JP2018106906A - Paste for electrode, and multilayer ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paste for an electrode that provides a cured product with balanced improvement in tensile strength and impact absorption.SOLUTION: The paste for an electrode comprises (A) metal particles, (B) a thermosetting resin, and (C) a curing agent. The component (B) comprises a bifunctional phenoxy resin whose weight average molecular weight is 50,000 or more.SELECTED DRAWING: None

Description

  The present invention relates to an electrode paste and a multilayer ceramic electronic component.

  With the spread of smartphones, tablets, etc., there is a demand for miniaturization and high performance of electronic components used in these, as well as multilayer ceramic capacitors (MLCC, Multi Layer Ceramic Capacitors) used as multilayer capacitors. There is a demand for a smaller and larger capacity.

  In particular, in recent years, the demand for on-vehicle MLCCs has been increasing with the trend toward the electrification of automobiles. When MLCC is used as an in-vehicle component, it must withstand various mechanical loads such as deflection strength as well as heat resistance and thermal shock resistance in order to withstand use under severe temperature environments. Much higher reliability is required than consumer equipment.

  In order to form such an MLCC external electrode, various conductive pastes for external electrodes have been proposed. For example, Patent Document 1 discloses a conductive filler, an epoxy resin, and a thermosetting or thermoplastic resin. A conductive resin paste in which a resin binder made of a mixture of at least two types of resins and a curing agent are dispersed in an organic medium has been proposed.

JP-A-6-267784

  As described above, MLCC used as an in-vehicle component requires excellent mechanical strength. Therefore, the electrode paste forming the external electrode has excellent tensile strength and high shock absorption when cured. What you have is required. Moreover, as for the said paste for electrodes, it is desirable for the hardened | cured material to have sufficient bending strength.

  However, the conductive resin paste of Patent Document 1 has a problem that at least sufficient tensile strength cannot be obtained.

  Accordingly, an object of the present invention is to provide an electrode paste that provides a cured product having improved tensile strength and impact absorption in a balanced manner. Another object of the present invention is to provide an electrode paste that provides a cured product having good deflection strength.

  The present inventors have intensively studied to solve the above problems. As a result, an electrode paste containing metal particles, a thermosetting resin, and a curing agent, wherein the thermosetting resin includes a bifunctional phenoxy resin having a specific weight average molecular weight solves the above problem. As a result, the present invention has been completed.

  That is, the above-described problem includes (A) metal particles, (B) a thermosetting resin, and (C) a curing agent, and the component (B) has a weight average molecular weight of 50,000 or more. This is solved by an electrode paste containing a functional phenoxy resin.

  ADVANTAGE OF THE INVENTION According to this invention, the paste for electrodes which provides the hardened | cured material with which the tensile strength and the impact absorption property were improved with sufficient balance is provided. Moreover, according to this invention, the paste for electrodes which gives the hardened | cured material which has favorable bending strength is provided.

  Embodiments of the present invention will be described below.

  The first aspect of the present invention includes (A) metal particles, (B) a thermosetting resin, and (C) a curing agent, and the component (B) has a weight average molecular weight of 50,000 or more. It is the paste for electrodes (it may only be called a "paste" in this specification) including the bifunctional phenoxy resin which is.

  As described above, in recent years, MLCCs have been used as in-vehicle components, and MLCCs that can withstand use in harsh environments are demanded. When such an MLCC is mounted on a circuit board, the external electrode of the MLCC is connected to the wiring electrode of the circuit board. Therefore, when an external force is applied to the circuit board on which the MLCC is mounted or the circuit board is bent, stress may be applied to the external electrode of the MLCC, and as a result, there is a possibility of leading to failure of the electronic device. The electrode paste for forming the external electrode is required to have high mechanical strength.

  Various electrode pastes have been studied in order to satisfy the mechanical strength that can withstand use as a vehicle-mounted application that is subjected to high temperatures and large vibrations and impacts. Under these circumstances, the present inventors have intensively studied to obtain an electrode paste that gives a cured product having an excellent balance between tensile strength and impact absorption. As a result, it has been found that the above problems can be solved by an electrode paste containing a bifunctional phenoxy resin having a weight average molecular weight of 50,000 or more as a thermosetting resin.

  The reason why the above effect can be achieved is unknown, but is estimated as follows. In addition, this invention is not limited by the following estimation.

  The electrode paste according to the present invention includes a bifunctional phenoxy resin having a weight average molecular weight of 50,000 or more as a thermosetting resin in addition to metal particles and a curing agent. If the bifunctional phenoxy resin has the same mass, it can be said that the larger the weight average molecular weight, the smaller the epoxy group contained (that is, the greater the epoxy equivalent). Therefore, when the phenoxy resin is cured, the number of reaction points (the number of epoxy groups) is reduced, so that the curing shrinkage of the resin is reduced.

  Here, regarding the tensile strength, it is considered that the actual tensile strength can be estimated as a value obtained by subtracting the strength decrease due to the curing shrinkage of the thermosetting resin from the true tensile strength. Therefore, it can be said that the actual tensile strength increases as the curing shrinkage of the thermosetting resin decreases.

  Therefore, from the above, the electrode paste according to the present invention is considered to improve the tensile strength of the cured product because the curing shrinkage is reduced due to the reduction of the reactive sites of the bifunctional phenoxy resin.

  On the other hand, when the weight average molecular weight of the bifunctional phenoxy resin is less than 50,000, the reaction points at the time of curing increase, and thus the curing shrinkage of the resin increases. As a result, sufficient tensile strength cannot be obtained.

  In addition, as described above, the larger the weight average molecular weight of the bifunctional phenoxy resin, the smaller the number of reaction points at the time of curing, so the crosslink density in the cured product becomes smaller. Since the value of tan δ (loss elastic modulus / storage elastic modulus) tends to increase as the crosslink density of the phenoxy resin decreases, it is considered that the tan δ of the cured product of the electrode paste according to the present invention increases. As a result, impact absorbability is improved and energy applied to the MLCC external electrode is easily absorbed.

  Therefore, according to the present invention, the tensile strength at the time of curing and the impact absorption (high tan δ) can be improved in a balanced manner according to the present invention.

  Furthermore, since the electrode paste according to the present invention is excellent in tensile strength and impact absorbability (high tan δ) as described above, the flexural strength is also improved.

  Hereinafter, the electrode paste of the present invention will be described in detail. Unless otherwise specified, measurements such as operation and physical properties are performed under conditions of room temperature (25 ° C.) / Relative humidity of 40% RH or more and 50% RH or less.

<Paste for electrodes>
The electrode paste of the present invention includes (A) metal particles, (B) a thermosetting resin, and (C) a curing agent. Furthermore, it is preferable that (D) silicone rubber particles are included. Hereinafter, each component will be described.

≪ (A) Metal particle≫
The electrode paste according to the present invention essentially contains metal particles (metal filler). A metal particle is a component used in order to ensure high electroconductivity. By including metal particles, a conductive path can be formed by contact between the metal particles.

  The material of the metal particles is not particularly limited as long as it has conductivity, and examples thereof include silver, gold, copper, platinum, aluminum, magnesium, nickel, iron, indium, palladium, and alloys thereof. Of these, silver, copper, palladium, and alloys thereof are preferable from the viewpoint of excellent conductivity. In particular, from the viewpoint of obtaining good conductivity, the metal particles (component (A)) preferably contain silver or copper as a main component. The “main component” is a component having the largest content among the components constituting the metal particles, and a trace amount of impure components that are included in the production may be contained in the metal particles. The content of the component is, for example, preferably 50% by mass or more in the metal particles, more preferably 70% by mass or more, particularly preferably 90% by mass or more, and particularly preferably 95% by mass or more. Preferable (upper limit: 100% by mass).

  In addition, a metal particle may be individual, or may mix and use 2 or more types.

  The shape of the metal particles is not particularly limited, and examples thereof include a spherical shape, a substantially spherical shape, a fiber shape, a rod shape, and a flat shape (plate shape). The metal particles may be in a form in which the surface of a certain metal particle is coated with another metal.

  When the metal particles are spherical or substantially spherical, the average particle diameter of the metal particles is not particularly limited, but is preferably 0.5 μm or more and 7 μm or less, and more preferably 1 μm or more and 5 μm or less. By setting the average particle diameter to 0.5 μm or more, an increase in contact resistance can be suppressed and the resistance value can be lowered. On the other hand, when the average particle size is 7 μm or less, workability when forming an external electrode or the like using the electrode paste is improved. In order to prepare metal particles having a particle diameter in such a predetermined range, classification may be performed using a sieve or the like. In this specification, “particle diameter” means the maximum distance among any two points on the particle outline, and the value of “average particle diameter” is scanning. A value calculated as an average value of particle diameters of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is adopted.

  When the metal particles are flat (plate-like), the average plate surface diameter of the metal particles is not particularly limited, but is preferably 1 μm or more and 10 μm or less, and more preferably 3 μm or more and 8 μm or less. By setting the average plate surface diameter to 1 μm or more, an increase in contact resistance can be suppressed and the resistance value can be lowered. On the other hand, when the average plate surface diameter is 10 μm or less, the workability when forming an external electrode or the like using the electrode paste is improved. The “average plate surface diameter” means the maximum distance among any two points on the contour line of the flat surface, and the measurement method is the same as described above.

  The content of metal particles in the electrode paste according to the present invention (the total amount when two or more metal particles are used) is not particularly limited, but is 70% by mass or more based on the total mass of the electrode paste. Is preferable, 80% by mass or more is more preferable, and 85% by mass or more is particularly preferable. If it is such a range, the electroconductivity of the hardened | cured material obtained with the paste for electrodes can be ensured favorable. On the other hand, although the upper limit of the content of the metal particles is not particularly limited, it is preferably 95% by mass or less and 90% by mass or less with respect to the total mass of the electrode paste from the viewpoint of further improving the effects of the present invention. More preferably.

≪ (B) Thermosetting resin≫
The electrode paste according to the present invention essentially contains a thermosetting resin. In the present specification, “thermosetting resin” is a concept of a thermoplastic resin, and means a resin that is irreversibly cured by heat. The thermosetting resin functions as a binder for the metal particles, and facilitates the formation of external electrodes and the like by thermosetting.

  The content of the thermosetting resin in the electrode paste according to the present invention (the total amount when two or more thermosetting resins are used) is not particularly limited, but is based on the total mass of the electrode paste. It is preferably 3% by mass or more, more preferably 5% by mass or more, and particularly preferably 8% by mass or more. If it is such a range, the sclerosis | hardenability of the paste for electrodes can be improved and the tensile strength and impact absorption property of the obtained hardened | cured material can be made favorable. On the other hand, the upper limit of the content of the thermosetting resin is not particularly limited, but from the viewpoint of obtaining sufficient conductivity, it is preferably 20% by mass or less and 15% by mass or less with respect to the total mass of the electrode paste. More preferably, it is more preferably less than 15% by mass, particularly preferably 13% by mass or less, and most preferably less than 10% by mass.

(Bifunctional phenoxy resin)
The electrode paste according to the present invention contains a bifunctional phenoxy resin having a weight average molecular weight of 50,000 or more as a thermosetting resin (component (B)). As described above, the inclusion of the phenoxy resin improves the tensile strength and impact absorption during curing. Moreover, the bending strength at the time of curing is also improved.

  The bifunctional phenoxy resin is generally a resin obtained by reacting an epihalohydrin and a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound and a divalent phenol compound, A resin having two epoxy groups therein.

One feature of the electrode paste according to the present invention is that it contains a bifunctional phenoxy resin, which is a polymer having a weight average molecular weight of 50,000 or more. When the weight average molecular weight is less than 50,000, the number of reaction points at the time of curing increases and the shrinkage of curing increases, resulting in a decrease in tensile strength. In addition, the crosslink density is increased and the impact absorbability is likely to be lowered. From the viewpoint of improving tensile strength, impact absorbability, and flexural strength, the weight average molecular weight of the bifunctional phenoxy resin is preferably more than 50,000, and more preferably 51,000 or more. On the other hand, the upper limit of the weight average molecular weight of the bifunctional phenoxy resin is not particularly limited, but is preferably 200,000 or less from the viewpoint of appropriately reducing the viscosity of the electrode paste and improving workability. In addition, the weight average molecular weight is more preferably 100,000 or less from the viewpoint that the electrode paste is easily dissolved in a solvent (organic solvent or the like). In addition, the said weight average molecular weight can be measured by the gel permeation chromatography (GPC) which used polystyrene as the standard substance, The example of a more detailed method is demonstrated in the below-mentioned Example. Moreover, it can confirm that it has two epoxy groups in 1 molecule (it is bifunctional) by analytical methods, such as < ¹ > H-NMR.

  The bifunctional phenoxy resin is not particularly limited as long as it satisfies the above-mentioned definition of the weight average molecular weight, for example, naphthalene skeleton, fluorene skeleton, biphenyl skeleton, anthracene skeleton, pyrene skeleton, xanthene skeleton, adamantane skeleton and dicyclopentadiene skeleton Phenoxy resin having at least one skeleton selected from the group consisting of: bisphenol A type phenoxy resin, bisphenol AD type phenoxy resin, bisphenol F type phenoxy resin, naphthalene type phenoxy resin, phenol novolac type phenoxy resin, cresol novolac type phenoxy resin Phenol aralkyl type phenoxy resin, biphenyl type phenoxy resin, triphenylmethane type phenoxy resin, dicyclopentadiene type phenoxy resin, glycine Glycol ester type phenoxy resin, glycidyl amine type phenoxy resin or the like. Among them, from the viewpoint of easy availability and further enhancing heat resistance and adhesion, the bifunctional phenoxy resin is a group consisting of bisphenol A type phenoxy resin, bisphenol AD type phenoxy resin and bisphenol F type phenoxy resin. Is preferably at least one selected from bisphenol A type phenoxy resin. The bifunctional phenoxy resin may be used alone or in combination of two or more.

  The epoxy equivalent of the bifunctional phenoxy resin is not particularly limited, but is preferably 5,000 g / eq or more, more preferably 6,000 g / eq or more, and 7,000 g from the viewpoint of further improving the effects of the present invention. / Eq or more is particularly preferable. On the other hand, the upper limit of the epoxy equivalent of the bifunctional phenoxy resin is not particularly limited, but is preferably 100,000 g / eq or less from the viewpoint of appropriately reducing the viscosity of the electrode paste and improving workability. Further, from the viewpoint of easy use of the electrode paste dissolved in a solvent, the epoxy equivalent is more preferably 50,000 g / eq or less, even more preferably 40,000 g / eq or less, 000 g / eq or less is particularly preferable.

  In the present specification, “epoxy equivalent” means “mass of an epoxy resin containing one equivalent of an epoxy group”, and the unit is [g / eq]. The epoxy equivalent can be measured according to JIS K7236: 2001.

  The thermosetting resin contained in the electrode paste according to the present invention as the component (B) may contain other thermosetting resins in addition to the bifunctional phenoxy resin. In this case, the content of the bifunctional phenoxy resin relative to the total mass of the total thermosetting resin (total (B) component) (when using two or more bifunctional phenoxy resins, the total amount) is not particularly limited. However, from the viewpoint of further improving the effect of the present invention, it is preferably 15% by mass or more, more preferably 20% by mass or more, and particularly preferably 25% by mass or more. On the other hand, the upper limit of the content of the bifunctional phenoxy resin is not particularly limited. The upper limit may be 100% by mass or less. However, since the bifunctional phenoxy resin has a high viscosity, it is 90% by mass from the viewpoint of appropriately reducing the viscosity of the electrode paste and improving workability. % Or less, more preferably 80% by mass or less, and particularly preferably 75% by mass or less.

  The bifunctional phenoxy resin in the electrode paste according to the present invention (when two or more bifunctional phenoxy resins are used, the total amount thereof) is not particularly limited, but is based on the total mass of the electrode paste. It is preferably 1% by mass or more, more preferably 1.5% by mass or more, and particularly preferably 2% by mass or more. If it is such a range, about the cured | curing material of the paste for electrodes, tensile strength and impact absorption can be made favorable. On the other hand, the upper limit of the content of the bifunctional phenoxy resin is not particularly limited, but is preferably 15% by mass or less and 8% by mass or less with respect to the total mass of the electrode paste from the viewpoint of obtaining sufficient conductivity. Is more preferable.

(Other thermosetting resins)
The electrode paste according to the present invention may contain other thermosetting resin as the component (B) in addition to the bifunctional phenoxy resin. Other thermosetting resins include, for example, epoxy resins, unsaturated polyester resins, thermosetting acrylic resins, urethane resins, alkyd resins, phenol resins, phenoxy resins (the above bifunctional having a weight average molecular weight of 50,000 or more) Phenoxy resins other than phenoxy resins; Here, “phenoxy resin” refers to those having a weight average molecular weight of 10,000 or more).

  Among them, from the viewpoint of high affinity with the bifunctional phenoxy resin, improving tensile strength and flexural strength, and facilitating viscosity adjustment of the electrode paste, other thermosetting resins are epoxy resins. preferable. The epoxy resin has a lower viscosity than the above bifunctional phenoxy resin and is soluble in various organic solvents. Therefore, when an external electrode of MLCC is produced using an electrode paste, workability is improved. it can. Therefore, the electrode paste according to the present invention preferably contains the phenoxy resin and the epoxy resin as the thermosetting resin (component (B)).

  The epoxy resin is a resin having one or more epoxy groups in one molecule. From the viewpoint of further improving the effects of the present invention, when an epoxy resin is used, the epoxy resin is preferably a bifunctional epoxy resin (that is, a resin having two epoxy groups in one molecule).

  The type of epoxy resin is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol AD type epoxy resin, bisphenol F type epoxy resin; polyvalent phenols such as catechol and resorcin, or polyvalents such as glycerin and polyethylene glycol Polyglycidyl ether obtained by reacting alcohol with epichlorohydrin; Glycidyl ether ester obtained by reacting hydroxycarboxylic acid such as p-oxybenzoic acid with epichlorohydrin; Polycarboxylic acid such as phthalic acid and terephthalic acid Polyglycidyl ester obtained from acid; novolak type epoxy resin; epoxidized polyolefin and the like. Among them, from the viewpoint of availability and affinity with other components (particularly phenoxy resin), the epoxy resin is selected from the group consisting of bisphenol A type epoxy resin, bisphenol AD type epoxy resin and bisphenol F type epoxy resin. The bisphenol A type epoxy resin is particularly preferable. In addition, an epoxy resin may be individual, or may mix and use 2 or more types.

  In particular, when the bifunctional phenoxy resin is at least one selected from the group consisting of a bisphenol A type phenoxy resin, a bisphenol AD type phenoxy resin, and a bisphenol F type phenoxy resin, the thermosetting resin further includes a bisphenol A type. It is preferable that at least one selected from the group consisting of epoxy resins, bisphenol AD type epoxy resins and bisphenol F type epoxy resins is included.

  The epoxy equivalent of the epoxy resin is not particularly limited, but is preferably less than 5,000 g / eq from the viewpoint of lowering the viscosity of the electrode paste containing the high viscosity phenoxy resin and improving workability, 000 g / eq or less, more preferably less than 500 g / eq, more preferably 450 g / eq or less, and particularly preferably 400 g / eq or less. On the other hand, the lower limit of the epoxy equivalent of the epoxy resin is not particularly limited, but is preferably 100 g / eq or more, and 200 g / eq or more from the viewpoint of improving the ease of handling and the curability of the electrode paste. And more preferred. The epoxy equivalent can be measured according to JIS K7236: 2001.

  The weight average molecular weight (Mw) of the epoxy resin is preferably less than 10,000 from the viewpoint of lowering the viscosity of the electrode paste containing the high viscosity phenoxy resin and improving workability, and 4,000 or less. More preferably, less than 1,000, even more preferably 500 or less, and most preferably 400 or less. On the other hand, 200 or more is preferable from the viewpoint of enhancing the ease of handling and the curability of the electrode paste. In addition, the weight average molecular weight of an epoxy resin can be measured by the gel permeation chromatography (GPC) which used polystyrene as the standard substance, The example of a more detailed method is demonstrated in the below-mentioned Example.

  The content of the epoxy resin in the electrode paste according to the present invention (when two or more epoxy resins are used, the total amount thereof) is not particularly limited, but is 0.5 mass relative to the total mass of the electrode paste. % To 15% by mass, more preferably 1.0% to 10% by mass, particularly preferably 1.5% to 8.0% by mass, and 2.0% by mass. The content is most preferably 7.0% by mass or less. Within such a range, the viscosity of the electrode paste can be controlled moderately without impairing the tensile strength and tan δ improvement effect of the phenoxy resin, which contributes to improved workability.

  Moreover, it is preferable that the thermosetting resin as the component (B) has the following composition from the viewpoint of improving the tensile strength and impact absorbability in a particularly well-balanced manner and improving workability. That is, the thermosetting resin as the component (B) includes a bifunctional phenoxy resin having a weight average molecular weight of 50,000 or more and 15% by mass to 90% by mass and an epoxy resin of 10% by mass to 85% by mass. The bifunctional phenoxy resin is preferably 20 to 80% by mass and more preferably 20 to 80% by mass of the epoxy resin, and the bifunctional phenoxy resin is 25 to 75% by mass. % Or less and 25 to 75% by mass of the epoxy resin are particularly preferable (however, in the above, the total amount of the bifunctional phenoxy resin and the epoxy resin is 100% by mass).

≪ (C) Curing agent≫
The electrode paste according to the present invention essentially contains a curing agent. Any curing agent may be used as long as it has a function of curing the above-described thermosetting resin, and those known in this technical field are used.

  The type of the curing agent is not particularly limited. For example, an acid anhydride curing agent; a cationic polymerization initiator; an organic phosphorus compound; an amine curing agent (however, excluding a tertiary amine compound); Well-known things, such as a tertiary amine compound, are mentioned.

  Examples of the acid anhydride curing agent include phthalic acid anhydride, trimellitic acid anhydride, pyromellitic acid anhydride, benzophenone tetracarboxylic acid anhydride, and the like.

  Examples of the cationic polymerization initiator include a thermal cationic polymerization initiator that generates a cationic species and / or a Lewis acid by heat, a photocationic polymerization initiator that generates a cationic species and / or a Lewis acid by light, and the like. In addition, there is no clear division between a thermal cationic polymerization initiator and a photocationic polymerization initiator, and some of them act as curing agents for both heat and light.

  Examples of the thermal cationic polymerization initiator include onium salt-based cationic polymerization initiators such as sulfonium salts, ammonium salts, pyridinium salts, phosphonium salts, iodonium salts; a combination of an aluminum complex and a silanol compound, an aluminum complex and bisphenol S Examples include aluminum complex composite cationic polymerization initiators such as combinations. Examples of the photocationic polymerization initiator include aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metallocene compounds, and the like.

  Examples of the organic phosphorus compound include organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine; and methyltributylphosphonium dimethylphosphate.

  Examples of amine curing agents (excluding tertiary amines) include aliphatic amines such as ethylenediamine and 1,3-diaminopropane, polyether amines such as triethylene glycol diamine and tetraethylene glycol diamine, Examples include alicyclic amines such as isophorone diamine and mensen diamine, and aromatic amines such as tetrachloro-p-xylene diamine and m-xylene diamine.

  Examples of the tertiary amine include 1,8-diazabicyclo (5,4,0) undecene-7, triethylenediamine, benzyldimethylamine, and triethanolamine.

  In addition to the above, as the curing agent, imidazole compound; amide curing agent; phenol curing agent; tetraphenyl boron salt; organic acid dihydrazide, boron halide amine complex, polymercaptan curing agent, isocyanate curing agent, block isocyanate A system curing agent or the like is used. Especially, as a hardening | curing agent contained in the paste for electrodes which concerns on this invention, an imidazole compound is preferable.

  Examples of the imidazole compound include 2-methylimidazole, 2-ethyl-4-methylimidazole (2E4MZ), 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ-PW). ), 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW), 2-phenylimidazole, 1-benzyl-2-methylimidazole, and other imidazole compounds.

  In addition, a hardening | curing agent may be individual, or may mix and use 2 or more types.

  The content of the curing agent in the electrode paste according to the present invention (when two or more curing agents are used, the total amount thereof) is not particularly limited, but is the total of the thermosetting resin (component (B)). It is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.5% by mass or more and 3% by mass or less, and 0.8% by mass or more and 2.0% by mass or less based on the mass. And particularly preferred. If it is such a range, the electrode paste which is excellent in the balance of the storage stability of an electrode paste and a cure rate, and gives a favorable cured product can be obtained.

  Further, the content of the curing agent in the electrode paste (the total amount when two or more curing agents are used) is not particularly limited, but is 0.01% by mass or more based on the total mass of the electrode paste. It is preferably 5% by mass or less, more preferably 0.02% by mass to 3% by mass, and particularly preferably 0.05% by mass to 1% by mass. If it is such a range, the electrode paste which is excellent in the balance of the storage stability of an electrode paste and a cure rate, and gives a favorable cured product can be obtained.

≪ (D) Silicone rubber particles≫
In addition to the components (A) to (C), the electrode paste according to the present invention preferably further includes silicone rubber particles in order to further improve the effects of the present invention. When the silicone rubber particles are contained, the silicone rubber particles themselves are plastically deformed at the tip of the crack generated in the electrode paste or the cured product, and the stress can be relaxed. Further, when the silicone rubber particles are present so as to fill the gaps between the cracks, the silicone rubber particles are deformed and act so that the gap distance between the cracks does not increase, so that the expansion of the cracks can be suppressed. Furthermore, when the silicone rubber particles are dispersed in the electrode paste or cured product, the stress is relaxed. As a result, excellent tensile strength and flexural strength can be obtained.

  Examples of the silicone rubber particles include silicone rubber particles obtained by crosslinking a linear polyorganosiloxane such as polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, and the like; the surface of the silicone rubber particles coated with a silicone resin, Examples include core-shell particles including a core of solid silicone particles and a shell of an organic polymer such as an acrylic resin. Among these, from the viewpoint of improving affinity with the thermosetting resin (component (B)) and dispersibility of the silicone particles in the electrode paste, the silicone particles are preferably the core-shell particles. Furthermore, although the mechanism is unknown, the dispersibility of the metal particles in the electrode paste can also be improved by using the core-shell particles.

  The silicone rubber particles may be used alone or in combination of two or more.

  The shape of the silicone rubber particles is not particularly limited, and examples thereof include a spherical shape, a substantially spherical shape, a fiber shape, a rod shape, and a flat shape.

  When the silicone rubber particles are spherical or substantially spherical, the average particle size of the silicone rubber particles is not particularly limited, but is preferably less than 1 μm. When the thickness is less than 1 μm, the adhesion when an external electrode or the like is formed using the electrode paste is improved. Furthermore, from the viewpoint of improving adhesion, the average particle size is more preferably 500 nm or less, and particularly preferably 300 nm or less. On the other hand, the lower limit of the average particle diameter of the silicone rubber particles is not particularly limited, but is preferably 10 nm or more. By making the average particle diameter 10 nm or more, the effect of relaxing the stress as described above can be easily obtained. The definitions and measuring methods of “particle diameter” and “average particle diameter” are as described above.

  The content of the silicone rubber particles in the electrode paste according to the present invention (when two or more types of silicone rubber particles are used, the total amount thereof) is not particularly limited, but is 0. 0 relative to the total mass of the electrode paste. The amount is preferably 1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1.0% by mass or more. If it is such a range, the effect of relieving the stress as described above can be easily obtained, and the tensile strength and the flexural strength are improved. On the other hand, the upper limit of the content of the silicone rubber particles is not particularly limited, but is preferably 5% by mass or less based on the total mass of the electrode paste from the viewpoint of obtaining sufficient conductivity and thermosetting. % Or less is more preferable, and 1.5% by mass or less is particularly preferable.

  From the above, the content of the silicone rubber particles is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less with respect to the total mass of the electrode paste. 1.0 mass% or more and 1.5 mass% or less is particularly preferable.

  From the viewpoint of further improving the effect of the present invention, the content of silicone rubber particles (when using two or more types of silicone rubber particles) with respect to the total mass of the thermosetting resin (component (B)) The total amount) is preferably 1% by mass to 40% by mass, more preferably 5% by mass to 30% by mass, and particularly preferably 10% by mass to 25% by mass.

≪Other ingredients (additives) ≫
The electrode paste according to the present invention is not limited to the components (A) to (C) and the component (D) added as necessary, as long as the effects of the present invention are not impaired. Agent). Examples of such other components include silane coupling agents, colorants, thixotropic agents, and the like.

  Examples of the silane coupling agent include silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-aminopropyltrimethoxysilane. Is mentioned.

  Examples of the colorant include dyes; inorganic pigments such as carbon black, titanium black, and iron black; and organic pigments such as aniline black.

  As the thixotropic agent, for example, any of inorganic and organic can be used. Examples of the inorganic thixotropic agent include silicic acid systems such as fine particle silicic anhydride or fumed silica, hydrous silicon magnesium systems such as sepiolite and chrysostyle, montmorillonite bentonites, and aluminum silicate systems such as zeolite. . Examples of the organic thixotropic agent include polyhydroxycarboxylic acid or its amide compound, sodium polyacrylate, dibenzal sorbite, and the like. In addition to these, organic bentonite in which organic molecules are adsorbed between layers may be used.

<< Preferred composition >>
The electrode paste according to the present invention preferably has the following composition from the viewpoint of particularly improving the tensile strength and impact absorbability in a well-balanced manner.

  That is, the electrode paste comprises (A) component 70% by mass to 95% by mass; (B) component 3% by mass to 20% by mass; (C) component 0.01% by mass to 5% by mass; Component D) It is preferable to contain 0.1% by mass or more and 5% by mass or less, (A) Component 80% by mass or more and 90% by mass or less; (B) Component 5% by mass or more and 15% by mass or less; (C) Component 0.02 mass% or more and 3 mass% or less; and (D) component It is more preferable when 0.5 mass% or more and 3 mass% or less are included, (A) component 85 mass% or more and 90 mass% or less; (B) Component 8 mass% or more and 13 mass% or less; (C) Component 0.05 mass% or more and 1 mass% or less; and (D) Component 1.0 mass% or more and 1.5 mass% or less are included especially preferably ( However, in the above, the sum of the components (A) to (D) Is 100% by weight).

<Method for producing electrode paste>
The electrode paste according to the present invention has a predetermined content of components (A) to (C) that are essential components, and component (D) and other components (additives) that are added as necessary. Thus, they can be produced by blending at the same time or sequentially and mixing them so that each component is uniformly dispersed.

  The mixing method is not particularly limited. For example, a kneader, a roll mill, a super mixer, a Henschel mixer, a high speed mixer, a ball mill, a steel mill, a homomixer, a homogenizer, a jet mill, a Banbury mixer, a batch kneader, or a twin screw extrusion. And a method using a mixing device such as a machine, a single screw extruder, a rotor type twin screw kneader. During mixing, heat treatment or cooling treatment may be performed as necessary.

  The mixing method and mixing order of the above components are not particularly limited, but the mixing method is preferably wet mixing in that the additive can be uniformly dispersed. In addition, by performing wet mixing, the electrode paste according to the present invention can be used by adding a solvent and adjusting the viscosity. Thereby, when forming external electrodes, such as MLCC, using the paste for electrodes which concerns on this invention, workability | operativity improves.

  The solvent used here is not particularly limited. For example, aromatic solvents such as benzene, toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, formamide, N-methylformamide, N, N -Amide solvents such as dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, 2-pyrrolidone, N-methylpyrrolidone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether , Ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene Recall mono -n- butyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol mono -n- butyl ether, etc. glycol ether solvents such as propylene glycol monomethyl ether acetate. Of these, glycol ether solvents are preferred because of the excellent solubility of the resulting electrode paste. In addition, the said solvent may be individual, or may mix and use 2 or more types.

  When an organic solvent is added to the electrode paste, the amount of the solvent added is not particularly limited, but the viscosity after addition (at 10 rpm at 25 ° C., measured with a Brookfield DV-III viscometer) is 5 It is preferable to add so as to be ˜30 Pa · s. Furthermore, it is more preferable that the viscosity is added so as to be 8 to 20 Pa · s. If it is such a range, the workability | operativity at the time of forming the external electrode using the paste for electrodes will improve.

  Further, the mixing time is not particularly limited, and is appropriately set according to the mixing method and the mixing apparatus to be used.

<Method for curing electrode paste>
The electrode paste according to the present invention is applied so as to have an appropriate size and shape, dried as necessary, and cured by subsequent heating. Thereby, the external electrode of MLCC can be formed.

  The method for applying the electrode paste is not particularly limited, and a conventionally known method such as a dipping method is used.

  The thickness (thickness after drying) of the applied electrode paste is not particularly limited, but is substantially 5 μm or more for the purpose of obtaining sufficient conductivity and strength. On the other hand, the upper limit of the thickness (thickness after drying) is not particularly limited, but is preferably 100 μm or less.

  The drying conditions are not particularly limited, but the temperature is preferably 80 ° C. or higher and 150 ° C. or lower, and the heating time is preferably 5 minutes or longer and 30 minutes or shorter. In addition, the temperature at the time of the said drying and heating time can be suitably set according to the thickness in which the paste for electrodes is applied, and the solvent to be used.

  The conditions for heat curing are not particularly limited, but the temperature is preferably 120 ° C. or higher and 250 ° C. or lower, and the heating time is preferably 1 hour or longer and 5 hours or shorter. By setting it as such a range, hardening of a thermosetting resin can fully be advanced. Moreover, when the silicone rubber particles are contained in the electrode paste, the modification of the silicone rubber particles due to heating can be suppressed. In addition, the temperature at the time of the heat curing and the heating time can be appropriately set according to the thickness to which the curing agent to be used and the electrode paste are applied. The atmosphere at the time of heat curing can be performed in air or in an inert gas such as nitrogen or argon. From the viewpoint of suppressing deterioration, it is preferable to carry out in an inert gas such as nitrogen.

<Application of electrode paste>
The electrode paste according to the present invention provides a cured product having excellent tensile strength and shock absorption. Specifically, the tensile strength after heat curing of the electrode paste is preferably 4.5 MPa or more, more preferably 5.0 MPa or more, and particularly preferably 6.0 MPa or more. In addition, the value measured by the measuring method as described in an Example is employ | adopted for the said tensile strength. On the other hand, the upper limit of the tensile strength is not particularly limited, but is substantially 10 MPa or less. Further, as to whether or not it has excellent shock absorption, the value of tan δ (loss elastic modulus / storage elastic modulus) after heat curing of the electrode paste is an index. Specifically, tan δ after curing of the electrode paste is preferably 0.45 or more, more preferably 0.50 or more, and particularly preferably 0.55 or more. When tan δ is 0.45 or more, the cured product of the electrode paste can exhibit sufficient shock absorption. In addition, the value measured with the measuring method as described in an Example is employ | adopted for said tan-delta. On the other hand, the upper limit of tan δ is not particularly limited, but is substantially 2.0 or less.

  The cured product formed by the electrode paste according to the present invention has excellent tensile strength and shock absorption. Therefore, the electrode paste according to the present invention is suitably used in the production of a multilayer ceramic electronic component having an external electrode, particularly a multilayer ceramic electronic component for vehicle use. That is, according to the second aspect of the present invention, there is provided a multilayer ceramic electronic component having an electrode formed by curing an electrode paste, and preferably a vehicle-mounted multilayer ceramic electronic component.

  Examples of the multilayer ceramic electronic component on which the external electrode is formed include a capacitor, a capacitor array, a thermistor, a varistor, an inductor, and an LC, CR, LR and LCR composite component.

≪Multilayer ceramic capacitor≫
A preferred form of the multilayer ceramic electronic component is a multilayer ceramic capacitor. Hereinafter, a method for manufacturing a multilayer ceramic capacitor will be outlined.

  First, an internal electrode conductive paste containing various metals or the like is screen-printed in a predetermined shape on a green sheet to form an internal electrode conductive paste film. The material for the internal electrode is not particularly limited, and examples thereof include a metal such as Cu, Ni, W, Mo, Ag, and Pd or an alloy thereof.

  Then, after laminating a plurality of green sheets on which the internal electrode conductive paste film is formed, and laminating and crimping the green sheets on which the conductive paste film is not formed so as to sandwich the green sheets, A laminated body (green chip) is obtained by cutting as necessary.

  And after performing a binder removal process to the obtained laminated body (green chip), the said green chip is baked in inert gas atmosphere or reducing atmosphere, and a capacitor chip body is obtained. In the capacitor chip body, dielectric layers made of a sintered body obtained by firing green sheets and internal electrodes are alternately laminated. The firing conditions are not particularly limited, and known conditions may be adopted as appropriate.

  When firing is performed in a reducing atmosphere, it is preferable to anneal the obtained capacitor chip body in order to reoxidize the dielectric layer.

  Next, the electrode paste (external electrode paste) according to the present invention is formed on the end face of the capacitor chip body so that the external electrode is electrically connected to each edge of the internal electrode exposed from the end face of the capacitor chip body. ) Is applied and then heat-cured to form an external electrode. In addition, since the curing conditions at this time are as described above, detailed description is omitted here. Then, if necessary, a plating process such as nickel plating or tin plating is performed on the surface of the external electrode to form a coating layer. In this way, a multilayer ceramic capacitor can be manufactured.

  The multilayer ceramic capacitor is described as an example of the multilayer ceramic electronic component. However, the ceramic electronic component according to the present invention is not limited to this.

  The effects of the present invention will be described using the following examples and comparative examples. In the following examples, unless otherwise specified, “parts” and “%” mean “parts by mass” and “% by mass”, respectively, and each operation was performed at room temperature (25 ° C.). In addition, this invention is not limited to an Example below.

<Measurement>
≪Resin weight average molecular weight≫
For measurement of the weight average molecular weight (Mw) of each resin, GPC (gel permeation chromatography) using THF (tetrahydrofuran) as a column solvent is used.

  Specifically, 1 mL of THF (using a degassed sample) is added to 1 mg of a measurement sample, and the mixture is sufficiently dissolved by stirring with a magnetic stirrer at room temperature. Subsequently, after processing with a membrane filter having a pore size of 0.45 μm to 0.50 μm, it is injected into a GPC (gel permeation chromatograph) apparatus.

  GPC measurement conditions are measured by stabilizing the column at 40 ° C., flowing THF (tetrahydrofuran) at a flow rate of 1 mL / min, and injecting about 100 μL of a sample having a concentration of 1 mg / mL.

  As the column, a commercially available polystyrene gel column is used in combination. As a detector, a refractive index detector (RI detector) or a UV detector is used.

  In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles. About 10 points are used as polystyrene for preparing a calibration curve.

≪Epoxy equivalent≫
It measured according to JIS K7236: 2001.

<Preparation of electrode paste>
Example 1
Copper powder as metal particles (CUSP40, manufactured by JOINM, average particle diameter: 4 μm and mixed powder of CFL07, manufactured by JOINM, average plate surface diameter: 7 μm), phenoxy resin as a thermosetting resin (Mitsubishi Chemical Corporation) Manufactured by jER (registered trademark, the same shall apply hereinafter) 1256, bisphenol A type bifunctional phenoxy resin, weight average molecular weight 51,000, epoxy equivalent 7,604 g / eq), and 2-phenyl-4,5-dihydroxy as a curing agent Methylimidazole (Cureazole (registered trademark) 2PHZ-PW, manufactured by Shikoku Kasei Kogyo Co., Ltd., 1% by mass with respect to the total amount of thermosetting resin) was adjusted to a three roll mill ( M-80E, manufactured by EXACT Co.) was used for 5 passes to prepare electrode paste 1. In Table 1, “(A) metal particles (mass%)” “thermosetting resin 1 (mass%)”, “thermosetting resin 2 (mass%)”, “(C) curing agent (mass%) ")" And "(D) Silicone rubber particles (mass%)" respectively indicate the content (ratio) of each component with respect to the total mass of the conductive paste.

  Further, at the time of mixing, an appropriate amount of diethylene glycol monoethyl ether acetate as a solvent was added, and the viscosity of the electrode paste was adjusted to be in the range of 10,000 to 16,000 cP (10 to 16 Pa · s). The viscosity of the electrode paste was measured at room temperature (25 ° C.) at 10 rpm using a Brookfield DV-III viscometer.

<< Examples 2 to 5 >>
Liquid epoxy resin in which silicone rubber particles are dispersed (KaneAce MX-960, manufactured by Kaneka Corporation, bisphenol A type bifunctional epoxy resin containing 25% by mass of silicone rubber particles, epoxy equivalent: 244 g / eq; average particle of silicone rubber particles Electrode pastes 2 to 5 were prepared in the same manner as in Example 1 except that 100 nm diameter and core-shell type) were further added and the composition ratio of each component was changed as shown in Table 1. In Table 1, the phenoxy resin (or a resin corresponding thereto) is referred to as “thermosetting resin 1”, and the epoxy resin as a dispersion medium for the silicone rubber particles is referred to as “thermosetting resin 2”. Describe. In Table 1, “Content of thermosetting resin 1 in component (B)” indicates the content of thermosetting resin 1 with respect to the total amount of thermosetting resin.

<< Comparative Examples 1-2 >>
As the thermosetting resin 1, a bifunctional epoxy resin having a weight average molecular weight of 370 (jER828, manufactured by Mitsubishi Chemical Corporation, bisphenol A type bifunctional epoxy resin) or a bifunctional epoxy resin having a weight average molecular weight of 900 is used instead of the phenoxy resin. Comparative electrode pastes 1 and 2 were prepared in the same manner as in Example 1 except that (jER1001, manufactured by Mitsubishi Chemical Corporation, bisphenol A type bifunctional epoxy resin) was used.

<< Comparative Examples 3-4 >>
Comparison was made in the same manner as in Comparative Example 1 or 2 except that the liquid epoxy resin in which the silicone rubber particles used in Example 2 and the like were dispersed was further added and the composition ratio of each component was changed as shown in Table 1. Electrode pastes 3 and 4 were prepared, respectively.

<< Comparative Example 5 >>
A comparative electrode paste 5 was prepared in the same manner as in Example 1 except that the thermosetting resin 1 was changed to a phenoxy resin having a weight average molecular weight of 22,000.

<Evaluation>
The electrode pastes obtained in the above examples and comparative examples were evaluated as follows.

≪Adhesive strength (tensile strength) ≫
Each paste obtained in the above examples and comparative examples was transferred and applied to an area of 10 mm × 10 mm on an aluminum plate having a length of 30 mm, a width of 10 mm, and a thickness of 20 mm so that the thickness was 80 μm. The paste was not applied, and an aluminum plate having the same shape as above was brought into close contact so that only the portion to which the paste was applied (10 mm × 10 mm range) overlapped. Then, it hold | maintained at 200 degreeC in oven for 3 hours, the paste was dried and hardened, and the test piece formed by the adhesion | attachment of the two aluminum plates was obtained.

  About said test piece, the adhesive force (tensile strength) was measured using the desktop precision universal testing machine Autograph AGS-10kNX (made by Shimadzu Corporation). Specifically, one aluminum plate of the test piece was sandwiched between the upper jig and the other aluminum plate was sandwiched between the lower jigs, and the tensile strength was measured at a tensile speed of 10 mm / min.

≪tanδ (loss elastic modulus / storage elastic modulus) ≫
On the PET film (SP-PET50C, thickness 50 μm, manufactured by Lintec Corporation), applicators were applied so that each paste obtained in the above Examples and Comparative Examples had a thickness of 50 μm. It was then placed in an oven and held at 180 ° C. for 3 hours to dry and cure the paste. The sample after the paste was cured was cut into a size of 5 mm × 20 mm, and the cured film was peeled off from the PET film to obtain a film-like cured product.

  About said film-like hardened | cured material, viscoelasticity measurement was performed using viscoelasticity measuring apparatus DMA7100 (made by Hitachi High-Tech Science Co., Ltd.). Specifically, the film-like cured product is installed in a measuring apparatus so that the long side is in the tensile direction, and is set to a frequency of 1 Hz, a measurement start temperature of 20 ° C., and a temperature increase rate of 5 ° C./min. Measurements were made. Tan δ (loss elastic modulus / storage elastic modulus) was the maximum value in the measurement.

≪Deflection strength test≫
A chip multilayer capacitor ceramic composite (3216 type) was prepared by baking a Cu electrode (first conductor layer connected to the internal electrode) on the internal electrode take-out surface.

  The pastes obtained in the above Examples and Comparative Examples were uniformly dip-coated on the end of the ceramic composite using a micro dip coater (manufactured by SDI Co., Ltd.). Then, it was dried at 140 ° C. for 15 minutes, held at 200 ° C. for 3 hours, the paste was cured to form a second conductor layer, and an external electrode was formed. Subsequently, nickel plating was performed by electrolytic plating, and then tin plating was performed to obtain a chip multilayer capacitor. Next, a solder paste having a composition of Sn-3.0Ag-0.5Cu is printed on the FR-4 substrate, and after mounting the multilayer ceramic capacitor, in-out 5 minutes at a peak temperature of 260 ° C. A reflow process was performed to prepare a test piece for evaluation.

  The test piece for evaluation was supported at two points with an interval of 90 mm using an autograph (manufactured by Shimadzu Corporation), and the change in capacity when the central portion was bent from the FR-4 substrate side was confirmed. At this time, an R230 mm jig was used, and the substrate was bent by 10 mm by applying pressure at a displacement speed of 1 mm / second. The evaluation criteria are as follows.

-Evaluation criteria-
◯: The decrease rate of the capacity after giving the deflection with respect to the initial capacity is less than 10% ×: The decrease ratio of the capacity after giving the deflection with respect to the initial capacity is 10% or more.

≪Comprehensive judgment≫
Based on the above evaluations, the electrode pastes according to Examples and Comparative Examples were ranked from a practical viewpoint. The evaluation criteria are as follows, and the larger the number, the better.

-Evaluation criteria-
5: Tensile strength is 6.0 MPa or more and tan δ is 0.55 or more 4: Tensile strength is 6.0 MPa or more and tan δ is 0.45 or more and less than 0.55 3: Tensile strength is 5.5 MPa or more and 6.0 MPa And tan δ is 0.55 or more 2: Tensile strength is 4.5 MPa or more and less than 5.5 MPa, and tan δ is 0.55 or more 1: Tensile strength is less than 4.5 MPa.

  From Table 1 above, it was shown that the electrode paste according to the present invention had high tensile strength and tan δ at the time of curing, and thus improved tensile strength and impact absorption in a well-balanced manner. Moreover, it was shown that the paste for electrodes which concerns on this invention is also excellent in the bending strength of hardened | cured material. On the other hand, none of the electrode pastes according to the comparative examples had sufficient tensile strength and did not have sufficient deflection strength.

Claims (8)

(A) metal particles, (B) a thermosetting resin, and (C) a curing agent,
The component (B) is an electrode paste containing a bifunctional phenoxy resin having a weight average molecular weight of 50,000 or more.   The electrode paste according to claim 1, further comprising (D) silicone rubber particles.   The electrode paste according to claim 2, wherein the component (D) is contained at a ratio of 0.1% by mass to 5% by mass with respect to the total mass of the electrode paste.   The electrode paste according to claim 2 or 3, wherein the average particle size of the component (D) is less than 1 µm.   The electrode paste according to any one of claims 2 to 4, wherein an average particle size of the component (D) is 10 nm or more.   The said (A) component is an electrode paste of any one of Claims 1-5 containing silver or copper as a main component.   The electrode paste according to any one of claims 1 to 6, comprising the component (A) in an amount of 85% by mass or more based on the total mass of the electrode paste.   A multilayer ceramic electronic component having an electrode obtained by curing the electrode paste according to any one of claims 1 to 7.