Conductive paste, electronic component, and laminated ceramic capacitor

Abstract

To provide a conductive paste which is excellent in printability, and an electronic component and a laminated ceramic capacitor using the same.SOLUTION: A conductive paste contains conductive powder, a dispersant, a binder resin, and an organic solvent, wherein the dispersant is a primary amine-based dispersant containing primary amine which has a branched hydrocarbon group having one or more branched chains, and has a molecular weight of 1,000 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to multilayer ceramic capacitors and other electronic components having internal electrodes, and to conductive pastes used to form internal electrodes of multilayer ceramic capacitors and electronic components. [Background technology]

[0002] As electronic devices such as mobile phones and digital devices become smaller and more powerful, there is a demand for smaller electronic components such as multilayer ceramic capacitors with higher capacitance. Among electronic components, multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by thinning these dielectric layers and internal electrode layers, it is possible to achieve smaller size and higher capacitance.

[0003] Multilayer ceramic capacitors are generally manufactured as follows: Dielectric green sheets are formed using a dielectric powder such as barium titanate (BaTiO3) and a binder resin. A conductive paste for the internal electrodes is printed on the surface of the dielectric green sheets in a predetermined electrode pattern and then dried to form a dry film that will become the internal electrode layer. The dielectric green sheets with the dry film formed on them are stacked in multiple layers to obtain a laminate, which is then integrated by heat and pressure bonding and then cut into chips. The chips are then subjected to a binder removal process in an oxidizing or inert atmosphere and then heated and fired in a reducing atmosphere to obtain fired chips. Finally, external electrode paste is applied to the fired chips and fired, and the resulting external electrodes are then nickel-plated or otherwise processed to complete the multilayer ceramic capacitor.

[0004] Generally, the conductive paste used to form the internal electrode layers contains a conductive powder, a dielectric powder, a binder resin, and an organic solvent, and may also contain a dispersant to improve the dispersibility of the conductive powder, etc.

[0005] Conductive pastes have the problem of increasing viscosity over time, which means that initially, electrode patterns of a predetermined thickness can be formed on dielectric green sheets with the desired viscosity, but as time passes, the viscosity increases, and it may become impossible to maintain the thickness within the predetermined range under the printing conditions initially used.

[0006] As a measure to improve the viscosity characteristics of a conductive paste, for example, Japanese Patent Application Laid-Open No. 2019-046581 describes a conductive paste characterized by containing, as a dispersant, a first acid-based dispersant having a molecular weight of 5000 or less and a branched hydrocarbon group with one or more branched chains, and a second acid-based dispersant other than the first acid-based dispersant. This conductive paste is said to have good viscosity stability and dispersibility.

[0007] Furthermore, as dielectric green sheets become thinner, the conductive paste is required to have improved surface smoothness when dried after application.

[0008] JP 2020-017405 A describes a conductive paste containing a predetermined amino acid-based dispersant and a predetermined amine-based dispersant as dispersants, the blending ratio of the amino acid-based dispersant to the amine-based dispersant being in the range of 1 / 4 to 1 / 2 by mass, and the total content of the amino acid-based dispersant and the amine-based dispersant being in the range of 0.7 to 1.2 mass% based on the entire conductive paste. This conductive paste is said to provide a dry film with high surface smoothness and high density after application. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2019-046581 [Patent Document 2] Japanese Patent Publication No. 2020-017405 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in recent years, the particle size of conductive powders has become smaller in association with the thinning of internal electrode layers, which has resulted in an increase in the specific surface area of ​​the particle surface. This increases the surface activity of the conductive powder (metal powder), which may result in a decrease in dispersibility and a decrease in viscosity characteristics.

[0011] Furthermore, conventional conductive pastes contain sarcosine or linear carboxylic acids as dispersants to reduce the viscosity, but these also reduce the surface smoothness of the dried film.

[0012] In view of the above circumstances, an object of the present disclosure is to provide a conductive paste with excellent printability, and an electronic component and a multilayer ceramic capacitor using the same. [Means for solving the problem]

[0013] A conductive paste according to an embodiment of the present disclosure includes a conductive powder, a dispersant, a binder resin, and an organic solvent. In particular, the conductive paste according to an embodiment of the present disclosure is characterized in that the dispersant is a primary amine-based dispersant that includes a branched hydrocarbon group having one or more branched chains and an amino group (—NH), and that includes a primary amine having a molecular weight of 1,000 or less.

[0014] The branched chain preferably branches from any of the carbon atoms at positions 1 to 3, assuming that the carbon atom bonded to the nitrogen atom is at position 1.

[0015] The primary amine preferably has a molecular weight of 400 or less.

[0016] The branched hydrocarbon group is preferably a branched alkyl group having 3 to 25 carbon atoms.

[0017] The primary amine is preferably at least one selected from the group consisting of 2-heptylamine, 2-ethylhexylamine, and 2-decyltetradecan-1-amine.

[0018] The dispersant is preferably contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder.

[0019] The conductive powder preferably contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. The conductive powder preferably has an average particle size of 0.05 μm or more and 1.0 μm or less. The content of the conductive powder in the conductive paste is preferably 30% by mass or more and 70% by mass or less based on the total amount of the conductive paste.

[0020] The conductive paste preferably contains a dielectric powder. The dielectric powder preferably contains a ceramic powder made of a perovskite oxide. The dielectric powder preferably has an average particle size of 0.01 μm or more and 0.5 μm or less. The content of the dielectric powder is preferably 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the conductive powder.

[0021] The binder resin preferably contains at least one of a cellulose-based resin, an acrylic-based resin, and a butyral-based resin, and the content of the binder resin is preferably 1 part by mass or more and 10 parts by mass or less relative to the conductive powder.

[0022] When the change in viscosity of the conductive paste immediately after production is taken as 0%, it is preferable that the change in viscosity after being left standing at 25° C. for 28 days is 30% or less.

[0023] The surface roughness of the dried film of the conductive paste depends on the average particle size of the conductive powder used. When the average particle size of the conductive powder is 0.2 μm or more and 1.0 μm or less, the average surface roughness Sa (arithmetic mean height) of the dried film is preferably 100 nm or less. When the average particle size of the conductive powder is 0.1 μm or more and less than 0.2 μm, the average surface roughness Sa of the dried film is preferably 60 nm or less. When the average particle size of the conductive powder is 0.05 μm or more and less than 0.1 μm, the average surface roughness Sa of the dried film is preferably 40 nm or less.

[0024] When the average surface roughness Sa (arithmetic mean height) of the dried film after application of the conductive paste immediately after production of the conductive paste is taken as the reference (0%), it is preferable that the change in the average surface roughness Sa of the dried film after application of the conductive paste after leaving the conductive paste at 25°C for 28 days ([(Sa after leaving for 28 days - Sa immediately after production) / Sa immediately after production] x 100) is -50% or more and 20% or less.

[0025] The conductive paste is preferably for use in an internal electrode of a multilayer ceramic capacitor.

[0026] An electronic component according to an embodiment of the present disclosure is characterized in that it has an internal electrode, and the internal electrode is formed using the conductive paste according to an embodiment of the present disclosure.

[0027] A multilayer ceramic capacitor according to one aspect of the present disclosure includes at least a laminate in which dielectric layers and internal electrode layers are stacked, and the internal electrode layers are formed using the conductive paste according to one aspect of the present disclosure. [Effects of the Invention]

[0028] According to one aspect of the present disclosure, there are provided a conductive paste with excellent printability, and an electronic component and a multilayer ceramic capacitor using the same. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1(A) is a perspective view showing a multilayer ceramic capacitor according to an example of an embodiment of the present disclosure, and FIG. 1(B) is a cross-sectional view of the multilayer ceramic capacitor. DETAILED DESCRIPTION OF THE INVENTION

[0030] 1.Conductive paste In one example of an embodiment of the present disclosure, the conductive paste includes a conductive powder, a dispersant, a binder resin, and an organic solvent. Alternatively, the conductive paste includes a conductive powder, a dielectric powder, a dispersant, a binder resin, and an organic solvent.

[0031] (1) Conductive powder In this example, the type of conductive powder that constitutes the conductive paste is not particularly limited. For internal electrodes of electronic components or internal electrode layers of multilayer components such as multilayer ceramic capacitors (MLCCs), for example, metal powders such as nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu), or alloy powders of these metals can be used.

[0032] Among these, Ni powder or Ni alloy powder is preferred from the viewpoints of conductivity, corrosion resistance, and cost. The Ni alloy may be, for example, an alloy of Ni with at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd. The Ni content in the Ni alloy is preferably 50% by mass or more, and more preferably 80% by mass or more. Furthermore, the Ni powder or Ni alloy powder may contain several hundred ppm of S to suppress rapid gas generation due to partial thermal decomposition of the binder resin during binder removal treatment.

[0033] The particle size of the conductive powder is not particularly limited, but the average particle size is preferably in the range of 0.05 μm to 1.0 μm, more preferably 0.05 μm to 0.5 μm, even more preferably 0.05 μm to 0.3 μm, and most preferably 0.05 μm to 0.12 μm. When the average particle size of the conductive powder is in the above range, the smoothness and density of the dried film are improved, and the conductive powder can be suitably used in conductive pastes for thin-film internal electrodes of electronic components or thin-film internal electrodes of multilayer ceramic capacitors.

[0034] The average particle size of the conductive powder is defined as the particle size that is 50% of the cumulative maximum diameter of 200 or more randomly selected conductive powder particles measured from an image observed at a magnification of 10,000 times using a scanning electron microscope (SEM).

[0035] The content of the conductive powder in the conductive paste is preferably 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 60% by mass or less, based on the total amount of the conductive paste. When the content of the conductive powder is within the above range, the conductivity and dispersibility of the conductive paste can be sufficiently improved.

[0036] (2) Dielectric powder The conductive paste of this example may contain dielectric powder. In the conductive paste for the internal electrodes of the multilayer ceramic capacitor, the dielectric powder is added as a sintering inhibitor for the conductive paste.

[0037] The dielectric powder used in the conductive paste for the internal electrodes of a multilayer ceramic capacitor is selected appropriately depending on the type of multilayer ceramic capacitor to be used. For example, ceramic powder containing a perovskite oxide containing Ba and Ti can be used, and preferably ceramic powder containing barium titanate (BaTiO).

[0038] It is also possible to use ceramic powders containing perovskite oxides in which the Ba and Ti atoms of barium titanate (BaTiO3) are replaced with other atoms such as Sn, Pb, and Zr. Furthermore, it is also possible to use ceramic powders in which various additives are added to perovskite oxides. As such ceramic powders, not only one type of ceramic powder but also two or more types of ceramic powders can be used.

[0039] The dielectric powder used in the conductive paste for the internal electrodes of multilayer ceramic capacitors preferably has the same or a similar composition as the dielectric powder used as the main component of the dielectric green sheets for multilayer ceramic capacitors. This prevents cracks from occurring at the interfaces between the dielectric layers and the internal electrode layers during the sintering process due to a shrinkage mismatch. Examples of such dielectric powders include perovskite oxides, as well as oxides such as ZnO, ferrite, PZT, BaO, Al2O3, Bi2O3, R (rare earth element)2O3, TiO2, and Nd2O3.

[0040] The particle size of the dielectric powder is not particularly limited, but its average particle size is preferably in the range of 0.01 μm to 0.5 μm, and more preferably 0.01 μm to 0.3 μm. When the average particle size of the dielectric powder is in the above range, when it is applied to a conductive paste for internal electrodes, it is possible to form sufficiently fine, thin, and uniform internal electrodes or internal electrode layers. The average particle size of the dielectric powder is also defined as the particle size at 50% of the cumulative value of the maximum diameters of 200 or more randomly selected conductive powder particles measured from an observation image at 10,000x magnification obtained with a scanning electron microscope (SEM).

[0041] When a dielectric powder is added, the content of the dielectric powder is preferably 1 to 30 parts by mass, and more preferably 3 to 30 parts by mass, per 100 parts by mass of the conductive powder. Furthermore, the content of the dielectric powder in the conductive paste is preferably 1 to 20% by mass, and more preferably 3 to 20% by mass, of the total amount of the conductive paste. When the content of the dielectric powder is within the above range, the sintering-inhibiting effect of the conductive paste is sufficiently obtained, and its conductivity and dispersibility are sufficiently ensured.

[0042] (3) Dispersant The conductive paste of this example is characterized by containing a predetermined dispersant. The dispersant is added to the organic vehicle together with the conductive powder and the dielectric powder. The dispersant maintains the dispersion state of the conductive powder in the conductive paste and has the function of suppressing viscosity changes of the conductive paste over time. Furthermore, by using the predetermined dispersant in the conductive paste of this example, it is possible to achieve both high viscosity stability in the conductive paste and high smoothness in the dried film.

[0043] In the conductive paste of this example, a primary amine-based dispersant is used as the dispersant, which contains a primary amine having a branched hydrocarbon group with one or more branched chains and an amino group (-NH2), and having a molecular weight of 1000 or less. A primary amine having a branched hydrocarbon group with one or more branched chains and an amino group (-NH2) refers to a primary amine whose substituent is composed of a hydrocarbon group, and the hydrocarbon group has at least one branched chain.

[0044] The present inventors have investigated various dispersants for use in conductive pastes and have found that the inclusion of a primary amine-based dispersant having a branched hydrocarbon group can achieve both high viscosity stability of the conductive paste and high smoothness of the dried film. The reason for this is thought to be that the presence of branched chains increases the area that each molecule constituting the dispersant covers on the surface of the conductive powder particles, thereby effectively inhibiting the adsorption of the binder resin to the conductive powder particles and / or the aggregation of the conductive powder particles.

[0045] The primary amine-based dispersant of this example is preferably composed solely of the primary amine. However, the primary amine-based dispersant of this example may contain a dispersant other than the primary amine as long as the effect of the primary amine-based dispersant is not impaired. In this case, the amount of the dispersant other than the primary amine added may be 0.2 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the conductive powder.

[0046] It is believed that primary amine-based dispersants contribute to improved dispersibility by preventing aggregation of solid particles through bonding of the amino group (-NH2) with conductive powders, binder resins, etc. Therefore, it is believed that the smaller the molecular weight of the dispersant within the above range, the greater the number of amino groups (-NH2) per unit weight can be, resulting in higher dispersibility. The molecular weight of the dispersant is preferably 400 or less, more preferably 300 or less, and even more preferably 100 to 200, taking into consideration factors such as cost, productivity, and ease of handling.

[0047] If the molecular weight of the primary amine is too small, problems may arise such as increased volatility making it difficult to handle or a lower flash point making it more dangerous. Therefore, the molecular weight of the primary amine is preferably 100 or more.

[0048] The branched hydrocarbon group constituting the primary amine dispersant may have any number of branched chains, so long as it is a branched hydrocarbon group having a main chain and one or more branched chains. However, two or more branched chains will not provide a greater effect, and the molecular weight will increase as the number of branched chains increases, increasing the amount added to achieve the same effect and increasing costs. Therefore, the number of branched chains is preferably one to three, and more preferably one, but four or more branched chains is not prohibited.

[0049] Furthermore, the number of carbon atoms constituting the main chain or each branched chain is preferably 1 or more and 20 or less. If the number of carbon atoms constituting the main chain or each branched chain exceeds 20, the overall molecular weight of the primary amine becomes too large, which may be disadvantageous in terms of ensuring dispersibility. In order to achieve high viscosity stability of the conductive paste and high smoothness of its dried film while also taking into consideration cost, productivity, handleability, etc., the number of carbon atoms constituting the main chain or branched chain is more preferably 2 or more and 15 or less, and even more preferably 3 or more and 10 or less.

[0050] The branched chain can branch from any carbon atom in the hydrocarbon group that constitutes the substituent. If the carbon atom bonded to the nitrogen atom that constitutes the amino group (-NH2) is considered to be the 1st position, the branched chain preferably branches from any of the carbon atoms at positions 1 to 3, more preferably from the 1st or 2nd carbon atom, and most preferably from the 1st carbon atom. This is thought to be because the branched chain is located close to the amino group (-NH2) that adsorbs to the conductive powder, which increases steric hindrance on the surface of the conductive powder.

[0051] As the primary amine-based dispersant applicable to this example, a wide range of aliphatic amines having branched chains without aromatic rings can be used, as long as the molecular weight and the number of carbon atoms in the branched hydrocarbon group are within the ranges of this disclosure. Primary amine-based dispersants containing aromatic rings have the problem that they are not sufficiently removed from the conductive paste when it is dried after printing the conductive paste on the dielectric green sheet, resulting in the generation of toxic benzene during the binder removal process. Although branched alkenyl groups having carbon double bonds can also be used as the branched hydrocarbon group, branched alkyl groups are preferred.

[0052] The branched hydrocarbon group is preferably a branched alkyl group having 3 to 25 carbon atoms.

[0053] Examples of primary amine dispersants that can be suitably used in the conductive paste of this example include isopropylamine (molecular formula: (CH3)2CHNH2, molecular weight: 59.11), isobutylamine (molecular formula: (CH3)2CHCH2NH2, molecular weight: 73.14), 2-aminopentane (molecular formula: CH3CH(NH2)C3H7, molecular weight: 87.17), isoamylamine (molecular formula: (CH3)2C2H5NH2, molecular weight: 87.17), 1,3-dimethylbutylamine (molecular formula: (CH3)2C3H4(CH3)NH2, molecular weight: 101.19), 4-heptylamine (molecular formula: C3H7CH(NH2)C3H7, molecular weight: 115.22), and 2-heptylamine (molecular formula: C5H 11 CH(NH2)CH3, molecular weight: 115.22), 2-ethylhexylamine (molecular formula: C4H9CH(C2H5)CH2NH2, molecular weight: 129.24), 2-aminooctane (molecular formula: C6H 13 CH(NH2)CH3, molecular weight: 129.25), 6-undecaneamine (molecular formula: CH 11 CH(NH2)CH 11 , molecular weight: 171.33), 2-butyl-n-octan-1-amine (molecular formula: CH 13 CH(C4H9)CH2NH2, molecular weight: 185.36), tridecan-7-amine (molecular formula: CH6H 11 CH(NH2)CH 11, molecular weight: 199.38), 8-pentadecanamine (molecular formula: CH 15 CH(NH2)C7H 15 , molecular weight: 227.44), 2-hexyldecan-1-amine (molecular formula: CH 13 CH(C8H 17 ) CH2NH2, molecular weight: 241.46), heptadecan-9-amine (molecular formula: CH 17 CH(NH2)C8H 17 , molecular weight: 255.49), 2-n-octyl-1-dodecylamine (molecular formula: CH 17 CH(C 10 H 21 ) CH2NH2, molecular weight: 297.57), 2-decyltetradecan-1-amine (molecular formula: C 10 H 21 CH(C 12 H 25 )CH2NH2, molecular weight: 353.68).

[0054] Among these, 4-heptylamine, 2-heptylamine, 2-ethylhexylamine, 2-aminooctane, 6-undecaneamine, 2-butyl-n-octan-1-amine, tridecane-7-amine, 8-pentadecanamine, 2-hexyldecan-1-amine, heptadecane-9-amine, and 2-n-octyl-1-dodecylamine are preferred, 2-heptylamine, 2-ethylhexylamine, and 2-decyltetradecane-1-amine are more preferred, and 2-heptylamine and 2-ethylhexylamine are most preferred.

[0055] On the other hand, polymers having an amino group (-NH2) are not applicable to the conductive paste of this example from the viewpoint of molecular weight.

[0056] As such a primary amine-based dispersant, not only one type of primary amine-based dispersant but also two or more types of primary amine-based dispersants can be used.

[0057] In this example, the primary amine dispersant is preferably contained in an amount of 0.2 to 2 parts by mass, more preferably 0.2 to 1 part by mass, per 100 parts by mass of the conductive powder. When the dispersant content is within the above range, high dispersibility of the conductive powder in the conductive paste can be obtained, the dry film density can be made sufficient, and changes in the viscosity of the conductive paste over time can be suppressed. In particular, when the molecular weight of the dispersant is 400 or less, high dispersibility of the conductive powder in the conductive paste can be obtained even when the ratio of the dispersant to 100 parts by mass is 0.2 to 1 part by mass.

[0058] The primary amine dispersant can be selected from commercially available products that satisfy the above properties, or can be produced using a known production method so as to satisfy the above properties.

[0059] (4) Binder resin The binder resin and the organic solvent constitute an organic vehicle. More specifically, the binder resin is dissolved in the organic solvent to prepare an organic vehicle, and the conductive powder or the conductor powder and the dielectric powder are dispersed in this organic vehicle to obtain the conductive paste.

[0060] The binder resin is not particularly limited, and known resins can be used. Examples of binder resins include cellulose-based resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, acrylic resins, and butyral-based resins such as polyvinyl butyral. Among these, it is preferable to contain ethyl cellulose from the viewpoints of solubility in solvents and combustion decomposition properties. Furthermore, when used in a conductive paste for internal electrodes, it is preferable to contain a butyral resin as the binder resin from the viewpoint of improving the adhesive strength with the dielectric green sheet. As such a binder resin, one type of binder resin can be used, or two or more types of binder resins can be used. Furthermore, the molecular weight of the binder resin is, for example, about 20,000 to 200,000.

[0061] The content of the binder resin is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 3 to 8 parts by mass, per 100 parts by mass of the conductive powder. Furthermore, the content of the binder resin is preferably 0.5 to 10% by mass, and more preferably 1 to 6% by mass, of the total amount of the conductive paste. When the content of the binder resin is within the above range, an organic vehicle with an appropriate viscosity can be prepared, and the conductivity and dispersibility of the conductive paste can be sufficiently improved.

[0062] (5) Organic solvents The organic solvent, together with the binder resin, constitutes the organic vehicle (organic solvent for the organic vehicle). The organic solvent also disperses the conductive powder, dielectric powder, and binder resin, adjusting the viscosity of the conductive paste to an appropriate range and enabling printing in a predetermined pattern (organic solvent for the conductive paste). The organic solvent is removed during the process of forming the internal electrodes (dry film).

[0063] In the conductive paste of this example, the organic solvent is not particularly limited, and for example, a known organic solvent that can dissolve the binder resin can be used. Among the organic solvents, the organic solvent for the organic vehicle is preferably the same as the organic solvent for the conductive paste that adjusts the viscosity of the conductive paste, in order to improve the compatibility of the organic vehicle.

[0064] Examples of organic solvents include: acetate-based solvents such as dihydroterpinyl acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy-3-methylbutyl acetate, and 1-methoxypropyl-2-acetate; Acetate ester solvents such as ethyl acetate, propyl acetate, isobutyl acetate, and butyl acetate, Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, 4-hydroxy-4-methyl-2-pentane, and isophorone, Terpene solvents such as terpineol and dihydroterpineol, Aliphatic hydrocarbon solvents such as tridecane, nonane, and cyclohexane, ethylene glycol ethers, glycol ether solvents such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether; Glycol solvents such as ethylene glycol, propylene glycol, and 2-ethyl-1,3-hexanediol, Examples include:

[0065] As such an organic solvent, one type of organic solvent can be used, or two or more types of organic solvents can be used.

[0066] The content of the organic solvent is preferably 40 parts by mass or more and 150 parts by mass or less relative to 100 parts by mass of the conductive powder. When the content of the organic solvent is within this range, the conductivity and dispersibility are excellent. Furthermore, the content of the organic solvent is preferably 20% by mass or more and 70% by mass or less, and more preferably 25% by mass or more and 60% by mass or less, relative to the total amount of the conductive paste. When the content of the organic solvent is within this range, it is possible to prepare an organic vehicle with an appropriate viscosity, and the conductivity and dispersibility of the conductive paste can be sufficiently improved.

[0067] (6) Other additives If necessary, known additives applicable to conductive pastes, such as antifoaming agents, plasticizers, thickeners, and chelating agents, can also be added to the conductive paste in this example.

[0068] (7) Viscosity stability The conductive paste of this example has excellent viscosity stability with very little change in viscosity over time, and therefore the conductive paste of this example shows little change in viscosity even when stored at room temperature (25°C) for a long period of time immediately after production.

[0069] More specifically, if the viscosity change immediately after production of the conductive paste of this example is 0%, the viscosity change after leaving it at room temperature (25°C) for 28 days is preferably 30% or less, and more preferably -25% to 15%. By reducing the viscosity change during storage, it is possible to sufficiently prevent the conductive powder and dielectric powder from separating due to a decrease in viscosity, and further to prevent the conductive powder and dielectric powder from settling.

[0070] The viscosity of the conductive paste of this example immediately after production was measured at a shear rate of 4 sec. -1 When measured under these conditions, the viscosity is preferably 10 Pa·s or more and 80 Pa·s or less, and more preferably 20 Pa·s or more and 60 Pa·s or less. When the viscosity is within the above range, the conductive paste can be applied to a variety of printing methods. The viscosity can also be measured using a rheometer.

[0071] (8) Surface smoothness The conductive paste of this example has excellent dispersibility of the conductive powder, and the dried film after application has high surface smoothness, with very little deterioration of the surface smoothness over time.

[0072] The surface roughness of the dried film of the conductive paste depends on the average particle size of the conductive powder used. When the average particle size of the conductive powder is 0.2 μm or more and 1.0 μm or less, the average surface roughness Sa (arithmetic mean height) of the dried film is preferably 100 nm or less. When the average particle size of the conductive powder is 0.1 μm or more and less than 0.2 μm, the average surface roughness Sa of the dried film is preferably 60 nm or less. When the average particle size of the conductive powder is 0.05 μm or more and less than 0.1 μm, the average surface roughness Sa of the dried film is preferably 40 nm or less, and more preferably 35 nm or less.

[0073] Furthermore, when the average surface roughness Sa (arithmetic mean height) of the dried film after application of the conductive paste immediately after production of the conductive paste in this example is taken as the reference (0%), the change in the average surface roughness Sa of the dried film after application of the conductive paste after leaving the conductive paste at 25°C for 28 days ([(Sa after leaving for 28 days - Sa immediately after production) / Sa immediately after production] x 100) is preferably -50% or more and 20% or less, and more preferably -50% or more and 10% or less.

[0074] The conductive paste of this example has excellent printability due to its excellent surface smoothness and extremely small deterioration over time. Furthermore, because the conductive paste of this example has excellent printability, the internal electrodes of electronic components or internal electrode layers of multilayer ceramic capacitors formed using the conductive paste of this example can be formed with high precision and have uniform width and thickness even when made thin.

[0075] (9) Manufacturing method of conductive paste The method for producing the conductive paste of this example is not particularly limited, and known methods can be used. The conductive paste can be produced, for example, by adding a conductive powder, a dispersant, and a binder resin, or a conductive powder, a dielectric powder, a dispersant, and a binder resin, to an organic solvent and stirring and kneading the mixture using a triple-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, allowing the dispersant to be distributed evenly across the surface, making it easier to obtain a uniform conductive paste.

[0076] Alternatively, a binder resin may be dissolved in a portion of an organic solvent to prepare an organic vehicle, and then a conductive powder, a dispersant, and an organic vehicle, or a conductive powder, a dielectric powder, a dispersant, and an organic vehicle, may be added to the organic solvent for preparing the paste, followed by stirring and kneading in the same manner to prepare a conductive paste.

[0077] (10) Applications (electronic components and multilayer ceramic capacitors) The conductive paste of this example can be suitably used for forming internal electrodes of electronic components, or for forming internal electrode layers of multilayer ceramic capacitors (MLCCs) that have at least a laminate in which dielectric layers and internal electrode layers are stacked.

[0078] The conductive paste of this example is not limited to multilayer ceramic capacitors and is widely applicable to the formation of internal electrodes in electronic components having internal electrodes, but the conductive paste of this example is particularly suitable for use in the internal electrodes of multilayer ceramic capacitors.

[0079] An example of a multilayer ceramic capacitor in which the conductive paste of this example is used to form its internal electrode layers will be described below with reference to Figure 1 (Figures 1A and 1B). The drawings may be represented schematically or at a different scale as appropriate. The positions and directions of components will be described with reference to the XYZ Cartesian coordinate system shown in Figure 1 as appropriate. In this XYZ Cartesian coordinate system, the X and Y directions are horizontal, and the Z direction is vertical (up and down).

[0080] The multilayer ceramic capacitor 1 includes a laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20. The multilayer ceramic capacitor 1 is manufactured by first printing a conductive paste on a dielectric green sheet and drying it to form a dry film. A plurality of dielectric green sheets having this dry film on their upper surfaces are stacked and pressure-bonded to obtain a laminate, which is then fired and integrated to produce the ceramic laminate 10 in which the internal electrode layers 11 and the dielectric layers 12 are alternately stacked. Thereafter, a pair of external electrodes 20 is formed on both ends of the ceramic laminate 10, thereby manufacturing the multilayer ceramic capacitor 1.

[0081] The dielectric green sheet is obtained by applying a dielectric layer paste obtained by adding an organic binder resin such as polyvinyl butyral and a solvent such as terpineol to a dielectric powder such as barium titanate 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 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.

[0082] The conductive paste of this example is printed (applied) on one side of a dielectric green sheet by a known method such as screen printing, and then dried to form a dry film. From the viewpoint of the requirement for thinning the internal electrode layer 11, the thickness of the conductive paste after printing is preferably set to a thickness that results in a dry film thickness of 1 μm or less.

[0083] The laminate is obtained by peeling the dielectric green sheets from the support film, laminating the dielectric green sheets and the dry film formed on one side thereof alternately, and then subjecting them to heat and pressure treatment. Protective dielectric green sheets that are not coated with conductive paste can also be placed on both sides of the laminate.

[0084] The laminate is cut to a predetermined size to form green chips, which are then subjected to a binder removal treatment and fired in a reducing atmosphere to produce a ceramic laminate 10. The binder removal treatment is preferably performed in air or an 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 maintained for 0.5 hours or higher and 24 hours or lower. The firing is performed in a reducing atmosphere to prevent oxidation of the metals used in the internal electrode layers. The temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the temperature is preferably maintained for 0.5 hours or higher and 8 hours or lower.

[0085] By firing the green chip, the organic binder resin in the dielectric green sheet is completely removed and the dielectric powder is fired to form the dielectric layer 12. The organic vehicle in the dried film is also removed and the conductive powder is sintered or melted to form an integrated body, thereby forming the internal electrode layer 11. This forms a fired multilayer ceramic body in which the dielectric layers 12 and the internal electrode layers 11 are alternately stacked. Note that, from the viewpoint of incorporating oxygen into the dielectric layers to increase reliability and suppressing reoxidation of the internal electrodes, the fired multilayer ceramic body can also be subjected to an annealing treatment.

[0086] A pair of external electrodes 20 is provided on the fired multilayer ceramic 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. The external electrode 20 is preferably made of, for example, copper, nickel, or an alloy thereof. [Example]

[0087] The present disclosure will be described in more detail below using examples and comparative examples, but the present disclosure is not limited to these examples and comparative examples.

[0088] [Materials used] (conductive powder) As the conductive powder, Ni powder (average particle size: 0.06 μm) was used.

[0089] (binder resin) As the binder resin, ethyl cellulose and polyvinyl butyral were used.

[0090] (organic solvent) As the organic solvent, dihydroterpinyl acetate, dihydroterpineol, and 2-ethyl-1,3-hexanediol were used.

[0091] [Evaluation method] (Viscosity of conductive paste) Using an Anton Paar rheometer, the shear rate was 4 sec -1 The viscosity was measured under the following conditions: If the viscosity immediately after production was between 20 Pa·s and 60 Pa·s, it was rated as A; if it was between 10 Pa·s and 80 Pa·s, but not A, it was rated as B; otherwise it was rated as C.

[0092] (Change in viscosity of conductive paste over time) The viscosity of each sample of conductive paste was measured using the method described above immediately after production and after leaving it at room temperature (25°C) for 28 days. The viscosity immediately after production was taken as the reference (0%), and the change in viscosity of the sample after each period was calculated as a percentage (%) ([(viscosity after leaving it for 28 days - viscosity immediately after production) / viscosity immediately after production] x 100). The smaller the change in viscosity of the conductive paste, the better. A rating of A was given to samples where the change in viscosity over 28 days was between -25% and 15%, a rating of B was given to samples where the change was not between -30% and 30%, and a rating of C was given to samples in all other cases.

[0093] (Surface roughness of dried conductive paste film) The conductive paste was applied to a glass substrate using an applicator (gap thickness 10 μm) and then dried in air at 120°C for 10 minutes to obtain a dry film with a thickness of approximately 3 μm. The average surface roughness Sa (arithmetic mean height) of the dry film was then measured using a surface roughness meter (Keyence Corporation, shape analysis laser microscope VK-X120). The smaller the Sa value, the smoother the surface of the dry film. A Sa value of 10 nm to 35 nm was evaluated as A, a value of 10 nm to 40 nm but not A was evaluated as B, and all other values ​​were evaluated as C.

[0094] (Change in surface roughness of dried conductive paste film over time) The average surface roughness Sa of the dried film of each sample was measured using the method described above immediately after production of the conductive paste and after leaving it at room temperature (25°C) for 28 days. The Sa immediately after production was taken as the reference (0%), and the change in Sa of the sample after each period was calculated as a percentage (%) ([(Sa after leaving it for 28 days - Sa immediately after production) / Sa immediately after production] x 100). The smaller the change in Sa of the conductive paste, the better. A rating of A was given to samples where the change in Sa over 28 days was between -50% and 10%, a rating of B was given to samples where it was not between -50% and 20%, and a rating of C was given to samples where it was not A but was between -50% and 20%, and all other ratings were given.

[0095] Example 1 The dispersant used was 2-heptylamine (molecular formula: CH), a primary amine dispersant with one branched chain. 11 The 2-heptylamine used was CH(NH2)CH3, molecular weight: 115.22. In 2-heptylamine, the branched chain branches from the carbon atom at position 1. Note that the carbon atom at position 1 is the carbon atom bonded to the amino group (-NH2).

[0096] A conductive paste was prepared by mixing 100 parts by mass of Ni powder with 5.78 parts by mass of ethyl cellulose resin, 1.02 parts by mass of polyvinyl butyral resin, 156 parts by mass of organic solvent, and 0.54 parts by mass of dispersant. The viscosity, viscosity stability, surface roughness, and surface roughness stability of the prepared conductive paste were evaluated using the methods described above.

[0097] Example 2 A conductive paste was prepared and evaluated in the same manner as in Example 1, except that 2-ethylhexylamine (molecular formula: CHCH(CH)CHNH, molecular weight: 129.24), a primary amine-based dispersant having one branched chain, was used as the dispersant in an amount of 0.60 parts by mass per 100 parts by mass of Ni powder. In 2-ethylhexylamine, the branched chain branches from the carbon atom at the second position.

[0098] Example 3 A conductive paste was prepared and evaluated in the same manner as in Example 2, except that the amount of 2-ethylhexylamine added was 0.93 parts by mass relative to 100 parts by mass of Ni powder.

[0099] Example 4 A conductive paste was prepared and evaluated in the same manner as in Example 2, except that the amount of 2-ethylhexylamine added was 2.00 parts by mass relative to 100 parts by mass of Ni powder.

[0100] Example 5 The dispersant used was 2-decyltetradecan-1-amine (molecular formula: C), a primary amine dispersant with one branched chain. 12 H 25 CH(C 10 H 21 A conductive paste was prepared and evaluated in the same manner as in Example 1, except that 2-decyltetradecan-1-amine (2-decyltetradecan-1-amine, molecular weight: 353.68) was used in an amount of 1.64 parts by mass per 100 parts by mass of Ni powder. In 2-decyltetradecan-1-amine, the branched chain branches from the carbon atom at the 2-position.

[0101] (Comparative Example 1) A conductive paste was prepared without using a dispersant by mixing 100 parts by mass of Ni powder with 5.78 parts by mass of ethyl cellulose resin, 1.02 parts by mass of polyvinyl butyral resin, and 156 parts by mass of an organic solvent, and then evaluated.

[0102] (Comparative Example 2) A conductive paste was prepared and evaluated in the same manner as in Example 1, except that a secondary amine-based dispersant, dipropylamine (molecular formula: (CH3CH2CH2)2NH, molecular weight: 101.19), was used as the dispersant and the amount added was 0.93 parts by mass per 100 parts by mass of Ni powder.

[0103] (Comparative Example 3) A conductive paste was prepared and evaluated in the same manner as in Example 1, except that a tertiary amine-based dispersant, N-butyldimethylamine (molecular formula: CH3(CH2)3N(CH3)CH3, molecular weight: 101.193), was used as the dispersant and the amount added was 0.47 parts by mass per 100 parts by mass of Ni powder.

[0104] Comparative Example 4 As a dispersant, stearylamine (molecular formula: CH3(CH2)), a primary amine dispersant without branched chains, was used. 17 A conductive paste was prepared and evaluated in the same manner as in Example 1, except that 0.93 parts by mass of NH2 (molecular weight: 269.51) was used and the amount added was set to 100 parts by mass of Ni powder.

[0105] (Comparative Example 5) As a dispersant, N-lauryldiethanolamine (molecular formula: CH3(CH2)), a tertiary amine dispersant, was used. 11 A conductive paste was prepared and evaluated in the same manner as in Example 1, except that N(CH2CH2OH)CH2CH2OH, molecular weight: 273.45) was used and the amount added was 1.27 parts by mass relative to 100 parts by mass of Ni powder.

[0106] (Comparative Example 6) As a dispersant, oleoyl sarcosine (molecular formula: C 21 H 39 A conductive paste was prepared and evaluated in the same manner as in Example 1, except that NO3, molecular weight: 353.547) was used and the amount added was 1.64 parts by mass relative to 100 parts by mass of Ni powder.

[0107] (Comparative Example 7) A conductive paste was prepared and evaluated in the same manner as in Comparative Example 6, except that the amount of oleoyl sarcosine added was 0.93 parts by mass relative to 100 parts by mass of Ni powder.

[0108] Table 1 shows the type of dispersant, the amount added, and the evaluation results of the conductive paste and its dried film.

[0109] As is clear from Table 1, by using a primary amine-based dispersant having a molecular weight of 50 to 1000 and having one or more branched chains, a conductive paste having excellent viscosity stability and higher dry film smoothness can be provided.

[0110] [Table 1] [Explanation of symbols]

[0111] 1. Multilayer ceramic capacitors 10. Ceramic laminate 11 Internal electrode layer 12 Dielectric layer 20 External electrode 21 External electrode layer

Claims

1. The conductive powder, the dispersant, the binder resin, and the organic solvent are included, and the dispersant has a branched hydrocarbon group having one or more branched chains and an amino group (—NH ２ ) and the primary amine-based dispersant contains a primary amine having a molecular weight of 1,000 or less.

2. The conductive paste according to claim 1 , wherein the branched chain branches from any one of the carbon atoms at positions 1 to 3, assuming that the carbon atom bonded to the nitrogen atom is at position 1.

3. The conductive paste according to claim 1 , wherein the primary amine has a molecular weight of 400 or less.

4. The conductive paste according to claim 3 , wherein the branched hydrocarbon group is a branched alkyl group having 3 to 25 carbon atoms.

5. 2. The conductive paste according to claim 1, wherein the primary amine is at least one selected from the group consisting of 2-heptylamine, 2-ethylhexylamine, and 2-decyltetradecane-1-amine.

6. The conductive paste according to claim 1 , wherein the dispersant is contained in an amount of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the conductive powder.

7. The conductive paste according to 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.

8. The conductive paste according to claim 1 , wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less.

9. The conductive paste according to claim 1 , comprising a dielectric powder, the dielectric powder comprising a ceramic powder made of a perovskite-type oxide.

10. The conductive paste according to claim 9 , wherein the dielectric powder has an average particle size of 0.01 μm or more and 0.5 μm or less.

11. The conductive paste according to claim 1 , wherein the binder resin includes at least one of a cellulose-based resin, an acrylic-based resin, and a butyral-based resin.

12. 2. The conductive paste according to claim 1, wherein the change in viscosity after being left at 25°C for 28 days is 30% or less, assuming that the change in viscosity immediately after production of the conductive paste is 0%.

13. 2. The conductive paste according to claim 1, wherein, when formed into a dry film, the dry film has an average surface roughness Sa (arithmetic mean height) of 100 nm or less when the average particle size of the conductive powder is 0.2 μm or more and 1.0 μm or less, an average surface roughness Sa of 60 nm or less when the average particle size of the conductive powder is 0.1 μm or more and less than 0.2 μm, and an average surface roughness Sa of 40 nm or less when the average particle size of the conductive powder is 0.05 μm or more and less than 0.1 μm.

14. When the average surface roughness Sa (arithmetic mean height) of the dried film after application of the conductive paste immediately after production of the conductive paste is taken as a reference (0%), the change in the average surface roughness Sa of the dried film after application of the conductive paste after leaving the conductive paste at 25 ° C. for 28 days ([(Sa after leaving for 28 days - Sa immediately after production) / Sa immediately after production] × 100) is -50% or more and 20% or less. The conductive paste according to claim 1.

15. 2. The conductive paste according to claim 1, which is for use in an internal electrode of a multilayer ceramic capacitor.

16. An electronic component having an internal electrode, the internal electrode being formed using the conductive paste according to claim 1.

17. A multilayer ceramic capacitor comprising at least a laminate in which dielectric layers and internal electrode layers are laminated, the internal electrode layers being formed using the conductive paste according to claim 1.

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