Conductive paste, electronic component, and multilayer ceramic capacitor

Abstract

Provided is a conductive paste of which adhesion with a base material is further improved.　The conductive paste comprises a conductive powder, a binder resin, an additive, and an organic solvent, the additive comprising a compound having a structure indicated by structural formula (1) or structural formula (2). (wherein R1, R2, and R3 each independently represent a saturated or unsaturated aliphatic hydrocarbon group comprising 2 to 12 carbon atoms, the aliphatic hydrocarbon group may be straight or branched, and one or more methylenes (-CH2-) included in the aliphatic hydrocarbon group may be substituted with oxygen (-O-)).

Description

Conductive paste, electronic components, and multilayer ceramic capacitors

[0001] The present invention relates to a conductive paste, an electronic component, and a multilayer ceramic capacitor.

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

[0003] For example, a multilayer ceramic capacitor is manufactured as follows: First, barium titanate (BaTiO ３ A conductive paste for internal electrodes is printed in a predetermined electrode pattern on the surface of a green sheet containing a dielectric powder such as ethylenediaminetetraacetic acid (EPO) and a binder resin, and then dried to form a dry film (conductive film). The dry film and green sheets are then alternately stacked to obtain a laminate. This laminate is then integrated by heat and pressure to form a pressed body. This pressed body is cut, subjected to an organic binder removal treatment in an oxidizing or inert atmosphere, and then fired to obtain fired chips. A paste for external electrodes is then applied to both ends of the fired chip, and after firing, the surfaces of the external electrodes are nickel-plated or the like to obtain a multilayer ceramic capacitor.

[0004] In the process of thermocompression bonding and cutting the laminate formed by stacking the dry film and the green sheet, if the adhesion between the dry film and the green sheet (substrate) is insufficient, the dry film (conductive film) may peel off from the green sheet (substrate) or the layer structure may become misaligned, resulting in the resulting multilayer ceramic capacitor not having the desired electrical characteristics.

[0005] For example, Patent Document 1 discloses a conductive paste containing a (meth)acrylic resin as a binder resin, an organic solvent, and a metal powder, with the aim of improving the adhesion of the conductive paste containing a (meth)acrylic resin as a binder resin to a ceramic green sheet, wherein the (meth)acrylic resin has a glass transition temperature Tg in the range of -60°C to 120°C, a hydroxy group content in the molecule in the range of 0.01% by mass to 5% by mass, an acid value in the range of 1 mgKOH / g to 50 mgKOH / g, and a weight average molecular weight in the range of 10,000 Mv to 350,000 Mv.

[0006] Furthermore, Patent Document 2 discloses a conductive paste for forming an electrode layer on a substrate, with the aim of providing a conductive paste capable of forming a conductive film having excellent adhesion to the substrate, the conductive paste comprising a conductive powder, a resin binder, an organic additive, and an organic solvent, wherein the organic additive comprises a (meth)acrylate compound having two or more (meth)acryloyl groups in one molecule and having a number average molecular weight of 1,000 or less.

[0007] Furthermore, Patent Document 3 discloses a dry film for an internal electrode of a multilayer ceramic capacitor, which is formed from a composition containing a conductive powder and an organic binder resin, with the aim of providing a dry film for an internal electrode that is excellent in adhesion to a dielectric layer and that can form an internal electrode whose shape does not change significantly before and after heat treatment, and which is characterized by having a Vickers hardness of 47 Hv or more and 51 Hv or less.

[0008] International Publication No. 2013 / 187183 Japanese Patent Application Laid-Open No. 2018-055933 Japanese Patent Application Laid-Open No. 2019-121744

[0009] In recent years, from the viewpoint of improving productivity and reducing costs, in the manufacturing process of a multilayer ceramic capacitor, when a laminate obtained by alternately laminating dry films and ceramic green sheets is heat-pressed to bond, the pressing time and pressure during the pressing are sometimes shortened and reduced.

[0010] However, when the pressing time or pressure during compression bonding is reduced, conventional conductive pastes do not provide sufficient adhesion between the dried film and the substrate, which can result in misalignment of the dried film and a decrease in yield. Therefore, there is a demand for a conductive paste that can further improve adhesion to the substrate when a dried film is formed.

[0011] In view of the above circumstances, an object of the present invention is to provide a conductive paste that can further improve adhesion to a substrate.

[0012] In a first aspect of the present invention, there is provided a conductive paste comprising a conductive powder, a binder resin, an additive, and an organic solvent, and comprising, as the additive, a compound having a structure represented by the following structural formula (1) or the following structural formula (2):

[0013] (However, R １ , R ２ , R ３ each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched. ２ -) may be replaced with oxygen (-O-).

[0014] The compound is preferably contained in an amount of 0.01% by mass or more and 2.0% by mass or less relative to the entire conductive paste. The compound preferably exhibits a maximum weight loss rate at a temperature of 200°C or higher in thermogravimetric analysis. The compound preferably has a molecular weight of 250 to 3,000. The conductive paste preferably further contains an acid dispersant and / or a basic dispersant. 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 to 1.0 μm. The binder resin preferably contains a butyral resin. The conductive paste preferably further contains ceramic powder. The ceramic powder preferably contains barium titanate. The ceramic powder preferably has an average particle size of 0.01 μm to 0.5 μm. The ceramic powder is preferably contained in an amount of 1% by mass to 20% by mass relative to the entire conductive paste. The conductive paste is preferably used for internal electrodes of multilayer ceramic components.

[0015] In a second aspect of the present invention, there is provided an electronic component formed using the conductive paste.

[0016] In a third aspect of the present invention, there is provided a multilayer ceramic capacitor having at least a laminate in which dielectric layers and internal electrode layers are laminated, the internal electrode layers being formed using the above-mentioned conductive paste.

[0017] The conductive paste of the present invention can further improve adhesion to a substrate, and in the manufacturing process of a multilayer ceramic capacitor, a dried film (internal electrode layer) formed using the conductive paste of the present invention has high adhesion to a green sheet (dielectric layer).

[0018] FIG. 1 is a perspective view and a cross-sectional view showing a multilayer ceramic capacitor according to an embodiment.

[0019] [Conductive Paste] The conductive paste of this embodiment contains a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent. Each component will be described in detail below.

[0020] (Conductive Powder) The conductive powder is not particularly limited, and metal powders can be used. For example, powders of one or more elements selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. Among these, powders of Ni or its alloys (hereinafter sometimes referred to as "Ni powder") are preferred from the viewpoints of conductivity, corrosion resistance, and cost. As the Ni alloy, for example, an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd can be used. The Ni content in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Furthermore, the Ni powder may contain several hundred ppm of element S to suppress rapid gas generation due to partial thermal decomposition of the binder resin during binder removal treatment.

[0021] The average particle size of the conductive powder is preferably 0.05 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. When the average particle size of the conductive powder is within the above range, it can be suitably used as an internal electrode paste for thin-film multilayer ceramic capacitors (multilayer ceramic components). The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value (SEM average particle size) obtained by measuring the particle size of each of a plurality of particles in an image observed with the SEM at a magnification of 10,000 times.

[0022] The content of the conductive powder is preferably 30% by mass or more and less than 70% by mass, 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 conductive paste has excellent conductivity and dispersibility.

[0023] (Ceramic Powder) The ceramic powder is not particularly limited, and for example, in the case of a paste for an internal electrode of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to be applied. As the ceramic powder, for example, a perovskite oxide containing Ba and Ti can be used, and preferably barium titanate (BaTiO ３ ) is included.

[0024] The ceramic powder may be a ceramic powder containing barium titanate as a main component and an oxide as a secondary component. Examples of the oxide include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements. Examples of the ceramic powder include barium titanate (BaTiO ３ Alternatively, a ceramic powder of a perovskite-type oxide ferroelectric may be used in which the Ba atoms or Ti atoms of the above-mentioned ferroelectric material are substituted with other atoms such as Sn, Pb, or Zr.

[0025] When used as a conductive paste for internal electrodes, the ceramic powder may have the same composition as the dielectric ceramic powder constituting the green sheets of a multilayer ceramic capacitor (electronic component). This prevents cracks from occurring at the interface between the dielectric layer and the internal electrode layer during the sintering process due to a mismatch in shrinkage. Examples of such ceramic powders include, in addition to those mentioned above, ZnO, ferrite, PZT, BaO, and Al. ２ O ３ , Bi ２ O ３ , R (rare earth element) ２ O ３ , TiO ２ , Nd ２ O ３ The ceramic powder may be one type or two or more types.

[0026] The average particle size of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, preferably 0.01 μm or more and 0.3 μm or less. When the average particle size of the ceramic powder is in the above range, when used as an internal electrode paste, a sufficiently fine, thin, and uniform internal electrode can be formed. The average particle size is a value determined by observation with a scanning electron microscope (SEM), and is the average value (SEM average particle size) obtained by measuring the particle size of each of multiple particles in an image observed with the SEM at a magnification of 50,000 times.

[0027] The content of the ceramic powder is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, based on the total mass of the conductive paste. When the content of the ceramic powder is within the above range, the conductive paste has excellent dispersibility and sinterability.

[0028] The content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the conductive powder.

[0029] (Binder Resin) The binder resin preferably contains a butyral-based resin. When used as an internal electrode paste, the butyral-based resin may be contained, or the butyral-based resin may be used alone, from the viewpoint of improving the adhesive strength with the green sheet. Examples of butyral-based resins include polyvinyl butyral (PVB). When the conductive paste contains a butyral-based resin, the adhesive strength with the green sheet can be further improved.

[0030] The content of the butyral resin may be, for example, 20% by mass or more, 40% by mass or more, or 60% by mass or more, based on the total amount of the binder resin. When the content of the butyral resin is within the above range, the adhesiveness is further improved, and the adhesive strength between the dried film and the green sheet (substrate) is improved.

[0031] The upper limit of the content of the butyral resin is not particularly limited, but may be, for example, 90% by mass or less, or 80% by mass or less, based on the total amount of the binder resin. When the content of the butyral resin is within the above range, the conductive paste has an appropriate hardness, and therefore, problems such as the printed film not peeling off from the support film and the electrodes being crushed during thermocompression bonding are less likely to occur.

[0032] The weight-average molecular weight (Mw) of the butyral resin may be 30,000 or more and 300,000 or less, 50,000 or more and 200,000 or less, or 100,000 or more and 150,000 or less. The glass transition temperature Tg of the butyral resin may be 50°C or more and 90°C or less, or 60°C or more and 80°C or less. By including the additives described below in addition to the butyral resin having the above properties, a conductive paste with improved adhesion can be obtained. The butyral resin may be used alone or in combination of two or more types.

[0033] Furthermore, a resin other than a butyral-based resin may be contained as a binder resin. The binder resin other than the above is not particularly limited, and known resins can be used, for example, cellulose-based resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, and acrylic resins. Among them, from the viewpoints of solubility in solvents and combustion decomposition properties, it is preferable to contain a cellulose-based resin, and it is more preferable to contain ethyl cellulose.

[0034] For example, when a cellulose-based resin is contained as the binder resin, the weight-average molecular weight (Mw) may be 10,000 or more and 300,000 or less, 30,000 or more and 250,000 or less, or 50,000 or more and 200,000 or less. The hydroxyl value of the cellulose-based resin is not particularly limited, but is preferably 0.1 mgKOH / g or more and 15 mgKOH / g or less, more preferably 0.5 mgKOH / g or more and 7 mgKOH / g or less, and even more preferably 1.5 mgKOH / g or more and 3 mgKOH / g or less. The cellulose-based resin may be contained alone or in combination of two or more types.

[0035] Furthermore, when the binder resin contains a cellulose-based resin and a butyral-based resin, from the viewpoint of improving adhesion, the butyral-based resin may be contained in an amount of 20% by mass or more, 40% by mass or more, more than 50% by mass, or 60% by mass or more relative to the total content (100% by mass) of the cellulose-based resin and the butyral-based resin. When the contents of both resins are within the above ranges, adhesion is further improved, and the adhesive strength between the dried film and the green sheet (substrate) may be improved. Furthermore, the upper limit of the butyral-based resin content is not particularly limited, and may be less than 100% by mass, 90% by mass or less, or 80% by mass or less. When the contents of both resins are within the above ranges, the conductive paste can have appropriate hardness, and defects such as the printed film not peeling off from the support film or the electrodes being crushed during thermocompression bonding are less likely to occur.

[0036] The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7% by mass or less, based on the total amount of the conductive paste. When the content of the binder resin is in the above range, the conductive paste has excellent conductivity and dispersibility.

[0037] The content of the binder resin is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 1 part by mass or more and 14 parts by mass or less, relative to 100 parts by mass of the conductive powder.

[0038] (Organic Solvent) The organic solvent is not particularly limited, and any known organic solvent capable of dissolving the binder resin can be used. Examples of the organic solvent include terpene-based solvents, acetate-based solvents, ether-based solvents, and ketone-based solvents.

[0039] Examples of the terpene solvent include terpineol, dihydroterpineol, and dihydroterpinyl acetate.

[0040] Examples of acetate solvents include isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate; glycol ether acetates such as ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy-3-methylbutyl acetate, and 1-methoxypropyl-2-acetate; glycol diacetates such as propylene glycol diacetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, and 1,6-hexanediol diacetate; and cyclohexanol acetate.

[0041] Examples of the ether solvent include propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether; ethylene glycol ethers such as diethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monohexyl ether, and ethylene glycol monohexyl ether; dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl-n-butyl ether, and dipropylene glycol dimethyl ether.

[0042] Examples of the ketone solvent include methyl isobutyl ketone, diisobutyl ketone, etc. When a ketone solvent is contained, it is possible to adjust the viscosity and improve the drying property without impairing the dispersibility.

[0043] The organic solvent preferably contains at least one selected from the group consisting of terpineol, dihydroterpineol, dihydroterpinyl acetate, propylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate. By containing such an organic solvent, excellent compatibility with the binder resin and excellent dispersibility of the filler can be achieved.

[0044] The total content of the organic solvent is preferably 20% by mass or more and 60% by mass or less, and more preferably 25% by mass or more and 45% by mass or less, based on the total amount of the conductive paste. When the content of the organic solvent is in the above range, the conductive paste has excellent conductivity and dispersibility.

[0045] The content of the organic solvent is preferably 50 parts by mass or more and 130 parts by mass or less, more preferably 60 parts by mass or more and 90 parts by mass or less, relative to 100 parts by mass of the conductive powder. When the content of the organic solvent is within the above range, the conductive powder has excellent conductivity and dispersibility.

[0046] One or more organic solvents may be used. For example, when two or more organic solvents are used, at least one selected from the group consisting of terpineol, dihydroterpineol, dihydroterpinyl acetate, propylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate may be included, along with a hydrocarbon solvent. Furthermore, at least one selected from methyl isobutyl ketone and diisobutyl ketone may be included in addition to these organic solvents.

[0047] Examples of hydrocarbon solvents include solvents containing tridecane, nonane, cyclohexane, mineral spirits, and naphthenic solvents. Of these, mineral spirits are preferred. The content of the hydrocarbon solvent may be 10% by mass or more and 50% by mass or less, or 20% by mass or more and 40% by mass or less, based on the total amount of organic solvents.

[0048] (Additives) (a) Ester Compound The conductive paste according to this embodiment contains, as an additive, a compound having a structural moiety represented by the following formula (A) or formula (B) (hereinafter also referred to as an “ester compound”).

[0049] (However, R １ represents a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched, and the aliphatic hydrocarbon group may contain one or more methylene groups (-CH ２ -) may be replaced with oxygen (-O-).

[0050] Specifically, the ester compound has a structure represented by the following structural formula (1) or (2).

[0051] In the above formulas (1) and (2), R １ , R ２ , R ３ each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched. ２ -) may be substituted with oxygen (-O-). １ , R ２ , and R ３ The number of carbon atoms is the number of methylene (-CH ２ -) carbon number.

[0052] When the conductive paste contains the ester compound, the adhesion of the dried film can be improved. Although the details of the reason for this are unclear, it is thought that, for example, the ester compound inhibits the interaction between resins, thereby moderately softening the dried film, and the softened dried film, which becomes more easily deformed, and the resins that do not interact, etc., tend to become entangled at the adhesive interface, thereby improving the adhesion between the dried film and the ceramic green sheet (dielectric layer).

[0053] In the above formulas (1) and (2), R １ and R ３ The lower limit of the number of carbon atoms in each of R may be independently 3 or more, or 5 or more. １ and R ３ The upper limit of the number of carbon atoms in each of R may be independently 10 or less, or 8 or less. １ and R ３ may have the same number of carbon atoms.

[0054] Also, R １ and R ３ may be an unsubstituted aliphatic hydrocarbon group, for example, a group having one methylene (—CH ２ -) may be replaced by oxygen (-O-).１ and R ３ may have a similar structure.

[0055] In the above (1) and (2), R ２ The lower limit of the number of carbon atoms in R may be 3 or more. ２ The upper limit of the number of carbon atoms in R may be 10 or less, or may be 8 or less. ２ is, for example, one or more methylene (—CH ２ The aliphatic hydrocarbon group may be substituted with oxygen (-O-), or may be an unsubstituted aliphatic hydrocarbon group.

[0056] The temperature at which the weight loss rate of the ester compound is maximized in thermogravimetric analysis (maximum thermal decomposition temperature) may be, for example, 200°C or higher, or 220°C or higher, and preferably 250°C or higher. When the maximum thermal decomposition temperature is within the above range, delamination and cracking of the laminate can be suppressed. Furthermore, the upper limit of the boiling point or thermal decomposition temperature is not particularly limited, but may be, for example, 450°C or lower, 400°C or lower, or 350°C or lower.

[0057] The maximum thermal decomposition temperature is a value determined by thermogravimetry (TG) using the following method: A thermal decomposition weight measuring device (NETSCH, STA25000REGULUS) was used to increase the temperature from 20°C to 550°C at a heating rate of 5°C / min in a nitrogen atmosphere, and the weight loss was measured. The temperature at which the differential loss on heating was greatest was defined as the maximum thermal decomposition temperature.

[0058] The molecular weight of the ester compound is preferably from 250 to 3000, more preferably from 250 to 1000, and even more preferably from 250 to 500. When the molecular weight of the ester compound is within the above range, the adhesion to the ceramic green sheet (dielectric layer) is further improved.

[0059] The content of the ester compound is preferably 0.01% by mass or more and 1.0% by mass or less with respect to the entire conductive paste. When the content of the ester compound is within the above range, the adhesion between the dried film and the ceramic green sheet (dielectric layer) is improved. From the viewpoint of further improving adhesion, the lower limit of the content of the ester compound may be 0.05% by mass or more, or 0.1% by mass or more with respect to the entire conductive paste. The upper limit of the content of the ester compound may be 0.7% by mass or less, or 0.4% by mass or less.

[0060] The upper limit of the content of the ester compound is not particularly limited, but may be, for example, 2% by mass or less, 1.8% by mass or less, 1.5% by mass or less, or 1.0% by mass or less. If the content of the ester compound exceeds 1.0% by mass, although adhesion is improved, thermal decomposition may occur and gas may be generated when the laminate of the dried film and the ceramic green sheet is subjected to a binder removal treatment. The content of the ester compound can be appropriately adjusted within the above range depending on the usage environment, etc.

[0061] The content of the ester compound can be appropriately set depending on the type and content of the binder resin. For example, the content of the ester compound may be set depending on the content of the butyral resin. The content of the ester compound may be, for example, 10 parts by mass or more and 90 parts by mass or less, 10 parts by mass or more and 60 parts by mass or less, or 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the butyral resin.

[0062] (b) Dispersant When the conductive paste contains a dispersant, the dispersibility of the conductive powder and ceramic powder can be improved. Examples of dispersants include acid dispersants, basic dispersants, nonionic dispersants, and amphoteric dispersants. It is preferable to contain at least one of an acid dispersant and a basic dispersant, and it is more preferable to contain an acid dispersant. These dispersants may be used alone or in combination of two or more.

[0063] The acid dispersant may include a carboxylic acid dispersant such as a higher fatty acid, a polycarboxylic acid dispersant, a phosphoric acid dispersant, an acid dispersant having an acidic group such as a polymer surfactant, etc., and preferably includes at least one of a polycarboxylic acid dispersant and a phosphoric acid dispersant. The polycarboxylic acid dispersant may also be a comb-shaped carboxylic acid having a comb structure.

[0064] The higher fatty acid may be an unsaturated carboxylic acid or a saturated carboxylic acid, and is not particularly limited, but examples thereof include those having 11 or more carbon atoms, such as stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. Of these, oleic acid or stearic acid is preferred.

[0065] The acid dispersant may be, for example, oleoyl sarcosine, which is a compound of glycine and oleic acid, or an alkyl monoamine salt type, which is an amide compound using a higher fatty acid such as stearic acid or lauric acid instead of oleic acid.

[0066] Furthermore, from the viewpoint of further improving the effect of suppressing separation between the conductive powder and the ceramic powder, a dicarboxylic acid may be contained. The dicarboxylic acid is a carboxylic acid having two carboxyl groups (COO- groups). The average molecular weight of the dicarboxylic acid is not particularly limited, but may be, for example, 200 or more and 1,000 or less.

[0067] Examples of basic dispersants include aliphatic amines such as laurylamine, rosinamine, cetylamine, myristylamine, and stearylamine. When the conductive paste contains the acid dispersant and the basic dispersant, the conductive paste may have better dispersibility and viscosity stability over time.

[0068] The dispersant is contained in an amount of, for example, 0.01% by mass or more and 3% by mass or less relative to the entire conductive paste. The range including the upper limit of the dispersant content may be 2% by mass or less, 1% by mass or less, or 0.5% by mass or less. When the dispersant content is within the above range, the dispersibility of the conductive paste can be improved and sheet attack and peeling failure of the green sheet can be suppressed.

[0069] (c) Other Additives The conductive paste of the present embodiment may contain other additives in addition to the above components, as needed. Examples of other additives that can be used include conventionally known additives such as antifoaming agents, plasticizers, surfactants, and thickeners.

[0070] (Conductive Paste) The method for producing the conductive paste according to the present embodiment is not particularly limited, and a conventionally known method can be used. The conductive paste can be produced, for example, by stirring and kneading the above-described components using a triple-roll mill, a ball mill, a mixer, or the like.

[0071] The conductive paste according to this embodiment contains the above-mentioned ester compound, thereby improving the adhesion between the dry film and the green sheet. One of the reasons for this improved adhesion is thought to be that, as described above, the ester compound inhibits the interaction between resins, thereby softening the dry film appropriately (lowering the glass transition temperature Tg), making it more susceptible to deformation.

[0072] For example, when the components of the conductive paste excluding the conductive powder and ceramic powder are dried at 120°C for 40 minutes to remove the organic solvent and prepare a dried body (evaluation sample), the glass transition temperature Tg of this dried body is preferably lower than the glass transition temperature Tg' of a dried body formed under similar conditions except that the ester compound is not included. The ester compound may lower the Tg by 10°C or more, 13°C or more, 15°C or more, or 20°C or more compared to Tg'. For example, the glass transition temperature Tg of the dried body (evaluation sample) may be 60°C or lower, 55°C or lower, or 50°C or lower. The lower limit of the glass transition temperature Tg is, for example, 30°C or higher.

[0073] When the conductive paste contains two or more types of resin as binder resins, multiple glass transition temperatures Tg may be measured depending on the resins contained, but the glass transition temperature Tg of the evaluation sample in this specification refers to the glass transition temperature Tg in the lowest temperature range. In addition, the glass transition temperature Tg of the above-mentioned dried body (evaluation sample) can be measured by the method described in the Examples.

[0074] Furthermore, when the conductive paste is applied to the surface of a substrate and dried at 75°C for 20 minutes to form a dry film, the Vickers hardness of the surface of the dry film at room temperature is preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less. The lower limit of the Vickers hardness (room temperature) is, for example, 3.5 or more.

[0075] The Vickers hardness of the surface of the dried film at 60°C is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less. The lower limit of the Vickers hardness (60°C) is, for example, 3 or more. When measuring the Vickers hardness (60°C), it is desirable to condition the dried film to be measured in advance by leaving it at 60°C for 3 minutes.

[0076] The conductive paste can be suitably used in electronic components such as multilayer ceramic capacitors, which have, for example, dielectric layers formed using dielectric green sheets and internal electrode layers formed using the conductive paste.

[0077] [Multilayer Ceramic Capacitor] Hereinafter, embodiments of the multilayer ceramic capacitor of the present invention will be described with reference to the drawings. In the drawings, schematic representations or scale changes may be used as appropriate. Furthermore, the positions and directions of components will be described with reference to an XYZ Cartesian coordinate system shown in FIG. 1 and other figures as appropriate. In this XYZ Cartesian coordinate system, the X and Y directions are horizontal directions, and the Z direction is vertical (up-down direction).

[0078] 1A and 1B are diagrams showing a multilayer ceramic capacitor 1. The multilayer ceramic capacitor 1 includes a ceramic laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and external electrodes 20.

[0079] A method for manufacturing a multilayer ceramic capacitor using the above-described conductive paste will now be described. First, the conductive paste is printed on a ceramic green sheet and dried to form a dry film. A plurality of ceramic green sheets, each having this dry film on its upper surface, are laminated by pressure bonding to obtain a laminate, which is then fired and integrated to produce a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately stacked. A pair of external electrodes 20 is then formed on both ends of the ceramic laminate 10 to produce a multilayer ceramic capacitor 1. This method will now be described in more detail.

[0080] First, a green sheet, which is an unfired ceramic sheet, is prepared. For example, this green sheet can be prepared by adding a binder resin such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate to form a dielectric layer paste. The paste is then applied to a support film such as a PET film in a sheet form and dried to remove the solvent. The thickness of the dielectric layer made of the 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.

[0081] Next, the conductive paste is printed and applied to one side of the green sheet, and then dried to form a dry film on one side of the green sheet, to prepare a plurality of sheets. Note that, from the viewpoint of the requirement for thinning of the internal electrode layer 11, it is preferable that the thickness of the dry film formed from the conductive paste is 1 μm or less after drying.

[0082] Next, the green sheets are peeled off from the support film, and the green sheets and the dry film formed on one side thereof are stacked alternately, followed by a heat and pressure treatment to obtain a laminate. Note that a configuration may be adopted in which protective ceramic green sheets not coated with the conductive paste are further placed on both sides of the laminate.

[0083] Next, the laminate is cut to a predetermined size to form green chips, and the green chips are subjected to a binder removal treatment and fired in a reducing atmosphere to produce a fired laminated ceramic body (ceramic laminate 10). The atmosphere in the binder removal treatment is air or N ２ It is preferable to carry out the debinding treatment in a gas atmosphere. The temperature during the debinding treatment is, for example, 200°C or higher and 400°C or lower. Furthermore, it is preferable to hold the above temperature for 0.5 hours or higher and 24 hours or lower during the debinding treatment. Furthermore, the firing is carried out in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layers, and the temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the temperature holding time during firing is, for example, 0.5 hours or higher and 8 hours or lower.

[0084] By firing the green chip, the organic binder in the ceramic green sheet is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12. Also, the organic vehicle in the dried film is removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode layer 11, thereby forming a multilayer ceramic fired body in which a plurality of dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that, from the viewpoint of taking oxygen into the dielectric layer to increase reliability and suppressing reoxidation of the internal electrodes, the fired multilayer ceramic fired body may be subjected to an annealing treatment.

[0085] Then, a pair of external electrodes 20 is provided on the produced fired multilayer ceramic body, thereby manufacturing the multilayer ceramic capacitor 1. For example, the external electrodes 20 include an external electrode layer 21 and a plating layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. Note that, for example, copper, nickel, or an alloy thereof can be suitably used as the material for the external electrodes 20. Note that electronic components other than multilayer ceramic capacitors can also be used as the electronic component.

[0086] EXAMPLES The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[0087] [Evaluation Method] (Adhesion Evaluation) A conductive paste (sample) was applied to the surface of a previously prepared green sheet containing barium titanate and polyvinyl butyral to form a conductive paste film with a wet film thickness of 35 μm. The resulting green sheet and the conductive paste film for the internal electrodes formed on its surface were dried at 75°C for 20 minutes to form a dried film on the green sheet. The dried sheet (dried film-green sheet) and another green sheet were stacked such that the conductive paste-coated surface was sandwiched between the green sheets, and then pressed at 40°C and 20 MPa for 20 seconds to form a laminate (for evaluation).

[0088] The obtained laminate was cut into 1 cm square pieces, and then both sides of the laminate were set on the jig of a tensile tester (AGS-50NX, manufactured by Shimadzu Corporation) using tape, and a tensile test was then performed. The breaking force (the force required to peel the dried film from the green sheet) was recorded at a test speed of 20 mm / min. The breaking force of each sample was evaluated as a percentage, with the breaking force of Comparative Example 1 being set as 100%.

[0089] (Hardness Measurement) The surface (dry film side) of the green sheet on which a conductive paste film (dry film) prepared under the same conditions as in the adhesion evaluation was formed was measured for Vickers hardness at n = 5 points using a micro Vickers hardness tester (Shimadzu Corporation, HMV-G21DT) under a test force of 98 mN, and the average value was calculated. The hardness measurement was performed by attaching the sample to a glass substrate and placing it on the heating stage, which is the sample holder of the hardness tester, at room temperature (25 ° C) without heating and at 60 ° C. When measuring the Vickers hardness (60 ° C), the dry film to be measured was first left at 60 ° C for 3 minutes to condition it, and then measured while heated at 60 ° C.

[0090] (Measurement of glass transition temperature Tg) The components contained in the conductive paste, excluding the conductive powder and ceramic powder, i.e., the ethyl cellulose resin, polyvinyl butyral resin, additives, and organic solvent, were weighed out in the same amounts as those contained in the conductive paste and mixed for 4 minutes at 2000 rpm using a planetary mixer (Thinky, ARE-310). The resulting liquid (mixture) was then applied to a PET film using an applicator to a wet film thickness of 254 μm, and dried at 120° C. for 40 minutes to obtain a sample for evaluation. The organic solvent in the mixture was removed during drying.

[0091] Using a differential scanning calorimeter (Netsch Japan Co., Ltd., DSC3100), 10 mg of the dried sample for evaluation was placed in an aluminum pan, and the temperature was raised from 0°C to 140°C at a heating rate of 10°C / min under a nitrogen stream of 100 mL / min. The glass transition temperature Tg on the low temperature region side was determined from the peak of the endothermic curve obtained.

[0092] (Measurement of thermal decomposition temperature) The thermal decomposition temperature of the additive used in the conductive paste was measured using a thermal decomposition weight measurement device (STA25000REGULUS, manufactured by Netsch). The measurement temperature atmosphere was nitrogen, and the temperature was raised from 20°C to 550°C at a heating rate of 5°C / min. The temperature at which the differential heat loss was greatest, i.e., the temperature at which the weight loss rate in thermogravimetric analysis was maximum, was defined as the thermal decomposition temperature (maximum thermal decomposition temperature).

[0093] [Materials Used] (Conductive Powder) Ni powder (SEM average particle size: 0.2 μm) was used as the conductive powder.

[0094] (Ceramic Powder) As the ceramic powder, barium titanate (BaTiO ３ (SEM average particle size 0.10 μm) was used.

[0095] (Binder Resin) As the binder resin, polyvinyl butyral resin (PVB) and ethyl cellulose resin (EC) were used.

[0096] (Dispersant) In the examples and comparative examples, a polycarboxylic acid-based dispersant, which is an acid-based dispersant, was used as the dispersant (additive) commonly contained.

[0097] (Additives) As the ester compounds, compounds 1-A and 2-A to 2-C in Table 1, which have the structure represented by the following structural formula (1) or the following structural formula (2), were used.

[0098]

[0099]

[0100] In addition, the following additives were used as comparative examples: Additive a: polycarboxylic acid having polyoxyalkylene as a graft chain (not having the structure of the above formula (1) or (2)); Additive b: oxyethylene laurylamine (polyetheramine); Additive c: dicarboxylic acid (2-(octadecen-1-yl)succinic acid).

[0101] (Organic Solvent) As the organic solvent, dihydroterpineol (DHT) and mineral spirits (MSA) were used.

[0102] [Example 1] A conductive paste was prepared by blending 49% by mass of conductive powder, 12% by mass of ceramic powder, 0.15% by mass of acid dispersant, 0.3% by mass of additive of formula (2-A), 2.5% by mass of binder resin (PVB:EC = 7:3 (mass ratio)), and the remainder being an organic solvent (DHT:MSA = 60:40 (mass ratio)) to a total of 100% by mass, and mixing these materials. The content of each material in the conductive paste and the evaluation results are shown in Table 1.

[0103] [Examples 1 to 9, Comparative Examples 1 to 4] Conductive pastes were prepared and evaluated in the same manner as in Example 1, except that the type and content of additives were changed as shown in Table 1. The content of each material in the conductive paste and the evaluation results are shown in Table 2.

[0104]

[0105] (Evaluation Results) Compared with the conductive pastes of Comparative Examples 1 to 4, which do not contain the ester compound represented by formula (1) or (2), the conductive pastes of Examples 1 to 9 had a lower glass transition point (Tg) in the low temperature range, a lower Vickers hardness, and improved adhesion.

[0106] When the conductive paste of the present invention is used to form internal electrodes of a multilayer ceramic capacitor, a highly reliable multilayer ceramic capacitor can be obtained with high productivity. Therefore, the conductive paste of the present invention is particularly suitable for use as internal electrodes of multilayer ceramic capacitors, which are chip components in electronic devices such as mobile phones and digital devices that are becoming increasingly miniaturized.

[0107] The technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above-mentioned embodiments may be omitted. Furthermore, the requirements described in the above-mentioned embodiments may be combined as appropriate. Furthermore, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated by reference into this description. Furthermore, to the extent permitted by law, the contents of Japanese Patent Application No. 2022-052665 are incorporated by reference into this description.

[0108] Embodiments of the present invention may include the following features.

[0109] [1] A conductive paste comprising a conductive powder, a binder resin, an additive, and an organic solvent, wherein the additive comprises a compound having a structure represented by the following structural formula (1) or the following structural formula (2). (However, R １ , R ２ , R ３ each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched. ２ -) may be replaced with oxygen (-O-).

[0110] [2] The conductive paste according to [1], wherein the compound is contained in an amount of 0.01 mass % or more and 2.0 mass % or less based on the entire conductive paste.

[0111] [3] The conductive paste according to [1] or [2], wherein the compound has a temperature at which the rate of weight loss in thermogravimetric analysis is maximized of 200°C or higher.

[0112] [4] The conductive paste according to any one of [1] to [3], wherein the compound has a molecular weight of 250 or more and 3,000 or less.

[0113] [5] The conductive paste according to any one of [1] to [4], further comprising an acidic dispersant and / or a basic dispersant.

[0114] [6] The conductive powder contains at least one metal powder selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. The conductive paste according to any one of [1] to [5].

[0115] [7] The conductive paste according to any one of [1] to [6], wherein the conductive powder has an average particle size of 0.05 μm or more and 1.0 μm or less.

[0116] [8] The conductive paste according to any one of [1] to [7], wherein the binder resin contains a butyral resin.

[0117] [9] The conductive paste according to any one of [1] to [8], further comprising ceramic powder.

[0118]

[10] The conductive paste according to [9], wherein the ceramic powder contains barium titanate.

[0119]

[11] The conductive paste according to [9] or

[10] , wherein the ceramic powder has an average particle size of 0.01 μm or more and 0.5 μm or less.

[0120]

[12] The conductive paste according to any one of [9] to

[11] , wherein the ceramic powder is contained in an amount of 1 mass % to 20 mass % of the entire conductive paste.

[0121]

[13] The conductive paste according to any one of [1] to

[12] , which is for use in an internal electrode of a multilayer ceramic component.

[0122]

[14] An electronic component formed using the conductive paste according to any one of [1] to

[13] .

[0123]

[15] A multilayer ceramic capacitor comprising at least a laminate in which dielectric layers and internal electrode layers are laminated, wherein the internal electrode layers are formed using the conductive paste according to

[13] .

[0124] REFERENCE SIGNS LIST 1 Multilayer ceramic capacitor 10 Ceramic laminate 11 Internal electrode layer 12 Dielectric layer 20 External electrode 21 External electrode layer 22 Plated layer

Claims

1. A conductive paste comprising a conductive powder, a binder resin, an additive, and an organic solvent, wherein the additive comprises a compound having a structure represented by the following structural formula (1) or (2): (However, R １ , R ２ , R ３ each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 2 to 12 carbon atoms, and the aliphatic hydrocarbon group may be linear or branched. ２ -) may be replaced with oxygen (-O-).

2. The conductive paste according to claim 1, wherein the compound is contained in an amount of 0.01% by mass or more and 2.0% by mass or less based on the entire conductive paste.

3. The conductive paste according to claim 1, wherein the compound exhibits a maximum weight loss rate at a temperature of 200°C or higher in thermogravimetric analysis.

4. The conductive paste according to claim 1, wherein the molecular weight of said compound is 250 or more and 3,000 or less.

5. The conductive paste according to claim 1, further comprising an acidic dispersant and / or a basic dispersant.

6. 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.

7. 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.

8. The conductive paste according to claim 1, wherein the binder resin comprises a butyral-based resin.

9. The conductive paste of claim 1, further comprising a ceramic powder.

10. The conductive paste of claim 9, wherein the ceramic powder comprises barium titanate.

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

12. The conductive paste according to claim 9, wherein the ceramic powder is contained in an amount of 1% by mass to 20% by mass based on the entire conductive paste.

13. The conductive paste according to claim 1, which is used for internal electrodes of multilayer ceramic parts.

14. An electronic component formed using the conductive paste according to any one of claims 1 to 13.

15. A multilayer ceramic capacitor comprising at least a laminate in which dielectric layers and internal electrode layers are laminated, wherein the internal electrode layers are formed using the conductive paste according to claim 13.