Conductive adhesive, sintered body of conductive adhesive, method for manufacturing a sintered body, electronic component, and method for manufacturing an electronic component.

Abstract

Provided is a novel electrically conductive adhesive which can yield a sintered body having low resistivity despite containing a thermosetting resin in addition to silver particles.　This electrically conductive adhesive contains silver particles and a thermosetting resin. The silver particles are provided with a protective layer that contains a compound represented by general formula (1). [In general formula (1), R1 is an alkyl group having 1-5 carbon atoms, and R2 is a hydrogen atom or an alkyl group having 1-5 carbon atoms.]

Description

[Technical Field]

[0001] The present invention relates to a conductive adhesive, a sintered body of the conductive adhesive, a method for producing the sintered body, an electronic component, and a method for producing the electronic component. [Background Art]

[0002] Conductive adhesives including die bond agents and the like are joining materials used for electronic components such as semiconductors, LEDs, and power semiconductors. As a joining method, it is generally known that joining to a substrate is performed by joining via application of pressure and heat, or sintering via heating without application of pressure. In recent years, from the viewpoint of simplicity and efficiency of the manufacturing process, development of pressure-free joining materials has progressed.

[0003] In recent years, development of conductive adhesives using silver particles has progressed. Silver particles have the characteristic of being easily sintered by heat treatment at a low temperature in a short time. For example, Patent Document 1 discloses a metal paste obtained by kneading a solid content composed of silver particles and a solvent, wherein the solid content is composed of silver particles containing 30% or more, based on the number of particles, of silver particles having a particle diameter of 100 to 200 nm, and the silver particles constituting the solid content are bonded with an amine compound having a total carbon number of 4 to 8 as a protective agent. According to the metal paste, silver particles can be sintered in a low temperature range, and furthermore, a sintered body having low resistance and a sintered body excellent in thermal conductivity can be formed. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-159096 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] In the field of conductive adhesives, there is a demand for lower resistivity values ​​in sintered bodies obtained by applying conductive adhesives to materials (e.g., substrates used in electronic components, semiconductor chips, etc.) and sintering them. However, sintered bodies of conductive adhesives containing thermosetting resins in addition to silver particles tend to have higher resistivity values ​​due to the presence of the thermosetting resin.

[0006] Under these circumstances, the primary objective of the present invention is to provide a novel conductive adhesive that yields a sintered body with a low resistivity despite containing a thermosetting resin in addition to silver particles. Furthermore, the present invention also aims to provide a sintered body of the conductive adhesive, a method for manufacturing the sintered body, an electronic component, and a method for manufacturing the electronic component. [Means for solving the problem]

[0007] The inventors diligently conducted research to solve the above problems. As a result, they discovered that in a conductive adhesive containing silver particles and a thermosetting resin, a sintered body with a low resistivity can be obtained by forming a protective layer containing a predetermined compound on the silver particles. The present invention was completed by further research based on this finding.

[0008] In other words, the present invention provides inventions in the following embodiments. Item 1. Silver particles and, Thermosetting resin and A conductive adhesive containing, The aforementioned silver particles are provided with a protective layer containing a compound represented by the following general formula (1) in a conductive adhesive. [ka] [In general formula (1), R 1 R is an alkyl group having 1 to 5 carbon atoms. 2 [This is either a hydrogen atom or an alkyl group with 1 to 5 carbon atoms.] Item 2. The conductive adhesive according to Item 1, wherein the thermosetting resin is an epoxy resin. Item 3. The conductive adhesive according to item 1 or 2, wherein the content of the silver particles is 70% by mass or more. Item 4. A conductive adhesive according to any one of items 1 to 3, further comprising a solvent. Item 5. The conductive adhesive according to Item 4, wherein the octanol / water partition coefficient (Log Pow) of the solvent is between -2 and 4. Item 6. A sintered body of a conductive adhesive as described in any one of items 1 to 5. Item 7. An electronic component formed by joining members together using the sintered body described in Item 6. Item 8. A method for manufacturing a sintered body, comprising the step of sintering a conductive adhesive described in any one of items 1 to 5 at a temperature of 100°C to 250°C. Item 9. A method for manufacturing electronic components in which members are joined together by a sintered body, A step of placing a conductive adhesive described in any one of items 1 to 5 between the members, The process involves sintering the conductive adhesive at a temperature of 100°C to 250°C, A method for manufacturing electronic components, comprising: [Effects of the Invention]

[0009] According to the present invention, a novel conductive adhesive can be provided that yields a sintered body with a low resistivity despite containing a thermosetting resin in addition to silver particles. Furthermore, according to the present invention, a sintered body of the conductive adhesive, a method for manufacturing the sintered body, an electronic component, and a method for manufacturing the electronic component can also be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This graph shows the relationship between the epoxy resin content (mass%) of the sintered body of the conductive adhesives in Examples 1-6 and Comparative Examples 1-3 and the resistivity (μΩ·cm) of the sintered body. [Modes for carrying out the invention]

[0011] The conductive adhesive of the present invention is a conductive adhesive containing silver particles and a thermosetting resin, characterized in that the silver particles are provided with a protective layer containing a compound represented by the following general formula (1). By having this configuration, the conductive adhesive of the present invention can provide a sintered body with a low specific resistance even though it contains a thermosetting resin in addition to the silver particles.

[0012]

Chemical Formula

[0013] In general formula (1), R 1 is an alkyl group having 1 to 5 carbon atoms, and R 2 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

[0014] Hereinafter, the conductive adhesive of the present invention, a sintered body of the conductive adhesive, a method for producing the sintered body, an electronic component, and a method for producing the electronic component will be described in detail. In the present specification, a numerical value connected by "~" means a numerical range including the numerical values before and after "~" as the lower limit and the upper limit. When a plurality of lower limits and a plurality of upper limits are described separately, any lower limit and upper limit can be selected and connected by "~".

[0015] 1. Conductive adhesive The conductive adhesive of the present invention contains silver particles and a thermosetting resin.

[0016] The silver particles are provided with a protective layer. Specifically, the silver particles are provided with a protective layer on the surface of particles formed of silver. Further, the protective layer contains the compound represented by the general formula (1). Since the conductive adhesive of the present invention contains the compound represented by general formula (1) in the protective layer, the silver particles have good dispersibility in a solvent, and a sintered body with a low specific resistance can be obtained.

[0017] As described above, in general formula (1), R 1R is an alkyl group having 1 to 5 carbon atoms, and from the viewpoint of more favorably exhibiting the effects of the present invention, it is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an alkyl group having 1 carbon atom (i.e., a methyl group). 2 This is either a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. From the viewpoint of more favorably exhibiting the effects of the present invention, it is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 carbon atom (i.e., a methyl group), and particularly preferably an alkyl group having 1 carbon atom (i.e., a methyl group). In other words, among the compounds represented by general formula (1), 2-hydroxyisobutyric acid and lactic acid (L-form, D-form, DL-form) are particularly preferred, and 2-hydroxyisobutyric acid is the most preferred. The protective layer may contain one compound represented by general formula (1) or two or more compounds.

[0018] Furthermore, the protective layer may contain compounds other than the compound represented by general formula (1). Examples of these different compounds include amine compounds, fatty acids, and hydroxy fatty acids (provided that these are hydroxy fatty acids other than the compound represented by general formula (1)). If the protective layer contains compounds other than the compound represented by general formula (1), there may be one or more such different compounds.

[0019] While there are no particular limitations on the amine compound, alkylamines are preferred from the viewpoint of more favorably achieving the effects of the present invention. While there are no particular limitations on the alkylamine, alkylamines with 3 to 18 carbon atoms in the alkyl group are preferred, and more preferably alkylamines with 4 to 12 carbon atoms in the alkyl group.

[0020] Preferred specific examples of alkylamines include ethylamine, n-propylamine, isopropylamine, 1,2-dimethylpropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, isoamylamine, tert-amylamine, 3-pentylamine, n-amylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-octylamine, 2-ethylhexylamine, n-nonylamine, n-aminodecane, n-aminoundecane, n-dodecylamine, and n-tridecylamine. Examples include 2-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-oleylamine, N-ethyl-1,3-diaminopropane, N,N-diisopropylethylamine, N,N-dimethylaminopropane, N,N-dibutylaminopropane, N,N-dimethyl-1,3-diaminopropane, N,N-diethyl-1,3-diaminopropane, N,N-diisobutyl-1,3-diaminopropane, N-lauryldiaminopropane, etc. Furthermore, examples include the secondary amine dibutylamine and the cyclic alkylamines cyclopropylamine, cyclobutylamine, cyclopropylamine, cyclohexylamine, cycloheptylamine, cyclooctylamine, etc. Among these, n-propylamine, isopropylamine, cyclopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, cyclobutylamine, n-amylamine, n-hexylamine, cyclohexylamine, n-octylamine, 2-ethylhexylamine, n-dodecylamine, n-oleylamine, N,N-dimethyl-1,3-diaminopropane, and N,N-diethyl-1,3-diaminopropane are preferred, and n-butylamine, n-hexylamine, cyclohexylamine, n-octylamine, n-dodecylamine, N,N-dimethyl-1,3-diaminopropane, and N,N-diethyl-1,3-diaminopropane are more preferred. The amine compounds may be used individually or in combination of two or more.

[0021] The fatty acid is not particularly limited, but preferably it is a fatty acid with an alkyl group having 3 to 18 carbon atoms, more preferably a fatty acid with an alkyl group having 4 to 18 carbon atoms. Preferred specific examples of fatty acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and α-linolenic acid. Other specific examples of fatty acids include cyclic alkylcarboxylic acids such as cyclohexanecarboxylic acid. Furthermore, as the hydroxy fatty acid, a compound having 3 to 24 carbon atoms and one or more hydroxyl groups (for example, one) can be used. In addition, examples of hydroxy fatty acids different from the compound represented by general formula (1) include 2-hydroxydecanoic acid, 2-hydroxydodecanoic acid, 2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxyeicosanoic acid, 2-hydroxydocosanoic acid, 2-hydroxytricosanoic acid, 2-hydroxytetracosanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxyundecanoic acid, and 3. Examples include hydroxydodecanoic acid, 3-hydroxytridecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxyhexadecanoic acid, 3-hydroxyheptadecanoic acid, 3-hydroxyoctadecanoic acid, ω-hydroxy-2-decenoic acid, ω-hydroxypentadecanoic acid, ω-hydroxyheptadecanoic acid, ω-hydroxyeicosanoic acid, ω-hydroxydocosanoic acid, 6-hydroxyoctadecanoic acid, ricinoleic acid, 12-hydroxystearic acid, and [R-(E)]-12-hydroxy-9-octadecenoic acid. Among these, hydroxy fatty acids having 4 to 18 carbon atoms and one hydroxyl group at a position other than ω (especially at position 12) are preferred, with ricinoleic acid and 12-hydroxystearic acid being more preferred. Fatty acids and hydroxy fatty acids may be used individually or in combination of two or more types.

[0022] In the silver particles of the present invention, the silver content of the silver particles is not particularly limited, as long as the effects of the present invention are achieved, but is preferably 95% by mass or more, and more preferably 98% by mass or more, with the silver particles as 100% by mass. Furthermore, the content of the protective layer of the silver particles is not particularly limited, as long as the effects of the present invention are achieved, but is preferably 1.5% by mass or less, more preferably 1.3% by mass or less, with the lower limit being preferably 0.05% by mass or more, with the silver particles as 100% by mass. The content of the protective layer of the silver particles can be measured by differential thermal analysis or thermogravimetric differential thermal analysis.

[0023] In the present invention, the proportion of the compound represented by general formula (1) in the protective layer of the silver particles is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more, and may also be 100% by mass. As described later, a method is preferably employed in which an amine compound or the like is attached to the surface of the silver particles, and then the amine compound is replaced with the compound represented by general formula (1). For this reason, the protective layer may contain amine compounds that remain unsubstituted.

[0024] The average particle diameter of the silver particles is not particularly limited, as long as it achieves the effects of the present invention, and is, for example, 20 nm or more, preferably 30 nm or more, more preferably 60 nm or more, and also, for example, 500 nm or less, preferably 400 nm or less, more preferably 250 nm or less. Preferred ranges for the average particle diameter include 20-500 nm, 20-400 nm, 20-250 nm, 30-500 nm, 30-400 nm, 30-250 nm, 60-500 nm, 60-400 nm, and 60-250 nm.

[0025] In this invention, the average particle diameter of silver particles is the volume-based average particle diameter measured for 200 randomly selected particles using image analysis software (e.g., Macview (manufactured by Mountec)) on an SEM image. For observation, a SED mode (secondary electron detector) is used, with an acceleration voltage of 20kV and an observation magnification of 5000 to 30000x, observing a range of 1 to 20 μm in width. The vertical direction of the SEM image is defined as a width that includes 200 or more (usually around 200 to 300) silver particles in the 1 to 20 μm range in width. Furthermore, the volume-based average particle diameter is a value measured assuming that the particles observed in the SEM image are spherical with a given diameter.

[0026] In the conductive adhesive of the present invention, the content of silver particles is not particularly limited as long as it does not produce the effects of the present invention, and is, for example, 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and also, for example, 95% by mass or less, preferably 93% by mass or less, more preferably 90% by mass or less, and preferred ranges include 70-95% by mass, 70-93% by mass, 70-90% by mass, 75-95% by mass, 75-93% by mass, 75-90% by mass, 80-95% by mass, 80-93% by mass, and 80-90% by mass.

[0027] The conductive adhesive of the present invention may contain silver particles other than those having a protective layer containing the compound represented by general formula (1). However, with the total proportion of silver particles being 100% by mass, the content of silver particles having a protective layer containing the compound represented by general formula (1) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably 100% by mass.

[0028] In the conductive adhesive of the present invention, silver particles may be single silver particles having a single average particle diameter (for example, in the range of 20 to 500 nm), or multiple silver particles having different average particle diameters (for example, in the range of 20 to 500 nm) may be used in combination. When multiple silver particles having different average particle diameters are used in combination, the ratio can be adjusted as appropriate to obtain the desired physical properties. For example, when using silver particles A1 with a small average particle diameter and silver particles A2 with a large average particle diameter in the range of 20 to 500 nm, the ratio of silver particles A1 to silver particles A2 can be in the range of 1 to 30:70 to 99. Silver particles containing the compound represented by the general formula (1) and having an average particle diameter in the range of 20 to 500 nm may be referred to as silver particle A.

[0029] The conductive adhesive of the present invention may contain, in addition to the silver particles A with an average particle diameter of 20 to 500 nm as described above, silver particles with a larger average particle diameter (for example, in the range of 0.5 to 5.5 μm). Silver particles with an average particle diameter in the range of 0.5 to 5.5 μm may be denoted as silver particles B. The protective layer for the silver particles may contain the compound represented by the general formula (1) above, or it may contain a compound different from the compound represented by the general formula (1) above (specific examples are as described above). From the viewpoint of more favorably achieving the effects of the present invention, the average particle size of silver particles B is preferably 0.6 μm or more at the lower limit, preferably 3.0 μm or less, more preferably 2.5 μm or less, and even more preferably 2.0 μm or less at the upper limit, with preferred ranges including 0.5 to 3.0 μm, 0.5 to 2.5 μm, 0.5 to 2.0 μm, 0.6 to 3.0 μm, 0.6 to 2.5 μm, and 0.6 to 2.0 μm.

[0030] In this invention, the average particle size of silver particles B can be measured by laser diffraction.

[0031] The silver particles B used in this invention may be commercially available or synthesized by known synthesis methods.

[0032] In the conductive adhesive of the present invention, silver particles A may be used alone, or silver particles A and silver particles B may be used in combination. When silver particles A and silver particles B are used in combination, the mass ratio of silver particles A to silver particles B should be in the range of (silver particles A:silver particles B) 30-70:70-30, preferably in the range of 35-65:65-35, and more preferably in the range of 40-60:60-40. By using silver particles A and silver particles B in combination in the above range ratio, higher shear strength can be obtained.

[0033] The thermosetting resin is not particularly limited, as long as it does not hinder the effects of the present invention, and examples include epoxy resins, acrylic resins, silicone resins, urethane resins, vinyl ester resins, phenolic resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, and polyimide resins. Among these, epoxy resins are particularly preferred. The thermosetting resin contained in the conductive adhesive of the present invention may be one type or two or more types.

[0034] In the conductive adhesive of the present invention, the content of the thermosetting resin is not particularly limited as long as it does not produce the effects of the present invention, and is, for example, 0.001% by mass or more, preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and also, for example, 10% by mass or less, preferably 7% by mass or less, more preferably 3% by mass or less, and preferred ranges include 0.001 to 10% by mass, 0.001 to 7% by mass, 0.001 to 3% by mass, 0.005 to 10% by mass, 0.005 to 7% by mass, 0.005 to 3% by mass, 0.01 to 10% by mass, 0.01 to 7% by mass, and 0.01 to 3% by mass.

[0035] Furthermore, the conductive adhesive of the present invention preferably further contains a solvent. The type of solvent is not particularly limited, as long as it does not hinder the effects of the present invention. The octanol / water partition coefficient (Log Pow) of the solvent is preferably -2 to 4, more preferably 0.5 to 3.75, and even more preferably 1 to 3.5. As described above, in the conductive adhesive of the present invention, the silver particles contain a compound represented by general formula (1) in the protective layer, resulting in good dispersibility of the silver particles in the solvent and a sintered body with low resistivity. In particular, when such an octanol / water partition coefficient (Log Pow) is used as the solvent, the dispersibility between the silver particles with the protective layer and the thermosetting resin becomes particularly good, which is preferable. In the present invention, specific examples of preferred solvents include hexyl carbitol (Log Pow: 1.7), texanol (Log Pow: 3.2), isopropyl alcohol (Log Pow: 0.05), α-terpineol (Log Pow: 2.98), diethylene glycol (Log Pow: -1.98), ethylene glycol (Log Pow: -1.36), 2-ethyl-1,3-hexanediol (Log Pow: 1.60), diethylene glycol mono-2-ethylhexyl ether (Log Pow: 2.23), butyl carbitol (Log Pow: 0.56), butyl carbitol acetate (Log Pow: 2.9), and butanediol (Log Pow: -0.34). Particularly preferred solvents are hexyl carbitol (Log Pow: 1.7) and texanol (Log Pow: 3.2). If the conductive adhesive of the present invention further contains a solvent, the solvent contained in the conductive adhesive may be one type or two or more types.

[0036] In the conductive adhesive of the present invention, the solvent content is not particularly limited as long as it does not produce the effects of the present invention, and is, for example, 2% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and also, for example, 20% by mass or less, preferably 17% by mass or less, more preferably 15% by mass or less, and preferred ranges are approximately 2-20% by mass, approximately 2-17% by mass, approximately 2-15% by mass, approximately 3-20% by mass, approximately 3-17% by mass, approximately 3-15% by mass, approximately 5-20% by mass, approximately 5-17% by mass, and approximately 5-15% by mass.

[0037] Furthermore, the conductive adhesive of the present invention may contain, in addition to the above-mentioned components, a curing agent (initiator) as another component. While not particularly limited as long as it promotes curing by mixing the silver particles and the thermosetting resin, examples include imidazole-based, hydrazide-based, boron trifluoride-amine complex, amine-imide, polyamine-based, tertiary amine, alkylurea-based, dicyandiamide-based, acid anhydride-based, phenol-based, and modified versions thereof, which can be used individually or as a mixture of two or more.

[0038] Among these curing agents (initiators), imidazole-based curing agents are preferred from the viewpoint of excellent storage stability at low temperatures and rapid curing. Known imidazole-based curing agents can be used as imidazole-based curing agents. More specifically, adducts of imidazole compounds with epoxy resins are exemplified. Examples of imidazole compounds include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-dodecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 4-methylimidazole.

[0039] Furthermore, the curing agent content in the conductive adhesive of the present invention is preferably 0.5% by mass or more and 20% by mass or less. This is because if the curing agent content is less than 0.5% by mass, the curing of the thermosetting resin may be insufficient and the adhesive properties may be poor, and if the curing agent content is more than 20% by mass, the curing agent may react during storage and the stability may decrease.

[0040] Furthermore, when the silver particles of the present invention are used in a conductive adhesive, the resistivity of the sintered body obtained by heating the conductive adhesive at 200°C for 60 minutes is preferably 30 μΩ·cm or less, more preferably 20 μΩ·cm or less, and even more preferably 10 μΩ·cm or less. The lower limit of this resistivity is, for example, 5 μΩ·cm or more. The method for measuring the resistivity of the sintered body is as follows, and is specifically measured by the method described in the examples.

[0041] <Resistivity> A conductive adhesive is uniformly applied to a polyimide film to a thickness of 2 mm x 60 mm x 50 μm, and then fired at a predetermined temperature (200°C) for 60 minutes to obtain a sintered body. Next, the resistance of the sintered body is measured at room temperature using a resistance meter (e.g., HIOKI RM3548), and the resistivity (volume resistance) is determined from the actual film thickness measured with a micrometer. This resistivity is the average value of measurements taken at four points on the sintered body.

[0042] 2. Method for manufacturing conductive adhesives The conductive adhesive of the present invention can be manufactured by mixing silver particles and a thermosetting resin, the silver particles and thermosetting resin being as described above. Furthermore, as described above, the conductive adhesive of the present invention may contain a solvent, and if it contains a solvent, the solvent is mixed in.

[0043] Next, an example of a method for producing silver particles having a protective layer containing a compound represented by general formula (1) is shown below.

[0044] First, a composition for producing silver particles (composition for preparing silver particles) is prepared. Specifically, a silver compound that will be the raw material for the silver particles, a compound represented by general formula (1) that will form a protective layer, and, if necessary, a compound different from the aforementioned general formula (1) (such as an amine compound) and a solvent are prepared. From the viewpoint of more favorably achieving the effects of the present invention, preferred silver compounds include silver nitrate and silver oxalate, with silver oxalate being particularly preferred. As for the solvent, the same solvents exemplified as those incorporated into the conductive adhesive described above are preferably exemplified.

[0045] Furthermore, in the preparation process of the conductive adhesive of the present invention, a solvent different from the solvent incorporated into the conductive adhesive may be used and then replaced with the solvent ultimately incorporated into the conductive adhesive. The different solvent is not particularly limited as long as it can disperse the silver particles, and for example, polar organic solvents can be used. Examples of polar organic solvents include ketones such as acetone, acetylacetone, and methyl ethyl ketone; ethers such as diethyl ether, dipropyl ether, dibutyl ether, tetrahydrofuran, and 1,4-dioxane; and 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-hexanediol, 1,6-hexanediol, 1,2-pentanediol, 1,5-pentanediol, and 2- Diols such as methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, 1,8-octanediol, and 2-ethyl-1,3-hexanediol; glycerol; straight-chain or branched-chain alcohols with 1 to 5 carbon atoms, alcohols such as cyclohexanol, 3-methoxy-3-methyl-1-butanol, and 3-methoxy-1-butanol; fatty acid esters such as ethyl acetate, butyl acetate, ethyl butyrate, ethyl formate, and texanol;Polyethylene glycol, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 3-methoxybutyl acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monohexyl ether, ethylene glycol monooctyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol Examples include glycols or glycol ethers such as cellulose monobutyl ether acetate, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, polypropylene glycol, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, and tripropylene glycol monobutyl ether; N,N-dimethylformamide; dimethyl sulfoxide; terpenes such as terpineol; acetonitrile; γ-butyrolactone; 2-pyrrolidone; N-methylpyrrolidone; and N-(2-aminoethyl)piperazine.

[0046] In addition to polar organic solvents, nonpolar organic solvents (hydrophobic organic solvents) may also be used as such solvents. Examples of nonpolar organic solvents include linear, branched, or cyclic saturated hydrocarbons such as hexane, heptane, octane, nonane, decane, 2-ethylhexane, and cyclohexane; alcohols such as linear or branched alcohols with 6 or more carbon atoms; aromatic compounds such as benzene, toluene, and benzonitrile; halogenated hydrocarbons such as dichloromethane, chloroform, and dichloroethane; methyl-n-amyl ketone; methyl ethyl ketone oxime; and triacetin. Among these, saturated hydrocarbons and linear or branched alcohols with 6 or more carbon atoms are preferred, and hexane, octane, decane, octanol, decanol, and dodecanol are more preferred. The solvent can be used alone or as a mixture of two or more.

[0047] A composition for preparing silver particles is obtained by mixing each component. The proportion of each component in the composition is adjusted as appropriate. For example, the content of silver oxalate in the composition is preferably about 20 to 70% by mass of the total amount of the composition. Furthermore, the content of the compound represented by general formula (1) to be attached to the surface of the silver particles is preferably about 5% to 55% by mass of the total amount of the composition. If an amine compound is attached to the surface of the silver particles, the content of the amine compound is preferably about 5% to 55% by mass of the total amount of the composition. Furthermore, if a fatty acid is attached to the surface of the silver particles, the content of the fatty acid is preferably about 0.1% to 20% by mass of the total amount of the composition. If a hydroxy fatty acid different from the compound represented by general formula (1) is attached to the surface of the silver particles, the content of the hydroxy fatty acid is preferably about 0.1% to 15% by mass of the total amount of the composition.

[0048] It is also possible to synthesize silver particles with a different compound (amine compound, etc.) attached to them using a silver particle preparation composition, and then to form the protective layer by substituting the amine compound, etc. for the compound represented by general formula (1) using the method described later.

[0049] Furthermore, the means of mixing each component are not particularly limited, and they can be mixed using general-purpose equipment such as mechanical stirrers, magnetic stirrers, vortex mixers, planetary mills, ball mills, three-roll mixers, line mixers, planetary mixers, and dissolvers. In order to avoid the temperature of the composition rising due to the effects of heat of dissolution, frictional heat, etc. during mixing and the initiation of the thermal decomposition reaction of silver particles, it is preferable to mix the components while keeping the temperature of the composition below, for example, 60°C or below, and especially below 40°C.

[0050] Next, the silver particle preparation composition is reacted in a reaction vessel, usually by heating, which causes a thermal decomposition reaction of the silver compound and generates silver particles. For the reaction, the composition may be introduced into a reaction vessel that has been heated beforehand, or the composition may be introduced into the reaction vessel and then heated.

[0051] The reaction temperature should be such that the thermal decomposition reaction proceeds and silver particles are formed, for example, around 50 to 250°C. The reaction time should be appropriately selected according to the desired average particle size and the corresponding composition of the composition. For example, the reaction time can range from 1 minute to 100 hours.

[0052] Since the silver particles produced by the thermal decomposition reaction are obtained as a mixture containing unreacted raw materials, it is preferable to purify the silver particles. Purification methods include solid-liquid separation and precipitation methods utilizing the difference in specific gravity between the silver particles and unreacted raw materials such as organic solvents. Solid-liquid separation methods include filter filtration, centrifugation, cyclone filtration, or decanting. To facilitate handling during purification, the mixture containing the silver particles may be diluted with a low-boiling point solvent such as acetone or methanol to adjust its viscosity.

[0053] The average particle size of the resulting silver particles can be adjusted by controlling the composition and reaction conditions of the silver particle manufacturing composition.

[0054] Method for replacing and adjusting amine compounds, etc., on the surface of silver particles. Using the method described above, silver particles (with an amine compound attached to their surface) are prepared and dispersed in a solvent. The solvent is the same as the one exemplified above. Next, the compound represented by general formula (1) is added in an amount ranging from 0.1 to 5 times the mass of the silver particles, and the mixture is stirred at room temperature to 80°C for 1 minute to 24 hours. This process replaces the amine compound attached to the surface of the silver particles with the compound represented by general formula (1). The silver particles from which the amine compound has been replaced can be recovered by the solid-liquid separation method described above.

[0055] 3. Sintered body of conductive adhesive The sintered body of the conductive adhesive of the present invention is obtained by sintering the conductive adhesive of the present invention as detailed in "1. Conductive Adhesive" above. In the sintered body of the conductive adhesive of the present invention, most of the components (compounds represented by general formula (1), etc.) and solvents adhering to the surface of the silver particles are removed by the high heat during sintering, and the sintered body is substantially composed of silver and thermosetting resin.

[0056] The sintering temperature is not particularly limited, but from the viewpoint of suitably sintering at a low temperature while increasing the shear strength and density of the resulting sintered body, for example, a temperature of 250°C or lower is preferred, preferably around 100°C to 250°C, and more preferably around 150°C to 250°C. From the same viewpoint, the sintering time is preferably around 0.4 hours to 2.0 hours, and more preferably around 0.5 hours to 1.2 hours. There is no need to pressurize the conductive adhesive of the present invention during sintering. That is, the conductive adhesive of the present invention can be suitably used in applications where no pressurization is required during sintering. However, pressurization may be applied during sintering of the conductive adhesive of the present invention, and if pressurization is applied, the pressure is, for example, around 10 to 30 MPa. Sintering can be carried out in an atmosphere such as air or an inert gas (nitrogen gas, argon gas). The sintering means is not particularly limited, and examples include ovens, hot air drying ovens, infrared drying ovens, laser irradiation, flash lamp irradiation, microwaves, etc.

[0057] The sintered body of the present invention preferably satisfies the resistivity value indicated in section "1. Conductive Adhesive".

[0058] 4. Electronic components The electronic component of the present invention comprises a portion where the components are bonded together by the sintered body of the present invention. That is, the electronic component of the present invention is formed by placing the conductive adhesive of the present invention, as detailed in "1. Conductive Adhesive" above, between the components of the electronic component (for example, between components included in a circuit), sintering the conductive adhesive, and bonding the components together.

[0059] The resistivity of the electronic component of the present invention can also be made low. [Examples]

[0060] The present invention will be described in more detail in the following examples, but the present invention is not limited thereto.

[0061] Details of each component used in the examples and comparative examples are as follows. Silver oxalate ((COOAg)2) is synthesized by the method described in Japanese Patent Publication No. 5574761. did. • Silver particles b (manufactured by DOWA Electronics Co., Ltd., product name AG 2-1C, silver particles with an average particle size of 0.6 μm and oleic acid attached to the surface) • N,N-diethyl-1,3-diaminopropane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) n-hexylamine (6 carbon atoms, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Ricinoleic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) • 2-Hydroxyisobutyric acid (manufactured by Fujifilm Wako Pure Chemical Corporation) • L-lactic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • 1-Butanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Methanol (manufactured by Fujifilm Wako Pure Chemical Corporation) • Hexylcarbitol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Bisphenol A type epoxy resin (manufactured by DIC Corporation, product name EXA-850CRP)

[0062] <Synthesis of silver particles a> In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (2.34 g), N,N-diethyl-1,3-diaminopropane (203 g), and 1-butanol (375 g) were added and stirred for about 1 minute. Then, silver oxalate (250 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles a. Subsequently, these glass centrifuge tubes were placed upright on a hot stirrer equipped with an aluminum block (HHE-19G-U, manufactured by Koike Precision Machinery Co., Ltd.), and stirred at 40°C for 30 minutes, followed by stirring at 90°C for another 30 minutes. After cooling, the magnetic stirring bar was removed, 15 g of methanol was added to each composition and stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (CF7D2, manufactured by Hitachi Koki Co., Ltd.) at 3000 rpm (approximately 1600 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. The process of adding 15 g of isopropyl alcohol, stirring, centrifugation, and removing the supernatant was repeated twice to recover silver particles a.

[0063] (Example 1) Using the dispersion of silver particles a obtained above (isopropyl alcohol), 0.5 times the mass of the silver particles was added to 2-hydroxyisobutyric acid, and the mixture was stirred at room temperature for 2 hours. After stirring, the magnetic stirring bar was removed, 15 g of methanol was added to each composition, and the mixture was stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (Hitachi Koki CF7D2) at 3000 rpm (approximately 1600 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. Next, the steps of adding 15 g of hexylcarbitol, stirring, centrifugation, and removing the supernatant were repeated twice to recover silver particles a1 (average particle size 100 nm) in which N,N-diethyl-1,3-diaminopropane adhering to the surface of the silver particles was replaced with 2-hydroxyisobutyric acid.

[0064] Next, the dispersions of silver particles a1 and silver particles b in hexyl carbitol were mixed with 0.1 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive. Mixing was performed using a Kurabo Mazelstar in a two-pass stirring priority mode. The silver particle content in the conductive adhesive was 84.2% by mass (the mass ratio of silver particles a1 to silver particles b was 1:1), the hexyl carbitol content was 15.0% by mass, and the epoxy resin content was 1.0% by mass.

[0065] (Example 2) In Example 1, a conductive adhesive was obtained in the same manner as in Example 1, except that a dispersion of silver particles a1 and silver particles b in hexyl carbitol was mixed with 0.3 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive with a silver particle content of 82.5% by mass (mass ratio of silver particles a1 to silver particles b: 1:1), a hexyl carbitol content of 15.0% by mass, and an epoxy resin content of 2.9% by mass.

[0066] (Example 3) In Example 1, a conductive adhesive was obtained in the same manner as in Example 1, except that a dispersion of silver particles a1 and silver particles b in hexyl carbitol was mixed with 0.5 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive with a silver particle content of 81.0% by mass (mass ratio of silver particles a1 to silver particles b: 1:1), a hexyl carbitol content of 14.9% by mass, and an epoxy resin content of 4.8% by mass.

[0067] (Example 4) Using the dispersion of silver particles a obtained above (isopropyl alcohol), L-lactic acid was added in an amount equal to 0.5 times the mass of the silver particles, and the mixture was stirred at room temperature for 2 hours. After stirring, the magnetic stirring bar was removed, 15 g of methanol was added to each composition, and the mixture was stirred with a vortex mixer. Then, centrifugation was performed using a centrifuge (Hitachi Koki CF7D2) at 3000 rpm (approximately 1600 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. Next, the steps of adding 15 g of hexylcarbitol, stirring, centrifugation, and removing the supernatant were repeated twice to recover silver particles a2 (average particle size 100 nm) in which N,N-diethyl-1,3-diaminopropane adhering to the surface of the silver particles was replaced with L-lactic acid.

[0068] Next, the dispersions of silver particles a2 and silver particles b in hexyl carbitol were mixed with 0.1 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive. Mixing was performed using a Kurabo Mazelstar in a two-pass stirring priority mode. The silver particle content in the conductive adhesive was 84.2% by mass (the mass ratio of silver particles a2 to silver particles b was 1:1), the hexyl carbitol content was 15.0% by mass, and the epoxy resin content was 1.0% by mass.

[0069] (Example 5) In Example 4, a conductive adhesive was obtained in the same manner as in Example 4, except that a dispersion of silver particles a2 and silver particles b in hexyl carbitol was mixed with 0.3 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive with a silver particle content of 82.5% by mass (mass ratio of silver particles a2 to silver particles b: 1:1), a hexyl carbitol content of 15.0% by mass, and an epoxy resin content of 2.9% by mass.

[0070] (Example 6) In Example 4, a conductive adhesive was obtained in the same manner as in Example 4, except that a dispersion of silver particles a2 and silver particles b in hexyl carbitol was mixed with 0.5 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive with a silver particle content of 81.0% by mass (mass ratio of silver particles a2 to silver particles b: 1:1), a hexyl carbitol content of 14.9% by mass, and an epoxy resin content of 4.8% by mass.

[0071] (Comparative Example 1) Using the dispersion of silver particles a obtained above (isopropyl alcohol), n-hexylamine was added in an amount equal to 0.5 times the mass of the silver particles, and the mixture was stirred at room temperature for 2 hours. After stirring, the magnetic stirring bar was removed, 15 g of methanol was added to each composition, and the mixture was stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (Hitachi Koki CF7D2) at 3000 rpm (approximately 1600 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. Next, the steps of adding 15 g of hexylcarbitol, stirring, centrifugation, and removing the supernatant were repeated twice to recover silver particles a3 (average particle size 100 nm) in which the N,N-diethyl-1,3-diaminopropane adhering to the surface of the silver particles was replaced with n-hexylamine.

[0072] Next, the dispersions of silver particles a3 and silver particles b in hexyl carbitol were mixed with 0.1 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive. Mixing was performed using a Kurabo Mazelstar in a two-pass stirring priority mode. The silver particle content in the conductive adhesive was 84.2% by mass (the mass ratio of silver particles a to silver particles b was 1:1), the hexyl carbitol content was 15.0% by mass, and the epoxy resin content was 1.0% by mass.

[0073] (Comparative Example 2) In Comparative Example 1, a conductive adhesive was obtained in the same manner as in Comparative Example 1, except that a dispersion of silver particles a3 and silver particles b in hexyl carbitol was mixed with 0.30 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive with a silver particle content of 82.5% by mass (mass ratio of silver particles a to silver particles b: 1:1), a hexyl carbitol content of 15.0% by mass, and an epoxy resin content of 2.9% by mass.

[0074] (Comparative Example 3) In Comparative Example 1, a conductive adhesive was obtained in the same manner as in Comparative Example 1, except that a dispersion of silver particles a3 and silver particles b in hexyl carbitol was mixed with 0.5 g of epoxy resin (bisphenol A type epoxy resin) to obtain a conductive adhesive with a silver particle content of 81.0% by mass (mass ratio of silver particles a to silver particles b: 1:1), a hexyl carbitol content of 14.9% by mass, and an epoxy resin content of 4.8% by mass.

[0075] <Manufacturing of sintered bodies and measurement of resistivity> A conductive adhesive was uniformly applied to a polyimide film to a thickness of 2 mm × 60 mm × 50 μm, and the film was fired at a predetermined temperature (200°C or 250°C) for 60 minutes to obtain a sintered body. Next, the resistance of the sintered body was measured at room temperature using a resistance meter (HIOKI RM3548) with a two-terminal measurement method, and the resistivity (volume resistance) value was determined from the actual film thickness measured with a micrometer. This resistivity value is the average of the values ​​measured at four locations on the sintered body. The measurement results of the resistivity are shown in Table 1 and Figure 1.

[0076] [Table 1]

[0077] <Evaluation of the dispersibility of silver particles> Next, the inventors evaluated the dispersibility of silver particles a1, a2, and a3 obtained above in various solvents. The results are shown in Table 2 below. The dispersibility was evaluated by adding each silver particle to various solvents at a concentration of 30% by mass, mixing and stirring at room temperature, allowing it to stand, and then visually assessing its state. The evaluation criteria are as follows. ○: Completely distributed △: Partial dispersion ×: Does not disperse (silver particles settle) [Table 2]

[0078] As shown in Table 2, silver particles a3 substituted with n-hexylamine do not disperse in polar solvents with an octanol / water partition coefficient (Log Pow) of -1.98 to -0.34 and instead precipitate, whereas silver particles a1 substituted with 2-hydroxyisobutyric acid and silver particles a2 substituted with L-lactic acid show improved dispersibility. Furthermore, silver particles a1 also exhibit good dispersibility in low-polarity solvents with an octanol / water partition coefficient (Log Pow) of 1.7 to 3.2, suggesting that they can be used in a variety of solvents used in the manufacture of conductive adhesives.

Claims

1. Silver particles and Thermosetting resin and A conductive adhesive containing, The silver particles include silver particles A with an average particle diameter of 20 to 500 nm and silver particles B with an average particle diameter of 0.5 to 5.5 μm. The aforementioned silver particles A are provided with a protective layer containing a compound represented by the following general formula (1) in a conductive adhesive. 【Chemistry 1】 [In general formula (1), R 1 R is an alkyl group having 1 to 5 carbon atoms. 2 [This is either a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.]

2. The conductive adhesive according to claim 1, wherein the thermosetting resin is an epoxy resin.

3. The conductive adhesive according to claim 1 or 2, wherein the content of the silver particles is 70% by mass or more.

4. A conductive adhesive according to any one of claims 1 to 3, further comprising a solvent.

5. The conductive adhesive according to claim 4, wherein the octanol / water partition coefficient (Log Pow) of the solvent is between -2 and 4.

6. A sintered body of a conductive adhesive according to any one of claims 1 to 5.

7. An electronic component formed by joining members together using the sintered body described in claim 6.

8. A method for manufacturing a sintered body, comprising the step of sintering a conductive adhesive according to any one of claims 1 to 5 at a temperature of 100°C to 250°C.

9. A method for manufacturing electronic components in which members are joined together by a sintered body, A step of placing a conductive adhesive according to any one of claims 1 to 5 between the members, The process involves sintering the conductive adhesive at a temperature of 100°C to 250°C, A method for manufacturing electronic components, comprising:

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