JP7494554B2 - Conductive paste, electronic components, and multilayer ceramic capacitors - Google Patents

Description

The present invention relates to a conductive paste, an electronic component, and a multilayer ceramic capacitor.

As electronic devices such as mobile phones and digital devices become smaller and more powerful, there is a demand for electronic components, including multilayer ceramic capacitors, to be smaller and have higher capacity. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by making these dielectric layers and internal electrode layers thinner, it is possible to achieve smaller size and higher capacity.

For example, a multilayer ceramic capacitor is manufactured as follows. First, a conductive paste for internal electrodes is printed in a predetermined electrode pattern on the surface of a dielectric green sheet containing a dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin, and then dried to form a dry film. Next, the dry film and the green sheet are alternately stacked to obtain a laminate. Next, this laminate is heated and pressed to be integrated to form a pressed body. This pressed body is cut, and after a binder removal process is performed in an oxidizing atmosphere or an inert atmosphere, it is fired to obtain a fired chip. Next, a paste for external electrodes is applied to both ends of the fired chip, and after firing, nickel plating or the like is performed on the surface of the external electrodes to obtain a multilayer ceramic capacitor.

Generally, the conductive paste used to form the internal electrode layer contains a conductive powder, a ceramic powder, a binder resin, and an organic solvent. The conductive paste may also contain a dispersant to improve the dispersibility of the conductive powder and other components. In recent years, as the internal electrode layers have become thinner, the particle size of the conductive powder has also tended to become smaller. When the particle size of the conductive powder is small, the specific surface area of the particle surface becomes large, which increases the surface activity of the conductive powder (metal powder), and this may result in a decrease in dispersibility and a decrease in viscosity characteristics.

Therefore, attempts have been made to improve the viscosity characteristics of conductive pastes over time. For example, Patent Document 1 describes a conductive paste that contains at least a metal component, an oxide, a dispersant, and a binder resin, in which the metal component is Ni powder whose surface composition has a specific composition ratio, the dispersant has an acid site amount of 500 to 2000 μmol/g, and the binder resin has an acid site amount of 15 to 100 μmol/g.

Also, Patent Document 2 describes a conductive paste for internal electrodes that is composed of conductive powder, resin, organic solvent, common material of ceramic powder mainly composed of _BaTiO3 , and coagulation inhibitor, the content of the coagulation inhibitor being 0.1% by weight or more and 5% by weight or less, and the coagulation inhibitor being a tertiary amine or secondary amine represented by a specific structural formula. According to Patent Document 2, this conductive paste for internal electrodes is said to suppress coagulation of common material components, have excellent long-term storage properties, and enable the thinning of multilayer ceramic capacitors.

On the other hand, when the internal electrode layer is thinned, it is required that the density of the dry film obtained by printing and drying a conductive paste for the internal electrode on the surface of the dielectric green sheet is high. For example, Patent Document 3 proposes a metal ultrafine powder slurry containing an organic solvent, a surfactant, and ultrafine metal particles, the surfactant being oleoyl sarcosine, the metal ultrafine powder slurry containing 70% by mass or more and 95% by mass or less of the metal ultrafine powder, and the surfactant containing more than 0.05 parts by mass and less than 2.0 parts by mass per 100 parts by mass of the metal ultrafine powder. According to Patent Document 3, by preventing the aggregation of ultrafine particles, it is possible to obtain an ultrafine metal powder slurry that is free of aggregated particles and has excellent dispersibility and dry film density.

JP 2015-216244 A JP 2013-149457 A JP 2006-063441 A

However, in recent years, as electrode patterns have become thinner, there is a demand for further improvements in the viscosity characteristics of the conductive paste over time, as well as an improvement in the dry film density after application.

In view of these circumstances, the present invention aims to provide a conductive paste that exhibits minimal change in viscosity over time and has improved dry film density.

In a first aspect of the present invention, a conductive paste is provided that includes a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, the dispersant includes an amine-based dispersant that is a secondary amine or a tertiary amine, and the binder resin includes an acrylic resin and a cellulose resin.

In a second aspect of the present invention, an electronic component is provided that is formed using the conductive paste.

In a third aspect of the present invention, a multilayer ceramic capacitor is provided that has at least a laminate in which dielectric layers and internal electrode layers are laminated, and the internal electrode layers are formed using the conductive paste.

The present invention provides a conductive paste that exhibits minimal change in viscosity over time and has improved dry film density after application.

FIG. 1 is a graph showing the evaluation results of dry film density (DFD) of Examples 1 to 3 and Comparative Example 1. FIG. 2 is a graph showing the evaluation results of dry film density (DFD) of Examples 4 to 6 and Comparative Example 2. FIG. 3 is a graph showing the change in viscosity over time of the conductive pastes of Examples 1 to 3 and Comparative Example 1. FIG. 4 is a graph showing the change in viscosity over time of the conductive pastes of Examples 4 to 6 and Comparative Example 2. 5A and 5B are a perspective view and a cross-sectional view showing the multilayer ceramic capacitor according to the embodiment.

[Conductive paste]
The conductive paste of the present embodiment includes a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, the dispersant includes an amine-based dispersant that is a secondary amine or a tertiary amine, and the binder resin includes an acrylic resin and a cellulose resin. Each component will be described in detail below.

(Conductive powder)
The conductive powder is not particularly limited, and metal powder can be used, for example, one or more metal powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Among these, Ni or its alloy powder is preferred from the viewpoints of conductivity, corrosion resistance, and cost. As the Ni alloy, for example, an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd (Ni alloy) can be used. The Ni content in the Ni alloy is, for example, 50 mass% or more, preferably 80 mass% or more. In addition, the Ni powder may contain about several hundred ppm of S in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during the binder removal process.

The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the average particle size of the conductive powder is within the above range, it can be suitably used as a conductive paste for the internal electrodes of thin-film multilayer ceramic capacitors, and for example, the smoothness and density of the dry film are improved. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of each of multiple particles from an image observed with an SEM at a magnification of 10,000 times.

The content of the conductive powder is preferably 30% by mass or more and less than 70% by mass, and more preferably 40% by mass or more and 60% by mass or less, based on the entire conductive paste. When the content of the conductive powder is within the above range, the conductive paste has excellent conductivity and dispersibility.

(ceramic powder)
The ceramic powder is not particularly limited, and for example, in the case of a conductive paste for an internal electrode of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to be applied. Examples of the ceramic powder include perovskite oxides containing Ba and Ti, and preferably barium titanate ( _BaTiO3 ).

The ceramic powder may be a ceramic powder containing barium titanate as a main component and an oxide as a subcomponent. The oxide may be an oxide of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, or one or more rare earth elements. An example of such a ceramic powder is a perovskite-type oxide ferroelectric ceramic powder in which the Ba and Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms, such as Sn, Pb, and Zr.

The conductive paste for the internal electrodes may use a powder of the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor. This suppresses the occurrence of cracks due to the mismatch of shrinkage at the interface between the dielectric layer and the internal electrode layer during the sintering process. In addition to the above, such ceramic powders include oxides such as ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , and TiO _2. Note that one type of ceramic powder may be used, or two or more types may be used.

The average particle size of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, and preferably 0.01 μm or more and 0.3 μm or less. When the average particle size of the ceramic powder is in the above range, it is possible to form a sufficiently fine, thin, and uniform internal curvature when used as a conductive paste for internal electrodes. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of each of multiple particles from an image observed with an SEM at a magnification of 50,000 times.

The content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of the conductive powder.

The content of the ceramic powder is preferably 1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 20% by mass or less, based on the entire conductive paste. When the content of the conductive powder is within the above range, the conductive paste has excellent conductivity and dispersibility.

(Binder resin)
The binder resin is selected from an acrylic resin and a cellulose resin. The binder resin may include an acrylic resin and a cellulose resin, or may be composed of an acrylic resin and a cellulose resin. By using these two types of resin, the stability of the viscosity characteristics and the dry film density are improved.

The binder resin preferably contains an acrylic resin and a cellulose resin as the main components. Here, "containing as the main components" means that the total amount of the acrylic resin and the cellulose resin is 70 parts by mass or more, preferably 90 parts by mass or more, and more preferably 95 parts by mass or more per 100 parts by mass of the binder resin.

The acrylic resin is preferably contained in an amount of 0.1 to 10 parts by mass, and more preferably 0.1 to 8 parts by mass, per 100 parts by mass of the conductive powder. The blending ratio (mass ratio) of the acrylic resin to the cellulose resin is preferably 1 part by mass of the acrylic resin to 0.5 to 20 parts by mass of the cellulose resin, and more preferably 1 to 15 parts by mass.

The acrylic resin refers to a (meth)acrylic resin. A (meth)acrylic resin is a polymer containing a (meth)acrylic acid ester as a main component, has a chemical structure (-CH ₂ -CH ₂ -) derived from the vinyl group of the (meth)acrylic acid ester in the main chain, and has depolymerizability. Note that "(meth)acrylic" means "acrylic or methacrylic".

Examples of (meth)acrylic acid esters include methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), methyl methacrylate (MMA), ethyl methacrylate (EMA), butyl methacrylate (BMA), 2-hydroxyethyl methacrylate (HEMA), benzyl methacrylate (BzMA), cyclohexyl methacrylate (CHMA), methacrylic acid (MAA), 2-ethylhexyl acrylate (HA), cyclohexyl acrylate CHA, and diethylene glycol. Examples of such acrylates include 2-ethylhexyl ether acrylate (M120), diethylene glycol monophenyl ether acrylate (M101A), lauryl acrylate (LA), lauryl methacrylate (LMA), isobornyl acrylate (IBXA), isobornyl methacrylate (IBXMA), 2-phenoxyethyl acrylate (POA), tetrahydrofurfuryl acrylate (THFA), 2-hydroxypropyl acrylate (HPA), and benzyl acrylate (BzA). These may be used alone or in combination of two or more.

In addition, the glass transition temperature (Tg) of the acrylic resin is preferably -100°C or higher and 100°C or lower, and more preferably -50°C or higher and 50°C or lower.

Examples of cellulose-based resins include methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose. From the viewpoints of solubility in solvents and combustion decomposition, it is preferable that the cellulose-based resin contains ethyl cellulose, and ethyl cellulose may be used. The molecular weight of the cellulose-based resin is, for example, about 20,000 to 200,000.

The content of the binder resin is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 8 parts by mass or less, per 100 parts by mass of the conductive powder.

The binder resin content is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 6% by mass or less, based on the total amount of the conductive paste.

(Organic solvent)
The organic solvent is not particularly limited, and any known organic solvent capable of dissolving the binder resin can be used.

Examples of organic solvents include acetate-based solvents such as dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, and dipropylene glycol methyl ether acetate, terpene-based solvents such as terpineol and dihydroterpineol, and hydrocarbon-based solvents such as tridecane, nonane, and cyclohexane. One type of organic solvent may be used, or two or more types may be used. When a terpene-based solvent is used as the organic solvent, it is preferable to use dihydroterpineol from the viewpoint of further improving the dry film density.

The content of the organic solvent is preferably 40 parts by mass or more and 100 parts by mass or less, and more preferably 65 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass of the conductive powder. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

The content of the organic solvent is preferably 20% by mass or more and 60% by mass or less, and more preferably 35% by mass or more and 55% by mass or less, based on the entire conductive paste. When the content of the organic solvent is within the above range, the conductive paste has excellent conductivity and dispersibility.

(Dispersant)
The conductive paste of the present embodiment contains an amine-based dispersant which is a secondary amine or a tertiary amine. By containing such an amine-based dispersant, the conductive powder in the conductive paste can be maintained in a dispersed state, and the viscosity change of the conductive paste over time can be reduced.

It is preferable that the amine-based dispersant does not have a high molecular weight. For example, the molecular weight may be 1500 or less, or 1000 or less. Furthermore, the lower limit of the molecular weight of the amine-based dispersant may be, for example, 150 or more, 200 or more, or 500 or more.

In addition, the amine-based dispersant is preferably a tertiary amine or a secondary amine represented by the following general formula (1):

(In the formula (1), R ₁ represents an alkyl group, an alkenyl group, or an alkynyl group having 8 to 18 carbon atoms, R ₂ represents an oxyethylene group, an oxypropylene group, or a methylene group, R ₃ represents an oxyethylene group, an oxypropylene group, or a methylene group, and R ₂ and R ₃ may be the same or different. In addition, the N atom in the formula (2) is not directly bonded to the O atom in R ₂ and R ₃ , Y is a number from 0 to 7, and Z is a number from 1 to 7.)

In the above (1), R ₁ represents an alkyl group, an alkenyl group, or an alkynyl group having 8 to 18 carbon atoms. When the carbon number of R ₁ is within the above range, the powder in the conductive paste has sufficient dispersibility and excellent solubility in the solvent. It is preferable that R ₁ is a linear hydrocarbon group.

In the above (1), _R2 represents an oxyethylene group, an oxypropylene group, or a methylene group, _R3 represents an oxyethylene group, an oxypropylene group, or a methylene group, and _R2 and _R3 may be the same or different. In addition, the N atom in formula (2) is not directly bonded to the O atom in _R2 and _R3 , Y is a number from 0 to 7, and Z is a number from 1 to 7.

For example, when _R2 is an oxyalkylene group represented by -(AO) _Y- (Y is 1 or more), the O atom at the end of the oxyalkylene group bonds to the H atom adjacent to _R2 . When _R2 is a methylene group, _R2 is represented by -( _CH2 ) _Y- , and when Y is 1 or 2, it forms a methyl group ( _-CH3 ) or an ethyl group ( _-CH2 - _CH3 ) together with the adjacent H element. When _R3 is an oxyalkylene group represented by -(AO) _Z- (Z is 1 or more), the O atom at the end of the oxyalkylene group bonds to the H atom adjacent to _R3 .

In the above formula (1), when Y is 0, the above amine-based dispersant is a secondary amine having an alkyl group, an alkenyl group, or an alkynyl group having 8 to 18 carbon atoms, one hydrogen group, and -(R ₃ ) _Z H.

Furthermore, in the above formula (1), when Y is 1 or more, the above amine-based dispersant is a tertiary amine having an alkyl group, an alkenyl group, or an alkynyl group having 8 to 17 carbon atoms, -(R ₂ ) _Y H, and -(R ₃ ) _Z H.

The dielectric constant of the amine-based dispersant is preferably 10 or less, more preferably 1 to 10, and even more preferably 2 to 10. If the dielectric constant of an amine-based dispersant that is not a polymer dispersant exceeds 10, the lipophilicity decreases and the dispersion of the conductive particles in the conductive paste cannot be maintained. The dielectric constant of the amine-based dispersant can be measured with an impedance meter.

The dielectric constant of an organic material is an index indicating the ease of polarization of the organic material, and depends on its molecular structure and functional group. For example, in the above formula (1), when one of R ₂ and R ₃ of the amine-based dispersant is an oxyethylene group or an oxypropylene group, the dielectric constant is high. In addition, when both R ₂ and R ₃ are an oxyethylene group and/or an oxypropylene group, the dielectric constant is further increased. From the viewpoint of further improving the viscosity stability after long-term storage, it is desirable that at least one of R ₂ and R ₃ of the amine-based dispersant is an oxyethylene group or an oxypropylene group.

In the above formula (1), when at least one of _R2 and _R3 is an oxyethylene group or an oxypropylene group, the dielectric constant of the amine-based dispersant is increased to an upper limit of 10, making it easier to maintain the dispersed state of the conductive powder in the conductive paste, and reducing viscosity changes over time and dynamic viscosity changes over time. The dielectric constant of the amine-based dispersant may be, for example, 5 or more, or 6 or more.

In the above formula (1), when _R2 is an oxyethylene group or an oxypropylene group, the dielectric constant tends to decrease as the value of Y increases. Similarly, when _R3 is an oxyethylene group or an oxypropylene group, the dielectric constant tends to decrease as the value of Z increases.

When at least one of _R2 and _R3 is an oxyethylene group or an oxypropylene group, it is desirable that the sum of the values of Y and Z is 3 or more. When the value of Z is 3 or more, the change in dynamic viscosity over time of the obtained conductive paste can be reduced. Moreover, each of the values of Y and Z may be 3 or more, or 5 or more.

Furthermore, when R ₂ and R ₃ are methylene groups, the value of Y can be appropriately selected from the range of 0 to 7, and the value of Z can be appropriately selected from the range of 1 to 7. When R ₂ and R ₃ are methylene groups, the value of Y may be 5 or less, or may be 3 or less. When R _{2 and R 3 are methylene groups, the value of Z may be 5 or less, or may be 3 or less. When R 2} and R ₃ are methylene groups, the dielectric constant may be 5 or less, or may be 3 or less.

The conductive paste contains an amine-based dispersant in an amount of 0.01 to 2 parts by mass, preferably 0.02 to 1 part by mass, per 100 parts by mass of conductive powder. When the amine-based dispersant is contained in the above range, viscosity changes over time can be suppressed and viscosity stability can be improved. Note that when the content of the amine-based dispersant exceeds 2 parts by mass, mesh marks may appear on the printed surface or the viscosity of the paste may be significantly reduced when the conductive paste is printed on a green sheet.

The amine-based dispersant may be selected from commercially available products that satisfy the above characteristics. The amine-based dispersant may also be manufactured to satisfy the above characteristics using a conventionally known manufacturing method.

The dispersant may also contain an amino acid-based dispersant. As shown in the following general formula (2), the amino acid-based dispersant preferably has an N-acylamino acid skeleton and a chain hydrocarbon group having 10 to 20 carbon atoms.

（ただし、式（２）中、Ｒ_４は、炭素数１０～２０の鎖状炭化水素を表す。）

(In the formula (2), R ₄ represents a chain hydrocarbon having 10 to 20 carbon atoms.)

In the above formula (2), _R4 represents a chain hydrocarbon group having 10 to 20 carbon atoms. The number of carbon atoms in _R4 is preferably 15 to 20. The chain hydrocarbon group may be a straight-chain hydrocarbon group or a branched hydrocarbon group. The chain hydrocarbon group may be an alkyl group, an alkenyl group, or an alkynyl group. _R4 is preferably a straight-chain hydrocarbon group, more preferably a straight-chain alkenyl group, and has a double bond.

The conductive paste contains the amino acid-based dispersant represented by the above formula (2) in an amount of 0.01 to 2 parts by mass, preferably 0.02 to 1 part by mass, more preferably 0.03 to 0.6 parts by mass, and may contain 0.1 to 0.6 parts by mass of the amino acid-based dispersant relative to 100 parts by mass of the conductive powder. When the amino acid-based dispersant is contained in the above range, the dry film density can be improved. Note that when the content of the amino acid-based dispersant exceeds 2 parts by mass, mesh marks may be generated on the printed surface or the viscosity of the paste may be significantly reduced when the conductive paste is printed on a green sheet.

The amino acid-based dispersant represented by the above formula (2) can be selected from commercially available products that satisfy the above characteristics. The amino acid-based dispersant may also be manufactured to satisfy the above characteristics using a conventionally known manufacturing method.

The dispersant (including the amino acid-based dispersant and amine-based dispersant) is preferably contained in an amount of 0.02 parts by mass or more and 4 parts by mass or less, and more preferably 0.04 parts by mass or more and 2 parts by mass or less, per 100 parts by mass of the conductive powder. When the content of the dispersant is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, and sheet attack and peeling failure of the green sheet can be suppressed.

The dispersant (including the amino acid-based dispersant and amine-based dispersant) is preferably contained in an amount of 3 mass% or less based on the entire conductive paste. The upper limit of the dispersant content is preferably 2.4 mass% or less, more preferably 2 mass% or less, and even more preferably 1 mass% or less. The lower limit of the dispersant content is not particularly limited, but is, for example, 0.01 mass% or more, preferably 0.05 mass% or more. When the dispersant content is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, and sheet attack and peeling failure of the green sheet can be suppressed.

The conductive paste may contain dispersants other than the amino acid-based dispersants and amine-based dispersants described above, provided that the effects of the present invention are not impaired. Examples of dispersants other than the above include acid-based dispersants including higher fatty acids and polymeric surfactants, cationic dispersants other than acid-based dispersants, nonionic dispersants, amphoteric surfactants, and polymeric surfactants. These dispersants may be used alone or in combination of two or more.

(Conductive paste)
The method for producing the conductive paste of the present embodiment is not particularly limited, and a conventionally known method can be used. The conductive paste can be produced, for example, by preparing the above-mentioned components and stirring and kneading them with a three-roll mill, a ball mill, a mixer, or the like. In this case, if a dispersant is applied to the surface of the conductive powder in advance, the conductive powder is sufficiently loosened without agglomeration, and the dispersant is distributed over the surface, making it easy to obtain a uniform conductive paste. Alternatively, the binder resin may be dissolved in an organic solvent for a vehicle to produce an organic vehicle, and the conductive powder, ceramic powder, organic vehicle, and dispersant may be added to the organic solvent for the paste, and the mixture may be stirred and kneaded with a mixer to produce the conductive paste.

Furthermore, the dry film density (DFD) of the dry film obtained by printing and then drying the conductive paste of this embodiment is, for example, preferably more than 4.8 g/cm ³ and may be more than 4.9 g/cm ^3. The upper limit of the dry film density (DFD) is not particularly limited, but may be 6.5 g/cm ³ or less. The dry film density of the conductive paste is measured by the method described in the examples.

Furthermore, the conductive paste of this embodiment has a viscosity (4 sec ^-1 ) after long-term storage (for example, after being left to stand for 30, 60, or 90 days from a reference time point) of preferably 80 Pa·s or less, or may be 70 Pa·s or less, 60 Pa·s or less, or may be 50 Pa·s or less. Furthermore, when the viscosity after being left to stand for 1 day from the reference time point is taken as the reference viscosity, the change in viscosity (4 sec ^-1 ) after long-term storage is preferably 3 times or less, or may be 2.5 times or less, or may be 2 times or less relative to the reference viscosity. The viscosity of the conductive paste is measured by the method described in the examples.

The conductive paste of this embodiment can be suitably used for electronic components such as multilayer ceramic capacitors. The conductive paste of this embodiment can also be suitably used for forming the internal electrode layers of multilayer ceramic capacitors.

The multilayer ceramic capacitor has at least a dielectric layer formed using a dielectric green sheet and an internal electrode layer formed using a conductive paste. In the multilayer ceramic capacitor, it is preferable that the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste are powders of the same composition. The multilayer ceramic capacitor manufactured using the conductive paste of this embodiment suppresses sheet attack and peeling failure of the green sheet even when the thickness of the dielectric green sheet is, for example, 3 μm or less.

[Electronic Components]
Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, the components may be depicted diagrammatically or at a different scale as appropriate. The positions and directions of components will be described with reference to an XYZ orthogonal coordinate system as shown in Figures 5A and 5B as appropriate. In this XYZ orthogonal coordinate system, the X and Y directions are horizontal directions, and the Z direction is vertical (up-down direction).

Figures 5A and 5B are diagrams showing a multilayer ceramic capacitor 1, which is an example of an electronic component according to an embodiment. The multilayer ceramic capacitor 1 includes a ceramic laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated, and an external electrode 20.

The method for manufacturing a multilayer ceramic capacitor using the conductive paste is described below. First, the conductive paste is printed on a ceramic green sheet and dried to form a dry film. A plurality of ceramic green sheets having this dry film on their upper surfaces are laminated by pressure bonding to obtain a laminate, and the laminate is then fired and integrated to produce a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately laminated. A pair of external electrodes 20 are then formed on both ends of the ceramic laminate 10 to produce a multilayer ceramic capacitor 1. The method is described in more detail below.

First, a ceramic green sheet, which is an unfired ceramic sheet, is prepared. Examples of this ceramic green sheet include a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a powder of a specific ceramic material such as barium titanate, and applying the resulting paste in the form of a sheet onto a support film such as a PET film, and then drying to remove the solvent. The thickness of the dielectric layer made of the ceramic green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less in view of the demand for miniaturization of multilayer ceramic capacitors.

Next, the above-mentioned conductive paste is printed (applied) on one side of the ceramic green sheet by a known method such as screen printing, and then dried to form a dry film, to prepare multiple sheets. Note that, from the viewpoint of the requirement to make the internal electrode layer 11 thin, it is preferable that the thickness of the printed conductive paste (dried film) is 1 μm or less after drying.

Next, the ceramic green sheet is peeled off from the support film, and the ceramic green sheet and the dry film formed on one side of the sheet are stacked alternately, and then a laminate is obtained by heating and pressing. Note that a configuration in which protective ceramic green sheets not coated with conductive paste are further placed on both sides of the laminate may be used.

Next, the laminate is cut to a predetermined size to form a green chip, and then the green chip is subjected to a binder removal treatment and fired under a reducing atmosphere to produce a laminated ceramic (ceramic laminate 10). The atmosphere in the binder removal treatment is preferably air or _N2 gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or higher and 400°C or lower. The temperature is preferably held for 0.5 hours or longer and 24 hours or shorter during the binder removal treatment. The firing is performed in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layer, and the temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the temperature is held for, for example, 0.5 hours or longer and 8 hours or shorter.

By firing the green chip, the organic binder in the green sheet is completely removed, and the ceramic raw powder is fired to form the ceramic dielectric layer 12. The organic vehicle in the dry film is also removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode, forming a multilayer ceramic sintered body in which multiple dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that the sintered multilayer ceramic sintered body may be annealed to incorporate oxygen into the dielectric layer to increase reliability and to suppress reoxidation of the internal electrodes.

Then, a pair of external electrodes 20 are provided on the produced multilayer ceramic sintered body to manufacture the multilayer ceramic capacitor 1. For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. Note that, for example, copper, nickel, or an alloy thereof can be suitably used as the material for the external electrode 20. Note that the electronic component is not limited to a multilayer ceramic capacitor, and may be an electronic component other than a multilayer ceramic capacitor.

The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[Evaluation method]
(Viscosity of conductive paste)
The viscosity of the conductive paste was measured at a flow curve measurement with a rheometer (Anton Paar Rheometer M501) at a rotation speed of 4 sec ^-1 at the reference time point, 24 hours after the production of the conductive paste, and after leaving the paste at rest for 30, 60, and 90 days from the reference time point at room temperature (25°C).The viscosity after leaving the paste at rest for one day from the reference time point was used as the reference viscosity, and the change in viscosity after leaving the paste at rest for 7, 14, 30, 60, and 90 days was shown.

(Dry Film Density)
20 mg of nickel paste was collected in a dome shape on glass and dried at 80 ° C. for 2 hours in a drying furnace. The dry film density (DFD) was calculated from the volume measured using a laser microscope (Keyence VK-X1000) and the weight difference before and after drying of the nickel paste.

[Example 1]
Ni powder (SEM average particle size 0.2 μm) 50 mass%, ceramic powder (BaTiO ₃ ; SEM average particle size 0.06 μm) 3.8 mass%, binder resin in a vehicle consisting of acrylic resin and ethyl cellulose resin was 3 mass% in total, and the blending ratio (mass ratio) of acrylic resin and ethyl cellulose resin was 1:2. 0.5 mass% of oxyethylene laurylamine (dielectric constant: 9.1) as an amine-based dispersant, 0.05 mass% of an amino acid-based dispersant, and terpineol were blended to a total of 100 mass%, and these materials were mixed to prepare a conductive paste. Note that the acrylic resin used was Marproof AM-515 manufactured by NOF Corporation. The amino acid-based dispersant is represented by the above general formula (2), and R ₄ has a straight-chain hydrocarbon group having 10 to 20 carbon atoms. The blending ratio of each component is shown in Table 1.

The change in viscosity and dry film density (DFD) of the conductive paste prepared was evaluated after leaving it for 7, 14, 30, 60, and 90 days relative to the reference viscosity. The evaluation results are shown in Figures 1 and 3.

[Example 2]
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that the Ni powder was 50 mass%, the ceramic powder was 3.8 mass%, the binder resin in the vehicle consisting of the acrylic resin and the ethyl cellulose resin was 3 mass% in total, and the blending ratio of the acrylic resin to the ethyl cellulose resin was 0.5:2.5. The blending ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 1 and 3.

[Example 3]
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that the Ni powder was 50 mass%, the ceramic powder was 3.8 mass%, the binder resin in the vehicle consisting of the acrylic resin and the ethyl cellulose resin was 3 mass% in total, and the blending ratio of the acrylic resin to the ethyl cellulose resin was 0.2:2.8. The blending ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 1 and 3.

[Example 4]
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that the terpineol in Example 1 was replaced with menthanol (dihydroterpineol: DHTPO) and mixed to a total of 100 mass %. The mixing ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 2 and 4.

[Example 5]
A conductive paste was prepared and evaluated in the same manner as in Example 4, except that the Ni powder was 50 mass%, the ceramic powder was 3.8 mass%, the binder resin in the vehicle consisting of the acrylic resin and the ethyl cellulose resin was 3 mass% in total, and the blending ratio of the acrylic resin to the ethyl cellulose resin was 0.5:2.5. The blending ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 2 and 4.

[Example 6]
A conductive paste was prepared and evaluated in the same manner as in Example 4, except that the Ni powder was 50 mass%, the ceramic powder was 3.8 mass%, the binder resin in the vehicle consisting of the acrylic resin and the ethyl cellulose resin was 3 mass% in total, and the blending ratio of the acrylic resin to the ethyl cellulose resin was 0.2:2.8. The blending ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 2 and 4.

[Comparative Example 1]
A conductive paste was prepared in the same manner as in Example 1, except that the acrylic resin was changed to polyvinyl butyral resin (PVB) at a mixing ratio of 1:2, the solvent was 100 mass% terpineol overall, and the amine-based dispersant was omitted. The mixing ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 1 and 3.

[Comparative Example 2]
A conductive paste was prepared in the same manner as in Example 4, except that the acrylic resin was changed to polyvinyl butyral resin (PVB) at a mixing ratio of 1:2, the solvent was 100 mass% of menthanol (dihydroterpineol) as a whole, and the amine-based dispersant was omitted. The mixing ratio of each component is shown in Table 1, and the evaluation results are shown in Figures 2 and 4.

(Evaluation results)
1 is a graph showing the evaluation results of the dry film density (DFD) of the conductive pastes of Examples 1 to 3, which used terpineol (TPO) as the organic solvent, and Comparative Example 1. As shown in FIG. 1, the conductive pastes of Examples 1 to 3, which contain acrylic resin and ethyl cellulose resin and use terpineol (TPO) as the organic solvent, have improved dry film density (DFD) compared to Comparative Example 1, which does not contain acrylic resin and amine-based dispersant.

Figure 2 is a graph showing the evaluation results of the dry film density (DFD) of the conductive pastes of Examples 4 to 6 and Comparative Example 2, which used menthol (dihydroterpineol: DHTPO) as the organic solvent. As shown in Figure 2, the conductive pastes of Examples 4 to 6, which contain acrylic resin and ethyl cellulose resin and use menthol (dihydroterpineol) as the organic solvent, have improved dry film density compared to Comparative Example 2, which does not contain acrylic resin or an amine-based dispersant.

In addition, the conductive pastes of Examples 4 to 6, which used dihydroterpineol (DHTPO) as the organic solvent, had a higher dry film density (DFD) than the conductive pastes of Examples 1 to 3, which used terpineol (TPO).

Figure 3 is a graph showing the evaluation results of the viscosity characteristics over time of the conductive pastes of Examples 1 to 3 and Comparative Example 1, which used terpineol (TPO) as the organic solvent. As shown in Figure 3, the conductive pastes of Examples 1 to 3 had smaller changes in viscosity after being left to stand for 30 days, 60 days, and 90 days from the reference point than the conductive paste of Comparative Example 1.

Figure 4 is a graph showing the evaluation results of the viscosity characteristics over time of the conductive pastes of Examples 4 to 6 and Comparative Example 2, which used dihydroterpineol (DHTPO) as the organic solvent. As shown in Figure 4, the conductive pastes of Examples 4 to 6 had smaller changes in viscosity after being left to stand for 30 days, 60 days, and 90 days from the base point than the conductive paste of Comparative Example 2.

From the above, it is clear that the conductive pastes of Examples 1 to 6, which contain acrylic resin, ethyl cellulose resin, and a specific amine-based dispersant, have improved dry film density, a small amount of viscosity change after being left to stand for a long period of time, and improved viscosity characteristics over time, compared to the conductive pastes of Comparative Example 1 and Comparative Example 2, which use similar organic solvents.

1... multilayer ceramic capacitor 10... ceramic laminate 11... internal electrode layer 12... dielectric layer 20... external electrode 21... external electrode layer 22... plating layer

Claims (7)

It contains conductive powder, ceramic powder, dispersant, binder resin and organic solvent.
The dispersant comprises an amine-based dispersant which is a secondary amine or a tertiary amine;
The binder resin contains an acrylic resin and a cellulose resin,
The organic solvent includes a terpene solvent.
The mass ratio of the acrylic resin to the cellulose resin is 1:1 to 20:2.
Conductive paste. The conductive paste according to claim 1, wherein the binder resin is contained in an amount of 1 part by mass to 10 parts by mass to 10 parts by mass to 100 parts by mass of the conductive powder. The conductive paste according to claim 1 or 2, wherein the acrylic resin is contained in an amount of 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the conductive powder. The conductive paste according to any one of claims 1 to 3 , wherein the amine-based dispersant has a dielectric constant of 10 or less. The conductive paste according to any one of claims 1 to 4 , wherein the acrylic resin has a glass transition temperature (Tg) of -100°C or more and 100°C or less. An electronic component formed by using the conductive paste according to any one of claims 1 to 5 . The laminate has at least a dielectric layer and an internal electrode layer stacked thereon,
A multilayer ceramic capacitor, wherein the internal electrode layers are formed using the conductive paste according to any one of claims 1 to 5 .

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