Flux and solder paste

Abstract

The flux of the present invention is a flux containing rosin, solvent, thixotropic agent, thiol compound, and activator. Its characteristic feature is that the thiol compound contains a compound (Tp) having a thiophenol skeleton in which one or more hydrogen atoms on a benzene ring are replaced by mercapto groups (-SH). Preferably, this compound (Tp) is at least one thiol compound selected from 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] This invention relates to fluxes and solder pastes.

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

[0003] Components are typically attached to a substrate and electrically connected to the substrate by soldering. Soldering uses flux, solder powder, and solder paste, which is a mixture of flux and solder powder.

[0004] Flux has the ability to chemically remove metal oxides present on the surfaces of the metals being welded and in the solder, and to allow metal elements to move at the boundary between them. Therefore, by using flux for welding, an intermetallic compound is formed between the two metals, resulting in a strong bond.

[0005] In soldering using solder paste, first, solder paste is printed onto a substrate, then components are mounted on it, and the substrate with the mounted components is heated using a furnace called a reflow oven. As a result, the solder powder contained in the solder paste melts, and the components are soldered onto the substrate.

[0006] The composition of the flux is appropriately selected based on the type of solder or the type of metal on the surface of the objects to be joined. For example, Patent Document 1 discloses a solder paste that uses a flux containing a base resin, solvent, thixotropic agent, activator, antioxidant, and rust inhibitor relative to a specific solder alloy powder.

[0007] Existing technical documents

[0008] Patent documents

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

[0010] The problem to be solved by the present invention

[0011] However, solder pastes mixed with flux and solder powder can sometimes have extended shelf lives depending on the application method. Furthermore, depending on storage conditions, the viscosity of the solder paste may increase over time, potentially preventing it from achieving its initial printability. In recent years, with the miniaturization and increasing complexity of electronic components, this issue has become increasingly prominent.

[0012] Therefore, the object of the present invention is to provide a flux that can further suppress the viscosity change of solder paste over time, and a solder paste using the flux.

[0013] Problem-solving methods

[0014] To address the aforementioned issues, the present invention employs the following configuration.

[0015] [1] A flux containing rosin, solvent, thixotropic agent, thiol compound and activator, wherein the thiol compound contains a compound (Tp) having a thiophenol skeleton having one or more hydrogen atoms on a benzene ring replaced by mercapto groups (-SH).

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

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

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

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

[0020] [6] The 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 flux.

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

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

[0023] [9] According to the flux described in [8], wherein the solvent (S3) is a solvent (S31) with a boiling point of 190°C or higher and 220°C or lower.

[0024]

[10] According to the flux of [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 the mass ratio of solvent (S1) / solvent (S31).

[0025]

[11] A solder paste comprising solder alloy powder and flux as described in any one of [1] to

[10] .

[0026] Effects of the present invention

[0027] According to the present invention, a flux capable of further suppressing the viscosity change of solder paste over time, and a solder paste using the flux, can be provided. Attached Figure Description

[0028] Figure 1 This is a graph showing the backflow curve in the evaluation of the "effect of suppressing void generation" in this embodiment. Detailed Implementation

[0029] (Fluoride)

[0030] The flux of this embodiment contains rosin, solvent, thixotropic agent, thiol compound, and activator. The thiol compound contains a compound (Tp) having a thiophenol skeleton in which one or more hydrogen atoms on a benzene ring are replaced by mercapto groups (-SH).

[0031] <Rosin>

[0032] Examples of rosin include, for instance, resin rosin, wood rosin, and oil rosin, as well as rosin derivatives derived from such resin rosin.

[0033] The rosin derivatives may 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, fumarate-modified rosin, etc.), as well as purified products, hydrides, and disproportions of the polymerized rosin, and purified products, hydrides, and disproportions of the α,β-unsaturated carboxylic acid modified products, etc.

[0034] Rosin can be used alone or in combination with two or more types.

[0035] As rosin, it is preferred to use at least one selected from polymerized rosin, acid-modified hydrogenated rosin, and hydrogenated rosin.

[0036] As an acid-modified hydrogenated rosin, acrylic acid-modified hydrogenated rosin is preferred.

[0037] Examples of hydrogenated rosin include substances obtained by hydrogenating natural resins containing a mixture of abietic acid and its isomers, such as rosin with dihydroabietic acid and tetrahydroabietic acid as the main components. "Main component" refers to a component that constitutes the compound and is present in a concentration of 40% or more by mass.

[0038] Relative to the total mass of the flux (100% by mass), the rosin content in the flux of this embodiment 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 even more preferably 25% by mass or more and 40% by mass or less.

[0039] <Solvent>

[0040] Examples of solvents include water, alcohols, glycol ethers, and terpineols.

[0041] Examples of alcohol-based solvents include isopropanol, 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-hexyn-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, and 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-cyclohexanediol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 2-hexyl-1-decanol, 2-methyl-2,4-pentanediol (hexanediol), octanediol, etc.

[0042] Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether (butyl ethylene glycol), ethylene glycol monohexyl ether (ethylene glycol hexyl ether), diethylene glycol monohexyl ether (hexyl diethylene glycol), 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 terpineols include α-terpineol, β-terpineol, γ-terpineol, and mixtures of terpineols (i.e., mixtures whose main component is α-terpineol and which contain β-terpineol or γ-terpineol).

[0044] Other solvents include, for example, dioctyl sebacate (DOS) and liquid paraffin.

[0045] Solvents can be used alone or in combination of two or more.

[0046] The flux of this embodiment is useful for suppressing the viscosity change of solder paste over time, wherein the solder paste contains a flux composed of solvents with different boiling points.

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

[0048] As a preferred method for solvents with different boiling points, one can be an example of having both a solvent with a boiling point of 250°C or higher (S1) and a solvent with a boiling point of 220°C or lower (S3).

[0049] Solvents with a boiling point above 250°C are referred to as component (S1), and solvents with a boiling point below 220°C are referred to as component (S3). In addition, solvents with a boiling point above 220°C and below 250°C are referred to as component (S2).

[0050] Solvents with a boiling point above 250℃ (S1)

[0051] Examples of components (S1) include, for example, diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C), diethylene glycol monohexyl ether (hexyl diethylene glycol) (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).

[0052] Solvents with a boiling point exceeding 220°C but below 250°C (S2)

[0053] Examples of (S2) components include, for example, 1,4-butanediol (boiling point 228°C), phenylene glycol (boiling point 237°C), butylcarbidol (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 components (S3) include, for instance, 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-hexyn-2,5-diol (boiling point 206°C), and α-terpineol (boiling point 218°C). (The above refers to solvents with a boiling point of 190°C or higher and 220°C or lower (these solvents are also called "solvent (S31)" or "(S31) component")); ethylene glycol monobutyl ether (butyl ethylene 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 refers to solvents with a boiling point of 160°C or higher and lower than 190°C (these solvents are also called "solvent (S32)" or "(S32) component")), etc.

[0056] From the viewpoint of easily suppressing the viscosity change of solder paste over time, it is preferable to use solvents with different boiling points, which are both components (S1) and (S31).

[0057] When both component (S1) and component (S31) are present, from the viewpoint of easily suppressing the viscosity change over time during solder paste preparation, the ratio (mass ratio) of component (S1) to component (S31) is preferably solvent (S1) / solvent (S31) = 55 / 45 or more and 95 / 5 or less, more preferably 60 / 40 or more and 90 / 10 or less. Furthermore, from the viewpoint of easily suppressing the generation of voids during soldering, solvent (S1) / solvent (S31) = 60 / 40 or more and 85 / 15 or less is preferred.

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

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

[0060] <Thixotropic agent>

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

[0062] Examples of ester-based thixotropic agents include, for example, ester compounds, specifically hydrogenated castor oil and ethyl myristate.

[0063] Examples of amide-based thixotropic agents include monoamides, diamides, and polyamides.

[0064] Examples of monoamides include laurylamide, palmitamide, stearamide, behenamide, hydroxystearamide, saturated fatty acid amide, oleamide, erucamide, unsaturated fatty acid amide, 4-methylbenzamide (p-toluamide), p-toluenemethaneamide, aromatic amide, hexamethylene hydroxystearamide, substituted amide, hydroxymethylstearamide, hydroxymethylamide, fatty acid ester amide, etc.

[0065] Examples of diamides include ethylenedicarboxylic acid (C6-24 carbon atoms in fatty acids) amides, ethylenedihydroxycarboxylic acid (C6-24 carbon atoms in fatty acids) amides, hexamethylenedicarboxylic acid (C6-24 carbon atoms in fatty acids) amides, hexamethylenedihydroxycarboxylic acid (C6-24 carbon atoms in fatty acids) amides, and aromatic diamides. Examples of fatty acids used as raw materials for these diamides include stearic acid (C18 carbon atoms), oleic acid (C18 carbon atoms), and lauric acid (C12 carbon atoms).

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

[0067] Examples of cyclic amide oligomers include amide oligomers obtained by condensing dicarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing tricarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing tricarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and diamines and triamines into a cyclic form, and amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and diamines and triamines into a cyclic form.

[0068] Examples of acyclic amide oligomers include amide oligomers obtained by the condensation polymerization of monocarboxylic acids with diamines and / or triamines to form acyclic compounds, and amide oligomers obtained by the condensation polymerization of dicarboxylic acids and / or tricarboxylic acids with monoamines to form acyclic compounds. When the amide oligomer contains a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as a terminal molecule, resulting in acyclic amide oligomers with reduced molecular weight. Furthermore, in the case of amide compounds obtained by the condensation polymerization of dicarboxylic acids and / or tricarboxylic acids with diamines and / or triamines to form acyclic compounds, the acyclic amide oligomer becomes an acyclic polymeric amide polymer. Additionally, acyclic amide oligomers also include amide oligomers obtained by the condensation polymerization of monocarboxylic acids and monoamines to form acyclic compounds.

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

[0070] Thixotropic agents can be used alone or in combination with two or more.

[0071] The thixotropic agent contained in the flux of this embodiment is preferably selected from at least one 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 ester-based thixotropic agents and amide-based thixotropic agents.

[0072] Hydrogenated castor oil is preferred as an ester-based thixotropic agent.

[0073] Polyamides are preferred as amide-based thixotropic agents.

[0074] The content of thixotropic agent in the flux of this embodiment is preferably 2% or more and 20% or less relative to the total mass (100% by mass) of the flux, more preferably 5% or more and 15% or less, and even more preferably 5% or more and 10% or less.

[0075] <Thiols>

[0076] In the flux of this embodiment, the thiol compound used is a substance containing a compound (Tp) having a thiophenol skeleton.

[0077] The "thiophenol skeleton" refers to the structure in which one or more hydrogen atoms on the benzene ring are replaced by thiol groups (-SH).

[0078] Compound (Tp)

[0079] As a compound (Tp), for example, thiols represented by the following general formula (Tp-0) are preferred.

[0080] [Chemical Formula 1]

[0081]

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

[0083] In the formula (Tp-0), examples of substituents in R include amino (-NH2), halogen atoms, alkyl, alkoxy, haloalkyl, hydroxyl, etc.

[0084] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0085] As an alkyl group, it can be straight-chain or branched, and preferably an alkyl group with 1 to 6 carbon atoms.

[0086] As an alkoxy group, an alkoxy group having 1 to 6 carbon atoms is preferred.

[0087] As a haloalkyl group, examples include groups in which some or all of the hydrogen atoms of the alkyl group are replaced by halogen atoms. The alkyl group can be straight-chain or branched, and is preferably an alkyl group with 1 to 6 carbon atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0088] From the viewpoint of easily improving the effect of suppressing the viscosity change of solder paste over time, the substituents in R are preferably amino or hydroxyl, and particularly preferably amino.

[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 greater than or equal to 0, preferably an integer from 0 to 3, more preferably an integer from 0 to 2, and particularly preferably 1.

[0091] As a preferred compound (Tp), for example, aminothiophenol represented by the following chemical formula (Tp-10) can be cited.

[0092] [Chemical Formula 2]

[0093]

[0094] In the chemical formula (Tp-10), the amino group is bonded to the thiol group on the benzene ring at any of the following positions: ortho (2-), meta (3-), or para (4-).

[0095] The compound (Tp) can be used alone or in combination with two or more compounds.

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

[0097] Among these compounds, from the viewpoint of more easily improving the effect of suppressing the viscosity of solder paste from changing over time, thiols selected from 2-aminobenzylthiophenol (x=y=1), 4-aminobenzylthiophenol (x=y=1), 3-aminobenzylthiophenol (x=y=1), and thiophenol (x=1, y=0) are preferred, thiols selected from 2-aminobenzylthiophenol (x=y=1), 4-aminobenzylthiophenol (x=y=1), and 3-aminobenzylthiophenol (x=y=1) are more preferred, thiols selected from 2-aminobenzylthiophenol (x=y=1) and 4-aminobenzylthiophenol (x=y=1) are even more preferred, and thiols selected from 2-aminobenzylthiophenol (x=y=1) and 4-aminobenzylthiophenol (x=y=1) are particularly preferred.

[0098] When 2-aminobenzylthiophenol (x = y = 1) and 4-aminobenzylthiophenol (x = y = 1) are used together, their mixing ratio (mass ratio) is preferably 2-aminobenzylthiophenol / 4-aminobenzylthiophenol = 1 / 9 to 9 / 1, more preferably 3 / 7 to 7 / 3, and even more preferably 4 / 6 to 6 / 4.

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

[0100] When the total content of compound (Tp) is above the lower limit of the preferred range, it is easy to further improve the effect of suppressing the viscosity change of solder paste over time; when it is below the upper limit of the preferred range, it is easy to suppress the generation of voids during soldering.

[0101] Thiol compounds may also be used in combination with thiols other than those mentioned above (Tp).

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

[0103] <Active Agent>

[0104] Examples of surfactants include halogenated surfactants, organic acids, and amines.

[0105] Halogen-based surfactants

[0106] Examples of halogen-based activators include, for example, amine hydrohalates and other organic halogen compounds.

[0107] Aminohydrohalides:

[0108] Amino halides are compounds formed by reacting amines with hydrogen halides. Examples of amines here include azoles, guanidines, alkylamines, and amino alcohols, as well as amines exemplified in the following description of amines. Examples of hydrogen halides include hydrides of iodine, bromine, chlorine, and fluorine.

[0109] Examples of amine hydrohalides include amine hydroiodide, amine hydrobromide, amine hydrochloride, and amine hydrofluoride.

[0110] Examples of amine hydroiodates include heterocyclic amine hydroiodates such as 2-methylpiperidine hydroiodate (2-methylpiperidine·HI), piperidine·HI, etc.; chain amine hydroiodates such as monoethylamine·HI, triethylamine·HI, 1-pentylamine·HI, 2-ethylhexylamine·HI, diallylamine·HI, etc.; alicyclic amine hydroiodates such as cyclohexylamine·HI; aromatic amine hydroiodates such as aniline·HI; and guanidine hydroiodates such as 1,3-diphenylguanidine·HI, etc.

[0111] Examples of amine hydrobromates include, for example, 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, rosinamine·HBr, hydrazine hydrate·HBr, trinonylamine·HBr, diethylaniline·HBr, 2-diethylaminoethanol·HBr, diallylamine·HBr, triethylamine·HBr, aniline·HBr, dimethylcyclohexylamine·HBr, rosinamine·HBr, 2-phenylimidazolium·HBr, 4-benzylpyridine·HBr, hydrazine monohydrobromide, hydrazine dihydrobromide, ethylenediamine dihydrobromide, etc.

[0112] Examples of amine hydrochlorides include, for example, 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, ammonium chloride, etc.

[0113] Examples of amine hydrofluoric acid salts include, for example, 1,3-diphenylguanidine hydrofluoric acid (1,3-diphenylguanidine·HF), diethylamine·HF, 2-ethylhexylamine·HF, cyclohexylamine·HF, ethylamine·HF, rosinamine·HF, etc.

[0114] Organic halogen compounds other than amino halides:

[0115] As an organic halogen compound other than amine hydrohalates, examples include halogenated aliphatic compounds having halogenated aliphatic hydrocarbon groups.

[0116] Halogenated aliphatic hydrocarbon groups are groups in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are replaced by halogen atoms.

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

[0118] Examples of halogenated fatty alcohols include, for example, 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-buten-1,4-diol.

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

[0120] R 5 -(R 6 ) m ···(3)

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

[0122] As R 5The heterocyclic ring with an m-valent heterocyclic group can be exemplified by a ring structure in which a portion of the carbon atom constituting an aliphatic or aromatic hydrocarbon ring is replaced by a heteroatom. Examples of heteroatoms in this heterocycle include oxygen, sulfur, and nitrogen atoms. This heterocycle is preferably a 3- to 10-membered ring, more preferably a 5- to 7-membered ring. Examples of such heterocycles include isocyanurate rings.

[0123] R 6 The halogenated aliphatic hydrocarbon group in the compound preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. Additionally, R... 6 The preferred compounds are brominated aliphatic hydrocarbon groups and chlorinated aliphatic hydrocarbon groups, with brominated aliphatic hydrocarbon groups being more preferred, and brominated saturated aliphatic hydrocarbon groups being even more preferred.

[0124] As a halogenated heterocyclic compound, examples include tri-(2,3-dibromopropyl)isocyanurate.

[0125] In addition, as organic halogen compounds other than amino halide salts, examples include halogenated carboxyl compounds, such as iodinated carboxyl compounds like 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoaminoanisic acid; chlorinated 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.

[0126] Alternatively, as halogen-based activators, salts formed by reacting amines with tetrafluoroboric acid (HBF4) or complexes formed by reacting amines with boron trifluoride (BF3) can be used. Examples of such complexes include boron trifluoride piperidine.

[0127] Halogenated surfactants can be used alone or in combination with two or more.

[0128] From the viewpoint of suppressing voids during soldering, the halogen-based activator contained in the flux of this embodiment is preferably an aminohydrohalogenate, more preferably an aminohydroiodide, further preferably at least one selected from heterocyclic aminohydroiodides and guanidine hydroiodides, particularly preferably a heterocyclic aminohydroiodides, and most preferably at least one selected from 2-methylpiperidine·HI and piperidine·HI.

[0129] In this embodiment, when the flux contains hydroiodide in addition to the above-mentioned compound (Tp), the mixing ratio (mass ratio) of compound (Tp) to hydroiodide exceeds 50 / 50, preferably 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.

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

[0131] When the total content of halogenated activators is above the lower limit of the above-mentioned preferred range, it is easy to suppress the generation of voids during soldering; when it is below the upper limit of the above-mentioned preferred range, it is easy to further improve the effect of suppressing the viscosity change of solder paste over time.

[0132] Organic acids

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

[0134] Examples of monocarboxylic acids include, for example, aliphatic monocarboxylic acids such as glycolic acid, mercaptoacetic 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-anisinic acid, m-anisinic acid, o-anisinic acid, p-hydroxyphenylacetic acid, and 2-quinolinecarboxylic acid.

[0135] Examples of dicarboxylic acids include, for example, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, eicosanoic acid, 2,4-diethylglutaric acid, fumaric acid, maleic acid, diethylene glycol, 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, pyridine dicarboxylic acid, and dibutylaniline diethanolic acid.

[0136] Examples of tricarboxylic acids include, for example, citric acid.

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

[0138] Examples of dimer and trimer acids include, for instance, dimer acids reacting with oleic acid and linoleic acid, trimer acids reacting with oleic acid and linoleic acid, dimer acids reacting with acrylic acid, trimer acids reacting with acrylic acid, dimer acids reacting with methacrylic acid, trimer acids reacting with methacrylic acid, dimer acids reacting with acrylic acid and methacrylic acid, trimer acids reacting with acrylic acid and methacrylic acid, dimer acids reacting with oleic acid, trimer acids reacting with linoleic acid, dimer acids reacting with linolenic acid, trimer acids reacting with linolenic acid, dimer acids reacting with acrylic acid and oleic acid, trimer acids reacting with acrylic acid and oleic acid, and dimer acids reacting with acrylic acid and linoleic acid. The reactions include: a trimeric acid as a product of the reaction of acrylic acid and linoleic acid; a dimer acid as a product of the reaction of acrylic acid and linolenic acid; a trimeric acid as a product of the reaction of acrylic acid and linolenic acid; a dimer acid as a product of the reaction of methacrylic acid and oleic acid; a trimeric acid as a product of the reaction of methacrylic acid and oleic acid; a dimer acid as a product of the reaction of methacrylic acid and linoleic acid; a dimer acid as a product of the reaction of methacrylic acid and linolenic acid; a dimer acid as a product of the reaction of methacrylic acid and linolenic acid; a dimer acid as a product of the reaction of oleic acid and linolenic acid; a dimer acid as a product of the reaction of oleic acid and linolenic acid; a dimer acid as a product of the reaction of linoleic acid and linolenic acid; a trimeric acid as a product of the reaction of linoleic acid and linolenic acid; a hydrogenated dimer acid as a hydrogenated product of the above-mentioned dimer acids; and a hydrogenated trimeric acid as a hydrogenated product of the above-mentioned trimeric acids.

[0139] For example, the dimer acid that is a reactant of oleic acid and linoleic acid is a dimer with 36 carbon atoms. Furthermore, the trimer acid that is a reactant of oleic acid and linoleic acid is a trimer with 54 carbon atoms.

[0140] Organic acids can be used alone or in combination with two or more.

[0141] The organic acid contained in the flux of this embodiment is preferably at least one selected from monocarboxylic acids, dicarboxylic acids and dimer acids, more preferably at least one selected from dicarboxylic acids and dimer acids, and even more preferably at least one selected from aliphatic dicarboxylic acids and dimer acids. From the viewpoint of suppressing the formation of solder balls, it is particularly preferred to use at least aliphatic dicarboxylic acids.

[0142] The aliphatic dicarboxylic acid is preferably selected from at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, and sebacic acid; more preferably selected from at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, and octanoic acid; even more preferably selected from at least one of 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% or more and 25% or less relative to the total mass (100% by mass) of the flux, more preferably 2% or more and 20% or less, and even more preferably 3% or more and 20% or less.

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

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

[0146] "amine"

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

[0148] Examples of azoles include, for instance, 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. Imidazole, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyltriazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyltriazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyltriazine ]-Ethyltriazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyltriazine isocyanuric acid adduct, 2-phenylimidazolium isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-benzyl Imidazole compounds such as imidazoline, 2,4-diamino-6-vinyltriazine, 2,4-diamino-6-vinyltriazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyltriazine, epoxy-imidazolium 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-pentylphenyl)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 including [(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]diethanol, 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-salicylicyl)amino-1,2,4-triazole, etc.; 5-phenyltetrazole, etc.

[0149] Examples of guanidines include, for example, 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 alkylamine compounds include, for example, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, stearylamine, etc.

[0151] Examples of amino alcohol compounds include, for instance, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine.

[0152] Amines can be used alone or in combination with two or more.

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

[0154] In the flux of this embodiment, from the viewpoint of suppressing solder ball formation, it is more preferable that the activator contains a triazole compound.

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

[0156] The content of the triazole compound, relative to the total mass (100% by mass) of the flux, is preferably more than 0% by mass and less than 0.99% by mass, more preferably more than 0.1% by mass and less than 0.5% by mass.

[0157] The content of guanidine, relative to the total mass (100% by mass) of the flux, is preferably 1% by mass or more and 5% by mass or less, more preferably 2% by mass or more and 4% by mass or less.

[0158] Furthermore, in the flux of this embodiment, from the viewpoint of suppressing solder ball formation, it is preferable to use an aliphatic dicarboxylic acid and a triazole compound as the activator. When using an aliphatic dicarboxylic acid and a triazole compound, the mixing ratio (mass ratio) of the aliphatic dicarboxylic acid and the triazole compound is preferably 90 / 10 or more and 95 / 5 or less.

[0159] <Other Ingredients>

[0160] In addition to rosin, solvent, thixotropic agent, thiol compound and activator, the flux in this embodiment may contain other ingredients as needed.

[0161] Other components include resins other than rosin, sulfur-containing compounds other than thiols, surfactants, antioxidants, metal passivators, silane coupling agents, etc.

[0162] Other resin components besides rosin include, for example, 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, etc.

[0163] 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 methylphenol-formaldehyde resin-type xylene resins, polyol-modified xylene resins, and polyoxyethylene addition xylene resins. Examples of acrylic-polyethylene copolymer resins include ethylene-acrylic acid copolymers.

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

[0165] Examples of surfactants include, for example, nonionic surfactants and weakly cationic surfactants.

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

[0167] Examples of weakly cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adduct, aromatic amine polyoxyethylene adduct, and polyamine polyoxyethylene adduct.

[0168] Other surfactants besides those mentioned above include, for example, polyoxyenyne diol, polyoxyenyne glycerol ether, polyoxyenyne alkyl ether, polyoxyenyne ester, polyoxyenyne alkylamine, and polyoxyenyne alkylamide.

[0169] In the flux of this embodiment described above, since it contains a specific thiol compound (Tp), it can further suppress the viscosity change of the solder paste over time when used. From the viewpoint of easily improving this effect, among the specific thiol compounds (Tp), it is preferable to use a thiol compound selected from aminobenzylthiophenol and benzylthiophenol, and more preferably, aminobenzylthiophenol. Among these aminobenzylthiophenols, compared with using 3-aminobenzylthiophenol, 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-aminobenzylthiophenol and 4-aminobenzylthiophenol. The reason is not yet clear, but it is speculated that the viscosity change of the solder paste over time is caused by the formation of a complex between the metal of the solder alloy and the acid in the flux system. Aminobenzylthiophenol forms a protective layer by adsorbing onto the metal surface, thereby suppressing the formation of a complex between the metal and the acid. In aminobenzylthiophenol, due to the electron-donating property of the -NH2 on the benzene ring, the electron density of the mercapto sulfur atom is increased. Therefore, it can be inferred that the adsorption of aminobenzylthiophenol at anionic defects on the solder alloy surface is further promoted, thus facilitating this effect. Furthermore, due to the electron-donating property of the -NH2 atom on the benzene ring, the electron density of the mercaptosulfonate atom increases more significantly in 2-aminobenzylthiophenol and 4-aminobenzylthiophenol than in 3-aminobenzylthiophenol, making it believed that it is easier to achieve the effect of suppressing the viscosity change of the solder paste over time.

[0170] In addition to specific thiol compounds, the flux of this embodiment preferably contains aminohydroiodide, which makes it easier to suppress the viscosity change of the solder paste containing the flux over time and suppress the generation of voids during soldering.

[0171] (solder paste)

[0172] The solder paste of this embodiment contains solder alloy powder and the flux described above.

[0173] Solder alloy powder can be composed of solder powder with Sn monomer; solder alloy powder of Sn-Ag system, Sn-Cu system, Sn-Ag-Cu system, Sn-Bi system or Sn-In system, etc.; or solder alloy powder with added Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc.

[0174] Alternatively, solder alloy powder can also be composed of Sn-Pb based powder or Sn-Pb based powder containing Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc.

[0175] The solder alloy powder is preferably a Pb-free solder.

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

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

[0178] In the solder paste of this embodiment described above, since a flux containing a specific thiol compound is used, it is difficult for viscosity changes to occur over time.

[0179] Furthermore, in the solder paste of this embodiment, when a flux containing further amine hydroiodide is used, it is difficult for viscosity changes to occur over time, and the generation of voids during soldering is also suppressed.

[0180] (Tackifying inhibitors for welding flux)

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

[0182] This thickening inhibitor contains a thiol compound with a benzene thiophenol skeleton in which more than one hydrogen atom on the benzene ring is replaced by a mercapto group (-SH).

[0183] The thiol compounds with a thiophenol skeleton mentioned here are the same as those in the above-mentioned "Compound (Tp)". From the viewpoint of more easily improving the effect of inhibiting the viscosity increase of solder paste over time, the thiol compounds with a thiophenol skeleton are 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 this thickening inhibitor, thiols other than those having a thiophenol skeleton may also be used.

[0185] Examples of thiols other than those having a thiophenol skeleton include 2-(dibutylamino)-4,6-dimercapto-1,3,5-triazine, 2-mercaptobenzothiazole, tert-dodecyl mercaptosulfonate, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate.

[0186] The content of the thiol compound with the thiophenol skeleton in the thickening inhibitor can be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass.

[0187] The thickening inhibitor of the soldering flux of this embodiment can be used in the same way as the <thiol compound> constituting the above-described (flux) for the application of soldering flux. The thickening inhibitor of this embodiment can typically be used as a formulation component of the soldering flux in embodiments in which a joint is prepared by a process of printing solder paste containing soldering flux and solder alloy powder onto a substrate, mounting a component on the printed area, and heating (reflow soldering).

[0188] The flux thickening inhibitor according to this embodiment can provide a flux that is difficult to produce solder paste with an increase in viscosity over time.

[0189] Example

[0190] The present invention will be described below through embodiments, but the present invention is not limited to the following embodiments.

[0191] <Preparation of flux>

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

[0193] The fluxes of the Examples and Comparative Examples were prepared by mixing the compounding components as shown in Tables 1-13. The compounding components used are shown below.

[0194] rosin:

[0195] Acrylic acid-modified hydrogenated rosin and hydrogenated rosin are used as rosin.

[0196] Solvent:

[0197] As a solvent with a boiling point above 250°C (S1), diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C) is used.

[0198] 1,4-Butanediol (boiling point 228°C) is used as a solvent (S2) with a boiling point above 220°C and below 250°C.

[0199] As solvents with a boiling point of 220°C or less (S3), solvents with a boiling point of 190°C or more and 220°C or less (S31) and solvents with a boiling point of 160°C or more and less than 190°C (S32) are used.

[0200] Solvents with a boiling point above 190°C and below 220°C (S31):

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

[0202] Solvents with a boiling point above 160℃ and below 190℃ (S32):

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

[0204] Thixotropic agents:

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

[0206] Sulfur-containing compounds:

[0207] As sulfur-containing compounds, thiols with a thiophenol skeleton (Tp), thiols other than compound (Tp), and other sulfur-containing compounds are used.

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

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

[0210] Thiols other than compound (Tp):

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

[0212] Other sulfur-containing compounds:

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

[0214] Surfactant:

[0215] As active agents, the following are used: hydroiodide, hydrobromide, amine hydrochloride, organic acid, and amine.

[0216] As hydroiodates, 2-methylpiperidine·HI, piperidine·HI, and 1,3-diphenylguanidine·HI are used.

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

[0218] Piperidine·HI is prepared using the same method as described above for the preparation of 2-methylpiperidine·HI, except that 2-methylpiperidine is replaced with piperidine (yield is approximately 100%).

[0219] Other hydroiodates are used as finished products.

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

[0221] 1,3-Diphenylguanidine·HCl was used as the amine hydrochloride.

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

[0223] Organic acids:

[0224] As organic acids, hydrogenated dimer acid, adipic acid, benzoic acid, and phenylsuccinic acid are used.

[0225] amine:

[0226] As amines, 1,3-di-o-tolylguanidine and 3-(N-salicylic acid)amino-1,2,4-triazole are used.

[0227] Other ingredients:

[0228] Ethylene-acrylic acid copolymer is used as an acrylic resin.

[0229] 2,2'-Methylenebis[6-(1-methylcyclohexyl)-p-cresol] is used as an antioxidant.

[0230] <Preparation of solder paste>

[0231] Solder pastes were prepared by separately mixing the fluxes and solder alloy powders described below. The prepared solder pastes contained, relative to the total amount of solder paste, with the flux content set at 11.5% by mass and the solder alloy powder content set at 88.5% by mass.

[0232] Solder alloy powder:

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

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

[0235] <Evaluation>

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

[0237] [Viscosity change of solder paste over time]

[0238] (1) Test methods

[0239] For freshly prepared solder paste, the viscosity was continuously measured using a viscometer (PCU-205, Malcom Corporation) at 10 rpm, 25°C, and in atmospheric conditions for 24 hours. The viscosity change rate over 24 hours was then calculated from the viscosity at the start of the measurement and the viscosity after 24 hours. The viscosity change over time was evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1-13.

[0240] (2) Evaluation Criteria

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

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

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

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

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

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

[0247] [Effect of suppressing void formation]

[0248] (1) Test methods

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

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

[0251] Next, reflow soldering is performed for soldering.

[0252] The reflux curve at this time is as follows: Figure 1 As shown.

[0253] The reflux profile was preheated at 150°C to 175°C for 85 seconds, and then at 220°C or higher for 40 seconds, with a peak temperature of 242°C.

[0254] X-rays were irradiated onto the substrate and the QFN junction from the vertical direction, 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 as a condition where voids exist when X-rays pass through at least one void. Voids with a diameter of 0.1 μm or more are considered as the detection target.

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

[0257] (2) Evaluation Criteria

[0258] 1 point: Porosity is less than 10%.

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

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

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

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

[0263] [Table 1]

[0264]

[0265] [Table 2]

[0266]

[0267] [Table 3]

[0268]

[0269] [Table 4]

[0270]

[0271] The results shown in Tables 1-4 confirm that the flux of the examples containing specific thiol compounds (Tp) has a lower viscosity change rate after 24 hours compared with the flux of the comparative examples containing sulfur-containing compounds that are not compounds (Tp), and the viscosity change of the solder paste over time is further suppressed (comparison of Examples 3, 8, 12, 16 with Comparative Examples 1-10).

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

[0273] Thiol

[0274] <3-Aminothiophenol

[0275] <2-Aminothiophenol, 4-Aminothiophenol

[0276] <and 2-aminobenzylthiophenol and 4-aminobenzylthiophenol

[0277] It can be seen that by combining 2-aminothiophenol and 4-aminothiophenol, better results can be achieved at low complexing amounts (Examples 4, 9 and 21).

[0278] [Table 5]

[0279]

[0280] The results shown in Table 5 confirm that by further containing aminohydroiodate, the viscosity of the solder paste does not easily change over time, and the formation 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 6-9 confirm that when using the fluxes of Examples 29-66, which contain a specific thiol compound (Tp) and aminohydroiodide, the viscosity change of the solder paste over time is difficult to occur, and the generation of voids during soldering is also suppressed.

[0290] [Table 10]

[0291]

[0292] [Table 11]

[0293]

[0294] [Table 12]

[0295]

[0296] [Table 13]

[0297]

[0298] As can be seen from the results shown in Tables 10-13, by comparing Examples 68, 81-84 with Example 86, in solvents with boiling points below 220°C (S3), compared with the case of combined solvents (S1) and solvent (S32), the viscosity change rate after 24 hours is lower in the case of combined solvents (S1) and solvent (S31), which makes it easier to suppress the viscosity change of solder paste over time.

[0299] A comparison of Examples 68, 81-84, 86 with Example 85 shows that, compared with the case of combined solvent (S1) and solvent (S2), the case of combined solvent (S1) and solvent (S3) makes it easier to suppress the generation of voids during soldering when making solder paste.

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

[0301] Regarding amine hydrohalates, when preparing solder paste, it can be confirmed that the effect of suppressing the formation of voids during soldering increases in the following order (Examples 68, 72, 87; Examples 88-91).

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

[0303] Regarding hydroiodates, when preparing solder paste, the effect of suppressing voids during soldering is most superior when using 2-methylpiperidine·HI or piperidine·HI (heterocyclic hydroiodates) (Examples 68, 72, 87).

[0304] The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the structure are possible without departing from the spirit of the present invention. The present invention is not limited by the foregoing description, but only by the scope of the appended claims.

Claims

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

2. The 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 flux according to claim 1, wherein, The active agent contains ammonium hydroiodide.

4. The flux according to claim 1, wherein, The solvent contains both a solvent with a boiling point above 250°C (S1) and a solvent with a boiling point below 220°C (S3).

5. The flux according to claim 4, wherein, The solvent (S3) is a solvent (S31) with a boiling point above 190°C and below 220°C.

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

7. A solder paste comprising solder alloy powder and flux as described in any one of claims 1 to 6.

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