Flux and solder paste

Abstract

Provided are a flux that can further suppress the occurrence of voids during soldering, and a solder paste that uses this flux. [Solution] The present invention provides a flux containing a resin, a solvent, a thixotropic agent, and an activator, wherein the thixotropic agent contains at least one compound selected from the group consisting of a compound (T1) represented by chemical formula (T-1) and a compound (T3) represented by chemical formula (T-3). [C1] TIFF0007817644000021.tif40170

Description

[Technical Field]

[0001] The present invention relates to a flux and a solder paste. [Background technology]

[0002] When manufacturing electronic components, soldering is used to fix components to a substrate and electrically connect the components to the substrate, using flux, solder powder, and a solder paste made by mixing the flux and solder powder. In soldering using solder paste, the solder paste is first printed on a board, components are then mounted, and the board with the components mounted is heated in a heating furnace called a reflow furnace, which melts the solder powder contained in the solder paste and bonds the components to the board, resulting in a bonded assembly.

[0003] Flux chemically removes metal oxides present in the solder and the metal surfaces of the objects being soldered, allowing the movement of metal elements at the interface between the two. Therefore, when soldering is performed using flux, an intermetallic compound is formed between the two, resulting in a strong bond.

[0004] Recently, with the trend toward more compact electronic devices and smaller circuit boards, there is a demand for space-saving, high-performance components. To address this demand, there has been an increase in the use of surface-mount components, particularly those with array terminal structures, such as BGA (Ball Grid Array) and CSP (Chip Size Package), primarily for the purpose of high-density mounting. In such surface mount components, the void ratio of the solder joints is controlled to ensure their performance. In response to this, attempts have been made to suppress the generation of voids in the solder joints of packages (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-198777 Summary of the Invention [Problem to be solved by the invention]

[0006] When voids occur in the solder of BGA or CSP during soldering, the voids become defects that can easily lead to reduced shear strength and drop strength. This can occur if voids suddenly occur that occupy a large area of ​​the cross section of the solder joint, even in a small number of solder balls out of a large number of solder balls.

[0007] However, in conventional technology, the average void area ratio of many solder balls has been used as an indicator for the area ratio of voids occupying the cross section of a solder joint. However, it is now required not only to reduce the average void area ratio of many solder balls, but also to suppress the occurrence of voids that occupy a large area (e.g., 20% or more) of the cross section of a solder joint.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flux that can further suppress the occurrence of voids during soldering, and a solder paste using this flux. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention employs the following configuration.

[0010] [1] A flux comprising a resin, a solvent, a thixotropic agent, and an activator, wherein the thixotropic agent comprises at least one selected from the group consisting of a compound (T1) represented by the following chemical formula (T-1) and a compound (T3) represented by the following chemical formula (T-3):

[0011] [ka]

[0012] [2] The flux according to [1], wherein the thixotropic agent includes both the compound (T1) and the compound (T3).

[0013] [3] The flux according to [1] or [2], wherein the total content of the compound (T1) and the compound (T3) is 0.5 mass % or more and 10 mass % or less with respect to the total mass (100 mass %) of the flux.

[0014] [4] The flux according to any one of [1] to [3], wherein the thixotropic agent further contains a compound (T2) represented by the following general formula (T-2):

[0015] [ka] [In the formula, R is an aliphatic hydrocarbon group having 11 to 15 carbon atoms.]

[0016] [5] The flux according to [4], wherein R in the general formula (T-2) is a linear alkyl group having 15 carbon atoms.

[0017] [6] The flux according to [4] or [5], wherein the total content of the compound (T1), the compound (T3), and the compound (T2) is 1 mass % or more and 15 mass % or less with respect to the total mass (100 mass %) of the flux.

[0018] [7] The flux according to any one of [4] to [6], wherein the mass ratio of the content of the compound (T2) to the total content of the compound (T1), the compound (T3), and the compound (T2) is 0.15 or more and 0.50 or less.

[0019] [8] A solder paste containing the flux according to any one of [1] to [7] and solder powder. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a flux that can further suppress the occurrence of voids during soldering, and a solder paste that uses this flux. According to the present invention, it is possible to particularly suppress the occurrence of voids that occupy a large area (for example, 20% or more) of the cross section of the solder joint. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 10 is a diagram showing a reflow profile in the evaluation of the examples. DETAILED DESCRIPTION OF THE INVENTION

[0022] (Flux) One embodiment of the flux according to the first aspect contains a resin, a solvent, a thixotropic agent, and an activator, wherein the thixotropic agent contains at least one compound selected from the group consisting of a compound (T1) represented by the following chemical formula (T-1) and a compound (T3) represented by the following chemical formula (T-3):

[0023] [ka]

[0024] <Resin> The resin contained in the flux of this embodiment can be rosin, copolymer, etc. Examples of copolymers include olefin / (α-substituted) acrylic acid resin.

[0025] <Rosin> In the present invention, "rosin" includes natural resins containing abietic acid as the main component, mixtures of abietic acid and its isomers, and chemically modified natural resins (sometimes referred to as rosin derivatives).

[0026] The content of abietic acid in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin. In this specification, the term "main component" refers to a component that is contained in a compound in an amount of 40 mass % or more.

[0027] Representative isomers of abietic acid include neoabietic acid, parastric acid, and levopimaric acid. Examples of the "natural resin" include gum rosin, wood rosin, tall oil rosin, and the like.

[0028] In the present invention, the term "chemically modified natural resin (rosin derivative)" includes the "natural resin" that has been subjected to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization, oligomerization, esterification, and Diels-Alder cycloaddition.

[0029] Examples of rosin derivatives include purified rosin and modified rosin. Examples of modified rosins include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), as well as purified products, hydrogenated products, and disproportionated products of the polymerized rosins, and purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap. Examples of rosin amines include dehydroabietylamine, dihydroabietylamine, etc. The rosin amine refers to a so-called disproportionated rosin amine.

[0030] <Olefin / (α-substituted) acrylic acid resin> The olefin / (α-substituted) acrylic acid resin has a repeating unit (a1) derived from an alkene and a repeating unit (a2) derived from an acrylic acid in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent (hereinafter referred to as "(α-substituted) acrylic acid"). In addition to the repeating unit (a1) and the repeating unit (a2), the olefin / (α-substituted) acrylic acid resin may also have a repeating unit (a3) ​​other than these. The (α-substituted) acrylic acid refers to either or both of acrylic acid and an acrylic acid in which the hydrogen atom bonded to the carbon atom at the α-position has been substituted with a substituent.

[0031] [Repeating unit (a1)] The repeating unit (a1) is derived from an alkene. Examples of the alkene include C n H 2n Here, n is an integer of 2 or more, preferably 2 or more and 10 or less, more preferably 2 or more and 6 or less, even more preferably 2 or more and 3 or less, and particularly preferably 2. C n H 2n Examples of the compound represented by the formula (I) include ethylene, propylene, isobutene, 1-butene, 1-pentene, 1-hexene, etc., and one or more selected from the group consisting of ethylene and propylene is preferred, with ethylene being more preferred.

[0032] Alternatively, examples of the alkene from which the repeating unit (a1) is derived include 1,3-butadiene and 2-methyl-1,3-butadiene.

[0033] The repeating unit (a1) contained in the olefin / (α-substituted) acrylic acid resin may be one type or two or more types.

[0034] [Repeating unit (a2)] The repeating unit (a2) is derived from (α-substituted) acrylic acid. In the repeating unit (a2), the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent. When the carbon atom at the α-position has a substituent, examples of the substituent include a linear or branched alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 5. Examples of the repeating unit (a2) include a repeating unit derived from acrylic acid and a repeating unit derived from methacrylic acid.

[0035] The repeating unit (a2) contained in the olefin / (α-substituted) acrylic acid resin may be one type or two or more types.

[0036] [Repeating unit (a3)] The repeating unit (a3) ​​is a repeating unit other than the repeating unit (a1) and the repeating unit (a2).

[0037] Examples of the repeating unit (a3) ​​include a repeating unit derived from an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent (hereinafter referred to as an "(α-substituted) acrylate ester"), a repeating unit derived from an alkylene oxide, and a repeating unit having an aromatic group.

[0038] The (α-substituted) acrylate ester refers to either or both of an acrylate ester and an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position is substituted with a substituent. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms.

[0039] The (α-substituted) acrylic ester is a reaction product of (α-substituted) acrylic acid and an alcohol, such as an alcohol having a linear carbon chain and 1 to 24 carbon atoms.

[0040] Examples of the (α-substituted) acrylic acid esters include acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, cyclohexyl acrylate, octyl acrylate, nonyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, benzyl acrylate, anthracene acrylate, glycidyl acrylate, 3,4-epoxycyclohexylmethane acrylate, and propyltrimethoxysilane acrylate; and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, nonyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, benzyl methacrylate, anthracene methacrylate, glycidyl methacrylate, 3,4-epoxycyclohexylmethane methacrylate, and propyltrimethoxysilane methacrylate. Of these, methyl acrylate, ethyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, and t-butyl methacrylate are preferred.

[0041] Examples of alkylene oxides include ethylene oxide, propylene oxide, isopropylene oxide, and butylene oxide.

[0042] Examples of the repeating unit having an aromatic group include a repeating unit having an aromatic group such as a phenyl group, a naphthyl group, etc. Examples of the repeating unit having a phenyl group include a repeating unit derived from styrene or a derivative thereof.

[0043] When the olefin / (α-substituted) acrylic acid resin has the repeating unit (a3), the repeating unit (a3) ​​contained in the olefin / (α-substituted) acrylic acid resin may be one type or two or more types.

[0044] In the olefin / (α-substituted) acrylic acid resin, the content of the repeating unit (a1) is preferably 10% by mass or more and 98% by mass or less, more preferably 40% by mass or more and 97% by mass or less, and even more preferably 65% ​​by mass or more and 95% by mass or less, based on the entire olefin / (α-substituted) acrylic acid resin (100% by mass). When the content of the repeating unit (a1) is equal to or greater than the lower limit of the above-mentioned preferred range, the electrical reliability of the bonded body is easily improved. When the content of the repeating unit (a1) is equal to or less than the upper limit of the above-mentioned preferred range, separation of the solder paste into solder powder and flux over time is easily suppressed. Furthermore, cracking of flux residue due to temperature changes is easily reduced. Furthermore, solderability is easily improved. Furthermore, the solubility of the olefin / (α-substituted) acrylic acid resin in the flux is easily improved.

[0045] In the olefin / (α-substituted) acrylic acid resin, the content of the repeating unit (a2) is preferably from 2 to 90% by mass, more preferably from 3 to 60% by mass, and even more preferably from 5 to 35% by mass, based on the entire olefin / (α-substituted) acrylic acid resin (100% by mass). When the content of the repeating unit (a2) is equal to or greater than the lower limit of the above-mentioned preferred range, separation of the solder paste into solder powder and flux over time is easily suppressed. Furthermore, cracking of the flux residue due to temperature changes is easily reduced. Furthermore, solderability is easily improved. Furthermore, the solubility of the olefin / (α-substituted) acrylic acid resin in the flux is easily improved. When the content of the repeating unit (a2) is equal to or less than the upper limit of the above-mentioned preferred range, the electrical reliability of the bonded body is likely to be improved.

[0046] When the olefin / (α-substituted) acrylic acid resin has the repeating unit (a3), the content of the repeating unit (a3) ​​in the olefin / (α-substituted) acrylic acid resin is preferably from 0.1 to 30% by mass, more preferably from 0.1 to 20% by mass, and even more preferably from 0.1 to 10% by mass, relative to the entire olefin / (α-substituted) acrylic acid resin (100% by mass).

[0047] The olefin / (α-substituted) acrylic acid resin may be a random copolymer or a block copolymer.

[0048] <Resins other than rosin and olefin / (α-substituted) acrylic acid resins> Examples of resins other than rosin and olefin / (α-substituted) acrylic acid resins include terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, methacrylic resins, polyethylene resins, and epoxy resins. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenolic resins include hydrogenated terpene phenolic resins. Examples of modified styrene resins include styrene acrylic resins and styrene maleic acid resins. Examples of modified xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene-added xylene resins.

[0049] In the flux of this embodiment, one type of resin may be used alone, or two or more types may be used in combination. Among the above, it is preferable to use a resin selected from the group consisting of rosin and copolymers, and it is more preferable to use a resin containing at least rosin. For example, the resin is preferably at least one selected from the group consisting of rosin and copolymers, more preferably at least one selected from the group consisting of modified rosin and olefin / (α-substituted) acrylic acid resin, still more preferably at least one selected from the group consisting of hydrogenated rosin, polymerized rosin, acid-modified hydrogenated rosin, and ethylene / acrylic acid copolymer, and it is particularly preferable to combine at least one selected from the group consisting of hydrogenated rosin, polymerized rosin, and ethylene / acrylic acid copolymer with acid-modified hydrogenated rosin. The acid-modified hydrogenated rosin is preferably acrylic acid-modified hydrogenated rosin.

[0050] The resin content in the flux of this embodiment is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 55% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less, relative to the total mass (100% by mass) of the flux.

[0051] <Solvent> Examples of the solvent contained in the flux of this embodiment include water, alcohol-based solvents, glycol ether-based solvents, and terpineols.

[0052] Examples of alcohol-based solvents include isopropyl alcohol, 1,2-butanediol, 1,3-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, 1,1,1-tris(hydroxymethyl)propane, 2-ethylhexylmethyl ... ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2-hexyl-1-decanol, octanediol, and the like.

[0053] Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether (EHDG), ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol: HeDG), diethylene glycol dibutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether; monoalkyl propylene glycols, and the like.

[0054] Examples of terpineols include α-terpineol, β-terpineol, γ-terpineol, and terpineol mixtures (that is, mixtures whose main component is α-terpineol and contain β-terpineol or γ-terpineol). Other solvents include, for example, dioctyl sebacate and liquid paraffin.

[0055] In the flux of this embodiment, one type of solvent may be used alone, or two or more types may be used in combination. Among the above, the solvent is preferably selected from the group consisting of glycol ether solvents, and it is more preferable to use at least one solvent selected from the group consisting of HeDG, EHDG, and tetraethylene glycol dimethyl ether, particularly from the viewpoint of viscosity stability when made into a solder paste and the melting property of the solder powder.

[0056] The content of the solvent in the flux of this embodiment is the balance in the flux, and is determined depending on the contents of the other components. For example, the content of the solvent in the flux of the present embodiment may be 20% by mass or more and 70% by mass or less, 25% by mass or more and 65% by mass or less, or 30% by mass or more and 60% by mass or less, relative to the total mass (100% by mass) of the flux.

[0057] <Thixotropic agent> The thixotropic agent contained in the flux of this embodiment includes at least one selected from the group consisting of a compound (T1) represented by the chemical formula (T-1) described below and a compound (T3) represented by the chemical formula (T-3). The thixotropic agent contained in the flux of this embodiment preferably contains at least one selected from the group consisting of the compound (T1) and the compound (T3), and further contains a compound (T2) represented by the general formula (T-2) described below, and more preferably contains both the compound (T1) and the compound (T3), and further contains a compound (T2). The thixotropic agent contained in the flux of this embodiment may further include other thixotropic agents in addition to the compound (T1), the compound (T3), and the compound (T2).

[0058] The total content of the thixotropic agent in the flux of this embodiment is preferably 1 mass % or more and 20 mass % or less, more preferably 2 mass % or more and 15 mass % or less, and even more preferably 3 mass % or more and 14 mass % or less, relative to the total mass (100 mass %) of the flux.

[0059] <Compound (T1) represented by chemical formula (T-1)> The compound (T1) represented by the chemical formula (T-1) has two N-hexadecanoyl groups in the molecule via a 1,2-ethanediyldiimino group (-NH-CH2CH2-NH-).

[0060] [ka]

[0061] <Compound (T3) represented by chemical formula (T-3)> The compound (T3) represented by the chemical formula (T-3) has two N-octadecanoyl groups in the molecule via a 1,2-ethanediyldiimino group (-NH-CH2CH2-NH-).

[0062] [ka]

[0063] In the flux of the present embodiment, the thixotropic agent contains at least one selected from the group consisting of the compound (T1) and the compound (T3), and preferably contains both the compound (T1) and the compound (T3). When the thixotropic agent contains both the compound (T1) and the compound (T3), the mass ratio of the two, expressed as compound (T1) / compound (T3), is preferably 1 / 99 to 99 / 1 from the viewpoint of suppressing the generation of voids, and more preferably 5 / 95 to 95 / 5, since this tends to further enhance the effect of suppressing the generation of voids.

[0064] The total content of the compound (T1) and the compound (T3) in the flux of this embodiment is preferably 0.5 mass % or more and 10 mass % or less, more preferably 0.8 mass % or more and 8 mass % or less, and even more preferably 1 mass % or more and 5.5 mass % or less, relative to the total mass (100 mass %) of the flux. When the total content of the compound (T1) and the compound (T3) is within the above-mentioned preferred range, the effect of suppressing void generation is easily obtained. When the total content is equal to or greater than the lower limit of the above-mentioned preferred range, the effect of suppressing void generation is easily further improved.

[0065] The total content of the compound (T1) and the compound (T3) in the flux of this embodiment is preferably 10 mass% or more, more preferably 15 mass% or more and 70 mass% or less, and even more preferably 20 mass% or more and 65 mass% or less, relative to the total mass (100 mass%) of the thixotropic agent. In this specification, "the total content of the compound (T1) and the compound (T3)" means the total content of the compound (T1) and the compound (T3) when the thixotropic agent contains both the compound (T1) and the compound (T3). When only the compound (T1) is selected from the two, it means the content of the compound (T1). When only the compound (T3) is selected from the two, it means the content of the compound (T3).

[0066] <Compound (T2) represented by general formula (T-2)> The compound (T2) represented by the general formula (T-2) has one N-octadecanoyl group and an acyl group (RC(=O)-) in the molecule, connected via a 1,2-ethanediyldiimino group (-NH-CHCH-NH-).

[0067] [ka] [In the formula, R is an aliphatic hydrocarbon group having 11 to 15 carbon atoms.]

[0068] In the formula (T-2), the aliphatic hydrocarbon group for R may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group, and may be linear or branched. Among these, the aliphatic hydrocarbon group for R is preferably a linear saturated aliphatic hydrocarbon group, and is more preferably a linear alkyl group having 11 carbon atoms or a linear alkyl group having 15 carbon atoms, and particularly preferably a linear alkyl group having 15 carbon atoms, because this tends to enhance the effect of suppressing void generation.

[0069] Specific examples of the compound (T2) represented by general formula (T-2) are shown below.

[0070] [ka]

[0071] In the flux of this embodiment, the compound (T2) may be used alone or in combination of two or more kinds. As the compound (T2), the compound represented by the chemical formula (T-2-1) and the compound represented by the chemical formula (T-2-3) are preferred because they can easily enhance the effect of suppressing void generation. Among these, the compound represented by the chemical formula (T-2-3) is more preferred because they can easily further enhance the effect of suppressing void generation.

[0072] The content of the compound (T2) in the flux of this embodiment is preferably 0.3 mass % or more and 10 mass % or less, more preferably 0.6 mass % or more and 7.5 mass % or less, and even more preferably 0.9 mass % or more and 5 mass % or less, relative to the total mass (100 mass %) of the flux. When the content of compound (T2) is within the above-mentioned preferred range, the effect of suppressing void generation is easily obtained. When the content is equal to or greater than the lower limit of the above-mentioned preferred range, the effect of suppressing void generation is easily further improved.

[0073] The content of the compound (T2) in the flux of this embodiment is preferably 5% by mass or more relative to the total mass (100% by mass) of the thixotropic agent, since this tends to enhance the effect of suppressing void generation. The content is more preferably 10% by mass or more, and even more preferably 15% by mass or more and 40% by mass or less, since this tends to further enhance the effect of suppressing void generation.

[0074] In the flux of this embodiment, when the thixotropic agent contains the three components of the compound (T1), the compound (T3), and the compound (T2), the total content of the three components of the compound (T1), the compound (T3), and the compound (T2) is preferably 1 mass % or more and 15 mass % or less, more preferably 1.5 mass % or more and 15 mass % or less, and even more preferably 2 mass % or more and 10 mass % or less, relative to the total mass (100 mass %) of the flux. When the total content of the three components, i.e., the compound (T1), the compound (T3), and the compound (T2), is within the preferred range, the effect of suppressing void generation is easily obtained. When the total content is equal to or greater than the lower limit of the preferred range, the effect of suppressing void generation is easily improved.

[0075] The total content of the three components, i.e., the compound (T1), the compound (T3), and the compound (T2), in the flux of this embodiment is preferably 20% by mass or more, more preferably 30% by mass or more and 85% by mass or less, and even more preferably 35% by mass or more and 80% by mass or less, relative to the total mass (100% by mass) of the thixotropic agent.

[0076] In the flux of the present embodiment, the mass ratio of the content of the compound (T2) to the total content of the compound (T1), the compound (T3), and the compound (T2) is preferably 0.15 or more and 0.50 or less, more preferably 0.20 or more and 0.50 or less, and even more preferably 0.30 or more and 0.50 or less. When the mass ratio is within the preferred range, the effect of suppressing void generation is easily obtained. When the mass ratio is equal to or greater than the lower limit of the preferred range, the effect of suppressing void generation is easily further improved.

[0077] In the flux of this embodiment, the total content of the compound (T1) and the compound (T2) relative to the total content of the compound (T1), the compound (T3), and the compound (T2) is preferably 15% by mass or more and 99% by mass or less, more preferably 25% by mass or more and 98% by mass or less, and even more preferably 35% by mass or more and 97% by mass or less. In the flux of this embodiment, the total content of the compound (T3) and the compound (T2) relative to the total content of the compound (T1), the compound (T3), and the compound (T2) is preferably 15% by mass or more and 99% by mass or less, more preferably 25% by mass or more and 98% by mass or less, and even more preferably 35% by mass or more and 97% by mass or less. When the total content of the compound (T1) and the compound (T2) and the total content of the compound (T3) and the compound (T2) are within the above-mentioned preferred ranges, the effect of suppressing void generation is easily obtained. When the total content of the compound (T1) and the compound (T2) is equal to or less than the upper limit of the above-mentioned preferred ranges, the effect of suppressing void generation is easily further improved.

[0078] In the flux of this embodiment, when the thixotropic agent contains the three components of the compound (T1), the compound (T3), and the compound (T2), preferred ratios of these three components, relative to the total content (100 mass%) of the three components, include an embodiment in which the content of the compound (T1) is from 0.5 to 85 mass%; the content of the compound (T3) is from 0.5 to 85 mass%; and the content of the compound (T2) is from 15 to 50 mass%; alternatively, preferred ratios of these three components, relative to the total content (100 mass%) of the three components, include an embodiment in which the content of the compound (T1) is from 2 to 75 mass%; the content of the compound (T3) is from 2 to 75 mass%; and the content of the compound (T2) is from 25 to 50 mass%.

[0079] <Other thixotropic agents> The thixotropic agent contained in the flux of this embodiment may include other thixotropic agents in addition to the above-mentioned compounds (T1), (T3) and (T2). Other thixotropic agents include, for example, amide-based thixotropic agents, ester-based thixotropic agents, and sorbitol-based thixotropic agents.

[0080] Examples of the amide-based thixotropic agent include monoamides, bisamides (excluding the above-mentioned compounds (T1), (T3) and (T2)), and polyamides. Examples of monoamides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, 4-methylbenzamide, aromatic amide, hexamethylenehydroxystearic acid amide, substituted amides, methylolstearic acid amide, methylol amide, and fatty acid ester amide. Examples of bisamides include ethylenebisfatty acid (fatty acid having carbon atoms of 6 to 24) amides, hexamethylenebisfatty acid (fatty acid having carbon atoms of 6 to 24) amides, aromatic bisamides, etc. Examples of fatty acids that are raw materials for the bisamides include stearic acid (having carbon atoms of 18), oleic acid (having carbon atoms of 18), lauric acid (having carbon atoms of 12), 12-hydroxystearic acid, etc. Examples of polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0081] Examples of the cyclic amide oligomer include an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid and a diamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid and a diamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid and a triamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid and a triamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, and a diamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, and a triamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a diamine, and a triamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid, a diamine, and a triamine, and an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, a diamine, and a triamine.

[0082] The acyclic amide oligomer may be an amide oligomer obtained by acyclic polycondensation of a monocarboxylic acid with a diamine and / or triamine, or an amide oligomer obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid with a monoamine. In the case of an amide oligomer containing a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as terminal molecules, resulting in an acyclic amide oligomer with a reduced molecular weight. Furthermore, when the acyclic amide oligomer is an amide compound obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid with a diamine and / or triamine, it becomes an acyclic high-molecular-weight amide polymer. Furthermore, the acyclic amide oligomer also includes an amide oligomer obtained by acyclic condensation of a monocarboxylic acid with a monoamine.

[0083] Examples of the ester-based thixotropic agent include ester compounds, and specific examples thereof include hydrogenated castor oil and ethyl myristate.

[0084] Examples of sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene(-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0085] In the flux of this embodiment, the other thixotropic agents may be used alone or in combination of two or more. Among the above, the other thixotropic agents preferably include at least one selected from the group consisting of amide-based thixotropic agents and ester-based thixotropic agents, and examples thereof include those including at least one selected from the group consisting of polyamides and hydrogenated castor oil.

[0086] The content of the other thixotropic agent in the flux of this embodiment is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 7.5% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less, relative to the total mass (100% by mass) of the flux. The content of the other thixotropic agent in the flux of this embodiment is, for example, 80 mass% or less, or may be 15 mass% or more and 70 mass% or less, or 20 mass% or more and 65 mass% or less, relative to the total mass (100 mass%) of the thixotropic agent.

[0087] <Activator> Examples of the activator contained in the flux of this embodiment include organic acids, amine compounds, and halogen compounds. In the flux of this embodiment, two or more activators may be used in combination. The activator is preferably selected from the group consisting of organic acids, amine compounds, and halogen compounds, and more preferably contains at least an organic acid. The total content of the activator in the flux of this embodiment is preferably 25 mass % or less, more preferably 2.5 mass % or more and 20 mass % or less, and even more preferably 5 mass % or more and 15 mass % or less, relative to the total mass (100 mass %) of the flux.

[0088] ≪Organic acid≫ Examples of the organic acid include carboxylic acids and organic sulfonic acids, including aliphatic carboxylic acids and aromatic carboxylic acids.

[0089] Examples of aliphatic monocarboxylic acids include caproic acid, 2-bromohexanoic acid, enanthic acid, caprylic acid, pelargonic acid, isopelargonic acid, capric acid, caproleic acid, lauric acid (dodecanoic acid), undecanoic acid, linderic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hiragonic acid, hydnocarpic acid, margaric acid, isostearic acid, elaidic acid, petroselinic acid, moroctic acid, eleostearic acid, talic acid, vaccenic acid, ricinoleic acid, vernolic acid, sterculic acid, nonadecanoic acid, eicosanoic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and myristic acid. Examples of aromatic monocarboxylic acids include salicylic acid, parahydroxyphenylacetic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, p-anisic acid; picolinic acid, dipicolinic acid, and 3-hydroxypicolinic acid. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, maleic acid, glutaric acid, diglycolic acid, citraconic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, o-phthalic acid, m-phthalic acid (isophthalic acid), and p-phthalic acid (terephthalic acid).

[0090] Further, examples of the carboxylic acid include tris(2-carboxyethyl) isocyanurate, 1,3-cyclohexanedicarboxylic acid; hydroxycarboxylic acids such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, citric acid, isocitric acid, malic acid, tartaric acid, and 12-hydroxystearic acid; dimer acid, trimer acid, hydrogenated dimer acid obtained by adding hydrogen to dimer acid, and hydrogenated trimer acid obtained by adding hydrogen to trimer acid.

[0091] Examples of organic sulfonic acids include aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include alkanesulfonic acids, alkanolsulfonic acids, etc.

[0092] Examples of alkanesulfonic acids include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, and dodecanesulfonic acid. Examples of alkanol sulfonic acids include 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, and 2-hydroxydodecane-1-sulfonic acid. Examples of aromatic sulfonic acids include 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, and xylenesulfonic acid, and among these, preferred are m-xylene-4-sulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0093] When an organic acid is used as an active agent, one type may be used alone or two or more types may be used in combination. Among the organic acids, it is preferable to include a dicarboxylic acid, and more preferable to include at least one selected from the group consisting of malonic acid, succinic acid, glutaric acid, suberic acid, and azelaic acid. Among these, the organic acid may be one containing a dicarboxylic acid and an aliphatic monocarboxylic acid, or one containing a dicarboxylic acid and a hydrogenated dimer acid. The content of the organic acid in the flux of this embodiment is preferably 15 mass % or less, more preferably 1 mass % or more and 13 mass % or less, and even more preferably 2.5 mass % or more and 12.5 mass % or less, relative to the total mass (100 mass %) of the flux.

[0094] <Amine compounds> Examples of the amine compound include rosin amine, azoles, guanidines, alkylamine compounds, and aminoalcohol compounds. Examples of rosin amines include those exemplified above in the section on <Rosin>.

[0095] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzophenone ... 1-Benzyl-2-phenylimidazole, 1-Cyanoethyl-2-phenylimidazole, 1-Cyanoethyl-2-undecylimidazolium trimellitate, 1-Cyanoethyl-2-phenylimidazolium trimellitate, 1-Dodecyl-2-methyl-3-benzylimidazolium chloride, 2-Methylimidazoline, 2-Phenylimidazoline, 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethoxy]-2,4-di ... ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazo imidazole compounds such as 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, and benzimidazole;1,2,4-Triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N Examples of suitable triazole compounds include N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, and 5-methylbenzotriazole; triazine compounds such as 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-s-triazine; and tetrazole compounds such as 5-phenyltetrazole.

[0096] Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, 1,3-di-o-cumenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine.

[0097] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0098] Examples of the amino alcohol compound include alkanolamines such as 1-amino-2-propanol and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0099] When an amine compound is used as an activator, one type may be used alone or two or more types may be used in combination. Among the amine compounds, it is preferable to include an azole, more preferably to include at least one selected from the group consisting of an imidazole compound and a triazole compound, and even more preferably to include a triazole compound. The content of the amine compound in the flux of this embodiment is preferably 5 mass % or less, more preferably 0.5 mass % or more and 4 mass % or less, and even more preferably 1 mass % or more and 3 mass % or less, relative to the total mass (100 mass %) of the flux.

[0100] <Halogen compounds> Examples of halogen compounds include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0101] Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of amines include aliphatic amines, azoles, and guanidines. Examples of hydrogen halides include chlorine, bromine, and iodine hydrides. Examples of the aliphatic amine include ethylamine, diethylamine, triethylamine, and ethylenediamine. Examples of the guanidines and azoles include those exemplified in the description of amines below.

[0102] Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds, which are compounds in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group have been substituted with halogen atoms. Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds. Examples of halogenated aliphatic alcohols include 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 1,4-dibromo-2-butanol, and trans-2,3-dibromo-2-butene-1,4-diol.

[0103] When a halogen compound is used as an activator, one type may be used alone or two or more types may be used in combination. Among the halogen compounds, a halogenated aliphatic compound may be used, and a halogenated aliphatic alcohol is preferably used. The content of the halogen compound in the flux of this embodiment is preferably 5 mass % or less, more preferably 0.5 mass % or more and 4 mass % or less, and even more preferably 1 mass % or more and 2.5 mass % or less, relative to the total mass (100 mass %) of the flux.

[0104] <Other ingredients> The flux of this embodiment may contain other components as needed in addition to the resin, solvent, thixotropic agent, and activator described above. Examples of other components include antioxidants, surfactants, silane coupling agents, and colorants.

[0105] <Antioxidants> Examples of the antioxidant include hindered phenol compounds and nitrogen compounds. The hindered phenol compound refers to a phenol compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at least on one of the ortho positions of the phenol.

[0106] Examples of the hindered phenol compounds include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-dihydroxy-3,3'-bis(α-methylcyclohexyl)propionate ... 1,6-Hexanediol-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4 -hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyphenyl)propionate hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, 2,2-methylenebis[6-(1-methylcyclohexyl)-4-methylphenol], and the like.

[0107] Examples of the nitrogen compound in the antioxidant include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based nitrogen compounds.

[0108] <Surfactants> Examples of surfactants include nonionic surfactants and cationic surfactants. Examples of nonionic surfactants include aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyhydric alcohol polyoxyethylene adducts, aliphatic alcohol polyoxypropylene adducts, aromatic alcohol polyoxypropylene adducts, and polyhydric alcohol polyoxypropylene adducts. Examples of cationic surfactants include diamine-terminated polyethylene glycol, diamine-terminated polyethylene glycol-polypropylene glycol copolymers, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, polyvalent amine polyoxyethylene adducts, and polyvalent amine polyoxypropylene adducts.

[0109] As described above, the flux of the present embodiment contains a resin, a solvent, at least one compound selected from the group consisting of the compound (T1) represented by the chemical formula (T-1) and the compound (T3) represented by the chemical formula (T-3), and an activator. By employing at least one of a compound (T1) having two N-hexadecanoyl groups and a compound (T3) having two N-octadecanoyl groups connected via a 1,2-ethanediyldiimino group (-NH-CHCH-NH-) in the molecule, this flux is able to enhance the effect of suppressing the generation of voids during the mounting of BGA components, etc. This flux is particularly able to suppress the generation of voids that occupy a large area (e.g., 20% or more) of the cross section of the solder joint.

[0110] The flux of preferred embodiment (1) contains a resin, a solvent, a thixotropic agent, and an activator. The thixotropic agent includes both the compound (T1) and the compound (T3), and further contains a compound (T2) represented by general formula (T-2), i.e., a compound having one N-octadecanoyl group and an acyl group (RC(=O)-) in the molecule via a 1,2-ethanediyldiimino group (-NH-CHCH-NH-). According to the flux of the embodiment (1), the effect of suppressing the occurrence of voids during the mounting of BGA components and the like can be further enhanced.

[0111] Alternatively, the flux of preferred embodiment (2) contains a resin, a solvent, a thixotropic agent, and an activator, and the thixotropic agent contains all of the compound (T1), the compound (T3), and the compound (T2). The total content of the compound (T1) and the compound (T2) is 15% by mass or more and 99% by mass or less with respect to the total content of the three components, namely the compound (T1), the compound (T3), and the compound (T2); the total content of the compound (T3) and the compound (T2) is 15% by mass or more and 99% by mass or less with respect to the total content of the three components; and the mass ratio of the content of the compound (T2) to the total content of the three components is 0.15 or more and 0.50 or less. According to the flux of the embodiment (2), the effect of suppressing the occurrence of voids during the mounting of BGA components and the like can be further enhanced.

[0112] (solder paste) One embodiment of the solder paste according to the second aspect contains the flux of the above-described embodiment and solder powder. Such a solder paste can be prepared by mixing the flux of the above-described embodiment with solder powder using a known method.

[0113] As the solder metal constituting the solder powder, a solder alloy of a known composition can be used. The solder alloy may be a solder containing only Sn, or may be a solder alloy such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, or Sn-In, or an alloy of these with Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P added. The solder alloy may be a Sn-Pb based solder alloy or a Sn-Pb based solder alloy to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. have been added. The solder alloy is preferably a solder alloy that does not contain Pb, and more preferably a solder alloy that contains Sn, Ag, and Cu (Sn—Ag—Cu-based solder alloy).

[0114] Flux Content: The content of the flux in the solder paste of this embodiment is preferably 5 to 30 mass %, and more preferably 5 to 15 mass %, relative to the total mass of the solder paste.

[0115] According to the solder paste of the present embodiment described above, the flux of the above-described embodiment is used, and therefore the effect of suppressing the occurrence of voids can be enhanced. The solder paste of this embodiment is particularly suitable for soldering to surface mount components such as BGA and CSP.

[0116] (Method of manufacturing a bonded body) One embodiment of the method for producing a bonded body according to the third aspect is a method including a step of obtaining a bonded body by soldering a component and a substrate, wherein the soldering is performed by reflow using the solder paste according to the second aspect. An embodiment of a method for producing such a bonded body will be described below. The method for manufacturing a bonded body according to this embodiment includes a solder paste application step, a component attachment step, and a reflow step in this order.

[0117] [Solder paste application process] In the solder paste application step, the solder paste according to the second aspect is applied to the surface of the substrate. Examples of the main substrate include a printed wiring board and a wafer. Examples of methods for applying the solder paste include a method of printing and applying the solder paste using a mask with openings, a method of ejecting the solder paste using a dispenser or the like, and a method of transferring the solder paste using a probe pin or the like.

[0118] [Parts installation process] In the component mounting step, components are mounted at predetermined positions on the substrate to which the solder paste has been applied. Examples of components include chips, integrated circuits, transistors, diodes, resistors, capacitors, semiconductor packages such as CSPs (Chip Size Packages), and BGA (Ball Grid Array) components.

[0119] [Reflow process] The atmosphere for the reflow operation in the reflow step may be, for example, a nitrogen gas atmosphere, a reducing gas atmosphere, or an air atmosphere. The reducing gas atmosphere may be formed, for example, by volatilizing a reducing compound in a reflow furnace, or by supplying a reducing gas obtained by passing nitrogen through a liquid reducing compound into the reflow furnace. As the reducing compound, formic acid is preferred. Reflow soldering in an air atmosphere (air reflow) generally refers to soldering in heated air (approximately 80 vol% nitrogen, approximately 20 vol% oxygen).

[0120] In the reflow process, the interior of a reflow furnace is heated, and the board after component mounting is heated to a temperature (i.e., peak temperature) higher than the melting point of the solder powder contained in the solder paste (this is called the main heating process). The heating temperature may be, for example, a temperature higher than the melting point of the solder powder by 5 to 30° C. The heating time may be, for example, 30 seconds to 3 minutes.

[0121] The reflow process may include a preheating step before the main heating step. In the preheating step, the board after mounting the components is heated in a reflow furnace at a temperature lower than the melting point of the solder powder contained in the solder paste. The heating temperature may be, for example, 130 to 220° C. The heating time may be, for example, 1 to 5 minutes.

[0122] According to the method for manufacturing a bonded body according to the present embodiment described above, the use of a solder paste containing the flux of the present embodiment suppresses the generation of voids in the bonded portion between the component and the substrate, making it possible to manufacture a highly reliable bonded body. This method for manufacturing a bonded body is particularly useful as a method for manufacturing a bonded body to which surface-mounted components such as BGAs and CSPs are soldered. [Example]

[0123] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0124] <Preparation of flux> (Examples 1 to 42, Comparative Example 1) Each flux of the examples and comparative examples was prepared by mixing the components so as to obtain the compositions shown in Tables 1 to 6.

[0125] In the table, the content of each component indicates the ratio (mass %) to the total mass (100 mass %) of the flux. "Compound (T2) / [Compound (T1) + Compound (T2) + Compound (T3)]" indicates the mass ratio of the content of compound (T2) to the total content of compound (T1), compound (T2), and compound (T3). The raw materials used are listed below.

[0126] ·resin Rosin and copolymers were used. The rosins used were acrylic acid modified hydrogenated rosin, hydrogenated rosin, and polymerized rosin. The copolymer used was an ethylene / acrylic acid copolymer.

[0127] ·solvent Diethylene glycol monohexyl ether (HeDG), diethylene glycol mono-2-ethylhexyl ether (EHDG), and tetraethylene glycol dimethyl ether were used, respectively.

[0128] Thixotropic agents The following bisamide, hydrogenated castor oil, and polyamide (saturated fatty acid polyamide, melting point 200° C. or less) were used.

[0129] Bisamide Compound (T1): A compound represented by the following chemical formula (T-1)

[0130] [ka]

[0131] Compound (T23): A compound represented by the following chemical formula (T-2-3) Compound (T21): A compound represented by the following chemical formula (T-2-1)

[0132] [ka]

[0133] Compound (T3): A compound represented by the following chemical formula (T-3)

[0134] [ka]

[0135] Ethylenebis(lauric acid amide): A compound represented by the following chemical formula

[0136] [ka]

[0137] Activators Organic acids, amine compounds and halogen compounds were used. The organic acids used were dimer acid, malonic acid, succinic acid, glutaric acid, suberic acid, azelaic acid, and 2-bromohexanoic acid. The amine compound used was 1,2,3-benzotriazole. The halogen compound used was trans-2,3-dibromo-2-butene-1,4-diol.

[0138] ·others Bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)] was used as the antioxidant.

[0139] <Preparation of solder paste> Each of the fluxes of the above-described Examples and Comparative Examples was mixed with the following solder powder to prepare a solder paste. Each of the prepared solder pastes contained 11 mass % flux and 89 mass % solder powder.

[0140] Solder powder: Powder made of a solder alloy containing 0.5 mass% Cu, 3.0 mass% Ag, and the remainder Sn. The solidus temperature of this solder alloy is 217°C and the liquidus temperature is 220°C. The size of the solder powder (particle size distribution) satisfies symbol 5 in the powder size classification (Table 2) of JIS Z 3284-1:2014.

[0141] <Evaluation> The ability to suppress void generation was evaluated as follows, and the evaluation results are shown in Tables 1 to 6.

[0142] [Evaluation of void generation suppression] The following main board and BGA components were used. Main board: Material: FR-4, thickness: 1.6 mm, pad size: 0.30 mmφ, pitch: 0.50 mm, surface treatment: Cu-OSP

[0143] BGA components: Board size 8mm x 8mm x thickness 1mm, pad size 0.30mmφ, pitch 0.50mm, surface treatment electroless NiAu (nickel gold); solder ball composition M705 (Sn-3.0Ag-0.5Cu), ball size 0.30mm, number of BGA bumps (I / O) 132 x number of BGA components 3 = 396 pieces

[0144] The prepared solder paste was printed on the main board using a 0.10 mm thick metal mask. After printing, BGA components were mounted on the main board and soldered by reflow in a nitrogen gas atmosphere with an oxygen concentration of 1000 ppm or less.

[0145] The reflow conditions (reflow profile) were to preheat from 130°C to 220°C over 90 seconds, and then continue heating at 220°C or higher for 42 seconds, with the peak temperature being 242°C. This reflow profile is shown in Figure 1.

[0146] After reflow, the void area was measured. In measuring the void area, if the X-ray passed through at least one void, it was determined that a void existed. Voids with a diameter of 0.1 μm or more were detected. After reflow, the bonded structure was irradiated with X-rays perpendicular to the substrate, and the area of ​​voids that occurred at the bonded portion between the bump and the pad was measured by analyzing the transmitted X-rays. This void area measurement was performed using an XD7600NT Diamond X-ray inspection system (manufactured by Nordson DAGE). Next, the ratio of the void area to the bump area (void area ratio (%)) was calculated, and the maximum value of the void area ratio (maximum void area ratio) among a total of 396 bumps was confirmed. The ability to suppress void generation was evaluated based on the following criteria: Ranks 1 to 4 were considered acceptable, and rank 5 was considered unacceptable.

[0147] Judgment criteria Rank 1: The maximum void area ratio was less than 10%. Rank 2: The maximum void area ratio was 10% or more and less than 15%. Rank 3: The maximum void area ratio was 15% or more and less than 18%. Rank 4: The maximum void area ratio was 18% or more and less than 20%. Rank 5: The maximum void area ratio was 20% or more.

[0148] [Table 1]

[0149] In Table 1, when the flux of Comparative Example 1 containing only hardened castor oil as the thixotropic agent was used, the evaluation result of the ability to suppress the generation of voids was poor.

[0150] In contrast, when the flux of Example 1 containing compound (T1) in addition to hydrogenated castor oil as a thixotropic agent, the flux of Example 3 containing compound (T3) in addition to hydrogenated castor oil, and the flux of Example 2 containing both compound (T1) and compound (T3) in addition to hydrogenated castor oil were used, the maximum void area ratio was less than 20%, which resulted in an improved effect of suppressing void generation compared to when the flux of Comparative Example 1 was used.

[0151] (i) When the fluxes of Examples 4 to 6 were used in combination with compound (T23) or compound (T21) as a thixotropic agent, the maximum void area ratio was less than 15%, and the effect of suppressing void generation was significantly improved. (ii) Among the fluxes of Examples 4 to 6, when the flux of Example 4, which further contains compound (T23) as a thixotropic agent, was used, the maximum void area ratio was less than 10%, and the effect of suppressing void generation was significantly improved.

[0152] When the flux of Example 7 containing 3.00 mass% of compound (T1) was used, and when the flux of Example 16 containing 3.00 mass% of compound (T3) was used, the evaluation of the void generation suppression ability was rank 3 in both cases. From this, it is considered that the effect of the fluxes of Examples 4 to 6 is not only due to the influence of the increased bisamide content, but is mainly due to the synergistic effect of the combined use of compound (T23) or compound (T21).

[0153] [Table 2]

[0154] In the results shown in Table 2, when the fluxes of Examples 8 to 11, 4, and 12 to 15 were used, the evaluation was judged to be rank 1 or 2, which indicated that the effect of suppressing void generation was very high. This confirms that the effect of suppressing void generation is more likely to be enhanced when the mass ratio represented by compound (T2) / [compound (T1) + compound (T2) + compound (T3)] is 0.15 or more and 0.50 or less. Furthermore, it can be confirmed that when the mass ratio is 0.30 or more and 0.50 or less, the effect of suppressing the generation of voids is more likely to be enhanced.

[0155] Furthermore, it can be confirmed that the effect of suppressing void generation is more likely to be enhanced when the ratio of the total content of compound (T1) and compound (T2) to the total content of compound (T1), compound (T3), and compound (T2) is 15 mass% or more and 99 mass% or less, and when the ratio of the total content of compound (T3) and compound (T2) is 15 mass% or more and 99 mass% or less. Furthermore, it can be confirmed that the effect of suppressing void generation is more likely to be enhanced when the ratio of the total content of compound (T1) and compound (T2) to the total content of compound (T1), compound (T3), and compound (T2) is 35 mass% or more and 97 mass% or less, and when the ratio of the total content of compound (T3) and compound (T2) is 35 mass% or more and 97 mass% or less.

[0156] [Table 3]

[0157] [Table 4]

[0158] [Table 5]

[0159] [Table 6]

[0160] In Tables 3 to 6, when the fluxes of Examples 11 and 17 to 42 to which the present invention is applied were used, the evaluation result was Rank 1 or 2 in all cases, confirming that the effect of suppressing void generation was good.

[0161] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the appended claims.

Claims

1. Contains resin, solvent, thixotropic agent and activator, the thixotropic agent comprises at least one selected from the group consisting of a compound (T1) represented by the following chemical formula (T-1) and a compound (T3) represented by the following chemical formula (T-3), A flux in which the total content of the compound (T1) and the compound (T3) is 1.5 mass % or more and 10 mass % or less with respect to the total mass (100 mass %) of the flux. 【Chemistry 1】

2. A composition comprising a resin, a solvent, a thixotropic agent, and an activator, the thixotropic agent comprises at least one compound selected from the group consisting of a compound (T1) represented by the following chemical formula (T-1) and a compound (T3) represented by the following chemical formula (T-3), and a compound (T2) represented by the following general formula (T-2): A flux in which the total content of the compound (T1) and the compound (T3) is 0.5 mass % or more and 10 mass % or less with respect to the total mass (100 mass %) of the flux. 【Chemistry 2】 【Transformation 3】 [In the formula, R is an aliphatic hydrocarbon group having 11 to 15 carbon atoms.]

3. The flux according to claim 2, wherein R in the general formula (T-2) is a linear alkyl group having 15 carbon atoms.

4. 3. The flux according to claim 2, wherein a total content of the compound (T1), the compound (T3), and the compound (T2) is 1 mass % or more and 15 mass % or less with respect to a total mass (100 mass %) of the flux.

5. 3. The flux according to claim 2, wherein a mass ratio of a content of the compound (T2) to a total content of the compound (T1), the compound (T3), and the compound (T2) is 0.15 or more and 0.50 or less.

6. A solder paste comprising the flux according to any one of claims 1 to 5 and solder powder.

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