Thickening inhibitor for soldering flux

Abstract

To provide a flux that makes it possible to further suppress temporal viscosity change in a solder paste, and a solder paste including the flux.SOLUTION: The present invention provides an agent for suppressing viscosity increase in a solder flux, which is used to suppress viscosity increase in a solder paste that contains solder alloy powder and a solder flux. The agent includes a thiol compound having a benzenethiol backbone in which at least one hydrogen atom on a benzene ring is substituted with a mercapto group (-SH). As the thiol compound having the benzenethiol backbone, at least one selected from the group consisting of 2-aminobenzene thiol, 4-aminobenzene thiol, 3-aminobenzene thiol and benzene thiol is preferable.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thickening inhibitor for soldering flux, a flux containing the same, and a solder paste.

Background Art

[0002] Fixing of components to a substrate and electrical connection of components to a substrate are generally performed by soldering. In soldering, a flux, solder powder, and a solder paste obtained by mixing a flux and solder powder are used. A flux has the function of chemically removing metal oxides present on the metal surface of a bonding object to be soldered and on the solder, and enabling the movement of metal elements at the boundary between the two. Therefore, by performing soldering using a flux, an intermetallic compound is formed between the two, and a strong bond can be obtained.

[0003] In soldering using a solder paste, first, the solder paste is printed on a substrate, then components are mounted, and the substrate on which the components are mounted is heated in a heating furnace called a reflow furnace. As a result, the solder powder contained in the solder paste melts, and the components are soldered to the substrate.

[0004] The compounding components of the flux are appropriately selected according to the type of solder or the metal type on the surface of the bonding object. For example, Patent Document 1 proposes a solder paste using a flux containing a base resin, a solvent, a thixotropic agent, an activator, an antioxidant, and a rust preventive for a specific solder alloy powder.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, solder paste, which is a mixture of flux and solder powder, can have long storage periods depending on how it is used. Furthermore, depending on the storage conditions, the viscosity of the solder paste can increase over time, leading to problems such as the inability to achieve its initial printing performance. This problem has become more apparent in recent years as electronic components have become smaller and more complex. Therefore, the present invention aims to provide a flux that can further suppress changes in the viscosity of solder paste over time, and a solder paste using the same. [Means for solving the problem]

[0007] To solve the above problems, the present invention employs the following configuration.

[0008] [1] A soldering flux viscosity inhibitor for which the viscosity increase of a solder paste containing solder alloy powder and soldering flux is suppressed, comprising a thiol compound having a benzenethiol skeleton in which one or more hydrogen atoms on a benzene ring are replaced with a mercapto group (-SH).

[0009] [2] The soldering flux viscosity inhibitor according to [1], wherein the thiol compound is at least one selected from the group consisting of 2-aminobenzenethiol, 4-aminobenzenethiol, 3-aminobenzenethiol, and benzenethiol. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a flux that can further suppress changes in the viscosity of solder paste over time, and a solder paste using the same. [Brief explanation of the drawing]

[0011] [Figure 1]This figure shows the reflow profile used to evaluate the [effect of suppressing void generation] in this embodiment. [Modes for carrying out the invention]

[0012] (Flux) The flux of this embodiment contains rosin, a solvent, a thixotropic agent, a thiol compound, and an activator. The thiol compound includes a compound (Tp) having a benzenethiol skeleton in which one or more hydrogen atoms on the benzene ring are replaced with mercapto groups (-SH).

[0013] <Rosin> Examples of rosin include raw material rosins such as gum rosin, wood rosin, and tall oil rosin, as well as derivatives obtained from said raw material rosin. Examples of such derivatives include purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, acid-modified rosin, acid-modified hydrogenated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid modified products (acrylic rosin, maleated rosin, fumarated rosin, etc.), as well as purified, hydrated, and disproportionated products of the polymerized rosin, and purified, hydrated, and disproportionated products of the α,β-unsaturated carboxylic acid modified products.

[0014] Rosin may be used alone or in a mixture of two or more types. As for the rosin, it is preferable to use at least one selected from the group consisting of polymerized rosin, acid-modified hydrogenated rosin, and hydrogenated rosin. As the acid-modified hydrogenated rosin, it is preferable to use acrylic acid-modified hydrogenated rosin. Examples of hydrogenated rosins include those obtained by hydrogenating natural resins containing a mixture of abietic acid and its isomers, such as rosins mainly composed of dihydroabietic acid and tetrahydroabietic acid. "Main component" refers to a component that makes up a compound and is present in an amount of 40% by mass or more.

[0015] In the flux of this embodiment, the rosin content is preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less, and still more preferably 25% by mass or more and 40% by mass or less with respect to the total mass (100% by mass) of the flux.

[0016] <Solvent> Examples of the solvent include water, alcohol solvents, glycol ether solvents, terpineols, and the like.

[0017] Examples of the alcohol solvents include isopropyl alcohol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, isobornyl cyclohexanol, 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-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, 2-methyl-2,4-pentanediol (hexylene glycol), octanediol, and the like. <0>

[0018] Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether (butyl glycol), ethylene glycol monohexyl ether (hexyl glycol), diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl propylene triglycol, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether, tripropylene glycol - n - butyl ether, and the like.

[0019] Examples of terpineols include α - terpineol, β - terpineol, γ - terpineol, and a terpineol mixture (i.e., a mixture whose main component is α - terpineol and contains β - terpineol or γ - terpineol). Examples of other solvents include, for example, dioctyl sebacate (DOS), liquid paraffin, and the like.

[0020] The solvent may be used alone or in combination of two or more. The flux of this embodiment is useful for suppressing the change in viscosity over time of a solder paste containing a flux having a composition in which solvents with different boiling points are combined.

[0021] In this specification, the "boiling point of the solvent" means the temperature of the solvent when the saturated vapor pressure of the target solvent becomes equal to 1 atm. A preferred form of solvents with different boiling points includes those having both a solvent (S1) with a boiling point of 250°C or higher and a solvent (S3) with a boiling point of 220°C or lower. Hereinafter, a solvent with a boiling point of 250°C or higher is also referred to as the (S1) component, and a solvent with a boiling point of 220°C or lower is also referred to as the (S3) component. Also, a solvent with a boiling point exceeding 220°C and less than 250°C is referred to as the (S2) component.

[0022] ≪Solvent (Sɪ) with a boiling point of 250 °C or higher≫ Examples of component (S1) include diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C), diethylene glycol monohexyl ether (hexyldiglycol) (boiling point 258°C), diethylene glycol dibutyl ether (boiling point 256°C), triethylene glycol monobutyl ether (boiling point 278°C), triethylene glycol butyl methyl ether (boiling point 261°C), and tetraethylene glycol dimethyl ether (boiling point 275°C).

[0023] Solvents with a boiling point above 220°C and below 250°C (S2) Examples of component (S2) include 1,4-butanediol (boiling point 228°C), phenyl glycol (boiling point 237°C), butyl carbitol (boiling point 231°C), and tripropylene glycol monomethyl ether (boiling point 243°C).

[0024] Solvents with a boiling point of 220°C or lower (S3) (S3) Component examples include, for example, 1,3-butanediol (boiling point 203°C), 1,2-butanediol (boiling point 194°C), 2-methyl-2,4-pentanediol (hexylene glycol) (boiling point 198°C), ethylene glycol monohexyl ether (hexyl glycol) (boiling point 208°C), 2,2-dimethyl-1,3-propanediol (boiling point 210°C), 2,5-dimethyl-2,5-hexanediol (boiling point 215°C), 2,5-dimethyl-3-hexyne-2,5-diol (boiling point 206°C), and α-terpineol. Examples include solvents with a boiling point of 218°C (or above, with a boiling point of 190°C to 220°C (these solvents are also referred to as "solvent (S31)" or "(S31) component")), ethylene glycol monobutyl ether (butyl glycol) (boiling point 171°C), 2,3-butanediol (boiling point 183°C), 2,3-dimethyl-2,3-butanediol (boiling point 174°C), and 1-ethynyl-1-cyclohexanol (boiling point 180°C) (solvents with a boiling point of 160°C to less than 190°C (these solvents are also referred to as "solvent (S32)" or "(S32) component")).

[0025] As for the form of solvents with different boiling points, it is preferable to have both component (S1) and component (S31) because it is easier to suppress changes in the viscosity of the solder paste over time. When both component (S1) and component (S31) are present, the ratio (mass ratio) of component (S1) to component (S31) is preferably 55 / 45 or more and 95 / 5 or less, and more preferably 60 / 40 or more and 90 / 10 or less, from the viewpoint of keeping the rate of viscosity change over time low when it is used as a solder paste. Furthermore, from the viewpoint of suppressing the generation of voids during soldering, it is preferable that solvent (S1) / solvent (S31) = 60 / 40 or more and 85 / 15 or less.

[0026] The total solvent content is the remainder in the flux. For example, the total solvent content in the flux of this embodiment is preferably 25% to 60% by mass, more preferably 30% to 50% by mass, and even more preferably 35% to 45% by mass, based on the total mass (100% by mass) of the flux.

[0027] <Tixotropic agents> Examples of thixotropic agents include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0028] Examples of ester-based thixotropes include ester compounds, specifically hydrogenated castor oil and ethyl myristate.

[0029] Examples of amide-based thixotropes include monoamides, bisamides, 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 (p-toluamide), p-toluenemethaneamide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amide, methylol stearate amide, methylol amide, and fatty acid ester amide. Examples of bisamides include ethylenebis fatty acid (fatty acid with 6-24 carbon atoms) amide, ethylenebishydroxy fatty acid (fatty acid with 6-24 carbon atoms) amide, hexamethylenebis fatty acid (fatty acid with 6-24 carbon atoms) amide, hexamethylenebishydroxy fatty acid (fatty acid with 6-24 carbon atoms) amide, and aromatic bisamides. Examples of fatty acids that are raw materials for the bisamides include stearic acid (18 carbon atoms), oleic acid (18 carbon atoms), and lauric acid (12 carbon atoms). 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 acyclic amide oligomers.

[0030] The aforementioned cyclic amide oligomers include amide oligomers obtained by cyclic polycondensation of a dicarboxylic acid and a diamine, amide oligomers obtained by cyclic polycondensation of a tricarboxylic acid and a diamine, amide oligomers obtained by cyclic polycondensation of a dicarboxylic acid and a triamine, amide oligomers obtained by cyclic polycondensation of a tricarboxylic acid and a triamine, amide oligomers obtained by cyclic polycondensation of a dicarboxylic acid and a tricarboxylic acid and a diamine, amide oligomers obtained by cyclic polycondensation of a dicarboxylic acid and a tricarboxylic acid and a triamine, amide oligomers obtained by cyclic polycondensation of a dicarboxylic acid, a diamine and a triamine, amide oligomers obtained by cyclic polycondensation of a tricarboxylic acid, a diamine and a triamine, and the like.

[0031] The aforementioned acyclic amide oligomers include amide oligomers obtained by acyclic polycondensation of a monocarboxylic acid and a diamine and / or triamine, and amide oligomers obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid and a monoamine. When an amide oligomer contains a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as a terminal molecule, resulting in an acyclic amide oligomer with a reduced molecular weight. Furthermore, when an acyclic amide oligomer is an amide compound obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid and a diamine and / or triamine, it becomes an acyclic polymer-based amide polymer. In addition, acyclic amide oligomers also include amide oligomers obtained by acyclic condensation of a monocarboxylic acid and a monoamine.

[0032] 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.

[0033] Thixopropyl alcohol may be used individually or in combination of two or more types. The thixotropic agent contained in the flux of this embodiment is preferably at least one selected from the group consisting of ester-based thixotropic agents and amide-based thixotropic agents, more preferably containing at least an amide-based thixotropic agent, and even more preferably a combination of an ester-based thixotropic agent and an amide-based thixotropic agent. Hydrogenated castor oil is preferred as the ester-based thixotropic agent. Polyamides are preferred as amide-based thixotropes.

[0034] In this embodiment, the thixotropic agent content in the flux is preferably 2% to 20% by mass, more preferably 5% to 15% by mass, and even more preferably 5% to 10% by mass, based on the total mass (100% by mass) of the flux.

[0035] <Thiol compounds> In the flux of this embodiment, the thiol compound used contains a compound (Tp) having a benzenethiol skeleton. A "benzenethiol skeleton" refers to a structure in which one or more hydrogen atoms on a benzene ring are replaced by a mercapto group (-SH).

[0036] ≪Compound (Tp)≫ Suitable examples of the compound (Tp) include thiol compounds represented by the following general formula (Tp-0).

[0037] [ka] [In the formula, R is a substituent. x is an integer greater than or equal to 1, indicating the number of mercapto groups (-SH). y is an integer greater than or equal to 0, indicating the number of substituents (R). However, 1 ≤ x + y ≤ 6.]

[0038] In the above formula (Tp-0), examples of substituents in R include an amino group (-NH2), a halogen atom, an alkyl group, an alkoxy group, an alkyl halide, a hydroxyl group, and the like. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. The alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 6 carbon atoms. As the alkoxy group, an alkoxy group having 1 to 6 carbon atoms is preferred. Examples of alkyl halides include groups in which some or all of the hydrogen atoms of the alkyl group are substituted with halogen atoms. These alkyl groups may be linear or branched, and are preferably alkyl groups having 1 to 6 carbon atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. In particular, the substituents in R are amino groups and hydroxyl groups, with amino groups being especially preferred, as they tend to enhance the effect of suppressing changes in the viscosity of the solder paste over time.

[0039] In the above formula (Tp-0), x is an integer of 1 or more, preferably an integer between 1 and 3, more preferably 1 or 2, and particularly preferably 1. y is an integer greater than or equal to 0, preferably an integer between 0 and 3, more preferably an integer between 0 and 2, and particularly preferably 1.

[0040] A preferred compound (Tp) is, for example, an aminobenzenethiol represented by the following chemical formula (Tp-10).

[0041] [ka]

[0042] In the chemical formula (Tp-10) above, the position of the amino group bonded to the mercapto group on the benzene ring may be the ortho (2-), meta (3-), or para (4-) position.

[0043] Compound (Tp) may be used alone or as a mixture of two or more compounds. The compound (Tp) contained in the flux of this embodiment is preferably a thiol compound represented by the general formula (Tp-0), and aminobenzenethiol (x is 1 or more, y is 1 or more) and benzenethiol (x is 1 or more, y=0) are more preferable because they can easily enhance the effect of suppressing changes in the viscosity of the solder paste over time. Among these, thiol compounds selected from the group consisting of 2-aminobenzenethiol (x=y=1), 4-aminobenzenethiol (x=y=1), 3-aminobenzenethiol (x=y=1), and benzenethiol (x=1, y=0) are preferred because they are more likely to suppress the viscosity change of the solder paste over time. Thiol compounds selected from the group consisting of 2-aminobenzenethiol (x=y=1), 4-aminobenzenethiol (x=y=1), and 3-aminobenzenethiol (x=y=1) are more preferred, thiol compounds selected from the group consisting of 2-aminobenzenethiol (x=y=1) and 4-aminobenzenethiol (x=y=1) are even more preferred, and using 2-aminobenzenethiol (x=y=1) and 4-aminobenzenethiol (x=y=1) in combination is particularly preferred.

[0044] When 2-aminobenzenethiol (x=y=1) and 4-aminobenzenethiol (x=y=1) are used in combination, the mixing ratio (mass ratio) is preferably 2-aminobenzenethiol / 4-aminobenzenethiol = 1 / 9 to 9 / 1, more preferably 3 / 7 to 7 / 3, and even more preferably 4 / 6 to 6 / 4.

[0045] In this embodiment, the total content of compound (Tp) in the flux is preferably 0.005% to 0.7% by mass, more preferably 0.01% to 0.5% by mass, and even more preferably 0.02% to 0.3% by mass, based on the total mass (100% by mass) of the flux. If the total content of compound (Tp) is above the lower limit of the preferred range described above, the effect of suppressing changes in the viscosity of the solder paste over time is more easily enhanced, and if it is below the upper limit of the preferred range described above, the generation of voids during soldering is more easily suppressed.

[0046] Other thiol compounds besides the compound (Tp) mentioned above may be used in combination with the thiol compound. Examples of thiol compounds other than compound (Tp) include 2-(dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate.

[0047] <Activating agent> Examples of activators include halogenated activators, organic acids, and amines.

[0048] ≪Halogenated Activators≫ Examples of halogenated activators include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0049] Amine hydrohalides: Amine hydrohalides are compounds obtained by reacting an amine with a hydrogen halide. Examples of amines include azoles, guanidines, alkylamine compounds, and amino alcohol compounds, as exemplified in the explanation of "amines" below. Examples of hydrogen halides include the hydrides of iodine, bromine, chlorine, and fluorine. Examples of amine hydrohalides include amine hydroiodide, amine hydrobromide, amine hydrochloride, and amine hydrofluoride.

[0050] Examples of amine hydroiodides include heteroalicyclic amine hydroiodides such as 2-pipecolin hydroiodide (2-pipecolin·HI) and piperidine·HI; linear amine hydroiodides such as monoethylamine·HI, triethylamine·HI, 1-pentanamine·HI, 2-ethylhexylamine·HI, and diallylamine·HI; alicyclic amine hydroiodides such as cyclohexylamine·HI; aromatic amine hydroiodides such as aniline·HI; and guanidine hydroiodides such as 1,3-diphenylguanidine·HI.

[0051] Examples of amine hydrobromides include 2-pipecolin hydrobromide (2-pipecolin·HBr), piperidine·HBr, diphenylguanidine·HBr, cyclohexylamine·HBr, hexadecylamine·HBr, stearylamine·HBr, ethylamine·HBr, 2-ethylhexylamine·HBr, pyridine·HBr, isopropylamine·HBr, diethylamine·HBr, dimethylamine·HBr, rosinamine·HBr, hydrazine hydrate·HBr, trinonylamine·HBr, diethylaniline·HBr, 2-diethylaminoethanol·HBr, diallylamine·HBr, triethylamine·HBr, aniline·HBr, dimethylcyclohexylamine·HBr, rosinamine·HBr, 2-phenylimidazole·HBr, 4-benzylpyridine·HBr, hydrazine monobromide, hydrazine dibromide, and ethylenediamine dibromide.

[0052] Examples of amine hydrochlorides include 1,3-diphenylguanidine hydrochloride (1,3-diphenylguanidine·HCl), ethylamine·HCl, stearylamine·HCl, diethylaniline·HCl, diethanolamine·HCl, dimethylamine·HCl, 2-ethylhexylamine·HCl, isopropylamine·HCl, cyclohexylamine·HCl, 1,3-diphenylguanidine·HCl, dimethylbenzylamine·HCl, dimethylcyclohexylamine·HCl, 2-diethylaminoethanol·HCl, diallylamine·HCl, diethylamine·HCl, triethylamine·HCl, butylamine·HCl, hexylamine·HCl, n-octylamine·HCl, dodecylamine·HCl, L-glutamic acid·HCl, N-methylmorpholine·HCl, betaine·HCl, pyridine·HCl, hydrazine monohydrochloride, hydrazine dihydrochloride, and ammonium chloride.

[0053] Examples of amine hydrofluorides include 1,3-diphenylguanidine hydrofluoride (1,3-diphenylguanidine·HF), diethylamine·HF, 2-ethylhexylamine·HF, cyclohexylamine·HF, ethylamine·HF, and rosinamine·HF.

[0054] Organic halogen compounds other than amine hydrohalogenates: Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds having a halogenated aliphatic hydrocarbon group. A halogenated aliphatic hydrocarbon group refers to an aliphatic hydrocarbon group in which some or all of the hydrogen atoms constituting the group are replaced by halogen atoms. Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0055] 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.

[0056] Examples of heterocyclic halogenated compounds include compounds represented by the following general formula (3).

[0057] R 5 -(R 6 ) m ...(3) R 5 R represents a heterocyclic group with m valence. 6 This represents a halogenated aliphatic hydrocarbon group.

[0058] R 5In this context, the heterocyclic group with an m-valence can be defined as a ring structure in which some of the carbon atoms constituting an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in this heterocyclic ring include oxygen atoms, sulfur atoms, nitrogen atoms, etc. This heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of this heterocyclic ring include isocyanurate rings. R 6 In this, the halogenated aliphatic hydrocarbon group is preferably having 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. Also, R 6 The group is preferably a brominated aliphatic hydrocarbon group or a chlorinated aliphatic hydrocarbon group, more preferably a brominated aliphatic hydrocarbon group, and even more preferably a brominated saturated aliphatic hydrocarbon group.

[0059] Examples of halogenated heterocyclic compounds include tris-(2,3-dibromopropyl)isocyanurate.

[0060] In addition, examples of organic halogen compounds other than amine hydrohalides include halogenated carboxyl compounds, such as iodized carboxyl compounds like 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chloride carboxyl compounds like 2-chlorobenzoic acid and 3-chloropropionic acid; and brominated carboxyl compounds like 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid.

[0061] Alternatively, halogenated activators can include, for example, salts obtained by reacting an amine with tetrafluoroboric acid (HBF4), or complexes obtained by reacting an amine with boron trifluoride (BF3). Examples of such complexes include boron trifluoride piperidine.

[0062] Halogenated activators may be used individually or in mixtures of two or more types. In this embodiment, the halogenated activator contained in the flux is preferably an amine hydrohalide salt, more preferably an amine hydroiodide salt, even more preferably at least one selected from the group consisting of heteroalicyclic amine hydroiodides and guanidine hydroiodides, particularly preferably a heteroalicyclic amine hydroiodide salt, and most preferably at least one selected from the group consisting of 2-pipecolin·HI and piperidine·HI.

[0063] If the flux of this embodiment contains an amine hydroiodide in addition to the compound (Tp) described above, the mixing ratio (mass ratio) of compound (Tp) and amine hydroiodide is preferably greater than 50 / 50 and 90 / 10 or less, more preferably 60 / 40 or more and 80 / 20 or less, and even more preferably 67 / 33 or more and 75 / 25 or less.

[0064] The total content of halogenated activators in the flux of this embodiment is preferably 0.01% to 5% by mass, more preferably 0.5% to 4% by mass, and even more preferably 1% to 2% by mass, based on the total mass (100% by mass) of the flux. If the total content of halogen-based activators is above the lower limit of the preferred range mentioned above, void formation during soldering is more easily suppressed, and if it is below the upper limit of the preferred range mentioned above, the effect of suppressing changes in the viscosity of the solder paste over time is more easily enhanced.

[0065] ≪Organic acid≫ Examples of organic acids include monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, cyanuric acid, dimer acid, and trimer acid. Examples of monocarboxylic acids include aliphatic monocarboxylic acids such as glycolic acid, thioglycolic acid, propionic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, 12-hydroxystearic acid, and glycine; and aromatic monocarboxylic acids such as benzoic acid, 3-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, salicylic acid, picolinic acid, p-anisic acid, m-anisic acid, o-anisic acid, parahydroxyphenylacetic acid, and 2-quinolinecarboxylic acid.

[0066] Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, 2,4-diethylglutaric acid, fumaric acid, maleic acid, diglycolic acid, dithioglycolic acid, tartaric acid, malic acid, and 1,3-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, phenylsuccinic acid, dipicolinic acid, and dibutylaniline diglycolic acid.

[0067] Examples of tricarboxylic acids include citric acid. Examples of cyanuric acid include tris(2-carboxyethyl) isocyanurate.

[0068] Examples of dimer acids and trimer acids include: dimer acid, a reaction product of oleic acid and linoleic acid; trimer acid, a reaction product of oleic acid and linoleic acid; dimer acid, a reaction product of acrylic acid; trimer acid, a reaction product of acrylic acid; dimer acid, a reaction product of methacrylic acid; trimer acid, a reaction product of methacrylic acid; dimer acid, a reaction product of acrylic acid and methacrylic acid; trimer acid, a reaction product of acrylic acid and methacrylic acid; dimer acid, a reaction product of oleic acid; trimer acid, a reaction product of linoleic acid; dimer acid, a reaction product of linoleic acid; trimer acid, a reaction product of linoleic acid; dimer acid, a reaction product of linoleic acid; trimer acid, a reaction product of acrylic acid and oleic acid; dimer acid, a reaction product of acrylic acid and linoleic acid; and acrylic acid and linoleic acid. Examples include trimer acid, a reaction product of acrylic acid and linolenic acid; dimer acid, a reaction product of acrylic acid and linolenic acid; dimer acid, a reaction product of methacrylic acid and oleic acid; dimer acid, a reaction product of methacrylic acid and oleic acid; dimer acid, a reaction product of methacrylic acid and linoleic acid; dimer acid, a reaction product of methacrylic acid and linoleic acid; dimer acid, a reaction product of methacrylic acid and linoleic acid; dimer acid, a reaction product of methacrylic acid and linoleic acid; dimer acid, a reaction product of oleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; hydrogenated dimer acid, a hydrogenated product obtained by adding hydrogen to each of the above-mentioned dimer acids; and hydrogenated trimer acid, a hydrogenated product obtained by adding hydrogen to each of the above-mentioned trimer acids. For example, dimer acid, a reaction product of oleic acid and linoleic acid, is a dimer with 36 carbon atoms. Trimer acid, another reaction product of oleic acid and linoleic acid, is a trimer with 54 carbon atoms.

[0069] Organic acids may be used individually or in mixtures of two or more types. The organic acid contained in the flux of this embodiment is preferably at least one selected from the group consisting of monocarboxylic acids, dicarboxylic acids, and dimer acids; more preferably at least one selected from the group consisting of dicarboxylic acids and dimer acids; even more preferably at least one selected from the group consisting of aliphatic dicarboxylic acids and dimer acids; and particularly preferably at least an aliphatic dicarboxylic acid is used from the viewpoint of suppressing the generation of solder balls. The aliphatic dicarboxylic acid is preferably at least one selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; more preferably at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid; even more preferably at least one selected from the group consisting of glutaric acid, adipic acid, and pimelic acid; and adipic acid is particularly preferred.

[0070] The total content of organic acids in the flux of this embodiment is preferably 1% to 25% by mass, more preferably 2% to 20% by mass, and even more preferably 3% to 20% by mass, based on the total mass (100% by mass) of the flux. The dicarboxylic acid content is preferably 1% to 10% by mass, more preferably 1% to 5% by mass, and even more preferably 2% to 5% by mass, based on the total mass (100% by mass) of the flux. The dimer acid (including hydrogenated dimer acid) content is preferably 2.5% to 20% by mass, more preferably 5% to 15% by mass, and even more preferably 7.5% to 12.5% ​​by mass, based on the total mass (100% by mass) of the flux.

[0071] ≪Amine≫ Examples of amines include azoles, guanidines, alkylamine compounds, and amino alcohol compounds.

[0072] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-ethyl -4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-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 Liazin, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazole, 2, Imidazole compounds such as 4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, 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 Examples of triazole compounds include [(xyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazole-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 3-(N-salicyroyl)amino-1,2,4-triazole, etc.; and 5-phenyltetrazole, etc.

[0073] 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.

[0074] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0075] Examples of amino alcohol compounds include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0076] Amines may be used individually or in mixtures of two or more. The flux of this embodiment preferably contains at least one amine selected from the group consisting of azoles and guanidines, and more preferably at least one amine selected from the group consisting of triazole compounds and guanidines. In the flux of this embodiment, it is even more preferable that the activator contains a triazole compound, from the viewpoint of suppressing the generation of solder balls. The total amine content in the flux of this embodiment is preferably 0.5% to 5% by mass, more preferably 1% to 4.5% by mass, and even more preferably 2% to 4% by mass, based on the total mass (100% by mass) of the flux. The content of the triazole compound is preferably more than 0% by mass and 0.99% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, based on the total mass (100% by mass) of the flux. The guanidine content is preferably 1% to 5% by mass, and more preferably 2% to 4% by mass, relative to the total mass (100% by mass) of the flux.

[0077] Furthermore, in the flux of this embodiment, from the viewpoint of suppressing the generation of solder balls, it is also preferable to use an aliphatic dicarboxylic acid and a triazole compound in combination as the activator. When using an aliphatic dicarboxylic acid and a triazole compound in combination, the mixing ratio (mass ratio) of the aliphatic dicarboxylic acid and the triazole compound is preferably aliphatic dicarboxylic acid / triazole compound = 90 / 10 or more and 95 / 5 or less.

[0078] <Other ingredients> In addition to rosin, solvent, thixotropic agent, thiol compound, and activator, the flux of this embodiment may contain other components as needed. Other components include resin components other than rosin, sulfur-containing compounds other than thiol compounds, surfactants, antioxidants, metal deactivators, and silane coupling agents.

[0079] Examples of resin components other than rosin 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, polyethylene resins, acrylic-polyethylene copolymer resins, epoxy resins, and the like. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenol resins include hydrogenated terpene phenol 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. Examples of acrylic-polyethylene copolymer resins include ethylene acrylic acid copolymers.

[0080] Examples of sulfur-containing compounds other than thiol compounds include tetraethyl thiuram disulfide, diisopropyl xanthogen disulfide, dihexyl sulfide, diphenyl disulfide, and 3-(2-benzothiazolylthio)propionic acid.

[0081] Examples of surfactants include nonionic surfactants and weak cationic surfactants. Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, and polyhydric alcohol polyoxyethylene adducts. Examples of weak cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, and polyhydric amine polyoxyethylene adducts. Other surfactants include, for example, polyoxyalkylene acetylene glycol, polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene ester, polyoxyalkylene alkylamine, and polyoxyalkylene alkylamide.

[0082] In the flux of this embodiment described above, since it contains a specific thiol compound (Tp), when used in solder paste, it can further suppress changes in the viscosity of the solder paste over time. Since this effect can be easily enhanced, it is preferable to use a thiol compound selected from the group consisting of aminobenzenethiol and benzenethiol among the specific thiol compounds (Tp), and among these, it is more preferable to use aminobenzenethiol. Among aminobenzenethiol, using at least one of 2-aminobenzenethiol and 4-aminobenzenethiol is more effective in suppressing changes in the viscosity of the solder paste over time than using 3-aminobenzenethiol. The reason for this is not clear, but it is presumed that changes in the viscosity of the solder paste over time occur when the metal of the solder alloy and the acid in the flux system form a complex. Aminobenzenethiol forms a protective layer by adsorption on the metal surface, suppressing the formation of a complex between the metal and the acid. In aminobenzenethiol, the electron-donating property of the -NH2 on the benzene ring increases the electron density of the mercapto group sulfur atom. Therefore, it is presumed that aminobenzenethiol is more likely to exhibit this effect because its adsorption to anionic defects on the solder alloy surface is more promoted. Furthermore, 2-aminobenzenethiol and 4-aminobenzenethiol are thought to be more effective in suppressing changes in the viscosity of solder paste over time because, compared to 3-aminobenzenethiol, they exhibit a higher rate of increase in the electron density of the mercapto sulfur atom due to the electron-donating properties of the -NH2 group on the benzene ring.

[0083] In this embodiment, the flux preferably contains an amine hydroiodide salt in addition to a specific thiol compound, which further suppresses changes in the viscosity of the solder paste containing the flux over time and reduces the generation of voids during soldering.

[0084] (Solder paste) The solder paste of this embodiment contains solder alloy powder and the flux described above. The solder alloy powder may consist of powder of elemental Sn solder; powder of solder alloys such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, or Sn-In; or powder of solder alloys to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added. Furthermore, the solder alloy powder may consist of a Sn-Pb system, or a solder alloy powder in which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added to the Sn-Pb system. The solder alloy powder is preferably a lead-free solder. As the solder alloy powder, for example, one with a melting point of 150 to 250°C can be used.

[0085] The flux content in the solder paste is preferably 5 to 30% by mass, and more preferably 5 to 15% by mass, relative to the total mass of the solder paste.

[0086] In the solder paste of this embodiment described above, a flux containing a specific thiol compound is used, so viscosity changes over time are less likely to occur. In addition, in the solder paste of this embodiment, if a flux containing amine hydroiodide is further included, viscosity changes over time are less likely to occur, and the generation of voids during soldering is also suppressed.

[0087] (Thickening inhibitor for soldering flux) The soldering flux viscosity inhibitor of this embodiment is a flux material suitable for suppressing viscosity increase in a solder paste containing solder alloy powder and soldering flux. Such a thickening inhibitor contains a thiol compound having a benzenethiol skeleton in which one or more hydrogen atoms on the benzene ring are replaced with a mercapto group (-SH). The thiol compound having a benzenethiol skeleton referred to here is the same as the compound (Tp) described above. In particular, since it is easier to further enhance the effect of suppressing the increase in viscosity of the solder paste over time, at least one of the thiol compounds having a benzenethiol skeleton selected from the group consisting of 2-aminobenzenethiol (x=y=1), 4-aminobenzenethiol (x=y=1), 3-aminobenzenethiol (x=y=1), and benzenethiol (x=1, y=0) is preferred.

[0088] Such a thickening inhibitor may also be used in combination with thiol compounds other than the thiol compound having the benzenethiol skeleton. Examples of thiol compounds other than the benzothiol skeleton mentioned above include 2-(dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate. The content of the thiol compound having a benzenethiol skeleton in the thickening inhibitor may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass.

[0089] The soldering flux viscosity inhibitor of this embodiment can be used in the same way as the thiol compounds that constitute the flux described above for soldering flux applications. Typically, the soldering flux viscosity inhibitor of this embodiment can be used as a compounding component of soldering flux in an embodiment in which a solder paste containing soldering flux and solder alloy powder is printed on a substrate, components are mounted on the printed area, and the solder is heated (reflowed). The soldering flux viscosity inhibitor of this embodiment makes it possible to provide a flux that is less prone to viscosity increase over time. [Examples]

[0090] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0091] <Preparation of flux> (Examples 1-91, Comparative Examples 1-10) The fluxes for the examples and comparative examples were prepared by mixing the ingredients as shown in Tables 1 to 13. The ingredients used are listed below.

[0092] Rosin: Acrylic acid-modified hydrogenated rosin and hydrogenated rosin were used as rosin.

[0093] solvent: Diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C) was used as the solvent (S1) with a boiling point of 250°C or higher. 1,4-butanediol (boiling point 228°C) was used as the solvent (S2) with a boiling point between 220°C and 250°C. As the solvent with a boiling point of 220°C or lower (S3), the following solvents with a boiling point of 190°C or higher and 220°C or lower (S31) and solvents with a boiling point of 160°C or higher and less than 190°C (S32) were used.

[0094] Solvents with a boiling point between 190°C and 220°C (S31): 1,3-Butanediol (boiling point 203°C), 1,2-Butanediol (boiling point 194°C), 2-Methyl-2,4-Pentanediol (Hexylene Glycol) (boiling point 198°C), Ethylene Glycol Monohexyl Ether (Hexyl Glycol) (boiling point 208°C), α-Terpineol (boiling point 218°C)

[0095] Solvents with a boiling point of 160°C or higher and less than 190°C (S32): 2,3-Butanediol (boiling point 183°C)

[0096] Thixotropic agents: Polyamide and hydrogenated castor oil were used as thixotropic agents.

[0097] Sulfur-containing compounds: As sulfur-containing compounds, the following were used: a thiol compound (Tp) having a benzenethiol skeleton, thiol compounds other than compound (Tp), and other sulfur-containing compounds.

[0098] Thiol compounds with a benzenethiol skeleton (Tp): Benzenthiol, 3-aminobenzenethiol, 2-aminobenzenethiol, 4-aminobenzenethiol

[0099] Thiol compounds other than compound (Tp): 2-(dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, tridecyl 3-mercaptopropionate Other sulfur-containing compounds: Tetraethylthiuram disulfide, diisopropyl xanthogen disulfide, dihexyl sulfide, diphenyl disulfide, 3-(2-benzothiazolylthio)propionic acid

[0100] Activating agent: As activators, the following amine hydroiodide salts, amine hydrobromide salts, amine hydrochloride salts, organic acids, and amines were used.

[0101] 2-pipecolin·HI, piperidine·HI, and 1,3-diphenylguanidine·HI were used as amine hydroiodides.

[0102] 2-Pipecoline·HI was prepared by adding 30 g of 2-pipecolin and hydrogen iodide in equimolar amounts to 70 g of isopropyl alcohol (IPA), mixing, allowing it to stand at room temperature (25°C) for 5 minutes to precipitate, and then drying the precipitate (yield approximately 100%). Piperidine-HI was produced by the same method as described above for the production of 2-pipecolin-HI, except that 2-pipecolin was replaced with piperidine (yield was approximately 100%). For the other amine hydroiodides, commercially available products were used.

[0103] 2-pipecolin·HBr, piperidine·HBr, and 1,3-diphenylguanidine·HBr were used as amine hydrobromide salts. 1,3-diphenylguanidine·HCl was used as the amine hydrochloride. For the aforementioned amine hydrobromide and amine hydrochloride, commercially available products were used.

[0104] Organic acids: Hydrogenated dimer acid, adipic acid, benzoic acid, and phenylsuccinic acid were used as organic acids.

[0105] Amine: 1,3-di-o-tolylguanidine and 3-(N-salicyloyl)amino-1,2,4-triazole were used as amines.

[0106] Other ingredients: Ethylene acrylic acid copolymer was used as the acrylic resin. 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] was used as an antioxidant.

[0107] <Preparation of Solder Paste> Solder paste was prepared by mixing the flux from each example with the solder alloy powder described below. In all of the prepared solder pastes, the flux content was 11.5% by mass and the solder alloy powder content was 88.5% by mass relative to the total amount of solder paste.

[0108] Solder alloy powder: The solder alloy powder used consisted of a solder alloy with 3% by mass of Ag, 0.5% by mass of Cu, and the remainder being Sn. The solidus temperature of this solder alloy was 217°C, and the liquidus temperature was 220°C. The size of the solder alloy powder was determined to meet the requirements of symbol 5 (particle size distribution) in the powder size classification (Table 2) of JIS Z 3284-1:2004.

[0109] <Rating> Using the solder paste prepared as described above, the following evaluations were conducted to assess the viscosity change of the solder paste over time and the effect of suppressing void formation, according to the test methods described below.

[0110] [Viscosity changes of solder paste over time] (1) Test method The viscosity of the solder paste immediately after mixing was measured using a viscometer (Malcolm Corporation, PCU-205) at a rotation speed of 10 rpm, a temperature of 25°C, and in air for 24 hours. The viscosity change rate after 24 hours was calculated from the viscosity at the start of measurement and the viscosity after 24 hours, and the viscosity change of the solder paste over time was evaluated according to the evaluation criteria below. The evaluation results are shown in Tables 1 to 13.

[0111] (2) Evaluation Criteria 1 point: The viscosity change rate after 24 hours was less than 10%. Point 2: The viscosity change rate after 24 hours was between 10% and 20%. 3 points: The viscosity change rate after 24 hours was between 20% and 30%. 4 points: The viscosity change rate after 24 hours was between 30% and 40%. 5 points: The viscosity change rate after 24 hours was between 40% and 50%. 6 points: The viscosity change rate after 24 hours was 50% or more.

[0112] [Effect of suppressing void generation] (1) Test method Using a metal mask (mask thickness 0.12 mm), solder paste for each example was printed onto a Cu-OSP treated substrate (substrate size 105 mm x 105 mm). Next, a QFN (with a side length of 8mm, a side length of 5.80mm for the bottom electrode, and a pad size of 5.80mm x 5.80mm) was mounted onto the substrate on which the solder paste had been printed. Next, reflow soldering was performed.

[0113] The reflow profile at that time is shown in Figure 1. The reflow profile involved preheating at 150°C to 175°C for 85 seconds, followed by holding at over 220°C for 40 seconds, with a peak temperature of 242°C.

[0114] The void area of ​​the bond between the substrate and the QFN was measured by irradiating it with X-rays from the vertical direction of the substrate and analyzing the transmitted X-rays. The XD7600NT Diamond X-ray inspection system (Nordson DAGE) was used to measure the void area. Void area was measured by assuming the presence of a void if X-rays passed through at least one void. Voids with a diameter of 0.1 μm or larger were targeted for detection. Next, the ratio of the total void area to the total area of ​​the lower electrode (which is considered to be 100% area ratio) was calculated and expressed as the void area ratio (%). The average value of the void area ratio for five soldered bodies was determined, and the effect of suppressing void generation during soldering was evaluated according to the evaluation criteria below. The evaluation results are shown in Tables 5 to 13.

[0115] (2) Evaluation Criteria Point 1: The void area ratio was less than 10%. Two points: The void area ratio was between 10% and 15%. 3. The void area ratio was between 15% and 20%. 4 points: The void area ratio was between 20% and 30%. 5 points: The void area ratio was 30% or more.

[0116] [Table 1]

[0117] [Table 2]

[0118] [Table 3]

[0119] [Table 4]

[0120] The results shown in Tables 1-4 confirm that the fluxes in the examples containing a specific thiol compound (Tp) showed a lower viscosity change rate after 24 hours compared to the fluxes in the comparative examples containing a sulfur-containing compound that does not correspond to compound (Tp), indicating that the viscosity change of the solder paste over time was more suppressed (comparison between Examples 3, 8, 12, and 16 and Comparative Examples 1-10).

[0121] For specific thiol compounds (Tp), when used in solder paste, the effect of suppressing changes in the viscosity of the solder paste over time was confirmed to be highest in the following order (Examples 3, 8, 12, 16, 22). Benzenthiol <3-aminobenzenethiol <2-aminobenzenethiol, 4-aminobenzenethiol <Combination use of 2-aminobenzenethiol and 4-aminobenzenethiol>

[0122] It has been observed that the combined use of 2-aminobenzenethiol and 4-aminobenzenethiol produces a higher effect with a smaller amount of formulation (Examples 4, 9, 21).

[0123] [Table 5]

[0124] The results shown in Table 5 confirm that by further including amine hydroiodide, the viscosity changes over time in the solder paste are less likely to occur, and the generation of voids during soldering is also suppressed.

[0125] [Table 6]

[0126] [Table 7]

[0127] [Table 8]

[0128] [Table 9]

[0129] The results shown in Tables 6-9 confirm that when using the fluxes in Examples 29-66, which contain a specific thiol compound (Tp) and an amine hydroiodide, the viscosity of the solder paste does not change easily over time, and the generation of voids during soldering is also suppressed.

[0130] [Table 10]

[0131] [Table 11]

[0132] [Table 12]

[0133] [Table 13]

[0134] From the results shown in Tables 10-13, a comparison between Examples 68, 81-84 and Example 86 reveals that, among solvents (S3) with a boiling point of 220°C or lower, the combination of solvent (S1) and solvent (S31) results in a lower viscosity change rate after 24 hours compared to the combination of solvent (S1) and solvent (S32), indicating that the viscosity change of the solder paste over time is more easily suppressed.

[0135] A comparison of Examples 68, 81-84, 86 and Example 85 shows that when solvent (S1) and solvent (S3) are combined, the generation of voids during soldering is more easily suppressed when the solder paste is formed, compared to when solvent (S1) and solvent (S2) are combined.

[0136] A comparison of Examples 68, 76-78 and Example 79 shows that the viscosity change of the solder paste over time can be suppressed by controlling the ratio of solvent (S1) to solvent (S31).

[0137] Regarding amine hydrohalides, when used as a solder paste, the following order of effectiveness in suppressing void formation during soldering was confirmed (Examples 68, 72, 87; Examples 88-91). Amine hydrochloride, amine hydrobromide < Guanidine hydroiodide < Heterolipidic amine hydroiodide

[0138] Regarding amine hydroiodides, when used as a solder paste, the most effective method for suppressing void formation during soldering is found to be when 2-pipecolin·HI or piperidine·HI (heteroalicyclic amine hydroiodides) are used (Examples 68, 72, 87).

Claims

[Claim 1] A soldering flux viscosity inhibitor that suppresses the increase in viscosity of a solder paste containing solder alloy powder and soldering flux, It comprises at least one thiol compound (Tp) selected from the group consisting of 2-aminobenzenethiol, 4-aminobenzenethiol, 3-aminobenzenethiol, and benzenethiol, A thickening inhibitor for soldering flux, wherein the content of the thiol compound (Tp) in the thickening inhibitor is 50% by mass or more and 100% by mass or less.

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