conductive bonding material

Abstract

The present invention provides a conductive bonding material that exhibits excellent adhesion between a sintered body obtained by sintering under low temperature, low pressure, and short-duration pressurization in a nitrogen or atmospheric environment, and a laminate of components, and that exhibits high mechanical strength (shear strength) when a shear force is applied to the sintered body of the laminate. [Solution] A conductive bonding material comprising silver particles having a compound represented by general formula (1) attached to the surface of the silver particles, and a solvent, for bonding a chip to a metal substrate, or a heat sink to a metal substrate under pressure. TIFF2026141953000006.tif4576 [In general formula (1), R 1 R is an alkyl group having 2 to 3 carbon atoms. 2 R is an alkyl group having 1 to 4 carbon atoms. 3 [This is either a hydrogen atom or an alkyl group with 1 to 4 carbon atoms.]

Description

[Technical Field]

[0001] This invention relates to a conductive bonding material. [Background technology]

[0002] In recent years, demand for miniaturized and highly functional electronic components, such as power devices, has been rapidly expanding. Power devices, as semiconductor elements that can reduce power loss and convert power efficiently, are becoming increasingly popular in fields such as electric vehicles and fast chargers, and demand is also expected to grow in new energy fields such as solar power generation systems.

[0003] As electronic components become smaller and more sophisticated, the amount of heat generated from semiconductor devices is increasing. However, if electronic components are exposed to high-temperature environments for extended periods, they may not be able to perform their functions properly.

[0004] Therefore, conductive bonding materials (die bonding materials) are made of highly heat-dissipating materials that can efficiently dissipate the heat generated from semiconductor elements. Because high heat dissipation is required for bonding materials used in electronic components, high-temperature lead solder containing a large amount of lead has been widely used in the past. However, high-temperature lead solder contains lead, which is harmful to the human body, and while research into lead-free solder is actively underway, there is a need to develop bonding materials with even greater heat dissipation capabilities.

[0005] In recent years, the development of conductive bonding materials containing silver particles has progressed as bonding materials with high heat dissipation properties. Silver particles have the characteristic of easily sintering with low temperature and short heat treatment. As bonding methods, bonding by pressurization and heating, or bonding to the substrate by sintering by heating without pressurization, are generally known.

[0006] For example, Patent Document 1 describes a conductive bonding material comprising silver particles, silver compound particles, and a dispersant for bonding a chip and a substrate under pressure, wherein the weight ratio of the silver particles to the silver compound particles is 30:70 to 70:30, and the porosity of the conductive bonding material after the chip and the substrate are pressure-bonded in air at 10 MPa and 280°C for 5 minutes is 15% or less.

[0007] However, while the bonding material described in Patent Document 1 can form a bonding layer with very low porosity under pressure, conventional conductive adhesives require high temperature and high pressure conditions and long bonding times to achieve strong bonding strength. Therefore, there is a need to develop a conductive bonding material that exhibits excellent adhesion to substrates and other materials, and can achieve high shear strength even under low temperature and low pressure conditions and short bonding times. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-092798 [Overview of the project] [Problems that the invention aims to solve]

[0009] Conductive bonding materials containing silver particles are in which silver particles are dispersed in a solvent. By applying them to the surface of components (for example, substrates used in electronic components, semiconductor chips, heat sinks, etc.) and sintering them, the components can be bonded together.

[0010] For example, when applying a conductive bonding material containing silver particles in the manufacturing process of components such as substrates, semiconductor chips, and heat sinks used in electronic components, it is necessary to carry out a manufacturing process under nitrogen atmosphere, low temperature and pressure conditions, and short bonding time in order to suppress the deterioration of the components (e.g., deterioration due to heating in the atmosphere). Furthermore, manufacturing under nitrogen atmosphere, low temperature and pressure conditions, and short bonding time also has the advantage of allowing the manufacturing process to be carried out under a constant environment.

[0011] Furthermore, when applying a conductive bonding material containing silver particles to copper components such as copper substrates, it is necessary to perform pressurized bonding in a nitrogen atmosphere or in an atmospheric atmosphere for a short period of time at low temperatures.

[0012] However, when a conventional conductive bonding material containing silver particles is applied to a component and sintered at low temperature for a short time under a nitrogen atmosphere to obtain a laminate, the adhesion of the sintered body to the component may not be sufficient (specifically, when a shear force is applied to the sintered body that is in close contact with the component, the mechanical strength (shear strength) of the laminate is low, and the sintered body and the component may easily separate). In addition, the sintering of the silver particles may be insufficient, and the intended performance may not be fully obtained.

[0013] Under these circumstances, the main objective of the present invention is to provide a conductive bonding material that exhibits excellent adhesion between the sintered body and the member when sintered on the surface of a member under low temperature, low pressure, and short-duration pressurization in a nitrogen or atmospheric environment, and that exhibits high mechanical strength (shear strength) when a shear force is applied to the sintered body of the laminate. Another objective is to provide a conductive bonding material with excellent sinterability. [Means for solving the problem]

[0014] The inventors diligently conducted research to solve the above problems. As a result, they obtained a novel finding that by using novel silver particles, which are composed of silver particles with a predetermined acidic compound attached to their surface, as a conductive bonding material, the sintered body obtained by sintering the conductive bonding material under a nitrogen atmosphere or an atmospheric atmosphere under pressure exhibits excellent adhesion (high shear strength is obtained) and sinterability between the sintered body and the copper member. The present invention was completed by further research based on this finding.

[0015] In other words, the present invention provides inventions in the following embodiments. Item 1. A conductive bonding material comprising silver particles, wherein a compound represented by the following general formula (1) is attached to the surface of the silver particles, and a solvent, for bonding a chip to a metal substrate, or a heat sink to a metal substrate under pressure. [ka] [In General Formula (1), R 1 is an alkyl group having 2 to 3 carbon atoms, and R 2 is an alkyl group having 1 to 4 carbon atoms, and R 3 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.]] Item 2. The conductive bonding material according to Item 1, wherein the silver particles have an average particle diameter of 60 to 600 nm.

Effects of the Invention

[0016] According to the present invention, there can be provided a conductive bonding material excellent in sinterability, which, after sintering of the conductive bonding material on a member surface under pressure in a nitrogen atmosphere or an air atmosphere, provides a laminate of the obtained sintered body and a copper member having excellent adhesion, and exhibits high mechanical strength (shear strength) when a shearing force is applied to the sintered body of the laminate.

Mode for Carrying Out the Invention

[0017] The present invention is a conductive bonding material which comprises silver particles having a compound represented by general formula (1) attached to the surface thereof, and a solvent, and is used for bonding a chip to a metal substrate or a heat radiator to a metal substrate under pressure.

Chemical Formula

[0018] In this specification, a numerical range 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 separately described, any lower limit and any upper limit can be selected and connected by "~".

[0019] conductive bonding material The conductive bonding material of the present invention is a conductive bonding material that contains silver particles having a compound represented by general formula (1) attached to the surface thereof and a solvent, and is used for bonding a chip to a metal substrate or a heat radiator to a metal substrate under pressure.

Chemical Formula

[0020] silver particles The silver particles of the present invention are particles containing silver. A compound represented by general formula (1) (hereinafter sometimes referred to as compound (1)) is attached to the surface of the silver particles. That is, the silver particles of the present invention have a structure in which compound (1) is attached to the surface of particles formed of silver.

[0021] In the present invention, particles formed of silver with no compound (1) attached to the surface (particles substantially composed only of silver) are expressed as "silver particles", and particles having compound (1) attached to the surface of particles formed of silver are also expressed as "silver particles" for convenience. When the expression "the silver particles of the present invention" is used, it means particles having compound (1) attached to the surface of particles formed of silver.

[0022] In the silver particles of the present invention, the compound (1) adhering to the surface of the silver particles can be described as forming a protective layer (or surface layer, etc.). Specifically, the silver particles have a protective layer on the surface of the particles composed of silver. The protective layer also contains the compound represented by the general formula (1) above. The conductive bonding material of the present invention, by containing silver particles having such a protective layer, exhibits excellent adhesion between the sintered body and the copper member obtained by sintering the conductive bonding material under a nitrogen atmosphere or an air atmosphere under pressure, and when a shear force is applied to the sintered body that is in close contact with the copper member in the laminate, high mechanical strength (shear strength) is exhibited. Furthermore, it exhibits excellent sinterability under both a nitrogen atmosphere and an air atmosphere.

[0023] As stated above, in general formula (1), R 1 The alkyl group has 2 to 3 carbon atoms, and from the viewpoint of more favorably exhibiting the effects of the present invention, it is preferable that the alkyl group has 2 carbon atoms.

[0024] Also, in general formula (1), R 2 The alkyl group has 1 to 4 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 to 2 carbon atoms.

[0025] Also, in general formula (1), R 3 This is either a hydrogen atom or an alkyl group having 1 to 4 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 2 carbon atoms, and more preferably a hydrogen atom.

[0026] From the viewpoint of exhibiting the effects of the present invention more favorably, among the compounds represented by general formula (1), 2-methylbutanoic acid, 2-ethylbutanoic acid, 2,2-dimethylbutanoic acid, 2-methylpentanoic acid, 2,2-dimethylpentanoic acid, 2-ethylpentanoic acid, 2-propylpentanoic acid, etc. are particularly preferred, and 2-methylpentanoic acid is particularly preferred. The protective layer may contain one compound represented by general formula (1) or two or more compounds.

[0027] The amount of compound (1) attached to the silver particles of the present invention is not particularly limited, 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, based on the mass of the silver particles as 100% by mass. The content of compound (1) attached to the silver particles can be measured by thermogravimetric differential thermal analysis.

[0028] 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. When the protective layer contains compounds other than the compound represented by general formula (1), there may be one or more such different compounds.

[0029] The amine compound is not particularly limited, but preferably it is an alkylamine with an alkyl group having 3 to 18 carbon atoms, and more preferably an alkylamine with an alkyl group having 4 to 12 carbon atoms.

[0030] 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, 2-(2-aminoethylamino)ethanol, etc. Among these, from the viewpoint of more favorably achieving the effects of the present invention, 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, 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, and n-hexylamine is particularly preferred.

[0031] In the silver particles of the present invention, the amount of amine compound attached is also adjusted as appropriate, similar to compound (1). The specific amount of amine compound attached is not particularly limited, but is preferably 1.5% by mass or less, more preferably 1.3% by mass or less, with the mass of the silver particles being 100% by mass, and the lower limit being 0.00% by mass, 0.01% by mass or more, etc. The content of the amine compound attached to the silver particles can be measured by differential thermal analysis.

[0032] Furthermore, fatty acids, hydroxy fatty acids, etc., may be attached to the surface of the silver particles. While there are no particular limitations on the fatty acids, preferred fatty acids are those with 3 to 18 carbon atoms in the alkyl group, and more preferably fatty acids with 4 to 18 carbon atoms in the alkyl group. Preferred specific examples of fatty acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic 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 alkyl carboxylic acids such as cyclohexanecarboxylic acid. As for hydroxy fatty acids, compounds having 3 to 24 carbon atoms and one or more hydroxyl groups (for example, one) can be used. Furthermore, examples of hydroxy fatty acids 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-hydroxydodecanoic acid. Examples include hydroxy fatty acids such as 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. Each fatty acid and hydroxy fatty acid may be used individually or in combination of two or more types.

[0033] In the silver particles of the present invention, the amount of fatty acids and hydroxy fatty acids attached can be adjusted as appropriate, similar to compound (1). The specific amount of fatty acids and hydroxy fatty acids attached is not particularly limited, but is preferably 1.5% by mass or less, more preferably 1.3% by mass or less, with the mass of the silver particles being 100% by mass, and the lower limit being 0.01% by mass, 0.01% by mass or more, etc. The content of fatty acids and hydroxy fatty acids attached to the silver particles can be measured by differential thermal analysis.

[0034] In addition, in the silver particles of the present invention, compound (1), amine compounds, fatty acids, and hydroxy fatty acids may be used in combination, or other compounds different from these may be attached to the surface of the silver particles, provided that compound (1) is attached to the surface and the effects of the present invention can be exhibited.

[0035] Furthermore, from the viewpoint of suitably exhibiting the effects of the present invention, the average particle diameter (primary particle diameter) of the silver particles is, for example, 600 nm or less, preferably 580 nm or less, more preferably 560 nm or less, and even more preferably 550 nm or less, and also preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 65 nm or more. Preferred ranges include 50-600 nm, 50-580 nm, 50-560 nm, 50-550 nm, 60-600 nm, 60-580 nm, 60-560 nm, 60-550 nm, 65-600 nm, 65-580 nm, 65-560 nm, and 65-550 nm.

[0036] For example, conductive bonding materials containing silver particles with an average particle size of approximately 100 nm (50-150 nm) exhibit excellent sinterability, making them suitable for use in bonding areas of thin-film power devices and solar cells. Furthermore, conductive bonding materials containing silver particles with an average particle size of approximately 200 nm (150-300 nm) exhibit low shrinkage while maintaining sinterability, making them suitable for bonding areas of power devices and power amplifiers. Similarly, conductive bonding materials containing silver particles with an average particle size of approximately 500 nm (300-600 nm) exhibit low shrinkage, making them suitable for bonding areas of thick-film power devices. Conductive bonding materials containing silver particles with an average particle size of approximately 150 nm (100-200 nm) can be sintered at low temperatures and in short times, and exhibit excellent heat dissipation after sintering, making them suitable for bonding heat dissipation components (heat sink applications) used in semiconductor devices. Although the required properties of conductive bonding materials differ depending on their application, the conductive bonding material of the present invention can be made suitable for each application by adjusting the average particle size of the silver particles of the present invention.

[0037] The average particle diameter (primary particle diameter) of the silver particles in this invention 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. Observation is performed using SED mode (secondary electron detector) 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 containing 200 or more (usually around 200 to 300) silver particles within the 1 to 20 μm range. 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. The specific measurement method is as described in the examples.

[0038] Furthermore, from the viewpoint of suitably exhibiting the effects of the present invention, it is preferable that the silver particles of the present invention exhibit at least one exothermic peak in the range of 120 to 300°C in thermogravimetric differential thermal analysis, more preferably at least one in the range of 120 to 160°C, and even more preferably at least one in the range of 160 to 300°C. Typically, one or more of these exothermic peaks are observed within these ranges.

[0039] Furthermore, the dried silver particle powder of the present invention preferably has a weight loss rate of 1.5% by weight or less when heated from 30°C to 500°C, as determined by thermogravimetric differential thermal analysis, and more preferably 0.05 to 1.3% by weight. The method for thermogravimetric differential thermal analysis is as follows.

[0040] <Thermogravimetric differential thermal analysis (TG-DTA)> The TG-DTA of silver particles dispersed in a solvent is measured using a thermogravimetric differential thermal analyzer (e.g., HITACHI G300 AST-2). The measurement conditions are: atmosphere: air (when measuring the silver content in the dispersion) or nitrogen (when measuring the exothermic peak and weight loss), measurement temperature: 30-500°C, heating rate: 10°C / min. From the obtained TG-DTA chart, the exothermic peak caused by the binding of silver particles in the TG-DTA analysis and the weight loss rate when heated from 30°C to 500°C are obtained by thermal analysis.

[0041] The silver content in the silver particles of the present invention is preferably 95% by mass or more, and more preferably 98% by mass or more.

[0042] Compound (1) is attached to the surface of the silver particles of the present invention. That is, the silver particles of the present invention are surface-treated with a treatment solution containing compound (1) (surface-treated silver particles). Compound (1) adheres to the surface of the silver particles and forms a protective layer.

[0043] Method for manufacturing silver particles An example of a method for producing silver particles according to the present invention is shown below.

[0044] First, a composition for producing the silver particles (particles composed of silver) of the present invention (composition for preparing silver particles) is prepared. Specifically, a silver compound to be used as a raw material for the silver particles, a compound (1) to be attached to the surface of the silver particles, and solvents to be used in each step (solvent used during the synthesis of silver particles, solvent for purifying silver particles, solvent for substitution with compound (1), etc.) are prepared.

[0045] The silver particles of the present invention are synthesized through a process of synthesizing silver particles (particles composed of silver) from a silver compound, a process of substituting the amine compound on the surface of the silver particles with an acid (protecting group) (i.e., compound (1)), and separation of the silver particles may be included in or between each of these processes.

[0046] From the viewpoint of achieving the effects of the present invention more favorably, preferred silver compounds include silver nitrate and silver oxalate, with silver oxalate being particularly preferred.

[0047] The solvent used when synthesizing silver particles from silver compounds is not particularly limited as long as silver particles composed of silver are synthesized, but it is preferable that it contains a polar organic solvent. 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 Glycols or glycol ethers such as ethers, diethylene glycol 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, tripropylene glycol monobutyl ether, etc.; N,N-dimethylformamide; dimethyl sulfoxide; terpenes such as terpineol; acetonitrile; γ-butyrolactone; 2-pyrrolidone; N-methylpyrrolidone;Examples include N-(2-aminoethyl)piperazine. Among these, from the viewpoint of more favorably achieving the effects of the present invention, linear or branched alcohols having 3 to 5 carbon atoms, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, terpineol, and texanol are preferred.

[0048] The solvent may include a nonpolar or hydrophobic solvent in addition to a polar organic solvent. 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 in mixtures of two or more.

[0049] In the process of synthesizing silver particles from a silver compound, a silver compound, an amine compound or compound (1), and a solvent are mixed to obtain a composition for preparing silver particles. 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. The content of the amine compound or compound (1) is preferably about 5 to 55% by mass of the total amount of the composition. If fatty acids are attached to the surface of the silver particles, the fatty acid content is preferably about 0.1 to 20% by mass of the total amount of the composition. If hydroxy fatty acids are attached to the surface of the silver particles, the hydroxy fatty acid content is preferably about 0.1 to 15% by mass of the total amount of the composition.

[0050] Once silver particles with an amine compound attached are synthesized, it is possible to replace the amine compound with compound (1) by the method described later.

[0051] Furthermore, the means of mixing each component are not particularly limited, and can be used with 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Method for replacing and preparing amine compounds 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.

[0056] The silver particle content in the conductive bonding material of the present invention is preferably 80% by mass or more, more preferably 83% by mass or more, even more preferably 85% by mass or more, and also preferably 95% by mass or less, more preferably 93% by mass or less, even more preferably 92% by mass or less. Preferred ranges include 80-95% by mass, 83-93% by mass, 85-92% by mass, etc.

[0057] solvent The conductive bonding material of the present invention further contains a solvent in addition to the silver particles of the present invention. Specific examples of preferred solvents in the present invention include diethylene glycol monohexyl ether (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 diethylene glycol monohexyl ether (Log Pow: 1.7), 2-ethyl-1,3-hexanediol (Log Pow: 1.60), diethylene glycol mono-2-ethylhexyl ether (Log Pow: 2.23), and texanol (Log Pow: 3.2). If the conductive bonding material of the present invention further contains a solvent, the solvent contained in the conductive bonding material may be one type or two or more types.

[0058] In the conductive bonding material 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.

[0059] The conductive bonding material of the present invention may further contain a resin. The resin is not particularly limited, and resins used in known conductive bonding materials containing silver particles can also be used in the present invention, such as thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include urethane resins, acrylic resins, methacrylic resins, polyvinyl alcohol resins, vinyl acetate resins, polycarbonate resins, polyorganosiloxane resins, and polyamide resins, and mixtures thereof may also be used. Examples of thermosetting resins 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.

[0060] Furthermore, when the conductive bonding material of the present invention contains a resin, the resin content in the conductive bonding material of the present invention is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and also preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 3% by mass or less. Preferred ranges include 0.001 to 10% by mass, 0.005 to 7% by mass, 0.01 to 3% by mass, etc.

[0061] Furthermore, a polymeric dispersant may be attached to the surface of the silver particles. Commercially available polymeric dispersants can be used as the polymeric dispersant. Examples of commercially available polymer dispersants include, for example, SOLSPERSE 11200, SOLSPERSE 13940, SOLSPERSE 16000, SOLSPERSE 17000, SOLSPERSE 18000, SOLSPERSE 20000, SOLSPERSE 24000, SOLSPERSE 26000, SOLSPERSE 27000, SOLSPERSE 28000, SOLSPERSE 36000, SOLSPERSE 41000, SOLSPERSE 45000, SOLSPERSE 79000, SOLSPERSE 85000, SOLSPERSE M387 (manufactured by Nippon Lubrizol Co., Ltd.); DISPERBY K-102, 110, 111, 170, 190, 194N, 2015, 2090, 2096 (BIK). Examples include: EFKA-46, EFKA-47, EFKA-48, EFKA-49 (manufactured by EFKA Chemical Co., Ltd.); Polymer 100, Polymer 120, Polymer 150, Polymer 400, Polymer 401, Polymer 402, Polymer 403, Polymer 450, Polymer 451, Polymer 452, Polymer 453 (manufactured by EFKA Chemical Co., Ltd.); Azisper PB711, Azisper PA111, Azisper PB811, Azisper PW911 (manufactured by Ajinomoto Co., Ltd.); Esream SP-0201, Esream MP-071K, Esream C-2091I, Esream C-2093I, Esream C-2095I (manufactured by NOF Corporation, "Esream" is a registered trademark), etc.

[0062] The amount of polymer dispersant attached is preferably 0.01 to 15% by mass. If the amount of polymer dispersant attached is 0.1% or more, the dispersion stability of the resulting bonding composition will be good, but if the amount is too high, the dispersion stability will decrease, and the bonding ability to the substrate may further decrease. From this viewpoint, a more preferable amount of polymer dispersant attached is 0.03 to 3% by mass, and an even more preferable amount is 0.05 to 2% by mass.

[0063] The conductive bonding material of the present invention may contain silver particles other than silver particles to which the compound represented by general formula (1) is attached. 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.

[0064] In the conductive bonding material of the present invention, silver particles may be single silver particles having a single average particle diameter (for example, in the range of 60 to 600 nm), or multiple silver particles having different average particle diameters (for example, within the range of 60 to 600 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 60 to 600 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) above, and having an average particle diameter in the range of 60 to 600 nm, may be referred to as silver particle A.

[0065] The conductive bonding material of the present invention may contain, in addition to the silver particles with an average particle diameter of 60 to 600 nm as described above, silver particles with a larger average particle diameter (for example, in the range of 0.6 to 5.5 μm). Silver particles with an average particle diameter in the range of 0.6 to 5.5 μm may be denoted as silver particle B. The protective layer for the silver particles may contain a compound represented by general formula (1), or it may contain a compound different from the compound represented by general formula (1) (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 0.6 to 3.0 μm, 0.6 to 2.5 μm, 0.6 to 2.0 μm, 0.6 to 3.0 μm, 0.6 to 2.5 μm, and 0.6 to 2.0 μm.

[0066] In this invention, the average particle size of silver particles B can be measured by laser diffraction.

[0067] The silver particles B used in this invention may be commercially available or synthesized by known synthesis methods.

[0068] In the conductive bonding material 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) 10 to 90:90 to 10, preferably in the range of 20 to 80:80 to 20, and more preferably in the range of 30 to 70:70 to 30. By using silver particles A and silver particles B in combination in the above range ratio, higher shear strength can be obtained.

[0069] According to the present invention, when silver particles, on which a compound represented by general formula (1) is attached to the surface of the silver particles, are bonded together with a solvent, a dried conductive bonding material, a chip and a metal substrate, or a heat sink and a metal substrate under pressure at 10 MPa, 200°C, or 220°C for 2 minutes under atmospheric pressure, the porosity of the conductive bonding material after bonding is 20% or less. Furthermore, under a nitrogen atmosphere, a similar effect can be obtained by extending the pressurization time. The solvent drying process is carried out at a temperature between 60°C and 160°C. The drying time is between 1 and 120 minutes.

[0070] Specifically, a conductive bonding material is placed on a silver-plated copper lead frame and dried at 100°C for 30 minutes using a hot plate. Next, a 5mm x 5mm gold-plated copper plate is mounted on top of it, and pressure bonding is performed using a pressure press manufactured by Imoto Seisakusho at 10 MPa, 200°C or 220°C for 2 minutes under air or nitrogen atmosphere conditions. The porosity of the conductive bonding material after pressure bonding can be measured by binarizing SEM images of the cross-section of the bonded layer.

[0071] The chip used for bonding with conductive bonding material can be any chip without particular limitations, but examples include semiconductor chips, IC chips, chip resistors, chip capacitors, chip inductors, sensor chips, light-emitting diode (LED) chips, etc., with semiconductor chips being preferred.

[0072] The metal substrate used for bonding with conductive bonding material is not particularly limited, but examples include silver, copper, nickel, gold, aluminum / silicone / copper alloy, titanium, titanium nitride, tungsten, polysilicon, tantalum, tantalum nitride, metal silicide, or combinations thereof, or substrates whose surfaces are plated with copper, gold, silver, etc., with copper, gold, and silver being preferred. The metal substrate in this invention includes structures in which a metal plate is mounted on an insulating heat dissipation circuit board.

[0073] The heat sink used in bonding with conductive bonding material is not particularly limited, but examples include metals, ceramics, glass, and resins. Among these, examples include metals such as stainless steel, aluminum, and copper, as well as graphite, diamond, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and aluminum oxide. In this invention, the heat sink can be processed into a form appropriate to the purpose. A laminate obtained by bonding the heat sink and a metal substrate can be used to obtain a heat sink that can be used for various applications.

[0074] <Porosity> The sintered body obtained in 0067 is embedded in epoxy resin (e.g., Bühler) along with the laminate, and left to cure for 24 hours. Next, the resin-embedded laminate is cut with a precision low-speed cutting machine (e.g., ALLIED TechCut4), and cross-sectional milling is performed using an ion mill (e.g., Hitachi High-Technologies IM4000PLUS). The cross-sectional milling is performed with a discharge voltage of 1.5kV, an acceleration voltage of 6kV, and an argon gas flow rate of 0.07cm³. 3 The process is carried out by irradiating the material with an ion beam at a rate of / min and a swing of ±30°. The cross-section of the sintered body obtained by cross-sectional milling is observed with a scanning electron microscope (SEM) to acquire an SEM image. For observation, the SED mode (secondary electron detector) is used, and a field of view of 60 μm in width is observed at an acceleration voltage of 20 kV and 2000x magnification. The vertical dimension of the SEM image is limited to a range of 10 μm to 200 μm in length of the silver sintered layer. This is because if the silver sintered layer is less than 10 μm, the mechanical strength may be compromised due to the properties of the bonded body, and if it exceeds 200 μm, the bulk of the laminate increases, making it difficult for outgassing during sintering to occur uniformly, which is disadvantageous from a reliability standpoint. The density is calculated by converting the obtained SEM image to a two-tone image of black and white using binarization software (Image j) and determining the density using the following relational formula. Porosity (%) = Sintered silver area (number of white pixels) ÷ Total sintered body area {Sintered silver area (number of white pixels) + Pore area (number of black pixels)} × 100

[0075] Furthermore, the conductive bonding material according to the present invention has excellent bonding strength and thermal conductivity because it can achieve a low porosity.

[0076] The method for measuring joint strength is not particularly limited, but one example is the method of measuring die shear strength, as described later in the examples. A load is applied in the shear direction to the bonded chip or heat sink, and the strength at which it breaks is defined as the joint strength. As a strength measuring instrument, for example, a Nordson Bond Tester Dage4000PLUS is used, and the measurement is performed at 25°C and a test speed of 1 mm / sec. When pressure bonding is performed under the same conditions as described above, the bonding strength is preferably 40 MPa or higher, and more preferably 50 MPa or higher, when measured at 25°C and a test speed of 1 mm / sec.

[0077] <Method for manufacturing conductive bonding material> A conductive bonding material according to the present invention can be obtained by mixing silver particles, on which a compound represented by general formula (1) is attached to the surface of the silver particles, with a solvent. The solvent may be added beforehand or afterward. Mixing can be done dry or wet using a solvent, and mortars, planetary ball mills, roll mills, propellerless mixers, etc., can be used.

[0078] <Manufacturing method for semiconductor device or heat sink> The conductive bonding material according to the present invention can be suitably used in a method for manufacturing a semiconductor device in which a chip and a metal substrate are bonded, or a heat sink in which a heat sink and a metal substrate are bonded. That is, the method for manufacturing the semiconductor device or heat sink includes a step of bonding the chip and a metal substrate, or the heat sink and a metal substrate, via the conductive bonding material according to the present invention. The chip, metal substrate, and heat sink can be those described above.

[0079] In the bonding process, the materials are subjected to pressure treatment at 4 to 30 MPa and 200 to 350°C for 1 to 30 minutes, and the void ratio of the conductive bonding material after the bonding process is 15% or less. Pressure bonding is performed under any conditions, including air, nitrogen, and reducing atmospheres such as hydrogen. While this is possible, it is preferable to do so under atmospheric or nitrogen conditions from the standpoint of productivity.

[0080] The pressure during the joining process is preferably 4 MPa or higher, and more preferably 7 MPa or higher, from the viewpoint of porosity. Furthermore, the upper limit of the pressure is preferably 30 MPa or lower, and more preferably 20 MPa or lower, from the viewpoint of damage to the chip or heat sink. The temperature at which the applied conductive bonding material is dried is preferably 60°C or higher, and more preferably 80°C or higher, from the viewpoint of solvent evaporation and the sintering start temperature. Furthermore, the upper limit of the temperature is preferably 160°C or lower, and more preferably 140°C or lower, in order to prevent the sintering from being completed prematurely. The temperature during the joining process is preferably 150°C or higher, and more preferably 200°C or higher, from the viewpoint of sinterability and shear strength. Furthermore, the upper limit of the temperature is preferably 350°C or lower, and more preferably 300°C or lower, from the viewpoint of damage to surrounding components. In the joining process, the pressurizing and heating treatment time is preferably 1 minute or more from the viewpoint of void ratio, and 30 minutes or less from the viewpoint of damage to surrounding members and productivity.

[0081] In bonding using the conductive bonding material according to the present invention, pressurization and heating are essential. By heating, the compound represented by general formula (1) adheres to the surface of the silver particles, and the silver particles sinter, resulting in good bonding between the chip and the metal substrate, or between the heat sink and the metal substrate. Due to this low porosity, the conductive bonding material after bonding approaches that of metal bulk, resulting in a semiconductor device or heat sink with high bonding strength, high thermal conductivity, and excellent heat dissipation. [Examples]

[0082] The present invention will be described in more detail in the following examples, but the present invention is not limited thereto.

[0083] Details of each component used in the examples and comparative examples are as follows. Silver oxalate ((COOAg)2) was synthesized by the method described in Japanese Patent Publication No. 5574761. 2-Methylpentanoic acid (Fujifilm Wako Pure Chemical Corporation) Ricinoleic acid (Fujifilm Wako Pure Chemical Corporation) N,N-diethyl-1,3-diaminopropane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) n-propanol (manufactured by Fujifilm Wako Pure Chemical Corporation) Isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 1-Butanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Octanoic acid (manufactured by Fujifilm Wako Pure Chemical Corporation) n-hexylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 2-(2-aminoethylamino)ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) Ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation) Texanol (manufactured by KH Neochem)

[0084] Silver particles were manufactured using the following procedure. When a larger quantity was required for evaluation, the necessary sample amount was prepared by increasing the number of trials using the same method.

[0085] Synthesis Example 1: Synthesis of Silver Particle 1 Silver particles 1 dispersed in a solvent were prepared by the following procedure. In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (0.05 g), N,N-diethyl-1,3-diaminopropane (3.3 g), and 1-butanol (7.5 g) were added and stirred for about 1 minute. Then, silver oxalate (5 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles 1. 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, and 15 g of 1-butanol 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 2500 rpm (centrifugal acceleration approximately 1110 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. The process of adding 15 g of 1-butanol, stirring, centrifugation, and removal of the supernatant was repeated twice to recover the silver particles. Next, using the resulting dispersion of silver particles (1-butanol solution), 2-methylpentanoic acid was added in an amount three times the mass of the silver particles, and the mixture was stirred at room temperature for 4 hours. After stirring, the magnetic stirring bar was removed, 15 g of isopropyl alcohol was added to the composition, and it was stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (Hitachi Koki CF7D2) at 2500 rpm (centrifugal acceleration approximately 1110 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. Next, the process of adding 15 g of texanol, stirring, centrifugation, and removal of the supernatant was repeated twice to recover silver particles 1. The obtained silver particles 1 were used in Example 1.

[0086] Synthesis Example 2: Synthesis of Silver Particle 2 Silver particles 2 dispersed in a solvent were prepared using the following procedure. In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (0.05 g), N,N-diethyl-1,3-diaminopropane (1.5 g), 2-(2-aminoethylamino)ethanol (1 g), ethylene glycol (2 g), and 1-butanol (5.5 g) were added and stirred for about 1 minute. Then, silver oxalate (5 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles 2. 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, and then stirred at 90°C for another 30 minutes. After cooling, the magnetic stirring bar was removed, and 15 g of 1-butanol was added to each composition and stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (Hitachi Koki CF7D2) at 2500 rpm (centrifugal acceleration approximately 1110 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. The process of adding 15 g of 1-butanol, stirring, centrifugation, and removing the supernatant was repeated twice to recover the silver particles. Next, using the obtained dispersion of silver particles (1-butanol solution), 2-methylpentanoic acid was added in an amount three times the mass of the silver particles, and the mixture was stirred at room temperature for 4 hours. After stirring, the magnetic stirring bar was removed, and 15 g of isopropyl alcohol was added to the composition and stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (Hitachi Koki CF7D2) at 2500 rpm (centrifugal acceleration approximately 1110 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. Next, the process of adding 15 g of texanol, stirring, centrifugation, and removing the supernatant was repeated twice to recover silver particles 2. The obtained silver particles 2 were used in Example 2.

[0087] Synthesis Example 3: Synthesis of Silver Particles 3 Silver particles 3 dispersed in a solvent were prepared by the following procedure. In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (0.05 g), N,N-diethyl-1,3-diaminopropane (3.3 g), and 1-butanol (7.5 g) were added and stirred for about 1 minute. Then, silver oxalate (5 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles 3. 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, and 15 g of n-propanol was added to each composition and stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (CF7D2, manufactured by Hitachi Koki) at 2500 rpm (centrifugal acceleration approximately 1110 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. The process of adding 15 g of n-propanol, stirring, centrifugation, and removal of the supernatant was repeated twice to recover the silver particles. Next, using the resulting dispersion of silver particles (n-propanol solution), octanoic acid was added in an amount three times the mass of the silver particles, and the mixture was stirred at room temperature for 4 hours. After stirring, the magnetic stirring bar was removed, 15 g of n-propanol was added to the composition, and it was stirred in a vortex mixer. Then, centrifugation was performed in a centrifuge (Hitachi Koki CF7D2) at 2500 rpm (centrifugal acceleration approximately 1110 × G) for 1 minute, and the supernatant was removed by tilting the centrifuge tube. Next, the process of adding 15 g of texanol, stirring, centrifugation, and removal of the supernatant was repeated twice to recover silver particles 3. The obtained silver particles 3 were used in Comparative Example 1.

[0088] Synthesis Example 4: Synthesis of 4 Silver Particles Silver particles 4 dispersed in a solvent were prepared by the following procedure. In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (0.05 g), N,N-diethyl-1,3-diaminopropane (1.5 g), 2-(2-aminoethylamino)ethanol (1 g), ethylene glycol (2 g), and 1-butanol (5.5 g) were added and stirred for about 1 minute. Then, silver oxalate (5 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles 4. 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, and then stirred at 90°C for another 30 minutes. After cooling, the magnetic stirring bar was removed, 15 g of n-propanol was added to each composition and stirred in a vortex mixer. Then, centrifugation was performed for 1 minute at 2500 rpm (centrifugal acceleration approximately 1110 × G) using a centrifuge (Hitachi Koki CF7D2), and the supernatant was removed by tilting the centrifuge tube. The process of adding 15 g of n-propanol, stirring, centrifugation, and removing the supernatant was repeated twice to recover the silver particles. Next, using the obtained dispersion of silver particles (n-propanol solution), octanoic acid was added in an amount three times the mass of the silver particles, and the mixture was stirred at room temperature for 4 hours. After stirring, the magnetic stirring bar was removed, 15 g of n-propanol was added to the composition and stirred in a vortex mixer. Then, centrifugation was performed for 1 minute at 2500 rpm (centrifugal acceleration approximately 1110 × G) using a centrifuge (Hitachi Koki CF7D2), and the supernatant was removed by tilting the centrifuge tube. Next, the process of adding 15 g of texanol, stirring, centrifugation, and removing the supernatant was repeated twice to recover the silver particles 4. The obtained silver particles 4 were used in Comparative Example 2.

[0089] Synthesis Example 5: Synthesis of Silver Particle 5 Silver particles 5 dispersed in a solvent were prepared by the following procedure. In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (0.05 g), N,N-diethyl-1,3-diaminopropane (3.3 g), and 1-butanol (7.5 g) were added and stirred for about 1 minute. Then, silver oxalate (5 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles 5. 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, and then at 90°C for another 30 minutes. After cooling, the magnetic stirring bar was removed, and 15 g of isopropyl alcohol 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 2500 rpm (centrifugal acceleration approximately 1110 × 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 removal of the supernatant was repeated twice to recover the silver particles. Next, using the resulting dispersion of silver particles (isopropyl alcohol solution), n-hexylamine was added in an amount equal to three times the mass of the silver particles, and the mixture was stirred at room temperature for 4 hours. After stirring, the magnetic stirring bar was removed, 15 g of isopropyl alcohol was added to the composition, and it was stirred with a vortex mixer. Then, centrifugation was performed for 1 minute at 2500 rpm (centrifugal acceleration approximately 1110 × G) using a centrifuge (Hitachi Koki CF7D2), and the supernatant was removed by tilting the centrifuge tube. Next, the process of adding 15 g of texanol, stirring, centrifugation, and removal of the supernatant was repeated twice to recover silver particles 5. The obtained silver particles 5 were used in Comparative Example 3.

[0090] Synthesis Example 6: Synthesis of Silver Particle 6 Silver particles 6 dispersed in a solvent were prepared by the following procedure. In a 50 mL glass centrifuge tube containing a magnetic stirring bar, ricinoleic acid (0.05 g), N,N-diethyl-1,3-diaminopropane (1.5 g), 2-(2-aminoethylamino)ethanol (1 g), ethylene glycol (2 g), and 1-butanol (5.5 g) were added and stirred for about 1 minute. Then, silver oxalate (5 g) was added and stirred for about 10 minutes to obtain a composition for preparing silver particles 6. 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, and then stirred at 90°C for another 30 minutes. After cooling, the magnetic stirring bar was removed, 15 g of isopropyl alcohol was added to each composition and stirred in a vortex mixer. Then, centrifugation was performed for 1 minute at 2500 rpm (centrifugal acceleration approximately 1110 × G) using a centrifuge (Hitachi Koki CF7D2), 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 the silver particles. Next, using the obtained dispersion of silver particles (isopropyl alcohol solution), n-hexylamine was added in an amount equal to three times the mass of the silver particles, and the mixture was stirred at room temperature for 4 hours. After stirring, the magnetic stirring bar was removed, 15 g of isopropyl alcohol was added to the composition and stirred in a vortex mixer, and then centrifugation was performed for 1 minute at 2500 rpm (centrifugal acceleration approximately 1110 × G) using a centrifuge (Hitachi Koki CF7D2), and the supernatant was removed by tilting the centrifuge tube. Next, the process of adding 15 g of texanol, stirring, centrifugation, and removing the supernatant was repeated twice to recover the silver particles 6. The obtained silver particles 6 were used in Comparative Example 4.

[0091] Observation using an electron microscope For each of the silver particles 1-6 obtained in each synthesis example, SEM images were acquired using a scanning electron microscope (SEM (JEOL JSM-IT500HR)).

[0092] <Measurement of Average Particle Diameter (Volume-Based Average Particle Diameter)> For each SEM image (width 1-20 μm) obtained in the <Observation by Electron Microscope> described above, the volume-based average particle diameter (primary particle diameter) of 200 randomly selected particles was measured using image analysis software (MacView (Mountec Co., Ltd.)). For the vertical direction of the SEM image, the range of width 1-20 μm was observed. The vertical direction of the SEM image was defined as the width containing 200 or more (usually around 200-300) silver particles within the 1-20 μm range. Note that the volume-based average particle diameter is a value measured assuming that the particles observed in the SEM image are spherical with that diameter. The results are shown in Table 1.

[0093] Manufacturing of conductive bonding materials (Examples 1 and 2, Comparative Examples 1-4) The solvent, Texanol, was added to achieve the compositions shown in Table 1, and the conductive bonding material was prepared to have a silver content of 85%. Mixing was performed using a Kurabo Mazelstar in a two-pass stirring priority mode. This yielded conductive bonding materials 1 to 6, which were used in the manufacture of sintered bodies.

[0094] Manufacturing of sintered bodies The conductive bonding materials 1 to 6 (silver particle dispersions) obtained in the examples and comparative examples were each pressure-sintered to produce sintered bodies. First, a substrate (silver-plated copper plate) was prepared. Next, the conductive bonding material was uniformly applied to the surface of each component to a coating thickness of 150 μm. By drying this at 100°C for 30 minutes, a laminate was obtained. Next, four copper plates (5mm x 5mm in size) with gold plating applied to their entire surface were placed on top of the dried coating. These were then covered with a PTFE sheet, and after covering both sides with metal, they were placed in a pressure bonding furnace. Next, under an atmospheric atmosphere, Example 1, Comparative Example 1, and Comparative Example 3 were pressurized and fired for 2 minutes at 200°C, 10 MPa and 220°C, 10 MPa, while Example 2, Comparative Example 2, and Comparative Example 4 were fired at 220°C, 10 MPa, for 2 minutes each. This caused each conductive adhesive to sinter between the substrate and the Cu plate, resulting in four laminates in which the substrate and Cu plate were joined via the sintered body.

[0095] Measurement of the mechanical strength (shear strength) of a sintered body For the laminates obtained in the manufacturing of the sintered body described above, a load was applied to the sintered body at room temperature using a bond tester (Nordson Dage4000PLUS) at a condition of 1 mm / s, and die shear tests were performed on each laminate to measure the maximum load at fracture. The shear strength value was obtained by dividing the maximum load obtained in this way by the bonding area. The measurement results are the average values ​​of four gold-plated Cu plates whose shear strength was measured. The measurement results of the shear strength are shown in Table 1.

[0096] <Determination of sinterability of sintered bodies> For the laminates after the shear strength test in the first phase, scanning electron microscope (SEM (JEOL JSM-IT500HR)) images (width 10-20 μm) were acquired. If 10 or more particles with a particle size of 1 μm or less were observed in the SEM image, it was marked as ×, indicating the presence of unsintered areas. If no particles with a particle size of 1 μm or less were observed, and an SEM image showing ductile fracture due to necking with the surrounding silver was obtained, it was marked as ○. The results are shown in Table 1.

[0097] <Determination of bonding area> For the chips that peeled off after the shear strength test in the previous period, the joints with the laminate were observed, and the joint area was estimated using a ruler. A circle (○) was marked if a silvery-white joint layer was formed over 20 mm² or more of the total 25 mm² area. A cross (×) was marked if the joint area was less than 20 mm², or if the joint area was not silvery-white (for example, showing the color of unsintered particles).

[0098] [Table 1]

[0099] As shown in Table 1, Example 1 exhibited a high shear strength of 75 MPa at a sintering temperature of 200°C. It also showed good sinterability, forming thick neckings and exhibiting a good bonding area to the copper plate. Example 2 also showed good sinterability and a wide bonding area to the copper plate interface. Therefore, as shown in Examples 1 and 2, it was confirmed that silver particles with the compound represented by general formula (1) attached possess the ability to sinter suitably under low-temperature and low-pressure conditions, regardless of particle size. On the other hand, Comparative Example 1 showed low strength at both 200°C and 220°C, and both Comparative Example 1 and Comparative Example 2 had unsintered portions and a small bonding area to the copper plate. Furthermore, in Comparative Example 3 and Comparative Example 4, areas with insufficient necking growth were observed, and the bonding rate to the interface was not good. From these results, as shown in Examples 1 and 2, conductive bonding materials containing silver particles with the compound represented by general formula (1) attached allow the protective layer to detach from the particle surface even at low temperatures, and sintering proceeds smoothly. On the other hand, when the compound used in the comparative example was applied as a protective layer, it is presumed that the protective layer did not detach sufficiently under low temperature and low pressure conditions, resulting in a lack of strong bonding.

Claims

1. A conductive bonding material comprising silver particles, wherein a compound represented by the following general formula (1) is attached to the surface of the silver particles, and a solvent, for bonding a chip to a metal substrate, or a heat sink to a metal substrate under pressure. 【Chemistry 1】 [In general formula (1), R １ R is an alkyl group having 2 to 3 carbon atoms. ２ R is an alkyl group having 1 to 4 carbon atoms. ３ [This is either a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.]

2. The conductive bonding material according to claim 1, wherein the average particle diameter of the silver particles is 60 to 600 nm.

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