Soldering flux and soldering paste

Abstract

This flux contains rosin, a solvent, a thixotropic agent, a thiol compound, and an active agent, and is characterized in that the thiol compound contains a compound (Tp) having a thiophenol skeleton in which one or more hydrogen atoms on a benzene ring are substituted with a mercapto group (-SH). The compound (Tp) is preferably at least one thiol compound selected from the group consisting of 2-aminothiophenol, 4-aminothiophenol, 3-aminothiophenol, and thiophenol. According to this flux, the viscosity change of the solder paste over time can be further suppressed.

Description

Technical Field

[0001] The invention relates to soldering flux and solder paste.

[0002] This application claims priority based on Japanese Patent Application No. 2022-117440 filed in Japan on July 22, 2022, and the contents are incorporated herein by reference. Background Art

[0003] Usually, fixing components to a substrate and electrically connecting components to the substrate are performed by soldering. In soldering, flux, solder powder, and solder paste mixed with flux and solder powder are used.

[0004] The flux has the ability to chemically remove metal oxides present on the metal surface of the object to be welded and in the solder, and to allow metal elements to move at the boundary between the two. Therefore, by using the flux for welding, an intermetallic compound is formed between the two, thereby obtaining a strong joint.

[0005] In soldering using solder paste, first, solder paste is printed on a substrate, components are mounted, and the substrate with components mounted is heated in a heating furnace called a reflow furnace, thereby melting solder powder contained in the solder paste and soldering the components to the substrate.

[0006] The ingredients of the flux are appropriately selected according to the type of solder or the type of metal on the surface of the object to be joined. For example, Patent Document 1 proposes a solder paste that uses a flux containing a base resin, a solvent, a thixotropic agent, an activator, an antioxidant, and a rust inhibitor for a specific solder alloy powder.

[0007] Prior art documents

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-361484 Summary of the invention

[0010] Problems to be solved by the present invention

[0011] However, the storage time of solder paste, which is a mixture of flux and solder powder, may be prolonged depending on the usage method. In addition, depending on the storage conditions of the solder paste, the viscosity of the solder paste increases over time, and the initial printing performance cannot be achieved. In recent years, with the development of miniaturization and complexity of electronic components, this problem has become more obvious.

[0012] Therefore, an object of the present invention is to provide a soldering flux capable of further suppressing a change in viscosity of a solder paste over time, and a solder paste using the flux.

[0013] Means of solving the problem

[0014] In order to solve the above-mentioned problems, the present invention adopts the following configuration.

[0015] [1] A soldering flux comprising rosin, a solvent, a thixotropic agent, a thiol compound and an activator, wherein the thiol compound comprises a compound (Tp) having a thiophenol skeleton in which one or more hydrogen atoms on a benzene ring are substituted with a mercapto group (—SH).

[0016] [2] The soldering flux according to [1], wherein the compound (Tp) is at least one thiol compound selected from 2-aminothiophenol, 4-aminothiophenol, 3-aminothiophenol and thiophenol.

[0017] [3] The soldering flux according to [2], wherein the compound (Tp) is at least one thiol compound selected from 2-aminothiophenol, 4-aminothiophenol, and 3-aminothiophenol.

[0018] [4] The soldering flux according to [3], wherein the compound (Tp) is at least one thiol compound selected from 2-aminothiophenol and 4-aminothiophenol.

[0019] [5] The soldering flux according to [4], wherein the compound (Tp) is a compound using 2-aminothiophenol and 4-aminothiophenol in combination.

[0020] [6] The soldering flux according to any one of [1] to [5], wherein the content of the compound (Tp) is 0.005 to 0.7% by mass relative to the total mass of the soldering flux.

[0021] [7] The soldering flux according to any one of [1] to [6], wherein the activator contains amine hydroiodide.

[0022] [8] The soldering flux according to any one of [1] to [7], wherein the solvent contains both a solvent (S1) having a boiling point of 250°C or higher and a solvent (S3) having a boiling point of 220°C or lower.

[0023] [9] The soldering flux according to [8], wherein the solvent (S3) is a solvent (S31) having a boiling point of 190°C or higher and 220°C or lower.

[0024]

[10] The soldering flux according to [9], wherein the ratio of the solvent (S1) to the solvent (S31) is 55 / 45 or more and 95 / 5 or less in terms of a mass ratio represented by solvent (S1) / solvent (S31).

[0025]

[11] A solder paste comprising a solder alloy powder and the flux according to any one of [1] to

[10] .

[0026] Effects of the Invention

[0027] According to the present invention, it is possible to provide a soldering flux capable of further suppressing a change in viscosity of a solder paste over time, and a solder paste using the flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a diagram showing a reflow curve in the evaluation of the “effect of suppressing the generation of voids” in this example. DETAILED DESCRIPTION

[0029] (Flux)

[0030] The soldering flux of the present embodiment contains rosin, a solvent, a thixotropic agent, a thiol compound, and an activator. The thiol compound contains a compound (Tp) having a thiophenol skeleton in which one or more hydrogen atoms on a benzene ring are substituted with a mercapto group (—SH).

[0031] <Rosin>

[0032] Examples of the rosin include raw material rosins such as gum rosin, wood rosin, and tall oil rosin, and rosin derivatives obtained from the raw material rosins.

[0033] The rosin derivatives include, for example, 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 (acrylated rosin, maleated rosin, fumarated rosin, etc.), as well as purified products, hydrogenated products and disproportionated products of the polymerized rosin, and purified products, hydrogenated products and disproportionated products of the α,β-unsaturated carboxylic acid-modified products.

[0034] The rosin may be used alone or in combination of two or more.

[0035] As the rosin, among the above, at least one selected from polymerized rosin, acid-modified hydrogenated rosin and hydrogenated rosin is preferably used.

[0036] As the acid-modified hydrogenated rosin, acrylic acid-modified hydrogenated rosin is preferably used.

[0037] Examples of hydrogenated rosin include those obtained by hydrogenating a natural resin containing a mixture of abietic acid and its isomers, such as rosin containing dihydroabietic acid and tetrahydroabietic acid as main components, etc. "Main component" refers to a component whose content in the compound is 40% by mass or more among the components constituting the compound.

[0038] The content of rosin in the flux of this embodiment is preferably 10% to 60% by mass, more preferably 20% to 50% by mass, and even more preferably 25% to 40% by mass, relative to the total mass of the flux (100% by mass).

[0039] <Solvent>

[0040] Examples of the solvent include water, alcohol solvents, glycol ether solvents, and terpineols.

[0041] Examples of the alcohol solvent include isopropyl alcohol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-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-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 (hexanediol), octanediol, etc.

[0042] Examples of the glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether (butyl glycol), ethylene glycol monohexyl ether (ethylene glycol hexyl ether), diethylene glycol monohexyl ether (hexyldiglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, tripropylene glycol methyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether, and tripropylene glycol n-butyl ether.

[0043] Examples of the terpineols include α-terpineol, β-terpineol, γ-terpineol, and a terpineol mixture (ie, a mixture whose main component is α-terpineol and contains β-terpineol or γ-terpineol).

[0044] Examples of other solvents include dioctyl sebacate (DOS) and liquid paraffin.

[0045] The solvent may be used alone or in combination of two or more.

[0046] The soldering flux of the present embodiment is useful for suppressing a change in viscosity over time of a solder paste containing a flux having a composition in which solvents having different boiling points are combined.

[0047] In the present specification, the "boiling point of a solvent" refers to the temperature of the solvent when the saturated vapor pressure of the target solvent is equal to 1 atmosphere.

[0048] A preferred embodiment of the solvents having different boiling points includes an embodiment having both a solvent (S1) having a boiling point of 250° C. or higher and a solvent (S3) having a boiling point of 220° C. or lower.

[0049] Hereinafter, a solvent having a boiling point of 250°C or higher is referred to as a component (S1), and a solvent having a boiling point of 220°C or lower is referred to as a component (S3). In addition, a solvent having a boiling point of more than 220°C and less than 250°C is referred to as a component (S2).

[0050] 《Solvents with a boiling point of 250°C or higher (S1)》

[0051] As the (S1) component, for example, diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C), diethylene glycol monohexyl ether (hexyl diglycol) (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), tetraethylene glycol dimethyl ether (boiling point 275°C), etc. can be mentioned.

[0052] 《Solvents with a boiling point exceeding 220°C and less than 250°C (S2)》

[0053] Examples of the component (S2) include 1,4-butanediol (boiling point 228° C.), benzene glycol (boiling point 237° C.), butyl carbitol (boiling point 231° C.), and tripropylene glycol monomethyl ether (boiling point 243° C.).

[0054] 《Solvents with a boiling point below 220°C (S3)》

[0055] Examples of the component (S3) include 1,3-butanediol (boiling point 203° C.), 1,2-butanediol (boiling point 194° C.), 2-methyl-2,4-pentanediol (hexanediol) (boiling point 198° C.), ethylene glycol monohexyl ether (ethylene glycol hexyl ether) (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 (boiling point 218° C.). (the above, solvents having a boiling point of 190°C or higher and 220°C or lower (this solvent is 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), 1-ethynyl-1-cyclohexanol (boiling point 180°C) (the above, solvents having a boiling point of 160°C or higher and less than 190°C (this solvent is also referred to as "solvent (S32)" or "(S32) component")), etc.

[0056] As an aspect of solvents having different boiling points, it is preferable to contain both the component (S1) and the component (S31) from the viewpoint of easily suppressing the change in viscosity of the solder paste over time.

[0057] When both the (S1) component and the (S31) component are present, the ratio (mass ratio) of the (S1) component to the (S31) component is preferably solvent (S1) / solvent (S31) = 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 easily suppressing the ratio of the viscosity change over time when the solder paste is prepared. Furthermore, from the viewpoint of easily suppressing the generation of voids during soldering, the ratio of the (S1) component to the (S31) component is preferably 60 / 40 or more and 85 / 15 or less.

[0058] The total content of solvent is the balance in the flux.

[0059] For example, the total content of the solvent in the flux of this embodiment is preferably 25 mass % to 60 mass % relative to the total mass of the flux (100 mass %), more preferably 30 mass % to 50 mass %, and further preferably 35 mass % to 45 mass %.

[0060] <Thixotropic agent>

[0061] Examples of the thixotropic agent include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0062] Examples of the ester-based thixotropic agent include ester compounds, and specific examples include hydrogenated castor oil and ethyl myristate.

[0063] Examples of the amide-based thixotropic agent include monoamide, bisamide, and polyamide.

[0064] Examples of the monoamide 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-toluene methane amide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amides, hydroxymethyl stearic acid amide, hydroxymethyl amide, and fatty acid ester amides.

[0065] Examples of the bisamides include ethylenebis fatty acid (the carbon number of fatty acid is C6-24) amide, ethylenebishydroxy fatty acid (the carbon number of fatty acid is C6-24) amide, hexamethylenebis fatty acid (the carbon number of fatty acid is C6-24) amide, hexamethylenebishydroxy fatty acid (the carbon number of fatty acid is C6-24) amide, aromatic bisamides, etc. Examples of fatty acids as raw materials of the bisamides include stearic acid (the carbon number is C18), oleic acid (the carbon number is C18), lauric acid (the carbon number is C12), etc.

[0066] Examples of the polyamide include polyamides such as saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0067] Examples of the cyclic amide oligomer include amide oligomers obtained by polycondensation of dicarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, diamine and triamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid, diamine and triamine into a ring, and amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid, diamine and triamine into a ring.

[0068] The non-cyclic amide oligomer can include amide oligomers obtained by polycondensation of monocarboxylic acid with diamine and / or triamine into non-cyclic, amide oligomers obtained by polycondensation of dicarboxylic acid and / or tricarboxylic acid with monoamine into non-cyclic, etc. In the case of amide oligomers containing monocarboxylic acid or monoamine, monocarboxylic acid and monoamine function as terminal molecules to become non-cyclic amide oligomers with reduced molecular weight. In addition, in the case of amide compounds obtained by polycondensation of dicarboxylic acid and / or tricarboxylic acid with diamine and / or triamine into non-cyclic, non-cyclic amide oligomers become non-cyclic macromolecular amide polymers. In addition, non-cyclic amide oligomers also include amide oligomers obtained by condensation of monocarboxylic acid and monoamine into non-cyclic.

[0069] Examples of the sorbitol-based thixotropic agent include dibenzylidene-D-sorbitol, di(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0070] The thixotropic agent may be used alone or in combination of two or more.

[0071] The thixotropic agent contained in the flux of the present embodiment is preferably at least one selected from an ester thixotropic agent and an amide thixotropic agent, more preferably at least an amide thixotropic agent, and still more preferably a combination of an ester thixotropic agent and an amide thixotropic agent.

[0072] As the ester-based thixotropic agent, hydrogenated castor oil is preferred.

[0073] As the amide-based thixotropic agent, polyamide is preferred.

[0074] The content of the thixotropic agent in the flux of the present embodiment is preferably 2 mass % to 20 mass % inclusive, more preferably 5 mass % to 15 mass % inclusive, and further preferably 5 mass % to 10 mass % inclusive, relative to the total mass of the flux (100 mass %).

[0075] <Thiol compounds>

[0076] In the soldering flux of the present embodiment, the thiol compound used includes a compound (Tp) having a thiophenol skeleton.

[0077] The "thiophenol skeleton" refers to a structure in which one or more hydrogen atoms on a benzene ring are substituted with a mercapto group (—SH).

[0078] 《Compound (Tp)》

[0079] As the compound (Tp), for example, a thiol compound represented by the following general formula (Tp-0) is preferably used.

[0080] [Chemical formula 1]

[0081]

[0082] [In the formula, R is a substituent. x is an integer greater than 1 and represents the number of mercapto groups (-SH). y is an integer greater than 0 and represents the number of substituents (R). 1≤x+y≤6.]

[0083] In the above formula (Tp-0), examples of the substituent in R include an amino group (-NH2), a halogen atom, an alkyl group, an alkoxy group, a halogenated alkyl group, and a hydroxyl group.

[0084] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0085] The alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 6 carbon atoms.

[0086] The alkoxy group is preferably an alkoxy group having 1 to 6 carbon atoms.

[0087] Examples of the halogenated alkyl group include groups in which a part or all of the hydrogen atoms of an alkyl group are substituted with halogen atoms. The alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 6 carbon atoms. Examples of the halogenated alkyl group include fluorine, chlorine, bromine, and iodine atoms.

[0088] Among them, from the viewpoint of easily improving the effect of suppressing the change in viscosity of the solder paste over time, the substituent in R is preferably an amino group or a hydroxyl group, and particularly preferably an amino group.

[0089] In the formula (Tp-0), x is an integer of 1 or more, preferably an integer of 1 to 3, more preferably 1 or 2, and particularly preferably 1.

[0090] y is an integer of 0 or more, preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and particularly preferably 1.

[0091] Preferred examples of the compound (Tp) include aminothiophenol represented by the following chemical formula (Tp-10).

[0092] [Chemical formula 2]

[0093]

[0094] In the chemical formula (Tp-10), the bonding position of the amino group to the mercapto group on the benzene ring may be any of the ortho position (2-), meta position (3-), or para position (4-).

[0095] The compound (Tp) may be used alone or in combination of two or more.

[0096] As the compound (Tp) contained in the flux of this embodiment, the thiol compound represented by the general formula (Tp-0) is preferred. From the viewpoint of easily improving the effect of suppressing the viscosity change of the solder paste over time, aminothiophenol (x is greater than 1, y is greater than 1) and thiophenol (x is greater than 1, y=0) are more preferred.

[0097] Among these compounds, from the viewpoint of making it easier to improve the effect of suppressing the change in solder paste viscosity over time, a thiol compound selected from 2-aminothiophenol (x=y=1), 4-aminothiophenol (x=y=1), 3-aminothiophenol (x=y=1) and thiophenol (x=1, y=0) is preferred, a thiol compound selected from 2-aminothiophenol (x=y=1), 4-aminothiophenol (x=y=1) and 3-aminothiophenol (x=y=1) is more preferred, a thiol compound selected from 2-aminothiophenol (x=y=1) and 4-aminothiophenol (x=y=1) is further preferred, and a combined use of 2-aminothiophenol (x=y=1) and 4-aminothiophenol (x=y=1) is particularly preferred.

[0098] When 2-aminothiophenol (x=y=1) and 4-aminothiophenol (x=y=1) are used in combination, the mixing ratio (mass ratio) thereof is preferably 2-aminothiophenol / 4-aminothiophenol=1 / 9 to 9 / 1, more preferably 3 / 7 to 7 / 3, and further preferably 4 / 6 to 6 / 4.

[0099] The total content of the compound (Tp) in the flux of the present embodiment is preferably 0.005 mass % to 0.7 mass %, more preferably 0.01 mass % to 0.5 mass %, and further preferably 0.02 mass % to 0.3 mass %, relative to the total mass (100 mass %) of the flux.

[0100] When the total content of the compound (Tp) is at least the lower limit of the preferred range, the effect of suppressing the viscosity change of the solder paste over time is easily improved, and when it is at most the upper limit of the preferred range, the generation of voids during soldering is easily suppressed.

[0101] Among the thiol compounds, thiol compounds other than the above-mentioned compound (Tp) may be used in combination.

[0102] Examples of thiol compounds other than compound (Tp) include 2-(dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecyl mercaptan, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate.

[0103] <Activator>

[0104] Examples of the activator include halogen-based activators, organic acids, and amines.

[0105] 《Halogen-based Activators》

[0106] Examples of the halogen-based activator include amine hydrohalide salts and organic halogen compounds other than amine hydrohalide salts.

[0107] Amine hydrohalides:

[0108] Amine hydrohalides are compounds formed by reacting amines with hydrogen halides. Examples of the amines herein include azoles, guanidines, alkylamine compounds, and amino alcohol compounds, and examples of the amines exemplified in the description of "amines" described later. Examples of the hydrogen halides include hydrides of iodine, bromine, chlorine, and fluorine.

[0109] Examples of the amine hydrohalide salt include amine hydroiodide, amine hydrobromide, amine hydrochloride, and amine hydrofluoride.

[0110] As amine hydroiodides, for example, there can be mentioned heteroalicyclic amine hydroiodides such as 2-methylpiperidine hydroiodide (2-methylpiperidine·HI) and piperidine·HI; chain amine hydroiodides such as monoethylamine·HI, triethylamine·HI, 1-pentylamine·HI, 2-ethylhexylamine·HI, 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.

[0111] Examples of the amine hydrobromide include 2-methylpiperidine hydrobromide (2-methylpiperidine·HBr), piperidine·HBr, diphenylguanidine·HBr, cyclohexylamine·HBr, hexadecylamine·HBr, stearylamine·HBr, ethylamine·HBr, 2-ethylhexylamine·HBr, pyridine·HBr, isopropylamine·HBr, diethylamine·HBr, dimethylamine·HBr, abietamine·HBr, hydrazine hydrate·HBr, trinonylamine·HBr, diethylaniline·HBr, 2-diethylaminoethanol·HBr, diallylamine·HBr, triethylamine·HBr, aniline·HBr, dimethylcyclohexylamine·HBr, abietamine·HBr, 2-phenylimidazole·HBr, 4-benzylpyridine·HBr, hydrazine monohydrobromide, hydrazine dihydrobromide, and ethylenediamine dihydrobromide.

[0112] Examples of the amine hydrochloride 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.

[0113] Examples of the amine hydrofluoride include 1,3-diphenylguanidine hydrofluoride (1,3-diphenylguanidine·HF), diethylamine·HF, 2-ethylhexylamine·HF, cyclohexylamine·HF, ethylamine·HF, and abietamine·HF.

[0114] Organic halogen compounds other than amine hydrohalides:

[0115] Examples of the organic halogen compound other than the amine hydrohalide salt include halogenated aliphatic compounds having a halogenated aliphatic hydrocarbon group.

[0116] The halogenated aliphatic hydrocarbon group refers to a group in which a part or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are substituted with halogen atoms.

[0117] Examples of the halogenated aliphatic compound include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0118] Examples of the halogenated aliphatic alcohol 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.

[0119] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (3).

[0120] R 5 -(R 6 ) m ···(3)

[0121] R 5 represents an m-valent heterocyclic group. 6 It represents a halogenated aliphatic hydrocarbon group.

[0122] As R 5The heterocyclic ring of the m-valent heterocyclic group in the formula (I) may be a ring structure in which a portion of the carbon atoms constituting the aliphatic hydrocarbon ring or the aromatic hydrocarbon ring are substituted with a heteroatom. Examples of the heteroatom in the heterocyclic ring include an oxygen atom, a sulfur atom, a nitrogen atom, and the like. The heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of the heterocyclic ring include an isocyanurate ring and the like.

[0123] R 6 The halogenated aliphatic hydrocarbon group in preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and still more preferably 3 to 5 carbon atoms. 6 A brominated aliphatic hydrocarbon group and a chlorinated aliphatic hydrocarbon group are preferred, a brominated aliphatic hydrocarbon group is more preferred, and a brominated saturated aliphatic hydrocarbon group is further preferred.

[0124] Specific examples of the halogenated heterocyclic compound include tris-(2,3-dibromopropyl)isocyanurate and the like.

[0125] In addition, as organic halogen compounds other than amine hydrohalides, for example, halogenated carboxyl compounds can be mentioned, including iodinated carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid, etc.; chlorinated carboxyl compounds such as 2-chlorobenzoic acid, 3-chloropropionic acid, etc.; brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, 2-bromobenzoic acid, etc.

[0126] Alternatively, as the halogen-based activator, for example, a salt formed by reacting an amine with tetrafluoroboric acid (HBF4) or a complex formed by reacting an amine with boron trifluoride (BF3) may be used. Examples of the complex include boron trifluoride piperidine and the like.

[0127] The halogen-based activators may be used alone or in combination of two or more.

[0128] As the halogen-based activator contained in the flux of the present embodiment, from the viewpoint of the effect of suppressing the generation of voids during welding, it is preferred to use amine hydrohalides, among which amine hydroiodides are more preferred, and it is further preferred to use at least one selected from heteroalicyclic amine hydroiodides and guanidine hydroiodides, it is particularly preferred to use heteroalicyclic amine hydroiodides, and it is most preferred to use at least one selected from 2-methylpiperidine·HI and piperidine·HI.

[0129] When the soldering flux of the present embodiment contains amine hydroiodide in addition to the above-mentioned compound (Tp), the mixing ratio (mass ratio) of the compound (Tp) and the amine hydroiodide exceeds compound (Tp) / amine hydroiodide = 50 / 50, and is preferably 90 / 10 or less, more preferably 60 / 40 or more and 80 / 20 or less, and further preferably 67 / 33 or more and 75 / 25 or less.

[0130] The total content of the halogen-based activators in the flux of this embodiment is preferably 0.01 mass % to 5 mass %, more preferably 0.5 mass % to 4 mass %, and even more preferably 1 mass % to 2 mass %, relative to the total mass of the flux (100 mass %).

[0131] When the total content of the halogen-based activators is at least the lower limit of the preferred range, the generation of voids during soldering can be easily suppressed, and when it is at most the upper limit of the preferred range, the effect of suppressing the viscosity change of the solder paste over time can be further improved.

[0132] Organic Acids

[0133] Examples of the organic acid include monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, cyanuric acid, dimer acid, and trimer acid.

[0134] Examples of the monocarboxylic acid include aliphatic monocarboxylic acids such as glycolic acid, thioglycolic acid, propionic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric 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, p-hydroxyphenylacetic acid, and 2-quinolinecarboxylic acid.

[0135] Examples of the dicarboxylic acid 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, dimercaptoacetic acid, tartaric acid, malic acid, and 1,3-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, phenylsuccinic acid, pyridinedicarboxylic acid, and dibutylanilinodiglycolic acid.

[0136] Examples of the tricarboxylic acid include citric acid and the like.

[0137] Examples of cyanuric acid include tris(2-carboxyethyl)isocyanurate and the like.

[0138] Examples of the dimer acid and trimer acid include a dimer acid as a reaction product of oleic acid and linoleic acid, a trimer acid as a reaction product of oleic acid and linoleic acid, a dimer acid as a reaction product of acrylic acid, a trimer acid as a reaction product of acrylic acid, a dimer acid as a reaction product of methacrylic acid, a trimer acid as a reaction product of methacrylic acid, a dimer acid as a reaction product of acrylic acid and methacrylic acid, a trimer acid as a reaction product of acrylic acid and methacrylic acid, a dimer acid as a reaction product of oleic acid, a trimer acid as a reaction product of oleic acid, a dimer acid as a reaction product of linoleic acid, a trimer acid as a reaction product of linolenic acid, a dimer acid as a reaction product of linolenic acid, a trimer acid as a reaction product of linolenic acid, a dimer acid as a reaction product of acrylic acid and oleic acid, a trimer acid as a reaction product of acrylic acid and linoleic acid, and a dimer acid as a reaction product of acrylic acid and linoleic acid. trimer acid which is a reaction product of acrylic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid and linolenic acid, trimer acid which is a reaction product of acrylic acid and linolenic acid, dimer acid which is a reaction product of methacrylic acid and oleic acid, trimer acid which is a reaction product of methacrylic acid and oleic acid, dimer acid which is a reaction product of methacrylic acid and linoleic acid, trimer acid which is a reaction product of methacrylic acid and linoleic acid, dimer acid which is a reaction product of methacrylic acid and linolenic acid, trimer acid which is a reaction product of methacrylic acid and linolenic acid, dimer acid which is a reaction product of oleic acid and linolenic acid, dimer acid which is a reaction product of linoleic acid and linolenic acid, trimer acid which is a reaction product of linoleic acid and linolenic acid, hydrogenated dimer acid which is a hydrogenated product obtained by hydrogenating the above dimer acids, hydrogenated trimer acid which is a hydrogenated product obtained by hydrogenating the above trimer acids, and the like.

[0139] For example, the dimer acid, which is a reaction product of oleic acid and linoleic acid, is a dimer having 36 carbon atoms. Also, the trimer acid, which is a reaction product of oleic acid and linoleic acid, is a trimer having 54 carbon atoms.

[0140] The organic acid may be used alone or in combination of two or more.

[0141] As the organic acid contained in the flux of the present embodiment, at least one selected from a monocarboxylic acid, a dicarboxylic acid and a dimer acid is preferably used, at least one selected from a dicarboxylic acid and a dimer acid is more preferably used, and at least one selected from an aliphatic dicarboxylic acid and a dimer acid is further preferably used. From the viewpoint of suppressing the generation of solder balls, it is particularly preferred to use at least an aliphatic dicarboxylic acid.

[0142] The aliphatic dicarboxylic acid is preferably at least one selected from 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 succinic acid, glutaric acid, adipic acid, pimelic acid and suberic acid, further preferably at least one selected from glutaric acid, adipic acid and pimelic acid, and particularly preferably adipic acid.

[0143] The total content of organic acids in the flux of this embodiment is preferably 1 mass % to 25 mass % inclusive, more preferably 2 mass % to 20 mass % inclusive, and further preferably 3 mass % to 20 mass % inclusive, relative to the total mass of the flux (100 mass %).

[0144] The content of the dicarboxylic acid is preferably 1 mass % to 10 mass % inclusive, more preferably 1 mass % to 5 mass % inclusive, and further preferably 2 mass % to 5 mass % inclusive, relative to the total mass (100 mass %) of the flux.

[0145] The content of the dimer acid (including hydrogenated dimer acid) is preferably 2.5 mass % to 20 mass % inclusive, more preferably 5 mass % to 15 mass % inclusive, and further preferably 7.5 mass % to 12.5 mass % inclusive, relative to the total mass (100 mass %) of the flux.

[0146] "amine"

[0147] Examples of the amine include azoles, guanidines, alkylamine compounds, and amino alcohol compounds.

[0148] Examples of the 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, 1-cyanoethyl-2-ethyl-4-methylimidazole, imidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecyl imidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecyl imidazole-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, ]-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-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazole chloride, 2-methylimidazoline, 2-phenyl imidazole compounds such as imidazoline, 2,4-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) triazole compounds such as 1-[(2-ethylhexylamino)methyl]benzotriazole, carboxybenzotriazole, 1-[N,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, 5-methylbenzotriazole, 3-(N-salicyloyl)amino-1,2,4-triazole, and 5-phenyltetrazolyl, etc.;

[0149] Examples of the guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylguanidine, 1,3-di-o-isopropylphenylguanidine, and 1,3-di-o-isopropylphenyl-2-propionylguanidine.

[0150] Examples of the alkylamine compound include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0151] Examples of the amino alcohol compound include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine and the like.

[0152] The amines may be used alone or in combination of two or more.

[0153] As the amine contained in the soldering flux of the present embodiment, at least one selected from azoles and guanidines is preferably used, and at least one selected from triazole compounds and guanidines is more preferably used.

[0154] In the soldering flux of the present embodiment, from the viewpoint of suppressing the generation of solder balls, it is more preferable that the activator contains a triazole compound.

[0155] The total content of amines in the flux of the present embodiment is preferably 0.5% by mass to 5% by mass, more preferably 1% by mass to 4.5% by mass, and even more preferably 2% by mass to 4% by mass, relative to the total mass of the flux (100% by mass).

[0156] 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.

[0157] The content of the guanidine is preferably 1 mass % to 5 mass % inclusive, and more preferably 2 mass % to 4 mass % inclusive, based on the total mass (100 mass %) of the flux.

[0158] In addition, in the soldering flux of the present embodiment, from the viewpoint of suppressing the generation of solder balls, it is also preferred to use aliphatic dicarboxylic acid and triazole compound as the activator. When aliphatic dicarboxylic acid and triazole compound are used together, the mixing ratio (mass ratio) of aliphatic dicarboxylic acid and triazole compound is preferably aliphatic dicarboxylic acid / triazole compound = 90 / 10 or more and 95 / 5 or less.

[0159] <Other ingredients>

[0160] The soldering flux of the present embodiment may contain other components as necessary in addition to the rosin, the solvent, the thixotropic agent, the thiol compound, and the activator.

[0161] Examples of other components include resin components other than rosin, sulfur-containing compounds other than thiol compounds, surfactants, antioxidants, metal deactivators, and silane coupling agents.

[0162] Examples of the resin component 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, and epoxy resins.

[0163] Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, etc. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins, etc. Examples of modified styrene resins include styrene acrylic resins, styrene maleic acid resins, etc. Examples of modified xylene resins include phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol type xylene resins, polyol modified xylene resins, polyoxyethylene added xylene resins, etc. Examples of acrylic acid-polyethylene copolymer resins include ethylene-acrylic acid copolymers, etc.

[0164] Examples of the sulfur-containing compound other than the thiol compound include tetraethylthiuram disulfide, diisopropyl xanthate disulfide, dihexyl sulfide, diphenyl disulfide, and 3-(2-benzothiazolylthio)propionic acid.

[0165] Examples of the surfactant include nonionic surfactants and weak cationic surfactants.

[0166] Examples of the nonionic surfactant include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, and polyhydric alcohol polyoxyethylene adducts.

[0167] Examples of the weak cationic surfactant include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, and polyamine polyoxyethylene adducts.

[0168] Examples of surfactants other than those described above include polyoxyalkylene acetylene glycols, polyoxyalkylene glycerol ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, and polyoxyalkylene alkylamides.

[0169] In the soldering flux of the present embodiment described above, since it contains a specific thiol compound (Tp), when used in solder paste, the viscosity change of the solder paste over time can be further suppressed. From the viewpoint of easily improving this effect, among the specific thiol compounds (Tp), it is preferred to use a thiol compound selected from aminothiophenol and thiophenol, wherein aminothiophenol is more preferably used. Among these aminothiophenols, it is easier to obtain the effect of suppressing the viscosity change of the solder paste over time by using at least one of 2-aminothiophenol and 4-aminothiophenol than by using 3-aminothiophenol. The reason is not clear, but it is speculated that the viscosity change of the solder paste over time is caused by the metal of the solder alloy forming a complex with the acid in the soldering flux system. Aminothiophenol forms a protective layer by adsorption on the metal surface, thereby suppressing the formation of a complex between the metal and the acid. In aminothiophenol, due to the electron-donating property of -NH2 located on the benzene ring, the electron density of the mercaptosulfur atom increases. Therefore, it is inferred that the adsorption of aminothiophenol at the anion defects on the solder alloy surface is further promoted, making it easier to obtain this effect. In addition, due to the electron-donating property of -NH2 on the benzene ring, the electron density of the mercaptosulfur atom increases at a higher rate in 2-aminothiophenol and 4-aminothiophenol than in 3-aminothiophenol, so it is believed that the effect of suppressing the viscosity change of the solder paste over time is more easily obtained.

[0170] The soldering flux of the present embodiment preferably contains an amine hydroiodide in addition to the specific thiol compound, so that the viscosity change over time of the solder paste containing the soldering flux can be more easily suppressed and the generation of voids during soldering can be suppressed.

[0171] (Solder Paste)

[0172] The solder paste of the present embodiment contains solder alloy powder and the above-mentioned flux.

[0173] The solder alloy powder can be composed of powder of solder of Sn alone; powder of solder alloy of Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi or Sn-In series; or powder of solder alloy to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P or the like is added.

[0174] In addition, the solder alloy powder can also be composed of powder of Sn-Pb system or powder of solder alloy with Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. added to the Sn-Pb system.

[0175] The solder alloy powder is preferably a solder that does not contain Pb.

[0176] As the solder alloy powder, for example, a solder alloy powder having a melting temperature of 150 to 250° C. can be used.

[0177] In the solder paste, the content of the flux is preferably 5 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the solder paste.

[0178] In the solder paste of the present embodiment described above, since the flux containing the specific thiol compound is used, the viscosity change over time is unlikely to occur.

[0179] Furthermore, in the solder paste of the present embodiment, when a flux further containing amine hydroiodide is used in combination, the viscosity change over time is unlikely to occur, and the generation of voids during soldering is also suppressed.

[0180] (Viscosity increase inhibitor for soldering flux)

[0181] The solder flux viscosity increase inhibitor of the present embodiment is a flux material suitable for suppressing an increase in the viscosity of a solder paste containing a solder alloy powder and the solder flux.

[0182] The viscosity increase inhibitor contains a thiol compound having a thiolphenol skeleton in which one or more hydrogen atoms on a benzene ring are substituted with a mercapto group (—SH).

[0183] The thiol compound having a thiophenol skeleton mentioned here is the same as the above-mentioned "Compound (Tp)". Among them, from the viewpoint of more easily improving the effect of suppressing the viscosity increase of the solder paste over time, the thiol compound having a thiophenol skeleton is preferably at least one selected from 2-aminothiophenol (x=y=1), 4-aminothiophenol (x=y=1), 3-aminothiophenol (x=y=1) and thiophenol (x=1, y=0).

[0184] In the viscosity increase inhibitor, a thiol compound other than the thiol compound having a thiolphenol skeleton may be used in combination.

[0185] Examples of thiol compounds other than the thiol compound having a thiol phenol skeleton include 2-(dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecyl mercaptan, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate.

[0186] The content of the thiol compound having a thiophenol skeleton in the viscosity increase inhibitor may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass.

[0187] The viscosity increase inhibitor of the soldering flux of this embodiment can be used for the purpose of the soldering flux in the same manner as the <thiol compound> constituting the above-mentioned (soldering flux). The viscosity increase inhibitor of this embodiment can be typically used as a compounding component of the soldering flux in an embodiment of preparing a joint body by a method having a step of printing a solder paste containing the soldering flux and solder alloy powder on a substrate, mounting a component on the printed portion, and heating (reflow soldering).

[0188] According to the soldering flux viscosity increase inhibitor of the present embodiment, it is possible to provide a soldering flux in which the viscosity of the solder paste is unlikely to increase over time.

[0189] Example

[0190] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0191] <Preparation of flux>

[0192] (Examples 1 to 91, Comparative Examples 1 to 10)

[0193] The fluxes of Examples and Comparative Examples were prepared by mixing and blending the components according to the compositions shown in Tables 1 to 13. The blending components used are shown below.

[0194] rosin:

[0195] As the rosin, acrylic acid-modified hydrogenated rosin or hydrogenated rosin was used.

[0196] Solvent:

[0197] As the solvent (S1) having a boiling point of 250°C or higher, diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C) was used.

[0198] As the solvent (S2) having a boiling point of more than 220° C. and less than 250° C., 1,4-butanediol (boiling point: 228° C.) was used.

[0199] As the solvent (S3) having a boiling point of 220°C or less, the following solvents (S31) having a boiling point of 190°C to 220°C and solvents (S32) having a boiling point of 160°C to less than 190°C are used.

[0200] Solvent (S31) having a boiling point of 190°C or higher and 220°C or lower:

[0201] 1,3-Butanediol (boiling point 203°C), 1,2-Butanediol (boiling point 194°C), 2-methyl-2,4-pentanediol (hexanediol) (boiling point 198°C), ethylene glycol monohexyl ether (ethylene glycol hexyl ether) (boiling point 208°C), α-terpineol (boiling point 218°C)

[0202] Solvents with a boiling point of 160°C or more and less than 190°C (S32):

[0203] 2,3-Butanediol (boiling point 183°C)

[0204] Thixotropic agent:

[0205] Polyamide and hydrogenated castor oil were used as thixotropic agents.

[0206] Sulfur compounds:

[0207] As the sulfur-containing compound, a thiol compound (Tp) having a thiolphenol skeleton, a thiol compound other than the compound (Tp), and other sulfur-containing compounds shown below were used.

[0208] Thiol compounds with a thiophenol skeleton (Tp):

[0209] Thiophenol, 3-aminothiophenol, 2-aminothiophenol, 4-aminothiophenol

[0210] Thiol compounds other than compound (Tp):

[0211] 2-(Dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecyl mercaptan, 2-ethylhexyl 3-mercaptopropionate, tridecyl 3-mercaptopropionate

[0212] Other sulfur compounds:

[0213] Tetraethylthiuram disulfide, diisopropyl xanthate disulfide, dihexyl sulfide, diphenyl disulfide, 3-(2-benzothiazolylthio)propionic acid

[0214] Active Agent:

[0215] As the activating agent, the following amine hydroiodide, amine hydrobromide, amine hydrochloride, organic acid, and amine were used.

[0216] As amine hydroiodide, 2-methylpiperidine·HI, piperidine·HI, and 1,3-diphenylguanidine·HI were used.

[0217] 2-Methylpiperidine·HI was prepared by adding and mixing equimolar amounts of 30 g of 2-methylpiperidine and hydrogen iodide in 70 g of isopropyl alcohol (IPA), allowing the mixture to stand at room temperature (25° C.) for 5 minutes to precipitate, and drying the precipitate (yield: about 100%).

[0218] Piperidine·HI was prepared in the same manner as the above-mentioned method for preparing 2-methylpiperidine·HI except that 2-methylpiperidine was replaced by piperidine (yield: about 100%).

[0219] Other amine hydroiodides are used ready-made.

[0220] As the amine hydrobromide, 2-methylpiperidine·HBr, piperidine·HBr, and 1,3-diphenylguanidine·HBr were used.

[0221] As the amine hydrochloride, 1,3-diphenylguanidine·HCl was used.

[0222] The amine hydrobromide and amine hydrochloride are used as finished products.

[0223] Organic Acids:

[0224] As the organic acid, hydrogenated dimer acid, adipic acid, benzoic acid, and phenylsuccinic acid were used.

[0225] amine:

[0226] As the amine, 1,3-di-o-tolylguanidine and 3-(N-salicyloyl)amino-1,2,4-triazole were used.

[0227] Other Ingredients:

[0228] As the acrylic resin, an ethylene-acrylic acid copolymer was used.

[0229] As an antioxidant, 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] was used.

[0230] <Preparation of Solder Paste>

[0231] The flux of each example and the following solder alloy powder were mixed to prepare solder pastes. In each of the prepared solder pastes, the content of the flux was 11.5% by mass and the content of the solder alloy powder was 88.5% by mass based on the total amount of the solder paste.

[0232] Solder Alloy Powder:

[0233] The solder alloy powder used was a solder alloy containing 3 mass % Ag, 0.5 mass % Cu, and the balance Sn. The solidus temperature of the solder alloy was 217°C, and the liquidus temperature was 220°C.

[0234] The size of the solder alloy powder satisfies symbol 5 (particle size distribution) of the classification of powder size in JIS Z3284-1:2004 (Table 2).

[0235] <Evaluation>

[0236] Using the solder paste prepared as described above, evaluations of [change in viscosity of the solder paste over time] and [effect of suppressing void generation] were performed according to the test methods described below.

[0237] [Changes in Viscosity of Solder Paste over Time]

[0238] (1) Test method

[0239] The viscosity of the solder paste immediately after preparation was measured using a viscometer (PCU-205 manufactured by Malcom Co., Ltd.) at a rotation speed of 10 rpm, a temperature of 25°C, and for 24 hours in the atmosphere. The viscosity change rate after 24 hours was calculated from the viscosity of the solder paste at the start of the measurement and the viscosity after 24 hours, and the viscosity change of the solder paste over time was evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1 to 13.

[0240] (2) Evaluation criteria

[0241] 1 point: The viscosity change rate after 24 hours was less than 10%.

[0242] 2 points: The viscosity change rate after 24 hours is 10% or more and less than 20%.

[0243] 3 points: The viscosity change rate after 24 hours is 20% or more and less than 30%.

[0244] 4 points: The viscosity change rate after 24 hours is 30% or more and less than 40%.

[0245] 5 points: The viscosity change rate after 24 hours is 40% or more and less than 50%.

[0246] 6 points: The viscosity change rate after 24 hours is 50% or more.

[0247] [Effect of suppressing void generation]

[0248] (1) Test method

[0249] The solder paste of each example was printed on a Cu-OSP-treated substrate (substrate size: 105 mm×105 mm) using a metal mask (mask thickness: 0.12 mm).

[0250] Next, a QFN (the length of one side is 8 mm, the length of one side of the lower surface electrode is 5.80 mm, and the pad size is 5.80 mm×5.80 mm) is mounted on the substrate on which the solder paste is printed.

[0251] Next, reflow is performed to perform soldering.

[0252] The reflow curve at this time is as follows Figure 1 shown.

[0253] The reflow profile was preheated at 150°C to 175°C for 85 seconds, above 220°C for 40 seconds, and a peak temperature of 242°C.

[0254] The bonded product of the substrate and the QFN was irradiated with X-rays from a vertical direction of the substrate and the transmitted X-rays were analyzed to measure the void area. The void area was measured using an XD7600NT Diamond X-ray inspection system (manufactured by Nordson DAGE).

[0255] The void area is measured when X-rays pass through at least one void, which is considered to be the presence of voids. Voids with a diameter of 0.1 μm or more are detected.

[0256] Next, the ratio of the total area of ​​the voids to the total area of ​​the lower electrode (the area ratio is set to 100%) was calculated as the void area ratio (%). The average value of the void area ratios in the five joints was calculated, and the effect of suppressing the generation of voids during welding was evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 5 to 13.

[0257] (2) Evaluation criteria

[0258] 1 point: The void area ratio is less than 10%.

[0259] 2 points: The void area ratio is 10% or more and less than 15%.

[0260] 3 points: The void area ratio is 15% or more and less than 20%.

[0261] 4 points: The void area ratio is 20% or more and less than 30%.

[0262] 5 points: The void area ratio is 30% or more.

[0263] [Table 1]

[0264]

[0265] [Table 2]

[0266]

[0267] [Table 3]

[0268]

[0269] [Table 4]

[0270]

[0271] From the results shown in Tables 1 to 4, it can be confirmed that the flux of the examples containing a specific thiol compound (Tp) has a lower viscosity change rate after 24 hours than the flux of the comparative examples containing a sulfur-containing compound that does not belong to the compound (Tp), and the viscosity change of the solder paste over time is further suppressed (comparison between Examples 3, 8, 12, 16 and Comparative Examples 1 to 10).

[0272] When a specific thiol compound (Tp) is used as a solder paste, the effect of suppressing the change in viscosity of the solder paste over time increases in the following order (Examples 3, 8, 12, 16, and 22).

[0273] Thiophenol

[0274] <3-Aminothiophenol

[0275] <2-aminothiophenol, 4-aminothiophenol

[0276] <Combination of 2-aminothiophenol and 4-aminothiophenol

[0277] It can be seen that by using 2-aminothiophenol and 4-aminothiophenol in combination, a higher effect can be exerted at a low compounding amount (Examples 4, 9 and 21).

[0278] [Table 5]

[0279]

[0280] From the results shown in Table 5, it was confirmed that by further containing amine hydroiodide, the viscosity change over time when the solder paste is prepared is less likely to occur, and the generation of voids during soldering can also be suppressed.

[0281] [Table 6]

[0282]

[0283] [Table 7]

[0284]

[0285] [Table 8]

[0286]

[0287] [Table 9]

[0288]

[0289] The results shown in Tables 6 to 9 confirm that when the fluxes of Examples 29 to 66 using a specific thiol compound (Tp) and amine hydroiodide in combination were used, the viscosity of the solder paste hardly changed over time and the generation of voids during soldering was also suppressed.

[0290] [Table 10]

[0291]

[0292] [Table 11]

[0293]

[0294] [Table 12]

[0295]

[0296] [Table 13]

[0297]

[0298] From the results shown in Tables 10 to 13, it can be seen that, by comparing Examples 68, 81 to 84 with Example 86, among the solvents (S3) having a boiling point below 220°C, the viscosity change rate after 24 hours in the case of the combination of solvent (S1) and solvent (S31) is lower than that in the case of the combination of solvent (S1) and solvent (S32), and it is easy to suppress the viscosity change of the solder paste over time.

[0299] By comparing Examples 68, 81 to 84, and 86 with Example 85, it can be seen that the combination of solvent (S1) and solvent (S3) makes it easier to suppress the generation of voids during welding when the solder paste is made, compared with the combination of solvent (S1) and solvent (S2).

[0300] Comparison between Examples 68 and 76 to 78 and Example 79 shows that the change in viscosity of the solder paste over time can be suppressed by controlling the ratio of the solvent (S1) to the solvent (S31).

[0301] When the amine hydrohalide salts were made into solder pastes, it was confirmed that the effect of suppressing the generation of voids during soldering increased in the following order (Examples 68, 72, 87; Examples 88 to 91).

[0302] Amine hydrochloride, amine hydrobromide <guanidine hydroiodide <heteroalicyclic amine hydroiodide

[0303] Regarding amine hydroiodides, when used in a solder paste, the effect of suppressing the generation of voids during soldering was most excellent when 2-methylpiperidine·HI and piperidine·HI (heteroalicyclic amine hydroiodides) were used (Examples 68, 72, and 87).

[0304] The preferred embodiments of the present invention are described above, but the present invention is not limited to these embodiments. Addition, omission, substitution and other changes of the structure can be made without departing from the scope of the present invention. The present invention is not limited by the above description, but only by the scope of the attached claims.

Claims

1. A soldering flux comprising rosin, a solvent, a thixotropic agent, a thiol compound and an activator, The thiol compound includes a compound (Tp) having a thiophenol skeleton in which one or more hydrogen atoms on a benzene ring are replaced by a mercapto group (—SH), The content of the compound (Tp) is 0.005 to 0.7 mass % relative to the total mass of the flux.

2. The soldering flux according to claim 1, wherein The compound (Tp) is at least one thiol compound selected from 2-aminothiophenol, 4-aminothiophenol, 3-aminothiophenol and thiophenol.

3. The soldering flux according to claim 1, wherein The activator contains an amine hydroiodide.

4. The soldering flux according to claim 1, wherein The solvent contains both a solvent (S1) having a boiling point of 250°C or higher and a solvent (S3) having a boiling point of 220°C or lower.

5. The soldering flux according to claim 4, wherein The solvent (S3) is a solvent (S31) having a boiling point of 190°C or higher and 220°C or lower.

6. The soldering flux according to claim 5, wherein The ratio of the solvent (S1) to the solvent (S31) is 55 / 45 or more and 95 / 5 or less in terms of a mass ratio represented by solvent (S1) / solvent (S31).

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

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