JP5400801B2 - Conductive paste for external electrode, multilayer ceramic electronic component having external electrode formed using the same, and method for manufacturing multilayer ceramic electronic component - Google Patents

Description

  The present invention relates to a conductive paste for external electrodes and a multilayer ceramic electronic component having external electrodes formed using the same.

  A conventional multilayer ceramic electronic component will be described by taking the multilayer ceramic capacitor shown in FIG. 1 as an example. The multilayer ceramic capacitor 1 has a structure in which an external electrode 4 is provided on an internal electrode extraction surface of a ceramic composite in which ceramic dielectrics 2 and internal electrodes 3 are alternately stacked.

  In forming the external electrode 4, a thermosetting conductive paste is frequently used because firing at a high temperature is not required. Typically, the surface of the external electrode 4 formed using a thermosetting conductive paste is provided with a plating layer 5 in order to increase the adhesive strength when soldering to a substrate or the like.

  In recent years, in order to improve the electrical characteristics (capacitance, tan δ) of multilayer ceramic electronic components, a thermosetting conductive paste in which high melting point metal particles and lower melting point metal particles are combined is used as an internal electrode. There has been proposed a technique for forming an external electrode excellent in bondability with each other (see Patent Documents 1 to 3). However, in order to meet the recent demand for higher performance such as high frequency response for multilayer ceramic electronic parts such as capacitors, when used as an external electrode, it provides even better electrical characteristics (capacitance, tan δ). There is a need for conductive pastes.

JP 2000-182883 A International Publication No. 2004/053901 Pamphlet International Publication No. 2007/072894 Pamphlet

  The present invention relates to a conductive paste for an external electrode that provides good electrical characteristics (capacitance, tan δ) when used as an external electrode of a multilayer ceramic electronic component, and a multilayer ceramic having the external electrode formed using the conductive paste The purpose is to provide electronic components.

  The present invention includes (A) metal particles having an average particle diameter of 0.2 to 30 μm and a melting point of 700 ° C. or more, and (B) an average particle diameter of 0.2 to 18 μm, and a melting point of 200 to 700 ° C. A copper-containing compound selected from the group consisting of metal particles of less than ° C. and (C) copper nitrate, copper cyanide, copper octoate, copper formate, copper acetate, copper oxalate, copper benzoate and copper acetylacetonate; The present invention relates to a conductive paste for an external electrode, comprising an amino compound; and optionally a paste obtained by mixing an organic solvent, and (D) a thermosetting resin.

  The present invention also relates to a multilayer ceramic electronic component having an external electrode formed using the conductive paste for external electrodes.

  By curing the conductive paste for external electrodes of the present invention, an external electrode of a multilayer ceramic electronic component having good electrical properties (capacitance, tan δ) is provided. In the present invention, a specific copper-containing compound is blended as a paste formed by mixing an amino compound and, optionally, an organic solvent, thereby forming the external electrode between the metal particles in the conductive paste and in the conductive paste. It is presumed that diffusion and alloying between the metal particles and the internal electrode proceed, and as a result, good electrical characteristics are considered to be obtained.

  In addition, according to the present invention, a multilayer ceramic electronic component having good electrical characteristics (capacitance, tan δ) on which the external electrode is formed is provided.

It is a schematic diagram of the conventional structure about the multilayer ceramic capacitor which is an example of a multilayer ceramic electronic component.

  The conductive paste for external electrodes of the present invention has (A) an average particle diameter of 0.2 to 30 μm, a metal particle having a melting point of 700 ° C. or more, and (B) an average particle diameter of 0.2 to 18 μm. From the group consisting of metal particles having a melting point of 200 ° C. or higher and lower than 700 ° C., and (C) copper nitrate, copper cyanide, copper octoate, copper formate, copper acetate, copper oxalate, copper benzoate and copper acetylacetonate The paste contains a selected copper-containing compound; an amino compound; and optionally an organic solvent, and (D) a thermosetting resin.

  (A) is a component for imparting conductivity to the external electrode, and is not particularly limited as long as it is a metal particle having an average particle diameter of 0.2 to 30 μm and a melting point of 700 ° C. or higher. The melting point of (A) is preferably 800 ° C. or higher. Although the upper limit of melting | fusing point is not specifically limited, Usually, it is 1800 degrees C or less, and 1600 degrees C or less is preferable. (A) can be used alone or in combination of two or more.

  Examples of (A) include Ag, Cu, Ni, Pd, Au, and Pt metal particles. Ag particles are preferable because excellent conductivity can be obtained relatively easily.

  Moreover, it is an alloy of Ag, Cu, Ni, Pd, Au and Pt and has a melting point of 700 ° C. or higher. Since excellent conductivity can be obtained relatively easily, particles of Ag alloy are preferable.

  The alloy particles include alloy particles composed of two or more elements selected from the group consisting of Ag, Cu, Ni, Pd, Au, and Pt. The binary Ag alloy includes an AgCu alloy. , AgAu alloy, AgPd alloy, AgNi alloy and the like, and the ternary Ag alloy includes AgPdCu alloy, AgCuNi alloy and the like.

  Further, the alloy particles are alloy particles composed of one or more elements selected from Ag, Cu, Ni, Pd, Au and Pt and one or more other elements, and have a melting point as the alloy. May be particles having a temperature of 700 ° C. or higher. Other elements include Zn, Al, and Sn. In the case of a binary alloy of Sn and Ag, the weight ratio of Sn to Ag is higher than that of 25.5: 74.5. An AgSn alloy can be used.

  The shape of (A) may be any shape such as a spherical shape, a flake shape, a flake shape, and a needle shape. These average particle diameters are preferably 0.2 to 20 μm, more preferably 0.2 to 20 μm because the surface state after printing or coating is good and excellent electrical conductivity can be imparted to the formed external electrode. 15 μm. In the present specification, the average particle diameter is the particle diameter in the case of a sphere, the diameter of the longest part in the case of flakes, the long diameter of the particle flakes in the case of flakes, and the length in the case of needles, respectively. Mean means. Unless otherwise specified, the average particle diameter of the metal particles is a value obtained by image analysis through observation with a scanning electron microscope (SEM).

  (A) is preferably an Ag particle from the viewpoint of conductivity, and spherical Ag particles having an average particle diameter of 0.2 to 5 μm and flaky Ag particles having an average particle diameter of 5 to 30 μm are 99: 1 to 75. : It is particularly preferable to include it in a weight ratio of 25.

  (B) is a component for imparting conductivity to the external electrode, and a component that contributes to improving the bondability of the ceramic composite with the internal electrode, and has an average particle size of 0.2 to 18 μm. If it is a metal particle whose melting | fusing point is 200 degreeC or more and less than 700 degreeC, it will not specifically limit. The melting point of (B) is preferably 300 to 500 ° C., since the bondability with the internal electrode can be obtained relatively easily. (B) can be used alone or in combination of two or more. The reason why (B) brings about good bondability with the internal electrode is not clearly understood, but (B) diffuses into the layer of the external electrode by heating when forming the external electrode. Is considered to be a cause. In addition, if it is the heating temperature which a thermosetting resin hardens | cures, even if it is the temperature lower than melting | fusing point of (B), a spreading | diffusion will arise and it can anticipate the improvement of adhesiveness with an internal electrode.

  Examples of (B) include Sn, In, Zn, and Bi metal particles. (B) is preferably non-Pb.

  Moreover, it is an alloy of Sn, In, and Bi, and includes particles having a temperature of 200 ° C. or higher and lower than 700 ° C. An Sn alloy is preferable because excellent conductivity can be obtained relatively easily. Examples of alloy particles include alloy particles composed of two or more elements selected from the group consisting of Sn, In, and Bi. Examples of binary alloys include SnIn alloys.

  Further, the alloy particles are alloy particles composed of one or more elements selected from Sn, In and Bi and one or more other elements, and the melting point of the alloy is 200 ° C. or higher and 700 ° C. Less than particles. Examples of other elements include Ag, Cu, Ni, Zn, Al, Pd, Au, and Pt. One or more elements selected from Sn, In, and Bi, and Ag, Cu, Ni, Zn, Al , Pd, Au, and an alloy composed of one or more elements selected from Pt. Specifically, a binary alloy such as SnZn alloy, SnAg alloy, SnCu alloy, SnAl alloy, InAg alloy, InZg alloy, BiAg alloy, BiNi alloy, BiZn alloy, or BiPb alloy has a melting point of 200 ° C. or higher and lower than 700 ° C. Examples of the ternary alloy include ternary alloys such as SnAgCu alloy, InAgCu alloy, and BiAgCu alloy, and particles having a melting point of 200 ° C. or higher and lower than 700 ° C.

  In the case of a binary alloy of Sn and Ag, an alloy having a Sn / Ag weight ratio greater than 25.5: 74.5 can be used. In particular, a SnAg alloy having a weight ratio of 50:50 to 89:11 is preferable.

  The shape of (B) may be any shape such as a spherical shape, a flake shape, a flake shape, and a needle shape. These average particle diameters are preferably 2 to 16 μm, preferably 7 to 14 μm from the viewpoint that the surface state after printing or coating is good, the conductivity can be imparted to the formed external electrode, and oxidation prevention. More preferred.

  (C) is a copper-containing compound selected from the group consisting of copper nitrate, copper cyanide, copper octoate, copper formate, copper acetate, copper oxalate, copper benzoate and copper acetylacetonate; an amino compound; Is a paste formed by mixing an organic solvent.

  The copper-containing compound is selected from the group consisting of copper nitrate, copper cyanide, copper octoate, copper formate, copper acetate, copper oxalate, copper benzoate and copper acetylacetonate, alone or in combination of two or more. Can be used in combination. Here, each said copper containing compound shall include an anhydride and a hydrate. For example, copper formate includes copper formate (anhydrous), copper formate (dihydrate) and copper formate (tetrahydrate), and copper acetate includes copper acetate (anhydride) and copper acetate (monohydrate). And copper nitrate includes copper nitrate (anhydride) and copper nitrate (trihydrate). Copper cyanide, copper octoate, copper oxalate, copper benzoate and copper acetylacetonate are usually anhydrous.

  As said copper containing compound, from the point of solubilization to an amino compound, copper formate (anhydride), copper formate (dihydrate), copper formate (tetrahydrate), copper acetate or copper acetate (one Hydrates) are preferred. In particular, copper formate (tetrahydrate) and copper acetate (anhydride) are preferable.

  An amino compound is a compound that contains one or more substituted or unsubstituted amino groups, and is a component that solubilizes the copper-containing compound. Examples of the substituent of the substituted amino group include an alkyl group. Amino compounds can be used alone or in combination of two or more. Examples of the amino compound include a chain amino compound, and a chain amino compound having 2 to 10 carbon atoms is preferable. An alicyclic ring-containing amino compound can also be used, for example, a cycloalkane ring-containing amino compound, preferably a cycloalkane ring-containing amino acid having 5 to 8 carbon atoms such as 1,2-diaminocyclohexane. Compounds.

Specifically, as the amino compound, the formula (i):
NR ¹ R ² R ³ (i)
(In the formula, R ¹ represents an alkyl group having 2 to 4 carbon atoms that is monosubstituted by a hydroxyl group, a methoxy group, an ethoxy group, or an amino group, and R ² and R ³ are each independently hydrogen. Or an amino compound having a carbon number of 1 to 3 which may be substituted with a hydroxyl group or an amino group), and at least one of R ² and R ³ is hydrogen. The amino compound is more preferable.

  From the viewpoint of solubilization, the amino compounds of formula (i) include 3-methoxypropylamine, 3-ethoxypropylamine, 1-amino-2-propanol, 3-amino-1-propanol, 2-aminoethanol, 2 -Amino-2-methyl-1-propanol, N-methyl-1,3-diaminopropane, 3,3'-diaminodipropylamine, 2-methoxyethylamine, 1,3-diaminopropane, 2- (2-amino A compound containing a primary amino group such as ethylamino) ethanol, a compound containing a secondary amino group such as N-methylethanolamine or 2,2′-iminodiethanol, or a compound such as 2-dimethylaminoethanol. It is preferable to use a compound containing a tertiary amino group, and 2-amino-2-methyl-1-propanol is particularly preferable.

  From the viewpoint of workability and the like, the viscosity can be adjusted by adding an organic solvent such as alcohols, ketones, ethers, and aromatic hydrocarbons depending on circumstances.

  Examples of the alcohols include methanol, ethanol, propanol, butanol, pentyl alcohol, terpineol, dihydroterpineol and the like.

  Examples of the ketones include acetone, methyl ethyl ketone, 2-pentanone, and 3-pentanone.

  Examples of the ethers include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether and the like.

  Examples of the aromatic hydrocarbons include toluene and xylene.

  It is preferable that an amino compound (for example, amino compound of a formula (i)) is 0.5-10 mol with respect to 1 mol of said copper containing compounds, More preferably, it is 1-6 mol.

  When copper formate (tetrahydrate) and 2-amino-2-methyl-1-propanol are used in combination, 2-amino-2-methyl-1-based on 1 mol of copper formate (tetrahydrate). 2-6 mol of propanol is preferable, More preferably, it is 3.5-4.5 mol. When copper acetate (anhydride) and 3-methoxypropylamine are used in combination, 1 to 6 moles of 3-methoxypropylamine are preferred, more preferably 2 to 4 moles per mole of copper acetate (anhydride). It is.

  (C) can be prepared by blending and mixing a specific copper-containing compound, an amino compound and optionally an organic solvent. The mixing is preferably performed at 20 to 65 ° C, more preferably 20 to 50 ° C, and stirring is performed until the exothermic reaction is completed.

  (D) functions as a binder and is not particularly limited as long as it is a thermosetting resin. Specifically, amino resins such as urea resin, melamine resin, and guanamine resin; bisphenol A type, bisphenol F type, phenol novolac type, tetrakis (hydroxyphenyl) ethane type that is a polyfunctional type having many benzene rings or Tris (hydroxyphenyl) methane type, cycloaliphatic epoxy resin; Oxetane resin; Resol type, alkylresole type, novolak type, alkyl novolak type, aralkyl novolak type phenolic resin; silicone epoxy, silicone polyester, etc. Examples include silicone-modified organic resins, bismaleimides, and polyimide resins. For example, BT resin can also be used. Among these, an epoxy resin is preferable from the viewpoint of improving the conductivity of the conductive paste for external electrodes due to volume shrinkage at the time of curing, and improving the adhesion between the conductive paste for external electrodes and the multilayer ceramic electronic component. Is more preferable, and the following general formula (1):

（式中、Ｘは（ＣＨ_２）pを示し、ｐは０〜３の整数である）で示されるエポキシ樹脂がさらに好ましく、式（１）においてｐが０である一般式（２）：

(Wherein X represents (CH ₂ ) p, p is an integer of 0 to 3), and an epoxy resin represented by general formula (2) in which p is 0 in formula (1):

で示される１，１，２，２−テトラキス（ヒドロキシフェニル）エタン型エポキシ樹脂が、特に好ましい。これらの樹脂は、単独で用いても、２種以上を併用してもよい。

A 1,1,2,2-tetrakis (hydroxyphenyl) ethane type epoxy resin represented by the formula is particularly preferred. These resins may be used alone or in combination of two or more.

  It is preferable to use a resin that is liquid at room temperature because the amount of the organic solvent used as a diluent can be reduced. Examples of such a liquid resin include a liquid epoxy resin and a liquid phenol resin. Further, a resin that is compatible with these liquid resins and that exhibits a solid or ultra-high viscosity at room temperature may be further added and mixed within a range in which the mixed system exhibits fluidity. Examples of such resins include high molecular weight bisphenol A type epoxy resins, diglycidyl biphenyl, novolac type epoxy resins, tetrabromobisphenol A type epoxy resins; resol type phenol resins, novolac type phenol resins, aralkyl novolac types A phenol resin etc. are illustrated.

  When using an epoxy resin, the curing mechanism may be a self-curing resin, a curing agent or a curing catalyst such as amines, imidazoles, acid anhydrides or onium salts, amino resin or phenol The resin may function as a curing agent for the epoxy resin. From the viewpoint of storage stability, 2-phenyl-4-methyl-5-hydroxymethylimidazole is particularly preferable.

  Among these, an epoxy resin that is cured by a phenol resin is preferable. The phenol resin may be a phenol resin initial condensate that is usually used as a curing agent for epoxy resins, and may be a resol type or a novolac type, but in order to obtain excellent heat cycle resistance, 50% by weight or more thereof. Is preferably an alkyl resol type, alkyl novolak type, aralkyl novolak type phenol resin, xylene resin or allyl phenol resin. The following general formula (3):

（式中、ｎは０〜３００である。）で示されるフェノール・ｐ−キシリレングリコールジメチルエーテル重縮合物であるアラルキルノボラック型フェノール樹脂も、好ましい。また、アルキルレゾール型フェノール樹脂の場合、優れた印刷適性を得るためには、平均分子量が２，０００以上であることが好ましい。これらのアルキルレゾール型又はアルキルノボラック型フェノール樹脂において、アルキル基としては、炭素数１〜１８のものを用いることができ、エチル、プロピル、ブチル、ペンチル、ヘキシル、オクチル、ノニル、デシルのような炭素数２〜１０のものが好ましい。

An aralkyl novolak type phenol resin which is a phenol / p-xylylene glycol dimethyl ether polycondensate represented by the formula (wherein n is 0 to 300) is also preferred. In the case of an alkyl resole type phenol resin, the average molecular weight is preferably 2,000 or more in order to obtain excellent printability. In these alkylresole type or alkyl novolac type phenol resins, alkyl groups having 1 to 18 carbon atoms can be used, and carbons such as ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, and decyl can be used. The thing of several 2-10 is preferable.

  Among these, since excellent adhesiveness is obtained and heat resistance is excellent, tetrakis (hydroxyphenyl) ethane type epoxy resin and aralkyl novolac type phenol resin, resol type phenol resin, xylene resin or allyl phenol resin A combination of 1,1,2,2-tetrakis (hydroxyphenyl) ethane type epoxy resin and aralkyl novolac type phenol resin, resol type phenol resin, xylene resin or allyl phenol resin is particularly preferable. When a combination of tetrakis (hydroxyphenyl) ethane type epoxy resin and aralkyl novolac type phenol resin, resol type phenol resin, xylene resin or allylphenol resin is used, the weight ratio of epoxy resin to phenol resin is 4: 1 to 1: The range of 4 is preferable, and 4: 1 to 1: 2 is more preferable. In addition, polyimide resin is also effective from the viewpoint of heat resistance.

  A thermoplastic resin may be used in combination with the thermosetting resin as long as the effects of the present invention are not impaired. As the thermoplastic resin, polysulfone, polyethersulfone, maleimide resin and the like are preferable.

  In order to further improve the electrical characteristics, the conductive paste for external electrodes of the present invention may further contain (E) metal fine particles having an average particle diameter of 15 to 150 nm and a melting point of 700 ° C. or higher. The shape of (E) is preferably spherical.

  Examples of the metal or alloy forming (E) include the metals or alloys listed in (A). In the case of a binary alloy of Sn and Ag, an alloy having a Sn / Ag weight ratio greater than 25.5: 74.5 can be used. In particular, a SnAg alloy having a weight ratio of 50:50 to 89:11 is preferable. (E) may be a system of three or more components containing 5% by weight or less of Cu, In, Bi, Ni and the like.

  In addition, (E), in combination with (B), results in good bonding with the internal electrode, and (a) the average particle diameter of (a) primary particles is preferably 15 to 150 nm, more preferably 40 to 150 nm, more preferably 50 to 150 nm, (b) the crystallite diameter is preferably 15 to 50 nm, more preferably 20 to 50 nm, and (c) the ratio of the average particle diameter to the crystallite diameter is preferably 1 10 to 10 and more preferably 1 to 7.5. In the present specification, the crystallite diameter is obtained by measuring the half-value width of the plane index (1,1,1) plane peak from the measurement by the powder X-ray diffraction method using Cu Kα ray as the radiation source. The result calculated from the formula.

  A method for producing Ag fine particles satisfying the above (a) to (c) will be described. Ag fine particles are prepared by mixing a silver salt of a carboxylic acid and an aliphatic primary amine in the presence or absence of an organic solvent, adding a reducing agent, and reacting at a reaction temperature of 20 to 80 ° C. It is obtained by precipitating fine particles.

  The silver salt of carboxylic acid is not particularly limited, but is preferably a silver salt of an aliphatic monocarboxylic acid, and more preferably silver acetate, silver propionate or silver butyrate. These can be used alone or in combination of two or more.

  The aliphatic primary amine is not particularly limited, but may be a chain aliphatic primary amine or a cyclic aliphatic primary amine. 3-methoxypropylamine, 3-aminopropanol or 1,2-diaminocyclohexane is preferred. These can be used alone or in combination of two or more.

  The amount of the aliphatic primary amine used is preferably 1 equivalent or more with respect to 1 equivalent of the silver salt of the carboxylic acid. Considering the influence of excess aliphatic primary amine on the environment, etc., 1 It is preferable that it is 0.0-3.0 equivalent, More preferably, it is 1.0-2.0 equivalent, Especially preferably, it is 1.3-1.7 equivalent.

  The silver salt of carboxylic acid and the aliphatic primary amine can be mixed in the absence or presence of an organic solvent. Examples of the organic solvent include alcohols such as ethanol, propanol, and butanol, and propylene glycol diester. Examples thereof include ethers such as butyl ether and aromatic hydrocarbons such as toluene. These can be used alone or in combination of two or more. The amount of the organic solvent used can be set to an arbitrary amount from the viewpoint of the convenience of mixing and the productivity of Ag fine particles in the subsequent steps.

  The mixing of the silver salt of the carboxylate and the aliphatic primary amine is preferably carried out while maintaining the temperature at 20 to 80 ° C, more preferably 20 to 60 ° C.

  As the reducing agent, formic acid, formaldehyde, ascorbic acid or hydrazine is preferable from the viewpoint of controlling the reaction, and formic acid is more preferable. These may be used alone or in combination of two or more.

  The amount of the reducing agent used is usually at least a redox equivalent with respect to the silver salt of the carboxylic acid, and the redox equivalent is preferably 0.5 to 5 times, more preferably 1 to 3 times. . When the silver salt of carboxylic acid is a silver salt of monocarboxylic acid and formic acid is used as the reducing agent, the amount of formic acid used in terms of mole is 0.5 to 1 with respect to 1 mole of silver salt of carboxylic acid. 0.5 mol is preferable, more preferably 0.5 to 1.0 mol, and still more preferably 0.5 to 0.75 mol.

  In the addition of the reducing agent and the subsequent reaction, the temperature is maintained at 20 ° C. to 80 ° C., preferably 20 to 70 ° C., more preferably 20 to 60 ° C.

  Ag fine particles precipitated by the reaction are allowed to settle and the supernatant is removed by decantation or the like, or a solvent such as alcohol such as methanol, ethanol or terpineol can be added and fractionated. Further, the layer containing Ag fine particles may be used as it is for the paste.

  In this invention, (A) is 55-85 weight part with respect to the sum total of the copper conversion amount of (A), (B), and (C), ie, a metal component total 100 weight part, (B) Is 10 to 45 parts by weight, the copper equivalent of (C) is 0.05 to 5 parts by weight, and (D) is preferably 5 to 20 parts by weight. Thereby, the printing appropriateness of the electroconductive paste for external electrodes, the electroconductivity of the external electrode obtained, and the joining property of the internal and external electrodes are achieved.

  In the present invention, (A) is more preferably 60 to 80 parts by weight, particularly preferably 65 parts by weight based on 100 parts by weight of the total of (A), (B) and (C) in terms of copper. -75 parts by weight, (B) is more preferably 15-40 parts by weight, particularly preferably 20-35 parts by weight, and (C) is more preferably 0.1 in terms of copper. It is -2 weight part, Especially preferably, it is 0.2-1 weight part, More preferably, it is 7-18 weight part from (D), Most preferably, it is 10-16 weight part.

  Furthermore, when (E) is blended in the present invention, (E) is 5 to 5 parts in total with respect to 100 parts by weight of the (A), (B), and (C) copper equivalents and (E). It is preferably 25 parts by weight. Thereby, the further improvement of an electrical property can be aimed at effectively. (E) is more preferably 5 to 20 parts by weight with respect to the total of 100 parts by weight of (A), (B) and (C) in terms of copper and (E), and particularly preferably 7 parts by weight. ~ 15 parts by weight.

  The conductive paste for external electrodes of the present invention is formulated with (A), (B), (C), (D) and optionally (E), and if necessary, a diluent is added to obtain a desired paste. The viscosity can be adjusted to an appropriate value depending on the method of printing or applying to the ceramic composite of the electronic component. For example, when used for screen printing, the apparent viscosity of the conductive paste at room temperature is preferably 10 to 500 Pa · s, and more preferably 15 to 300 Pa · s.

  Organic solvents used for the diluent include aromatic hydrocarbons such as toluene, xylene, mesitylene and tetralin; ethers such as tetrahydrofuran; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone; Lactones such as pyrrolidone and 1-methyl-2-pyrrolidone; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and corresponding propylene Ether alcohols such as glycol derivatives; their corresponding esters such as acetate; and malonic acid Methyl esters of dicarboxylic acids such as succinic acid, diesters, such as ethyl esters are exemplified. The amount of the organic solvent used is arbitrarily selected depending on the type and amount of (A), (B), (C), (D) and optionally (E), the method of printing or applying the paste, and the like.

  In addition to the conductive paste for external electrodes, if necessary, an aluminum chelate compound such as diisopropoxy (ethylacetoacetate) aluminum; titanic acid such as isopropyl triisostearoyl titanate as a dispersion aid Esters; aliphatic polycarboxylic acid esters; unsaturated fatty acid amine salts; surfactants such as sorbitan monooleate; or polymer compounds such as polyesteramine salts and polyamides may be used. Moreover, you may mix | blend an inorganic and organic pigment, a silane coupling agent, a leveling agent, a thixotropic agent, an antifoamer, etc.

  The conductive paste for an external electrode can be prepared by uniformly mixing the compounding components by a mixing means such as a reika machine, a propeller stirrer, a kneader, a roll, and a pot mill. Although preparation temperature is not specifically limited, For example, it can prepare at normal temperature, specifically 20-30 degreeC.

  Using the thus obtained conductive paste for external electrodes, a multilayer ceramic electronic component having external electrodes can be formed according to a known method. For example, the conductive paste for external electrodes is printed or applied to the internal electrode take-out surface of the ceramic composite of the multilayer ceramic capacitor by an arbitrary method such as screen printing, transfer, or dip coating. It prints or apply | coats so that the thickness of the external electrode after hardening becomes like this. Preferably it is 1-300 micrometers, More preferably, it is 20-100 micrometers. In the case of using an organic solvent, it is dried at room temperature or by heating after printing or coating. Subsequently, in order to obtain an external electrode, it can harden | cure at 80-450 degreeC, for example, specifically 200-350 degreeC, for example. Moreover, after making it dry at 80-160 degreeC, it can also be hardened at 200-350 degreeC. In addition, in order to fully exhibit the effect of the blending of (B) and (C), the curing temperature is preferably 250 to 350 ° C. The conductive paste for external electrodes of the present invention is simple because it does not need to be placed in an inert gas atmosphere during curing.

  Although hardening time can be changed with hardening temperature etc., 1 to 60 minutes are preferable from the point of workability | operativity. However, when hardening at 250 degrees C or less, it is preferable to set it as 10 to 60 minutes from the point of bondability with an internal electrode. For example, when the resin in the paste is an epoxy resin using a phenol resin as a curing agent, curing can be performed at 200 to 350 ° C. for 10 to 60 minutes to obtain an external electrode. In order to prevent the volatile components in the paste from vaporizing at a stretch and generating blisters and cracks in the coating film, it is desirable to avoid rapid heating (for example, rapid heating to 300 ° C. or higher). The temperature of the ceramic composite is the same as the temperature of the alumina substrate when a K-type thermocouple is fixed with a polyimide tape on an alumina substrate having a width of 20 mm, a length of 20 mm, and a thickness of 1 mm, and placed in a reflow furnace. did. The holding time was the time after the temperature of the alumina substrate reached the holding temperature.

  The ceramic composite of the multilayer ceramic electronic component used in the present invention may be produced by any known method. In the present invention, the ceramic composite refers to a sintered body in which ceramic layers and internal electrode layers are alternately laminated, or a laminated body in which resin / ceramic hybrid materials and internal electrodes are alternately laminated. The ceramic layer or the resin / ceramic hybrid material has properties suitable for the desired electronic component, for example, a capacitor having dielectric properties, and may be obtained by any known method. Also, the internal electrode layer is not particularly limited, but a base metal that is inexpensive and easily available, such as nickel or copper, is preferably used as the internal electrode. In particular, when the surface of the internal electrode of the ceramic composite contains nickel, Cu is more likely to form an alloy with Ni than Ag, which improves the bondability and electrical characteristics (capacitance, tan δ). I can expect. Among these, (A) is Ag particles or Ag alloy particles, and (B) is preferable in combination with SnAg alloy particles because formation of a Cu—Ni—Sn—Ag alloy can be expected. The ceramic composite is preferably a ceramic composite in which the internal electrode is nickel. The multilayer ceramic electronic component of the present invention may be, for example, a capacitor, a capacitor array, a thermistor, a varistor, an inductor, and an LC, CR, LR and LCR composite component.

  The obtained multilayer ceramic electronic component is plated on the electrode layer surface as necessary in order to further increase the adhesive strength when soldered and mounted on a substrate or the like. The plating process is performed according to a known method, but it is preferable to perform lead-free plating in consideration of the environment. For example, the surface of the external electrode is subjected to nickel plating by electrolytic plating such as a Watt bath or electroless plating, and then further subjected to solder plating or tin plating by electrolytic plating or electroless plating.

  The multilayer ceramic electronic component obtained by plating the surface of the external electrode formed with the conductive paste for external electrode of the present invention thus obtained has excellent electrical characteristics and is useful for mounting on a circuit board or the like. It is a thing.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited by these examples.

(Preparation of paste)
Each component was mixed with the composition of the following Table 1, and each paste of an Example and a comparative example was prepared (the number in a table | surface is a weight part unless there is a notice).

１）平均粒子径０．３μｍ、純度９９．５％以上
２）平均粒子径１２μｍ、純度９９％以上
３）球状、平均粒子径２．５μｍ、純度９９％以上、融点４１０℃
４）球状、平均粒子径２．５μｍ、純度９９％以上、融点５９０℃
５）平均粒子径３．０μｍ、純度９９％以上、融点４２０℃
６）銅換算量
７）銅換算量
８）銀換算量
９）銅換算量
１０）１，１，２，２−テトラキス（ヒドロキシフェニル）エタン型固形エポキシ樹脂、エポキシ当量：２００（ｇ／ｅｑ）
１１）アラルキルノボラック型フェノール樹脂（フェノール・ｐ−キシリレングリコールジメチルエーテル重縮合物）、ＯＨ当量１６９
１２）２−フェニル−４−メチル−５−ヒドロキシメチルイミダゾール
１３）粘度が約２０Ｐａ・Ｓになるように適量添加（粘度は、ブルックフィールドＤＶ−１型粘度系で１０ｒｐｍにて室温で測定した）。

1) Average particle diameter 0.3 μm, purity 99.5% or more 2) Average particle diameter 12 μm, purity 99% or more 3) Spherical, average particle diameter 2.5 μm, purity 99% or more, melting point 410 ° C.
4) Spherical shape, average particle size 2.5 μm, purity 99% or more, melting point 590 ° C.
5) Average particle size 3.0 μm, purity 99% or more, melting point 420 ° C.
6) Copper equivalent 7) Copper equivalent 8) Silver equivalent 9) Copper equivalent 10) 1,1,2,2-tetrakis (hydroxyphenyl) ethane type solid epoxy resin, epoxy equivalent: 200 (g / eq)
11) Aralkyl novolac type phenolic resin (phenol / p-xylylene glycol dimethyl ether polycondensate), OH equivalent 169
12) 2-Phenyl-4-methyl-5-hydroxymethylimidazole 13) Appropriate amount added so that the viscosity is about 20 Pa · S (viscosity was measured at room temperature at 10 rpm in a Brookfield DV-1 type viscosity system) .

(C) in Table 1 is as follows.
Cu-containing paste 1: 0.3 mol of copper formate (tetrahydrate) (manufactured by Nippon Chemical Industry Co., Ltd.) and 1.2 mol of 2-amino-2-methyl-propanol were charged into a 500 cm ³ volume flask. The mixture was stirred at room temperature for 5 hours to prepare a paste in which copper formate (tetrahydrate) was solubilized.
Cu-containing paste 2: 0.3 mol of copper acetate (anhydride) and 1.2 mol of 3-methoxypropylamine were charged into a 500 cm ³ volume flask and stirred at room temperature for 5 hours to obtain copper acetate (anhydride). A solubilized paste was prepared.

The Ag fine particle-containing paste and Cu fine particle-containing paste in Table 1 are as follows.
Ag fine particle-containing paste: 4.0 kg (45.0 mol) of 3-methoxypropylamine was placed in a 10 L glass reaction vessel. While stirring, the reaction temperature was maintained at 45 ° C. or lower, and 5.0 kg (30.0 mol) of silver acetate was added. Immediately after the addition, the solution became a transparent solution and dissolved, but as the addition proceeded, the solution gradually became turbid, and when the entire amount was added, it became an ash brown cloudy viscous solution. Thereto was slowly added dropwise 0.73 kg (15.0 mol) of 95% by weight formic acid. Vigorous exotherm was observed immediately after the addition, while the reaction temperature was maintained at 30 to 45 ° C. Initially, the turbid viscous solution changed from brown to black. The reaction was terminated after the entire amount was added dropwise. The reaction mixture was allowed to stand at 40 ° C. and separated into two layers. The upper layer is a yellow transparent liquid, and black Ag fine particles settled in the lower layer. The upper layer liquid did not contain an Ag component. The liquid in the upper layer was removed by decantation, and the layers were separated using methanol to obtain true spherical Ag fine particles having an Ag content of 89% by weight.
The obtained Ag fine particles are as follows. Average particle diameter 130 nm, crystallite diameter 40 nm, average particle diameter / crystallite diameter = 3.25. Here, the average particle diameter is an average value of Haywood diameters obtained by image analysis by observing with a scanning electron microscope (SEM), and the crystallite diameter is measured by an X-ray diffraction measuring apparatus (M18XHF22) manufactured by Mac Science. The half-value width of the plane index (1, 1, 1) plane peak using Cu Kα ray as a radiation source is obtained by measurement, and is a value calculated from the Scherrer equation.

  Cu fine particle-containing paste: Dispersion in methanol (Cu fine particle 54 wt%). Average particle diameter of Cu fine particles is 30 nm.

[Preparation of multilayer ceramic capacitor sample]
Each paste shown in Table 1 is applied to the internal electrode take-out surface of the ceramic composite (3216 type, B characteristics, nickel internal electrode, theoretical capacity 10 μF) of the chip multilayer capacitor so that the thickness after curing is about 20 μm. After dip-coating with an esi Paloma printing machine (model number: MODEL 2001) and drying at 150 ° C. for 30 minutes, curing was performed in the air at 300 ° C. for 40 minutes to form an external electrode. Subsequently, nickel plating was performed in a watt bath, and then tin plating was performed by electrolytic plating to obtain a chip multilayer capacitor.

[Measurement of resistivity]
Using a 250-mesh stainless steel screen on an alumina substrate having a width of 20 mm, a length of 20 mm, and a thickness of 1 mm, zigzag pattern printing of a length of 71 mm, a width of 1 mm, and a thickness of 20 μm was performed, and after drying at 150 ° C. for 10 minutes, Curing was performed at 300 ° C. for 40 minutes in the air to form an external electrode. The thickness of the zigzag pattern was determined from the average of 6 numerical values measured so as to intersect the pattern with a surface roughness shape measuring instrument (product name: Surfcom 1400) manufactured by Tokyo Seimitsu. After curing, the specific resistance was measured by the 4-terminal method using an LCR meter. The results are shown in Table 2. Examples 1 to 13 were 0.3 to 2.7 × 10 ⁻⁴ Ω · cm. Comparative Example 7 was 3.7 × 10 ⁻⁴ Ω · cm.

[Measurement of capacitance and dissipation factor]
The initial capacitance and dielectric loss tangent (tan δ) of the chip multilayer capacitor element obtained above were measured at a frequency of 1 kHz at room temperature using Agilent 4278A. Next, at -55 ° C for 30 minutes, heat cycle resistance test (-55 ° C / 125 ° C (30 minutes / 30 minutes); 750 cycles), and moisture resistance test (pressure cooker test: 121 ° C at 2 atm (20 hours) )) The subsequent electrical characteristics were measured in the same manner as the initial characteristics.

  When the pastes of Examples 1 to 8 are used to form the external electrodes of the chip multilayer capacitor element, compared to the case of using the paste of Comparative Example 1 that does not contain (C), the specific resistance, capacitance, tan δ was produced. Further, in Examples 3 and 6, the capacitance and tan δ were remarkably improved as compared with the case where the paste of Comparative Example 2 containing the same amount of Cu fine particles in terms of copper was used. Further, as shown in Example 5, when Ag fine particles were used in combination, the specific resistance, capacitance, and tan δ were particularly excellent in a balanced manner.

  The conductive paste for external electrodes of the present invention can provide good electrical characteristics (capacitance, tan δ) when used as an external electrode of a multilayer ceramic electronic component. Capacitors, capacitor arrays, thermistors, varistors, This is useful for forming inductors and external electrodes of multilayer electronic components such as LC, CR, LR and LCR composite components.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Ceramic dielectric 3 Internal electrode 4 External electrode 5 Plating process layer

Claims (16)

(A) Ag particles and / or Ag alloy particles having an average particle diameter of 0.2 to 30 μm and a melting point of 700 ° C. or higher;
(B) SnAg alloy particles having an average particle diameter of 0.2 to 18 μm and a melting point of 200 ° C. or higher and lower than 700 ° C .;
(C) a copper-containing compound selected from the group consisting of copper nitrate, copper cyanide, copper octoate, copper formate, copper acetate, copper oxalate, copper benzoate and copper acetylacetonate; amino compounds; and optionally organic A paste formed by mixing a solvent;
(D) containing a thermosetting resin,
A conductive paste for external electrodes of ceramic electronic components containing nickel as a main component in internal electrodes .   The copper-containing compound in (C) is from copper formate (anhydride), copper formate (dihydrate), copper formate (tetrahydrate), copper acetate (anhydride) and copper acetate (monohydrate). The conductive paste for external electrodes according to claim 1, which is at least one selected from the group consisting of: The amino compound in (C) has the formula (i): NR ¹ R ² R ³ (i)
In the formula, R ¹ represents a C 2-4 alkyl group monosubstituted by a hydroxyl group, a methoxy group, an ethoxy group, or an amino group, and are R ² and R ³ each independently hydrogen? The conductive paste for external electrodes according to claim 1 or 2, which is at least one of amino compounds represented by the formula (1) or an alkyl group having 1 to 3 carbon atoms which may be substituted with a hydroxyl group or an amino group.   The amino compound of formula (i) in (C) is 3-methoxypropylamine, 3-ethoxypropylamine, 1-amino-2-propanol, 3-amino-1-propanol, 2-aminoethanol, N-methylethanol Amine, 2-amino-2-methyl-1-propanol, N-methyl-1,3-diaminopropane, 3,3′-diaminodipropylamine, 2-methoxyethylamine, 1,3-diaminopropane, 2,2 The electrically conductive paste for external electrodes according to claim 3, which is at least one selected from the group consisting of '-iminodiethanol, 2-dimethylaminoethanol and 2- (2-aminoethylamino) ethanol. (A) is 55 to 85 parts by weight, (B) is 10 to 40 parts by weight with respect to a total of 100 parts by weight of the (A), (B), and (C) copper equivalents, The conductive paste for external electrodes according to any one of claims 1 to 4, wherein the copper equivalent of C) is 0.05 to 5 parts by weight and (D) is 5 to 20 parts by weight.   (A) is composed of (A1) spherical Ag particles having an average particle diameter of 0.2 to 5 μm and (A2) flaky Ag particles having an average particle diameter of 5 to 30 μm, and the weight ratio of (A1) and (A2) The conductive paste for external electrodes according to any one of claims 1 to 5, wherein is 99: 1 to 75:25.   The external electrode conductivity according to any one of claims 1 to 6, wherein (B) is a SnAg alloy particle having a Sn to Ag weight ratio of 89:11 to 25.5: 74.5. paste.   The conductive paste for external electrodes according to any one of claims 1 to 7, wherein (D) contains an epoxy resin. The epoxy resin has the formula (1):

(Wherein, X is _(CH 2) shows the _p, p is an integer of 0 to 3) represented by the claim 8 of the conductive paste for external electrodes.   (E) The electrically conductive paste for external electrodes of any one of Claims 1-9 which further contains the metal particle whose melting | fusing point is 700 degreeC or more whose average particle diameter is 15-150 nm.   A multilayer ceramic electronic component having an external electrode formed using the conductive paste for external electrodes according to any one of claims 1 to 10 on a ceramic composite.   The multilayer ceramic electronic component according to claim 11, wherein the internal electrode of the ceramic composite is mainly composed of Ni.   The multilayer ceramic electronic component according to claim 11 or 12, wherein a nickel plating layer is further formed on the surface of the external electrode, and then a tin plating layer is formed.   The multilayer ceramic electronic component according to any one of claims 11 to 13, wherein the multilayer ceramic electronic component is any one of a capacitor, a capacitor array, a thermistor, a varistor, an inductor, and an LC, CR, LR, and LCR composite component. (1) A step of preparing a conductive paste for an external electrode according to any one of claims 1 to 10 and a ceramic composite to be provided with the external electrode;
(2) a step in which the internal electrode of the ceramic composite is mainly composed of nickel, and a conductive paste for external electrodes is printed or applied on the internal electrode take-out surface of the ceramic composite and dried; and
(3) A process of forming the external electrode by holding the ceramic composite obtained in (2) at 250 to 350 ° C. for 10 to 60 minutes.
A method for producing a multilayer ceramic electronic component, comprising: (4) The method for producing a multilayer ceramic electronic component according to claim 15, which is obtained by further forming a nickel plating layer on the surface of the external electrode and then forming a tin plating layer.

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