JP2020188111A - Paste for internal electrode, and manufacturing method of laminate ceramic electronic component - Google Patents

Abstract

To provide a paste for an internal electrode, which can prevent the sintering during calcination while common material powder is added thereto for preventing a crack.SOLUTION: A paste for an internal electrode comprises: conductive powder; common material powder configured of dielectric particles; and a dispersion medium. The dielectric particles are metal oxide particles having a perovskite structure represented by the following general formula: ABO3. In the above formula, an A site includes at least Ba, and a B site contains at least Ti. Further in the paste for an internal electrode, the mole ratio (A/B) of atoms that occupy the A site in the above formula to atoms that occupy the B site is 0.89 to 0.99, and the average particle size of the common material powder is 10 nm or larger and 50 nm or smaller. According to this, sintering during calcination can be prevented while the common material powder for preventing a crack is added thereto.SELECTED DRAWING: None

Description

The present invention relates to an internal electrode paste. More specifically, the present invention relates to an internal electrode paste used for forming an internal electrode layer of a laminated ceramic electronic component.

A multilayer ceramic capacitor (MLCC) has a structure in which a large number of dielectric layers containing a dielectric (ceramic material) and an internal electrode layer containing a conductive metal are laminated. In this MLCC, a paste for an internal electrode, which is a precursor of an internal electrode layer, is applied to the surface of a dielectric green sheet, which is a precursor of a dielectric layer, and then co-firing is performed in a state where a large number of the dielectric green sheets are laminated. It is made by doing.

Patent Documents 1 and 2 disclose techniques relating to such a dielectric layer of MLCCs. For example, in Patent Document 1, a dielectric powder in which a Ti-rich and rare earth element-dissolved layer is formed on the outermost layer of core particles made of barium titanate (BaTIO ₃ ), and the surface thereof is coated with a Ba compound. Is disclosed. By using such a dielectric powder, it is possible to prevent the occurrence of a short circuit in the MLCC in which the dielectric layer is thinned. Further, Patent Document 2 discloses a method for producing barium titanate particles having a fine and uniform particle diameter and having a rectangular shape as barium titanate particles suitable for the dielectric layer of MLCC. There is.

By the way, when the paste for the internal electrode and the dielectric green sheet are co-baked, cracks (breakage) or the like may occur in the internal electrode layer due to the difference in the behavior during firing (firing start temperature, firing shrinkage rate, etc.). .. Therefore, in the MLCC manufacturing process, a ceramic material of the same type as the dielectric used for the dielectric layer is added to the internal electrode paste as a co-material powder, and the behavior of the internal electrode paste and the dielectric green sheet during behavior. Is being approximated.

Japanese Unexamined Patent Publication No. 2013-163614 JP-A-2017-202942

However, the paste for internal electrodes containing the co-material powder has a problem of deterioration in heat resistance. Specifically, in the paste for internal electrodes containing the co-material powder, excessive sintering (grain growth) may occur during firing, which may cause various defects in the internal electrode layer after formation. The present invention has been made to solve such a problem, and provides a paste for an internal electrode that can prevent sintering during firing even though a co-material powder is added to prevent cracks. The purpose is.

In order to solve the above-mentioned problems, the present inventors have investigated the cause of deterioration of heat resistance in the paste for internal electrodes containing the co-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 as it is as the co-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 as the dielectric used for forming the dielectric layer. In this barium titanate, barium (Ba) occupies the A site in the crystal structure, and titanium (Ti) occupies the B site. Then, as disclosed in Patent Document 1 and the like, in barium titanate used as a dielectric, an atom (Ba) occupying the A site and an atom occupying the B site are used to improve the dielectric constant. The molar ratio (A / B) with (Ti) is controlled to be approximately 1 (for example, 1.000 or more and 1.008 or less). On the other hand, in the co-material powder contained in the internal electrode layer, the above A / B has not been particularly studied, and dielectric particles having an A / B of the same level as that of the dielectric layer side (that is, about A / B = 1) are contained. It was used. As a result of various experiments and studies on this point, the present inventors have found a surprising finding that the higher the A / B is, the more likely the sintering occurs during firing. As a result of further experiments and studies, it was discovered that the occurrence of sintering can be suppressed by using dielectric particles having an A / B of 0.99 or less as a co-material powder.
Furthermore, as a result of repeated experiments, the present inventors have discovered that the average particle size of the co-material powder also affects the heat resistance, and "A / B of the dielectric particles" and "the average particle size of the co-material powder". It was found that syntaring during firing can be appropriately prevented by controlling the above to an appropriate range.

The paste for internal electrodes disclosed herein is based on the above findings. Such an internal electrode paste is a conductive paste used for forming an internal electrode layer of a laminated ceramic electronic component, and includes a conductive powder, a co-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: ABO ₃ (1). The A site in the above formula (1) contains at least Ba, and the B site contains at least Ti. The internal electrode paste disclosed herein has a molar ratio (A / B) of 0.89 or more and 0.99 or less of the atom occupying the A site and the atom occupying the B site in the formula (1). Moreover, the average particle size of the co-material powder is 10 nm or more and 50 nm or less.
As described above, in the paste for the internal electrode disclosed here, the "A / B of the dielectric particles" and the "average particle diameter of the co-material powder" are controlled in appropriate ranges, so that cracks can be prevented. Despite the addition of the co-material powder, syntaring during firing can be prevented.

In a preferred embodiment of the internal electrode paste disclosed herein, the A site in the formula (1) is at least one selected from the group consisting of Ca, Mg, Sr, La, Zn, and Sb in addition to Ba. including. Even when such an element is added to the A site instead of Ba, the anti-sintering effect of the technique disclosed herein can be appropriately exerted.

In a preferred embodiment of the internal electrode paste disclosed herein, the B site in formula (1) is at least selected from the group consisting of Zr, Ce, Nb, Y, Dy, Ho, and Sm in addition to Ti. Includes one. Even when such an element is added to the B site instead of Ti, the effect of preventing sintering by the technique disclosed herein can be appropriately exhibited.

In a preferred embodiment of the internal electrode paste disclosed herein, the A / B is 0.96 or more. Thereby, syntaring during firing can be more preferably prevented.

In a preferred embodiment of the internal electrode paste disclosed herein, a value obtained by dividing the Ba elution amount (Ba elution rate) per unit time when the co-material powder is impregnated with water by the specific surface area of the co-material powder. Is 10 or less. In this co-material powder having a high "Ba elution rate / specific surface area", a large amount of Ba can be eluted from the dielectric particles to serve as a sintering aid that promotes syntaring. In this embodiment, since such elution of Ba is suppressed, the occurrence of sintering can be suitably prevented.

Further, as another aspect of the technique disclosed herein, a method for manufacturing a laminated ceramic electronic component is provided. Such a manufacturing method includes a preparatory step of preparing the internal electrode paste of any of the above-described aspects, an application step of applying the internal electrode paste to the surface of the dielectric green sheet, and a dielectric to which the internal electrode paste is applied. It includes a firing step of firing a body green sheet.
As described above, the internal electrode paste disclosed herein can prevent sintering during firing. Therefore, by using such an internal electrode paste, it is possible to manufacture a laminated ceramic electronic component having a high-performance internal electrode layer in which various problems due to sintering of co-material powder are prevented.

In a preferred embodiment of the manufacturing method disclosed herein, in the firing step, high-speed firing is performed in which the rate of temperature rise from room temperature to the maximum firing temperature is 600 ° C./hr or more. In the paste for internal electrodes having an A / B of 0.99 or less, the number of atoms occupying the A site of the dielectric particles is reduced. 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, causing problems such as a decrease in the dielectric constant of the dielectric layer after firing. there is a possibility. Therefore, when a paste for an internal electrode having an A / B of 0.99 or less is used, high-speed firing as in this embodiment is performed, and elements move from the dielectric layer side to the internal electrode layer side. It is preferable that the dielectric layer and the internal electrode layer are sintered before.

It is sectional drawing schematically explaining the structure of the MLCC manufactured by the manufacturing method which concerns on one Embodiment of this invention. It is a surface SEM photograph (10000 times) of the sample 1 after firing. It is a surface SEM photograph (10000 times) of the sample 2 after firing.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art. In this specification, the notation "A to B" indicating the numerical range means "A or more and B or less".

[Paste for internal electrodes]
The paste for internal electrodes disclosed herein is a conductive paste used for forming an internal electrode layer of a laminated ceramic electronic component. Such an internal electrode paste contains (A) a conductive powder, (B) a co-material powder, and (C) a dispersion medium as main constituent components. The (B) co-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. There is.

The internal electrode paste disclosed herein has a molar ratio (A / B) of 0.89 or more and 0.99 or less of the atom occupying the A site and the atom occupying the B site of the dielectric particles. Yes, and the average particle size of the co-material powder is 10 nm or more and 50 nm or less. It has been confirmed by experiments carried out by the present inventors that syntaring during firing can be prevented by using such an internal electrode paste. Hereinafter, the paste for internal electrodes disclosed herein will be specifically described.

(A) Conductive powder The conductive powder may be any material that can be the main component of a highly electrically conductive conductor (which can be a conductor film) such as an electrode, a conducting wire, or a conducting film in an electronic element or the like. That is, as the conductive powder, various powder materials having desired conductivity can be used without particular limitation. As an example of such a conductive powder, nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu), ruthenium (Ru), rhodium (Rh), osmium ( Examples thereof include simple metals such as Os), iridium (Ir), aluminum (Al), and tungsten (W), and alloys containing these metals. Further, as the conductive powder, any one of the above-mentioned metal materials may be used alone, or two or more of them may be used in combination. It is preferable that the conductive powder uses a metal material having a melting point lower than the sintering temperature of the dielectric layer of MLCC (for example, about 1300 ° C.). Examples of metal materials having such a melting point include Rh, Pt, Pd, Cu, Au, and Ni. Among these, noble metals such as Pt and Pd are preferable from the viewpoint of melting point and conductivity. However, considering the low price, Ni is preferable. The conductive powder may be produced by a conventionally known method, and is not limited to that produced by a special method. For example, a metal powder produced by a well-known reduction precipitation method, gas phase reaction method, gas reduction method or the like can be used as the conductive powder.

The content ratio of the conductive powder in the paste for the internal electrode is not particularly limited, and can be appropriately adjusted as needed. From the viewpoint of forming an internal electrode layer having excellent electrical conductivity and high density, the content ratio of the conductive powder is 30% by mass or more when the total weight of the internal electrode paste is 100% by mass. It is preferable, it is more preferably 40% by mass or more, and further preferably 45% by mass or more. On the other hand, the upper limit of the content ratio of the conductive powder is not particularly limited and may be 95% by mass or less. However, considering that the paste viscosity is kept low to improve workability, the upper limit of the content ratio of the conductive powder is preferably 80% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less. preferable.

Further, the dimensions (particle diameter) of the particles constituting the conductive powder (hereinafter, also referred to as “conductive particles”) are not particularly limited, and the dimensions applicable to this type of internal electrode paste can be applied without limitation. For example, the average particle size of the conductive powder may be about several nm to several tens of μm. In the present specification, the "average particle size" means D ₅₀ (median diameter) in the particle size distribution of the powder material. Such D ₅₀ can be measured by, for example, a particle size distribution measuring device based on a conventionally known laser diffraction method, light scattering method, or the like.

When the internal electrode layer is thinned for the production of a small MLCC, it is required that the size of the conductive powder is 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 at the time of producing the small MLCC is preferably less than 3 μm, more preferably less than 2 μm, and further preferably less than 1.5 μm. It is particularly preferably less than 1.2 μm, for example, less than 1 μm. Further, from the viewpoint of stably forming the internal electrode layer of the 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, and 0.6 μm or less. More preferably, 0.5 μm or less is further preferable, 0.4 μm or less is particularly preferable, and for example, 0.3 μm or less. Further, by using such a conductive powder having a small average particle size, it is possible to form an internal electrode layer having a smooth surface (typically, the arithmetic average roughness Ra is 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 0.01 μm or more. However, in consideration of preventing agglomeration of conductive particles due to an increase in surface activity, the lower limit of the average particle diameter of the conductive powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, and 0.12 μm. The above is more preferable.

Further, from the viewpoint of suppressing the aggregation of conductive particles and improving the homogeneity, dispersibility, storage stability, etc. of the prepared paste, the specific surface area of the conductive powder is 10 m ² / g or less (typically). the ^{1m 2} / ^g~8m 2 / g, for example ^{2m 2} / ^g~6m 2 / g) are preferable. In addition, the conductive powder having such a specific surface area can also contribute to improving the electrical conductivity of the internal electrode layer after firing. In the present specification, the "specific surface area" is based on the gas adsorption amount measured by the gas adsorption method (constant volume adsorption method) using nitrogen (N ₂ ) gas as an adsorbent, and is based on the BET method (for example, one BET point). The value (BET specific surface area) calculated by the method).

The shape of the conductive particles is not particularly limited, and may be spherical or non-spherical (for example, a rugby ball shape). From the viewpoint of suppressing an increase in the viscosity of the paste, the shape of the conductive particles is preferably a true sphere or a substantially spherical shape. For example, the average aspect ratio of the conductive particles is typically 1-2, preferably 1-1.5. The "aspect ratio" in the present specification is calculated based on electron microscope observation, and is the length of the long side with respect to the length (a) of the short side when a rectangle circumscribing the particles constituting the powder is drawn. It means the ratio (b / a) of (b). The average aspect ratio is the arithmetic mean value of the aspect ratio obtained for 100 particles.

(B) Co-material powder The paste for internal electrodes disclosed here contains co-material powder. Such a co-material powder is composed of dielectric particles (metal oxide particles) having a composition similar to that of the dielectric layer of MLCC. By dispersing these dielectric particles among the conductive particles, the firing behavior (heat shrinkage rate, firing shrinkage history, thermal expansion coefficient) of the internal electrode paste and the dielectric green sheet can be approximated, and cracks after firing, etc. can be approximated. Can be prevented.

In the paste for internal electrodes disclosed herein, metal oxide particles having a perovskite structure represented by the following formula (1) are used as the dielectric particles constituting the co-material powder.
ABO ₃ (1)

The dielectric particles represented by the above formula (1) are metal oxide particles based on barium titanate (BaTIO ₃ ). That is, the A site in the above formula (1) contains at least barium (Ba), and the B site contains at least titanium (Ti).
An element other than Ba may be added to the A site in the above formula (1). Examples of elements that can occupy the A site other than Ba include calcium (Ca), magnesium (Mg), strontium (Sr), lanthanum (La), zinc (Zn), antimony (Sb) and the like. On the other hand, the B site may also be similarly added with an element other than Ti. Examples of elements that can occupy the B site other than Ti include zirconium (Zr), cerium (Ce), niobium (Nb), ittrium (Y), dysprosium (Dy), holmium (Ho), and samarium (Sm). Be done.

Then, in the paste for internal electrodes disclosed here, "(1) an atom occupying A site (hereinafter referred to as" A site atom ") and an atom occupying B site (hereinafter referred to as" B site atom ") are used. The molar ratio (A / B) and (2) average particle size of the co-material powder are controlled within a predetermined range. This makes it possible to prevent the occurrence of necking in the firing process. Hereinafter, each element controlled in the internal electrode paste disclosed herein will be specifically described.

(1) Molar ratio of A-site atom to B-site atom (A / B)
On the dielectric layer side of a general MLCC, the A / B of the dielectric particles is controlled to 1 or more in order to improve the dielectric constant. However, as a result of the studies by the present inventors, it has been found that when the A / B of the dielectric particles added as the co-material powder of the internal electrode layer becomes large, sintering during firing tends to occur. Although not intended to limit the present invention, the reason for this phenomenon is that when the proportion of A-site atoms in the dielectric particles increases, the A-site atoms (typically Ba) have a crystal structure. It is presumed that this is because the eluted A-site atom acts as a sintering aid because it is easily eluted to the outside.
On the other hand, in the paste for internal electrodes disclosed here, the molar ratio (A / B) of the A-site atom and the B-site atom (typically Ti) constituting the dielectric particles is 0.99 or less. Is controlled by. Therefore, it is possible to suppress the elution of A-site atoms and function as a sintering aid, and to suppress syntaring during firing. From the viewpoint of more preferably suppressing sintering during firing, the upper limit of A / B is preferably 0.98 or less, more preferably 0.975 or less, and even more preferably 0.97 or less. On the other hand, in the paste for internal electrodes disclosed here, since the lower limit of A / B is set to 0.89 or more, it is said that the dielectric particles in the paste are hard to react with the dielectric layer of MLCC during firing. It has an effect. From the viewpoint of more preferably exerting such an effect, the lower limit of A / B is preferably 0.90 or more, more preferably 0.91 or more, further preferably 0.92 or more, and particularly preferably 0.96 or more. ..

The "molar ratio of A-site atom to B-site atom (A / B)" can be obtained by performing fluorescent X-ray analysis using the glass beet method on the co-material powder. In this fluorescent X-ray analysis, a calibration curve is prepared using standard materials having different compositions of Ba and Ti, and the molar ratio can be obtained by using the calibration curve. The same applies to the examples described later.

Further, in the paste for internal electrodes disclosed herein, the Ba elution amount (ppm / hr) per unit time when the co-material powder is impregnated with water is determined by the specific surface area (m ² / g) of the co-material powder. It has been confirmed that the sintering suppressing effect tends to improve as the divided value (Ba elution rate / specific surface area) decreases. From the viewpoint of more preferably exerting the sintering suppressing effect, the above-mentioned "Ba elution rate / specific surface area" is preferably 10 or less, preferably 8 or less, more preferably 7 or less, and 6.6 or less. Is more preferable, and 6.3 or less is particularly preferable, 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 is not eluted), 0.5 or more, or 1 or more. May be good.
The above-mentioned "Ba elution amount per unit time" can be measured by the following procedure. First, alcohol (for example, ethanol) is added to the internal electrode paste to make it liquid, and then ultrasonic dispersion is performed for 1 hour. A magnet is placed on the bottom surface of the container to allow the conductive powder to settle, and the co-material powder is settled. And collect the supernatant liquid. The co-material powder and the supernatant obtained by repeating this step three times are dried under a temperature condition of 90 ° C. Then, 0.5 g of the dried sample is collected and held in a state of being impregnated with 250 ml of water for at least 100 hours or more (for example, 120 hours, 150 hours, 250 hours). Then, after 20 hours or more have passed from the start of holding, elution of 3 or more points of Ba at a certain impregnation time (for example, 24 hours, 48 hours, 72 hours, 96 hours, 120 hours after impregnation). The amount (ppm) is measured based on ICP (Inductively Coupled Plasma) analysis. Then, the Ba elution amount with respect to the impregnation time is plotted, and the slope thereof is calculated as "Ba elution amount per unit time". It is preferable to use the method of least squares when determining the slope. Further, as will be described in detail later, a resin component such as a binder may be added to the paste for the internal electrode. When such a resin component is added, it is preferable to perform a degreasing treatment (for example, heat treatment at 430 ° C., air atmosphere) on the dried sample.
Further, the specific surface area of the co-material powder can be measured by the same procedure as the specific surface area of the conductive powder described above. From the viewpoint of suppressing the elution of Ba from the dielectric particles, the specific surface area of the co-material powder is preferably 80 m ² / g or less, preferably 50 m ² / g or less, preferably 30 m ² / g or less, and preferably 20 m. ² / g or less is preferable.

(2) Average Particle Diameter of Common Material Powder Further, in the paste for internal electrodes disclosed herein, the average particle size (D ₅₀ ) of the common material powder is controlled to be 10 nm or more and 50 nm or less. As the average particle size of the co-material powder becomes smaller, the surface activity of the dielectric particles becomes higher and it becomes easier 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 co-material powder becomes too large, necking may occur during firing. In consideration of this point, in the paste for internal electrodes disclosed here, the average particle size of the co-material powder is controlled to 10 nm or more. On the other hand, if the average particle size of the co-material powder becomes too large, the dielectric in the internal electrode layer becomes large regardless of the presence or absence of necking, which may deteriorate the performance of the MLCC. Therefore, in the paste for internal electrodes disclosed here, the average particle size of the co-material powder is controlled to 50 nm or less. From the viewpoint of more preferably preventing necking during firing and preventing deterioration of the performance of the internal electrode layer, the average particle size of the co-material powder is preferably 20 nm or more and 50 nm or less, and more preferably 30 nm or more and 50 nm or less. More preferably, it is 35 nm or more and 50 nm or less.

As described above, according to the internal electrode paste disclosed herein, the A / B of the dielectric particles is controlled to 0.89 or more and 0.99 or less, and the average particle diameter of the co-material powder is 10 nm. Since it is controlled to 50 nm or less, it is possible to prevent sintering during firing even though the co-material powder is added to prevent cracks.

(C) Dispersion medium The dispersion medium is a liquid medium that disperses a powder material (conductive powder, co-material powder, etc.). The detailed components of such a dispersion medium are not particularly limited, and an organic solvent that can be used for this kind of internal electrode paste can be appropriately used. Further, since this dispersion medium is a component that is premised on disappearing by drying and firing, a high boiling point organic solvent having 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) is used. It is preferably contained as a main component. The "main component" here means a component that occupies 50 vol% or more when the total volume of the dispersion medium is 100 vol%.

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 a dispersion medium include sclareol, citronellol, phytol, geranyllinarool, texanol, benzyl alcohol, phenoxyethanol, 1-phenoxy-2-propanol, tarpineol, dihydroterpineol, isoborneol, butylcarbitol, diethylene glycol and the like. Alcohol-based solvent; ester-based solvent such as tarpineol acetate, dihydroterpineol acetate, isobornyl acetate, carbitol acetate, diethylene glycol monobutyl ether acetate; mineral spirit and the like. Of these, alcohol solvents and ester solvents can be preferably used.

It is preferable that the content ratio of the dispersion medium in the paste for the internal electrode is appropriately adjusted in consideration of workability when it is applied to the surface of the dielectric green sheet. The workability at the time of surface application (printing) is not particularly limited because it may vary depending on other components, but for example, the content of the dispersion medium is 70% by mass or less when the total weight of the paste is 100% by mass. (Preferably 5% by mass to 60% by mass, more preferably 30% by mass to 50% by mass). As a result, suitable fluidity can be imparted to the paste, workability at the time of surface application can be improved, and self-leveling property of the paste can be enhanced to form an internal electrode layer having a smoother surface.

(D) Other components In the internal electrode paste disclosed here, components that can be used for this type of internal electrode paste can be used without particular limitation as long as the above-mentioned sintering prevention effect is not impaired. Hereinafter, an example of other components that can be used in the paste for internal electrodes disclosed herein will be described.

(1) Binder The binder (binder) is an organic component that contributes to improving the fixability to the surface of the dielectric green sheet and the bondability between particles in the paste. The binder can also function as a vehicle (which can be a liquid phase medium) when dissolved in the dispersion medium described above. Further, like the above-mentioned dispersion medium, the binder is a component that is premised on disappearing by firing. Therefore, it is preferable that the binder is an organic compound that is easily burned during firing (typically, an organic compound having a burning temperature of 500 ° C. or lower). The specific binder component is not particularly limited, and a known organic compound that can be used for the internal electrode paste can be used without particular limitation. Examples of such binders include rosin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyvinyl acetal-based resins, acrylic resins, urethane-based resins, epoxy-based resins, phenol-based resins, polyester-based resins, and ethylene-based resins. Examples include organic polymer compounds. Although it cannot be said unconditionally because it depends on the combination with the above-mentioned dispersion medium, among these organic compounds, cellulosic resin, polyvinyl alcohol resin, polyvinyl acetal resin, acrylic resin and the like are suitable as binders. Further, as the binder, any one of the above-mentioned organic compounds may be used, or two or more of them may be used in combination. Further, although not explicitly described, a copolymer obtained by copolymerizing the monomer components of any two or more of the above resins, a block copolymer, or the like may be used.

The binder content in the internal electrode paste is not particularly limited, but it is preferably adjusted appropriately so that suitable fixability can be exhibited in consideration of the content of the conductive powder. For example, when the content of the conductive powder is 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, and 2 More than parts by mass is particularly preferable. On the other hand, from the viewpoint of preventing performance deterioration of the internal electrode layer due to residual binder after the firing step, the content of the binder is preferably 10 parts by mass or less, preferably 7 parts by mass or less, based on 100 parts by mass of the conductive powder. More preferably, 5 parts by mass or less is further preferable, and 4 parts by mass or less is particularly preferable.

(2) Dispersant The dispersant suppresses 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. As described above, the diameter of the inorganic powder tends to decrease as the internal electrode layer becomes thinner. The dispersant is preferably used when such an inorganic powder having a small particle size (typically, an inorganic powder having an average particle size of 1 μm or less) is used. The type of the dispersant is not particularly limited, and one or more of the various known dispersants can be selected as needed. Specific examples of the dispersant include surfactant-type dispersants (also referred to as low-molecular-weight dispersants), polymer-type dispersants, and inorganic-type dispersants.

Examples of the surfactant-type dispersant include a dispersant mainly composed of an alkyl sulfonate, a dispersant mainly composed of a quaternary ammonium salt, and a dispersant mainly composed of an alkylene oxide compound of a higher alcohol. Examples thereof include a dispersant mainly composed of a valence alcohol ester compound and a dispersant mainly composed of an alkyl polyamine compound.
Further, as the polymer type dispersant, for example, a dispersant mainly composed of a fatty acid salt such as a carboxylic acid or a polycarboxylic acid, and a polycarboxylic acid in which a hydrogen atom in a part of the carboxylic acid groups is substituted with an alkyl group. Dispersants mainly composed of partially alkyl ester compounds, dispersants mainly composed of polycarboxylic acid alkylamine salts, dispersants mainly composed of polycarboxylic acid partially alkyl ester compounds having an alkyl ester bond in a part of polycarboxylic acid, Dispersants mainly composed of polystyrene sulfonates, polyisoprene sulfonates, polyalkylene polyamine compounds, dispersants mainly composed of sulfonic acid compounds such as naphthalene sulfonates and formalin condensate salts of naphthalene sulfonate, polyethylene glycol, etc. Dispersants mainly composed of hydrophilic polymers, dispersants mainly composed of polyether compounds, dispersants mainly composed of poly (meth) acrylic compounds such as poly (meth) acrylates and poly (meth) acrylamides, Etc. can be mentioned. Among the dispersants, the polymer-type dispersant is suitable because it exhibits a repulsive effect due to steric hindrance and can effectively disperse the inorganic powder over a long period of time. The weight average molecular weight of such a polymer-type dispersant is not particularly limited, but as a preferable example, it is about 300 to 50,000 (for example, 500 to 20,000).
Examples of the inorganic dispersant include phosphates such as orthophosphate, metaphosphate, polyphosphate, pyrophosphate, tripolyphosphate, hexamethaphosphate, and organic phosphate, and ferric sulfate. , Iron salts such as ferrous sulfate, ferric chloride, and ferrous chloride, aluminum salts such as aluminum sulfate, polyaluminum chloride, and sodium aluminate, calcium sulfate, calcium hydroxide, and dicalcium phosphate, etc. Examples thereof include dispersants mainly composed of calcium salts.
In the paste for internal electrodes disclosed herein, any one of the above-mentioned components may be contained alone, or a combination of two or more thereof may be contained as a dispersant.

(3) Additives In addition to the above-mentioned binders and dispersants, the pastes for internal electrodes disclosed here include thickeners, plasticizers, pH adjusters, stabilizers, leveling agents, defoamers, and antioxidants. Agents, preservatives, colorants (pigments, dyes, etc.) and the like may be added. As for these, those that can be used as a general paste for internal electrodes can be used without particular limitation, and thus detailed description thereof will be omitted.

Considering the purpose of preventing the syntering of the co-material powder, it is preferable that the sintering aid is not substantially added to the paste for the internal electrode disclosed here. Examples of such a sintering aid include barium carbonate (BaCO ₃ ), calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), zinc oxide (ZnO), and lanthanum oxide (La ₂ O ₃ ). In addition, in this specification, "substantially no sintering aid is added" means that a component that can be interpreted as a sintering aid is not intentionally added. Therefore, when a component that can be interpreted as a sintering aid is contained in a trace amount due to the raw material, the manufacturing process, or the like, the concept of "substantially no sintering aid is added" in the present specification. Included in. For example, the content of the component that can be interpreted as a sintering aid is 0.01 mol% or less (preferably 0.005 mol% or less, more preferably 0.001 mol% or less, still more preferably 0.001 mol% or less, based on 100 mol% of the co-material powder. When it is 0.0005 mol% or less, particularly preferably 0.0001 mol% or less), it can be said that "substantially not added".

[Use]
The paste for internal electrodes disclosed here has been described above. The internal electrode paste disclosed herein is used in the manufacture of multilayer ceramic electronic components (eg, multilayer ceramic capacitors (MLCCs)). Next, the manufacturing method disclosed herein will be described. Such a production method includes at least (A) a preparation step, (B) an application step, and (C) a firing step.

(A) Preparation step In this step, the paste for internal electrodes disclosed here is prepared. Generally, the paste for an internal electrode is prepared by dispersing a conductive powder and a co-material powder in a dispersion medium. Although not particularly limited, a conductive powder slurry in which the conductive powder is dispersed in the dispersion medium and a co-material powder slurry in which the co-material powder is dispersed in the dispersion medium are separately prepared and mixed. It is preferable to prepare a paste for internal electrodes by. Thereby, a paste in which the conductive powder and the co-material powder are highly dispersed can be easily obtained. The material can be stirred and mixed by using various conventionally known stirring and mixing devices such as a roll mill, a magnetic stirrer, a planetary mixer, and a disper.

In the production method disclosed herein, the A / B of the dielectric particles is 0.89 or more and 0.99 or less, and the average particle diameter of the co-material powder is 10 nm or more and 50 nm or less in this step. Prepare the paste for the internal electrode.

Further, the means for preparing the co-material powder having an average particle diameter of 10 nm or more and 50 nm or less is not particularly limited because conventionally known means can be adopted. For example, the average particle size of the co-material powder can be adjusted to 10 nm or more and 50 nm or less by pulverizing and classifying the co-material powder having a predetermined average particle size.

(B) Applying step In the applying step, the paste for the internal electrode is applied to the surface of the dielectric green sheet. As a method for applying the internal electrode paste, for example, a printing method such as screen printing, gravure printing, offset printing and inkjet printing, or a coating method such as a spray coating method or a dip coating method can be adopted. Among these, a gravure printing method, a screen printing method, an inkjet printing, or the like that can apply a precise paste at high speed can be preferably adopted.

(C) Firing step In the firing step, the dielectric green sheet to which the paste for the internal electrode is applied is fired at a predetermined temperature. Thereby, a dielectric layer having an internal electrode layer formed on the surface can be obtained. 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.

When the paste for internal electrodes disclosed here is used, it is preferable to perform high-speed firing in the firing step. The term "high-speed firing" as used herein refers to increasing the rate of temperature rise at the initial stage of the firing process and shortening the time required to reach the maximum firing temperature. When the internal electrode paste disclosed here is used, the elements (Ba, Ca, etc.) that can occupy the A site move from the dielectric layer side to the internal electrode layer side in the firing step, and the dielectric layer after firing is used. Dielectric constant may decrease. In consideration of this point, it is preferable to perform high-speed firing to sinter the dielectric layer and the internal electrode layer at the initial stage of the firing step to suppress the movement of A-site atoms from the dielectric layer to the internal electrode layer. .. The rate of temperature rise in such high-speed firing is preferably 600 ° C./hr or higher, more preferably 1000 ° C./hr or higher, further preferably 2500 ° C./hr or higher, and particularly preferably 5000 ° C./hr or higher. The firing time (holding time at the maximum temperature) when high-speed firing is performed is preferably 20 minutes or less (typically 5 to 20 minutes, for example, about 10 minutes).

(D) Degreasing Step In the manufacturing method disclosed here, it is preferable that the (D) degreasing step is provided between the above-mentioned (B) printing step and (C) firing step. In this degreasing step, the paste for the internal electrode is heated at a temperature lower than that in the firing step to remove organic materials (dispersion medium, binder, etc.) in the paste. This makes it possible to appropriately prevent firing defects due to residual organic material. The maximum temperature in the degreasing step is preferably about 100 ° C. to 1000 ° C., more preferably about 300 ° C. to 800 ° C. The rate of temperature rise in the degreasing step is preferably 100 ° C./hr to 400 ° C./hr, and the heating time (holding time at the maximum temperature) is preferably 1 hour or more (for example, 6 hours or more).

[Multilayer ceramic capacitor]
Next, a multilayer ceramic capacitor (MLCC) will be described as an example of a multilayer ceramic electronic component manufactured by using the paste for internal electrodes disclosed herein. FIG. 1 is a schematic cross-sectional view illustrating the configuration of the MLCC.

As shown in FIG. 1, the multilayer ceramic capacitor (MLCC) 1 is a chip type capacitor in which a large number of dielectric layers 20 and internal electrode layers 30 are laminated alternately and integrally. A pair of external electrodes 40 are provided on the side surface of the laminated chip 10 composed of the dielectric layer 20 and the internal electrode layer 30. As an example, the internal electrode layer 30 is connected to external electrodes 40 which are alternately different in the stacking order. As a result, a compact and large-capacity MLCC in which a capacitor structure composed of a dielectric layer 20 and a pair of internal electrode layers 30 sandwiching the dielectric layer 20 is connected in parallel is constructed. The internal electrode layer 30 of the MLCC1 is formed by firing the internal electrode paste disclosed herein. As described above, since the paste for internal electrodes disclosed herein can prevent sintering during firing, it is possible to form a high-performance internal electrode layer 30 in which various problems due to sintering of co-material powder are prevented. ..

[Test example]
Next, some test examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the test examples.

[1] First Test In this test, two types of internal electrode pastes having different A / B of dielectric particles were prepared, and each internal electrode paste was fired.

(1) Preparation of Sample A paste for an internal electrode was prepared in which a conductive powder, a co-material powder, and a binder (ethyl cellulose) were dispersed in a dispersion medium (isobornyl acetate) (Samples 1 and 2). Here, as the conductive powder, Ni powder having an average particle diameter of 0.2 μm was used. Further, as the co-material powder, BaTIO ₃ powder having an average particle diameter of 50 nm was used. The amount of the co-material powder (BaTIO ₃ powder) added 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 co-material powder was different in each of Samples 1 and 2. The A / B of each sample is shown in Table 1.

(2) Heat resistance evaluation Each of Samples 1 and 2 was subjected to a degreasing step (heating time: 20 minutes, heating atmosphere: N ₂ gas) in which the temperature was raised to 600 ° C. at a heating rate of 200 ° C./h. The binder was removed. Then, a firing step (heating time: 10 minutes, heating atmosphere: 1% H ₂ gas mixed N ₂ gas) was carried out in which the temperature was raised to 1250 ° C. at a heating rate of 7000 ° C./h. Then, SEM photographs of each sample after firing were taken, and the particle size distribution was analyzed to obtain 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. Table 1 shows D ₁₀ , D ₅₀ , and D ₉₀ of each sample. Then, based on the SEM photograph and the analysis result of the particle size distribution, those judged to have sintered in the dielectric particles are evaluated as heat resistance "x", and those judged to have suppressed sintering are heat resistant "x". ○ ”was evaluated.

In Sample 1 having an A / B of 1.000, BaTiO ₃ particles having a large particle size were attached to the surface of the Ni particles (see FIG. 2). On the other hand, in Sample 2 having an A / B of 0.96, the particle size of the BaTiO ₃ particles on the surface of the Ni particles was relatively small (see FIG. 3). As shown in Table 1, in sample 1, all of D ₁₀ , D ₅₀ , and D ₉₀ have a large particle size as a whole, whereas in sample 2, the large particle size is suppressed. It was. From these results, it was found that the A / B of the dielectric particles affects the heat resistance of the paste for the internal electrode, and the sintering tends to be suppressed as the A / B decreases.

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

(1) Sample preparation In this test, in addition to the above-mentioned samples 1 and 2, seven types of co-material powder (BaTIO ₃ powder) having different A / B of dielectric particles and an average particle diameter (D ₅₀ ) were prepared. , These co-material powders were used to prepare pastes for internal electrodes (Samples 1 to 9). The other components of Samples 3 to 9 except for the co-material powder were the same as those of Sample 1.

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

As shown in Table 2, among the test objects, the heat resistance of Samples 2, 4 and 9 was high, and sintering during firing was prevented. From this, if a co-material powder having an A / B of dielectric particles of 0.89 to 0.99 and an average particle diameter of 10 nm or more and 50 nm or less is used, sintering during firing can be appropriately prevented. I found that I could do it.

[3] Third test In this test, the amount of Ba elution of samples 1 to 9 used in the second test was examined.

(1) Measurement of specific surface area In this test, first, the BET specific surface area (m ² / g) of samples 1 to 9 was measured. Since the specific procedure for measuring the specific surface area has already been described, detailed description thereof will be omitted here. The measurement results are shown in Table 3.

(2) Measurement of Ba elution amount Next, the co-material powder was extracted from the internal electrode paste of each sample, and the extracted co-material powder was impregnated with water to obtain "Ba elution amount per unit time (ppm / hr). I asked. Then, a value (Ba elution rate / specific surface area) was calculated by dividing the "Ba elution amount per unit time" by the above "specific surface area". Since the specific procedure for measuring the "Ba elution amount per unit time" has already been described, detailed description thereof will be omitted here. The measurement results are shown in Table 3.

As described above, in the samples 2, 4 and 9 in which high heat resistance was confirmed in the above-mentioned second test, the "Ba elution rate / specific surface area" tended to be lower than that of the other samples. From this result, it is understood that the elution of Ba from the dielectric particles is suppressed in the co-material powder having the A / B of the dielectric particles of 0.99 or less, which affects the suppression of sintering. Will be done. From this, it is presumed that the reason why the syntaring could be prevented in the paste for the internal electrode having the A / B of the dielectric particles of 0.99 or less was that the elution of Ba, which could function as a sintering aid, was suppressed. ..

Although the present invention has been described in detail above, these are merely examples, and the present invention can be modified in various ways without departing from the gist thereof.

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

Claims (7)

A paste for internal electrodes used to form the internal electrode layer of laminated ceramic electronic components.
It contains a conductive powder, a co-material powder composed of dielectric particles, and a dispersion medium.
The dielectric particles have a general formula:
ABO ₃ (1)
(Here, the A site in the above formula (1) contains at least Ba, and the B site contains at least Ti), which is a metal oxide particle having a perovskite structure represented by the above formula (1).
The molar ratio (A / B) of the atom occupying the A site and the atom occupying the B site in the formula (1) is 0.89 or more and 0.99 or less, and
A paste for an internal electrode, characterized in that the average particle size of the co-material powder is 10 nm or more and 50 nm or less. The paste for an internal electrode according to claim 1, wherein the A site in the formula (1) contains at least one selected from the group consisting of Ca, Mg, Sr, La, Zn, and Sb in addition to the Ba. .. The B site in the formula (1) includes at least one selected from the group consisting of Zr, Ce, Nb, Y, Dy, Ho, and Sm in addition to the Ti, according to claim 1 or 2. The paste for internal electrodes described. The paste for an internal electrode according to any one of claims 1 to 3, wherein the A / B is 0.96 or more. Any one of claims 1 to 4, wherein the value obtained by dividing the Ba elution amount per unit time when the co-material powder is impregnated with water by the specific surface area of the co-material powder is 10 or less. The paste for internal electrodes described in. The preparatory step for preparing the paste for the internal electrode according to any one of claims 1 to 5.
An application step of applying the internal electrode paste to the surface of the dielectric green sheet, and
A method for manufacturing a laminated ceramic electronic component, which includes a firing step of firing the dielectric green sheet to which the internal electrode paste is applied. The method for manufacturing a laminated ceramic electronic component according to claim 6, wherein in the firing step, high-speed firing is performed in which the rate of temperature rise from room temperature to the maximum firing temperature is 600 ° C./hr or more.