Binding conductor paste

Abstract

Provided is a binding conductor paste that has excellent stability during continuous discharge and excellent stability in storage, and can suppress the production of voids during sintered compact molding.　This binding conductor paste includes: metal nanoparticles (A) that have an average grain diameter of at least 1 nm and less than 100 nm; and a dispersion medium containing an organic solvent (a), an organic solvent (b), and an organic solvent (c). The metal nanoparticles (A) are surface-coated with an organic protective agent that includes an amine and are dispersed in the dispersion medium. The organic solvents (a)–(c) are mutually differing compounds and satisfy formulas (1)–(6). (1) 150°C ≤ Ta ≤ 250°C (2) 150°C ≤ Tb ≤ 250°C (3) 250°C ≤ Tc ≤ 350°C (4) δa ≥ 10.0 (5) δc ≤ 9.0 (6) δc ≤ δb ≤ δa (In the formulas, Ta–Tc represent the boiling points of the respective organic solvents (a)–(c), and δa–δc represent the Hansen solubility parameters of the respective organic solvents (a)–(c).)

Description

Bonding Conductive Paste

[0001] The present disclosure relates to a bonding conductor paste for connecting electronic elements, for example, for forming sintered bodies such as conductor wiring and bonded structures. More specifically, the present disclosure relates to a bonding conductor paste used for forming conductor wiring and bonded structures for connecting electronic elements such as power semiconductor elements and LED elements. This application claims priority to Japanese Patent Application No. 2021-194501, filed in Japan on November 30, 2021, the contents of which are incorporated herein by reference.

[0002] When mounting electronic elements such as power semiconductor elements and LED elements, it is necessary to bond multiple materials with high strength, and for this purpose, conductor wiring, bonding structures, or wiring boards equipped with these are used.

[0003] As a method for forming the conductor wiring, for example, a method is known in which a conductor paste containing conductive particles and an organic solvent is applied onto an insulating substrate by a printing method, and then sintered to produce the conductor wiring.

[0004] For example, Patent Document 1 discloses a bonding conductor paste containing conductive particles and a specific ether-based solvent, and describes that the use of the bonding conductor paste enables uniform printing and the formation of high-precision conductor wiring and bonding structures that can connect a substrate and an electronic element with high bonding strength.

[0005] Patent Document 2 discloses a bonding material made of a silver paste containing silver particles, a solvent, and an additive, which contains a first solvent made of a diol and a second solvent made of a polar solvent having a lower surface tension than the first solvent, and the additive is a triol. It is described that this bonding material can prevent bubbles from being trapped during the formation of a coating film, even if the coating film is made thick, and can prevent voids from being generated in the silver bonding layer.

[0006] Patent Document 3 discloses a paste-like metal particle composition containing specific metal particles and two volatile dispersion media with different dielectric constants, the two volatile dispersion media being in a mixing ratio such that they are not completely miscible at room temperature, and states that this composition can suppress sedimentation of the metal particles.

[0007] JP 2020-194786 A JP 2017-201057 A International Publication No. 2008 / 062548

[0008] However, when a conductive paste using an ether-based solvent is applied using a dispenser, the solvent tends to float up inside the syringe, which causes a problem that when such a conductive paste is continuously dispensed using a dispenser, the weight of the dispensed paste is difficult to stabilize.

[0009] Furthermore, conductive pastes using two or more solvents tend to have poor storage stability, with the metal particles and solvent easily separating after storage (especially after storage at low temperatures), and the ejection stability after storage tends to be poor.

[0010] To improve the discharge stability of the conductive paste, it is possible to use a highly polar solvent instead of a low-polarity solvent such as ether. However, conductive pastes using highly polar solvents tend to produce voids when sintered, resulting in poor bonding strength.

[0011] Therefore, an object of the present disclosure is to provide a bondable conductor paste that is excellent in stability during continuous discharge and storage stability, and that can suppress the occurrence of voids during the formation of a sintered body.

[0012] The inventors of the present disclosure conducted extensive research to solve the above problems and found that a bondable conductor paste containing specific metal nanoparticles and a dispersant containing three specific organic solvents has excellent stability during continuous discharge and storage stability, and can suppress the generation of voids during the formation of a sintered body. The present disclosure relates to a product completed based on these findings.

[0013] That is, the present disclosure provides a bondable conductor paste comprising metal nanoparticles (A) having an average particle size of 1 nm or more but less than 100 nm, and a dispersion medium containing organic solvents (a), (b), and (c), wherein the metal nanoparticles (A) are surface-coated with an organic protective agent containing an amine and dispersed in the dispersion medium, and the organic solvents (a), (b), and (c) are different compounds, and the paste satisfies the following formulas (1) to (6): 150°C≦Ta≦250°C (1) 150°C≦Tb≦250°C (2) 250°C≦Tc≦350°C (3) δa≧10 (4) δc≦9 (5) δc≦δb≦δa (6) [where Ta to Tc respectively represent the boiling points of the organic solvents (a) to (c), and δa to δc respectively represent the Hansen solubility parameters of the organic solvents (a) to (c)]. ]

[0014] The bonding conductive paste preferably contains spherical metal particles (B) having an average particle size of 0.5 to 1 μm and flat metal flakes (C) having an average particle size of 1 to 10 μm.

[0015] The total content of the metal nanoparticles (A), spherical metal particles (B), and flat metal flakes (C) in the above-mentioned bondable conductor paste is preferably 80 to 99.5% by mass.

[0016] The content of the metal nanoparticles (A) in all the metal particles contained in the bondable conductor paste is preferably 50 mass % or less.

[0017] The organic protective agent preferably contains, as the amine, an aliphatic hydrocarbon monoamine (1) comprising an aliphatic hydrocarbon group and one amino group, the total number of carbon atoms in the aliphatic hydrocarbon group being 6 or more, and further contains at least one of an aliphatic hydrocarbon monoamine (2) comprising an aliphatic hydrocarbon group and one amino group, the total number of carbon atoms in the aliphatic hydrocarbon group being 5 or less, and an aliphatic hydrocarbon diamine (3) comprising an aliphatic hydrocarbon group and two amino groups, the total number of carbon atoms in the aliphatic hydrocarbon group being 8 or less.

[0018] The bonding conductive paste preferably contains an organic solvent other than the organic solvent (a), the organic solvent (b), and the organic solvent (c).

[0019] It is preferred that the organic solvents (a), (b), and (c) are homogeneously dissolved at room temperature and do not undergo phase separation.

[0020] The bonding conductor paste of the present disclosure has excellent stability during continuous dispensing and storage stability, and can suppress the generation of voids during the formation of a sintered body. Therefore, the bonding conductor paste can be stably and continuously dispensed using a dispenser. Furthermore, because voids are less likely to occur, it is possible to produce sintered bodies such as conductor wiring and bonded structures with high bonding strength, and wiring boards including these.

[0021] 1 shows an SAT image of the surface of a sintered body after measuring the die shear strength of the sample produced in Example 1. FIG. 2 shows an SAT image of the surface of a sintered body after measuring the die shear strength of the sample produced in Comparative Example 5. FIG. 3 shows an SAT image of the surface of a sintered body after measuring the die shear strength of the sample produced in Comparative Example 7. FIG. 4 shows an SEM image of the sintered body in the cross section of the sample produced in Example 1. FIG. 5 shows an SEM image of the sintered body in the cross section of the sample produced in Comparative Example 5. FIG. 6 shows an SEM image of the sintered body in the cross section of the sample produced in Comparative Example 7.

[0022] [Bondable Conductor Paste] The bondable conductor paste of the present disclosure is a paste-like composition that can form a conductor and bond components together using the conductor. The bondable conductor paste is a bondable conductor paste for forming, for example, a sintered body (e.g., conductor wiring, bonded structure) for connecting electronic elements.

[0023] The bonding conductor paste contains at least metal nanoparticles (A) having an average particle size of 1 nm or more and less than 100 nm, and a dispersion medium containing organic solvents (a), (b), and (c). In the bonding conductor paste, the metal nanoparticles (A) are dispersed in the dispersion medium.

[0024] (Dispersion Medium) The dispersion medium contains at least an organic solvent (a), an organic solvent (b), and an organic solvent (c). The organic solvents (a), (b), and (c) are different compounds and satisfy the following formulas (1) to (6). Only one type of organic solvent (a), organic solvent (b), and organic solvent (c) may be used, or two or more types may be used. 150°C≦Ta≦250°C (1) 150°C≦Tb≦250°C (2) 250°C≦Tc≦350°C (3) δa≧10.0 (4) δc≦9.0 (5) δc≦δb≦δa (6)

[0025] In the formula, Ta to Tc respectively represent the boiling points of the organic solvents (a) to (c), and δa to δc respectively represent the Hansen solubility parameters of the organic solvents (a) to (c). In this specification, the Hansen solubility parameter is sometimes referred to as the "SP value" and abbreviated as "δ".

[0026] The organic solvents (a) to (c) may be any solvents that dissolve uniformly and become liquid when mixed in the compounding ratio used in the above-mentioned bondable conductor paste, and each of them may be liquid or solid at room temperature.

[0027] The organic solvent (a) at least satisfies formula (1). That is, the boiling point Ta of the organic solvent (a) satisfies 150° C.≦Ta≦250° C., preferably 150° C.<Ta<250° C., more preferably 155° C.≦Ta≦220° C., and even more preferably 160° C.≦Ta≦200° C. By using an organic solvent (a) having a boiling point within the above range, the dispersion medium is easily volatilized during sintering, and a sintered body can be easily formed.

[0028] The organic solvent (a) at least satisfies the formula (4) [δa≧10.0]. The SP value δa of the organic solvent (a) is 10.0 or more, preferably 10.3 or more, more preferably 10.4 or more, within the range satisfying the formula (6). When the δa is 10.0 or more, the dispersibility of the metal nanoparticles (A) is excellent, and separation between the metal particles and the dispersion medium can be made less likely to occur. The δa of the organic solvent (a) is, for example, 16.0 or less, and may be 15.0 or less.

[0029] Examples of the organic solvent (a) include alcohol solvents, urea-based solvents, and aprotic polar solvents. Examples of the alcohol solvent include compounds having one or more hydroxy groups, and among these, tertiary alcohols and ether alcohols are preferred. The alcohol solvent may have two or more hydroxy groups. Examples of the ether alcohol include compounds having an ether bond and a hydroxy group, such as (poly)alkylene glycol monoalkyl ethers and alkoxy-substituted alcohols.

[0030] Specific examples of the organic solvent (a) include pinacol (δ 10.7, boiling point 172°C), tetramethylurea (δ 10.6, boiling point 177°C), 3-methoxybutanol (δ 10.6, boiling point 161°C), 1-methylcyclohexanol (δ 10.4, boiling point 155°C), and methyl carbitol (diethylene glycol monomethyl ether) (δ 10.7, boiling point 193°C).

[0031] The organic solvent (b) at least satisfies formula (2). That is, the boiling point Tb of the organic solvent (b) satisfies 150°C ≦ Tb ≦ 250°C, preferably 150°C < Tb < 250°C, more preferably 180°C ≦ Tb ≦ 248°C, and even more preferably 200°C ≦ Tb ≦ 245°C. By using an organic solvent (b) having a boiling point within the above range, the dispersion medium is easily volatilized during sintering, making it easy to form a sintered body. Furthermore, by using an organic solvent (b) having a boiling point of 250°C or less, it is possible to suppress the generation of voids during sintering.

[0032] The organic solvent (b) at least satisfies formula (6). The SP value δb of the organic solvent (b) is preferably 8.0 to 12.0, more preferably 8.5 to 11.0, and even more preferably 9.0 to 10.5, within the range satisfying formula (6). When the δb is within the above range, the compatibility of the organic solvent (a) and the organic solvent (c) is improved, they are less likely to separate, and the continuous ejection stability and storage stability tend to be more excellent.

[0033] Examples of the organic solvent (b) include alcohol solvents, ester solvents, ketone solvents, and amine-based solvents. Examples of the alcohol solvent include solvent compounds having one or more hydroxy groups, and among these, tertiary alcohols, ether alcohols, and ester alcohols are preferred. Ether alcohols are compounds having an ether bond and a hydroxy group, such as (poly)alkylene glycol monoalkyl ethers and alkoxy group-substituted alcohols. Ester alcohols are compounds having an ester bond and a hydroxy group, such as (poly)alkylene glycol monoalkyl ether monoesters. Examples of ester solvents include diacetates of diols such as (poly)alkylene glycols. Preferred ketone solvents are cyclic ketones. Preferred amine-based solvents are alkylamines.

[0034] The organic solvent (b) is selected on the premise that it satisfies the formula (6) in relation to the organic solvents (a) and (c). Specific examples of the organic solvent (b) include d-camphor (δ 10.4, boiling point 204°C), 1-heptanol (δ 10.0, boiling point 177°C), butyl carbitol (diethylene glycol monobutyl ether) (δ 10.2, boiling point 231°C), ethyl carbitol (diethylene glycol monoethyl ether) (δ 10.5, boiling point 196°C), tripropylene glycol monomethyl ether (δ 9.4, boiling point 243°C), α-terpineol (δ 9 .3, boiling point 220°C), dihydroterpineol (δ 9.0, boiling point 210°C), 1,3-butanediol diacetate (δ 9.2, boiling point 232°C), propylene glycol diacetate (δ 9.3, boiling point 190°C), butyl carbitol acetate (δ 9.0, boiling point 247°C), dipropylene glycol butyl ether (δ 9.2, boiling point 230°C), isophorone (δ 9.5, boiling point 213°C), 1-decanol (δ 9.6, boiling point 230°C), propylene glycol monobutyl ether (δ 9.0, boiling point 170°C), 1-nonanol (δ 9.8, boiling point 214°C), etc. may be used.

[0035] The boiling point Tb of the organic solvent (b) is preferably higher than the boiling point Ta of the organic solvent (a), i.e., Tb > Ta. The temperature difference between Tb and Ta [Tb - Ta] is preferably 2°C or more, more preferably 5°C or more, and even more preferably 10°C or more. When the temperature difference is 2°C or more, the generation of voids during sintering can be further suppressed.

[0036] The organic solvent (c) at least satisfies formula (3). That is, the boiling point Tc of the organic solvent (c) satisfies 250°C ≦ Tc ≦ 350°C, preferably 250°C < Tc < 350°C, more preferably 250°C < Tc ≦ 320°C, and even more preferably 250°C < Tc ≦ 300°C. By using an organic solvent (c) having a boiling point within the above range, rapid evaporation of the organic solvents (a) and (b) during sintering can be suppressed, and the generation of voids can be suppressed.

[0037] The organic solvent (c) at least satisfies formula (5) [δc≦9.0]. The SP value δc of the organic solvent (c) is 9.0 or less, preferably 8.7 or less, and more preferably 8.5 or less. By making the δ 9.0 or less, it is possible to suppress the generation of voids during sintering. The δc of the organic solvent (c) is, for example, 6.0 or more, and may be 7.0 or more.

[0038] Examples of the organic solvent (c) include ether solvents, alkane solvents, and ester solvents. Examples of the ether solvent include (poly)alkylene glycol dialkyl ethers. Examples of the alkane solvent include alkanes having 14 or more carbon atoms (e.g., 14 to 20 carbon atoms). Examples of the ester solvent include esters of (poly)alkylene glycol alkyl ethers and fatty acids.

[0039] Specific examples of the organic solvent (c) include dibutyl carbitol (diethylene glycol dibutyl ether) (δ 8.3, boiling point 255°C), tetradecane (δ 7.9, boiling point 254°C), and hexadecane (δ 8.0, boiling point 287°C).

[0040] The boiling point Tc of the organic solvent (c) is preferably higher than the boiling point Tb of the organic solvent (b), i.e., Tc > Tb. The temperature difference between Tc and Tb [Tc - Tb] is preferably 2°C or more, more preferably 6°C or more, and even more preferably 10°C or more. When the temperature difference is 2°C or more, the generation of voids during sintering can be further suppressed.

[0041] The boiling point Tc of the organic solvent (c) is preferably higher than the boiling point Ta of the organic solvent (a), i.e., Tc > Ta. The temperature difference between Tc and Ta [Tc - Ta] is preferably 30°C or more, more preferably 50°C or more, and even more preferably 60°C or more. When the temperature difference is 30°C or more, the generation of voids during sintering can be further suppressed.

[0042] The SP value δa of organic solvent (a), the SP value δb of organic solvent (b), and the SP value δc of organic solvent (c) satisfy the relationship of the above formula (6) [δc≦δb≦δa]. In particular, it is preferable that δb is higher than δc, i.e., δc<δb is satisfied. It is also preferable that δa is higher than δb, i.e., δb<δa is satisfied.

[0043] The difference between δb and δc [δb - δc] is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.5 or more. When the difference is 0.1 or more, the dispersibility of the metal particles is superior and the continuous ejection stability is superior. The difference is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. When the difference is 2.0 or less, the metal particles and the dispersion medium are less likely to separate, and the continuous ejection stability and storage stability are superior.

[0044] The difference between δa and δb [δa - δb] is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.5 or more. When the difference is 0.1 or more, the dispersibility of the metal particles is superior and the continuous ejection stability is superior. The difference is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. When the difference is 2.5 or less, the metal particles and the dispersion medium are less likely to separate, and the continuous ejection stability and storage stability are superior.

[0045] The difference between δa and δc [δa - δc] is 1.0 or more, preferably 1.5 or more, and more preferably 2.0 or more, based on formulas (4) and (5). When the difference is 1.0 or more, the generation of voids during sintering can be further suppressed. The difference is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. When the difference is 5.0 or less, the metal particles and the dispersion medium are less likely to separate, resulting in better continuous ejection stability and storage stability.

[0046] The ratio of organic solvent (a) to the total amount of organic solvent (a), organic solvent (b), and organic solvent (c) (100% by mass) [organic solvent (a) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 15 to 50% by mass. When the ratio is within the above range, the dispersion medium is easily volatilized during sintering, a sintered body can be easily formed, and the dispersibility of metal particles is superior.

[0047] The ratio of organic solvent (b) to the total amount of organic solvent (a), organic solvent (b), and organic solvent (c) (100% by mass) [organic solvent (b) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 15 to 50% by mass. When the ratio is within the above range, the compatibility of the organic solvents is excellent, and the continuous ejection stability and storage stability are further improved.

[0048] The proportion of organic solvent (c) relative to 100% by mass of the total of organic solvents (a), (b), and (c) [organic solvent (c) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 15 to 50% by mass. When the proportion is within the above range, the generation of voids during sintering can be further suppressed.

[0049] The content of organic solvent (c) relative to 100 parts by mass of organic solvent (a) is preferably 20 to 400 parts by mass, more preferably 30 to 300 parts by mass, and even more preferably 50 to 200 parts by mass. When the content is within the above range, the blending amounts of organic solvent (a) and organic solvent (c) are well balanced, and void suppression during sintering and dispersibility of metal particles are improved.

[0050] The content of organic solvent (b) relative to 100 parts by mass of the total amount of organic solvent (a) and organic solvent (c) is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 40 to 100 parts by mass. When the content is within the above range, the compatibility between organic solvent (a) and organic solvent (c) is further improved, and continuous ejection stability and low-temperature storage stability are further improved.

[0051] The dispersion medium may contain other solvents (organic solvents) in addition to organic solvents (a), (b), and (c). The total content of organic solvents (a), (b), and (c) in the dispersion medium is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, relative to 100% by mass of the total amount of the dispersion medium. When the content is 50% by mass or more, the dispersibility of metal particles and the compatibility of each organic solvent are excellent, and continuous discharge stability, storage stability, and void formation suppression during sintering are excellent.

[0052] When the organic solvents (a), (b), and (c) are mixed in the blending ratio used for the above-mentioned bondable conductive paste, it is preferable that the organic solvents (a), (b), and (c) dissolve uniformly at room temperature and do not undergo phase separation. Furthermore, it is preferable that the organic solvents (a), (b), and (c) dissolve uniformly at room temperature and do not undergo phase separation in the above-mentioned bondable conductive paste. It is particularly preferable that no phase separation occurs at 22 to 28°C (preferably 10 to 30°C, more preferably 0 to 35°C).

[0053] (Metal Nanoparticles (A)) The metal nanoparticles (A) have a configuration in which the surfaces of the metal nanoparticles are coated with an organic protective agent containing an amine, more specifically, a configuration in which unshared electron pairs of the amine are electrically coordinated on the surfaces of the metal nanoparticles. By having this configuration, the metal nanoparticles (A) are prevented from re-aggregating with each other, and can stably maintain a highly dispersed state in the bondable conductor paste. Only one type of metal nanoparticle (A) may be used, or two or more types may be used.

[0054] The average particle diameter of the metal nanoparticles (A) is 1 nm or more but less than 100 nm, preferably 2 to 80 nm, more preferably 5 to 70 nm, and even more preferably 10 to 60 nm. The average particle diameter is the size excluding the protective agent coating the surface (i.e., the size of the metal nanoparticles themselves). The average particle diameter is determined as the average particle diameter (median diameter) converted into a volume distribution based on particle diameters determined by transmission electron microscope (TEM) observation, assuming an aspect ratio of 1. When two or more types of metal nanoparticles (A) are contained, the average particle diameter refers to the average particle diameter of all metal nanoparticles (A).

[0055] Examples of metals constituting the metal nanoparticles (A) include conductive metals, such as gold, silver, copper, nickel, aluminum, rhodium, cobalt, ruthenium, platinum, palladium, chromium, indium, etc. Among these, silver particles (i.e., silver nanoparticles) are preferred as the metal nanoparticles, since they can be fused to each other at a temperature of about 100°C and can form connecting members for electronic components and the like that have conductivity even on general-purpose plastic substrates with low heat resistance.

[0056] The metal nanoparticles (A) are surface-modified metal nanoparticles whose surfaces are coated with an organic protective agent containing an amine. The amine may be used alone or in combination with two or more other amines. The organic protective agent may also contain a compound other than the amine.

[0057] The amine is a compound in which at least one hydrogen atom of ammonia is substituted with a hydrocarbon group, and includes primary amines, secondary amines, and tertiary amines. The amine may be a monoamine or a polyamine such as a diamine.

[0058] Among the amines, those represented by the following formula (a-1), in which R １ , R ２ , R ３ are the same or different and are each a hydrogen atom or a monovalent hydrocarbon group (R １ , R ２ , R ３ and R are both hydrogen atoms), and a monoamine (1) having a total carbon number of 6 or more, represented by the following formula (a-1), １ , R ２ , R ３ are the same or different and are each a hydrogen atom or a monovalent hydrocarbon group (R １ , R ２ , R ３ and R are both hydrogen atoms), and a monoamine (2) having a total carbon number of 5 or less, and a monoamine represented by the following formula (a-2), ８ is a divalent hydrocarbon group, and R ４ ~R ７ are the same or different and are a hydrogen atom or a monovalent hydrocarbon group, and preferably contain at least one selected from diamines (3) having a total carbon number of 8 or less, and particularly preferably contain a combination of monoamine (1) and monoamine (2) and / or diamine (3).

[0059] Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Among these, an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are preferred, and an aliphatic hydrocarbon group is particularly preferred. Therefore, as the monoamine (1), monoamine (2), and diamine (3), an aliphatic monoamine (1), an aliphatic monoamine (2), and an aliphatic diamine (3) are preferred.

[0060] Examples of monovalent aliphatic hydrocarbon groups include alkyl groups and alkenyl groups. Examples of monovalent alicyclic hydrocarbon groups include cycloalkyl groups and cycloalkenyl groups. Examples of divalent aliphatic hydrocarbon groups include alkylene groups and alkenylene groups. Examples of divalent alicyclic hydrocarbon groups include cycloalkylene groups and cycloalkenylene groups.

[0061] R １ , R ２ , R ３ Examples of the monovalent hydrocarbon group in include alkyl groups having about 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, decyl, dodecyl, tetradecyl, and octadecyl; alkenyl groups having about 2 to 20 carbon atoms, such as vinyl, allyl, methallyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, and 5-hexenyl; cycloalkyl groups having about 3 to 20 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclooctyl; and cycloalkenyl groups having about 3 to 20 carbon atoms, such as cyclopentenyl and cyclohexenyl.

[0062] R ４ ~R ７ Examples of the monovalent hydrocarbon group in １ , R ２ , R ３ Among the examples of the monovalent hydrocarbon group in the above, those having 7 or less carbon atoms can be mentioned.

[0063] R ８Examples of the divalent hydrocarbon group in the formula (I) include alkylene groups having 1 to 8 carbon atoms, such as methylene, methylmethylene, dimethylmethylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, and heptamethylene; and alkenylene groups having 2 to 8 carbon atoms, such as vinylene, propenylene, 1-butenylene, 2-butenylene, butadienylene, pentenylene, hexenylene, heptenylene, and octenylene.

[0064] The above R １ ~R ８ The hydrocarbon group in the formula (I) may be substituted with various substituents [e.g., halogen atoms, oxo groups, hydroxy groups, substituted oxy groups (e.g., C １−４ Alkoxy group, C ６−１０ Aryloxy group, C ７−１６ Aralkyloxy group, C １−４ acyloxy group, etc.), carboxy group, substituted oxycarbonyl group (e.g., C １−４ Alkoxycarbonyl group, C ６−１０ Aryloxycarbonyl group, C ７−１６ The hydroxyl group and carboxyl group may be protected with a protecting group commonly used in the field of organic synthesis.

[0065] Monoamine (1) is a compound having the function of imparting high dispersibility to metal nanoparticles, and examples thereof include primary amines having a linear alkyl group such as hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, and octadecylamine; primary amines having a branched alkyl group such as isohexylamine, 2-ethylhexylamine, and tert-octylamine; primary amines having a cycloalkyl group such as cyclohexylamine; primary amines having an alkenyl group such as oleylamine; and N,N-dipropylamine. secondary amines having a straight-chain alkyl group such as N,N-dibutylamine, N,N-dipentylamine, N,N-dihexylamine, N,N-dipeptylamine, N,N-dioctylamine, N,N-dinonylamine, N,N-didecylamine, N,N-diundecylamine, N,N-didodecylamine, and N-propyl-N-butylamine; secondary amines having a branched-chain alkyl group such as N,N-diisohexylamine and N,N-di(2-ethylhexyl)amine; tertiary amines having a straight-chain alkyl group such as tributylamine and trihexylamine; and tertiary amines having a branched-chain alkyl group such as triisohexylamine and tri(2-ethylhexyl)amine.

[0066] Among the monoamines (1), amines having a linear alkyl group with a total of 6 or more carbon atoms (particularly primary amines) are preferred because they can ensure a greater distance between metal nanoparticles when the amino group is adsorbed onto the surface of the metal nanoparticle, thereby improving the effect of preventing aggregation of the metal nanoparticles. Furthermore, in terms of ease of availability and ease of removal during sintering, the upper limit of the total carbon number in the monoamine (1) is preferably about 18, more preferably 16, and particularly preferably 12. Particularly preferred examples of the monoamine (1) include hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, and dodecylamine.

[0067] Furthermore, among monoamines (1), amines having a branched alkyl group (particularly primary amines) can impart high dispersibility to metal nanoparticles with a smaller amount due to the steric factor of the branched alkyl group compared to amines having a linear alkyl group with the same total number of carbon atoms. Therefore, the amine can be efficiently removed during sintering, especially at low temperatures, and sintered bodies with better conductivity can be obtained, which is preferable.

[0068] As the amine having a branched alkyl group, particularly preferred are amines having a branched alkyl group with a total of 6 to 16 (preferably 6 to 10) carbon atoms, such as isohexylamine and 2-ethylhexylamine, and from the viewpoint of steric factors, amines having a branched alkyl group with a structure in which it branches at the second carbon atom from the nitrogen atom, such as 2-ethylhexylamine, are particularly effective.

[0069] Among them, the monoamine (1) preferably includes an aliphatic hydrocarbon monoamine which comprises an aliphatic hydrocarbon group and one amino group, and the total number of carbon atoms in the aliphatic hydrocarbon group is 6 or more.

[0070] Monoamine (2) has a shorter hydrocarbon chain than monoamine (1), and therefore is thought to have a low ability to impart high dispersibility to silver nanoparticles, but it is more polar than monoamine (1) and has a higher coordination ability to metal atoms, and therefore is thought to have a complex formation promoting effect. Furthermore, because the hydrocarbon chain is short, it can be removed from the surface of metal nanoparticles in a short time (for example, 30 minutes or less, preferably 20 minutes or less) even during low-temperature sintering, and a sintered body with excellent conductivity can be obtained.

[0071] Examples of the monoamine (2) include primary amines having a total of 2 to 5 carbon atoms and having a linear or branched alkyl group, such as ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, and tert-pentylamine; and secondary amines having a total of 2 to 5 carbon atoms and having a linear or branched alkyl group, such as N-methyl-N-propylamine, N-ethyl-N-propylamine, N,N-dimethylamine, and N,N-diethylamine.

[0072] As the monoamine (2), preferred are primary amines having a total of 2 to 5 carbon atoms (preferably 4 to 5 carbon atoms) and having a linear or branched alkyl group, such as n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, and tert-pentylamine, and particularly preferred are primary amines having a total of 2 to 5 carbon atoms (preferably 4 to 5 carbon atoms) and having a linear alkyl group, such as n-butylamine.

[0073] Among these, the monoamine (2) is preferably an aliphatic hydrocarbon monoamine (2) which comprises an aliphatic hydrocarbon group and one amino group and in which the total number of carbon atoms in the aliphatic hydrocarbon group is 5 or less.

[0074] Diamine (3) has a total carbon number of 8 or less (e.g., 1 to 8). Its polarity is higher than that of monoamine (1), and its coordination ability to metal atoms is enhanced. Therefore, it is believed to have a complex formation promoting effect. Furthermore, diamine (3) promotes thermal decomposition at lower temperatures and in shorter times during the thermal decomposition process of the complex. Therefore, the use of diamine (3) allows for more efficient production of metal nanoparticles. Furthermore, surface-modified metal nanoparticles coated with a protective agent containing diamine (3) exhibit excellent dispersion stability in dispersion media containing highly polar solvents. Furthermore, because diamine (3) has a short hydrocarbon chain, it can be removed from the surface of metal nanoparticles in a short time (e.g., 30 minutes or less, preferably 20 minutes or less) even during low-temperature sintering, resulting in sintered bodies with excellent conductivity.

[0075] Examples of the diamine (3) include ethylenediamine, 1,3-propanediamine, 2,2-dimethyl-1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, and 1,5-diamino-2-methylpentane, which are represented by R in formula (a-2). ４ ~R ７ is a hydrogen atom, and R ８ is a linear or branched alkylene group; diamines in which R in formula (a-2) such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyl-1,3-propanediamine, N,N'-diethyl-1,3-propanediamine, N,N'-dimethyl-1,4-butanediamine, N,N'-diethyl-1,4-butanediamine, and N,N'-dimethyl-1,6-hexanediamine ４ , R ６ are the same or different and are linear or branched alkyl groups; R ５ , R ７ is a hydrogen atom, and R ８ is a linear or branched alkylene group; diamines in which R in formula (a-2) such as N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dimethyl-1,4-butanediamine, N,N-diethyl-1,4-butanediamine, and N,N-dimethyl-1,6-hexanediamine ４ , R ５ are the same or different and are linear or branched alkyl groups, and R ６ , R ７ is a hydrogen atom, and R ８ is a linear or branched alkylene group.

[0076] Among these, R in formula (a-2) ４ , R ５ are the same or different and are linear or branched alkyl groups, and R ６ , R ７ is a hydrogen atom, and R ８is a linear or branched alkylene group [particularly, R ４ , R ５ is a linear alkyl group, and R ６ , R ７ is a hydrogen atom, and R ８ is a linear alkylene group] is preferred.

[0077] R in formula (a-2) ４ , R ５ are the same or different and are linear or branched alkyl groups, and R ６ , R ７ In diamines in which R is a hydrogen atom, i.e., diamines having a primary amino group and a tertiary amino group, the primary amino group has a high coordination ability with metal atoms, but the tertiary amino group has a poor coordination ability with metal atoms, so the complex formed is prevented from becoming overly complex, and therefore, in the thermal decomposition step of the complex, thermal decomposition can be performed at a lower temperature and in a shorter time. Among these, diamines having a total carbon number of 6 or less (e.g., 1 to 6) are preferred, and diamines having a total carbon number of 5 or less (e.g., 1 to 5) are more preferred, because they can be removed from the surface of metal nanoparticles in a short time during low-temperature sintering.

[0078] Among these, the diamine (3) is preferably an aliphatic hydrocarbon diamine (3) which comprises an aliphatic hydrocarbon group and two amino groups and in which the total number of carbon atoms in the aliphatic hydrocarbon group is 8 or less.

[0079] When the amines contain a monoamine (1) in combination with a monoamine (2) and / or a diamine (3), the proportions of these amines are not particularly limited, but are preferably within the following ranges based on the total amount of amines [monoamine (1) + monoamine (2) + diamine (3); 100 mol %]: Monoamine (1) content: for example, 5 to 65 mol % (the lower limit is preferably 10 mol %, more preferably 15 mol %, and the upper limit is preferably 50 mol %, more preferably 40 mol %, and even more preferably 35 mol %); Monoamine (2) and diamine (3) total content: for example, 35 to 95 mol % (the lower limit is preferably 50 mol %, more preferably 60 mol %, and even more preferably 65 mol %, and the upper limit is preferably 90 mol %, more preferably 85 mol %).

[0080] Furthermore, when monoamine (2) and diamine (3) are used together, the contents of monoamine (2) and diamine (3) are preferably within the following ranges based on the total amount of amines [monoamine (1) + monoamine (2) + diamine (3); 100 mol %]: Monoamine (2): For example, 5 to 70 mol % (the lower limit is preferably 10 mol %, more preferably 15 mol %, and the upper limit is preferably 65 mol %, more preferably 60 mol %) Diamine (3): For example, 5 to 50 mol % (the lower limit is preferably 10 mol %, and the upper limit is preferably 45 mol %, more preferably 40 mol %)

[0081] When the content of monoamine (1) is equal to or greater than the lower limit, the dispersion stability of the metal nanoparticles is excellent, whereas when the content is equal to or less than the upper limit, the amine tends to be easily removed by low-temperature sintering.

[0082] When the content of the monoamine (2) is within the above range, the complex formation promoting effect is easily obtained, sintering at a low temperature in a short time is possible, and further, the diamine (3) is easily removed from the surface of the metal nanoparticles during sintering.

[0083] When the content of diamine (3) is within the above range, the effect of promoting complex formation and the effect of promoting thermal decomposition of the complex are easily obtained. Furthermore, the surface-modified metal nanoparticles coated with a protective agent containing diamine (3) exhibit excellent dispersion stability in a dispersion medium containing a highly polar solvent.

[0084] In the above-mentioned bondable conductor paste, when monoamine (2) and / or diamine (3) having high coordination ability to metal atoms are used, the amount of monoamine (1) used can be reduced depending on the ratio of their use. In the case of sintering at low temperatures for a short time, these amines are easily removed from the surface of the metal nanoparticles, and the sintering of the metal nanoparticles can be sufficiently progressed.

[0085] The amine used as the organic protective agent may contain amines other than monoamine (1), monoamine (2), and diamine (3). The total content of monoamine (1), monoamine (2), and diamine (3) in the total amines contained in the organic protective agent is, for example, preferably 60% by mass or more (e.g., 60 to 100% by mass), more preferably 80% by mass or more, and even more preferably 90% by mass or more. That is, the content of the other amines is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0086] The amount of the amines [particularly, monoamine (1) + monoamine (2) + diamine (3)] used is not particularly limited, but is preferably about 1 to 50 moles per mole of metal atom of the metal compound that is the raw material for the metal nanoparticles, and is preferably 2 to 50 moles, particularly preferably 6 to 50 moles, in that surface-modified metal nanoparticles can be obtained substantially without solvent. When the amount of the amines used is equal to or greater than the lower limit, metallic silver compounds that are not converted into complexes are less likely to remain in the complex formation step, and the uniformity of the metal nanoparticles is increased in the subsequent thermal decomposition step, making it possible to suppress particle enlargement and the remaining metal compounds that are not thermally decomposed.

[0087] The organic protective agent may contain other organic protective agents in addition to the amine. Examples of the other organic protective agents include aliphatic monocarboxylic acids. Use of aliphatic monocarboxylic acids tends to further improve the dispersibility of the metal nanoparticles (A).

[0088] Examples of the aliphatic monocarboxylic acid include saturated aliphatic monocarboxylic acids having 4 or more carbon atoms, such as butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, and icosanoic acid; and unsaturated aliphatic monocarboxylic acids having 8 or more carbon atoms, such as oleic acid, elaidic acid, linoleic acid, palmitoleic acid, and eicosenoic acid.

[0089] Among these, saturated or unsaturated aliphatic monocarboxylic acids having 8 to 18 carbon atoms (e.g., octanoic acid, oleic acid, etc.) are preferred. When the carboxyl group of the aliphatic monocarboxylic acid is adsorbed onto the surface of a metal nanoparticle, the saturated or unsaturated aliphatic hydrocarbon chain having 8 to 18 carbon atoms acts as a steric hindrance, ensuring spacing between the metal nanoparticles and improving the ability to prevent aggregation of the metal nanoparticles. Furthermore, the aliphatic monocarboxylic acids are preferred because they are easy to obtain and can be easily removed during sintering.

[0090] The amount of the aliphatic monocarboxylic acid used is, for example, about 0.05 to 10 moles, preferably 0.1 to 5 moles, and more preferably 0.5 to 2 moles, per mole of metal atom in the metal compound. When the amount of the aliphatic monocarboxylic acid used is equal to or greater than the lower limit, the stability-improving effect is more easily achieved. When the amount used is equal to or less than the upper limit, the effect of the aliphatic monocarboxylic acid is sufficiently obtained, while excess aliphatic monocarboxylic acid is less likely to remain.

[0091] The metal nanoparticles (A) surface-coated with an organic protective agent containing an amine can be produced by a known or conventional method. For example, the metal nanoparticles (A) can be produced through a process of mixing a metal compound with an organic protective agent containing an amine to form a complex containing the metal compound and the amine (complex formation process), a process of thermally decomposing the complex (thermal decomposition process), and, if necessary, a process of washing the reaction product (washing process).

[0092] The bonding conductor paste may contain other conductive particles (particularly other metal particles) other than the metal nanoparticles (A). In particular, the bonding conductor paste preferably uses a combination of metal particles (groups) having different average particle sizes, since this allows for the formation of conductor wiring or bonded structures with even lower electrical resistance and excellent electrical properties.

[0093] Examples of the shape of the other metal particles include spherical, flat, and polyhedral shapes. Conductive particles of different shapes may be used in combination, or only conductive particles of the same shape may be used.

[0094] As the other metal particles, particularly preferred are spherical metal particles (B) having an average particle size of 0.5 to 1 μm and flat metal flakes (C) having an average particle size of 1 to 10 μm.

[0095] (Spherical Metal Particles (B)) When spherical metal particles (B) larger in size than the metal nanoparticles (A) are used in combination with the metal nanoparticles (A), the resulting sintered body is formed such that the gaps between the relatively large spherical metal particles (B) are filled with the relatively small metal nanoparticles (A), allowing for the formation of denser conductor wiring and bonded structures with high bonding strength and high conductivity. Only one type of spherical metal particle (B) may be used, or two or more types may be used.

[0096] The spherical metal particles (B) may be surface-modified metal particles whose surfaces are coated with an organic protective agent. The surface-modified metal particles have excellent dispersibility in organic solvents because the spacing between the metal particles is secured and aggregation is suppressed.

[0097] The metal constituting the spherical metal particles (B) may be a conductive metal, such as those exemplified and explained as the metal constituting the above-mentioned metal nanoparticles (A). In particular, the metal particles preferably contain the same metal as the metal nanoparticles (A) from the viewpoint of increasing the bonding strength, and more preferably are silver particles.

[0098] The organic protective agent is not particularly limited, and examples thereof include known or commonly used organic protective agents used as protective agents (stabilizers) for metal particles. Examples of the organic protective agent include organic protective agents having functional groups such as a carboxy group, a hydroxy group, a carbonyl group, an amide group, an ether group, an amino group, a sulfo group, a sulfonyl group, a sulfinic acid group, a sulfenic acid group, a mercapto group, a phosphate group, and a phosphite group. One or more of the organic protective agents may be used.

[0099] The average particle size (median size) of the spherical metal particles (B) is 0.5 to 1 μm, preferably 0.6 to 0.9 μm. The average particle size can be measured by a laser diffraction / scattering method. When two or more types of spherical metal particles (B) are contained, the average particle size refers to the average particle size of all the spherical metal particles (B).

[0100] (Flat metal flakes (C)) When flat metal flakes (C) are used in combination with metal nanoparticles (A), the sintering of the flat metal flakes (C) themselves is also performed, and the necking between the metal particles becomes thicker, making it possible to obtain a stronger sintered body. Only one type of flat metal flake (C) may be used, or two or more types may be used.

[0101] The flat metal flakes (C) may be surface-modified metal flakes having a configuration in which the surfaces of the metal flakes are coated with an organic protective agent. The surface-modified metal flakes have excellent dispersibility in organic solvents because the spacing between the metal flakes is secured and aggregation is suppressed.

[0102] The metal constituting the flat metal flakes (C) may be a conductive metal, such as those exemplified and explained as the metal constituting the above-mentioned metal nanoparticles (A). In particular, the metal particles preferably contain the same metal as the metal nanoparticles (A) from the viewpoint of increasing the bonding strength, and more preferably are silver particles.

[0103] The organic protective agent is not particularly limited, and examples thereof include known or commonly used organic protective agents used as protective agents (stabilizers) for metal particles. Examples of the organic protective agent include organic protective agents having functional groups such as a carboxy group, a hydroxy group, a carbonyl group, an amide group, an ether group, an amino group, a sulfo group, a sulfonyl group, a sulfinic acid group, a sulfenic acid group, a mercapto group, a phosphate group, and a phosphite group. One or more of the organic protective agents may be used.

[0104] The average particle size (median size) of the flat metal flakes (C) is 1 to 10 μm, preferably 2 to 5 μm. The average particle size can be measured by a laser diffraction / scattering method. When two or more types of flat metal flakes (C) are contained, the average particle size refers to the average particle size of all the flat metal flakes (C).

[0105] The content of metal nanoparticles (A) in the bondable conductor paste is preferably 5% by mass or more, more preferably 10% by mass or more, based on 100% by mass of all conductive metal particles. A content of 5% by mass or more allows for the formation of denser conductor wiring and bonded structures. The content is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. A content of 50% by mass or less allows for sufficient blending of spherical metal particles (B) and flat metal flakes (C).

[0106] The content of the spherical metal particles (B) in the bondable conductor paste is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably more than 50% by mass, based on 100% by mass of all conductive metal particles. When the content is 30% by mass or more, the effect of blending the spherical metal particles (B) is more easily achieved. The content is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. When the content is 85% by mass or less, the blending amount of the metal nanoparticles (A) and the flat metal flakes (C) can be sufficient.

[0107] The content of the flat metal flakes (C) in the bondable conductor paste is preferably 10% by mass or more, more preferably 15% by mass or more, based on 100% by mass of all conductive metal particles. When the content is 10% by mass or more, the effect of incorporating the flat metal flakes (C) is more easily achieved. The content is preferably 65% ​​by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. When the content is 65% by mass or less, the amount of metal nanoparticles (A) and spherical metal particles (B) incorporated can be sufficient.

[0108] The total content of the metal nanoparticles (A), spherical metal particles (B), and flat metal flakes (C) relative to the total amount of conductive particles contained in the bondable conductor paste (100% by mass) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. When the content is 70% by mass or more, the dispersibility of the metal particles is superior, and continuous discharge stability and storage stability are also superior.

[0109] (Bondable conductor paste) The content of metal particles in the bondable conductor paste is preferably 70 to 99.5% by mass, more preferably 80 to 98% by mass, and even more preferably 85 to 95% by mass, based on 100% by mass of the total amount of the bondable conductor paste. When the content is within the above range, the dispersibility of the metal particles is excellent, and continuous discharge stability and storage stability are also excellent. Furthermore, it is preferable that the total content of metal nanoparticles (A), spherical metal particles (B), and flat metal flakes (C) in the bondable conductor paste is within the above range.

[0110] The content of the dispersion medium (particularly the organic solvent) in the bonding conductor paste is preferably 0.5 to 30 mass%, more preferably 2 to 20 mass%, and even more preferably 5 to 15 mass%, relative to 100 mass% of the total amount of the bonding conductor paste. When the content is within the above range, the dispersibility of the metal particles is superior. Furthermore, it is preferable that the total content of the organic solvents (a), (b), and (c) in the bonding conductor paste is within the above range.

[0111] The total content of the metal particles and the dispersion medium in the above-mentioned bondable conductor paste is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, relative to 100% by mass of the total amount of the above-mentioned bondable conductor paste.

[0112] The above-mentioned bonding conductor paste may contain other components in addition to the metal particles and the dispersion medium. The above-mentioned bonding conductor paste may contain, for example, an adhesive or an additive (for example, a polymer compound having a molecular weight of 10,000 or more, such as an epoxy resin, a silicone resin, or an acrylic resin). However, the content ratio thereof is, for example, 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less, relative to 100% by mass of the total amount of the bonding conductor paste. Therefore, with the above-mentioned bonding conductor paste, the interaction between the metal particles or between the metal particles and the substrate is not inhibited by the non-conductive component derived from the polymer compound, and a conductive wiring or bonded structure with excellent conductivity [electrical resistance value is, for example, 10 × 10 −６Ω cm or less, preferably 9.0 × 10 −６ Ω cm or less, more preferably 8.5 × 10 −６ Ω cm or less, more preferably 7.0 × 10 −６ Ω·cm or less] can be formed.

[0113] The bondable conductor paste of the present disclosure contains, as a dispersion medium for dispersing metal nanoparticles (A), an organic solvent (a) that is a relatively high-polarity solvent and an organic solvent (c) that is a relatively low-polarity solvent, thereby providing excellent dispersibility of the metal nanoparticles (A), reducing separation between the metal particles and the dispersion medium, and suppressing the generation of voids during sintering. Furthermore, by incorporating an organic solvent (b) with intermediate polarity, the compatibility between the organic solvents (a) and (c) is improved, reducing separation between the organic solvents, and providing excellent continuous discharge stability and storage stability.

[0114] (Sintered body) The bonding conductor paste of the present disclosure can be applied to a substrate by a printing method (specifically, a dispenser printing method, a mask printing method, a screen printing method, an inkjet printing method, etc.) and then sintered to form a sintered body, which can form a conductor wiring or a bonded structure. Among these, the bonding conductor paste is preferably printed by a dispenser printing method from the viewpoint of excellent continuous discharge stability.

[0115] The sintering temperature is, for example, 150° C. or higher and lower than 300° C., preferably 170 to 250° C. The sintering time is, for example, 0.1 to 2 hours, preferably 0.5 to 1 hour.

[0116] The sintering may be carried out in an air atmosphere, a nitrogen atmosphere, an argon atmosphere, or the like. Among these, carrying out the sintering in an air atmosphere is preferred because it is economical and allows the production of conductor wiring or bonded structures with lower electrical resistance values.

[0117] The thickness of the bonding conductor paste applied to the substrate is such that the thickness of the conductor wiring or bonded structure formed by the above method is, for example, in the range of 15 to 400 μm, preferably 20 to 250 μm, and more preferably 40 to 200 μm.

[0118] Examples of substrates on which conductor wiring and junction structures are formed include ceramic substrates, SiC substrates, gallium nitride substrates, metal substrates, glass epoxy substrates, BT resin substrates, glass substrates, resin substrates, etc. The shape of the conductor wiring and junction structures is not particularly limited as long as they are shapes that allow electronic elements to be connected.

[0119] A sintered body (e.g., conductor wiring or a bonded structure) formed on a substrate using the above-mentioned bondable conductor paste exhibits excellent bond strength to the substrate because the conductive particles are densely gathered by sintering and melt together. For example, the bond strength (in accordance with JIS Z3198) when a silver-plated copper substrate and a silver-plated Si chip are bonded is preferably 10 MPa or more, more preferably 25 MPa or more, even more preferably 30 MPa or more, and particularly preferably 40 MPa or more.

[0120] The void fraction measured using a scanning acoustic tomography (SAT) in a sintered body (e.g., conductor wiring or a bonded structure) formed on a substrate using the above-mentioned bondable conductor paste is preferably 15% or less, more preferably less than 8%. A void fraction of 15% or less results in higher bond strength. A high void fraction indicates a large number of voids at the bonded interface, etc., and is thought to reduce the heat transfer area between the bonded parts in the bonded body. During semiconductor operation, a narrow heat transfer area is fatal for dissipating heat, increasing the likelihood of heat spots occurring and leading to failure. The void fraction can be measured specifically by the method described in the examples.

[0121] Because the above-mentioned bonding conductor paste has the above-mentioned properties, it can be preferably used for the purpose of producing electronic components (for example, power semiconductor modules, LED modules, etc.) using a printing method.

[0122] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. Furthermore, each invention according to this disclosure is not limited by the embodiments or the following examples, but is limited only by the scope of the claims.

[0123] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0124] (Average Particle Diameter of Metal Nanoparticles (A)) Hereinafter, the average particle diameter (median diameter) of metal nanoparticles (A) was measured by the following method. A suspension containing surface-modified silver nanoparticles prepared in Preparation Example 1 was observed using a transmission electron microscope. Observation was performed at 100,000 magnification, with 4 fields of view x 50 particles. The observation points were areas where large and small particles coexisted. The number particle size distribution was determined by analyzing the image. This number particle size distribution was converted to a volume particle size distribution using a known conversion formula, assuming that the particles have an aspect ratio of 1. The average particle size (median diameter) was determined from this particle size distribution and used as the average particle size of the metal nanoparticles (A).

[0125] (Average particle size of spherical metal particles (B) and flat metal flakes (C)) The values ​​are measured by a laser diffraction / scattering method.

[0126] The metal particles and solvents used are as follows: [Metal particles] Surface-modified silver nanoparticles (Preparation Example 1): average particle size (median size) 50 nm AG-2-8F: trade name "AG-2-8F", manufactured by Dowa Electronics Co., Ltd., spherical silver particles, average particle size (median size) 0.8 μm 41-104: trade name "41-104", manufactured by Technic, flat silver flakes, average particle size (median size) 3.3 μm [Solvent (I): Highly polar solvent] Pinacol: δ 10.7, boiling point 172°C, manufactured by Tokyo Chemical Industry Co., Ltd. Tetramethylurea: δ 10.6, boiling point 177°C, manufactured by Daicel Corporation 3-Methoxybutanol: δ 10.6, boiling point 161°C, manufactured by Daicel Corporation 1-Methylcyclohexanol: δ 10.4, boiling point 155°C, manufactured by Tokyo Chemical Industry Co., Ltd. [Solvent (II): Medium polarity solvent] Tripropylene glycol monomethyl ether: δ 9.4, boiling point 243°C, manufactured by Ando Para-Chemie Co., Ltd. Dihydroterpineol: δ 9.0, boiling point 210°C, manufactured by Nippon Terpene Chemical Co., Ltd. Propylene glycol monobutyl ether: δ 9.0, boiling point 170°C, manufactured by Tokyo Chemical Industry Co., Ltd. 1-Nonanol: δ 9.8, boiling point 214°C, manufactured by Tokyo Chemical Industry Co., Ltd. 1-Dodecanol: δ 9.3, boiling point 262°C, manufactured by Tokyo Chemical Industry Co., Ltd. [Solvent (III): Low polarity solvent] Dibutyl carbitol: δ 8.3, boiling point 255°C, manufactured by Tokyo Chemical Industry Co., Ltd. Tetradecane: δ 7.9, boiling point 254°C, manufactured by Tokyo Chemical Industry Co., Ltd. Hexadecane: δ 8.0, boiling point 287°C, manufactured by Tokyo Chemical Industry Co., Ltd. Dipropylene glycol methyl-n-propyl ether: δ 8.2, boiling point 203°C, manufactured by Daicel Corporation

[0127] Preparation Example 1 (Preparation of Surface-Modified Silver Nanoparticles) Silver oxalate (molecular weight: 303.78) was obtained from silver nitrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and oxalic acid dihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) 40.0 g (0.1317 mol) of the silver oxalate was charged into a 500 mL flask, and 60 g of n-butanol was added thereto to prepare an n-butanol slurry of silver oxalate. To the resulting slurry, an amine mixture of 115.58 g (1.5802 mol) of n-butylamine (molecular weight: 73.14, reagent manufactured by Tokyo Chemical Industry Co., Ltd.), 51.06 g (0.3950 mol) of 2-ethylhexylamine (molecular weight: 129.25, reagent manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.), and 17.02 g (0.1317 mol) of n-octylamine (molecular weight: 129.25, reagent manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise at 30°C. After the addition, the mixture was stirred at 30°C for 1 hour to promote the complex formation reaction between silver oxalate and the amine. After the formation of the silver oxalate-amine complex, the mixture was heated at 110°C for 1 hour to thermally decompose the silver oxalate-amine complex, yielding a suspension containing dark blue surface-modified silver nanoparticles.

[0128] The resulting suspension was cooled, and 120 g of methanol (special grade, reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred. The surface-modified silver nanoparticles were then precipitated by centrifugation, and the supernatant was removed. Next, 120 g of dibutyl carbitol (diethylene glycol dibutyl ether) was added and stirred. The surface-modified silver nanoparticles were then precipitated by centrifugation, and the supernatant was removed. In this manner, wet surface-modified silver nanoparticles containing dibutyl carbitol were obtained. Measurements using a thermobalance (TG / DTA6300, manufactured by SII) showed that the silver content of the surface-modified silver nanoparticles in the total amount (100% by mass) of wet surface-modified silver nanoparticles was 86.5% by mass. That is, the wet surface-modified silver nanoparticles contained a total of 13.5% by mass of amine and dibutyl carbitol, which were present as organic protective agents for surface modification. The average particle diameter (median diameter) of the wet surface-modified silver nanoparticles was 50 nm.

[0129] Example 1 (Preparation of Bondable Conductive Paste) Product name "41-104" (25.50 g), AG-2-8F (59.50 g), pinacol (3.48 g), tripropylene glycol methyl ether (3.48 g), and dibutyl carbitol (1.14 g) were added and mixed in a planetary centrifugal mixer (ARE-310, manufactured by THINKYO CORPORATION) to prepare Liquid A. 90.32 g of Liquid A was added to 17.34 g of the wet surface-modified silver nanoparticles (containing 13.5% by mass of dibutyl carbitol) obtained in Preparation Example 1, and the mixture was mixed in a planetary centrifugal mixer (ARE-310, manufactured by THINKYO CORPORATION) to obtain a black-gray bondable conductive paste (1).

[0130] Examples 2 to 6 and Comparative Examples 1 to 8 Bondable conductor pastes were prepared in the same manner as in Example 1, except that the formulation was changed as shown in Table 1. The numerical values ​​of each component shown in Table 1 indicate "parts by mass."

[0131] <Evaluation> The bondable conductor pastes obtained in the examples and comparative examples were evaluated as follows, and the results are shown in the table.

[0132] The equipment used in the evaluation is as follows: [Equipment] Syringe: Clear Syringe PSY-10E-M, manufactured by Musashi Engineering Co., Ltd. Nozzle: Precision Nozzle Φ0.4 mm Luer Lock HN-0.4N, manufactured by Musashi Engineering Co., Ltd. Dispenser: Desktop Coating Robot SHOTMASTER200DS, manufactured by Musashi Engineering Co., Ltd. Dispenser Controller: ML-5000XII, manufactured by Musashi Engineering Co., Ltd. Adapter Tube: AT-10E-H-1.0M, manufactured by Musashi Engineering Co., Ltd. Sintering Furnace: VS-320, manufactured by Budatec Co., Ltd. Universal Bond Tester: Die Shear Tester SERIES4000, manufactured by Nordson DAGE Co., Ltd. Ultrasonic Imaging Device: FineSAT FS300II, manufactured by Hitachi High-Tech Corporation; Scanning Electron Microscope (SEM), product name "JEOL JSM-F100", manufactured by JEOL Ltd.; Milling device, product name "ArBlade5000", manufactured by Hitachi, Ltd.

[0133] (1) Continuous Discharge Stability 10 mL of the bonding conductive paste obtained in the Examples and Comparative Examples was filled into a syringe, and a nozzle and an adapter tube were attached. The syringe was set in a dispenser, and after a trial injection at a pressure of 0.2 MPa was performed until continuous dispensing was possible, 400 shots were continuously dispensed onto a plate. The injection time was adjusted according to the viscosity of the paste, and continuous dispensing was performed until the filled paste was used up, and the dispensed weight for every 400 shots was measured. Conductive pastes with a dispensing volume of ±20% or less per 400 shots were evaluated as ◯, conductive pastes with a dispensing volume of more than ±20% but less than 30% as △, and conductive pastes with a dispensing volume of more than ±30% as ×.

[0134] (2) Continuous Discharge Stability After Refrigerated Storage The bondable conductor pastes obtained in the Examples and Comparative Examples were stored in a refrigerator at 0 to 5°C for 7 days, and then the conductor pastes were returned to room temperature. The continuous discharge stability after refrigerated storage was evaluated in the same manner as in the evaluation of the continuous discharge stability described above.

[0135] (3) Die shear strength The bonding conductor pastes obtained in the examples and comparative examples were applied by dispenser printing to an Ag-plated substrate (1) (a copper substrate having a 1 mm thick copper substrate on which a 5 μm Ni-P layer was formed by electroless plating, a 0.3 μm pure Pd layer was further formed by electrolytic plating, and a 1 μm semi-gloss silver layer was formed on the outermost surface by electrolytic plating) to form a coating film. Next, a Si dummy chip (2) (chip dimensions 3 mm × 3 mm, Si thickness 675 μm, Si dummy chip with a 0.2 μm Ti layer and a 1 μm Ag layer formed on the Si by sputtering) with Ag sputtering on the bonding surface was mounted on the formed coating film under a load of 0.1 kgf. The sample in which the Si dummy chip was mounted on the substrate via the bonding conductor paste was heated in a sintering furnace from 25°C to 200°C at a heating rate of 5°C / min in an air atmosphere, and then sintered at 200°C for 60 minutes to produce a sample (substrate (1) / sintered bonding conductor paste / dummy chip (2)). The bond strength between the substrate (1) and the dummy chip (2) was measured for the obtained samples (n=4) using a universal bond tester at room temperature in accordance with JIS Z3198 to evaluate the bondability.

[0136] (4) SAT Evaluation For the samples prepared for the die shear strength evaluation, the peeling state of the bonding interface was observed using an ultrasonic imaging device and a 25 MHz reflection probe. The image of the observation results was divided into 100 parts, and in each enlarged image, the parts where the length of the long side of the white part was 100 μm or more were defined as voids. The area occupied by the white part in each of the 100 divided images was determined by image processing to be the void ratio, and the average value of the overall void ratio was defined as the void ratio. A void ratio of less than 8% was defined as ○, a void ratio of 8% to 30% was defined as △, and a void ratio of 30% or more was defined as ×.

[0137] (5) SEM Image Results For the samples prepared for the evaluation of die shear strength, the center of the chip was cut and the cross section was polished using a milling device. Next, the bonded cross section was observed using a scanning electron microscope with the magnification adjusted.

[0138]

[0139] As shown in Table 1, the bonding conductor pastes of the examples had excellent continuous discharge stability and continuous discharge stability after refrigerated storage. Furthermore, SAT evaluation revealed that void generation was suppressed and the pastes were evaluated as having high die shear strength. On the other hand, when only solvent (III), a low-polarity solvent, was used as the dispersion medium, separation between the silver particles and the organic solvent occurred, resulting in poor continuous discharge stability (Comparative Example 1). When solvent (I), a high-polarity solvent, and solvent (III), a low-polarity solvent, were used in combination as the dispersion medium, separation between the silver particles and the organic solvent occurred during low-temperature storage, resulting in poor low-temperature storage stability (Comparative Examples 2 and 3). Even when solvent (I) and solvent (II), a medium-polarity solvent, were used in combination, no clear separation was observed during low-temperature storage because solvent (III) was not added, but continuous discharge stability was insufficient (Comparative Example 4). When solvent (III) was used in combination with solvent (II), a medium-polarity solvent, the absence of solvent (I) resulted in poor dispersibility of silver particles, insufficient continuous discharge stability and void suppression, and weak die shear strength (Comparative Examples 5 to 7). Furthermore, even when solvents (I), (II), and (III) were used in combination, if the relationship between the boiling points of solvent (III) did not satisfy formula (3), the solvent evaporation rate could not be suppressed, and void suppression was insufficient (Comparative Example 8). Furthermore, as shown in Figures 1 to 3, while Example 1 had an SAT rating of ○, Comparative Example 5 had an SAT rating of △, and Comparative Example 7 had an SAT rating of ×, numerous voids were observed. Furthermore, as shown in Figures 4 to 6, SEM observation revealed that no large voids were observed within the bonded body in Example 1, whereas large voids were observed within the bonded body in Comparative Examples 5 and 7.

[0140] Variations of the invention according to the present disclosure are described below: [Appendix 1] A bondable conductor paste comprising metal nanoparticles (A) having an average particle size of 1 nm or more and less than 100 nm, and a dispersion medium containing organic solvents (a), (b), and (c), wherein the metal nanoparticles (A) are surface-coated with an organic protective agent containing an amine and are dispersed in the dispersion medium, and the organic solvents (a), (b), and (c) are mutually different compounds and satisfy the following formulas (1) to (6): 150°C≦Ta≦250°C (1) 150°C≦Tb≦250°C (2) 250°C≦Tc≦350°C (3) δa≧10.0 (4) δc≦9.0 (5) δc≦δb≦δa (6) [Where Ta to Tc respectively represent the boiling points of the organic solvents (a) to (c), and δa to δc respectively represent the Hansen solubility parameters of the organic solvents (a) to (c)] [Appendix 2] A bondable conductor paste according to Appendix 1, comprising spherical metal particles (B) having an average particle size of 0.5 to 1 μm and flat metal flakes (C) having an average particle size of 1 to 10 μm. [Appendix 3] The bondable conductor paste according to Appendices 2, wherein the total content of the metal nanoparticles (A), spherical metal particles (B), and flat metal flakes (C) in the bondable conductor paste is 80 to 99.5 mass%. [Appendix 4] The bondable conductor paste according to Appendices 2 or 3, wherein the metal constituting the spherical metal particles (B) is silver. [Appendix 5] The bondable conductor paste according to any one of Appendices 2 to 4, wherein the average particle diameter of the spherical metal particles (B) is 0.6 to 0.9 μm. [Appendix 6] The bondable conductor paste according to any one of Appendices 2 to 5, wherein the metal constituting the flat metal flakes (C) is silver. [Appendix 7] The bondable conductor paste according to any one of Appendices 2 to 6, wherein the average particle diameter of the flat metal flakes (C) is 2 to 5 μm. [Appendix 8] The content of spherical metal particles (B) in 100% by mass of all conductive metal particles contained in the bondable conductor paste is 30% by mass or more (preferably 40% by mass or more, more preferably more than 50% by mass). A bondable conductor paste according to any one of Appendices 2 to 7.[Appendix 9] The bondable conductor paste according to any one of Appendices 2 to 8, wherein the content of spherical metal particles (B) is 85% by mass or less (preferably 80% by mass or less, more preferably 70% by mass or less) based on 100% by mass of all conductive metal particles contained in the bondable conductor paste. [Appendix 10] The bondable conductor paste according to any one of Appendices 2 to 9, wherein the content of flat metal flakes (C) is 10% by mass or more (preferably 15% by mass or more) based on 100% by mass of all conductive metal particles contained in the bondable conductor paste. [Appendix 11] The bondable conductor paste according to any one of Appendices 2 to 10, wherein the content of flat metal flakes (C) is 65% by mass or less (preferably 50% by mass or less, more preferably 40% by mass or less) based on 100% by mass of all conductive metal particles contained in the bondable conductor paste. [Appendix 12] A bondable conductor paste according to any one of Appendices 2 to 11, wherein the total content of the metal nanoparticles (A), spherical metal particles (B), and flat metal flakes (C) relative to the total amount of conductive particles contained in the bondable conductor paste (100 mass%) is 70 mass% or more (preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 95 mass% or more).

[0141] [Appendix 13] A bondable conductor paste according to any one of Appendices 1 to 12, wherein the content of metal nanoparticles (A) in all metal particles contained in the bondable conductor paste is 50% by mass or less (preferably 30% by mass or less, more preferably 20% by mass or less). [Appendix 14] A bondable conductor paste according to any one of Appendices 1 to 13, wherein the content of metal nanoparticles (A) in 100% by mass of all conductive metal particles contained in the bondable conductor paste is 5% by mass or more (preferably 10% by mass or more). [Appendix 15] The bondable conductor paste according to any one of Appendices 1 to 14, wherein the organic protective agent includes, as the amine, an aliphatic hydrocarbon monoamine (1) consisting of an aliphatic hydrocarbon group and one amino group, the total number of carbon atoms in the aliphatic hydrocarbon group being 6 or more, and further includes at least one of an aliphatic hydrocarbon monoamine (2) consisting of an aliphatic hydrocarbon group and one amino group, the total number of carbon atoms in the aliphatic hydrocarbon group being 5 or less, and an aliphatic hydrocarbon diamine (3) consisting of an aliphatic hydrocarbon group and two amino groups, the total number of carbon atoms in the aliphatic hydrocarbon group being 8 or less. [Appendix 16] The bondable conductor paste according to any one of Appendices 1 to 15, comprising an organic solvent other than organic solvent (a), organic solvent (b), and organic solvent (c). [Appendix 17] The bondable conductor paste according to any one of Appendices 1 to 16, wherein organic solvent (a), organic solvent (b), and organic solvent (c) are homogeneously dissolved at room temperature and do not undergo phase separation. [Appendix 18] The bonding conductor paste according to any one of Appendices 1 to 17, wherein the boiling point Ta of the organic solvent (a) satisfies 150°C < Ta < 250°C (preferably 155°C ≦ Ta ≦ 220°C, more preferably 160°C ≦ Ta ≦ 200°C). [Appendix 19] The bonding conductor paste according to any one of Appendices 1 to 18, wherein the organic solvent (a) has an SP value δa of 10.3 or more (preferably 10.4 or more). [Appendix 20] The bonding conductor paste according to any one of Appendices 1 to 19, wherein the organic solvent (a) has an SP value δa of 16.0 or less (preferably 15.0 or less). [Appendix 21] The bonding conductor paste according to any one of Appendices 1 to 20, wherein the organic solvent (a) is one or more selected from the group consisting of alcohol solvents, urea-based solvents, and aprotic polar solvents.[Appendix 22] The bonding conductor paste according to any one of Appendices 1 to 21, wherein the boiling point Tb of the organic solvent (b) satisfies 150°C < Tb < 250°C (preferably 180°C ≦ Tb ≦ 248°C, more preferably 200°C ≦ Tb ≦ 245°C). [Appendix 23] The bonding conductor paste according to any one of Appendices 1 to 22, wherein the SP value δb of the organic solvent (b) is 8.0 to 12.0 (preferably 8.5 to 11.0, more preferably 9.0 to 10.5). [Appendix 24] The bonding conductor paste according to any one of Appendices 1 to 23, wherein the organic solvent (b) is one or more selected from the group consisting of alcohol solvents, ester solvents, ketone solvents, and amine-based solvents. [Appendix 25] The bonding conductor paste according to any one of Appendices 1 to 24, wherein the boiling point Tb of the organic solvent (b) is higher than the boiling point Ta of the organic solvent (a). [Appendix 26] The bonding conductor paste according to Appendices 25, wherein the temperature difference [Tb - Ta] between the boiling point Tb of the organic solvent (b) and the boiling point Ta of the organic solvent (a) is 2°C or more (preferably 5°C or more, more preferably 10°C or more). [Appendix 27] The bonding conductor paste according to any one of Appendices 1 to 26, wherein the boiling point Tc of the organic solvent (c) satisfies 250°C < Tc < 350°C (preferably 250°C < Tc ≦ 320°C, more preferably 250°C < Tc ≦ 300°C). [Appendix 28] The bonding conductor paste according to any one of Appendices 1 to 27, wherein the SP value δc of the organic solvent (c) is 8.7 or less (more preferably 8.5 or less). [Appendix 29] The bonding conductor paste according to any one of Appendices 1 to 28, wherein the SP value δc of the organic solvent (c) is 6.0 or more (preferably 7.0 or more). [Appendix 30] The bondable conductor paste according to any one of Appendices 1 to 29, wherein the organic solvent (c) is one or more selected from the group consisting of ether solvents, alkane solvents, and ester solvents. [Appendix 31] The bondable conductor paste according to any one of Appendices 1 to 30, wherein the boiling point Tc of the organic solvent (c) is higher than the boiling point Tb of the organic solvent (b). [Appendix 32] The bondable conductor paste according to Appendices 31, wherein the temperature difference [Tc - Tb] between the boiling point Tc of the organic solvent (c) and the boiling point Tb of the organic solvent (b) is 2°C or more (preferably 6°C or more, more preferably 10°C or more). [Appendix 33] The bondable conductor paste according to any one of Appendices 1 to 32, wherein the boiling point Tc of the organic solvent (c) is higher than the boiling point Ta of the organic solvent (a).[Appendix 34] A bondable conductor paste according to Appendix 33, wherein the temperature difference [Tc - Ta] between the boiling point Tc of the organic solvent (c) and the boiling point Ta of the organic solvent (a) is 30°C or more (preferably 50°C or more, more preferably 60°C or more).

[0142] [Appendix 35] The bondable conductor paste according to any one of Appendices 1 to 34, wherein the SP value δb of the organic solvent (b) is higher than the SP value δc of the organic solvent (c). [Appendix 36] The bondable conductor paste according to Appendices 35, wherein the difference [δb - δc] between the SP value δb of the organic solvent (b) and the SP value δc of the organic solvent (c) is 0.1 or more (preferably 0.2 or more, more preferably 0.5 or more). [Appendix 37] The bondable conductor paste according to Appendices 35 or 36, wherein the difference [δb - δc] between the SP value δb of the organic solvent (b) and the SP value δc of the organic solvent (c) is 2.0 or less (preferably 1.5 or less, more preferably 1.3 or less). [Appendix 38] The bondable conductor paste according to any one of Appendices 1 to 37, wherein the SP value δa of the organic solvent (a) is higher than the SP value δb of the organic solvent (b). [Appendix 39] A bonding conductor paste according to Appendix 38, wherein the difference [δa - δb] between the SP value δa of the organic solvent (a) and the SP value δb of the organic solvent (b) is 0.1 or more (preferably 0.2 or more, more preferably 0.5 or more). [Appendix 40] A bonding conductor paste according to Appendix 38 or 39, wherein the difference [δa - δb] between the SP value δa of the organic solvent (a) and the SP value δb of the organic solvent (b) is 2.5 or less (preferably 2.0 or less, more preferably 1.8 or less). [Appendix 41] A bonding conductor paste according to any one of Appendices 1 to 40, wherein the difference [δa - δc] between the SP value δa of the organic solvent (a) and the SP value δc of the organic solvent (c) is 1.5 or more (preferably 2.0 or more). [Appendix 42] The bondable conductor paste according to Appendices 41, wherein the difference [δa - δc] between the SP value δa of the organic solvent (a) and the SP value δc of the organic solvent (c) is 5.0 or less (preferably 4.0 or less, more preferably 3.0 or less). [Appendix 43] The bondable conductor paste according to any one of Appendices 1 to 42, wherein the ratio of the organic solvent (a) to the total amount of the organic solvents (a), (b), and (c) (100 mass%), [organic solvent (a) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}], is 5 to 70 mass% (preferably 10 to 60 mass%, more preferably 15 to 50 mass%).[Appendix 44] The bonding conductor paste according to any one of Appendices 1 to 43, wherein the ratio of the organic solvent (b) to the total amount of the organic solvent (a), the organic solvent (b), and the organic solvent (c) (100% by mass) [organic solvent (b) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is 5 to 70% by mass (preferably 10 to 60% by mass, more preferably 15 to 50% by mass). [Appendix 45] The bonding conductor paste according to any one of Appendices 1 to 44, wherein the ratio of the organic solvent (c) to the total amount of the organic solvent (a), the organic solvent (b), and the organic solvent (c) (100% by mass) [organic solvent (c) / {organic solvent (a) + organic solvent (b) + organic solvent (c)}] is 5 to 70% by mass (preferably 10 to 60% by mass, more preferably 15 to 50% by mass). [Appendix 46] A bondable conductor paste according to any one of Appendices 1 to 45, wherein the content of the organic solvent (c) is 20 to 400 parts by mass (preferably 30 to 300 parts by mass, more preferably 50 to 200 parts by mass) per 100 parts by mass of the organic solvent (a). [Appendix 47] A bondable conductor paste according to any one of Appendices 1 to 46, wherein the content of the organic solvent (b) is 10 to 200 parts by mass (preferably 20 to 150 parts by mass, more preferably 40 to 100 parts by mass) per 100 parts by mass of the total amount of the organic solvent (a) and the organic solvent (c). [Appendix 48] The total content of the organic solvent (a), the organic solvent (b), and the organic solvent (c) in the dispersion medium is 50% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more) relative to 100% by mass of the total amount of the dispersion medium. A bonding conductor paste according to any one of Appendices 1 to 47.

[0143] [Appendix 49] The bonding conductor paste according to any one of Appendices 1 to 48, wherein the content of metal particles in the bonding conductor paste is 70 to 99.5% by mass (preferably 80 to 98% by mass, more preferably 85 to 95% by mass) relative to 100% by mass of the total amount of the bonding conductor paste. [Appendix 50] The bonding conductor paste according to any one of Appendices 1 to 49, wherein the content of dispersion medium in the bonding conductor paste is 0.5 to 30% by mass (preferably 2 to 20% by mass, more preferably 5 to 15% by mass) relative to 100% by mass of the total amount of the bonding conductor paste. [Appendix 51] The bonding conductor paste according to any one of Appendices 1 to 50, wherein the total content of metal particles and dispersion medium in the bonding conductor paste is 70% by mass or more (preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more) relative to 100% by mass of the total amount of the bonding conductor paste. [Appendix 52] The bondable conductor paste according to any one of Appendices 1 to 51, wherein the bonding strength (based on JIS Z3198) when a silver-plated copper substrate and a silver-plated Si chip are bonded via a sintered body of the bondable conductor paste is 10 MPa or more (preferably 25 MPa or more, more preferably 30 MPa or more, and even more preferably 40 MPa or more). [Appendix 53] The bondable conductor paste according to any one of Appendices 1 to 52, wherein the void fraction in the sintered body of the bondable conductor paste measured using an ultrasonic imaging device is 15% or less (preferably less than 8%).

Claims

1. The dispersion medium includes metal nanoparticles (A) having an average particle size of 1 nm or more and less than 100 nm, and an organic solvent (a), an organic solvent (b), and an organic solvent (c), the metal nanoparticles (A) are surface-coated with an organic protective agent containing an amine and are dispersed in the dispersion medium; A bondable conductor paste, wherein the organic solvent (a), the organic solvent (b), and the organic solvent (c) are different compounds and satisfy the following formulas (1) to (6): 150°C ≦ Ta ≦ 250°C (1) 150°C ≦ Tb ≦ 250°C (2) 250°C ≦ Tc ≦ 350°C (3) δ a ≧ 10.0 (4) δc≦9.0 (5) δc≦δb≦δa (6) [In the formula, Ta to Tc represent the boiling points of the organic solvents (a) to (c), respectively, and δa to δc represent the Hansen solubility parameters of the organic solvents (a) to (c), respectively.]

2. 2. The bondable conductor paste according to claim 1, comprising spherical metal particles (B) having an average particle size of 0.5 to 1 μm and flat metal flakes (C) having an average particle size of 1 to 10 μm.

3. The total content of the metal nanoparticles (A), spherical metal particles (B), and flat metal flakes (C) in the bonding conductor paste is 80 to 99.5 mass%. The bonding conductor paste according to claim 2.

4. The bonding conductor paste according to any one of claims 1 to 3, wherein the content of metal nanoparticles (A) in all metal particles contained in the bonding conductor paste is 50 mass% or less.

5. 4. The bondable conductor paste according to claim 1, wherein the organic protective agent contains, as the amine, an aliphatic hydrocarbon monoamine (1) consisting of an aliphatic hydrocarbon group and one amino group, the aliphatic hydrocarbon group having a total carbon number of 6 or more, and further contains at least one of an aliphatic hydrocarbon monoamine (2) consisting of an aliphatic hydrocarbon group and one amino group, the aliphatic hydrocarbon group having a total carbon number of 5 or less, and an aliphatic hydrocarbon diamine (3) consisting of an aliphatic hydrocarbon group and two amino groups, the aliphatic hydrocarbon groups having a total carbon number of 8 or less.

6. The bondable conductor paste according to any one of claims 1 to 3, further comprising an organic solvent other than the organic solvent (a), the organic solvent (b), and the organic solvent (c).

7. The bondable conductor paste according to any one of claims 1 to 3, wherein the organic solvent (a), the organic solvent (b), and the organic solvent (c) are uniformly dissolved at room temperature and do not undergo phase separation.