Silver sintered body, semiconductor device, silver-containing composition, and method for manufacturing silver sintered body

Abstract

To provide a silver sintered body showing extensibility and suppressed in crack occurrence, and a silver-containing composition for producing the silver sintered body, capable of producing the silver sintered body even when high pressure is not applied during sintering.SOLUTION: A silver sintered body has a ratio of crystal grains having a diameter of 0.5 to 1.2 μm of 40% or more relative to all crystal grains when a grain size distribution of crystal grains in the silver sintered body is measured on an area basis by an electron beam backscatter diffraction method. A silver-containing composition contains first silver particles and second silver particles, the first silver particles have a primary particle diameter of 200 nm or less, and an average secondary particle diameter is 2 μm or less. A particle size at the time of 50% accumulation of the second silver particles measured by a laser diffraction / scattering particle size distribution measurement is less than 1.5 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silver sintered body, a semiconductor device, a silver-containing composition, and a method for producing a silver sintered body. [Background technology]

[0002] Silver metal is widely used as a recording material and a printing plate material, and is also widely used as a highly conductive material due to its excellent electrical conductivity, and as a heat dissipation material due to its excellent thermal conductivity.

[0003] As a method for forming metallic silver, for example, a method of forming metallic silver by using a printing method with an ink containing a material capable of forming metallic silver is known. This method has little waste of materials required for forming metallic silver and is suitable for mass production. However, such a method using printing, particularly the metallic silver formed by firing a material capable of forming metallic silver at a relatively low temperature, such as 350° C. or lower, has the problem that the metallic silver is less ductile than bulk metallic silver and is easily brittle. When brittle metallic silver is used as a wiring material for electronic components or a bonding material for semiconductors, it may reduce the reliability of the product.

[0004] In response to this, a method has been disclosed in which a paste containing silver microflake powder is used to form a silver sintered body with low porosity (3%) and relatively ductility by applying a pressure of 5 MPa or more at a sintering temperature of 300°C or less (see Non-Patent Document 1). However, when a silver sintered body for bonding a semiconductor element to an electrode is formed under high pressure, there is a risk of unintended damage to the semiconductor element, the substrate, etc. Furthermore, there are limitations on the pressure device used, which can cause problems such as limiting the printing area of ​​the silver sintered body and making it difficult to apply uniform pressure to three-dimensionally printed ink.

[0005] In response to this, methods have been disclosed for obtaining a silver sintered body at a sintering temperature of 300° C. or less without applying pressure (see Non-Patent Documents 2-3 and Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2013 / 133085 [Non-patent literature]

[0007] [Non-Patent Document 1] T. Herboth, M. Guenther, A. Fix and J. Wilde, “Failure mechanisms of sintered silver interconnections for power electronic applications,” in 2013 IEEE 63rd Electronic Components and Technology Conference, 2013. [Non-patent document 2] Chen, C., Nagao, S., Zhang, H. et al. Journal of Elec Materi (2017) 46: 1576. [Non-patent document 3] John G. Bai, Member, IEEE, Zhiye Zach Zhang, Jesus N. Calata, and Guo-Quan Lu, Low-Temperature Sintered Nanoscale Silver as a Novel Semiconductor Device-Metallized Substrate Interconnect Material, IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 29, NO. 3, SEPTEMBER 2006. Summary of the Invention [Problem to be solved by the invention]

[0008] However, the silver sintered bodies obtained by these methods exhibited brittle behavior in which the stress immediately became zero after a stress exceeding the maximum tensile strength (maximum stress) was generated, and the ductility was insufficient.

[0009] Incidentally, nano-sized or submicron-sized silver particles have the advantage that they can be sintered and formed into a film at a relatively low temperature of 350° C. or less. However, there is a problem in that the thicker the film, the more likely it is to crack due to the volumetric shrinkage of the silver sintered body that occurs as the sintering proceeds.

[0010] As described above, it has been difficult to obtain a silver sintered body that exhibits ductility and suppresses the occurrence of cracks by sintering the material for obtaining the silver sintered body without applying high pressure.

[0011] An object of the present invention is to provide a silver sintered body that exhibits ductility and suppresses the occurrence of cracks, and a silver-containing composition for producing the silver sintered body, which allows the silver sintered body to be produced without applying high pressure during sintering. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a silver sintered body, in which, when the particle size distribution of crystal grains in the silver sintered body is measured on an area basis by electron backscatter diffraction, the proportion of crystal grains having a particle size of 0.5 to 1.2 μm to all crystal grains is 40% or more. In the silver sintered body of the present invention, the porosity is preferably 35% or less.

[0013] The present invention also provides a semiconductor device comprising a substrate and a semiconductor element bonded to the substrate, wherein an electrode provided on the substrate and the semiconductor element are bonded by a silver sintered body, and the silver sintered body is the silver sintered body of the present invention.

[0014] The present invention also provides a silver-containing composition comprising first silver particles and second silver particles, wherein the first silver particles have a primary particle diameter of 200 nm or less and an average secondary particle diameter of 2 μm or less, and the second silver particles have a particle diameter at 50% accumulation of less than 1.5 μm, as measured by laser diffraction / scattering particle size distribution measurement. In the silver-containing composition of the present invention, it is preferable that either or both of the first silver particles and the second silver particles are obtained by thermal decomposition or reduction of silver β-ketocarboxylate or silver oxalate.

[0015] The present invention also provides a method for producing a silver sintered body, wherein, when the particle size distribution of crystal grains in the silver sintered body is measured on an area basis by electron backscatter diffraction, the proportion of crystal grains having a particle size of 0.5 to 1.2 μm to all crystal grains is 40% or more, and the method includes the steps of: depositing the silver-containing composition of the present invention onto an object on which the silver sintered body is to be formed; and sintering the deposited silver-containing composition at a temperature of 350°C or less and a pressure of 1 MPa or less to form the silver sintered body. [Effects of the Invention]

[0016] According to the present invention, there are provided a silver sintered body that exhibits ductility and suppresses the occurrence of cracks, and a silver-containing composition for producing the silver sintered body, which can produce the silver sintered body without applying high pressure during sintering. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view schematically showing an example of a joined body having a silver sintered body as a joining portion according to an embodiment of the present invention. FIG. [Figure 2] 1 is a cross-sectional view schematically showing an example of a semiconductor device having a silver sintered body according to an embodiment of the present invention as a joint portion. [Figure 3] FIG. 2 is a plan view showing the shape and size of a printed layer of a silver-containing composition in an example. DETAILED DESCRIPTION OF THE INVENTION

[0018] <<Silver-containing composition>> A silver-containing composition according to one embodiment of the present invention contains first silver particles and second silver particles, wherein the first silver particles have a primary particle diameter of 200 nm or less and an average secondary particle diameter of 2 μm or less, and the second silver particles have a particle diameter at 50% accumulation of less than 1.5 μm, as measured by laser diffraction / scattering particle size distribution measurement. By using the silver-containing composition of this embodiment, a silver sintered body that exhibits ductility and suppresses the occurrence of cracks can be produced without applying high pressure during sintering. Furthermore, by using the silver-containing composition of this embodiment, it is possible to produce a silver sintered body having a high maximum stress.

[0019] <First silver particles> The primary particle diameter of the first silver particles is 200 nm or less, and may be, for example, 150 nm or less, 100 nm or less, or 50 nm or less. When the primary particle diameter of the first silver particles is 200 nm or less, a silver sintered body that exhibits ductility and suppresses the occurrence of cracks can be produced without applying high pressure to the silver-containing composition during sintering of the silver-containing composition.

[0020] There is no particular lower limit to the primary particle diameter of the first silver particles. For example, when the primary particle diameter is 1 nm or more, the production of a silver sintered body becomes easier.

[0021] The first silver particles are preferably formed by a chemical reaction of a silver-containing compound having silver atoms as constituent atoms. The silver-containing compound may be either an inorganic compound having silver atoms (inorganic silver compound) or an organic compound having silver atoms (organic silver compound).

[0022] Examples of the silver-containing compound include compounds that form silver upon thermal decomposition or reduction. Examples of such silver-containing compounds include silver carboxylates (silver salts of carboxylic acids) having a group represented by the formula "-COOAg."

[0023] [Silver carboxylate] The silver carboxylate is not particularly limited as long as it has a group represented by the formula "-COOAg". For example, the number of groups represented by the formula "-COOAg" may be one or two or more. Furthermore, the position of the group represented by the formula "-COOAg" in the silver carboxylate is also not particularly limited.

[0024] Examples of the silver carboxylate include silver β-ketocarboxylate having a carbonyl group (—C(═O)—) at the β-position of a group represented by the formula “—COOAg,” and silver carboxylates other than the silver β-ketocarboxylates.

[0025] (Silver β-ketocarboxylate (1)) Examples of the silver β-ketocarboxylate include silver β-ketocarboxylate represented by the following general formula (1) (sometimes abbreviated herein as "silver β-ketocarboxylate (1)").

[0026] [ka] (In the formula, R represents an aliphatic hydrocarbon group having 1 to 20 carbon atoms, in which one or more hydrogen atoms may be substituted with a substituent, a phenyl group, a hydroxyl group, an amino group, or a group represented by the general formula "R 1 -CY 1 2-," "CY 1 3-," "R 1 -CHY 1 -," "R 2 O-," "R 5 R 4 N-", "(R 3 O)2CY 1 -" or "R 6 -C(=O)-CY 1 2-" is a group represented by the formula: Y 1 are each independently a fluorine atom, a chlorine atom, a bromine atom, or a hydrogen atom; R1 is an aliphatic hydrocarbon group having 1 to 19 carbon atoms or a phenyl group; R 2 is an aliphatic hydrocarbon group having 1 to 20 carbon atoms; R 3 is an aliphatic hydrocarbon group having 1 to 16 carbon atoms; R 4 and R 5 are each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms; R 6 is an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a hydroxyl group, or a group represented by the formula "AgO-"; X 1 are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a phenyl group or a benzyl group in which one or more hydrogen atoms may be substituted with a substituent, a cyano group, an N-phthaloyl-3-aminopropyl group, a 2-ethoxyvinyl group, or a group represented by the general formula "R 7 O-," "R 7 S-," "R 7 -C(=O)-" or "R 7 -C(=O)-O-; R 7 is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a thienyl group, or a phenyl or diphenyl group in which one or more hydrogen atoms may be substituted with a substituent.

[0027] In the formula, R represents an aliphatic hydrocarbon group having 1 to 20 carbon atoms, in which one or more hydrogen atoms may be substituted with a substituent, a phenyl group, a hydroxyl group, an amino group, or a group represented by the general formula "R 1 -CY 1 2-," "CY 1 3-," "R 1 -CHY 1 -," "R 2 O-," "R 5 R 4 N-", "(R 3 O)2CY 1 -" or "R 6 -C(=O)-CY 1 2-" is a group represented by

[0028] The aliphatic hydrocarbon group having 1 to 20 carbon atoms in R may be linear, branched, or cyclic (aliphatic cyclic group), and if cyclic, may be monocyclic or polycyclic. The aliphatic hydrocarbon group may be either a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. The aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. Preferred examples of the aliphatic hydrocarbon group in R include alkyl groups, alkenyl groups, and alkynyl groups.

[0029] Examples of the linear or branched alkyl group for R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a 1-methylbutyl group, a 2-methylbutyl group, an n-hexyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,1-dimethylbutyl group, a 2,2-dimethylbutyl group, a 3,3-dimethylbutyl group, a 2, 3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, 3-ethylbutyl group, 1-ethyl-1-methylpropyl group, n-heptyl group, 1-methylhexyl group, 2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1,1-dimethylpentyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 4,4-dimethylpentyl group, 1-ethylpentyl group, 2-ethylpentyl group, 3-ethylpentyl group, 4-ethylpentyl, 2,2,3-trimethylbutyl, 1-propylbutyl, n-octyl, isooctyl, 1-methylheptyl, 2-methylheptyl, 3-methylheptyl, 4-methylheptyl, 5-methylheptyl, 1-ethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, 5-ethylhexyl, 1,1-dimethylhexyl, 2,2-dimethylhexyl, 3,3-dimethylhexyl, 4,4-dimethylhexyl, 5,5-dimethylhexyl, 1,2, 3-trimethylpentyl group, 1,2,4-trimethylpentyl group, 2,3,4-trimethylpentyl group, 2,4,4-trimethylpentyl group, 1,4,4-trimethylpentyl group, 3,4,4-trimethylpentyl group, 1,1,2-trimethylpentyl group, 1,1,3-trimethylpentyl group, 1,1,4-trimethylpentyl group, 1,2,2-trimethylpentyl group, 2,2,3-trimethylpentyl group, 2,2,4-trimethylpentyl group, 1,3,3-trimethylpentyl group, 2,3,3-trimethylpentyl group, 3,3,Examples of such groups include 4-trimethylpentyl, 1-propylpentyl, 2-propylpentyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl groups. Examples of the cyclic alkyl group for R include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a norbornyl group, an isobornyl group, a 1-adamantyl group, a 2-adamantyl group, and a tricyclodecyl group.

[0030] Examples of the alkenyl group in R include groups in which one single bond (CC) between carbon atoms in the alkyl group in R is replaced with a double bond (C=C). Examples of such alkenyl groups include vinyl groups (ethenyl groups, -CH=CH2), allyl groups (2-propenyl groups, -CH2-CH=CH2), 1-propenyl groups (-CH=CH-CH3), isopropenyl groups (-C(CH3)=CH2), 1-butenyl groups (-CH=CH-CH2-CH3), 2-butenyl groups (-CH2-CH=CH-CH3), 3-butenyl groups (-CH2-CH2-CH=CH2), cyclohexenyl groups, and cyclopentenyl groups.

[0031] Examples of the alkynyl group in R include groups in which one single bond (CC) between carbon atoms in the alkyl group in R is replaced with a triple bond (C≡C). Examples of such alkynyl groups include an ethynyl group (-C≡CH), a propargyl group (-CH2-C≡CH), and the like.

[0032] In the aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by R, one or more hydrogen atoms may be substituted with a substituent. Preferred examples of the substituent include a fluorine atom, a chlorine atom, and a bromine atom. In addition, the number and positions of the substituents in the aliphatic hydrocarbon group are not particularly limited. When there are multiple substituents, these multiple substituents may be the same or different from one another. That is, all the substituents may be the same, all the substituents may be different, or only some of the substituents may be different.

[0033] In the phenyl group represented by R, one or more hydrogen atoms may be substituted with a substituent. Preferred examples of the substituent include saturated or unsaturated monovalent aliphatic hydrocarbon groups having 1 to 16 carbon atoms, monovalent groups formed by bonding the aliphatic hydrocarbon groups to an oxygen atom, fluorine atoms, chlorine atoms, bromine atoms, hydroxyl groups (-OH), cyano groups (-C≡N), and phenoxy groups (-O-CH). In the phenyl group having a substituent, the number and positions of the substituents are not particularly limited. When the phenyl group has a plurality of substituents, the plurality of substituents may be the same or different. Examples of the aliphatic hydrocarbon group as a substituent include the same aliphatic hydrocarbon groups as those for R, except that they have 1 to 16 carbon atoms.

[0034] Y in R 1 are each independently a fluorine atom, a chlorine atom, a bromine atom, or a hydrogen atom. 1 -CY 1 2-," "CY 1 3-" and "R 6 -C(=O)-CY 1 In "2-", there are multiple Y 1 may be the same or different from each other.

[0035] R in R 1 is an aliphatic hydrocarbon group having 1 to 19 carbon atoms or a phenyl group (C6H5-). 1Examples of the aliphatic hydrocarbon group in include the same aliphatic hydrocarbon groups as those in R, except that they have 1 to 19 carbon atoms. R in R 2 is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, and examples thereof include the same aliphatic hydrocarbon groups as those described above for R. R in R 3 R is an aliphatic hydrocarbon group having 1 to 16 carbon atoms. 3 Examples of the aliphatic hydrocarbon group in include the same aliphatic hydrocarbon groups as those in R, except that they have 1 to 16 carbon atoms. R in R 4 and R 5 are each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms. 4 and R 5 may be the same or different, and R 4 and R 5 Examples of the aliphatic hydrocarbon group in include the same aliphatic hydrocarbon groups as those in R, except that they have 1 to 18 carbon atoms. R in R 6 R is an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a hydroxyl group, or a group represented by the formula "AgO-". 6 Examples of the aliphatic hydrocarbon group in include the same aliphatic hydrocarbon groups as those in R, except that they have 1 to 19 carbon atoms.

[0036] Among the above, R is a linear or branched alkyl group, a group represented by the general formula "R 6 -C(=O)-CY 1 2-”, a hydroxyl group, or a phenyl group. 6 is preferably a linear or branched alkyl group, a hydroxyl group, or a group represented by the formula "AgO-".

[0037] In general formula (1), X 1are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a phenyl group or a benzyl group (C6H5-CH2-) in which one or more hydrogen atoms may be substituted with a substituent, a cyano group, an N-phthaloyl-3-aminopropyl group, a 2-ethoxyvinyl group (C2H5-O-CH=CH-), or a group represented by the general formula "R 7 O-," "R 7 S-," "R 7 -C(=O)-" or "R 7 It is a group represented by "-C(=O)-O-". X 1 Examples of the aliphatic hydrocarbon group having 1 to 20 carbon atoms in R include the same aliphatic hydrocarbon groups as those in R.

[0038] X 1 Examples of the halogen atom in include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. X 1 In the phenyl group and benzyl group in the above, one or more hydrogen atoms may be substituted with a substituent. Preferred examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a nitro group (-NO2), etc. In the phenyl group and benzyl group having a substituent, the number and positions of the substituents are not particularly limited. When the number of substituents is multiple, these multiple substituents may be the same or different.

[0039] X 1 R in 7 R is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a thienyl group (C4H3S-), or a phenyl or diphenyl group (biphenyl group, C6H5-C6H4-) in which one or more hydrogen atoms may be substituted with a substituent. 7 Examples of the aliphatic hydrocarbon group in R include the same aliphatic hydrocarbon groups as those in R, except that they have 1 to 10 carbon atoms. 7Examples of the substituents possessed by the phenyl group and diphenyl group in the above formula (1) include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom), etc. In the phenyl group and diphenyl group having a substituent, the number and positions of the substituents are not particularly limited. When the number of substituents is multiple, these multiple substituents may be the same or different. R 7 When X is a thienyl group or a diphenyl group, 1 There are no particular limitations on the bonding position to the adjacent group or atom (oxygen atom, sulfur atom, carbonyl group, carbonyloxy group) in the formula (I). For example, the thienyl group may be either a 2-thienyl group or a 3-thienyl group.

[0040] In the general formula (1), two X 1 may be bonded as a single group to the carbon atom sandwiched between the two carbonyl groups via a double bond. 1 Examples of the group include a group represented by the formula "=CH-C6H4-NO2".

[0041] X 1 Among the above, R is a hydrogen atom, a linear or branched alkyl group, a benzyl group, or a group represented by the general formula "R 7 Preferably, at least one of X is a group represented by "-C(=O)-". 1 is preferably a hydrogen atom.

[0042] Silver β-ketocarboxylates (1) include silver 2-methylacetoacetate (CH3-C(=O)-CH(CH3)-C(=O)-OAg), silver acetoacetate (CH3-C(=O)-CH2-C(=O)-OAg), silver 2-ethylacetoacetate (CH3-C(=O)-CH(CH2CH3)-C(=O)-OAg), silver propionylacetate (CH3CH2-C(=O)-CH2-C(=O)-OAg), and isobutyl Silver pivaloyl acetate ((CH3)2CH-C(=O)-CH2-C(=O)-OAg), silver caproyl acetate (CH3(CH2)3CH2-C(=O)-CH2-C(=O)-OAg), silver 2-n-butylacetoacetate (CH3-C(=O)-CH(CH2CH2CH2CH3)-C(=O)-OAg), 2-benzyl Silver acetoacetate (CH3-C(=O)-CH(CH2C6H5)-C(=O)-OAg), silver benzoylacetate (C6H5-C(=O)-CH2-C(=O)-OAg), silver pivaloylacetoacetate ((CH3)3C-C(=O)-CH2-C(=O)-CH2-C(=O)-OAg), silver isobutyrylacetoacetate ((CH3)2CH-C(=O)-CH2-C(=O)-CH2-C(=O)-O Silver 2-acetylpivaloyl acetate ((CH3)3C-C(=O)-CH(-C(=O)-CH3)-C(=O)-OAg), silver 2-acetylisobutyryl acetate ((CH3)2CH-C(=O)-CH(-C(=O)-CH3)-C(=O)-OAg), or silver acetonedicarboxylate (AgO-C(=O)-CH2-C(=O)-CH2-C(=O)-OAg).

[0043] In this embodiment, the silver β-ketocarboxylate (1) may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination and ratio thereof can be adjusted as desired.

[0044] (Silver carboxylate (4)) Examples of silver carboxylates other than the silver β-ketocarboxylate include silver carboxylates represented by the following general formula (4) (sometimes abbreviated herein as "silver carboxylate (4)").

[0045] [ka] (In the formula, R 8 represents an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a carboxy group, or a group represented by the formula "-C(=O)-OAg", and when the aliphatic hydrocarbon group has a methylene group, one or more of the methylene groups may be substituted with a carbonyl group.

[0046] In the formula, R 8 is an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a carboxy group (—COOH), or a group represented by the formula “—C(═O)—OAg.” R 8 The aliphatic hydrocarbon group in R may be the same as the aliphatic hydrocarbon group in R, except that it has 1 to 19 carbon atoms. 8 The aliphatic hydrocarbon group in the formula (I) preferably has 1 to 15 carbon atoms, and more preferably 1 to 10 carbon atoms.

[0047] R 8 When the aliphatic hydrocarbon group in the formula (I) has a methylene group (-CH2-), one or more of the methylene groups may be substituted with a carbonyl group. The number and position of the methylene groups that may be substituted with a carbonyl group are not particularly limited, and all of the methylene groups may be substituted with a carbonyl group. Here, the term "methylene group" refers not only to a single group represented by the formula "-CH2-", but also to a single group represented by the formula "-CH2-" in an alkylene group in which multiple groups represented by the formula "-CH2-" are linked together.

[0048] The silver carboxylate (4) is preferably silver pyruvate (CH3-C(=O)-C(=O)-OAg), silver acetate (CH3-C(=O)-OAg), silver butyrate (CH3-(CH2)2-C(=O)-OAg), silver isobutyrate ((CH3)2CH-C(=O)-OAg), silver 2-ethylhexanoate (CH3-(CH2)3-CH(CH2CH3)-C(=O)-OAg), silver neodecanoate, silver oxalate (AgO-C(=O)-C(=O)-OAg), or silver malonate (AgO-C(=O)-CH2-C(=O)-OAg). Also preferred are those in which one of the two groups represented by the formula "-COOAg" in the above silver oxalate (AgO-C(=O)-C(=O)-OAg) is a group represented by the formula "-COOH" (HO-C(=O)-C(=O)-OAg, HO-C(=O)-CH2-C(=O)-OAg).

[0049] In this embodiment, the silver carboxylate (4) may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination and ratio thereof can be adjusted as desired.

[0050] The silver carboxylate is preferably the silver β-ketocarboxylate or silver oxalate, and more preferably the silver β-ketocarboxylate (1) or silver oxalate. That is, the first silver particles are preferably obtained by thermal decomposition or reduction of the silver β-ketocarboxylate or silver oxalate, and more preferably obtained by thermal decomposition or reduction of the silver β-ketocarboxylate (1) or silver oxalate.

[0051] The average secondary particle diameter of the first silver particles is 2 μm or less, and may be, for example, 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less. When the average secondary particle diameter of the first silver particles is 2 μm or less, a silver sintered body that exhibits ductility and suppresses the occurrence of cracks can be produced without applying high pressure to the silver-containing composition during sintering of the silver-containing composition.

[0052] There is no particular lower limit to the average secondary particle size of the first silver particles. For example, when the average secondary particle size is 0.1 μm or more, the occurrence of cracks in the silver sintered body is further suppressed.

[0053] <Second silver particles> The second silver particles differ from the first silver particles in that the particle size at 50% accumulation (herein sometimes abbreviated as "D50") of the second silver particles, measured by laser diffraction / scattering particle size distribution measurement, is less than 1.5 μm. When the second silver particles have a D50 of less than 1.5 μm, a silver sintered body exhibiting ductility and suppressing the occurrence of cracks can be produced without applying high pressure to the silver-containing composition during sintering of the silver-containing composition. The D50 of the second silver particles may be, for example, any one of 1.3 μm or less, 0.9 μm or less, and less than 0.4 μm.

[0054] There is no particular limitation on the lower limit of the D50 of the second silver particles. For example, when the D50 is 0.1 μm or more, the production of a silver sintered body becomes easier.

[0055] The second silver particles may be, for example, flake-shaped particles having a single crystal structure, the largest plane of which is a lattice plane (111).

[0056] The secondary silver particles may have a thickness of 0.03 to 0.2 μm and a maximum diameter of 0.1 to 2 μm, for example. Here, the maximum diameter of the secondary silver particles refers to the maximum length of a line segment connecting any two points located on the contour of the secondary silver particles in an identified image of the secondary silver particles. Examples of the identified image include an image observed with an electron microscope and an image-processed version of the observed image.

[0057] The second silver particles may be formed by a chemical reaction of a silver-containing compound having silver atoms as constituent atoms. Examples of the silver-containing compound that forms the second silver particles include the same silver-containing compounds that form the first silver particles.

[0058] The second silver particles can be obtained by a known method, for example, using a silver-containing compound that generates second silver particles by its reduction reaction and using an additive that controls the crystal growth direction during the reduction reaction. In this embodiment, commercially available products may be used as the second silver particles.

[0059] The silver-containing composition contains first silver particles and second silver particles. In the silver-containing composition, the ratio of the content (parts by mass) of the first silver particles to the content (parts by mass) of the second silver particles (sometimes abbreviated herein as the "mass ratio of first silver particles / second silver particles") is preferably 5 / 95 to 50 / 50, more preferably 7 / 93 to 35 / 65, and may be, for example, any of 9 / 91 to 25 / 75 and 12 / 88 to 20 / 80. When the mass ratio of the first silver particles / second silver particles is within this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced without applying high pressure to the silver-containing composition during sintering. In particular, the greater the ratio of the second silver particles, the higher the maximum stress and ductility of the silver sintered body.

[0060] The proportion of the silver content (parts by mass) in the silver-containing composition relative to the total mass of the silver-containing composition (sometimes abbreviated as "silver concentration" in this specification) is preferably 60 to 95 mass%, more preferably 70 to 92 mass%, and may be, for example, either 75 to 89 mass% or 78 to 86 mass%. When the silver concentration is within this range, a silver sintered body that exhibits ductility and suppresses the occurrence of cracks can be more easily produced, even without applying high pressure to the silver-containing composition during sintering. Here, "silver content (parts by mass)" means "the total content (parts by mass) of the first silver particles and the second silver particles," and "silver concentration" means "the total concentration of the first silver particles and the second silver particles."

[0061] <Aliphatic carboxylic acids with 8 to 11 carbon atoms> The silver-containing composition further contains an aliphatic carboxylic acid having 8 to 11 carbon atoms (referred to herein as "C 8~11 The above C may be blended with an aliphatic carboxylic acid. 8~11 By using a silver-containing composition containing an aliphatic carboxylic acid, the maximum stress and ductility of the silver sintered body are further improved.

[0062] Said C 8~11 The aliphatic carboxylic acid is not particularly limited as long as it is an aliphatic carboxylic acid having 8 to 11 carbon atoms. C 8~11 The aliphatic carboxylic acid may be any of a chain aliphatic carboxylic acid in which the aliphatic group is linear or branched, a cyclic aliphatic carboxylic acid in which the aliphatic group is cyclic (an alicyclic group), and an aliphatic carboxylic acid in which the aliphatic group has both a linear or branched moiety and a cyclic moiety. C 8~11 The aliphatic carboxylic acid may be either a saturated aliphatic carboxylic acid or an unsaturated aliphatic carboxylic acid. C 8~11 The number of carboxy groups in the aliphatic carboxylic acid may be one or two or more. 8~11 The position of the carboxy group in the aliphatic carboxylic acid is not particularly limited.

[0063] C 8~11 Because aliphatic carboxylic acids have a moderately high boiling point, they tend to remain on the surface of the silver-containing composition during the formation of the silver sintered body during the production of the silver sintered body from the silver-containing composition described below. This is thought to suppress the rapid drying of the surface of the silver-containing composition and its vicinity, thereby suppressing the occurrence of cracks in the silver sintered body.

[0064] C 8~11 The boiling point of the aliphatic carboxylic acid is preferably 180 to 270°C, more preferably 200 to 260°C, and particularly preferably 215 to 255°C. 8~11 The boiling point of the aliphatic carboxylic acid is the lower limit or more, and thus C 8~11The effect of using an aliphatic carboxylic acid is more pronounced. 8~11 When the boiling point of the aliphatic carboxylic acid is equal to or lower than the upper limit, C is easily absorbed into the sintered silver body. 8~11 The residual aliphatic carboxylic acid is highly suppressed.

[0065] C 8~11 The aliphatic carboxylic acid is preferably a chain aliphatic carboxylic acid, more preferably a branched chain aliphatic carboxylic acid. C 8~11 The aliphatic carboxylic acid is preferably a saturated aliphatic carboxylic acid. C 8~11 The aliphatic carboxylic acid is more preferably a chain saturated aliphatic carboxylic acid, and even more preferably a branched saturated aliphatic carboxylic acid.

[0066] Particularly preferred branched saturated aliphatic carboxylic acids include neodecanoic acid (CH 19 COOH), 2-propylvaleric acid (also known as 2-propylpentanoic acid, (CH3CH2CH2CH(CH3CH2CH2)COOH), and 3,5,5-trimethylhexanoic acid ((CH3)3CCH2CH(CH3)CH2COOH). In this specification, neodecanoic acid refers to a mixture of isomers of saturated aliphatic monocarboxylic acids having 10 carbon atoms, and the mixture always contains a branched saturated aliphatic monocarboxylic acid having 10 carbon atoms. Thus, unless otherwise specified, neodecanoic acid does not refer to only one type of compound. The combination and ratio of two or more saturated aliphatic monocarboxylic acids having 10 carbon atoms in neodecanoic acid can be adjusted as desired.

[0067] C used during blending 8~11 The aliphatic carboxylic acids may be used alone or in combination of two or more kinds, and when two or more kinds are used, the combination and ratio thereof can be adjusted as desired.

[0068] C 8~11 Most preferably, the aliphatic carboxylic acid is neodecanoic acid.

[0069] <Other ingredients> The silver-containing composition comprises first silver particles, second silver particles, and C 8~11 The composition may contain other components that do not fall into the category of either aliphatic carboxylic acids or components derived therefrom.

[0070] The silver-containing composition may contain only one type of other component, or two or more types. When two or more types are contained, the combination and ratio thereof can be adjusted as desired.

[0071] [solvent] A preferred example of the other component is a solvent. The solvent is not particularly limited as long as it does not impair the effects of the present invention. Specific examples of the solvent include ethylene glycol, diethylene glycol, terpineol, diethylene glycol monobutyl ether, and diethylene glycol monobutyl ether acetate.

[0072] <<Method of manufacturing the silver-containing composition>> The silver-containing composition may be, for example, a raw material composition (1) containing first silver particles, a raw material composition (2) containing second silver particles, and optionally C 8~11 The composition can be produced by mixing (blending) an aliphatic carboxylic acid and, if necessary, other components. Examples of the other components that may be contained in the silver-containing composition when it is produced include the other components described above as being contained in the silver-containing composition.

[0073] <Raw material composition (1)> The raw material composition (1) may be, for example, a composition obtained by blending the silver-containing compound with a nitrogen-containing compound having a nitrogen atom as a constituent atom, and may further comprise a reducing agent. The raw material composition (1) that has been heat-treated after blending the silver-containing compound and the nitrogen-containing compound contains first silver particles produced by thermal decomposition of the silver-containing compound. Furthermore, the raw material composition (1) containing the reducing agent contains first silver particles produced by the reduction of the silver-containing compound.

[0074] [Silver-containing compounds] The silver-containing compound, which is a blending component of raw material composition (1), is the same as the silver-containing compound described above as a material for forming the first silver particles.

[0075] The silver-containing compound used in producing the raw material composition (1) may be one type only, or two or more types. When two or more types are used, the combination and ratio thereof can be adjusted as desired.

[0076] [Nitrogen-containing compounds] Examples of the nitrogen-containing compound include amine compounds having 25 or less carbon atoms.

[0077] (amine compounds) The amine compound has 1 to 25 carbon atoms and may be any of a primary amine, a secondary amine, and a tertiary amine. The amine compound may be either linear or cyclic. In the amine compound, the number of nitrogen atoms constituting the amine moiety (for example, in the case of a primary amine, the nitrogen atoms constituting the amino group (—NH)) may be 1 or 2 or more. In addition, the position of the nitrogen atom constituting the amine moiety in the amine compound is not particularly limited.

[0078] Examples of the primary amine include monoalkylamines, monoarylamines, mono(heteroaryl)amines, diamines, and the like, in which one or more hydrogen atoms may be substituted with a substituent.

[0079] The alkyl group constituting the monoalkylamine may be any of linear, branched, and cyclic, and examples of such alkyl groups include the same as the alkyl groups in R. The alkyl group is preferably a linear or branched alkyl group having 1 to 19 carbon atoms, or a cyclic alkyl group having 3 to 7 carbon atoms. Specific examples of preferred monoalkylamines include n-butylamine, n-hexylamine, n-octylamine, n-dodecylamine, n-octadecylamine, isobutylamine, sec-butylamine, tert-butylamine, 3-aminopentane, 3-methylbutylamine, 2-heptylamine (2-aminoheptane), 2-aminooctane, 2-ethylhexylamine, and 1,2-dimethyl-n-propylamine.

[0080] Examples of the aryl group constituting the monoarylamine include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, etc. The aryl group preferably has 6 to 10 carbon atoms.

[0081] The heteroaryl group constituting the mono(heteroaryl)amine has a heteroatom as an atom constituting the aromatic ring skeleton, and examples of the heteroatom include a nitrogen atom, a sulfur atom, an oxygen atom, and a boron atom. The number of heteroatoms constituting the aromatic ring skeleton is not particularly limited and may be one or two or more. When there are two or more heteroatoms, these heteroatoms may be the same or different from one another. That is, these heteroatoms may all be the same, all be different, or only some may be different. The heteroaryl group may be either monocyclic or polycyclic, and the number of ring members (the number of atoms constituting the ring skeleton) is not particularly limited, but is preferably a 3- to 12-membered ring.

[0082] Examples of the heteroaryl group that is a monocyclic group having 1 to 4 nitrogen atoms include a pyrrolyl group, a pyrrolinyl group, an imidazolyl group, a pyrazolyl group, a pyridyl group, a pyrimidyl group, a pyrazinyl group, a pyridazinyl group, a triazolyl group, a tetrazolyl group, a pyrrolidinyl group, an imidazolidinyl group, a piperidinyl group, a pyrazolidinyl group, and a piperazinyl group. Such a heteroaryl group is preferably a 3- to 8-membered ring, and more preferably a 5- or 6-membered ring. Examples of the heteroaryl group that is monocyclic and has one oxygen atom include a furanyl group, and such a heteroaryl group is preferably a 3- to 8-membered ring, and more preferably a 5- or 6-membered ring. Examples of the monocyclic heteroaryl group having one sulfur atom include a thienyl group, and such a heteroaryl group is preferably a 3- to 8-membered ring, and more preferably a 5- or 6-membered ring. Examples of the monocyclic heteroaryl group having 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms include an oxazolyl group, an isoxazolyl group, an oxadiazolyl group, and a morpholinyl group. Such a heteroaryl group is preferably a 3- to 8-membered ring, and more preferably a 5- or 6-membered ring. Examples of the monocyclic heteroaryl group having 1 to 2 sulfur atoms and 1 to 3 nitrogen atoms include a thiazolyl group, a thiadiazolyl group, and a thiazolidinyl group. Such a heteroaryl group is preferably a 3- to 8-membered ring, and more preferably a 5- or 6-membered ring. Examples of the heteroaryl group that is a polycyclic group having 1 to 5 nitrogen atoms include an indolyl group, an isoindolyl group, an indolizinyl group, a benzimidazolyl group, a quinolyl group, an isoquinolyl group, an indazolyl group, a benzotriazolyl group, a tetrazolopyridyl group, a tetrazolopyridazinyl group, and a dihydrotriazolopyridazinyl group. Such a heteroaryl group is preferably a 7- to 12-membered ring, and more preferably a 9- to 10-membered ring. Examples of the polycyclic heteroaryl group having 1 to 3 sulfur atoms include a dithianaphthalenyl group and a benzothiophenyl group. Such a heteroaryl group is preferably a 7- to 12-membered ring, and more preferably a 9- or 10-membered ring. Examples of the polycyclic heteroaryl group having 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms include a benzoxazolyl group and a benzoxadiazolyl group. Such a heteroaryl group is preferably a 7- to 12-membered ring, and more preferably a 9- or 10-membered ring. Examples of the polycyclic heteroaryl group having 1 to 2 sulfur atoms and 1 to 3 nitrogen atoms include a benzothiazolyl group and a benzothiadiazolyl group. Such a heteroaryl group is preferably a 7- to 12-membered ring, and more preferably a 9- or 10-membered ring.

[0083] The diamine may have two amino groups, and the positional relationship of the two amino groups is not particularly limited. Preferred examples of the diamine include the monoalkylamine, monoarylamine, or mono(heteroaryl)amine in which one hydrogen atom other than the hydrogen atom constituting the amino group (-NH2) is substituted with an amino group. The diamine preferably has 1 to 10 carbon atoms, and more preferred examples include ethylenediamine, 1,3-diaminopropane, and 1,4-diaminobutane.

[0084] Examples of the secondary amine include dialkylamines, diarylamines, and di(heteroaryl)amines in which one or more hydrogen atoms may be substituted with a substituent.

[0085] The alkyl group constituting the dialkylamine is the same as the alkyl group constituting the monoalkylamine, and is preferably a linear or branched alkyl group having 1 to 9 carbon atoms, or a cyclic alkyl group having 3 to 7 carbon atoms. The two alkyl groups in one molecule of the dialkylamine may be the same or different. Specific examples of preferred dialkylamines include N-methyl-n-hexylamine, diisobutylamine, and di(2-ethylhexyl)amine.

[0086] The aryl group constituting the diarylamine is similar to the aryl group constituting the monoarylamine, and preferably has a carbon number of 6 to 10. Furthermore, the two aryl groups in one diarylamine molecule may be the same or different.

[0087] The heteroaryl group constituting the di(heteroaryl)amine is the same as the heteroaryl group constituting the mono(heteroaryl)amine, and is preferably a 6- to 12-membered ring. Furthermore, the two heteroaryl groups in one molecule of the di(heteroaryl)amine may be the same or different.

[0088] Examples of the tertiary amine include trialkylamines and dialkylmonoarylamines in which one or more hydrogen atoms may be substituted with a substituent.

[0089] The alkyl groups constituting the trialkylamine are the same as the alkyl groups constituting the monoalkylamine, and are preferably linear or branched alkyl groups having 1 to 19 carbon atoms, or cyclic alkyl groups having 3 to 7 carbon atoms. The three alkyl groups in one trialkylamine molecule may be the same or different from one another. That is, the three alkyl groups may all be the same, all be different, or only some may be different. Specific examples of preferred trialkylamines include N,N-dimethyl-n-octadecylamine and N,N-dimethylcyclohexylamine.

[0090] The alkyl group constituting the dialkylmonoarylamine is the same as the alkyl group constituting the monoalkylamine, and is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, or a cyclic alkyl group having 3 to 7 carbon atoms. The two alkyl groups in one molecule of the dialkylmonoarylamine may be the same or different. The aryl group constituting the dialkylmonoarylamine is the same as the aryl group constituting the monoarylamine, and preferably has 6 to 10 carbon atoms.

[0091] So far, we have mainly described chain-like amine compounds, but the amine compound may also be a heterocyclic compound in which the nitrogen atom constituting the amine moiety is part of a ring skeleton structure (heterocyclic skeleton structure). That is, the amine compound may also be a cyclic amine. In this case, the ring structure (the ring containing the nitrogen atom constituting the amine moiety) may be either monocyclic or polycyclic, and the number of ring members (the number of atoms constituting the ring skeleton) is not particularly limited, and may be either an aliphatic ring or an aromatic ring. A preferred example of the cyclic amine is pyridine.

[0092] In the primary amines, secondary amines, tertiary amines, and quaternary ammonium salts, the "hydrogen atoms optionally substituted with substituents" refer to hydrogen atoms other than those bonded to the nitrogen atoms constituting the amine moiety. The number of substituents is not particularly limited, and may be one, two, or more, or all of the hydrogen atoms may be substituted with substituents. When there are multiple substituents, these multiple substituents may be the same or different from one another. That is, the multiple substituents may all be the same, all different, or only some may be different. Furthermore, the positions of the substituents are also not particularly limited.

[0093] Examples of the substituent in the amine compound include an alkyl group, an aryl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, a trifluoromethyl group (-CF), etc. Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.

[0094] When the alkyl group constituting the monoalkylamine has a substituent, the alkyl group is preferably a linear or branched alkyl group having 1 to 9 carbon atoms and having an aryl group as a substituent, or a cyclic alkyl group having 3 to 7 carbon atoms and having an alkyl group having 1 to 5 carbon atoms as a substituent. Specific examples of monoalkylamines having such a substituent include 2-phenylethylamine, benzylamine, and 2,3-dimethylcyclohexylamine. In addition, the aryl group and alkyl group as substituents may further have one or more hydrogen atoms substituted with halogen atoms. Examples of monoalkylamines having substituents substituted with halogen atoms include 2-bromobenzylamine. Here, examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0095] When the aryl group constituting the monoarylamine has a substituent, the aryl group is preferably an aryl group having 6 to 10 carbon atoms and having a halogen atom as a substituent. Specific examples of monoarylamines having such a substituent include bromophenylamine. Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0096] When the alkyl group constituting the dialkylamine has a substituent, the alkyl group is preferably a linear or branched alkyl group having 1 to 9 carbon atoms and having a hydroxyl group or an aryl group as a substituent. Specific examples of dialkylamines having such a substituent include diethanolamine and N-methylbenzylamine.

[0097] The nitrogen-containing compound used in producing the raw material composition (1) may be one kind or two or more kinds, and when two or more kinds are used, the combination and ratio thereof can be adjusted as desired.

[0098] The amine compound is preferably n-propylamine, n-butylamine, n-hexylamine, n-octylamine, n-dodecylamine, n-octadecylamine, isobutylamine, sec-butylamine, tert-butylamine, 3-aminopentane, 3-methylbutylamine, 2-heptylamine, 2-aminooctane, 2-ethylhexylamine, 2-phenylethylamine, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, N-methyl-n-hexylamine, diisobutylamine, N-methylbenzylamine, di(2-ethylhexyl)amine, 1,2-dimethyl-n-propylamine, N,N-dimethyl-n-octadecylamine, or N,N-dimethylcyclohexylamine.

[0099] In raw material composition (1), the amount of the nitrogen-containing compound is preferably 0.1 to 5 mol, more preferably 0.1 to 3 mol, per 1 mol of the silver-containing compound, and may be, for example, 0.2 to 2 mol or 0.2 to 1 mol. When the amount is within this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced without applying high pressure to the silver-containing composition during sintering.

[0100] [Reducing agent] The reducing agent is not particularly limited.

[0101] The reducing agent used in the blending may be one type only, or two or more types, and when two or more types are used, the combination and ratio thereof can be adjusted as desired.

[0102] A preferred example of the reducing agent is formic acid.

[0103] When a reducing agent is used, the amount of the reducing agent in raw material composition (1) is preferably 0.2 to 5 mol, more preferably 0.3 to 3 mol, per 1 mol of the silver-containing compound, and may be, for example, 0.4 to 2 mol or 0.4 to 1 mol. When the amount is within this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced without applying high pressure to the silver-containing composition during sintering.

[0104] [Other ingredients] The raw material composition (1) may be a composition containing other components that do not fall into any of the categories of the silver-containing compound, the nitrogen-containing compound, and the reducing agent. The other components in the raw material composition (1) are not particularly limited as long as they do not impair the effects of the present invention. Examples of the other components in the raw material composition (1) include the other components previously described as components that may be contained in the silver-containing composition.

[0105] The other components used in producing the raw material composition (1) may be one type only, or two or more types. When two or more types are used, the combination and ratio thereof can be adjusted as desired.

[0106] In raw material composition (1), the ratio of the total amount (parts by mass) of the silver-containing compound, the nitrogen-containing compound, and the reducing agent to the total mass of the ingredients is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, 95% by mass or more or 99% by mass or more. When the ratio is in this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced without applying high pressure to the silver-containing composition during sintering.

[0107] <Method for producing raw material composition (1)> The raw material composition (1) can be obtained by blending the silver-containing compound, the nitrogen-containing compound, and, if necessary, the reducing agent and the other components. After blending the components, the resulting mixture can be used as raw material composition (1) as is, or can be used as raw material composition (1) after, if necessary, performing a known post-treatment or purification operation.

[0108] The order of mixing the components is not particularly limited. An example of a preferred method of mixing the components is to add the silver-containing compound to the nitrogen-containing compound and mix them, and then, if necessary, add the reducing agent to the resulting mixture and mix them. When the other components are blended, they may be blended at a timing suitable for the other components.

[0109] The mixing method is not particularly limited, and may be appropriately selected from known methods such as a method of mixing by rotating a stirrer or stirring blades, etc.; a method of mixing using a mixer, three-roll mill, kneader, bead mill, etc.; and a method of mixing by adding ultrasound.

[0110] The temperature during blending of the components is not particularly limited as long as the components do not deteriorate, but is preferably −5 to 60° C. The temperature during blending may be adjusted appropriately depending on the types and amounts of the components so that the mixture obtained by blending has a viscosity that allows easy stirring. The blending time of each component is not particularly limited as long as the components do not deteriorate, but is preferably 10 minutes to 36 hours.

[0111] The above-described production method produces raw material composition (1) containing first silver particles having the above-described primary particle size and average secondary particle size. In this case, the primary particle size and average secondary particle size of the first silver particles may be adjusted by, for example, adjusting the production conditions of raw material composition (1), such as the stirring conditions in each step.

[0112] <Raw material composition (2) and its manufacturing method> Examples of the raw material composition (2) include one obtained by the same method as in the case of raw material composition (1) (sometimes referred to in this specification as "raw material composition (2-1)"). However, it is preferable that the production conditions for raw material composition (2-1), such as the blending order of the components, the mixing method, the blending temperature, and the blending time, be appropriately adjusted so as to obtain secondary silver particles having a D50 of less than 1.5 μm, and preferably further so as to obtain secondary silver particles that are flaky, have a single crystal structure, and have the largest plane of the lattice plane (111). When the silver particles obtained for the purpose of producing the raw material composition (2-1) are not in a flake form, the raw material composition (2-1) can be obtained by adjusting the silver particles to a flake form.

[0113] Examples of the raw material composition (2) include a composition obtained by dispersing pre-produced secondary silver particles in a solvent (sometimes referred to in this specification as "raw material composition (2-2)").

[0114] Examples of the solvent that is a blended (contained) component of the raw material composition (2-2) include the same solvents that are contained in the silver-containing composition described above.

[0115] The raw material composition (2-2) may contain other components that do not fall into either the category of secondary silver particles or the category of the solvent. The other components in the raw material composition (2-2) are not particularly limited as long as they do not impair the effects of the present invention. Examples of the other components in the raw material composition (2-2) include the other components previously described as components that may be contained in the silver-containing composition.

[0116] The other components contained in the raw material composition (2-2) may be one type only, or two or more types. When there are two or more types, the combination and ratio thereof can be adjusted as desired.

[0117] In raw material composition (2-2), the ratio of the total content (parts by mass) of the second silver particles and the solvent to the total mass of raw material composition (2-2) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, 95% by mass or more or 99% by mass or more. When the ratio is in this range, a silver sintered body that exhibits ductility and suppresses the occurrence of cracks can be more easily produced, even without applying high pressure to the silver-containing composition during sintering of the silver-containing composition.

[0118] The proportion of silver content (silver concentration) in raw material composition (2-2) relative to the total mass of raw material composition (2-2) is not particularly limited, but is preferably 70 to 95 mass%, more preferably 75 to 95 mass%, and may be, for example, either 80 to 95 mass% or 85 to 95 mass%. When the proportion is in this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced, even without applying high pressure to the silver-containing composition during sintering.

[0119] The raw material composition (2-2) can be obtained by blending the secondary silver particles, the solvent, and, if necessary, the other components. After blending the components, the resulting mixture may be used as raw material composition (2-2) as is, or may be used as raw material composition (2-2) after, if necessary, performing a known post-treatment or purification operation.

[0120] The order in which the components are mixed when producing the raw material composition (2-2) is not particularly limited. The mixing method used in producing the raw material composition (2-2) is not particularly limited, and may be the same as the mixing method used in producing the raw material composition (1), for example. When the other components are blended, they may be blended at a timing suitable for the other components.

[0121] The temperature during blending of the components in the production of the raw material composition (2-2) is not particularly limited as long as the components do not deteriorate, but is preferably 15 to 35° C. The blending temperature may be adjusted appropriately depending on the types and amounts of the components so that the blended mixture has a viscosity that allows easy stirring. The blending time of each component is not particularly limited as long as the components do not deteriorate, but is preferably 10 to 60 minutes.

[0122] As described above, both raw material composition (1) and raw material composition (2) may be prepared by blending the silver-containing compound, the nitrogen-containing compound, and, if necessary, a reducing agent. That is, in this embodiment, either or both of the first silver particles and the second silver particles may be obtained using the silver-containing compound, and it is preferable that either or both of the first silver particles and the second silver particles are obtained by thermal decomposition or reduction of the silver-containing compound. It is more preferable that either or both of the first silver particles and the second silver particles are obtained by thermal decomposition or reduction of silver β-ketocarboxylate or silver oxalate, and it is even more preferable that at least the first silver particles are obtained by thermal decomposition or reduction of silver β-ketocarboxylate or silver oxalate.

[0123] C 8~11 When an aliphatic carboxylic acid is used, the ratio of C to the total mass of the components in the silver-containing composition is 8~11 The proportion of the amount (parts by mass) of aliphatic carboxylic acid (in this specification, "C 8~11The aliphatic carboxylic acid content (sometimes abbreviated as "aliphatic carboxylic acid content") is preferably 0.5 to 10 mass%, more preferably 1 to 8 mass%, and may be, for example, either 1.4 to 6.5 mass% or 1.8 to 5 mass%. When the content is within this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced, even without applying high pressure to the silver-containing composition during sintering of the silver-containing composition.

[0124] In the silver-containing composition, the ratio of the amount (parts by mass) of raw material composition (1) to the amount (parts by mass) of raw material composition (2) (sometimes abbreviated herein as "mass ratio of raw material composition (1) / raw material composition (2)") is preferably 5 / 95 to 35 / 65, more preferably 9 / 91 to 31 / 69, and may be, for example, any of 13 / 87 to 27 / 73 and 17 / 83 to 23 / 77. When the mass ratio of raw material composition (1) / raw material composition (2) is within this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced, even without applying high pressure to the silver-containing composition during sintering of the silver-containing composition.

[0125] The ratio of raw material composition (1), raw material composition (2), and C to the total mass of the blended components in the silver-containing composition 8~11 The ratio of the total amount (parts by mass) of the aliphatic carboxylic acid and the silver-containing composition is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, 95% by mass or more or 99% by mass or more. When the ratio is in this range, a silver sintered body that exhibits ductility and suppresses cracking can be more easily produced without applying high pressure to the silver-containing composition during sintering.

[0126] After blending (mixing) the raw materials, the resultant product may be used as a silver-containing composition as is, or may be used as a silver-containing composition after further performing a known post-treatment or purification operation as necessary.

[0127] The order of blending the raw materials is not particularly limited. As an example of a preferred method of blending the raw materials, raw material composition (1) and raw material composition (2) are mixed, and then, if necessary, the obtained mixture is mixed with C 8~11 and an aliphatic carboxylic acid. When the other components are blended, they may be blended at a timing suitable for the other components.

[0128] The mixing method used in producing the silver-containing composition is not particularly limited, and may be the same as the mixing method used in producing raw material composition (1), for example.

[0129] The temperature during blending of the raw materials is not particularly limited as long as the raw materials do not deteriorate, but is preferably 15 to 35° C. The blending temperature may be adjusted appropriately depending on the types and amounts of the raw materials so that the blended mixture has a viscosity that allows easy stirring. The blending time of each raw material is not particularly limited as long as the blended components do not deteriorate, but is preferably 2 to 60 minutes.

[0130] <<Silver sintered body>> In a silver sintered body according to one embodiment of the present invention, when the grain size distribution of the crystal grains in the silver sintered body is measured on an area basis by an electron backscattered diffraction pattern (EBSD) method, the proportion of crystal grains with a grain size of 0.5 to 1.2 μm to all crystal grains (sometimes abbreviated in this specification as "the proportion of crystal grains (0.5 to 1.2 μm)") is 40% or more. By satisfying these conditions, the silver sintered body of this embodiment exhibits ductility and suppresses the occurrence of cracks. Furthermore, the silver sintered body of this embodiment can also increase the maximum stress. Such a silver sintered body of this embodiment is suitable, for example, as a wiring material for electronic components or a bonding material for semiconductors. For example, as described below, the silver sintered body of this embodiment is suitable for use as a bonding portion in a bonded body in which a conductive first component and a conductive second component are bonded via a bonding portion. Even when such a bonded body is placed in an environment with large temperature changes, the stress generated in the bonding portion is alleviated, thereby suppressing peeling between the first component or the second component and the bonding portion. The silver sintered body is particularly suitable for use as a bonding portion between an electrode on a substrate and a semiconductor element, and is particularly suitable for constituting a semiconductor device that is expected to operate at high temperatures of 200°C or higher.

[0131] The proportion of the crystal grains (0.5 to 1.2 μm) is preferably 43% or more, and may be, for example, either 50% or more or 60% or more. When the proportion of the crystal grains (0.5 to 1.2 μm) is equal to or more than the lower limit, the ductility of the silver sintered body is further increased, and the occurrence of cracks is further suppressed. There is no particular upper limit to the proportion of crystal grains (0.5 to 1.2 μm). For example, the silver sintered body in which the proportion of crystal grains (0.5 to 1.2 μm) is 70% or less is easier to manufacture.

[0132] When the grain size distribution of the crystal grains in the silver sintered body is measured on an area basis by electron backscatter diffraction (EBSD), the ratio of crystal grains with a grain size of 0.5 μm or more to all crystal grains (sometimes abbreviated as "the ratio of crystal grains (0.5 μm or more)" in this specification) is preferably 70% or more, more preferably 80% or more, and may be, for example, either 85% or more or 90% or more. When the ratio of crystal grains (0.5 μm or more) is equal to or greater than the lower limit, the ductility of the silver sintered body is increased, and the occurrence of cracks is further suppressed. There is no particular upper limit to the proportion of crystal grains (0.5 μm or larger). For example, the silver sintered body in which the proportion of crystal grains (0.5 μm or larger) is 97% or less is easier to manufacture.

[0133] A test piece of the silver sintered body having a width of 5 mm, a length of the measurement target portion of 6 mm, and a thickness of 0.2 mm was prepared, and the test piece was tensioned in the length direction at a tension rate of 1 × 10 -4 When a tensile test is carried out by pulling the test piece at 1 / sec, the maximum stress of the test piece is preferably 70 MPa or more, and may be, for example, 85 MPa or more or 100 MPa or more. The upper limit of the maximum stress is not particularly limited. For example, the test piece (sintered silver body) having a maximum stress of 120 MPa or less is easier to manufacture. During the above-mentioned tensile test, the fracture surface occurring in the silver sintered body is perpendicular or nearly perpendicular to the direction of the force applied to the silver sintered body during the tensile test.

[0134] The breaking strain of the test piece during the tensile test, measured when the maximum stress of the test piece is measured, is preferably 4.5% or more, and may be, for example, 5.3% or more, or 6% or more. The upper limit of the breaking strain is not particularly limited. For example, the test piece (sintered silver body) having a breaking strain of 8% or less is easier to manufacture.

[0135] The porosity of the silver sintered body is preferably 35% or less, more preferably 33% or less, and may be, for example, either 25% or less or 29% or less. The lower limit of the porosity is not particularly limited. For example, the test piece (silver sintered body) having a porosity of 5% or more is easier to manufacture. In this embodiment, by using the silver-containing composition, a silver sintered body can be produced by firing (sintering) the silver-containing composition under normal pressure (atmospheric pressure) without applying pressure to the silver-containing composition, as described below.

[0136] The thickness of the silver sintered body is not particularly limited and can be selected arbitrarily depending on the purpose. The silver sintered body produced using the silver-containing composition has sufficiently high strength and is free from cracks even when the thickness is made sufficiently large (thick film). For example, the thickness of the silver sintered body is preferably 50 μm or more, and may be any of 65 μm or more and 80 μm or more. On the other hand, the silver sintered body having a thickness of 150 μm or less can be produced more easily.

[0137] <<Manufacturing method for sintered silver body>> The silver sintered body of this embodiment can be produced by heating (firing) the silver-containing composition according to one embodiment of the present invention described above to sinter the first silver particles and second silver particles in the silver-containing composition.

[0138] The temperature rise rate of the silver-containing composition during heating in the production of the silver sintered body is not particularly limited, but is preferably 3 to 20°C / min, and may be, for example, 3 to 15°C / min. When the temperature rise rate is within this range, a silver sintered body having the desired properties can be produced more efficiently.

[0139] The firing temperature of the silver-containing composition (the temperature at which the silver-containing composition is sintered) during production of the silver sintered body is preferably 350° C. or lower, and may be, for example, either 330° C. or lower or 310° C. or lower. When the firing temperature is equal to or lower than the upper limit, residual stress in the resulting silver sintered body is reduced, and for example, when the silver sintered body is used as a joint between conductive parts, the joining strength is improved. The firing temperature of the silver-containing composition (the temperature at which the silver-containing composition is sintered) is preferably 250° C. or higher, and may be, for example, 270° C. or higher or 290° C. When the firing temperature is equal to or higher than the lower limit, a silver sintered body with higher purity can be obtained.

[0140] In this specification, sintering of the silver-containing composition is synonymous with sintering of the first silver particles and the second silver particles.

[0141] In producing the silver sintered body, the firing time of the silver-containing composition (the time for sintering the silver-containing composition) is preferably 30 to 120 minutes, and may be, for example, 50 to 90 minutes. By keeping the firing time (sintering time) within this range, a silver sintered body with the desired properties can be produced more efficiently.

[0142] The firing of the silver-containing composition (sintering of the first silver particles and the second silver particles) may be carried out by applying a pressure of the same level as conventionally applied to the silver-containing composition, but it can also be carried out by applying only a low pressure, or by applying no pressure at normal pressure (atmospheric pressure). By applying a low pressure below a certain level or by firing (sintering) without applying pressure, for example, when the silver sintered body is used as a joint between an electrode on a substrate and a semiconductor element, unintentional damage to fragile components disposed around the silver sintered body can be suppressed.

[0143] The pressure applied to the silver-containing composition during sintering (the firing pressure of the silver-containing composition) is preferably 1 MPa or less, and may be, for example, 0.7 MPa or less or 0.4 MPa or less. When the pressure is equal to or less than the upper limit, the above-mentioned effects obtained by the low pressure become more pronounced.

[0144] A preferred method for producing the silver sintered body includes, for example, a step of adhering the silver-containing composition to an object on which the silver sintered body is to be formed, and a step of sintering the adhered silver-containing composition at a temperature of 350°C or less and a pressure of 1 MPa or less to form the silver sintered body. According to the above-described manufacturing method, by using the silver-containing composition, a silver sintered body that exhibits ductility and suppresses the occurrence of cracks can be manufactured without applying high pressure during sintering.

[0145] In producing the silver sintered body, the silver-containing composition is applied to a desired location in a desired shape, and then fired. Examples of methods for attaching the silver-containing composition to a target location include known methods such as printing, coating, etc. When a layer of the silver-containing composition is formed by these printing, coating, etc., and this layer is then fired, the resulting silver sintered body has good ductility and is also inhibited from cracking.

[0146] Examples of the printing method include screen printing, flexographic printing, offset printing, dip printing, inkjet printing, dispenser printing, jet dispenser printing, gravure printing, gravure offset printing, and pad printing.

[0147] Examples of the coating method include methods using various coaters such as a spin coater, an air knife coater, a curtain coater, a die coater, a blade coater, a roll coater, a gate roll coater, a bar coater, a rod coater, and a gravure coater; methods using a wire bar; and methods using a coating device such as a slot die.

[0148] <<zygote>> The silver sintered body of this embodiment is suitable as, for example, a wiring material for electronic components or a bonding material for semiconductors. For example, the silver sintered body of this embodiment is suitable for use as a substitute for solder and as a bonding portion between conductive components. That is, an example of a joined body having such a joint is a conductive joined body in which a conductive first part (sometimes abbreviated simply as "first part" in this specification) and a conductive second part (sometimes abbreviated simply as "second part" in this specification) are joined via a joint, and the joint is the silver sintered body according to one embodiment of the present invention described above.

[0149] FIG. 1 is a cross-sectional view schematically showing an example of the bonded body of the present embodiment. The bonded body 101 shown here is configured by bonding a conductive first component 2 and a conductive second component 3 via a bonding portion 1. The joint 1 is made of the silver sintered body of this embodiment.

[0150] The first part 2 is in the form of a sheet, a plate or a block. The first component 2 may be made of one layer (single layer) or may be made of two or more layers. When the first component 2 is made of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited. In this specification, not only in the case of the first part, "multiple layers may be the same or different from one another" means "all layers may be the same, all layers may be different, or only some layers may be the same," and further, "multiple layers are different from one another" means "at least one of the constituent materials and thicknesses of each layer is different from one another."

[0151] When the first component 2 is made up of multiple layers, for example, one or more layers on the bonding portion 1 side of the first component 2 may be layers that improve adhesion to the bonding portion 1.

[0152] The thickness of the first component 2 can be set arbitrarily depending on the purpose of the joined body 101, and is not particularly limited. The thickness of the first component 2 may be, for example, 10 to 10,000 μm.

[0153] When the first component 2 is made up of multiple layers, the total thickness of the layers should be set to the preferred thickness of the first component 2 described above.

[0154] Here, the first part 2 is shown to be in the shape of a sheet, a plate, or a block, but the first part 2 may be in any other shape, and the shape of the first part 2 can be selected arbitrarily depending on the purpose.

[0155] The second part 3 is in the form of a sheet, a plate or a block. The second component 3 may be made of one layer (single layer) or two or more layers. When the second component 3 is made of multiple layers, these multiple layers may be the same or different from one another, and the combination of these multiple layers is not particularly limited.

[0156] When the second component 3 is made up of multiple layers, for example, one or more layers on the bonding portion 1 side of the second component 3 may be layers that improve adhesion to the bonding portion 1.

[0157] The thickness of the second component 3 can be set arbitrarily depending on the purpose of the bonded body 101, and is not particularly limited. The thickness of the second component 3 may be, for example, 10 to 10,000 μm.

[0158] When the second component 3 is made up of a plurality of layers, the total thickness of the layers should be set to the preferred thickness of the second component 3 described above.

[0159] Here, the second part 3 is shown to be in the shape of a sheet, a plate, or a block, but the second part 3 may have any other shape, and the shape of the second part 3 can be selected arbitrarily depending on the purpose.

[0160] The joint 1 is made of the silver sintered body of this embodiment and is conductive, as described above in detail. The joint 1 is in the form of a sheet, a plate or a block. The bonding part 1 may be made up of one layer (single layer) or two or more layers. When the bonding part 1 is made up of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited.

[0161] When the joint 1 is made up of a plurality of layers, the total thickness of the layers should be set to the thickness of the silver sintered body described above.

[0162] Here, the joint 1 is shown to be in the form of a sheet, plate, or block, but the joint 1 may also be in any other shape, and the shape of the joint 1 can be selected arbitrarily depending on the purpose.

[0163] In the joined body 101, one first part 2 and one second part 3 are joined by one joint 1, but the joining form is not limited to this. In the joined body of this embodiment, for example, one first part and two or more second parts may be joined by one joint, in which case the two or more second parts may all be the same, all be different, or only some may be different. Furthermore, in the joined body of this embodiment, for example, one first component and two or more second components may be joined by two or more joining portions. In this case, the number of second components and the number of joining portions may be the same or different. Furthermore, the two or more second components may all be the same, all be different, or only some may be different. The numbers of first components and second components illustrated here may be reversed.

[0164] <Semiconductor device> A preferred example of the bonded body is a semiconductor device comprising a substrate and a semiconductor element bonded to the substrate, in which an electrode provided on the substrate and the semiconductor element are bonded by a bonding portion (silver sintered body), and the bonding portion is the silver sintered body according to one embodiment of the present invention described above.

[0165] FIG. 2 is a cross-sectional view schematically showing an example of the semiconductor device of this embodiment. The semiconductor device 102 shown here is configured to include a substrate 20 and a semiconductor element 31 bonded to the substrate 20 . An electrode 21 is provided on one surface of the substrate 20, and the electrode 21 and the semiconductor element 31 are joined by a joint 11. The joint 11 is made of the silver sintered body of this embodiment.

[0166] The substrate 20 may be a known substrate such as a resin substrate, and is not particularly limited. The thickness of the substrate 20 may be, for example, 200 to 10,000 μm.

[0167] The electrode 21 is included in the first component and may be a known electrode such as a metal electrode, without any particular limitation. The thickness of the electrode 21 may be, for example, 10 to 5000 μm.

[0168] The semiconductor element 31 is included in the second component and may be a known element, for example an element made of a semiconductor such as silicon, silicon carbide or gallium nitride. The thickness of the semiconductor element 31 may be, for example, 50 to 800 μm.

[0169] The joint 11 is electrically conductive, the details of which are as explained above. The thickness of the joint 11 may be, for example, 10 to 200 μm.

[0170] The bonding form between the electrode 21 and the semiconductor element 31 in the bonded body 102 via the bonding portion 11 may be similar to the bonding form between the first component 2 and the second component 3 in the bonded body 101 via the bonding portion 1.

[0171] <<Method of manufacturing the bonded body>> The joined body can be produced by a manufacturing method including, for example, a step of obtaining a heated product of the silver-containing composition by heating the silver-containing composition adhered to the surface of one or both of the first and second components at a temperature of 60°C or higher without solidifying it (this step may be referred to herein as a "preheating step"); and a step of joining the first and second components with a silver sintered body formed from the heated product by firing the heated product while bringing the first and second components into contact with each other through the heated product (this step may be referred to herein as a "joining step").

[0172] The method for applying the silver-containing composition to the surface of either or both of the first component and the second component is the same as the method for applying the silver-containing composition to a target location, as described above.

[0173] In the manufacturing method of this embodiment, the reason for carrying out the preheating step is that the bonding strength of the silver sintered body (i.e., the bonding portion) increases significantly. In the preheating step, the first part and the second part are not in contact (integrated) with each other through the silver-containing composition being heated.

[0174] The heating temperature of the silver-containing composition in the preheating step may be, for example, any one of 65°C or higher, 70°C or higher, and 75°C or higher.

[0175] The upper limit of the heating temperature of the silver-containing composition in the preheating step is not particularly limited. For example, the heating temperature is preferably 120° C. or less, so that solidification of the silver-containing composition can be easily avoided.

[0176] In the preheating step, the time for which the silver-containing composition is heated at a temperature of 60°C or higher without solidifying (sometimes abbreviated as "preheating time" in this specification) is preferably 0.1 to 30 minutes, and may be, for example, 0.5 to 10 minutes. By keeping the preheating time within this range, the desired heated product can be produced more efficiently.

[0177] The heated product obtained in the preheating step typically does not have the luster that is characteristic of silver, and this external appearance characteristic also makes it possible to distinguish the heated product from the desired silver sintered body.

[0178] The temperature rise rate during firing of the heated object in the bonding step may be the same as the temperature rise rate during heating of the silver-containing composition during production of the silver sintered body, as described above.

[0179] The firing temperature during firing of the heated material in the bonding step (the sintering temperature of the first silver particles and the second silver particles) may be the same as the firing temperature of the silver-containing composition (the temperature at which the silver-containing composition is sintered) during the production of the silver sintered body, as described above.

[0180] In this embodiment, the total time of the firing time (sintering time of the first silver particles and the second silver particles) when firing the heated material in the bonding step and the preheating time may be, for example, the same as the firing time of the silver-containing composition (the time to sinter the silver-containing composition) when producing the silver sintered body described above.

[0181] In the bonding step, as in the case of the method for producing a silver sintered body described above, the heated product of the silver-containing composition (sintering of the first silver particles and the second silver particles) may be fired by applying a pressure of the same level as conventionally applied to the heated product, or by applying only a low pressure, or by firing (sintering) the heated product without applying any pressure at normal pressure (atmospheric pressure). By applying a low pressure below a certain level or by firing (sintering) without applying any pressure, excessive pressure is not applied to the first and second components, and unintended damage to the first and second components can be suppressed.

[0182] <Method of manufacturing a semiconductor device> Of the bonded structure, the semiconductor device can be manufactured by using an electrode as the first component and a semiconductor element as the second component in the above-described method for manufacturing a bonded structure. [Example]

[0183] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the examples shown below.

[0184] [Example 1] <<Production of Silver-Containing Composition>> <Production of Raw Material Composition (1)> 2-Ethylhexylamine (0.4 times the molar amount of silver 2-methylacetoacetate described below) was added to a beaker, and then silver 2-methylacetoacetate (52.9 g) was added thereto so that the liquid temperature was 40°C or less. The resulting mixture was stirred for 15 minutes using a mechanical stirrer. Next, formic acid (0.65 times the molar amount of silver 2-methylacetoacetate) was added dropwise to the resulting stirred solution over 10 minutes so that the solution temperature was 60°C or below, and the resulting solution was further stirred at 26°C for 1.5 hours. In this way, a raw material composition (1) was obtained.

[0185] The raw material composition (1) obtained above was cooled and freeze-fractured. The fracture surface of the freeze-fractured specimen was observed using a scanning electron microscope (SEM, "Cryo FIC-SEM FEI, Helios NanoLab600") at an acceleration voltage of 1 kV (backscattered electron image). Then, using image analysis software ("Image J."), SEM images at a magnification of 10,000 times were processed to identify silver particle aggregates. From the identification results, the maximum diameter of each silver particle aggregate was calculated. The number of observed silver particle aggregates was set to 700 or more. Here, "maximum diameter" refers to the maximum length of the line segment connecting any two points located on the contour line in the identified image of the silver particle aggregate. As a result, the average value of the maximum diameters, i.e., the average secondary particle diameter of the silver particles, was 296 nm.

[0186] Furthermore, when the fracture surface of the freeze-fractured material was observed using a transmission electron microscope (TEM), it was found that each silver particle aggregate was composed of silver particles with a primary particle diameter of 200 nm or less. In addition, since the minimum length of the line segment connecting any two points located on the contour line in the above-mentioned identification image of the silver particle aggregate was 56 nm, it was inferred that the primary particle diameter of the silver particles constituting the silver particle aggregate was less than 56 nm.

[0187] <Production of Silver-Containing Composition> A dispersion of silver flakes in ethylene glycol ("N300" manufactured by Tokusen Kogyo Co., Ltd.) was prepared as raw material composition (2) (more specifically, raw material composition (2-2)). In raw material composition (2), the proportion of the silver content (silver concentration) relative to the total mass of raw material composition (2) was 90.3 mass%. The silver flakes had a single crystal structure, and the largest plane was a lattice plane (111). The particle size at 50% accumulation (D50) of the silver flakes was 0.3 μm as measured by laser diffraction / scattering particle size distribution measurement. When the silver flakes were observed using an SEM, the thickness of the silver flakes was approximately 50 nm or less.

[0188] The raw material composition (1) (12 parts by mass) and raw material composition (2) (50 parts by mass) obtained above were mixed at room temperature and mixed for 3 minutes using a planetary stirrer, thereby obtaining the silver-containing composition shown in Table 1.

[0189] <<Manufacturing of Silver Sintered Body (Joined Body) (1)>> A copper substrate measuring 12 mm × 8 mm × 0.8 mm and a copper chip measuring 4 mm × 4 mm × 0.8 mm were prepared. A titanium film (0.1 μm thick) and a silver film (1 μm thick) were laminated in this order on the bonding surface of the copper substrate and the bonding surface of the copper chip, respectively, by sputtering.

[0190] Next, a printed layer of the silver-containing composition obtained above, measuring 5 mm x 5 mm x 0.1 mm, was formed by screen printing on the silver film of the copper substrate (in other words, the sputtered surface). Next, the printed layer was preheated at 80°C for 45 seconds under atmospheric pressure without pressure (normal pressure) using a programmable hot plate (AS ONE Corporation "EC-1200NP"), and then a copper chip was placed on the preheated printed layer. At this time, when viewed from above in a plan view, the center of the preheated material and the center of the copper chip were aligned, and the copper chip was positioned so that the periphery of the preheated material and the periphery of the copper chip were in equilibrium. Next, the obtained laminate was heated from room temperature to 300°C at a heating rate of 5°C / min in the atmosphere without pressure (normal pressure), and held at 300°C for 60 minutes to sinter the silver-containing composition, thereby forming a silver sintered body measuring 5 mm x 5 mm x 0.1 mm. The fired product was then allowed to cool to room temperature. As a result, a bonded body was obtained in which the copper base material and the copper chip were bonded together by a bonding portion made of a silver sintered body.

[0191] <<Manufacturing of Sintered Silver (2)>> The silver-containing composition obtained above was sealed in a bottle and degassed by stirring with a planetary stirrer. Next, a printed layer of the degassed silver-containing composition was formed by screen printing on one side of a stainless steel (SUS) plate measuring 70 mm × 120 mm × 1.1 mm. The shape and size of the printed layer were as shown in Figure 3 (thickness: 0.2 mm). Figure 3 is a plan view showing the shape and size of the printed layer of the silver-containing composition in this example.

[0192] Next, using a programmable hot plate ("EC-1200NP" manufactured by AS ONE Co., Ltd.), the formed printed layer was heated from room temperature to 300°C at a heating rate of 5°C / min under atmospheric conditions without pressure (normal pressure), and then held at 300°C for 60 minutes to sinter the silver-containing composition, thereby forming a silver sintered body. Next, the obtained fired product was allowed to cool to room temperature, and the silver sintered body was peeled off from the SUS plate to prepare a test piece.

[0193] <<Evaluation of sintered silver (1)>> <Measurement of maximum stress and breaking strain during tensile testing> At room temperature, the rectangular portions (7 mm on each side) at both ends of the test piece in the longitudinal direction were clamped with a precision universal testing machine (Instron Model 5566), and the test piece was subjected to a tensile test in which it was pulled in the longitudinal direction, and the stress was measured. The pulling speed at this time was 1 × 10 -4 / sec. The load obtained from the load cell when the test piece was pulled was divided by the cross-sectional area of ​​the test piece to obtain the nominal stress, and the maximum value was defined as the maximum stress. The crosshead displacement was divided by the length (6 mm) of a portion of the test piece near the center in the longitudinal direction (a portion 6 mm long in the longitudinal direction of the test piece) to obtain the strain, and the strain when the stress became 0 was defined as the fracture strain. The results are shown in Table 1.

[0194] <Calculation of porosity of sintered silver body> The same test piece (sintered silver body) as the test piece used in the above tensile test was prepared. Next, the test specimen was cut perpendicular to the longitudinal direction at the center of its longitudinal direction using scissors. The cut test specimen was embedded in resin, and the cross section was mechanically polished and ion milled. The cross section was then observed using an SEM at an accelerating voltage of 5 kV (backscattered electron image), and the black areas were classified as voids, and the porosity was calculated. The results are shown in Table 1.

[0195] <Calculating the percentage of crystal grains (0.5 to 1.2 μm) in sintered silver> Of the cross sections of the test pieces obtained above after cutting, a region near the center in the width direction of the test piece was analyzed by the EBSD method using an SEM. A grain map was created with a specified misorientation of 5° and a distance between measurement points of 50 nm, and the proportion of crystal grains (0.5 to 1.2 μm) was calculated. The results are shown in Table 1. Table 1 also shows the proportion of crystal grains with a grain size of 0.5 μm or more to all crystal grains as the "proportion of crystal grains (0.5 μm or more)."

[0196] <<Manufacturing of Sintered Silver (3)>> The silver-containing composition obtained above was sealed in a bottle and degassed by stirring with a planetary stirrer. Next, a printed layer of the degassed silver-containing composition was formed by screen printing on one surface of a copper substrate measuring 12 mm × 8 mm × 0.8 mm. The planar shape of the printed layer was rectangular, its size was 5 mm × 5 mm, and its thickness was set to three values: 100 μm, 200 μm, and 300 μm. In other words, three printed layers with different thicknesses were formed.

[0197] Next, using a programmable hot plate ("EC-1200NP" manufactured by AS ONE Co., Ltd.), the formed printed layer was heated from room temperature to 300°C at a heating rate of 10°C / min under atmospheric conditions without pressure (normal pressure), and then held at 300°C for 60 minutes to bake the silver-containing composition, thereby forming a film-like silver sintered body.

[0198] <<Evaluation of sintered silver (2)>> <Measurement of thickness of sintered silver body> The resulting silver sintered body was then allowed to cool to room temperature, and the thickness of the silver sintered body was measured using a laser microscope. The results are shown in Table 1.

[0199] <<Production of silver-containing compositions, production and evaluation of silver sintered bodies>> [Example 2] A silver-containing composition was prepared in the same manner as in Example 1. Next, in the production of the silver sintered body (1) to (3), the silver-containing composition (the printed layer) was fired in the air under no pressure (normal pressure) at 300°C for 60 minutes, but in the air under a pressure of 1 MPa at 350°C for 60 minutes, and a silver sintered body (joined body) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0200] [Reference example 1] A silver-containing composition was prepared in the same manner as in Example 1. Next, in the production of the silver sintered body (1) to (3), the silver-containing composition (the printed layer) was fired in the air under no pressure (normal pressure) at 300°C for 60 minutes, but in the air under a pressure of 20 MPa at 300°C for 10 minutes, and a silver sintered body (joined body) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0201] [Reference example 2] A silver-containing composition was prepared in the same manner as in Example 1. Next, in the production of the silver sintered body (1) to (3), the silver-containing composition (the printed layer) was fired in the air under no pressure (normal pressure) at 300°C for 60 minutes, but in the air under a pressure of 20 MPa at 350°C for 10 minutes, and a silver sintered body (joined body) was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0202] [Example 3] The silver-containing composition shown in Table 1 was obtained in the same manner as in Example 1, except that, during production of the silver-containing composition, raw material composition (1) (12 parts by mass) and raw material composition (2) (50 parts by mass) were mixed at room temperature, and neodecanoic acid (1.265 parts by mass) was further added thereto. Next, a silver sintered body (joined body) was produced and evaluated in the same manner as in Example 1, except that this silver-containing composition was used and the preheating time for the printed layer in the production of the silver sintered body (1) was changed from 45 seconds to 75 seconds. The results are shown in Table 1.

[0203] [Comparative Example 1] <<Preparation of Comparative Silver-Containing Composition>> A raw material composition (1) was produced in the same manner as in Example 1, and this was used as a comparative silver-containing composition.

[0204] <<Production and evaluation of sintered silver>> A silver sintered body (joined body) was produced and evaluated in the same manner as in Example 1, except that the comparative silver-containing composition (raw material composition (1)) was used instead of the silver-containing composition. The results are shown in Table 1.

[0205] Comparative Example 2 <<Preparation of Comparative Silver-Containing Composition>> The same raw material composition (2) as in Example 1 was prepared and used as a comparative silver-containing composition.

[0206] <<Production and evaluation of sintered silver>> A silver sintered body (joined body) was produced and evaluated in the same manner as in Example 1, except that the comparative silver-containing composition (raw material composition (2)) was used instead of the silver-containing composition. The results are shown in Table 1.

[0207] In Table 1, “C 8~11 In the column "Aliphatic carboxylic acid blending ratio (mass%)", the type of aliphatic carboxylic acid is also listed together with the value. Furthermore, "-" in any other column means that the data has not been acquired or could not be acquired.

[0208] [Table 1]

[0209] In Examples 1 to 3, a silver sintered body having a high maximum stress, ductility, and sufficient thickness was obtained without applying a high pressure during sintering of the silver-containing composition. In Examples 1 to 3, the fracture strain during the tensile test was 5.5% or more (5.5 to 6.5%), the thickness of the silver sintered body was 52 μm or more (52 to 100 μm), and no cracks occurred in these silver sintered bodies.

[0210] In Examples 1 to 3, the proportion of crystal grains (0.5 to 1.2 μm) in the silver sintered body was 44.5% or more (44.5 to 64.4%).

[0211] Furthermore, in Examples 1 to 3, the maximum stress during the tensile test was 79 MPa or more (79 to 115 MPa), and the silver sintered bodies had better properties.

[0212] A comparison between Example 1 and Example 3 confirmed that the use of neodecanoic acid improved the maximum stress and ductility of the silver sintered body.

[0213] In contrast, in Reference Examples 1 and 2, silver sintered bodies with insufficient ductility were obtained. In Reference Examples 1 and 2, the proportion of crystal grains (0.5 to 1.2 μm) in the silver sintered body was 24.3% or less (3.6 to 24.3%).

[0214] In Comparative Examples 1 and 2, a silver sintered body of sufficient thickness was not obtained. In Comparative Example 1, the silver concentration of the silver-containing composition was low (63.3 mass%), and as a result, a silver sintered body with a thickness of more than 21 μm was not obtained. In Comparative Example 2, the silver concentration of the silver-containing composition was high (90.3 mass%), and as a result, a silver sintered body in which cracking was suppressed was not obtained. In Comparative Example 2, a silver sintered body with a maximum thickness of 37 μm was obtained, but cracks occurred in this silver sintered body. In order to perform the tensile test, a silver sintered body with a thickness of 50 μm or more is required, but as described above, in Comparative Examples 1 and 2, a silver sintered body with a thickness of 50 μm or more in which cracking was suppressed could not be obtained, and therefore, the maximum stress and breaking strain could not be measured in these Comparative Examples. Therefore, in Comparative Examples 1 and 2, other items were not evaluated either. [Industrial Applicability]

[0215] The present invention can be used as a conductive bonded body, for example, as a wiring material for electronic components or a bonding material for semiconductors. [Explanation of symbols]

[0216] 1, 11... Joint portion, 2... Conductive first part, 20... Substrate, 21... Electrode, 3... Conductive second part, 31... Semiconductor element, 101... Joint body, 102... Semiconductor device

Claims

1. A silver sintered body, When the grain size distribution of the crystal grains in the silver sintered body is measured on an area basis by electron backscatter diffraction with a specified misorientation of 5°, the proportion of crystal grains having a grain size of 0.5 to 1.2 μm to all crystal grains is 40% or more, A silver sintered body, wherein the porosity of the silver sintered body is 35% or less.

2. A silver sintered body as described in claim 1, wherein, when the particle size distribution of the crystal grains in the silver sintered body is measured on an area basis using electron backscatter diffraction with a specified orientation difference of 5°, the proportion of crystal grains with a particle size of 0.5 μm or more to all crystal grains is 70% or more.

3. A semiconductor device comprising a substrate and a semiconductor element bonded to the substrate, the electrodes provided on the substrate and the semiconductor element are joined by a silver sintered body, When the grain size distribution of the crystal grains in the silver sintered body is measured on an area basis by electron backscatter diffraction with a specified orientation difference of 5°, the proportion of crystal grains having a grain size of 0.5 to 1.2 μm to all crystal grains is 40% or more.

4. A semiconductor device comprising a substrate and a semiconductor element bonded to the substrate, the electrodes provided on the substrate and the semiconductor element are joined by a silver sintered body, The semiconductor device, wherein the silver sintered body is the silver sintered body according to claim 1 or 2.

5. 1. A silver-containing composition comprising: the silver-containing composition contains first silver particles and second silver particles, the first silver particles have a primary particle diameter of 200 nm or less and an average secondary particle diameter of 2 μm or less; the second silver particles have a 50% cumulative particle size of less than 1.5 μm, as measured by laser diffraction / scattering particle size distribution measurement; A silver-containing composition, wherein the ratio of the content (parts by mass) of the first silver particles to the content (parts by mass) of the second silver particles is 7 / 93 to 35 / 65.

6. A method for producing a silver sintered body, comprising: When the particle size distribution of the crystal grains in the silver sintered body is measured on an area basis by electron backscatter diffraction, the ratio of crystal grains having a particle size of 0.5 to 1.2 μm to all crystal grains is 40% or more, The method for producing the silver sintered body includes the steps of: applying the silver-containing composition according to claim 5 to an object on which the silver sintered body is to be formed; and sintering the deposited silver-containing composition at a temperature of 350°C or less and a pressure of 1 MPa or less to form the silver sintered body.

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