal electrode paste disclosed here, the "A/B of the dielectric particles" and the "average particle size of the coexisting material powder" are controlled within an appropriate range. Thus, although the coexisting material powder is added in order to prevent fracture, it is possible to prevent sintering during firing.

In a preferred method of the internal electrode paste disclosed here, the A site in formula (1) includes not only Ba but also selected from the group consisting of Ca, Mg, Sr, La, Zn, and Sb At least one of them. When such an element is added to the A site instead of Ba, the anti-sintering effect based on the technique disclosed here can be suitably exhibited.

In a preferred mode of the internal electrode paste disclosed here, the B site in formula (1) includes not only Ti, but also a group selected from the group consisting of Zr, Ce, Nb, Y, Dy, Ho, and Sm. At least 1 in the group. When such an element is added to the B site instead of Ti, the anti-sintering effect based on the technique disclosed here can be suitably exhibited.

In a preferred embodiment of the internal electrode paste disclosed here, the A/B is 0.96 or more. As a result, sintering during firing can be prevented more suitably.

In a preferred embodiment of the internal electrode paste disclosed herein, the amount of Ba eluted per unit time (Ba elution rate) when the coexisting material powder is impregnated in water is divided by the specific surface area of the coexisting material powder. 10 or less. In the coexisting material powder with a high "Ba elution rate/specific surface area", a large amount of Ba is eluted from the dielectric particles, which can serve as a sintering aid that promotes sintering. In this method, such elution of Ba is suppressed, and therefore, the occurrence of sintering can be suitably prevented.

In addition, as another aspect of the technology disclosed here, a method of manufacturing a laminated ceramic electronic component is provided. The manufacturing method includes: a preparation step of preparing the paste for internal electrodes in any of the above methods; a applying step of applying the paste for internal electrodes to the surface of the dielectric green sheet; and a firing step of applying the paste for internal electrodes The dielectric green sheet is fired. As described above, the internal electrode paste disclosed here can prevent sintering during firing. Therefore, by using the internal electrode paste, it is possible to manufacture a multilayer ceramic electronic component which has a high-performance internal electrode layer that prevents various defects caused by the sintering of the coexisting material powder.

In a preferable aspect of the manufacturing method disclosed here, the following high-speed firing is performed in the firing step: the temperature increase rate from room temperature to the highest firing temperature is 600° C./hour or more. In the internal electrode paste with A/B of 0.99 or less, the number of atoms occupying the A site of the dielectric particles decreases. Therefore, in the firing step, elements (Ba, Ca, etc.) that can occupy the A site move from the dielectric layer side to the internal electrode layer side, which may cause defects such as a decrease in the dielectric constant of the firing dielectric layer. Happening. Therefore, in the case of using a paste for internal electrodes with A/B of 0.99 or less, it is preferable to perform high-speed firing as in this embodiment before the elements move from the dielectric layer side to the internal electrode layer side. , The dielectric layer and the internal electrode layer are sintered.

Hereinafter, suitable embodiments of the present invention will be described. It should be noted that the matters necessary to implement the present invention other than the matters specifically mentioned in this specification can be implemented based on the general technical knowledge of a person skilled in the art in the prior art in the field. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in the field. It should be noted that the expression "A to B" that indicates the numerical range in this manual means "A or more and B or less".

[Paste for Internal Electrodes] The paste for internal electrodes disclosed here is a conductive paste for forming internal electrode layers of multilayer ceramic electronic components. The internal electrode paste contains (A) conductive powder, (B) coexisting material powder, and (C) dispersion medium as main constituent components. In addition, the (B) coexisting material powder of the internal electrode paste contains metal oxide particles (typically barium titanate (BaTiO ₃ )) having a perovskite structure represented by ABO ₃ as dielectric particles.

Furthermore, for the internal electrode paste disclosed here, the molar ratio (A/B) of the atoms occupying the A site and the atoms occupying the B site of the dielectric particles is 0.89 or more and 0.99 or less, and the coexisting material powder The average particle size is 10 nm or more and 50 nm or less. According to experiments conducted by the inventors, it was confirmed that by using the paste for internal electrodes, sintering during firing can be prevented. Hereinafter, the internal electrode paste disclosed here will be specifically described.

(A) Conductive powder The conductive powder only needs to be a material that can become a main component of highly conductive conductive objects (which may be conductive films) such as electrodes, wires, and conductive films in electronic components. That is, among the conductive powders, various powder materials having desired conductivity can be used without particular limitation. As an example of the conductive powder, nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu), ruthenium (Ru), rhodium (Rh) ), osmium (Os), iridium (Ir), aluminum (Al), tungsten (W) and other metals, and alloys containing these metals. In addition, the conductive powder may be used alone or in combination of two or more of the metal materials. It should be noted that among the conductive powders, it is preferable to use a metal material having a melting point lower than the sintering temperature (for example, about 1300° C.) of the dielectric layer of MLCC. As an example of such a metal material having a melting point, Rh, Pt, Pd, Cu, Au, and Ni can be given. Among them, from the viewpoint of melting point and conductivity, noble metals such as Pt and Pd are preferred. However, if low price is also considered, Ni is preferred. It should be noted that the conductive powder can be produced by a conventionally known method, and it is not limited to the production by a special method. For example, a metal powder produced by a well-known reduction precipitation method, gas phase reaction method, gas reduction method, etc. can be used as the conductive powder.

The content rate of the conductive powder in the paste for internal electrodes is not specifically limited, It can adjust suitably as needed. It should be noted that, from the viewpoint of forming an internal electrode layer with excellent conductivity and high density, when the total weight of the internal electrode paste is 100% by mass, the content of the conductive powder is preferably 30% by mass or more , It is more preferably 40% by mass or more, and still more preferably 45% by mass or more. On the other hand, the upper limit of the content rate of conductive powder is not specifically limited, It may be 95 mass% or less. However, in consideration of reducing the viscosity of the paste and improving workability, the upper limit of the content of the conductive powder is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less.

In addition, the size (particle diameter) of the particles constituting the conductive powder (hereinafter also referred to as “conductive particles”) is not particularly limited, and the size applicable to such internal electrode paste can be used without limitation. For example, the average particle diameter of the conductive powder may be about several nm to several tens of μm. It should be noted that the "average particle diameter" in this specification refers to D ₅₀ (median particle diameter) in the particle size distribution of the powder material. The D ₅₀ can be measured, for example, by a particle size distribution measuring device based on a conventionally known laser diffraction method, a light scattering method, or the like.

It should be noted that when the internal electrode layer is thinned in order to produce a small MLCC, the size of the conductive powder is required to be smaller than the thickness of the internal electrode layer (dimension in the stacking direction). For example, the cumulative 90% particle size (D ₉₀ ) of the conductive powder when making a small MLCC is preferably less than 3 μm, more preferably less than 2 μm, still more preferably less than 1.5 μm, particularly preferably less than 1.2 μm, for example, less than 1 μm. In addition, from the viewpoint of stably forming the internal electrode layer of a small MLCC, the average particle size (D ₅₀ ) of the conductive powder is usually set to 1 μm or less, preferably 0.8 μm or less, more preferably 0.6 μm or less, and more preferably It is 0.5 μm or less, particularly preferably 0.4 μm or less, for example, 0.3 μm or less. In addition, if such a conductive powder with a small average particle size is used, it is also possible to form an internal electrode layer with a smooth surface (typically with an arithmetic average roughness Ra of 5 nm or less). On the other hand, the lower limit of the average particle size (D ₅₀ ) of the conductive powder is not particularly limited, and may be 0.005 μm or more, or may be 0.01 μm or more. However, in consideration of preventing aggregation of conductive particles due to an increase in surface activity, the lower limit of the average particle size of the conductive powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.12 μm or more.

In addition, from the viewpoints of suppressing aggregation of conductive particles and improving the homogeneity, dispersibility, and storage stability of the prepared paste, the specific surface area of the conductive powder is preferably 10 m ² /g or less (typically 1 m ² /g~8 m ² /g, for example, 2 m ² /g~6 m ² /g). In addition, the conductive powder having such a specific surface area can also contribute to improving the conductivity of the internal electrode layer after firing. It should be noted that the "specific surface area" in this specification refers to the gas adsorption amount measured based on the gas adsorption method (constant volume adsorption method) using nitrogen (N ₂ ) gas as the adsorbate, according to the BET method (for example BET one point method) and calculated value (BET specific surface area).

The shape of the conductive particles is not particularly limited, and may be spherical or non-spherical (for example, a football shape). In addition, from the viewpoint of suppressing the increase in the viscosity of the paste, the shape of the conductive particles is preferably spherical or substantially spherical. For example, the average aspect ratio of the conductive particles can be typically 1 to 2, preferably 1 to 1.5. It should be noted that the "aspect ratio" in this specification refers to the length of the long side (b) relative to the length of the short side when a rectangle that circumscribes the particles constituting the powder is calculated based on electron microscope observation (A) Ratio (b/a). The average aspect ratio is the arithmetic average of the aspect ratios obtained for 100 particles.

(B) Coexisting material powder The internal electrode paste disclosed here contains coexisting material powder. The coexisting material powder is composed of dielectric particles (metal oxide particles) having a composition similar to that of the dielectric layer of MLCC. By dispersing the dielectric particles between the conductive particles, the firing behavior (thermal shrinkage rate, firing shrinkage history, thermal expansion coefficient) of the internal electrode paste and the dielectric green sheet can be approximated, which can prevent Occurrence of cracks after firing.

In the internal electrode paste disclosed here, as the dielectric particles constituting the coexisting material powder, metal oxide particles having a perovskite structure represented by the following formula (1) are used. ABO ₃ (1)

The dielectric particles represented by the formula (1) are metal oxide particles based on barium titanate (BaTiO ₃ ). That is, in the formula (1), the A site contains at least barium (Ba), and the B site contains at least titanium (Ti). It should be noted that, in the A position in the formula (1), elements other than Ba may be added. Examples of elements that can occupy the A site in addition to Ba include calcium (Ca), magnesium (Mg), strontium (Sr), lanthanum (La), zinc (Zn), antimony (Sb), and the like. On the other hand, like the B site, elements other than Ti may be added. Examples of elements that can occupy the B site in addition to Ti include zirconium (Zr), cerium (Ce), niobium (Nb), yttrium (Y), dysprosium (Dy), 鈥 (Ho), samarium (Sm), etc. .

Moreover, in the internal electrode paste disclosed here, "(1) Mole of atoms occupying A site (hereinafter referred to as "A site atom") and atoms occupying B site (hereinafter referred to as "B site atom") Ratio (A/B)" and "(2) Average particle size of coexisting material powder" are controlled within the specified range. Thereby, the occurrence of necking in the firing step can be prevented. Hereinafter, each element controlled in the internal electrode paste disclosed here will be specifically described.

(1) The molar ratio of atom A to atom B (A/B) In the dielectric layer side of a general MLCC, in order to improve the dielectric constant, the A/B of the dielectric particles is controlled to be 1 or more. However, as a result of research conducted by the present inventors, it was determined that if the A/B of the dielectric particles added as the coexisting material powder of the internal electrode layer increases, sintering during firing is likely to occur. It is not intended to limit the present invention, but the reason for this phenomenon is presumed to be that if the ratio of A-site atoms in the dielectric particles increases, the A-site atoms (typically Ba) become easy to elute into the crystal structure. Externally, the eluted A-site atoms function as a sintering aid. In contrast, in the internal electrode paste disclosed here, the molar ratio (A/B) of the A-site atoms and the B-site atoms (typically Ti) constituting the dielectric particles is controlled to be 0.99 or less. Therefore, it is possible to suppress the elution of A-site atoms to function as a sintering aid, and to suppress sintering during firing. In addition, from the viewpoint of more suitably suppressing sintering during firing, the upper limit of A/B is preferably 0.98 or less, more preferably 0.975 or less, and still more preferably 0.97 or less. On the other hand, for the internal electrode paste disclosed here, the lower limit of A/B is set to 0.89 or more. Therefore, the dielectric particles in the paste have an effect of becoming less likely to react with the dielectric layer of the MLCC during firing. . From the viewpoint of more suitably exerting the effect, the lower limit of the A/B is preferably 0.90 or more, more preferably 0.91 or more, still more preferably 0.92 or more, particularly preferably 0.96 or more.

It should be noted that the "molar ratio (A/B) of the atoms at the A site and the atoms at the B site" can be determined as follows: the coexisting material powder is subjected to fluorescent X-ray analysis by the glass bead method. In this fluorescent X-ray analysis, a calibration curve is prepared using standard samples with different compositions of Ba and Ti, and by using the calibration curve, the molar ratio can be obtained. It should be noted that the same applies to the embodiments described later.

In addition, in the internal electrode paste disclosed here, it was confirmed that the amount of Ba eluted per unit time (ppm/hour) when the coexisting material powder was immersed in water was divided by the specific surface area of the coexisting material powder (m ² / g) The obtained value (Ba elution rate/specific surface area) becomes lower, and the sintering suppression effect tends to be improved. It should be noted that, from the viewpoint of more suitably exerting the sintering suppression effect, the "Ba dissolution rate/specific surface area" is suitably 10 or less, preferably 8 or less, more preferably 7 or less, and still more preferably 6.6 Or less, particularly preferably 6.3 or less, for example, 4.8 or less. On the other hand, the lower limit of "Ba elution rate/specific surface area" is not particularly limited, and may be 0 (Ba does not eluate), may be 0.5 or more, and may be 1 or more. It should be noted that the aforementioned "Ba dissolution amount per unit time" can be measured according to the following procedure. First, after adding alcohol (for example, ethanol) to the internal electrode paste to form a liquid state, ultrasonic dispersion is performed for 1 hour, and a magnet is placed on the bottom of the container to settle the conductive powder, and the coexisting material powder and supernatant are recovered. The coexisting material powder and supernatant obtained by repeating this step three times were dried under the temperature condition of 90°C. Then, 0.5 g of the dried sample is collected and kept in a state of being immersed in 250 ml of water for at least 100 hours (for example, 120 hours, 150 hours, 250 hours). Then, after more than 20 hours have elapsed since the start of the maintenance, a constant impregnation time was measured based on ICP (Inductively Coupled Plasma) analysis (for example, after 24 hours, 48 hours, 72 hours, 96 hours after impregnation) , 120 hours later) the elution amount of Ba above 3 points (ppm). Then, the Ba eluted amount was plotted against the immersion time, and the slope was calculated as the "Ba eluted amount per unit time". It should be noted that when calculating the slope, it is better to use the least square method. In addition, as described in detail later, a resin component such as a binder may be added to the internal electrode paste. When adding such a resin component, it is preferable to subject the dried sample to a degreasing treatment (for example, heat treatment at 430° C. in an air atmosphere). In addition, the specific surface area of the coexisting material powder can be measured in the same procedure as the specific surface area of the conductive powder. It should be noted that, from the viewpoint of suppressing the elution of Ba from the dielectric particles, the specific surface area of the coexisting material powder is preferably 80 m ² /g or less, preferably 50 m ² /g or less, and more preferably 30 m ² /g or less, preferably 20 m ² /g or less.

(2) Average particle size of the coexisting material powder Further, in the internal electrode paste disclosed here, the average particle size (D ₅₀ ) of the coexisting material powder is controlled to be 10 nm or more and 50 nm or less. As the average particle size of the coexisting material powder becomes smaller, the surface activity of the dielectric particles becomes higher and becomes easy to aggregate. Therefore, even if the A/B of the dielectric particles is controlled to 0.99 or less, if the average particle size of the coexisting material powder becomes excessively large, necking may occur during firing. Considering this point, in the internal electrode paste disclosed here, the average particle size of the coexisting material powder is controlled to 10 nm or more. On the other hand, if the average particle size of the coexisting material powder is excessively large, the dielectric in the internal electrode layer will increase regardless of the presence or absence of necking, which may reduce the performance of the MLCC. Therefore, in the internal electrode paste disclosed here, the average particle size of the coexisting material powder is controlled to 50 nm or less. It should be noted that, from the viewpoint of more suitably preventing necking during firing and preventing performance degradation of the internal electrode layer, the average particle size of the coexisting material powder is preferably 20 nm or more and 50 nm or less, more preferably 30 nm or more and 50 nm or less, more preferably 35 nm or more and 50 nm or less.

As above, according to the internal electrode paste disclosed here, the A/B of the dielectric particles is controlled to be 0.89 or more and 0.99 or less, and the average particle size of the coexisting material powder is controlled to be 10 nm or more and 50 nm or less. In order to prevent fracture, the coexisting material powder is added, but sintering during firing can still be prevented.

(C) Dispersion medium The dispersion medium is a liquid medium in which powder materials (conductive powder, coexisting material powder, etc.) are dispersed. The detailed components of the dispersion medium are not particularly limited, and organic solvents that can be used in such internal electrode pastes can be suitably used. In addition, the dispersion medium is a component on the premise that it disappears by drying and firing. Therefore, it preferably contains a high boiling point with a boiling point of about 180°C or higher and 300°C or lower (for example, 200°C or higher and 250°C or lower). The organic solvent is the main component. In addition, the "main component" here refers to a component that accounts for 50 vol% or more when the total volume of the dispersion medium is 100 vol%.

In addition, from the viewpoint of film formation stability and the like, the dispersion medium is preferably one that can impart excellent fluidity while maintaining the dispersibility of the powder material. Examples of such dispersion media include sclareol, citronellol, phytol, geranyllinalool, Texanol, benzyl alcohol, phenoxyethanol, 1-phenoxy-2-propanol , Terpineol, dihydroterpineol, isobornol, butyl carbitol, diethylene glycol and other alcohol solvents; terpine acetate, dihydroterpine acetate, isobornyl acetate, carbitol acetate Esters, diethylene glycol monobutyl ether acetate and other ester solvents; mineral essential oils, etc. Among them, alcohol-based solvents and ester-based solvents can be preferably used.

In addition, the content ratio of the dispersion medium in the paste for internal electrodes is preferably adjusted appropriately in consideration of workability when applying to the surface of the dielectric green sheet. The workability at the time of surface imparting (printing) can also vary depending on other components, so it is not particularly limited. For example, when the total weight of the paste is 100% by mass, the content of the dispersion medium can be 70% by mass or less (more It is preferably 5 mass% to 60 mass%, more preferably 30 mass% to 50 mass%). Thereby, suitable fluidity can be imparted to the paste, the workability during surface application can be improved, the leveling properties of the paste can be improved, and an internal electrode layer with a smoother surface can be formed.

(D) Other ingredients As long as the internal electrode paste disclosed here does not impair the anti-sintering effect, the components that can be used in such internal electrode paste can be used without particular limitation. Hereinafter, an example of other components that can be used in the internal electrode paste disclosed here will be described.

(1) Adhesive The binder is an organic component that contributes to the improvement of the anchoring property to the surface of the dielectric green sheet and the bonding of the particles in the paste. In addition, when the binder is dissolved in the dispersion medium, it can function as an excipient (which may be a liquid phase medium). In addition, like the dispersion medium, the binder is a component on the premise that it disappears by firing. Therefore, the binder is preferably an organic compound (typically an organic compound with a firing temperature of 500° C. or lower) that is easily burned out during firing. The components of the specific binder are not particularly limited, and known organic compounds that can be used in the internal electrode paste can be used without particular limitations. Examples of the binder include rosin resins, cellulose resins, polyvinyl alcohol resins, polyvinyl acetal resins, acrylic resins, polyurethane resins, epoxy resins, and phenolic resins. , Polyester resin, vinyl resin and other organic polymer compounds. It also depends on the combination with the dispersion medium. Therefore, it cannot be generalized. Among these organic compounds, cellulose resins, polyvinyl alcohol resins, polyvinyl acetal resins, acrylic resins, etc. are used as binders. suitable. In addition, any one of the organic compounds described above may be used for the binder, or two or more of them may be used in combination. Furthermore, it is not clearly described, but copolymers, block copolymers, etc. obtained by copolymerizing monomer components of any two or more of the resins described above may also be used.

In addition, the content ratio of the binder in the internal electrode paste is not particularly limited, and it is preferable to appropriately adjust the content of the conductive powder in consideration of the appropriate anchoring properties. For example, when the content of the conductive powder is set to 100 parts by mass, the content of the binder is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 1.5 parts by mass or more, particularly preferably 2 parts by mass More than. On the other hand, from the viewpoint of preventing performance degradation of the internal electrode layer caused by the remaining binder after the firing step, the content of the binder relative to 100 parts by mass of the conductive powder is preferably 10 parts by mass or less, more preferably It is 7 parts by mass or less, more preferably 5 parts by mass or less, particularly preferably 4 parts by mass or less.

(2) Dispersant The dispersant is used to suppress the aggregation of inorganic particles (conductive particles, dielectric particles, etc.) in the paste. Specifically, as the dispersant, an organic compound having a function of stabilizing the solid-liquid interface between the inorganic particles and the dispersion medium and preventing the aggregation of the inorganic particles can be used. It should be noted that, as described above, as the internal electrode layer becomes thinner, the diameter of the inorganic powder tends to be reduced. The dispersant is suitably used when such an inorganic powder with a small particle diameter (typically an inorganic powder with an average particle diameter of 1 μm or less) is used. The type of the dispersant and the like are not particularly limited, and one or two or more kinds can be selected from various known dispersants as necessary. As a specific example of a dispersing agent, a surfactant type dispersing agent (also referred to as a low molecular type dispersing agent), a polymer type dispersing agent, an inorganic type dispersing agent, etc. are mentioned.

It should be noted that as surfactant-type dispersants, for example, a dispersant mainly composed of alkyl sulfonates, a dispersant mainly composed of quaternary ammonium salts, and alkylene oxide compounds composed mainly of higher alcohols may be mentioned. Dispersant, polyol ester compound-based dispersant, alkyl polyamine compound-based dispersant, etc. In addition, examples of polymer-type dispersants include: dispersants mainly composed of fatty acid salts such as carboxylic acids or polycarboxylic acids, and polycarbonates in which hydrogen atoms in a part of the carboxylic acid groups are substituted by alkyl groups. A dispersant mainly composed of a carboxylic acid partial alkyl ester compound, a dispersant mainly composed of a polycarboxylic acid alkylamine salt, and a polycarboxylic acid partial alkyl ester compound having an alkyl ester bond in a part of the polycarboxylic acid Main dispersant, polystyrene sulfonate, polyisoprene sulfonate, polyalkylene polyamine compound as the main dispersant, naphthalene sulfonate, naphthalenesulfonate formaldehyde condensate salt, etc. Dispersant based on acid compounds, dispersant based on hydrophilic polymers such as polyethylene glycol, dispersant based on polyether compounds, poly(meth)acrylate, poly(meth)propylene Dispersants mainly composed of poly(meth)acrylic compounds such as amides. It should be noted that among the dispersants, polymer-based dispersants can exhibit the repelling effect caused by steric hindrance and enable the inorganic powder to be effectively dispersed over a long period of time, so it is suitable. In addition, the weight average molecular weight of such a polymer-type dispersing agent is not specifically limited, As a suitable example, it is about 300-50,000 (for example, 500-20000). In addition, as an inorganic dispersant, for example, a dispersant mainly composed of the following substances: orthophosphate, metaphosphate, polyphosphate, pyrophosphate, tripolyphosphate, hexametaphosphate, and organic Phosphates such as phosphate, iron sulfate, ferrous sulfate, ferric chloride, and iron salts such as ferrous chloride, aluminum sulfate, polyaluminum chloride, and aluminum salts such as sodium aluminate, calcium sulfate, calcium hydroxide, and Calcium salts such as dibasic calcium phosphate. In the internal electrode paste disclosed here, any one of the above-mentioned components may be included alone, or a combination of two or more of them may be included as a dispersant.

(3) Additives In the internal electrode paste disclosed here, in addition to the binder and dispersant, thickeners, plasticizers, pH adjusters, stabilizers, levelers, defoamers, antioxidants, and anticorrosive agents can be added. Agents, colorants (pigments, dyes, etc.), etc. Regarding these, substances that can be used in general internal electrode pastes can be used without particular restrictions, and therefore, detailed descriptions are omitted.

In addition, when considering the purpose of preventing the sintering of the coexisting material powder, it is preferable that substantially no sintering aid is added to the internal electrode paste disclosed here. Examples of the sintering aid include barium carbonate (BaCO ₃ ), calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), zinc oxide (ZnO), lanthanum oxide (La ₂ O ₃ ), and the like. In addition, in this specification, "the sintering aid is not substantially added" means that there is no intention to add a component that can be interpreted as a sintering aid. Therefore, it can be construed that when the components of the sintering aid are derived from raw materials, manufacturing steps, etc. and are included in a small amount, the concept of "substantially not adding a sintering aid" is included in this specification. For example, relative to 100 mol% of the coexisting material powder, it can be explained that the content of the sintering aid component is 0.01 mol% or less (preferably 0.005 mol% or less, more preferably 0.001 mol% or less, and further preferably 0.0005 mol% or less , Particularly preferably 0.0001 mol% or less), it can be said to be "substantially not added".

[use] Above, the internal electrode paste disclosed here has been described. The internal electrode paste disclosed here can be used to manufacture multilayer ceramic electronic parts (such as multilayer ceramic capacitors (MLCC)). Next, the manufacturing method disclosed here will be described. The manufacturing method includes at least: (A) a preparation step, (B) an application step, and (C) a firing step.

(A) Preparation steps In this step, the internal electrode paste disclosed here is prepared. Generally, the internal electrode paste is prepared by dispersing conductive powder and coexisting material powder in a dispersion medium. It is not particularly limited, but it is preferable to separately prepare a conductive powder slurry in which conductive powder is dispersed in a dispersion medium and a coexistent material powder slurry in which a coexistent material powder is dispersed in a dispersion medium, and mix them to prepare an internal electrode Use paste. Thereby, a paste in which conductive powder and coexisting material powder are highly dispersed can be easily obtained. In addition, the stirring and mixing of materials can be performed using conventionally well-known various stirring and mixing apparatuses, for example, a roll mill, a magnetic stirrer, a planetary stirrer, a disperser, etc.

Furthermore, in the manufacturing method disclosed here, in this step, an internal electrode is prepared in which the A/B of the dielectric particles is 0.89 or more and 0.99 or less, and the average particle size of the coexisting material powder is 10 nm or more and 50 nm or less Use paste.

In addition, the means for preparing the coexisting material powder having an average particle diameter of 10 nm or more and 50 nm or less can be a conventionally known means, so it is not particularly limited. For example, by pulverizing and classifying the coexisting material powder having a predetermined average particle diameter, the average particle diameter of the coexisting material powder can be adjusted to 10 nm or more and 50 nm or less.

(B) Granting steps In the applying step, the internal electrode paste is applied to the surface of the dielectric green sheet. As a method of applying the paste for internal electrodes, for example, printing methods such as screen printing, gravure printing, offset printing, and inkjet printing, spray coating methods, and coating methods such as dip coating methods can be used. Among them, a gravure printing method, a screen printing method, an inkjet printing, etc., capable of applying precision paste at high speed can be suitably used.

(C) Firing steps In the firing step, the dielectric green sheet to which the paste for internal electrodes is applied is fired at a predetermined temperature. In this way, a dielectric layer having an internal electrode layer formed on the surface can be obtained. It should be noted that the firing temperature (maximum firing temperature) in this step is preferably about 500°C to 1500°C, more preferably about 1000°C to 1500°C.

In addition, when using the paste for internal electrodes disclosed here, it is preferable to perform high-speed baking in a baking process. The "high-speed firing" in this manual refers to shortening the time until the highest firing temperature is reached by increasing the heating rate at the beginning of the firing step. If the internal electrode paste disclosed here is used, in the firing step, elements (Ba, Ca, etc.) that can occupy the A site move from the dielectric layer side to the internal electrode layer side, and there is a fired dielectric Possibility of lowering the dielectric constant of the layer. Considering this point, it is preferable to perform high-speed firing. At the beginning of the firing step, the dielectric layer and the internal electrode layer are sintered to suppress the movement of A-site atoms from the dielectric layer to the internal electrode layer. It should be noted that the temperature increase rate in the high-speed firing is preferably 600°C/hour or higher, more preferably 1000°C/hour or higher, still more preferably 2500°C/hour or higher, particularly preferably 5000°C/hour or higher. In addition, the firing time (holding time at the highest temperature) when high-speed firing is performed is preferably 20 minutes or less (typically 5 minutes to 20 minutes, for example, about 10 minutes).

(D) Degreasing step It should be noted that, in the manufacturing method disclosed here, it is preferable to provide a (D) degreasing step between the (B) printing step and (C) the firing step. In this degreasing step, the internal electrode paste is heated at a temperature lower than the temperature of the firing step to remove organic materials (dispersion medium, binder, etc.) in the paste. Thereby, it is possible to appropriately prevent the firing failure caused by the residue of the organic material. It should be noted that the maximum temperature in the degreasing step is preferably about 100°C to 1000°C, more preferably about 300°C to 800°C. In addition, the temperature increase rate in the degreasing step is preferably 100°C/hour to 400°C/hour, and the heating time (holding time at the highest temperature) is preferably 1 hour or more (for example, 6 hours or more).

[Multilayer ceramic capacitors] Next, a multilayer ceramic capacitor (MLCC) as an example of a multilayer ceramic electronic component manufactured using the internal electrode paste disclosed here will be described. Fig. 1 is a schematic cross-sectional view schematically illustrating the structure of an MLCC.

As shown in FIG. 1, a multilayer ceramic capacitor (MLCC) 1 is a chip-type capacitor in which a plurality of dielectric layers 20 and internal electrode layers 30 are alternately and integrally laminated. A pair of external electrodes 40 are provided on the side surfaces of the laminated sheet 10 formed of the dielectric layer 20 and the internal electrode layer 30. As an example, the internal electrode layers 30 are alternately connected to different external electrodes 40 in the order of stacking. As a result, it is possible to construct a small and large-capacity MLCC in which a capacitor structure formed by the dielectric layer 20 and a pair of internal electrode layers 30 sandwiching the dielectric layer 20 are connected in parallel. In addition, the internal electrode layer 30 of the MLCC 1 is formed by firing the internal electrode paste disclosed here. As described above, the internal electrode paste disclosed here can prevent sintering during firing, and therefore, can form a high-performance internal electrode layer 30 that prevents various defects caused by the sintering of the coexisting material powder.

[Test Example] Next, several test examples related to the present invention will be described, but it is not intended to limit the content shown in the test examples of the present invention.

[1] The first test In this test, two types of internal electrode pastes with different A/B of the dielectric particles were prepared, and the respective internal electrode pastes were fired.

(1) Preparation of samples Prepare a paste for internal electrodes (sample 1, sample 2) in which conductive powder, coexisting material powder, and binder (ethyl cellulose) are dispersed in a dispersion medium (isobornyl acetate). Here, among the conductive powders, Ni powder having an average particle diameter of 0.2 μm is used. In addition, as the coexisting material powder, BaTiO ₃ powder with an average particle diameter of 50 nm was used. In addition, the addition amount of the coexisting material powder (BaTiO ₃ powder) was set to 15 wt% of the conductive powder (Ni powder). Then, in this test, the A/B of the dielectric particles (BaTiO ₃ ) constituting the coexisting material powder was different in each of samples 1 and 2. Table 1 shows A/B of each sample.

(2) Heat resistance evaluation For samples 1 and 2, respectively, a degreasing step (heating time: 20 minutes, heating atmosphere: N ₂ gas) of heating up to 600° C. at a heating rate of 200° C./hour was performed to remove the binder. Thereafter, a firing step (heating time: 10 minutes, heating atmosphere: 1% H ₂ gas mixed with N ₂ gas) of heating up to 1250° C. at a heating rate of 7000° C./hour was implemented. Then, an SEM photograph of each sample after firing was taken, and the particle size distribution was analyzed to determine D ₁₀ , D ₅₀ , and D ₉₀ . The SEM photograph of sample 1 is shown in FIG. 2, and the SEM photograph of sample 2 is shown in FIG. 3. In addition, D ₁₀ , D ₅₀ , and D _{90 of} each sample are shown in Table 1. Then, based on the SEM photograph and the analysis result of the particle size distribution, the case where it was determined that sintering occurred in the dielectric particles was evaluated as heat resistance "×", and the case where it was determined that sintering was suppressed was evaluated as heat resistance "○".

[Table 1]

In sample 1 with an A/B of 1.000, BaTiO ₃ particles with a large particle size adhered to the surface of Ni particles (see FIG. 2). On the other hand, in sample 2 with A/B of 0.96, the particle size of the BaTiO ₃ particles on the surface of the Ni particles became smaller (see FIG. 3). Moreover, as shown in Table 1, in Sample 1, D ₁₀ , D ₅₀ , and D ₉₀ were all increased in particle size as a whole, while in Sample 2, the increase in particle size was suppressed. From these results, it is understood that the A/B of the dielectric particles affects the heat resistance of the internal electrode paste, and as the A/B decreases, sintering tends to be suppressed.

[2] The second test Next, in this test, the specific composition conditions of the internal electrode paste that can appropriately prevent the occurrence of sintering were investigated.

(1) Preparation of samples In this experiment, on the basis of the samples 1 and 2, 7 kinds of coexisting material powders (BaTiO ₃ ) with different A/B and average particle diameters (D ₅₀ ) of the dielectric particles were prepared. Powder), using these coexisting material powders to prepare internal electrode paste (sample 1 to sample 9). It should be noted that the components other than the coexisting material powder in samples 3 to 9 are the same as those in sample 1.

(2) Evaluation of heat resistance Following the same procedure as the first test, the heat resistance of each sample was evaluated. That is, after performing a degreasing step and a firing step on the internal electrode paste of each sample, surface SEM observation and particle size distribution analysis were performed, and based on these results, the heat resistance was evaluated. The results are shown in Table 2.

[Table 2]

As shown in Table 2, among the test objects, Sample 2, Sample 4, and Sample 9 have high heat resistance and can prevent sintering during firing. From this, it can be seen that if the A/B of the dielectric particles is 0.89 to 0.99 and the average particle size is 10 nm or more and 50 nm or less coexisting material powder, it is possible to appropriately prevent sintering during firing.

[3] The third test In this test, the amount of Ba eluted in samples 1 to 9 used in the second test was investigated.

(1) Measurement of specific surface area In this test, first, the BET specific surface area (m ² /g) of sample 1 to sample 9 is measured. It should be noted that the specific procedure for measuring the specific surface area has already been described, so detailed description is omitted here. The measurement results are shown in Table 3.

(2) Determination of Ba dissolution Next, the coexisting material powder was extracted from the internal electrode paste of each sample, and the extracted coexisting material powder was impregnated in water to obtain the "Ba eluted amount per unit time (ppm/hour)". Then, the value obtained by dividing the "Ba eluted amount per unit time" by the "specific surface area" (Ba eluted rate/specific surface area) is calculated. It should be noted that the specific procedure for measuring the "Ba eluted amount per unit time" has already been described, and therefore, the detailed description is omitted here. The measurement results are shown in Table 3.

[table 3]

As described above, in the second test, it was confirmed that in samples 2, samples 4, and 9 with high heat resistance, the "Ba elution rate/specific surface area" tended to be lower than those of other samples. According to the result, in the coexisting material powder with the A/B of the dielectric particles of 0.99 or less, the elution of Ba from the dielectric particles is suppressed, which can be interpreted as an influence on the suppression of sintering. From this, it is inferred that the reason why sintering can be prevented in the internal electrode paste having A/B of the dielectric particles of 0.99 or less is that the elution of Ba that can function as a sintering aid is suppressed.

The present invention has been described in detail above, but these are only examples, and various changes can be made to the present invention without departing from the gist of the invention.

1: Multilayer ceramic capacitor (MLCC) 10: Multilayer film 20: Dielectric layer 30: Internal electrode layer 40: External electrode

1 is a schematic cross-sectional view schematically illustrating the structure of an MLCC manufactured by a manufacturing method according to an embodiment of the present invention. Fig. 2 is a SEM photograph (10000 times) of the surface of sample 1 after firing. Fig. 3 is a SEM photograph (10000 times) of the surface of sample 2 after firing.

Claims (7)

A paste for internal electrodes for forming internal electrode layers of laminated ceramic electronic parts, the paste for internal electrodes is characterized by comprising: conductive powder; coexisting material powder composed of dielectric particles; and a dispersion medium, said The dielectric particles are metal oxide particles having a perovskite structure represented by the following general formula (1), ABO ₃ (1) (here, the A position in the formula (1) includes at least Ba and B Site contains at least Ti), the molar ratio (A/B) of the atom occupying the A site to the atom occupying the B site in the formula (1) is 0.89 or more and 0.99 or less, and the average particle size of the coexisting material powder The diameter is 10 nm or more and 50 nm or less. The internal electrode paste according to claim 1, wherein the A position in the formula (1) includes not only the Ba but also a group selected from the group consisting of Ca, Mg, Sr, La, Zn, and Sb At least one of them. The internal electrode paste according to claim 1 or claim 2, wherein the B position in the formula (1) includes not only the Ti, but also selected from Zr, Ce, Nb, Y, Dy, Ho, At least one of the group consisting of Sm. The internal electrode paste according to any one of claims 1 to 3, wherein the A/B is 0.96 or more. The internal electrode paste according to any one of claims 1 to 4, wherein the amount of Ba eluted per unit time when the coexisting material powder is immersed in water is divided by the specific surface area of the coexisting material powder The obtained value is 10 or less. A manufacturing method of laminated ceramic electronic parts, including: The preparation step is to prepare the internal electrode paste described in any one of claim 1 to claim 5; An applying step, applying the internal electrode paste to the surface of the dielectric green sheet; and In the firing step, the dielectric green sheet to which the internal electrode paste is applied is fired. The method for manufacturing a multilayer ceramic electronic component according to claim 6, wherein in the firing step, the following high-speed firing is performed: the temperature increase rate from room temperature to the highest firing temperature is 600° C./hour or more.

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