TWI798301B - Conductive paste, electronic parts, and laminated ceramic capacitors - Google Patents

Abstract

The present invention provides a conductive paste having a viscosity suitable for gravure printing and having excellent dispersibility of the paste, and the like. The conductive paste of the present invention contains conductive powder, a dispersant, a binder resin, and an organic solvent, and the dispersant contains an alkyl phosphate compound as an acidic dispersant, and the binder resin contains an acetal resin, and an organic The solvent contains a glycol ether solvent.

Description

Conductive paste, electronic parts, and laminated ceramic capacitors

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

Along with the miniaturization and high performance of electronic equipment such as mobile phones and digital devices, miniaturization and high capacity are also desired for electronic components including laminated ceramic capacitors and the like. A laminated ceramic capacitor has a structure in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated. By reducing the thickness of the dielectric layers and internal electrode layers, miniaturization and high capacity can be achieved.

For example, a laminated ceramic capacitor can be manufactured in the following manner. First, on the surface of a dielectric green sheet containing a dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin, an internal layer containing conductive powder, a binder resin, and an organic solvent is printed in a predetermined electrode pattern. The electrode slurry (conductive slurry) is dried to form a dry film. Next, the dry film and the dielectric green sheet are stacked in multiple layers so as to alternately overlap, and then heated and pressure-bonded to integrate them to form a pressure-bonded body. The press-bonded body is cut, subjected to an organic binder removal treatment in an oxidizing gas or an inert gas, and then fired to obtain a fired wafer. Next, a paste for external electrodes is applied to both ends of the fired wafer, and after firing, nickel plating or the like is performed on the surface of the external electrodes to obtain a laminated ceramic capacitor.

As a printing method for printing conductive paste on dielectric green sheets, screen printing is generally used conventionally, but due to the miniaturization, thinning and productivity improvement of electronic equipment, higher Productivity to print finer electrode patterns.

As one of the printing methods of conductive paste, gravure plate is proposed as a continuous printing method in which conductive paste is transferred from the plate by filling the recesses provided on the plate with conductive paste and pressing the plate to the surface to be printed. printing method. The gravure printing method has high printing speed and excellent productivity. When using the gravure printing method, it is necessary to appropriately select a binder resin, a dispersant, a solvent, and the like in the conductive paste, and to adjust characteristics such as viscosity to a range suitable for gravure printing.

For example, Patent Document 1 describes a conductive paste for forming an internal conductor film by gravure printing. The internal conductor film has a plurality of ceramic layers and The internal conductor film in the laminated ceramic electronic parts of the internal conductor film of the specific interface extension, the conductive paste contains 30 to 70% by weight of solid content containing metal powder, 1 to 10% by weight of ethoxylate containing The ratio is 49.6% or more of ethyl cellulose resin component, 0.05~5% by weight of dispersant and solvent component as the balance, and the viscosity η _0.1 at a shear rate of 0.1 (s ^-1 ) is 1Pa. A thixotropic fluid whose viscosity η _0.02 at a shear rate of 0.02 (s ^-1 ) satisfies the conditions expressed by the specific formula s or more.

In addition, Patent Document 2 describes a conductive paste that is used for forming an internal conductor film by gravure printing similarly to the above-mentioned Patent Document 1, and contains 30 to 70% by weight of The solid content of the metal powder, 1~10% by weight of the resin component, 0.05~5% by weight of the dispersant, and the balance of the solvent component, and the viscosity at a shear rate of 0.1 (s ^-1 ) is 1Pa. For a thixotropic fluid with a shear rate of 0.1 (s ^-1 ) as a reference, the rate of change in viscosity at a shear rate of 10 (s ^-1 ) is 50% or more.

According to the above-mentioned patent documents 1 and 2, the above-mentioned conductive paste has a viscosity of 1 Pa when the shear rate is 0.1 (s ^-1 ). The thixotropic fluid of s or more can obtain stable continuous printability at high speed in gravure printing, and can manufacture laminated ceramic electronic parts such as laminated ceramic capacitors with good production efficiency.

In addition, Patent Document 3 describes a conductive paste for gravure printing, which contains conductive powder (A), organic resin (B), organic solvent (C), additive (D) and dielectric powder (E). The conductive paste for internal electrodes of laminated ceramic capacitors, the organic resin (B) is composed of polyvinyl butyral with a degree of polymerization of 10,000 to 50,000 and ethyl cellulose with a weight average molecular weight of 10,000 to 100,000, organic The solvent (C) is composed of any one of propylene glycol monobutyl ether, or a mixed solvent of propylene glycol monobutyl ether and propylene glycol methyl ether acetate, or a mixed solvent of propylene glycol monobutyl ether and mineral spirits, and the additive (D) consists of a separation inhibitor agent and a dispersant, and the separation inhibitor is composed of a composition containing a polycarboxylate polymer or a polycarboxylate. According to Patent Document 3, the conductive paste has a viscosity suitable for gravure printing, improves the uniformity and stability of the paste, and has good drying properties.

[Prior technical literature] 【Patent Literature】

[Patent Document 1] Japanese Patent Laid-Open No. 2003-187638

[Patent Document 2] Japanese Patent Laid-Open No. 2003-242835

[Patent Document 3] Japanese Unexamined Patent Publication No. 2012-174797

Along with the reduction in the thickness of the internal electrode layer in recent years, the particle size of the conductive powder also tends to be reduced. When the particle size of the conductive powder is small, the specific surface area of the particle surface increases, so the surface activity of the conductive powder (metal powder) becomes high, and the dispersibility of the conductive paste may decrease, so it is required Conductive paste with higher dispersibility.

In addition, when the gravure printing method is used to print the conductive paste, the viscosity of the paste is required to be lower than that of the screen printing method, so the dispersion of the paste can be considered due to the sedimentation of the conductive powder with a large specific gravity. reduced sex. In addition, in the conductive pastes described in the aforementioned Patent Documents 1 and 2, although the dispersibility of the slurry is improved by removing lumps in the conductive paste using a filter, a step of removing lumps is required. , so the manufacturing process tends to become complicated.

In view of such a situation, an object of the present invention is to provide an electrically conductive paste having a paste viscosity suitable for gravure printing and having excellent dispersibility and productivity of the paste.

A first aspect of the present invention provides a conductive paste containing conductive powder, a dispersant, a binder resin, and an organic solvent, the dispersant containing an alkyl phosphate compound as an acidic dispersant, and the binder resin containing acetal It is a resin, and the organic solvent contains a glycol ether-based solvent.

In addition, the acid-based dispersant is preferably an alkylpolyoxyalkylene phosphate compound.

In addition, the dispersant may further contain an alkali-based dispersant. Also, the dispersant is preferably contained in a total amount of 0.2 parts by mass or more and 1 part by mass or less based on 100 parts by mass of the conductive powder.

The conductive powder is preferably a metal powder containing at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. In addition, the average particle diameter of the conductive powder is preferably not less than 0.05 μm and not more than 1.0 μm. Moreover, it is desirable that an electroconductive paste contains ceramic powder. Also, the ceramic powder preferably contains a perovskite-type oxide. In addition, the average particle diameter of the ceramic powder is preferably not less than 0.01 μm and not more than 0.5 μm. Also, the conductive paste is ideally used for internal electrodes of laminated ceramic parts. Also, ideally, the viscosity of the conductive paste at a shear rate of 100sec ^-1 is 0.8Pa. Below S, the viscosity is 0.19Pa when the shear rate is 10000sec ^-1 . Below S.

A second aspect of the present invention provides an electronic component formed using the above-mentioned conductive paste.

A third aspect of the present invention provides a laminated ceramic capacitor comprising at least a laminate formed by laminating dielectric layers and internal electrodes formed using the above-mentioned conductive paste.

The conductive paste of the present invention has a viscosity suitable for gravure printing, and is excellent in dispersibility and productivity of the paste. In addition, electrode patterns of electronic components such as laminated ceramic capacitors formed using the conductive paste of the present invention have excellent printability of the conductive paste and uniform thickness when forming thinned electrodes.

1‧‧‧Laminated Ceramic Capacitors

10‧‧‧Ceramic laminate

11‧‧‧internal electrode layer

12‧‧‧dielectric layer

20‧‧‧External electrodes

21‧‧‧External electrode layer

22‧‧‧Electroplating layer

[ Fig. 1 ] A perspective view and a cross-sectional view showing a multilayer ceramic capacitor according to an embodiment of the present invention.

[Conductive Paste]

The conductive paste of this embodiment contains conductive powder, a dispersant, a binder resin, and an organic solvent. Each component will be described in detail below.

(conductive powder)

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

The average particle diameter of the conductive powder is preferably from 0.05 μm to 1.0 μm, more preferably from 0.1 μm to 0.5 μm. When the average particle size of the conductive powder is within the above range, it can be suitably used as a slurry for an internal electrode of a thinned multilayer ceramic capacitor, and for example, the smoothness and dry film density of a dry film can be improved. In this specification, unless otherwise specified, the average particle diameter of the conductive powder refers to the particle diameter calculated from the specific surface area obtained by the BET method. For example, the calculation formula of the average particle diameter of nickel powder is as follows.

Average particle size=6/S.A×ρ...(Formula)

(ρ=8.9 (true density of nickel), S.A=BET specific surface area of nickel powder)

The content of the conductive powder is preferably from 30% by mass to 70% by mass with respect to the entire conductive paste, more preferably from 40% by mass to 65% by mass. When content of electroconductive powder exists in the said range, electroconductivity and dispersibility are excellent.

(ceramic powder)

The conductive paste may contain ceramic powder. The ceramic powder is not particularly limited. For example, in the case of a paste for internal electrodes of a laminated ceramic capacitor, a known ceramic powder can be appropriately selected according to the type of laminated ceramic capacitor to be used. Examples of the ceramic powder include perovskite-type oxides containing Ba and Ti, preferably barium titanate (BaTiO ₃ ). In addition, one type of ceramic powder may be used, or two or more types may be used.

As the ceramic powder, a ceramic powder containing barium titanate as a main component and an oxide as a subcomponent can be used. Examples of oxides include one or more oxides selected from the group consisting of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and rare earth elements.

In addition, as ceramic powder, for example, perovskite-type oxide ferroelectric ceramics in which Ba atoms and Ti atoms of barium titanate (BaTiO ₃ ) are substituted with other atoms such as Sn, Pb, and Zr can also be mentioned. powder.

As the ceramic powder in the slurry for internal electrodes, powder having the same composition as that of the dielectric ceramic powder constituting the dielectric green sheet of the laminated ceramic capacitor can be used. Accordingly, generation of cracks due to shrinkage mismatch at the interface between the dielectric layer and the internal electrode layer in the sintering process can be suppressed. Such ceramic powders include, for example, ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , TiO ₂ , Nd ₂ O ₃ and other oxides.

The average particle size of the ceramic powder is, for example, from 0.01 μm to 0.5 μm, preferably from 0.01 μm to 0.3 μm. When the average particle size of the ceramic powder is within the above range, when used as a slurry for internal electrodes, a sufficiently thin and uniform internal electrode can be formed. The average particle diameter of the ceramic powder is a particle diameter calculated from the specific surface area obtained by the BET method in the same manner as the above-mentioned conductive powder.

The content of the ceramic powder is preferably not less than 1 part by mass and not more than 30 parts by mass, more preferably not less than 3 parts by mass and not more than 30 parts by mass, based on 100 parts by mass of the conductive powder.

The content of the ceramic powder is preferably from 1 mass % to 20 mass % with respect to the whole conductive paste, more preferably from 3 mass % to 20 mass %.

(Binder resin)

The binder resin contains an acetal-based resin. As the acetal-based resin, butyral-based resins such as polyvinyl butyral are preferable. When the binder resin contains an acetal-based resin, the viscosity can be adjusted to a viscosity suitable for gravure printing, and the adhesive strength with the green sheet can be further improved. The binder resin may contain, for example, 20% by mass or more of acetal-based resin, 30% by mass or more, or 60% by mass or more of the entire binder resin, or may consist of only acetal-based resin.

The content of the acetal-based resin is preferably 1 to 10 parts by mass, more preferably 1 to 8 parts by mass, based on 100 parts by mass of the conductive powder.

In addition, the binder resin may contain other resins than the acetal-based resin. Other resins are not particularly limited, and known resins can be used. Examples of other resins include cellulose-based resins such as methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and nitrocellulose, and acrylic resins. , Combustion and decomposability, etc., Ethyl cellulose is ideal. In addition, the molecular weight of the binder resin is, for example, about 20,000 to 200,000.

The content of the binder resin is preferably not less than 1 part by mass and not more than 10 parts by mass, more preferably not less than 1 part by mass and not more than 8 parts by mass, based on 100 parts by mass of the conductive powder.

The content of the binder resin is preferably from 0.5% by mass to 10% by mass with respect to the entire conductive paste, more preferably from 0.5% by mass to 6% by mass. When content of binder resin is in the said range, electroconductivity and dispersibility are excellent.

(Organic solvents)

The organic solvent contains at least one of a glycol ether-based solvent and an acetate-based solvent, and preferably contains a glycol ether-based solvent.

Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, and ethylene glycol monohexyl ether. (2) Ethylene glycol ethers, and propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether (PNB), etc. Among them, propylene glycol monoalkyl ethers are preferable, and propylene glycol monobutyl ether is more preferable. When the organic solvent contains a glycol ether-based solvent, it is excellent in compatibility with the above-mentioned binder resin and excellent in drying property.

The organic solvent may contain, for example, 25% by mass or more of a glycol ether-based solvent, or may contain 50% by mass or more of a glycol ether-based solvent based on the entire organic solvent, or may consist of only a glycol ether-based solvent. Moreover, a glycol ether solvent may be used individually by 1 type, and may use 2 or more types together.

Examples of acetate-based solvents include dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl Glycol ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy 3-methylbutyl acetate, 1-methoxypropyl-2-acetate, etc. .

When the organic solvent contains an acetate-based solvent, for example, it may contain a solvent selected from dihydroterpineol acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate. An acetate-based solvent (A) of at least one of the ester group. Among them, isobornyl acetate is more preferable. The acetate-based solvent is preferably contained in an amount of 90% by mass or more and 100% by mass or less, more preferably 100% by mass, with respect to the entire organic solvent other than the glycol ether-based solvent.

In addition, when the organic solvent contains an acetate-based solvent, for example, the above-mentioned acetate-based solvent (A) and a solvent selected from ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate may be included. at least one acetate-based solvent (B). When using such a mixed solvent, the viscosity adjustment of an electroconductive paste can be performed easily, and the drying rate of an electroconductive paste can be accelerated.

In the case of a mixed solution containing an acetate-based solvent (A) and an acetate-based solvent (B), it is desirable to contain acetic acid in an amount of 50 mass % or more and 90 mass % or less with respect to the entire acetate-based solvent The ester-based solvent (A) is more preferably contained in an amount of 60% by mass or more and 80% by mass or less. In the case of the above mixed solution, the acetate-based solvent (B) is contained in an amount of 10% by mass to 50% by mass, more preferably 20% by mass to 40% by mass, based on the entire acetate-based solvent.

In addition, the organic solvent may contain other organic solvents other than the glycol ether-based solvent and the acetate-based solvent. It does not specifically limit as another organic solvent, A well-known organic solvent which can dissolve the said binder resin can be used. Examples of other organic solvents include acetate-based solvents such as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate; ketone-based solvents such as methyl ethyl ketone and methyl isobutyl ketone; Terpine solvents such as terpineol and dihydroterpineol, aliphatic hydrocarbon solvents such as tridecane, nonane, and cyclohexane, etc. Among them, an aliphatic hydrocarbon solvent is preferable, and mineral spirits are more preferable among the aliphatic hydrocarbon solvents. In addition, one kind or two or more kinds of other organic solvents may be used.

The organic solvent may contain, for example, a glycol ether-based solvent as a main solvent and an aliphatic hydrocarbon solvent as a sub-solvent. In this case, based on 100 parts by mass of the conductive powder, it is desirable to contain 30 to 50 parts by mass of the glycol ether solvent, more preferably to contain 40 to 50 parts by mass. 100 parts by mass, for example, 15 to 80 parts by mass of aliphatic hydrocarbon solvent, preferably 20 to 80 parts by mass, more preferably 20 to 40 parts by mass.

The content of the organic solvent is preferably not less than 50 parts by mass and not more than 130 parts by mass, more preferably not less than 60 parts by mass and not more than 90 parts by mass, based on 100 parts by mass of the conductive powder. When content of an organic solvent exists in the said range, electroconductivity and dispersibility are excellent.

The content of the organic solvent is preferably not less than 20% by mass and not more than 50% by mass, more preferably not less than 25% by mass and not more than 45% by mass with respect to the entire conductive paste. When content of an organic solvent exists in the said range, electroconductivity and dispersibility are excellent.

(Dispersant)

The conductive paste of this embodiment preferably contains an acid-based dispersant having phosphorus as an acid-based dispersant, and preferably contains an alkyl phosphate compound among them. The inventors of the present invention have studied various dispersants for dispersants used in conductive pastes. Although the reason for this is not clear, they have found that by using the above-mentioned binder resin and organic solvents containing The dispersant of the base ester compound can greatly suppress the generation of lumps when forming the internal electrodes, thereby improving the dispersibility of the slurry.

Alkyl phosphate compounds are phosphate esters having an alkyl group. In addition, the alkyl phosphate compound preferably has a polyoxyalkylene structure, and is preferably an alkyl polyoxyalkylene phosphate compound.

In addition, the alkyl phosphate compound may be a dispersant having a linear structure or a dispersant having a complicated branched structure (for example, two or more branches), and is preferably a linear structure.

The alkyl phosphate compound preferably contains, for example, a compound represented by the following chemical formula (1).

In the above chemical formula (1), X represents a linear alkyl group having 1 to 18 carbon atoms, Y represents -(OCH ₂ CH ₂ )n-, and n is 1 to 18.

Although the details are unclear, it is presumed that by using an alkyl phosphate compound as a phosphorus-containing dispersant, the phosphoric acid site is adsorbed on the surface of conductive powder or the like to neutralize the surface potential or inert the hydrogen bond site, and in addition to The specific three-dimensional structure containing alkyl groups in parts other than phosphoric acid can effectively inhibit the aggregation of conductive powder and the like, thereby further improving the stability of slurry viscosity.

In addition, the phosphorus-containing acid-based dispersant may also be a mixture of an alkyl phosphate compound and other phosphoric acid-based dispersants, but it is preferably composed of an alkyl phosphate compound, more preferably an alkyl polyoxyalkylene phosphate compound. . In addition, although the phosphorus-containing acid-based dispersant may be a mixture, it is preferably a single compound.

The phosphorous-containing acid-based dispersant may be contained, for example, at 0.2 to 2 parts by mass based on 100 parts by mass of the conductive powder, preferably at least 0.2 to 1 part by mass. When content of the acid-type dispersing agent containing phosphorus exists in the said range, the dispersibility of the electroconductive powder in an electroconductive paste is excellent.

The phosphorous-containing acid-based dispersant is contained, for example, in an amount of 3% by mass or less with respect to the entire conductive paste. The upper limit of the content of the phosphorus-containing acid-based dispersant is preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1% by mass or less. The lower limit of the content of the phosphorus-containing acid-based dispersant is not particularly limited, and is, for example, 0.1% by mass or more.

Phosphorus-containing acid-based dispersants such as alkyl phosphate compounds, for example, can be selected from commercially available products that satisfy the above characteristics. In addition, the above-mentioned dispersant can also be manufactured using conventionally known manufacturing methods to meet the above-mentioned characteristics.

The conductive paste may use only the above-mentioned phosphorus-containing acid-based dispersant as a dispersant, or may use other acid-based dispersants conventional to the phosphorus-containing acid-based dispersant. Examples of other acid-based dispersants include higher fatty acids, polymer surfactants, and the like. These dispersants can be used alone or in combination of two or more.

The higher fatty acid may be an unsaturated carboxylic acid or a saturated carboxylic acid, and is not particularly limited, and examples thereof include stearic acid, oleic acid, behenic acid, myristic acid, palmitic acid, linoleic acid, and lauric acid , linolenic acid and other higher fatty acids with more than 11 carbon atoms. Among them, oleic acid or stearic acid is preferable.

The other acid-based dispersants are not particularly limited, and include surfactants selected from the following surfactants: alkyl monoamine salt type represented by monoalkylamine salt, N- Alkyl (C14~C18) propylene diamine dioleate represented by alkyl diamine salt type, alkyl trimethyl ammonium chloride represented by alkyl trimethyl ammonium chloride type, palm alkyl diamine salt type represented by Alkyl dimethyl benzyl ammonium salt type represented by methyl benzyl ammonium chloride, quaternary ammonium salt type represented by alkyl/dipolyoxyethylene methyl ammonium chloride, alkyl pyridinium salt type, di Tertiary amine type represented by methylstearylamine, polyoxyethylene alkylamine type represented by polyoxypropylene/polyoxyethylene alkylamine, N,N',N'-tris(2-hydroxyethyl )-N-Alkyl(C14~18)1,3-diaminopropane is an oxyethylene addition type of diamine represented by

In addition, the dispersant may contain dispersants other than the acid-based dispersant. As a dispersant other than an acidic dispersant, an alkaline dispersant, a nonionic dispersant, an amphoteric dispersant, etc. are mentioned. These dispersants can be used alone or in combination of two or more.

Examples of the alkali-based dispersant include aliphatic amines such as laurylamine, polyethylene glycol laurylamine, rosinamine, cetylamine, myristylamine, and stearylamine. When an alkali-based dispersant is also included in the conductive paste along with the phosphorous-containing acid-based dispersant, both viscosity stability over time and slurry dispersibility can be achieved at a very high level.

For example, based on 100 parts by mass of the conductive powder, an alkali-based dispersant may be contained at least 0.01 parts by mass and less than 2 parts by mass, preferably at least 0.01 parts by mass and at most 1 part by mass, more preferably at least 0.02 parts by mass. It is not more than 0.02 mass part or more and 0.5 mass part or less more preferably. Also, for example, based on 100 parts by mass of the above-mentioned acid-based dispersant, the alkali-based dispersant may be contained in an amount of 10 parts by mass to 300 parts by mass, preferably in a range of 50 parts by mass to 150 parts by mass. When the alkali-based dispersant is contained within the above range, the viscosity stability of the slurry over time is more excellent.

For example, the alkali-based dispersant is contained in an amount of 0% by mass to 2.5% by mass relative to the entire conductive paste, preferably 0% by mass to 1.5% by mass, more preferably 0% by mass to 1.0% by mass, More preferably, it contains 0.1 mass % or more and 1.0 mass % or less, and it is still more preferable that it contains 0.1 mass % or more and 0.8 mass % or less. When the alkali-based dispersant is contained in the above-mentioned range, the viscosity stability of the slurry over time is more excellent.

In the conductive paste, the content of the entire dispersant (including acid-based dispersants containing phosphorus and other optional dispersants) may be, for example, 0.2 parts by mass or more based on 100 parts by mass of the conductive powder. 2 parts by mass or less, preferably 0.2 parts by mass or more and 1 part by mass or less. When the content of the dispersant (as a whole) exceeds the above-mentioned range, the dryness of the conductive paste deteriorates, sheet erosion occurs, and the green sheet may not be peeled from the PET film of the backing paper.

(other ingredients)

The electroconductive paste of this embodiment may contain other components other than the said components as needed. As other components, for example, conventionally known additives such as defoamers, plasticizers, surfactants, and thickeners can be used.

(conductive paste)

The method for producing the conductive paste of this embodiment is not particularly limited, and a conventionally known method can be used. For example, the conductive paste can be produced by stirring and kneading each of the above-mentioned components with a three-roll mill, a ball mill, a mixer, or the like. At this time, if the dispersant is pre-coated on the surface of the conductive powder, the conductive powder can be sufficiently dispersed without agglomeration, and the dispersant spreads over the surface, making it easy to obtain a uniform conductive paste. In addition, it is also possible to dissolve the binder resin in a part of the organic solvent in advance, and after preparing the organic vehicle, add conductive powder, ceramic powder, dispersant, and organic vehicle to the organic solvent for slurry adjustment, and then stir, kneading to prepare a conductive paste.

The ideal viscosity of the conductive paste is 0.8Pa when the shear rate is 100sec ^-1 . Below S. When the viscosity at a shear rate of 100 sec ^-1 is within the above range, it can be suitably used as an electroconductive paste for gravure printing. If it exceeds the above range, the viscosity may be too high and may not be suitable for gravure printing. The lower limit of the viscosity when the shear rate is 100sec ^-1 is not particularly limited, for example, it is 0.2Pa. S and above.

Also, the ideal viscosity of the conductive paste is 0.19Pa when the shear rate is 10000sec ^-1 . Below S, more ideally 0.18Pa. Below S. When the viscosity at a shear rate of 10000 sec ^-1 is within the above range, it can be suitably used as an electrically conductive paste for gravure printing. When exceeding the said range, a viscosity may become too high and it may not be suitable for gravure printing. The lower limit of the viscosity when the shear rate is 10000sec ^-1 is not particularly limited, for example, it is 0.05Pa. S and above.

The conductive paste can be suitably used for electronic components such as laminated ceramic capacitors. A laminated ceramic capacitor has a dielectric layer formed using a dielectric green sheet and an internal electrode layer formed using a conductive paste.

For a laminated ceramic capacitor, it is desirable that the dielectric ceramic powder contained in the dielectric green sheet and the ceramic powder contained in the conductive paste have the same composition. The multilayer ceramic device produced using the conductive paste of this embodiment can suppress sheet erosion and peeling failure of the dielectric green sheet even when the thickness of the dielectric green sheet is, for example, 3 μm or less.

[electronic parts]

Hereinafter, embodiments of electronic components and the like according to the present invention will be described with reference to the drawings. In the drawings, it may be shown in a schematic form or changed in scale as appropriate. In addition, the position, direction, etc. of a component are demonstrated referring suitably the XYZ rectangular coordinate system shown in FIG. 1 etc. FIG. In this XYZ rectangular coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (vertical direction).

A in FIG. 1 and B in FIG. 1 are diagrams showing a laminated ceramic capacitor 1 as an example of an electronic component of the embodiment. Multilayer ceramic capacitor 1 has ceramic laminate 10 and external electrodes 20 in which dielectric layers 12 and internal electrode layers 11 are alternately laminated.

Hereinafter, a method of manufacturing a laminated ceramic capacitor using the above-mentioned conductive paste will be described. First, a conductive paste is formed on a dielectric green sheet by a printing method, and a dry film is formed. A plurality of dielectric green sheets having the dry film on the upper surface are stacked by pressure bonding, and then fired to integrate them, thereby preparing a laminated ceramic fired body (ceramic layer Integrated body 10). Thereafter, the laminated ceramic capacitor 1 is produced by forming a pair of external electrodes at both end portions of the ceramic laminate 10 . Hereinafter, a more detailed description will be given.

First, a dielectric green sheet as an unfired ceramic sheet is prepared. Examples of the dielectric green sheet include paste for dielectric layers obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to predetermined ceramic powder such as barium titanate. It is a dielectric green sheet formed by coating a support film such as a PET film in a sheet shape and drying to remove the solvent. Also, the thickness of the dielectric layer made of the dielectric green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less in view of the need for miniaturization of laminated ceramic capacitors.

Next, a plurality of sheets in which the internal electrode layers 11 made of the conductive paste were formed by printing and coating the above-mentioned conductive paste on one surface of the dielectric green sheet by the gravure printing method were prepared. In addition, the thickness of the internal electrode layer 11 made of the conductive paste is desirably 1 μm or less after drying from the viewpoint of the requirement for thinning the internal electrode layer 11 .

Next, the dielectric green sheet is peeled from the support film, and the dielectric green sheet and the conductive paste (dry film) formed on one surface of the dielectric green sheet are alternately arranged. After lamination, a laminated body (press-bonded body) is obtained by heating and pressurizing. In addition, a configuration may be adopted in which protective dielectric green sheets not coated with the conductive paste are further arranged on both surfaces of the laminate (press-bonded body).

Next, after the laminated body is cut into a predetermined size to form a green wafer, the green wafer is subjected to a binder removal process and fired under a reducing gas, whereby a laminated ceramic fired body (ceramic laminated body) is prepared. body 10). In addition, the gas atmosphere in the binder removal process is ideally the air or N ₂ gas atmosphere. The temperature at the time of performing binder removal process is 200 to 400 degreeC, for example. In addition, the retention time at the above-mentioned temperature when performing the binder removal treatment is preferably not less than 0.5 hours and not more than 24 hours. In addition, in order to suppress the oxidation of the metal used in the internal electrode layer, the firing is performed in a reducing gas atmosphere, and the temperature when firing the laminate is, for example, 1000°C to 1350°C. The temperature retention time is, for example, not less than 0.5 hours and not more than 8 hours.

By firing the green wafer, the organic binder in the green sheet is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12 . In addition, the organic vehicle in the internal electrode layer 11 is removed, and nickel powder or nickel alloy powder as a main component is sintered or melted to integrate, thereby forming the internal electrode, and further forming the dielectric layer 12 and the internal electrode layer 11. Multilayer The ceramic laminated body 10 which is laminated|stacked alternately. In addition, an annealing treatment may be performed on the fired ceramic laminate 10 from the viewpoint of improving reliability by bringing oxygen into the interior of the dielectric layer and suppressing reoxidation of internal electrodes.

Then, the laminated ceramic capacitor 1 is manufactured by providing a pair of external electrodes 20 to the prepared ceramic laminate 10 . 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 . In addition, as a material of the external electrode 20, for example, copper, nickel, or alloys thereof can be preferably used. In addition, electronic components other than laminated ceramic capacitors may be used as the electronic components.

【Example】

Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to an Example at all.

[Evaluation method]

(Viscosity of conductive paste)

Using a rheometer, the viscosity after production of the electroconductive paste was measured under conditions of a shear rate of 100 sec ^-1 and 10000 sec ^-1 .

(Dispersibility of conductive paste)

The dispersibility of the conductive paste was evaluated by the following method.

On a glass substrate (2 inches), a sample (prepared conductive paste) was printed (GAP thickness=5 μm) and dried. Drying is carried out in a belt furnace at a maximum temperature of 120-150°C in an atmospheric gas environment. The dried film (2 cm x 2 cm, thickness 3 μm) obtained after drying was observed with an optical microscope at ×100 (eyepiece, objective lens; 10 times each) while irradiating light (backlight) from the backside of the glass substrate (backlight = from The back surface of the glass substrate was irradiated with light), and the presence or absence of lumps was confirmed. When no lumps were observed, the dispersibility of the conductive paste was evaluated as "good", and when one or more lumps were observed, the dispersibility of the conductive paste was evaluated as "poor". ".

[use material]

(conductive powder)

As the conductive powder, Ni powder (average particle diameter: 0.3 μm) was used.

(ceramic powder)

As the ceramic powder, barium titanate (BaTiO ₃ ; average particle diameter: 0.06 μm) was used.

(Binder resin)

As the binder resin, polyvinyl butyral resin (PVB, acetal resin) and ethyl cellulose (EC) were used.

(Dispersant)

(1) An alkylpolyoxyalkylene phosphate compound is used as the acid-based dispersant (A).

(2) Rosinamine (B), polyethylene glycol laurylamine (C), and oleylamine (D) were used as alkali-based dispersants.

(3) Use phosphoric acid-based dispersant (E) containing phosphoric acid polyester (polyester with phosphoric acid group) as the main component and the balance as phosphoric acid as the acid-based dispersant (A) other than the above-mentioned acid-based dispersant (A) for comparison).

(Organic solvents)

As the organic solvent, propylene glycol monobutyl ether (PNB, glycol ether solvent), mineral spirits (MA), and terpineol (TPO) were used.

[Example 1]

Based on 100 parts by mass of Ni powder as conductive powder, 25 parts by mass of ceramic powder, 0.28 parts by mass of acid-based dispersant (A) as a dispersant, 4 parts by mass of EC as a binder resin, and 2 Parts by mass of PVB, 48 parts by mass of PNB as an organic solvent, and 21 parts by mass of MA were mixed to prepare an electroconductive paste. The viscosity of the prepared conductive paste and the dispersibility of the paste were evaluated by the above method. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 2]

As a dispersant, except having used 0.5 mass parts of acidic dispersants (A), it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 3]

As a dispersant, except having used 1.0 mass parts of acidic dispersants (A), it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 4]

Except having mixed 0.28 mass parts of acid-type dispersants (A) and 0.10 mass parts of rosin amines (B) as a dispersant, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 5]

The acid-based dispersant (A) of 0.28 mass parts and the polyethylene glycol laurylamine (C) of 0.10 mass parts are mixed as dispersant, except that, prepare conductive paste in the same manner as in Example 1 and Make an evaluation. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 6]

Except having mixed 0.28 mass parts of acidic dispersants (A) and 0.10 mass parts of oleylamine (D) as a dispersant, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 7]

Except having mixed 0.28 mass parts of acidic dispersants (A) and 0.22 mass parts of oleylamine (D) as a dispersant, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 8]

Except having mixed 0.56 mass parts of acidic dispersants (A) and 0.44 mass parts of oleylamine (D) as a dispersant, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 9]

As binder resin, except having used only 6 mass parts of PVB, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Example 10]

As an organic solvent, except having used 57 mass parts of PNB and 12 mass parts of MA, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Comparative example 1]

As a dispersant, use 0.28 parts by mass of phosphoric acid-based dispersant (E) containing phosphoric acid polyester as the main component and 0.10 parts by mass of alkali-based dispersant (B), in the same manner as in Example 1 Conductive pastes were prepared and evaluated. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Comparative example 2]

As an organic solvent, except having used only terpineol (TPO), it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Comparative example 3]

As binder resin, except having used only EC, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

[Comparative example 4]

Except having used only EC as a binder resin, and having used only terpineol as an organic solvent, it carried out similarly to Example 1, and prepared and evaluated the electroconductive paste. The contents of the dispersant and the like of the conductive paste are shown in Table 1, and the evaluation results of the viscosity and dispersibility of the conductive paste are shown in Table 2.

(Evaluation results)

The viscosity of the conductive paste of the embodiment is 0.34~0.69Pa when the shear rate is 100sec- ¹ . S, the viscosity when the shear rate is 10000sec ^-1 is 0.12~0.19Pa. S, is the viscosity suitable for gravure printing. In addition, no lumps were observed on the surface of the dried film after printing with the conductive paste of this example, indicating that the dispersibility of the paste is excellent.

On the other hand, in the conductive paste of Comparative Example 1 using a phosphoric acid-based dispersant (E) other than the acid-based dispersant (A), lumps were observed on the surface of the dried film after printing, indicating that the paste poor dispersion. In addition, Comparative Example 2 in which the organic solvent is outside the scope of the present invention, Comparative Example 3 in which the binder resin is outside the scope of the present invention, and Comparative Example 4 in which the organic solvent and the binder resin are outside the scope of the present invention In the conductive paste, the viscosity suitable for gravure printing cannot be obtained. Therefore, in Comparative Examples 2 to 4, an appropriate dry film could not be obtained, and evaluation of dispersibility could not be performed.

【Industrial Utilization】

The conductive paste of the present invention has a viscosity suitable for gravure printing, and the dispersion of the paste is good. Therefore, the conductive paste of the present invention is particularly suitable as a raw material for internal electrodes of laminated ceramic capacitors that are chip parts of electronic equipment such as mobile phones and digital devices, and is particularly suitable as a conductive paste for gravure printing. .

Claims (12)

A conductive paste comprising conductive powder, a dispersant, a binder resin, and an organic solvent, wherein the dispersant contains an alkyl phosphate compound as an acidic dispersant; the binder resin contains acetal resin; the aforementioned organic solvent contains a glycol ether solvent; wherein, the aforementioned alkyl phosphate compound contains a compound represented by the following chemical formula (1):

In the aforementioned chemical formula (1), X represents a linear alkyl group having 1 to 18 carbon atoms, Y represents -(OCH ₂ CH ₂ )n-, and n is 1 to 18. The conductive paste described in claim 1, wherein the dispersant further contains an alkali-based dispersant. The conductive paste described in claim 1, wherein the above-mentioned dispersant is contained in a total amount of 0.2 to 1 part by mass based on 100 parts by mass of the conductive powder. The conductive paste described in claim 1, wherein the conductive powder contains at least one metal powder selected from the group consisting of Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. The conductive paste as described in item 1 of the scope of the patent application, wherein the conductive powder The average particle diameter is not less than 0.05 μm and not more than 1.0 μm. The conductive paste described in claim 1, wherein the conductive paste contains ceramic powder. In the conductive paste described in claim 6, the ceramic powder contains a perovskite oxide. The conductive paste described in claim 6 or 7 of the patent claims, wherein the average particle size of the ceramic powder is not less than 0.01 μm and not more than 0.5 μm. The conductive paste described in claim 1 of the patent application, wherein the above-mentioned conductive paste is used for internal electrodes of laminated ceramic parts. Such as the conductive paste described in Item 1 of the scope of the patent application, wherein the viscosity of the aforementioned conductive paste is 0.8Pa at a shear rate of 100sec ^-1 . Below S, the viscosity is 0.19Pa when the shear rate is 10000sec ^-1 . Below S. An electronic component is characterized in that it is an electronic component formed by using the conductive paste described in any one of items 1 to 10 of the scope of application. A laminated ceramic capacitor characterized in that it has at least a laminate formed by laminating dielectric layers and internal electrodes, and the internal electrodes use the conductivity described in any one of claims 1 to 10 of the patent application slurry is formed.

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